Poly(vinyl alcohol) as a structuring agent for peroxotungstic acid

• Published in: Journal of molecular liquids Vol. 269; pp. 92 - 100
• Main Authors: de Moura, Diego Soares, Pazinato, Julia Cristina Oliveira, Pereira, Marcelo Barbalho, Mertins, Omar, Silva, Emerson Rodrigo, Garcia, Irene Teresinha Santos
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-11-2018
• Subjects: Peroxotungstic acid; Poly(vinyl alcohol); Structure-directing agent; Transition metal oxide; Transition metal oxide; Poly(vinyl alcohol); Structure-directing agent; Peroxotungstic acid
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/j.molliq.2018.08.015

Poly(vinyl alcohol) (PVAL) is an interesting architecture-directing material and is useful for synthesizing transition metal oxides through the sol-gel method. In this work, the interaction between PVAL and peroxotungstic acid (PTA) in aqueous media was investigated by conductivity, zeta potential, small-angle X-ray scattering, isothermal titration calorimetry and fluorescence measurements. The strong exothermic effect and the change in organization in aqueous media, from extended chains to compact chains forming fractal structures, confirm the interaction between PTA and PVAL. Powders were obtained from these systems by removal of water and subsequent calcination. An increase in the crystal size and changes in morphology were observed with the increasing of PVAL concentration. The band gap values, obtained by diffuse reflectance spectroscopy, were between 2.50 and 2.60 eV and showed that the obtained oxides are able to absorb light in the visible part of the electromagnetic spectra.
•Poly(vinyl alcohol) is an architecture-directing agent for peroxotungstic acid.•PVAL and PTA develop two levels of organization in aqueous medium: a local structural level and fractal-like aggregates.•Structured tungsten oxide semiconductors with low band gap.•Monoclinic crystal oxide absorb radiation in the visible region of the electromagnetic spectrum.