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Low-temperature red long-persistent luminescence of Pr3+ doped NaNbO3 with a perovskite structure
摘要： Long persistent luminescence (LPL) phosphors can keep emitting light after the removal of excitation sources under thermal disturbances at room temperature, which provides a wide application from emergency signs to in vivo biological imaging. Unfortunately, these phosphors will exhibit poor LPL performance once the thermal activation energy is not sufficient to release the captured carriers from the traps at low-temperature. Herein, a red phosphor of Pr3+ doped NaNbO3 with a perovskite structure is designed, which realizes a low-temperature LPL. The red emission (λem=612 nm) is ascribed to the 1D2→3H4 transition of Pr3+ ions, and LPL can be visually recognized over 16 hours after the removal of the excitation source at 200 K. Low-temperature thermoluminescence curves, temperature-dependent photoluminescence spectra indicate that abundant traps (≤ 0.6 eV) exist in NaNbO3: Pr3+, which is critical for ensuring the low-temperature LPL. The investigation on low-temperature LPL properties of NaNbO3: Pr3+ helps us to reveal the importance of defects structure, and provides new opportunities in exploring luminescence materials applied in an extreme conditions.
关键词： low-temperature,persistent luminescence,defects structure,phosphors
更新于2025-09-23 15:23:52
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Crystal structure, optical and electrical properties of metal-halide compound [C7H16N2][ZnCl4]
摘要： A new organic–inorganic hybrid compound [C7H16N2][ZnCl4] was synthesized by hydrothermal method and characterized by single-crystal X-ray diffraction, IR and Raman spectroscopy, optical absorption, differential scanning calorimetry and dielectric measurements. Single crystal diffraction results showed that [C7H16N2][ZnCl4] crystallizes in the monoclinic system, space group P21/c at room temperature. In the molecular arrangement, the tetrachlorozincate anions are connected to organic cations through N-H...Cl hydrogen bonds. The Raman and IR analyses confirm the presence of the organic groups and the anionic entities. UV–Visible absorption spectrum revealed the energy of the optical band gap. DSC measurements indicated that [C7H16N2][ZnCl4] undergoes three sequential phase transitions at 287, 338 and 356 K. The dielectric study proved the ferroelectric properties below the 338K and indicates their classical character for this compound. The analysis of Nyquist plots revealed the contribution of the bulk mechanism and the grain boundaries.
关键词： Phase transitions,Hybrid material,Crystal structure,Optical absorption,Ferroelectric properties,Conduction mechanism
更新于2025-09-23 15:23:52
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Enhanced electrical conductivity of silver nanoparticles decorated fabrics with sandwich micro-structure coating layer based on “silver colloid effect”
摘要： Surface modification of nonconductor fabric substrate for enhancing electrical conductivity is a desirable work of flexible wearable devices. In our work, silver conductive layer with sandwich micro-structure was decorated on polyester fabric, and such a sandwich micro-structure layer is composed of the inner polyurethane (PU) as the interface binder, the filling layer of the precipitating silver nanoparticles (AgNPs) as the conductive path via in-situ chemical synthesis, the outer PU layer as the shielding layer. The obtained sandwich micro-structure PET fabric possessed six orders of magnitude higher conductivity than that of the case without sandwich micro-structure. Such marvelous increasing conductivity can be attributed to the “silver colloid effect” which is deemed as approximation of conductive principle of silver conductive adhesives. The present study provides a potential strategy and theoretical basis for the preparation of low concentration silver conductive fabrics.
关键词： Silver colloid effect,Nanoparticles,Quantum tunnelling effect,Sandwich micro-structure,Polymers
更新于2025-09-23 15:23:52
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Ultra-broadband metamaterial absorber with graphene composites fabricated by 3D printing
摘要： An ultra-broadband electromagnetic (EM) absorber composed of composite metamaterials was designed, fabricated and characterized. Polylactic-acid/reduced graphene oxide (PLA/RGO) composites with different amounts of RGO were prepared as a primary material collection. To provide good impedance matching and efficient wave attenuation, the multilayer absorbers were designed with a gradient index (GRIN) of characteristic impedance by manipulating the RGO content and the geometric parameters of the unit cell. The absorbers with different numbers of layers were fabricated by a material extrusion process, and then the reflection loss (RL) of the prepared samples was measured. Results showed that the methodology for designing a metamaterial absorber with gradient impedance and fabricating through a 3D printing process was effective in producing ultra-broadband absorbers. The seven-layer absorber achieved an absorption above 90% in a broad bandwidth of 4.5–40 GHz. This work could provide inspiration for upgrading the performance of some conventional absorbing composites through a rational design of the composite proportion and structure.
