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1.
  • Kuklin, Artem V., et al. (author)
  • Electronic and optical properties of C16S8 and C16S4Se4 molecules and crystals
  • 2022
  • In: New Journal of Chemistry. - Cambridge, United Kingdom : Royal Society of Chemistry. - 1144-0546 .- 1369-9261. ; 46:28, s. 13513-13518
  • Journal article (peer-reviewed)abstract
    • Hetero[8]circulenes have been proposed as promising fluorescent emitters for organic light-emitting diodes and as emerging materials in the construction of organic solar cells. Among them, octathio[8]circulene (C16S8) and its derivative tetrathiotetraseleno[8]circulene (C16S4Se4) crystals have been highlighted as efficient charge transport materials in field-effect devices. Using density functional theory, we investigate in this paper the electronic and optical properties of the C16S8 and C16S4Se4 molecules and crystals in order to revise previously reported controversial experimental data and report highly reproducible new results. We find that formation of the crystals results in a significant band gap decrease (similar to 0.6-0.7 eV) caused by relatively strong intermolecular interactions. A partial replacement of S atoms with Se atoms also leads to a small band gap reduction. The C16S8 crystal demonstrates a band gap of 3.32 eV, while a band gap of 3.20 eV is found for C16S4Se4. Both C16S8 and C16S4Se4 compounds are optically transparent in the visible region, confirming the absence of red coloration reported previously in one of experimental papers. The C16S8 and C16S4Se4 crystals demonstrate anisotropic electronic, mechanical and optical properties. These findings might initiate future experimental studies of the red color origin for C16S8 and provide insight for the design and engineering of C16S8 and C16S4Se4 based charge transport and optical devices.
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2.
  • Begunovich, Lyudmila V., et al. (author)
  • Single-layer polymeric tetraoxa[8]circulene modified by s-block metals : toward stable spin qubits and novel superconductors
  • 2021
  • In: Nanoscale. - : Royal Society of Chemistry. - 2040-3364 .- 2040-3372. ; 13:9, s. 4799-4811
  • Journal article (peer-reviewed)abstract
    • Tunable electronic properties of low-dimensional materials have been the object of extensive research, as such properties are highly desirable in order to provide flexibility in the design and optimization of functional devices. In this study, we account for the fact that such properties can be tuned by embedding diverse metal atoms and theoretically study a series of new organometallic porous sheets based on two-dimensional tetraoxa[8]circulene (TOC) polymers doped with alkali or alkaline-earth metals. The results reveal that the metal-decorated sheets change their electronic structure from semiconducting to metallic behaviour due to n-doping. Complete active space self-consistent field (CASSCF) calculations reveal a unique open-shell singlet ground state in the TOC-Ca complex, which is formed by two closed-shell species. Moreover, Ca becomes a doublet state, which is promising for magnetic quantum bit applications due to the long spin coherence time. Ca-doped TOC also demonstrates a high density of states in the vicinity of the Fermi level and induced superconductivity. Using the ab initio Eliashberg formalism, we find that the TOC-Ca polymers are phonon-mediated superconductors with a critical temperature T-C = 14.5 K, which is within the range of typical carbon based superconducting materials. Therefore, combining the proved superconductivity and the long spin lifetime in doublet Ca, such materials could be an ideal platform for the realization of quantum bits.
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3.
  • Begunovich, Lyudmila, V, et al. (author)
  • Triple VTe2/graphene/VTe2 heterostructures as perspective magnetic tunnel junctions
  • 2020
  • In: Applied Surface Science. - : ELSEVIER. - 0169-4332 .- 1873-5584. ; 510
  • Journal article (peer-reviewed)abstract
    • New perspective 1.4 nm thick spin-polarized triple heterostructures based on graphene sandwiched between two vanadium ditelluride monolayers (VTe2/graphene/VTe2) were studied using ab initio DFT technique. Both possible trigonal prismatic (H-VTe2) and octahedral (T-VTe2) VTe2 phases were considered to design and study graphene-based heterostructures. It was shown that the interaction with graphene changes the electronic structure of 2D T-VTe2 from metallic to half-metallic, making T phase perspective to be used for magnetic tunnel junctions. The electronic subsystem of graphene fragment is slightly hole doped. Calculated tunnel magne-toresistance ratio for the favorable heterostructure configuration estimated within the Julliere model is 220%, which opens a way to use VTe2/graphene/VTe2 as prospective magnetic tunnel junction in novel spintronic nanodevices based on tunnel magnetic resistance and spin transfer torque effects.
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4.
  • Karaush-Karmazin, Nataliya N., et al. (author)
  • Structure, stability and electronic properties of one-dimensional tetrathia- and tetraselena[8]circulene-based materials : a comparative DFT study
  • 2020
  • In: New Journal of Chemistry. - : Royal Society of Chemistry. - 1144-0546 .- 1369-9261. ; 44:17, s. 6872-6882
  • Journal article (peer-reviewed)abstract
    • Conjugated polymers gain much attention due to the promising applications in organic electronic device technology. In this work, we theoretically study the structures and electronic properties of a novel class of nanostructures, namely one-dimensional tetrathia[8]circulenes (TTC) and tetraselena[8]circulenes (TSC) predicted to be promising semiconducting soft materials. It is found that all nanoribbons are thermodynamically stable and that their electronic properties depend significantly on the type of fusing between the monomers. In particular, the band gap tends to decrease while moving from the directly fused TTC/TSC ribbons to the structures coupled via a benzene-core linker and then to the ribbons fused through a four-membered ring. Therefore, both coupling type and length of oligomers allow one to manipulate the electronic and optical properties of the studied ribbons. The band structure calculations of infinite nanoribbons reveal direct band gaps that decrease from 2.28 to 2.14 eV for the TTC ribbons of the first and second fusion types. The TSC structures demonstrate the same trend exhibiting band gap narrowing from 2.41 (type I) up to 2.11 eV (type II). The type III ribbons possess a lack of periodicity due to the close-lying energy minima for the possible twisting configurations of TTC and TSC moieties relative to the linking four-membered ring.
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5.
  • Anithaa, V. S., et al. (author)
  • Adsorption of volatile organic compounds on pristine and defected nanographene
  • 2022
  • In: Computational and Theoretical Chemistry. - : Elsevier. - 2210-271X .- 2210-2728. ; 1211
  • Journal article (peer-reviewed)abstract
    • Adsorption of volatile organic compounds (VOCs) which are a class of air pollutants affecting the environment and human health is considered as the favourable technology for enrichment, separation and utilization of VOCs. In the present work, the adsorption properties of air polluting carbocyclic and heterocyclic VOCs such as toluene, p-xylene and indole onto pristine/defected nanographene (with and without dopants) are investigated using density functional theory (DFT). Adsorption of indole is higher (-0.544 to -1.786 eV) in pristine/defected nanographene (with and without dopant) than p-xylene and toluene. The reactivity of defect on adsorption of VOCs is found high for indole with defected nanographene (DG) and toluene with DG-N indicating the influence of sheet type for adsorption rely on the type of the VOCs adsorbate. The charge transfer and type of interaction between the sheet and VOCs are interpreted using Hirshfeld charge analysis, QTAIM and RDG analysis. The influence of VOCs adsorption is high on the electronegativity and electrophilicity index of the pristine/defected nanographene whereas energy gap and hardness show less influence. The noticeable changes in the TDOS and energy gap on adsorption of VOCs with respect to the type of sheet infers that the doped defected sheet have high affinity than the pristine sheet moreover, the suitable sheet for adsorption of VOCs depends on the type of VOCs adsorbate.
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6.
