The antimicrobial activities of zirconia (ZrO2) nanoparticles and zirconium mixed ligand complexes were studied on bacterial strains of E. coli, S. aureus and fungal strain of A. niger. The nanoparticles of zirconia and Zr(IV) complexes with different amino acids as ligands were synthesized by hydrothermal method. X-ray diffraction (XRD) and HRTEM confirmed the crystalline nature and morphology of the synthesized products. The antimicrobial studies revealed that the zirconia exhibits activity only against the E. coli, whereas, the Zr(IV) complexes exhibits activity against both the bacteria: gram -ve E. coli and gram +ve S. aureus as well as fungal strains. The Zr(IV) complexes are found to possess significant antifungal activity against A. niger. The results are indicative of crystal plane-dependent antimicrobial activity of zirconia nanoparticles and complexes. The observed difference in the antibacterial activity of ZrO2 crystals and Zr(IV) complexes may be ascribed to the atomic arrangements of different exposed surfaces. On the basis of the study, it could be speculated that the ZrO2 nanoparticles with the same surface areas but with different shapes i.e., different active facets will show different antimicrobial activity.
Vertically aligned GaN nanotowers (NTs) were grown on the Si (111) substrate by plasma-assisted molecular beam epitaxy to design a highly responsive ultraviolet (UV) photodetector. The UV detector fabricated on a bare GaN-NT array yielded highly sensitive and repeatable device characteristics attributed by high responsivity (R), low noise equivalent power (NEP), and a high external quantum efficiency (EQE) of 484.77 A/W, 1.76 × 10 −13 W.Hz -1/2 , and 1.85 × 10 5 %, respectively. Furthermore, the developed UV photodetector demonstrated fast response with excellent stability when functionalized with Au nanoparticles and ZnO nanorods. This hybridized GaN-NT-based device with ZnO nanorods and Au nanoparticles significantly accelerated the performance of the device where a prominent threeorder reduction under dark current is observed along with gigantic R, lower NEP, and an extremely enhanced EQE of 7042 A/W, 1.84 × 10 −14 W.Hz -1/2 , and 2.7 × 10 6 %, respectively. The mechanism elaborating the enhanced device performance with a localized surface plasmon effect has been discussed through an energy band diagram. The fabricated highly sensitive device can lead the path toward future optoelectronic applications of integrated III-nitride technology.
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