关键词： Microwave absorption,Multilayer structure,3D printing,Composite materials,Metamaterials
更新于2025-09-23 15:23:52
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Graphdiyne: A promising nonlinear optical material modulated by tetrahedral alkali-metal nitrides
摘要： A new series of the functionalized graphdiyne (GDY) material was designed by adsorbing the tetrahedral Li3NM molecules on the largely delocalized π-conjugated GDY surface, namely Li3NM@GDY (M = Li, Na, K), and its structure, chemical stability, electronic property, and the first hyperpolarizability were investigated by using the density functional theory computations. Our results reveal that the Li3NM molecules can interact with three triangular holes on the GDY surface, in which the van der Waals interactions play a crucial role in enhancing the structural stability. Meanwhile, the total NPA charges on the Li3NM molecules are gradually increased from Li to K, and the Li3NM molecules can transfer an electron to GDY, forming intramolecular electron donor and acceptor pairs. All of studied complexes exhibit the giant static first hyperpolarizabilities (βtot), up to ~2.88 × 105 a.u. for Li3NK@GDY, which can be explained by two-level expression from the TDDFT calculations. This study will inevitably stimulate further synthesis of the novel graphdiyne-based nonlinear optical materials.
关键词： Graphdiyne,Electronic structure,TDDFT,Charge transfer,Nonlinear optical property
更新于2025-09-23 15:23:52
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Data-driven and probabilistic learning of the process-structure-property relationship in solution-grown tellurene for optimized nanomanufacturing of high-performance nanoelectronics
摘要： Two-dimensional (2-D) semiconductors have been intensely explored as alternative channel materials for future generation ultra-scaled transistor technology [1–8]. However, significant roadblocks (e.g., poor carrier mobilities [9–11], instability [4,5,10], and vague potential in scaling-up [10,12–15]) exist that prevent the realization of the current state-of-the-art 2-D materials’ potential for energy-efficient electronics. The emergent solution-grown tellurene exhibits attractive attributes, e.g., high room-temperature mobility, large on-state current density, air-stability, and tunable material properties through a low-cost, scalable process, to tackle these challenges [16]. Nevertheless, the fundamental manufacturing science of the hydrothermal processing for tellurene remains elusive. Here, we report on the first systematic, data-driven learning of the process-structure-property relationship in solution-grown tellurene, revealing the process factors’ effects on tellurene’s production yield, dimensions, and transistor-relevant properties, through a holistic approach integrating both the experimental explorations and data analytics. We further demonstrate the application of such fundamental knowledge for developing tellurene transistors with optimized and reliable performance, which can enable the cost-effective realization of high-speed, energy-efficient electronics.
关键词： Process-structure-property relationship,2-D materials,Energy-efficient electronics,Nanomanufacturing,Tellurene,Data-driven learning
更新于2025-09-23 15:23:52
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Asymmetric Diarylethenes with Oxidized 2-Alkylbenzothiophen-3-yl Units: Chemistry, Fluorescence, and Photoswitching
摘要： Reversibly photoswitchable diarylethenes (DAEs) with fluorescent closed forms are applied in biology- and material science-related super-resolution microscopy. Yet, their full photoswitchable capacities remain unrevealed and unexplored. Due to limitations in synthesis, only 1,2-[bis-(2-ethyl-1-benzothiophene-1,1-dioxide-3-yl)]perfluorocyclopentenes with two identical or very similar aryl groups attached to C-6 and C-6′ have been prepared so far. DAEs with increased Stokes shifts related to asymmetric structures and the presence of 'push–pull' substituents are introduced in the present study, and their switching power is studied. The new 'simplified' asymmetric DAEs possess higher cycloreversion quantum yields, but lower emission efficiencies than their known analogs with extended π-conjugation paths. Fatigue resistance in organic (acetonitrile and methanol) and aqueous solvents is studied, and the performance in reversible saturable optical fluorescence transition (RESOLFT) microscopy is evaluated. The push–pull structures show an outstanding increase in fatigue resistance, compared with a reference (H/H) diarylethene. Fatigue resistances on the order of thousands of cycles have been observed in acetonitrile solutions without exclusion of air oxygen. The structure–property relationships and facile preparation procedures enable rational design of DAEs applicable as photoswitchable fluorescent probes. A new setup and methodology for measuring switching performance of fluorescent DAEs are introduced.
