Conformationally Adaptive SERS Receptors: Reconfiguring Binding Environments via Dynamic Gauche – Trans Transitions for Broad-Spectrum Ion Sensing

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Abstract
Chemical receptors capable of broadly differentiating small ions remain constrained by static binding architectures that limit adaptability across chemically diverse analytes. Here, we introduce sodium 3-mercaptoethanesulfonate (MES-Na) as a surface-bound, conformationally adaptive SERS receptor that exploits the coexistence of gauche and trans states as an intrinsic sensing dimension. Upon anchoring to a plasmonic silver surface, ion binding selectively redistributes the populations of coexisting conformations rather than inducing a single static complex. This conformation-dependent population modulation generates analyte-specific spectral responses governed by relative binding preferences instead of absolute interaction strength. Using this mechanism, we achieve accurate differentiation of 17 inorganic salts comprising cations spanning charges from +1 to +3 and both monatomic and polyatomic anions, with classification accuracies of 99.6% at micromolar concentrations, substantially outperforming a conformationally rigid control receptor. Beyond single-analyte identification, the bidirectional conformational response enables reliable individual and multiplex quantification of mixed ionic systems, with correlation coefficients exceeding 0.92. In addition, spectral augmentation based on experimentally resolved cation- and anion-specific responses enables accurate identification of previously unobserved cation-anion combinations. Collectively, this work establishes dynamic conformational redistribution as a general sensing principle in which population ratio modulation encodes rich interaction information that enables scalable, broad-range ion sensing.
Funding Information
  • Ministry of Education - Singapore (C-33-18-279-V12)
  • Ministry of Education - Singapore (RG93/24)
  • Research Fund for International Senior Scientists (W2431015)
  • Singapore National Research Foundation Investigatorship (NRF-NRFI08-2022-0011)
  • National Natural Science Foundation of China
  • Competitive Research Programme (NRF-CRP26-2021-0002)

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