scholarly journals Surface Charge Transfer Doping of MoS2 Monolayer by Molecules with Aggregation-Induced Emission Effect

Nanomaterials ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 164
Author(s):  
Ruihao Sun ◽  
Shiyu Sun ◽  
Xiu Liang ◽  
Hongyu Gong ◽  
Xingshuang Zhang ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Surface Charge ◽  
Density Functional ◽  
Transient Absorption ◽  
Transition Metal Dichalcogenides ◽  
Chemical Vapor ◽  
Density Functional Theory Calculations ◽  
Photoelectron Spectra ◽  
Aggregation Induced Emission ◽  
Wide Range

Surface charge transfer doping has attracted much attention in modulating the optical and electrical behavior of 2D transition metal dichalcogenides (TMDCs), where finding controllable and efficient dopants is crucial. Here, 1,1,2,2-tetraphenylethylene (TPE) derivative molecules with aggregation-induced emission (AIE) effect were selected as adjustable dopants. By designing nitro and methoxyl functional groups and surface coating, controlled p/n-type doping can be achieved on a chemical vapor deposition (CVD) grown monolayer, MoS2. We investigated the electron transfer behavior between these two dopants and MoS2 with fluorescence, Raman, X-ray photoelectron spectra and transient absorption spectra. 1,1,2,2-Tetrakis(4-nitrophenyl)ethane (TPE-4NO2) with a negative charge aggregation can be a donor to transfer electrons to MoS2, while 1,1,2,2-Tetrakis(4-methoxyphenyl)ethane (TPE-4OCH3) is the opposite and electron-accepting. Density functional theory calculations further explain and confirm these experimental results. This work shows a new way to select suitable dopants for TMDCs, which is beneficial for a wide range of applications in optoelectronic devices.

Graphene adlayer growth between nonepitaxial graphene and Ni(111) substrate: a promising theoretical scheme

2020 ◽  
Author(s):  
Lijuan Meng ◽  
Jinlian Lu ◽  
Yujie Bai ◽  
Lili Liu ◽  
Tang Jingyi ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Density Functional Theory ◽  
Chemical Vapor Deposition ◽  
Molecular Dynamics Simulations ◽  
Vapor Deposition ◽  
Density Functional ◽  
Chemical Vapor ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Dynamics Simulations

Understanding the fundamentals of chemical vapor deposition bilayer graphene growth is crucial for its synthesis. By employing density functional theory calculations and classical molecular dynamics simulations, we have investigated the...

scholarly journals Solution-Processed OLEDs Based on Thermally Activated Delayed Fluorescence Copper(I) Complexes with Intraligand Charge-Transfer Excited State

Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 1125
Author(s):  
Teng Teng ◽  
Jinfan Xiong ◽  
Gang Cheng ◽  
Changjiang Zhou ◽  
Xialei Lv ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Density Functional ◽  
Delayed Fluorescence ◽  
Quantum Yields ◽  
Functional Theory ◽  
Solution Processed ◽  
Thermally Activated Delayed Fluorescence ◽  
Light Emitting ◽  
Thermally Activated ◽  
Wide Range

A new series of tetrahedral heteroleptic copper(I) complexes exhibiting efficient thermally-activated delayed fluorescence (TADF) in green to orange electromagnetic spectral regions has been developed by using D-A type N^N ligand and P^P ligands. Their structures, electrochemical, photophysical, and electroluminescence properties have been characterized. The complexes exhibit high photoluminescence quantum yields (PLQYs) of up to 0.71 at room temperature in doped film and the lifetimes are in a wide range of 4.3–24.1 μs. Density functional theory (DFT) calculations on the complexes reveal the lowest-lying intraligand charge-transfer excited states that are localized on the N^N ligands. Solution-processed organic light emitting diodes (OLEDs) based on one of the new emitters show a maximum external quantum efficiency (EQE) of 7.96%.

scholarly journals Imaging and identification of point defects in PtTe2

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Kuanysh Zhussupbekov ◽  
Lida Ansari ◽  
John B. McManus ◽  
Ainur Zhussupbekova ◽  
Igor V. Shvets ◽  
...  
Keyword(s):  
Point Defects ◽  
Density Functional ◽  
Transition Metal Dichalcogenides ◽  
Density Functional Theory Calculations ◽  
Charge Carrier Mobility ◽  
Scanning Tunneling Spectroscopy ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Recombination Rates ◽  
And Performance

