Good Luminescence Properties Research Articles

Exploration of the structural and optical properties of a red-emitting phosphor K2TiF6:Mn4+**Project supported by the National Natural Science Foundation of China (Grant No. 11574220), Fundamental Research Funds for the Central Universities, China (Grant No. SWU118055), and the Special Program for Applied Research on Super Computation of the NSFC-Guangdong Joint Fund (the second phase), China.

The exploration of the appropriate red phosphor with good luminescence properties is an important issue in the development of current white light-emitting diode (WLED) devices. Transition metal Mn-doped compounds are fascinating luminescent materials. Herein, we performed a systematic theoretical study of the microstructure and optical properties of K2TiF6:Mn4+ using the CALYPSO structure search method in combination with first-principles calculations. We uncovered a novel structure of K2TiF6:Mn4+ with space group P-3m1 symmetry, where the impurity Mn4+ ions are accurately located at the center of the MnF6 octahedra. Based on our developed complete energy matrix diagonalization (CEMD) method, we calculated transition lines for 2Eg → 4A2, 4A2 → 4T2, and 4A2 → 4T2 at 642, nm, 471 nm, and 352 nm, respectively, which are in good agreement with the available experimental data. More remarkably, we also found another transition (4A2 → 2T2) that lies at 380 nm, which should be a promising candidate for laser action.

Bismuth(III) based Metal Organic Frameworks: Luminescence, Gas Adsorption, and Antibacterial Studies

BiIII‐MOFs 1–4 were prepared via solvothermal method using four organic linkers; 2‐mercapto‐3‐methyl‐4‐thiazoleacetic acid (H2MMTA), 2,6‐naphthalenedicarboxylic acid (2,6‐NDA), 4,6‐dihydroxy‐2‐mercaptopyrimidine (H2DMP), and 4‐mercaptobenzoic acid (H2MBA), respectively. The resulting MOFs were structurally/morphologically characterized by UV/Vis, AAS/ICP‐MS, Fourier transform infrared spectroscopy (FT‐IR), 1H NMR, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and powder X‐ray diffraction technique. All these MOFs showed good luminescence properties exhibiting blue luminescence. N2 gas adsorption isotherms of 1–4 confirmed the porosity of these frameworks. In order to evaluate the effect of metal ion upon chelation, the free organic linkers and respective MOFs were screened for their antibacterial potential against some pathogenic bacteria and appreciable activity was observed.

A Novel Tb@Sr-MOF as Self-Calibrating Luminescent Sensor for Nutritional Antioxidant.

Sesamol, is well-known antioxidant and can reduce the rate of oxidation and prolong expiration date. It is also potentially antimutagenic and antihepatotoxic, the detection of sesamol is important and remains a huge challenge. Herein, a new 3D alkaline earth Sr metal organic framework [Sr(BDC)·DMAC·H2O]n (BDC = benzene-1,4-dicarboxylate; DMAC = N,N-dimethylacetamide) is synthesized and a probe based on Tb3+ functionalized Sr-MOF. The Tb(3+)@Sr-MOF showed good luminescence and thermal property. Due to the energy competition between sesamol and ligand, the luminescence intensity of sesamol increases meantime luminescence intensity of Tb3+ decreases, the ratio of the emission intensities (I344/I545) linearly increases with sesamol in concentrations ranging from 1 × 10−7 to 8 × 10−4 M. Furthermore, the fluorescence-detected circular test shows that the composite Tb(3+)@Sr-MOF can serve as ratiometric sensor for sensing of sesamol. This is the first example for self-calibrated detecting sesamol based on metal-organic framework (MOF).

Luminescent fluorinated chiral liquid crystalline oligomers containing Eu(III) complexes

