A needle-like reusable surface-enhanced Raman scattering substrate, and its application to the determination of acetamiprid by combining SERS and thin-layer chromatography.

A micro surface-enhanced Raman scattering (SERS) substrate has been fabricated by electrochemical deposition of dendrite-like gold on carbon fiber needles (Au-CFNs). Scanning electron microscopy and energy dispersive spectroscopy were used to confirm the presence of the gold nanostructure on the CFNs. This substrate has a Raman scattering enhancement factor as high as 3.3 × 10^7 when using rhodamine 6G as the reporter molecule. The high SERS sensitivity is attributed to the massive hotspots on gold bulges that enhance the local surface plasmon resonance. The Au-CFN substrate was reproduced 10 times after electrochemically wiping off the analytes from the needle-like electrode. The substrate has attractive features such as convenient sampling, low sample dosage, and minimal invasion. It was applied, in combination with thin-layer chromatography, for the determination of acetamiprid on vegetables. The result was more accurate because the sample information of both the surface and the bulk can be obtained at the same time after inserting the tip of this needle substrate into the TLC plate. The limit of detection for acetamiprid is 0.05 μg⋅mL-1 and the linear range is 0.1-10 μg⋅mL-1. Graphical abstract A reusable micro needle-like SERS substrate was fabricated and applied for pesticide residue analysis. The SERS signal of acetamiprid can be acquired on the tip of this micro needle-like Au-CFN substrate. This substrate can be reused for 10 times.