ORIGINAL PAPER NiTiO 3 nanoparticles encapsulated with SiO 2 prepared by sol–gel method K. P. Lopes Æ L. S. Cavalcante Æ A. Z. Simo ˜es Æ R. F. Gonc ¸alves Æ M. T. Escote Æ J. A. Varela Æ E. Longo Æ E. R. Leite Received: 5 July 2007 / Accepted: 19 October 2007 / Published online: 16 November 2007 Ó Springer Science+Business Media, LLC 2007 Abstract NiTiO 3 (NTO) nanoparticles encapsulated with SiO 2 were prepared by the sol–gel method resulting on core-shell structure. Changes on isoelectric point as a function of silica were evaluated by means of zeta poten- tial. The NTO nanoparticles heat treated at 600°C were characterized by X-ray diffraction, transmission electron microscopy (TEM) and energy dispersive X-ray analysis. TEM observations showed that the mean size of NTO is in the range of 2.5–42.5 nm while the thickness of SiO 2 shell attained 1.5–3.5 nm approximately. Keywords Nanoparticles  Coating  Sol–gel method  NiTiO 3  Silica 1 Introduction The increasing necessity of functional materials in several areas of knowledge has stimulated researchers of the whole world to study methodologies that result in materials with optimized specific properties, becoming them attractive for the scientific and technological point of view [1]. In the field of nanotechnology, it has been increasing the pro- cessing of nanocomposites [2]. A composite can be defined as a material formed by two or more constituents which offers properties that are not possible to obtain from a individual components [3]. However, a nanocomposite constitutes a new multiphasic material, where one of the phases possesses dimensions in nanometric scale [2, 4]. Several methods for modification of inorganic particles surface exist in literature [2, 5, 6]. A method of production of nanocomposites that combines flexibility in the choice of the phases, control of homogeneity and of the aggre- gation of particles is desirable. Many times, the modification is made by deposition of a composition in the particles surface which can remain on it by simple elec- trostatic interactions or chemical bonding. A good route for synthesis of nanocomposites is based on chemical method of metallic alkoxide hydrolysis [7]. Metallic alkoxides such as tetraethylortosilicate (TEOS) are highly water-reactive compounds that possess bonds of the type metal–oxygen–carbon. A polymeric gel is formed K. P. Lopes  L. S. Cavalcante (&)  R. F. Gonc ¸alves  E. R. Leite Laborato ´rio Interdisciplinar de Eletroquı ´mica e Cera ˆmica, Departamento de Quı ´mica, Universidade Federal de Sa ˜o Carlos, P.O. Box 676, Sa ˜o Carlos, SP 13565-905, Brazil e-mail: laeciosc@bol.com.br K. P. Lopes e-mail: kirian@liec.ufscar.br R. F. Gonc ¸alves e-mail: rosana.gon@liec.ufscar.br E. R. Leite e-mail: derl@power.ufscar.br A. Z. Simo ˜es  J. A. Varela  E. Longo Laborato ´rio Interdisciplinar em Cera ˆmica, Departamento de Fı ´sico-Quı ´mica, Instituto de Quı ´mica, Universidade Estadual Paulista, P.O. Box 355, Araraquara, SP 14801-907, Brazil e-mail: alezipo@yahoo.com J. A. Varela e-mail: varela@iq.unesp.br E. Longo e-mail: elson@iq.unesp.br M. T. Escote Centro de Engenharia, Modelagem e Cie ˆncias Sociais Aplicadas, Universidade Federal do ABC, Rua Catequese 240, Santo Andre ´, SP 09090-400, Brazil e-mail: marcia.escote@ufabc.edu.br 123 J Sol-Gel Sci Technol (2008) 45:151–155 DOI 10.1007/s10971-007-1649-0