Nitrogen-doped graphene quantum dots (N-GQDs), with superior biocompatibility, strong resistance to photobleaching and convenient surface grafting, have sparked a surge of related-bio applications. In this study, combined with chromium picolinate (CrPic), N-GQDs synthesized by a facile hydrothermal approach are used to construct an environmentally-friendly sensor for the detection of cholesterol by exploiting the fluorescence enhancement of N-GQDs/CrPic. Herein, CrPic is grafted on N-GQDs via the linker of cysteamine (Cys), and the fluorescence of the N-GQDs is quenched by photoinduced electron transfer (PET), wherein CrPic functions as an electron donating group and the N-GQDs serves as an electron accepting group. Besides, cholesterol is stimulated to form a favourable complex with N-GQDs/CrPic because CrPic also acts as a potential receptor for cholesterol by strong affinity and π–π interaction, and the fluorescence of N-GQDs/CrPic is enhanced indicating that cholesterol could impede electron transfer from CrPic to the N-GQDs. This N-GQDs/CrPic-based sensor has been successfully applied to selectively determine the concentration of cholesterol with a linear range of 0–520 μM and a limit of detection (LOD) of 0.4 μM. Meanwhile, this present sensing strategy in human serum has acceptable practicability, reproducibility and precision.

Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) have been frequently observed in marine aquatic environments; however, little information is available on the occurrence of these compounds in freshwater aquatic environments, including freshwater lakes. In this study, we investigated the occurrence and spatial distribution of typical OH-PBDEs, including 2′-OH-BDE-68, 3-OH-BDE-47, 5-OH-BDE-47, and 6-OH-BDE-47 in surface sediments of Taihu Lake. 3-OH-BDE-47 was the predominant congener, followed by 5-OH-BDE-47, 2′-OH-BDE-68, and 6-OH-BDE-47. Distributions of these compounds are drastically different between sampling site which may be a result of differences in nearby point sources, such as the discharge of industrial wastewater and e-waste leachate. The positive correlation between ∑OH-PBDEs and total organic carbon (TOC) was moderate (r = 0.485, p < 0.05), and site S3 and S15 were excluded due to point source pollution, suggesting that OH-PBDEs concentrations were controlled by sediment TOC content, as well as other factors. The pairwise correlations between the concentrations of these compounds suggest that these compounds may have similar input sources and environmental behavior. The target compounds in the sediments of Lake Taihu pose low risks to aquatic organisms. Results show that OH-PBDEs in Lake Taihu are largely dependent on pollution sources. Because of bioaccumulation and subsequent harmful effects on aquatic organisms, the concentrations of OH-PBDEs in freshwater ecosystems are of environmental concern.

Bisphenol A (BPA) is one of the most prevalent environmental endocrine disrupting chemicals with potential estrogenic activity. Herein we report a facile electrochemical sensing strategy for ultrasensitive detection of BPA based on the hybrid of AuNPs decorated reduced graphene oxide (RGO). This Au@PDA-RGO hybrid was synthesized by in-situ growth of AuNPs induced by polydopamine (PDA) on RGO. Since PDA acts as a moderate reducing agent and an effective linker, AuNPs scatter well on RGO with controllable density, homogeneous size and uniform distribution. With the aid of chitosan (Chit), an electrochemical tyrosinase (Tyr) biosensor based on Au@PDA-RGO was constructed on glassy carbon electrode (Tyr/Au@PDA-RGO-Chit/GCE). This immobilization matrix possesses high conductivity, large active areas and a suitable biological microenvironment. As a result, the constructed Tyr biosensor exhibited good analytical performance for BPA with a high sensitivity of 0.2569 A M−1, a wide linear range from 12.5 nM to 3.68 μM, and a low detection limit of 0.10 nM (S/N = 3). This method was also applied to detect BPA in plastic products, showing good agreement with the values detected by HPLC-MS/MS.

We report on a highly sensitive electrochemical biosensor for determination of cholesterol. The biosensor was fabricated by co-immobilizing bi-enzymes, cholesterol oxidase (ChOx), and horseradish peroxidase (HRP). Voltammetric technique such as cyclic voltammetry and impedance experiment were used to study the characterization of modified electrode step by step. The developed sensor is cheap, disposable, portable and exhibits higher sensitivity. The biosensor expressed a wide linear range up to 300 mg dL–1 in a physiological condition (pH 7.0), with a correlation coefficient of 0.9969. A sensitivity of 13.28 μA mg–1 dL cm−2 which makes it very promising for the clinical determination of cholesterol.

