Photoluminescence Emission Induced by Localized States in Halide Passivated Colloidal Two-Dimensional WS2 Nanoflakes

Engineering physicochemical properties of two-dimensional transition metal dichalcogenide (2D-TMD) materials by surface manipulation is essential for their practical and large-scale application especially for colloidal 2D-TMDs that are plagued by the unintentional formation of structural defects during the synthetic procedure. However, the available methods to manage surface states of 2D-TMDs in solution-phase are still limited hampering the production of high quality colloidal 2D-TMD inks to be straightforwardly assembled into actual devices. Here, we demonstrate an efficient solution-phase strategy to passivate surface defect states of colloidally synthetized WS2 nanoflakes with halide ligands, resulting in the activation of the photoluminescence emission. Photophysical investigation and density functional theory calculations suggest that halide atoms enable the suppression of non-radiative recombination through the elimination deep gap trap states, and introduce localized states in the energy band structure from which excitons efficiently recombine. Halide passivated WS2 nanoflakes importantly preserve colloidal stability and photoluminescence emission after several weeks of storing in ambient atmosphere, corroborating the potential of our developed 2D-TMD inks.

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Photoluminescence emission induced by localized states in halide-passivated colloidal two-dimensional WS2 nanoflakes

Journal of Materials Chemistry C ◽

10.1039/d0tc05285j ◽

2021 ◽

Author(s):

Rosanna Mastria ◽

Anna Loiudice ◽

Jan Vávra ◽

Concetta Nobile ◽

Riccardo Scarfiello ◽

...

Keyword(s):

Optical Properties ◽

Transition Metal ◽

Transition Metal Dichalcogenides ◽

Solution Phase ◽

Localized States ◽

Two Dimensional ◽

Photoluminescence Emission ◽

Metal Dichalcogenides

A solution-phase halide passivation strategy to engineer the optical properties of two-dimensional transition metal dichalcogenides synthesized by a colloidal approach.

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Excited States Calculations of MoS2@ZnO and WS2@ZnO Two-Dimensional Nanocomposites for Water-Splitting Applications

Energies ◽

10.3390/en15010150 ◽

2021 ◽

Vol 15 (1) ◽

pp. 150

Author(s):

Yin-Pai Lin ◽

Boris Polyakov ◽

Edgars Butanovs ◽

Aleksandr A. Popov ◽

Maksim Sokolov ◽

...

Keyword(s):

Density Functional Theory ◽

Optical Properties ◽

Water Splitting ◽

Excited States ◽

Density Functional ◽

Visible Region ◽

Transition Metal Dichalcogenide ◽

Two Dimensional ◽

Functional Theory ◽

Exchange Correlation

Transition metal dichalcogenide (TMD) MoS2 and WS2 monolayers (MLs) deposited atop of crystalline zinc oxide (ZnO) and graphene-like ZnO (g-ZnO) substrates have been investigated by means of density functional theory (DFT) using PBE and GLLBSC exchange-correlation functionals. In this work, the electronic structure and optical properties of studied hybrid nanomaterials are described in view of the influence of ZnO substrates thickness on the MoS2@ZnO and WS2@ZnO two-dimensional (2D) nanocomposites. The thicker ZnO substrate not only triggers the decrease of the imaginary part of dielectric function relatively to more thinner g-ZnO but also results in the less accumulated charge density in the vicinity of the Mo and W atoms at the conduction band minimum. Based on the results of our calculations, we predict that MoS2 and WS2 monolayers placed at g-ZnO substrate yield essential enhancement of the photoabsorption in the visible region of solar spectra and, thus, can be used as a promising catalyst for photo-driven water splitting applications.

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Layer-dependent topological phase in a two-dimensional quasicrystal and approximant

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2015164117 ◽

2020 ◽

Vol 117 (42) ◽

pp. 26135-26140

Author(s):

Jeffrey D. Cain ◽

Amin Azizi ◽

Matthias Conrad ◽

Sinéad M. Griffin ◽

Alex Zettl

Keyword(s):

Density Functional ◽

Density Functional Theory Calculations ◽

Transition Metal Dichalcogenide ◽

Material System ◽

Two Dimensional ◽

Topological Properties ◽

Scanning Transmission ◽

Layered Transition Metal ◽

Low Dimensional ◽

Physical Phenomena

The electronic and topological properties of materials are derived from the interplay between crystalline symmetry and dimensionality. Simultaneously introducing “forbidden” symmetries via quasiperiodic ordering with low dimensionality into a material system promises the emergence of new physical phenomena. Here, we isolate a two-dimensional (2D) chalcogenide quasicrystal and approximant, and investigate their electronic and topological properties. The 2D layers of the materials with a composition close to Ta1.6Te, derived from a layered transition metal dichalcogenide, are isolated with standard exfoliation techniques, and investigated with electron diffraction and atomic resolution scanning transmission electron microscopy. Density functional theory calculations and symmetry analysis of the large unit cell crystalline approximant of the quasicrystal, Ta21Te13, reveal the presence of symmetry-protected nodal crossings in the quasicrystalline and approximant phases, whose presence is tunable by layer number. Our study provides a platform for the exploration of physics in quasicrystalline, low-dimensional materials and the interconnected nature of topology, dimensionality, and symmetry in electronic systems.

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Disordered hyperuniformity in two-dimensional amorphous silica

Science Advances ◽

10.1126/sciadv.aba0826 ◽

2020 ◽

Vol 6 (16) ◽

pp. eaba0826 ◽

Cited By ~ 2

Author(s):

Yu Zheng ◽

Lei Liu ◽

Hanqing Nan ◽

Zhen-Xiong Shen ◽

Ge Zhang ◽

...

