The present review provides modern strategies for various kinds of luminescent nanomaterial based security inks for high end anti-counterfeiting applications.

Demonstration of new strategy for designing multi-stage excitable highly-luminescent Y₂O₃:Yb³⁺/Er³⁺ nanorod assisted security ink for protection against counterfeiting.

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.