A novel fluorescent probe based on N,S,P codoped carbon nanodots (N,S,P-CNDSac) is very simple and quickly fabricated by a one-step hydrothermal pyrolysis of Saccharomyces cerevisiae and utilized for label-free and “on–off–on” sequential detection of manganese(VII) and l-ascorbic acid (l-AA). The fluorescence of N,S,P-CNDSac can be effectively quenched by Mn(VII) based on an inner filter effect (IFE) and recovered upon the addition of l-AA due to the easy conversion of Mn(VII) to reduced states (i.e., Mn(IV), Mn(II), and Mn(0)) by l-AA. This probe exhibited favorable selectivity and sensitivity toward Mn(VII) and l-AA with detection limits of 50 nmol/L and 1.2 μmol/L, respectively. Simultaneously, an “AND” logic gate based on the as-fabricated N,S,P-CNDSac has been constructed. Also, the as-proposed fluorescent probe was extended to detect Mn(VII) and l-AA in biosystems. Furthermore, the as-constructed fluorescent probe system was successfully applied to the analyses of Mn(VII) in tap water, Fenhe River water, and medicinal herb samples with satisfactory results. The proposed method is simple and easily accessible, demonstrating the great potential of N,S,P-CNDSac in biosensing, disease diagnosis, cellular labeling, and environmental monitoring.Keywords: AND logic gate; l-ascorbic acid; manganese(VII) ion; medicinal herbs samples; N,S,P codoped carbon nanodots; waste microorganism;

•Exploring lung DNA damage effects exposed to 1-NP with different doses.•Clarifying lung DNA damage repair gene expression induced by 1-NP.•Investigating oxidative stress and metabolic enzyme change caused by 1-NP.•DNA damage exerts an important role in 1-NP-induced lung genotoxicity.1-Nitropyrene (1-NP) is a mutagenic and carcinogenic pollutant very widespread in the environment. However, the relative investigations on genotoxicity, oxidative stress and metabolic enzymes in lungs of mammalian caused by 1-NP have not been fully established. In this study, the 1-NP solutions at 3 dosages (1.0 × 10−5, 4.0 × 10−5 and 1.6 × 10−4 mg/kg body weight) were respectively given to rats by the intratracheal instillation. The responses of 1-NP on DNA damage and repair, oxidative stress and metabolism biomarkers in rat lungs after exposure to 1-NP were measured. The results showed 1-NP at three dosages induced obvious DNA strand breaks, 8-OH-dG formation and DNA-protein cross-link in rat lungs compared with the control. Higher dosage 1-NP (4.0 × 10−5 and 1.6 × 10−4 mg/kg body weight) greatly activated DNA repair gene OGG1 and inhibited MTH1 and XRCC1 expressions, and they significantly elevated the levels of GADD153, heme oxygenase-1 and malondialdehyde and decreased SOD activity, accompanied by the increases of CYP450, CYP1A1, CYP1A2 and GST levels. These results suggested the genotoxicity of 1-NP might rely on 1-NP-caused DNA damage and its combined effects on the suppression of DNA repair and the enhancement of oxidative stress and metabolic enzyme activity.Download high-res image (115KB)Download full-size image

•Fast synthesis of phosphorus/nitrogen dual-doped CQDs (PNCQDs) by acid-base neutralization carbonization method.•On-off-on fluorescence probing of Cr(VI) and AA by PNCQDs.•Cellular imaging and detecting Cr(VI) and AA in biosystem by PNCQDs.•Determining AA content in fresh fruits and commercial fruit juices by PNCQDs/Cr(VI) mixture.Chromium (VI) [Cr(VI)] is a harsh environmental contaminates and has been proved to be highly toxic, carcinogenic and mutagenic. Therefore, developing an inexpensive, good selective and highly sensitive nanoprobe for the detection of Cr(VI) is in urgent demand. Recently, the highly fluorescent carbon quantum dots (CQDs) have been successfully utilized as efficient fluorescent nanoprobes for the detection of ions, pH and molecular substances. In this work, an “on-off” fluorescence phosphorus/nitrogen dual-doped CQDs (PNCQDs) probe was developed for the determination of Cr(VI) based on inner filter effect (IFE). The proposed PNCQDs nanoprobe shows its distinct merits of simplicity, convenience, fast implementation, good selectivity and high sensitivity towards Cr(VI), allowing its potential application in the determination of Cr(VI) in environment and biosystem. In addition, the chelation effect of the functional groups in reductant and Cr(VI), and the easy-conversion of Cr(VI) to reduced states (i.e. Cr(III) and Cr(0)) by reductants makes the minimization of IFE with a concomitant recovery of PNCQDs fluorescence possible. Hence, the PNCQDs/Cr(VI) hybrid was used as an “off-on” fluorescence probe for sensing ascorbic acid (AA), which is a model reductant. For the detection of Cr(VI), the linear range and the limit of detection achieved were 1.5–30 μmol/L and 23 nmol/L, respectively. For the detection of AA, the linear range and the limit of detection obtained were 5.0–200 μmol/L and 1.35 μmol/L, respectively. The as-constructed “on-off-on” PNCQDs fluorescent nanoprobe was successfully applied for detecting Cr(VI) and AA in biosystem. Furthermore, the as-constructed fluorescent sensing system was successfully applied to the analyses of AA in fresh fruits and in commercial fruit juices with satisfactory results.Download high-res image (247KB)Download full-size image

Ambient fine particulate matter (PM2.5) is a complex mixture associated with lung cancer risk. PM2.5-bound nitro-polycyclic aromatic hydrocarbons (NPAHs) have been demonstrated to possess mutagenicity and carcinogenicity. Previous studies showed that PM2.5 induced DNA damage, whereas there is little knowledge of whether 9-nitroanthracene (9-NA), a typical compound of NPAHs in PM2.5, causes DNA damage. Also, the regulating mechanisms of PM2.5 and 9-NA in DNA damage and repair are not yet fully established. Here we sought to investigate the molecular mechanisms of DNA damage and repair in the lungs of male Wistar rats exposed to PM2.5 (1.5 mg per kg body weight) or three different dosages of 9-NA. And then DNA strand breaks, 8-OH-dG formation, DNA–protein crosslink and DNA repair gene expressions in rat lungs were analyzed. In addition, alteration in oxidative stress factors and metabolic enzymes were detected. The results showed that (1) PM2.5 and higher dosage 9-NA (4.0 × 10−5 and 1.2 × 10−4 mg per kg body weight) significantly caused lung DNA damage, accompanied by increasing OGG1 expression while inhibiting MTH1 and XRCC1 expression, elevating the levels of GADD153, hemeoxygenase-1 and malondialdehyde, and promoting the activities of CYP450 isozymes and glutathione S-transferase. (2) 1.3 × 10−5 mg kg−1 9-NA exposure couldn't cause DNA damage and oxidative stress. (3) At the approximately equivalent dose level, PM2.5-induced DNA damage effects were more obvious than 9-NA with positive correlation. It suggests that DNA damage caused by PM2.5 and 9-NA may be mediated partially through influencing the DNA repair capacity and enhancing oxidative stress and biotransformation, and this negative effect of 9-NA might be related to the PM2.5-induced lung genotoxicity.

In this study, water-soluble N-acetyl-L-cysteine-protected palladium nanoparticles (NAC-PdNPs) were synthesised. The obtained NAC-PdNPs were well characterised by UV-vis absorption spectroscopy, infrared spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. The as-synthesised NAC-PdNPs were found to be polydisperse in nature with an average particle size of 2.17 ± 0.20 nm. As such, a reverse-phase high-performance liquid chromatographic (RP-HPLC) methodology coupled with UV-vis absorption detection has been developed for separating and analysing this as-synthesised NAC-PdNPs product. A gradient elution program with mobile phase mixtures of methanol/water containing 50 mM tetrabutylammonium fluoride was successfully applied to separate the as-synthesised NAC-PdNPs sample. The spectral characteristics of each RP-HPLC-separated NAC-PdNPs fractions were captured online using a diode array detector. In addition, most major RP-HPLC fractions were collected and further characterised by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) in order to elucidate their chemical compositions. The mass spectra suggest that the NAC-PdNPs as-synthesised product is indeed a complex mixture of small PdNPs comprising Pd10(NAC)7, Pd11(NAC)7, Pd11(NAC)8, Pd12(NAC)9, Pd13(NAC)6, Pd13(NAC)9, Pd14(NAC)5, Pd14(NAC)9, Pd15(NAC)9, Pd17(NAC)11, and Pd20(NAC)11. The UV-vis spectral characteristics of the separated NAC-PdNPs are closely related to the number of Pd atoms. This study highlights the values of using high-resolution chromatography together with UV-vis absorption spectroscopy and MALDI-TOF MS for revealing the hidden properties of each individual PdNPs species in a PdNPs product.

The formation of S-nitrosothiols (SNO) in protein cysteine residues is an important post-translational modification elicited by nitric oxide (NO). This process is involved in virtually every class of cell signaling and has attracted considerable attention in redox biology. On the other hand, their unique structural characters make SNO potentially useful synthons. In this review, we summarized the fundamental chemical/physical properties of SNO. We also highlighted the reported chemical reactions of SNO, including the reactions with phosphine reagents, sulfinic acids, various nucleophiles, SNO-mediated radical additions, and the reactions of acyl SNO species.

A new visual fluorescent probe based on carbon nano-dots (CNDs) has been facilely synthesized via one step microwave-assisted pyrolysis and utilized for sequential detection of arginine (Arg) and Cu2+ by fluorescent and colorimetric dual-readout assay. The fluorescence of CNDs can be effectively quenched by Arg, and recovered upon addition of Cu2+ due to the competitive binding of Arg and Cu2+ that leads Arg to escape from the surface of CNDs. The probe displayed high sensitivity and selectivity toward Arg and Cu2+ over other analytes with a low detection limit of 0.26 μM and 0.17 μM, respectively. Meanwhile, the CNDs can also give dual responsive signals of a visible color change (yellow–pink–light yellow). According to this phenomenon, an “AND” logic gate based on the novel CNDs has been constructed. More importantly, the probe was also extended to cellular imaging. The proposed method was simple with ease of operation, which demonstrated great potential in bio-sensing, disease diagnosis or environmental monitoring.

A novel biosensor was fabricated based on the immobilization of tyrosinase and N-acetyl-L-cysteine-capped gold nanoparticles onto the surface of the glassy carbon electrode via the film forming by chitosan. The NAC-AuNPs (N-acetyl-L-cysteine-capped gold nanoparticles) with the average size of 3.4 nm had much higher specific surface area and good biocompatibility, which were favorable for increasing the immobilization amount of enzyme, retaining the catalytic activity of enzyme and facilitating the fast electron transfer. The prepared biosensor exhibited suitable amperometric responses at −0.2 V for phenolic compounds vs. saturated calomel electrode. The parameters of influencing on the working electrode such as pH, temperature, working potential were investigated. Under optimum conditions, the biosensor was applied to detect catechol with a linear range of 1.0 × 10−7 to 6.0 × 10−5 mol•L−1 , and the detection limit of 5.0 × 10−8 mol•L−1 (S/N=3). The stability and selectivity of the proposed biosensor were also evaluated.

•PDDA-Gr/PdNPs were synthesized by one-pot hydrothermal approach.•A sensitive electrochemical sensor for triclosan was successfully achieved.•The sensor has wide linear range, low detection limit and acceptable stability.•This method was applied to determine the real samples without pretreatment.In this paper, poly (diallyldimethylammonium chloride) functionalized graphene/palladium nanoparticles (PDDA-Gr/PdNPs) have been successfully synthesized through a simple one-pot method with the use of PDDA as stabilizing agents. The electrochemical response of triclosan on the PDDA-Gr/PdNPs modified glassy carbon electrode (GCE) is greatly enhanced comparing to the PDDA-Gr/GCE or the bare GCE. It is suggested that the nanocomposite exhibited good electron transfer ability and catalytic activity. Under the optimal conditions, the oxidation current increased linearly with the concentration of triclosan in the range of 9.0 nM to 20.0 μM. The detection limit was estimated to be 3.5 nM (S/N=3). Besides, the electrochemical sensor presented superior reproducibility, excellent anti-interference performance and long-term stability. What is more, the method is promising for the determination of trace amounts of triclosan in water samples.Poly (diallyldimethylammonium chloride) functionalized graphene/palladium nanoparticles (PDDA-Gr/PdNPs) have been successfully synthesized and used as an enhanced material for electrochemical detection of triclosan. This sensor exhibits a wide linear rang and low limit of detection. It presents excellent reproducibility, anti-interference performance and long-term stability. The method is highly simple, effective and cost efficient.

•A new colorimetric and ratiometric fluorescence probe for hydrogen sulfide is developed.•The use of Michael acceptor as the sensing group of H2S shows high selectivity and sensitivity.•Probe 1 for hydrogen sulfide detection is based on intramolecular charge transfer (ICT) mechanism.A new 4-hydroxy-1,8-naphthalimide-based compound (probe 1) has been designed and synthesized. The colorimetric and fluorescent properties of probe 1 towards hydrogen sulfide (H2S) were investigated in detail. The results show that the probe 1 could selectively and sensitively recognize H2S rather than other reactive sulfur species. The reaction mechanism of this probe is an intramolecular cyclization caused by the Michael addition of H2S to give 4-hydroxy-1,8-naphthalimide. The intramolecular charge transfer of 4-hydroxy-1,8-naphthalimide is significant. Probe 1 quickly responded to H2S and showed a 75-fold fluorescence enhancement in 5 min. Moreover, probe 1 could detect H2S quantitatively with a detection limit as low as 0.23 μM.

Innovative phosphorus and nitrogen dual-doped hollow carbon dots (PNHCDs) have been fabricated for anticancer drug delivery and biological imaging. The functional groups of PNHCDs are introduced by simply mixing glucose, 1,2-ethylenediamine, and concentrated phosphoric acid. This is an automatic method without external heat treatment to rapidly produce large quantities of PNHCDs, which avoid high temperature, complicated operations, and long reaction times. The as-prepared PNHCDs possess small particle size, hollow structure, and abundant phosphate/hydroxyl/pyridinic/pyrrolic-like N groups, endowing PNHCDs with fluorescent properties, improving the accuracy of PNHCDs as an optical monitoring code both in vitro and in vivo. The investigation of PNHCDs as an anticancer drug nanocarrier for doxorubicin (DOX) indicates a better antitumor efficacy than free DOX owing to its enhanced nuclear delivery in vitro and tumor accumulation in vivo, which results in highly effective tumor growth inhibition and improved targeted therapy for cancer in clinical medicine.Keywords: biological imaging; doxorubicin delivery; hollow carbon dots; nanocarrier; phosphorus and nitrogen dual-doped

N-doping carbon dots (N-CDs) were prepared by microwave-assisted pyrolysis of dl-malic acid and ethanolamine as precursors. The material served as an excellent matrix for the detection of the environmental pollutants hydroxy-polycyclic aromatic hydrocarbons (OH-PAHs) by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) in negative ion mode. The obtained N-CDs exhibited good UV absorption capacity and favorable solubility. The use of the N-CDs matrix exhibited low matrix background interference and was beneficial to improve the signal response due to the specific π-conjugated polyaromatic structure and the doping of nitrogen atoms. The developed method was found to have good reproducibility and sensitivity. The N-CDs as a new matrix also were employed for the detection of OH-PAHs in real PM2.5 samples. The mass concentrations of Σ-hydroxy-pyrene, Σ-dihydroxy-anthraquinone, and Σ-dihydroxy-benzo(a)pyrene on the collected PM2.5 samples ranged from 0.125 to 0.136 ng/m3, 0.039 to 0.052 ng/m3, and 0.053 to 0.072 ng/m3, respectively. This work extends the application field of N-CDs and provides a good candidate of matrix for MALDI-TOF MS detection of environmental pollutants.

