Studies Of Electrochemical Sensors Based On PH-Responsive Materials Polyacrylic Acid And Chitosan

As an important part of electrochemical modified electrodes,modified materials have been widely concerned by scientists from all over the world for a long time.In the initial stage,we usually use single-function materials for the preparation of electrochemical sensors,however,in the last decade,with the rapid development of responsive materials,more and more researchers have been working on smart electrochemical sensors.pH-Responsive polymers are a common group of stimuli-responsive polymers that can respond to solution pH by undergoing structural and property changes,and according to these properties,we can combine it with nanomaterials,such as carbon nanomaterials and metal nanomaterials,which have excellent conductivity and electrocatalytic properties,to prepare novel pH-switchable electrochemical(bio)sensors.The main research content and results of this paper are shown below:(1)We used a simple esterification reaction to effectively combine a pH-sensitive polymer,polyacrylic acid(PAA)with carbon nanomaterials,graphene oxide(GO)and multi-walled carbon nanotubes(MCNTs)to prepare an exceptional nanocomposite,GO-MCNTs-PAA,which has a great water solubility and superb electrical properties.Further,we develop an electrical biosensor for the determination of histamine based on the immobilization of diamine oxidase into the GO-MCNTs-PAA membrane.(2)A pH-sensitive electrochemical sensor for the detection of ascorbic acid(AA)was prepared by mixing two pH-sensitive materials,chitosan(CS)and Polyethyleneimine(PEI)on the glassy carbon electrode.Potassium ferricyanide,as a probe solution,was used to study the pH-sensitive characteristic of the modified electrode.The experimental results showed that the modified electrode could not effectively detect AA at pH 9 and showed "off" state,while at pH 4,it showed excellent detection of AA.The linear detection range was from 10 μM to 0.9 mM toward AA with the limit of detection(LOD)of 4.52 μM(S/N=3).(3)Silver nanoparticles(AgNPs)with good dispersibility was prepared by a simple chemical reduction reaction,and then we used it to effectively combine with chitosan(CS)and ionic liquids(IL)to prepare a pH-sensitive electrochemical sensor for the detection of hydrogen peroxide(H2O2).The modified electrode showed the "off"state in the pH 8 solution while showed the "on" state in the pH 5 solution.Determination of H2O2 was carried out by amperometry,and the amperometric response of the sensor varied linearly ranging from 0.25 μM to 25.9 mM with LOD of 0.03 μM.Further,the modified electrode was used for the determination of H2O2 in real samples from medical hydrogen peroxide,giving values of recovery found by standard addition method in the range of 95.6%-103.8%.