Hydrothermal synthesis and optical property of ZnS/CdS composites

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Articles

I.

INTRODUCTION

Semiconductor nano/micromaterials have aroused widespread attention owing to their superior properties,¹and enormous potentials for improved performance and extended capabilities in the industrial fields,²such as sensing gases and humidity,³sensitizers,⁴laser devices,^5,6photocatalysts,⁷luminescent materials.⁸Among these semiconductor materials, ZnS and CdS are important ones, which are regarded as the direct band gap semiconductors with band gap energies of 3.6 and 2.42 eV, respectively.^9,10However, continuous research shows that semiconductor nano/micromaterials are not confined to single components, but extended to composite structures, where a noticeable enhancement in respect of properties can be obtained.^11,12Therefore, the potential for studying composites with enhanced properties shows promising research prospects.

Several authors have reported that ZnS nano/micromaterials exhibited high efficiencies^13-15when they were used as photodegradation catalysts. Considering that the composite structures created a possibility--think of the composites as different materials, properties, and functionalities rolled into one,¹⁶it is expected that a higher photocatalytic activity can be obtained. Recently, considerable efforts have been devoted to the preparation and design of the semiconductor composites for their superior performances. So, increasingly great progress has been made in the preparation of CdS/ZnS. Mani et al.¹⁷reported that CdS-ZnS core-shell nanoparticles could be synthesized by means of the microemulsion route and their size could be controlled by changing the microemulsion drop size. Deshpande et al.¹⁸synthesized polymer-supported CdS·ZnS nanocomposites, which exhibit better visible-light-mediated photoactivity for splitting of water, as compared to corresponding pure CdS or ZnS containing coupons. Kim et al.¹⁹prepared CdS/ZnS core-shell nanorods, stabilized them by mercaptopropionic acid in water and discovered improved optical properties as compared to bare CdS nanorods. Herein, it is necessary to further explore the new preparation method of semiconductor nano/micromaterials and study their extended performances.

In this paper, CdS/ZnS spherical composites were synthesized successfully by combining a hydrothermal route with a homogeneous precipitation process. And CdS nanoparticles were found to be assembled on the surfaces of the cubic ZnS microspheres. Furthermore, the emission peak of the as-obtained ZnS/CdS composites not only exhibited an obvious blue shift and an enhancement in its fluorescent intensity compared to the pure ZnS microspheres but also showed...