Nanocatalysts depended colorimetric assay possesses the advantage of fast detection and provides a novel avenue for the detection of hydrogen sulfide (H2S). The exploration of nanocatalysts with superior catalytic activity is challenging to achieve ultrasensitive colorimetric assay of H2S. Herein, 1.7 ± 0.2 nm ruthenium nanoparticles (Ru NPs) were prepared and exhibited outstanding catalytic hydrogenation activity. The degradation rate constants of orange I in the presence of Ru NPs were 4-, 47- and 165-fold higher than those of platinum (Pt) NPs, iridium (Ir) NPs and control groups without catalysts. H2S-induced deactivation of Ru NP catalysts was designed for the sensitive colorimetric assay of H2S, attributing to the poor thiotolerance of Ru NPs. A standard linear curve between the rate constants and the concentration of H2S was established. The limit of detection (LOD) was as low as 0.6 nM. A Ru NPs based colorimetric principle was also used to fabricate colorimetric paper strips for the on-site visual analysis of H2S. The proposed approach shows potential prospective for the preparation of highly selective colorimetric NP sensors for specific purposes.Keywords: Catalytic activity; Colorimetric assay; H2S detection; Paper strips; Ru nanoparticles;

High-purity semiconducting single-walled carbon nanotubes (s-SWNTs) can be obtained by conjugated polymer wrapping. However, further purification of sorted s-SWNTs and high costs of raw materials are still challenges to practical applications. It is inevitable that a lot of polymers still cover the surface of s-SWNTs after separation, and the cost of the polymer is relatively higher than that of SWNTs. Here, we demonstrated a facile isolated process to improve the quality of s-SWNT solutions and films significantly. Compared with the untreated s-SWNTs, the contact resistance between the s-SWNT and the electrode is reduced by 20 times, and the thin-film transistors show 300% enhancement of current density. In this process, most of the polymers can be recycled and reused directly without any purification, which can greatly decrease the cost for s-SWNT separation. The results presented herein demonstrate a new scalable and low-cost approach for large-scale application of s-SWNTs in the electronics industry.Keywords: contact resistance; purification; recyclable; semiconducting; single-walled carbon nanotubes; thin-film transistors;

Novel phosphorescent iridium complex (pq)2Ir(cys) (where pq = 2-phenylquinoline, cys = l-cysteine) was synthesized and characterized. Bearing a pH-activatable carboxyl group, the complex can act as lab-on-a-molecule for determination of a trace amount of Hg2+, based on the fact that its phosphorescence can be sensitively and selectively quenched by Hg2+. Furthermore, its phosphorescence is reversibly responsive to pH changes in a wide pH range 7–13. Thus, the molecule was developed as highly selective orthogonal signaling protocol for Hg2+ and pH detection by one channel.Keywords: Hg2+; Iridium complex; Lab-on-a-molecule; pH; Phosphorescence;

•A water-soluble and highly phosphorescent iridium complex was synthesized and characterized.•The phosphorescence of the Ir complex can be sensitively and selectively quenched by tryptophan.•The phosphorescence of the Ir complex is further enhanced upon binding with bovine serum albumin.•The enhancement in the phosphorescence of Ir complex by bovine serum albumin can be effectively quenched by Cu2+.•The iridium complex can not only serve as a multifunctional chemosensor, it can also be used for cell imaging.A water-soluble and highly phosphorescent cyclometallated iridium complex [(pq)2Ir(bpy-COOK)]+Cl- (where pq=2-phenylquinoline, bpy-COOK= potassium 2,2′-bipyridine-4,4′-dicarboxylate) (Ir) has been synthesized and characterized. Its phosphorescence can be sensitively and selectively quenched by tryptophan through a photoinduced electron-transfer (PET) process. Furthermore, the phosphorescence of Ir is drastically increased upon binding with bovine serum albumin (BSA), and the enhanced signal is effectively quenched in the presence of Cu2+. Thus, Ir can be used as a multifunctional chemosensor for tryptophan, BSA, and Cu2+ determination as well as for cell imaging.A water-soluble cyclometallated iridium complex with its phosphorescence sensitively and selectively responsive to tryptophan, bovine serum albumin and copper ions.

•A facile in situ reduction and one-step calcination method was developed to fabricate an electrochemical sensor material.•The sensing material was prepared with self polymerization method by using a non-toxic, and low cost precursor.•The electrode material featured with multi-active sites and multi-element co-doping.•Electrochemical oxidation performance promoted by synergistic action of Cu NPs and nitrogen doped graphene.•The sensor has outstanding sensitivity and selectivity compared with other graphite-based electrodes.Copper nanoparticles modified nitrogen doped reduced graphene oxide 3-D superstructure was successively prepared via a two-step reaction. Polydopamine was used as nitrogen source for the fabrication of nitrogen doped reduced graphene oxide and reducing agent for in-situ reduction of CuCl2. After calcination under nitrogen protection, the conductivity, electron transfer ability and electrocatalytic activity of nanocomposites were substantially improved. The enhanced redox property could be attributed to the difference in the electronegativity of carbon and nitrogen atoms of the 3-D superstructure. By using this composite material, an electrochemical sensor was constructed for the detection of dihydroxybenzene isomers, which exhibited excellent sensitivity (with limit of detection at 81•131 nmol L∧1 levels), wide linear ranges (0.5•720 α/4mol L∧1) and good selectivity. Hence it was directly applied for the simultaneous determination of dihydroxybenzene isomers in contaminated samples (e.g., waste waters).

