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Morphological characteristics of nanoholes induced by single-shot femtosecond laser ablation of borates and aluminate silicates
摘要： Single-shot femtosecond laser ablation experiments with linearly and circularly polarized light were conducted in order to investigate the morphological characteristics of surface nanostructures in lithium borate crystals and glasses, a strontium borate crystal, lanthanide containing borate crystals, and aluminate silicate crystals: Li2B4O7 (LTB) and LiB3O5 (LBO) crystals and Li2O?2B2O3 (LTB) and Li2O?3B2O3 (LBO) glasses; SrB4O7 (SBO) crystal; Li6Gd(BO3)3 (LGB) and LaSc3(BO3)4 (LSB) crystals; and Ca2Al2SiO7 (CAS) and CaSrAl2SiO7 (CSAS) crystals. In the present study, the material and laser polarization dependance of the morphology of nanoholes was examined in these crystals and glasses. A single nanohole or two holes (a primary hole and a secondary hole) were observed in the borate and aluminate silicate crystals. The size of the nanohole is not restricted by the diffraction limit but instead is dependent on the laser fluence and the materials. It is suggested that the formation of these secondary nanoholes in the studied crystals is attributed to a spontaneous reshaping of the incoming Gaussian pulse into a Gaussian–Bessel pulse. In the LTB and LBO crystals, nanoholes (both primary and secondary holes) with subwavelength sides exhibit a quadrilateral (approximately square or rectangular) morphology, regardless of linear or circular polarization. The sides of the quadrilateral nanoholes lie approximately in the {h h 0} planes on the LTB crystal and in the ({h 0 0} and {0 0 l}) planes on the LBO crystal. We found that the nanohole morphology did not reflect the spatial distribution of the laser intensity. These phenomena were the first observations on the anisotropic morphology of nanoholes. These morphologies do not correspond to the circular symmetric pattern of the Gaussian intensity distribution of the incoming laser beam. This is contrary to the expectations based on the generally accepted laser ablation mechanism. The quadrilateral nanoholes could be an inherent morphology in the LTB and LBO crystals. The morphology of the network structure in their quadrilateral holes in the LTB and LBO crystals is considered to reflect the continuous BO3 and/or BO4 3? 5? respective tetragonal or orthorhombic unit cells, in which self-tapped excitons are formed in an initial process under multiphoton excitation. In contrast, the SBO, LGB, LSB, CAS, and CSAS crystals and the LTB and LBO glasses exhibit circular nanoholes with subwavelength diameters independent of the laser polarization, the structure, or the composition. The isotropic morphology of nanoholes in these samples reflects the circular pattern of the Gaussian intensity profile of the focused laser beam.
关键词： borate,single pulse,aluminosilicate,scanning electron microscopy,crystal structure,nanohole morphology,femtosecond laser ablation,nanostructuring
更新于2025-09-23 15:19:57
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Solvent-controlled assembly of two Zn(II) coordination polymers constructed from 1,3,5-tris(1-imidazolyl)benzene and 2,5-dichloroterephthalic acid with fluorescent recognition of carcinogenic dye in chloroform
摘要： Two Zn(II) coordination polymers, [Zn2(tib)2(BDC-Cl2)(HBDC-Cl2)2](cid:1)2H2O (1) and [Zn(tib)(BDC-Cl2)](cid:1)H2O (2), were synthesized by reaction of 1,3,5-tris(1-imidazolyl)benzene (tib) and 2,5-dichloroterephthalic acid (H2BDC-Cl2) with Zn2t under solvothermal conditions. The results of X-ray single-crystal analysis show that 1 possesses a 1-D chain structure, while 2 exhibits a 2-D layer structure with {44(cid:1)62} topology. Both display a 3-D supramolecular framework through hydrogen bonding interactions. Experimental results indicated that the ratio of solvent may regulate the structural formation of the polymers. 1 and 2 were further characterized by powder X-ray diffraction (PXRD), IR spectroscopy, thermogravimetric analysis (TGA), and elemental analysis. Notably, 1 and 2 possess the ability to identify chloroform by emitting specific fluorescence spectra. Both can detect carcinogens in dyes by the modified fluorescent signal of the compound in chloroform.
