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Achieving Amorphous Ultralong Room Temperature Phosphorescence by Coassembling Planar Small Organic Molecules with Polyvinyl Alcohol
摘要： Development of novel strategies for achieving amorphous ultralong organic phosphorescence (UOP) at room temperature is highly desired. Herein, a simple approach is reported by coassembling small organic molecules with polyvinyl alcohol (PVA) to afford amorphous UOP. These small organic molecules with planar conformation present quenched triplet state emission in an excessive stacking solid state. When coassembling these molecules with PVA, their planar structures are well confined in coassembly films. Such a confined environment leads to restricted molecular rotation and vibration, permitting these molecules to show stable triplet state and generate UOP. In control studies, corresponding structurally distorted molecules are also coassembled with PVA. However, they exhibit very weak or quenched UOP, since distorted structures with molecular rotation and vibration could easily dissipate the excitation energy in dilute film state. By employing this polymer confinement strategy, multicomponent luminescence dyes are further coassembled with PVA for multicolor luminescence displays, providing multicolor, uniform, and flexible luminescence films. This work demonstrates a general strategy of employing small organic molecules to coassemble with PVA to obtain amorphous UOP, which greatly expands the scope of organic molecules for developing simple but useful UOP films.
关键词： ultralong organic phosphorescence,distorted molecules,coassembly,planar molecules,flexible luminescence films
更新于2025-09-09 09:28:46
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Temperature Dependence of the Luminescence Spectra of a 5CB Liquid Crystal and its Phase Transitions
摘要： The spectroluminescence properties of 4cyano4'pentylbiphenyl CH3(CH2)4(C6H4)2CN (5CB) were studied in the temperature range 4.2–297 K. A red shift of the fluorescence spectrum was noted with increasing temperature. The long-wavelength shifts in these spectra were also analyzed. Comparison of the temperature dependence curves for the emission at the band maxima λmax and their halfwidths Δλ/2 in the fluorescence spectra and the results of a differential scanning calorimetry (DSC) study showed that phase transitions occur in the 5CB liquid crystals at ~230 and ~260 K.
关键词： liquid crystal,phase transition,differential scanning calorimetry,luminescence,low temperature,conformation change
更新于2025-09-09 09:28:46
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Mesoporous silica modified luminescent Gd2O3:Eu nanoparticles: physicochemical and luminescence properties
摘要： Highly colloidal Gd2O3:Eu nanoparticles (core-NPs) were synthesized by thermal decomposition via weak base at low temperature. The sol–gel chemical process was employed for silica layer surface coating to increase solubility, colloidal stability, biocompatibility, and non-toxicity at the ambient conditions. XRD results indicate the highly puri?ed, crystalline, single phase, and cubic phase Gd2O3 nanocrystals. TEM image shows that the mesoporous thick silica layer was effectively coated on the core nanocrystals, which have irregular size with nearly spherical shape and grain size about 10–30 nm. An absorption spectra and zeta potential results in aqueous media revealed that solubility, colloidal stability, and biocompatibility character were enhanced from core to core–shell structure because of silica layer surface encapsulation. The samples, demonstrated excellent photoluminescence properties (dominant emission 5D0 → 7F2 transition in the red region at 610 nm), indicated to be used in optical bio-detection, bio-labeling, etc. The photoluminescence intensity of the silica shell modi?ed core/shell NPs was suppressed relatively core-NPs; it indicates the multi-photon relaxation pathways arising from the surface coated high vibrational energy molecules of the silanol groups. The core/nSiO2/mSiO2 nanocrystals display strong emission (5D0 → 7F2) transition along with excellent solubility and biocompatibility, which may ?nd promising applications in the photonic based biomedical ?eld.
关键词： silica,Gadolinium oxide,Biocompatible,Luminescence properties,Zeta potential,Mesoporous
更新于2025-09-09 09:28:46
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Optical Spectroscopy Methods in the Estimation of the Thermal Stability of Bimetallic Pd–Rh/Al2O3 Three-Way Catalysts
摘要： A series of three-way catalysts containing palladium and rhodium were prepared by an incipient wetness impregnation of support with aqueous solution of [Pd(NH3)4](NO3)2 and Na3[Rh(NO2)6] compounds. Both pure and La-doped aluminum oxides were used as a support. The catalysts showed very close activity under stoichiometric and reductive conditions, but were different in terms of thermal stability being tested in a prompt thermal aging regime. UV–Vis and luminescence spectroscopies were found to be informative for diagnostics of rhodium and palladium concentration and state, thus giving the possibility to follow the changes taking place with active components (migration, agglomeration, bulk diffusion).
