Hydrothermal Preparation of Nanoscale Cesium Tungsten Bronze Using Ammonium Paratungstate

Recently, two-dimensional (2D) nanomaterials has attract a great attention due to its unknown physical, chemical, electrical and optical properties. For instance, graphene nanosheets mechanically exfoliated from graphite show very high carrier mobility, excellent thermal conductivity and optical properties, which inspires lots of other 2D materials such as graphene oxide (GO) , hexagonal boron nitride (h-BN), transition metal carbides and carbonitrides (MXenes), as well as graphitic carbon nitride (g-C3N4) 161 are well studied.

Recently, nanoscale cesium tungsten bronze (Cs_xW03) has been reported as a novel candidate for NIR absorbents is leading to a flurry of research activity due to its wide absorption spectrum. This is significantly different from the light absorption properties of tungsten trioxide (WO₃) and its composites, which does not have any absorption in the NIR region.

Thus. Firstly, a hydrothermal preparation of nanoscale cesium tungsten bronze using Ammonium paratungstate was designed to produce two-dimensional Cs_xWO₃ nanosheets by using ammonium paratungstate as a tungsten source, CsCl as a cesium source.

The preparation process are as below:

Firstly, add a calculated amount of ammonium paratungstate to deionized water and keep stirring to prepare a uniform ammonium paratungstate aqueous solution (0.05 M). Secondly. a particular amount of thiourea and HCl (8 M) were sequentially added to 20 mL of ammonium paratungstate aqueous solution under vigorous stirring. Subsequently, 0.5 ml of oleylamine and 0.5 mmol CsCl were added into the above mixture. The total volume of the mixture was set to 25 ml employing deionized water. After that, the obtained solution was transferred into a Teflon-lined autoclave with 50 ml. internal volume, followed by reacting at 220 DC for 20 h. After cooling down to room temperature, the blue products were centrifuged at 8000 rpm to harvest solids, washed by H₂0 and EtOH until neutral, respectively, and finally dried under vacuum at 60 °c overnight.

To sum up, the hydrothermal preparation of nanoscale cesium tungsten bronze using Ammonium paratungstate was conducted. And the Cs_xWO₃ with a two-dimensional nanostructure was successfully manufactured. The rectangular nanosheets possess the broadest absorption spectrum and strongest photoresponse property, which leads to a rapid conversion of photo-energy to heat. These results show that the Cs_xWO₃ nanosheets have enormous potential as a promising candidate for the applications in optical filters, solar collector and photo-thermal ablation therapy.

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