•The Ir NPs were rapidly prepared using tannin acid as stabilizer in one-pot reaction.•The Ir NPs showed excellent peroxidase-like activity.•The catalytic mechanism of the Ir NPs was verified by ESR assay.•Different peroxide substrates were used for judging the catalytic mechanism of the Ir NPs.•The Ir NPs were successfully used for the colorimetric determination of H2O2 and xanthine.A facile and efficient method was developed for the preparation of iridium nanoparticles (Ir NPs) with superior peroxidase-like activity. Under the catalytic action of the Ir NPs, the peroxidase substrate 3,3,5,5-tetramathylbenzidine (TMB) can be oxidized by H2O2 to form a blue-colored production oxTMB. Kinetic analysis indicated that the catalytic behavior was in accordance with the typical Michaelis-Menten kinetics and the catalytic reaction followed the ping-pang mechanism. Electron Spin Resonance (ESR) experiment showed that no hydroxyl radical formed in the reaction process. Peroxide substrates with different electron withdrawing ability (benzoyl peroxide, H2O2 and artemisinin) were used to study the catalytic reactions and results indicated that H2O2 can oxidize TMB with much faster rate than artemisinin and slower rate than benzoyl peroxide. These results suggest an electron transfer mechanism was involved in the system of TMB-H2O2-Ir NPs. By using TMB as the colorimetric substrate, H2O2 can be rapidly determined and the method was extended for the determination of xanthine based on its production of H2O2 in the presence of xanthine oxidase. The prepared Ir NPs exhibit good stability in wide range of pH and temperature. The Ir NPs retained at least 90% of their initial catalytic activity after stored at ambient temperature for three months. The high specificity for H2O2 and the excellent stability of the peroxidase-like Ir NPs showed the great application potential in biotechnology field.Iridium nanoparticles (Ir NPs) peroxidase-like mimic was prepared using nature stabilizer tannin acid with one-pot production in aqueous solution. Based on the electron transfer mechanism, the Ir NPs can be used for the catalytically oxidizing of TMB with H2O2 to form blue oxTMB.

A novel method for latent fingerprint (LFP) detection was developed, which is based on the specific adsorption of nitric oxide (NO) on the hydrophobic ridges of fingerprints and the visualization of the fluorescence image after application of a fluorescent probe 1,2-diaminoanthraquinone (DAQ). The inherent lipophilic properties of NO allow its selective adsorption on the lipid component of fingerprints and DAQ is able to react with the adsorbed NO forming a fluorescent product, the 1,2-diaminoanthraquinone triazole derivative (DAQ-TZ). Through this two-step treatment and a CCD imaging process, the obtained fluorescent LFPs were satisfactory, and the second and third level information can be clearly observed. The method was proved to be universally applicable to many different substrate materials and effective for LFPs aged as long as 30 days.

Nitrogen and iron phosphides (i.e., FeP) doped carbon nanotubes (N/FeP-CNT), featured with multi-element co-doping, multi-active sites, and uniform distribution were prepared and characterized. The synergistic effect of nitrogen doped carbon nanotubes (N-CNT) and FeP improved the electrical conductivity and electrocatalytic properties of the modified electrode, which provided a new analysis platform for simultaneous detection of dihydroxybenzoic acid isomers (DHBA isomers). Low detection limits (i.e., 124, 65, and 221 nmol L−1 for 2,4-DHBA, 3,4-DHBA, and 2,5-DHBA, respectively) and wide detection range (i.e., 0.5-600, 0.5-560, and 0.5–820 μmol L−1 for 2,4-DHBA, 3,4-DHBA, and 2,5-DHBA, respectively) were obtained for DHBA isomers. In addition, the electrode exhibited good anti-interference ability and long-term stability for the determination of DHBA isomers.

A one-step controlled hydrothermal method was described to prepare highly fluorescent polymer dots (PDs) by using polyethylene glycol as the carbon source. The synthesized PDs with an average diameter of 2.5 nm exhibit strong blue fluorescence with high quantum yields (QYs, up to 19%). Further modification of these PDs with glutathione (GSH) endows the resultant GSH–PDs with bi-functional fluorescence responses to temperature and Fe3+. Interestingly, the fluorescence signal of the GSH–PDs is reversibly responsive to the environmental temperature in the range of 20–75 °C. As the GSH–PDs exhibit good biocompatibility, they can pervade the MC3T3-E1 cells and enable the measurement of temperature over the physiological range of 20–45 °C using the confocal fluorescence imaging method. The GSH–PDs were also explored as a fluorescent probe for Fe3+ ion detection, and the linear response range in 0.1–10 μM was observed with a detection limit of 3.7 nM. Thus, the bi-functional measurement of temperature and Fe3+ ions was achieved by the fluorescent PD chemosensor.

Microcystins (MCs) are cyanobacterial hepatotoxins capable of accumulation into animal tissues. To determine the total microcystins in water, a novel analytical method, including ozonolysis, methylation of 2-methyl-3-methoxy-4-phenylbutyric acid (MMPB) with methylchloroformate (MCF) and gas chromatography mass spectrometry (GC-MS) detection was developed. The results show that MCs can be oxidized by ozone to produce MMPB at ambient temperature, proving ozonation is an effective, rapid and green method for the transformation of MCs to MMPB without secondary pollution. The oxidation conditions as well as the esterification process were optimized and, subsequently applied to analysis of environmental samples. The method shows wide linear range and high sensitivity with a detection limit of 0.34 μg L−1. The established method was successfully applied to the analysis of microcystins in water samples.

Efficient nanoprobes for fluorescent and magnetic resonance multimodal imaging (MRI/FI) are in high demand in bioimaging. Herein, a nanoprobe with fluorescent gold nanoclusters (NCs) and magnetic iron oxide composite materials (Fe3O4@AuNCs) was prepared for dual bioimaging. The AuNCs were synthesized using the glutathione (GSH) template. The hydrophobic Fe3O4 magnetic nanoparticles (MNPs) were capped with cetyltrimethyl ammonium bromide (CTAB) to obtain hydrophilic Fe3O4 MNPs. Subsequently, the Fe3O4@AuNCs were prepared by the adsorption of Fe3O4–CTAB on the GSH–AuNCs through electrostatic attraction. The resultant Fe3O4@AuNCs, having an average size of 13.5 nm, can be readily dispersed in water, which displayed a strong red fluorescence (λEm = 650 nm) with a quantum yield of 4.3%. Confocal laser scanning microscopy studies proved that the Fe3O4@AuNCs have good photostability and low cytotoxicity to 293T cells. The magnetic properties of Fe3O4@AuNCs showed that this material was a T2-based contrast agent for MRI with a transverse relaxivity r2 of 20.4 mM−1 S−1. Furthermore, the signal intensity of the T2-weighted MRI decreased with an increase in the concentration. The dual optical and magnetic properties of the synthesized Fe3O4@AuNCs were applicable to dual fluorescence and MR-based imaging.

