Glucose mediated synthesis of gold nanoshells: A facile and eco-friendly approach conferring high colloidal stability

In this paper, we report a novel, eco-friendly method for the preparation of gold nanoshells (GNS) with unprecedented colloidal stability. Gold shell layers were grown on silica nanospheres by utilizing glucose. Nanoshell morphology was optimized by varying the molar ratio of glucose to gold, and was characterized using UV-vis spectroscopy and transmission electron microscopy (TEM). The colloidal stability of the prepared nanoshells was compared to those made using formaldehyde reductant, using sequential extinction intensity measurements and electron microscopy. Fourier transform infrared spectroscopy was used to elucidate their surface chemistry. Uniformity and homogeneity in the shells was achieved at a molar ratio of 2, followed by shell thinning at higher glucose concentrations. These colloids exhibited remarkable stability, compared to those prepared with the commonly reported protocol, where formaldehyde is employed as the reducing agent. The key role played by glucose in imparting high stability, in conjunction with its reducing properties is demonstrated. Furthermore, the sensing potential of these nanoshells was demonstrated using surface enhanced Raman scattering (SERS) in the near-infrared region on an optical fiber platform. The present approach offers an eco-friendly route for the production of nanoshells with high stability, augmenting their use for sensing and in vivo applications, where highly stable and unaggregated nanoshells are preferred. By eliminating the routinely used noxious formaldehyde, this method presents itself as a safe, scalable and direct route for the synthesis of glucose capped nanoshells, which are much sought after for therapeutic applications