Novel LaFeO 3 /Ag 2 CO 3 nanocomposites are synthesized by co-precipitation method for photocatalytic degradation of Rhodamine B (RhB) and p -chlorophenol under visible light irradiation. Heterostructures between LaFeO 3 and Ag 2 CO 3 semiconductors are formed during the synthesis of these nanocomposites. Among the nanocomposites prepared with different ratios of LaFeO 3 and Ag 2 CO 3 , 1% LaFeO 3 /Ag 2 CO 3 shows the highest photocatalytic activity for the degradation of RhB. Maximum electron–hole pair decoupling efficiency is observed in 1% LaFeO 3 /Ag 2 CO 3 , which causes the greater activity of the heterostructure. Degradation efficiency of 99.5% for RhB and 59% for p -chlorophenol has been obtained under natural sunlight within 45 min. Interestingly, the stability of Ag 2 CO 3 is improved dramatically after making nanocomposite, and no decomposition of the catalyst was observed even after several photocatalytic cycles. Reactive oxygen species scavenging experiments with p -benzoquinone, isopropyl alcohol, and ammonium oxalate suggest that a major degradation process is caused by holes. Degradation of RhB into small organic moieties is detected using LC–MS technique. Further, the efficient mineralization of the degradation products occurs during the catalytic process.

Bismuth based host materials for doping rare earth ions gained considerable interest due to the possibility of forming crystalline homogeneous solid solution phases over a wide range and their excellent luminescent properties. In the present manuscript, a facile synthesis method for preparation of nanocrystalline NaBi(MoO 4 ) 2 and their optical properties are presented. The influence of various synthetic parameters such as precursor concentration, reaction time and reaction temperature on phase formation have been investigated and revealed that these nanoparticles can be synthesized even at 5 °C within 5 min with a Bi/Mo ratio of 1:4. All the doped and undoped samples show scheelite type tetragonal structure. Formation of solid solution between NaBi(MoO 4 ) 2 and NaEu(MoO 4 ) 2 over the complete range of compositions could be achieved. A systematic decrease in the unit cell parameters is observed with increasing concentration of Eu 3+ ion in NaBi 1−x Eu x (MoO 4 ) 2 . Investigations on the luminescence properties of europium doped samples show excellent red luminescence upon excitation at 465 nm. The quantum efficiency calculated from experimental luminescence studies shows optimum photoluminescence properties in NaBi 0.9 Eu 0.1 (MoO 4 ) 2 nanoparticles with the highest quantum efficiency of 50%.

Nanomaterials of NaBi0.9Eu0.1(MoO4)2 were prepared by a simple coprecipitation method in ethylene glycol medium at room temperature. Substitution of bismuth with lanthanum resulted a single-phase solid solution (NaBi0.9–x La x Eu0.1(MoO4)2, 0.0 ≤ x ≤ 0.9) in the complete range of compositions. The linear relationship observed for unit cell parameters, Raman shifts, and FTIR peak positions with lanthanum concentration confirmed the solid solution formation. The band gap of the NaBi0.9–x La x Eu0.1(MoO4)2 nanomaterials widens from 3.36 to 4.4 eV with increasing La3+ concentration in these solid solutions. These nanomaterials show strong red emission upon excitation with UV–visible light. The emission properties of Eu3+ are improving with increasing the La3+ content. The band gap of the solid solution plays a crucial role in the improvement of emission properties and is highly dependent on the excitation wavelength. This improvement is marginal while exciting with 464 nm light due to the reduction in the inter Eu3+ ion energy transfer brought by the lattice expansion, whereas drastic improvement is observed when exciting at 280 and 394 nm light due to the combined effect of band gap and lattice expansion. The quantum efficiency estimated from emission spectra and excited state lifetime values revealed that NaLa0.9Eu0.1(MoO4)2 nanomaterials are best in the series with ∼70% efficiency. These materials can be a suitable red phosphor for white light-emitting diodes (WLEDs)

Water oxidation is an energy-consuming, four-electron-transfer reaction and is essential for solar fuel production from water. Catalysts based on precious metals such as RuO2 and IrO2 show high efficiency for oxygen evolution reaction. However, these catalysts are less abundant and expensive. To date, earth-abundant water oxidation catalysts still exhibit less activity for water oxidation. Herein, we report the synthesis of high surface area Mn2O3 nanomaterials for an efficient photocatalytic water oxidation catalyst. The synthesis process involves three simple steps. In the first step, CaMnO3 is synthesized by the citrate-gel method. In the second step, CaMnO3 is transformed into freestanding layers of ε-MnO2 by selective removal of Ca2+. In the third step, these layers are converted into irregularly shaped two-dimensional Mn2O3 flakes (AD-Mn2O3) by calcination at 550 °C. These AD-Mn2O3 nanostructures show 4 times higher surface area (127 m2 g–1) when compared to the irregularly shaped Mn2O3 nanoparticles (CG-Mn2O3) synthesized by the citrate-gel method at the same temperature. The AD-Mn2O3 nanostructures show super hydrophilicity with a contact angle of zero degree. This material exhibits excellent photocatalytic water oxidation activity with a turnover frequency of 1.53 × 10–3 s–1, which is twice the activity shown by CG-Mn2O3. This study can help in developing an earth-abundant, cost-effective, efficient catalyst for overall water splitting.

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