AbstractThe properties and performance of two-dimensional (2D) materials can be greatly affected by point defects. PtTe2, a 2D material that belongs to the group 10 transition metal dichalcogenides, is a type-II Dirac semimetal, which has gained a lot of attention recently due to its potential for applications in catalysis, photonics, and spintronics. Here, we provide an experimental and theoretical investigation of point defects on and near the surface of PtTe2. Using scanning tunneling microscopy and scanning tunneling spectroscopy (STS) measurements, in combination with first-principle calculations, we identify and characterize five common surface and subsurface point defects. The influence of these defects on the electronic structure of PtTe2 is explored in detail through grid STS measurements and complementary density functional theory calculations. We believe these findings will be of significance to future efforts to engineer point defects in PtTe2, which is an interesting and enticing approach to tune the charge-carrier mobility and electron–hole recombination rates, as well as the site reactivity for catalysis.

scholarly journals Ultrafast proton release reaction and primary photochemistry of phycocyanobilin in solution observed with fs-time-resolved mid-IR and UV/Vis spectroscopy

2021 ◽  
Author(s):  
Maximilian Theiß ◽  
Merten Grupe ◽  
Tilman Lamparter ◽  
Maria Andrea Mroginski ◽  
Rolf Diller
Keyword(s):  
Density Functional ◽  
Transient Absorption ◽  
Vibrational Analysis ◽  
Density Functional Theory Calculations ◽  
Chem Phys ◽  
Molecular Structures ◽  
Ir Absorption ◽  
Time Resolved ◽  
Time Constants ◽  
Vis Spectroscopy

AbstractDeactivation processes of photoexcited (λex = 580 nm) phycocyanobilin (PCB) in methanol were investigated by means of UV/Vis and mid-IR femtosecond (fs) transient absorption (TA) as well as static fluorescence spectroscopy, supported by density-functional-theory calculations of three relevant ground state conformers, PCBA, PCBB and PCBC, their relative electronic state energies and normal mode vibrational analysis. UV/Vis fs-TA reveals time constants of 2.0, 18 and 67 ps, describing decay of PCBB*, of PCBA* and thermal re-equilibration of PCBA, PCBB and PCBC, respectively, in line with the model by Dietzek et al. (Chem Phys Lett 515:163, 2011) and predecessors. Significant substantiation and extension of this model is achieved first via mid-IR fs-TA, i.e. identification of molecular structures and their dynamics, with time constants of 2.6, 21 and 40 ps, respectively. Second, transient IR continuum absorption (CA) is observed in the region above 1755 cm−1 (CA1) and between 1550 and 1450 cm−1 (CA2), indicative for the IR absorption of highly polarizable protons in hydrogen bonding networks (X–H…Y). This allows to characterize chromophore protonation/deprotonation processes, associated with the electronic and structural dynamics, on a molecular level. The PCB photocycle is suggested to be closed via a long living (> 1 ns), PCBC-like (i.e. deprotonated), fluorescent species.

scholarly journals Long-lived charge separation following pump-wavelength–dependent ultrafast charge transfer in graphene/WS2 heterostructures

2021 ◽  
Vol 7 (9) ◽  
pp. eabd9061
Author(s):  
Shuai Fu ◽  
Indy du Fossé ◽  
Xiaoyu Jia ◽  
Jingyin Xu ◽  
Xiaoqing Yu ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Charge Separation ◽  
Transient Absorption ◽  
Transition Metal Dichalcogenides ◽  
Thermionic Emission ◽  
Great Promise ◽  
Metal Dichalcogenides ◽  
Ultrafast Charge Transfer ◽  
Device Operation ◽  
Interfacial Charge

Van der Waals heterostructures consisting of graphene and transition metal dichalcogenides have shown great promise for optoelectronic applications. However, an in-depth understanding of the critical processes for device operation, namely, interfacial charge transfer (CT) and recombination, has so far remained elusive. Here, we investigate these processes in graphene-WS2 heterostructures by complementarily probing the ultrafast terahertz photoconductivity in graphene and the transient absorption dynamics in WS2 following photoexcitation. We observe that separated charges in the heterostructure following CT live extremely long: beyond 1 ns, in contrast to ~1 ps charge separation reported in previous studies. This leads to efficient photogating of graphene. Furthermore, for the CT process across graphene-WS2 interfaces, we find that it occurs via photo-thermionic emission for sub-A-exciton excitations and direct hole transfer from WS2 to the valence band of graphene for above-A-exciton excitations. These findings provide insights to further optimize the performance of optoelectronic devices, in particular photodetection.

