Preparation of novel amphiphilic silicon quantum dots grafted with different alkyl chains and their application in stabilizing Pickering emulsion for enhanced oil recovery

Nowadays, the nanoparticles had attracted tremendous attention in enhanced oil recovery (EOR) due to their ultrasmall size, large specific surface area and unique quantum effect. In this research, the amphiphilic silicon quantum dots (SiQDs) were successfully modified by different alkyl chains through the facile process. The SiQDs were characterized by Fourier transform infrared spectrometer (FT-IR), dynamic light scattering (DLS), transmission electron microscopy (TEM), scanning electron microscope (SEM), X-ray diffraction (XRD) and atomic force microscope (AFM). The water contact angle, interfacial tension (IFT) and expansion modulus were measured to evaluate interfacial properties. Compared with the hexyltrimethoxysilane and octyltrimethoxysilane, the propyltrimethoxysilane with short alkyl chain significantly improved the interfacial activity of the SiQDs@C3–0.3 % to reduce the IFT from 51.0 mN/m to 9.8 mN/m. It was found that both the alkyl chain length of the silane coupling agent and its dosage could significantly affect the amphiphilicity of the SiQDs. Moreover, the optical microscopy, the static multiple light scattering and the rheometer were employed to confirm the remarkable stability and the high viscosity of SiQDs@C3–0.3 % stabilized emulsion, which were attributed to the rigid interfacial film and the three-dimensional interparticle network generated by the SiQDs@C3–0.3 %. Finally, the core-flooding experiments suggested the SiQDs@C3–0.3 % stabilized emulsion enhanced oil recovery by 22.1 %.