Surface-enhanced Raman scattering (SERS)-active substrates assembled by two types of metallic nanoparticles (NPs) were fabricated. Aptamers driven Au nanoflower (Au NF)–Ag NP core–satellite assemblies exhibited amplified SERS signals and achieved the sensitive detection of microcystin-LR (MC-LR) in Tai lake water with the limit of detection (LOD) of 8.6 ± 0.4 pM.

A sensitive surface-enhanced Raman scattering (SERS) signal dependent double detection of mycotoxins is achieved for the first time, without the aid of nucleic acid amplification strategies. SERS labels embedded Ag@Au core–shell (CS) nanoparticles (NPs) as novel SERS tags are successfully prepared through a galvanic replacement-free deposition. SERS tags produce stable and quantitative SERS signal, emerging from the plasmonic coupling at the junction of Ag core and Au shell. SERS tags engineered Raman aptasensors are developed for the double detection of ochratoxin A (OTA) and aflatoxin B1 (AFB1) in maize meal. The limits of detection (LODs) are as low as 0.006 ng/mL for OTA and 0.03 ng/mL for AFB1. The developed protocol can be extended to a large set of different SERS tags for the sensitive detection of multiple targets that possess different lengths of aptamers.Keywords: Ag core; double detection; embed; mycotoxins; SERS

Carbon membranes have been extensively applied in gas separation field, and the cost and performance of membranes strongly rely on the properties of the substrate material. In this study, effective nanoporous carbon membranes were prepared by pencil coating of the macroporous ceramics, followed by carbonization treatment of polyfurfuryl alcohol (PFA) coated on the pencil-modified ceramics substrates. The decoration of the macroporous ceramics substrates with pencil effectively repairs surface defects and decreases surface roughness, and greatly prevents PFA from penetrating into the ceramics substrates during pyrolysis. The as-prepared carbon membranes showed high gas permeability and permselectivity properties. This work provides an efficient method to fabricate nanoporous carbon membranes with enhanced gas separation performance.

•Sensitive detection of nitroaromatic compounds was achieved by combining the reduction and the ECL electrode in one cell.•The use of a mesh electrode allowed the reduced products can be detected in-situ with an electrochemiluminescence electrode.•The electrochemical deposition of copper nanoparticles on the mesh electrode greatly enhanced the reduction efficiency.•The mixed electrolytic solution of phosphate and sulfate allowed the electrochemical reduction and the ECL detection in one phase.•The involvement of the dissolved oxygen in the electrochemical reduction of nitroaromatic compounds was proved.An integrative method based on the combination of electrochemical reduction (ECR) and in-situ electrochemiluminescence (ECL) detection was developed for the sensitive detection of the nitroaromatic compounds (NACs), including 4-nitrotoluene (4-NT), 2,4-dinitrotoluene (2,4-DNT), 2,4,6-trinitrotoluene (TNT). An electrochemical flow cell including two working electrodes was fabricated with poly(dimethylsiloxane) (PDMS) to achieve the dual functions. The first one is a copper mesh electrode, acting as the reductor to convert the NACs to aminoaromatic compounds (AACs). Electrochemical deposition of copper nanoparticles on the surface of the copper mesh was conducted to further increase the reduction efficiency. The second one is an ECL electrode, which was used for in-situ detection of the reduced products. The ECL electrode was fabricated by the immobilization of Ru(bpy)32+ on a glassy carbon electrode (GCE) with the Nafion/the multi-wall carbon nanotubes (MWCNTs) composite film. The copper mesh electrode was arranged directly underneath the ECL electrode to ensure the reduced products could be immediately detected in-situ. An electrolytic solution consists of 33.3 mmol/L Na2SO4 and 16.7 mmol/L phosphate buffer solution (PBS, pH7.0) was found to be optimum for both the electrochemical reduction of the NACs and the ECL detection. The ECL intensities were proportional to the concentrations of 4-NT, 2,4-DNT and TNT in the range from 1.0 × 10−9 to 1.0 × 10−5, 3.5 × 10−9 to 1.0 × 10−5 and 7.5 × 10−9 to 1.0 × 10−5 mol/L respectively. The limit of detections (LOD) were 4.0 × 10−10, 1.7 × 10−9 and 3.1 × 10−9 mol/L respectively for 4-NT, 2,4-DNT and TNT. The reduction mechanism was preliminarily investigated and it was found that the presence of oxygen was critical for the reduction process, suggesting that the reductive oxygen species O2−,OH could be involved in the NACs reduction process.

•Two novel ionic iridium complexes with high electrochemiluminescent efficiency were synthesized and characterized.•The photophysical, electrochemical and electrochemiluminescent properties of the ionic iridium complexes were investigated.•The DFT calculations were carried out to elucidate the difference between ionic and neutral iridium complexes.Two ionic iridium complexes, (bpq)2Ir(bpy)+PF6− (1) and (bpq-OCH3)2Ir(bpy)+PF6− (2), where bpq is 6-methyl-2,4-diphenyl quinolone anion, bpy is 2,2′-bipyridine, were synthesized and structurally characterized. Their photophysical, electrochemical and electrochemiluminescence properties were investigated. With the conjugated phenyl substitution, the π–π ligand center transitions in the emission process were enhanced, resulting in a broad and strong photoluminescence emission. The photoluminescence quantum yields were measured to be 0.214, 0.209, respectively for complex 1 and 2. The complex 1 also exhibited greater electrochemiluminescence efficiency than the complex 2. To further elucidate the influence of different structures on the electrochemical and electrochemiluminescence properties, the density functional theory calculations were performed on the complexes 1, 2 along with other four well documented bis-cyclometalated iridium complexes. The calculation revealed that about 90% electronic density in the lowest unoccupied molecular orbital were distributed in N∧N auxiliary ligand for ionic complexes, whereas most electronic density were distributed in C∧N main ligand for neutral complexes.