关键词： photoluminescence,photonics,photochemistry,structure–property relationships
更新于2025-09-23 15:23:52
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Electrochromic 2,4,6-triphenyl-1,3,5-triazine based esters with electron donor-acceptor structure
摘要： Ten tripod-shaped electrochromic materials (compound 1–10) were designed and synthesized by esterification of 4,4',4''-s-triazine-2,4,6-triyl-tribenzoic acid with different alcohols and phenols. These materials have a 2,4,6-triphenyl-1,3,5-triazine core and three ester side arms, forming an electron donor–π-acceptor structure. The electrochemical and optical properties of 1–10 were characterized by cyclic voltammetry and ultraviolet–visible spectroelectrochemistry. The conjugated structure of 1–10 markedly influenced their electrochemical properties. Electrochromic devices containing some of these compounds (1, 2, 4, 5, and 10) displayed intense color changes, fast switching times (<2 s), high optical contrast (>60%), good switching stability, high optical density (>1.0), and high coloring efficiency (>1000 cm2 C?1). The colored state of these devices strongly depended on the conjugated structure of the tripod-shaped component. Short chain lengths (compounds 1 and 2) and electron-donating groups (compounds 4, 5, 8, and 10) were beneficial to electrochromic properties, whereas a longer chain length (compound 3) and electron-withdrawing groups (compounds 6 and 9) adversely affected electrochromic properties.
关键词： Electron donor-acceptor structure,2,4,6-Triphenyl-1,3,5-triazine based esters,Tripod-shaped electrochromic materials,Electrochromic devices
更新于2025-09-23 15:23:52
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Control of Circularly Polarized Luminescence by Orientation of Stacked π-Electron Systems
摘要： New planar chiral building blocks based on 4,7,12,15-tetrasubstituted [2.2]paracyclophanes were obtained via a synthetic route involving an optical resolution step. Planar chiral enantiomers, comprising of two fluorophores that were stacked to form a V-shaped higher-ordered structure, were synthesized from these building blocks. The V-shaped molecules emitted intense circularly polarized luminescence (CPL). Their chiroptical properties were compared with those of X-shaped molecules bearing the same two fluorophores stacked together. CPL sign of the X-shaped molecule was opposite to that of the V-shaped molecule, which is supported by the theoretical results, indicating that CPL sign can be controlled by the orientation of the stacked fluorophores.
关键词： circularly polarized luminescence,planar chirality,higher-ordered structure,[2.2]paracyclophane
更新于2025-09-23 15:23:52
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Identification performance of two luminescent lanthanide–organic frameworks
摘要： By the reaction of organic ligands, 2-(3,4-dimethylphenyl)-1H-imidazole-4,5-dicarboxylic acid (H3DMPhIDC) and terephthalic acid (H2DCB) with Eu3+ or Tb3+ ions, respectively, two luminescent metal-organic frameworks (MOFs) [Ln(H2DMPhIDC)(DCB)]n [Ln = Eu (1); Tb (2)] have been constructed. Both MOFs 1 and 2 are isostructural and show two-dimensional structures, which were fully characterized by single crystal X-ray diffraction, elemental analysis, and infrared spectroscopy. Both MOFs have excellent thermal and water stability, and indicate characteristic lanthanide metallic luminescence. Importantly, they can significantly recognize Fe3+ cation in aqoues solutions. Their sensing mechanisms have been suggested according to structural analyses, PXRD data and UV-Vis determinations.
关键词： recognition,crystal structure,luminescent MOFs,fluorescence quenching
更新于2025-09-23 15:23:52