Biofuel-Assisted combustion pathway to zirconium ferrite: Ligand-Field perturbations and defect chemistry for advanced photonic and electrochemical applications
摘要
Biofuels and chelating agents derived from Plumeria rubra and Caesalpinia pulcherrima floral extracts were used to synthesise Zirconium ferrite (ZrFe2O4) nanostructures through sustainable solution combustion. The process produced pure cubic spinel ZrFe2O4 (Fd3m) with crystallite sizes ranging from 44 to 48 nm. The yield was affected by a controlled microstrain of 3.6 × 10− 4 to 9.7 × 10− 5 and by rapid self-propagating combustion at temperatures between 250 and 350 °C. UV-Vis-NIR spectra revealed ligand-to-metal charge transfer and d-d transitions caused by the fuel’s unique ligand-field effects. Crystal-field engineering enabled adjustable band gaps of 1.925–2.253 eV, indirect band gaps of 1.354–1.714 eV, Racah parameters ranging from 476 to 558 cm− 1, and ‘β’ values from 0.453 to 0.517. Strong defect-mediated radiative recombination was observed in photoluminescence, with quantum yields from 0.293 to 0.374 and lifetimes of 1.0 to 2.85 ns. The colorimetric performance was precise, showing a luminous efficacy of 235 lm W− 1 and a CCT range of 13,600 − 16,868 K. Electrochemical analysis indicated a diffusion coefficient of 3.6 × 10− 8 cm2 s− 1, a quasi-reversible Fe3+/Fe2+ redox behaviour, and notable amino acid sensitivity with an R2 value of 0.981. Green-synthesized ZrFe2O4 with ligand engineering is well-suited for photonic, biosensing, and energy-storage applications. The material displays excellent electrochemical, optical, and structural integration.