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Journal of Nanotechnology
Volume 2012 (2012), Article ID 195761, 5 pages
http://dx.doi.org/10.1155/2012/195761
Research Article

In Situ Chemical Oxidation of Ultrasmall MoOx Nanoparticles in Suspensions

Department of Materials Science and Engineering, University of Texas at Dallas, 800 W Campbell Road, RL10, Richardson, TX 75080, USA

Received 8 June 2012; Accepted 23 July 2012

Academic Editor: Mallikarjuna Nadagouda

Copyright © 2012 Yun-Ju Lee 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

Nanoparticle suspensions represent a promising route toward low cost, large area solution deposition of functional thin films for applications in energy conversion, flexible electronics, and sensors. However, parameters such size, stoichiometry, and electronic properties must be controlled to achieve best results for the target application. In this report, we demonstrate that such control can be achieved via in situ chemical oxidation of MoOx nanoparticles in suspensions. Starting from a microwave-synthesized suspension of ultrasmall (d~2 nm) MoOx nanoparticles in n-butanol, we added H2O2 at room temperature to chemically oxidize the nanoparticles. We systematically varied H2O2 concentration and reaction time and found that they significantly affected oxidation state and work function of MoOx nanoparticle films. In particular, we achieved a continuous tuning of MoOx work function from 4.4 to 5.0 eV, corresponding to oxidation of as-synthesized MoOx nanoparticle (20% Mo6+) to essentially pure MoO3. This was achieved without significantly modifying nanoparticle size or stability. Such precise control of MoOx stoichiometry and work function is critical for the optimization of MoOx nanoparticles for applications in organic optoelectronics. Moreover, the simplicity of the chemical oxidation procedure should be applicable for the development of other transition oxide nanomaterials with tunable composition and properties.