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Synthesis and Optical Properties of the Eu2+-Doped Alkaline-Earth Metal Hydride Chlorides AE7H12Cl2 (AE = Ca and Sr)
摘要： In our study of the optical properties of Eu2+-doped alkaline-earth metal hydride chlorides AE7H12Cl2 (AE = Ca and Sr) we observe yellow (AE = Sr) and orange-red (AE = Ca) emission. Compared to the emission energies of Eu2+ - doped fluorides, chlorides and mixed fluoride chlorides, this corresponds to a wide redshift of the Eu2+ 4f65d1–4f7 emission. We explain this observation with the strong polarizability of the hydride anion and therefore its strong nephelauxetic effect, which shifts the 5d barycenter to lower energy. Furthermore, the redshift is even significant compared to other known hydride chlorides and hydride oxide chlorides, which is probably caused by the relatively short AE2+/Eu2+?H? distances, or it might also be caused by impurity-trapped exciton states. We have also investigated the temperature dependence of the photoluminescence lifetimes and the thermal stability. Even though the compounds are probably not ideal for phosphor application due to their low stability against air and moisture, our study underlines the large influence of the highly polarizable hydride anion on the optical properties of divalent europium and shows that Eu2+ could be used as a probe in mixed anionic system to determine the hydride content.
关键词： Hydride Chlorides,Eu2+ Luminescence,Alkaline-Earth Metals
更新于2025-09-23 15:22:29
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Endoscopic Cerenkov luminescence imaging and image-guided tumor resection on hepatocellular carcinoma-bearing mouse models
摘要： Detecting deep tumors inside living subject is still challenging for Cerenkov luminescence imaging (CLI). In this study, a high-sensitivity endoscopic CLI (ECLI) system was developed with a dual-mode deep cooling approach to improve the imaging sensitivity. System was characterized through a series of ex vivo studies. Furthermore, subcutaneous and orthotropic human hepatocellular carcinoma (HCC) mouse models were established for ECLI guided tumor resection in vivo. The results showed that the ECLI system had spatial resolution (62.5 μm) and imaging sensitivity (6.29×10-2 kBq/μl 18F-FDG). While the results from both subcutaneous and orthotropic HCC mouse models demonstrate the effectiveness of the system to intraoperatively guide the surgery of deep tumors such as liver cancer. Overall, the developed system exhibits promising potential for the applications of tumor precise resection and novel nanoprobe based optical imaging.
关键词： Endoscopy,Image-guided surgery,Hepatocellular carcinoma (HCC),Cerenkov luminescence imaging
更新于2025-09-23 15:22:29
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Role of electron and hole centers in energy transfer in BaBrI crystals
摘要： In this paper we study a role of F-centers, hole centers and excitons in energy transfer in Eu-doped BaBrI crystals. Optical absorption spectra, thermally stimulated (TSL) and photostimulated (PSL) luminescence in wide temperature range 7-300 K are studied in undoped and doped with different concentrations of Eu ions BaBrI crystals. Based on experimental and calculated results two possible energy tranfer processes from host to Eu2+ ions are established.
关键词： energy transfer,thermoluminescence,alkali earth halides,scintillators,bromide,iodide,F-center,photostimulated luminescence
更新于2025-09-23 15:22:29
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Validation of the model of TSL isothermal decay in dosimetric α-Al2O3 crystals
摘要： New features of isothermal build-up of thermally stimulated luminescence (TSL) related to deep traps in anion-deficient alumina single crystals are revealed. It was found that the TSL build-up at 630-750 K depends on the structure of the glow curve and is associated with the presence of a high-temperature component with Tm=700 K. Isothermal TSL build-up for the peak at 573 K is well expressed in UV-irradiated samples and is very weak after sample irradiation by a pulsed electron beam. The TSL build-up for this peak is registered for the luminescence of F centres but is absent for the emission of F2+ centres and chromium ions. The obtained results confirm the validity of the kinetic model of the TSL build-up that takes into account the process of thermal ionization of the excited states of F centres in aluminum oxide.
关键词： TSL build-up,Deep traps,Thermal Ionization of F centres,Aluminum oxide,Thermally stimulated luminescence
更新于2025-09-23 15:22:29
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Fine-Tuning Aromatic Stacking and Single-Crystal Photoluminescence through Coordination Chemistry
摘要： Organic aromatics usually show a decrease in fluorescence efficiency in the solid state on account of well-known aggregation induced quenching. We have found that single crystals of coordination polymers consisting of γ-aminobutyric acid functionalized naphthalenediimide ligand (H2GABA-NDI) can give rise to highly emissive, broad, and red-shifted photoluminescence (PL) in the solid state. To better understand the origin of the bandwidth broadening with the π–π stacking distances, we performed time-resolved PL studies in a series of polymers with a variety of metal centers. We conclude that the broad steady-state PL signals is originated from a superposition of two emissive states with differing energy and lifetimes, with the lower energy one produced by the interchromophoric interactions mediated by π–π stacking of neighboring NDI units. Our work demonstrates that coordination chemistry is an effective tool to modulate interchromophoric couplings and that simple PL analysis can be used as a measure of the degree of π-stacking.
关键词： crystal engineering,luminescence,photochemistry,stacking interactions,coordination modes
更新于2025-09-23 15:22:29
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Aggregation-amplified circularly polarized luminescence from axial chiral boron difluoride complexes
摘要： The development of small organic molecules with intense and switchable circularly polarized luminescence (CPL) is currently attracting great interest due to their promising applications in chiroptical devices and sensors. In this paper, CPL-active BF2-bridged azaanthracene dimers (BA1 and BA2) were facilely synthesized by incorporating boron difluoride unit to the bi-naphthalene. BA1 and BA2 show moderate CPL in diluted solutions, however, BA2 exhibited aggregation-amplified red CPL with large dissymmetry factor up to 1.6×10?2. Moreover, acid-/base-triggered CPL switch off/on were also realized via disaggregation/aggregation of BA2 in tetrahydrofuran (THF)/water binary solvents.
