Heterojunctions and optical properties of ZnO/SnO2 nanocomposites adorned with quantum dots

Semiconductor oxide nanocomposites have attracted widespread attention because of their potential to combine desirable properties of different nanoscale building blocks to achieve advantageous optical properties. Among these semiconductor oxides, SnO₂ and ZnO semiconductor materials as well-known direct wide band gaps have numerous applications in micro/nanodevices, gas sensors and catalyst supports due to their excellent optoelectronic and highly sensitive gas sensing properties. Herein, ZnO/SnO ₂ nanocomposites have been successfully prepared from Zn(NO ₃)₂·6H₂O and SnCl₄· 5H₂O by sol-gel method and supercritical fluid drying processes. Micro/nanostructural analysis revealed the presence of heterojunction frameworks in the ZnO/SnO₂ nanocomposites. These heterojunction frameworks were adorned with ZnO and SnO₂ quantum dots. The size distribution of ZnO and SnO₂ quantum dots ranged from 3-7 nm. These quantum dots were dispersed uniformly on the ZnO/SnO₂ heterojunction frameworks. Experimental results indicated that calcination temperatures could affect the optical properties of ZnO/SnO₂ nanocomposites. The photoluminescence intensity increased when the calcination temperature increased from 500-700 °C. This is attributed to the decrease in the number of surface dangling bonds of ZnO and SnO₂ quantum states. © 2014 Elsevier B.V.