Search

Broadband infrared (IR) absorption is sought after for wide range of applications. Graphene can support IR plasmonic waves tightly bound to its surface, leading to an intensified near-field. However, the excitation of graphene plasmonic waves usually relies on resonances. Thus, it is still difficult to directly obtain both high near-field intensity and high absorption rate in ultra-broad IR band. Herein, a novel method is proposed to directly realize high near-field intensity in broadband IR band by graphene coated manganous oxide microwires featured hierarchical nanostructures (HNSs-MnO@Gr MWs) both experimentally and theoretically. Both near-field intensity and IR absorption of HNSs-MnO@Gr MWs are enhanced by at least one order of magnitude compared to microwires with smooth surfaces. The results demonstrate that the HNSs-MnO@Gr MWs support vibrational sensing of small organic molecules, covering the whole fingerprint region and function group region. Compared with the graphene-flake-based enhancers, the signal enhancement factors reach a record high of 10

Organic–inorganic halide perovskites are emerging materials for photovoltaic applications with certified power conversion efficiencies (PCEs) over 25%. Generally, the microstructures of the perovskite materials are critical to the performances of PCEs. However, the role of the nanometer-sized grain boundaries (GBs) that universally existing in polycrystalline perovskite films could be benign or detrimental to solar cell performance, still remains controversial. Thus, nanometer-resolved quantification of charge carrier distribution to elucidate the role of GBs is highly desirable. Here, we employ correlative infrared-spectroscopic nanoimaging by the scattering-type scanning near-field optical microscopy with 20 nm spatial resolution and Kelvin probe force microscopy to quantify the density of electrons accumulated at the GBs in perovskite polycrystalline thin films. It is found that the electron accumulations are enhanced at the GBs and the electron density is increased from 6 × 1019 cm−3 in the dark to 8 × 1019 cm−3 under 10 min illumination with 532 nm light. Our results reveal that the electron accumulations are enhanced at the GBs especially under light illumination, featuring downward band bending toward the GBs, which would assist in electron-hole separation and thus be benign to the solar cell performance. Correlative infrared-spectroscopic nanoimaging by the scattering-type scanning near-field optical microscopy and Kelvin probe force microscopy quantitatively reveal the accumulated electrons at GBs in perovskite polycrystalline thin films.

Four new metal coordination complexes, namely, [Na(BTA)]n (1), [K2(BTA)2(μ2-H2O)]n (2), and [M(BTA)2(H2O)2]n (M=Ca(II) and Sr(II) for 3 and 4, respectively) [BTA=2-(1H-benzotriazol-1-yl) acetic anion], have been obtained under hydrothermal condition, by reacting the different alkali and alkaline-earth metal hydroxides with HBTA. Complexes 1–4 were structurally characterized by X-ray single-crystal diffraction, EA, IR, PXRD, and thermogravimetry analysis (TGA). These complexes display low-dimensional features displaying various two-dimensional (2D) and one-dimensional (1D) coordination motifs. Complex 1 displays a 2D layer with the thickness of 1.5 nm and possesses a topologic structure of a 11 nodal net with Schlafli symbol of {318}. Complex 2 also shows a thick 2D sheet and its topologic structure is a 9 nodes with Schlafli symbol of {311×42}. Complexes 3 and 4 possess a 1D linear chain and further stack via hydrogen bonding interactions to generate a three-dimensional supramolecular architecture. These results suggest that both the coordination preferences of the metal ions and the versatile nature of this flexible ligand play a critical role in the final structures. The luminescent spectra show strong emission intensities in complexes 1–4, which display violet photoluminescence. Additionally, ferroelectric, dielectric and nonlinear optic (NLO) second-harmonic generation (SHG) properties of 2 are discussed in detail.

Five new coordination complexes, [CdI2(3-PyBim)](H2O)3 (1), [Cd(SO4)(3-PyBim)(H2O)4] (2), [CdCl2(4-PyBim)2(H2O)2] (3), [CdBr2(4-PyBim)2(H2O)2] (4) and [CdI2(4-PyBim)2(H2O)2] (5) [3-PyBim=2-Pyridin-3-yl-1H-benzoimidazole, 4-PyBim=2-Pyridin-4-yl-1H-benzoimidazole], were obtained under hydrothermal conditions and characterized by single crystal X-ray diffraction, IR, elemental analysis, and powder X-ray diffraction. All of the complexes have mononuclear structures. Among the crystal structures of these complexes, there exist a variety of intermolecular hydrogen bonding interactions and π⋯π interactions, which further extend to a 3-D supramolecular architecture. The solid state photoluminescent properties of 1–5 vary with the electronegativity of the coordination anion. Additionally, the thermogravimetric analyses of these complexes are discussed.

