Preparetion Method of 2H Phase Single-layer Tungsten Disulfide Nanosheet

Tungsten disulfide (WS₂) has the same structure as molybdenum disulfide. It is a typical sandwich layer structure. Due to its relatively weak van der Walls force between layers, it can also be stripped into single or few layers of nanosheets. It is considered to be another equivalent. An important two-dimensional nanosheet material with unique physical, chemical and electrical properties.

There are more and more researches on tungsten disulfide. It is generally believed that there are three phases in tungsten disulfide, namely 1T, 2H and 3R phases. Among them, 1T phase is WS2 with one SWS monolayer as the smallest repeating unit stack. The 2H and 3R phases are stacked with two and three S-W-S monolayers as the smallest repeating unit. Most of WS₂ in nature exists in the 2H stable phase, and the 1T and 3R phases belong to the metastable structure and can be converted to the 2H phase under certain conditions. Since the WS₂ of the single-layer 2H phase has lost the characteristic that the bilayer is the smallest repeating unit, it is also called the 1H phase. In applications, 2H phase monolayer tungsten disulfide nanosheets exhibit good semiconductor properties and are intended to be used in semiconductor devices such as supercapacitors and transistors.

The preparation method of the 2H phase single-layer tungsten disulfide nanosheet comprises the following steps:

Weigh 0.004 mol of lithium acetate and 0.002 mol of ammonium thiotungstate, respectively, and mix and grind for 1 h in an agate mortar. The ground mixture was placed in a corundum crucible, placed in a tube furnace, and protected by argon gas. The temperature is programmed to 200 ° C, and kept for 10 h, then continue to cool down to room temperature with argon gas to obtain a lithium-plated 2H phase tungsten sulfide (Li2WS4) block; the lithium-insulated tungsten sulfide block is placed in 50 mL of deionized water. In the container, ultrasonic dispersion for 10 min, the dispersed suspension was centrifuged to separate the precipitate on a centrifuge rotating at 1000 r/min; the precipitate after removal of the precipitate was centrifuged three times with water and ethanol at a centrifuge speed of 10000 r/min. The soluble impurities such as Li2S were removed, and the washed precipitate was ultrasonically dispersed in 100 mL of absolute ethanol. The concentration of the 2H phase single layer WS2 was about 0.8 mg/mL, and the thickness was 0.80 nm by atomic force microscopy. X-photoelectron energy The spectrum is shown as 2H phase.

The 2H phase single-layer WS₂ nanosheet obtained by the above scheme has a thickness of less than 1 nm and can be used for research of new semiconductor materials such as supercapacitors, liquid crystal displays, and photocatalysts.

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