关键词： crystal structure analysis,mixed-ligand strategy,carcinogen identification,Zinc(II)-coordination polymers,fluorescent recognition
更新于2025-09-23 15:19:57
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On symmetry of rare-earth scandium borate RESc3(BO3)4 (RE = Ce, Nd) laser crystals
摘要： Symmetry, structural features, and point defects in the Czochralski-grown single crystals with the initial compositions CeSc3(BO3)4 (CSB-1.0) and Nd1.25Sc2.75(BO3)4 (NSB-1.25) are studied by the full-profile Rietveld method on synchrotron X-ray powder data. The space group P321 is first established and confirmed for CSB-1.0 and NSB-1.25 crystals, respectively. The features of synchrotron diffraction patterns that distinguish the space group Р321 from the R32 one are given. The site occupancies in both structures are refined and resulted in the stoichiometric composition for CeSc3(BO3)4, which coincides with the nominal composition, and the composition [Nd0.455(1)Sc0.045(39)(1)]Nd0.500(2)Sc3(BO3)4 ((Nd0.955Sc0.045(39))Sc3(BO3)4), which differs from the initial Nd1.25Sc2.75(BO3)4 one, with partial occurrence of Sc ions in one of the trigonal-prismatic sites. An analysis of literature data on single crystals with the general formula RESc3(BO3)4 (RE ? Ce, Pr, Nd) together with the results of present study of powdered single crystals gives reason to exclude a crystallization of these compounds and solid solutions based on them in the space group R32. The correlation between the refined compositions of RESc3(BO3)4 crystals (RE ? La, Ce, Pr, Nd), having a specific space group, and compositions of initial charge is given.
关键词： Crystal structure,Czochralski technique,Optical materials,Point defects,Synchrotron radiation
更新于2025-09-23 15:19:57
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Searching the crystal structure of silicon using the generalized scaled hypersphere search method with the rapid nuclear motion approximation
摘要： The scaled hypersphere search method with the rapid nuclear motion approximation was applied for the prediction of the crystal structure of silicon. Five well-known structures and one novel structure were found. The space group of the novel structure found is Imma. By comparing this with the two known silicon structures in the same space group, it is found that one of these well-known Imma structures and the novel Imma structure are similar. According to our ab initio calculations based on the projector augmented wave method with the Perdew–Burke–Ernzerhof functional, the novel structure is a semiconductor, with calculated band gap 0.89 eV.
关键词： scaled hypersphere search method,crystal structure prediction,silicon,semiconductor,rapid nuclear motion approximation
更新于2025-09-23 15:19:57
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Topochemical Path in High Lithiation of MoS <sub/>2</sub>
摘要： Lithiation of MoS2/RGO (reduced graphite oxide) electrodes repeatedly reached experimental capacities larger than 1000 mA·g–1, corresponding to at least 6 lithium equivalents per gram of MoS2. At our best knowledge, a convincing explanation is still missing in literature. In most cases, phase separation into Li2S and elemental Mo was assumed to occur. However, this can only explain capacities up to 669 mA·g–1, corresponding to an exchange of four Li. Formation of LiMo alloys could resolve the problem but the Li/Mo system does not contain any binary phases. If signs for Li2S formation were found, indeed experimental capacities were below 700 mAh·g–1. Here we present a topochemical mechanism, which sustains multiple charge/discharge cycles at 1000 mAh·g–1, corresponding to an exchange of at least 6 Li per formula unit MoS2. This topochemical reaction route prevents decomposition into binary phases and thus avoids segregation of the components of MoS2. Throughout the whole lithiation/delithiation process, distinct layers of Mo are preserved but extended or shrunk by slight movements and reshuffling of sulfur and lithium atoms. On addition of 6 Li per formula unit to MoS2, all central sulfur atoms are hosted in mutual Mo–S layers such that formal S2– and Mo2– anions appear coordinated by lithium cations. Indeed, similar structures are known in the field of Zintl phases. Our first-principles crystal structure prediction study describes this topological path through conversion reactions during the lithiation/delithiation processes. All optimized phases along the topological path exhibit a distinct Mo layering giving rise to a series of dominant scattering into pseudo 001 reflections perpendicular to these Mo planes. The mechanism we present here explains why such high capacities can be reached reversibly for MoS2/RGO nano composites.