This work reports a novel signal amplification strategy based on three-dimensional ordered macroporous C60-poly(3,4-ethylenedioxythiophene)-1-butyl-3-methylimidazolium hexafluorophosphate (3DOM C60-PEDOT-[BMIm][BF6]) for ultrasensitive detection of thrombin by cascade catalysis of Au-PEDOT@SiO2 microspheres and alcohol dehydrogenase (ADH). Au-PEDOT@SiO2 microspheres were constructed not only as nanocarriers to anchor the large amounts of secondary thrombin aptamers but also as nanocatalysts to catalyze the oxidation of ethanol efficiently. Significantly, the electrochemical signal was greatly enhanced based on cascade catalysis: First, ADH catalyzed the oxidation of ethanol to acetaldehyde with the concomitant generation of NADH in the presence of β-nicotinamide adenine dinucleotide hydrate (NAD+). Then, gold nanoparticles (AuNPs) as nanocatalysts could effectively catalyze NADH to produce NAD+ with the help of PEDOT as redox probe. Under the optimal conditions, the proposed aptasensor exhibits a linear range of 2 × 10−13 to 2 × 10−8 M with a low detection limit of 2 × 10−14 M for thrombin detection and shows high sensitivity and good specificity.

•Spirolactone and spirothiolactone rhodamine-pyrene probes, PyRbS and PyRbO were synthesized.•The two probes showed colorimetric and fluorimetric response to Hg2 + ion with high sensitivity and selectivity in a short time.•PyRbS could be used as a ratiometric probe and could monitor intracellular Hg2 + levels with low cytotoxicity.Two new rhodamine B-based fluorescent probes PyRbS and PyRbO containing pyrene moiety were designed and synthesized. Both of the probes showed colorimetric and fluorometric sensing abilities for Hg2 + with high selectivity over other metal ions. The binding analysis using Job's plot suggested 1:1 stoichiometry for the complexes formed for Hg2 +. Compared with PyRbO, the PyRbS showed higher selectivity and sensitivity due to the thiophilic property of Hg2 + ion. The PyRbS exhibited the linear fluorescence quenching to Hg2 + in the range of 0.3 to 4.8 μM (λex = 365 nm) and 0.3 to 5.4 μM (λex = 515 nm), and the detection limit was 0.72 μM. Moreover, ratiometric changes of PyRbS with Hg2 + in absorption spectrum were observed, which could not be obtained in the combination of PyRbO with Hg2 +. In addition, the methyl thiazolyl tetrazolium (MTT) assay demonstrated that RbPyS had low cytotoxicity and was successfully used to monitor intracellular Hg2 + levels in living cells.

A highly sensitive electrochemical sensor for the detection of mercury(II) ions (Hg2+) was developed by using a three dimensional ordered macroporous polyaniline–platinum (3DOM PANI–Pt) composite film as a sensing platform. 3DOM PANI–Pt was realized by electrochemical co-deposition of Pt nanoparticles and PANI into the sacrificed silica template through the redox reaction involving the monomer aniline (AN) and PtCl62−. The G-rich oligonucleotide strand functionalized Au nanoparticle was employed as the Hg2+-mediated structural switch and to enhance the sensitivity. In the absence of Hg2+, the oligonucleotide strand formed an intramolecular duplex where the G-rich sequence was partially caged. In the presence of Hg2+, the release of the G-rich sequence was observed due to the stabilization of T–Hg2+–T, which formed an active G-quadruplex DNAzyme and catalyzed the reduction of H2O2. Under the optimal conditions, the current signal of H2O2 increased with increasing Hg2+ concentration in the dynamic range from 10−13 to 10−6 M, and the detection limit up to 8.7 × 10−14 M was seen. Further, the sensor was successfully utilized for the determination of Hg2+ in an authentic aquatic sample, with an acceptable accuracy compared to the method commercially available. In this paper, we proposed a general and simple strategy because only one oligonucleotide strand was required for both Hg2+ recognition and signal amplification, potentially allowing the detection of other metal ions or trace pollutants in environmental matrices by simply employing various DNA or aptamer probes.