Glucose biosensors have attracted increased attention, as the rapid and sensitive detection of glucose is highly desirable for diabetes diagnosis. In this article, we designed a type of lysozyme functionalized fluorescence copper nanoclusters (Lys-CuNCs) to detect glucose levels in blood samples. Fluorescence measurements were carried out to optimize the synthesis conditions (e.g. mass ratio, pH and reaction time) for the biosensor. Under optimum conditions, the obtained Lys-CuNCs with an average diameter of 2 nm exhibited bright orangey-red fluorescence with high quantum yields (up to 5.6%). The fluorescence signal of Lys-CuNCs was quenched upon the addition of glucose, presumably due to the reduction of Cu(I) on the NCs surface by glucose. Thus the Lys-CuNCs can be served as a biosensor for glucose detection and two linear response ranges respectively in 0.03–10 μM and 0.5–10 mM of glucose were observed with a detection limit of 1.9 nM. Furthermore, this biosensor showed superior selectivity for various interferences, including light radiation, metal ions, carbohydrates and amino acids. In view of these properties, the Lys-CuNCs biosensor was applied in the determination of glucose in blood samples, and the results agreed well with that obtained from a currently used clinical method. Finally the visualized fluorescence variation of Lys-CuNCs may further enable the rapid and simple detection of glucose level in blood.

A flow injection analysis (FIA) method was developed for the rapid and environmentally friendly determination of the acidity of thermal conductive oil. The acid number (AN) of the oil sample was obtained by online measurement of the concentration change of the standard KOH solution before and after the interaction with the oil sample. To ensure the adequate reaction of KOH with the acid in oil, the oil sample and KOH solution were segmented into small droplets in the confluence tube with the help of a coiled wire. The parameters, such as the mixing ratio of KOH with oil, the length of mixing tube, and the flow rate of the two mixing streams, were optimized. Then, the FIA manifolds was integrated to a three-dimensional (3D)-printed FIA system (3DFIA), which was used for the determination of the AN in real oil samples. The results showed that the AN values in the range of 0.20–6.4 mg of KOH/g oil can be accurately determined with a limit of detection of 0.177 mg of KOH/g and a sampling frequency of 10 h–1. Also, the results obtained with the 3DFIA system agreed well with that obtained from the conventional FIA system as well as the standard titration method. The new method not only exhibited good precision and rapidity of analysis but also completely eliminated the use of organic solvents.

Temperature measurement in biology and medical diagnostics, along with sensitive temperature probing in living cells, is of great importance; however, it still faces significant challenges. Metal nanoclusters (NCs) with attractive luminescent properties may be promising candidates to overcome such challenges. Here, a novel one-step synthetic method is presented to prepare highly fluorescent copper NCs (CuNCs) in ambient conditions by using glutathione (GSH) as both the reducing agent and the protective layer preventing the aggregation of the as-formed NCs. The resultant CuNCs, with an average diameter of 2.3 nm, contain 1–3 atoms and exhibit red fluorescence (λem = 610 nm) with high quantum yields (QYs, up to 5.0%). Interestingly, the fluorescence signal of the CuNCs is reversibly responsive to the environmental temperature in the range of 15–80 °C. Furthermore, as the CuNCs exhibit good biocompatibility, they can pervade the MC3T3-E1 cells and enable measurements over the physiological temperature range of 15–45 °C with the use of the confocal fluorescence imaging method. In view of the facile synthesis method and attractive fluorescence properties, the as-prepared CuNCs may be used as photoluminescence thermometers and biosensors.

A facile, one-pot green method is presented for the preparation of water-soluble luminescent copper nanoclusters (Cu-NCs) from copper dichloride and cysteine as the precursor and stabilizer, respectively. The Cu-NCs are characterized by high resolution transmission electron microscopy, X-ray photoelectron spectroscopy, fluorescence, UV–Vis, and Raman spectroscopy. The Cu-NCs have an average size of 3.5 nm and are stable in aqueous solution at least for 2 weeks. Under photo excitation with 365 nm light, the Cu-NCs display strong green fluorescence with the maximum of emission at 490 nm and a quantum yield of 5.6 %. Fluorescence is quenched by Cr(VI) ion, and this effect was exploited to develop a highly selective method for the determination of Cr(VI). The detection limit of this probe is as low as 43 nM.

In this study, a simple gold nanoparticles (Au NPs) driven electrochemiluminescence (ECL) aptasensor was fabricated for the sensitive detection of fumonisin B1 (FB1), taking advantages of the weak background noise and good ECL efficiency of the ionic iridium (Ir) complex, the high affinity and specificity of aptamers for targets, and the large specific surface and excellent conductivity of Au NPs. Different amounts of Ir complex were loaded on the surface of Au NPs through mercaptoethylamine. The Au NP–Ir complex served as a nanoprobe and was applied in the development of an ECL-aptasensor, and a limit of detection (LOD) as low as 0.27 ng mL−1 was achieved for FB1. The proposed method not only has high sensitivity, but also showed good accuracy and stability. The principle proposed in this paper could be widely applicable in the development of nanomaterial-driven ECL-aptasensors for other mycotoxin detection.

We report on a novel strategy for electrochemiluminescent (ECL) chemical sensing by making use of an electrode modified with organosilica nanoparticles (OSiNPs) that are loaded with an iridium(III) complex Ir(pq)2(acac) (where pq stands for 2-phenylquinoline and acac stands for acetylacetonato). Three kinds of OSiNPs have been prepared by using vinyltrimethoxysilane, vinyltriethoxysilane, and phenyltrimethoxysilane, respectively, as the precursors. The OSiNPs were spherical in shape, uniform in size, and highly monodisperse in the aqueous phase. The luminescence properties of the Ir(III) complex remain unchanged after encapsulation. The ECL properties of the modified electrodes were evaluated by using 2-(dibutylamino)ethanol (DBAE) as the coreactant (analyte). The electrode prepared from phenyltrimethoxysilane as the precursor exhibited the best sensitivity for DBAE and gives a detection limit as low as 5.0 × 10−9 mol L−1 and a linear range from 1.0 × 10−8 to 1.0 × 10−6 mol L−1.

