Flexible SERS Substrate of Cotton swab-AgMOF Combination with Smartphone app for Explosives Detection

A simple method was developed for one-step synthesis of silver-based metal-organic skeleton (AgMOF) and in situ growth on flexible cotton swabs (CS). In this work, the CS-AgMOF has been obtained by new synthetic routes using benzene-1,3,5-tricarboxylic acid (HBTC) and AgNO dissolved in a ethanol/water mixture in the presence of CS used to stabilize AgMOF and to control their availability. Fast crystal growth was obtained at the metastable interface between the ethanol/water mixture. The flexible CS-AgMOF substrate was subjected to surface-enhanced Raman scattering (SERS) for the detection of single and multiple explosives. SERS peak intensity versus concentration changes were rapidly detected and analyzed using a self-developed smartphone-based app system, which performs quantitative detection of the analyte. The results showed that explosives (cyclotrimethylene-trinitramine, RDX; trinitrotoluene, TNT) can be detected with a high sensitivity, with a limit of detection (LOD) of RDX and TNT was 0.1 and 0.5 mM, respectively. The flexible SERS substrate, CS-AgMOF, in conjunction with a Raman spectrometer and a smartphone-based app system, possesses practical applications primarily owing to the low cost and simple sampling technique.