- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
[IEEE 2019 21st International Conference on Transparent Optical Networks (ICTON) - Angers, France (2019.7.9-2019.7.13)] 2019 21st International Conference on Transparent Optical Networks (ICTON) - Tuning the electron band structure of graphene for optoelectronics
摘要： Graphene, a conjugated sp2 carbon sheet arranged in a two-dimensional honeycomb-like lattice, shows the unique electronic structure in which conical shaped π-electron conduction and valence bands meet at the Dirac point. The properties of graphene are largely controlled by the Fermi level and the density of π-electron states, which can be used for tuning graphene to specific optoelectronic and electrochemical applications. We report a computational study of the electron states and electrochemical response towards I?/I3 redox mediator used in dye sensitized solar cells. We consider the influence of lattice deformations and magnetic field combined with covalently bonded moieties and charged ions on the heterogeneous electron transfer kinetics.
关键词： uniaxial strain,density of electron states,graphene,heterogeneous electron transfer,Landau levels
更新于2025-09-12 10:27:22
-
Guest Inclusion Modulates Concentration and Persistence of Photogenerated Radicals in Assembled Triphenylamine Macrocycles
摘要： Substituted triphenylamine (TPA) radical cations show great potential as oxidants and as spin containing units in polymer magnets. Their properties can be further tuned by supramolecular assembly. Here, we examine how the properties of photogenerated radical cations, intrinsic to TPA macrocycles, are altered upon their self-assembly into 1D columns. These macrocycles consist of two TPAs and two methylene ureas which drive the assembly into porous organic materials. Advantageously, upon activation the crystals can undergo guest exchange in a single-crystal-to-single-crystal transformation generating a series of isoskeletal host-guest complexes whose properties can be directly compared. Photoinduced electron transfer, initiated using 365 nm LED’s, affords radicals at room temperature as observed by EPR spectroscopy. The line shape of the EPR spectra and the quantity of radicals can be modulated by both polarity and heavy atom inclusion of the encapsulated guest. These photogenerated radicals are persistent, with half-lives between 1-7 days and display no degradation upon radical decay. Re-irradiation of the samples can restore the radical concentration back to a similar maximum concentration, a feature that is reproducible over several cycles. EPR simulations of a representative spectrum indicate two species, one containing two N hyperfine interactions and an additional broad signal with no resolvable hyperfine interaction. Intriguingly, TPA analogs without bromine substitution also exhibit similar quantities of photogenerated radicals, suggesting that supramolecular strategies can enable more flexibility in stable TPA radical structures. These studies will help guide the development of new photoactive materials.
关键词： photoinduced electron transfer,supramolecular assembly,radical cations,triphenylamine,EPR spectroscopy
更新于2025-09-12 10:27:22
-
A Method for Estimating the Functionality of TiO2/Quantum Dot Multilayer Hybrid Structures Based on the Generation of Reactive Oxygen Species
摘要： A new technique for estimating the efficiency of electron transfer from a CdSe/ZnS quantum dot (QD) to TiO2 nanoparticles based on the generation of reactive oxygen species by hybrid structures is presented. It was demonstrated that in the formed multilayer hybrid structures of TiO2/QD, photoinduced electron transfer is realized with an efficiency of 26%.
关键词： hybrid structures,photoinduced electron transfer,semiconductor quantum dots,titanium dioxide nanoparticles,reactive oxygen species
更新于2025-09-12 10:27:22
-
Design of new Imidazole-derivative dye having donor-Π-acceptor moieties for highly efficient organic-dye-sensitized solar cells
摘要： In the present work, we have synthesised donors/acceptor substituted derivative of imidazole 4-(1-(3-chloro-4-nitrophenyl)-4,5-diphenyl-1H-imidazol-2-yl)benzoic acid (CNI) via one-pot synthetic method and has been characterized by spectroscopic methods such as IR, SEM and EDX. The photophysical properties like, solvatochromic shift and quantum yield of the CNI dye were found to be 1.85% and 0.57 respectively. The increase in absorbance and decrease in fluorescence spectra with different concentrations of TiO2 nanoparticles confirmed the possibility of interactions between dye and TiO2 nanoparticles. The Rehm-Weller relation suggests that, decrease in fluorescence of CNI dye was due to photo-induced electron transfer process and the Stern-Volmer studies suggest that, the fluorescence quenching mechanism was due to combined dynamic and static quenching process. The theoretical and experimental methods. Further, photosensitization of TiO2 nanoparticles from CNI dye has been investigated using absorption, steady state and time resolved fluorescence methods. Photovoltaic energy conversion efficiency and fill factor of fabricating CNI dye sensitized solar cell.
