Xianxiang Wang

A novel electrochemical sensor based on Au@PANI composites film modified glassy carbon electrode binding molecular imprinting technique for the determination of melamine

A novel molecularly imprinted electrochemical sensor for the rapid detection of melamine was reported in this paper. Glassy carbon electrode (GCE) was modified by Au and polyaniline composites (Au@PANI) deposited on the surface of GCE and were used to increase the electrode sensitivity and to amplify the sensor signal. Melamine template molecule was further assembled onto Au@PANI by the formation of hydrogen bonds, can implement the selective detection of melamine. This simple but efficient electrochemistry analysis platform presents a low detection limit of 1.39×10-6µmolL-1 for detection of melamine, which is remarkably lower than the currently used methods and the previous reports. So, this method may open a new way for the determination of melamine which enables low cost, effective and sensitive determination. This shows the sensor can be potentially utilized for the detection of melamine in food, which allows the sensitive and selective determination of melamine from milk and feed.

Physicochemical Profiles of the Marketed Agrochemicals and Clues for Agrochemical Lead Discovery and Screening Library Development.

Combinatorial chemistry, high‐throughput and virtual screening technologies have been extensively used for discovering agrochemical leads from chemical libraries. The knowledge of the physicochemical properties of the marketed agrochemicals is useful for guiding the design and selection of such libraries. Since the earlier profiling of marketed agrochemicals, the number and types of marketed agrochemicals have significantly increased. Recent studies have shown the change of some physicochemical properties of oral drugs with time. There is a need to also profile the physicochemical properties of the marketed agrochemicals. In this work, we analyzed the key physicochemical properties of 1751 marketed agrochemicals in comparison with the previously‐analyzed herbicides and insecticides, 106 391 natural products and 57 548 diverse synthetic libraries compounds. Our study revealed the distribution profiles and evolution trend of different types of agrochemicals that in many respects are broadly similar to the reported profiles for oral drugs, with the most marked difference being that agrochemicals have a lower number of hydrogen bond donors. The derived distribution patterns provided the rule of thumb guidelines for selecting potential agrochemical leads and also provided clues for further improving the libraries for agrochemical lead discovery.

A novel molecularly imprinted electrochemical sensor based on graphene quantum dots coated on hollow nickel nanospheres with high sensitivity and selectivity for the rapid determination of bisphenol S

In this paper, a novel molecularly imprinted electrochemical sensor (MIECS) based on a glassy carbon electrode (GCE) modified with graphene quantum dots (GQDs) coated on hollow nickel nanospheres (hNiNS) for the rapid determination of bisphenol S (BPS) was proposed for the first time. HNiNS and GQDs as electrode modifications were used to enlarge the active area and electron-transport ability for amplifying the sensor signal, while molecularly imprinted polymer (MIP) film was electropolymerized by using pyrrole as monomer and BPS as template to detect BPS via cyclic voltammetry (CV). Scanning electron microscope (SEM), energy-dispersive spectrometry (EDS), CV and differential pulse voltammetry (DPV) were employed to characterize the fabricated sensor. Experimental conditions, such as molar ratio of monomer to template, electropolymerization cycles, pH, incubation time and elution time were optimized. The DPV response of the MIECS to BPS was obtained in the linear range from 0.1 to 50μM with a low limit of detection (LOD) of 0.03μM (S/N = 3) under the optimized conditions. The MIECS exhibited excellent response towards BPS with high sensitivity, selectivity, good reproducibility, and stability. In addition, the proposed MIECS was also successfully applied for the determination of BPS in the plastic samples with simple sample pretreatment.

A Sensitive fluorescent assay for trypsin activity in biological samples using BSA-Au nanoclusters

A novel, simple, sensitive, and selective fluorometric method was developed for measuring trypsin in biological samples in this article. The method was based upon measuring the quenching of the fluorescence intensity of the bovine serum albumin (BSA) stabilized Au nanoclusters by enzymatic proteolysis. The calibration plot for trypsin was achieved over the concentration range 1-60 nmol L-1 with a correlation coefficient of 0.995 and a limit of detection of 0.6 nmol L-1. The method was also used satisfactorily for the assessment of the trypsin activity and the results showed that the Michaelis-Menten (Km) and catalytic (Kcat) constant values of trypsin for BSA-Au nanoclusters substrate were 1.6×10-5 mol L-1 and 3.8 s-1 at 37 oC, respectively. This enzyme biosensor is of considerable interest due its promise for simple procedure and the established method has great potential in detection of other proteases in clinical diagnostics of various diseases.

