Ag Microplasma-Engineered Nanoassemblies on Cellulose Papers for Surface-Enhanced Raman Scattering and Catalytic Nitrophenol Reduction

Nanoassemblies of nanostructures on flexible substrates are important for fundamental study and applications. However, current methods to produce nanoassemblies usually are time-consuming, are complicated, and involve toxic and expensive chemicals. Here we demonstrate an effective one-step fabrication of flexible silver (Ag) nanoparticle based microplasma-engineered nanoassemblies (AgMENs) on cellulose papers using a unique microplasma-induced electrochemical method. The as-fabricated AgMENs show exceptional plasmonic properties for surface-enhanced Raman scattering (SERS) detection and catalytic ability for nitrophenol reduction. Ag nanoparticles (NPs) with crystalline-twinned nanostructures can be synthesized and deposited on cellulose papers in one step with ambient condition using microplasmas, providing enhanced charge transportation during Raman scattering. Three-dimensional (3D) confocal micro-Raman scattering study shows that a large SERS volume was formed in the as-fabricated AgMENs, achieving detection limits down to picomolar (10–12 M) and nanomolar (10–9 M) concentrations for rhodamine 6G (R6G) and folic acid (FA), respectively. The catalytic reduction of 4-nitrophenol (4-NP) of AgMENs was observed to have a pseudo-first-order rate constant of 1.13 min–1 and a low apparent activation energy of 4.6 kJ/mol for AgMENs. Our work opens an avenue of a scalable fabrication of flexible metal nanoparticle based substrates under ambient conditions for fundamental study and emerging applications including catalysis, sustainable energy, and biomedical imaging.