X‑ray-Irradiation-Induced Discoloration and Persistent Radioluminescence for Reversible Dual-Mode Imaging and Detection Applications

The combination of X-ray-irradiation-induced photochromism and persistent radioluminescence in a single material presents an exciting avenue for multi-functional applications such as optical memory, anti-counterfeiting, and X-ray detection and imaging. However, developing such a material remains a significant challenge. Here, a white Ba3MgSi2O8:Mn2+ photochromic phosphor was prepared, exhibiting a white-to-orange color change (>20 h for bright field) and good persistent radioluminescence emission (>90 min for dark field) in response to X-ray radiation. The photochromic phosphor also demonstrated accelerated bleaching and recovery after 14 min of 254 nm UV light stimulation. This Ba3MgSi2O8:Mn2+-based flexible film displayed simultaneous reversible photochromism and recoverable persistent luminescence, providing dual-mode X-ray imaging and detection capabilities, as well as good reproducibility and read/write erasability. This study suggests that combining X-ray-induced photochromism and persistent radioluminescence in a single material is a promising approach to design advanced photonic materials for information security, cryptography, and smart anti-counterfeiting applications

Upconversion Emission Enhancement of NaYF₄:Yb,Er Nanoparticles by Coupling Silver Nanoparticle Plasmons and Photonic Crystal Effects

Metal nanoparticle plasmons or the photonic crystal effect are being widely used to modify luminescence properties of materials. However, coupling of surface plasmons with photonic crystals are seldom reported for enhancing luminescence of materials. In this paper, a new method for upconversion emission enhancement of rare-earth doped nanoparticles is reported, attributed to the coupling of surface plasmons with photonic band gap effects. Opal/Ag hybrid substrates were prepared by depositing Ag nanoparticles on the top layer of opals by magnetron sputtering. The selective enhancement of red or green upconversion emission of NaYF₄:Yb³⁺,Er³⁺ nanoparticles on the opal/Ag hybrid substrates is attributed to the coupling effect of surface plasmons and Bragg reflection of the photonic band gap. In addition, the upconversion emission enhancement of NaYF₄:Yb³⁺,Er³⁺ nanoparticles on the opal/Ag hybrid substrate is attributed to the excitation enhancement was obtained when the excitation light wavelengths overlap with the photonic band gaps of opal/Ag hybrid substrates. We believe that these enhancement effects based on the coupling of metal nanoparticles with the photonic band gap could be extended to other light-emitting materials, which may result in a new generation of lighting devices