CERAMICS INTERNATIONAL Available online at www.sciencedirect.com Ceramics International 38 (2012) 6659–6664 Controlled synthesis and optical properties of doughnut-aggregated hollow sphere-like CuS Hui Qi, Jianfeng Huang n , Liyun Cao, Jianpeng Wu, Jiayin Li Key Laboratory of Auxiliary Chemistry and Technology for Chemical Industry, Ministry of Education, Shaanxi University of Science and Technology, Xi’an 710021, P.R. China Received 10 February 2012; received in revised form 15 May 2012; accepted 17 May 2012 Available online 23 May 2012 Abstract Three-dimensional (3D) doughnuts-like copper sulfide (CuS) particles were successfully synthesized by a facile microwave hydrothermal method employing polyvinylpyrrolidone (PVP) as the surfactant. The products were characterized by X-ray diffraction, field-emission scanning electron microscopy and UV–vis diffuse reflectance spectra. Results show that the products are selectively fabricated by varying the S/Cu molar ratio from 3 to 7, exhibiting a morphology change from uniform aggregated spheres to single doughnuts-like structures. Comparison of the UV–vis absorption spectra of these particles reveals that an obvious red-shift of  70 nm is found from the single doughnuts to the assembled doughnuts. Moreover, these spectra were calculated to show the bandgap of the as- prepared CuS particles varies from 1.46 eV to 1.64 eV with the morphology change from the single doughnuts-like to the aggregated spheres-like structures, respectively, indicating that the optical properties of the product may be strongly related to the state of their morphologies. & 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Keywords: Copper sulfide; Doughnut-like hollow spheres; Microwave hydrothermal method; Semiconductors 1. Introduction In recent years, there has been increasing interest in the controlled synthesis of inorganic nano/microstructures with hollow interiors because of their widespread potential applica- tions in the photonic crystals, catalysis, artificial cells, drug delivery and the protection of light sensitive components [1]. The general approach for preparation of hollow structures has involved the use of various removable or sacrificial templates, including hard ones such as monodisperse silica [2] or polymer latex spheres [3] as well as soft ones. However, hollow structures prepared from hard templating routes usually suffer from disadvantages related to high cost and tedious synthetic procedures. It is highly desirable to develop one-pot synthesis of hollow inorganic materials without hard templates. As one of the most important semiconductors, copper sulfide (CuS) is a promising material with potential applications in many fields, such as photothermal conver- sion [4], electrodes [5], and solar cell devices [6]. The controlled synthesis and self-organization of CuS with special morphologies and sizes have attracted considerable attention in the recent decades due to their outstanding properties and potential applications in numerous fields. Considerable efforts have been devoted to the synthesis of various CuS morphologies such as nanorods [7], nanowires [8], nanoplates [9,10], nanoflakes [11] and tubular struc- tures assembled by nanoflake-built microspheres [12]. Besides, the preparation CuS particles with hollow sphere- like strucutures is also under investigation [3,13,14] to show potential technological applications in optical [3] and sensor- ing [14] properties. However, long reaction times [3,14] and difficulties in controlling uniform shaped structures [15] still exist to expect further investigation on both synthesize approach improvment and precise morphology control of CuS particles. In this work, a facile and economical microwave hydro- thermal method is employed to prepare 3D CuS hollow microspheres aggregated by doughnut-like structures firstly. www.elsevier.com/locate/ceramint 0272-8842/$36.00 & 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved. http://dx.doi.org/10.1016/j.ceramint.2012.05.053 n Corresponding author. Tel./fax: þ86 029 8616 8802. E-mail addresses: qihui2005ty@126.com (H. Qi), hjfnpu01@163.com (J. Huang).