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).

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.

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.

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).

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.

Raman mapping and in situ SERS spectroelectrochemical studies of 6-mercaptopurine SAMs on the gold electrode.

The self-assembled monolayers (SAMs) of 6-mercaptopurine (6MP) were formed at the roughened polycrystalline gold surfaces in acid and alkaline media. The time-dependent Raman mapping spectral analysis in conjunction with the quantum calculations for the vibrational modes using ab initio BLYP/6-31G method suggested that both of the resulted 6MP SAMs adopted the same adsorption mode through the S atom of pyrimidine moiety and the N7 atom of the imidazole moiety anchoring the gold surface in a vertical way. The in situ surface-enhanced Raman scattering spectroelectrochemical experiment was conducted to examine the stability of the SAMs at various bias potentials. It was found that the detaching process of the 6MP SAMs from the surface involved one electron reduction as the voltage was applied at ca. 0.7 V vs a standard calomel electrode.