Gold nanochestnut arrays as ultra-sensitive SERS substrate for detecting trace pesticide residue

In comparison to conventional spectroscopic techniques based on chromatography, surface-enhanced Raman spectroscopy (SERS) enables the rapid identification and detection of trace pesticide residues present in trace amounts in the environment and foods. Herein, a facile approach to fabricate unique gold nanochestnuts (GNCs) as an ultra-sensitive SERS substrate for detecting trace pesticide residues has been developed based on anodic aluminum oxide (AAO) templates. The GNCs are synthesized through the galvanic replacement of Ag on the top of Ni nanorod arrays. The as-prepared GNCs have well-controlled structural parameters, and importantly have unique anisotropic morphologies that benefit the enhancement in SERS performance. As a result, rhodamine 6 G (R6G) can be efficiently detected with GNCs as the SERS substrate even with a concentration of only 10^-12 M, and the Raman enhancement factor reaches up to 5.4 × 10⁹ at this concentration. Further SERS measurement of thiram indicates a remarkable SERS-active sensitivity of the as-prepared GNCs with a detection limit of thiram up to 10^-14 M. The GNCs also exhibit a high signal-to-noise ratio.