A novel ratiometric mitochondrial cysteine (Cys)-selective two-photon fluorescence probe has been developed on the basis of a merocyanine as the fluorophore and an acrylate moiety as the biothiol reaction site. The biocompatible and photostable acrylate-functionalized merocyanine probe shows not only a mitochondria-targeting property but also highly selective detection and monitoring of Cys over other biothiols such as homocysteine (Hcy) and glutathione (GSH) and hydrogen sulfide (H2S) in live cells. In addition, this probe exhibits ratiometric fluorescence emission characteristics (F518/F452), which are linearly proportional to Cys concentrations in the range of 0.5–40 μM. More importantly, the probe and its released fluorophore, merocyanine, exhibit strong two-photon excited fluorescence (TPEF) with two-photon action cross-section (Φσmax) of 65.2 GM at 740 nm and 72.6 GM at 760 nm in aqueous medium, respectively, which is highly desirable for high contrast and brightness ratiometric two-photon fluorescence imaging of the living samples. The probe has been successfully applied to ratiometrically image and detect mitochondrial Cys in live cells and intact tissues down to a depth of 150 μm by two-photon fluorescence microscopy. Thus, this ratiometric two-photon fluorescent probe is practically useful for an investigation of Cys in living biological systems.

•Fluorescent pH probe based on indole derivatives and pyridine was constructed.•Probe exhibits sensitive pH responded linearly within the range of 3.0–4.6.•Probe has good cell membrane permeability and monitor pH fluctuations in live cells.In this paper, we report a novel pH fluorescent probe, 1,1-dimethyl-2-((E)-2-(pyridin-4-yl)vinyl)-1H-benzo[e]indole (PVBI), for imaging in living cells via ethylene bridging of indole derivatives and pyridine. The pH titration indicated that the probe exhibits sensitive pH-dependent behavior with pKa 3.87 and responded linearly and rapidly to minor pH fluctuations within the range of 3.0–4.6 (linear coefficient of 0.9968). Thus PVBI could be potentially useful for quantitative determination of pH within the acidic window. Also, PVBI displays a notably large Stokes shift of 93 nm which could effectively reduce the excitation interference. Moreover, PVBI possesses highly selective response to H+ over various metal ions, good photostability and excellent reversibility. The confocal laser scanning microscope images for PVBI diffusing into cells in real-time and detection of pH in living cells were achieved successfully, suggesting the probe has excellent cell membrane permeability and could be applied to monitor pH fluctuations in living cells.

A new colorimetric probe, 5-chlorosalicylaldehyde fluorescein hydrazone (CSFH), has been synthesized and characterized by infrared spectroscopy, nuclear magnetic resonance spectroscopy, mass spectrometry, elemental analysis and X-ray single crystal diffraction. CSFH had nearly no absorption in visible region. In the presence of copper(II) ion a rapid color changes from colorless to yellow along with an obvious new absorption band appeared at 495 nm. CSFH was highly selective to Cu2+ only in the aqueous solution, instead of common metal ions. The absorbance intensity and the color of CSFH solution increased gradually with the increase of Cu2+ concentration. Common metal ions did not show any interference on the determination of Cu2+. The chemical stoichiometric ratio between the CSFH and Cu2+ was 1:1 and corresponding association constant was 6.85 × 105 L mol−1, and the linear range for Cu2+ detection was 0.25–14 μmol L−1. The detection limits were 0.25 μmol L−1 and 1.0 μmol L−1 of Cu2+ using the UV-Vis changes and the visual color changes by the naked eye respectively. The proposed method was applied to the determination of Cu2+ in drinking water samples and the recoveries were 96–106%. The preparation of CSFH exhibited the quick, simple and facile advantages. The results showed that CSFH can be a good candidate for simple, rapid and sensitive colorimetric detection of Cu2+ in aqueous solution.

Less toxic elements nitrogen and sulfur co-doped carbon-based dots (NSCDs) have been prepared by microwave-assisted pyrolysis of citric acid and N-acetyl-L-cysteine as the carbon source and N,S-dopant, respectively. The structure and optical properties of NSCDs are characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, elemental analysis, Fourier transform infrared spectroscopy, UV-vis absorption, and photoluminescence spectroscopy. The mechanism for the formation of NSCDs is also discussed. The as-prepared NSCDs show small size distribution and excellent dispersibility. Their strong blue fluorescence is observed when the excitation wavelength is between 260 nm and 380 nm. Moreover, they exhibit high tolerance to various external conditions including external cations, pH values, and continuous UV excitation. More strikingly, as the emission of NSCDs is efficiently quenched by Cr(VI), the as-prepared NSCDs are employed as a highly sensitive and selective probe for Cr(VI) detection. The linear range is 0.5–125 μM Cr(VI) with the detection limit 20 nM. The as-synthesized NSCDs have been successfully applied for Cr(VI) sensing and cell imaging.

•A new method for the synthesis of ferromagnetic CoPt NPs was reported.•A new pathway for the nanopatterned CoPt NPs in large scale and at low cost was provided.•The method as demonstrated in the text can be used for generation of various nanopatternd metallic and metal alloy NPs.Ferromagnetic (L10 phase) CoPt alloy nanoparticles (NPs) have attracted widely research interests due to their potential application in data storage, catalysis and biomedicine, etc. In this manuscript, we report the fabrication of L10 CoPt NPs by employing Co-containing and Pt-containing polymer blend as a single-source precursor without any post-annealing treatment. The average size of the resulting L10 CoPt NPs is 6.54 nm with a reasonably narrow size standard deviation of 1.28 nm. The coercivity of L10 CoPt NPs is 362 Oe and 1026 Oe at 300 K and 10 K, respectively. We also fabricated the nanoline and nanodot arrays through nanoimprinting the polymer blend which then underwent pyrolysis to generate L10 CoPt NPs-based nanoline array. The successful transfer of the pre-defined patterns of the stamps onto the surface of the polymer blend implies that this material holds great application potential in data storage system and electronics based on magnetic nanostructures.

•A fluorescent probe is developed using butadiene bridging of two indole derivatives.•Probe is linearly proportional to extreme acidity range of 2.3–3.6 with pKa 2.89.•Probe has good cell membrane permeability and monitor pH fluctuations in E.coli.A novel fluorescent probe for extreme acidity is developed using biocompatible indole derivative as the fluorophore. The probe is linearly proportional to extreme acidity range of 2.3–3.6 with pKa 2.89. Moreover, it displays promising spectroscopic features such as large Stokes shift (145 nm), highly selective response to H+ over various metal ions, good photostability and excellent reversibility. The confocal laser scanning microscope images display the probe possesses excellent cell membrane permeability, and is further applied successfully to monitor pH fluctuations of extreme acidity range in E. coli cells without influence of autofluorescence and native cellular species in biological systems.

•A new Sciff base fluorescence probe for Hg2+is designed and synthesized.•The probe can sensitively and selectively detect Hg2+in weakly acidic and neutral pH conditions.•The probe can detect Cu2+in weakly alkaline conditions by using “masking” reagent.A new Schiff base fluorescent probe, 2-(4-(diphenylamine)benzylidene) thiosemicarbazide (DPBT), was synthesized and its sensing behavior to metal ions were studied by UV–vis and fluorescence spectra. The results show that DPBT can detect Hg2+sensitively and selectively in weakly acidic and neutral conditions, they form a complex with 2:1. The linear range was 0.095–1.14 µM and the detection limit was 0.15 nM. In weakly alkaline conditions, DPBT can interaction with Hg2+and Cu2+at the same time. We use “masking” reagent, NaBH4, to reduce Hg2+to Hg°, the detection of Cu2+were achieved. They formed 1:1 complex with the binding constant of 4×104 M−1, a good linear relationship in 0.45–3.6 µM and the detection limit of 0.17 µM. The proposed method was used to determine Hg2+and Cu2+in tap water and waste water samples.

•UHPLC is a powerful analytical method for separating complex mixtures of C-dots.•UHPLC is applied to study C-dots synthesized from various experimental conditions.•UHPLC together with optical spectroscopy and mass spectrometry is helpful.•UHPLC can determine the spectral and structural features of C-dots fractions.A fast and green approach to synthesize carbon dots (C-dots) by microwave-assisted pyrolysis of precursor chitosan as the carbon source and glacial acetic acid as the condensation agent has been developed. Ultra-high performance liquid chromatography (UHPLC) has been applied to study C-dots samples prepared with various synthetic conditions including amount of chitosan, concentration of acetic acid and reaction time. All the as-prepared C-dots samples are complex mixtures of C-dots species which can be separated by UHPLC within 16 min. All the separated C-dots peaks display a distinctive absorption bands at 261–271 nm corresponding to the n→π* transition of C=O bond. The obtained chromatograms indicate the composition and complexity of an as-synthesized C-dots sample which is commonly neglected. In addition, high-performance liquid chromatography is employed to fractionate the C-dots sample. The separated C-dots fractions are collected and characterized by photoluminescence (PL) spectroscopy and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The PL spectra of the fractions display emission peaks at 427–446 nm upon excitation at 340 nm. The C-dots fractions are fully anatomized by MALDI-TOF MS, displaying their fragmentation mass ion features and indicating the surface functionalities of C-dots. The findings highlight the virtues of UHPLC to separate and reveal the unique characteristics of individual C-dots product which may have potential applications in the fields of bioanalysis, bioimaging, catalysis, chemosensing, energy storage, and optoelectronics device.

β-Amyloid(Aβ) plaques and intracellular neurofibrillary lesions in the brain are markers of Alzheimer’s disease(AD). The ability to safely decrease Aβ concentrations is potentially important as a preventive strategy for AD. The interactions between vanillin and Aβ polypeptide were investigated via fluorescence spectroscopy and atomic force microscopy(AFM). The results of fluorescence and synchronous spectroscopies illustrate that the intrinsic fluorescence of tyrosine(Tyr) residues in Aβ1-42 aggregates can be quenched strongly upon the formation of vanillin-Aβ1-42 complex. Thioflavine T(ThT)-induced fluorescence changes indicated that Aβ1-42 aggregates could be disaggregated by vanillin, and the AFM images of Aβ1-42 enunciated the depolymerization of Aβ1-42 aggregates by vanillin in a dose-dependent manner. Vanillin may be a potential pharmacological agent for the treatment of AD.

Phosphorous and nitrogen co-doped carbon dots (P,N-CDs) with satisfactory quantum yield have been prepared through one-step acidic oxidation of pumpkin by H3PO4 at low temperature (90 °C). The as-prepared P,N-CD is relatively monodisperse with a narrow size distribution. The P,N-CD displays a remarkable emission enhancement in the yellow fluorescence region (λem = 550 nm) when the pH is increased from 1.5 to 7.4. The pKa value of P,N-CDs was found to be 4.17 and it shows linear response to the physiological range of pH 4.7–7.4, which is valuable for near-neutral cytosolic pH research. It is observed that P,N-CDs are superior fluorescent bioimaging agents in animals and cells thanks to their excellent solubility and ultra-low toxicity. In addition, P,N-CDs display a notably large Stokes shift of 125 nm, good reversibility and could effectively avoid the influence of autofluorescence in biological systems. The confocal fluorescent microscopic images of subcellular distribution and the detection of pH in MCF-7 cells were achieved successfully, suggesting that P,N-CDs have excellent cell membrane permeability and are further applied successfully to monitor pH fluctuations in live cells with negligible autofluorescence.

A novel ratiometric emission fluorescent probe, 1,1-dimethyl-2-[2-(quinolin-4-yl)vinyl]-1H-benzo[e]indole (QVBI), is facilely synthesized via ethylene bridging of benzoindole and quinoline. The probe exhibits ratiometric fluorescence emission (F522nm/F630nm) characteristics with pKa 3.27 and linear response to extreme-acidity range of 3.8–2.0. Also, its high fluorescence quantum yield (Φ = 0.89) and large Stokes shift (110 nm) are favorable. Moreover, QVBI possesses highly selective response to H+ over metal ions and some bioactive molecules, good photostability, and excellent reversibility. The probe has excellent cell membrane permeability and is further applied successfully to monitor pH fluctuations in live cells and imaging extreme acidity in Escherichia coli cells without influence of autofluorescence and native cellular species in biological systems.

•Fast synthesis of nitrogen-doped carbon dots (N-CDs) by microwave method.•Optimization of synthesis of N-CDs.•Fluorescence sensing of Fe3+ by N-CDs.•Cell imaging and detecting Fe3+ in biosystem by N-CDs.A fast and facile approach to synthesize highly nitrogen (N)-doped carbon dots (N-CDs) by microwave-assisted pyrolysis of chitosan, acetic acid and 1,2-ethylenediamine as the carbon source, condensation agent and N-dopant, respectively, is reported. The obtained N-CDs are fully characterized by elemental analysis, transmission electron microscopy, high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction pattern, X-ray photoelectron spectroscopy, UV–vis absorption, and photoluminescence spectroscopy. Doping N heteroatoms benefits the generation of N-CDs with stronger fluorescence emission. As the emission of N-CDs is efficiently quenched by Fe3+, the as-prepared N-CDs are employed as a highly sensitive and selective probe for Fe3+ detection. The detection limit can reach as low as 10 ppb, and the linear range is 0.010–1.8 ppm Fe3+. The as-synthesized N-CDs have been successfully applied for cell imaging and detecting Fe3+ in biosystem.

•A new colorimetric and ratiometric fluorescence probe for H2S is developed.•The use of the diselenide bond as the sensing group of H2S shows high selectivity and sensitivity.•The probe is applied in measuring H2S in bovine plasma and bioimaging in cells.A new ratiometric fluorescence probe for hydrogen sulfide is developed. The design was based on a H2S-mediated diselenide cleavage and intramolecular cyclization to release the fluorophore. The probe showed high selectivity and sensitivity for H2S over other reactive sulfur species and was successfully applied for the detection of H2S in bovine plasma and bioimaging in live cells.

A simple and rapid method that uses synthesized magnetic graphene composites as both an adsorbent for enrichment and as a matrix in MALDI-TOF MS analysis was developed for the detection of nitropolycyclic hydrocarbons (nitro-PAHs) in PM2.5 samples. Three nitro-PAHs were detected down to sub pg μL−1 levels based on calculations from an instrumental signal-to-noise better than 3, which shows the feasibility of using the new materials in MALDI-TOF MS as a potential powerful analytical approach for the analysis of nitro-PAHs in PM2.5 samples.

