Surfactant-mediated modulation of morphology and charge transfer dynamics in tungsten oxide nanoparticles

Tungsten Oxide (WO3) is a well-known transition metal oxide which exhibits non-toxicity and stability in its nanoparticle form. It is a potential candidate for a variety of applications due to its low cost and facile synthesis process. In the present work, WO3 nanoparticles were synthesized via facile acid-coprecipitation method to explore the effect of surfactants on the morphology of WO3 nanoparticles and thus, on its structural, optical and electrochemical properties. The morphology analysis revealed the formation of spherical nanoparticles in the absence of any surfactant while nanoflakes and nanosheets were observed in the presence of cetyltrimethylammonium bromide (CTAB) and polyethylene glycol (PEG), respectively. Moreover, the presence of surfactants was found to influence the crystallinity state of the samples. The different morphologies exhibited optical band gap of 2.2-2.7 eV as analyzed by UV-vis spectroscopy along with other optical properties like absorbance range and refractive index. The electrochemical properties of the samples were studied by employing potentio electrochemical impedance spectroscopy (PEIS) and cyclic voltammetry (CV) techniques. CV analysis revealed the diffusion-controlled behavior of the samples which may be suitable for photovoltaic applications. Furthermore, impedance study showed the presence of Warburg impedance which indicates that there is an infinite layer of excitons on the surface of thin film, further suggesting WO3 as a prominent material for solar cell applications. The incorporation of surfactants resulted in the reduction of charge transfer resistance indicating more efficient charge transfer process.