Functionalized Alkoxysilanes as a Key to Efficient Synthesis of Au@SiO2 Core–Shell Composite Nanoparticles

Composite nanoparticles (CNPs) with noble metal (Au or Ag) cores and silica shells serving as carriers for various target compounds are of considerable interest for solving various applied problems, including the tumor theranostics, the creation of highly sensitive sensors, super-bright emitters (including nanolasers), and various metamaterials. The conventional precursor for the synthesis of such shells is tetraethoxysilane (TEOS), which is, however, characterized by a low affinity for metal core surfaces and a poor solubility in water. Moreover, the hydrolytic condensation of TEOS yields a dense network of Si–O–Si bonds, which negatively affects the shell capacity for a target compound. All these drawbacks significantly complicate both the synthesis of CNPs and their subsequent loading. In this paper, the possibilities and advantages of alternative approaches to the creation of CNPs based on the replacement of TEOS with functionalized alkoxysilanes are analyzed. The main attention is focused on the particles obtained using γ-mercaptopropyltrimethoxysilane.