The electrochemical deposition of Pt-Ru nanoparticles on carbon nanotube electrode and their electrocatalytic properties have been investigated in this paper. Carbon nanotubes (CNTs) used in this paper are grown directly on graphite substrate by chemical vapor deposition (CVD). The Pt-Ru nanoparticles are synthesized by potentiostatic method from 0.5M H2SO4 aqueous solutions with ruthenium chloride and chloroplatinic acid at 0.25V. The micrographs of Pt-Ru/CNT/graphite electrode are characterized by scanning electron microscopy. The electrocatalytic properties of Pt-Ru/CNT/graphite electrodes for methanol oxidation have been investigated by cyclic voltammetry in 1.0M CH3OH+0.5M H2SO4 aqueous solutions. The effect of ratios of Pt to Ru in the deposition bath solution on the electrocatalytical properties of Pt-Ru/CNT/graphite electrode was also investigated. The results show that the peak potential for methanol oxidation shifts to lower potential and the existing Ru can improve the stability and activity of electrode for methanol oxidation. This may be attributed to the bifunctional mechanism of Ru to Pt, which also reveals that CNTs have good potential applications as catalyst supports in direct methanol fuel cell (DMFC).

Immobilization of DNA on carbon nanotubes plays an important role in the development of new types of miniature DNA biosensors. Electrochemical characteristics of the immobilization of calf thymus DNA molecules on the surfaces of multi-walled carbon nanotubes (MWNTs) have been investigated by cyclic voltammetry and electrochemical impedance analysis. The peak currents for Fe(CN)63/Fe(CN)64redox couple observed in the cyclic voltammograms decrease and the electron-transfer resistance (Ret) obtained from the Nyquist plots increase due to the immobilization of DNA molecules (dsDNA or ssDNA) on the surfaces of MWNTs. Most of calf thymus DNA are covalently immobilized on MWNTs via diimide-activated amidation between the carboxylic acid groups on the carbon nanotubes and the amino groups on DNA bases, though the direct adsorption of the DNA molecules on MWNTs can be observed. Additionally, the interaction between DNA molecules immobilized on MWNTs and small biomolecules (ethidium bromide) can be observed obviously by cyclic voltammetry and electrochemical impedance analysis. This implies that the DNA molecules immobilized at the surface of MWNTs, with little structure change, still has the ability to interact with small biomolecules.

imum response current density were calculated to be 7.17mM and 7.32μAcm-2, respectively.

An amperometric glucose biosensor is developed, based on immobilization of glucose oxidase (GOX) in an electrochemically polymerized, non-conducting poly (o-aminophenol) (POAP) film at Prussian blue (PB)-modified platinum (Pt) microelectrode. Effects of polymerization cycle number for POAP and PB, applied potential used in the determination, pH value of the detection solution and electroactive compounds on the amperometric response of the sensor were investigated and discussed. The electroactive property and rough surface of PB film result in the improvement of the detection limit and the increase of the maximum response current and sensitivity. The biosensor based on Pt/PB/POAP/GOX electrode has two times lower detection limit, five times larger maximum current and nine times higher sensitivity than those of the biosensor based on Pt/POAP/GOX electrode. Additionally, the biosensor shows fast response time, large response current, and good anti-interferent ability for l-ascorbic acid, uric acid and acetaminophen. Excellent reproducibility and stability of biosensor are also observed.

The electrochemical behavior of L-cysteine (CySH) on platinum (Pt)/carbon nanotube (CNT) electrode was investigated by cyclic voltammetry. CNTs used in this study were grown directly on graphite disk by chemical vapor deposition. Pt was electrochemically deposited on the activated CNT/graphite electrode by electroreduction of Pt(IV) complex ion on the surface of CNTs. Among graphite, CNT/graphite, and Pt/CNT electrodes, improved electrochemical behavior of CySH oxidation was found with Pt/CNT electrode. On the other hand, a sensitive CySH sensor was developed based on Pt/CNT/graphite electrode. A linear calibration curve can be observed in the range of 0.5μM-0.1mM. The detection limit of the Pt/CNT electrode is 0.3μM (signal/noseD3). EVects of pH, scan rate, and interference of other oxidizable amino acids were also investigated and discussed. Additionally, the reproducibility, stability, and applicability of the Pt/CNT electrode were evaluated.