  • Avramov, Pavel, V, et al. (author)
  • Topological and quantum stability of low-dimensional crystalline lattices with multiple nonequivalent sublattices
  • 2022
  • In: New Journal of Physics. - : Institute of Physics (IOP). - 1367-2630. ; 24:10
  • Journal article (peer-reviewed)abstract
    • The terms of topological and quantum stabilities of low-dimensional crystalline carbon lattices with multiple non-equivalent sublattices are coined using theoretical analysis, multilevel simulations, and available experimental structural data. It is demonstrated that complex low-dimensional lattices are prone to periodicity breakdown caused by structural deformations generated by linear periodic boundary conditions (PBC). To impose PBC mandatory limitations for complex low-dimensional lattices, the topology conservation theorem (TCT) is introduced, formulated and proved. It is shown that the lack of perfect filling of planar 2D crystalline space by structural units may cause the formation of (i) structure waves of either variable or constant wavelength; (ii) nanotubes or rolls; (iii) saddle structures; (iv) aperiodic ensembles of irregular asymmetric atomic clusters. In some cases the lattice can be stabilized by aromatic resonance, correlation effects, or van-der-Waals interactions. The effect of quantum instability and periodicity breakdown of infinite structural waves is studied using quasiparticle approach. It is found that both perfect finite-sized, or stabilized structural waves can exist and can be synthesized. It is shown that for low-dimensional lattices prone to breakdown of translation invariance (TI), complete active space of normal coordinates cannot be reduced to a subspace of TI normal coordinates. As a result, constrained TI subspace structural minimization may artificially return a regular point at the potential energy surface as either a global/local minimum/maximum. It is proved that for such lattices, phonon dispersion cannot be used as solid and final proof of either stability or metastability. It is shown that ab initio molecular dynamics (MD) PBC Nose-Hoover thermostat algorithm constrains the linear dimensions of the periodic slabs in MD box preventing their thermostated equilibration. Based on rigorous TCT analysis, a flowchart algorithm for structural analysis of low-dimensional crystals is proposed and proved to be a powerful tool for theoretical design of advanced complex nanomaterials.
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7.
  • Baryshnikov, Gleb V., et al. (author)
  • Cyclo[18]carbon : Insight into Electronic Structure, Aromaticity, and Surface Coupling
  • 2019
  • In: The Journal of Physical Chemistry Letters. - : AMER CHEMICAL SOC. - 1948-7185. ; 10:21, s. 6701-6705
  • Journal article (peer-reviewed)abstract
    • Cyclo[18]carbon (C-18) is studied computationally at the density functional theory (DFT) and ab initio levels to obtain insight into its electronic structure, aromaticity, and adsorption properties on a NaCl surface. DFT functionals with a small amount of Hartree-Fock exchange fail to determine the experimentally observed polyyne molecular structure, revealing a cumulene-type geometry. Exchange-correlation functionals with a large amount of Hartree-Fock exchange as well as ab initio CASSCF calculations yield the polyyne structure as the ground state and the cumulene structure as a transition state between the two inverted polyyne structures through a Kekule distortion. The polyyne and the cumulene structures are found to be doubly Huckel aromatic. The calculated adsorption energy of cyclo[18]carbon on the NaCl surface is small (37 meV/C) and almost the same for both structures, implying that the surface does not stabilize a particular geometry.
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8.
  • Gusev, Alexey, et al. (author)
  • Structure and tuneable luminescence in polymeric zinc compounds based on 3-(3-pyridyl)-5-(4-pyridyl)-1,2,4-triazole
  • 2020
  • In: Polyhedron. - : Elsevier BV. - 0277-5387 .- 1873-3719. ; 191
  • Journal article (peer-reviewed)abstract
    • Inorganic-organic hybrid polymers based on 3-(3-pyridyl)-5-(4-pyridyl)-1,2,4-triazole (3,4-Hbpt) ligand were synthesized and subsequently characterized by single-crystal X-ray diffraction, FT-IR spectra, elemental analyses, thermogravimetric (TG) analyses and PXRD. The X-ray diffraction analyses revealed that the complexes [Zn(3,4-Hbpt)Cl-2] and [Zn(3,4-Hbpt)Br-2] possess a 1-D helical chain structure constructed of the 3,4-Hbpt ligands connecting the zinc cations. The [Zn(3,4-bpt)(OAc)] complex demonstrates a 2D sheet structure bridged by tridentate 3,4-bpt-anions. All compounds exhibit substantial thermal stability and show photo-fluorescent properties that result from the ligand pi-pi* transition. Ultraviolet-to-visible tunable emission for two of the complexes is observed.
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9.
  • Karaush-Karmazin, Nataliya N., et al. (author)
  • Impact of molecular and packing structure on the charge-transport properties of hetero[8]circulenes
  • 2021
  • In: Journal of Materials Chemistry C. - : ROYAL SOC CHEMISTRY. - 2050-7526 .- 2050-7534. ; 9:4, s. 1451-1466
  • Journal article (peer-reviewed)abstract
    • In organic photovoltaic cells, absorption of light leads to the formation of excitons, which then diffuse to the donor/acceptor interface to generate photocurrent. The distance from which excitons can reach the interface is constrained by the exciton diffusion length, which has been difficult to quantitatively model or predict due to structural and energetic disorder. Modern non-fullerene acceptors have been shown to possess exceptionally large diffusion lengths, along with well-defined molecular and packing structures, suggesting that a predictive framework for materials design and computational screening may be possible. In this work, we demonstrate that the large diffusion coefficient recently observed in an archetypical non-fullerene acceptor, IDIC, can be accurately quantified using density functional theory, and that the low energetic disorder means that the crystal structure provides a meaningful starting point to understand exciton motion in thin films. Accounting for the short- and long-range excitonic interactions, as well as spatiotemporal disorder, we demonstrate that both Monte-Carlo techniques and a simple sum-over-rates method can accurately predict experimental values for exciton diffusivity and diffusion length. The simplicity and accuracy of this approach are directly linked to the structural order of these materials, and an electronic coupling profile that is unusually resilient to thermal distortions - highlighting the potential of the sum-over-rates method for computational materials screening. Moreover, we show that these factors, combined with the low reorganisation energy and significant long-range electronic coupling, lead to diffusion rates that approach the upper limit of incoherent energy transfer and long diffusion lengths that relieve constraints on organic solar cell device architectures.
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10.
  • Kuklin, Artem, V, et al. (author)
  • CrI3 magnetic nanotubes : A comparative DFT and DFT plus U study, and strain effect
  • 2020
  • In: Physica. E, Low-Dimensional systems and nanostructures. - : Elsevier. - 1386-9477 .- 1873-1759. ; 123
  • Journal article (peer-reviewed)abstract
    • In this paper, structural and electronic properties of CrI3 magnetic nanotubes (NTs) are studied using density functional theory. Both armchair and zigzag CrI3 nanotubes demonstrate a high correlation in strain energy between each other independently on accounting the Hubbard correction. The strain energies decrease with expansion of the tube diameter making the tubes' synthesis with a diameter larger than 45 angstrom to be energetically possible. The nanotubes of both zigzag and armchair chirality are ferromagnetic semiconductors with band gaps close to that of the CrI3 monolayer. The band gaps are suppressed by reducing the tube diameters due to the structural stress leading to deformation of the Cr-I crystal field and changes in the bond lengths. The external strain can be utilized to flexibly tune the electronic properties of CrI3 nanotubes with the desired spin-up/spindown band gap ratio. Strong distortion of the octahedral Cr-I crystal field under compression results in nontrivial behavior in the spin-up band gap of (4, 4) tube. Stretching of tubes leads to the enhancement of the exchange energy that should result in higher Curie temperature, therefore providing a good platform for potential applications in spintronic nanodevices.
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11.
  • Kuklin, Artem V., et al. (author)
  • Point and complex defects in monolayer PdSe2 : Evolution of electronic structure and emergence of magnetism
  • 2021
  • In: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 104:13
  • Journal article (peer-reviewed)abstract
    • Layered transition-metal dichalcogenides (TMDs) constitute an emerging class of materials that provide researchers a platform to realize fundamental studies and to design promising optoelectronic devices. While defects are an almost unavoidable part of TMDs, they bring additional interesting properties absent in defect-free layers. Moreover, the controlled introduction of defects in TMDs makes it possible to tailor the electromagnetic properties of the materials. Here we report defect-induced properties of single-layer PdSe2 and demonstrate the emergence of magnetism at the nanoscale. Our first-principle calculations indicate that Se vacancies create in-gap defect states, which can be responsible for trapping of carriers. The complex square V-Pd(+)4Se vacancy induces spin-polarized states with a total local magnetic moment of 2 mu B per defect, making it possible to introduce magnetization into PdSe2 and therefore expand the family of two-dimensional (2D) magnets. The defect formation energies are much lower compared to many other TMD materials that can explain the presence of a large number of Se defects after mechanical exfoliation of PdSe2 layers, while the central location of the Pd atoms preserves them from exfoliation-induced defect formation. The negatively charged vacancies are prone to form and in many cases demonstrate spin-polarized states. The small diffusion barrier of V-Se in 2D PdSe2 leads to an easy room-temperature migration, while V-pd demonstrates a high diffusion barrier preventing its spontaneous migration. As a guide for experimentalists, we simulate and characterize scanning tunneling microscope images in valence and conduction states and estimate the electron-beam energy for a controllable production of various defect patterns. These intriguing findings make PdSe2 an ideal platform to study defect-induced phenomena.
