Nanocomposites and nanomaterials

Changes in the chemical, structural and photonic properties of TiO2 and ZnO nanoparticles upon co-milling with polypropylene
Skurikhina O.1, Tothova E.1, Markovic S.2, Senna M.1,3
1 Institute of Geotechnics of SAS, Watsonova 45, 040 01 Košice, Slovak Republic. 
E-mail: skurikhina@saske.sk
2 Institute of Technical Sciences of SASA, Knez Mihailova 35/IV, 11000 Belgrade, Republic of Serbia. 
3 Department of Applied Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohokuku, 223-8522 Yokohama, Japan.

Upon milling metal oxides nanoparticles with hydrocarbon, abstraction of oxygen takes place at their boundary, leaving oxygen vacancies in the oxides. This triggers many unusual properties upon irradiation of electromagnetic waves. Here we report effects of milling TiO2 and ZnO nanoparticles with polypropylene (PP) particles. Coloring and associated increase in the visible light absorption was the first distinctive observation. We therefore observed related photocatalytic activity of the milling products. Since the photocatalytic activity upon milling contains an overall consequence of many different properties, among others, specific surface area, near surface band gaps or lattice defects including oxygen vacancies mentioned above, some irregular changes in the methylene blue (MB) degradation upon visible light irradiation were observed. For instance, milling TiO2 with PP for 60 min exhibited complex changes with partial increase in the photocatalytic activity, but prolonged milling decreased the activity. By detailed examination including subsequent heating, we discuss the positive factors of enhancing photocatalytic activity upon co-milling, based on various characterization including vibrational, electromagnetic and resonance spectroscopic techniques.