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 secondstep 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.

Automated summary

This study reports a simple electrodeposition strategy for the fabrication of highly surface-roughened gold nanostructure arrays, which exhibit improved SERS intensity with high uniformity. The fabricated thorny gold nanostructure arrays show high SERS sensitivity and detection limits for rhodamine 6G and ferbam, with promising applications in molecular detection. Calibration curves achieved using the fabricated rough gold nanoarrays demonstrate potential for semi-quantitative or quantitative detection. This work offers a facile and effective approach for the rational design of uniform, reproducible, and sensitive SERS substrates.