Non-centrosymmetric bismuth-based (C9H12N4)2[BiBr6]⋅Cl⋅4H2O hybrid material:Detailed investigation of optical properties, and antibacterial study

This study explores the optical and antibacterial properties of Bis(5-amino-3-methyl-1-phenyl-1H-1,2,4triazolium) hexabromobismuthate (III) chloride tetrahydrate. Diffuse reflectance spectroscopy conducted in the 200-1100 nm wavelength range revealed a direct optical band gap of 2.24 eV, determined via Tauc's method, classifying the material as a direct bandgap semiconductor. The Urbach energy of 454 meV indicates notable structural disorder and a high density of localized states within the band gap. Analysis of optical constants, including the extinction coefficient, highlights efficient light absorption and UV attenuation, further supported by skin depth calculations that confirm the material's suitability as a UV-protective layer. Density of States (DOS) calculations, based on Density Functional Theory (DFT), validated the electronic structure and bandgap, aligning well with experimental results and reinforcing the material's potential in optoelectronic applications. Additionally, antibacterial evaluations revealed significant inhibition against multiple bacterial strains, outperforming the individual organic and inorganic components. This highlights its dual functionality, combining optical and antimicrobial properties. These findings underscore the potential of this bismuth-based hybrid material for diverse applications in optoelectronics, UV shielding, and biomedical coatings, paving the way for future advancements in multifunctional material design.