关键词： Metal migration,Prompt thermal aging,UV–Vis spectroscopy,Three-way catalysts,Luminescence spectroscopy
更新于2025-09-09 09:28:46
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Enhancement of the red emission in Ba <sub/>3</sub> (PO <sub/>4</sub> ) <sub/>2</sub> :Eu3+ by addition of charge compensator Na+
摘要： Ba2.96(PO4)2:0.04Eu3+ (S1) and Ba2.92Na0.04(PO4)2:0.04Eu3+ (S2) were prepared by solid state reaction. The phases and luminescent properties of the obtained phosphors were characterized. The results demonstrate that the phosphors particles emit an intensive red light under excitation at 395 nm. Both phosphors can be efficiently excited by ultraviolet and blue light, and the emission spectra mainly consist of two emission peaks at 591 nm and 611 nm. The crystallographic sites of Eu3+ ions in Ba3(PO4)2 host were discussed on the base of emission spectra and its host crystal structure. By introducing the charge compensator Na+ into the S1 phosphor, its emission intensity was enhanced, indicating that S2 could serve as a promising red-emitting phosphor for UV LED applications.
关键词： charge compensator,barium orthophosphate,Phosphors,luminescence,photoluminescence
更新于2025-09-09 09:28:46
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Mixed-ligand strategy affording two new metal-organic frameworks: Photocatalytic, luminescent and anti-lung cancer properties
摘要： Mixed-ligand strategy afforded two new metal-organic frameworks (MOFs), namely [Ni(L)0.5(4,40-bipy)0.5(H2O)2]n (1) and [Zn2(L)(bpp)2]n (2) (H4L ? 1,3-di(30,50-dicarboxylphenyl)benzene, 4,40-bipy ? 4,40 ebipyridine and bpp ? 1,3-di(4-pyridyl)propane), which were further characterized by elemental analyses, powder X-ray diffraction analyses and single crystal X-ray diffraction analyses. Compound 1 features a 4-fold interpenetrated 3D framework with (3,4)-connected dmd-type topology, and compound 2 features a 3D complicated framework with 4-connected topology. Moreover, the photocatalytic activity of compound 1 for the degradation of methyl blue (MB) and luminescent property of compound 2 were investigated in detail. In addition, the anti-lung cancer activities of both complexes have been evaluated via the MTT assay against three human lung cancer cells A549, H1299 and PC9.
关键词： Topology,Photocatalytic activity,Mixed-ligand strategy,Luminescence
更新于2025-09-09 09:28:46
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The Preparation and Optical Properties of Ni(II) and Mn(II) Doped in ZnTe Nanobelt/Nanorod by Using Chemical Vapor Deposition
摘要： The doping techniques are often used to modify the properties of semiconductors. Transition metal ion doping in semiconductor can lead to dilute magnetic semiconductors (DMSs), which may initiate some novel properties related to spins. In contrast to the wide band semiconductor ZnO, ZnSe and CdS crystal the transition metal (TM) ion aggregate can be the origin of the ferromagnetic behaviors, which influence their optical properties mainly through the exciton-spin interactions due to their high exciton binding energy. For narrow band semiconductor, the carrier-spin coupling is the main cause of magnetism as observed in ZnTe. The ZnTe nanobelt for DMS with the TM ions such as Ni(II) and Mn(II) doping mainly induce the excess carrier effect in the lattice after photo-excitation, whose optical properties are also strongly depended on the fabrication method structure and morphology. Photo-excited carriers and electron–phonon interaction (but less excitons) are responsible for their large redshifts in ZnTe nanostructures. The strong interaction between the doped magnetic ion spins and holes, electron–phonon coupling, p–d hybridization as well as local electron correlation in TM ions determined their optical properties. TM ions incorporation in ZnTe lattice has suppressed the broad defect emission band far from the bandedge and broadened the electron correlations and electron hole plasma band near bandedge when excited by the rising excitation powers. We also identified that the polarized PL of Ni(II) and Mn(II) doped samples to calculate the strain dependence of band splitting near valance band.