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12.
  • Kuklin, Artem V., et al. (author)
  • Spontaneous Decomposition of Fluorinated Phosphorene and Its Stable Structure
  • 2019
  • In: The Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 10:22, s. 7086-7092
  • Journal article (peer-reviewed)abstract
    • Single- and few-layer black phosphorus possesses interesting properties suitable for various optoelectronic applications where graphene cannot be applied due to its vanishing band gap. As phosphorene tends to degrade in environments, various approaches including fluorination have been explored to passivate its surface. Several structures of fluorinated phosphorene have thus recently been reported to demonstrate this approach. On the basis of a combination of first-principles electronic structure calculations and ab initio molecular dynamics, we reconsider the structure of fluorinated phosphorene marking previously reported configurations as thermodynamically unstable with a tendency to decompose spontaneously. We reveal the mechanism of fluorination and propose novel thermodynamically and energetically stable structures containing double fluorine units with enhanced antioxidative stability caused by the fluorination-induced negative electrostatic potential on the surface of phosphorene. The partially fluorinated structure demonstrates almost the same band gap compared to bare phosphorene, making it possible to utilize them in nano-optoelectronic applications.
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13.
  • Kuklin, A. V., et al. (author)
  • Strong Topological States and High Charge Carrier Mobility in Tetraoxa[8]circulene Nanosheets
  • 2018
  • In: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 122:38, s. 22216-22222
  • Journal article (peer-reviewed)abstract
    • Here we report structural and electronic properties of a new family of two-dimensional covalent metal-free organic frameworks based on tetraoxa[8]circulene with different types of fusing. All nanosheets demonstrate high thermodynamic stability and unique electronic properties depending on the fusing type. Among three types of nanosheets, only two demonstrate semiconducting properties exhibiting 1.37 and 1.84 eV direct band gaps, while another one is found to be a semimetal, which hosts strong topological states and enhances the band gap (∼87 meV) induced by spin-orbit coupling that exceeds by several orders of magnitude that gap in graphene. Tetraoxa[8]circulene-based nanosheets are also predicted to be good organic semiconductors due to a clearly observable quantum confinement effect on the band gap size in oligomers and relatively low effective masses, which result in high carrier mobility. Owing to the versatility of chemical design, these materials have the potential to expand applications beyond those of graphene.
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14.
  • Kuklin, Artem, V, et al. (author)
  • Structural stability of single-layer PdSe2 with pentagonal puckered morphology and its nanotubes
  • 2020
  • In: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 22:16, s. 8289-8295
  • Journal article (peer-reviewed)abstract
    • Two-dimensional (2D) materials have gained a lot of attention being a new class of materials with unique properties that could influence future technologies. Concomitant computational design and discovery of new two-dimensional materials have therefore become a significant part of modern materials research. The stability of these predicted materials has emerged as the main issue due to drawbacks of the periodic boundary condition approximation that allow one to pass common criteria of stability. Here, based on first-principle calculations, we demonstrate structural stability and instability of several recently proposed 2D materials with pentagonal morphology including the experimentally exfoliated single-layer PdSe2. It is found that an appropriate orientation of the central Pd sublattice with respect to Se-2 dimers effectively compensates all mechanical stress and preserves the planar structure of the PdSe2 nanoclusters, while the flakes of all other materials having pentagonal morphology exhibit non-zero curvature induced by excessive interatomic forces. The relative energies of the PdSe2 monolayer and nanotubes per formula unit also confirm that the planar monolayer is a global energy minimum. Like the monolayer, (n,0) PdSe2 tubes are indirect band gap semiconductors with similar band gaps, while (n,n) tubes reveal indirect-direct band gap transitions following the increase of the tube diameter. Small strain energies of large diameter tubes propose their possible experimental realization for various optoelectronic applications.
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15.
  • Sumi, Naoya, et al. (author)
  • Direct Visualization of Nearly Free Electron States Formed by Superatom Molecular Orbitals in a Li@C-60 Monolayer
  • 2021
  • In: The Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 12:32, s. 7812-7817
  • Journal article (peer-reviewed)abstract
    • Using scanning tunneling microscopy (STM) and density functional theory (DFT) calculations, we directly determine the spatial and energetic distributions of superatom molecular orbitals (SAMOs) of an Li@C-60 monolayer adsorbed on a Cu(111) surface. Utilizing a weakly bonded [Li+@C-60] NTf2- (NTf2-: bis(trifluoromethanesulfonyl)imide) salt makes it possible to produce a Li@C-60 monolayer with high concentration of Li@C-60 molecules. Because of the very uniform adsorption geometry of Li@C-60 on Cu(111), the p(z)-SAMO, populated above the upper hemisphere of the molecule, exhibits an isotropic and delocalized nature, with an energy that is significantly lower compared to that of C-60. The isotropic overlapping of p(z)-SAMOs in the condensed monolayer of Li@C-60 results in a laterally homogeneous STM image contributing to the formation of a free-electron-like states. These findings make an important step toward further basic research and applicative utilization of Li@C-60 SAMOs.
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16.
  • Suresh, Rahul, et al. (author)
  • Cyclo[18]carbon Formation from C(18)Br(6) and C18(CO)(6) Precursors
  • 2022
  • In: The Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 13:44, s. 10318-10325
  • Journal article (peer-reviewed)abstract
    • Although cyclo[18]carbon has been isolated experimentally from two precursors, C18Br6 and C-18(CO)(6), no reaction mechanisms have yet been explored. Herein, we provide insight into the mechanism behind debromination and decarbon-ylation. Both neutral precursors demonstrate high activation barriers of similar to 2.3 eV, while the application of an electric field can lower the barriers by 0.1-0.2 eV. The barrier energy of the anion-radicals is found to be significantly lower for C18Br6 compared to C-18(CO)(6), confirming a considerably higher yield of cylco[18] carbon when the C18Br6 precursor is used. Elongation of the C-Br bond in the anion-radical confirms its predissociation condition. Natural bonding orbital analysis shows that the stability of C-Br and C-CO bonds in the anion-radicals is lower compared to their neutral species, indicating a possible higher yield. The applied analysis provides crucial details regarding the reaction yield of cyclo[18]carbon and can serve as a general scheme for tuning reaction conditions for other organic precursors.
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17.
  • Wu, Hongwei, et al. (author)
  • Multidimensional Structure Conformation of Persulfurated Benzene for Highly Efficient Phosphorescence
  • 2021
  • In: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 13:1, s. 1314-1322
  • Journal article (peer-reviewed)abstract
    • It is a challenge to acquire, realize, and comprehend highly emissive phosphorescent molecules. Herein, we report that, using persulfurated benzene compounds as models, phosphorescence can be strongly enhanced through the modification of molecular conformation and crystal growth conditions. By varying the peripheral groups in these compounds, we were able to control their molecular conformation and crystal growth mode, leading to one- (1D), two- (2D), and three-dimensional (3D) crystal morphologies. Two kinds of typical molecular conformations were separately obtained in these crystals through substituent group control or the solvent effect. Importantly, a symmetrical 3,3-conformer exhibits that a planar central benzene ring prefers a 3D-type crystal growth mode, demonstrating high phosphorescence efficiency. Such outcome is attributed to the strong crystal protection effect of the 3D crystal and the bright global minimum (GM) boat-like T-1 state of the symmetrical 3,3-conformer. The conformation studies further reveal small deformation of the inner benzene ring in both singlet and triplet states. The GM boat-like T-1 state is indicated by theoretical calculations, which is far away from the conical intersection (CI) point between the S-0 and T-1 potential energy surfaces. Meanwhile, the small energy gap between S-1 and T-1 states and the considerable spin-orbit coupling matrix elements allow an efficient population of the T-1 state. Combined with the crystal protection and conformation effect, the 3,3- conformer crystal shows high phosphorescence efficiency. The unsymmetrical 2,4-conformer conformation with the twisted central benzene ring leads to 1D or 2D crystal growth mode, which has a weak crystal protection effect. In addition, the unsymmetrical conformation has a dark GM T-1 state that is very close to the T-1-S-0 CI point, implying an efficient nonradiative T-1-S-0 quenching. Thus, weak phosphorescence was observed from the unsymmetrical conformation. This study provides an insight for the development of highly emissive phosphorescent materials.
