Preparation Methods of the Molybdenum Disulfide

Molybdenum disulfide (MoS2) is a type of transition metal sulfide with glossy lead gray solid powder. It is synthesized and appears black, which has stable chemical property.

There are many preparation methods of MoS2, details are as follows:

1.0 Mechanical peeling method

The mechanical peeling method is widely used to prepare ultra-thin two-dimensional materials. Up to now, mechanical exfoliation is the simplest way to produce the cleanest, highly crystalline and atomically thin nanosheet layered material. However, this method is inefficient and difficult to control the material size and layer number, so it is not suitable for large-scale practical application.

2.0 Liquid phase stripping method

To prepare two-dimensional layered material, the mechanical stripping method is a kind of low yield way. It is necessary to find a simple way with high quality and good yield to prepare two-dimensional materials with single-layer and few layer. Liquid phase stripping is a reliable method that produce two-dimensional material with single and few layers in large quantity. Lithium ion intercalation and liquid-phase ultrasonic method are mainly used to peel off MoS2 nanosheets. Lithium ion intercalation method is to use intercalation agent(such as n-butyl lithium, lithium hydroxide etc.) to embed into bulk MoS2, which increases the interlayer spacing and weakens the van der Waals force between layers, and then obtain a single layer or few layers of MoS2 nanosheets by ultrasound.

3.0 Chemical vapor deposition

Chemical Vapor Deposition (CVD) can synthesize two-dimensional material with large area, uniform thickness ,controllable size and the atomic layer thickness. The working principle is to reduce the molybdenum source to MoS2 using sulfur source vapor at high temperature and deposit it on on the base. When CVD is used to prepare MoS2 nanoplates, the sulfur source is generally obtained by heating sulfur powder, while molybdenum source is mainly from molybdenum trioxides powder and molybdenum pentachloride. However, it has quite high requirement for the environment and laboratory equipment.

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