3-[3-(4-Fluorophenyl)-1-(1-methylethyl)-1H-indol-2-yl]-(E)-2-propenal (FMIP) was used as a ratiometric fluorescent pH probe with favorable optical properties for strong-acidity pH detection in living cells. The probe exhibits ratiometric fluorescence emission (I528 nm/I478 nm) characteristics with pKa 3.90 and linear response to strong-acidity range of 3.3–4.5. The major features of the probe include large Stokes shift (163 nm at pH 7.0 and 113 nm at pH 3.5), high selectivity and good photostability. More importantly, the probe has excellent cell membrane permeability and is further applied successfully to monitor pH in living cells.

•Electrochemical sensor has been developed to detect trace amount of luteolin based on SH-β-CD-GNs/AuNPs.•The nanocomposite integrates the unique properties of GNs/AuNPs and CDs.•The method can be applied to detect luteolin in real sample.•This approach is facile, sensitive and cost-efficient.In this work, a simple and highly sensitive electrochemical method was developed to detect luteolin based on thio-β-cyclodextrin functionalized graphene/gold nanoparticles modified glassy carbon electrode (SH-β-CD-GNs/AuNPs/GCE). The peak currents of luteolin on the SH-β-CD-GNs/AuNPs/GCE can be greatly enhanced compared to the SH-β-CD-GNs/GCE and the bare GCE. It suggests that the nanocomposite not only shows the excellent electrical properties of GNs and AuNPs but also exhibits higher enrichment ability of cyclodextrins via the host-guest interaction between cyclodextrin and luteolin. At the SH-β-CD-GNs/AuNPs/GCE, the peak currents increased linearly with the concentration of luteolin in the range of 10.0 pM to 10.0 μM. The detection limit was estimated to be 3.3 pM (S/N = 3), which was more sensitive or comparable with the previous electrochemical sensors for luteolin detection. The analytical performance of this sensor has been evaluated for the detection of luteolin in human serum with satisfactory results. Furthermore, the method might open up a new possibility by using the nanohybrids to monitor other flavonoids which can form host–guest complexes with cyclodextrins.

Exposure to ambient fine particulate matter (PM2.5) increases the risk of respiratory disease. Although previous mitochondrial research has provided new information about PM toxicity in the lung, the exact mechanism of PM2.5-mediated structural and functional damage of lung mitochondria remains unclear. In this study, changes in lung mitochondrial morphology, expression of mitochondrial fission/fusion markers, lipid peroxidation, and transport ATPase activity in SD rats exposed to ambient PM2.5 at different dosages were investigated. Also, the release of reactive oxygen species (ROS) via the respiratory burst in rat alveolar macrophages (AMs) exposed to PM2.5 was examined by luminol-dependent chemiluminescence (CL). The results showed that (1) PM2.5 deposited in the lung and induced pathological damage, particularly causing abnormal alterations of mitochondrial structure, including mitochondrial swelling and cristae disorder or even fragmentation in the presence of higher doses of PM2.5; (2) PM2.5 significantly affected the expression of specific mitochondrial fission/fusion markers (OPA1, Mfn1, Mfn2, Fis1, and Drp1) in rat lung; (3) PM2.5 inhibited Mn superoxide dismutase (MnSOD), Na+K+-ATPase, and Ca2+-ATPase activities and elevated malondialdehyde (MDA) content in rat lung mitochondria; and (4) PM2.5 induced rat AMs to produce ROS, which was inhibited by about 84.1% by diphenyleneiodonium chloride (DPI), an important ROS generation inhibitor. It is suggested that the pathological injury observed in rat lung exposed to PM2.5 is associated with mitochondrial fusion–fission dysfunction, ROS generation, mitochondrial lipid peroxidation, and cellular homeostasis imbalance. Damage to lung mitochondria may be one of the important mechanisms by which PM2.5 induces lung injury, contributing to respiratory diseases.

The aim of this study was to investigate the chemical compositions of chalk dust and examine the adverse effects of fine chalk particle matters (PM2.5) on rat alveolar macrophages (AMs) in vitro. Morphologies and element concentrations of chalk particles were analyzed using quantitative energy-dispersive electron probe X-ray microanalysis (ED-EPMA). The oxidative response of AMs exposed to chalk PM2.5 was measured by luminol-dependent chemiluminescence (CL). The results showed that (1) Chalk dust was mainly composed of gypsum (CaSO4), calcite (CaCO3)/dolomite (CaMg(CO3)2), and organic adhesives; (2) Fine chalk particles induced the AM production of CL, which was inhibited by about 90% by diphenyleneiodonium chloride (DPI). Based on these results, we showed that cytotoxicity of chalk PM2.5 may be related to the reactive oxygen species (ROS) generation.The chemical compositions of chalk dust were investigated and the adverse effects of fine chalk particle matters (PM2.5) on rat alveolar macrophages (AMs) in vitro were examined. The result showed that cytotoxicity of chalk PM2.5 may be related to the reactive oxygen species (ROS) generation.

•A label-free fluorescent aptasensor for K+ ion in aqueous solution is fabricated.•Berberine is applied in aptasensor based on its senstivity for DNA for the first time.•The limit of the detection is 31 nM, lower than those of previously reported aptamer-based K+ ion assays.•The presented approach is rapid, simple, cost-effective and suitable for real sample.A simple, rapid and label-free fluorescent aptasensor was fabricated for the detection of potassium ion (K+ ion) in aqueous solution using K+ ion-stabilized single stranded DNA (ssDNA) with G-rich sequence as the recognition element and a fluorescent dye, berberine, as the fluorescence probe. In the presence of K+ ion, the G-rich ssDNA is promoted to form the aptamer–target complex with a G-quadruplex conformation, and berberine binding to the G-quadruplex structure results in the enhancement of its fluorescence. The fluorescence intensity of the sensing system displayed a calibration response for K+ ion in the range of 0–1600 μM with a detection limit of 31 nM (S/N = 3) and a relative standard deviation (RSD) of 0.45%. This label-free fluorescence aptasensor is conveniently and effectively applicable for analysis of K+ ion in blood serum samples with the recovery range of 81.7–105.3%. The assay for detection of potassium ion is easy, economical, robust, and stable in rough conditions.Graphical abstract

•Biosensing ATP with a new berberine/exonuclease I probe system is demonstrated.•Exonuclease I is used to recognize and digest ATP-bound aptamers.•The aptasensor gives low background unparalleled by non-enzyme-based assays.•Sensitive and selective detection of ATP is achieved.•A response for ATP in a wide range from 0.5 μM to 17.5 mM is obtained.A novel aptamer-based label-free assay for sensitive and selective detection of ATP was developed. This assay employs a new aptamer/fluorescent probe system that shows resistance to exonuclease I (Exo I) digestion upon binding to ATP molecules. In the absence of ATP, the complex between the ATP-binding aptamer (ATP–aptamer) and a DNA binding dye, berberine, is digested upon the addition of exonuclease I, leading to the release of berberine into solution and consequently, quenched berberine fluorescence. In the presence of ATP, the ATP-binding aptamer folds into a G-quadruplex structure that is resistant to Exo I digestion. Accordingly, berberine is protected in the G-quadruplex structure and high fluorescence intensity is observed. As such, based on the fluorescence signal change, a label-free fluorescence assay for ATP was developed. Factors affecting the analysis of ATP including the concentration of ATP-binding aptamer, reaction time, temperature and the concentration of Exo I were comprehensively investigated. Under optimal conditions, the fluorescence intensity of the sensing system displayed a response for ATP in a wide range up to 17.5 mM with a detection limit of 140 nM.

•PVP–GNs–NiNPs–CS nanocomposites were firstly synthesized.•The nanocomposites can act as enhanced material for non-enzymaticglucose detection.•This glucose sensor has prominent feasibility for real sample analysis.•The approach is highly simple, effective and cost efficient.In this report, a new nanocomposite was successfully synthesized by chemical deposition of nickel nanoparticles (NiNPs) on polyvinylpyrrolidone (PVP) stabilized graphene nanosheets (GNs) with chitosan (CS) as the protective coating. The as obtained nanocomposite (PVP–GNs–NiNPs–CS) was characterized by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Benefiting from the synergistic effect of GNs (large surface area and high conductivity), NiNPs (high electrocatalytic activity towards the glucose oxidation) and CS (good film-forming and antifouling ability), a nonenzymatic electrochemical glucose sensor was established. The nanocomposite displays greatly enhanced electrocatalytic activity towards the glucose oxidation in NaOH solution. The PVP–GNs–NiNPs–CS based electrochemical glucose sensor demonstrates good sensitivity, wide linear range (0.1 μM–0.5 mM), outstanding detection limit (30 nM), attractive selectivity, good reproducibility, high stability as well as prominent feasibility for the real sample analysis. The proposed experiment might open up a new possibility for widespread use of non-enzymatic sensors for monitoring blood glucose owing to its advantages of low cost, simple preparation and excellent properties for glucose detection.A new nanocomposite was successfully synthesized by chemical deposition of nickel nanoparticles (NiNPs) on polyvinylpyrrolidone (PVP) stabilized graphene nanosheets (GNs) with chitosan (CS) as the protective coating (PVP–GNs–NiNPs–CS). Combining the unique properties of PVP, GNs, NiNPs and CS, a non-enzymatic electrochemical glucose sensor was demonstrated. The method is highly simple, effective and cost efficient.

•Palladium nanoparticles (PdNPs) are synthesized in N,N′-dimethylformamide (DMF).•The DMF-PdNPs product is successfully separated by reversed-phase HPLC.•The collected DMF-PdNPs fractions are fully characterized by MALDI-TOF MS.Metal nanoparticles (NPs) have recently attracted considerable attention in many areas of research including bioscience, chemistry and material science. Regrettably, most current and past work usually focuses on studies of multi-component NPs mixture where there is a plethora of NPs species co-existing. This work highlights the merits of reverse-phase high-performance liquid chromatography (RP-HPLC) for disclosing the genuine properties of individual palladium nanoparticles (PdNPs) species present in an as-synthesized N,N′-dimethylformamide-stabilized PdNPs product (DMF-PdNPs) which might have been previously hidden or misinterpreted. DMF-PdNPs is successfully separated by RP-HPLC that smaller DMF-PdNPs are approximately eluted first and then follow by the large ones on a C18 column. The separation fractions are further collected and determined their chemical compositions by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The results unambiguously reveal that the as-synthesized DMF-PdNPs product is indeed a complex mixture of ultrasmall PdxNPs (x=10–20) stabilized with different numbers of DMF ligands. It is anticipated that the separated fractions afforded by RP-HPLC will offer more accurate determinations of the catalytic, electronic, optical and toxicological properties of metal NPs which might have been previously misinterpreted.

An organic salt based on double 1,3,4-oxadiazole derivatives as fluorophores and BAPTA as a receptor has been designed for detection of Cd2+. The fluorescent probe exhibits high selectivity for Cd2+ and a low detection limit of 20 nM in aqueous solution, making it useful for Cd2+ imaging in living MCF-7 cells.

An organic salt as a fluorescent probe based on intramolecular charge transfer for Ca2+ determination is developed. Ca2+ can be detected by ratiometric emission at 490 and 594 nm with an excitation wavelength of 405 nm. This probe is highly selective for Ca2+ over other divalent metal cations and displays a large Stokes shift of 189 nm that can avoid interference of the excitation light beam and autofluorescence of biological samples. The dissociation constant for Ca2+ is 2.25 ± 0.47 μM and pertinent to Ca2+ detection in cellular resting and dynamic states. The probe demonstrates its application in monitoring Ca2+ in living cells under confocal microscopic imaging.

3-Mercaptopropionic acid (MPA)-capped ZnS:Cu/ZnS core/shell quantum dots (QDs) have been synthesized via a facile aqueous coprecipitation method and characterized by fluorescence, UV-Vis absorption, infrared spectroscopy and transmission electron microscopy. The fluorescence of ZnS:Cu/ZnS could be increased in the presence of uric acid (UA). The affecting factors for the fluorescence of ZnS:Cu/ZnS were examined including pH, temperature and reacting time. Under the optimized conditions, the fluorescence intensity of the ZnS:Cu/ZnS QDs against the UA concentration showed a linear response in the range of 0.66 μM to 3.3 μM with the correlation coefficient (R2) 0.9973 and the limit of detection 0.044 μM. Most relevant molecules and physiological ions had no effect on the detection of UA. The feasibility of the developed method was further demonstrated by determining the concentration of uric acid in human urine samples and the recoveries were 95% ∼ 103%. Our work provides a sensitive, selective and convenient fluorescence method to determine UA in real samples.

The pollution characteristics of ambient fine particulate matter (PM2.5) containing polycyclic aromatic hydrocarbons (PAHs) and nitrated PAHs (NPAHs) in samples collected during a typical winter time period in Taiyuan of China were investigated. The obtained results revealed that the mean mass concentrations of PM2.5, ΣPAHs (sum of 16 PAHs) and ΣNPAHs (sum of 3 NPAHs) on PM2.5 were 161.4 μg/m3, 119.8 ng/m3 and 0.446 ng/m3, respectively. Diagnostic ratios of PAHs and NPAHs implied that coal consumption might be the main source of the PM2.5 pollution. The measured PM2.5 mass concentrations, BaP equivalent toxicity (28.632 ng/m3) and individual carcinogenicity index (3.14 × 10−5) were much higher than those of the recommended safety standards.The main source of serious PM2.5 pollution in a typical Taiyuan's winter time period was coal combustion. PAHs and NPAHs on the PM2.5 may have a significant impact on human health and cancer risk.

•DM-β-CD functionalized graphene nanosheets (DM-β-CD-GNs) were firstly synthesized.•The nanocomposite integrated the unique properties of graphene and DM-β-CD.•An electrochemical sensing platform was developed to detect flavonoid drugs.•This method is simple, cost-efficient and sensitive.In this study, 2,6-dimethyl-β-cyclodextrin (DM-β-CD) functionalized graphene nanosheets (DM-β-CD-GNs) were successfully synthesized by a simple wet-chemical strategy. The as obtained DM-β-CD-GNs were characterized by UV–vis spectroscopy, Fourier transform Infrared (FT-IR) spectroscopy, atomic force microscopy (AFM) and transmission electron microscopy (TEM). The new nanocomposite possesses the unique properties of graphene (large surface area and high conductivity) and DM-β-CD (high supramolecular recognition and enrichment capability). Based on the above properties, a highly sensitive electrochemical sensor was developed to detect two flavonoid drugs (isoquercitrin and baicalin). At the DM-β-CD-GNs modified glassy carbon electrode (DM-β-CD-GNs/GCE), the peak currents of the two drugs increased dramatically compared with that on the bare GCE and GNs/GCE which due to the synergetic effects of GNs and DM-β-CD molecules. The linear response ranges for isoquercitrin and baicalin are 10 nM–3.0 μM and 0.04 μM –3.0 μM, with the detection limits of 4 nM and 10 nM, respectively. The method might open up a new possibility for the widespread use of electrochemical sensors for monitoring of ultra-trace flavonoid drugs owing to its advantages of simple preparation, low cost, high sensitivity, good stability and reproducibility.

