The synergistic effect of binary CdTiO₂ and ternary NiCdTiO₂ on the photocatalytic efficiency of TiO₂ nanoparticles was investigated. The SEM analysis demonstrates spherical TiO₂ NPs of different sizes present in agglomerated form. The structural analysis of the nanocomposites reveals a porous structure for TiO₂ with well deposited Cd and Ni NPs. TEM images show NiCdTiO₂ nanocomposites as highly crystalline particles having spherical and cubical geometry with an average particle size of 20 nm. The EDX and XRD analysis confirm the purity and anatase phase of TiO₂, respectively. Physical features of NiCdTiO₂ nanocomposite were determined via BET analysis which shows that the surface area, pore size and pore volume are 61.2 m²/g, 10.6 nm and 0.1 cm³/g, respectively. The absorbance wavelengths of the CdTiO₂ and NiCdTiO₂ nanocomposites have shown red shift as compared to the neat TiO₂ due to coupling with Ni and Cd that results in the enhanced photocatalytic activity. The photocatalytic activity demonstrated that TiO₂, CdTiO₂ and NiCdTiO₂ degrade methylene blue (MB) and methyl green (MG) about 76.59, 82, 86% and 63.5, 88, 97.5%, respectively, at optimum reaction conditions.

Four new carboxylates complexes with general formula R₂SnL₂ and R₃SnL, where R = n-butyl (1, 3), methyl (2, 4) and L = 4-Chlorophenoxyacetate, were synthesized in significant yields. FT-IR analysis revealed a chelating (1 and 2) and a bridging bidentate (3 and 4) coordination modes for the carboxylate ligand in solid state which was further confirmed by the single crystal X-ray analysis of complex 4. The NMR data (¹H, ¹³C and ¹¹⁹Sn) revealed a higher coordination number around the tin center in R₂SnL₂ (1 and 2) compared to R₃SnL (3 and 4). A close matching was observed between the experimental and calculated structures (obtained at B3LYP/6-31G* + LANL2DZ basis set). Quantum chemical analysis indicates that the carboxylate moiety has the major contribution in the formation of filled and unfilled orbitals as well as in ligand to ligand intramolecular charge transfer during the electronic transitions. The cytotoxicity data of the screened compounds evaluated against lung cancer cell line (A549) and normal lung fibroblast cell line (MRC-5) revealed that 1, 3 and 4 have shown dose dependent cytotoxic effects while HL and 2 have shown steady and low cytotoxic activities. The antibacterial activity of complexes 1–4 is higher than that of HL. Molecular docking study showed an intercalation binding mode for complex 3 with DNA (docking score = −3.6005) involving four polar interactions. Complex 3 docking with tubulin (PDB ID 1SA0) with colchicine as a target protein resulted in three polar interactions (docking score −5.2957). Further, the docking analysis of the HL and 1–4 has shown an adequate interactions with the coronavirus SARS-CoV-2 spike protein, nucleocapsid protein and human angiotensin converting enzyme (ACE2).

The strong nonpolar triple bond of nitrogen (NN) is a big challenge in its fixation, which is an extremely important process to obtain essential chemicals and energy carriers. Accordingly, the electrocatalytic nitrogen reduction reaction (NRR) to produce ammonia (NH₃) using sustainable energy sources is considered a possible way to solve this problem. However, owing to the poor catalytic activity of materials, this approach for the production of NH₃ is still far from meeting industrial requirements. In this article, the fundamentals of N₂ fixation, recent progress in N₂ fixation reactions, and different electrocatalysts, such as metal-based oxides, carbides, sulfides, and nitrides, single-atom catalysts, and carbonaceous catalysts, used in recent years are reviewed. Furthermore, challenges faced in the nitrogen fixation process and strategies to improve its efficiency are also highlighted.