Application Of Nickel Oxyhydroxide Modified Silicon Photoelectrode In Detecting Analysis

Detection of harmful substances such as heavy metal ions,organic matter is the popular direction of chemical science all the time.All kinds of chemical technology have their unique advantage.With the development of the application of electrochemical detection,the modified film is becoming interesting because it can improve the original electrode's sensitivity,selectivity and so on.Therefore,how to choose better experiment conditions such as modification technique and experiment environment is necessary to develop the technology innovation.Silicon is a good semiconductor,and it can be better used to photoelectric sensor research owing to its photoelectrical effect.There are various forms nickel oxyhydroxides which can be used to modify silicon electrode to achieve the best detection of metal ions in the optimum environment condition.Compared with the traditional buffer solution in the electrochemical measurement,one of highlights in this paper is using deionized water as measurement medium to realize the detection of heavy metal ions at zero voltage.First,we use platinum coated n-type silicon to detect heavy metal ions by photoelectrochemical methods with substances which have photoelectriochemical features.Next,we use NiOOH modified n-type silicon,NiOOH/Pt/Si photoanode repeat all steps to finish the detection of Hg(?)when catechol as a photo-electrochemical probe.NiOOH modified n-type silicon was obtained by cyclic voltammetry in 0.2 M KOH using Ni/Pt/n-Si as working electrode.This research uses non-conductive deionized water environment to achieve the detection of metal ions,offered a new idea to improve performance of silicon-based photoelectrochemical sensors.The research can be mainly divided into three parts as following:1.Photocurrent response of hydroquinone or catechol on Pt/Si electrode and its application for heavy metal ions determinationA platinum film(Pt)and an aluminum layer was coated on the polished and back surface of the n-type silicon wafer,respectively,by vacuum vapor deposition technology.The Ptmodifying silicon(Pt/n-Si)was used as photoanode to detect heavy metal ions,like Hg(?),Cu(?),Cd(?),Pb(?)in deionized water by chronoamperometry method without any voltage.Then we add a constant concentration of hydroquinone(HQ)or catechol(CC)in this experiment environment,continuing our research for heavy metal ions.We find that the existence of heavy metal ions possess catalytic photoelectric chemical behavior of hydroquinone and catechol.Among them the best response is from Hg(?)ions.But the selectivity and sensitivity of this silicon electrode are not good enough,we need to try our best to modify the n-type silicon electrode to improve the performance of the detection of heavy metal ions.2.Photocurrent determination of Hg(?)ions by NiOOH modified silicon electrodeGiven catechol and hydroquinone photoelectric catalysis by heavy metal ions,we just need to do is how to improve the sensitivity of detection.This research used Ni/Pt double layers coated n-type silicon as working electrode.Nickel oxide hydroxide(NiOOH)was formed by cyclic voltammetry in alkaline solution on Ni/Pt/n-Si electrodes.The measurement setup still is a two electrode system at zero voltage.When the catechol existed in deionized water,the sensitivity of the detection of Hg(?)ions could be significantly enhanced with a better linear relationship.In addition,we also try to conduct this experiment in the real water samples.The linear range was from 10 nM to 450 nM for Hg(?)ions concentration.The limit(S/N = 3)of detection reaches to 5.4 nM,7.2 nM and 5.2 nM in three kinds of pure drinking water,respectively.This photoelectric chemical detection of Hg(?)ions has a certain significance,because the maximum allowable levels of Hg(?)ions in drinking water is 30 nM and 10 nM from the world health organization(WHO)regulations and the United States environmental protection agency(EPA),respectively.3.Photoelectrochemical detection of dopamine(DA)and ascorbic acid(AA)by NiOOH modified silicon electrodeFirstly,a NiOOH/Pt/n-Si electrode was used as sensitive component to detect DA and AA in phosphate buffer solution by cyclic voltammetry.Both of them have higher photocurrent response,but there is no clear distinction when adding the concentration of 300 ?M.Secondly,we change the environment of detection.We do the same research in deionized water with a better good result.AA has a significantly better response than DA since the photocurrentcurves' linear relationship of AA is much better than that of DA.In brief,this NiOOH/Pt/n-Si electrode showed considerable stability and repeatability in all experiments.But its anti-interference ability was not good enough and the detection limit and the selectivity will be further improved.