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18.
  • Zhao, Xue, et al. (author)
  • BCN-Encapsulated Nano-nickel Synergistically Promotes Ambient Electrochemical Dinitrogen Reduction
  • 2020
  • In: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 12:28, s. 31419-31430
  • Journal article (peer-reviewed)abstract
    • The electricity provided by solar or wind power can drive nitrogen in the atmosphere, combining with ubiquitous water to form ammonia, and distributed production methods can alleviate the irreversible damage to the environment caused by the energy-intensive Haber-Bosch process. Here, we have designed a novel Ni-doped BCN heterojunction (S/M-BOPS-1) as a catalyst for the electrochemical nitrogen reduction reaction (NRR). The ammonia yield rate and Faraday efficiency in NRR driven by S/M-BOPS-1 reach up to 16.72 mu g(-1) h(-1) cm(-2) and 13.06%, respectively. Moreover, S/M-BOPS-1 still maintains high NRR activity and excellent stability after recycling for eight times and long-time operation of 12 h. Using density functional theory calculations, we reveal a possible NRR path for N-2 to NH3 on Ni, BCN, and the S/M-BOPS-1 composite surfaces. The interaction between the BCN matrix and Ni nanoparticles promotes a synergetic effect for the electrochemical NRR efficiency due to the partial electron transfer from the Ni particles to BCN that inhibits hydrogen evolution reaction and decreases the rate-determining step on Ni surfaces toward NRR by similar to 1.5 times. Therefore, efficient NRR performance can be achieved by tuning the electronic properties of non-noble metals via the formation of a heterointerface.
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19.
  • Zhao, Xue, et al. (author)
  • Efficient Ambient Electrocatalytic Ammonia Synthesis by Nanogold Triggered via Boron Clusters Combined with Carbon Nanotubes
  • 2020
  • In: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 12:38, s. 42821-42831
  • Journal article (peer-reviewed)abstract
    • Currently, the development of stable electrochemical nitrogen reduction reaction (ENRR) catalysts with high N-2 conversion activity and low cost to instead of the traditional Haber-Bosch ammonia production process of high-energy consumption remains a great challenge for researchers. Here, we have immobilized reductive closo-[B12H11](-) boron clusters on a carbon nanotubes (CNT) surface and have successfully prepared a novel Au-CNT catalyst with extraordinary ENRR activity after adding HAuCl4 to the CNT-[B12H11](-) precursor. The excellent properties of ammonia yield (57.7 mu g h(-1) cm(-2)) and Faradaic efficiency (11.97%) make it possible to achieve using this Au-CNT catalyst in large-scale industrial production of ammonia. Furthermore, its outstanding cyclic stability and long-term tolerability performance make it one of the most cost-effective catalysts to date. Here, by means of density functional theory we disclose the associative mechanism of N-2-to-NH3 conversion on the Au(111) surface, providing visual theoretical support for the experimental results.
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20.
  • Zhao, Xue, et al. (author)
  • Potassium ions promote electrochemical nitrogen reduction on nano-Au catalysts triggered by bifunctional boron supramolecular assembly
  • 2020
  • In: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 8:26, s. 13086-13094
  • Journal article (peer-reviewed)abstract
    • The electrochemical way of reducing nitrogen to ammonia presents green and economic advantages to dial down irreversible damage caused by the energy-intensive Haber-Bosch process. Here, we introduce an advanced catalyst CB[7]-K-2[B12H12]@Au with highly dispersed and ultrafine nano-gold. The CB[7]-K-2[B12H12]@Au electrochemically driven ammonia yield and Faraday efficiency is as high as 41.69 mu g h(-1)mg(cat.)(-1)and 29.53% (at -0.4 Vvs.RHE), respectively, reaching the US Department of Energy (DOE) utility index of ambient ammonia production along with excellent cycle stability and tolerance that indicates a high potential of industrial practical value. Experimental results and theoretical calculations show that the key to an excellent electrochemical nitrogen reduction performance lies in the smart design of the CB[7]-K-2[B12H12]@Au catalyst combining the stable substrate anchored Au nanoparticles and K(+)ions that effectively prevent the hydrogen evolution reaction and polarize *N(2)leading to lowering of the rate determining step. This research will promote the further development of electrochemical ammonia production with low environmental impact.
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21.
  • Chen, Hualong, et al. (author)
  • Direct Observation of Photon Induced Giant Band Renormalization in 2D PdSe2 Dichalcogenide by Transient Absorption Spectroscopy
  • 2023
  • In: Small. - : John Wiley & Sons. - 1613-6810 .- 1613-6829. ; 19:46
  • Journal article (peer-reviewed)abstract
    • Insight into fundamental light-matter interaction as well as underlying photo-physical processes is crucial for the development of novel optoelectronic devices. Palladium diselenide (PdSe2), an important representative of emerging 2D noble metal dichalcogenides, has gain considerable attention owing to its unique optical, physical, and chemical properties. In this study, 2D PdSe2 nanosheets (NSs) are prepared using the liquid-phase exfoliation method. A broadband carrier relaxation dynamics from visible to near-infrared bands are revealed using a time-resolved transient absorption spectrometer, giving results that indicate band filling and bandgap renormalization (BGR) effects in the 2D PdSe2 NSs. The observed blue-shift of the transient absorption spectra at the primary stage and the subsequent red-shift can be ascribed to this BGR effect. These findings reveal the many-body character of the 2D TMDs material and may hold keys for applications in the field of optoelectronics and ultrafast photonics.
  •  
22.
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23.
  • Deng, Xuefan, et al. (author)
  • A new strategy for boron cluster-based metal boride (Co2B) synthesis and its applicability to electrocatalytic nitrate reduction
  • 2024
  • In: Chemical Engineering Journal. - : Elsevier. - 1385-8947 .- 1873-3212. ; 485
  • Journal article (peer-reviewed)abstract
    • To achieve efficient conversion of nitrate to ammonia, it is necessary to design and develop electrode materials with high activity and efficiency for the electrocatalytic reduction reaction of nitrate (NO3RR). Due to its unique semi-metallic properties, the vacancy orbitals of boron are prone to accommodate electrons, so doping element B with transition metals is expected to change the local electronic configuration of the metal, which in turn affects the corresponding catalytic reaction. Here, we propose a new strategy for the preparation of metal borides by using dodecahydro-closo-dodecaborate and Co2+ complexed and calcined to prepare a novel metal boride-Co2B for electrocatalytic nitrate reduction. This modification considerably enhances the performance of NO3RR. Co2B exhibited a Faradaic efficiency of NH4+ (FENH4+) as high as 96.61 % at -0.5 V vs. RHE, achieving a remarkable NH4+ yield of 5.73 mg h-1 mgcat - 1. This study provides a new approach for designing catalysts for environmentallyfriendly ammonia synthesis.
  •  
24.