An electrochemiluminescence (ECL) sensor with molecularly imprinted polymer (MIP) film was developed for the detection of heroin. The sensor was prepared by re-modifying the molecularly imprinted polymer film onto Ru(bpy)32+ modified glassy carbon electrode. The electrochemical and electrochemiluminescence behavior of the sensor was investigated. The proposed sensor displayed high sensitivity and excellent selectivity for the target molecule heroin. Under the optimal conditions (a scan rate of 100 mV s−1 and incubation time of 5 min in 0.1 M PBS), a linear response for heroin was achieved in the range of 1.0 × 10−14–1.0 × 10−10 M with a detection limit of 4.0 × 10−15 M (S/N = 3). The sensor was successfully applied for the determination of heroin in urine and saliva with the recovery rates in the range of 97%–104%.A highly sensitive and selective sensor for heroin determination was developed by the incorporation of a molecularly imprinted polymer with electrochemiluminescence detection. The sensor was successfully applied for the determination of heroin in urine and saliva with satisfactoryrecovery rates.

•We outline the synthesis strategies of gold nanoclusters (AuNCs).•We discuss the fluorescence and the electrochemiluminescence of AuNCs.•We summarize applications of AuNCs in chemical analysis and bioimaging.•We suggest the outlook and potential challenges facing luminescent AuNCs.Luminescent gold nanoclusters (AuNCs), composed of a few to about 100 gold atoms, have attracted considerable attention due to their molecule-like properties. These include the discrete electronic states and size-dependent fluorescence resulting from their size, which is comparable to the Fermi wavelength of conduction electrons. AuNCs have proved to be ideal fluorescence labels for biological applications and environmental monitoring and surveillance, thanks to an attractive set of features (e.g., ultra-small size, good biocompatibility and excellent photostability). This article covers in detail the synthesis strategies and optical properties, and highlights recent advances in analytical and biological applications of water-soluble luminescent AuNCs. We also discuss the potential challenges facing luminescent AuNCs in making breakthroughs in synthesis and biological applications.

A novel protocol for simultaneous determination of ascorbic acid (AA), dopamine (DA) and uric acid (UA) based on double-walled carbon nanotubes (DWNTs)/choline (Ch) modified glassy carbon electrode (GCE) was presented. Ch was covalently immobilized on the GCE through oxygen atoms. The Ch monolayer provides a positively charged monolayer, which could attract negatively charged DWNTs through electrostatic interaction. In the simultaneous determination of aforementioned three analytes using CV, the electrochemical signals were well separated into three oxidation peaks with peak potential differences of 0.182 V (AA–DA), 0.146 V (DA–UA) and 0.328 V (AA–UA). In amperometric studies of AA, DA and UA, the modified electrode exhibited wide linear ranges of 0.10–777 μM, 0.06–314 μM and 0.25–344 μM and low detection limits of 0.03, 0.03, and 0.05 μM, respectively. Amperometric responses of AA, DA and UA were within 1 s. Moreover, this modified electrode was further applied to determine AA, DA and UA in real samples with satisfactory results.

A new strategy for the fabrication of an electroluminescence sensor was proposed based on the incorporation of electroluminescence (ECL) detection and the molecular imprinting technology (MIT). The sensor fabrication consisted of two steps, the first one was the immobilization of the light emitting material Ru(bpy)32+ on a GC electrode with the well-established Nafion/the multi-wall carbon nanotube (MWCNT) composite film method and the second step involves re-modification of the Ru(bpy)32+/Nafion/MWCNT electrode with a thin film of molecularly imprinted sol–gel polymers with methamphetamine (MA) as the template molecules. The as-prepared sensor exhibited a very high sensitivity and excellent selectivity toward the target molecule MA. A detection limit as low as 4.0 × 10−15 M was achieved for MA with a wide calibration range from 1.0 × 10−10 to 1.0 × 10−14 M. The high sensitivity of the sensor allowed the drugs in a closed container to be detected by their odors.

Various microcystins (MCs) produced by cyanobacteria pose a potential threat to water resources, therefore, the determination of the total MCs rather than the content of some specific types of MCs in water is of great importance. Oxidation of MCs causes cleavage of the Adda moiety of microcystins to 2-methyl-3-methoxy-4-phenylbutyric acid (MMPB). In this paper, a new method based on the derivatization of MMPB with methylchloroformate is proposed for the sensitive determination of total MCs. The oxidation conditions as well as the esterification process were optimized through a series of batch experiments. With the optimized procedure, a detection limit as low as 0.56 μg L−1 was achieved for total MCs and the method was successfully applied to the determination of MCs in real samples. A comparison study by using the LC-MS method for direct quantification of the MMPB was also conducted to validate the proposed method. The results proved that the technique is highly sensitive and convenient for the quantification of total MCs in water samples. As an additional feature, the method does not require the use of toxic and expensive standards of MCs in the environmental monitoring.

