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CH3NH3PbBr3 Nanocrystals Formed in situ in Polystyrene Used for Increasing the Color Rendering Index of White Leds
摘要： A new method is proposed for the formation of MAPbBr3 nanoparticles in situ in a dispersion of polystyrene in toluene in the absence (MAPbBr3@PS) and presence of a broad-band luminophor (MAPbBr3/GAG:Ce@PS). This method permits the lossless use of perovskite, a uniform distribution of the luminophor nanoparticles in the polymer matrix, and maintenance of a high photoluminescence quantum yield (~46%). The samples derived from MAPbBr3 have green photoluminescence with a maximum showing a blue shift in going from bulk perovskite powder to films due to a size effect. The use of nanocomposite films MAPbBr3/GAG:Ce@PS in white LEDs permits enhancement of the color rendering index to 92 with correlation color temperature >5800 K.
关键词： nanocomposite films,quantum yield,photoluminescence,hybrid halide perovskite
更新于2025-09-11 14:15:04
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Near-Infrared Microlasers from Self-assembled Spiropyrane-Based Microsphercial Caps
摘要： Near-infrared (NIR) microlasers play a significant role in telecommunication and biomedical tissue imaging. However, it remains a big challenge to realize NIR microlasers due to the difficulty in preparing highly efficient NIR luminescent materials and perfect optical resonators. Here we propose a molecular design strategy to creatively realize the first spiropyrane-based NIR microlasers with low threshold from self-assembled microsphercial caps. Tetraphenylethylene (TPE) moiety with a highly twisted conformation provides a large free volume to facilitate the photoisomerization process of spiropyrane (SP) and enhance NIR emission of merocyanine in the solid state. Moreover, self-assembled TPE-SP microsphercial caps simultaneously serve as gain media and resonating microcavities, providing optical gain and feedback for NIR laser oscillations with a low threshold (3.68 μJ/cm2). These results are beneficial for deeply understanding the SP microstructures-lasing emission characteristic relationship and provide a useful guideline for the rational molecular design of NIR microlasers with special functionalities.
关键词： tetraphenylethylene twisted conformation,spiropyrane,enhanced quantum yield,self-assembled microsphercial cap,NIR microlaser
更新于2025-09-11 14:15:04
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Changes in the photosynthesis properties and photoprotection capacity in rice (Oryza sativa) grown under red, blue, or white light
摘要： Non-photochemical quenching (NPQ) of the excited state of chlorophyll a is a major photoprotective mechanism plants utilize to survive under high light. Here, we report the impact of long-term light quality treatment on photosynthetic properties, especially NPQ in rice. We used three LED-based light regimes, i.e., red (648–672 nm), blue (438–460 nm), and “warm” white light (529–624 nm), with the incident photon flux density of 300 μmol photons m?2 s?1, the difference in the absorbed photon flux densities by leaves grown under different light quality being less than 7%. Our results show that blue light, as compared to white light, induced a significant decrease in Fv/Fm, a decreased rate of reduction of P700+ after P700 was completely oxidized; furthermore, blue light also induced higher NPQ with an increased initial speed of NPQ induction, which corresponds to the qE component of NPQ, and a lower maximum quantum yield of PSII, i.e., Y(II). In contrast, rice grown under long-term red light showed decreased Y(II) and increased NPQ, but with no change in Fv/Fm. Furthermore, we found that rice grown under either blue or red light showed decreased transcript abundance of both catalase and ascorbate peroxidase, together with an increased H2O2 content, as compared to rice grown under white light. All these data suggest that even under a moderate incident light level, rice grown under blue or red light led to compromised antioxidant system, which contributed to decreased quantum yield of photosystem II and increased NPQ.
