Preparation and enhanced oil recovery study of amphiphilic Janus nanosheets

This study introduced an innovative approach for the synthesis of amphiphilic Janus nanosheets. Thermally expandable microspheres (TEMS) were used as a template, and tetraethyl orthosilicate (TEOS) was used as a silicon source. Janus spheres with TEMS as the core and SiO2 as the shell (TEMS@SiO2) were synthesized under alkaline conditions. Janus spheres (TEMS@SiO2-NH2) were further modified by aminopropyltriethoxysilane (APTES). Janus nanosheets (SiO2-NH2) were obtained by heating to expand the TEMS. Amphiphilic Janus nanosheets C16-SiO2-NH2 (CSAJN) were prepared by modifying Janus nanosheets (SiO2-NH2) with hexadecyltrimethoxysilane (HDTMS). CSAJN was characterized by fourier transform infrared spectroscopy (FT-IR)、thermogravimetry (TG)、a laser particle size analyzer、scanning electron microscopy (SEM)、(tetraethyl orthosilicate) TEM、and a contact angle goniometer. The results indicated that CSAJN had a lamellar structure with a thickness of 41 nm and a size of 260 nm. The interfacial tension of CSAJN nanofluid (1000 mg/L) at the oil–water interface was 1.4 mN/m at 60 °C. CSAJN nanofluid (1000 mg/L) exhibited excellent emulsification ability at 60 °C, with an emulsification index of 0.68 over 240 h. CSAJN nanofluid (1000 mg/L) could maintain stability after 10 days. CSAJN nanofluid (1000 mg/L) demonstrated outstanding wetting properties, transforming from oil-wet to water-wet on core slices (103° to 39.4°). Compared to water flooding, CSAJN nanofluid (1000 mg/L) significantly enhanced oil recovery.