Synthesis of tungsten nanoparticles by solvothermal decomposition of tungsten hexacarbonyl

Tungsten nanoparticles were prepared by thermal decomposition of tungsten hexacarbonyl [W(CO)6] (2 mmol) at 160 °C in presence of a mixture of (1:1) surfactants, oleic acid (6 mmol) and trioctyl phosphine oxide (TOPO) (6 mmol) under a blanket of Ar gas. The synthesized tungsten nanoparticles without surfactant are flocculated. With increase in concentration of surfactant mixture to 12 mmol each, agglomeration of several tungsten nanoparticles are observed. Characterization of surfactant coated tungsten nanoparticles were carried out using Fourier transform infrared spectroscopy (FTIR). Chemical characterizations of synthesized tungsten nanoparticles were done using X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-optical emission spectrometry (ICP-OES) and LECO gas analyzers. XPS study shows the W0 oxidation state of tungsten nanopowders. Structural characterization of synthesized tungsten nanoparticles were conducted by X-ray diffraction (XRD), which shows that the as-synthesized tungsten nanoparticles are amorphous in nature and they become body centered cubic crystalline after annealing. Particle size, shape and distribution were characterized using small-angle X-ray scattering (SAXS), environmental scanning electron microscopy (ESEM) and transmission electron microscopy (TEM).