Effect of different synthesis routes on the morphology, optical, colorimetric, and photocatalytic properties of β-Ag2MoO4 microcrystals

Abstract

In this paper, the effect of different synthesis methods, such as controlled precipitation (CP), sonochemical (SC), hot solution ion injection with fast cooling (HSIIFC), and conventional hydrothermal (CH) in obtaining silver beta molybdate (β-Ag2MoO4) were reported. X-ray diffraction patterns, Rietveld refinement data, cluster modeling, micro-Raman, and Fourier transform infrared spectroscopies confirmed that all β-Ag2MoO4 crystals have a spinel-like cubic structure, space group (Fd\(\stackrel{-}{3}\)m), and symmetry point group (\({O}_{h}^{7}\)). Field emission scanning electron microscopy (FE-SEM) images showed that through different synthetic routes, it is possible to obtain monophasic crystals, such as regular/irregular polyhedral, potatoes, and non-uniform. Ultraviolet-Visible (UV-Vis) spectroscopy measurements in absorbance mode showed three main absorptions (280, 310, and 340 nm). In contrast, the UV-Vis analysis in diffuse reflectance mode showed a tail of energy absorption in the UV spectrum range (3.25 eV and 3.3 eV). The quantitative data from the colorimetric analysis indicated that the β-Ag2MoO4 crystals are desirable for developing inorganic pigments with a beige to brown shade. Photocatalytic tests were performed using four lamps: UV-C, UV-B, UV-A, and visible light. The β-Ag2MoO4 crystals prepared by the PC method showed a higher degradation rate ≈ 85.12% for the rhodamine B dye solution under 240 min of exposure to UV-C light.