Di-frequency ultrasound synergistic activation of two piezoelectric catalysts for SERS determination of ultratrace chlorothalonil

Ultrasound-driven piezoelectric enhancement is interesting to scientists. These effects are used to fabricate piezoelectric nanogenerator (PENG) and triboelectric nanogenerator (TENG) for energy harvesting and self-powered sensing. There are no reports about di-frequency ultrasound piezoelectric nanocatalysts in water phase, and their application to SERS quantitative analysis. Therefore, developing a selective and sensitive ultrasound piezoelectric nanocatalysts-SERS method is of great importance. In this study, using piezoelectric nanoquartz (SiO₂) and polytetrafluoroethylene (PTFE) as substrates, chlorothalonil (CTN) as template molecule, and poly(3,4-ethylenedioxythiophene) (PE) as the molecularly imprinted layer, two new nanosurface molecularly imprinted polymer nanocatalysts of SiO₂@PE and PTFE@PE were synthesized via a solvothermal procedure. Under simultaneously applied dual-frequency ultrasonic irradiation (28/80 kHz), the two nanocatalysts significantly enhanced the electron transfer in the 3,3′,5,5′-tetramethylbenzidine (TMB)–H₂O₂ reaction, producing the oxidized TMB (TMBox) with strong SERS activity. Binding of CTN to the probe inhibited the catalysis, resulting in the SERS signal decreasing linearly. This strategy notably improved detection sensitivity, increasing the slope ratio of 42.7 times, with detection limit of 5 pmol/L CTN. Based on the results, a reasonable difrequency ultrasound piezoelectric nanocatalytic enhanced mechanism was proposed.