- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Halogen-free GeO <sub/>2</sub> conversion: electrochemical reduction <i>vs.</i> complexation in (DTBC) <sub/>2</sub> Ge[Py(CN) <sub/>n</sub> ] ( <i>n</i> = 0…2) complexes
摘要： Halogen-free GeO2 conversion: electrochemical reduction vs. complexation in (DTBC)2Ge[Py(CN)n] (n = 0…2) complexes?
关键词： halogen-free conversion,germanium,catecholate complexes,electrochemical reduction,DFT calculations
更新于2025-09-19 17:15:36
-
Theoretical study of the structural and electronic properties of impurities in non-passivated silicon thin nanowires
摘要： In this work, we report theoretical results for the presence of the B, C, N, O and F as impurities in non-passivated [001] thin silicon nanowires. The results for the formation energies show that some dopants tend to segregate to the nanowire surfaces, as observed for passivated [110] ones, but at the double negative charge state. The most stable site for the considered impurities is the interstitial one, where the dopants make bridges with the lateral surface Si atoms, below to this surface, except for the oxygen and ?uorine ones, which stay close to the central Si atom. For the neutral carbon, nitrogen and ?uorine impurities, the surface π-states located at the facets are ?lled and a small bandgap appears in the calculated impurity band structures. However, if they were at the double negative charge state, the nanowire metallicity is recovered. Considering the boron and oxygen dopants, the neutral charge state enhances the metallic character at the opposite side of the nanowire where they are, which is reduced when two extra electrons are injected in the system and thus, opening slightly the nanowire bandgap. Our results clearly indicate that doping (or creating vacancies in) these nanowires with acceptors, as well as with hydrogen atoms, can reduce the thin nanowire metallic behavior.
关键词： Electronic structure,Silicon thin nanowires,First row impurities,DFT calculations,Formation energies
更新于2025-09-19 17:15:36
-
Identification and optical features of the Pb4Ln2O7 series (Ln = La, Gd, Sm, Nd), genuine 2D-van der Waals oxides.
摘要： We report on the identification and survey of the Pb4Ln2O7 series (Ln= La, Gd, Sm and Nd) which turn out to be real Van der Waals 2D oxides. In the neutral layers, strong covalent Pb-O bonds together with external stereoactive Pb2+ lonepairs, which play as sensitizers, lead to an ideal matrix for enhanced and tunable luminescence by lantanide emittors, tested here for Sm3+ and Eu3+ doping. DFT calculations and preliminary exsolution experiments validate the weak bonding between the layers separated by 3.5 ? and suggest a undirect to direct crossover realized by isolating the layers.
关键词： lanthanide doping,luminescence,2D materials,Van der Waals oxides,DFT calculations
更新于2025-09-19 17:15:36
-
Extending the ?-electron conjugation in 2D planar graphitic carbon nitride: Efficient charge separation for overall water splitting
摘要： We report the direct overall pure water splitting by visible light excited graphitic carbon nitride incorporated with conjugated aromatic rings without using sacrificial agents. We fabricated the modified graphitic carbon nitride polymer samples by copolymerization of melamine with 2,4,6-triaminopyrimidine and 1,3,5-triaminobenzene, containing a few-carbon (pyrimidine) to all-carbon (benzene) aromatic rings. Solid state 13C NMR shows that the core molecular skeleton of g-C3N4 remained intact even after the incorporation of benzene and pyrimidine aromatic rings into g-C3N4 chemical structure. Upon substitution of benzene aromatic ring in the place of triazine ring, the optical band gap energy of g-C3N4 is narrowed down from 2.8 eV to 2.1 eV with negative shifts of valence and conduction bands and due to the formation of defects like nitrogen vacancies. The DFT calculations predict that the benzene doped carbon nitride polymer has localized charge densities over valence band maxima and conduction band minima in different parts of heptazine rings, which assist in reducing the recombination rate of the charge carriers. The benzene ring incorporated carbon nitride photoelectrode shows higher photocurrent with lesser charge transfer resistance than the parent g-C3N4 and pyrimidine doped g-C3N4 polymers. This demonstrates the importance of the extended conjugation in g-C3N4 due to the presence of aromatic benzene rings. This is further corroborated by photoluminescence and electron paramagnetic resonance measurements. As a result, the benzene ring incorporated carbon nitride is more active than the pyrimidine ring incorporated carbon nitride for solar water splitting. The benzene ring incorporated carbon nitride polymer directly splits water and generates about 7 μmol h-1 of hydrogen with apparent quantum yield of 1.6% at 450 nm in the absence of sacrificial reagents, achieving turnover number of 1.6.