Keyword(s):

Amorphous Silica ◽

Density Functional ◽

Large Scale ◽

Single Layer ◽

Topological Defects ◽

Density Functional Theory Calculations ◽

Density Fluctuations ◽

Atomic Scale ◽

Two Dimensional ◽

Wave Localization

Disordered hyperuniformity (DHU) is a recently proposed new state of matter, which has been observed in a variety of classical and quantum many-body systems. DHU systems are characterized by vanishing infinite-wavelength normalized density fluctuations and are endowed with unique novel physical properties. Here, we report the discovery of disordered hyperuniformity in atomic-scale two-dimensional materials, i.e., amorphous silica composed of a single layer of atoms, based on spectral-density analysis of high-resolution transmission electron microscopy images. Moreover, we show via large-scale density functional theory calculations that DHU leads to almost complete closure of the electronic bandgap compared to the crystalline counterpart, making the material effectively a metal. This is in contrast to the conventional wisdom that disorder generally diminishes electronic transport and is due to the unique electron wave localization induced by the topological defects in the DHU state.

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An efficient approach for large-scale two-dimensional guillotine cutting stock problems

Journal of the Operational Research Society ◽

10.1038/sj.jors.2600638 ◽

1998 ◽

Vol 49 (12) ◽

pp. 1270-1277 ◽

Cited By ~ 2

Author(s):

D Fayard ◽

M Hifi ◽

V Zissimopoulos

Keyword(s):

Large Scale ◽

Cutting Stock ◽

Two Dimensional ◽

Efficient Approach ◽

Guillotine Cutting

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First-Principles Evaluation of the Potential of Borophene as a Monolayer Transparent Conductor

10.26434/chemrxiv.5439880 ◽

2017 ◽

Author(s):

Lyudmyla Adamska ◽

Sridhar Sadasivam ◽

Jonathan J. Foley ◽

Pierre Darancet ◽

Sahar Sharifzadeh

Keyword(s):

First Principles ◽

Density Functional ◽

State Of The Art ◽

Transparent Electrode ◽

Visible Range ◽

Two Dimensional ◽

Transparent Conductor ◽

Many Body ◽

Functional Theory ◽

Many Body Perturbation Theory

Two-dimensional boron is promising as a tunable monolayer metal for nano-optoelectronics. We study the optoelectronic properties of two likely allotropes of two-dimensional boron using first-principles density functional theory and many-body perturbation theory. We find that both systems are anisotropic metals, with strong energy- and thickness-dependent optical transparency and a weak (<1%) absorbance in the visible range. Additionally, using state-of-the-art methods for the description of the electron-phonon and electron-electron interactions, we show that the electrical conductivity is limited by electron-phonon interactions. Our results indicate that both structures are suitable as a transparent electrode.

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Design and Synthesis of Two-Dimensional Covalent Organic Frameworks with Four-Arm Cores: Prediction of Remarkable Ambipolar Charge-Transport Properties

10.26434/chemrxiv.7766786.v2 ◽

2019 ◽

Author(s):

Simil Thomas ◽

Hong Li ◽

Raghunath R. Dasari ◽

Austin Evans ◽

William Dichtel ◽

...

Keyword(s):

Charge Transport ◽

Organic Semiconductors ◽

Density Functional ◽

Polymer Networks ◽

Two Dimensional ◽

Covalent Organic Frameworks ◽

X Ray Diffraction ◽

Zinc Porphyrin ◽

Design And Synthesis ◽

Predicted Values

We have considered three two-dimensional (2D) π-conjugated polymer networks (i.e., covalent organic frameworks, COFs) materials based on pyrene, porphyrin, and zinc-porphyrin cores connected via diacetylenic linkers. Their electronic structures, investigated at the density functional theory global-hybrid level, are indicative of valence and conduction bands that have large widths, ranging between 1 and 2 eV. Using a molecular approach to derive the electronic couplings between adjacent core units and the electron-vibration couplings, the three π-conjugated 2D COFs are predicted to have ambipolar charge-transport characteristics with electron and hole mobilities in the range of 65-95 cm2V-1s-1. Such predicted values rank these 2D COFs among the highest-mobility organic semiconductors. In addition, we have synthesized the zinc-porphyrin based 2D COF and carried out structural characterization via powder X-ray diffraction and surface area analysis, which demonstrates the feasability of these electroactive networks.

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Benchmark of Simplified Time-Dependent Density Functional Theory for UV-Vis Spectral Properties of Porphyrinoids

10.26434/chemrxiv.9912860 ◽

2019 ◽

Author(s):

Kamal Batra ◽

Stefan Zahn ◽

Thomas Heine

Keyword(s):

Density Functional Theory ◽

Density Functional ◽

Large Scale ◽

Absolute Error ◽

Time Dependent ◽

Basis Set ◽

Basis Sets ◽

Functional Theory ◽

Framework Materials ◽

Dependent Density

We thoroughly benchmark time-dependent density- functional theory for the predictive calculation of UV/Vis spectra of porphyrin derivatives. With the aim to provide an approach that is computationally feasible for large-scale applications such as biological systems or molecular framework materials, albeit performing with high accuracy for the Q-bands, we compare the results given by various computational protocols, including basis sets, density-functionals (including gradient corrected local functionals, hybrids, double hybrids and range-separated functionals), and various variants of time-dependent density-functional theory, including the simplified Tamm-Dancoff approximation. An excellent choice for these calculations is the range-separated functional CAM-B3LYP in combination with the simplified Tamm-Dancoff approximation and a basis set of double-ζ quality def2-SVP (mean absolute error [MAE] of ~0.05 eV). This is not surpassed by more expensive approaches, not even by double hybrid functionals, and solely systematic excitation energy scaling slightly improves the results (MAE ~0.04 eV).

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