- 标题
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- 实验方案
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Synthesis, characterization and comparative studies of nonlinear optical chromophores with rod-like, Y-shaped and X-shaped configurations
摘要： A series of highly polarizable nonlinear optical (NLO) chromophores ZJ1-4 with three different configurations, including rod-like, Y-shaped and X-shaped configurations, have been synthesized with facile routes and systematically studied. The resulted chromophores exhibited excellent thermal stabilities. The relationship between molecular configuration and NLO activity was analyzed from the theoretical calculation and experiment. The molecular dipole moment of chromophore ZJ4 was enhanced by X-shaped structure with two acceptors. Meanwhile, the tendency of forming anti-parallel interactions could be inhibited by disk-like molecular configuration with larger steric hindrance. ZJ4 exhibits the largest EO activity of 103 pm/V, and both of molecular and material NLO properties are improved for the chromophore ZJ4 with the X-shaped configuration compared with corresponding benchmark chromophore ZJ1 with rod-like molecular structure.
关键词： shape,nonlinear optic,electro-optic,structure-property relationship,chromophores
更新于2025-09-23 15:23:52
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Efficient near-infrared photocatalysts based on NaYF4:Yb3+,Tm3+@NaYF4:Yb3+,Nd3+@TiO2 core@shell nanoparticles
摘要： In this work, we fabricated NaYF4:Yb3+,Tm3+@NaYF4:Yb3+,Nd3+@TiO2 (Tm@Nd@TiO2) core@shell nanoparticles and investigated their near-infrared (NIR) photocatalytic activities. Comparing to traditional TiO2 based upconversion (UC) photocatalysts (i.e., NaYF4:Yb3+,Tm3+@TiO2, named Tm@TiO2), Tm@Nd@TiO2 exhibits enhanced photocatalytic activity under NIR light irradiation. The photocatalytic activity of Tm@Nd@TiO2 under 980, 808, and 980+808 nm laser irradiation is 4.40, 5.84, and 9.83 times as high as that of Tm@TiO2 under only 980 nm irradiation, respectively. The ethylene degradation rate of Tm@Nd@TiO2 under 980+808 nm laser irradiation is 6.4 times as that of Tm@TiO2. The photocatalytic activity of Tm@Nd@TiO2 under visible+NIR irradiation is even comparable with (~2/3) that under UV light irradiation during Rhodamine B (RhB) degradation. The enhanced photocatalytic activity of Tm@Nd@TiO2 can be attributed to the stronger light absorption in NIR region ascribed to Nd3+, lower water absorption and the enhanced UC emission of Tm@Nd with unique core@shell nanostructures. This work can provide a possible route to improve the NIR photocatalytic activity and stimulate the applications in many other fields.
关键词： upconversion,near-infrared irradiation,photocatalyst,core@shell structure
更新于2025-09-23 15:23:52
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Nano-BaTiO3 phase transition behavior in coated BaTiO3-based dielectric ceramics
摘要： In this work, the phase structure of BaTiO3 nanopowders produced by the alkoxide-hydroxide and the hydrothermal method, respectively, was systemically investigated. BaTiO3 nanopowders with cubic phase produced by the alkoxide-hydroxide method could transform to tetragonal phase when heated to about 1100oC. Cubic to tetragonal phase transformation behavior of BaTiO3 nanopowders coated with 0.3BZT-0.7BT or 0.03Nb2O5-0.01Co2O3 was studied. The internal stress within core-shell structure was proposed to explain the BaTiO3 phase transformation behaviors. The mismatch of thermal expansion coefficient between core and shell plays a crucial role in cubic to tetragonal phase transformation of BaTiO3. By tuning the composition of shell and the ratio of the shell to the core, the cubic BaTiO3 core can transform to tetragonal phase successfully after sintering at 1100oC in BaTiO3 based ceramics with core-shell structure and it is mainly resulted by the reduced internal stress between the shell and core.