A copper-catalyzed trifluoromethylation of aryl, vinyl and alkyl zinc reagents with Togni's reagent was described. Mechanistic studies indicated that the aryl group is initially transferred from the zinc reagent to hypervalent iodine to form a tri-substituted hypervalent iodine intermediate. Consequent reductive-elimination via a concerted bond-forming step and/or radical pathway from this intermediate generates the trifluoromethylated arenes.

A novel multichannel chemosensor DR3 juxtaposed with a rhodamine chromophore and the electrochemical characterization of an ethynylferrocene group was developed. This chemosensor could selectively recognized Cu2+ in the presence of other competing ions in a wide pH range, which exhibits multiple responses for UV/vis absorption, fluorescence emission, and electrochemical parameters.

A ferrocene unit is introduced into the salicylaldehyde Rhodamine 6G hydrazone with an alkynyl group to constitute a new chemosensor, R6G-FC, for specifically sensing Cu2+ over other metal ions with multisignals. Upon interaction with Cu2+ in aqueous solution, R6G-FC expresses a detectable fluorescence enhancement along with changes in UV–vis absorption spectra and electrochemical parameters due to the binding-induced spirolactam ring-opening process in Rhodamine 6G. The complexation process between R6G-FC and Cu2+ can be carried out within a wide pH range in a short response time and with a good reversibility. R6G-FC also exhibits an excellent performance in sensing Cu2+ in the “dip-stick” method with an evident color gradation, and confocal fluorescence microscopy imaging results reveal that R6G-FC can be used to visualize Cu2+ in living HeLa cells with low cytotoxicity.

•Mucin 1 is mostly studied as a marker for identifying breast cancer in early stages.•A sandwich-type aptasensor with dual signal amplification was designed for MUC 1.•Electrodeposited poly(o-phenylenediamine)/Au nanoparticles film was used as carrier.•Thionine functionalized carbon nanotubes were used as tags for secondary aptamer.•The MUC 1 aptasensor exhibited a wider linear range and a lower detection limit.Mucin 1 (MUC 1), as a most studied mucin, has become a useful marker for identifying breast cancer in the early stages. In this work, a novel method for the determination of MUC 1 in serum was developed based on a sandwich-type electrochemical aptasensor, which combined a dual signal amplification strategy of poly(o-phenylenediamine)–Au nanoparticles (PoPD–AuNPs) hybrid film as carrier and AuNPs functionalized silica/multiwalled carbon nanotubes core–shell nanocomposites (AuNPs/SiO2@MWCNTs) as tracing tag. The PoPD–AuNPs film provides a suitable microenvironment for stabilizing the primary aptamer (Apt) assembly, and the AuNPs/SiO2@MWCNTs enhances the surface area for immobilizing abundant secondary Apts as well as load large amounts of electrochemical probe thionine (Thi). In the presence of MUC 1, the sandwich-type recognition reacted on the aptasensor surface, and the Thi-AuNPs/SiO2@MWCNTs nanoprobes were captured onto the electrode surface to form biocomplex. AuNPs and MWCNTs could facilitate the electron transfer from Thi to the electrode, thus amplifying the detection response. Under the optimized experimental conditions, the proposed sensing strategy provided a wider linear dynamic range over three orders of magnitude with the detection limit down to 1 pM. Moreover, the aptasensor demonstrated good precision, acceptable stability and reproducibility.

•Free thyroxine concentration in serum is an essential indicator of thyroid function.•An enzyme-free sandwich electrochemical immunosensor for FT4 was fabricated.•3D ordered porous chitosan–Au nanoparticles modified electrode was first prepared.•Magnetic multiwall carbon nanotubes were used as label of secondary antibody.•The FT4 immunosensor could be applied in clinical assay due to good selectivity.The measurement of free thyroxine concentration in serum is considered to be an essential indicator of thyroid function. Here, a novel enzyme-free sandwich electrochemical immunosensor for the detection of FT4 antigen based on the immobilization of primary antibody (Ab1) on three dimensional ordered macroporous chitosan–Au nanoparticles hybrid (3DOM CS–AuNPs) film electrode, and magnetic multiwall carbon nanotubes (MMWCNTs) were used as label of secondary antibody (Ab2). The 3DOM CS–AuNPs film electrode was constructed by one-step electrodeposition of CS–AuNPs composite onto Au electrode with silica opal template. MMWCNTs were prepared by chemical co-precipitation of Fe2+ and Fe3+ salts on carboxylated MWCNTs. Ru(bpy)32+ labeled anti-FT4 (Ru(bpy)32+–Ab2) was covalently attached to MMWCNTs through the formation of amide bond between the carboxylic groups of MWCNTs and the amine groups of antibody. Under the optimal conditions, FT4 was detected in a concentration range from 0.71 fg mL−1 to 1.15 pg mL−1 with a correlation coefficient of 0.998 and a detection limit of 0.20 fg mL−1. Moreover, the immunosensor showed excellent selectivity, good stability, satisfactory reproducibility and regeneration. Importantly, the developed method was used to assay clinical serum specimens, achieving a good relation with those obtained from the commercialized electrochemiluminescent method.

