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Synthesis and Photophysical Properties of Rhenium(I)-Alkynyl Molecular Rectangles
摘要： A series of highly conjugated, rigid Re(I)-based molecular rectangles {[fac-Re(CO)3Br]2(μ-bpy) (μ-L)}2 (1, L = 1,4-bis(42 -pyridylethynyl)benzene, bpeb; 2, L = 1,4-bis(42 -pyridylethynyl)naphthalene, bpen; 3, L = 1,4-bis(42 -pyridylethynyl)anthracene, bpea; and bpy = 4,42 -bipyridine) containing two different types of pyridyl ligands were synthesized, characterized and their photophysical properties studied. Successful emission color tuning was achieved by incorporating rigid alkynyl ligands into the Re(I) rectangles. Complexes 1-3 exhibited an intense absorption bands with a high e value at > 340 nm in THF solution, which is attributed to mixed two metal-to-ligand charge transfer dp(Re) → p*(bpy) and dp(Re) → p*(alkynyl)) along with ligand-to-ligand charge transfer (1LLCT)/ and intraligand charge transfer (1ILCT) transitions. Compound 1 featured a broad and structureless emission band at 619 nm, which was attributed to the emission of 3MLCT dp(Re) → p*(bpy) and/or [dp(Re) → p*(alkynyl)] characteristics with an additional luminescence at 431 nm. Whereas complexes 2 and 3 displayed an intraligand (IL) emission at 445 and 489(sh), 521 nm. These compounds represent a new class of visible light-harvesting materials that exhibit greatly enhanced emission decay lifetimes as a result of intervening ligand triplet states (3LLCT/3ILCT) present on the alkynyl appended naphthalene and anthracene chromophores, as evidenced by transient absorption spectra.
关键词： rhenium,quenching,Rectangles,alkynyl ligands,luminescence
更新于2025-09-09 09:28:46
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Evolution of ferroelectric and piezoelectric response by heat treatment in pseudocubic BiFeO3–BaTiO3 ceramics
摘要： Heat treatment of ceramics is an important process to tailor the fine electromechanical properties. To explore the criteria for optimized heat treatment in a perovskite structure of (1–x)Bi1.05FeO3–xBaTiO3 (BF–BT100x) system, the structural phase relation, ferroelectric and piezoelectric response of BF–BT36 and BF–BT40 ceramics prepared by furnace cooling (FC) and quenching process were investigated. The X-ray diffraction examination showed single pseudocubic perovskite structure for all the ceramics. The homogenous microstructure was obtained for all ceramics with relatively large grain size in the furnace cooled samples. Well saturated ferroelectric hysteresis loops and enhanced piezoelectric constant (d33 = 97 pC/N) were achieved by quenching process. Dielectric curve of BF–BT36 showed large dielectric constant at its Curie temperature, however, BF–BT40 showed diffused relaxor-like dielectric anomalies. Quenched BF–BT36 samples showed typical butterfly like field induced strain curves, however negative strain decreased in BF–BT40 ceramics. From these investigated study, it is observed that BF–BT ceramics are very sensitive to the heat treatment process (furnace cooling and quenching) on the dielectric, electromechanical properties.
关键词： Quenching process,Electric field induced strain,Dielectric relaxation,BF–BT
更新于2025-09-09 09:28:46
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Microalgae biochar-derived carbon dots and their application in heavy metal sensing in aqueous systems
摘要： This research seeks a coupled solution for managing the large amounts of biochar produced by microalgae biofuel production, and the necessity for novel, economic and accurate heavy metal sensing methods. Therefore, this study evaluated the transformation of microalgae biochar (MAB) into carbon dots (Cdots) and their subsequent application as heavy metal ion sensors in aqueous systems. The experimental phase included the transformation of MAB into microalgae biochar-derived carbon dots (MAB–Cdots), MAB–Cdot characterisation and the evaluation of the MAB–Cdots as transducers for the detection of four heavy metal ions (Pb2+, Cu2+, Cd2+, and Ni2+). MAB–Cdot fluorescence was stable over a wide range of pH and resistant to photo-bleaching, making them suitable as fluorescence probes. The MAB–Cdot fluorescence was quenched by all of the metal ions and displayed different quenching levels. Depending upon the ions involved, MAB–Cdots were used to detect the presence of heavy metal ions from concentrations of 0.012 μM up to 2 mM by measuring the reduction in fluorescence intensity. Neutral and slightly alkaline pHs were optimal for Cu2+ Ni2+ and Pb2+ heavy metal quenching. To quantify the concentration of the heavy metal ions, linear and logarithmic functions were used to model the MAB–Cdot fluorescence quenching. The sensing mechanism was determined to be reversible and purely collisional with some fluorophores less accessible than the others. This work demonstrated the ability to produce Cdots from microalgae biochar, examined their application as a transducer for detecting heavy metal ions in aqueous systems and paves the way for novel sensing systems using MAB-Cdots.
