Development of Amphiphilic Janus Molybdenum Disulfide Nanosheets and Their Application for Enhanced Oil Recovery

Amphiphilic Janus molybdenum disulfide (MoS2) nanosheets have emerged as promising candidates for enhanced oil recovery (EOR) due to their low cost and exceptional interfacial properties. Nevertheless, research on the modification methods for Janus MoS2 remains scarce. In this article, we prepared amphiphilic Janus molybdenum disulfide nanosheets (L-MoS2-C) by double-sided modification of molybdenum disulfide (MoS2) using a starch template method. Specifically, l-glutamic acid (l-Glu) with hydrophilic carboxyl group was grafted onto one side of the nanosheets, while cetyltrimethylammonium bromide (CTAB) with hydrophobic alkyl chain was used on the other. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray analysis (EDS) characterizations confirmed the functionalization of CTAB and l-Glu molecules over the surfaces of MoS2 nanosheets. Benefiting from the amphiphilic properties, L-MoS2-C nanosheets presented excellent dispersion stability in brine and spontaneously accumulate at the oil–water interface, forming an elastic interfacial film. At 0–10,000 mg/L NaCl concentration, the size distribution of L-MoS2-C was centered in the range of 300–500 nm. At an ultralow concentration (0.005 wt %), L-MoS2-C can reduce the interfacial tension by approximately 60% and stabilize emulsions as an emulsifier. Furthermore, L-MoS2-C possesses remarkable wettability alteration capability, altering the contact angle of the quartz plate surface from 104.3 to 30.3°, thereby converting capillary resistance into driving force. Micromodel flooding and core flooding experiments demonstrate that these superior properties enable L-MoS2-C nanofluid to effectively mobilize remaining and residual oil after water flooding at an ultralow concentration, contributing an additional 15.1% oil recovery. This work introduces a novel amphiphilic modification method for MoS2, offering a low-cost, high-performance, and highly promising nanoflooding agent for tertiary oil recovery in sandstone reservoirs.