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- 2018
- Signal-to-Noise Ratio (SNR)
- Infinite Gain Multiple Feedback (IGMF)
- Visible Light Communications (VLC)
- LED
- Trans-Impedance Amplifier (TIA)
- Optoelectronic Information Science and Engineering
- University of Northumbria
- University of Huddersfield
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Salt Effect in Ion-Pair Dynamics after Bimolecular Photoinduced Electron Transfer in a Room-Temperature Ionic Liquid
摘要： Bimolecular photoinduced electron transfer between perylene and two quenchers was investigated in an imidazolium room-temperature ionic liquid (RTIL) and in a dipolar solvent mixture of the same viscosity using transient absorption on the subpicosecond to submicrosecond timescales. Whereas charge separation dynamics were similar in both solvents, significant differences were observed in the temporal evolution of the ensuing radical ions: although small, the free ion yield is significantly larger in the RTIL, and recombination of the ion pair to the triplet state of perylene is more efficient in the dipolar solvent. The temporal evolution of reactant, ion and triplet state populations could be well reproduced using Unified Encounter Theory. This analysis reveals that the observed differences can be explained by the strong screening of the Coulomb potential in the ion pair by the ionic solvent. In essence, RTILs favor free ions compared to highly dipolar solvents of the same viscosity.
关键词： unified encounter theory,free ions,spin conversion,charge recombination,transient absorption,charge separation
更新于2025-09-23 15:21:21
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Soluble and insoluble polymer-inorganic systems based on poly(methyl methacrylate), modified with ZrO2-LnO1.5 (Ln = Eu, Tb) nanoparticles: Comparison of their photoluminescence
摘要： The study of the lanthanide ion luminescence as a function of their environment in polymer-inorganic composites is necessary for better understanding of the electron energy transfer processes in a condensed state. From a practical point of view, these materials are promising for optics and medicine. The nanoparticles of ZrO2-LnO1.5 (Ln = Eu, Tb) solid solutions were synthesized by hydrothermal method. The surface functionalization of the obtained nanoparticles by vinyl groups was carried out using 3-(trimethoxysilyl)propyl methacrylate. Soluble and cross-linked composites based on poly(methyl methacrylate) with ZrO2-LnO1.5 nanoparticles were synthesized using radical polymerization in solution and bulk. Molecular weight, thermal stability, and microhardness of the obtained composite materials were determined. The influence of both the polymerization conditions and the forming composite structure on the lanthanide ion photoluminescence in ZrO2 nanoparticles covalently bonded to the polymer matrix was studied. The combination of ZrO2-EuO1.5 and ZrO2-TbO1.5 nanoparticles in the poly(methyl methacrylate) resulted in the production of composites with photoluminescence spectra overlapping the red and green regions of the visible range. It was shown that the structure of the composite affects the absorbing capacity of luminescent centers and allows shifting the excitation spectrum in the longer wavelength region.
关键词： hydrothermal synthesis,poly(methyl methacrylate),rare-earth ions,solid solutions,zirconia,hybrid nanomaterials
更新于2025-09-23 15:21:21
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Dual-Emitting Quantum Dot Complex Nanoprobe for Ratiometric and Visual Detection of Hg2+ and Cu2+ ions
摘要： Herein we report the use of a dual emitting quantum dot complex (QDC; composed of blue emitting metal-methylsalicylaldimine complex being on the surface of orange emitting Mn2+-doped ZnS quantum dot) for ratiometric and visual detection of Hg2+ and Cu2+ ions - following the alterations in luminescence color, intensity ratio, chromaticity and hue of the QDC.
