Electrodeposition of rough gold nanoarrays for surface-enhanced Raman scattering detection

Highlights: • Highly surface-roughened gold nanostructure arrays are grown on a Si wafer by a simple electrodeposition strategy. • The fabricated arrays of gold nanostructures show remarkably improved surface-enhanced Raman scattering activity. • Simulation reveals that lots of hot spots are generated by the thorny Au nanostructures. • The fabricated SERS substrate showed high sensitivity to the fungicide ferbam in water. We report a simple electrodeposition strategy to fabricate highly surface-roughened Au nanostructure arrays grown on a silicon wafer. Finite element method simulation reveals that lots of hot spots were generated around the tips of nanothorns and in the gaps between neighboring nanothorns by both plasmon coupling and ''lightning-rod'' effects. It was found that roughening the as-electrodeposited Au nanocones by a subsequent second-step electrodeposition induced a six times improvement in SERS intensity. The peak intensities of SERS spectra show a narrow distribution with a small relative standard deviation of 6.6%, confirming the high uniformity of the fabricated thorny Au nanostructure array SERS substrate. A high SERS sensitivity of the fabricated thorny Au nanostructure arrays was confirmed by a detectable concentration limit of 1 pM rhodamine 6G aqueous solutions. The SERS substrate also showed a high detection sensitivity toward ferbam with a limit of detection of about 2.40 nM. Calibration curves with a linear correlation of logarithmic SERS intensity with logarithmic concentration for R6G and 3,3′,4,4′-tetrachlorobiphenyl (PCB-77, a persistent organic pollutant) were achieved by using the fabricated rough gold nanoarrays, demonstrating a promising application in semi-quantitative or even quantitative detection. This work offered a facile but effective approach toward the rational designs of uniform, reproducible and sensitive SERS substrates for molecular detection.