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Ho‐based lead‐free double perovskite microcrystals (MCs), Cs2NaHo1‐xYbxCl6, are synthesized and demonstrated to be promising optical temperature sensing materials by understanding the concentration‐dependent upconversion (UC) luminescence mechanisms. By optimizing the dopant concentration, a dominant emission shifting from red to green is successfully achieved in an activator‐rich system. During this process, the red to green emission intensity ratio (R/G) can be changed from 12.5 (pure red light) to 0.14 (pure green light). It is clarified that the cross‐relaxation (CR) process between activator and the energy transfer process between Yb3+ and Ho3+ are the key mechanisms of UC luminescence intensity and R/G ratio variation. Moreover, the intensity of red and green UC emission shows strong dependence on temperature, resulting from the competition between CR and energy transfer in the emission levels. The high‐sensitivity Ho‐based thermometer can be obtained by Cs2NaHo0.99Yb0.01Cl6 MCs with bright red UC luminescence, whose fluorescence intensity ratio thermometer gains maximum relative sensitivities reaching 0.68% K−1 at 400 K. The multicolor UC luminescence quantitative modeling mentioned here is crucial for understanding the concentration‐dependence UC luminescence characteristics and to optimize the design of the Ho‐based thermometer. This study can be an extension of the application range for perovskite UC materials. [ABSTRACT FROM AUTHOR]

Cs2AgInCl6 lead-free double perovskites are environmentally benign with easily modulated fluorescence. However, their wide band gap (∼3.3 eV) and forbidden optical transitions limit their visible application. Herein, we prepared Cs2AgInCl6 microcrystals (MCs) and corresponding doped samples (bismuth: Bi3+, samarium: Sm3+, and Bi3+–Sm3+) to achieve such a functionality by a precipitation method at low temperature (80 °C). Bi3+-doped Cs2AgInCl6 MCs introduce 1S0 to 1P1 absorption with a fluorescence enhancement at lower excitation energy (370 nm). Although the f–f transition of Sm3+ is parity forbidden, Bi3+–Sm3+ co-doped Cs2AgInCl6 MCs show a combination of luminescence in the visible range with two sharp additional spectral features at 567 and 600 nm, which are attributed to the 4G5/2 → 6H5/2 (∼567 nm) and 4G5/2 → 6H7/2 (∼600 nm) transitions of Sm3+ ions. We proposed a mechanism in which Cs2AgInCl6:Bi–Sm MCs achieve mutual enhancement of fluorescence through recombination of self-trapped excitons and energy-transfer transitions. Moreover, thermogravimetric (TG) analysis indicated that the materials have remarkable thermal stability. Afterwards, light-emitting diodes (LEDs) with bright yellow light were fabricated by combining Cs2AgInCl6:Bi–Sm MCs with a 365 nm chip, and the corresponding color coordinate is about (0.535, 0.440) with a 2000 K correlated color temperature (CCT). [ABSTRACT FROM AUTHOR]

Recently, lead‐free materials with stable photoluminescence (PL) at room temperature, such as vacancy‐ordered double perovskites have drawn wide attention. Herein, Te4+‐doped all‐inorganic lead‐free Cs2Zr1−xTexCl6 perovskite microcrystals (MCs) are reported. The obtained pure Cs2ZrCl6 perovskite MCs exhibit a blue emission, while Cs2Zr1−xTexCl6 perovskite MCs show a broad and strong yellow emission with ultrahigh photoluminescence quantum yield (PLQY) up to 79.46% at room temperature. The structure and optical properties of perovskite MCs are investigated in detail by experiments and theoretical calculations. The mechanism that 3P1 of Te can be partially frozen at the low temperature regarding Cs2Zr1−xTexCl6 perovskite MCs is proposed. White light emitting diodes (WLEDs) with a color coordinate of (0.344, 0.333), a correlated color temperature of 4959 K, a color rendering index (Ra) of 74.8, and a high light efficiency of 91.16 lm W−1, are fabricated by the prepared Cs2Zr1−xTexCl6 perovskite MCs powder with a commercial near‐UV LED (NUV‐LED) chip (450 nm). The results suggest that Te4+‐doped all‐inorganic lead‐free perovskite MCs show great potential in the next‐generation solid‐state lightings. [ABSTRACT FROM AUTHOR]

Objective: To explore the types of pathogens causing lower respiratory tract infections (LTRIs) in children and construction of a predictive model for monitoring secondary asthma caused by LTRIs., Methods: Seven hundred and seventy-five children with LTRIs treated from June 2017 to July 2024 were selected as research subjects. Bacterial isolation and culture were performed on all children, and drug sensitivity tests were conducted on the isolated pathogens; And according to whether the child developed secondary asthma during treatment, they were divided into asthma group (n = 116) and non-asthma group (n = 659); Using logistic regression model to analyze the risk factors affecting secondary asthma in children with LTRIs, and establishing machine learning (ie nomogram and decision tree) prediction models; Using ROC curve analysis machine learning algorithms to predict AUC values, sensitivity, and specificity of secondary asthma in children with LTRIs., Results: 792 pathogenic bacteria were isolated from 775 children with LTRIs through bacterial culture, including 261 Gram positive bacteria (32.95%) and 531 Gram negative bacteria (67.05%). Logistic regression model analysis showed that Glycerophospholipids, Sphingolipids and radiomics characteristics were risk factors for secondary asthma in children with LTRIs (P < 0.05). The AUC, sensitivity, and specificity of nomogram prediction for secondary asthma in children with LTRIs were 0.817(95CI: 0.760-0.874), 82.3%, and 76.6%, respectively; The AUC of decision tree prediction for secondary asthma in children with LTRIs is 0.926(95% CI: 0.869-0.983), with a sensitivity of 96.7% and a specificity of 87.8%., Conclusion: LTRIs in children are mainly caused by Staphylococcus aureus, Streptococcus pneumoniae, Staphylococcus epidermidis, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa; In addition, machine learning combined with multi-omics prediction models has shown good ability in predicting LTRIs combined with asthma, providing a non-invasive and effective method for clinical decision-making., Competing Interests: The authors report no conflicts of interest in this work., (© 2024 Rao et al.)

