Brief communication A simple route to the synthesis of high-quality NiO nanoparticles C.T. Meneses 1,2, *, W.H. Flores 1 , F. Garcia 2 and J.M. Sasaki 1 1 Departamento de Fı´sica, Universidade Federal do Ceara ´, Campus do Pici, CP 6030, 60455-760, Fortaleza, CE, Brazil; 2 Laborato ´rio Nacional de Luz Sı´ncrotron, CP 6192, CEP 13084-971, Campinas, SP, Brazil; *Author for correspondence (Tel.: +55-85-4008-9917; Fax: +55-85-4008-9450; E-mail: cristiano@fisica.ufc.br) Received 16 December 2005; accepted in revised form 2 April 2006 Key words: gelatin, nanoparticles, nickel oxide, Rietveld refinement, X-ray powder diffraction Abstract Dispersed nickel oxide nanoparticles were obtained by a simple and low-cost method using a mixture of gelatin as organic precursor and NiCl 2 6H 2 O as Ni source. The average particle size was estimated from X-ray powder diffraction (XRPD) peaks using the Rietveld refinement. The values ranged from 3.2 to 79 nm. We observed that the particle size changes as a function of synthesis time, with a notable decrease after the addition of NaOH to the solution. Field emission scanning electron microscopy (FE-SEM) measurements show that particles have well defined shapes and are dispersed in an organic matrix. X-ray absorption near edge spectroscopy (XANES) shows also the formation of fcc NiO nanoparticles structures. Introduction In recent years, synthesis processes to grow dis- persed nanoparticles in a matrix have attracted the attention of several researchers. However, the growth of dispersed nanoparticles with homoge- nous sizes is not easy. The great interest to obtain nanoparticles is related to various applications in different fields, such as catalysis (Turky, 2003), electrochromic films (Ferreira et al., 1996), mag- netic materials (Kodama et al., 1997; Bødker et al. 2000) and battery cathodes (Makkus et al., 1994). Several methods have been studied to make NiO nanoparticles using sometimes expensive products or difficult methods. Xiang et al. (2002) synthe- sized NiO nanoparticles with sizes of 190 nm using air-calcination of precipitates obtained with NiCl 2 –(NH 4 )CO 3 and alcohol. Bødker et al. (2000) produced particles with sizes around 9–15 nm by annealing precipitates Ni(OH) 2 added to HNO 3 to disperse them. Turky (2003), obtained NiO by thermal decomposition of nickel carbonate in air at different temperatures with sizes around 30– 275 nm. Another method used to produce NiO nanoparticles with a size of 30 nm uses a flame spray pyrolysis reactor to start the aqueous solu- tion (Seo et al., 2003). The latter in particular is a very expensive method and uses high temperatures. These processes to obtain NiO nanoparticles are efficient, but none of them present dispersed nanoparticles, easy methods and low cost com- pared to that shown in this paper and others works with different materials (Duque et al., 2001; Mac- eˆdo & Sasaki, 2002; Medeiros et al., 2004). In this work we report a new method, which uses commercial gelatin to obtain NiO nanoparticles dispersed in an organic matrix. Structural characterization by X-ray absorption spectroscopy (XAS) and X-ray powder diffraction (XRPD) were used to certify the existence of fcc Journal of Nanoparticle Research (2007) 9:501–505 Ó Springer 2006 DOI 10.1007/s11051-006-9109-2