Jinxiang Zeng

New Nanocomposite Based on Prussian Blue Nanoparticles/Carbon Nanotubes/Chitosan and Its Application for Assembling of Amperometric Glucose Biosensor

Abstract A new nanocomposite was developed by combination of prussian blue (PB) nanoparticles and multiwalled carbon nanotubes (MWNTs) in the matrix of biopolymer chitosan (CHIT). The PB and MWNTs had a synergistic electrocatalytic effect toward the reduction of hydrogen peroxide. The CHIT/MWNTs/PB nanocomposite‐modified glassy carbon (GC) electrode could amplify the reduction current of hydrogen peroxide by ∼35 times compared with that of CHIT/MWNTs/GC electrode and reduce the response time from ∼60 s for CHIT/PB/GC to 3 s. Besides, the CHIT/MWNTs/PB nanocomposite‐modified GC electrode could reduce hydrogen peroxide at a much lower applied potential and inhibit the responses of interferents such as ascorbic acid (AA) uric acid (UA) and acetaminophen (AC). With glucose oxidase (GOx) as an enzyme model, a new glucose biosensor was fabricated. The biosensor exhibited excellent sensitivity (the detection limit is down to 2.5 µM), fast response time (less than 5 s), wide linear range (from 4 µM to 2 mM), and good selection.

Layer-by-layer assembled carbon nanotube films with molecule recognition function and lower capacitive background current.

Multilayer films of multiwalled carbon nanotubes (MWCNTs) with molecule recognition function were assembled on glassy carbon (GC) electrode with lower capacitive background current by two steps: first, MWCNTs interacted with beta-cyclodextrin (beta-CD) with the aid of sonication to form beta-CD-MWCNTs nanocomposite, then the beta-CD-MWCNTs nanocomposite was assembled on GC electrode using layer-by-layer (LBL) method based on electrostatic interaction of positively charged biopolymer chitosan and negatively charged MWCNTs. The assembled beta-CD-MWCNTs multilayer films were characterized by scanning electron microscopy (SEM) and cyclic voltammetry. The SEM indicated that the MWCNTs multilayer films with beta-CD were somewhat more compact than that of the MWCNTs multilayer films without beta-CD. The cyclic voltammetric results indicated that the assembled MWCNTs with beta-CD on GC electrode exhibited lower capacitive background current than the assembled MWCNTs without beta-CD. The MWCNTs multilayer films with beta-CD were studied with respect to the electrocatalytic activity toward dopamine (DA). Compared with the MWCNTs multilayer films without beta-CD, the MWCNTs multilayer films with beta-CD possesses a much lower capacitive background current and higher electrocatalytic activity in phosphate buffer, which was ascribed to the relatively compact three-dimensional structure of the MWCNTs multilayer films with beta-CD and the excellent molecule recognition function of beta-CD.

Determination of ultratrace lead with bismuth film electrodes based on magneto-voltammetry

A novel method for the determination of Pb2+ with bismuth film electrodes (BFEs) based on magneto-voltammetry was investigated. In the presence of a 0.6 T external magnetic field, square wave voltammetry of Pb2+ was performed with BFEs. A high concentration of Fe3+ was added to the analytes to generate a large cathodic current during the preconcentration step. A Lorentz force from the flux of net current through the magnetic field resulted in convection. Then, more Pb2+ deposited onto the electrode and larger stripping peak currents were observed. BFEs that were prepared by simultaneously depositing the bismuth and Pb2+ on an electrode offered a mercury-free environment for this determination. This method exhibits a high sensitivity of 4.61 µA µM−1 for Pb2+ over the 1 × 10−8 to 1 × 10−6 M range. A detection limit as low as 8.5 × 10−10 M was obtained with only 1-min preconcentration. The method was successfully applied to determine Pb2+ in real water samples.

Study on Chromium (VI) Reduction Kinetics by Pseudomonas aeruginosa Using a Combined System of Acoustic Wave Impedance Analyzer and UV-Vis Spectrophotometer

A novel system combining acoustic wave impedance (AWI) analyzer with UV-vis spectrophotometer was developed for the study of chromium (VI) reduction kinetics by Pseudomonas aeruginosa. AWI gave information about the growth of Pseudomonas aeruginosa, and UV-vis spectrophotometer gave information about the concentration of chromium (VI) simultaneously. A combined system response model, for chromium (VI) reduction kinetics at lower initial chromium (VI) concentrations, was derived and proved based on the novel system. Taking into account the effect of bacterial growth on chromium (VI) reduction, the new model successfully simulated chromium (VI) bioremediation process. By fitting chromium (VI) reduction data toward the derived model, the kinetic parameters related to the process were obtained. When the concentration of peptone was 10 g L−1, the half-velocity reduction rate constant KC and the maximum specific chromium (VI) reduction rate constant νmax were 0.7682 mg chromium (VI) L−1 and 2.5814 × 10−12 mg chromium (VI) cells−1 h−1, respectively. It was found that the combined system can provide real-time, reliable, and two-dimensional kinetic information, and can be applied to study other biological processes.

A Novel Sensitive Method for the Determination of Cadmium and Lead Based on Magneto‐Voltammetry

Abstract A novel method for the ultratrace determination of Cd2+ and Pb2+ based on magneto‐voltammetry was developed. In the presence of a low strength magnetic field of 0.6 T, square wave stripping voltammetry (SWSV) of Cd2+ and Pb2+ was performed in this determination. A high concentration of redox species Fe3+ was added to the analytes to generate a large cathodic current during the preconcentration step. A large Lorentz force arising from the flux of net current through the magnetic field resulted in convective solution flow due to magnetohydrodynamics. Then more metal ions deposited on the electrode surface at a faster rate and an enhancement as large as 160% for the stripping peak current was observed. Under the optimal conditions, this method exhibits high sensitivities of 5.67 µA µM−1 for Cd2+ and 6.98 µA µM−1 for Pb2+, over the 1×10−8 – 1×10−6 mol l−1 range. Detection limits as low as 9.0×10−10 and 8.6×10−10 mol l−1 for Cd2+ and Pb2+ were obtained with a 2 min preconcentration time, respectively. The method was successfully applied to detect Cd2+ and Pb2+ in real water samples and the results were in agreement with atomic absorption spectrometry.