An “on-off-on” fluorescent probe for ascorbic acid based on Cu-ZnCdS quantum dots and α-MnO2 nanorods

This work established a fluorescence approach for detecting ascorbic acid (AA) based on Cu-ZnCdS quantum dots (Cu-ZnCdS QDs) and α-MnO2 nanorods. Cu-ZnCdS QDs and α-MnO2 nanorods were characterized by high-resolution transmission electron microscopy (HRTEM), fluorescence spectroscopy, inductively coupled plasma optical emission spectroscopy (ICP-OES) and X-ray diffraction (XRD). In the presence of α-MnO2 nanorods, the fluorescence of Cu-ZnCdS QDs was greatly quenched through the inner filter effect (IFE). Subsequently, AA can trigger the decomposition of the α-MnO2 nanorods which can reduce α-MnO2 to Mn2+ and recover the fluorescence. Under optimal conditions, a linear relation was obtained over the range 5.02−401.77 μM with a 31.62 μM detection limit. Through applying the fluorescent sensing system for detecting AA, a satisfactory result is obtained with recoveries ranging from 89.23% to 110.99%.

Enhanced amperometric sensing using a NiCo2O4/nitrogen-doped reduced graphene oxide/ionic liquid ternary composite for enzyme-free detection of glucose

In our work, a NiCo2O4/nitrogen-doped reduced graphene oxide/ionic liquid (NiCo2O4/N-rGO/IL) nanocomposite was prepared using hydrothermal treatment and calcination followed by a facile reaction with stirring. The composite material was characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), FTIR spectra and thermogravimetric analysis (TGA). The biosensing properties of NiCo2O4/N-rGO/IL, NiCo2O4/N-rGO and NiCo2O4 towards glucose were studied based on a glassy carbon electrode. The NiCo2O4/N-rGO/IL nanocomposite exhibits excellent electrocatalytic activity towards glucose, with a sensitivity of 3.76 mA mM−1 cm−2 and a good linear response from 0.001 mM to 4.555 mM at a potential of +0.5 V. The limit of detection can reach 0.18 μM. It also shows significant electrochemical sensitivity, reproducibility and long-term stability. The good electrocatalytic activity is attributed to the synergistic effect of the metal oxides, graphene oxide and the IL. The N-doping of rGO accelerates the electron transfer of the IL further and enhances its electrochemical properties. In addition, the sensor is effectively applied to the determination of glucose in a human blood serum sample.

A bifunctional NiCo2S4/reduced graphene oxide@polyaniline nanocomposite as a highly-efficient electrode for glucose and rutin detection

A novel NiCo2S4/reduced graphene oxide@polyaniline (NiCo2S4/rGO@PANI) composite was synthesized by a facile two-step hydrothermal treatment and calcination, which was coupled with an in situ polymerization process. A bifunctional electrochemical sensor was developed for glucose electrocatalysis and rutin oxidation based on this composite modified glassy carbon electrode (GCE). The as-prepared composite was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FT-IR). Furthermore, the NiCo2S4/rGO@PANI/GCE composite displayed excellent electrocatalytic activity towards glucose in the linear range of 1–7000 μM and a detection limit of 0.14 μM (S/N = 3). And for rutin, the linear range was 0.01–200 μM with a low detection limit of 0.007 μM (S/N = 3). The sensitivity of this sensor for glucose and rutin was evaluated to be 4.924 and 75.50 μA μM−1 cm−2, respectively. In addition, this sensor delivered high selectivity, good reproducibility, and long-term stability. The modified electrode was also employed to determine glucose in human blood serum samples and rutin in orange juice, buckwheat tea, and compound rutin tablet samples.