Construction And Application Of Electr-Chemical Sensors Based On Charged Polymers

Charged polymer refers to the polymer compound containing ionizable groups,which is polymerized by many monomers through covalent bonds.Charged polymers applied in the electrochemical sensor fields have attracted much attention due to their specific functional groups,controllable structure,stable physical and chemical properties,excellent electron transfer capabilities and good biocompatibility.In this paper,a series of electrochemical sensors based on the glass carbon electrode and laser drawn glass pipette were constructed by making full use of the excellent properties of charged polymers,and the corresponding researches were carried out,in which include not only the applied research on the detection of environmental pollutants and some important ions in the life system,but also the basic research on the protein adsorption behavior of single charged polymer nanoparticles in nanomedicine.The obtained research results fully demonstrate the practicability of charged polymers,expanding their new application fields.The main research contents are as follows:?1?A simple,sensitive and p H-responsive electrochemical sensor for the detection of hydroquinone?HQ?was developed based on a p H responsive block copolymer polystyrene-b-poly?acrylic acid??PS-b-PAA?and graphene oxide?GO?composite film?PPG?modified glassy carbon electrode?GCE?.The electrochemical behaviors of HQ at the PPG/GCE were studied by cyclic voltammetry and electrochemical impedance spectroscopy.The peak current of the PPG/GCE electrode toward HQ was significantly enhanced at p H 7.0 and greatly suppressed below p H 6.0,which are caused by swelling and shrinking of p H-responsive block copolymer and the synergistic effect with GO.The PPG/GCE exhibited a reversible“On/Off”switch for the HQ electrochemical behaviors between p H 4.0 and p H 7.0.When the p H of the buffer solution is 7.0,the PPG/GCE is in the“On”state,the linear detection range of HQ is from 16?M to 104?M with a detection limit as low as 0.34?M.Furthermore,the PPG/GCE can also successfully detect the HQ concentration of the lake water sample with the recovery rate ranging from 99.75%to 100.5%,indicating that the PPG/GCE sensor provided a powerful avenue for simple,sensitive and convenient detection of HQ.?2?A novel type of electrochemical sensor?PG/GCE?for heavy metal ions has been prepared by using poly?L-glutamic acid??PGA?and graphene oxide?GO?composite materials to modify the GCE.The sensor makes full use of the good binding properties of PGA for the heavy metal ions(such as Cu²⁺,Cd²⁺,and Hg²⁺)as well as good electron conductivity of GO.Under optimized experimental conditions,the contents of Cu²⁺,Cd²⁺,and Hg²⁺in aqueous solution were accurately detected by using differential pulse anodic stripping voltammetry method?DPASV?.The linear range of PG/GCE for Cu²⁺,0.024?M,0.015?M and 0.032?M,respectively.Moreover,the PG/GCE is successfully applied to the determination of Cu²⁺,Cd²⁺,and Hg²⁺in real samples.The research results show that the modified electrode not only has the advantages of simple preparation,high sensitivity,and good stability,but also can be applied to the detection of heavy metal ions in actual samples.?3?Based on the principle of anion exchange,a electrochemical sensor(Fe?CN?₆^3-/GO-Pim/GCE)for the detection of pyrophosphate ion?PPi?was constructed by using poly?1-vinyl-3-butylimidazole chloride??Pim?and graphene oxide?GO?composite material and the electrochemical probe Fe?CN?₆^3-.The sensor makes full use of the different binding affinity between Pim and Fe?CN?₆^3-as well as that between Pim and PPi.The current drop??I?of Fe?CN?₆^3-/GO-Pim/GCE after soaking in different concentrations of PPi was measured by differential pulse voltammetry?DPV?,and there was a good linear relationship between the concentration of PPi and?I from 0.01 m M to 0.8 m M with a detection limit as low as 9.43?M.Furthermore,the sensor can also successfully detect the content of PPi in toothpaste samples with the recovery rate ranging from 95.7%to 100.2%.This study not only provides a simple yet effective route to the determination of PPi,but also opens a new way to developing electrochemical sensors for electrochemically inert species by fully utilizing the supramolecular principles.?4?DNA-functionalized glass micropipets were successfully prepared,and for the first time demonstrate that ion current rectification can be observed at the micrometer scale in symmetric electrolyte solution with DNA modified micropipets,which we call micrometer scale ion current rectification?MICR?.To qualitatively understand MICR,a three-layer model including a charged layer,an electrical double layer,and a bulk layer is proposed.The results of finite element simulation based on Poisson and Nernst-Planck equations qualitatively verify the correctness of the experimental results and the proposed model.DNA functionalized glass micropipette successfully detected the concentration of electrochemically inactive Ca²⁺in solution by ion current rectification method,and there was a good linear relationship between the concentration of Ca²⁺and rectification ratio in the range of 0.25 m M to 5 m M.The research shows that the MICR-based sensors could potentially be used to monitor some important electrochemically inactive substances in the brain system.?5?A new method for label-free analysis of the heterogeneity of protein adsorption on single nanoparticles based on particle collision events at the orifice of a nanopipette was first reported.The dwell time of the particles at the orifice of a nanopipette was strongly dependent on the amount of protein adsorbed on individual polystyrene?PS?particles.Therefore,by counting the dwell time,not only could be obtained the amount of protein adsorbed on PS particles,but also could be used to analyze the heterogeneity of protein adsorption at the single particle level under the same experimental conditions.This method not only opens a new approach to the study of the heterogeneity of physicochemical parameters at the surface of nanoparticles,but also provides a label-free way to analyze the protein adsorption behavior of individual particles,and provides a new thinking to evaluate the anti-protein adsorption performance of nanoparticles.