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

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.