The Study Of Preparation Electrochemical Properties And Surface Modification Of Boron-doped Diamond Thin Film

Boron-doped diamond film has the unique combination of outstanding physical and chemical properties, and has been recognized as a very attractive electrode material due to its advantages in comparison with the traditional electrodes. The properties could be further improved through the surface functionalization and modification, which results in the enhancement of applications in biomedical and chemical sensing, electrochemical microelectrode and surface enhanced Raman spectroscopy. In this paper, boron-doped nanocrystalline and polycrystalline diamond films with different boron contents were prepared on Si(100) substrates through controlling B/C ratio in the gas by microwave plasma chemical vapor deposition using trimethyl boron as a boron source. The electrochemical properties of boron-doped nanocrystalline diamond film electrodes and the direct electrochemical detection of glucose were investigated by cyclic voltammetry method. Amine groups were modified to the boron-doped nanocrystalline diamond film surface through photochemical reaction, and layer of gold nanoparticles with high density was immobilized onto amine active diamond surface through self-assembly.The boron doping into diamond resulted in the decrease of growth rate of nanocrystalline and polycrystalline diamond films, and the increase of sp2 carbon content. The increasing of B/C ratio resulted in the formation of ball-like clusters with inhomogeneous size of nanocrystalline diamond film grains, and the reduction of grain size and the increase of crystal defects of polycrystalline diamond films. Two new characteristic peaks located at 500 and 1220cm-1 resulted from Fano interference due to boron doping were observed in the visible Raman spectra of both nanocrysatlline and polycrystalline diamond films.The results of electrochemical performance showed that the boron-doped nanocrystalline diamond film electrode exhibited a wide electrochemical potential window,and nearly reversible electrode reaction, excellent stability and diffusion-controlled reaction kinetics in K3Fe(CN)6 electroyte. The glucose can be directly oxidized and selectively detected in the presence of uric acid (UA) and ascorbic acid (AA) in alkali solution at boron-doped nanocrystalline diamond film electrode, and the wide linear response range and low detection limit was achieved.Amino groups were bonded covalently on the hydrogen-terminated boron-doped nanocrystalline diamond film surface via a photochemical reaction with allylamine. The Amino groups modification rate was about 3.43% after UV photochemical reacting for 12h, and the hydrophilic of the boron-doped nanocrystalline diamond film was improved. Furthermore, gold nanoparticles with different size were immobilized on the amine-temminated diamond surface by self-assembly, and a high dense and well-distributed gold nanoparticles monolayer was obtained. The application of the gold nanoparticles modified boron-doped nanocrystalline diamond film in the surface enhanced Raman spectroscopy was also investigated and a high Raman activity was observed.