  • Gao, Lingfeng, et al. (author)
  • A Facile Approach for Elemental-Doped Carbon Quantum Dots and Their Application for Efficient Photodetectors
  • 2021
  • In: Small. - : John Wiley & Sons. - 1613-6810 .- 1613-6829. ; 17:52
  • Journal article (peer-reviewed)abstract
    • The present work demonstrates a facile hydrothermal approach to synthesize lanthanide-doped carbon quantum dots (CQDs) with europium and/or gadolinium elements. Taking the advantage of broadband adsorption in the ultraviolet-visible region, the doped QDs are directly used as building blocks for photo-electrochemical (PEC)-type photodetectors (PDs) and their performance is systematically investigated under various conditions. The europium (Eu) and gadolinium (Gd) co-doped (C:EuGd) QDs exhibit better photo-response than the single-elemental doped ones and also show outstanding long-term stability. According to the apparent response to light from 350 to 400 nm, the C:EuGd QDs are demonstrated to hold great potential for narrow-band PDs. This work highlights the practical applications of lanthanide-doped CQDs for PDs, and the results are beneficial for the development of elemental-doped CQDs in general.
  •  
25.
  • Gao, Lingfeng, et al. (author)
  • Applications of Few-Layer Nb2C MXene : Narrow-Band Photodetectors and Femtosecond Mode-Locked Fiber Lasers
  • 2021
  • In: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 15:1, s. 954-965
  • Journal article (peer-reviewed)abstract
    • Although the physicochemical properties of niobium carbide (Nb2C) have been widely investigated, their exploration in the field of photoelectronics is still at the infancy stage with many potential applications that remain to be exploited. Hence, it is demonstrated here that few-layer Nb2C MXene can serve as an excellent building block for both photoelectrochemical-type photodetectors (PDs) and mode-lockers. We show that the photoresponse performance can be readily adjusted by external conditions and that Nb2C NSs exhibit a great potential for narrow-band PDs. The demonstrated mechanism was further confirmed by work functions predicted by density functional theory calculations. In addition, as an optical switch for passively mode-locked fiber lasers, ultrastable pulses can be demonstrated in the telecommunication and mid-infrared regions for Nb2C MXene, and as high as the 69th harmonic order with 411 MHz at the center wavelength of 1882 nm can be achieved. These intriguing results indicate that few-layer Nb2C nanosheets can be used as building blocks for various photoelectronic devices, further broadening the application prospects of two-dimensional MXenes.
  •  
26.
  • Gao, Lingfeng, et al. (author)
  • Hetero-MXenes : Theory, Synthesis, and Emerging Applications
  • 2021
  • In: Advanced Materials. - : John Wiley & Sons. - 0935-9648 .- 1521-4095. ; 33:10
  • Research review (peer-reviewed)abstract
    • Since their discovery in 2011, MXenes (abbreviation for transition metal carbides, nitrides, and carbonitrides) have emerged as a rising star in the family of 2D materials owing to their unique properties. Although the primary research interest is still focused on pristine MXenes and their composites, much attention has in recent years been paid also to MXenes with diverse compositions. To this end, this work offers a comprehensive overview of the progress on compositional engineering of MXenes in terms of doping and substituting from theoretical predictions to experimental investigations. Synthesis and properties are briefly introduced for pristine MXenes and then reviewed for hetero-MXenes. Theoretical calculations regarding the doping/substituting at M, X, and T sites in MXenes and the role of vacancies are summarized. After discussing the synthesis of hetero-MXenes with metal/nonmetal (N, S, P) elements by in situ and ex situ strategies, the focus turns to their emerging applications in various fields such as energy storage, electrocatalysts, and sensors. Finally, challenges and prospects of hetero-MXenes are addressed. It is anticipated that this review will be beneficial to bridge the gap between predictions and experiments as well as to guide the future design of hetero-MXenes with high performance.
  •  
27.
  • Gao, Lei, et al. (author)
  • Hydrophilic Cocrystals with Water Switched Luminescence
  • 2024
  • In: Angewandte Chemie International Edition. - : John Wiley & Sons. - 1433-7851 .- 1521-3773. ; 63:8
  • Journal article (peer-reviewed)abstract
    • Utilizing water molecules to regulate the luminescence properties of solid materials is highly challenging. Herein, we develop a strategy to produce water-triggered luminescence-switching cocrystals by coassembling hydrophilic donors with electron-deficient acceptors, where 1,2,4,5-Tetracyanobenzene (TCNB) was used as the electron acceptor and pyridyl benzimidazole derivatives were used as the electron donors enabling multiple hydrogen-bonds. Two cocrystals, namely 2PYTC and 4PYTC were obtained and showed heat-activated emission, and such emission could be quenched or weakened by adding water molecules. The cocrystal structure exhibited the donor molecule that can form multiple hydro bonds with water and acceptor molecules due to the many nitrogen atoms of them. The analyses of the photophysical data, powder X-ray diffraction, and other data confirmed the reversible fluorescence "on-off" effects were caused by eliminating and adding water molecules in the crystal lattice. The density functional theory calculations indicate that the vibration of the O-H bond of water molecules in the cocrystal can absorb the excitation energy and suppress fluorescence. Furthermore, the obtained cocrystals also showed temperature, humidity, and H+/NH4+ responsive emission behavior, which allows their applications as thermal and humidity sensors, and multiple information encryptions. This research paves the way for preparing intelligent hydrophilic organic cocrystal luminescent materials. Hydrophilic donors with electron-deficient acceptors were coassembled to achieve luminescence-switching cocrystals triggered by water molecules. The obtained cocrystals show a strong water absorption ability and excellent fluorescence properties. The emission of cocrystals can be reversibly switched by heating and water. Finally, the obtained cocrystals show potential applications in temperature-humidity and acid-base responses.+image
  •  
28.
  • Gao, Lingfeng, et al. (author)
  • Optical Properties of Few-Layer Ti3CN MXene : From Experimental Observations to Theoretical Calculations
  • 2022
  • In: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 16:2, s. 3059-3069
  • Journal article (peer-reviewed)abstract
    • Despite the emerging interest in research and development of Ti3CN MXene nanosheet (NS)-based optoelectronic devices, there is still a lack of in-depth studies of the underlying photophysical processes, like carrier relaxation dynamics and nonlinear photon absorption, operating in such devices, hindering their further and precise design. In this paper, we attempt to remedy the situation by fabricating few-layer Ti3CN NSs via combining selective etching and molecular intercalation and by investigating the carrier relaxation possesses and broadband nonlinear optical responses via transient absorption and Z-scan techniques. These results are complemented by first-principle theoretical analyses of the optical properties. Both saturable absorption and reverse saturable absorption phenomena are observed due to multiphoton absorption effects. The analysis of these results adds to the understanding of the basic photophysical processes, which is anticipated to be beneficial for the further design of MXene-based devices.
  •  
29.
  • Gao, Lingfeng, et al. (author)
  • PbSe Nanocrystals Produced by Facile Liquid Phase Exfoliation for Efficient UV-Vis Photodetectors
  • 2021
  • In: Advanced Functional Materials. - : John Wiley & Sons. - 1616-301X .- 1616-3028. ; 31:17
  • Journal article (peer-reviewed)abstract
    • Lead selenide (PbSe)-based nanomaterials have been extensively investigated as building blocks for next-generation optoelectronic devices owing to their unique properties. In this work, PbSe nanocrystals (NCs) have been successfully fabricated by a facile liquid phase exfoliation approach and directly applied as active materials for photo-electrochemical (PEC)-type photodetectors (PDs). Taking advantage of broadband absorption and fast carrier dynamics, the PbSe NCs-based PDs exhibit excellent photo-current density (11.88 μA cm−2), photo-responsivity (12.37 mA W−1), response/recovery time (0.12/0.13 s), and long-term cycling stability. The working mechanism of PbSe NCs-based PDs is explored by density functional theory calculations based on their structural and electronic properties under various conditions. It is anticipated that this contribution paves the way to readily fabricate low-dimensional PbSe NCs and extend their practical applications in PEC-type PDs.
  •  
30.
