Structure and photoluminescence of ZnO/niobate composites self-assembled from Zn(NH3)42+ solution with different pH and contents

ZnO/niobate composites were first synthesised through the exfoliation of layered niobate and restacking of nanosheets in Zn(NH3)(4)(2+) solution, followed by heat-treatment. The effects of pH and content of Zn(NH3)(4)(2+) solution on the structure and interlayer guests of the self-assembled compounds were systematically investigated. All the as-prepared samples obtained at the conditions of 0.1 mol L-1 Zn(NH3)(4)(2+) with pH from 11.2 to 12.7, can be indexed to tetragonal symmetry. The amount of interlayer Zn-species tends to decrease slightly as the pH value increases, while it increases markedly with an increase of Zn(NH3)(4)(2+) content and subsequently affects the photoluminescence of the heated-samples. Photoluminescent Spectra of all the heated-samples show blue-shifts of 0.15-0.22 eV with respects to the bulk ZnO band gap (3.26 eV) due to quantum confinement. The UV emission at 359 nm obviously weakens and the emission at 398 nm gradually enhances as content of Zn(NH3)(4)(2+) increases from 0.1 to 0.8 mol L-1. (C) 2009 Elsevier B.V. All rights reserved.