Synthesis of Lateral Size-Controlled Monolayer 1H-MoS2@Oleylamine as Supercapacitor Electrodes

A new wet chemistry approach, based on the hot-injection thermolytic decomposition of the single-source precursor [Mo2O2S2(S2COEt)(2)] in oleylamine, is described for the production of nanodimensional 1H-MoS2@oleylamine. High quality freestanding MoS2 nanosheets capped with oleylamine have been prepared and subjected to detailed compositional analyses for the first time. The selection of the appropriate reaction temperatures (200-325 degrees C) in the simple yet robust procedure allows control of the lateral nanosheet dimensions which range from 4.5 to 11.5 nm, as 1H-MoS2@oleylamine entities which maintain a consistent chemical composition (MoS2.oleylamine(0.28-0.33)). This work provides the first example of atomic resolution STEM imaging of these fine-scale nanosheet materials, providing new insights into their morphology and demonstrating that those freestanding MoS2 nanosheets are pure, highly crystalline, randomly oriented monolayers. The 1H-MoS2@oleylamine samples were analyzed by attenuated total reflectance FT-infrared spectroscopy spectroscopy (ATR-FTIR), transmission electron microscope (TEM) imaging, aberration corrected scanning transmission electron microscope (STEM) imaging, energy dispersive X-ray (EDX) spectrum imaging, powder X-ray diffractometry (p-XRD), thermogravimetric analysis (TGA), and Raman spectroscopy. Composite materials of the as-synthesized MoS2 nanosheets and exfoliated graphene were then used to construct coin-cell supercapacitor electrodes with a specific capacitance of 50 mF/cm(2), demonstrating its utility as an energy storage material.