Hybrid structure design, preparation of Ag-GO SERS optical fiber probe and its chemical, electromagnetic enhancement mechanism

Abstract

Incorporating Ag-graphene oxide hybrid material (Ag-GO) on optical fiber offers a novel approach for flexible ultrasensitive detection in biomedical and environmental areas. In this work, Ag-GO surface-enhanced Raman scattering (SERS) optical fiber probe was synthesized by a SnCl2-sensitized solvothermal method and modified Hummer’s method. After optimizing SERS test parameters, SERS performance of the fiber probes synthesized by different synthetic procedures of GO, Ag-GO hybrid structures and GO concentration are compared. The obtained GO shows superior ability to quench fluorescence by reducing the photobleaching of dyes. GO with high oxidation degree is preferred. Compared to Ag and hybrid structures including GO/Ag and GO/Ag/GO, Ag/GO fiber probe exhibits strongest enhancement due to π-π stacking and charge transfer process from lone pair of electrons on GO to the molecules. Ag/GO fiber probe with 5 mg/mL GO displays strongest SERS enhancement. Apart from chemical enhancement, it is worthwhile to note that GO is also found to selectively enhance specific vibrations regarding π bond or lone pair of electrons. The fiber probe shows high sensitivity (10−9 M R6G), good reproducibility (RSD of 3.5%) and good stability. Moreover, the enhanced area of Ag-GO fiber probe occurs in core area and cladding edge. The enhancement mechanism of Ag-GO fiber probe is that, as GO provides an additional route for excited dyes to decay through its Fermi level, photobleaching of dyes is reduced by charge transfer process. The enhancement is a synergic effect of chemical enhancement of GO, electromagnetic enhancement of silver and waveguide propagation of optical fiber.