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Au30Si12: A DFT study of the pentakis icosidodechedron
摘要： A stable hollow cage containing 30 gold atoms and 12 silicon atoms, Au30Si12, has been studied using density functional theory and compared with the icosahedral Au42. The results show that the Au42 cage is an icosahedron structure which is composed of 20 trigonal-planar faces, and it has 12 vertexes. The Au30Si12 is pentakis icosidodechedron structure constructed by 80 triangular faces and it has 42 vertexes. This Au30Si12 molecular cluster also is Ih point group symmetry. The doped Si atoms make the Au30Si12 clusters more compact and enhance the stability of gold fullerence. The p-d hybridizations between Si and Au atoms play a significant role in forming the cagelike structure. The HOMO-LUMO gap is only 0.18eV, suggesting its chemical activities. Therefore, the hollow space within Au30Si12 can be used to accommodate foreign atoms and emphasizes the benefit of studying endohedral fullerenes and may have potential applications in semiconductor and microelectronic industry.
关键词： Au30Si12 fullerene,density functional theory,electronic structure
更新于2025-09-09 09:28:46
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Design of Surface Acoustic Wave Sensors Functionalized with Bisphenol S Based Molecules for Lead Ions Detection
摘要： This study concerns the design of surface acoustic wave sensors functionalized with bisphenol S based molecules for lead ions detection. (4-hydroxyphenyl, 4′-benzyloxyphenyl) sulfone (M1), (4-hydroxyphenyl,4′-anthrylmethyloxyphenyl) sulfone (M2) and (4,4′-bis (anthrylmethyloxyphenyl)) sulfone (M3) were synthesized and then drop-coated on the SAWs sensing areas. Gravimetric results indicate that the limit of detection of the three sensors is in the picomolar range and that the M3/SAW sensor has the highest affinity towards lead ions compared to M1/SAW and M2/SAW. Density functional theory (DFT) calculations were investigated to support experimental results and to understand the nature of interactions involved between lead ions and the three synthetized molecules.
关键词： surface acoustic wave sensors,density functional theory calculations,lead ions
更新于2025-09-09 09:28:46
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Heteroleptic Copper(I) Complexes Prepared from Phenanthroline and Bis-Phosphine Ligands: Rationalization of the Photophysical and Electrochemical Properties
摘要： The electronic and structural properties of ten heteroleptic [Cu(NN)(PP)]+ complexes have been investigated. NN indicates 1,10-phenanthroline (phen) or 4,7-diphenyl-1,10-phenanthroline (Bphen); each of these ligands is combined with five PP bis-phosphine chelators, i.e., bis(diphenylphosphino)methane (dppm), 1,2-bis(diphenylphosphino)ethane (dppe), 1,3-bis(diphenylphosphino)propane (dppp), 1,2-bis(diphenylphosphino)benzene (dppb), and bis[(2-diphenylphosphino)phenyl] ether (POP). All complexes are mononuclear, apart from those based on dppm, which are dinuclear. Experimental data—also taken from the literature and including electrochemical properties, X-ray crystal structures, UV?vis absorption spectra in CH2Cl2, luminescence spectra and lifetimes in solution, in PMMA, and as powders—have been rationalized with the support of density functional theory calculations. Temperature dependent studies (78?358 K) have been performed for selected complexes to assess thermally activated delayed fluorescence. The main findings are (i) dependence of the ground-state geometry on the crystallization conditions, with the same complex often yielding different crystal structures; (ii) simple model compounds with imposed C2v symmetry ([Cu(phen)(PX3)2]+; X = H or CH3) are capable of modeling structural parameters as a function of the P?Cu?P bite angle, which plays a key role in dictating the overall structure of [Cu(NN)(PP)]+ complexes; (iii) as the P?Cu?P angle increases, the energy of the metal-to-ligand charge transfer absorption bands linearly increases; (iv) the former correlation does not hold for emission spectra, which are red-shifted for the weaker luminophores; (v) the larger the number of intramolecular π-interactions within the complex in the ground state, the higher the luminescence quantum yield, underpinning a geometry locking effect that limits the structural flattening of the excited state. This work provides a general framework to rationalize the structure?property relationships of [Cu(NN)(PP)]+, a class of compounds of increasing relevance for electroluminescent devices, photoredox catalysis, and solar-to-fuels conversion, which so far have been investigated in an unsystematic fashion, eluding a comprehensive understanding.