  • Gao, Lingfeng, et al. (author)
  • Ultra-Small 2D PbS Nanoplatelets : Liquid-Phase Exfoliation and Emerging Applications for Photo-Electrochemical Photodetectors
  • 2021
  • In: Small. - : John Wiley & Sons. - 1613-6810 .- 1613-6829. ; 17:5
  • Journal article (peer-reviewed)abstract
    • 2D PbS nanoplatelets (NPLs) form an emerging class of photoactive materials and have been proposed as robust materials for high-performance optoelectronic devices. However, the main drawback of PbS NPLs is the large lateral size, which inhibits their further investigations and practical applications. In this work, ultra-small 2D PbS NPLs with uniform lateral size (11.2 +/- 1.7 nm) and thickness (3.7 +/- 0.9 nm, approximate to 6 layers) have been successfully fabricated by a facile liquid-phase exfoliation approach. Their transient optical response and photo-response behavior are evaluated by femtosecond-resolved transient absorption and photo-electrochemical (PEC) measurements. It is shown that the NPLs-based photodetectors (PDs) exhibit excellent photo-response performance from UV to the visible range, showing extremely high photo-responsivity (27.81 mA W-1) and remarkable detectivity (3.96 x 10(10) Jones), which are figures of merit outperforming currently reported PEC-type PDs. The outstanding properties are further analyzed based on the results of first-principle calculations, including electronic band structure and free energies for the oxygen evolution reaction process. This work highlights promising applications of ultra-small 2D PbS NPLs with the potential for breakthrough developments also in other fields of optoelectronic devices.
  •  
31.
  • Jiang, Xiantao, et al. (author)
  • Two-dimensional MXenes : From morphological to optical, electric, and magnetic properties and applications
  • 2020
  • In: Physics reports. - : Elsevier. - 0370-1573 .- 1873-6270. ; 848
  • Research review (peer-reviewed)abstract
    • MXenes, generally referring to two-dimensional (2D) transition-metal carbides, nitrides, and carbonitrides, have received tremendous attention since the first report in 2011. Extensive experimental and theoretical studies have unveiled their enormous potential for applications in optoelectronics, photonics, catalysis, and many other areas. Because of their intriguing mechanical and electronic properties, together with the richness of elemental composition and chemical decoration, MXenes are poised to provide a new 2D nanoplatform for advanced optoelectronics. This comprehensive review, intended for a broad multidisciplinary readership, highlights the state-of-the-art progress on MXene theory, materials synthesis techniques, morphology modifications, opto-electromagnetic properties, and their applications. The efforts exploring the device performance limits, steric configurations, physical mechanisms, and novel application boundaries are comprehensively discussed. The review is concluded with a compelling perspective, outlook as well as non-trivial challenges in future investigation of MXene-based nano-optoelectronics.
  •  
32.
  • Kuklin, A. V., et al. (author)
  • Quasiparticle electronic structure and optical spectra of single-layer and bilayer PdSe2 : Proximity and defect-induced band gap renormalization
  • 2019
  • In: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 99:24
  • Journal article (peer-reviewed)abstract
    • The fundamental properties of recently synthesized single- and bilayer PdSe2 are investigated using accurate many-body perturbation GW theory to quantitatively examine their electronic structure and explain the insufficiency of previously reported experimental and theoretical results. Including electron-hole interactions responsible for exciton formation, we solve the Bethe-Salpeter equation on top of the GW0 approximation to predict the optical properties. The fundamental quasiparticle band gaps of single- and bilayer PdSe2 are 2.55 and 1.89 eV, respectively. The optical gap of monolayer PdSe2 reduces significantly due to a large excitonic binding energy of 0.65 eV comparable to that of MoSe2, while an increase of the layer number decreases the excitonic binding energy to 0.25 eV in bilayer PdSe2. The giant band gap renormalization of ∼36-38% in the bilayer (BL) PdSe2/graphene heterostructure has a high impact on the construction of PdSe2-based devices and explains the experimentally observed band gap. The small value of the experimental optical gap of single-layer (SL) PdSe2 (1.3 eV) can be explained by the presence of Se vacancies, which can drop the Tauc-estimated optical gap to ∼1.32 eV. The absorption spectra of both mono- and bilayer PdSe2 cover a wide region of photon energy, demonstrating promising application in solar cells and detectors. These findings provide a basis for a deeper understanding of the physical properties of PdSe2 and PdSe2-based heterostructures.
  •  
33.
  • Kuklin, Artem V., et al. (author)
  • Superatom Molecular Orbitals of Li@C-60 : Effects of the Li Position and the Substrate
  • 2022
  • In: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 126:37, s. 15891-15898
  • Journal article (peer-reviewed)abstract
    • Understanding the character of superatom molecular orbitals (SAMOs) of fullerenes, especially those of the endohedral fullerenes, can potentially facilitate the utility of these molecules in organic electronics beyond conventional limits. However, the detailed nature of SAMOs in molecular films on substrates has yet to be unraveled. Using density functional theory, we investigate the wavefunction distributions and electronic structures of SAMO states of a Li@C-60 monolayer in dependence on the position of Li within the cage and the type of substrate species. We find that the characteristics of the SAMOs in terms of shape and energy are quite sensitive to the Li position due to different charge redistributions. The substrate affects the intermolecular distances in the Li@C-60 films and modifies the widths and dispersion of the SAMO bands while retaining energetics similar to that of the isolated Li@C-60 monolayer. The substrate also affects the SAMO effective masses, making it possible to tune them via substrate-induced interaction. A properly chosen substrate can so be beneficial for Li confinement and SAMO stability, reflecting the molecule-substrate interaction and the charge transfer at the interface. These findings provide insights into the design and engineering of SAMOs of molecular films.
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34.
  • Kuklin, Artem V., et al. (author)
  • Two-Dimensional Gold Halides : Novel Semiconductors with Giant Spin-Orbit Splitting and Tunable Optoelectronic Properties
  • 2020
  • In: The Journal of Physical Chemistry Letters. - : AMER CHEMICAL SOC. - 1948-7185. ; 11:22, s. 9759-9765
  • Journal article (peer-reviewed)abstract
    • We introduce a new family of 2D materials with unique structure and optoelectronic properties, namely, single-layer gold(I) halides (AuHals). We propose their stability as well as structural, electronic, and optical properties using first-principles calculations. The cleavage energy is found to be similar to that of graphene from graphite, indicating the possibility for mechanical exfoliation. We show that AuHals are stable and have tunable direct (AuBr) and indirect (AuI) band gaps depending on the number of layers. We discuss the possible origin of the giant spin-orbit coupling (SOC) induced conduction band splitting in terms of orbital-decomposed band structure to guide future investigations on the design of materials with highly effective SOC. Exceptionally high excitonic binding energy, high hole mobility, and tunable band gaps indicate that AuHals are promising candidates for optoelectronic devices with excellent performance.
  •  
35.
  • Melchakova, Iu, et al. (author)
  • Towards spin quantum materials : Structure and potential energy profiles of weakly interacting arrays of iron porphyrin complexes at graphene armchair nanoribbon
  • 2020
  • In: Chemical Physics Letters. - : Elsevier. - 0009-2614 .- 1873-4448. ; 755
  • Journal article (peer-reviewed)abstract
    • The atomic structure, the rates of atomic spin polarization and potential energy profiles of heterostructure composed by iron porphyrin deposited on armchair graphene nanoribbon (FeP/AGNR) were investigated using density functional theory (DFT). The multiplicity of the Fe+2 ion in iron porphyrin for all possible types of coordination was determined as a triplet. Two possible 12 and 16 types of FeP coordination on AGNR were located with 0.43 and 0.15 kcal/mol forward and reversed potential barriers and 39% and 61% Arrhenius populations, respectively. It was found that FeP/AGNR can be used for perspective spin quantum applications due to localized spin-flip transition in IRA spectral region.
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36.
  • Suresh, Rahul, et al. (author)
  • Revolutionizing physics : a comprehensive survey of machine learning applications
  • 2024
  • In: Frontiers in Physics. - : Frontiers Media S.A.. - 2296-424X. ; 12
  • Research review (peer-reviewed)abstract
    • In the context of the 21st century and the fourth industrial revolution, the substantial proliferation of data has established it as a valuable resource, fostering enhanced computational capabilities across scientific disciplines, including physics. The integration of Machine Learning stands as a prominent solution to unravel the intricacies inherent to scientific data. While diverse machine learning algorithms find utility in various branches of physics, there exists a need for a systematic framework for the application of Machine Learning to the field. This review offers a comprehensive exploration of the fundamental principles and algorithms of Machine Learning, with a focus on their implementation within distinct domains of physics. The review delves into the contemporary trends of Machine Learning application in condensed matter physics, biophysics, astrophysics, material science, and addresses emerging challenges. The potential for Machine Learning to revolutionize the comprehension of intricate physical phenomena is underscored. Nevertheless, persisting challenges in the form of more efficient and precise algorithm development are acknowledged within this review.