关键词： Phase transitions,BaTiO3 nanopowders,Internal stress.,Core-shell structure
更新于2025-09-23 15:23:52
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studied with angle-resolved photoemission spectroscopy
摘要： We study the band structure of twinned and detwinned BaFe2As2 using angle-resolved photoemission spectroscopy. The combination of measurements in the ordered and normal states along four high-symmetry momentum directions (Γ/Z-X/Y) enables us to identify the complex reconstructed band structure in the ordered state in great detail. We clearly observe the nematic splitting of the dxz and dyz orbitals as well as folding due to magnetic order with a wave vector of (π, π, π). We are able to assign all observed bands. In particular we suggest an assignment of the electron bands different from previous reports. The high-quality spectra allow us to achieve a comprehensive understanding of the band structure of BaFe2As2.
关键词： band structure,BaFe2As2,angle-resolved photoemission spectroscopy,magnetic order,nematic splitting
更新于2025-09-23 15:23:52
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Highly Ordered 3D Microstructure Based Electronic Skin Capable of Differentiating Pressure, Temperature, and Proximity
摘要： Electronic skin are devices that mimic the functionalities of human skin, which require high sensitivity, large dynamic range, high spatial uniformity, low-cost and large area processability, and the capacity to differentiate various external inputs. We herein introduce a versatile droplet-based microfluidic-assisted emulsion self-assembly (DMESA) process to generate 3-dimensional microstructure based high-performance capacitive and piezoresistive pressure sensors for electronic skin applications. Our technique can generate uniformly sized micropores that are self-assembled in an orderly close-packed manner over a large area, which results in high spatial uniformity. The size of the micropores can easily be tuned from 100-500 μm, through which sensitivity and dynamic range were controlled to as high as 0.86 kPa-1 and up to 100 kPa. Our device can be printed on curvilinear surfaces and be molded into various shapes. We furthermore demonstrate that by simultaneously utilizing capacitive and piezoresistive pressure sensors, we can distinguish between pressure and temperature, or between pressure and proximity. These demonstrations make our process and sensors highly useful for a wide variety of electronic skin applications.
关键词： multimodal sensation,microporous structure,tactile sensing,decoupled stimuli
更新于2025-09-23 15:23:52
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Structural and photoluminescence investigations of Cr3+ mixed Li2O—Bi2O3—ZrO2—SiO2 glass ceramics for optoelectronic device application
摘要： Chromium oxide mixed Li2O―Bi2O3―ZrO2―SiO2 (Cr3+:LBZS) glasses were crystallized by heat treatment. Structural (X-ray di?raction, surface morphology, energy dispersion, DTA, FT-IR and Raman) and spectroscopic (optical absorption and luminescence), of these Cr3+:LBZS glass ceramics were studied. XRD pattern of Cr3+: LBZS glass ceramic samples exhibited distinct crystalline peaks. SEM images of the Cr3+: LBZS glass ceramic materials have revealed well identi?ed and distributed crystals of reformed size. The glass transition (Tg) and various crystallization temperatures (Tc1), (Tc2) and (Tc3) of these ceramics were identi?ed by DTA analysis. The shift in the wavenumbers of di?erent symmetrical and asymmetrical band positions of these glass ceramics were analysed by FT-IR and Raman studies. The optical bandgap (Eo), CFSE (Dq) and nephelauxetic ratio (β) were calculated. Photoluminescence properties were also investigated.
关键词： Luminescence,FTIR,DTA,Structure,Cr3+: LBZS glass ceramics,Optical
更新于2025-09-23 15:23:52
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(S)TEM methods contributions to improve the fabrication of InGaN thin films on Si, and InN nanostructures on flat Si and rough InGaN
摘要： The main results of a complete study by Transmission and Scanning-Transmission Electron Microscopies ((S)TEM) are described for (i) InGaN/Si (111) heterostructures in the whole compositional range of the alloys, and (ii) InN quantum dots (InN QDs) directly grown on Si wafers or on relatively rough InGaN/Si (111) templates. The combination of many (S)TEM-based techniques allowed to evaluate different characteristics of the systems under study: (InN QD/) InGaN/Si and InN QD/Si interfaces and crystal qualities, structural and chemical imperfections and other important features. InxGa1-xN thin films are often identified as single-crystalline, very homogeneous in composition, and mostly wurtzite-type, remarkably at any value of x. Also, (S)TEM techniques revealed that the InN nanostructures were hexagonal single crystals, mostly epitaxial to the supporting lattice. The InN crystals also exhibited partially cubic arrangements when allocated onto In-rich InxGa1-xN (i.e. x > 0.7).
