Formation and Thermal Stability of Gold-Silica Nanohybrids: Insight into the Mechanism and Morphology by Electron Tomography

TL;DR

This study presents a simple synthesis method for gold-silica hybrids, investigates their 3D morphology using electron tomography, and analyzes their formation mechanism and thermal stability up to 400°C, relevant for catalysis and biotech applications.

Contribution

It introduces a straightforward synthesis route and provides the first detailed 3D characterization of gold-silica hybrids during formation and heating.

Findings

Hybrid morphology evolves from a soft self-assembled structure.

Good thermal stability up to 400°C, with gold migration beyond.

3D electron tomography reveals hetero-unit ordering and formation process.

Abstract

Gold-silica hybrids are appealing in different fields of applications like catalysis, sensors, drug delivery, and biotechnology. In most cases, the morphology and distribution of the hetero-units play significant roles in their functional behavior. Methods of synthesizing these hybrids, with variable ordering of the hetero-units, are replete; however, a complete characterization in three dimensions could not be achieved yet. A simple route to the synthesis of Au-decorated SiO2 spheres is demonstrated and a study on the 3D ordering of the hetero-units by scanning transmission electron microscopy (STEM) tomography is presented at the final stage, intermediate stages of formation, and after heating the hybrid. The final hybrid evolves from a soft self-assembled structure of Au nano-particles. The hybrid shows good thermal stability up to 400 C, beyond which the Au particles start migrating inside the SiO2 matrix. This study provides an insight in the formation mechanism and thermal stability of the structures which are crucial factors for designing and applying such hybrids in fields of catalysis and biotechnology. As the method is general, it can be applied to make similar hybrids based on SiO2 by tuning the reaction chemistry as needed.