Two novel three-dimensional metal-coordination polymers [Cd2(L)4(μ2-X)(X)(H2O)]n [X = Cl (1) and Br (2)] have been solvothermally synthesized by the self-assembly of an unsymmetric bridging ligand, [L = 2-(1H-imidazol-1-ylmethyl)-1H-benzoimidazole], and cadmium salts with different anions, respectively. The two complexes are isostructural and exhibit an acentric sqp-net, in which the cadmium ions act as unusual five-connected nodes. The induction of the flexible and unsymmetric ligand leads them to crystallize in a noncentrosymmetric polar packing arrangement, which displays a second harmonic generation response and ferroelectric behaviors.

The free ligand, 2-(1H-imidazole-1-yl)acetate (Hima, 1), was crystallized from the mixture solution of 1. Two new coordination polymers, [Ag(Hima)(NO3)] (2) and {[Pb(Hima)2(NO3)](NO3)}n (3), are achieved by reaction of a flexible Hima, AgNO3 and Pb(NO3), respectively. In 2, the silver(I) atom is coordinated by four oxygen atoms from three carboxylate groups and one nitrate ion in a distorted tetrahedral environment. The free ligand Hima acts as the tridentate coordination mode, which bridges the silver atoms into a zigzag chain featuring a rare [Ag2(carboxylato-O,O′)(carboxylato-μ1,1-O)] six-membered ring. The intra-dimer Ag···Ag distance is 2.966(l) A. In 3, Pb(II) atom exhibits an eight-coordinated dodecahedral coordination geometry, in which a unique 1-D chain structure with dicubane-like can be observed. In two polymers, the ligand Hima exhibits new and unique coordination modes. Solid-state fluorescence spectra reveal that the emission bands of complex 2 center at 462 and 510 nm (λex = 280 nm). In 3, the emission peaks locate at 465 and 547 nm upon excitation at 280 nm. In addition, they have been characterized by IR spectra and TG analysis.

One new one-dimensional neutral coordination polymer [Zn(BTA)2(H2O)]n (1) was hydrothermally synthesized by the self-assembly of the flexible and unsymmetric bridging ligand, 2-(1H-benzotriazol-1-yl)acetic acid, and zinc nitrate. The induction of the unsymmetric ligand leads it to crystallize in non-centrosymmetric polar packing arrangement, which displays second harmonic generation response and ferroelectric behavior, which provides a new strategy for designing functional coordination compounds.

Eight new metal coordination complexes, namely, [Co(BTA)2(H2O)4]·6H2O (1), [Ni(BTA)2(H2O)4]·6H2O (2), [Cu2(HBTA)4(BTA)2]·2H2O (3), [Ag(BTA)(H2O)]n (4), [Zn(BTA)2(H2O)]n (5), [Cd(BTA)2(H2O)]n (6), [Cu2(μ3-OH)(BTA)3]n (7), and [Mn(BTA)2(H2O)2]n (8) [HBTA = 2-(1H-benzotriazol-1-yl)acetic acid], were obtained under hydrothermal conditions, by reacting the different metal salts with HBTA. The ligand HBTA was characterized by melting point (m.p.), elemental analysis (EA), infrared spectroscopy (IR), 1H NMR, and X-ray single-crystal diffraction. Complexes 1–8 were structurally characterized by X-ray single-crystal diffraction, EA, IR, PXRD, and thermogravimetry analysis (TGA). These complexes all display low-dimensional features displaying various zero-dimensional (0D), one-dimensional (1D), and two-dimensional (2D) coordination motifs. Complexes 1 and 2 are isostructural and mononuclear; they show unique decamer water clusters with bis-boat conformations, which further extend to a 1D metal–water chain. Through intermolecular hydrogen bonds, these 1D metal–water chains extend to 3D supramolecular networks. Complex 3 shows a bi-nuclear structure. Complex 4 displays a 1D tape structure. There exist weak interactions between Ag⋯Ag. Complexes 5 and 6 form a 1D linear chain bridged by BTA anions. Complex 7 exhibits a 2D layer containing tetranuclear butterfly [Cu4(CO2)4(μ3-OH)] secondary building units (SBUs). Complex 8 possesses a 2D layer and further stacks via hydrogen bonding interactions to generate a three-dimensional supramolecular architecture. These results suggest that both the coordination preferences of the metal ions and the versatile nature of this flexible ligand play a critical role in the final structures. The luminescent spectra show strong emission intensities in complexes 3, 4, 5, and 6. Complexes 3, 5 and 6 display blue photoluminescence. However, complex 4 exhibits green fluorescence. Variable-temperature magnetic susceptibility measurements reveal the existence of antiferromagnetic interactions in both 7 and 8. Additionally, the ferroelectric and second-harmonic generation (SHG) properties of 5 are discussed in detail.