Flexible, label free and low-cost paper based microfluidic SERS substrates for thiram detection

Herein, a low-cost, label free Flexible Paper based microfluidic SERS sensor for thiram detection has been demonstrated. Hydrophilic wells of different sizes were engraved by wax-coated mould printing on paper using a hot laminator. The hydrophilic nature of the wells was confirmed by contact angle measurement. Silver nanoparticles (AgNPs) decorated GO nano-hybrid (Ag-rGO), was synthesized using wet chemical route. The uniform distribution of spherical AgNPs (∼ 40 nm) on GO was achieved. The synthesized Ag-rGO was then drop-casted on hydrophilic wells for thiram detection and fM sensitivity has been achieved. The limit of detection (LOD) and Enhancement factor (EF) were found to be 0.36 × 10−16 M and 5.2 × 1012 respectively. The reproducibility and uniformity of the fabricated substrates were tested, with RSD value < 5 % and < 3 % respectively. The recovery time of the sensors was examined for 2 months and the deviation in the intensity has been found to be < 4 %. Selectivity test was performed in the mixture of spinach leaves with thiram, the fM sensitivity with RSD value of 4.9 % was achieved. Thus, the Ag-rGO/wax paper (Ag-rGO/WP)- SERS sensor has the inherent potential to be used as an on-site portable sensing platform for food safety applications.