Layered hexagonal 2H WS2 nanoparticles with preferred c-axis orientation for visible light photodetection

Abstract

Tungsten disulfide (WS 2 ) nanoparticles were synthesized via a hydrothermal route and characterized to establish the correlation between their structural characteristics and visible-light photodetection performance. X-ray diffraction confirmed a highly crystalline hexagonal 2H-WS 2 phase with an average crystallite size of 18.7 nm and preferential c-axis orientation. Raman analysis further confirmed the layered structure through characteristic E 2 g 1 (382 cm -1 ) and A 1 g (406 cm -1 ) vibrational modes, while Fourier-Transform Infrared spectroscopy verified the characteristic W S bonding. Morphological analysis revealed hierarchical, flower-like architectures self-assembled from ultrathin nanosheets, and compositional analysis confirmed a near-stoichiometric W:S ratio of 1:2.04. The nanoparticles exhibited a direct optical band gap of 2.1 eV, attributed to quantum confinement, and a zeta potential of −21.96 mV, confirming a negatively charged surface. The pellet-based photodetector delivered a maximum photocurrent of 2.88 × 10 -4 A, responsivity of 2.31 × 10 -3 A W -1 , and detectivity of 4.22 × 10 7 Jones under 470 nm illumination at an intensity of 15 mW cm -2 . These findings demonstrate the strong influence of crystallinity, c-axis orientation, and defect-assisted charge transport on the photoresponse of hydrothermally grown WS 2 nanoparticles.