Abstract
Recent studies on tungsten oxide preparation are mainly motivated by its applications in smart windows, energy harvesting and, recently, in cancer therapy. Peroxotungstic acid (PTA) is an important precursor to obtain tungsten oxide in an environmentally-friendly way, through the colloidal synthesis in aqueous media. Despite giving chemically pure products, PTA originates oxides with various morphologies depending on the experimental conditions, a subject open to discussion. PTA, in the presence of sodium dodecyl sulfate (SDS) as architecture-directing agent, was investigated in ethanol/water medium by small angle X-ray scattering (SAXS), fluorescence, surface tension and conductivity measurements; the morphology of tungsten oxide obtained from the precursor systems was also characterized by scanning electron microscopy (SEM). PTA/SDS/ethanol/water systems show a two-level organization in which small micelles are aggregated as fractal structures. There is an inverse correlation between gyration radius of the fractal structures of the PTA/SDS systems and particle size of the tungsten oxide films. The interaction of PTA with SDS is observed by reducing the Gibbs energy of micellization; also, it is evidenced that the supressive effect of PTA on pyrene emission is overrided in presence of SDS.
Highlights
Tungsten oxide, an n-type semiconductor that presents electrochromic and photochromic properties, has drawn attention as material for light harvesting, due to its band gap situated, in general, in the visible part of the electromagnetic spectrum
The results of conductivity, pH, small angle X-ray scattering (SAXS) and fluorescence spectroscopy of the precursor/structuring system composed of Peroxotungstic acid (PTA)/sodium dodecyl sulfate (SDS)/NaCl/ethanol/water will be discussed in relation to model systems containing SDS/ethanol/water and SDS/NaCl/ethanol/water
The value of critical micellar concentration (CMC) found for the SDS/ethanol/water system was 8.69 mmol L-1, a value higher than that found when only water was used as the solvent (8.2 mmol L-1).[24]
Summary
An n-type semiconductor that presents electrochromic and photochromic properties, has drawn attention as material for light harvesting, due to its band gap situated, in general, in the visible part of the electromagnetic spectrum.
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