Preparation of (Lu,Y)3(Al,Sc,Cr)2Al3O12 phosphor ceramics with high thermal stability for near-infrared LED/LD

Near-infrared (NIR) phosphor-converted light-emitting diodes/laser diodes (LEDs/LDs) are prospective lighting sources for NIR spectroscopy. However, developing NIR phosphor materials with desired thermal robustness and high photoelectric efficiency is a crucial challenge for their applications. In this work, based on the cationic radius matching effect, a series of (Lu,Y)3(Al,Sc,Cr)2Al3O12 NIR phosphor ceramics (LuYScCr NIR-PCs) were fabricated by vacuum sintering. Excellent thermal stability (95%@150 ℃) was obtained in the prepared NIR-PCs, owing to their weak electron–phonon coupling effect (small Huang–Rhys factor). Being excited at 460 nm, NIR-PCs realized a broadband emission (650–850 nm) with internal quantum efficiency (IQE) of 60.68%. Combining NIR-PCs with LED/LD chips, the maximum output power of the encapsulated LED prototype was 447 mW@300 mA with photoelectric efficiency of as high as 18.6 %@180 mA, and the maximum output power of the LD prototype was 814 [email protected] A. The working temperatures of NIR-PCs were 70.8 ℃@300 mA (LED) and 102.8 ℃@3 A (LD). Finally, the prepared NIR-PCs applied in food detection were verified in this study, demonstrating their anticipated application prospects in the future

Geotechnical characterization of an alluvial fanglomerate

The Department of Energy (DOE) has recently announced that the Superconducting Super Collider (SSC) will soon be built somewhere in the United States. Preliminary geophysical studies indicate that the Sierrita site 35 miles southwest of Tucson has geological conditions that would facilitate construction of the SSC. The Maricopa site southwest of Phoenix is also one of the two potential sites in Arizona. However, several additional geotechnical investigations were required to convincingly demonstrate the suitability of these two locations. The present research program identified the geotechnical properties of the soils at the two sites through various levels of laboratory and field testing. The significance of these results are discussed and recommendations are given

The cost-effectiveness of conducting three versus two reverse transcriptionpolymerase chain reaction tests for diagnosing and discharging people with COVID-19 : evidence from the epidemic in Wuhan, China

Objectives The objectives were to evaluate the effectiveness of conducting three versus two reverse transcription-PCR (RT-PCR) tests for diagnosing and discharging people with COVID-19 with regard to public health and clinical impacts by incorporating asymptomatic and presymptomatic infection and to compare the medical costs associated with the two strategies. Methods A model that consisted of six compartments was built. The compartments were the susceptible (S), the asymptomatic infective (A), the presymptomatic infective (L), the symptomatic infective (I), the recovered (R), and the deceased (D). The A, L and I classes were infective states. To construct the model, several parameters were set as fixed using existing evidence and the rest of the parameters were estimated by fitting the model to a smoothed curve of the cumulative confirmed cases in Wuhan from 24 January 2020 to 6 March 2020. Input data about the cost-effectiveness analysis were retrieved from the literature. Results Conducting RT-PCR tests three times for diagnosing and discharging people with COVID-19 reduced the estimated total number of symptomatic cases to 45013 from 51144 in the two-test strategy over 43 days. The former strategy also led to 850.1 quality-adjusted life years (QALYs) of health gain and a net healthcare expenditure saving of CN¥49.1 million. About 100.7 QALYs of the health gain were attributable to quality-adjusted life day difference between the strategies during the analytic period and 749.4 QALYs were attributable to years of life saved. Conclusions More accurate strategies and methods of testing for the control of COVID-19 may reduce both the number of infections and the total medical costs. Increasing the number of tests should be considered in regions with relatively severe epidemics when existing tests have moderate sensitivity.Medicine, Faculty ofNon UBCPopulation and Public Health (SPPH), School ofReviewedFacult

