Sensitive Surface-Enhanced Raman Spectroscopy (SERS) Detection of Glucose on Multilayer Graphene Nanoplatelets

SERS is an emerging technique for the rapid sensing of key bioactive molecules, such as glucose, which has relatively low signal levels using normal Raman spectroscopy. SERS of glucose at extremely low concentration levels or high enhancement factors (EFs) is demonstrated here using relatively inexpensive, commercial multilayer graphene nanoplatelet (GNP) substrates produced from natural graphite. Three approaches for modifying the GNPs for SERS were used: the first method involved drop-coating of gold nanoparticles from solution on the GNPs, the second method used a combination of drop-coating the gold nanoparticles followed by the deposition of tri-ethylene glycol (TEG) layers to partition the glucose on the surfaces of the gold nanoparticles to further increase the SERS signal, and the third method used irradiation of the GNPs in a nitrogen-argon radio frequency (RF) plasma to create nitrogenous defect sites on the graphene layers to increase the SERS signal. Glucose in aqueous solutions was detected at concentrations down to 10-8 M, 10-10 M and 10-11 M, respectively, with corresponding high enhancement factors (EFs) for the three types of modified GNP substrates.