•A novel rhodamine B derivative 3-bromo-5-methylsalicylaldehyde rhodamine B hydrazone (BMSRH) was synthesized and characterized.•BMSRH have a rapid, selective and sensitive response to Cu2+.•The response of BMSRH to Cu2+ is reversible .•BMSRH can be a good colorimetric probe for Cu2+ determination.A novel rhodamine derivative 3-bromo-5-methylsalicylaldehyde rhodamine B hydrazone (BMSRH) has been synthesized by reacting rhodamine B hydrazide with 3-bromo-5-methylsalicylaldehyde and developed as a new colorimetric probe for the selective and sensitive detection of Cu2+. Addition of Cu2+ to the solution of BMSRH results in a rapid color change from colorless to red together with an obvious new band appeared at 552 nm in the UV–vis absorption spectra. This change is attributed to the spirocycle form of BMSRH opened via coordination with Cu2+ in a 1:1 stoichiometry and their association constant is determined as 3.2 × 104 L mol−1. Experimental results indicate that the BMSRH can provide a rapid, selective and sensitive response to Cu2+ with a linear dynamic range 0.667–240 μmol/L. Common interferent ions do not show any interference on the Cu2+ determination. It is anticipated that BMSRH can be a good candidate probe and has potential application for Cu2+ determination. The proposed probe exhibits the following advantages: a quick, simple and facile synthesis.Graphical abstract

β-Cyclodextrin (β-CD) and its derivatives carboxymethyl-β-CD (CM-β-CD) and 2,6-dimethyl-β-CD (DM-β-CD) modified magnetic nanoparticles (CD-MNPs) were synthesized via layer-by-layer method. CDs grafted onto Fe3O4 MNPs were demonstrated by transmission electron microscopy, Fourier transform infrared and Zeta potential. Magnetic properties of CM-β-CD-MNPs, DM-β-CD-MNPs and β-CD-MNPs were characterized by vibrating sample magnetometer and the magnetic saturation values were 47, 46 and 44 emu g−1, respectively. CD-MNPs as drug carriers were investigated by inclusion behavior and in vitro release using ketoprofen (KP) as a model drug. The maximum adsorption quantities of CM-β-CD-MNPs, DM-β-CD-MNPs and β-CD-MNPs for KP were 37.03, 7.63 and 25.12 mg g−1, respectively, and the loading behaviors followed the Langmuir adsorption isotherm model with monolayer adsorption. The release profiles of KP released from KP-loaded CD-MNPs were rapid in initial 60 min and then gradually tend to level off, the release efficiency order was CM-β-CD-MNPs > β-CD-MNPs > DM-β-CD-MNPs, which was consistent with the order of inclusion capability. Therefore, the CD-MNPs were promising candidates for drug delivery.

We report on an electrochemical aptasensor for the ultrasensitive determination of thrombin. A glassy carbon electrode modified with a graphene-porphyrin nanocomposite exhibits excellent electrochemical activity and can be used as a redox probe in differential pulse voltammetry of the porphyrin on its surface. The thrombin aptamer is then immobilized via p-stacking interactions between aptamer and graphene and π-π stacking with porphyrin simultaneously. The resulting electrochemical aptasensor displays a linear response to thrombin in the 5–1,500 nM concentration range and with a limit of detection of 0.2 nM (at an S/N of 3). The sensor benefits from the synergetic effects of graphene (with its high conductivity and high surface area), of the porphyrin (possessing excellent electrochemical activity), and of the aptamer (with its high affinity and specificity). This kind of aptasensor conceivably represents a promising tool for bioanalytical applications.

•A novel fluorescein derivative furfuraldehyde fluorescein hydrazone (FFH) was synthesized and characterized.•FFH have a rapid, selective and sensitive response to Cu2+.•FFH has good solubility in ethanol and aqueous solution media.•FFH can be a good colorimetric probe for Cu2+ determination.A novel fluorescein derivative furfuraldehyde fluorescein hydrazone (FFH) has been synthesized by reacting fluorescein hydrazide with furfuraldehyde and characterized by 1H NMR, 13C NMR, MS and elemental analysis. Addition of Cu2+ to the solution of FFH results in a rapid color change from colorless to yellow together with an obvious new band appeared at 502 nm in the UV–vis absorption spectra. This change is attributed to the spirocycle form of FFH opened via coordination with Cu2+ in a 1:1 stoichiometry and their association constant is determined as 6.1 × 104 L mol−1. Experimental results indicate that the FFH can provide a rapid, selective and sensitive response to Cu2+ with a linear dynamic range 6.6–330 μmol/L. Common interferent ions do not show any interference on the Cu2+ determination. It is anticipated that FFH can be a good candidate probe and has potential application for Cu2+ determination in aqueous solution.Graphical abstract

•This paper attests that jatrorrhizine has high binding affinity with HSA.•Jatrorrhizine effectively quenched the fluorescence of HSA molecules through static mechanism.•The energy transfer from HSA molecules to jatrorrhizine occurs with high probability.•Experimental data show that jatrorrhizine interacts with HSA mainly via electrostatic force.•Molecular calculation shows that π–π staking and hydrogen bond also stabilize the complex on site I.In this work, the interaction of jatrorrhizine with human serum albumin (HSA) was studied by means of UV–vis and fluorescence spectra. The intrinsic fluorescence of HSA was quenched by jatrorrhizine, which was rationalized in terms of the static quenching mechanism. The results show that jatrorrhizine can obviously bind to HSA molecules. According to fluorescence quenching calculations, the bimolecular quenching constant (kq), apparent quenching constant (KSV) at different temperatures were obtained. The binding constants K are 4059 L mol−1 and 1438 L mol−1 at 299 K and 304 K respectively, and the number of binding sites n is almost 1. The thermodynamic parameters determined by the Van’t Hoff analysis of the binding constants (ΔH −12.25 kJ mol−1 and ΔS 28.17 J mol−1 K−1) clearly indicate that the electrostatic force plays a major role in the process. The efficiency of energy transfer and the distance between the donor (HSA) and the acceptor (jatrorrhizine) were calculated as 22.2% and 3.19 nm according to Föster’s non-radiative energy transfer theory. In addition, synchronous fluorescence spectroscopy reveals that jatrorrhizine can influence HSA’s microstructure. That is, jatrorrhizine is more vicinal to tryptophane (Trp) residue than to tyrosine (Tyr) residue and the damage site is also mainly at Trp residue. Molecular modeling result shows that jatrorrhizine–HSA complex formed not only on the basis of electrostatic forces, but also on the basis of π–π staking and hydrogen bond. The research results will offer a reference for the studies on the biological effects and action mechanism of small molecule with protein.Graphical abstractThe binding behavior of jatrorrhizine with HSA was studied by UV–vis, fluorescence and molecular modeling examinations. Jatrorrhizine has high binding affinity with HSA by effectively quenched the fluorescence of HSA molecules via static mechanism. The binding sites, the type of interaction and the energy transfer process were revealed. The thermodynamic parameters indicate that electrostatic force plays an important role in the binding. The energy transfer from HSA molecules to jatrorrhizine occurs with high probability. Furthermore, the molecular modeling was performed to explore the possible binding site and assess the microenvironment around the bound jatrorrhizine.Figure optionsDownload full-size imageDownload as PowerPoint slide

•A novel Lys-AuNCs fluorescence probe for cyanide anion detection was developed.•Lys-AuNCs could be served as a “naked-eye” optical probe for cyanide anion.•The probe was environmentally-friendly and synthesized conveniently.Lysozyme-stabilized gold nanoclusters (Lys-AuNCs) have been synthesized and utilized as a fluorescent probe for selective detection of cyanide (CN−). Lys-AuNCs had an average size of 4 nm and showed a red emission at 650 nm (λex = 370 nm). The fluorescence of Lys-AuNCs could be quenched by CN−. An excellent sensitivity and selectivity toward the detection of CN− in aqueous solution was observed. The fluorescence intensity was linear with the CN− concentration in the range of 5.00 × 10−6 M–1.20 × 10−4 M with a detection limit as low as 1.9 × 10−7 M. Also, the addition of CN− to Lys-AuNCs could induce an obvious color change from light yellow to colorless. Correspondingly, a bright red fluorescence disappeared and a blue fluorescence appeared. The results indicated that Lys-AuNCs could be applied in detection of cyanide on environmental aspects.Graphical abstract

•A simple HPLC method is applied to separate a very complex mixture of carbon nanodots.•The elution order follows with the sizes of carbon nanodots from the smallest to the largest.•Dialysis membrane is used to remove the reaction matrix from the carbon nanodots product.Amino/hydroxyl-functionalized fluorescent carbon nanodots (C-NanoD) are conveniently synthesized based on hydrothermal carbonization of chitosan at 180 °C. Dialysis membranes with small cut-off masses (500–1000 Da) were found useful for removing the side-products and low molecular mass species to purify the C-NanoD product. Herein, reversed-phase high-performance liquid chromatography (RP-HPLC) has been successfully applied to fractionate the C-NanoD product. The elution order of the C-NanoD species present in the sample follows approximately their core sizes from small to large. The separated C-NanoD fractions are collected and characterized by UV absorption spectroscopy, photoluminescence (PL) spectroscopy, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), and transmission electron microscopy (TEM). All the C-NanoD fractions display a distinctive absorption band at 300 nm, attributing to the n→π⁎ transition of CO bond. The PL spectra of the fractions display emission peaks at 400–415 nm which are slightly red-shifted with their increase in relative molecular masses. The C-NanoD fractions are fully anatomized by MALDI-TOF MS, displaying their fragmentation mass ion features. The core sizes of some selected C-NanoD are determined as 1.6, 1.8, 2.5, and 3.1 nm by TEM which are in consistent with their HPLC elution order. The findings highlight the virtues of RP-HPLC to fractionate and reveal the unique characteristics of individual C-NanoD species present in an as-synthesized C-NanoD product which may have potential applications in the fields of bioanalysis, bioimaging, catalysis, chemosensing, energy storage, and optoelectronics device.

A ratiometric fluorescent probe for Ca2+ based on 1,3,4-oxadiazole derivative has been designed and developed. The probe exhibits a large Stokes shift of 202 nm and a highly selective ratiometric emission response (490/582 nm) to Ca2+ over other metal cations. Additionally, the probe can readily reveal the changes of intracellular Ca2+ concentration in living human umbilical vein endothelial cells.

A novel indolo[3,2-b]carbazole derivative containing B(Mes)2 groups, 5,11-dibutyl-2,8-bis(dimesitylboryl) indolo[3,2-b]carbazole (DBDMBICZ), was synthesized and structurally characterized by elemental analysis, NMR, MS. The thermal, electrochemical and photophysical properties of DBDMBICZ were characterized by thermogravimetric analysis, electrochemical methods, UV–vis absorption spectroscopy and fluorescence spectroscopy. DBDMBICZ exhibited high fluorescence quantum yields (Φmax = 0.76) in solution and excellent thermal stability (Td = 290 °C, Tg = 170 °C) and electrochemical stability. The multi-layered OLEDs devices with the configuration of ITO/NPB/CBP/light-emitting layer/Bphen/LiF/Al are fabricated by using DBDMBICZ as light-emitting layer. The devices show the same pure blue emissions at different voltages and relative good electroluminescent performances. The results indicate that DBDMBICZ has potential applications as an excellent optoelectronic material in optical field.Graphical abstractHighlights► We synthesized a novel dimesitylboron-based indolo[3,2-b]carbazole derivative (DBDMBICZ). ► DBDMBICZ exhibited high fluorescence quantum yields in solution and excellent thermal stability. ► Efficient OLEDs fabricated with DBDMBICZ show pure blue emission and relative good electroluminescent performances.

•A novel asymmetric indolo[3,2-b]carbazole compound.•which incorporate a benzothiazole unit (electron-acceptor) and a dimesitylboron unit (electron-acceptor) to 2- and 8-position of indolo[3,2-b]carbazole (electron-donor) respectively.•was investigated as a highly selective ratiometric fluorescence sensor with remarkable colour changes for fluoride ion.A novel asymmetric acceptor–π-donor–π-acceptor compound, 2-benzothiazolyl-8-dimesitylboryl-5,11-dihexylindolo[3,2-b]carbazole (BDDICZ), has been successfully synthesized by introducing a benzothiazole (electron-acceptor) moiety and a dimesitylboron (electron-acceptor) group to 2-position and 8-position of indolo[3,2-b]carbazole (an electron-donor), respectively. The structure of BDDICZ was fully characterized by NMR, MS and elemental analysis and was studied by both experimental and theoretical methods. Our results demonstrate that BDDICZ is a sensitive ratiometric fluorescence probe which shows remarkable color change with fluoride ion (F−). The theoretical calculations confirm that BDDICZ can readily react with tetrabutylammonium fluoride (Bu4N+F−) to form an adduct of (Bu4N)+(BDDICZ·F)−. Moreover, BDDICZ possesses appropriate HOMO and LUMO energy states and a high fluorescence quantum yield, indicating its potential application as an ideal hole-transporting and/or light-emitting material in optoelectronic devices.

A novel fluorescent calcium indicator with a 490/582 nm ratiometric emission has been designed and synthesized. The indicator exhibits a highly selective ratiometric emission response to Ca2+ over other metal cations and a large Stokes shift of 202 nm. Moreover, its practical cell imaging capability for intracellular Ca2+ in the resting- and dynamic-state has been demonstrated in human umbilical vein endothelial cells using a confocal laser scanning microscope.A new ratiometric emission Ca2+ indicator was developed and its ability to detect changes of Ca2+ in live cells was demonstrated by confocal laser scanning microscope.

A novel carbazole derivative, N,N′-bis(9-ethyl-9H-carbazol-3-yl)-(ethane-1,2-diamine), has been synthesized by reacting 3-amino-9-ethylcarbazole with glyoxal and characterized by 1H NMR, infrared spectroscopy, elemental analysis and mass spectra. The strong fluorescence emission at 438 nm of the derivative is effectively and selectively quenched by Cr3+. A 1:1 complex is formed between the carbazole derivative and Cr3+ and their association constant is 1.4 × 104 L mol−1. The results indicate that the carbazole derivative can provide a rapid, selective and sensitive response to Cr3+ in a linear dynamic range 1.0–20 μmol L−1 with a limit of detection of 0.10 μmol L−1 at pH 7.4. Common interferent ions do not show any interference with the Cr3+ determination. It is anticipated that the carbazole derivative could be a good candidate probe and has potential application for Cr3+ determination.

A novel ratiometric fluorescence probe based on protein–silver nanoclusters (NCs) for mercuric ion (Hg2+) has been synthesized and characterized. A facile and simple one-step method for the synthesis of fluorescent Ag NCs, using bovine serum albumin (BSA) without preprocessing as a scaffold was developed. BSA assembled Ag NC (BSA-Ag NCs) were first found to exhibit ratiometric fluorescence with blue emission at 480 nm and red emission at 634 nm. Upon the addition of Hg2+, the emission of BSA-Ag NCs at 480 nm gradually increased and at 634 nm steadily decreased. The presence of Hg2+ induced a color change from light yellow to colorless and a bright red fluorescence to blue fluorescence. The determination of Hg2+ based on ratiometric fluorescence was developed. The linear dynamic range was from 5.0 × 10−8 M to 2.5 × 10−5 M with a detection limit of 4.87 × 10−8 M. The relative standard deviation (RSD) at 0.30 μM for Hg2+ of six replicates determination was 2.8%. The BSA-Ag NCs were conveniently and easily synthesized, so could serve as a “naked-eye” fluorescent probe for Hg2+. The probe may be a good candidate for the application of sensing Hg2+ in environmental analysis and fluorescence imaging.

