Sequential Solvent Exchange Method for Controlled Exfoliation of MoS₂ Suitable for Phototransistor Fabrication

Abstract

In this study, flakes of molybdenum disulfide (MoS2) with controlled size and thickness are prepared through sequential solvent exchange method by sonication in dimethylformamide (DMF) and N-methyl-2-pyrrolidone (NMP) solvents. While NMP acts more effectively in reducing the thickness of flakes, DMF shows better potential in conserving the lateral size of nanosheets. The distribution of size and thickness of nanoflakes as a function of sonication time verifies that extended sonication results in dramatic drop of the dimension of the exfoliated flakes. This technique leads to the formation of few-layered MoS2 flakes without further drop of their lateral dimensions. It has been observed that by exposing the bulk MoS2 powders to oxygen plasma, the exfoliation process is accelerated without converting to 2H-MoS2 structures. Finally, a phototransistor has been fabricated based on few-layered MoS2 layers with a field effect mobility of ∼2.1 cm2 V–1 s–1 showing a high response to laser excitation of 532 nm wavelength.

A high performance supercapacitor based on decoration of MoS2/reduced graphene oxide with NiO nanoparticles

“…MoS 2 nanosheets were also achieved using the two-step exfoliation method presented by our group in the previous report. 26 In this technique, the bulk MoS 2 powder was exfoliated in NMP solvent at 400 W power sonication (7 s "on" and 3 s "off") for 15 min and then centrifuged. In order to remove the unexfoliated akes, the dispersion was diluted with a poor solvent (IPA) and subsequently subjected to low speed centrifugation.…”

“…1b with a nal concentration of 12 mL mg À1 as reported in our previous study. 26 The morphology of GO and exfoliated MoS 2 sheets, using SEM, TEM, and AFM analyses, is demonstrated in Fig. 2.…”

“…25 Our recently reported solvent exchanged sonication technique provided a high yield production of large lateral size MoS 2 few layers. 26 Although the low conductivity of pure MoS 2 limits its capacitance performance, its hybrid structure with rGO possesses higher capability for charge storage. 27 Moreover, a variety of metal oxide structures such as RuO 2 , IrO 2 , and NiO have been presented as pseudocapacitor electrodes with outstanding electrochemical potentials.…”

“…32 MoS 2 nanosheets were also produced with the aid of solvent sonication of bulk material based on our introduced solvent exchange method. 26 Moreover, NiO thin lm with 10 nm thickness was deposited on both rGO and MoS 2 /rGO electrodes and annealed at 350 C for 30 min under a ow of argon gas. The thermal energy imparted during annealing converts the NiO thin lm into NiO nanoparticles on the electrode surfaces.…”

The High Surface Ratio Micro-MoS<sub>2</sub> Grain Composed of MoS<sub>2</sub> Nanosheet Prepared with One-Step Hydrothermal Synthesis

“…Graphene was the first 2D material to be found [4] [5]. Graphene has very high carrier mobility, strength, surface area and thermal conduction capability [6] [7] [8] [9] [10], so graphene has great potential applicant in many fields. But graphene's band gap is zero, limiting its electronic applications.…”