Effect of Silver Nitrate Precursor Concentration on the Structural and Morphological Properties of Ag2O Nanoparticles Synthesized by the Sol–Gel Method

Abstract

Silver oxide (Ag₂O) nanoparticles have been synthesized by simple sol–gel method using different concentrations of silver nitrate (AgNO3) (0.5 M and 1.0 M) and then calcined at 250 °C. This work has focused on the effect of the precursor concentration on the phase, crystallinity and morphology of the product. The X-ray diffraction (XRD) analysis confirmed the formation of a single phase – the cubic structure of Ag₂O (space group Pn-3m, JCPDS card no. 41-1104) and revealed that both the samples exhibited the characteristic (111), (200), (220), (311) and (222) reflections. The intensity and sharpness of the diffraction peaks increased with the concentration of the sample and the average crystallite size estimated by the Scherrer equation was found to be 0.5 M (approx. 21.8 nm) and 1.0 M (approx. 30.7 nm) respectively, which showed that the higher the concentration the better the crystallinity. Field-emission scanning electron microscopy (FE-SEM) showed almost spherical, cauliflower-like agglomerates with the measured feature sizes ranging from about 44 to 72 nm, and which increased as the precursor concentration increased. It was observed that only silver and oxygen were present by energy-dispersive X-ray (EDX) analysis, and the ratio of Ag:O was found to be about 2:1, suggesting the presence of Ag₂O. The elemental maps revealed the uniform distribution of both elements without any trace of other impurities. The Fourier Transform Infrared (FTIR) spectrum exhibited a prominent band of metal–oxygen stretching around 540 cm⁻¹ corresponding to Ag–O stretching, and weaker bands due to the surface hydroxyl groups, adsorbed water, and residual nitrate species. The results show that the concentration of the precursor is an easy and effective parameter to control the crystallite size and crystallinity of the sol–gel Ag₂O nanoparticles at low calcination temperature.