Electrochemical Sensor Based On PH Sensitive Polymer

In recent years,the research of electrochemical sensors in the fields of environmental detection,food safety and nutrition,medicine and clinical diagnosis has continued to deepen.With the requirements such as sensitivity and selectivity improving,a single material can no longer meet actual needs.Stimuli-responsive polymers are polymers that can quickly respond to external micro stimuli.It can be used in the electrochemical field to improve its selectivity and achieve environmental response.The proper addition of carbon materials and other conductive materials can improve the stability and sensitivity of the composite material.In this paper,a mixture of carbon materials,photoelectric materials and pH-sensitive polymers are used to modify electrodes to construct an electrochemical sensing platform with pH-sensitive switchable behavior,so as to realize intelligent detection of different target.The specific content is as follows:（1）Synthesize independent zinc oxide nanorods by hydrothermal method,then synthesize zinc oxide@zeolite-like imidazole skeleton（Zn O@ZIF-8）through a simple chemical bath,and then combine it with chitosan（CS）and polyethylene imine（PEI）and carboxylated multi-walled carbon nanotubes（MWCNTs-COOH）,mixed as modified materials and modified on the glassy carbon electrode.It is found through experiments that the CS/PEI/MWCNTs-COOH/Zn O@ZIF-8 composite modified electrode has a detection limit of 2.46μM for ascorbic acid（AA）at pH=4,and the linear range is 10μM～110μM and 110μM～580μM.At the same time,the modified electrode has outstanding pH reversibility.（2）The zeolite imidazole ester framework（ZIF-8）was synthesized by hydrothermal method,and then carbonized at high temperature in N₂ to obtain nitrogen-doped porous carbon-zinc oxide（NPC-Zn O）nanopolyhedral black powder,which was combined with pH-sensitive materials CS,Ionic liquid（IL）,graphene quantum dots（GQDs）are prepared into composite materials and modified on the electrode,constructing a pH smart electrochemical sensor CS/IL/GQDs/NPC-Zn O to detect dopamine（DA）.The experimental results show that the linear range of the modified electrode is 8.57～334.3μM,and the detection limit is 1.68μM.The modified electrode has good pH reversibility and stability.（3）Graphene quantum dots-titanium dioxide（GQDs-Ti O₂）were synthesized,and then combined with the pH-sensitive polymer polyurethane-polyethylene glycol（PAE-PEG）and MWCNTs-COOH to prepare a pH-responsive composite film PAE-PEG/MWCNTs-COOH/GQDs-Ti O₂.At pH=6,the molecular chain of PAE-PEG is in a stretched state,hydroquinone（HQ）is difficult to reach the electrode surface through the polymer membrane,and the electrochemical behavior of hydroquinone cannot proceed;when pH=9,PAE-PEG polymer chain shrinks,making MWCNTs-COOH contact with the electrode surface,the modified membrane interface resistance is reduced,the electron transfer rate is accelerated,and the electrochemical behavior of HQ on the composite electrode is turned on.Experiments show that the detection limit of the modified electrode is 0.148μM,and the linear range is 1.5μM～279μM.