A novel glucose biosensor based on the catalytic effect of platinum nanoparticles (PtNPs) on the enzymatic reaction for the glucose determination has been developed. PtNPs were in-situ synthesized on the surface of the eggshell membrane (ESM) upon which glucose oxidase (GOx) had been simultaneously immobilized accompanied by the synthesis of the PtNPs to produce a GOx-PtNPs/ESM. The glucose biosensor was fabricated by positioning the GOx-PtNPs/ESM on the surface of a dissolved oxygen sensor. The glucose concentration was quantified by the decrease of dissolved oxygen. The effect of the amount of K2PtCl4 (0.1 M), the volume of the GOx (1%, w/v), reaction time, pH, phosphate buffer concentration and temperature on the response of the glucose biosensor were studied in detail. This biosensor exhibited a response time of less than 30 s, a wide linear concentration range of 10–225 μM and a detection limit of 5 μM, good repeatability (RSD = 1.03%, n = 10), and satisfactory reproducibility (RSD = 0.54%, n = 5). The biosensor retained 90.0% of its initial response after 8 months at 25 °C. Common interferents such as D-fructose, citric acid, sucrose, L-ascorbic acid and so on did not any give significant interference. The proposed biosensor was successfully applied for the determination of glucose concentration in human blood serum with recoveries between 93.6% and 102.8%.

The combination of novel nanomaterials and biomolecule recognition units is promising in developing sensitive biosensors. This paper presents a facile approach for the preparation of water-soluble electroactive dye-Orange II functionalized graphene nanosheets (O-GNs). The successful attachment of Orange II on the surface of graphene nanosheets not only prevents the agglomeration of the as-formed graphene nanocomposite in aqueous media, but also endows graphene nanosheets with excellent electroactive property. Integrating the unique properties of the as-prepared O-GNs (high conductivity, high specific surface area and electroactive function) with high affinity and specificity of aptamer, a new label-free electrochemical biosensing concept is demonstrated for the “signal-on” detection of targets such as thrombin and lysozyme. The present O-GNs-based aptasensor exhibits good current response to the above proteins. The linear ranges for thrombin and lysozyme are 1.0×10−12–4.0×10−10 M and 5.0×10−12–7.0×10−10 M, with the detection limit of 3.5×10−13 M and 1.0×10−12 M, respectively. In contrast to the common laborious and expensive labeling approaches, the present O-GNs based aptasensing process is highly simple, cost-efficient and does not need labeling and modification of aptamers or introduce additional electrochemical probes.Highlights► Orange II functionalized graphene nanosheets (O-GNs) were synthesized. ► O-GNs act as both enhanced material and in-situ probe for the electrochemical detection. ► Label-free aptasensing platform for “signal-on” detection of protein was proposed. ► The process is highly simple and does not need the introduction of additional electrochemical probes.

We report a novel and environmentally friendly fluorescent probe for detecting copper ion (Cu2+) using glutathione (GS)-protected Au nanoclusters (GS-Au NCs). The fluorescence-based sensing behavior by GS-Au NCs toward metal ions was investigated in buffered aqueous media. Among the metal ions studied, Cu2+, Hg2+ and Pb2+ were found to efficiently quench the fluorescence emission of GS-Au NCs. In differentiation of Cu2+ and Hg2+ (or Pb2+), we found that (1) in the presence of Pb2+, the GS-Au NCs solution first appeared turbidity, but with ethylenediaminetetraacetate (EDTA) added to the solution, the fluorescence recovered and the turbidity disappeared; (2) in the presence of Hg2+, EDTA could not recover the quenched fluorescence of GS-Au CNs by Hg2+, which is in contrast with Pb2+ and Cu2+. The Cu2+ detection limit was determined to be approximately 86 nM based on the fluorescence quenching and linear fluorescence response in the Cu2+ concentration range 1.00 × 10−7 to 6.25 × 10−6 mol/L. The high sensitivity of 86 nM Cu2+ and selectivity to Cu2+ among 17 types of metal cations make GS-Au NCs a good candidate for fluorescent sensors for Cu2+.

A series of oxazole derivatives, 5-methyl-2-(p-methylphenyl)-4-acetyl oxazole (MMPAO), 5-methyl-2-(p-methoxyphenyl)-4-acetyl oxazole (MOPAO), 5-methyl-2-(p-N,N′-dimethylamino-phenyl)-4-acetyl oxazole (MDMAPAO) and 5-methyl-2-(p-N,N′-diphenylaminophenyl)-4-acetyl oxazole (MDPAPAO) have been synthesized and studied to compare their photophysical properties. The UV–visible absorption spectra of MDMAPAO and MDPAPAO are bathochromatically shifted as compared to that of MMPAO and MOPAO. The fluorescence emission of MDPAPAO is very sensitive to the polarity of solvents. The magnitude of change in the dipole moment was calculated using the Lippert–Mataga equation. MDPAPAO shows the highest change in the dipole moment (Δu = 13.3D) than that of the other three oxazole derivatives. The spectral properties including fluorescence quantum yield and lifetime were determined in solvents with different polarities. MDPAPAO displays the highest fluorescence quantum yield and lifetime, following a bi-exponential fluorescent decay fashion. Our result demonstrates that the excited state of MDPAPAO possesses the property of intramolecular charge transfer.Graphical abstractHighlights► Four compounds with oxazole and benzene rings have been synthesized. ► The ICT was observed with the enhancing of the electron-donor ability. ► 5-Methyl-2-(p-N,N-diphenylamino phenyl)-4-acetyl oxazole shows obvious ICT.

The designed synthesis of graphene-based nanocomposites for enhancing their different potential application is of great interest recently. In this paper, we demonstrated a new class of high-quality graphene-based nanocomposites: metal coordination polymer–graphene nanosheets (MCPGNs). The as-obtained nanocomposite, combining the unique properties of graphene (excellent conductivity and high specific surface area) and MCPs (tunable pore size, large internal surface areas and versatility of functionality), can act as an efficient matrix to immobilize glucose oxidase (GOD). Furthermore, the as-prepared MCPGNs exhibit better conductivity and electrocatalytic activity for H2O2 reduction than graphene. Based on these excellent properties, a sensitive electrochemical biosensing platform for glucose was fabricated. This novel biosensor displays a linear response range between 50 nM and 1 mM with a detection limit of 5 nM. Our work not only provides a facile, effective and general route for the synthesis of a variety of MCP–graphene nanohybrids, but also sets an example for fabricating an electrochemical biosensor with this new kind of nanohybrid as an enhanced material and can be easily extended to other biosensors. These interesting results suggested the great potential of MCP–graphene nanocomposites in the field of electroanalytical chemistry.

The preparation of neutral red covalently-functionalized graphene nanosheets (NR-FGN) is presented via replacement of the carboxyl acid groups at the edges of graphene nanosheets using NR. The obtained NR-FGN was characterized by UV-vis, Fourier transform infrared (FT-IR), Raman spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM). It was found that the introduction of NR at the edges of graphene nanosheets (GN) improved the solubility and stability of the graphene. The electrochemical impedance result further confirmed that NR-FGN could effectively accelerate the electron transfer. Due to the synergic effect between GN and NR, the nanocomposite exhibited excellent electrocatalytic activity toward the oxidation of uric acid.

A facile strategy for the preparation of meso-terakis(4-methoxyl-3-sulfonatophenyl) porphyrin (T(4-Mop)PS4)-graphene hybrid nanosheets (TGHNs) was demonstrated for the first time, which combines the features of both graphene (high conductivity and large specific surface area) and porphyrins (photochemical electron-transfer ability and excellent electrochemical activity). The as-obtained TGHNs were characterized by UV-vis spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, atomic force microscopy, transmission electron microscopy and cyclic voltammetry, which confirmed that the porphyrin had been effectively functionalized on the surface of graphene. Combined with the high affinity and specificity of an aptamer, a simple, rapid, sensitive and label-free electrochemical aptasensor was successfully fabricated for adenosine triphosphate (ATP) detection. The proposed TGHN-based aptasensor achieved the direct electron transfer of porphyrin and showed good affinity and specificity towards ATP, which avoided interference such as the introduction of labeled-substances and the [Fe(CN)6]3−/4− probe. The preferable linear range for ATP was from 2.2 nM to 1.3 μM (R = 0.9982) with a detection limit of 0.7 nM.

A novel nanocomposite of palladium nanoparticles-modified fullerene (Pd NPs-C60) was fabricated by an electrodeposition technique on a glassy carbon (GC) electrode and its electrochemical properties were studied. It was found that Pd NPs incorporating with C60 can enhance its sensitivity and selectivity to CH4 at ambient conditions. The Pd NPs-C60 modified GC electrode shows better electron-transfer behavior than that of bare GC, pristine C60 modified GC, and Pd NPs modified GC electrodes. The Pd NPs-C60 modified GC electrode displays stable and reproducible response to CH4 and could be used repeatedly. Our results demonstrate that the Pd NPs-C60 nanocomposite should be a promising and useful nanomaterial for developing sensitive electrochemical sensors.

An ethanol biosensor was fabricated based on a Methylobacterium organophilium-immobilized eggshell membrane and an oxygen (O2) electrode. A linear response for ethanol was obtained in the range of 0.050–7.5 mmol/L with a detection limit of 0.025 mmol/L (S/N = 3) and a R.S.D. of 2.1%. The response time was less than 100 s at room temperature and ambient pressure. The optimal loading of bacterial cells on the biosensor membrane is 40 mg (wet weight). The optimal working conditions for the microbial biosensor are pH 7.0 phosphate buffer (50 mmol/L) at 20–25 °C. The interference test, operational and storage stability of the biosensor are studied in detail. Finally, the biosensor is applied to determine the ethanol contents in various alcohol samples and the results are comparable to that obtained by gas chromatographic method and the results are satisfactory. Our proposed biosensor provides a convenient, simple and reliable method to determine ethanol content in alcoholic drinks.

The formation of the inclusion complex of p-sulfonatocalix[6]arene (SCX6) with different forms of vitamin B6 (VB6) was studied by using fluorescence spectroscopy. VB6 can exist in one of three forms (the acidic form, neutral zwitterionic form and basic form) depending on pH. The fluorescence intensities of acidic and basic forms of VB6 remarkably decreased in presence of SCX6. SCX6 preferred to form 1:1 inclusion complexes with acidic and basic forms of VB6 but hardly form inclusion complex with neutral zwitterionic form. According to the nonlinear curve fitting method, the inclusion constant (K) for the formation of inclusion complexes of acidic and basic forms of VB6 with SCX6 were evaluated to be 1.4 × 104 and 9 × 103 L/mol, respectively. The binding affinity of SCX6 towards acidic form is attributed to hydrogen bonds and hydrophobic interaction, furthermore, additional electrostatic interaction also plays a crucial role. The possible inclusion mode was given by 1H NMR technique.

A novel A-π-D-π-D-π-A type compound, containing two benzothiazole rings as electron acceptors and two N-ethylcarbazole groups as electron donors, (E)-1,2-bis(3-(benzothiazol-2-yl)-9-ethylcarbazol-6-yl)ethene (BBECE), was synthesized and characterized by elemental analysis, NMR, MS and thermogravimetric analysis. Electrochemical property of compound BBECE was studied by cyclic voltammetry analysis. The absorption and emission spectra of BBECE was experimentally determined in several solvents and simultaneously computed using density functional theory (DFT) and time-dependent density functional theory (TDDFT). The calculated absorption and emission wavelengths are coincident with the measured data. The lowest-lying absorption spectra can be mainly attributed to intramolecular charge transfer (ICT), and the fluorescence spectra can be mainly described as originating from an excited state with intramolecular charge transfer (ICT) character. The molecular orbitals (HOMO and LUMO), the ionization potential (IP), the electron affinity (EA) and reorganization energy of compound BBECE were also investigated using density functional theory (DFT). The results show that compound BBECE exhibited excellent thermal stability and electrochemical stability as well as high fluorescence quantum yield, indicating its potential applications as an excellent optoelectronic material in optical fields.Graphical abstractHighlights► Compound contains two benzothiazole rings as electron acceptors and two N-ethylcarbazole groups as electron donors. ► Compound exhibits excellent thermal stability and electrochemical stability as well as high fluorescence quantum yields. ► Compound might be used as excellent optoelectronics materials in optical field.

The binding mode and mechanism of the interactions between two planar cationic alkaloids chelerythrine (Che) and sanguinarine (San) with calf thymus DNA (ctDNA) were systematically investigated at pH 5.40 using UV–vis absorption spectroscopy, fluorescence spectroscopy and cyclic voltammetry. Che and San show strong fluorescence at 570 and 589 nm, respectively. Che displays fluorescence enhancement with ctDNA whereas the fluorescence of San is quenched on interaction with ctDNA. In addition, UV–vis spectra of both alkaloids show apparent hypochromicity and are bathochromic shifted, indicating that they could intercalate into ctDNA bases. The fluorescence polarization of Che and San increases in the presence of ctDNA, again implying the intercalation of two alkaloids with ctDNA. This conclusion was also supported by the results obtained from anion quenching and cyclic voltammetry. The binding constants of both alkaloids with ctDNA were calculated in the order of 105 L/mol. San binds with ctDNA 3-fold stronger than Che. The stoichiometric bindings are five nucleotides per Che or San. Electrostatic binding also exists between the alkaloids and DNA helix. Finally, theoretical calculations show that only certain parts of Che and San molecules intercalate into the DNA helix.Graphical abstractThis paper attests that Che and San form stable complexes with ctDNA, and represents the first attempt to utilize CV and molecular calculation methods. UV, fluorescence titration, and CV measurements all show that Che and San interact with DNA mainly via intercalation. Electrostatic binding also exists. The affinity of Che for DNA is slightly weaker than that of San. The stiochiometry of the binding was determined to be five nucleotides per San and Che. Che and San intercalate to DNA with C, D ring and A, B ring part, respectively.Highlights► This paper attests that Che and San exhibit significant bindings to calf thymus DNA. ► Experimental data show that Che and San interact with DNA mainly via intercalation. ► Electrostatic binding also exists. ► Studies support that San has higher binding affinity towards DNA as compared to Che. ► Molecular calculation shows that Che and San intercalate to DNA with different part.

The inclusion interaction between propranolol (PPL) and p-sulfonatocalix[6]arene (SCX6) was investigated by fluorescence and 1H NMR spectroscopy. Influences of pH, temperature, ionic strength and the concentration of SCX6 were examined in detail. In phosphate buffer solution with pH 7.5, the fluorescence of PPL dramatically quenched upon addition of SCX6 revealing the formation of inclusion complexes between PPL and SCX6. The stoichiometric ratio was verified to be 1:1 by the continuous variation method. The inclusion constant of PPL-SCX6 complexes was calculated as 2.2 × 104 L/mol by the nonlinear curve fitting method. 1H NMR titration spectra testified that the aliphatic chain of PPL may be partially penetrated into the hydrophobic cavity of SCX6. This was confirmed by molecular dynamics calculations.Graphical abstractThe inclusion interaction of propranolol with p-sulfonatocalix[6]arene is verified using fluorescence and 1H NMR spectroscopy. Upon addition of p-  sulfonatocalix[6]arene, significant chemical shift variations of methyl proton, Hb′,Hb of propranolol are observed, suggesting that the aliphatic chain of propranolol is penetrated into the hydrophobic cavity of p-sulfonatocalix[6]arene to form host–guest complex with a tilt-in conformation. Highlights► We study the inclusion interaction of p-sulfonated calix[6]arene with propranolol. ► The inclusion constant is obtained by the nonlinear curve fitting method. ► Effects of pH, temperature, the ionic strength and concentration of the host are investigated. ► 1H NMR testified that aliphatic chain of PPL partially enters into the cavity of SCX6. ► The result obtained by molecular dynamics calculations is in agreement with 1H NMR.

