The Preparation And Application Of Micro/Nano Electrochemical Sensors

A long-standing goal in electrochemistry is to develop high sensitivity and high spatial resolution electrochemical techniques to better understand the mechanisms of charge transfer processes at the interface as well as to facilitate related applications.Ultra-microelectrodes are regarded as promising tools to research electrochemical processes at the microscale.They own the ability to do electrochemistry in smaller spaces,at faster time scales,and with higher sensitivity due to the advantages of small size,high signal-to-noise ratio and fast mass transfer speed.Therefore,ultra-microelectrodes have been widely applied in single cell analysis,fast reaction kinetics and electrochemical probe imaging.We worked on designing and assembling the ultra-microelectrode with functional polymer materials,constructed two functional micro-sensors based on different response principles,and studied their various properties and applications.The details are as follows:1.pH Sensor Based on Poly(maleic acid-acrylic)Modified Nanopipette.A pH-responsive electrochemical sensor was designed and prepared for extracellular pH(pHe)analysis.First,poly(maleic acid-acrylic)was assembled on the inner wall of a 65 nm nanopore.And the inner wall carried different charge at different pH solution due to the different protonation degree of the polymer,which could regulate the rectified current.The same extent of H+inside a nanochannel produced a higher change in the local pH due to the confinement into a femtoliter volume,generating amplification.Therefore,the pH response effect,reversibility and stability of the electrode were investigated in detail.As the result,the electrode was sensitive to slight pH change,and had good stability and repeatability.By adjusting the pH of the solution and changing the applied voltage,the selective transport of ionic species was fully regulated.At last,the pH sensor was used for pHe detection of cancer cell.In the confined space of the melanoma cluster a pH change from 7.0 to 6.3 was detected2.Preparation and Characterization of Micrometric Organic Electrochemical Transistors(Micro-OECTs).The work constructed Micrometric Organic Electrochemical Transistors(Micro-OECTs)with PEDOT:PSS as the active layer,which were made on the tip of dual carbon microelectrodes derived from carbon deposition inside tapered double-barrel micropipettes.The conducting polymers PEDOT:PSS were easily electrodeposited on the surface to comprise the transistor channel.In the OECTs,the conductivity of the active layer can be modulated by the drift of cations between the electrolyte and the conducting film under an applied gate voltage.Their related characteristics were investigated to provide a design basis for subsequent applications.We found that the channel current was sensitive to the small potential change,and the response time of the device to different applied gate voltages was about 400 ms.The transfer curves of the Micro-OECTs shifted to lower gate voltage with the increase of the cation concentration.And the signal amplification and ion response performance of Micro-OECTs were related to the gate.For the device with an Ag/AgCl gate electrode,the response of cations with different concentration showed Nernstian relationship.For devices with Pt and Au gate electrodes,ion sensitivities showed super Nernstian relationship.It is expected that the tapered Micro-OECTs with high sensitivity will become powerful tools for the analysis of living cells.