关键词： Heavy metal ion,Carbon dots,Renewable nanomaterials,Quenching,Biochar,Microalgae,Fluorescence sensors
更新于2025-09-09 09:28:46
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Determination of the activity of alkaline phosphatase based on?aggregation-induced quenching of the fluorescence of?copper nanoclusters
摘要： A rapid method is described for synthesis of copper nanoclusters (CuNCs) by utilizing L-histidine as the stabilizer and ascorbic acid (AA) as the reductant. The CuNCs display blue-green fluorescence with excitation/emission peaks at 390/485 nm. A sensitive fluorometric assay was worked out for determination of alkaline phosphatase (ALP) activity. If the ALP substrate p-nitrophenylphosphate (PNPP) is enzymatically hydrolyzed, it forms p-nitrophenol (PNP) which reduces the fluorescence of CuNCs because its absorption band at 410 nm overlaps the excitation peak of CuNCs at 390 nm. In addition, the amino groups and imidazole groups on the surface of CuNCs possibly form a complex with the phenol groups of PNP. This induces aggregation-induced quenching of the fluorescence of CuNCs. The fluorescent probe has a linear analytical range that extends from 0.5 mU·mL?1 to 40 mU·mL?1 and a detection limit of 45 μU·mL?1.
关键词： Alkaline phosphatase,Aggregation-induced quenching,Fluorometry,Inner filter effect,L-Histidine,Copper nanoclusters
更新于2025-09-04 15:30:14
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Dinuclear Eu(III) complexes with macrocyclic tetraphosphine tetraoxide ligand and their photoluminescence properties
摘要： Dinuclear Eu(III) complexes with macrocyclic tetraphosphine tetraoxide ligand (1, 5, 9, 13-Tetraphosphacyclohexadecane-1, 5, 9, 13-tetraphenyl-1, 5, 9, 13-tetraoxide) that keep the Eu(III) ions apart were synthesized and their photoluminescence properties were investigated. It was found that quantum yield of Eu(III) complex 2 in ethyl acetate was excellent (? =0.54) even at a large concentration (1×10?3 mol/l) and strong photoluminescence was obtained. Macrocyclic TPTO ligand has a function of a “separator” of Eu(III) ions that prevents concentration quenching in the Eu(III) complexes.
关键词： Photoluminescence intensity,Quantum yields,Concentration quenching,Macrocyclic tetraphosphine tetraoxide ligand,Europium complex
更新于2025-09-04 15:30:14
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Applicability of Dy-doped yttrium aluminum garnet (YAG:Dy) in phosphor thermometry at different oxygen concentrations
摘要： Phosphor thermometry is a method used to measure temperature based on the temperature-dependent phosphorescence of phosphors and elucidate heat transfer phenomena, such as high-temperature gas flow. Although various rare earth-doped thermographic phosphors are in use, the effect of oxygen concentration on their phosphorescence has not been sufficiently explored. We explore herein the applicability of Dy-doped yttrium aluminum garnet (YAG:Dy), a well-known rare earth-doped phosphor with temperature sensitivity above 1000 K, in phosphor thermometry at different oxygen concentrations. A third-harmonic Nd:YAG laser excited the sample. Phosphorescence was measured using a photomultiplier tube for lifetime detection. A spectrometer was used to detect the intensity ratio between two emission lines. The chamber was filled with a nitrogen–oxygen mixture with a controlled concentration. The phosphorescence intensity ratio depended on temperature over a wide temperature range and varied with the oxygen concentration, especially above 1000 K. The YAG:Dy lifetimes could be detected over the entire temperature range and remained constant up to 1000 K. In addition, the lifetimes decreased with the increasing oxygen concentration, especially above 1000 K, confirming the oxygen quenching effect. Consequently, YAG:Dy is confirmed to be sensitive to oxygen concentration for determining the intensity ratio and lifetime, especially above 1000 K.
