CMC/SrAl2O4:Dy luminescent nanofibers: synthesis, characterization, and applications in optical encryption and authentication

This study investigates the synthesis and characterization of sodium carboxymethyl cellulose (CMC) modified SrAl 2 O 4 :Dy 3+ phosphor spun nanofibers. The phosphor was synthesized via a sol-gel method and incorporated into a CMC polymer matrix through electrospinning, resulting in uniform spherical nanoparticles with sizes ranging from 15–20 nm, as confirmed by TEM analysis. XRD and SEM analyses demonstrated enhanced structural ordering and modified surface morphology, with roughness parameters (Ra) increasing from 46.17 nm for pure CMC to 47.68 nm for the 3 wt% SrAl 2 O 4 :Dy 3+ composite. The composite exhibited strong photoluminescence with three emission bands at 485 nm (blue), 580 nm (yellow), and 625 nm (red) under 399 nm excitation, yielding CIE coordinates of (0.35, 0.33) and an optical energy gap of 2.84 eV for the 3 wt% doped sample. Dielectric measurements revealed a significant improvement in energy storage capacity, with the dielectric constant (ε') increasing from ∼12 for pure CMC to ∼18 for the 3 wt% composite at 1 kHz and 298 K. Temperature-dependent studies identified relaxation mechanisms, with the dielectric relaxation time (τ) decreasing from 59.5 μs to 0.20 μs at 3 wt% doping. These results highlight the material's potential for advanced optical encryption, authentication, and energy storage applications, combining tunable luminescence with enhanced electrical properties. • Sol-gel and electrospinning produced CMC-modified SrAl 2 O 4 :Dy nanofibers with 15-20 nm size. • SrAl 2 O 4 :Dy enhanced CMC matrix structural order, confirmed by XRD and SEM analyses. • Tricolor emission at 485, 580, 625 nm under 399 nm with CIE (0.35, 0.33). • Enhanced dielectric properties and energy storage with complex relaxation behavior.