Letter to the Editor Structural and optical properties of ZnS/MgNb 2 O 6 heterostructures L.P.S. Santos a,⇑ , L.S. Cavalcante b , M.T. Fabbro c,d , H. Beltrán Mir c , E. Cordoncillo c , J. Andrés e , E. Longo f a Instituto Federal do Maranhão, Departamento de Química/INCTMN, Campus Monte Castelo, Av. Getúlio Vargas, 04, CEP. 65030-005, São Luís-MA, Brazil b Universidade Estadual do Piauí, CCN-DQ-GERATEC, João Cabral, N. 2231, P.O. Box 381, CEP: 64002-150, Teresina-PI, Brazil c Universitat Jaume I, Departamento de Química Inorgánica y Orgánica, Campus del Riu Sec, E-12071 Castellón, Spain d Universidade Federal de São Carlos, Departamento de Química, CDMF/INCTMN, Via Washington Luiz, Km 235, P.O. Box 676, CEP. 13565-905, São Carlos-SP, Brazil e Universitat Jaume I, Departamento de Química Física y Analítica, Campus del Riu Sec, E-12071 Castellón, Spain f Universidade Estadual Paulista, Instituto de Química, CDMF/INCTMN, Rua Francisco Degni, 55, CEP. 14800-900, Araraquara-SP, Brazil article info Article history: Received 10 September 2014 Received in revised form 8 December 2014 Accepted 9 December 2014 Available online 17 December 2014 Keywords: ZnS/MgNb 2 O 6 Chemical synthesis Heterostructures Band gap Photoluminescence abstract In this letter, we report a simple and efficient synthetic procedure where the first step is a coprecipitation/calcination method used to obtain magnesium niobate MgNb 2 O 6 (MN) nanocrystals and in the second stage a microwave assisted hydrothermal method (MAH) is employed to synthesize zinc sulfide (ZnS) nanocrystals and ZnS/ MN heterostructures. These heterostructures were characterized by X-ray diffraction (XRD), micro-Raman (MR) spectroscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high-resolution TEM (HR-TEM), selected area electron diffraction (SAED), energy dispersive X-ray spectrometry (EDX). XRD patterns and MR spectra indicate that MN and ZnS nanocrystals have an orthorhombic and cubic structure, respectively. FE-SEM, TEM and HR-TEM images proved the presence of aggregated MN nanocrystals, ZnS nanocrystals and the presence of ZnS nanocrystals on the surface of MN nano- crystals. Their optical properties were investigated by ultravio- let–visible spectroscopy (UV–vis) and photoluminescence (PL) measurements at room temperature. ZnS/MN heterostructures show a decrease in the values for the optical band gap with respect http://dx.doi.org/10.1016/j.spmi.2014.12.007 0749-6036/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +55 16 3351 8214, mobile: +55 16 99199 4343. E-mail address: presleyserejo@gmail.com (L.P.S. Santos). Superlattices and Microstructures 79 (2015) 180–192 Contents lists available at ScienceDirect Superlattices and Microstructures journal homepage: www.elsevier.com/locate/superlattices