Electrostatic enrichment at nanoporous hotspots: A general strategy for charge-selective SERS detection in complex...

Achieving controllable nanostructures and tunable molecular adsorption/orientation remains a key challenge in advancing surface-enhanced Raman spectroscopy (SERS) toward efficient enhancement and ultrasensitive detection. This work reports nanoporous pAg-Au-SPE substrates combined with a pH-regulated electrostatic capture electrochemical SERS (EC-SERS) strategy for sensitive detection of thiacloprid (THIA). Ag₇O₈NO₃ micropyramids on Au-SPE were reduced with NaBH₄ to form nanoporous Ag micropyramids with precisely tunable pore sizes, resulting in controllable nanostructures with dense and uniformly distributed hotspots. Under acidic conditions, THIA is protonated, and applying a potential of -0.7 V renders the pAg-Au-SPE surface negatively charged, driving electrostatic capture and enrichment of THIA at hotspots. Experimental and theoretical results reveal that protonated THIA anchors its positively charged nitrogen atoms near the Ag surface, reorienting from near-planar to more perpendicular adsorption and enhancing SERS signals. Using the intrinsic band of pAg-Au-SPE as an internal standard, the EC-SERS strategy achieves a detection limit of 1.36 nM, three orders of magnitude lower than conventional SERS (1.41 μM), and yields results in real samples that agree well with HPLC. This work can be extended to sensitive detection of diverse hazardous analytes and offers new perspectives for advancing SERS applications.