ABSTRACTLuminescent fluorinated chiral liquid crystalline oligomers containing Eu(III) complexes (Eu-LCOs) with good liquid crystalline properties and obvious luminescence properties were prepared using Poly(methylhydrogeno)siloxane (PMHS), chiral liquid crystalline monomer (M1), fluorinated liquid crystalline monomer (M2), fluorinated Eu(III) complex (M3). The chemical structures, liquid crystalline behaviours of Eu-LCOs were characterised by various experimental techniques. The introduction of small quantity of fluorinated Eu(III) complexes endowed the oligomers with excellent luminescence properties. The Eu(III) complexes did not change the liquid crystalline textures of the oligomers. Fourier transform infrared imaging showed that Eu(III) complexes were evenly distributed in oligomers. In order to express the mutual effect and distribution of the components, a structural representation of Eu-LCOs was established. The Eu-LCOs displayed wide mesophase temperature ranges and reversible mesomorphic phase transitions. The Eu-LCOs can emit soft red light when being excited. Luminescence intensities of Eu-LCOs gradually increased with an increase of Eu(III) complexes from 0 to 1.0 mol%. However, the luminescence intensities of Eu-LCOs decreased monotonically with the increase of temperature in liquid crystalline phase.

JOES: An application software for Judd-Ofelt analysis from Eu3+ emission spectra

In this paper we will be presenting JOES (Judd-Ofelt from Emission Spectra), an application software for calculation of the Judd-Ofelt intensity parameters and derived quantities from the emission spectra of Eu3+ doped materials. The program is written to be user friendly and it requires no previous experience in the field of study. This Free and Open-Source program written in JAVA, works on Windows, Linux and MAC OS operating systems. Program has been tested on three europium doped oxides with good luminescent properties: TiO2:Eu3+, ZrO2:Eu3+ and Nb2O5:Eu3+. We wish to give to the researchers this theoretical tool which can make the calculations easier, faster and more reliable.

Synthesis of bamboo-like 3C-SiC nanowires with good luminescent property via nano-ZrO2 catalyzed chemical vapor deposition technique

This work provides a novel chemical vapor deposition technique to synthesize bamboo-like 3C-SiC nanowires (NWs) at low temperature (1200 °C) in absence of Ar gas by Si and phenolic resin powders, and catalyzed by trace nano-ZrO2 particles. The obtained bamboo-like 3C-SiC NWs were dozens of microns in length and composed of two alternating structure units with periodical fluctuating diameter, and the diameters of nodes and stems were 50–70 nm and 40–50 nm, respectively. Nano ZrO2 catalyst was key factor for SiC NWs formation and growth because ZrO2 triggered reactions to generate more SiO(g) and CO(g), and activated SiO (g) and CO (g) by weakening Si–O and C–O bond strength. The reciprocal formation of ZrC and ZrO2 occurred repeatedly led to SiC growing into bamboo-like NWs. The bamboo-like SiC NWs have good violent-blue luminescent property.

A novel phosphor of Eu3+-activated Na3GaF6: Synthesis, structure, and luminescence properties

A series of novel Na3Ga(1-x)F6:xEu3+(x = 1%, 3%, 5%, 7% and 10%) phosphors were synthesized by hydrothermal synthesis method. The crystal structure and luminescence properties of Na3GaF6:Eu3+ were characterized by X-ray powder diffraction (XRD), Scanning electron microscope (SEM), photoluminescence (PL) and photoluminescent excitation spectra (PLE) as well as decay curves. The results indicated that Eu3+ can replace Ga3+ in the lattice of Na3GaF6 without any impurity. The micro-particle of the phosphor was uniform and regular with a smooth surface. Upon 395 nm excitation, the phosphors show intense reddish-orange color including a series of narrow peaks attributed to the typical f–f transition of Eu3+. Not like most of other rare-earth doped sample, the Na3GaF6:Eu3+ phosphors show obvious anti-thermal quenching behavior. All the results demonstrated that Na3GaF6:Eu3+ phosphors exhibit good luminescent properties and might have a potential to applications in lighting technology.

Fabrication Flexible and Luminescent Nanofibrillated Cellulose Films with Modified SrAl₂O₄: Eu, Dy Phosphors via Nanoscale Silica and Aminosilane.

Flexible 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized nanofibrillated cellulose (ONFC) films with long afterglow luminescence containing modified SrAl2O4: Eu2+, Dy3+ (SAOED) phosphors were fabricated by a template method. Tetraethyl orthosilicate (TEOS) and (3-aminopropyl) trimethoxy-silane (APTMS) were employed cooperatively to improve the water resistance and compatibility of the SAOED particles in the ONFC suspension. The structure and morphology after modification evidenced the formation of a superior SiO2 layer and coarse amino-compounds on the surface of the phosphors. Homogeneous dispersions containing ONFC and the modified phosphors were prepared and the interface of composite films containing the amino-modified particles showed a more closely packed structure and had less voids at the interface between the cellulose and luminescent particles than that of silica-modified phosphors. The emission spectra for luminescent films showed a slight blue shift (3.2 nm) at around 512 nm. Such flexible films with good luminescence, thermal resistance, and mechanical properties can find applications in fields like luminous flexible equipment, night indication, and portable logo or labels.