关键词： Dye sensitized solar cell (DSSC),TiO2 nanoparticles,Photo induced Electron transfer,Fluorescence quenching,Imidazoles derivatives
更新于2025-09-12 10:27:22
-
Rational design of SM315-based porphyrin sensitizers for highly efficient dye-sensitized solar cells: A theoretical study
摘要： To explore high-efficiency dye-sensitized solar cells (DSSCs), five D-π-A type porphyrin dyes derived from SM315 synthesized by Gr?tzel et al with electron-rich units D1-D5 as donors were investigated using density functional theory (DFT) and time-dependent density functional theory (TD-DFT). The enhanced light harvesting abilities of all designed dyes are reflected by widened light harvesting efficiency curves, extended absorption spectra to near-infrared region and ~84 nm red-shifted maximum absorption wavelengths as well as double increased oscillator strengths. Mainly contributed by the remarkable increment of predicted short-circuit current density, the predicted overall efficiency of the design dyes increases by ~27% compared to SM315. Especially, S101 could be the most promising candidate with the highest predicted overall efficiency of 16.7% among all of dyes. The dynamic simulations of interfacial electron transfer of all the investigated dyes expound that the excited electrons inject almost totally into semiconductor TiO2 within 200 fs. This work would provide guidance for exploring potential sensitizers in highly efficient DSSCs.
关键词： porphyrin sensitizer,interfacial electron transfer,power-conversion efficiency,dye-sensitized solar cell
更新于2025-09-12 10:27:22
-
Excited state structural dynamics of 4-cyano-4′-hydroxystilbene: deciphering the signatures of proton-coupled electron transfer using ultrafast Raman loss spectroscopy
摘要： The photo-initiated proton-coupled electron transfer (PCET) process plays a crucial role in the context of light harvesting in various biological and chemical systems. Molecular model systems are typically employed to understand the mechanisms underlying the functioning of complex biological systems. Some molecular dyads based on the PCET property have been particularly designed to achieve efficient sunlight-to-fuel production. Organic photoacids are potential sources for such applications since they exhibit an enhancement in their acidity upon photoexcitation, facilitating the mimicking of some of the biological processes. p-Hydroxybenzylideneimidazolinone (p-HBI), an organic photoacid, is a key chromophore in green fluorescent protein, which exhibits green emission due to excited state proton transfer. Herein, we investigate the structural changes and dynamics of 4-cyano-40-hydroxystilbene (CHSB), an analogue of p-HBI, in the presence of an external base, t-butylamine (TBA), using the techniques of ultrafast transient absorption, emission and ultrafast Raman loss spectroscopy.
关键词： excited state dynamics,Raman loss spectroscopy,proton-coupled electron transfer,photoacids,ultrafast spectroscopy
更新于2025-09-12 10:27:22
-
CdTe Quantum Dots Modified with Cysteamine: A New Efficient Nanosensor for the Determination of Folic Acid
摘要： In this paper, we report the synthesis, characterization, and application of a new fluorescent nanosensor based on water-soluble CdTe quantum dots (QDs) coated with cysteamine (CA) for the determination of folic acid (FA). CdTe/CA QDs were characterized by high-resolution transmission electron microscopy, the zeta potential, and Fourier-transform infrared (FT-IR), UV-visible, and fluorescence spectroscopy. CdTe QDs coated with mercaptopropionic acid (MPA) and glutathione (GSH) were prepared for comparison purposes. The effect of FA on the photoluminescence intensity of the three thiol-capped QDs at pH 8 was studied. Only CdTe/CA QDs showed a notable fluorescence quenching in the presence of FA. Then, a nanosensor based on the fluorescence quenching of the CdTe QDs at pH 8 was explored. Under optimum conditions, the calibration curve showed a linear fluorescence quenching response in a concentration range of FA from 0.16 to 16.4 μM (R2 = 0.9944), with a detection limit of 0.048 μM. A probable mechanism of fluorescence quenching was proposed. The nanosensor showed good selectivity over other possible interferences. This method has been applied for FA quantification in orange beverage samples with excellent results (recoveries from 98.3 to 103.9%). The good selectivity, sensitivity, low cost, and rapidity make CdTe /CA QDs a suitable nanosensor for FA determination.
