OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 3 2025 a b Fig. 1. (a) Side-view of ZnO–NGM paste on FTO substrate, (b) Top view showing surface morphology Fig. 2. UV–Vis absorption spectrum of as-synthesized ZnO nanoparticles exhibiting a narrowabsorption peak at 367 nm, suggesting a direct bandgap transition and validating nanoscale crystallinity for optoelectronic and sensing purposes 1800 SHIMADZU. This peak is related to a direct bandgap energy of about 3.38 eV, which verifies the semiconducting nature of the ZnO nanostructures. The blue shift of the absorption edge from the bulk ZnO (~375 nm) as shown in Fig. 2 indicates a quantum confinement effect, a signature of the nanoscale size of the particles. The sharp and steep slope of the absorption also indicates the high crystallinity and purity of the as-synthesized ZnO nanoparticles. These optical characteristics render the material particularly apt for humidity sensing, UV photodetectors, and other optoelectronic uses, where there is a need for a fast and sensitive response to environmental stimuli. SEM images (in Fig. 3) indicated well-distributed ZnO nanoparticles with well-defined morphology. Higher magnification images indicatedwell-dispersed particleswith increased surface texture and observable agglomeration in certain areas. The scanning was performed using a JEOL JSM-6490A scanning electron microscope (JEOL Ltd., Japan). The addition of NGM enhanced the surface roughness and uniformity of distribution. The increased roughness increases the number of active sites, which aids in better water molecule adsorption, which is essential for enhanced humidity sensing performance [3]. XRD patterns showed a well-crystallized hexagonal structure of ZnO (quartzite). Peak broadening and minor shifts were noted with increasing NGM concentration, which are signs of successful NGM
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