Upon addition of a small amount of bromocyclohexane, propranolol displays room temperature phosphorescence in γ-cyclodextrin solution without deoxygenation. Several factors including the pH, and the concentration of γ-cyclodextrin and bromocyclohexane, which affect the room temperature phosphorescence (RTP) intensity and room temperature phosphorescence lifetime of propranolol are studied in detail. Under optimal conditions, the room temperature phosphorescence lifetimes of propranolol enantiomers are measured. The experimental results show that the associated phosphorescence decay curves can be best fitted to mono-exponential patterns and room temperature phosphorescence lifetimes of R- and S-propranolol are 4.60 ms and 5.74 ms, respectively. The difference of the room temperature phosphorescence lifetimes of R- and S-propranolol is 22.05%. Based on that, chiral discrimination of propranolol enantiomers is carried out successfully by time-resolved phosphorescence.

In this paper, 4-dimethylamino 2,5-dihydroxy chalcone (DMADHC), which exhibits excited state intramolecular charge transfer (ICT) characteristics, was synthesized and characterized. A sensitive optochemical sensor for Fe3+ ion was developed using DMADHC as fluorescence receptor. The fluorescence of DMADHC was gradually quenched with the addition of Fe3+ ion, which attributed to the formation of 1:1 complex between DMADHC and Fe3+ ion. The sensor exhibited excellent selectivity for Fe3+ ion over a large number of cation ions such as alkali, alkaline earth and transitional metal ions with a linear range of 3.984×10−7–1.135×10−5 and a limit of detection of 8.223×10−8 mol/L. On this basis, the sensor was preliminary applied to the determination of the content of iron ions in multi-vitamin tablet with satisfied results and the recoveries were in the 95–100% interval, and precision (n=5) was better than 5%.Highlights► A fluorescence receptor, 4-dimethylamino 2,5-dihydroxy chalcone was synthesis by one-step reaction. ► Its intramolecular charge transfer fluorescence characteristics could be blocked by Fe3+ ion. ► Based on this, an optochemical sensor for Fe3+ ion was developed. ► Importantly, our proposed method is particularly useful for determination of Fe3+ ion in real sample.

Naproxen enantiomers possess strong room temperature phosphorescence (RTP) in β-cyclodextrin (β-CD) system with a small amount of 1,2-dibromoethane (1,2-DBE) under ambient conditions. The effects of pH, concentration of β-CD, and 1,2-DBE on the RTP of naproxen enantiomers have been investigated in detail. Time-resolved RTP spectroscopy shows that both naproxen enantiomers exhibit biexponential decay pattern with lifetimes of τ1 = 4.79 ± 0.13 and τ2 = 1.51 ± 0.096 ms for R-naproxen and τ1 = 6.67 ± 0.15 and τ2 = 2.13 ± 0.061 ms for S-naproxen. The lifetime differences between these enantiomers are Δτ1 = 1.88 and Δτ2 = 0.62 ms, indicating that chiral discrimination of naproxen enantiomers can be achieved in β-CD/1,2-DBE system. Naproxen enantiomers can form stable complexes with β-CD and 1,2-DBE in stoichiometric ratios of 1:1:2 and 1:1:1 (naproxen:β-CD:1,2-DBE), and the association constants are 3.20 × 103 M−4 and 2.43 × 103 M−3 for the S- and R-enantiomers, respectively. The chiral discrimination of R-naproxen and S-naproxen is realized via their difference in interaction with the chiral cavity of β-CD due to their difference in stereochemical structure. Finally, molecular modeling is performed to determine the chiral recognition on a molecular level, and the results are in good agreement with the experimental data.

Cadmium (Cd) is an environmental pollutant and has been found to pose a potential threat to human health. Isoquercitrin (IQ) is one of the most important flavonoids and has been demonstrated to exhibit potent antioxidant effects on plants and yeast cells. However, only few studies have investigated the antioxidative activities of reactive oxygen species (ROS) and the nitrite scavenging activities of IQ against Cd-induced oxidation in mouse. The present work was to investigate the ROS and nitrite-scavenging activities of IQ in vitro as well as its preventive effects against lipid peroxidation and protein oxidative damage in liver and kidney of mouse induced by Cd2+ using spectrophotometry. Our results showed that IQ possesses scavenging abilities for superoxide anion, hydroxyl radical and nitrite. Such scavenging capacities increase with the concentration of IQ. Moreover, cadmium chloride (CdCl2) (2.5 mg/kg body weight, i.p. CdCl2) significantly inhibited the activities of superoxide dismutase and catalase and raised the levels of malondialdehyde, nitric oxide, protein carbonyl, and the coefficients of DNA-protein crosslinks in livers and/or kidneys of mice. IQ attenuated the Cd2+-induced biochemical alterations in the livers and/or kidneys of mice, indicating that the formation of ROS and nitrite is possibly reduced. Our work demonstrates that IQ possesses ROS and nitrite-scavenging capacities and plays a significant role in combating Cd2+-induced toxicity in animals.

An amperometric glucose biosensor based on an n-alkylamine-stabilized palladium nanoparticles (PdNPs)-glucose oxidase (GOx) modified glassy carbon (GC) electrode has been successfully fabricated. PdNPs were initially synthesized by a biphase mixture of water and toluene method using n-alkylamines (dodecylamine, C12-NH2 and octadecylamine, C18-NH2) as stabilizing ligands. The performance of the PdNPs-GOx/GC biosensor was studied by cyclic voltammetry. The optimum working potential for amperometric measurement of glucose in pH 7.0 phosphate buffer solution is −0.02 V (vs. Ag/AgCl). The analytical performance of the biosensor prepared from C18-PdNPs-GOx is better than that of C12-PdNPs-GOx. The C18-PdNPs-GOx/GC biosensor exhibits a fast response time of ca. 3 s, a detection limit of 3.0 μM (S/N = 3) and a linear range of 3.0 μM–8.0 mM. The linear dependence of current density with glucose concentration is 70.8 μA cm−2 mM−1. The biosensor shows good stability, repeatability and reproducibility. It has been successfully applied to determine the glucose content in human blood serum samples.

The interaction mechanism between human serum albumin (HSA) and 1-phenyl-3(fluorenone-2-yl)-5-(9-ethylcarbazole-3-yl)-2-pyrazoline (PFEP) was investigated by fluorescence and absorption titration techniques in combination with molecular modeling method. Stern–Volmer plots at different temperatures proved that PFEP could quench the intrinsic fluorescence of HSA attributed to a static quenching procedure. The association constants were calculated in the range of 1 × 105–8 × 105 mol−1 at different pH conditions, and the stoichiometric ratio of binding was 1:1 between PEEP and HSA. Molecular modeling study showed that the distance between indole moiety of the Trp214 residue and the carbazole group at the terminal of PFEP was 4.45 Å in the optimal model.

The determination method of catechol by fluorescence quenching was developed. The assay was based on the combination of the unique property of gold nanoparticles with tyrosinase enzymatic reaction. In the presence of tyrosinase, the fluorescence of gold nanoparticles was quenched by catechol which can be employed to detect catechol. Under the optimal conditions, a linear range 5.0 × 10−7–1.0 × 10−3 mol L−1 and a detection limit 1.0 × 10−7 mol L−1 of catechol were obtained. o-Quinone intermediate produced from the enzymatic catalyzed oxidation of catechol was considered to play the main role in the fluorescence quenching.

A novel carbazole-based compound 5, 3,6-bis[(N-ethylcarbazole-3-yl)-propene-1-keto]-N-ethylcarbazole has been designed, synthesized and characterized. The absorption and fluorescence spectra in solvents of different polarities prove that the compound has a distinct intramolecular charge transfer character. Compound 5 can be used as a new class of fluorescent probe or biosensor due to its sensitivity to the local microenvironment such as solvent polarity.

A rapid and simple near-infrared (NIR) luminescence quenching method for the detection of phenolic compounds based on combining the unique property of N-acetyl-l-cysteine-protected gold nanoparticles (NAC-AuNPs) and tyrosinase (Tyr) enzymatic reactions is described. This method relies on the luminescence quenching of NAC-AuNPs–tyrosinase (NAC-AuNPs–Tyr) hybrid material by phenolic compounds. The quinone intermediates produced from enzymatic catalytic oxidation of phenolic compounds were believed to play a major role in the luminescence quenching. Dynamic quenching mechanism was confirmed by using time-resolved luminescence spectroscopy. Optimization of the experimental parameters including the concentration of NAC-AuNPs–Tyr (20 μg/mL), excitation wavelength (450 nm), pH (6.0), and temperature (20 °C) has been determined. A linear range 0.5 μM to 1.0 mM and a detection limit 0.1 μM of catechol were obtained under optimal conditions. The sensitivity of different phenolic compounds was compared and follows the trend: catechol > p-cresol > phenol. The proposed NIR luminescence quenching method exhibits high sensitivity, good repeatability, and long-term stability, demonstrating potential for further development to NIR luminescence phenol biosensors.

A novel mode-filtered light fiber optic pH sensor was developed by inserting an optical fiber immobilized with a pH-sensitive indicator into a fused-silica capillary. In the experiment, two different indicators, bromocresol green and cresol red, had been used for pH sensing. The sensor immobilized with indicator bromocresol green or cresol red showed the response to pH in the range of 2.0–8.0 and 9.0–13.0, respectively. The sensors showed good reproducibility and reversibility within the dynamic pH range and the response times (t95%) were within 120 s. The interference of some common cations to the sensors was investigated and K+ and Pb2+ were the potential interferents to the sensor immobilized with bromocresol green.

The interactions of brilliant cresyl violet (BCV) with herring sperm DNA in γ-cyclodextrin (γ-CD) supramolecular system were studied by UV-vis absorption spectroscopy and cyclic voltammetry (CV). Both UV-vis absorption and CV data show that the interaction of BCV with DNA depends on the concentration ratio of BCV to DNA (R), the initial concentration of BCV and γ-CD. The binding constants of BCV monomer, (BCV)2 dimer and (BCV)2-γ-CD inclusion complex with DNA are 1.64 × 105, 2.56 × 104 and 2.32 × 103 M−1, respectively. It was observed that γ-CD can affect the interactive mode of BCV with DNA. If R is larger than 0.5, the (BCV)2-γ-CD inclusion complex will retain intact and bind to DNA via the electrostatic attraction forces. By contrast, when R is smaller than 0.5, the inclusion complex will be partially dissociated and the free BCV monomer is intercalated into the double-helix structure of DNA attributing to the more favorable microenvironment of DNA for the BCV monomer. Our work postulates the importance of the initial concentration of dye and host molecule on the interaction of dye with DNA in living bodies.

Palladium nanoparticles (PdNPs) have been synthesized using n-alkylamines (Cn−NH2) as stabilizing ligands. The NP size and distribution were controlled by varying the initial mole ratio of PdCl2/Cn−NH2 and carbon chain lengths of Cn−NH2 including hexylamine (C6−NH2), dodecylamine (C12−NH2), and octadecylamine (C18−NH2). The average PdNP sizes were 20 ± 2.0, 6.0 ± 0.8, 5.6 ± 0.8, 6.5 ± 0.9, and 5.2 ± 0.8 nm prepared with 1:7 PdCl2/C6−NH2, 1:7 PdCl2/C12−NH2, 1:7 PdCl2/C18−NH2, 1:5 PdCl2/C18−NH2, and 1:9 PdCl2/C18−NH2, respectively. The particle size decreased with the increase in the carbon chain length of Cn−NH2. The as-synthesized n-alkylamine stabilized PdNPs (Cn−NH2−PdNPs) were fully characterized by transmission electron microscopy, X-ray powder diffraction, UV−visible absorption spectroscopy, infrared (IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), proton nuclear magnetic resonance (1H NMR) spectroscopy, thermogravimetric analysis, graphite furnace atomic absorption spectrometry, and mass spectrometry. The interaction of C18−NH2 with PdNPs was verified by IR, XPS, and 1H NMR spectra, demonstrating that the amine functionalities were successfully linked to the Pd core surfaces. The PdNPs are soluble and stable in apolar solvents such as benzene, chloroform, n-hexane, and toluene. The electrochemical reactions between CH4 and Cn−NH2−PdNPs on Pd electrodes were studied by cyclic voltammetry and chronoamperometry. These PdNPs reacted readily and produced good response to CH4 at ambient conditions. The sensitivity to CH4 depends on the PdNPs prepared from various n-alkyl chain lengths of Cn−NH2 and also the mole ratio of PdCl2/Cn−NH2. It was determined that PdNPs synthesized from 1:7 PdCl2/C18−NH2 displayed the best electrocatalytic oxidization of CH4. The C18−NH2−PdNP (5.6 nm) modified Pd electrode could be used repeatedly and had a stable and reproducible response to CH4.

Cryptophane-E was synthesized from vanillin by a three-step method, and its absorption and fluorescence spectroscopic properties were determined. Two absorption bands at about 245–260 and 280–290 nm were observed for cryptophane-E and the fluorescence emission maxima were at 320–330 nm depending on the solvent used. The interaction of cryptophane-E with CHCl3 was studied in detail by absorption and fluorescence spectroscopies. The results showed that cryptophane-E and CHCl3 can easily form a stable 1:1 host–guest inclusion complex. Their binding constant (K) was determined by Benesi–Hildebrand equation and the nonlinear least squares fit method. The binding constant is largest in ethyl acetate, followed by dioxane and with acetonitrile as the smallest. In addition, the effect of guest volume on the host–guest inclusion complex was investigated. Guest molecules including CH2Cl2 and CCl4 were unable to form inclusion complex with cryptophane-E because of sizes mismatching with the host cavity.

A group of novel cage-like compounds cryptophanes A and E were synthesized from vanillin by a three-step method. The intermolecular interaction between cryptophanes (A and E) and fullerene (C60) was investigated in detail by absorption, fluorescence and 1H NMR spectroscopy. The absorption of C60 at 410–650 nm decreased in the presence of cryptophanes A or E. The decrease in absorption intensity was proportional to the concentration of cryptophanes A or E. On the other hand, the fluorescence intensity of cryptophanes A or E decreased and the emission maxima were blue-shifted with the increase in C60 concentration. These results suggest that contact charge transfer (CCT) complexes can be formed from C60 with cryptophanes A or E. In addition, the electrochemical behavior of cryptophanes (A and E) and C60 was studied by cyclic voltammetry. The redox currents of cryptophanes (A and E) decreased and the peak potentials were shifted on addition of C60. The changes in the chemical shifts (Δδ) of aromatic protons of cryptophanes (A and E) in their NMR spectra further support that CCT complexes were formed with cryptophanes as the electron donors and C60 as the electron acceptor.