关键词： aggregation-induced emission,bodipy,circularly polarized luminescence,switch,dyes and pigments
更新于2025-09-23 15:22:29
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Insights into the element gradient in the grain and luminescence mechanism of the long afterglow material Sr2MgSi2O7: Eu2+,Dy3+
摘要： In the long afterglow luminescent material, the defects play an important role on the afterglow performance, but the understanding of the traps are still not uniform. In this research, the long afterglow material Sr2MgSi2O7: Eu2t,Dy3t is treated by the acid corrosion liquid with different times to research gradient distribution of elements from outside to inside the grain of the long afterglow materials, the effect of the gradient on the structure, photoluminescence performance, long afterglow properties as well as the mechanism of luminescence are discussed. When the grain surface is destroyed, the initial brightness falls sharply, but the decrease of decay times are not obvious, that is caused by the different distribution of defects. The amounts of element Sr and O increase, but the Eu and Dy decrease from the outside to the inside the grain, the aggregate defects (VO$$EuSr)n which act as shallow traps are proposed, and meanwhile the isolated defects VO$$ act as deep traps. A new luminescent model is put forward to account for the long afterglow photoluminescence phenomenon, the shallow traps and the deep traps play different roles on the long afterglow properties, and most of the problems that exist in the long afterglow materials can be explained by this model.
关键词： Luminescence,Mechanism of luminescence,Afterglow properties,Grain surface,Sr2MgSi2O7:Eu2t,Dy3t
更新于2025-09-23 15:21:21
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Self-Assembly of Amphiphilic Schiff Base and Selectively Turn on Circularly Polarized Luminescence by Al3+
摘要： We designed glutamide-derived amphiphilic Schiff bases containing three different aldehyde moieties for the fabrication of circularly polarized luminescence (CPL) emitting materials. Upon self-assembly in acetonitrile, Schiff bases featuring 4-(dimethylamino)-2-hydroxylbenzaldehyde and 1-hydroxy-2-naphthaldehyde groups form supramolecular gels with twist and fiber structures, respectively, while Schiff bases featuring 2-hydroxy-1-naphthaldehyde groups forms precipitation with flakes structures. Although emission and circular dichroism (CD) signals can be detected from the supramolecular gels formed by amphiphilic Schiff bases, none of them exhibits circularly polarized luminescence (CPL). While Mg2+, Zn2+ and Al3+ can both significantly enhance the fluorescence of the Schiff bases, interestingly, only Al3+ ion is able to turn on the CPL emission. This study on the one hand provides a simple method to the fabrication of CPL emitting supramolecular materials, and on the other hand offers a novel way to the sensing of aluminum ion with supramolecular materials.
关键词： Self-assembly,Schiff bases,Circularly polarized luminescence,Al3+,Supramolecular gels
更新于2025-09-23 15:21:21
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Influence of molecular fluorophores on the research field of chemically synthesized carbon dots
摘要： Carbon dots (CDs) – small crystalline or amorphous carbon-based nanoparticles – have attracted much attention as promising fluorescent materials for a wide range of applications. One of their widely accepted advantages is the simplicity of the formation of highly luminescent CDs from a wide variety of organic precursors. At the same time, several recent studies on these chemically synthesized CDs raised questions about the nature of the resulting products. Their strong fluorescence can arise due to the presence of molecular organic fluorophores, not necessary CDs, as was assumed in the earlier publications. In this review, we consider fundamental characteristics of CDs and discuss several issues that currently prevent a better understanding of their structure-property correlation. Analysis of recent related studies identifying the presence of organic fluorophores in CDs with an emphasis on the optical properties of the synthesis products shows that their emission characteristics may be a complex interplay of stand-alone molecular fluorophores and their aggregates, possibly embedded in an amorphous carbon/polymer network. The review concludes with an outlook towards the challenges in the field of the bottom-up synthesized CDs, and their proper identification within the variety of the organic side-products eventually formed during the synthesis.
关键词： Luminescence,Chemical synthesis,Carbon dots,Optical properties,Molecular fluorophores,Aggregation
更新于2025-09-23 15:21:21
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Luminescent silicon oxycarbide thin films obtained with monomethyl-silane by hot-wire chemical vapor deposition
摘要： The use of silicon-based materials can represent enormous advantages to develop optoelectronic devices. The preparation of luminescent silicon oxycarbide thin films deposited by the hot-wire CVD technique using monomethyl-silane as single and safer source of silicon and carbon atoms is here reported. The conditions for deposition that allow obtaining an intense emission on these thin films in a wide region of the visible spectrum at low deposition temperature without further thermal annealing are presented. When the oxygen flow rate was increased, a transition from silicon carbide to silicon oxycarbide was observed. X-ray diffraction confirms the presence of nanocrystalline material. Measurements showed that the origin of the photoluminescence may be to a combination of quantum confinement effects and defects in the silicon oxycarbide matrix, mainly those related to oxygen deficient centers and hydrogen and carbon-related defects. The obtained results are promising for the development of light emitting devices compatible with current technologies at low cost.
关键词： white luminescence,Silicon oxycarbide,HW-CVD,monomethyl-silane
更新于2025-09-23 15:21:21