Prolonging the lifetime of excited electrons of QDs by capping them with π-conjugated thiol ligands

2014 ◽  
Vol 2 (16) ◽  
pp. 2939-2943 ◽  
Author(s):  
Jie Chang ◽  
Hongbo Xia ◽  
Suli Wu ◽  
Shufen Zhang
Keyword(s):  
Energy Levels ◽  
Excited Electron ◽  
Band Edge ◽  
Lumo Energy ◽  
Stable Environment ◽  
Cdte Qds ◽  
Thiol Ligands ◽  
New Strategy

A new strategy is reported here to stabilize the excited electrons within QDs using-conjugated ligand. An electron delocalized field is formed by mixing the LUMO energy levels of π-conjugated ligand with conductive band-edge energy (Ecb) of CdTe QDs, which will supply the excited electron with a more stable environment.

SURFACE-CHARGE-ENABLED PHOTOLYTIC HYDROGEN GENERATION IN V2O5·H2O/Au NANOCONJUGATES

MRS Advances ◽  
2016 ◽  
Vol 1 (46) ◽  
pp. 3121-3126
Author(s):  
Sunith Varghese ◽  
Charuksha Walgama ◽  
Mark Wilkins ◽  
Sadagopan Krishnan ◽  
Kaan Kalkan
Keyword(s):  
Surface Charge ◽  
Hydrogen Generation ◽  
Hydrogen Reduction ◽  
Energy Levels ◽  
Sol Gel ◽  
Band Edge ◽  
Conduction Band Edge ◽  
Current Voltage ◽  
Negative Surface ◽  
Negative Surface Charge

ABSTRACTThe present work investigates sol-gel synthesized vanadium oxyhydrate (V2O5·H2O) nanowires decorated with Au nanoparticles as potential photolytic H2 generators. As determined by UV photoelectron and optical spectroscopies, the conduction band edge of V2O5·H2O lies 0.6 eV below standard H+ reduction potential, implying no H2 can be generated. On the contrary, as measured by gas chromatography, our nanoconjugates yield reproducible light-to-hydrogen conversion efficiency of 5.3%, for the first hour of photolysis under 470 nm excitation. To explain the observed hydrogen reduction, we have hypothesized the vanadia electron energy levels are raised by some negative surface charge. With the objective of validating this hypothesis, we have performed cyclic current-voltage measurements. The derived conduction and valence band edge energies are not only consistent with the optical band gaps, but also validate the hypothesized energy increase by 1.6 eV, respectively. The negative surface charge is also corroborated by the ζ-potential. Based on the measured pH of 2.4, we attribute the negative surface charge to Lewis acid nature of the nanowires, establishing dative bonding with OH−. The present work establishes the importance of surface charge in photoelectrochemical reactions, where it can be instrumental and enabling in photolytic fuel production.

scholarly journals Electronic Structure of Two New Bis-Schiff Base Ligands using DFT Method

2021 ◽  
pp. 10-15
Author(s):  
Elham Abdalrahem Bin Selim ◽  
Mohammed Hadi Al–Douh ◽  
Hassan Hadi Abdullah ◽  
Dahab Salim Al–Nohey
Keyword(s):  
Experimental Data ◽  
Biological Activity ◽  
Metal Ion ◽  
Energy Levels ◽  
Dft Method ◽  
Ftir Spectra ◽  
Schiff Base Ligands ◽  
Lumo Energy ◽  
Homo Lumo ◽  
Good Agreement

Two bis-Schiff Bases 1 and 2 are ligands that can coordinate with manganese metal to form stable complexes and have biological activity. Thermodynamic parameters, HOMO-LUMO energy levels and FTIR spectra of two ligands have been computed using B3LYP/6-311++G(d,p) functional of the DFT calculations. Both ligands are favored thermodynamically, and the ligand 1 has been shown to be more stable than ligand 2. The Polarizability values of two ligands have been investigated. The results refer that ligand 2 interacts earlier than ligand 1 to the metal ion. The FTIR spectra of two ligands have been evaluated. All results show the good agreement between the theoretical and experimental data.

Dispiroacridine-indacenobisthiophenes positional isomers: Impact of the bridge on the physicochemical properties

2021 ◽  
Author(s):  
Jean-David Peltier ◽  
Benoît Heinrich ◽  
Bertrand Donnio ◽  
Olzhas A. Ibraikulov ◽  
Thomas Heiser ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Physicochemical Properties ◽  
Physical Properties ◽  
Charge Transport ◽  
Energy Levels ◽  
Molecular Organization ◽  
Positional Isomers ◽  
Lumo Energy ◽  
Positional Isomerism ◽  
Homo Lumo

We report the influence of positional isomerism on the electronic (electrochemical HOMO/LUMO energy levels), photophysical and physical properties (molecular organization, crys¬¬tallinity and phase transitions) and charge transport properties of dispiroacridine-in¬da¬ce¬no¬bis¬thio¬phene...