The inclusion complexes of isoquercitrin (IQ) with cyclodextrins (CDs) including β-cyclodextrin (β-CD), hydroxypropyl-β-cyclodextrin (HP-β-CD) and dimethyl-β-cyclodextrin (DM-β-CD) have been investigated using the methods of steady-state fluorescence, UV–vis absorption and induced circular dichroism. The stoichiometric ratio of the three complexes was found to be 1:1 and the stability constants (K) were estimated from spectrofluorometric titrations, as well as the thermodynamic parameters. Maximum inclusion ability was measured in the case of DM-β-CD due to the increased hydrophobicity of the host cavity, followed by HP-β-CD and β-CD. The effect of pH on the complexation process was also quantitatively assessed. IQ exists in different molecular forms depending on pH and β-CDs were most suitable for inclusion of the neutral form of IQ. The phase-solubility diagrams obtained with β-CD, HP-β-CD and DM-β-CD were all classical AL type. And DM-β-CD provided the best solubility enhancement, 12.3-fold increase compared to 2.8- and 7.5-fold increase for β-CD and HP-β-CD. The apparent stability constants obtained from the solubility data at 25 °C were comparable with those obtained from the fluorescence assays. Moreover, 1H NMR was carried out, which revealed that the IQ favorably inserted into the inner cavity from the chromone part instead of the phenyl part, which was in agreement with molecular modeling studies.

The interaction of methyl blue (MB) with human serum albumin (HSA) was studied by fluorescence and absorption spectroscopy. The intrinsic fluorescence of HSA was quenched by MB, which was rationalized in terms of the static quenching mechanism. The number of binding sites and the apparent binding constants at different temperatures were obtained from the Stern–Volmer analysis of the fluorescence quenching data. The thermodynamic parameters determined by the van’t Hoff analysis of the binding constants (ΔH°=39.8 kJ mol−1 and ΔS°=239 J mol−1 K−1) clearly indicate that binding is absolutely entropy-driven and enthalpically disfavored The efficiency of energy transfer and the distance between the donor (HSA) and the acceptor (MB) were calculated as 60% and 2.06 nm from the Förster theory of non-radiation energy transfer.

Methane gas sensor was fabricated based on electrocatalytic properties of the Pd/MWNT nanocomposites on indium tin oxide (ITO) glass substrates. A linear response for methane was obtained in the range of 0–16% (v/v) with a detection limit of 0.167% (v/v) and R.S.D. of 4.1%. After 100 times sensing or stable stored more than 12 months in atmosphere, unconspicuous measurable decrease was observed. The response time was less than 60 s at room temperature and ambient pressure. Some common potential interferents in samples such as N2, CO, CO2, ethane, propane, pentane, methanol, ethanol, H2 and NH3 were investigated and all the effects were less than 5% on the response for 3.0% (v/v) methane. The sensor was applied to methane determinations in man-made gas samples, the results are satisfied.

The mode and mechanism of the interaction of morphine chloride, an important alkaloid compound to calf thymus deoxyribonucleic acid (ct DNA) was investigated from absorption and fluorescence titration techniques. Hypochromic effect was founded in the absorption spectra of morphine when concentration of DNA increased. The decreased fluorescence study revealed non-cooperative binding of the morphine to DNA with an affinity of 3.94 × 103 M−1, and the stoichiometry of binding was characterized to be about one morphine molecule per nucleotide. Stern–Volmer plots at different temperatures proved that the quenching mechanism was static. Ferrocyanide quenching study showed that the magnitude of KSV of the bound morphine was lower than that of the free one. In addition, it was found that ionic strength could affect the binding of morphine and DNA. Fluorescence polarization and denatured DNA studies also applied strong evidences that morphine molecule was partially intercalated between every alternate base pairs of ct DNA. As observed from above experiments, intercalation was well supported as the binding mode of morphine and ct DNA.

A methanol-utilizing strain (ME25) using methanol (MeOH) as the sole carbon source has been isolated from methane-generating pits. ME25 was identified as Methylobacterium organophilium by its physiological characteristics and 16SrDNA sequence. A MeOH biosensor was then developed by immobilizing ME25 along with sensor for dissolved oxygen (O2). Its response is based on the depletion of O2 following oxidation of MeOH by the bacteria. The decrease in O2 is linearly related to the MeOH concentration in the range from 1.6 mg·L−1 to 4800 mg·L−1 and the detection limit for MeOH is 0.27 mg·L−1. The response time of the biosensor is around 20 min.

The spectroscopic characterizations of solid substrate room temperature phosphorescence (SS-RTP) of palmatine (Pal) have been studied. Strong RTP signal at 615 nm can be induced on filter paper in the presence of TIAc. The interaction between calf thymus DNA (ctDNA) and Pal has been investigated at pH 6.90 using fluorescence, UV–vis, SS-RTP and cyclic voltammogram spectroscopy. Strong binding affinity of Pal with DNA is revealed from the absorption and fluorescence studies in the liquid state. With the addition of ctDNA, the fluorescence intensity of Pal is enhanced greatly and UV–vis spectra show no apparent hypochromicity and red shift, which indicates that Pal intercalates into ctDNA bases. However, this conclusion could not explain the phenomena from fluorescence polarization and denatured DNA measurements, which indicate that groove binding is at least the main binding mode. Binding constant and binding site size have been calculated to be 2.57 × 104 L/mol and 0.16 based on Scatchard plot from fluorescence titration data. Groove binding has also been supported by phosphorescence lifetime and anion quenching experiments. Above studies demonstrate that there should exist intercalative binding and groove binding in the interaction of Pal and DNA. Furthermore, cyclic voltammogram study suggests that electrostatic binding exists at the same time exactly. Taken together, the binding model obtained in this study is mixed-mode.

A novel chemical modified nickel (Ni) electrode based on multi-walled carbon nanotubes (MWCNTs), Nafion film and nickel hydroxide has been successfully fabricated for methane (CH4) detection at ambient conditions. The morphology of the MWCNTs–Nafion/Ni(OH)2 film was characterized by transmission electron microscopy and the electrochemical properties of the Ni modified electrode were studied by cyclic voltammetry. The MWCNTs–Nafion/Ni(OH)2–Ni electrode showed good catalytic effect on the oxidation of CH4 in 1.0 M NaOH. In addition, the modified electrode was free from nitrogen and oxygen interferences. When differential pulse voltammetry was applied to the MWCNTs–Nafion/Ni(OH)2–Ni electrode, a good linear relationship between the oxidation peak current (i) and CH4 concentration (Cmethane) was obtained: i = 1.841Cmethane + 46.25, where i is in μA and Cmethane is in 0.0–16.0% (v/v). The relative standard deviation for detection of 3.0% (v/v) CH4 was 1.80% (n = 5). The proposed Ni modified electrode is anticipated to provide a promising technique to detect CH4 at ambient conditions.

Palladium nanoparticles (PdNPs) were electrolessly deposited on 1,6-hexanediamine grafted multi-walled carbon nanotubes (MWCNTs) to form nanocomposite which was then characterized by scanning electron microscopy, proton nuclear magnetic resonance spectroscopy, and infrared spectroscopy. First, the electrocatalytic activity of MWCNT/PdNPs for methane (CH4) on a gold electrode in 0.50 M H2SO4 was studied by cyclic voltammetry and the results demonstrated that MWCNT/PdNPs could be employed to oxidize CH4. A simple CH4 sensor was then fabricated by depositing the MWCNT/PdNPs nanocomposite onto an indium tin oxide substrate. The effects of carrier gas, amount of nanocomposite and temperature on the response of the sensor were investigated in detail. The sensor exhibits good sensitivity and selectivity to CH4 in dry air at ambient conditions. It showed linear response to CH4 at 0–16% v/v with a detection limit of 0.167% v/v (signal/noise = 3). The response and recovery times were less than 35 and 12 s, respectively. Common gases such as N2, CO and CO2 showed no interference but H2 and NH3 displayed slight interference to the sensor.

A novel pyrazoline derivative, named 1-phenyl-3-biphenyl-5-(N-ethylcarbazole-3-yl)-2-pyrazoline, was synthesized, and its structure was confirmed by means of IR, 1H NMR, and elementary analysis. The compound emits strong yellow fluorescence. Decrease of fluorescence intensity of the pyrazoline derivative in the presence of calf thymus DNA (ct DNA) is observed, and the quenching obey Stern–Volmer equation. There is a single quenching mechanism for the complex, which belongs to static quenching. KI quenching study shows that the magnitude of KSV of the bound pyrazoline is lower than that of the free one. It is also found that ionic strength could affect the interaction. Binding constants for pyrazoline with ct DNA and salmon sperm DNA (ss DNA) are in the same order of 104 mol L−1, and binding site size are about 1 per base pairs. Experimental results indicate that the new compound might insert into DNA base pairs by intercalative binding mode.

The luminescence behaviors of Cu(II) meso-tetrakis (4-N-methyl-pyridiniumyl) porphyrin (Cu(II)TMPyP) and Co(II) meso-tetrakis (4-N-methyl-pyridiniumyl) porphyrin (Co(II)TMPyP) are investigated, and their interactions with calf thymus DNA (ctDNA) are studied by UV–vis, fluorescence and resonance light scattering (RLS) and based on the changes of UV–vis spectra, fluorescence and RLS spectra, the intrinsic binding constants of Cu(II)TMPyP/Co(II)TMPyP with ctDNA are obtained in the case of phosphate buffer solution (pH 7.2), respectively. According to the experimental results, it can be inferred that the interaction model of Cu(II)TMPyP with ctDNA is intercalative binding, while Co(II)TMPyP is the long-range assembly on the molecular surface of ctDNA.

Cryptophane-A was synthesized from vanillin by a three-step method and its spectroscopic properties in different organic solvents were determined. Two absorption bands at about 240–250 and 280–290 nm were observed for cryptophane-A. A fluorescence emission peak was obtained at 320–330 nm using a solution of ∼10−5 M cryptophane-A. The interaction of cryptophane-A with chlorinated compounds CHnCl4 − n (n = 0, 1, 2) in dioxane and ethyl acetate solvents were studied in detail by fluorescence spectroscopy, respectively. The results show that cryptophane-A is well suited for inclusion of CH2Cl2 to form a stable 1:1 complex and the binding constant was estimated to be 19 ± 2 M−1. These results were also confirmed by 1H NMR and CPK models. Larger similar molecules such as CHCl3 and CCl4 are unable to enter the cavity of cryptophane-A because of their bigger sizes. However, the fluorescence emission of cryptophane-A can be efficiently quenched by CHCl3 and CCl4, following the Stern–Volmer relationship.

The spectral characteristics of four fluorescent dyes: tetrabromofluorescein (TBF), tetrachlorotetrabromofluorescein (TTF), lissamine rhodamine RB 200 (LSR) and methylene violet (MV) were studied by fluorescence and paper substrate room temperature phosphorescence (PS-RTP) methods. The factors affected the luminescence were investigated including pH value, paper substrate and drying conditions, etc. The fluorescence polarizations and PS-RTP lifetimes of these compounds were obtained. The intensity of fluorescence and phosphorescence of TBF and TTF increased in the presence of DNA. Contrarily, that of LSR and MV decreased. The fluorescence quenching and polarization studies indicate that TTF, LSR and MV intercalate into DNA base pairs. In addition, the interaction of TBF with DNA is the comprehensive interaction of two modes: intercalation and groove binding. It was also found that ionic strength could affect the binding of fluorescent dyes and DNA.

The fluorescence properties of a newly synthesized compound, 1,5-diphenyl-3-(N-ethylcarbazole-3-yl)-2-pyrazoline (DEP) have been studied. On excitation at 352 nm, the fluorescence spectrum exhibits a large red shift with an increase in the polarity of solvents. The intensity of the band is different in different solvents as well. The change in the dipole moment in various solvents at room temperature has been characterized by the absorption and steady state fluorescence techniques and calculated based on the Lippert–Mataga equation. DEP has an increase of dipole moment of 2.83 D units on excitation to the lowest singlet state. It is concluded that photo-induced charge transfer from N (1) to C (3) actually exists in the excited state of the pyrazoline moiety. Its fluorescence property is relative to viscosity and temperature of solvents. The ϕf of DEP in neutral medium or basic medium is higher than acidic medium. In addition, when the concentration of DEP is higher than 10−3 M, its fluorescence is quenched by the collision of each molecule. The red shift of the maximum emission of DEP attributes to the formation of aggregates and the conjugate system is strengthened.

An alcohol biosensor for the measurement of ethanol has been developed. It comprises an alcohol oxidase/chitosan immobilized eggshell membrane and a commercial oxygen sensor. Ethanol determination is based on the depletion of dissolved oxygen content upon exposure to ethanol solution. The decrease in oxygen level was monitored and related to the ethanol concentration. The biosensor response depends linearly on ethanol concentration between 60 μM and 0.80 mM with a detection limit of 30 μM (S/N = 3) and 1 min response time. In the optimization studies of the enzyme biosensor the most suitable enzyme and chitosan amounts were found to be 1.0 mg and 0.30% (w/v), respectively. The phosphate buffer (pH 7.4, 25 mM) and room temperature (20–25 °C) were chosen as the optimum working conditions. In the characterization studies of the ethanol biosensor some parameters such as interference effects, operational and storage stability were studied in detail. The biosensor was also tested with various wine samples. The results of this newly developed biosensor were comparable to the results obtained by a gas chromatographic method.

An uric acid biosensor fabricated from a uricase-immobilized eggshell membrane and an oxygen electrode was presented. The detection schemes involve the enzymatic reactions of the uricase leading to the depletion of dissolved oxygen level upon exposure to uric acid solution. The decrease in oxygen level was monitored and related to the uric acid concentration. The scanning electron micrographs show the microstructure of the eggshell membrane within which the uricase is successfully immobilized. The effects of enzyme loading, pH, temperature, and phosphate buffer concentration on the response of the biosensor were investigated in detail. The uric acid biosensor has a linear response range of 4.0–640 μM with a detection limit of 2.0 μM (S/N = 3). The response time was less than 100 s. The biosensor exhibited good repeatable response to a 0.10 mM uric acid solution with a relative standard deviation of 3.1% (n = 7). The reproducibility of fabrication of the biosensors using four different membranes was good with a R.S.D. of 3.2%. The biosensor showed extremely good stability with a shelf-life of at least 3 months. Some common potential interferents in samples such as glucose, urea, ascorbic acid, lactic acid, glycine, dl-α-alanine, dl-cysteine, KCl, NaCl, CaCl2, MgSO4, and NH4Cl showed no interferences on the response of the uric acid biosensor. The biosensor was successfully applied to determine the uric acid level in some human serum and urine samples, and the results agreed well with those obtained by a commercial colorimetric assay kit.

The interaction between biliverdin and bovine serum albumin (BSA) has been studied by steady fluorescence spectroscopy, synchronous fluorescence and resonance light scanning spectra. The binding of biliverdin to BSA quenches the tryptophan residue fluorescence and the results show that both static and dynamic quenching occur together with complex formation. The binding constant and binding sites of biliverdin to BSA at pH 7.1 are calculated to be 3.33 × 108 L/mol and 1.54, respectively, according to the double logarithm regression curve. In addition, the distance between the biliverdin and BSA is estimated to be 1.25 nm using Föster's equation on the basis of the fluorescence energy transfer. Furthermore the synchronous fluorescence spectra show that the microenvironment of the tryptophan residues has not obvious changes, which obeys the phase distribution model. Finally, the thermodynamic data show that biliverdin molecules enter the hydrophobic cavity of BSA via hydrophobic interaction.

