Mesoporous Au films assembled on flexible cellulose nanopaper as high-performance SERS substrates

Abstract

The fabrication of nanoarchitectured mesoporous gold films on flexible cellulose nanofiber (CNF) paper is reported for high-performance surface-enhanced Raman scattering (SERS) substrates via an electrochemical deposition method using polymeric micelles. Silver nanowires (AgNWs) are coated onto 2,2,6,6-tetramethylpiperidine-1-oxy-oxidized CNF nanopaper (TEMPO-CNF), and the resulting AgNW@TEMPO-CNF substrate is used as a conductive electrode to guide the thickness-controllable electrodeposition of mesoporous Au. Interestingly, the electrodeposition of mesoporous Au on the AgNW@TEMPO-CNF nanopaper formed a dense network of anisotropic nanoscale creases and channels, whereas deposition on flat Au electrodes makes round mesopores. Numerical simulations performed on both types of structures show that these anisotropic mesopores create more hotspots per unit area than the round mesopore films. Importantly, the mAu@AgNW@TEMPO-CNF nanopaper enables the highly sensitive detection of rhodamine 6G at concentrations as low as 100 fM, with an enhancement factor of 8.72 × 1011 and excellent reproducibility. As a demonstration of their utility in practical chemical detection measurements, the SERS substrates are used to detect the pesticide thiram and a model gas, 2-naphthalenethiol; the detection limits were 10 fM and 1 ppb, respectively. SERS substrates composed of mAu@AgNW@TEMPO-CNF nanopaper may serve as an inexpensive, flexible, and stable chemical detection platform to sense both solution- and gas-phase analytes.