Unveiling Electrostatic Interaction Modulated Sensitive and Selective SERS Detection for Negatively Charged Molecules.

Strengthening the interaction between the target and SERS substrate is crucial for sensitive SERS detection; we thereby explored the molecular structure-dependent SERS sensitivity for negatively charged targets on the positively charged SERS substrate. Both experimental and theoretical studies confirm that the SERS sensitivity is determined by the electrostatic interaction between the target and linker. This interaction is not only manipulated by the protonation capacity of the linker and its surface adsorption configuration and geometry but also significantly determined by the target's structure, encompassing electronegativity and the number of interaction sites. The optimized interaction leads to a marked improvement in detection sensitivity of up to 1-3 orders of magnitude. The interaction mechanism revealed in this work not only provides theoretical guidance and technical support for electrostatically driven SERS detection but also offers a conceptual framework that can be extended to various SERS detections based on diverse surface forces.