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All-inorganic cesium lead halide perovskite materials have potential applications in mini/micro-LED display applications due to their excellent photoelectric properties. However, these materials have an uncontrollable tendency to form large-sized crystals and poor stability, which is not conducive to miniaturized optoelectronic applications. Herein, a novel Cs4PbBr6@KBr color conversion film (Cs4PbBr6@KBr CCFs) with both excellent luminescence properties and high stability was in situ constructed by using inkjet printing technology. The improvement in performance is attributed to the reduction in perovskite defects within the structure and the isolation of oxygen and water by the surface modification layer, which is related to the higher solubility product of KBr. The Cs4PbBr6@KBr CCFs printed on a PET flexible substrate present a high-resolution dot matrix of 16.7 μm and a homogeneous and bright green emission with a high photoluminescence quantum yield of 94%. Moreover, the Cs4PbBr6@KBr CCFs retain 65% of their initial intensity after being aged at 70 °C for 16 h, which is superior to that of perovskite CCFs without the coating of KBr. These results indicate that the Cs4PbBr6@KBr composite has excellent potential in realizing mini/micro-LED displays with high resolution and anti-counterfeiting lables. [ABSTRACT FROM AUTHOR]

Due to the different sensitivities of the 2E and 4T2 energy levels of Cr3+ to the local environment, Cr3+-doped fluorescent materials appear as excellent candidates for highly sensitive temperature sensing based on luminescence intensity ratio technology. However, a way to broaden the strict Boltzmann temperature measuring range is rarely reported. In this work, through Al3+ alloying strategy, a series of SrGa12−xAlxO19:0.5%Cr3+(x = 0, 2, 4, and 6) solid-solution phosphors were synthesized. Remarkably, the introduction of Al3+ can play a role in regulating the crystal field around Cr3+ and the symmetry of [Ga/AlO6] octahedron, realizing the synchronous tuning of 2E and 4T2 energy levels when the temperature changes in a wide range, achieving the purpose of increasing the intensity difference of 2E → 4A2 and 4T2 → 4A2 transitions, so as to extend the temperature sensing range. Among all samples, SrGa6Al6O19:0.5%Cr3+ showed the widest temperature measuring range from 130 K to 423 K with Sa of 0.0066 K−1 and Sr of 1% K−1@130 K. This work proposed a feasible way to extend the temperature sensing range for transition metal-doped LIR-mode thermometers. [ABSTRACT FROM AUTHOR]

Perovskites based on CsPbX3 (X = Cl, Br, I) have promising applications in solar cells, light-emitting diodes, and photodetectors. In this paper, the phase stability of inorganic metal halide perovskite CsPbCl3 under hydrostatic pressure and anion substitution is studied using density functional theory (DFT), and this modification is explained by the interaction of the octahedrons and transformation of the bond-orbital coupling. In addition, two space groups, P4/mbm and Amm2, which are stable under stress, are subjected to anion substitution; then, the structural stability and band gap change of CsPbCl3−yXy (X = Br, I; y = 0, 1, 2, 3) are analyzed after applying stress; finally, the electronic structures and optical properties of the six most stable components are presented. The effect of stress and anions on the components' optoelectronic properties is closely linked with the crystal's structural alteration mechanism. These results show that stress and anion modulation can significantly change the optoelectronic properties of materials, which make these materials have broad application prospects. Furthermore, stress can be used as an effective tool for screening the most stable material structure. [ABSTRACT FROM AUTHOR]

The key to developing laser-driven solid-state lighting lies in high-performance color converters, which must be thermally robust under the high-power density excitation of a laser. Phosphor-in-glass (PiG) films are considered as a kind of promising color converter for laser lighting, but the poor thermal dissipation of the glass matrix will cause large thermal quenching of the PiG films and hence low luminous flux of lighting sources. In this work, Al2O3 particles, acting as a heat transfer medium, are introduced into the La3Si6N11:Ce3+ (LSN:Ce3+) PiG film to form a composite color converter for realizing high-brightness laser lighting. By optimizing the ratio of glass frits to Al2O3 as well as the film thickness, the Al2O3–LSN:Ce3+ composite PiG film shows a luminance saturation threshold of 23.08 W mm−2, which is 26.3% higher than that of the Al2O3-free LSN:Ce3+ PiG film (18.27 W mm−2). The luminous flux of the composite PiG film under blue laser excitation is improved by 51.4% and reaches 3120 lm, and the luminous flux of the laser-driven white light can reach up to 2886 lm. It indicates that the Al2O3–LSN:Ce3+ composite PiG film would be an interesting color converter for producing high-brightness laser-driven white light. [ABSTRACT FROM AUTHOR]

Drug release systems with fluorescence detection have emerged as a potential application for the biological area of diagnosis and therapy. Carbon dots (CDs) are a promising fluorescence probe for application in a drug release system due to their excellent biocompatibility, low toxicity, chemical inertness, and non-blinking fluorescence emission. Herein, we developed a composite nanocarrier based on fluorescent CDs and polyvinylpyrrolidone (PVP) through an electrospinning technology. The as-prepared PVP/CD–ketoprofen (PVP/CD–KET) composite nanofiber presents bright blue-light fluorescence with a photoluminescence quantum yield (QY) of 65.7% and was utilized for loading a water-insoluble drug and moreover for monitoring the drug release process. In vitro tests indicate that the photoluminescence emission intensity of the CDs and the cumulative amount of KET released from the PVP/CD–KET composite nanofiber gradually increase with the release time. Furthermore, the emission intensity of the CDs as a function of the cumulative released amount of KET can be summarized by a power function. The correlation between the emission intensity of CDs and drug release amount can be potentially used to monitor the drug release process. [ABSTRACT FROM AUTHOR]

