Real-time optofluidic surface-enhanced Raman spectroscopy based on a graphene oxide/gold nanorod nanocomposite

Abstract

We demonstrate a glass microcapillary fiber as an optofluidic platform for surface enhanced Raman spectroscopy (SERS), the inner walls of which are coated with a graphene oxide (GO)/gold nanorod (AuNR) nanocomposite. A simple thermal method is used for the coating, allowing for the continuous deposition of the nanocomposite without surface functionalization. We show that the AuNRs can be directly and nondestructively identified on the GO inside the capillaries via identification of the Au-Br SERS peak, as Br- ions from the AuNR synthesis remain on their surface. The coated microcapillary platform is, then, used as a stable SERS substrate for the detection of Rhodamine 6G (R6G) and Rhodamine 640 (RH640) at concentrations down to 10^-7 and 10^-9 M, respectively. As the required sample volumes are as low as a few hundred nanoliters, down to ~75 femtograms of analyte can be detected. The fiber also allows for the detection of the molecules at acquisition times as low as 0.05 s, indicating the platform's suitability for real-time sensing.