High efficiency upconversion in PVP passivated Dy₂O₃: Er³⁺ nanoparticles enabling solid-state lighting, radiation sensing, forensic security and anti-counterfeiting applications

Abstract

Efficient near-infrared (NIR) to visible upconversion (UC) materials are essential for advancing optoelectronic, radiation sensing, and security devices. In this work, Dy₂O₃:Er³ ⁺ nanoparticles were synthesized using a solution combustion method and surface-passivated with 9 wt% polyvinylpyrrolidone (PVP) to suppress surface defects and enhance emission efficiency. X-ray diffraction confirmed a cubic phase structure with crystallite size reduced from 22 to 14 nm due to polymer-controlled growth inhibition. Fourier-transform infrared spectra verified PVP coordination with Dy–O and Er–O bonds, while FESEM and HRTEM analyses revealed coral-like nanostructures with a polymer coating (∼28 nm average size) and minimized agglomeration. UV–Vis diffuse reflectance spectra indicated bandgap widening from 4.92 to 5.11 eV, consistent with quantum confinement effects. X-ray photoelectron spectroscopy verified stable trivalent Dy³ ⁺ and Er³ ⁺ states and formation of an oxygen/nitrogen-rich interface. Under 980 nm excitation, strong UC emissions were observed at 578 nm and 670 nm. The optimized 9 mol% Er³ ⁺doped sample exhibited an outstanding quantum yield of 84.19 %, a high color rendering index (CRI = 92), and a correlated color temperature (CCT = 5905 K), fulfilling white-light illumination standards. Thermoluminescence measurements under gamma irradiation showed a stable glow peak near 325 °C with trap depths between 0.80–1.17 eV, indicating reliable radiation sensing performance. Demonstrations in latent fingerprint visualization and anti-counterfeiting applications confirm the multifunctionality of the developed material. Overall, PVP-passivated Dy₂O₃:Er³ ⁺ nanoparticles exhibit superior optical efficiency, structural stability, and functional versatility, establishing them as promising candidates for next-generation optoelectronic, radiation sensing, forensic and security applications