Cs_x WO₃ nanoparticles in the range of 2050 nm have been successfully synthesized by the supercritical solvothermal approach, where after dissolving WCl₆ and CsOH in a mixed solution of water, ethanol and oleic acid, the solution was heated at 300°C. The products were characterized by X-ray diffraction, TEM, HR-TEM, EDS, laser particle size analysis and thermographic measurements. Cs_x WO₃ nanoparticles showed the high transparency in the visible region, excellent shielding performance of the near-infrared light and limited reflectance of light in the range of 2002700 nm, indicating the strong absorption of NIR light on the nanosized Cs_x WO₃ . Cs_x WO₃  nanoparticles also exhibited quick conversion of photo-energy to local heat. 

 

Near-infrared, with the wavelength of 0.75-1.4 µm and the frequency of 214-400THz is defined by the water absorption, and commonly used in fiber optic telecommunication because of low attenuation losses in the SiO2 glass (silica) medium. Image intensifiers are sensitive to this area of the spectrum. Examples include night vision devices such as night vision goggles. Near-infrared spectroscopy (NIRS) is a spectroscopic method that uses the near-infrared region of the electromagnetic spectrum (from about 700 nm to 2500 nm). Typical applications include medical and physiological diagnostics and research including blood sugar, pulse oximetry, functional neuroimaging, sports medicine, elite sports training, ergonomics, rehabilitation, neonatal research, brain computer interface, urology (bladder contraction), and neurology (neurovascular coupling). There are also applications in other areas as well such as pharmaceutical, food and agrochemical quality control, atmospheric chemistry, and combustion research.