关键词： turnover number,benzene,DFT calculations,Carbon nitride,apparent quantum yield,charge separation,pyrimidine,water splitting
更新于2025-09-19 17:15:36
-
Photoluminescence in <i>m</i> -carborane–anthracene triads: a combined experimental and computational study
摘要： New hybrids synthesized by linking two anthracenyl units to the Ccluster atoms of a non- (4), a mono- (5) and a di-iodinated (6) m-carborane fragment through CH2 spacers, along with their full characterization, are reported. Noticeably, bonding the m-carborane fragment to the anthracene moieties produces a significant increase of more than two-fold in the intrinsic fluorescence quantum yield (fF) of the anthracene itself, with values of fF 4 60% in THF and fF 4 48% in toluene, although it does not alter the absorption and emission patterns of the fluorophore in solution. A red-shift of the emission maximum with respect to the solution is observed in the aggregate state (THF/H2O, 1 : 99 v/v), along with moderate quantum yields; compounds 4 and 5 show fF = 22 and 19%, respectively, whereas 6 has a lower value (fF = 8%). The di?erence between the fF values in the aggregate state has been attributed to the arrangement of dimers for each compound in the solid state structures. X-ray crystal structures of compounds 4 and 5 show the anthracene units to be roughly parallel, whereas such an arrangement is clearly disrupted in compound 6. Such di?erences have been analyzed by Hirshfeld surfaces, decomposed fingerprint plots for the three compounds and DFT calculations. The combined results from the supramolecular analyses and DFT studies support the idea that a less delocalized system in the case of 6 can be explained by the di?erent packing in the aggregate or solid state for this di-iodo-derivative. The observed arrangement of molecules of 6 seems to be related to a larger number of H(cid:2) (cid:2) (cid:2)I contacts, with respect to the non-iodinated or mono-iodinated compounds, 4 or 5. According to this assumption, there is a direct relationship between the structure in the solid state and the PL properties; in the m-carborane derivatives, small changes in their structures have caused variations in the photophysical properties, especially in the quantum e?ciency.
关键词： X-ray diffraction,anthracene,m-carborane,Hirshfeld surfaces,photoluminescence,DFT calculations,fluorescence quantum yield
更新于2025-09-19 17:15:36
-
A large Stokes shift, sequential, colorimetric fluorescent probe for sensing Cu2+/S2- and its applications
摘要： Copper ions (Cu2+) and sulfide (S2?) are important markers in many physiologies and pathological processes. In this work, a new near-infrared fluorescent probe 1 for colorimetric and sequential detection of Cu2+/S2? was designed and developed. The probe showed a rapid (less than 1 min), highly selective and sensitive response toward copper ions. Notably, the probe could also be applied to detect S2? through reversible formation-separation of complex 1-Cu2+ and CuS with a large Stokes shift of 234 nm. The detection limit for Cu2+ and S2? was found to be 1.8 × 10-8 M and 1.5 × 10-8 M, respectively. Furthermore, the binding stoichiometry between 1 and Cu2+ was found to be 1:1, the binding mode was also demonstrated using density functional theory (DFT) calculations and contrastive compound research. In addition, the probe was successfully applied in real water samples assay for the detection of Cu2+, and the strip papers experiments also showed that probe 1 can be used to detect Cu2+ and S2?.
关键词： DFT calculations,Colorimetric,Near-infrared,Sulfide,Large Stokes shift,Copper ions
更新于2025-09-19 17:15:36
-
Chiral differentiation of <scp>d</scp> - and <scp>l</scp> -isoleucine using permethylated β-cyclodextrin: infrared multiple photon dissociation spectroscopy, ion-mobility mass spectrometry, and DFT calculations
摘要： Chiral di?erentiation of protonated isoleucine (Ile) using permethylated b-cyclodextrin (perCD) in the gas-phase was studied using infrared multiple photon dissociation (IRMPD) spectroscopy, ion-mobility, and density functional theory (DFT) calculations. The gaseous protonated non-covalent complexes of perCD and D-Ile or L-Ile produced by electrospray ionization were interrogated by laser pulses in the wavenumber region of 2650 to 3800 cm?1. The IRMPD spectra showed remarkably di?erent IR spectral features for the D-Ile or L-Ile and perCD non-covalent complexes. However, drift-tube ion-mobility experiments provided only a small di?erence in their collision cross-sections, and thus a limited separation of the D- and L-Ile complexes. DFT calculations revealed that the chiral distinction of the D- and L-complexes by IRMPD spectroscopy resulted from local interactions of the protonated Ile with perCD. Furthermore, the theoretical results showed that the IR absorption spectra of higher energy conformers (by B13.7 kcal mol?1) matched best with the experimentally observed IRMPD spectra. These conformers are speculated to be formed from kinetic-trapping of the solution-phase conformers. This study demonstrated that IRMPD spectroscopy provides an excellent platform for di?erentiating the subtle chiral di?erence of a small amino acid in a cyclodextrin-complexation environment; however, drift-tube ion-mobility did not have su?cient resolution to distinguish the chiral di?erence.
