Experimental and Theoretical Correlation of Modulated Architectures of β-Ag2MoO4 Microcrystals: Effect of Different Synthesis Routes on the Morphology, Optical, Colorimetric, and Photocatalytic Properties

Abstract

In this paper, the effect of different synthesis methods, such as controlled precipitation (CP), sonochemical (SC), hot solution ion injection with fast cooling, and conventional hydrothermal (CH) in obtaining beta-disilver molybdate (β-Ag 2 MoO 4 ) are explained in details. X-ray diffraction patterns, Rietveld refinement data, cluster modeling, micro-Raman, and Fourier transform infrared spectroscopies confirmed that all β-Ag 2 MoO 4 crystals have a spinel-like cubic structure, space group (Fd 3 m), and symmetry point group (O 7 h ). 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 polyhedrons (cubes, cuboctahedron, trapezohedron, rhombic dodecahedron), potatoes, and non-uniform. The crystal shape observed experimentally was modeled based on Rietveld refinement data and FE-SEM images obtained by KrystalShaper. First-principles quantum mechanical calculations based on density functional theory were employed to modulate the surfaces of the material and to obtain their surface energy (E surf ) values. From these E surf values in association with the Wulff construction, the evolution of the crystals shape was achieved correlating with the experimental results when different synthesis methods are used. Ultraviolet-Visible (UV-Vis) spectroscopy measurements in absorbance mode showed three main absorptions (280, 310, and 340 nm), while the UV-Vis analyses 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-Ag 2 MoO 4 crystals are desirable for developing inorganic pigments with a beige to brown shade. Photocatalytic assays were performed using four lamps: UV-C, UV-B, UV-A, and visible light. The β-Ag 2 MoO 4 crystals prepared by the CP method showed a higher degradation rate at 85.12% for the rhodamine B dye solution under 240 min exposure to UV-C light.

High-Temperature Friction and Wear Behavior of Nickel-Alloy Matrix Composites with the Addition of Molybdate

“…To better comprehend the composite's wear behavior at elevated temperatures, the element distribution and the phase constituents of the worn surface were analyzed by the micro-zone Raman spectrum (Figure 13) and by SEM (with EDS) (Figures 14-16). Results indicate that the main phase constituents are BaMoO 4 , Ag 2 MoO 4 , and NiCr 2 O 4 [39][40][41], and the intensity of these oxides increases as the testing temperature rises from 25 to 800 • C (Figure 13c), which is consistent with the previously reported results. Furthermore, it has been shown that the oxide layer with these constituents can reduce friction and wear effectively in a tribopair system [6,28].…”

Tracking of structural defects induced by Eu-doping in β-Ag2MoO4: their influences on electrical properties

“…Comprehending the intricate relationship between the structure, defect nature, and electrical transport properties is paramount in the design of multifunctional semiconductors. Molybdates with the molecular formula X 2 MoO 4 , where X = Li, Tl, and Ag, have garnered significant attention within the scientific community due to their remarkable photocatalytic properties, 1,2 applications in scintillators, 3 sensors, [4][5][6] optical fibers, 7 as well as their outstanding performance in diverse applications such as antibacterial, 8 antifungal, 9 antiviral, 10 tribological, 11 microwave dielectric, 12 and supercapacitor electrode 13 applications. Furthermore, highly pure β-Ag 2 MoO 4 with a spinel-type cubic structure has been synthesized for catalysis applications due to its electronic properties.…”

Characterization and Formation Mechanism of Ag2MoO4 Crystals via Precipitation Method: Influence of Experimental Parameters and Crystal Morphology

“…Ag 2 MoO 4 is an interesting semiconductor, with a band gap around 3.30 eV [1,2], depending on the polymorph, and it has recently been attracting a lot of interest for its excellent properties, that can find applications in many fields. It has a high electrical conductivity [3], exhibits photoluminescence [3,4], suggesting a possible use as a sensor, it has been claimed that it could be use as supercapacitor [5], it is an excellent catalyst for many organic reactions [6][7][8], and it has shown good antimicrobial capabilities [2,9,10]. These aspects are also combined with very low toxicity [9] and excellent ease of chemical synthesis [1,3].…”

“…It has a high electrical conductivity [3], exhibits photoluminescence [3,4], suggesting a possible use as a sensor, it has been claimed that it could be use as supercapacitor [5], it is an excellent catalyst for many organic reactions [6][7][8], and it has shown good antimicrobial capabilities [2,9,10]. These aspects are also combined with very low toxicity [9] and excellent ease of chemical synthesis [1,3].…”

“…This material has been synthesized by many different routes, including solid-state reactions, classical or microwave-assisted hydrothermal methods, and sonochemical processes [3]. However, considering its high insolubility in water, (pKs = 11.6), one of the most practical ways to obtain it is through a controlled precipitation process.…”