João Victor Barbosa Moura

The rare-earth compound cerium­(III) molybdate (Ce₂(MoO₄)₃) has gained attention due to its diverse industrial applications, such as photocatalysis, corrosion inhibition, self-repair of protective layers, as well as antiviral and antibacterial properties. However, its response to extreme temperature conditions remains insufficiently explored. This study employs ambient powder X-ray diffraction (PXRD), UV–vis diffuse reflectance spectroscopy, scanning electron microscopy (SEM), and Raman spectroscopy techniques to confirm the successful hydrothermal synthesis of a crystalline sample of the Ce₂(MoO₄)₃ compound. Subsequently, in situ temperature-dependent (13–973 K) XRD and Raman scattering (293–998 K) studies were conducted. Rietveld analysis of diffraction patterns reveals a stable low-temperature phase (13–303 K) and anomalies in the high-temperature evolution (T > 583 K) of lattice parameters and the sample’s microstrain and crystallite size. In the high-temperature (T > 848 K) Raman spectra of Ce₂(MoO₄)₃, an additional band emerges at 452 cm^–1; the observed anomalies are attributed to an isostructural phase transition (IPT). This type of phase transition is among the rarest phenomena reported in the literature. Our findings enhance the understanding of the physical properties of Scheelite-type compounds and emphasize the importance of investigating these uncommon phenomena. This knowledge can potentially drive the development of novel materials and expand their applications in materials science.

This study reports on the synthesis, characterization, and application of sodium-lanthanum molybdate [NaLa(MoO₄)₂] as a photocatalyst in the degradation process of Coomassie Brilliant Blue G-250 (CBB-250), an environmentally toxic and recalcitrant dye derived from triphenylmethane. The highlighted ceramic material was produced by coprecipitation, and its properties were studied using a range of physicochemical techniques including compositional, crystallographic, and morphological analyses. Among the most relevant information, X-ray diffraction (XRD), Raman spectroscopy, and Fourier transform infrared (FTIR) spectroscopy confirmed the formation of NaLa (MoO₄)₂ crystals with a tetragonal arrangement. Additionally, the scanning electron microscope (SEM) images provide evidence of the production of overlapping plate-like microstructures. The nitrogen adsorption isotherms demonstrated that the molybdate obtained exhibits mesoporous organization, with a surface area and pore diameter equivalent to 45.7 m² g^-1 and 6.54 nm, respectively. Photocatalytic tests, performed under ultraviolet light irradiation for 120 min, indicated that NaLa(MoO₄)₂ has high oxidative reactivity, achieving a degradation of >95% of the CBB-250 dye present in the system. The reaction velocity constants, estimated in accordance with the Langmuir-Hinshelwood equation, substantiate that NaLa(MoO₄)₂ enhances the reaction kinetics (13.7 × 10^-3 min^-1) throughout the photochemical treatment. In light of the growing scientific interest in effective strategies for the removal of emerging pollutants from contamination matrices, NaLa(MoO₄)₂ represents a promising avenue for the development of innovative technologies in this field.

Background: The development of nanostructured materials for cancer therapy has garnered significant interest due to their unique physicochemical properties, including enhanced surface area and tunable electronic structures, which can facilitate targeted drug delivery and oxidative stress modulation. This study investigates the anticancer potential of monoclinic silver dimolybdate nanorods (m-Ag₂Mo₂O₇) against aggressive breast (MDA-MB-231) and prostate (PC-3) cancer cells and explores their in vivo pharmacokinetic behavior. Methods: m-Ag₂Mo₂O₇ nanorods were synthesized via a hydrothermal method and characterized using XRD, SEM, Raman, and FTIR spectroscopy. In vitro cytotoxicity was evaluated using MTT assays on MDA-MB-231 and PC-3 cell lines across concentrations ranging from 1.56 to 100 µg/mL. In vivo biodistribution and radiopharmacokinetics were assessed using technetium-99m-labeled nanorods in male Swiss rats, with gamma counting employed for tissue uptake analysis and pharmacokinetic parameter determination. Results: m-Ag₂Mo₂O₇ nanorods exhibited a modest cytotoxic effect on MDA-MB-231 cells, with 50 µg/mL reducing cell viability by 23.5% (p < 0.05), while no significant cytotoxicity was observed in PC-3 cells. In vivo studies revealed predominant accumulation in the stomach, liver, spleen, and bladder, indicating reticuloendothelial system uptake and renal clearance. Pharmacokinetic analysis showed a rapid systemic clearance (half-life ~6.76 h) and a low volume of distribution (0.0786 L), suggesting primary retention in circulation with minimal off-target diffusion. Conclusions: While m-Ag₂Mo₂O₇ nanorods display limited standalone cytotoxicity, their ability to induce oxidative stress and favorable pharmacokinetic profile support their potential as adjuvant agents in cancer therapy, particularly for chemoresistant breast cancers. Further studies are warranted to elucidate their molecular mechanisms, optimize combinatorial treatment strategies, and assess long-term safety in preclinical models.