Rinse, Repeat: An Efficient and Reusable SERS and Catalytic Platform Fabricated by Controlled Deposition of Silver Nanoparticles on Cellulose Paper

Grafting metal nanoparticles (NPs) on flexible platforms is being increasingly attempted to advance their usage in the field of catalysis, sensing, energy storage, etc. However, anchoring NPs on substrates is nontrivial as it involves surface modification of the NPs and/or the substrate, which makes the whole process tedious. Here, we extend the classical silver-mirror reaction to unmodified filter paper achieving a controllable deposition of Ag NPs. The Ag NPs/filter paper thus obtained was employed as an enhanced Raman scattering (SERS) substrate achieving detection limits down to picomolar (10(-12) M) and nanomolar (10(-9) M) concentrations for rhodamine 6G and rhodamine B, with an enhancement factor (EF) of 1.42 X 10(10) and 0.659 X 10(6), respectively. To check its usage for practical applications, the substrate was extended to detect trace amounts of illicit dyes used on common vegetables and contaminants in rain, pond, and tap water with excellent reproducibility. Moreover, the as-prepared Ag paper can be directly employed for 4-nitrophenol reduction, which can be completely reduced to 4-aminophenol (4-AP) in a single step within seconds. The substrate can be reused several times over without any noticeable change in its catalytic activity. Finally, we studied the chemical transformation of 4-nitrophenol to 4-aminophenol by studying the concomitant spectral response, thereby integrating catalysis and SERS on a single substrate. This method thus provides a facile avenue to low-cost paper-based functional substrates for multimodal applications.