Picloram (PCR), a vastly utilized chlorinated herbicide, is very stable in water and soil with severe ecological and health impacts. It is necessary to establish a fast and highly sensitive technique for accurately detecting trace level PCR in agricultural and environmental samples. We employed a temperature-responsive poly(N-vinylcaprolactam)-tethered multiwalled carbon nanotubes (MWCNT-PVCL) decorated gold nanoparticles (Au@MWCNT-PVCL) catalyst on the electrochemical sensor for the sensitive "On/Off" switch-like detection of PCR. The effect of temperature-sensitive catalyst surface chemistry on electrocatalytic activity was scrutinized. Results showed that the hydrophilic surface of PVCL at 25 °C (<lower critical solution temperature (LCST)) extended to bury the electroactive sites of Au nanoparticles and MWCNT, and the PCR unable to pass over the PVCL to achieve electron exchange process, signifying the "Off" state. Surface wettability of the prepared Au@MWCNT-PVCL then spontaneously switched its hydrophilic to hydrophobic surface one at 40 °C (>LCST) that immensely upgraded PCR oxidation on the catalyst in the electrochemical reaction, signifying the "On" state. The detection of the Au@MWCNT-PVCL modified electrode ranged from 0.02-183 μM with a low detection limit (LOD) of 1.5 nM at 40 °C toward PCR. The proposed sensor was successfully used to detect PCR in real agricultural and environmental samples.
Keywords: Agricultural and environmental samples; Au@MWCNT-PVCL; Hazardous herbicide; Picloram; Thermo-reversible sensor.
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