  •  
37.
  • Suresh, Rahul, et al. (author)
  • Superatom Molecular Orbitals of Endohedral C82
  • 2023
  • In: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 127:39, s. 8126-8132
  • Journal article (peer-reviewed)abstract
    • Understanding superatom molecular orbital (SAMO) states in fullerene derivatives has been in the limelight ever since the first discovery of SAMOs owing to the fundamental interest in this topic as well as to the possible applications in molecular switches and other organic electronics. Nevertheless, very few reports have been published on SAMO states of larger fullerenes so far. Using density functional theory, we attempt to partially remedy this situation by presenting a study on SAMO states in C(82 )and its Ca and Sc endohedrally doped derivatives, comparing results with previous relevant findings for C-60. We find that C-82 possesses higher SAMO energies compared to C-60, as associated with the symmetry of the molecule, and that endohedral doping leads to energetically favorable side positions of Ca and Sc inside the C-82 cage. Among the two, Sc@C-82 has more stable SAMO states compared to Ca@C(82 )as reflected by the shift in the density of states, while the charge states are found to be similar. In the case of the monolayer form, the p z - and 2s-SAMO orbitals overlap with the nearest neighbors, causing parabolic band dispersion with the formation of near free electron states and that the SAMO state energies move closer to the Fermi energy compared to the related molecules. These findings provide promising information about the distribution of SAMO states in C-82 fullerene, which can be further relevant in studies of SAMO states of higher fullerenes and for coming applications of these systems.
  •  
38.
  • Venkatakrishnan, Padmavathy, et al. (author)
  • Superatom molecular orbital in C80
  • 2024
  • In: Journal of Computational Chemistry. - : John Wiley & Sons. - 0192-8651 .- 1096-987X. ; 45:12, s. 827-833
  • Journal article (peer-reviewed)abstract
    • The Superatom Molecular Orbitals (SAMO) in fullerene derivatives are of great interests which gives a wide basement for many electronic applications. In this work, the Density Functional Theory reveals the SAMO states of endohedrally doped C-80 derivatives with Li, Sc, Mn, Ti, Ca, Fe, and Co atoms in molecular and periodic structures. The choice and position of metal atoms in endohedrally doped C-80 derivatives largely affects the orientation of SAMO energies and wavefunction distributions. Among various derivatives, the Co-substituted C-80 constitutes the lowest SAMO energy. The charge transfer study infers the influence of metal atoms inside the cage on SAMO energies. At higher energies, p(z)-, 2(s)-, and p(xy)- SAMO bands have been overlapped with higher dispersion bands which depict the increased intermolecular interaction in delocalized bands causing a larger dispersion. These results give new insights for future studies on lowering SAMO energy nearly to the fermi level in higher fullerenes.
  •  
39.
  • Wang, Zhengxi, et al. (author)
  • Platinum group nanoparticles doped BCN matrix : Efficient catalysts for the electrocatalytic reduction of nitrate to ammonia
  • 2024
  • In: Journal of Colloid and Interface Science. - : Elsevier. - 0021-9797 .- 1095-7103. ; 664, s. 84-95
  • Journal article (peer-reviewed)abstract
    • The effective treatment of nitrate (NO3- ) in water as a nitrogen source and electrocatalytic NO3- reduction to ammonia (NH3 ) (NRA) have become preferred methods for NO3--to-NH3 conversion. Achieving efficient NO3--to-NH3 conversion requires the design and development of electrode materials with high activity and efficiency for the electrocatalytic NRA reaction. Herein, based on the special properties of dodecahydro- closo -dodecaborate anions, a BCN matrix, loaded with platinum -group nanoparticles (namely, Pd/BCN, Pt/BCN, and Ru/BCN), was prepared using a simple method for the electrocatalytic NRA reaction. Results showed that Pd/BCN exerts the best catalytic effect on the NRA reaction. The NH3 production rate reached 12.71 mg h- mgcat.-1 at -1.0 V vs. RHE. Faraday efficiency reached 91.79 %, which can be attributed to the more uniform distribution of the nanoparticles. Furthermore, Pd/BCN exhibited high cycling stability and resistance to ionic interference. Moreover, the density functional theory calculations indicated that small and well -distributed Pd nanoclusters in the BCN matrix have a large active surface area and promote the catalytic process. This study provides a new strategy to design catalysts for green ammonia synthesis.
  •  
40.
  • Xu, Xiaoran, et al. (author)
  • Synthesis of iron-boride/carbon-nitride composites and their applications in chemodynamic therapy
  • 2024
  • In: Journal of Colloid and Interface Science. - : Elsevier. - 0021-9797 .- 1095-7103. ; 658, s. 276-285
  • Journal article (peer-reviewed)abstract
    • Chemodynamic therapy (CDT) is an emerging treatment strategy that inhibits tumor growth by catalyzing the generation of reactive oxygen species (ROS), such as hydroxyl radicals (center dot OH), using specific nanomaterials. Herein, we have developed a new class of iron-based nanomaterials, i.e., iron-based borides (FeB), using the superchaotropic effect of a boron cluster (closo-[B12H1212-) and organic ligands, followed by high-temperature calcination. Experimental data and theoretical calculations revealed that FeB nanoparticles exhibit a Fentonlike effect, efficiently decomposing hydrogen peroxide into center dot OH and thus increasing the concentration of ROS. FeB nanomaterials demonstrate excellent catalytic performance, efficiently generate ROS, and exert significant antitumor effects in cell experiments and animal models. Therefore, FeB nanomaterials have
  •  
41.
  • Yamada, Yoichi, et al. (author)
  • Field emission angular distribution from single molecules
  • 2023
  • In: Carbon. - : Elsevier. - 0008-6223 .- 1873-3891. ; 213
  • Journal article (peer-reviewed)abstract
    • We demonstrate that the field emission from a single molecule at the apex of a metallic tip exhibits a well-defined angular distribution pattern (field emission angular distribution, FAD) with a spherical harmonics shape, regardless of the species of the molecule. From carefully controlled simultaneous measurements of the emission pattern, the emission current and emission energy, we deduced the formation mechanism of the FAD pattern in which the electron from the metallic tip resonantly tunnels into vacuum via a molecule-induced state situated at the Fermi level of the tip. The characteristic FAD patterns were consistent with the Fourier transform of the superatom molecular orbitals (SAMOs). Thus, the present method is unique for real-time imaging of the SAMOs, or the low-lying Rydberg states, of single molecules.
  •  
42.
  • Zhao, Xue, et al. (author)
  • Copper confined in vesicle-like BCN cavities promotes electrochemical reduction of nitrate to ammonia in water
  • 2021
  • In: Journal of Materials Chemistry A. - : ROYAL SOC CHEMISTRY. - 2050-7488 .- 2050-7496. ; 9:41, s. 23675-23686
  • Journal article (peer-reviewed)abstract
    • Electrochemical methods to convert high-concentration nitrates present in sewage into high-value-added ammonia do not just alleviate the problem of environmental pollution but also provide less energy-intensive alternatives to the Haber-Bosch process. In this work, a metal-boron organic polymer precursor was annealed at high temperature to obtain copper nanoparticles encapsulated in a vesicle-like BCN matrix (BCN@Cu). In the electrochemical reduction of nitrate (E-NIRR), this species exhibited excellent catalytic activity. Specifically, the ammonia yields of BCN@Cu under applied potentials of -0.3 V, -0.4 V, -0.5 V, and -0.6 V versus the reversible hydrogen electrode were 271.1 mu mol h(-1) mg(cat.)(-1), 354.8 mu mol h(-1) mg(cat.)(-1), 435.6 mu mol h(-1) mg(cat.)(-1), and 576.2 mu mol h(-1) mg(cat.)(-1), respectively, and the corresponding Faraday efficiencies were 86.3%, 88.0%, 89.3%, and 88.9%. Isotope labeling experiments with (NO3-)-N-15 confirmed that the detected ammonia had originated from the electrochemical reduction of NO3- on the catalyst surface. Moreover, the E-NIRR activity of BCN@Cu remained high even after using it ten consecutive times or 20 h of continuous operation, suggesting the practicality of the industrial application of BCN@Cu. The presence of copper was key in determining BCN@Cus E-NIRR activity, while the presence of boron greatly improved its catalytic performance. Furthermore, density functional theory calculations indicated that BCN does not itself promote the reaction but rather assists the dispersion of Cu nanoparticles, thereby expanding the catalysts active surface area.
