Ultrasound-promoted covalent functionalization of CNFs with thermo-sensitive PNIPAM via grafting-from strategy for on/off switchable electrochemical determination of clothianidin

A thermo-sensitive poly (N-isopropylacrylamide) covalently grafted carbon nanofibers (CNFs-g-PNIPAM) was designed and synthesized via ultrasonic grafting-from strategy for the first time. CNFs-g-PNIPAM could well perform the reversible regulation of hydrophilic/hydrophobic states in aqueous solution upon the switching of the temperature signal. Such distinctive property, CNFs-g-PNIPAM modified glassy carbon electrode (CNFs-g-PNIPAM/GC electrode) shows on/off switchability and temperature-tunable electrocatalytic activity towards clothianidin (CLD) that can be stimulated by external temperature. Cyclic voltammetry of CLD at the CNFs-g-PNIPAM/GC electrode displayed higher peak current at 25 degrees C showing the on state; at 40 degrees C, the peak current was significantly suppressed, showing the off state. The CNFs-g-PNIPAM/GC electrode reveal the better electrochemical performance of 'on/off switching effect compared to virgin PNIPAM, due to the large surface area, good electron-transfer, and an intrinsic property of introduced CNFs. Moreover, this switchable sensing platform allows determining CLD in a good sensitivity (2.32 mu A mu M-1 cm(-2)) with a low detection limit (LOD) of 0.03 mu M at 25 degrees C compared to 40 degrees C (LOD = 1.3 mu M). Besides, this method was successfully applied to the determination of CLD in spiked apple extract and lake water samples. The switchable electrocatalytic performance of CNFs-g-PNIPAM/GC electrode may greatly enhance the flexibility of its application in the area of electrochemical sensor and electrocatalysis.