Jianzhang Zhou

Oxidation and adsorption of deoxyribonucleic acid at highly ordered pyrolytic graphite electrode

It shows that calf thymus DNA(CT DNA) can be adsorbed at a highly ordered pyrolytic graphite (HOPG) electrode and detected by differential pulse voltammetry (DPV) and electrochemical atomic force microscopy (ECAFM). It is found that controlled potential pre-polarization influences largely the adsorption of dsDNA while it has little influence on ssDNA. It is demonstrated that ECAFM is useful to exploit adsorption of DNA at HOPGE. The mode of adsorption of DNA at the HOPG electrode that fits best with the experimental data is proposed.

Electrochemical behaviors of DNA at mercury film electrode

Abstract DNA was studied by means of cyclic voltammetry (CV) in combination with a mercury film electrode (MFE) using conventional CV, differential pulse voltammetry (DPV), alternating current voltammetry (ACV). The MFE is sufficiently stable and can be used to study electrochemical behaviors of DNA in negative potential region. This means that MFE is ready to be one kind of solid electrode at which more useful electrochemical techniques can be carried out, such as spectroelectrochemical techniques. Redox characters of DNA treated by pure perchloric acid (HClO 4 ) was studied at MFE. It seems that pure HClO 4 would not only bring about the denaturation of DNA but the degradation of it. Pure HClO 4 is not suitable for performing the denaturation of DNA.

Synergetic effect enhanced photoelectrocatalysis.

We report synergetic effect enhanced photoelectrocatalysis, in which Fe(3+) and Br(-) are used as the acceptors of photogenerated charges on TiO2 nanoparticles. The kinetic rate of interfacial charge transfer is promoted from (4.0 ± 0.5) × 10(-4) cm s(-1) (TiO2/(O2, Br(-))) to (1.5 ± 0.5) × 10(-3) cm s(-1) (TiO2/(Fe(3+), Br(-))). The synergetic effect provides a valuable approach to the design of photoelectrocatalytic systems.

Nanofabrication of the gold scanning probe for the STM-SECM coupling system with nanoscale spatial resolution

Scanning probe is the key issue for the electrochemical scanning probe techniques (EC-SPM) such as EC-scanning tunnel microscopy (STM), EC-atomic force microscopy (AFM) and scanning electrochemical microscopy (SECM), especially the insulative encapsulation of the nanoelectrode probe for both positioning and electrochemical feedbacks. To solve this problem, we develop a novel fabrication method of the gold nanoelectrodes: firstly, a micropipette with nanomter-sized orifice was prepared as the template by a laser puller; secondly, the inside wall of micropipette apex was blocked by compact and conic Au nano-piece through electroless plating; thirdly, the Au nano-piece was grown by bipolar electroplating and connected with a silver wire as a current collector. The fabricated Au nanoelectrode has very good voltammetric responses for the electrodic processes of both mass transfer and adsorption. The advantage lies in that it is well encapsulated by a thin glass sealing layer with a RG value lowered to 1.3, which makes it qualified in the SECM-STM coupling mode. On one hand, it can serve as STM tip for positioning which ensures the high spatial resolution; on the other hand, it is a high-quality nanoelectrode to explore the local chemical activity of the substrate. The nanofabrication method may promote the SPM techniques to obtain simultaneously the physical and chemical images with nanoscale spatial resolution, which opens a new approach to tip chemistry in electrochemical nanocatalysis and tip-enhanced spectroscopy.

Direct correlation of electrochemical behaviors with anti-thrombogenicity of semiconducting titanium oxide films

Biomaterials-associated thrombosis is dependent critically upon electrochemical response of fibrinogen on material surface. The relationship between the response and anti-thrombogenicity of biomaterials is not well-established. Titanium oxide appears to have good anti-thrombogenicity and little is known about its underlying essential chemistry. We correlate their anti-thrombogenicity directly to electrochemical behaviors in fibrinogen containing buffer solution. High degree of inherent n-type doping was noted to contribute the impedance preventing charge transfer from fibrinogen into film (namely its activation) and consequently reduced degree of anti-thrombogenicity. The impedance was the result of high donor carrier density as well as negative flat band potential.

Responsive surface charge transfer doping effect of reductive bio-molecules (glucose, fucoidan, and heparin) contacting on semiconducting titanium oxide films

Titanium oxide films appear to have extensive potentials in various applications largely because of its unique semiconducting properties. Usually, attentions are paid to characterize or tailor their surface electronic states, depending upon specific working circumstances as well as the requirements by their functional performances. Nevertheless, very rarely concern has been taken to the responsive effect on their electronic surface states when they come into contact with surrounding environments, which actually plays an important or even decisive role in their subsequent functions. For instance, cases like biomedical application could normally render the surface sequentially contacting with varying ambient media. In this study, we implemented initial contacting titanium oxide film with three representative bio-molecules (glucose, fucoidan, and heparin), and investigated the responsive effect of charge transfer doping on its electronic properties and its bio-performance. It was shown that the contacting imposed apparently n-type surface-charge-transfer-doping effect on the titanium oxide films. Their surface resistivity increased; their photo-luminance emissions were obviously quenched; their hydrophilic properties were improved; and denaturalization of fibrinogen on the surface was suppressed. Electrons were assigned to inject into titanium oxide film to produce the n-type doping effect. Our finding suggests that the semiconductor biomaterials surface properties and performances might be largely or even decisively influenced by the initial contacting of ambient conditions.

Spectroscopic and photoelectrochemical properties of DNA/CdS nanoparticle composites

DNA/CdS nanoparticle composites (DNA/CdS NPC) containing single or double strands and different concentrations of DNA were constructed in aqueous solutions. The effect of DNA on the photoelectrochemical properties of DNA/CdS NPC was investigated and the spectroscopic properties of DNA/CdS NPC were characterized by TEM, UV-Vis, IR, and fluorescent spectrometry. The results showed that CdS nanoparticles (CdS NPs) were combined with DNA strands through the electrostatic interaction; DNA templates did not affect the band gap of CdS NPs; DNA-templated CdS NPs had a higher density of surface states than that stabilized by Na4P2O7, which enhanced the photoluminescence (PL) intensity whereas restrained the photocurrent response of CdS NPs. Besides, there was certain dependency of both the increase of PL intensity and the decrease of photocurrent response on DNA concentrations in DNA/CdS NPC. The composites were hopeful for applications in both fluorescent tagged detections and quantitative analysis of DNA.

Confined etchant layer technique (CELT) for micromanufacture

Confined etchant layer technique (CELT) is an electro-and/ or photo- chemically induced chemical etching method for micromanufacture originated by our research group, which is distinguished from the LIGA and EFAB. To obtain the micro-/nano- meter precision, there are three strategies of CELT: (1) electro- and/or photo- chemical generation of etchant on the surface of tool; (2) confining the etchant layer to a thickness of micro-/nano- meter; (3) Approaching tool to the workpiece for micromanufacturing. CELT have been proved successful in the micromanufacture on conductive, semiconductive and also insulate workpiece. In this paper, our work on CELT will be reviewed and future research will also be prospected.