Zinc sulfide (ZnS) is a wide direct band gap semiconductor and one of the most typical and important II-VI compound semiconductors. ZnS has attracted widespread attention in materials science due to its wide applications in optoelectronics, photovoltaics, catalysis, and bioimaging. In addition, researchers are exploring incorporating zinc sulfide into composite materials to enhance their mechanical, electrical, thermal or flame-retardant properties. In this article, Alfa Chemistry introduces the synthesis and multifunctional applications of zinc sulfide in various fields.
ZnS crystallizes in various polymorphs, primarily as the zinc-blende (zincite) and wurtzite phases. The choice of synthesis method significantly influences the resulting crystal structure and properties. These methods include vapor-phase deposition techniques (chemical vapor deposition, physical vapor deposition), solution-based techniques (hydrothermal synthesis, sol-gel method), and solid-state reactions. These synthesis techniques allow the production of high-quality zinc sulfide materials with controllable properties.
For example, layered zinc sulfide (LZnS) can be successfully synthesized via a hydrothermal method. By further introducing it into polymethylmethacrylate (PMMA) through in-situ bulk polymerization, PMMA/LZnS nanocomposites can be obtained. The nanocomposite material has the advantages of PMMA, ZnS and layered materials at the same time, showing improved thermal stability, flame retardancy and optical properties.
Preparation of PMMA/LZnS nanocompsoites. 
Thanks to its wide bandgap, ranging from 3.5 to 3.9 eV, ZnS exhibits excellent luminescent properties, making it a versatile material for efficient light emission and detection in the visible and ultraviolet spectrum. ZnS finds wide applications in optoelectronic devices such as light-emitting diodes (LEDs), photodetectors, and thin film transistors (TFTs).
In addition, ZnS can generate photon holes, and the energy level changes and energy gap broadening caused by the quantum size effect enhance its redox ability. It is also an excellent photocatalytic semiconductor.
Yu-Shuan Sue et al. successfully synthesized ZnS nanowires (ZnS NWs) using thermal evaporation based on the vapor-liquid-solid (VLS) method. Photosensing examination shows that the assembled ZnS nanowire photodetector possesses UVB radiation preferential properties. In terms of photocatalytic activity, ZnS NWs exhibit enhanced photocatalytic performance, which is attributed to the optoelectronic properties of its semiconductor material itself.
The schematic diagram of ZnS NWs synthesized by thermal evaporation. 
ZnS, possessing advantageous thermal properties and chemical stability, represents a promising candidate in the pursuit of efficient flame retardant materials. The flame retardant effect of zinc sulfide is mainly achieved from three aspects: carbon formation, free radical scavenging and preventing heat transfer.
ZnS nanoparticles can be introduced into the chlorinated styrene-butadiene rubber (Cl-SBR) matrix through a simple two-roller mixing technique. Researches have shown that there are strong interfacial interactions between rubber chains and ZnS nanoparticles. The addition of ZnS nanoparticles significantly enhanced the thermal stability, flame retardancy, and oil resistance of the nanocomposites. 
The interaction between ZnS nanoparticles and Cl-SBR.