This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2023 New J. Chem. Cite this: DOI: 10.1039/d2nj05012a ZnS–RGO nanocomposite structures: synthesis, characterization and field emission properties Sanjeewani R. Bansode,* Mahendra A. More and Rishi B. Sharma * Zinc sulphide–reduced graphene oxide (ZnS–RGO) nanocomposite structures with varying sulphur con- tent were synthesized by a simple solvothermal process. The various ZnS–RGO nanocomposite struc- tures were characterized by XRD, SEM, TEM, Raman spectroscopy and field emission (FE) techniques. The SEM images revealed that the size of the ZnS nanospheres was in the range of B500–2000 nm. Field emission (FE) measurements on the various ZnS–RGO nanocomposite emitters were carried out in an ultra-high vacuum (UHV) environment (P o 1  10 8 mbar). The highest current density of B1490 mA cm 2 was recorded from the nanocomposite at an applied field of 6.40 V mm 1 . The fluctuations in the field emission current were within 15%. Due to higher current density and lower fluctuations in the emission current, the ZnS–RGO nanocomposite material could find useful applica- tions in the development of efficient vacuum nano electronic devices and flat panel displays. 1. Introduction In recent years, two-dimensional (2D) materials have attracted the attention of researchers. 1,2 Layered materials like graphene, its composites, and reduced graphene oxide (RGO) are well established 2D materials. The atomically sharp edges, rapid electron transport along the surface, and robust structure of 2D materials offer unique advantages for the development of efficient field emission devices. Towards this objective, researchers have studied the field emission behaviour of single layer graphene, multilayer graphene, few layer graphene and reduced graphene oxide. 3–5 The semiconducting ZnS, being a nontoxic, non-hazardous and eco-friendly material with the work function of 7 eV, finds several applications in optoelec- tronics, energy storage, UV and gas sensors, flat panel displays and field emission devices. 6–9 Synthesis strategies for different nanostructures of ZnS in the form of nanowire, flower-like microspheres, hollow ZnS nanospheres and porous ZnO micro- spheres have been reported in the literature by researchers. 10–13 Field emission studies of ZnS nanobelts, ZnS arrays and nanotubes, ZnS branched nanotubes and ZnS hexagonal pyr- amids have been reported in the literature. 14–17 It is well known that graphene nanostructures tend to re-stack resulting in reduction of their effective emitting area. This reduction in the emitting area may cause deterioration in their field emis- sion behaviour. To prevent the graphene layers from stacking, it is considered appropriate to prepare suitable nanocomposite heterostructures for achieving superior field emission proper- ties. Nanostructured composites of graphene with CdS and ZnS, and RGO with ZnS have been synthesised by researchers using different methods for various technological applications. 18–21 Rathi and Kundalwal have employed a novel technique of ultrasonic dual mixing to prepare a functionalised MWCNT/ epoxy nanocomposite system with enhanced mechanical and fracture properties. 22 We have recently observed that ZnS nano- spheres grow on RGO nanosheets. 23 In the present paper, we report the detailed field emission studies of ZnS–RGO nano- composite structures synthesized by a simple and cost effective one-step solvothermal method with different sulphur contents. 2. Experimental 2.1 Synthesis of pristine ZnS nanostructures Using a solvothermal route, the ZnS nanostructures were synthesized by using ethanol as a solvent. In a typical solvother- mal setup, 1.5 g zinc chloride (ZnCl 2 , anhydrous, powder, Z99.99%, Sigma Aldrich) and 0.75 g thiourea (CH 4 N 2 S, ACS reagent, Z99.0%, Sigma Aldrich) were dissolved in 40 ml of ethanol and stirred for 15 min at room temperature. The prepared solution was transferred into a Teflon-lined stainless- steel autoclave of 80 ml capacity. Then, the autoclave was placed in a furnace at 180 1C for 16 h. After completion of the reaction, the furnace was allowed to cool naturally to room temperature. The final product was collected from the autoclave and washed with ethanol and deionised (DI) water. The washed product was Centre for Advanced Studies in Materials Science and Condensed Matter Physics, Department of Physics, Savitribai Phule Pune University, Pune-411007, Maharashtra, India. E-mail: srbansode4@gmail.com, rbs@physics.unipune.ac.in, rbsharma111@gmail.com Received 12th October 2022, Accepted 12th December 2022 DOI: 10.1039/d2nj05012a rsc.li/njc NJC PAPER Published on 13 December 2022. Downloaded by Savitribai Phule Pune University on 1/9/2023 9:31:36 AM. View Article Online View Journal