Insights into the correlation between the molecular conformational change and AIE activity of 2,5-bis(dimesitylboryl)-3,4-diphenylsiloles

2016 ◽  
Vol 4 (32) ◽  
pp. 7541-7545 ◽  
Author(s):  
Bin Chen ◽  
Han Nie ◽  
Rongrong Hu ◽  
Anjun Qin ◽  
Zujin Zhao ◽  
...  
Keyword(s):  
Conformational Change ◽  
Energy Levels ◽  
Lumo Energy

Three novel AIEgens with low-lying LUMO energy levels are developed from p–π conjugated 2,5-bis(dimesitylboryl)-3,4-diphenylsiloles.

scholarly journals Synthesis and Characterisation of Novel Thiophene Based Azomethine Polymers and Study of Their Liquid Crystalline, Electrochemical and Optoelectronic Properties

2017 ◽  
Vol 25 (5) ◽  
pp. 345-362 ◽  
Author(s):  
Omer Yasin Al-Janabi ◽  
Peter J.S. Foot ◽  
Emaad Taha Al-Tikrity ◽  
Peter Spearman
Keyword(s):  
Cyclic Voltammetry ◽  
Liquid Crystalline ◽  
Room Temperature ◽  
Energy Levels ◽  
Band Gaps ◽  
Gas Liquid Chromatography ◽  
Lumo Energy ◽  
Chemical Structures ◽  
Homo And Lumo ◽  
Homo And Lumo Energy

This work reports the synthesis, structural characterisation, liquid crystallinity, luminescence and electroluminescence of novel thiophene azomethine polymers. The polymers under study were prepared via oxidative polymerisation of four novel monomers at room temperature using iron (III) chloride. The chemical structures of the prepared monomers and polymers were confirmed by infrared and 1H and 13CNMR spectroscopy. Molecular masses were determined for monomers and polymers by gas/liquid chromatography-mass spectrometry (GC/LC-MS) and by gel-permeation (size exclusion) chromatography (SEC), respectively. Thermal stability studies of the prepared materials were achieved by thermogravimetric analysis (TGA), and the onset of weight loss To and the endset Tmax were calculated from the thermograms. Liquid crystalline mesophases and phase changes of the monomers and polymers were studied by differential scanning calorimetry (DSC) and polarised optical microscopy (POM), and the glass transition temperatures Tg of the polymers were determined from the DSC curves. The electrochemical band gaps, HOMO and LUMO energy levels were measured by cyclic voltammetry. UV-visible absorption-emission spectra (liquid and solid films) of the polymers were obtained at room temperature with different solvents. Optical band gaps were calculated from the absorption edges, and were in good agreement with those estimated from cyclic voltammetry. Mixing the polymers with lanthanide salts such as EuCl3 and YbCl3 gave modified fluorescence, and the light emitted was much more intense than that from the pure polymers. Polymer based light-emitting diodes (PLEDs) were fabricated by spin coating, and their current-voltage characteristics were measured. In preliminary work, the polymer devices were found to produce electroluminescent spectra similar to the PL spectra of the corresponding samples. Molecular modelling studies were performed both on polymer segments and monomer molecules; the absorption spectra of the prepared polymers, HOMO and LUMO energy levels were calculated with ZINDO using AMI geometry optimisation.

Fine-Tuning the Luminescence and HOMO–LUMO Energy Levels in Tetranuclear Gold(I) Fluorinated Amidinate Complexes

2012 ◽  
Vol 51 (4) ◽  
pp. 2010-2015 ◽  
Author(s):  
Hanan E. Abdou ◽  
Ahmed A. Mohamed ◽  
José M. López-de-Luzuriaga ◽  
Miguel Monge ◽  
John P. Fackler
Keyword(s):  
Energy Levels ◽  
Fine Tuning ◽  
Lumo Energy ◽  
Homo Lumo

Dibenzo[a,e]pentalenes with Low-Lying LUMO Energy Levels as Potential n-Type Materials

2018 ◽  
Vol 83 (2) ◽  
pp. 656-663 ◽  
Author(s):  
David C. Grenz ◽  
Maximilian Schmidt ◽  
Daniel Kratzert ◽  
Birgit Esser
Keyword(s):  
Energy Levels ◽  
Lumo Energy
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