关键词： electrochemical properties,bis-phosphine ligands,photophysical properties,phenanthroline,thermally activated delayed fluorescence,density functional theory,heteroleptic copper(I) complexes
更新于2025-09-09 09:28:46
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Rationalizing and Controlling the Surface Structure and Electronic Passivation of Cesium Lead Halide Nanocrystals
摘要： Colloidal lead halide perovskite nanocrystals (NCs) have recently emerged as versatile photonic sources. Their processing and luminescent properties are challenged by the lability of their surfaces, i.e. the interface of the NC core and the ligand shell. On the example of CsPbBr3 NCs, we model the nanocrystal surface structure and its effect on the emergence of trap states using density functional theory. We rationalize the typical observation of a degraded luminescence upon aging or the luminescence recovery upon post-synthesis surface treatments. The conclusions are corroborated by the elemental analysis. We then propose a strategy for healing the surface trap states and for improving the colloidal stability by the combined treatment with didodecyldimethyl ammonium bromide and lead bromide and validate this approach experimentally. This simple procedure results in robust colloids, which are both highly pure and exhibit high photoluminescence quantum yields of up to 95-98%, retained even after 3-4 rounds of washing.
关键词： trap states,didodecyldimethyl ammonium bromide,luminescence recovery,photoluminescence quantum yields,lead bromide,CsPbBr3 NCs,density functional theory,Colloidal lead halide perovskite nanocrystals,surface structure
更新于2025-09-09 09:28:46
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Band structure and giant Stark effect in two-dimensional transition-metal dichalcogenides
摘要： We present a comprehensive study of the electronic structures of 192 configurations of 39 stable, layered, transition-metal dichalcogenides using density-functional theory. We show detailed investigations of their monolayer, bilayer, and trilayer structures’ valence-band maxima, conduction-band minima, and band gap responses to transverse electric fields. We also report the critical fields where semiconductor-to-metal phase transitions occur. Our results show that band gap engineering by applying electric fields can be an effective strategy to modulate the electronic properties of transition-metal dichalcogenides for next-generation device applications.
关键词： two-dimensional materials,band structure,giant-Stark effect,density functional theory,electric field,transition metal dichalcogenides
更新于2025-09-09 09:28:46
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Local Electronic Structure of Molecular Heterojunctions in a Single-Layer 2D Covalent Organic Framework
摘要： The synthesis of a single-layer covalent organic framework (COF) with spatially modulated internal potentials provides new opportunities for manipulating the electronic structure of molecularly defined materials. Here, the fabrication and electronic characterization of COF-420: a single-layer porphyrin-based square-lattice COF containing a periodic array of oriented, type II electronic heterojunctions is reported. In contrast to previous donor–acceptor COFs, COF-420 is constructed from building blocks that yield identical cores upon reticulation, but that are bridged by electrically asymmetric linkers supporting oriented electronic dipoles. Scanning tunneling spectroscopy reveals staggered gap (type II) band alignment between adjacent molecular cores in COF-420, in agreement with first-principles calculations. Hirshfeld charge analysis indicates that dipole fields from oriented imine linkages within COF-420 are the main cause of the staggered electronic structure in this square grid of atomically–precise heterojunctions.
关键词： type II heterojunctions,covalent organic frameworks,density functional theory,scanning tunneling microscopy and spectroscopy,electronic structure
更新于2025-09-09 09:28:46
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Bandgap Tunability in a One-Dimensional System
摘要： The ability to tune the gaps of direct bandgap materials has tremendous potential for applications in the ?elds of LEDs and solar cells. However, lack of reproducibility of bandgaps due to quantum con?nement observed in experiments on reduced dimensional materials, severely affects tunability of their bandgaps. In this article, we report broad theoretical investigations of direct bandgap one-dimensional functionalized isomeric system using their periodic potential pro?le, where bandgap tunability is demonstrated simply by modifying the potential pro?le by changing the position of the functional group in a periodic supercell. We found that bandgap in one-dimensional isomeric systems having the same functional group depends upon the width and depth of the deepest potential well at global minimum and derived correlations are veri?ed for known synthetic as well as natural polymers (biological and organic), and also for other one-dimensional direct bandgap systems. This insight would greatly help experimentalists in designing new isomeric systems with different bandgap values for polymers and one-dimensional inorganic systems for possible applications in LEDs and solar cells.
