The SERS substrates were prepared using different concentrations of Gum Arabic and 5 mM AgNO3 solutions. Gum Arabic solutions were mixed by hand with a glass rod at ambient temperature. For the electrochemical deposition, the two solutions were mixed with 1:1 ratio and a small aliquot (2 μL) was dropped on a chip surface to cover the working electrode, the on chip pseudo reference and counter electrodes. AgNO3 and Gum Arabic solutions were mixed just before the SERS substrate fabrication, as given enough time, AgNO3 and Gum Arabic would chemically react to form Ag nanoparticles. Electrochemical deposition was undertaken with an Ivium pock-etSTAT handheld potentiostat using the parameters presented in Table (below). Ag-GA substrates were then rinsed in DI water and dried under a nitrogen flow for several seconds.