The electrochemical and electrochemiluminescent (ECL) properties of six bis-cyclometalated iridium(III) complexes (ppy)2Ir(N-phenylacetamide) (1), (ppy)2Ir(N-phenylbenzamide) (2), (ppy)2Ir(N-naphthylbenzamide) (3), (ppy)2Ir(N-phenylmethacrylamide) (4), (pq)2Ir(N-phenylmethacrylamide) (5) and (pq)2Ir(acac) (6) were studied in acetonitrile, where ppy is phenylpyridine anion, pq is phenylquinoline anion and acac is acetylacetone anion. These complexes exhibited quasi-reversible one-electron oxidation waves with the oxidation potentials varied from 0.95 to 1.51 V (vs. SCE) and the first irreversible reduction peaks fell into the range of −1.58 to −1.86 V. The effects of the different ligands on the redox potentials and electrochemical reversibility were elucidated by the energies and compositions of the frontier orbitals. The relative ECL efficiencies of the complexes 1–6 were 0.032, 0.020, 0.014, 0.041, 0.11 and 26.0 respectively when referenced to Ru(bpy)32+ and the differences in ECL efficiency were rationalized by the density functional theory (DFT) calculations. The energy gap between the lowest unoccupied molecular orbital (LUMO) of anodic product (M+) and the deprotonated product (TPA) determined the electron transfer efficiency to generate the excited states. Other factors such as the lifetime of the radical intermediates, the oxidation potential gaps between the M and TPA, the amount of M+ generation and the luminescence efficiency (Φem) were also considered in comparison of different ECL systems.Highlights► The electrochemistry and ECL of bis-cyclometalated iridium(III) complexes are elucidated by DFT. ► The LUMO energies of M+ obtained by DFT are used to estimate the efficiency of M* generation. ► Energy and composition of frontier orbital affect electrochemical potential and reversibility. ► The results provide guidelines for the design of iridium complexes with high ECL efficiency.

The electrochemiluminescence (ECL) of four iridium complexes ((phenylpyridine)2Ir(acetylaniline), (phenylpyridine)2Ir(N-phenylmethacrylamide), (phenylpyridine)3Ir [Ir(ppy)3] and (phenylquinoline)2Ir(acetylacetone) [(pq)2Ir(acac)]) was studied in the presence of ammonia as the coreactant in dimethylformamide (DMF) solution. The frontier orbital theory was utilized to elucidate their electrochemistry and ECL properties. The (pq)2Ir(acac), exhibiting the highest ECL efficiency with NH3, was chosen to be luminophore and its ECL reaction with ammonia was further explored for the detection of NH3. At the optimized conditions, a good linear relationship between the logarithm of the ECL intensity and the logarithm of the NH3 concentration was obtained in the concentration range from 1.0 × 10−7 to 1.0 × 10−3 M. The detection limit is 4 × 10−8 M (S/N = 3). The method was applied to the detection of NH3 in the atmosphere with recovery of 92.5–101.9%.Graphical abstractHighlights► Ammonia can act as coreactant to induce the ECL of iridium complexes in DMF. ► The ECL efficiencies were rationalized by the HOMO and LUMO energy levels. ► The complex (pq)2Ir(acac) was selected for the detection of NH3 in atmosphere.

Agarose gel electrophoresis (AGE) is one of the low-cost and large-scale separation techniques for the separation of metallic single-walled carbon nanotubes (m-SWCNTs) and semiconducting single-walled carbon nanotubes (s-SWCNTs). The separated m-SWCNTs were divided into several parts and characterized by the UV-visible-near infrared absorption spectra and the Raman spectra respectively. The results show that the moieties with the fastest electrophoresis migration rate contain more m-SWCNTs. Furthermore, the effects of different agarose concentrations on the separation efficiencies of SWCNTs were investigated. It was found that higher concentration of agarose gel was beneficial to the enrichment of the m-SWCNTs, and the separation efficiency of the m-SWCNTs could be realized by increasing the charge density on the surface of the SWCNTs.

The formation of 2,8-dichlorodibenzo-p-dioxin and other harmful degradation products in the photo-degradation process of triclosan is of increasing concern. Here we worked on the identification of polymerized products at high triclosan concentration and on the mechanism of photoreaction. Five dimmers and two trimers of triclosan were detected by liquid chromatography-mass spectrum analysis. 2,8-dichlorodibenzo-p-dioxin was also identified by comparing with an authentic standard. Relatively low pH and high concentration favored the polymerization of triclosan. Three main routes of photoreaction were postulated, namely dechlorination, ring closure and polymerization.

A novel amperometric sensor based on electropolymerized molecularly imprinted polymer (MIP) for triclosan detection is reported. The sensor was prepared by electropolymerizing o-phenylenediamine (o-PD) on a glassy carbon electrode in the presence of template triclosan. The template can be quickly removed by NaOH solution. After incubating in acetate buffer for 15 min, the sensor response sensitively to triclosan over a linear range of 2.0 × 10− 7 to 3.0 × 10− 6 mol/L and a detection limit as low as 8.0 × 10− 8 mol/L is obtained. This sensor provides an efficient way for eliminating interferences from compounds with similar structures to that of triclosan.

Quaternary ammonium surfactants are important ingredients that are frequently formulated into hair care products to modify the properties of hair surface. The adsorption kinetics, isotherms and association structures of cationic surfactants on hair surface, however, are not fully understood due to the heterogeneous nature of human hair fibers. In this work, a quaternary ammonium of surfactant, dimethylpabamidopropyl laurdimonium tosylate (DDABDT) was chosen as a probe to investigate the adsorption behavior of cationic surfactant on cuticles of scalp hair. The results reveal that the adsorption kinetics fit to a pseudo-second-order kinetic model and the adsorption isotherms fit to the Freundlich adsorption model. With the increase of DDABDT adsorption, the wettability of hair fibers changes from hydrophobic to hydrophilic. The association structure could be monolayer or bilayer depending on the initial concentration of the surfactant. In the monolayer structure, the ‘anchor’ surfactant molecules are believed to adsorb vertically on the surface of hair fibers through electrostatic interaction. In the bilayer structure, the second layer molecules may then pile up on top of the first layer with charged groups orienting outward. The thickness of DDABDT film on hair fibers treated with 5 × 10−4 mol/l DDABDT solution is measured to be 5.42 nm on average with a force–distance method. This figure is very close to the two times of the theoretical molecular size of the DDABDT molecule.

