Real-Time Monitoring of Molecules in Aqueous Solution via a Surface-Functionalized Ag-Anodic Aluminum Oxide Surface-Enhanced Raman Scattering Platform

Real-time monitoring of molecular species in aqueous solutions is crucial for diverse scientific applications, from biomedical diagnostics to environmental analysis. In this study, we investigate the selective detection and discrimination of specific molecules in aqueous solution samples using a Ag-coated anodized aluminum oxide (Ag-AAO) surface functionalized with thiol molecules. Our investigation harnesses the power of surface-enhanced Raman scattering (SERS) synergized with principal component analysis (PCA) to elucidate the distinctive signatures of aqueous dopamine and l-tyrosine molecules. By scrutinizing the Raman spectra of surface-treated molecules, we unveil nuanced variations driven by the unique functional groups of the thiol molecules and their dynamic interactions with the target molecules in solution. Notably, we observe different alterations in the SERS spectra of Ag-AAO surface-functionalized boronic acid molecules for detection of dopamine and l-tyrosine, even at a concentration as low as 10^-8 M. Moreover, the spectral PCA elucidates the discrimination of dopamine and l-tyrosine within the aqueous environment attributed to the different molecular interactions near SERS-active hotspots. Our findings facilitate real-time monitoring of minute analytes with exceptional molecular selectivity, ushering in an era of precise chemical analysis in aqueous solutions.