关键词： Chemical Vapor Deposition (CVD),Transition Metal Ion,Polarization,Dilute Magnetic Semiconductor (DMS),Luminescence,II–VI Semiconductor
更新于2025-09-09 09:28:46
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Synthesis and Photophysical Properties of Rhenium(I)-Alkynyl Molecular Rectangles
摘要： A series of highly conjugated, rigid Re(I)-based molecular rectangles {[fac-Re(CO)3Br]2(μ-bpy) (μ-L)}2 (1, L = 1,4-bis(42 -pyridylethynyl)benzene, bpeb; 2, L = 1,4-bis(42 -pyridylethynyl)naphthalene, bpen; 3, L = 1,4-bis(42 -pyridylethynyl)anthracene, bpea; and bpy = 4,42 -bipyridine) containing two different types of pyridyl ligands were synthesized, characterized and their photophysical properties studied. Successful emission color tuning was achieved by incorporating rigid alkynyl ligands into the Re(I) rectangles. Complexes 1-3 exhibited an intense absorption bands with a high e value at > 340 nm in THF solution, which is attributed to mixed two metal-to-ligand charge transfer dp(Re) → p*(bpy) and dp(Re) → p*(alkynyl)) along with ligand-to-ligand charge transfer (1LLCT)/ and intraligand charge transfer (1ILCT) transitions. Compound 1 featured a broad and structureless emission band at 619 nm, which was attributed to the emission of 3MLCT dp(Re) → p*(bpy) and/or [dp(Re) → p*(alkynyl)] characteristics with an additional luminescence at 431 nm. Whereas complexes 2 and 3 displayed an intraligand (IL) emission at 445 and 489(sh), 521 nm. These compounds represent a new class of visible light-harvesting materials that exhibit greatly enhanced emission decay lifetimes as a result of intervening ligand triplet states (3LLCT/3ILCT) present on the alkynyl appended naphthalene and anthracene chromophores, as evidenced by transient absorption spectra.
关键词： rhenium,quenching,Rectangles,alkynyl ligands,luminescence
更新于2025-09-09 09:28:46
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AIP Conference Proceedings [Author(s) 6TH INTERNATIONAL CONFERENCE ON PRODUCTION, ENERGY AND RELIABILITY 2018: World Engineering Science & Technology Congress (ESTCON) - Kuala Lumpur, Malaysia (13–14 August 2018)] - Synthesis of carbon dots and their optical properties
摘要： In this paper, carbon dots were synthesized from glucose, soot and ethylene glycol by hydrothermal treatment. The resulting carbon dots were characterized by luminescent spectrometry and spectrophotometry. The spectra exhibit bright luminescence in the blue region and strong absorption in the ultraviolet region. All samples exhibit typical excitation wavelength-dependent properties.
关键词： optical properties,hydrothermal treatment,luminescence,absorption,carbon dots
更新于2025-09-09 09:28:46
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Up-Conversion Photoluminescence of Sol–Gel Derived CaY <sub/>2</sub> O <sub/>4</sub> Powders Under 980 nm Excitation
摘要： Up-conversion is an anti-stokes process that can convert near-infrared light into visible light. Besides the requirement of high optical conversion ef?ciency, the thermochemical stability of the host materials is critical for in practical applications, and a stable oxide host material is optimal. CaY2O4 follows the same ordered structure of CaFe2O4, which is composed of an (R2O4)2? (R = rare earth metal) framework of double octahedral moieties with rare earth ions residing within the framework. CaY2O4 is a promising host material due to its favorable characteristics such as high chemical and thermal stability, low-phonon energy, and environment friendliness. Rare earth ion (Er3+ and Yb3+)-doped nano-crystalline phosphors were prepared by a sol–gel process. The synthesized sample was characterized by X-ray diffraction analysis and the crystallite size was con?rmed by Scherrer’s formula and transmission electron microscopy. The surface morphology of the powders was determined by scanning electron microscopy. X-ray diffraction patterns con?rmed their pure orthorhombic structure after annealing at 1,200 °C and the morphology of particles was found to be a nearly spherical shape with a diameter of the order of ～100 nm. Photoluminescence properties of the powders were measured by exciting the samples with a 980 nm diode laser at room temperature. Under the 980-nm laser excitation, the green and red up-conversion emissions were observed at around 520–540 nm, 540–570 nm and 640–680 nm, which, are attributed to the transitions of 2H11/2 →4I15/2, 4S3/2 →4I15/2 and 4F9/2 →4I15/2 of Er3+ ions, respectively. The up-conversion intensity as a function of laser power shows that the up-conversion mechanism corresponding to green and red emissions occurs via a two-photon process.
关键词： Up-Conversion Phosphor,CaY2O4,Luminescence
更新于2025-09-09 09:28:46