A critical review on modulation of NiMoO4-based materials for photocatalytic applications

White-light emission in Yb3+/Er3+/Tm3+- and Yb3+/Er3+/Tm3+/Ho3+-dopedα-NiMoO4nanoparticles

Yb³⁺/Er³⁺/Tm³⁺- and Yb³⁺/Er³⁺/Tm³⁺/Ho³⁺-dopedα-NiMoO₄nanoparticles were synthesized using a microwave hydrothermal method and studied for white-light emission under 980 nm laser diode excitation. White upconversion (UC) light was successfully obtained with the appropriate control of blue, green, and red emissions by successfully tuning the Er³⁺and Ho³⁺concentrations in Yb³⁺/Er³⁺/Tm³⁺- and Yb³⁺/Er³⁺/Tm³⁺/Ho³⁺-dopedα-NiMoO₄, respectively. In addition, the white color emission was shown by the CIE chromaticity coordinates of samples. The energy transfer mechanisms are explained in detail based on the emission spectra and pump power density-dependent UC luminescence intensity in rare earth (Yb³⁺/Er³⁺/Tm³⁺and Yb³⁺/Er³⁺/Tm³⁺/Ho³⁺)-dopedα-NiMoO₄nanoparticles. The results indicate that Yb³⁺/Er³⁺/Tm³⁺- and Yb³⁺/Er³⁺/Tm³⁺/Ho³⁺-dopedα-NiMoO₄nanoparticles can be good candidates for white-light devices.

A critical review on strategies for improving efficiency of BaTiO3-based photocatalysts for wastewater treatment

Barium titanate (BaTiO₃) photocatalysts with perovskite structures are promising candidates for the effective removal of hazardous organic pollutants from water/wastewater owing to several advantages, including low cost, non-toxicity, high stability, environmental friendliness, favorable band positions, high oxygen vacancies, multiple crystal phases, rapid migration of charge carriers at the surface, band bending, spontaneous polarization, and easy tailoring of the sizes and morphologies. However, this high dielectric/ferroelectric material is only active in UV light (band gap: 3.2 eV), which reduces the photocatalytic degradation performance. To make barium titanate more suitable for photocatalysis, the surfaces of the powders can be modified to broaden the absorption band. In this paper, various strategies for improving photocatalysis of barium titanate for removing organic pollutants (mostly dyes and drugs) from water/wastewater are critically reviewed. They include modifying the sizes and morphologies of the particles by varying the reaction times and synthesis temperatures, doping with metals/non-metals, loading with noble metal NPs (Ag and Au), and fabrication of heterojunction photocatalysts (conventional type II and Z-scheme). The current challenges and possible future directions of BaTiO₃-based materials are also discussed. This comprehensive review is expected to advance the design of highly efficient BaTiO₃-based materials for photocatalytic applications in water/wastewater treatment.