Production of beads like hollow nickel oxide nanoparticles using colloidal-gel electrospinning methodology Nasser A. M. Barakat Æ Abd El-Nasser M. Omran Æ Santosh Aryal Æ Faheem A. Sheikh Æ Hyo Kyoung Kang Æ Hak Yong Kim Received: 23 July 2007 / Accepted: 24 September 2007 / Published online: 31 October 2007 Ó Springer Science+Business Media, LLC 2007 Abstract In the present study colloidal-gel electrospin- ning technique is proposed to produce new shape of nickel oxide hollow nanoparticles. In the colloidal-gel process, a colloidal precursor was prepared by dissolving nickel acetate tetra hydrate in ethanol at 352 K. The precursor was mixed with poly(vinyl acetate)/N, N-dimethylform- amide (14 wt%). The polymer-precursor mixture was electrospun at relatively low voltage depending on the concentration of nickel acetate in the precursor. The obtained mat was dried under vacuum at 353 K for 24 h, and then sintered at 827 K for 3 h. The XRD and SEM results indicated that the proposed methodology produces pure nickel oxide hollow nanoparticles with beads-like form. Introduction In recent years, nanostructured materials have been actively studied due to both scientific interests and poten- tial applications. Among them, much attention has been focused on the research field of nanoscale oxide particles of transition metals, which are gaining continuous importance for various applications such as catalysts, passive elec- tronic components, and ceramic materials [1]. Nickel oxide (NiO) is a very important material extensively used in catalysis [2], battery cathodes [3, 4], gas sensors [5], electrochromic films [6], and magnetic materials [7]. Sev- eral researchers have prepared NiO nanoparticles by various methods like sol–gel [8], surfactant-mediated synthesis [9], thermal decomposition [10], and polymer- matrix assisted synthesis [11]. It is noteworthy mentioning that the reported methods produced nearly one shape of nickel oxide nanoparticles; namely cubic. Also, some of them suffer from the lack of homogeneity in the produced nanoparticles [12]. Here, we offer new methodology for production of homogenous hollow nickel oxide nanopar- ticles having beads-like form via modification of the traditional sol–gel electrospinning technique. In this study, mixture of colloidal solution and polymer has been electrospun rather than the real-solution/polymer mixture in the ordinary sol–gel electrospinning process. The colloidal solution (precursor) was prepared by mixing nickel acetate tetra hydrate and ethanol at 352 K (i.e., at the boiling point of ethanol). At this temperature ethanol can carry big amount of nickel acetate (up to 50 wt%) without precipitation of nickel acetate particles. The precursor was mixed with 14% (wt) poly(vinyl acetate) (PVAc) solution (solvent was N,N-dimethylformamide (DMF)) with ratio of 3:2. After good mixing the mixture was electrospun and dried under vacuum at 353 K for 24 h. Scanning electron N. A. M. Barakat Á A. E.-N. M. Omran Á F. A. Sheikh Á H. Y. Kim Department of Bionano System Engineering, College of Engineering, Chonbuk National University, Jeonju 561-756, Republic of Korea N. A. M. Barakat Chemical Engineering Department, Faculty of Engineering, El-Minia University, El-Minia, Egypt S. Aryal Center for Healthcare Technology Development, Chonbuk National University, Jeonju 561-756, Republic of Korea H. K. Kang Á H. Y. Kim (&) Department of Textile Engineering, Chonbuk National University, Jeonju 561-756, Republic of Korea e-mail: khy@chonbuk.ac.kr 123 J Mater Sci (2008) 43:860–864 DOI 10.1007/s10853-007-2190-9