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

Abstract

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 ecofriendly 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.

Application of Turkevich Method for Gold Nanoparticles Synthesis to Fabrication of SiO2@Au and TiO2@Au Core-Shell Nanostructures

“…Following work of Halas [ 11 ], several approaches to fabrication of core-shell nanostructures based on the silica core and gold shell have been reported [ 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ]. The most commonly used approach to synthesis of core-shell nanostructures based on silica and gold involves a two-step process, deposition of gold seeds on functionalized silica surface, followed by gold shell growth.…”

“…In the first studies on synthesis of silica-gold core-shell nanostructures, sodium borohydride was used as a reducing agent [ 11 ], however one of the most often used reducing agent in SiO 2 @Au nanostructures synthesis is formaldehyde [ 20 , 21 , 22 ]. Due to the toxicity of formaldehyde, researchers have also looked for safer alternatives to it, such as glucose [ 23 ] or ascorbic acid [ 24 ]. Also, hydroxylamine [ 25 ] and CO [ 26 ] were used as reducing agents.…”

Gold nanoparticles and nanostructures in optical biosensors

“…74 In a recent report from our group, green synthesis of silica gold core shell using glucose and successful application of these core shell nanoparticles as SERS probe are demonstrated. 75 In a highly specific detection of E. coli bacteria, 76 SERS based heterogeneous sandwich immunoassay was performed using AuNPs and AuNRs (Fig. 7), and their signal intensity was compared.…”

Synthesis of Finely Controllable Sizes of Au Nanoparticles on a Silica Template and Their Nanozyme Properties

“…Au NP-assembled SiO 2 nanostructures have been investigated in various elds [44,50,[52][53][54][55][56][57][58][59][60][61][62] and have been found to have many merits due to the combined properties of Au NPs and of the silica core, simultaneously utilizing the outstanding and unique features of Au NPs as well as the inert and versatile feature of SiO 2 [53,55,56,63]. In addition, the absorbance spectra of the nanostructures can be tuned across the visible and infrared regions by controlling the size of the Au NPs [38,39,64,65].…”