Simple preparation of broadband UV filters based on TiO2 coated with aqueous extracts of native trees from the Chaco region of Argentina.

The native forest of northwestern Argentina, as part of the Chaco region, is a rich and unexploited source of phytochemical compounds for medicinal/cosmetic applications. In the present study, fruit, leaf, branch, and bark organs of the native trees Sarcomphalus mistol (Mistol, M) and Schinopsis lorentzii (Quebracho Colorado santiagueño, QC) were harvested, and aqueous plant extracts (PE) were prepared. The spectroscopic (UV-Vis absorbance, diffuse reflectance, ATR-FTIR) and antioxidant (TEAC, Folin-Ciocalteu) properties of PE were characterized and used as TiO2 coating material to obtain a series of TiO2@PE nanocomposites. These materials showed almost null photocatalytic activity compared to aqueous suspensions of bare TiO2, displaying yellowish to brownish coloration and high long-term stability in both freshwater and seawater model solutions. The loss of photocatalytic activity in TiO2@PE was associated with the combination of the internal filter effect and the antioxidant/radical capacity exerted by the phytochemicals of the PE coating, with higher broadband photoprotection for the nanocomposites prepared with QC extracts. Thus, this study shows the potential capacity of the forest resources of the Chaco region of Argentina for the development of new cosmetic and/or sun protection formulations.

An approach to the photocatalytic mechanism in the TiO2-nanomaterials microorganism interface for the control of infectious processes.

The approach of this timely review considers the current literature that is focused on the interface nanostructure/cell-wall microorganism to understand the annihilation mechanism. Morphological studies use optical and electronic microscopes to determine the physical damage on the cell-wall and the possible cell lysis that confirms the viability and microorganism death. The key parameters of the tailoring the surface of the photoactive nanostructures such as the metal functionalization with bacteriostatic properties, hydrophilicity, textural porosity, morphology and the formation of heterojunction systems, can achieve the effective eradication of the microorganisms under natural conditions, ranging from practical to applications in environment, agriculture, and so on. However, to our knowledge, a comprehensive review of the microorganism/nanomaterial interface approach has rarely been conducted. The final remarks point the ideal photocatalytic way for the effective prevention/eradication of microorganisms, considering the resistance that the microorganism could develop without the appropriate regulatory aspects for human and ecosystem safety.

Wet-Chemical Preparation of TiO2-Based Composites with Different Morphologies and Photocatalytic Properties.

TiO2-based composites have been paid significant attention in the photocatalysis field. The size, crystallinity and nanomorphology of TiO2 materials have an important effect on the photocatalytic efficiency. The synthesis and photocatalytic activity of TiO2-based materials have been widely investigated in past decades. Based on our group's research works on TiO2 materials, this review introduces several methods for the fabrication of TiO2, rare-earth-doped TiO2 and noble-metal-decorated TiO2 particles with different morphologies. We focused on the preparation and the formation mechanism of TiO2-based materials with unique structures including spheres, hollow spheres, porous spheres, hollow porous spheres and urchin-like spheres. The photocatalytical activity of urchin-like TiO2, noble metal nanoparticle-decorated 3D (three-dimensional) urchin-like TiO2 and bimetallic core/shell nanoparticle-decorated urchin-like hierarchical TiO2 are briefly discussed.