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

•ZnO/SnO2 nanocomposites were prepared by supercritical fluid drying processes.•ZnO/SnO2 nanocomposites present the hertrojunction frameworks.•ZnO/SnO2 hertrojunctions were adorned with ZnO and SnO2 quantum dots.•Photoluminescence was attributed to surface dangling bonds of quantum states.

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/SnO2 nanocomposites have been successfully prepared from Zn(NO3)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.

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