Preparation of Pickering emulsion stabilized by novel amphiphilic silicon quantum dots and its application in enhanced oil recovery

Abstract

In this article, a three-step method was suggested for synthesizing amphiphilic silicon quantum dots (A-SiQDs) through a simple and mild reaction process. The A-SiQDs were used to stabilize the Pickering emulsion. The A-SiQDs were characterized by high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectrometer (FTIR), X-ray photoelectron spectrometer (XPS), and dynamic light scattering (DLS). The A-SiQDs had high interfacial modulus and can reduce the interfacial tension from 20.69 mN·m−1 to 1.97 mN·m−1. Moreover, A-SiQDs had the ability to alter the wettability of the core from oil-wet to water-wet. The Pickering emulsion stabilized by 0.2 wt% A-SiQDs can still maintain more than 70% of the emulsion index (EI) after 30 days. And the Pickering emulsion exhibited excellent stability even at 90 °C. It was found that the addition of salts can improve the stability of emulsion. The network structure formed by the hydrogen bonds and hydrophobic interactions between A-SiQDs around the emulsion droplets results in enhancing shear resistance and stability of the Pickering emulsion. The Pickering emulsion flooding and microscopic visualization displacement results indicated that the Pickering emulsion can increase oil recovery by 17.9% through reducing the water–oil mobility ratio and expanding the swept area. This paper proposes a simple and innovative method for the synthesis of A-SiQDs and also provides a new nanoparticle with better performance for stabilizing Pickering emulsion.