Optical anti-counterfeiting has been developed as a promising optical-sensing technique. A self-activated ${{\rm KGaSiO}_4}$ phosphor was successfully prepared using the traditional solid-state method. The photoluminescence spectra of the as-synthesized phosphors indicate that the ultra-narrow band emission with green light peak at 503 nm is obtained when phosphors are excited by 254 nm UV light. Additionally, the measured afterglow curve shows that the emission of this phosphor can last more than 1200 s after UV excitation stops, which indicates that ${{\rm KGaSiO}_4}$ is a potential candidate for anti-counterfeiting materials. The luminescent and decay mechanism are discussed by theoretical calculation and thermo-luminescent spectra in detail. The theoretical model can provide support for explaining the mechanism of narrow band or persistent phosphor.
Phosphor-converted white LEDs rely on combining a blue-emitting InGaN chip with yellow and red-emitting luminescent materials. The discovery of cyan-emitting (470–500 nm) phosphors is a challenge to compensate for the spectral gap and produce full-spectrum white light. Na 0.5 K 0.5 Li 3 SiO 4 :Eu 2+ (NKLSO:Eu 2+ ) phosphor was developed with impressive properties, providing cyan emission at 486 nm with a narrow full width at half maximum (FWHM) of only 20.7 nm, and good thermal stability with an integrated emission loss of only 7% at 150 °C. The ultra-narrow-band cyan emission results from the high-symmetry cation sites, leading to almost ideal cubic coordination for UCr 4 C 4 -type compounds. NKLSO:Eu 2+ phosphor allows the valley between the blue and yellow emission peaks in the white LED device to be filled, and the color-rendering index can be enhanced from 86 to 95.2, suggesting great applications in full-spectrum white LEDs.
Jie Wei,En-Kang Wu,Ji-Hao Zhang,Zhen Zhang,Xiao-Cong Tang,Tian Qiang,Yong-Woo Jang,Xiao-Feng Gu,Meng Zhao,Svetlana von Gratowski,Jun-Ge Liang,Ming-Yang Yan,Cong Wang
Acetone sensors continue to command significant attention as a robust platform for emissions control, industrial safety monitor, and diagnostic analysis of human exhaled gas for diabetes monitoring. This study presents the design and fabrication of an ultra-narrowband, interdigital capacitor (IDC)-based three-level split ring resonator (TSRR) microwave gas sensor for rapid acetone detection. MXene-TiO 2 composites with varying mass ratios were deposited onto the resonator surface to evaluate the gas-sensitive properties of TiO 2 /MXene materials across acetone concentrations of 10–500 ppm. Results demonstrate that the microwave acetone sensor incorporating the TiO 2 /MXene (3 wt%) composite exhibits exceptional performance: high sensitivity (1544 mdB/ppm), rapid response and recovery durations (130 s and 140 s, respectively), superior selectivity, and excellent stability under high-humidity conditions—significantly surpassing existing microwave gas sensors. Furthermore, the gas-sensing mechanism was elucidated through impedance-matching circle diagrams corresponding to varying acetone concentrations. MXene materials, renowned for their expansive specific surface area, exhibit considerable promise in gas sensing applications, particularly for room-temperature acetone detection with high selectivity and sensitivity extending to ppb concentrations. This investigation introduces a novel paradigm for room-temperature acetone gas detection, as evidenced by the development of triboelectric plasma-regulated high-sensitivity sensors.
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