Theoretical study of the reactions between singlet oxygen and chlorophenols is an important aspect in understanding the reaction mechanism of the dye-sensitized photodegradation. With the intention of finding certain predictors to be used for the determination of the most probable reaction path and estimating the dye-sensitized photodegradation rates of chlorophenols, the reactions of 1O2 with six chlorophenols (CPs), including 2-chlorophenol (2-CP), 3-CP, 4-CP, 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP) and pentachlorophenol (PCP), were investigated by using the density functional theory. Results suggested that 1,3-addition to a double bond connected to a hydrogen-carrying group, resulting in the formation of allylic hydroperoxides, and 1,4-addition to chlorophenols to form of hydroperoxide ketones are thermodynamically more likely to take place. Furthermore the reaction barrier of the former one is lower than that of later one, which tends to conclude that 1,3-addition to a double bond connected to a hydrogen-carrying group to form allylic hydroperoxides is the most likely route both in gas phase and aqueous solution. Those reactions are thermodynamically more likely to take place in presence of water, but the reaction barriers increased. Also it was observed that with the increase of chlorine substitutions, the reactions become less exergonic and kinetically less favorable due to the increase in reaction barriers.

A novel chemiluminescence (CL) reaction of chlorophenols (CPs), including 2-chlorophenol (2-CP), 4-CP, 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP) and pentachlorophenol (PCP) was reported, which was based on the oxidation of the phototransformed CPs by N-bromosuccinimide (NBS). It was found that the dye-sensitized phototransformation is a prerequisite for the subsequent CL reaction, and the presence of 1.9×10–2 mol L−1 Triton X-100 or 3.7×10–3 mol L−1 CTAB can greatly enhance the CL intensity. A neutral sample solution with the presence of 2×10–5 mol L−1 fluorescein (FL) was found to be optimum for the phototransformation of 2-CP, 4-CP, 2,4-DCP and PCP, but a lower pH of 5.3 was more suitable for 2,4,6-TCP. Based on the CL reaction, detection limits of 8.6×10−8, 1.1×10−7, 1.5×10–7, 4.6×10–8 and 3.0×10−5 mol L−1 were achieved, respectively, for 2-CP, 4-CP, 2,4-DCP, 2,4,6-TCP and PCP with the optimized conditions in the flow system. The mechanism of the phototransformation and the subsequent CL reaction were preliminarily studied and it was suggested that the singlet oxygen formed in the dye-sensitization process was responsible for the conversion of CPs into light-emitting precursors. These intermediate products were suggested to be peroxide compounds after testing by a luminal-based post-column CL detection experiment.

The formation of 2,8-dichlorodibenzo-p-dioxin (2,8-DCDD) in the photolytic degradation of triclosan has evoked a great concern for its safety and environmental fate. The photochemical behaviour of triclosan in daily-used chemical products, in which triclosan is present in relatively high concentrations and coexists with surfactants, was, however, addressed less frequently. The present work is focused on the mechanistic aspects of triclosan photodegradation in an aqueous medium with a relatively high concentration (≥ 30 mg L−1) and on the influence of pH (8.7 and 10.5) and surfactants (Triton X100, SDS, and CTMAB) on this process. The results demonstrated that photodegradation was strongly affected by the pH and the presence of surfactants. Photodegradation products, including 2,4-dichlorophenol (2,4-DCP), 5-chloro-2-(4-chlorophenoxyl)-phenol, 2,8-DCDD, dimers, trimers, and other intermediates, were identified. Based on the analysis of photoproducts, homolytic scission of ether bond, dechlorination, ring closure, and photo-polymerisation were proposed as the main routes of triclosan photodegradation.

•A facile and efficient strategy is firstly developed for the synthesis of Ru NPs.•Ru NPs are stable and uniform with the controllable sizes from 2.6 to 51.5 nm.•Ru NPs exhibit size-dependent and superior catalytic hydrogenation activity.Ruthenium (Ru) featured with an unusual catalytic behavior is of great significance in several heterogeneous and electro-catalytic reactions. The preparation of tractable Ru nanocatalysts and the building of highly active catalytic system at ambient temperature remains a grand challenge. Herein, a facile strategy is developed for the controllable preparation of Ru nanoparticles (NPs) with the sizes ranging from 2.6 to 51.5 nm. Ru NPs show superior size-dependent catalytic performance with the best kinetic rate constant as high as −1.52 min−1, which could far surpass the other traditional noble metals. Ru NPs exert exceedingly efficient low-temperature catalytic activity and good recyclability in the catalytic reduction of nitroaromatic compounds (NACs) and azo dyes. The developed catalytic system provides a distinguishing insight for the artificial preparation of Ru NPs with desired sizes, and allows for the development of rational design rules for exploring catalysts with superior catalytic performances, potentially broadening the applications of metallic NP-enabled catalytic analysis.Download high-res image (127KB)Download full-size image

A novel protocol for simultaneous determination of ascorbic acid (AA), dopamine (DA) and uric acid (UA) based on double-walled carbon nanotubes (DWNTs)/choline (Ch) modified glassy carbon electrode (GCE) was presented. Ch was covalently immobilized on the GCE through oxygen atoms. The Ch monolayer provides a positively charged monolayer, which could attract negatively charged DWNTs through electrostatic interaction. In the simultaneous determination of aforementioned three analytes using CV, the electrochemical signals were well separated into three oxidation peaks with peak potential differences of 0.182 V (AA–DA), 0.146 V (DA–UA) and 0.328 V (AA–UA). In amperometric studies of AA, DA and UA, the modified electrode exhibited wide linear ranges of 0.10–777 μM, 0.06–314 μM and 0.25–344 μM and low detection limits of 0.03, 0.03, and 0.05 μM, respectively. Amperometric responses of AA, DA and UA were within 1 s. Moreover, this modified electrode was further applied to determine AA, DA and UA in real samples with satisfactory results.