Formation of Mono- and Polynuclear Luminescent Lanthanide Complexes based on the Coordination of Preorganized Phosphonated Pyridines.

A series of polynuclear assemblies based on ligand L (1,4,7-tris[hydrogen (6-methylpyridin-2-yl)phosphonate]-1,4,7-triazacyclononane) has been developed. The coordination properties of ligand L with LnIII (Ln = La, Eu, Tb, Yb, Lu) have been studied in water (pH = 7.0) and in D2O (pD = 7.0) by UV-absorption spectrometry, spectrofluorimetry, 1H and 31P NMR, DOSY, ESI-mass spectrometry, and X-ray diffraction. This nonadentate ligand forms highly stable mononuclear complexes in water and provides a very efficient shielding of the Ln cations, as emphasized by the very good luminescence properties of the Yb complex in D2O, especially regarding its lifetime (τD2O = 10.2 μs) and quantum yield (ϕD2O = 0.42%). In the presence of excess LnIII cation, polynuclar complexes of [(LnL)2Ln x] stoichiometry (x = 1 and x = 2) are observed in solution. In the solid state, a dinuclear complex of La could be isolated and structurally characterized by X-ray diffraction, unraveling the presence of strong hydrogen bonding interactions between a La(H2O)93+ cation and the [LaL]3- complex.

Luminescence properties of LiYF4:Yb3+, Er3+ phosphors: A study on influence of synthesis temperature and dopant concentration

Yb3+ and Er3+ doped LiYF4:RE3+ (RE = Yb, Er) phosphors have been synthesized using solid state reaction of pre-converted rare earth fluorides and lithium fluoride. Structural and morphological properties of the synthesized fluoride phosphors are examined. Upconversion emission studies performed in the developed phosphors showed blue, green and red emission bands under 980 nm excitation. Effect of Yb3+ ions concentration and synthesis temperature on the upconversion emission bands has been investigated. As the synthesis temperature increased the phosphors exhibited intense upconversion luminescence. The colour co-ordinate analysis confirmed the strong green emission under upconversion process. Luminescence in synthesized phosphors have also been investigated with respect to 378 nm excitation. The prepared phosphors have shown good luminescent properties and could be a potential candidate for luminescent based device fabrications.

The Impact of Atmosphere on the Local Luminescence Properties of Metal Halide Perovskite Grains.

Metal halide perovskites are exceptional candidates for inexpensive yet high-performing optoelectronic devices. Nevertheless, polycrystalline perovskite films are still limited by nonradiative losses due to charge carrier trap states that can be affected by illumination. Here, in situ microphotoluminescence measurements are used to elucidate the impact of light-soaking individual methylammonium lead iodide grains in high-quality polycrystalline films while immersing them with different atmospheric environments. It is shown that emission from each grain depends sensitively on both the environment and the nature of the specific grain, i.e., whether it shows good (bright grain) or poor (dark grain) luminescence properties. It is found that the dark grains show substantial rises in emission, while the bright grain emission is steady when illuminated in the presence of oxygen and/or water molecules. The results are explained using density functional theory calculations, which reveal strong adsorption energies of the molecules to the perovskite surfaces. It is also found that oxygen molecules bind particularly strongly to surface iodide vacancies which, in the presence of photoexcited electrons, lead to efficient passivation of the carrier trap states that arise from these vacancies. The work reveals a unique insight into the nature of nonradiative decay and the impact of atmospheric passivation on the microscale properties of perovskite films.

Morphologies and Properties of PET Nano Porous Luminescence Fiber: Oil Absorption and Fluorescence-Indicating Functions.

