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Electronic Structure of Chlorophyll a Solution Investigated by Photoelectron Yield Spectroscopy
摘要： Various bio-related processes are driven by electron transfer reactions. Therefore the electronic structures of bio-molecules in their living environment are keys of their functionalities. One significant example photosynthesis which has attracted much attention due to urgent necessity of clean energy source. In this study, we carried out photoelectron yield spectroscopy (PYS) measurements to demonstrate the electronic structures of oligomerizedChl-a molecules, which is known as an essential reaction center of the photosystem in general green plants, under the atmospheric environment. The ionization energies of the Chl-a aggregates are successfully derived.
关键词： Photoelectron Yield Spectroscopy,Polarization energy,Light harvesting antenna,Photosynthesis,Photosystem,Electronic structure,Ionization energy,Reaction center,Chlorophyll a
更新于2025-09-23 15:23:52
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Theoretical and experimental insights into the effects of oxygen-containing species within CNTs towards triiodide reduction
摘要： Heteroatom-doped micro/nano-structured carbon materials feature unique superiorities for replacement of noble metal Pt counter electrode (CE) in dye-sensitized solar cells. Nevertheless, the effects of oxygen-containing species on/within carbon matrix on its electrocatalytic activity are seldomly considered and concerned, which will be hindered by a trade off between oxygen defects and conductivity. Herein, we present activated carbon nanotubes (P-CNTs) with abundant active edge sites and oxygen species for simultaneous achieving the activation of sidewalls and open ends. Also, the positive effects of oxygen species are decoupled by experimental data together with theoretical analysis. When capitalizing on the P-CNTs as the CE of DSSCs, the device delivers a high power conversion efficiency of 8.35% and an outstanding electrochemical stability, outperforming that of Pt reference (8.04%). The density functional theory calculation reveals that compared with the carboxylic groups, the hydroxyl groups and carbonyl groups on the surface of CNTs can greatly reduce the ionization energy of reaction, accelerate the electron transfer from external circuit to triiodide, thus being responsible for an enhanced electrocatalytic performance. This work demonstrates that a certain amount of oxygen atoms within carbon materials is also indispensable for the improvement in the reactivity of the triiodide.
关键词： Counter electrodes,Triiodide reduction,Defective carbon nanotubes,Ionization energy,Electrochemical stability,Oxygen species
更新于2025-09-23 15:23:52
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Determination of the first ionization energy of polonium by resonance ionization spectroscopy – Part II: Measurement of odd-parity Rydberg states at CERN–ISOLDE
摘要： Polonium (Po) is one of the rarest elements in Earth's crust. None of its isotopes are stable and sufficient amounts for systematic experimental studies of its most fundamental properties are only available by artificial production. At the radioactive ion beam facility ISOLDE at CERN, 208Po was produced by proton-induced spallation of uranium. Using the technique of in-source Resonance Ionization Spectroscopy the ionization threshold was probed with a tunable dye laser. A spectrum of 110 previously undocumented odd-parity Rydberg states was observed. Applying the Rydberg formalism to the data enabled the determination of the first ionization energy of polonium as 67896.310(14)(30) cm?1 or 8.4180700(18)(37) eV. This is a precision improvement of more than 600 over the existing literature value. A comparison with the homologous elements sulfur, selenium and tellurium enabled the assignment of the electron configuration of the resonances found in the spectrum.