关键词： Non-photochemical quenching of the excited state of chlorophyll a,Effective quantum yield of PSII,Light quality,Quantum yield of regulated energy dissipation in PSII,Oryza sativa,Antioxidant system
更新于2025-09-10 09:29:36
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Design Principles for Trap-Free CsPbX <sub/>3</sub> Nanocrystals: Enumerating and Eliminating Surface Halide Vacancies with Softer Lewis Bases
摘要： We introduce a general surface passivation mechanism for cesium lead halide perovskite materials (CsPbX3, X = Cl, Br, I) that is supported by a combined experimental and theoretical study of the nanocrystal surface chemistry. A variety of spectroscopic methods are employed together with ab initio calculations to identify surface halide vacancies as the predominant source of charge trapping. The number of surface traps per nanocrystal is quantified by 1H NMR spectroscopy, and that number is consistent with a simple trapping model in which surface halide vacancies create deleterious under-coordinated lead atoms. These halide vacancies exhibit trapping behavior that differs between CsPbCl3, CsPbBr3, and CsPbI3. Ab initio calculations suggest that introduction of anionic X-type ligands can produce trap-free band gaps by altering the energetics of lead-based defect levels. General rules for selecting effective passivating ligand pairs are introduced by considering established principles of coordination chemistry. Introducing softer, anionic, X-type Lewis bases that target under-coordinated lead atoms results in absolute quantum yields approaching unity and monoexponential luminescence decay kinetics, thereby indicating full trap passivation. This work provides a systematic framework for preparing highly luminescent CsPbX3 nanocrystals with variable compositions and dimensionalities, thereby improving fundamental understanding of these materials and informing future synthetic and post-synthetic efforts towards trap-free CsPbX3 nanocrystals.
关键词： charge trapping,nanocrystals,surface passivation,ab initio calculations,halide vacancies,CsPbX3,ligand exchange,quantum yield
更新于2025-09-10 09:29:36
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Camouflaged Nanosilver with Excitation Wavelength Dependent High Quantum Yield for Targeted Theranostic
摘要： The present study shows the thorough investigations on optical properties and hydrodynamic diameters of glutathione (GSH) stabilized nanosilver clusters (AgNC) at different stages of synthesis and engineering for the optimized absolute quantum yield to generate fluorescent images of Dalton Lymphoma Ascites (DLA) tumour bearing mice. The initial increment of quantum yield was wavelength dependent and finally it became 0.509 which was due to the camouflaging or entrapment of AgNC in macrophages membranes. The potentiality of macrophages membrane camouflaged silver nanoclusters (AgM) was reflected in the cell viability assay and confocal based live dead cell assay where the AgM has better cell killing effect compared to AgNC with reduced dosage and in vivo mice imaging generated the clear visualization at the tumour sites. Therefore, from the present study, it can be considered that the camouflaged nanosilver can be used for targeted theranostic applications.
关键词： nanosilver clusters,macrophage membrane,theranostic,fluorescence imaging,quantum yield
更新于2025-09-10 09:29:36
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14.2: <i>Invited Paper:</i> Quantum Yield Measurement Using Organic Dyes as References for Semiconductor Nanocrystals
摘要： A method of using series of organic dyes as reference to measure the quantum yield efficiency (QY) for semiconductor nanocrystals (Quantum Dots, QDs) in solution state is reported. In the proposed method, the sensitivity of the fluorescence spectrophotometer on wavelength as well as the excitation power intensity is considered to improve the accuracy.
关键词： Semiconductor Nanocrystals,Quantum Dots,QDs,Quantum Yield Efficiency Measurment
更新于2025-09-09 09:28:46
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Mn <sup>4+</sup> -Doped Heterodialkaline Fluorogermanate Red Phosphor with High Quantum Yield and Spectral Luminous Efficacy for Warm-White-Light-Emitting Device Application
摘要： Narrow band red-emitting Mn4+-doped fluoride phosphor is an essential red component of modern white-light-emitting-diode (WLED) devices. Its luminescence has sensitivity to structure and influences the performance of WLED. In this paper, we report a high-performance Mn4+ phosphor based on a new heterodialkaline fluorogermanate, CsNaGeF6:Mn4+. As determined by the single-crystal X-ray diffraction analysis, the CsNaGeF6 compound crystallizes in the orthorhombic crystal system with space group Pbcm (No. 57). Under excitation by 360 and 470 nm photons, CsNaGeF6:Mn4+ emits intense red light near 630 nm with a high quantum yield of 95.6%. The electronic energy levels of the Mn4+ ion in Cs2GeF6, Na2GeF6, and CsNaGeF6 are calculated using the exchange charge model of crystal-field theory. The local Mn4+ environment inducing different zero-phonon-line emissions in the structures is probed by electron paramagnetic resonance. The Mn4+-doped heterodialkaline fluorogermanate CsNaGeF6:Mn4+ exhibits broader emission as a result of the lowest symmetry. It has higher quantum yield than Na2GeF6:Mn4+ and higher spectral luminous efficacy than Cs2GeF6:Mn4+. Given the good thermal stability and efficient luminescence, a prototype warm-WLED device with a color rendering index of 92.5, a correlated color temperature of 3783 K, and a luminous efficacy of 176.3 lm/W has been fabricated by employing the CsNaGeF6:Mn4+ phosphor as the red component. Our results not only reveal that a high-performance Mn4+ red phosphor is achieved through cationic substitutions but also construct a relationship of performance?structure to guide the design of Mn4+ phosphors in the future.
