Plasmon-coupled 3D porous hotspots architecture for super-sensitive quantitative SERS sensing of toxic substances on real sample surface
This paper reports a facile, fast, and cost-effective method to the synthesis of three-dimensional (3D) porous AgNPs/Cu composites as SERS substrate for super-sensitive and quantitative detection of drug and pesticide residues. 3D porous hotspots architecture was constructed by depositing plasmonic AgNPs on 3D porous copper foam. Cu porosity and AgNPs particle sizes were optimized for the highest SERS enhancement in a controlled manner. Both finite-difference time domain (FDTD) simulations and experimental results revealed that more than 1000-fold enhancement was achieved due to the strong plasmonic coupling between Ag and Cu formed hotspots. This make it ultrasensitive detect multiple analytes as low as 10-11 M (crystal violet, CV), 10-9 M (malachite green, MG), 10-11 M (acephate), and 10-9 M (thiram) even with a portable Raman device. Moreover, this 3D solid substrate has a good uniformity (RSD ＜ 11 %) and superior stability (＜ 14 % signal loss), allowing for SERS practical detections. Importantly, by simply wiping the real sample surface using the substrate, it successfully detects CV and MG residues on crayfish with low concentration of 10-9 M and 10-7 M, respectively. Further, the substrate can also be applied to detect acephate on eggplant and thiram on apple surface, and low concentration of 10-9 M and 10-7 M were achieved, respectively. Note that all of these SERS detections on real samples have a broad dynamic concentration range and a good linear dependence of the peak intensity to the logarithmic concentration. In addition, as a “proof of concept”, multi-component detection on the real sample are demonstrated. This 3D solid substrate possessing excellent detection sensitivity, diversity, and accuracy allows rapid and reliable determination of real-world samples.