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Evaluation of Photoelectric Characteristics of a Volume DBD Excited by Power Density Modulation
摘要： Photoelectric characteristics are an important reference for high-voltage discharges and are closely related to the excited mode of the high-voltage source. In this paper, we built a large-scale volume dielectric barrier discharge (DBD) system, which is composed of multilayer parallel-plate DBD electrodes and is excited by a high-voltage source in the power density modulation (PDM) mode. Subsequently, we analyzed the applied energy equation and evaluated the DBD systems photoelectric characteristics. The results show that the energy values of different applied voltage cycles during a PDM period exhibit significant differences. However, the average energy in a PDM period is approximately constant. Moreover, the equivalent capacitance of the DBD cell is a function of both the applied voltage and energy density. For the DBD cell, with the increase in both the applied voltage and energy loaded on the DBD cell, the total equivalent capacitance (C) is approximately constant, the dielectric capacitance (Cd) increases exponentially and decreases linearly, while the discharge gap capacitance (Cg) decreases and increases in the same cases. In addition, the relative intensities of the discharge emission increase and the energy efficiency ratios of the relative photoquantum yield of active species decline with the increase in both the applied voltage and energy density loaded on the DBD cell. The experimental results have been analyzed by evaluating the influence of the electrical parameters, and the underlying physical principles have been discussed. This paper clearly demonstrates that the photoelectric characteristics of the DBD reactor are significantly influenced by both the applied voltage and energy density, thus providing helpful insights into the energy evaluation and application of high-voltage discharges.
关键词： Applied energy,power density modulation (PDM),photoelectric characteristics,relative photo-quantum yield,energy efficiency ratio (EER)
更新于2025-09-09 09:28:46
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Luminescence and energy transfer studies of Ce3+/Dy3+ doped fluorophosphate glasses
摘要： The fluorophosphate (PKABfNf:P2O5+K2O+Al2O3+BaF2+NaF2) glasses doped with single and co-doped (Ce and/or Dy) were prepared by conventional melt quenching technique and characterized their luminescence properties. The emission spectra of co-doped glass (PKABfNfCeDy) showed a broad blue band of Ce3+ ions combined with the sharp peaks of Dy3+ ions. Judd-Ofelt (JO) intensity parameters have been obtained from the optical absorption spectra of 1.0 mol % of Dy3+ (PKABfNfDy1.0) glass. JO theory has been used to find the radiative properties of PKABfNfDy1.0 glass by using Futchbauer-Ladenbergh formula. The (Ce3+/Dy3+) co-doped glass exhibit radiative energy transfer (ET) from Ce3+ to Dy3+ upon UV excitation and then intensity is increased with increase in Dy3+ ion concentration. The ET mechanism from Ce3+ to Dy3+ ion has been analyzed. The theoretical ET efficiency and quantum yield values were calculated from the emission spectrum of the Ce3+ and (Ce3+/Dy3+) co-doped glasses. These results suggest that the co-doped PKABfNfCeDy glasses are promising candidate for commercial white light applications.
关键词： W-LEDs,Dysprosium,Fluorophosphate glasses,Energy transfer,Judd-Ofelt analysis,Quantum yield,Cerium
更新于2025-09-09 09:28:46
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Phosphorus and chlorine co-doped carbon dots with strong photoluminescence as a fluorescent probe for ferric ions
摘要： Usually, carbon dots (CDs) display a relatively weak fluorescence quantum yield (QY). In order to obtain brighter CDs, phosphorus and chlorine co-doped CDs (P,Cl-CDs) were prepared via hydrothermal treatment of maltose in the presence of phosphoric and hydrochloric acids. The new CDs are highly monodispersed in water solution, have high fractions of P (14.4 atomic%) and Cl (8.9 atomic%), and exhibited yellow fluorescence with a QY of 15%. This is higher than that of monoatomic doped CDs (8.7 and 9.3% for P-CDs and Cl-CDs, respectively). The P,Cl-CDs are highly photostable, and fluorescence is strongly (statically) quenched by Fe(III). Fluorescence decreases with increasing concentration of Fe(III) in the range from 0.1–8.0 μmol?L-1, with a 60 nmol?L-1 detection limit. The doped CDs are shown to be a viable nanoprobe for the fluorometric determination of Fe(III) in spiked serum and water samples.
