Energy-level rich nanorings hybridizing Ag, Au and AgCl as high-performance SERS substrate for numerous molecules.

The current surface-enhanced Raman scattering (SERS) substrates typically feature a single energy level, posing challenges in coordinating electromagnetic enhancement (EM) and chemical enhancement (CM), thereby limiting the sensitive detection of numerous crucial target molecules. In this study, novel aggregated nanorings (a-NRs) hybridizing Ag, Au and AgCl are constructed as SERS substrates. On one hand, the obtained a-NRs exhibit robust localized surface plasmon resonance absorption, whose wavelength can be tuned to match three commonly used laser wavelengths (532, 633 and 785 nm) to gain strong EM effect. On the other hand, these materials possess the Fermi levels of Au nanoparticles and Au/Ag alloy, in addition to the valence band and conduction band of AgCl. The abundant energy levels of the obtained a-NRs facilitate increased charge transfer opportunities for molecules, leading to a strong CM effect. Therefore, the obtained a-NRs show ultra-high SERS sensitivity towards numerous molecules. Moreover, the unique chemical composition makes the obtained a-NRs have good long-term stability in terms of SERS activity. Besides providing high-performance SERS substrates, the valuable experience for coordinating EM and CM to construct highly active SERS substrate demonstrated in this work are expected to significantly advance the application of SERS.