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Advances in Materials Science and Engineering
Volume 2012, Article ID 748098, 15 pages
http://dx.doi.org/10.1155/2012/748098
Research Article

The Role of pH in PEG-b-PAAc Modification of Gadolinium Oxide Nanostructures for Biomedical Applications

1Center for Technologies against Cancer (CTC), Tokyo University of Science, 2669 Yamazaki Noda, Chiba 278-0022, Japan
2Department of Materials Science and Technology, Tokyo University of Science, 2641 Yamazaki Noda, Chiba 278-8510, Japan

Received 6 February 2012; Accepted 26 June 2012

Academic Editor: Dachamir Hotza

Copyright © 2012 Eva Hemmer et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Upconversion and near-infrared emitting Gd2O3:Er3+,Yb3+ nanostructured phosphors (nanoparticles and nanorods) for applications in bioimaging have been synthesized by precipitation methods and hydrothermal treatment. Variation of the material synthesis conditions (additives and pH) allows controlling particle size (40 nm to μm range) and rod aspect ratio (5 to 18). It was shown that PEG-b-PAAc (poly(ethylene glycol) poly(acrylic acid) block polymer) is suitable to provide the required chemical durability, dispersion stability, and noncytotoxic behaviour for biomedical applications, where the coating of Gd2O3 with a protecting and biocompatible layer is essential in order to prevent the release of toxic Gd3+ ions. Physicochemical properties of the Gd2O3:Er3+,Yb3+ nanostructures modified with PEG-b-PAAc have been investigated by TG-DTA, FT-IR, and DLS revealing a strong influence of modification conditions, namely, pH of the reaction media, on the nature of the PEG-b-PAAc layer.