RESUMO
The analysis of human body composition and food composition requires high-efficiency broadband near-infrared (NIR) lighting sources to achieve a portable, appropriately sized equipment. Herein, we develop a whitlockite-type NIR phosphor Sr9Sc(PO4)7:Cr3+ with an emission centered at 860 nm and full width at half-maximum of 147 nm. Due to the structural characteristics of the matrix, the 60 mol % Cr3+ substitution at the Sc3+ sites gives an internal quantum efficiency up to 56.5%. By replacing Sr with Ba and Ca, we observe a nontypical spectral shift phenomenon and discuss the influence of the second-sphere effect on octahedral Cr3+ ions. To evaluate the diagnostic application, we design a NIR ceramic device with a high optical power of 27.38 mW and high heat dissipation, which can decrease surface working temperature by nearly 50 °C for digital intraoral application. This study provides the research of the second-sphere coordination effect for selective octahedral sites such as Ca, Sr, and Ba coordinated by O atoms on a whitlockite-type crystal. Furthermore, the device promotes a nonionizing solution for detecting dental caries, tooth calcification, and diagnostic application.
Assuntos
Fosfatos de CálcioRESUMO
Two types of infrared fluoride phosphors, Cr3+-doped K3AlF6 and K3GaF6, were developed in this research. The K3Al1-xF6:xCr3+ and K3Ga1-yF6:yCr3+ fluoride phosphors were proven to be pure phase via X-ray diffraction refinement, which demonstrated that the procedure can be applied to large-scale production. Electron paramagnetic resonance measurements indicated that Cr3+ ions in cubic with respect to noncubic are coupled better with K3GaF6 than with K3AlF6. The main differences between these two phosphors, the site symmetry and pressure behavior of the spectra, were obtained in temperature- and pressure-dependent spectra. According to the calculation results, Cr3+ in fluorine coordination at ambient pressure indicates an intermediate crystal field. For the phosphor-converted light-emitting diodes (LEDs) fabricated from these two phosphors, the spectral range is from 650 to 1000 nm, which resulted in a radiant flux of 7-8 mW with an input power of 1.05 W. The research reveals detailed luminous properties, which will lead to a new way of studying Cr3+-doped fluoride phosphors and their application in LEDs.
RESUMO
All-inorganic CsPbX3 (X=I, Br, Cl) perovskite quantum dots (PQDs) have been investigated because of their optical properties, such as tunable wavelength, narrow band, and high quantum efficiency. These features have been used in light emitting diode (LED) devices. LED on-chip fabrication uses mixed green and red quantum dots with silicone gel. However, the ion-exchange effect widens the narrow emission spectrum. Quantum dots cannot be mixed because of anion exchange. We address this issue with a mesoporous PQD nanocomposite that can prevent ion exchange and increase stability. We mixed green quantum-dot-containing mesoporous silica nanocomposites with red PQDs, which can prevent the anion-exchange effect and increase thermal and photo stability. We applied the new PQD-based LEDs for backlight displays. We also used PQDs in an on-chip LED device. Our white LED device for backlight display passed through a color filter with an NTSC value of 113 % and Rec. 2020 of 85 %.