关键词： Hg2+ ions,Cu2+ ions,ratiometric detection,quantum dot complex,visual detection
更新于2025-09-23 15:21:01
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Photoluminescence of (Zn, Pb, Mn)S Quantum Dots in Polyacrylate Matrix
摘要： Solutions of (Zn, Pb, Mn)S quantum dots with different molar ratios between cations are produced by colloidal synthesis in a methyl methacrylate (MMA) medium. By the thermal polymerization of MMA in a block, the colloidal solutions are converted into the vitreous state. The optical transparency of the poly(MMA)/(Zn, Pb, Mn)S composites at the wavelengths >500 nm reaches 90% at a thickness of the absorbing layer up to 5 mm. The photoluminescence of the composites in the spectral range 400–480 nm is defined by the recombination of electrons at the levels of defects of the ZnS crystal structure, and photoluminescence in the range 520–620 nm by the 4T1 → 6A1 electronic transition in Mn2+ ions. Photoluminescence excitation is a result of interband transitions in ZnS, with energy transfer from the conduction band of ZnS to the levels of Mn2+ ions. The luminescence spectrum depends on the molar ratio between Mn2+ and Pb2+ ions, the order of introduction of substances into the reaction mixture, and the excitation-radiation wavelength.
关键词： acrylate composites,lead ions,doping,luminescence,manganese ions,zinc sulfide,quantum dots
更新于2025-09-23 15:21:01
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Variation of the oscillator strengths for the <i>α</i> emission lines of the one- and two-electrons ions in dense plasma
摘要： We present the results of a detailed theoretical study on the variation of the oscillator strengths for the 1s ! 2p transition of the H-like ions and the 1s2 1S ! 1s2p 1P transition of the He-like ions (or, inversely, the Lyman-a and Hea emission lines, respectively) subject to external plasma which meet the spatial and temporal criteria of the Debye-H€uckel (DH) approximation. Our study shows that the resulting oscillator strength decreases for the Hea line for He-like ions, similar to the Lyman-a emission lines for all H-like ions, as the effect of the external plasma increases with the decreasing Debye length D in terms of a reduced Debye length kD ? Zeff D. A nearly universal feature is demonstrated for a scaled oscillator strength as a function of the reduced Debye length kD ? (Z (cid:2) 1)D for different He-like ions that meet the same criteria for the DH model. The percentage changes of the oscillator strengths from their plasma-free values are substantially greater than those for the corresponding change for the redshifts of the Lyman-a and Hea emission lines subject to outside dense plasma. Should these general features be demonstrated experimentally, the theoretical procedure presented in this study could easily be applied to extrapolate from a single calculation for one He-like ion to other He-like ions, which could offer an alternative to complement other diagnostic efforts of the dense plasma.
关键词： He-like ions,oscillator strengths,dense plasma,Debye-H€uckel approximation,H-like ions
更新于2025-09-23 15:21:01
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Oriented Crystallization of Mixeda??Cation Tin Halides for Highly Efficient and Stable Leada??Free Perovskite Solar Cells
摘要： As the most promising lead-free branch, tin halide perovskites suffer from the severe oxidation from Sn2+ to Sn4+, which results in the unsatisfactory conversion efficiency far from what they deserve. In this work, by facile incorporation of methylammonium bromide in composition engineering, formamidinium and methylammonium mixed cations tin halide perovskite films with ultra-highly oriented crystallization are synthesized with the preferential facet of (001), and that oxidation is suppressed with obviously declined trap density. MA+ ions are responsible for that impressive orientation while Br- ions account for their bandgap modulation. Depending on high quality of the optimal MA0.25FA0.75SnI2.75Br0.25 perovskite films, their device conversion efficiency surges to 9.31% in contrast to 5.02% of the control formamidinium tin triiodide perovskite (FASnI3) device, along with almost eliminated hysteresis. That also results in the outstanding device stability, maintaining above 80% of the initial efficiency after 300 h of light soaking while the control FASnI3 device fails within 120 h. This paper definitely paves a facile and effective way to develop high-efficiency tin halide perovskites solar cells, optoelectronic devices, and beyond.