A polyethylene terephthalate nano porous luminescence fiber (PNPLF) was prepared through electrospun technology. The SEM and TEM images show that the surfaces of the fibers are covered with pores. The diameter of the fiber is 250-500 nm, and the diameter of the pores is 20-180 nm. The water and oil contact angles of PNPLF are 135° and 27°, respectively. The oil absorption value of the as-prepared PNPLF achieves 135 g/g and has a good oil absorption function. The as-prepared PNPLF has good luminescence properties and fluorescent-indicating function. Even trace amounts of oil can also cause obvious change of fluorescence intensity of PNPLF which has a good stability from 20 °C to 70 °C. The breaking stress of yarn of PNPLF reaches 117cN. Furthermore, the good mechanical properties and thermal properties of PNPLF provide important basic conditions for their wide applications.

Multifunctional Lanthanide-Doped Core/Shell Nanoparticles: Integration of Upconversion Luminescence, Temperature Sensing, and Photothermal Conversion Properties.

Multifunctional integration on single upconversion nanoparticles (UCNPs), such as the simultaneous achievement of imaging, sensing, and therapy, will be extremely attractive in various application fields. Herein, we demonstrated that single core/shell NaGdF4:Yb/Er-based UCNPs (<10 nm) with a highly Yb3+ or Nd3+ doped shell simultaneously exhibited good upconversion luminescence (UCL), temperature sensing, and photothermal conversion properties under 980 or 808 nm excitation, respectively. The spatial separation between the emission/sensing core and the heating shell was able to tailor the competition between the light and heat generation processes, and hence higher UCL efficiency and enhanced heating capability were achieved by introducing the rational core/shell design. Especially, Nd3+-sensitized core/shell nanoparticles were excitable to the laser at a more biocompatible wavelength of 808 nm, and hence the heating effect of water was greatly minimized. The heating and sensing capabilities of Nd3+-sensitized core/shell UCNPs with smaller sizes (<10 nm) were confirmed in aqueous environment under single 808 nm laser excitation, implying their promising applications in imaging-guided and temperature-monitored photothermal treatments.

Luminescence properties of mechanochemically synthesized lanthanide containing MIL-78 MOFs.

Three metal-organic framework (MOF) compounds, Ln0.5Gd0.5{C6H3(COO)3}; Ln = Eu, Tb, and Dy with a MIL-78 structure, have been synthesized by a solvent-free mechanochemical method from stoichiometric mixtures of benzene 1,3,5-tricarboxylic acid, C6H3(COOH)3, also known as trimesic acid, and the respective lanthanide carbonates, Ln2(CO3)3·xH2O, Ln = Eu, Gd, Tb and Dy. MIL-78 (Ln0.5Gd0.5) shows the characteristic red, green, and yellow luminescence of Eu3+, Tb3+, and Dy3+, respectively. Efficient intramolecular energy transfer from the ligand triplet state to the excited states of Ln3+ ions can be observed. The lifetimes and quantum yields of these compounds are studied and discussed in detail. Among the three compounds, the Tb3+ containing compound shows the longest lifetime and highest quantum yield due to a smaller contribution from non-radiative decay pathways and better matching of the lowest triplet energy level of the benzenetricarboxylate ligand and the resonance level of Tb3+.

Formation of highly luminescent cesium bismuth halide perovskite quantum dots tuned by anion exchange.

Cs3Bi2Br9 quantum dots (QDs) with photoluminescence quantum yields (PLQYs) of up to 22% were prepared through the steady binding of octylammonium bromide and oleic acid. Excellent thermal stability and good luminescence properties have been achieved as intrinsic features of the inorganic halide perovskites, as well as the effective passivation of surface trap-states.

Hydrothermal synthesis and inkjet printing of hexagonal-phase NaYF4: Ln3+ upconversion hollow microtubes for smart anti-counterfeiting encryption

Rare-earth doped NaYF4 upconversion hollow microtubes with good luminescence properties were synthesized by PAA mediated hydrothermal method and used for constructing smart anti-counterfeiting encryption by inkjet printing.

Hybrid organic–inorganic lead bromide perovskite supercrystals self-assembled with l-cysteine and their good luminescence properties

The assembled supercrystals induced by crosslinking of l-cysteine exhibit strong fluorescence, high stability and a PL lifetime of 642 ns.

Isostructural lanthanide-based metal-organic frameworks: structure, photoluminescence and magnetic properties.

