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. γ, δ and θ) via a hydrothermal method with varying calcination temperatures. The synthesized θ-Al2O3 nanowires were well characterized by XRD, FTIR, SEM/EDAX, AFM and HRTEM techniques. Microstructural analysis confirmed that the dimensions of the individual θ-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 θ-Al2O3 nanowires was ~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 ~2.23 nanoseconds. The obtained photoluminescence results with a decay time of nanoseconds suggest that the θ-Al2O3 phase could be an exceptional choice for next generation fast optical sensors.