The interaction between 3,3-bis(4-hydroxy-1-naphthyl)-phthalide (NPP) and bovine serum albumin (BSA) have been studied by fluorescence spectroscopy. The binding of NPP quenches the BSA fluorescence. By the fluorescence quenching results, it was found that the binding constant K = 5.30 × 104 L mol−1, and number of binding sites n = 0.9267. In addition, according to the synchronous fluorescence spectra of BSA, the results showed that the fluorescence spectra of BSA mainly originate from the tryptophan residues. Finally, the distance between the acceptor NPP and BSA was estimated to be 1.94 nm using Föster's equation on the basis of fluorescence energy transfer. The interaction between NPP and BSA has been verified as consistent with the static quenching procedure and the quenching mechanism is related to the energy transfer.

Studies on the luminescence spectra behaviors of seven quinines on solid substrate (SS-RTP) were performed. Experimental conditions, such as heavy atom type, pH and drying time of the sample, etc. on solid substrate room temperature phosphorescence (SS-RTP) or solid substrate delayed fluorescence (SS-DF), were studied in detail. CdCl2 could induce strongest RTP or DF emission of these quinolones. In addition, a comparative study on the spectral behavior of seven quinolones was given, including low temperature phosphorescence (LTP), low temperature fluorescence (LTF) and spectra methioned above. New determination methods for the analysis of seven quinolones by solid substrate room temperature fluorescence (SS-RTF), SS-RTP or SS-DF with filter paper as solid substrate were presented. Analytical characteristics of these methods of seven quinolones were studied. The linear dynamic ranges (LDR), the limit of detection (LOD) and the relative standard deviation (R.S.D.) were valued. Recoveries of seven quinolones in human urine samples were from 98.1% to 104.3%.

Ultrasonic-assisted extraction (UAE) of American ginseng polysaccharides (AGP) was investigated using response surface methodology. Three-factor-three-level Box-Behnken design was employed to optimize the ultrasonic power, extraction time and ratio of water to raw material to obtain a high AGP yield. The analysis of variance and response surface plots indicated that ultrasonic power was the most important factor affecting the extraction yield. The optimal conditions were ultrasonic power 400 W, extraction time 71 min, and ratio of water to raw material 33 mL g−1. Under these conditions, the yield of AGP was 8.09%, which was agreed closely to the predicted value. Gas chromatography (GC) analysis showed that AGP was composed of arabinose, rhamnose, galactose, glucose, and galacturonic acid. Fourier transform infrared spectra revealed the general characteristic absorption peaks of AGP. In addition, AGP exhibited good immunostimulating activities by up-regulating the production of nitric oxide and cytokines. Compared with hot water extraction, UAE required shorter extraction time and gave a higher extraction yield, without changing the structure and immunostimulating activity of AGP. The results indicated that UAE could be an effective and advisable technique for the large scale production of plant polysaccharides.

A glucose biosensor using a glucose oxidase (GOx)-immobilized nylon net with glutaraldehyde as cross-linking reagent and an oxygen (O2) electrode for the determination of glucose has been fabricated. The detection scheme was based on the utilization of dissolved O2 in oxidation of glucose by the membrane bound GOx. Crucial factors including O-alkylation temperature, reaction times of nylon net with dimethyl sulfate, l-lysine, and glutaraldehyde, and enzyme loading were examined to determine the optimal enzyme immobilization conditions for the best sensitivity of the developed glucose biosensor. In addition, the effects of pH and concentration of phosphate buffer on the response of the biosensor were studied. The glucose biosensor had a linear range of 18 μM to 1.10 mM with the detection limit of 9.0 μM (S/N = 3) and response time of 80 s. The biosensor exhibited both good operational stability with over 200 measurements and long-term storage stability. The results from this biosensor compared well with those of a commercial glucose assay kit in analyzing human serum glucose samples.

A microbial biosensing system for the measurement of methane has been developed using an immobilized mixed culture of Pseudomonas aeruginosa and Klebsiella sp. together with a dissolved oxygen (O2) sensor. When methane was applied to the biosensing system, the dissolved O2 content decreased until a steady-state was reached. The biosensing system response depends linearly on methane concentration between 1.0 and 5.0% (v/v) with a detection limit of 0.3% (v/v) (S/N = 3) and a 100-s response time. Phosphate buffer (pH 7.0, 25 mM) and room temperature (20–25 °C) were chosen as the optimum working conditions. Some parameters including pH, temperature, operational and storage stability were studied in detail for characterization of the biosensing system.

•PM2.5 induces heart mitochondrial morphological damage of rats.•Mitochondrial fission/fusion gene expression is important regulation mechanism.•Proinflammatoy cytokine level changes are accompanied with mitochondrial damage.•Alterations in oxidative stress and calcium homeostasis are focused on.Epidemiological studies suggested that ambient fine particulate matter (PM2.5) exposure was associated with cardiovascular disease. However, the underlying mechanism, especially the mitochondrial damage mechanism, of PM2.5-induced heart acute injury is still unclear. In this study, the alterations of mitochondrial morphology and mitochondrial fission/fusion gene expression, oxidative stress, calcium homeostasis and inflammation in hearts of rats exposed to PM2.5 with different dosages (0.375, 1.5, 6.0 and 24.0 mg/kg body weight) were investigated. The results indicated that the PM2.5 exposure induced pathological changes and ultra-structural damage in hearts such as mitochondrial swell and cristae disorder. Furthermore, PM2.5 exposure significantly increased specific mitochondrial fission/fusion gene (Fis1, Mfn1, Mfn2, Drp1 and OPA1) expression in rat hearts. These changes were accompanied by decreases of activities of superoxide dismutase (SOD), Na+K+-ATPase and Ca2+-ATPase and increases of levels of malondialdehyde (MDA), inducible nitric oxide synthase (iNOS) and nitric oxide (NO) as well as levels of pro-inflammatory mediators including TNF-α, IL-6 and IL-1β in rat hearts. The results implicate that mitochondrial damage, oxidative stress, cellular homeostasis imbalance and inflammation are potentially important mechanisms for the PM2.5-induced heart injury, and may have relations with cardiovascular disease.Download full-size image

In the study, we present the results of thermodynamic simulation of CaSO4 water-salt systems containing Ca2+, Mg2+, Na+, K+ and HCO-3 at 37°C. The results showed that the solubility of CaSO phase increased with increasing NaCl as wells as KCl concentration in the range of 0.0 to 2.0 M and 0.0 to 1.0 M, respectively. Remarkably, enhanced effect of MgCl2 on the solubility of CaSO4 phase was much larger than that of KCl or NaCl. The only exception was CaCl2, which was found to reduce solubility value of CaSO4 in aqueous solution at 37°C with the increase of CaCl2 concentration. Also, the solubility of CaSO4 phase in mixed salt solutions was investigated at 37°C. The common ion effect was the main factor on the solubility of CaSO4 in the mixed salts solution. Furthermore, CaSO4 solubility was reduced by small amounts of NaHCO3 in mixed solutions. These studies are of relevance in the estimating the changes of various salts in blood plasma and production of salt with low impurities of Ca2+ and SO42- ions, as well as estimating oceanic-containing CaSO4 uptake of CO2.

A novel carbazole derivative, N,N′-bis(9-ethyl-9H-carbazol-3-yl)-(ethane-1,2-diamine), has been synthesized by reacting 3-amino-9-ethylcarbazole with glyoxal and characterized by 1H NMR, infrared spectroscopy, elemental analysis and mass spectra. The strong fluorescence emission at 438 nm of the derivative is effectively and selectively quenched by Cr3+. A 1:1 complex is formed between the carbazole derivative and Cr3+ and their association constant is 1.4 × 104 L mol−1. The results indicate that the carbazole derivative can provide a rapid, selective and sensitive response to Cr3+ in a linear dynamic range 1.0–20 μmol L−1 with a limit of detection of 0.10 μmol L−1 at pH 7.4. Common interferent ions do not show any interference with the Cr3+ determination. It is anticipated that the carbazole derivative could be a good candidate probe and has potential application for Cr3+ determination.

An organic salt based on double 1,3,4-oxadiazole derivatives as fluorophores and BAPTA as a receptor has been designed for detection of Cd2+. The fluorescent probe exhibits high selectivity for Cd2+ and a low detection limit of 20 nM in aqueous solution, making it useful for Cd2+ imaging in living MCF-7 cells.

A ratiometric fluorescent probe for Ca2+ based on 1,3,4-oxadiazole derivative has been designed and developed. The probe exhibits a large Stokes shift of 202 nm and a highly selective ratiometric emission response (490/582 nm) to Ca2+ over other metal cations. Additionally, the probe can readily reveal the changes of intracellular Ca2+ concentration in living human umbilical vein endothelial cells.

A facile strategy for the preparation of meso-terakis(4-methoxyl-3-sulfonatophenyl) porphyrin (T(4-Mop)PS4)-graphene hybrid nanosheets (TGHNs) was demonstrated for the first time, which combines the features of both graphene (high conductivity and large specific surface area) and porphyrins (photochemical electron-transfer ability and excellent electrochemical activity). The as-obtained TGHNs were characterized by UV-vis spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, atomic force microscopy, transmission electron microscopy and cyclic voltammetry, which confirmed that the porphyrin had been effectively functionalized on the surface of graphene. Combined with the high affinity and specificity of an aptamer, a simple, rapid, sensitive and label-free electrochemical aptasensor was successfully fabricated for adenosine triphosphate (ATP) detection. The proposed TGHN-based aptasensor achieved the direct electron transfer of porphyrin and showed good affinity and specificity towards ATP, which avoided interference such as the introduction of labeled-substances and the [Fe(CN)6]3−/4− probe. The preferable linear range for ATP was from 2.2 nM to 1.3 μM (R = 0.9982) with a detection limit of 0.7 nM.

The designed synthesis of graphene-based nanocomposites for enhancing their different potential application is of great interest recently. In this paper, we demonstrated a new class of high-quality graphene-based nanocomposites: metal coordination polymer–graphene nanosheets (MCPGNs). The as-obtained nanocomposite, combining the unique properties of graphene (excellent conductivity and high specific surface area) and MCPs (tunable pore size, large internal surface areas and versatility of functionality), can act as an efficient matrix to immobilize glucose oxidase (GOD). Furthermore, the as-prepared MCPGNs exhibit better conductivity and electrocatalytic activity for H2O2 reduction than graphene. Based on these excellent properties, a sensitive electrochemical biosensing platform for glucose was fabricated. This novel biosensor displays a linear response range between 50 nM and 1 mM with a detection limit of 5 nM. Our work not only provides a facile, effective and general route for the synthesis of a variety of MCP–graphene nanohybrids, but also sets an example for fabricating an electrochemical biosensor with this new kind of nanohybrid as an enhanced material and can be easily extended to other biosensors. These interesting results suggested the great potential of MCP–graphene nanocomposites in the field of electroanalytical chemistry.

The preparation of neutral red covalently-functionalized graphene nanosheets (NR-FGN) is presented via replacement of the carboxyl acid groups at the edges of graphene nanosheets using NR. The obtained NR-FGN was characterized by UV-vis, Fourier transform infrared (FT-IR), Raman spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM). It was found that the introduction of NR at the edges of graphene nanosheets (GN) improved the solubility and stability of the graphene. The electrochemical impedance result further confirmed that NR-FGN could effectively accelerate the electron transfer. Due to the synergic effect between GN and NR, the nanocomposite exhibited excellent electrocatalytic activity toward the oxidation of uric acid.

Phosphorous and nitrogen co-doped carbon dots (P,N-CDs) with satisfactory quantum yield have been prepared through one-step acidic oxidation of pumpkin by H3PO4 at low temperature (90 °C). The as-prepared P,N-CD is relatively monodisperse with a narrow size distribution. The P,N-CD displays a remarkable emission enhancement in the yellow fluorescence region (λem = 550 nm) when the pH is increased from 1.5 to 7.4. The pKa value of P,N-CDs was found to be 4.17 and it shows linear response to the physiological range of pH 4.7–7.4, which is valuable for near-neutral cytosolic pH research. It is observed that P,N-CDs are superior fluorescent bioimaging agents in animals and cells thanks to their excellent solubility and ultra-low toxicity. In addition, P,N-CDs display a notably large Stokes shift of 125 nm, good reversibility and could effectively avoid the influence of autofluorescence in biological systems. The confocal fluorescent microscopic images of subcellular distribution and the detection of pH in MCF-7 cells were achieved successfully, suggesting that P,N-CDs have excellent cell membrane permeability and are further applied successfully to monitor pH fluctuations in live cells with negligible autofluorescence.

A novel ratiometric fluorescence probe based on protein–silver nanoclusters (NCs) for mercuric ion (Hg2+) has been synthesized and characterized. A facile and simple one-step method for the synthesis of fluorescent Ag NCs, using bovine serum albumin (BSA) without preprocessing as a scaffold was developed. BSA assembled Ag NC (BSA-Ag NCs) were first found to exhibit ratiometric fluorescence with blue emission at 480 nm and red emission at 634 nm. Upon the addition of Hg2+, the emission of BSA-Ag NCs at 480 nm gradually increased and at 634 nm steadily decreased. The presence of Hg2+ induced a color change from light yellow to colorless and a bright red fluorescence to blue fluorescence. The determination of Hg2+ based on ratiometric fluorescence was developed. The linear dynamic range was from 5.0 × 10−8 M to 2.5 × 10−5 M with a detection limit of 4.87 × 10−8 M. The relative standard deviation (RSD) at 0.30 μM for Hg2+ of six replicates determination was 2.8%. The BSA-Ag NCs were conveniently and easily synthesized, so could serve as a “naked-eye” fluorescent probe for Hg2+. The probe may be a good candidate for the application of sensing Hg2+ in environmental analysis and fluorescence imaging.

A novel glucose biosensor based on the catalytic effect of platinum nanoparticles (PtNPs) on the enzymatic reaction for the glucose determination has been developed. PtNPs were in-situ synthesized on the surface of the eggshell membrane (ESM) upon which glucose oxidase (GOx) had been simultaneously immobilized accompanied by the synthesis of the PtNPs to produce a GOx-PtNPs/ESM. The glucose biosensor was fabricated by positioning the GOx-PtNPs/ESM on the surface of a dissolved oxygen sensor. The glucose concentration was quantified by the decrease of dissolved oxygen. The effect of the amount of K2PtCl4 (0.1 M), the volume of the GOx (1%, w/v), reaction time, pH, phosphate buffer concentration and temperature on the response of the glucose biosensor were studied in detail. This biosensor exhibited a response time of less than 30 s, a wide linear concentration range of 10–225 μM and a detection limit of 5 μM, good repeatability (RSD = 1.03%, n = 10), and satisfactory reproducibility (RSD = 0.54%, n = 5). The biosensor retained 90.0% of its initial response after 8 months at 25 °C. Common interferents such as D-fructose, citric acid, sucrose, L-ascorbic acid and so on did not any give significant interference. The proposed biosensor was successfully applied for the determination of glucose concentration in human blood serum with recoveries between 93.6% and 102.8%.