A series of the anhydrous lanthanide-based metal-organic frameworks (Ln-MOFs) were successfully synthesized under hydrothermal conditions of Ln(iii) ions with 3,4'-oxybis(benzoate) (3,4'-oba), oxalate (ox) and 1,10-phenanthroline (phen). Structural analyses revealed that they are isostructural 3D open-frameworks with the formula of [Ln(3,4'-oba) (phen)(ox)0.5]n (Ln = Sm for 1, Eu for 2, Gd for 3, Tb for 4, and Dy for 5) and the topology of {33·43·58·6}. Within the 3D structure, the [LnO6N2] units are bridged by ox to form [Ln2ox] dimers and then are further connected by 3,4'-oba ligands. These complexes feature high chemical stabilities in common solvents, boiling water, and acidic (pH = 3) and alkaline (pH = 13) solutions and high thermal stability even up to 400 °C. The photoluminescence and magnetic properties were studied. Especially, 2 shows bright red emission with a high luminescence efficiency of 40.51%. We mainly discuss the luminescence properties of 2 in common solvents and inorganic ions. It shows luminescence stability in common solvents and the ability to detect ammonia and Fe3+ ions under a long excitation wavelength (350 nm). Significantly, magnetic studies reveal that the Dy-MOF, 5, shows a typical single-molecule magnetic behavior. Under zero dc field, compound 5 shows temperature and frequency dependent out-of-phase (χ''M) signals, indicating the existence of slow magnetic relaxation.

SYNTHESIS AND CHARACTERIZATION OF NOVEL 4-CYNANOPHENYL-FUNCTIONALIZED N4,N4,N4′,N4′-TERAPHENYLBENZIDINE (TPB) AS HOLE TRANSPORTING MOLECULAR MATERIALS

In this study, a new cyanophenyl-functionalized N4,N4,N4′,N4′-tetraphenylbenzidine (TPB) containing employable hole-transporting components has been synthesized with Pd-catalyzed Suzuki-Miyaura cross coupling reaction. N4,N4,N4′,N4′tetrakis-(4′-cynobiphenyl-4-yl)-biphenyl-4,4′-diamine (TPB-CN) was well characterized by 1H NMR, 13C NMR and CHN elemental analysis. The compound TPB-CN exhibited good thermal stability and luminescence properties. Time Dependent Density Functional Theory (TDDFT) computation was carried out to investigate the structural parameters and to understand the photophysical properties of the novel TPB-CN compound. The experimental and theoretical calculations performed to calculate absorption maxima in DCM by UV-Vis and TD-B3LYP/6-31g(d,p) were compared with each other. To identify crystal structure and to determine optical band gap of TPB-CN compound, its film form, which was coated on the glass substrate by spin coating, was used. The band gap of TPB-CN compound both in film and in solution was determined from the optical absorption measurements.

Highly biocompatible, monodispersed and mesoporous La(OH)3:Eu@mSiO2 core-shell nanospheres: Synthesis and luminescent properties

Monodispersed La(OH)3:Eu nanospheres(core-NSs) were synthesized by urea-based homogeneous co-precipitation process, where mesoporous silica layer was coated over the surface of luminescent La(OH)3:Eu core-NSs. The XRD data exhibit the high crystalline, single hexagonal-shaped La(OH)3:Eu core and silica modified La(OH)3:Eu@mSiO2 (core-shell) NSs. Monodispersibility, spherical shaped, high surface area and mesoporosity were identified by TEM analysis and were further confirmed by BET analysis. The as-synthesized samples are highly soluble in aqueous media at ambient conditions. Spectroscopic analyses were also carried out to examine the impact of surface modification on structural, surface chemistry, optical and luminescence behavior of the as-designed silica coated core-shell NSs. The emission spectral study revealed that the luminescence intensity of magnetic-dipole transition (590 nm, 5D0 → 7F1) is dominant with respect to electric-dipole (614 nm, 5D0 → 7F2) transition. The high crystallinity of the hydroxide products supports the existence of good photoluminescence intensity, a good indication for their future use in detection of biomacromolecules through hypersensitive emission (614 nm, 5D0 → 7F2) transition. Excellent biocompatibility, cell viability and good luminescence properties suggested that the as-prepared core-shell NSs are an ideal candidate for luminescence biolabeling/bioimaging and as an optical bio-probe.