In situ electrochemical surface modification of Au electrodes for simultaneous label-free SERS detection of ascorbic acid, dopamine and uric acid

Simultaneous detection of biomolecules with high sensitivity and selectivity is highly demanded for point-of-care diagnosis. Here, a simple solution-based surface-enhanced Raman spectroscopy (SERS) method is presented to facilitate rapid and direct ternary detections of ascorbic acid (AA), dopamine (DA) and uric acid (UA) in urine. The approach focuses on in situ surface modification of Au nanopillar electrode by Au electrodeposition in the presence of target molecules. Formation of new plasmonic nanostructures on the nanopillar array effectively perturbs the biomolecules adsorbed on the Au surface and confines the target molecules in solution into active regions of the generated hotspots, resulting in the significant amplifications of Raman signals within 60 s. The method enabled reliable label-free detections of AA, DA, and UA at relevant physiological ranges with detection limits of 1, 0.1 and 1 nM, respectively. To the best of our knowledge, this is the first demonstration of simultaneous detection and quantification of the biomolecules by SERS. The practical applicability of this novel method was ascertained by the analysis with non-pretreated human urine.