Preparation Of Boron Doped Diamond And Its Application In Sensors

Diamond is a typical multi-functional material with high hardness,high thermal conductivity,and corrosion resistance.Pure diamond is an insulator,and diamond doped with a certain amount of boron impurities will become p-type semiconductor,or even become a conductor after heavy boron doped.And the change of boron doping concentration directly affects its electrical properties.In addition,boron-doped diamond?BDD?films have great advantages in electrochemical field,such as low background current,wide potential window and high electrochemical stability.However,its electrochemical performance is mainly affected by boron doping concentration in BDD.Therefor,BDD films were prepared by electron-assisted hot filament chemical vapor deposition?EA-HFCVD?in this paper,and the effects of boron content on the quality and electrochemical properties of BDD films were emphasized to study.Studies had shown that,the boron source flow rate increased from 3 to 36 sccm,the quality of all BDD films was as follows:diamond grain integrity,diamond grain size increased,non-diamond carbon content remained at a low level,and the BDD films maintained high crystallinity.Raman spectra of{100}and{111}crystal planes of BDD films both showed the sp³ carbon-carbon bond characteristic peaks,and the intensity of the peaks showed a decreasing trend.When the boron source flow rate reached 36sccm,the B/C atomic ratio on the surface of the BDD film was about 10000 ppm,the carrier concentration was 6.57×10²⁰ cm^-3,and its conductivity was the best.From the electrochemical performance analysis of the BDD films,it showed that the potential window of BDD film decreased gradually with the increase of boron concentration.The potential window measured in phosphate buffer?pH 7?was wider,and the maximum potential window measured by BDD/Ta electrode with boron flow rate of 3 sccm was 3.88V.The electron transfer rate constant and electrochemical active area of BDD/Ta electrodes both increased with the increasing of boron concentration.The effective active surface area of BDD/Ta electrode with a boron source flow rate of 36 sccm was 1.31 cm² and its electron transfer rate constant reached 2.4×10^-1 cm·s^-1.Studies on the electrochemical response of BDD/Ta electrodes to benzene organic pollutants and biomolecules indicated that BDD/Ta electrodes showed high oxidation activity for organic molecules bearing a benzene ring,such as phenol,hydroquinone,catechol,resorcinol,aniline,2-aminophenol,and 4-aminophenol.The sensitivity of BDD/Ta electrode with a boron source flow rate of 36 sccm to hydroquinone was 0.316?A?M^-1cm^-2 and its limit of detection was 0.59?M.Besides,the analysis of dopamine and melatonin showed that BDD/Ta electrode had high detection sensitivity and strong anti-interference ability.The limits of detection for dopamine and melatonin were 0.02?M and 0.18?M,respectively.The results showed that BDD/Ta electrode prepared with a boron source flow rate in the range of15-36 sccm had fast electron transfer rate,high selectivity and high sensitivity to analytes,and was suitable to use in electrochemical sensors.Simultaneous detection of multi-target substances by BDD/Ta electrodes optimized to only change boron content was realized.In addition,BDD/Ta electrode with high boron source flow rate has high electrocatalytic oxidation performance,and it will have good prospects if it is used as wastewater treatment electrode of advanced oxidation technology.