Efficient synthesis of Gd-doped ZnWO₄@GO composite and investigation of luminescence properties

Abstract

This work investigates the structural, multi-excitation luminescence, and alpha-induced scintillation properties of a Gd-doped zinc tungstate/graphene oxide (ZnWO₄/GO: Gd) ternary nanocomposite. Pristine ZnWO₄, GO, and the ZnWO₄/GO: Gd composite were synthesized via a facile co-precipitation route combined with a modified Hummers' method. Comprehensive characterizations using XRD, XPS, TEM, FE-SEM, EDS, and FTIR confirmed the formation of the monoclinic wolframite ZnWO₄ phase with predominantly spherical nanoparticles (average size ∼111 nm) uniformly anchored onto the 2D GO sheets. Under ultraviolet illumination and ion-beam bombardment (2.2 MeV protons and 5.5 MeV alpha), the composite exhibited broad blue emission centered at 460–465 nm. This emission enhancement and spectral modulation are attributed to the synergistic interplay between Gd³⁺-mediated defect engineering in the host matrix and accelerated interfacial charge extraction facilitated by the GO network. Under irradiation with a 9.8 kBq ²⁴¹Am alpha source, the ZnWO₄/GO: Gd composite achieved a net counting rate of 2518 ± 2.9 counts s⁻¹, representing an approximately 2.69-fold enhancement (∼169% increase) compared to the ZnWO₄:Gd reference (936 ± 1.8 counts s⁻¹) under identical detection geometries. Furthermore, the ternary composite demonstrated high linearity with respect to alpha-source activity and a fast scintillation response time of approximately 0.59 μs. These results demonstrate the strong potential of Gd-modified ZnWO₄/GO nanocomposites as cost-effective, scalable, and efficient phosphors for ionizing-radiation detection and optoelectronic sensing applications.