关键词： Semiconductors,TEM,Heterojunctions,Crystal structure.,Nitride materials,Crystal growth,Transmission Electron Microscopy
更新于2025-09-23 15:23:52
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Quantification of collagen fiber structure using second harmonic generation imaging and two-dimensional discrete Fourier transform analysis: Application to the human optic nerve head
摘要： Second Harmonic Generation (SHG) microscopy is widely used to image collagen fiber microarchitecture due to its high spatial resolution, optical sectioning capabilities and relatively non-destructive sample preparation. Quantification of SHG images requires sensitive methods to capture fiber alignment. This paper presents a 2D Discrete Fourier Transform (DFT) based method for collagen fiber structure analysis from SHG images. The method includes integrated Periodicity Plus Smooth Image Decomposition (PPSID) for correction of DFT edge discontinuity artefact, avoiding the loss of peripheral image data encountered with more commonly used windowing methods. Outputted parameters are: the collagen fiber orientation distribution, aligned collagen content and the degree of collagen fiber dispersion along the principal orientation. We demonstrate its application to determine collagen microstructure in the human optic nerve head, showing its capability to accurately capture characteristic structural features including radial fiber alignment in the innermost layers of the bounding sclera and a circumferential collagen ring in the mid-stromal tissue. Higher spatial resolution rendering of individual lamina cribrosa beams within the nerve head is also demonstrated. Validation of the method is provided in the form of correlative results from wide-angle X-ray scattering (WAXS) and application of the presented method to other fibrous tissues.
关键词： Second Harmonic Generation,edge effect artefact correction,Discrete Fourier Transform,optic nerve head,collagen fiber structure,Non-linear microscopy
更新于2025-09-23 15:23:52
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Crystal growth and characterization of γ-glycine grown from AgSO4 for nonlinear optical applications
摘要： In the present work 0.1 M to 0.5 M proportions of silver sulphate (AgSO4) added glycine single crystals were grown by slow solvent evaporation method. The Powder XRD study confirms that the grown crystals have γ-glycine crystal structure and it crystallizes into a hexagonal structure with a non-centrosymmetric space group of P31. The dielectric constant and dielectric loss of grown crystal was carried out as a function of frequency and the results were discussed. The positive photoconducting nature of the grown crystals was studied by the photoconductivity study. Second harmonic generation (SHG) efficiency of the grown γ-glycine crystal was assessed by using Nd: YAG laser. The results confirms that the grown crystals have higher efficiency compared to the reference (KDP) crystal.
关键词： B2. Dielectric Materials,A1. X-ray diffraction,A1. Crystal structure,B2. Nonlinear optic materials
更新于2025-09-23 15:23:52
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Enhanced piezoelectric properties and temperature stability of Bi4Ti3O12-based Aurivillius ceramics via W/Nb substitution
摘要： This work provides an effective method of inducing structure distortion, relieving the tetragonal strain of the TiO6 octahedron and decreasing the concentration of oxygen vacancies to improve the piezoelectricity and temperature stability of BIT ceramics. Bi4Ti2.98W0.01Nb0.01O12 possesses an optimum piezoelectric coefficient (d33) of 32 pC/N, a high Tc of 655 °C and a large resistivity of 3 × 106 Ω·cm at 500 °C. The maximum d33 reported here is approximately quadruple than that of pure BIT (~7 pC/N). Moreover, the d33 of W/Nb co-doped BIT and the in-situ temperature stability of the compression-mode sensor present a highly stable characteristic in the range of 25–600 °C. These results imply that W/Nb-modified BIT ceramics is a promising candidate for application at high temperatures of up to 600 °C.
关键词： Bi4Ti3O12,Structure distortion,Piezoelectric properties,Oxygen vacancy,Temperature stability
更新于2025-09-23 15:23:52