Preparation And Characterization Of The Novel Sensor Of High Density Polyethylene Coated Gold Nanoelectrode

In order to improve detection sensitivity and reduce the effective surface area of the bare gold nanoelectrode（bare GNE）tip,the response currents of several polymer materials coated bare GNE were discussed.By comparing I-t curves,the high density polyethylene（HDPE）was used to encapsulate the electrodes to prepare gold nanoelectrodes（GNE）.Then based on such nanoelectrodes for modification and characterization,the following three electrodes were prepared and applied to the detection of neurotransmitter dopamine（DA）molecules and nitrite ions（NO₂^-）.First,a gold nanoparticle（GNP）-gold nanoelectrode（GNE）（GNP-on-GNE）was prepared,and used differential pulse voltammetry（DPV）to detect the response current of DA,and also used the Surface enhanced Raman spectroscopy（SERS）technology to characterize the nanoelectrode.By comparing the change of the response current before and after modification,it was found that the GNE has a higher response current to DA after modification of gold nanoparticles（GNPs）than GNE which only modified4-mercaptobenzoic acid（4-MBA）molecules.By comparing the relationship between the concentration of DA and the corresponding oxidation peak current,it was found that the oxidation peak current of DA shows a good linear relationship with its concentration in the range of 0⁸00 nM,respectively,the detection of limit can reach to 1×10^-99 M.Through the SERS characterization,it was found that this electrode had strong SERS signals which can also be demonstrated the success of such electrode preparation.Nest,we chose the cucurbit[7]uril molecule as the modified molecule and prepared the second kind of nanoelectrode by self-assembly technique,CB[7]@GNE.First,DA is added,and then silver nanoparticles（AgNPs）are added to form a hot-spot to achieve the SERS signal enhancement.This method allows nanoelectrodes to be applied real-time and on-site detection of DA.At last,in order to detect NO₂^-,palladium nanoparticles-gold nanoelectrodes（PdNPs-on-GNE）were prepared.Cyclic voltammetry（CV）and DPV two kinds of methods were used to separately detect NO₂^-.It can be seen from the CV curve that as the concentration of NO₂^-increases,the response current also becomes larger,indicating that the electrode can detect NO₂^-.When using DPV method,it can be seen that the response current obtained has a certain linear relationship with the concentration of NO₂^-,this kind of nanoelectrode shows a good recognition effect when detecting NO₂^-.When the NO₂^-concentration was between 10 nM to 180 nM,a good linear regression equation was presented,the detection of limit can reach to 1×10^-8M.The results show that this electrode can detect NO₂^-in real time,fast and accurate.