Silver Nanocube-Decorated PVDF Membranes for SERS Substrates

In this study, we report that silver nanocubes (AgNCs)can be synthesizedvia the silver mirror reaction (SMR) within 1 min. To extend the reactiontime, the sharp-edge AgNCs quickly denucleated and collapsed intosmall spherical Ag nanoparticles and became aggregates. Based on thisdiscovery, we developed an easy-to-make membrane-based surface-enhancedRaman scattering (SERS) substrate with superior sensitivity and reproducibility.The entire fabrication process, including AgNC synthesis from SMR,membrane pretreatment, and AgNC deposition on the membrane by suctionfiltration, was completed within 30 min. The SERS intensity of R6Gincreased 48-fold after the pretreatment of the polyvinylidene difluoride(PVDF) membrane with methanol and NaCl aqueous solutions. The PVDF-basedSERS substrate successfully verified attomolar (aM) sensitivity toR6G using 3 x 3 mu L of an aqueous sample on a 3 x 3mm(2) substrate. To validate the practicality of the developedSERS substrate as a SERS sensor, it was applied to the detection ofmalachite green, cocaine, 2,6-pyridinedicarboxylic acid, and tetracycline,with limits of detection of 10 ppb, 1 ppm, 1 ppm, and 1 ppm, respectively.However, the SERS substrate maintained up to 80% sensitivity for only3 days. Fortunately, a freshly prepared SERS substrate can be quicklyfabricated on demand; thus, shelf-life or long-term stability is nolonger a concern.