Recently, single-band ratiometric (SBR) thermometry has emerged as an innovative approach to traditional fluorescence thermometry, overcoming uncertainties associated with emission spectrum overlap or scattering while maintaining high spatial resolution and remote monitoring. This paper presents a novel Cs 2 NaEuCl 6 perovskite prepared through a slow-cooling solution method. Additionally, it proposes a temperature sensor model that relies on the thermal quenching of charge-transfer state absorption. Mechanical studies highlight the role of lattice positive thermal expansion in affecting Eu 3+ emission. Conversely, a significant emission enhancement is observed upon excitation corresponding to both the ground state and excited state absorption. The distinct luminescent behavior of this Eu 3+ -activated halide perovskite model makes it suitable for developing a highly sensitive SBR-type sensor with a relative sensitivity (S r ) exceeding 1.5% K -1 and temperature resolution (𝛿T) below 1 K at room temperature. Furthermore, it demonstrates the thermal stability during multiple heating-cooling cycles. Finally, the practical applicability of the proposed SBR model is demonstrated by employing a self-manufactured film sensor that enables precise real-time temperature detection for electronic components. The work is regarded as a significant stride toward the development of cutting-edge and exquisitely sensitive thermometers based on lanthanide-based halide double perovskites., (© 2024 Wiley‐VCH GmbH.)

Low-dimension perovskite materials have attracted wide attention due to their excellent optical properties and stability. Herein, Sb 3+ -doped Cs 2 ZrCl 6 crystals are synthesized by a coprecipitation method in which Sb 3+ ions partially replace Zr 4+ ions. The Cs 2 ZrCl 6 : x Sb 3+ powder shows blue and orange-red emissions under a 254 and 365 nm light, respectively, due to the [ZrCl 6 ] 2- octahedron and [SbCl 6 ] 3- octahedron. The photoluminescence quantum yield (PLQY) of Cs 2 ZrCl 6 : x Sb 3+ ( x = 0.1) crystals is up to 52.5%. According to experimental and computational results, the emission mechanism of the Cs 2 ZrCl 6 : x Sb 3+ crystals is proposed. On the one hand, a wide blue emission with a large Stokes shift is caused by the self-trapping excitons of [ZrCl 6 ] 2- octahedra under a 260 nm excitation. On the other hand, the luminescence mechanism of [SbCl 6 ] 3- octahedron is divided into two parts: 1 P 1 → 1 S 0 (490 nm) and 3 P 1 → 1 S 0 (625 nm). The broad-band emission, high PLQY, and excellent stability endow the Cs 2 ZrCl 6 : x Sb 3+ powders with the potential for the fabrication of white light-emitting diodes (WLEDs). A WLED device is fabricated using a commercial 310 nm NUV chip, which shows a high color rendering index of 89.7 and a correlated color temperature of 5333 K. In addition, the synthesized Cs 2 ZrCl 6 : x Sb 3+ crystals can be also successfully used for information encryption. Our work will provide a deep understanding of the photophysical properties of Sb 3+ -doped perovskites and facilitate the development of Cs 2 ZrCl 6 : x Sb 3+ crystals in encrypting multilevel optical codes and WLEDs.

Due to the toxicity and instability issues of lead halide perovskites, lead-free perovskites have recently emerged as a viable alternative. However, significant optical band gaps of lead-free perovskites exert influence on their luminescent properties. Fortunately, the addition of dopants becomes an efficacious solution. The current widely utilized methods for synthesizing perovskites almost require high temperatures, a long period, and atmosphere protection, which cost more energy and resources. In this paper, we report that Rb 2 ZrCl 6 : x Sb 3+ perovskite phosphors can be easily prepared by a wet grinding approach at room temperature, which is a more efficient and facile process. Due to the self-trapped excitons of the host structure and Sb 3+ ions, the produced samples display blue-white and orange fluorescence under UV lamp irradiation at 254 and 365 nm, respectively. In the photoluminescence spectrum, the doped perovskite exhibits an emission peak at 630 nm under excitation at 365 nm. Importantly, the prepared phosphors have tunable emissions related to the excitation wavelength. In addition, our produced powders show remarkable stability at room temperature, laying the foundations for this approach to be widely used in perovskite production.

Fluorescence intensity ratio (FIR) thermometry, a new contactless temperature measurement, can achieve accurate measurements in a harsh environment. In this work, all-inorganic lead-free Cs 2 AgInCl 6 : Er-Yb and Cs 2 AgBiCl 6 : Er-Yb microcrystals emit bright green up-conversion emission, which are synthesized by precipitation at a low temperature (80 °C). In up-conversion emission, FIR of the 2 H 11/2 → 4 I 15/2 band to the 4 S 3/2 → 4 I 15/2 band exhibits temperature dependence, which can be used as the temperature measurement parameter, so-called FIR thermometry. Moreover, the theoretically accurate measurement range is from 100 to 600 K, achieving maximum absolute sensitivities from 0.0130 to 0.0113 K -1 , respectively. The principle of up-conversion and high sensitivity is well explained by calculating the partial density of states. Compared to the reported thermometry materials based on the FIR method, the prepared all-inorganic lead-free Cs 2 AgInCl 6 : Er-Yb and Cs 2 AgBiCl 6 : Er-Yb microcrystals show outstanding temperature measurement width and sensitivity, becoming a potential candidate for high-sensitivity optical temperature sensors.