Click Reaction Functionalization of Hydroxylated Nanoparticles by Cyclic Azasilanes for Colloidal Stability in Oilfield Applications

The growing interest in functionalized nanoparticles and their implementation in oilfield applications (e.g., drilling fluids and enhanced oil recovery (EOR)) facilitate the ongoing efforts to improve their chemical functionalization performance in stabilization of water based or hydrocarbon based nanofluids. Cyclic azasilanes (CAS), substituted 1-aza-2-silacyclopentanes, possess a strained 5-member ring structure. Adjacent Si and N atoms in the ring provide opportunity for highly efficient covalent surface functionalization of hydroxylated nanoparticles through a catalyst-free and byproduct-free click reaction. In this work, hydroxylated silica, alumina, diamond, and carbon coated iron core-shell nanoparticles have been studied for monolayer CAS functionalization. Two cyclic azasilanes with different R groups at N atom, such as methyl (CAS-1) and aminoethyl (CAS-2), have been utilized to functionalize nanoparticles. All reactions were found to readily proceed under mild conditions (room temperature, ambient pressure) during 1 - 2 hours of sonication. CAS functionalized adducts of hydroxylated nanoparticles have been isolated and their microstructure, composition, solubility and thermal stability have been characterized. As a result, it has been demonstrated, for the first time, that covalent surface modification with cyclic azasilanes can be extended beyond the previously known porous silicon structures to hydroxylated silica, alumina and carbon nanoparticles. The developed methodology was also shown to provide access to the nanoparticles with the hydrophilic or hydrophobic surface functional groups needed to enable oilfield applications (e.g., EOR, tracers, drilling fluids) that require stable water based or hydrocarbon based colloidal systems.