Paper-based SERS active substrates on demand

Surface Enhanced Raman Spectroscopy (SERS) is an important technique for molecular analysis under ambient conditions, and the use of paper-based silver nanostructures as a disposable SERS substrate is an attractive option for low-cost, point-of-use analysis. However, the activity of pre-fabricated silver nanostructures is affected by tarnishing and necessitates either storage under inert gas conditions or use of a protective layer on the surface. But neither of these approaches are satisfactory in terms of cost and performance in real-world settings. To address this, we report a print-expose-develop process, based on silver-halide photography, to fabricate SERS active silver nanowire networks on demand using a desktop inkjet printer. This process involves only the printing of silver and halide salt solutions and obviates the need for complex colloidal ink formulation steps reported in earlier studies on inkjet printed SERS substrates. Significantly, the printed and photo-exposed silver halide films retain silver in a stable latent-image form for more than 1 year under ambient conditions. Upon demand at the point-of-use, the latent silver can be easily developed into highly active SERS-active nanostructures, with average EF similar to 10(4), by dipping in a standard photographic developer solution and rinsing.