A new pyrene derivative BF bearing a furan group was synthesized via a one-step reaction as a colorimetric and ratiometric chemosensor for Al3+ in ethanol–H2O (9:1, v/v, pH 7.2, HEPES buffer) solution. This chemosensor could selectively recognize Al3+ in the presence of other competing ions. Low limit of detection (LOD) and high association constant revealed its superior sensitivity and binding affinity toward Al3+. Besides, the probe BF performed perfectly in a reversibility test using EDTA. The mechanism of the interaction has been confirmed by 1H NMR titration. Importantly, chemosensor BF has also been utilized to detect Al3+ on test paper strips, which showed its potential for practical applications.A new pyrene derivative BF bearing a furan group was synthesized via a one-step reaction as a colorimetric and ratio metric chemosensor for Al3+ in ethanol–H2O (9:1, v/v, pH 7.2, HEPES buffer) solution.

•Basic information on the physicochemical properties of ginkgo starch will assist industrial application.•Response surface methodology optimized the preparation of high-amylose starch using isoamylase.•The morphological and physicochemical characteristics of normal and high-amylose ginkgo starches were comparedA high-amylose starch was prepared from ginkgo by hydrolysis using isoamylase and its structures (morphology and crystallinity) and physicochemical properties (swelling factor, water solubility and gelatinization) were determined. The experiments used response surface methodology to determine the optimum parameters for enzymatic hydrolysis: pH 5.0 at 52 °C for 170 min, using an enzyme dose greater than 100 IU/ml. The experimentally observed maximum yield of ginkgo amylose under these conditions was 74.74% and the blue value was 0.756. The high-amylose ginkgo starch showed an irregular surface and porous inner structure while the native starch granules were oval with a smooth surface. X-ray showed that the high-amylose starch displayed a V-type structure. Because of its high amylose content and different structural characteristics, high-amylose starch exhibited a higher gelatinization peak temperature (109.25 °C) and water solubility, and a lower crystallinity (19.13%), gelatinization enthalpy (63.83 J/g), and swelling power. The present study has indicated that high-amylose starch prepared using isoamylase has unique functional properties, which lays the foundation for the wider application of ginkgo starch.

A highly sensitive electrochemical sensor for the detection of mercury(II) ions (Hg2+) was developed by using a three dimensional ordered macroporous polyaniline–platinum (3DOM PANI–Pt) composite film as a sensing platform. 3DOM PANI–Pt was realized by electrochemical co-deposition of Pt nanoparticles and PANI into the sacrificed silica template through the redox reaction involving the monomer aniline (AN) and PtCl62−. The G-rich oligonucleotide strand functionalized Au nanoparticle was employed as the Hg2+-mediated structural switch and to enhance the sensitivity. In the absence of Hg2+, the oligonucleotide strand formed an intramolecular duplex where the G-rich sequence was partially caged. In the presence of Hg2+, the release of the G-rich sequence was observed due to the stabilization of T–Hg2+–T, which formed an active G-quadruplex DNAzyme and catalyzed the reduction of H2O2. Under the optimal conditions, the current signal of H2O2 increased with increasing Hg2+ concentration in the dynamic range from 10−13 to 10−6 M, and the detection limit up to 8.7 × 10−14 M was seen. Further, the sensor was successfully utilized for the determination of Hg2+ in an authentic aquatic sample, with an acceptable accuracy compared to the method commercially available. In this paper, we proposed a general and simple strategy because only one oligonucleotide strand was required for both Hg2+ recognition and signal amplification, potentially allowing the detection of other metal ions or trace pollutants in environmental matrices by simply employing various DNA or aptamer probes.