Silica-Coated Mn-Doped CsPb(Cl/Br)₃ Inorganic Perovskite Quantum Dots: Exciton-to-Mn Energy Transfer and Blue-Excitable Solid-State Lighting

Tunability of emitting colors of perovskite quantum dots (PQDs) was generally realized via composition/size modulation. Due to their bandgap absorption and ionic crystal features, the mixing of multiple PQDs inevitably suffers from reabsorption and anion-exchange effects. Herein, we address these issues with high-content Mn²⁺-doped CsPbCl₃ PQDs that can yield blue-excitable orange Mn²⁺ emission benefited from exciton-to-Mn energy transfer and Cl-to-Br anion exchange. Silica-coating was applied to improve air stability of PQDs, suppress the loss of Mn²⁺, and avoid anion-exchange between different PQDs. As a direct benefit of intense multicolor emissions from Mn²⁺-doped PQD@SiO₂ solid phosphors, a prototype white light-emitting diode with excellent optical performance and superior light stability was constructed using green CsPbBr₃@SiO₂ and orange Mn: CsPb­(Cl/Br)₃@SiO₂ composites as color converters, verifying their potential applications in the field of optoelectronics

Unveiling Dopant‐Induced Ultrafast Exciton Dynamics in Mn/Yb Codoped Perovskite Nanocrystals

Abstract Perovskite nanocrystals (NCs) with intentionally introduced Mn2+/Yb3+ activators enable tunable emissions covering UV‐orange‐NIR spectral range. However, the exact microscopic energy transfer mechanisms in this system remain unknown. Herein, Mn/Yb codoped CsPbCl3 perovskite NCs with triple emissions originated from exciton recombination of host, 3d–3d transition of Mn2+ and 4f–4f transition of Yb3+ are prepared. Femtosecond resolution transient absorption spectra performed on the pristine CsPbCl3, Mn‐doped, Yb‐doped and Mn/Yb codoped samples clarify efficient and simultaneous energy transfer (ET) from excitons to Mn2+ and Yb3+ dopants. It is testified the sensitizations of dopants mainly result from the trapped hole, taking 285 ps for Mn2+ and 17 ps for Yb3+ respectively, which make less trapped hole recombine with de‐localized carriers. Importantly, energy transfer processes from host to Mn2+ and Yb3+ activators emerge as competition, and the ET probability of exciton‐to‐Mn2+ is higher than that of exciton‐to‐Yb3+. Finally, control experiments further prove that tunable Mn2+ orange emission and Yb3+ NIR emission are achievable via elaborate adjustment of the dopant concentrations

Full-Spectral Fine-Tuning Visible Emissions from Cation Hybrid Cs_1–<i>m</i>FA<i>_m</i>PbX₃ (X = Cl, Br, and I, 0 ≤ <i>m</i> ≤ 1) Quantum Dots

Full-color visible emissions are particularly crucial for applications in displays and lightings. In this work, we developed a facile room-temperature ligand-assisted supersaturated recrystallization synthesis of monodisperse, cubic structure Cs_1–<i>m</i>FA<i>_m</i>PbX₃ (X = Cl, Br, and I or their mixtures Cl/Br and Br/I, 0 ≤ <i>m</i> ≤ 1) hybrid perovskite quantum dots (QDs). Impressively, cation substitution of Cs⁺ by FA⁺ was beneficial in finely tuning the band gap and in exciton recombination kinetics, improving the structural stability, and raising the absolute quantum yields up to 85%. With further assistance of anion replacement, full-spectral visible emissions in the wavelength range of 450–750 nm; narrow full width at half-maxima, and a wide color gamut, encompassing 130% of National Television System Committee television color standard, were achieved. Finally, Cs_1–<i>m</i>FA<i>_m</i>PbX₃-polymer films retaining multicolor luminescence are prepared and a prototype white light-emitting diode device was constructed using green Cs_0.1FA_0.9PbBr₃ and red Cs_0.1FA_0.9Br_1.5I_1.5 QDs as color converters, certainly suggesting their potential applications in the optoelectronics field