[REVIEW][OPEN ACCESS] Dispersion and surface functionalization of oxide nanoparticles for transparent photocatalytic and UV-protecting coatings and sunscreens

Sci. Technol. Adv. Mater. 14 (2013) 023001
doi:10.1088/1468-6996/14/2/023001

Bertrand Faure, German Salazar-Alvarez, Anwar Ahniyaz, Irune Villaluenga, Gemma Berriozabal, Yolanda R De Miguel and Lennart Bergström

Abstract

This review describes recent efforts on the synthesis, dispersion and surface functionalization of the three dominating oxide nanoparticles used for photocatalytic, UV-blocking and sunscreen applications: titania, zinc oxide, and ceria. The gas phase and liquid phase synthesis is described briefly and examples are given of how weakly aggregated photocatalytic or UV-absorbing oxide nanoparticles with different composition, morphology and size can be generated. The principles of deagglomeration are reviewed and the specific challenges for nanoparticles highlighted. The stabilization of oxide nanoparticles in both aqueous and non-aqueous media requires a good understanding of the magnitude of the interparticle forces and the surface chemistry of the materials. Quantitative estimates of the Hamaker constants in various media and measurements of the isoelectric points for the different oxide nanoparticles are presented together with an overview of different additives used to prepare stable dispersions. The structural and chemical requirements and the various routes to produce transparent photocatalytic and nanoparticle-based UV-protecting coatings, and UV-blocking sunscreens are described and discussed.

Correlating material-specific layers and magnetic distributions within onion-like Fe3O4/MnO/γ-Mn2O3 core/shell nanoparticles

J. Appl. Phys. 113, 17B531 (2013)

K. L. Krycka; J. A. Borchers; M. Laver; G. Salazar-Alvarez; A. López-Ortega; M. Estrader; S. Suriñach; M. D. Baró; J. Sort; J. Nogués

DOI: 10.1063/1.4801423

Abstract
The magnetic responses of two nanoparticle systems comprised of Fe₃O₄/γ-Mn₂O₃ (soft ferrimagnetic, FM/hard FM) and Fe₃O₄/MnO/γ-Mn₂O₃ (soft FM/antiferromagnetic, AFM/hard FM) are compared, where the MnO serves to physically decouple the FM layers. Variation in the temperature and applied field allows for Small Angle Neutron Scattering (SANS) measurements of the magnetic moments both parallel and perpendicular to an applied field. Data for the bilayer particle indicate that the graded ferrimagnetic layers are coupled and respond to the field as a single unit. For the trilayer nanoparticles, magnetometry suggests a Curie temperature (T_C) ≈ 40 K for the outer γ-Mn₂O₃component, yet SANS reveals an increase in the magnetization associated with outer layer that is perpendicular to the applied field above T_C during magnetic reversal. This result suggests that the γ-Mn₂O₃ magnetically reorients relative to the applied field as the temperature is increased above 40 K.

6 PhD positions in Physical, Inorganic, Materials and Environmental Chemistry

6 PhD positions in Physical, Inorganic, Materials and Environmental Chemistry at the Department of Materials and Environmental Chemistry. Reference number SU FV-1026-13 (project numbers – see below). Deadline for applications: May 2, 2013.

Application to the graduate research program (PhD studies) at MMK, April 2013
The Department of Materials and Environmental Chemistry (MMK), www.mmk.su.se, offers 6 new places for graduate students after an application procedure as described below.

General information
The extensive research activities of MMK, hosting the Berzelii Center EXSELENT for development of nanoporous materials for catalysis, span over Materials and Solid State Chemistry focusing on different classes of materials; e.g. ceramics and glasses, self-assembled and porous materials, and soft matter. The work often encompasses synthesis, characterisation by X-ray diffraction and electron microscopy, NMR studies, modelling with computer simulations of materials with a potential for various applications. Environmental aspects are an important part of the research activities, where refined natural or anthropogenic inorganic and organic chemicals and materials are studied in relation to their sole or combined impact on, and interaction with biological and non-biological systems in our global environment.

More information about available projects, requirements, and details about the application procedure at:

http://www.su.se/english/about/vacancies/phd-studies/6-phd-positions-in-physical-inorganic-materials-and-environmental-chemistry-1.129642