  •  
43.
  • Zhao, X., et al. (author)
  • Persistent radical pairs trigger nano-gold to highly efficiently and highly selectively drive the value-added conversion of nitroaromatics
  • 2021
  • In: Chem Catalysis. - : Elsevier BV. - 2667-1107 .- 2667-1093. ; 1:5, s. 1118-1132
  • Journal article (peer-reviewed)abstract
    • The development of advanced catalyst materials capable of efficiently capturing solar energy to drive the beneficial conversion of chemicals is a key part of the blueprint for “liquid sunlight.” Here, highly dispersed ultrafine nano-Au (B/TPTH3@Au) was anchored in situ on B/TPTH3 formed by alternate cross-linking of closo-[B12H12]2− and protonated 2,4,6-tris(4-pyridyl)-1,3,5-triazine. B/TPTH3@Au is an outstanding heterogeneous photocatalyst that converts low-value-added nitroaromatics into high-value-added azoaromatics. Compared with the slow kinetics of previous catalysts, the time required for the conversion of nitroaromatics to azoaromatics driven by B/TPTH3@Au is reduced by at least 10 times. These improvements could be derived from the synergy between the carrier B/TPTH3 (as a stable radical pair) and the nano-gold, including continuous electron transport in the functional carrier B/TPTH3 and the anchoring of highly dispersed ultrafine nano-Au with a strong localized surface plasmon resonance effect.
  •  
44.
  • Zhao, Xue, et al. (author)
  • Simultaneous anchoring of Ni nanoparticles and single-atom Ni on BCN matrix promotes efficient conversion of nitrate in water into high-value-added ammonia
  • 2022
  • In: Chemical Engineering Journal. - : Elsevier. - 1385-8947 .- 1873-3212. ; 433:Part 2
  • Journal article (peer-reviewed)abstract
    • Electrochemical synthesis of ammonia driven by clean energy is expected to realize the supply of ammonia for distributed production of industry and agriculture. Here, nickel nanoparticles and nickel in the form of single atoms were simultaneously anchored on the electrochemically active carrier BCN matrix through a structured domain strategy, which realized a high-efficiency, high-value-added, conversion of nitrate in sewage. Specifically, the electrochemical nitrate reduction reaction (NIRR) driven by BCN@Ni in alkaline media achieves an ammonia yield rate as high as 2320.2 μg h−1 cm−2 (at −0.5 V vs RHE), and Faraday efficiency as high as 91.15% (at −0.3 V vs RHE). Even in neutral and acidic media, the ammonia yield rates of NIRR driven by BCN@Ni are as high as 1904.2 μg h−1 cm−2 and 2057.4 μg h−1 cm−2, respectively (at −0.4 V vs RHE). The 15NO3- isotope labeling experiment verified that the recorded ammonia all came from the electrochemical reduction of NO3– on BCN@Ni. Density functional theory (DFT) calculations show that both nano-Ni and single-atom Ni in BCN@Ni have the ability to electrochemically convert NO3– into NH3, and that the addition of BCN can further promote the NIRR on Ni.
  •  
45.
  • Zhao, Xue, et al. (author)
  • Two-dimensional BCN matrix inlaid with single-atom-Cu driven electrochemical nitrate reduction reaction to achieve sustainable industrial-grade production of ammonia
  • 2021
  • In: APPLIED MATERIALS TODAY. - : Elsevier. - 2352-9407. ; 25
  • Journal article (peer-reviewed)abstract
    • Electrochemical methods have been proven to effectively eliminate nitrates in sewage and convert them into high value-added ammonia products. Here, after annealing treatment of metal boron cluster organic polymers formed by the combination of 1,10-phenanthroline, Cu2+ and closo-[B12H12](2)(-), a Cu single-atom doped BCN (B-doped CN) with a diamond-shaped nanosheet structure was obtained. In the electrochem-ical reduction reaction of nitrate, BCN-Cu exhibits excellent catalytic activity, specifically: 1) the ammonia yield rate reached as high as 498.85 mu g h(-1) cm(-2), 1047.14 mu g h(-1) cm(-2), 1900.07 mu g h(-1) cm(-2) and 3358.74 mu g h(-1) cm(-2) at -0.3 V, -0.4 V, -0.5 V and -0.6 V vs reversible hydrogen electrode, respectively, and Faradaic efficiency is 95.90%, 97.28%, 98.23% and 97.37%; 2) after repeated use of BCN-Cu 10 times or continuous operation for 16 h, the activity against electrochemical reduction reaction of nitrate anions is almost unchanged. The (NO3-)-N-15 isotopic labeling experiment proved that the detected NH3 comes from the reduction of NO3- on BCN-Cu. Control experiments show that the presence of Cu determines whether BCN-Cu has the possibility of catalyzing electrochemical reduction reactions of nitrate, and the presence of the B element enhances the catalytic activity of BCN-Cu. Density functional calculations indicate that in the water phase the process of reducing NO3- to NH3 on Cu-0 is an exothermic reaction, and that the adsorption process of NO3- on Cu-0 is the rate-determining step.
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46.
  • Zhao, Y., et al. (author)
  • Bismuth nanoplatelets : universal synthetic strategy and emerging application for PEC-type photodetectors
  • 2023
  • In: MATERIALS TODAY NANO. - : Elsevier BV. - 2588-8420. ; 23
  • Journal article (peer-reviewed)abstract
    • Bi nanoplatelets (NPLs) with a narrow size distribution and high yield have been successfully fabricated by a novel two-step sonication-assisted solvothermal method. Applied as photo-electrochemical (PEC)-type photodetectors (PDs), it is shown that the Bi NPLs exhibit a pronounced photo-response ranging from the ultraviolet to the visible regions. The photo-response performance of Bi NPLs-based PDs was adjusted by external conditions and interpreted by density functional theory calculations in terms of the formation of the respective Bi-based compounds. The PEC results demonstrate that the optimal photocurrent density (P-ph) and photoresponsivity (R-ph) can reach 12.27 mu A/cm(2) and 3016 mu A/W in alkaline electrolytes, respectively. Besides, the Bi NPLs-based PDs exhibit superb long-term cycling stability (similar to 97.86% remained after 1000 cycles). We conclude that Bi NPLs demonstrate great promise as an emerging building block for the design of high-performance PEC-type PDs as well as other novel optoelectronic devices, holding the potential for breakthrough developments in these fields.
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47.
  • Zhao, Yiming, et al. (author)
  • Fabrication of lead telluride quantum dots and their application in photoelectrochemical-type photodetectors
  • 2023
  • In: Nano Today. - : ELSEVIER SCI LTD. - 1748-0132 .- 1878-044X. ; 52
  • Journal article (peer-reviewed)abstract
    • IV-VI semiconductors have been extensively applied in photo-electrochemical (PEC)-type photodetectors. However, electrolytes with relatively high concentrations have been addressed which could induce electro-chemical reactions during the measurement and result in a performance decrement. In this work, lead telluride quantum dots (PbTe QDs) with uniform size distribution are fabricated for PEC-type photodetectors and their performance is systematically investigated in electrolytes with concentrations as low as 10-4 mol/L. As revealed, the PbTe QD-based photodetectors show apparent photo-response with excellent stability in 1000 cycles (decrement of 0.018 % per cycle). In addition, the as-fabricated photodetectors show a broadband response to light in a region of 350-700 nm. These results are well supported by density functional theory calculations based on structural features and electronic and optical properties. Hence, we envisage that this work paves the way to fabricate high-performance photodetectors in relatively low-concentration electrolytes, which also can extend their applications to other optoelectronic devices.
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