关键词： topological path,Crystal structure prediction,Total energy calculations,MoS2,Li-Mo-S ternary phases,Li-ion battery,Lithium
更新于2025-09-23 15:19:57
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Investigations on single crystal growth and nonlinear optical studies of 2-Hydroxy-1-naphthaldehyde
摘要： The optically good quality single crystals of 2-Hydroxy-1-naphthaldehyde (2H1N) were grown by vertical Bridgman method. The thermal behavior of the grown crystal was studied by thermogravimetric and differential thermal analysis (TG-DTA). The cell parameters of the grown 2H1N crystal were confirmed by single crystal X-ray diffraction (SXRD). The powder XRD (PXRD) was carried out to identify the crystalline planes. The nature of bonding and structure of 2H1N was analyzed using 1HNMR and 13CNMR. Functional groups of 2H1N crystal were confirmed by Fourier transform infrared (FTIR) spectral analysis. The optical transmittance was determined by the UV–Vis NIR spectral analysis and the grown crystal has good optical transparency in the visible region (300-900 nm). To analyze the third order nonlinear optical properties, z-scan study was carried out and the nonlinear optical parameters like refractive index (1.30 x 10-7cm2/W), absorption coefficient (0.0410-4cm/W) and the third order nonlinear optical susceptibility (1.90 x 10-6 esu) was determined. The optical limiting behavior and clamping measurements of 2H1N was 37.3 mW and 1.08 mW respectively. The dielectric constant (~12) and low dielectric loss as a function of frequency were measured to ensure the 2H1N has better optical application.
关键词： A2. Vertical Bridgman technique,A1. Crystal structure,B3. Nonlinear optics,B1. organic compounds,B2. Nonlinear optic materials
更新于2025-09-19 17:15:36
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Symmetry and Topology Code of Cluster Crystal Structure Self-Assembly for Metal Oxides: Cs11O3-mP56, Rb(Cs11O3)-oP30, Cs(Cs11O3)-oP60, Rb3(Rb4)(Cs11O3)-oP84, (Cs4)(Cs6)(Cs11O3)-hP24, Rb9O2-mP22, (Rb3)(Rb9O2)-hP28, and (Rb2O)3(Rb13)-cF176
摘要： Geometric and topologic analysis was carried out for metal oxides Cs11O3-mP56, Rb(Cs11O3)-oP30, Cs(Cs11O3)-oP60, Rb3(Rb4)(Cs11O3)-oP84, (Cs4)(Cs6)(Cs11O3)-hP24, Rb9O2-mP22, (Rb3)(Rb9O2)-hP28, and (Rb2O)3(Rb13)-cF176, which are formed from oxygen-containing metal melts. Special algorithms of partitioning structural graphs into cluster structures (the TOPOS program package) were used to identify the precursor clusters of crystal structures. The precursor clusters participating in crystal structure self-assembly were identified to be three-octahedral Cs11O3, two-octahedral Rb9O2, octahedral Cs6, tetrahedral Cs4 and Rb4, and icosahedral Rb13. The symmetry and topology code of crystal structure self-assembly from precursor clusters was reconstituted as: primary chain → microlayer → microframework. The Cs11O3 and Rb9O2 crystal structures were found to be self-assembled from three-octahedral clusters Cs11O3 and two-octahedral clusters Rb9O2, respectively. The Rb(Cs11O3) and Cs(Cs11O3) framework structures are assembled from clusters Cs11O3 and accommodate Rb and Cs atoms in their voids. The Rb3(Rb4)(Cs11O3) framework structure is assembled from clusters Cs11O3 and Rb4 and accommodates Rb atoms in its voids. The (Cs6)(Cs4)(Cs11O3) framework structure is self-assembled from clusters Cs11O3, Cs6, and Cs4. The Rb3(Rb9O2)-hP28 framework structure is assembled from clusters Rb9O2 and atoms Rb; the (Rb2O)3(Rb13) framework structure is assembled from icosahedra Rb13 and clusters Rb2O.
