Zongrang Zhang

Direct electrochemistry and bioelectrocatalysis of horseradish peroxidase based on gold nano-seeds dotted TiO2 nanocomposite.

Gold nano-seeds (GNSs) (capital EF, Cyrillic=2-5 nm) were dotted in TiO(2) colloids and the horseradish peroxidase (HRP) was successfully immobilized on the as-made GNSs-TiO(2) nanocomposite by a convenient and effective method. The matrix integrates the merits of both GNSs and TiO(2), which provides a favorable microenvironment for the immobilization of HRP. The cyclic votammetric results demonstrated that the entrapped HRP achieves direct electron transfer at glassy carbon electrode (GCE). A pair of stable and quasi-reversible redox peaks with a small peak-to-peak separation of 43 mV was observed in phosphate buffer solution. The GNSs stabilized by TiO(2) colloids acted sufficiently as the conducting tunnel to promote the electron transfer. As a result, the electrochemical behaviors were improved in virtue of the synergic effect of TiO(2) and GNSs. The Nafion/HRP-GNSs-TiO(2)/GCE displayed an excellent and rapid electrocatalytic response to the reduction of H(2)O(2). The proposed biosensor exhibited a good linear response in the range from 4.1 x 10(-5) to 6.3 x 10(-4) mol L(-1), with a detection limit of 5.9 x 10(-6) mol L(-1) (at the ration of signal to noise, S/N=3). The apparent Michaelis-Menten constant was estimated to be 0.63 mmol L(-1). Furthermore, the biosensor possesses satisfactory stability and good reproducibility.

Synthesis of anti-aggregation silver nanoparticles based on inositol hexakisphosphoric micelles for a stable surface enhanced Raman scattering substrate

We report a novel method of synthesizing a kind of silver nanoparticles aided by the inositol hexakisphosphoric micelle as a soft template and stabilizer. By controlling the reaction time, UV-vis and TEM observations of the size growth of the nanoparticles are performed. Careful examinations of surface enhanced Raman scattering (SERS) spectra of 2-mercaptopyridine (2-Mpy) on the as-produced silver nanoparticles exhibit very stable and reproducible Raman signals within about 4 months.

A facile method for preparation of gold nanoparticles with high SERS efficiency in the presence of inositol hexaphosphate

This paper described a facile method for preparation of gold nanoparticles with high efficient SERS activity within short reaction time in the presence of an environmentally benign and low-cost reagent named inositol hexaphosphate (IP(6)). IP(6) acted as a tunable cross-linker to obtain a suitable separation (about 2nm) between the neighboring particles for certain surface plasmons by adjusting the dosages of IP(6). When the molar ratio of Au to IP(6) was 10:1, gold particles presented in nano-pearl-necklace pattern, demonstrating the high enhancement factor (>10(7)) for 2-mercaptopyridine (2-Mpy) Raman scattering and high stability (>2months).

Phytic Acid-Based Layer-by-Layer Assembly for Fabrication of Mesoporous Gold Film and Its Biosensor Application

Phytic acid was introduced as a binder to construct a controllable structure at an electrode surface. In this paper, phytic acid and gold nanoparticles were assembled onto the surface of a gold electrode layer-by-layer to form a three-dimensional mesoporous gold interface. Then, a high sensitive horseradish peroxidase (HRP) biosensor was prepared based on the proposed mesoporous interface. Atomic force microscopy, Raman spectroscopy, and electrochemical impedance spectroscopy were applied to characterize the process of forming nanofilms. Hydrogen peroxide was detected with the aid of a hydroquinone mediator to transfer electrons between the electrode and the HRP. The immobilized HRP displayed the feature of a peroxidase and gave an excellent electrocatalytic response to the reduction of H 2 O 2 . The biosensor showed a linear response to H 2 O 2 over a concentration range from 6.5 × 10 ―6 to 1.4 × 10 ―5 mol L ―1 with a detection limit of 3.3 × 10- 6 mol L ―1 (signal-to-noise ratio = 3). The Michaelis-Menten constant (K app M ) was estimated to be 0.078 mmol L ―1 . The biosensor exhibited high sensitivity, good accuracy, and acceptable stability.

Insight in the Relationship between the Structure and Property of Methimazole Monolayers on a Silver Surface: Electrochemical and Raman Study

Methimazole (MMI) monolayers on the silver surface were studied by electrochemical impedance spectroscopy (EIS), electrochemical polarization measurement, and surface-enhanced Raman scattering (SERS) spectroscopy. The EIS mechanism of the silver surface with MMI monolayers was fitted with the mode of LR(QR)(QR), and the electrochemical polarization experimental results showed a high inhibitive efficiency around 82.6%. SERS results indicated that the MMI molecule with a tilted orientation anchored at the silver surface via S(6), N(2), and N(5) atoms, resulting in a strong interaction between the MMI molecule and the surface. In situ electrochemical SERS observation suggested that the molecule experienced a transition state of the adsorption because of the electrochemical hydrogen evolution reaction occurred about -0.1 V vs SCE.

Botanical micelle and its application for direct electrochemical biosensor

This paper is concerned about the entrapment of horseradish peroxidase (HRP) within botanical inositol hexakisphosphoric (IP(6)) micelles for the preparation of enzyme biosensor. The good affinity of IP(6) micelles with the enzyme provides naturally biocompatible microenvironment for the enzyme immobilization, achieving the direct electron transfer between HRP and electrode surface. The resulting biosensor to H(2)O(2) detection exhibits a low detection limit of 0.1 μmol L(-1) (S/N = 3), a quick response time (3s), and a long-term stability. The apparent Michaelis-Menten constant is quite tiny about 0.0016 mmol L(-1).