关键词： chiral differentiation,ion-mobility mass spectrometry,permethylated β-cyclodextrin,IRMPD spectroscopy,DFT calculations,isoleucine
更新于2025-09-19 17:15:36
-
Synthesis, characterization of ((CH3)3S)2SnI6-nCln and ((CH3)3S)2SnI6-nBrn (n=1, 2) perovskites and use in dye-sensitized solar cells
摘要： New air-stable ((CH3)3S)2SnI6-nCln and ((CH3)3S)2SnI6-nBrn (n=1, 2) defect perovskites were synthesized and their physicochemical properties were established. Rietveld analysis on the recorded XRD patterns revealed the presence of cubic structural modification with a 0D network of [SnI6-nCln] and [SnI6-nBrn] octahedra. The vibrational and electronic properties of the mixed-anion based trimethylsulfoinum Tin (IV) perovskites investigated using Raman and UV–vis spectroscopy showed that upon substitution of Cl/Br for I, the electronic band gap slightly increased, while the lattice vibrations were also largely affected. Density functional theory (DFT) calculations permitted to determine the density of states (DOS) distribution and corresponding band energy structures, confirming the obtained increase of direct band gap values with halogen substitution. The lead-free Sn(IV)-based compounds were successfully incorporated as hole transporting materials (HTMs) in sensitized nanocrystalline solar cells (DSCs). For these devices, power conversion efficiencies as high as 5% were obtained, under 1 sun (A.M. 1.5G) illumination. Electrochemical impedance spectroscopic analysis indicated that the maximum device performance is associated with high charge recombination resistance and low electron transfer resistance at dye/perovskite and perovskite/Pt interfaces, respectively.
关键词： nanocrystalline solar cells,Sn-based Perovskites,DFT calculations.,hole-transporting material
更新于2025-09-19 17:13:59
-
Remote Modification of Bidentate Phosphane Ligands Controlling the Photonic Properties in Their Complexes: Enhanced Performance of [Cu(RNa??xantphos)(N <sup>^</sup> N)][PF <sub/>6</sub> ] in Lighta??Emitting Electrochemical Cells
摘要： A series of copper(I) complexes of the type [Cu(HN-xantphos)(N^N)][PF6] and [Cu(BnN-xantphos)(N^N)][PF6], in which N^N = bpy, Mebpy, and Me2bpy, HN-xantphos = 4,6-bis(diphenylphosphanyl)-10H-phenoxazine and BnN-xantphos = 10-benzyl-4,6-bis(diphenylphosphanyl)-10H-phenoxazine is described. The single crystal structures of [Cu(HN-xantphos)(Mebpy)][PF6] and [Cu(BnN-xantphos)(Me2bpy)][PF6] confirm the presence of N^N and P^P chelating ligands with the copper(I) atoms in distorted coordination environments. Solution electrochemical and photophysical properties of the BnN-xantphos-containing compounds (for which the highest-occupied molecular orbital is located on the phenoxazine moiety) are reported. The first oxidation of [Cu(BnN-xantphos)(N^N)][PF6] occurs on the BnN-xantphos ligand. Time-dependent density functional theory (TD-DFT) calculations have been used to analyze the solution absorption spectra of the [Cu(BnN-xantphos)(N^N)][PF6] compounds. In the solid-state, the compounds show photoluminescence in the range 518–555 nm for [Cu(HN-xantphos)(N^N)][PF6] and 520–575 nm for [Cu(BnN-xantphos)(N^N)][PF6] with a blue-shift on going from bpy to Mebpy to Me2bpy. [Cu(BnN-xantphos)(Me2bpy)][PF6] exhibits a solid-state photoluminescence quantum yield of 55% with an excited state lifetime of 17.4 μs. Bright light-emitting electrochemical cells are obtained using this complex, and it is shown that the electroluminescence quantum yield can be enhanced by using less conducting hole injection layers.
关键词： DFT calculations,electroluminescence,photophysics,light-emitting electrochemical cells,ionic copper complexes
更新于2025-09-19 17:13:59
-
An effective combination reaction involved with sputtered and selenized Sb precursors for efficient Sb2Se3 thin film solar cells
摘要： Sputtering followed by post annealing is extensively used for fabrication of copper indium gallium selenide (CIGS), copper zinc tin sulfide (CZTS) and copper zinc tin sulfur selenide (CZTSSe) thin film solar cells. In this work, Sb2Se3 as an emerging alternative absorber was fabricated by an effective combination reaction of annealing sputtered Sb metallic precursors under Se vapor. Self-assembled growth of Sb2Se3 thin films consist of large grains that across the whole films have been successfully fulfilled via this combination reaction. Sb2Se3 thin films with desired orientation, stoichiometric composition and high-quality Sb2Se3/CdS heterojunction could be achieved once a proper selenization scenario was employed. Further, by selecting Sb films as precursors, the thickness of interfacial MoSe2 located at the back-contact region can be well controlled, leading to a significant enhancement in fill factor (FF) of the devices. This is in good accordance with our DFT simulation results which demonstrated Se vapor would be prone to react with the Sb lattice thermodynamically and thus limiting the thickness of the MoSe2 layer. Finally, a champion Sb2Se3 thin film solar cell with power conversion efficiency of 6.15% was achieved, which represents the highest efficiency of sputtered Sb2Se3 solar cells.
关键词： DFT calculations,Sb2Se3 solar cell,Magnetron sputtering,Selenization,Combination reaction
更新于2025-09-19 17:13:59