A highly sensitive, flexible SERS sensor for malachite green detection based on Ag decorated microstructured PDMS substrate fabricated from Taro leaf as template

A bio-inspired flexible surface enhanced Raman spectroscopy (SERS) sensor for malachite green (MG) detection has been fabricated by coating Ag on a structured surface of polydimethylsiloxane (PDMS) substrate using textured nano/microstructured Taro leaf as template. The Ag-coated microcavity structured PDMS exhibits high adhesion, hydrophobic behavior (water contact angle ∼128 ± 1°) and serves as a concentrator for the analyte/probe molecule responsible for enhanced SERS intensity. The SERS activity of the fabricated Ag/PDMS flexible sensor having MG as probe molecules shows an enhancement factor of ∼2.06 × 105 over bulk MG molecules. The fabricated SERS sensor is showed the high sensitivity and good signal reproducibility. Sensitivity for very low MG concentration (∼10−11 M) is reported which is attributed to the presence of high local field produced by Ag granular film and nanovoids onto PDMS surface. AFM and Raman characterizations have revealed the formation of nanovoids on Ag/PDMS structures to create plasmonic hotspots that results in enhanced SERS activity and high sensitivity. Further, the SERS signal under bending strain (tested between 180° and 100° bending), is also detectable for very low concentration of MG (as low as 10−7 M) even at substrate bending angles of 100° that establishes the proposed SERS sensor system as an exceptional candidate for flexible MG SERS sensor applications.