scholarly journals Rolling the WSSe Bilayer into Double-Walled Nanotube for the Enhanced Photocatalytic Water-Splitting Performance

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 705
Author(s):  
Lin Ju ◽  
Jingzhou Qin ◽  
Liran Shi ◽  
Gui Yang ◽  
Jing Zhang ◽  
...  
Keyword(s):  
Water Splitting ◽  
Density Functional ◽  
Transition Metal Dichalcogenides ◽  
Density Functional Theory Calculations ◽  
Stable Configuration ◽  
Photocatalytic Water Splitting ◽  
Stacking Pattern ◽  
Metal Dichalcogenides ◽  
Photocatalytic Performances ◽  
Carrier Separation

For the emerging Janus transition metal dichalcogenides (TMD) layered water-splitting photocatalysts, stacking the monolayers to form bilayers has been predicted to be an effective way to improve their photocatalytic performances. To achieve this, the stacking pattern plays an important role. In this work, by means of the density functional theory calculations, we comprehensively estimate energetical stability, light absorption and redox capacity of Janus WSSe bilayer with different stacking patterns. Unfortunately, the Janus WSSe bilayer with the most stable configuration recover the out-of-plane symmetry, which is not in favor of the photocatalytic reactions. However, rolling the Janus WSSe bilayer into double-walled nanotube could stabilize the appropriate stacking pattern with an enhanced instinct dipole moment. Moreover, the suitable band edge positions, high visible light absorbance, outstanding solar-to-hydrogen efficiency (up to 28.48%), and superior carrier separation promise the Janus WSSe double-walled nanotube the potential for the photocatalytic water-splitting application. Our studies not only predict an ideal water-splitting photocatalyst, but also propose an effective way to improve the photocatalytic performances of Janus layered materials.

scholarly journals Interfacial chemical bond and internal electric field modulated Z-scheme Sv-ZnIn2S4/MoSe2 photocatalyst for efficient hydrogen evolution

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Xuehua Wang ◽  
Xianghu Wang ◽  
Jianfeng Huang ◽  
Shaoxiang Li ◽  
Alan Meng ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Electric Field ◽  
Hydrogen Evolution ◽  
Density Functional ◽  
Monochromatic Light ◽  
Density Functional Theory Calculations ◽  
Internal Electric Field ◽  
Apparent Quantum Yield ◽  
Paramagnetic Resonance ◽  
High Hydrogen

AbstractConstruction of Z-scheme heterostructure is of great significance for realizing efficient photocatalytic water splitting. However, the conscious modulation of Z-scheme charge transfer is still a great challenge. Herein, interfacial Mo-S bond and internal electric field modulated Z-scheme heterostructure composed by sulfur vacancies-rich ZnIn2S4 and MoSe2 was rationally fabricated for efficient photocatalytic hydrogen evolution. Systematic investigations reveal that Mo-S bond and internal electric field induce the Z-scheme charge transfer mechanism as confirmed by the surface photovoltage spectra, DMPO spin-trapping electron paramagnetic resonance spectra and density functional theory calculations. Under the intense synergy among the Mo-S bond, internal electric field and S-vacancies, the optimized photocatalyst exhibits high hydrogen evolution rate of 63.21 mmol∙g−1·h−1 with an apparent quantum yield of 76.48% at 420 nm monochromatic light, which is about 18.8-fold of the pristine ZIS. This work affords a useful inspiration on consciously modulating Z-scheme charge transfer by atomic-level interface control and internal electric field to signally promote the photocatalytic performance.

Interfacial defect engineering and Photocatalysis Properties of hBN/MX2(M = Mo, W, and X = S, Se) Heterostructures

2021 ◽  
Author(s):  
Zhihai Sun ◽  
Jiaxi Liu ◽  
Ying Zhang ◽  
Ziyuan Li ◽  
Leyu Peng ◽  
...  
Keyword(s):  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Band Alignment ◽  
Type I ◽  
Defect Engineering ◽  
Wide Range ◽  
Interfacial Defects ◽  
Significant Research ◽  
P Type ◽  
The Impact