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A one-step controlled hydrothermal method was described to prepare highly fluorescent polymer dots (PDs) by using polyethylene glycol as the carbon source. The synthesized PDs with an average diameter of 2.5 nm exhibit strong blue fluorescence with high quantum yields (QYs, up to 19%). Further modification of these PDs with glutathione (GSH) endows the resultant GSH–PDs with bi-functional fluorescence responses to temperature and Fe3+. Interestingly, the fluorescence signal of the GSH–PDs is reversibly responsive to the environmental temperature in the range of 20–75 °C. As the GSH–PDs exhibit good biocompatibility, they can pervade the MC3T3-E1 cells and enable the measurement of temperature over the physiological range of 20–45 °C using the confocal fluorescence imaging method. The GSH–PDs were also explored as a fluorescent probe for Fe3+ ion detection, and the linear response range in 0.1–10 μM was observed with a detection limit of 3.7 nM. Thus, the bi-functional measurement of temperature and Fe3+ ions was achieved by the fluorescent PD chemosensor.

We report on a novel strategy for electrochemiluminescent (ECL) chemical sensing by making use of an electrode modified with organosilica nanoparticles (OSiNPs) that are loaded with an iridium(III) complex Ir(pq)2(acac) (where pq stands for 2-phenylquinoline and acac stands for acetylacetonato). Three kinds of OSiNPs have been prepared by using vinyltrimethoxysilane, vinyltriethoxysilane, and phenyltrimethoxysilane, respectively, as the precursors. The OSiNPs were spherical in shape, uniform in size, and highly monodisperse in the aqueous phase. The luminescence properties of the Ir(III) complex remain unchanged after encapsulation. The ECL properties of the modified electrodes were evaluated by using 2-(dibutylamino)ethanol (DBAE) as the coreactant (analyte). The electrode prepared from phenyltrimethoxysilane as the precursor exhibited the best sensitivity for DBAE and gives a detection limit as low as 5.0 × 10−9 mol L−1 and a linear range from 1.0 × 10−8 to 1.0 × 10−6 mol L−1.

Surface-enhanced Raman scattering (SERS)-active substrates assembled by two types of metallic nanoparticles (NPs) were fabricated. Aptamers driven Au nanoflower (Au NF)–Ag NP core–satellite assemblies exhibited amplified SERS signals and achieved the sensitive detection of microcystin-LR (MC-LR) in Tai lake water with the limit of detection (LOD) of 8.6 ± 0.4 pM.

Various microcystins (MCs) produced by cyanobacteria pose a potential threat to water resources, therefore, the determination of the total MCs rather than the content of some specific types of MCs in water is of great importance. Oxidation of MCs causes cleavage of the Adda moiety of microcystins to 2-methyl-3-methoxy-4-phenylbutyric acid (MMPB). In this paper, a new method based on the derivatization of MMPB with methylchloroformate is proposed for the sensitive determination of total MCs. The oxidation conditions as well as the esterification process were optimized through a series of batch experiments. With the optimized procedure, a detection limit as low as 0.56 μg L−1 was achieved for total MCs and the method was successfully applied to the determination of MCs in real samples. A comparison study by using the LC-MS method for direct quantification of the MMPB was also conducted to validate the proposed method. The results proved that the technique is highly sensitive and convenient for the quantification of total MCs in water samples. As an additional feature, the method does not require the use of toxic and expensive standards of MCs in the environmental monitoring.

A new strategy for the fabrication of an electroluminescence sensor was proposed based on the incorporation of electroluminescence (ECL) detection and the molecular imprinting technology (MIT). The sensor fabrication consisted of two steps, the first one was the immobilization of the light emitting material Ru(bpy)32+ on a GC electrode with the well-established Nafion/the multi-wall carbon nanotube (MWCNT) composite film method and the second step involves re-modification of the Ru(bpy)32+/Nafion/MWCNT electrode with a thin film of molecularly imprinted sol–gel polymers with methamphetamine (MA) as the template molecules. The as-prepared sensor exhibited a very high sensitivity and excellent selectivity toward the target molecule MA. A detection limit as low as 4.0 × 10−15 M was achieved for MA with a wide calibration range from 1.0 × 10−10 to 1.0 × 10−14 M. The high sensitivity of the sensor allowed the drugs in a closed container to be detected by their odors.

Efficient nanoprobes for fluorescent and magnetic resonance multimodal imaging (MRI/FI) are in high demand in bioimaging. Herein, a nanoprobe with fluorescent gold nanoclusters (NCs) and magnetic iron oxide composite materials (Fe3O4@AuNCs) was prepared for dual bioimaging. The AuNCs were synthesized using the glutathione (GSH) template. The hydrophobic Fe3O4 magnetic nanoparticles (MNPs) were capped with cetyltrimethyl ammonium bromide (CTAB) to obtain hydrophilic Fe3O4 MNPs. Subsequently, the Fe3O4@AuNCs were prepared by the adsorption of Fe3O4–CTAB on the GSH–AuNCs through electrostatic attraction. The resultant Fe3O4@AuNCs, having an average size of 13.5 nm, can be readily dispersed in water, which displayed a strong red fluorescence (λEm = 650 nm) with a quantum yield of 4.3%. Confocal laser scanning microscopy studies proved that the Fe3O4@AuNCs have good photostability and low cytotoxicity to 293T cells. The magnetic properties of Fe3O4@AuNCs showed that this material was a T2-based contrast agent for MRI with a transverse relaxivity r2 of 20.4 mM−1 S−1. Furthermore, the signal intensity of the T2-weighted MRI decreased with an increase in the concentration. The dual optical and magnetic properties of the synthesized Fe3O4@AuNCs were applicable to dual fluorescence and MR-based imaging.

Microcystins (MCs) are cyanobacterial hepatotoxins capable of accumulation into animal tissues. To determine the total microcystins in water, a novel analytical method, including ozonolysis, methylation of 2-methyl-3-methoxy-4-phenylbutyric acid (MMPB) with methylchloroformate (MCF) and gas chromatography mass spectrometry (GC-MS) detection was developed. The results show that MCs can be oxidized by ozone to produce MMPB at ambient temperature, proving ozonation is an effective, rapid and green method for the transformation of MCs to MMPB without secondary pollution. The oxidation conditions as well as the esterification process were optimized and, subsequently applied to analysis of environmental samples. The method shows wide linear range and high sensitivity with a detection limit of 0.34 μg L−1. The established method was successfully applied to the analysis of microcystins in water samples.