Carbon dots (CDs) have attracted extensive attention over the past decade due to their excellent advantages. However, few attempts have been reported for realizing the long-wavelength emission, especially for obtaining efficient solid-state red emission with high photoluminescence quantum yield (QY). Herein, we developed highly red light emitting CDs by the step-by-step surface modifications of the nitrogen-doped CDs. By introducing hexadecyltrimethyl ammonium bromide to modulate a red CD aqueous solution, the photoluminescence QY increases from 23.2% to 43.6%. Furthermore, we dispersed CDs in a PVP matrix for a solid-state film, where the solid-state quenching was effectively suppressed, and high QY (41.3%) of red light emission was achieved. Taking advantage of the as-prepared red light emitting CDs combining with the reported high quantum yield blue and green light emitting CDs, we realized UV-pumped WLEDs with tunable correlated color temperature from 7879 to 2961 K. Moreover, a high color rendering index (CRI) of 93 for WLEDs was realized, which is superior than the best records for the semiconductor quantum dot based WLEDs. Finally, the red light emitting CDs were demonstrated to have promising application as a red color converter in traditional YAG-based WLEDs to improve their CCT and CRI. [ABSTRACT FROM AUTHOR]

Carbon dots (CDs) exhibit excellent ultraviolet (UV) absorption and tunable photoluminescence over the full visible light range, which endows CDs with huge potential to be designed as efficient full-color emitting phosphors for UV to white light conversion. However, the low quantum yield (QY) for white light emission and solid-state quenching dramatically limit their optoelectronic applications. We proposed an effective strategy for modulating the emitting states of colloidal CDs by introducing hexadecyltrimethyl ammonium bromide. Consequently, white light emission with tunable correlated color temperature from 8121 K to 3623 K was realized. Furthermore, we dispersed CDs in a PVP matrix for solid-state films, where the solid-state quenching was effectively avoided. A white light-emitting QY of 38.7% was thus achieved through the inhibition of non-radiative electron–hole recombination as well as the cooperation between the intrinsic state of the carbogenic cores and the surface-related state of the organic ligands. The white light emitting QY is much higher than that of other reported CDs (ca. 15% in the soluble state and not reported in the solid-state) and is comparable to that of the nanophosphors with the highest UV pumped single-component white light emissions reported in the literature. [ABSTRACT FROM AUTHOR]

A very simple approach to quantitative analysis is proposed based on the technology of digital image processing using three-dimensional (3D) spectra obtained by high-performance liquid chromatography coupled with a diode array detector (HPLC-DAD). As the region-based shape features of a grayscale image, Zernike moments with inherently invariance property were employed to establish the linear quantitative models. This approach was applied to the quantitative analysis of three compounds in mixed samples using 3D HPLC-DAD spectra, and three linear models were obtained, respectively. The correlation coefficients (R2) for training and test sets were more than 0.999, and the statistical parameters and strict validation supported the reliability of established models. The analytical results suggest that the Zernike moment selected by stepwise regression can be used in the quantitative analysis of target compounds. Our study provides a new idea for quantitative analysis using 3D spectra, which can be extended to the analysis of other 3D spectra obtained by different methods or instruments. [ABSTRACT FROM AUTHOR]

Due to the different sensitivities of the 2 E and 4 T 2 energy levels of Cr 3+ to the local environment, Cr 3+ -doped fluorescent materials appear as excellent candidates for highly sensitive temperature sensing based on luminescence intensity ratio technology. However, a way to broaden the strict Boltzmann temperature measuring range is rarely reported. In this work, through Al 3+ alloying strategy, a series of SrGa 12- x Al x O 19 :0.5%Cr 3+ ( x = 0, 2, 4, and 6) solid-solution phosphors were synthesized. Remarkably, the introduction of Al 3+ can play a role in regulating the crystal field around Cr 3+ and the symmetry of [Ga/AlO 6 ] octahedron, realizing the synchronous tuning of 2 E and 4 T 2 energy levels when the temperature changes in a wide range, achieving the purpose of increasing the intensity difference of 2 E → 4 A 2 and 4 T 2 → 4 A 2 transitions, so as to extend the temperature sensing range. Among all samples, SrGa 6 Al 6 O 19 :0.5%Cr 3+ showed the widest temperature measuring range from 130 K to 423 K with S a of 0.0066 K -1 and S r of 1% K -1 @130 K. This work proposed a feasible way to extend the temperature sensing range for transition metal-doped LIR-mode thermometers.

Perovskites based on CsPbX 3 (X = Cl, Br, I) have promising applications in solar cells, light-emitting diodes, and photodetectors. In this paper, the phase stability of inorganic metal halide perovskite CsPbCl 3 under hydrostatic pressure and anion substitution is studied using density functional theory (DFT), and this modification is explained by the interaction of the octahedrons and transformation of the bond-orbital coupling. In addition, two space groups, P 4/ mbm and Amm 2, which are stable under stress, are subjected to anion substitution; then, the structural stability and band gap change of CsPbCl 3- y X y (X = Br, I; y = 0, 1, 2, 3) are analyzed after applying stress; finally, the electronic structures and optical properties of the six most stable components are presented. The effect of stress and anions on the components' optoelectronic properties is closely linked with the crystal's structural alteration mechanism. These results show that stress and anion modulation can significantly change the optoelectronic properties of materials, which make these materials have broad application prospects. Furthermore, stress can be used as an effective tool for screening the most stable material structure.