Sol–gel synthesis of ZnO–SnO 2 nanocomposites and their morphological, structural and optical properties Suresh Kumar • Ravi Nigam • Virender Kundu • Neena Jaggi Received: 11 December 2014 / Accepted: 6 February 2015 Ó Springer Science+Business Media New York 2015 Abstract In the present work ZnO/SnO 2 nanocomposites have been synthesized by sol–gel method. Different sam- ples were prepared by annealing the precipitate at 600 and 750 °C. The structural and morphological studies of ZnO/ SnO 2 nanocomposites were carried out by XRD, SEM and EDX. Optical properties were studied by UV–Vis and photoluminescence spectroscopy. The increase in the size of the ZnO/SnO 2 nanocomposites with the presence of Zn 2 SnO 4 at the higher temperature is observed. The optical band gap of ZnO/SnO 2 nanocomposites decreases with the increase in the annealing temperature. The study reveals that the findings will be helpful in the band gap engineering of the ZnO/SnO 2 nanocomposites for novel applications. In order to exploit these distinctive properties of ZnO/SnO 2 nanocomposites for the realization of nanoscale devices, the effect of temperature on the morphology and optical properties of ZnO/SnO 2 nanocomposites were studied. ZnO/SnO 2 nanocomposites found potential applications in optoelectronics, photocatalysis, gas sensor and solar cell. 1 Introduction ZnO, SnO 2 and their composites nanostructures have been studied by my researcher in recent years because of their fascinating properties and their applications in advanced optoelectronic devices, solar cell, sensors and other nanoelectronics devices. Sohila et al. [1] and Vijayalakshmi et al. [2] reported the synthesis of ZnO based nanocompos- ites such as ZnO/CuO and ZnO/SnS and studied their mor- phological and optical properties. ZnO and SnO 2 are widely studied oxide semiconductor materials and have energy bang gap of 3.37 and 3.6 eV respectively and the energy band gap of ZnO/SnO 2 composites depends on Zn/Sn molar ratio in the composite material [3]. ZnO and SnO 2 coupled oxide semiconductors have distinguished characteristics of both the component oxides with tunable properties that enable it for novel applications [4]. The study of such coupled oxides semiconductors is important in tailoring the properties of future chemical sensors [5]. The coupled oxide semicon- ductors such as ZnO/SnO 2 system possesses high photo catalytic efficiency i.e. higher charge separation and higher range of photo excitation energy rather than single semi- conductor photo catalyst [4–6]. ZnO/SnO 2 nanostructures had exhibited higher photo catalytic activities than that of SnO 2 or ZnO rods alone [5–9]. Ali et al. [10] and Uddin et al. [11] have reported photocatalytic properties of ZnO/SnO 2 nanostructures for degradation of organic dyes. The hetero- junction structure between ZnO/SnO 2 plays very important role in improving its sensing properties [12]. In ZnO/SnO 2 nanostructures, enhanced near-band gap emissions com- pared to SnO 2 nanowires has been reported and proved to be an excellent candidate for ultrasensitive gas sensors [3, 4]. Davis et al. [12], Song et al. [13], Jia et al. [14] and Liangyuan et al. [15] have reported ZnO/SnO 2 nanostruc- tures/nanocomposites based sensors for NO 2 , ethanol etc. ZnO/SnO 2 composite nanostructures are a promising can- didate for anode material in rechargeable lithium-ion battery. Ahmed et al. [16] studied ZnO/SnO 2 composite structure for the lithium-ion battery electrode and showed an excellent improvement in lithium storage capacity as compared with pure ZnO. Liu et al. [3], Asokan et al. [4], Yang et al. [5] and S. Kumar (&) Á V. Kundu Department of Electronic Science, Kurukshetra University, Kurukshetra 136119, India e-mail: sawan2k2@yahoo.co.in R. Nigam Á N. Jaggi Department of Physics, National Institute of Technology, Kurukshetra 136119, India 123 J Mater Sci: Mater Electron DOI 10.1007/s10854-015-2826-5