关键词： Quantum yield,Phosphorus,Fluorescent probe,Chlorine,Co-doped carbon dots
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
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Molecular motors with high quantum efficiency and visible-light responsiveness: Meeting two challenges in one design
摘要： The development of light-driven rotary molecular motors is guided by a number of key goals regarding performance and applicability. While a variety of approaches to achieve high quantum yields for small UV-driven motors have been discovered, such as incorporating a protonated or alkylated nitrogen Schiff base, less progress has been made toward the goal to power molecular motors with nondestructive visible light, which will facilitate their future usage in radiation-sensitive environments. Here, we present non-adiabatic molecular dynamics simulations based on multiconfigurational quantum chemistry to demonstrate that Schiff-base motors can maintain high quantum yields also when their conjugated systems are sufficiently large for them to rather be driven by visible light. In particular, we show that a visible-light responsive Schiff-base motor featuring dihydropyridinium and cyclopentenylidene motifs achieves quantum yields of almost 70% for each of the two photoisomerizations that underlie its rotary motion.
关键词： Molecular devices,Quantum yield,Rotary motion,Molecular dynamics,Visible light
更新于2025-09-04 15:30:14
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Fluorescence quantum yield of CDOM in coastal zones of the Arctic seas
摘要： Along with traditional optical indices, calculated from absorption and ?uorescence spectra to describe chromophoric dissolved organic matter (CDOM) naturally occurring in water, the ?uorescence quantum yield (FQY) becomes signi?cant. Knowledge of CDOM optical properties is important for satellite remote sensing as well as for lidar ground-true measurements. The FQY as a function of excitation wavelength within 240–500 nm range for a variety of the Arctic shelf waters was determined for the ?rst time in order to identify the characteristic chromophores peculiar to di?erent regions of the Arctic basin a?ected by freshwater runo?. The surface water samples were collected during several cruises in 2015–2017 in the following sites: the mouth areas of the Khatanga and Lena Rivers (the Laptev Sea), the delta area of the Northern Dvina River (the White Sea), desalinated waters of the Kara Sea (in?uenced by freshwater of the Ob and Yenisei Rivers) and the East Siberian Sea (in?uenced by freshwaters of the Indigirka and Kolyma Rivers), as well the shelf areas of those seas not a?ected by terrigenous runo?. To characterize DOM, conventional optical indices SR, HIX, and BIX were calculated. In most cases, important humic character of DOM was established, while the contribution of autochthonous organic matter varied from low to intermediate level. For the samples with terrestrial impact, the FQY decreased from excitation at 240 nm to 270–280 nm and then increased, demonstrating two peaks at 340 and 380 nm, with constant decrease towards longer excitation wavelengths; at λex = 380 nm FQY varied from 1.4% to 3.1%. In some cases, additional maximum at 270 nm of FQY-excitation dependency was observed as an indicator of autochthonous nature of biological material. Minimal FQY was measured for the White Sea surface waters, the maximal for the Laptev and East Siberian seas.
关键词： optical properties,fluorescence quantum yield,CDOM,Arctic seas,remote sensing
更新于2025-09-04 15:30:14
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Deep blue emitting Cu( <scp>i</scp> ) tripod complexes. Design of high quantum yield materials showing TADF-assisted phosphorescence
摘要： In a previous investigation, it was shown that [Cu(tpym)(PPh3)]PF6 1 with tpym = tris(2-pyridyl)methane represents a deep blue emitter (λmax = 466 nm) though with a low emission quantum yield ΦPL if doped in a polymer (7%) or dissolved in a ?uid solvent (?1%). In this study, we present new tripod compounds with [Cu(tpym)(P(o-tol)3)]PF6 2 and [Cu(tpym)(P(o-butyl-ph)3)]PF6 3 with sterically demanding ligands: P(o-tol)3 = tris(ortho-tolyl)phosphine and P(o-butyl-ph)3 = tris(ortho-n-butylphenyl)phosphine. These compounds show high emission quantum yields even in a ?uid solution (dichloromethane) reaching a benchmark value for 3 of ΦPL = 76%. This becomes possible due to the speci?c design of rigidifying the complexes. Importantly, the deep blue emission color is maintained or even further blue shifted to λmax = 452 nm (compound 3 powder). Compound 2 is characterized photophysically in detail. In particular, it is shown that the lowest excited triplet state T1 experiences very e?cient spin–orbit coupling (SOC). Accordingly, the phosphorescence decay rate is as large as 5 × 104 s?1 (20 μs) belonging to the fastest T1 → S0 transition values (shortest decay times) reported so far. Investigations down to T = 1.5 K reveal a large total zero-?eld splitting (ZFS) of 7 cm?1 (0.9 meV). Although thermally activated delayed ?uorescence (TADF) grows in at T ≥ 160 K, the phosphorescence of 2 still dominates (60%) over TADF (40%) at ambient temperature. Thus, the compound represents a singlet harvesting-plus-triplet harvesting material, if applied in an OLED.
关键词： TADF-assisted phosphorescence,Deep blue emitting,Cu(I) tripod complexes,high quantum yield
更新于2025-09-04 15:30:14