关键词： one-dimensional systems,polymers,nanoribbons,density functional theory,bandgap
更新于2025-09-09 09:28:46
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Synthesis, Structure, and Properties of the Layered Oxide Chalcogenides Sr <sub/>2</sub> CuO <sub/>2</sub> Cu <sub/>2</sub> S <sub/>2</sub> and Sr <sub/>2</sub> CuO <sub/>2</sub> Cu <sub/>2</sub> Se <sub/>2</sub>
摘要： The structures of two new oxide chalcogenide phases, Sr2CuO2Cu2S2 and Sr2CuO2Cu2Se2, are reported, both of which contain infinite CuO2 planes containing Cu2+ and which have Cu+ ions in the sulfide or selenide layers. Powder neutron diffraction measurements show that Sr2CuO2Cu2Se2 exhibits long-range magnetic ordering with a magnetic structure based on antiferromagnetic interactions between nearest-neighbor Cu2+ ions, leading to a √2a × √2a × 2c expansion of the nuclear cell. The ordered moment of 0.39(6) μB on the Cu2+ ions at 1.7 K is consistent with the value predicted by density functional theory calculations. The compounds are structurally related to the cuprate superconductors and may also be considered as analogues of the parent phases of this class of superconductor such as Sr2CuO2Cl2 or La2CuO4. In the present case, however, the top of the chalcogenide-based valence band is very close to the vacant Cu2+ 3d states of the conduction band, leading to relatively high measured conductivity.
关键词： oxide chalcogenides,Sr2CuO2Cu2Se2,Sr2CuO2Cu2S2,density functional theory,cuprate superconductors,magnetic ordering
更新于2025-09-09 09:28:46
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Estimating the Individual Spectroscopic Properties of Three Unique Eu <sup>III</sup> Sites in a Coordination Polymer
摘要： We isolated a coordination polymer with the formula [Eu3(3,5-dcba)9(H2O)(dmf)3]·2dmf, with three unique EuIII coordination sites in the asymmetric unit, with the EuIII ions bridged by 3,5-dichlorobenzoato (3,5-dcba) ligands. The coordination polymer crystallized in the triclinic space group P1? with unit cell dimensions a = 12.4899(15), b = 16.326(2), and c = 25.059(3) ?, α = 84.271(3)°, β = 84.832(3)°, and γ = 68.585(3)° and V = 4725.2(10) ?3. The characteristic 5D0 → 7FJ (J = 0?4) EuIII transitions were observed upon ligand-centered excitation. Emission lifetimes of 0.825 ± 0.085 and 1.586 ± 0.057 ms were observed and were attributed to the sites with coordination of water or dimethylformamide (dmf) molecules to each ion, respectively. Through a combination of spectroscopy and calculations, we determined the photophysical properties of each unique EuIII site. Energy-transfer rates ligand → EuIII were determined for each unique site using the overlapped polyhedra method. The rates depend on the coordinated water molecules and the different donor?acceptor distances. The two sites without coordinated water molecules and shortest donor?acceptor distance display the fastest energy-transfer rate ligand → EuIII, whereas the site with coordinated water molecules and longest donor?acceptor distance displays the slowest energy-transfer rate. Donor?acceptor distances were estimated computationally and were confirmed by calculating the frontier orbitals in the asymmetric units of the polymer using density functional theory.
关键词： coordination polymer,photophysical properties,energy-transfer rates,density functional theory,EuIII
更新于2025-09-09 09:28:46
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Designing Long-Range Charge Delocalization from First Principles
摘要： Efficient electronic communication over long distances is a desirable property of molecular wires. Charge delocalization in mixed-valence (MV) compounds where two redox centers are linked by a molecular bridge is a particularly well-controlled instance of such electronic communication, thus lending itself to comparisons between theory and experiment. We study how to achieve and control long-range charge delocalization in cationic organic MV systems by means of Kohn–Sham density functional theory (DFT), and show that a captodative substitution approach recently suggested for molecular conductance (T. Stuyver et al., J. Phys. Chem. C 122, 3194 (2018)) greatly enhances charge delocalization in para-phenylene-based wires. To ensure the adequacy of our DFT methods, we validate different protocols for organic MV systems of different lengths. The BLYP35 hybrid functional combined with a polarizable continuum model, established by Renz and Kaupp, is indeed capable of correctly describing experimentally observed length-dependent charge delocalization, in contrast to the long-range corrected functionals ω-B97X-D and ω-PBE. We also discuss the implications of these results for a first-principles description of the transition between coherent tunneling and incoherent hopping regimes in molecular conductance.
关键词： Charge Delocalization,Molecular Wires,Mixed-Valence Compounds,Quantum Electronic Structure,Density Functional Theory
更新于2025-09-09 09:28:46