RESEARCH PAPER Characterization and applications of as-grown b-Fe 2 O 3 nanoparticles prepared by hydrothermal method Mohammed M. Rahman • Aslam Jamal • Sher Bahadar Khan • Mohd Faisal Received: 23 December 2010 / Accepted: 17 February 2011 / Published online: 5 March 2011 Ó Springer Science+Business Media B.V. 2011 Abstract The production of low-dimensional nano- particles (NPs) with appropriate surface modification has attracted increasing attention in biological, bio- chemical, and environmental applications including chemical sensing, photocatalytic degradation, separa- tion, and purification of toxic molecules from the matrices. In this study, iron oxide NPs have been prepared by hydrothermal method using ferric chloride and urea in aqueous medium under alkaline condition (pH 9 * 10). As-grown low-dimensional NPs have been characterized by UV–vis spectroscopy, FT-IR, X-ray diffraction, Field emission scanning electron microscopy, Raman spectroscopy, High-resolution Transmission electron microscopy, and Electron Dif- fraction System. The uniformity of the NPs size was measured by the scanning electron microscopy, while the single phase of the nanocrystalline b-Fe 2 O 3 was characterized using powder X-ray diffraction tech- nique. As-grown NPs were extensively applied for the photocatalytic degradation of acridine orange (AO) and electrochemical sensing of ammonia in liquid phase. Almost 50% photo-catalytic degradation with AO was observed in the presence of UV sources (250 W) with NPs. b-Fe 2 O 3 NP-coated gold electrodes (GE, surface area 0.0216 cm 2 ) have enhanced ammo- nia-sensing performances in their electrical response (I–V characterization) for detecting ammonia in liquid phase. The performances of chemical sensor were investigated, and the results exhibited that the sensi- tivity, stability, and reproducibility of the sensor improved significantly using b-Fe 2 O 3 NPs on GE surface. The sensitivity was approximately 0.5305 ± 0.02 lAcm -2 mM -1 , with a detection limit of 21.8 ± 0.1 lM, based on a signal/noise ratio of 3 with short response time. Keywords Iron oxide nanoparticles  Optical properties  Structural properties  Photodegradation  Acridine orange  Chemical sensors Introduction Semiconducting nano-materials have attracted much attention because of their unique properties and potential applications in all the areas of science (Kumar and Singhal 2007). The simplest synthetic route to nanomaterials is probably self aggregation, in which ordered aggregates are formed in a spon- taneous process (Whitesides and Boncheva 2002). M. M. Rahman  A. Jamal  S. B. Khan  M. Faisal Department of Chemistry, Faculty of Sciences and Arts, Najran University, P. O. Box 1988, Najran 11001, Kingdom of Saudi Arabia M. M. Rahman (&)  A. Jamal  S. B. Khan  M. Faisal Center for Advanced Materials and Nano-Engineering (CAMNE), Najran University, P. O. Box 1988, Najran 11001, Kingdom of Saudi Arabia e-mail: mmrahmanh@gmail.com 123 J Nanopart Res (2011) 13:3789–3799 DOI 10.1007/s11051-011-0301-7