关键词： trap density,methylammonium bromide,oriented crystallization,tin halide perovskites,divalent tin ions
更新于2025-09-23 15:21:01
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Synergic effect of pore size engineering and an applied electric field on the controlled permeation of alkali metal atoms and ions across pristine and defect-containing h-BN sheets
摘要： The permeation and selectivity of alkali metal atoms and ions through normal and defected hexagonal boron nitride was studied in the presence and absence of water and an electric field. The defects include one (VB & VN), two (VBN) and three atom (VN2B) vacancies. The morphology and size of the pore (defect) in the h-BN sheet significantly affect the energy barriers. These results indicate that an h-BN sheet with appropriate pore size possesses good Li/Li+ selectivity. The permeation of lithium atoms through VN2B-h-BN is almost a barrierless process (1.75 kcal mol?1). Moreover, the VBN h-BN nanosheet selectively allows the passage of Li atoms at room temperature with the highest selectivity ratio of 1.58 × 1013. The presence of water molecules increases the barrier of alkali metal atom permeation. The effect of water molecules is more pronounced for alkali metal atom permeation through a defected h-BN nanosheet as compared to alkali metal ions. An applied electric field perpendicular to the h-BN sheet further decreases the permeation barriers. For example, the energy barrier is reduced to 31 kcal mol?1 (from 34 kcal mol?1) in the presence of an electric field for the permeation of lithium through H2O–VB h-BN–H2O. These studies can be extended to investigate the separation capability of porous hexagonal boron nitride nanosheets for other metal atoms and ions.
关键词： electric field,permeation,water molecules,alkali metal atoms,hexagonal boron nitride,defects,ions,selectivity
更新于2025-09-23 15:21:01
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Crown-Porphyrin Ligand for Optical Sensors Development
摘要： A novel porphyrin ligand, Zn(II)TPP-BPI-crown (ZnPC), functionalized with two dibenzo-crown-ether moieties was synthesized and tested as cation-sensitive ionophore. Fluorescence studies on ligand sensitivity towards a number of different metal cations (Na+, K+, Li+, Ca2+, Mg2+, Co2+, Cd2+, Pb2+, Cu2+, Zn2+ and NH4+) were carried out first in solution and then inside polymeric membrane optodes. Emission light signal was sufficiently brilliant to be captured by a low-cost computer webcam, while a commercial blue-light LED served as monochromic excitation light source. The influence on the ZnPC optode response of the lipophilic sites functionalization was investigated. The visibly (naked eye) observed color change of sensing material from green to red demonstrated the suitability of the ZnPC-based optodes to perform fast monitoring of Cu(II) ions in the concentration range between 6.6 × 10?7 and 2.4 × 10?2 mol/L with a low detection limit (estimated by s/n = 3 method) of 0.3 mg/L, which is lower than WHO guideline value of 2 mg/L.
关键词： chemical optical sensor,novel Zn(II)-porphyrin ligand functionalized with two dibenzo-crown-ether moieties,naked eye detection of Cu(II) ions
更新于2025-09-23 15:21:01
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Alkali Metal Ions: A Secret Ingredient for Metal Nanocluster-Sensitized Solar Cells
摘要： The presence of alkali metal ions (AMIs) during the adsorption of thiolated Au nanoclusters (NCs) onto TiO2 plays a critical role in achieving high power conversion efficiency and suppressing anomalous current?voltage hysteresis in metal nanocluster-sensitized solar cells. This hidden role of the AMIs is intimately related to the adsorption strength between the NCs and TiO2, indicating the importance of seeking a comprehensive understanding of NC?TiO2 interfaces and devising interfacial engineering techniques to support the next advance in light energy conversion applications of NCs.
关键词： alkali metal ions,metal nanoclusters,current?voltage hysteresis,power conversion efficiency,solar cells
更新于2025-09-23 15:21:01
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Measuring the difference in nuclear charge radius of Xe isotopes by EUV spectroscopy of highly charged Na-like ions
摘要： The difference in the mean-square nuclear charge radius of xenon isotopes was measured utilizing a method based on extreme ultraviolet spectroscopy of highly charged Na-like ions. The isotope shift of the Na-like D1 (3s 2S1/2 ? 3p 2P 1/2) transition between the 124Xe and 136Xe isotopes was experimentally determined using the electron-beam ion-trap facility at the National Institute of Standards and Technology. The mass-shift and the ?eld-shift coef?cients were calculated with enhanced precision by the relativistic many-body perturbation theory and multicon?guration Dirac-Hartree-Fock method. The mean-square nuclear charge radius difference was found to be δ(cid:2)r 2(cid:3)136,124 = 0.269(42) fm2. Our result has smaller uncertainty than previous experimental results and agrees with the literature values.
关键词： Na-like ions,EUV spectroscopy,xenon isotopes,isotope shift,nuclear charge radius
更新于2025-09-23 15:21:01