CIE-confirmed blue luminescence of SrFeO2 ferrite nanoparticles for LED theranostics

Abstract

Oral cancer poses a significant health challenge, particularly due to late-stage diagnoses that diminish survival rates. Effective early screening depends on reliable optical sources within the blue spectral region (400–500 nm), critical for exciting tissue autofluorescence in non-invasive detection. This study details the synthesis of SrFeO₂ nanoparticles using a straightforward sol–gel method, alongside comprehensive characterization of their multifunctional properties. X-ray diffraction (XRD) confirmed a monoclinic structure with space group P21/c structure, while TEM imaging revealed nanoparticle sizes averaging 31 nm, albeit with minor aggregation. Optical studies showed a narrow direct band gap of ∼1.7 eV and strong visible-light activity. Photoluminescence spectra exhibited distinct red-near-infrared emissions at 416 nm, 438 nm, 468 nm, 506 nm and 525 nm, alongside a bluish emission tone validated by CIE 1931 chromaticity coordinates (x = 0.1711, y = 0.1170), confirming suitability for blue LED applications. The blue luminescence is attributed to the unique square-planar Fe²⁺ coordination within the SrFeO₂ lattice. Magnetic measurements demonstrated superparamagnetism at room temperature with negligible coercivity and a saturation magnetization of 1.23 emu. The coexistence of stable blue luminescence, red-NIR emission, low band gap, and superparamagnetic behaviour establishes SrFeO₂ as a novel, eco-friendly, and cost-effective multifunctional nanomaterial. These results highlight its dual promise: as a blue-emitting platform for LED-assisted oral cancer theranostics and as a candidate for integrated optoelectronic–magnetic devices, spintronic systems, and advanced display technologies.