关键词： octahedral,and icosahedral precursor clusters,crystal structure self-assembly,and Rb metal oxides,Cs,tetrahedral,Rb-,Cs-
更新于2025-09-19 17:15:36
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Theoretical study on the charge transport properties of three series dicyanomethylene quinoidal thiophene derivatives
摘要： It is very important to analyse the most advantageous connection style for quinoidal thiophene derivatives, which are used in n-type organic semiconductor transport materials. In the present work, the charge transport properties of three series of quinoidal thiophene derivatives, oligothiophene (series A), thienothiophene (series B) and benzothiophene (series C), are systematically investigated by employing the full quantum charge transfer theory combined with kinetic Monte-Carlo simulation. The single crystal structures of the molecules we constructed were predicted using the USPEX program combined with density functional theory (DFT) and considering the dispersion corrected. Our theoretical results expounded that how the different connection styles, including oligo-, thieno-, benzo- thiophene in the quinoidal thiophenes derivatives, effectively tune their electronic structures, and revealed that how their intermolecular interactions affect the molecular packing patterns and hence their charge transport properties by symmetry-adapted perturbation theory (SAPT). In the meanwhile we also elucidated the role of end-cyano groups in noncovalent interactions. Furthermore, it is clarified that the quinoidal thiophene derivatives show excellent carrier transport properties due to their optimal molecular stacking motifs and larger electronic couplings besides low energy gap. In addition, our theoretical results demonstrate that quinoidal oligothiophene derivatives (n=3~5) with more thiophene rings will have ambipolar transport properties, quinoidal thienothiophene and benzothiophene derivatives should be promising alternatives as n-type OSC. When we focused only on the electronic transport properties in the three series of molecules, quinoidal benzothiophene derivatives are slightly better than quinoidal oligothiophene and thienothiophene derivatives.
关键词： Crystal structure prediction,Dicyanomethylene quinoidal thiophene,N-type and ambipolar organic semiconductors,Charge transport property,Intermolecular interactions
更新于2025-09-19 17:15:36
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Syntheses, structures, optical properties, and electronic structures of Ba6Cu2GSn4S16 (G = Fe, Ni) and Sr6D2FeSn4S16 (D = Cu, Ag)
摘要： Ba6Cu2GSn4S16 (G = Fe, Ni), and Sr6D2FeSn4S16 (D = Cu, Ag) were synthesized in an A-B-P-Q (A = Sr, Ba; B = Cu, Ag, Li; P = Sn, Ge; Q = S, Se, Te) system, through the introduction of the Fe and Ni atoms. The four compounds were found to be isostructural. They crystallize in space group ??4?3?? (no. 220) of the three-dimensional cubic structure. The structure is composed of SnS4 and (Cu|G)S4 by sharing corners with Ba2+ cations distributed in the channels of the Ba6Cu2GSn4S16 (G = Fe, Ni). The structure is composed of SnS4 and (D|Fe)S4 by sharing corners with Sr2+ cations distributed in the channels of the Sr6D2FeSn4S16 (D = Cu, Ag). The UV-vis diffuse reflectance spectra showed the Ba6Cu2FeSn4S16, Ba6Cu2NiSn4S16, Sr6Cu2FeSn4S16, and Sr6Ag2FeSn4S16 energy band gaps to be 1.20 eV, 0.82 eV, 1.53 eV and 1.87 eV, respectively.
关键词： band gap,optical properties,crystal structure,Chalcogenide
更新于2025-09-19 17:15:36
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Synthesis and Fluorescence Properties of a Structurally Characterized Hetero-Hexanuclear Zn(II)-La(III) Salamo-Like Coordination Compound Containing Auxiliary Ligands
摘要： A hetero-hexanuclear Zn(II)-La(III) coordination compound, [{(ZnL)2La}2(bdc)2](NO3)2 (H2bdc = terephthalic acid) has been synthesized with a symmetric Salamo-like bisoxime, and characterized by elemental analyses, IR, UV-Vis, fluorescent spectroscopy, and single-crystal X-ray diffraction analysis. All of the Zn(II) ions are pentacoordinated by N2O2 donator atoms from the (L)2? unit and one oxygen atom from one terephthalate anion. The Zn(II) ions adopt trigonal bipyramidal geometries (τZn1 = 0.61, τZn2 = 0.56). The La(III) ions are decacoordinated in the Zn(II)-La(III) coordination compound and has a distorted bicapped square antiprism geometry. Meanwhile, the photophysical property of the Zn(II)-La(III) coordination compound was also measured and discussed.
关键词： crystal structure,photophysical property,Salamo-like bisoxime,Zn(II)-La(III) coordination compound
更新于2025-09-19 17:15:36