关键词： electron transfer,folic acid nanosensor,positive quantum dots,fluorescence quenching
更新于2025-09-12 10:27:22
-
Green low-temperature-solution-processed in situ HI modified TiO2/SnO2 bilayer for efficient and stable planar perovskite solar cells build at ambient air conditions
摘要： Planar structures for halide perovskite solar cells with the high efficiencies typically use high-temperature processed TiO2 as the electron transporting layers (ETLs). Here, we demonstrate that an in-situ passivation strategy for TiO2 film through the introduction of HI during low-temperature preparation process. HI not only controls hydrolysis of TiO2 precursor but also eliminates defects and suppresses trap states in TiO2 film. Meanwhile, the double-layer architecture is constructed by coating TiO2 with SnO2 layer, the double ETLs can improve the photovoltaic performance of methylamine lead iodide (MAPbI3) perovskite solar cells. The TiO2(HI)/SnO2 ETL can effectively reduce the interfacial charge recombination and facilitate electron transfer. More importantly, the preparation of TiO2 and SnO2 are totally performed at low-temperature (150 °C) and the devices are fabricated in uncontrolled ambient conditions. Our best-performing planar perovskite cell using such a TiO2(HI)/SnO2 ETL has achieved a maximum power conversion efficiency (PCE) of 16.74%, and the devices exhibit good stability which maintaining 85% and 83% of their initial efficiency after heating at 100 °C for 22 h and under illuminating upon 1 sun irradiation for 6 h, respectively. Our results suggest a new approach for further improving the stability of PSCs fabricated in the air condition.
关键词： perovskite solar cell,electron transfer layer,ambient condition,TiO2/SnO2
更新于2025-09-12 10:27:22
-
Electron Transfer Kinetics at Graphene Quantum Dot Assembly Electrodes
摘要： Electrochemical performance of nanostructured carbon electrodes was evaluated using cyclic voltammetry and a simple simulation model. The electrodes were prepared from soluble precursors by anodic electrodeposition of two sizes of graphene quantum dot assemblies (HBC and CQD) onto conductive support. Experimental and simulated voltammograms enabled the extraction of the following electrode parameters: conductivity of the electrodes (a combination of ionic and electronic contributions), density of available electrodes states at different potentials and tunneling rate constant (Marcus-Gerischer model) for interfacial charge transfer to ferrocene/ferrocenium (Fc/Fc+) couple. The parameters indicate that HBC and CQD have significant density of electronic states at potentials more positive than –0.5 V vs Ag/Ag+. Enabled by these large densities, the electron transfer rates at the Fc/Fc+ thermodynamic potential are several orders of magnitude slower than those commonly observed on other carbon electrodes. This study is expected to accelerate the discovery of improved synthetic carbon electrodes by providing fast screening methodology of their electrochemical behavior.
关键词： cyclic voltammetry,kinetics,interface,electrode,electron transfer,graphene quantum dots
更新于2025-09-12 10:27:22
-
Novel Fluorescent C2-Symmetric Sequential On-Off-On Switch for Cu2+ and Pyrophosphate and Its Application in Monitoring of Endogenous Alkaline Phosphatase Activity
摘要： A doubly armed hydrazone-based FLRHYDDFP probe selectively detects Cu2+ and pyrophosphate (PPi) ions through an colorimetric response-“colorless → yellow → colorless”- as well as “on-off-on” photonic switching response under physiological conditions in a sequential manner. The binding stoichiometries of the analytes Cu2+ and PPi were 1:2 and 2:4 for FLRHYDDFP-Cu2+ and Cu2+/PPi, respectively. The sequential sensing ability of FLRHYDDFP toward Cu2+ and PPi, attributed to effective complexation-aided d→π* electron transfer (ET) from Cu2+ to FLRHYDDFP and intramolecular charge/electron transfer from FLRHYDDFP to FLRHYDDFP+, resulted in the formation of a non-symmetric Cu2+ chelate that provided a yellow-colored solution with a significant bathochromic shift from 376 to 446 nm in the UV-Vis spectrum and quenching in the emission spectrum. Upon addition of PPi, Cu2+ was extruded from the complex, resulting in a revival of the fluorescence centered at 572 nm. Thus, sequential addition of Cu2+ and PPi yielded a colorless–yellow–colorless transition under visible light and on-off-on switching under 365-nm light (fluorescence). The lowest detection limits for Cu2+ and PPi, when using colorimetric and fluorimetric methods, were in the sub-micromolar and nanomolar levels, respectively. By exploiting this PPi sensing strategy, invitro as well as endogenous alkaline phosphatase activity could be monitored effectively, as demonstrated by exploiting the intracellular production or residual PPi in human salivary glands (normal) and cancer cell lines.
关键词： Endogenous Alkaline Phosphatase,C2v Symmetry,d→π* Electron Transfer,Intramolecular Charge/Electron Transfer,Human Salivary Gland Cells and Cancer Cells,Hydrazone
更新于2025-09-11 14:15:04