Zhousheng Yang

A l-cysteine sensor based on Pt nanoparticles/poly(o-aminophenol) film on glassy carbon electrode

Platinum nanoparticles (nano-Pt) and poly(o-aminophenol) (POAP) were fabricated onto the glassy carbon electrode(GCE) to form the nano-Pt/POAP/GCE for the electrochemical determination of L-cysteine. The POAP film was obtained through electrochemical polymerization of o-aminophenol on GCE. The nano-Pt was electrochemically deposited onto the surface of the activated POAP/GCE The resultant nano-Pt/POAP/GCE was characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), and showed excellent electrochemical response to L-cysteine at low oxidative potential in Britton-Robinson (BR) buffer solution (pH=3.0), with good stability and sensitivity, and featured with a low detection limit (0.08 microM, signal/noise=3) and wide linear range (0.4 microM-6.3mM).The mechanism for the electrochemical oxidation of L-cysteine on the nano-Pt/POAP/GCE was also investigated.

Amperometric sensors based on Ni/Al and Co/Al layered double hydroxides modified electrode and their application for hydrogen peroxide detection

Two different hydrogen peroxide sensors were constructed with Ni/Al and Co/Al layered double hydroxides (LDHs) modified glassy carbon electrodes (GCE). Ni (Co)/Al-LDHs were synthesized by electrochemical method and were characterized by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The advantages and shortcoming of the two hydrogen peroxide sensors were described in detail. Compared to Co/Al-LDHs modified electrode, sensors fabricated by Ni/Al-LDHs showed quicker heterogeneous electron transfer rate constants (k(s)), lower detection and better reproducibility. But Co/Al-LDHs modified electrode held the advantages of wider linear range and higher sensitivity. Further more, the different catalytic redox mechanisms of hydrogen peroxide on the Ni/Al/GCE and Co/Al/GCE were firstly comparatively explored.

Synthesis, characterization and properties of hollow nickel phosphide nanospheres

Nickel phosphide (Ni12P5) hollow nanospheres with a mean diameter of 100 nm and a shell thickness of 15–20 nm have been successfully prepared by a hydrothermal-microemulsion route, using NaH2PO2 as a phosphorus source. XRD, EDS, (HR)TEM, SEM and the SAED pattern were used to characterize the final product. Experiments showed that the as-prepared nickel phosphide hollow nanospheres could selectively catalytically degrade some organic dyes such as methyl red and Safranine T under 254 nm UV light irradiation. At the same time, the nickel phosphide hollow nanospheres showed a stronger ability to promote electron transfer between the glass–carbon electrode and adrenalin than nickel phosphide honeycomb-like particles prepared by a simple hydrothermal route. A possible formation process for nickel phosphide hollow nanospheres was suggested based on the experimental results.

The interaction of taurine–salicylaldehyde Schiff base copper(II) complex with DNA and the determination of DNA using the complex as a fluorescence probe

The interaction of taurine-salicylaldehyde Schiff base copper(II) (Cu(TSSB)2(2+)) complex with DNA was explored by using UV-vis, fluorescence spectrophotometry, and voltammetry. In pH 7.4 Tris-HCl buffer solution, the binding constant of the Cu(TSSB)2(2+) complex interaction with DNA was 3.49 x 10(4) L mol(-1). Moreover, due to the fluorescence enhancing of Cu(TSSB)2(2+) complex in the presence of DNA, a method for determination of DNA with Cu(TSSB)2(2+) complex as a fluorescence probe was developed. The fluorescence spectra indicated that the maximum excitation and emission wavelength were 389 nm and 512 nm, respectively. Under optimal conditions, the calibration graphs are linear over the range of 0.03-9.03 microg mL(-1) for calf thymus DNA (CT-DNA), 0.10-36 microg mL(-1) for yeast DNA and 0.01-10.01 microg mL(-1) for salmon DNA (SM-DNA), respectively. The corresponding detection limits are 7 ng mL(-1) for CT-DNA, 3 ng mL(-1) for yeast DNA and 3 ng mL(-1) for SM-DNA. Using this method, DNA in synthetic samples was determined with satisfactory results.

Oxidative damage to DNA by 1,10-phenanthroline/l-threonine copper (II) complexes with chlorogenic acid

The oxidative DNA damage by copper (II) complexes in the presence of chlorogenic acid was explored using agarose gel electrophoresis. The extent of pBR322 DNA damage was enhanced significantly with increasing concentration of [Cu-phen-Thr] complex and incubation time. A fluorescence quenching activity of calf thymus DNA–EB was observed more remarkably with chlorogenic acid than without chlorogenic acid. The fluorescence measurements suggested that [Cu-phen-Thr] complex not only can bind to DNA by intercalation but also can damage the double strand DNA in the presence of chlorogenic acid. Further, 8-hydroxy-2′-deoxyguanosine, a biomarker of DNA oxidative damage was determined by electrochemical method. The control experiments revealed that the structure of copper (II) complexes affected capability of complex to DNA damage. The planar structure copper (II) complex showed high efficiency to DNA damage. The chlorogenic acid as biological reductant could improve copper (II) complex to DNA damage. A mechanism on [Cu-phen-Thr] complex to DNA damage in the presence of chlorogenic acid was proposed.

