Time-resolved and photoluminescence spectroscopy of θ-Al₂O₃ nanowires for promising fast optical sensor applications.

Herein, we have demonstrated the high yield facile growth of Al2O3 nanowires of uniform morphology with different polymorph phases (e.g. gamma, delta and theta) via a hydrothermal method with varying calcination temperatures. The synthesized theta-Al2O3 nanowires were well characterized by XRD, FTIR, SEM/EDAX, AFM and HRTEM techniques. Microstructural analysis confirmed that the dimensions of the individual theta-Al2O3 nanowires are approximately in the ranges 5-20 nm in width and 40-150 nm in length, and the aspect ratio is up to 20. AFM results evidenced the uniform distribution of the nanowires with controlled morphology. Furthermore, UV-vis spectroscopic data reveal that the estimated optical band gap of the theta-Al2O3 nanowires was similar to 5.16 eV. The photoluminescence spectrum exhibits blue emission upon excitation at a wavelength of 252 nm. Time-resolved spectroscopy demonstrates that these nanowires illustrate a decay time of similar to 2.23 nanoseconds. The obtained photoluminescence results with a decay time of nanoseconds suggest that the theta-Al2O3 phase could be an exceptional choice for next generation fast optical sensors.