关键词： Rydberg series,Polonium,Resonance ionization spectroscopy,Ionization potential,Ionization energy
更新于2025-09-19 17:15:36
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Acceptor Gradient Polymer Donors for Non-Fullerene Organic Solar Cells
摘要： In organic solar cells, maximizing the open-circuit voltage (VOC) via minimization of the ionization energy or electron a?nity o?sets of the blended donor and acceptor often comes at the expense of achieving a considerable amount of short-circuit current (JSC). To explore a hypothesis for the design of materials that may circumvent this tradeo?, eight structurally similar polymers were synthesized consisting of a ?uorinated/non-?uorinated benzothiadiazole (BTDF/BTD) strong acceptor moiety, a thiophene ester (TE) weak acceptor, and various donor units composed of bithiophene (T2), biEDOT, and benzodithiophene (BDT) to form six acceptor gradient and two nongradient polymers. The acceptor gradient motif was designed and theorized to induce more facile exciton dissociation in low driving force solar cells by creating a further separated intramolecular charge-transfer state between the strong BTD acceptor and various donor units through a bridging TE component. Solar cells were fabricated using the eight polymers blended with phenyl-C71-butyric-acid methyl ester (PC71BM) to reveal two top performing isomeric polymers, T2-BTDF-(TE2) and TE2-BTDF-(T2), which were further tested with several non-fullerene acceptors (NFAs): EH-IDTBR, ITIC, and ITIC-4F. In order to fabricate optimally performing solar cells, a 0.2 eV ionization energy o?set was found to be essential or the short-circuit current of the NFA cells diminished dramatically. Ultimately, optimized NFA solar cells were fabricated using ITIC-4F paired with each of the top performing polymers to produce an average PCE of 7.3% for TE2-BTDF-(T2) (nongradient) and 3.6% for T2-BTDF-(TE2) (gradient). The acceptor gradient e?ect was not shown to reduce the amount of charge recombination in NFA solar cells mainly due to the inability to fabricate solar cells, with minimal ionization energy or electron a?nity o?sets along with morphological complications. This work stresses the importance of acquiring accurate ionization energies and electron a?nities when characterizing solar cell energetics, as di?erences as small as 0.1 eV in the o?sets can make a signi?cant impact on overall charge collection.
关键词： acceptor gradient polymers,open-circuit voltage,electron affinity offset,charge recombination,organic solar cells,non-fullerene acceptors,ionization energy offset,short-circuit current
更新于2025-09-11 14:15:04
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Chemo-treated 4T1 breast cancer cells radiation response measured by single and multiple cell ionization using infrared laser trap
摘要： We present a study that uses a laser trapping technique for measurement of radiation sensitivity of untreated and chemo-treated cancer cells. We used a human mammary tumor cell line (4T1) treated by an antitumor compound, 2-Dodecyl-6-methoxycyclohexa-2, 5-diene-1,4-dione (DMDD), which was extracted from the root of Averrhoa carambola L. The untreated control group, and both 2-hour and 24-hour treated groups of 4T1 cells were used in this study. The absorbed threshold ionization energy (TIE) and the threshold radiation dose (TRD) were determined using a high-power infrared laser (at 1064 nm) trap by single and multiple cells trapping and ionization. The results were analyzed using descriptive and t-statistics. The relation of the TIE and TRD to the mass of the individual cells were also analyzed for different hours of treatment in comparison with the control group. Both TIE and TRD decrease with increasing treatment periods. However, the TRD decreases with mass regardless of the treatment. Analyses of the TRD for single vs multiple cells ionizations within each group have also consistently showed this same behavior regardless of the treatment. The underlying factors for these observed relations are explained in terms of radiation, hyperthermia, and chemo effects.
关键词： threshold ionization energy,chemo-treated cancer cells,threshold radiation dose,4T1 breast cancer cells,laser trapping technique,DMDD,radiation sensitivity
更新于2025-09-11 14:15:04
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The effect of chalcogen and metal on the electronic properties and stability of metal–chalcogenides clusters, TM6Xn(PH3)6 (TM = Mo, Cr, Re, Co, Ni; X = Se, Te; n = 8,5)
摘要： We have performed a comparative study of the electronic structure, stability, and magnetic properties of a series of metal–chalcogen clusters stabilized by PH3 ligands. Clusters studied include TM6X8(PH3)6, TM = Cr, Mo, Re, Co, X = Se, Te, and Ni6X(PH3)6, X = Se, and Te. We find that the phosphine ligands act as charge donors, transferring charge to the metal sites, creating an electrostatic effect that lowers the ionization energy. The electronic structure of the cluster also has a significant effect on its charge donor properties, as the Re cluster has a closed electronic shell with a charge state of +2, making it an alkaline earth superatom. The chromium clusters are found to have a series of close lying magnetic isomers. Selenium is a better charge acceptor than tellurium and this causes the telluride clusters to have lower ionization potentials, while the enhanced charge transfer to selenium increases the binding energy of the phosphine ligand.
关键词： metal–chalcogen clusters,PH3 ligands,ionization energy,superatom,stability,charge transfer,magnetic properties,electronic structure
更新于2025-09-10 09:29:36