Abstract Van der Waals (VDW) heterostructures have attracted significant research interest due to their tunable interfacial properties and potential in a wide range of applications such as electronics, optoelectronic, and heterocatalysis. In this work, the impact of interfacial defects on the electronic structures and photocatalytic properties of hBN/MX2(M = Mo, W, and X = S, Se) are studied using density functional theory calculations. The results reveal that the band alignment of hBN/MX2 can be adjusted by introducing vacancies and atomic doping. The type-I band alignment of the host structure was maintained in the heterostructure with n-type doping in the hBN sublayer. Interestingly, the band alignment changed to the type-II heterostructrue as VB defect and p-type doping was introduced in the hBN sublayer. This could be profitable for the separation of photo-generated electron−hole pairs at the interfaces and is highly desired for heterostructure photocatalysis. In addition, two Z-type heterostructures including hBN(BeB)/MoS2, hBN(BeB)/MoSe2, and hBN(VN)/MoSe2 were achieved, showing reducing band gap and ideal redox potential for water splitting. Our results reveal the possibility of engineering the interfacial and photocatalysis properties of hBN/MX2 heterostructures via interfacial defects.

scholarly journals Selective 13C labelling reveals the electronic structure of flavocoenzyme radicals

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Erik Schleicher ◽  
Stephan Rein ◽  
Boris Illarionov ◽  
Ariane Lehmann ◽  
Tarek Al Said ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Blue Light ◽  
Density Functional ◽  
Double Resonance ◽  
Density Functional Theory Calculations ◽  
Microwave Frequency ◽  
Fine Tuning ◽  
Electron Nuclear Double Resonance ◽  
Intermediate Radical ◽  
Wide Range

AbstractFlavocoenzymes are nearly ubiquitous cofactors that are involved in the catalysis and regulation of a wide range of biological processes including some light-induced ones, such as the photolyase-mediated DNA repair, magnetoreception of migratory birds, and the blue-light driven phototropism in plants. One of the factors that enable versatile flavin-coenzyme biochemistry and biophysics is the fine-tuning of the cofactor’s frontier orbital by interactions with the protein environment. Probing the singly-occupied molecular orbital (SOMO) of the intermediate radical state of flavins is therefore a prerequisite for a thorough understanding of the diverse functions of the flavoprotein family. This may be ultimately achieved by unravelling the hyperfine structure of a flavin by electron paramagnetic resonance. In this contribution we present a rigorous approach to obtaining a hyperfine map of the flavin’s chromophoric 7,8-dimethyl isoalloxazine unit at an as yet unprecedented level of resolution and accuracy. We combine powerful high-microwave-frequency/high-magnetic-field electron–nuclear double resonance (ENDOR) with 13C isotopologue editing as well as spectral simulations and density functional theory calculations to measure and analyse 13C hyperfine couplings of the flavin cofactor in DNA photolyase. Our data will provide the basis for electronic structure considerations for a number of flavin radical intermediates occurring in blue-light photoreceptor proteins.

Adsorption mechanism of CO molecule on Al(111) surface: periodic DFT investigation

2018 ◽  
Vol 96 (12) ◽  
pp. 993-999 ◽  
Author(s):  
Chenhong Xu ◽  
Suqin Zhou ◽  
Jing Chen ◽  
Yuxiang Wang ◽  
Lei He
Keyword(s):  
Charge Transfer ◽  
Density Functional ◽  
Adsorption Mechanism ◽  
Bond Activation ◽  
Aluminum Surface ◽  
Hollow Site ◽  
Functional Theory ◽  
Wide Range ◽  
Adsorption Of Co ◽  
Adsorption Energies

The adsorption mechanism of the CO molecule on Al(111) surface has been investigated systematically at the atom-molecule level by the method of periodic density functional theory. The adsorption energies, adsorption structures, charge transfer, and density of states have been calculated in a wide range of coverage. It is found that the hcp-hollow site is the energetically favorable site. A significant positive correlation has been found between the adsorption energy (Eads) and coverage. The adsorbed CO molecules are almost perpendicular on the surface with the C atom facing the surface. There is an obvious charge transfer from Al atoms to the C atom; the Al atoms that have interaction with the C atom offer the most charge. The 4σ, 1π, and 5σ molecular orbitals of CO are found to contribute to bonding with the Al. The charges filling in the 2π molecular orbital contribute to C–O bond activation. In conclusion, the passivation of aluminum surface and the activation of CO molecule occur simultaneously in the adsorption of CO on Al surface.

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