关键词： quantum yield,spectral luminous efficacy,Mn4+-doped fluoride phosphor,warm-white-light-emitting diode,heterodialkaline fluorogermanate
更新于2025-09-09 09:28:46
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Highly Efficient and Robust Photocatalytic Systems for CO <sub/>2</sub> Reduction Consisting of a Cu(I) Photosensitizer and Mn(I) Catalysts
摘要： The development of highly efficient, selective, and durable photocatalytic CO2 reduction systems that only use earth-abundant elements is key for both solving global warming and tackling the shortage of energy and carbon resources. Here, we successfully developed CO2 reduction photocatalysts using [Cu2(P2bph)2]2+ (CuPS) (P2bph = 4,7-diphenyl-2,9-di(diphenylphosphinotetramethylene)-1,10-phenanthroline) as a redox photosensitizer and fac-Mn(X2bpy)(CO)3Br (Mn(4X)) (X2bpy = 4,4′-X2-2,2′-bipyridine (X = ?H and ?OMe) or Mn(6mes) (6mes = 6,6′-(mesityl)2-2,2′-bipyridne)) as the catalyst. The most efficient photocatalysis was achieved by Mn(4OMe): The total quantum yield of CO2 reduction products was 57%, the turnover number based on the Mn catalyst was over 1300, and the selectivity of CO2 reduction was 95%. Electronic and steric effects of the substituents (X) in the Mn complexes largely affected both the photocatalytic efficiency and the product selectivity. For example, the highest selectivity of CO formation was achieved by using Mn(6mes) (selectivity SCO = 96.6%), whereas the photocatalytic system using Mn(4H) yielded HCOOH as the main product (SHCOOH = 74.6%) with CO and H2 as minor products (SCO = 23.7%, SH2 = 1.7%). In these photocatalytic reactions, CuPS played its role as an efficient and very durable redox photosensitizer, while remaining stable in the reaction solution even after a turnover number of 200 had been reached (the catalyst used had a turnover number of over 1000).
关键词： turnover number,Cu(I) photosensitizer,Mn(I) catalysts,photocatalytic CO2 reduction,earth-abundant elements,quantum yield,product selectivity
更新于2025-09-09 09:28:46
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Photoluminescence of the integrating sphere walls, its influence on the absolute quantum yield measurements and correction methods
摘要： Determination of the absolute quantum yield (QY) of photoluminescence (PL) or electroluminescence is commonly performed using an integrating sphere (IS) – versatile device for radiometry applications. The key feature of IS is very high diffused reflectance of its internal surface. Two materials are commonly used: (a) the sintered high-density polytetrafluoroethylene (Spectralon) and (b) materials based on barium sulphate (Spectrafect). Using PL-micro-spectroscopy we show that both materials reveal PL from localized centers excitable by UV, blue and green light emitting broad PL spectrum extending up to the red spectral region. The main effect of PL from IS-walls is introduction of non-constant parasitic background which is mixed with PL from a tested sample during the QY measurements. We develop theoretical description of QY determination which includes effects of PL from IS walls. This allows us to propose and test a reliable and universal correction for the IS-related PL background. Finally, a method of “black sample” is proposed and applied to estimate PL QY of Spectrafect which is shown to decrease from 0.09 to 0.015% for excitation shift from 320 to 440 nm.
关键词： photoluminescence,integrating sphere,Spectrafect,Spectralon,quantum yield
更新于2025-09-09 09:28:46
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Spectral-Luminescent Properties of 2-(2,6-Difluorophenyl)-5-phenyl-[2-acetyl(benzoyl)oxyphenyl]-1,3,4-oxadiazoles
摘要： 2-(2,6-Difluorophenyl)-5-phenyl(2-hydroxyphenyl)-1,3,4-oxadiazoles were synthesized by cyclization of N-(2,6-difluorobenzoil) derivatives of benzohydazide or salicylhydrazide in thionyl chloride. When acylating 2-[5-(2,6-difluorophenyl)-1,3,4-oxadiazole-2-yl]phenol by acetyl or benzoyl chloride corresponding acetate and benzoate were obtained. Spectral-luminescent properties of the synthesized compounds were studied.
关键词： 2,5-diaryl-1,3,4-oxadiazoles,organic luminophors,luminescence,luminescence quantum yield
更新于2025-09-09 09:28:46