Determination of 1-naphthol with denatured DNA-modified pretreated glassy carbon electrode

Abstract A highly sensitive electrochemical biosensor for the detection of trace amount of 1‐naphthol was designed. Acid‐denatured DNA were immobilized onto the pretreated glassy carbon electrode (GCE(ox)) surface. Two well‐defined oxidation peaks were observed on the denatured DNA‐modified GCE(ox) at about +0.80 V and +1.10 V (vs. Ag/AgCl) in 0.10‐M acetate buffer (pH 5.0). The peak current of the guanine residue decreased with increasing concentration of 1‐naphthol. The optimum experimental conditions for the detection of 1‐naphthol were explored, and the calibration was linear for 1‐naphthol in the range of 1.0×10−8−1.1×10−6 M, with a correlation coefficient of 0.998. The limit of detection (LOD) was 5.0×10−9 M (S/N=3).

Sensitive electrochemical determination of promethazine hydrochloride based on the poly(p-aminobenzene sulfonic acid)/flowerlike ZnO crystals composite film

ZnO crystals were synthesized by a hydrothermal decomposition process in the presence of poly(vinylpyrrolidone) as the surfactant, then characterized by scanning electron microscopy and X-ray diffraction. The composites of flowerlike ZnO combined with poly(p-aminobenzene sulfonic acid) (p-ABSA) were immobilized on a glassy carbon electrode for constructing a sensitive electrochemical sensor. The electrocatalytic response to PHZ on the prepared sensor was measured using cyclic voltammetry and differential pulse voltammetry (DPV) in PBS buffer (pH 8.0). The fabricated sensor was successfully used for the detection of promethazine hydrochloride (PHZ) in a 0.10 M phosphate buffer solution (PBS) at pH 8.0. Under optimal conditions, the linear concentration range of PHZ obtained at p-ABSA/ZnO composite film using DPV technique was 0.01 μM to 59.84 μM (R = 0.997) and the detection limit was 0.004 μM at S/N = 3. Furthermore, the prepared sensor displayed voltammetric responses with excellent reproducibility, high sensitivity and stability for PHZ. Therefore, the p-ABSA/ZnO composite film has become a promising application for quantitative determination of PHZ.

Electrocatalytic Oxidation of Hydrogen Peroxide Based on the Shuttlelike Nano-CuO-Modified Electrode

CuO nanocrystals were prepared with hydrothermal synthesis method. The morphology of the nano-CuO was characterized by scanning electron microscopy. The prepared shuttlelike CuO nanocrystals were modified to glass carbon electrode (GCE) to form nano-CuO/GCE modified electrode. The obtained modified electrode showed an excellent electrocatalytic property towards hydrogen peroxide in 0.01 M NaOH containing 0.09 M KCl electrolyte. Under the optimal experiment conditions, the electrocatalytic response current of this sensor was proportional to the H2O2 concentration in the range of 0.02 μM~250 μM with a detection limit down to 7 nM (signal/noise = 3). The sensitivity was calculated to be 227 μA/mM. The H2O2 sensor exhibited low detection limit, fast response time, and good reproducibility and could be applied to determine hydrogen peroxide.

Detection of DNA Damage Induced by Hydroquinone and Catechol Using an Electrochemical DNA Biosensor

DNA damage induced by hydroquinone and catechol was detected by an electrochemical method. Calf thymus DNA was immobilized onto the surface of a pretreated glassy carbon electrode (GCE(ox)) to form a DNA/GCE(ox) modified electrode. Then the DNA/GCE(ox) was incubated in acetate buffer solution containing hydroquinone or catechol at a constant potential for the desired time. Differential pulse voltammetric experiments were then performed. The anodic peaks corresponding to the oxidation of guanisine and adenosine on the electrode could be observed on voltammetric curves. The experimental results showed that DNA damage could be detected using electrochemical DNA biosensors. The extent of DNA damage could be electrochemically recognized via the change of the anodic peak current. DNA damage induced by hydroquinone was greater than that by catechol. The response conditions were optimized with respect to DNA concentration, pH, ionic strength, and other variables.

A novel electrochemical sensor based on a glassy carbon electrode modified with Cu–MWCNT nanocomposites for determination of hydroquinone

A new electrochemical sensor based on copper nanoparticles (Cu NPs) and multi-walled carbon nanotubes (MWCNTs) was fabricated for the determination of hydroquinone (HQ). A type of spotty-like Cu NP located on MWCNT (Cu–MWCNT) nanocomposites was synthesized with a microwave-assisted method. The morphology and phase of Cu–MWCNTs nanocomposite were characterized using scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were performed to characterize the electrochemical performance and surface characteristics of the as-prepared sensor. The composite electrode exhibited excellent activity with increased electrochemical signals towards the redox of HQ, owing to the synergistic effect of Cu NPs and MWCNTs. Under the optimized conditions, the linear response range was from 0.10 to 100 μM for HQ. The detection limit for HQ was as low as 0.04 μM. Moreover, the modified electrode presented a good reproducibility and excellent anti-interference performance. The performance of the developed sensor for the detection of HQ was evaluated in practical samples with satisfying results.