Study Of Fabrication And Electrochemical Properties Of Carbon Based Nanoelectrode

Nanoelectrodes are tiny electrodes that at least one dimension have nano scale. Nanoelctrodes have many different characteritics, which are different from macro-electrodes. Nanoelectrodes become more and more important in study of basic electrochemistry and applied electrochemistry. One of the most important advantages is that nanoelectrodes allow chemists to study electrochemistry inside a small space. These small spaces include single-cell electrochemistey and the increasingly popular single-molecule electrochemistry etc. The development of nanoelectrodes has extended the application of scanning electrochemical microscopy(SECM). Another important nanosensor is nanopipette electrodes. As a special kind of nanoelectrodes, Nanopipette is easier to be fabricated and can be as smaller than 10 nm. Quartz and borocilicate nanopipette has been used in analytical chemistry, nanoelectrochemistry and the tips of scanning probe microscopy(SPM). In this paper, chemical vapor deposition was used to prepare different types of carbon nanoelectrodes. And they were modified for electroanalytical chemistry, which include measurement of cell transmembrane, single nanoparticle electrocatalysis, rectification and resistive pulse sensor. These applications extend the application of nanoelectrodes. In addition, three phase electrode(TPE) was used to study high hydrophobic anion transfer. This paper includes five main parts:1. CVD was used to prepare carbon nanoelectrodes. By changing the size and shape of nanopipette and CVD conditions to deposit carbon only inside nanopipettes. Completely filled carbon nanoelctrodes, “nanosampler” carbon nanoelectrodes, open carbon nanopipette and carbon nanoelectrodes with carbon completely encased inside melted quartz. The size can be as small as 1-10 nm. RG(RG:the size ratio of insulator part to conductive part) can be 1.2-1.5. TEM and electrochemical cyclic voltammetry were used to characterize different types of carbon nanoelectrodes. Experimental results implied that the structure and electrochemical properties of carbon nanoelectrodes were closely related. They have many potential applications in measurement inside cell, single molecule electrochemistry and single nanoparticle electrocatalysis.2. The completely filled carbon nanoelectrodes were etched at 400℃ to remove carbon and a nanocavity at tip end was obtained. Then Pt black was deposited inside the cavity and TEM images ware obtained. The platinized carbon nanoelectrodeswere used as amperometric probes in SECM. This kind of tip have high specific surface aera and can be used as potentiometric probes. Platinized carbon nanoelectrodes can be positioned near a cell surface by SECM for transmembrane potential measurement. Different from platinized platinum nanoelectrodes, carbon nanoelectros have thin insulating layer. Biological was still live after penetration.3. Single gold nanoparticle(Au NP) was attached onto surface of carbon nanoelctrodes via different methods( physical absorption and electro-static interaction) and the catalytic effect was studied. TEM images and voltammograms of Fc Me OH oxidation indicate that single Au NP was attached. Then carbon annoelctrodes with single Au NP was used to study catalytic effect to HER. Experimental results implied that carbon nanoelectrodes with single Au NP attached by physical absorption have stronger catalytic effect compared to those attached through polyphenelene layer. This method was applicable for study of catalytic effect of single metal nanoparticle with different size, shape and different attaching metrods.4. Carbon nanopipettes(CNPs) ware used as rectification sensor, resistive pulse sensor and dual-channel electrochemical probes. Experimental results implied that the chaging and electric double layer of inner wall of nanopipette canbe changed by bising carbon layer, which can affect the ion current rectification and the absorption and desorption processes of nanopipette. Different content of current rectification can be obtained by biasing carbon with different voltages, which implied that CNP can be used as tunable resistive pulse nanosensors for detection of specific analytes. CNP can also be used as dual channel electrochemicalprobes, which can record ion current through nanopipette and oxidation/reduction cureent of molecules on carbon nanoring simultaneously.5. Fc based TPE was used to study high hydrophobic TPBs anion transferand their hydrophobicity. Experimental results impled that the normally used DMFc based TPE was not applicable for study of high hydrophobic anion TPBs ion transfer while Fc base TPE can satisfy this requirement. Taking advantage of this advantage, the hydrophobic scale of five anions was studied and compared, which follows a descending order: TFPB->TPBCl->TPFB->TPBF->TPB-.