关键词： Lifetime method,Intensity ratio method,Oxygen quenching,Phosphor thermometry
更新于2025-09-04 15:30:14
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Temperature-dependent photoluminescence processes of GaInP top cell irradiated with 11.5?MeV and 1.0?MeV electrons
摘要： The effects of 11.5 MeV electrons irradiation on the GaInP top cell of GaInP/GaAs/Ge triple-junction solar cells have been investigated by temperature-dependent photoluminescence (PL) measurements. The thermal quenching of PL intensity is observed in the temperature range of 10 K–270 K, attributing to the nonradiative recombination centers H2 (Ev + 0.55 eV) hole trap and H3 (Ev + 0.76 eV) hole trap. A slight negative thermal quenching (NTQ) of PL intensity exists at nearly 300 K and could be associated with the 0.18 eV intermediate states. The temperature-dependent photoluminescence process of GaInP top cell irradiated with 11.5 MeV electrons differs with that irradiated with 1.0 MeV electrons.
关键词： Photoluminescence,Electron irradiation,GaInP top cell,Negative thermal quenching
更新于2025-09-04 15:30:14
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Facile Synthesis of ZnO Nanorods/GO Composite and Its Optical Performance
摘要： The ZnO nanorods/GO composite was fabricated by facilely covering monolayer or few-layer graphene oxide (GO) film on the uniformly distributed ZnO nanorods, which was synthesized on Si substrate using a solution method. The as-synthesized products were characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM), as well as X-ray diffraction (XRD). The photoluminescence (PL) measurement indicates that the ZnO nanorods have a strong ultraviolet (UV) emission centered at ～391 nm attributed to the recombination of free excitons and a defect-related visible emission centered at ～530 nm. After the nanorods were covered with GO film, the PL intensity of the composite is quenched compared to that of the bare one at the same excitation condition. The fluorescence quenching mechanism suggests that there is an interfacial charge-transfer process between the excited ZnO and the GO film, and the composite fabricated in this experiment be possible to improve the photocatalysis performance.
关键词： Photocatalyst,Nanorod Array,Zinc Oxide,Graphene Oxide,Fluorescence Quenching
更新于2025-09-04 15:30:14
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The effect of the medium-range configuration on the atomistic fracture behaviour of vitreous silica
摘要： Using molecular dynamics simulations, we prepare vitreous silica by quenching molten silica to ambient temperature. Varying the quenching rate, we show that the latter barely influences the short-range order, whereas the medium-range configuration is significantly affected. We subject the prepared silica specimens to tension until fracture occurs and demonstrate the effect on the material behaviour. We evaluate the medium-range configuration in terms of the ring statistics of the glass network structure. Linking the ring statistics with the deformation and fracture behaviour of vitreous silica, we provide a topologically motivated explanation of the material behaviour.
关键词： quenching rate,fracture behaviour,vitreous silica,medium-range configuration,molecular dynamics
更新于2025-09-04 15:30:14
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Magnesium and nitrogen co-doped carbon dots as fluorescent probes for quenchometric determination of paraoxon using pralidoxime as a linker
摘要： Carbon dots codoped with magnesium and nitrogen (Mg,N-CDs) were synthesized via a one-step microwave-assisted method. They display blue fluorescence (with excitation/emission peaks at 380/460 nm and a 33% quantum yield) and possess high dispersity in aqueous solution. The fluorescence of the Mg,N-CDs is highly sensitive to paraoxon in the presence of pralidoxime (PAM) acting as the linking agent. Electron transfer from Mg,N-CDs to paraoxon in the presence of PAM leads to the fluorescence quenching of Mg,N-CDs. The concentration of paraoxon is determined by measuring the quenching efficiency of the Mg,N-CD-PAM assay system. Fluorescence drops with increasing concentrations of paraoxon in the 0.005–3.0 μM range, and the limit of detection is 0.87 nM. The method is highly selective for paraoxon even in the presence of possible interferences. Real sample study of tap and river water showed the assay to have good repeatability and accuracy.
关键词： Quantum yield,Oxime,Electron transfer,Fluorescence quenching,Organophosphorus pesticides
更新于2025-09-04 15:30:14