Studies On Temperature Sensitive Electrochemical Sensor Based On N-vinyl Caprolactam Polymer

In recent years,with the in-depth research on various composite materials,electrochemical sensors have been further developed.A single material is increasingly unable to meet the research requirements,and materials having different kinds of characteristics exhibit synergistic effects by mixing to modify the electrode to make the electrochemical sensor have superior properties.Thermosensitive polymers refer to a class of "smart" polymers whose solubility changes with temperature.Nanomaterials often have excellent properties about electron transport and electrocatalysis due to the unique small size,surface,and quantum size characteristic.In this thesis,we prepared a temperature-sensitive polymer/nanocomposite by ultrasonic mixing of a temperature-sensitive polymer and a nanomaterial,and then modified it on an electrode to form a temperature-responsive biosensor with excellent electrochemical catalytic performance.Repeated changes in the temperature of the external environment can achieve intelligent regulation of biosensors,which can form a reversible "switching" effect,thus opening up a new direction in the field of electrochemical research.The main work of this thesis is as follows:(1)The temperature-sensitive polymer polystyrene-polyN–vinylcaprolactam-polystyrene(PS-PNVCL-PS)was synthesized by reversible addition-fragmentation(RAFT)method and ultrasonically mixed with MWCNTs-COOH,then drop them on glassy carbon electrode to form(PS-PNVCL-PS)/MWCNTs-COOH composite membrane to detect 4-Acetamino phenol(AP).With the LCST of 49°C(PS-PNVCL-PS)as the boundary,when the external solution temperature is higher than 49°C,the electrochemical response of AP on(PS-PNVCL-PS)/ MWCNTs-COOH/GCE is particularly strong,when the outside solution temperature is lower than 49°C,the electrochemical response is weak.Repeatedly changing the temperature of the solution,the peak current decay of AP is small,which proves that the composite membrane modified glassy carbon electrode has a reversible "on-off" effect on the detection of AP.And in the high temperature "on" state,when S/N = 3,the detection limit of AP concentration is 0.068 μmol/L,the linear range is 0.4 ~ 78.8 μmol/L and 78.8 ~ 142.8 μmol/L.(2)The temperature-sensitive copolymer poly(N-vinylcaprolactam-co-N-vinylimidazole)(P(NVCL-co-NVI))was synthesized by precipitation polymerization,and composited with the mixed acid-treated graphitized multi-walled carbon nanotubes(GMWCNTs-COOH),then P(NVCL-co-NVI)/GMWCNTs composite film with temperature response characteristics was prepared,and modified glassy carbon electrode was used to detect hydroquinone(HQ).The LCST of P(NVCL-co-NVI)was 36 ℃,so the composite membrane modified electrode repeatedly detected HQ at 20°C and 48°C with a significant "on-off" effect.In the "on" state,the detection limit of HQ is 0.34 μmol/L,and has a good linear relationship with current at 1.6-9.6 μmol/L and 9.6-555.6 μmol/L.(3)The temperature-sensitive copolymer poly(N–vinylcaprolactam–comethacrylic acid(P(NVCL-co-MAA))was synthesized by free radical polymerization,and the Au nanoparticles(AuNPs)modified glassy carbon electrode was detected.Epinephrine(EP),The LCST of P(NVCL-co-MAA)is 40°C,so the modified electrode with this composite membrane repeatedly detects the "on-off" effect of EP at 20°C and 48°C.The detection range of EP concentration is wide,ranging from 1.6 to 505.2 μmol/L,and the detection limit is 0.56 μmol/L.