Promising Luminescence Properties Research Articles

Anti-leishmanial study of discrete tetrahedral zinc(ii) β-oxodithioester complexes

New zinc(ii) complexes of β-oxodithioester, with characterized crystal structures, demonstrate efficient anti-leishmanial activity, semiconducting behaviour, and promising luminescence properties.

Structural and luminescence properties of Y2O3:Ho3+ phosphor: Potential applications in plant cultivation LEDs and thermoluminescent dosimetry

Structural and luminescence properties of Y2O3:Ho3+ phosphor: Potential applications in plant cultivation LEDs and thermoluminescent dosimetry

Colloidal suspensions of totally inorganic perovskites nanoparticles: A new photoluminescent emission in the near-IR

Luminescent materials have attracted great attention due to the amazing applications. In this sense, perovskite halide materials have shown promising luminescent properties which allows them to be useful in various applications such as LEDs, sensors. In this work, colloidal suspensions of CsPbI3 and Pd-doped CsPbI3 perovskite nanoparticles were prepared at different temperatures, and their structure and luminescence properties were characterized to analyse the effect of the synthesis temperature and the Pd-doping. With the increase of temperature, the main photoluminescence band of perovskite nanoparticles are slightly red-shifted. But the most amazing result is that the Pd-doped CsPbI3 shows a new emission band at 877 nm under excitation at 785 nm. Therefore, this compound may be used as a highly sensitive luminescent sensor in several applications, such as in biosystems due to their emission in the first biological window under NIR excitation.

Design of CDs/SiO2 Composite Phosphors via a Double Hydrolysis Reaction and their Expectable Luminescence Performance

Carbon dots (CDs), as an emerging carbon material, have attracted considerable interest for their promising luminescent properties. However, the inevitable aggregation of CDs in solid-state results in some bottleneck problems such as aggregation-induced quenching and foster resonance energy transfer. Therefore, developing solid-sate CDs with good luminescent performance is still a challenge. Herein, a simple and low-cost approach is presented to prepare the solid-state CDs/SiO2 composite in which the CDs were well dispersed and embedded in inorganic silica gel, hence restraining the natural issues of the solid-state CDs. As expected, the CDs/SiO2 composite phosphors showed higher fluorescence intensity about twice than the CDs aqueous solution, and a high photoluminescence quantum yield of 21%. This work would be of significance for the preparation of CDs and even their practical applications.

Red-emitting carbon dots as luminescent agent in wide-range water detection in organic solvents and polarity-selective zebrafish imaging

Heteroatom-doped carbon dots with promising luminescent properties are excellent candidates for sensing and imaging applications. Herein, we reported a facile one-step hydrothermal synthesis of highly-fluorescent red-emitting carbon dots (R-CDs) with quantum yield of 37.2 %. R-CDs exhibit a maximum emission band at 640 nm under the excitation wavelength of 500 nm. Furthermore, R-CDs show excitation-dependent and solvent-engineered fluorescent characteristics that the luminescent properties could be greatly affected by polarity. Due to the sensitivity to polarity, a quick and precise approach for wide-range water detection in organic solvents has been developed. Because of the low autofluorescence background, R-CDs were applied to the zebrafish larvae imaging. Polarity-selective bright red light from R-CDs is seen in the low-polarity organs like yolk sac and eyes, which contain abundant lipids and lipoprotein. Our results demonstrate that R-CDs could be used as bio-imaging agents and fluorescent sensors for quantitative and visual water detection in various organic solvents. • High-fluorescent red-emitting carbon dots are synthesized from hydrothermal treatment of DMAB and boric acid. • Bright red emission at 640 nm (λ ex = 500 nm) and high QY of 37.2 % are achieved. • The variation of the emission intensity of R-CDs is highly dependent on solvent polarity. • Polarity-selective bright red light from R-CDs is seen in the low-polarity organs like yolk sac and eyes.

Impact of Li concentration in KMgF3:Eu,Yb fluoroperovskite on structure and luminescence properties

In this work, europium, ytterbium, and lithium doped fluoroperovskite type-KMgF 3 (KMgF 3 :Eu,Yb,Li) was synthesized using the sol-gel method. The structural and luminescence properties of KMgF 3 :Eu,Yb,Li compound were investigated by radioluminescence, thermoluminescence (TL), and optically stimulated luminescence (OSL) methods. Different contents of the alkali metal lithium (Li) co-dopant have been studied regarding the influence on the structure and luminescence properties. The structures of the samples were studied using the x-ray diffraction (XRD) method. We found cubic-KMgF 3 (Parascandolaite) and tetragonal-MgF 2 phases for all produced samples. Additional Eu, Yb doping, and Li co-doping resulted in the formation of hexagonal-Li 2 O 2 and cubic-MgO phases while reducing the MgF 2 phase in KMgF 3 dispersions that were confirmed with XRD and Rietveld refinement analyses. Moreover, the lattice parameters of KMgF 3 were calculated for the undoped and Li co-doped samples. Scanning electron microscope images revealed increased crystalline formations with increasing Li concentration in the structure. Fourier transform infrared spectroscopy indicated a reduction of Mg-F bands for all samples due to Mg +2 ion substitutions with Eu, Yb doping, and Li co-doping. It was observed that the intensity of the TL peaks in the TL glow curves appeared as the Li concentration increased without shifting the peak positions as a function of temperature. The OSL curves of KMgF 3 :Eu,Yb,Li decayed slowly and the luminescence intensity reached a maximum with 15 mol% Li content. The obtained results tend to suggest that the investigated Eu- and Yb-doped and Li co-doped parascandolaite polycrystals exhibit promising luminescent properties and could be considered as appropriate candidates for various technological applications including radiation dosimetry. • Eu, Yb and Li doped KMgF 3 powders were synthesized using the sol-gel method. • Li co-doping has led to developing novel dosimetric material as KMgF 3 :Eu,Yb,Li. • The phase composition and structural analysis were performed to determine the Li effect on the KMgF 3 . • The effect of Li co-dopant was demonstrated by examining the basic RL, TL and OSL properties of KMgF 3 .

Theoretical probe of absorption and fluorescence emission characteristics of highly luminescent ReL(CO)3X (L = 12H-indazolo[5,6-f][1,10]phenanthroline and X = F, Cl, Br, I): a DFT/TD-DFT study

Four novel rhenium (Re) tricarbonyl complexes (ReL(CO)3X; X = F, Cl, Br, I and L = 12H-indazolo[5,6-f][1,10]phenanthroline) with promising luminescent properties were investigated using a DFT/TD-DFT approach at the ωB97X-D3/6-31 + G(d,p)//LANL2DZ level of theory. The effects of halogen co-ligands (F, Cl, Br and I) and solvents (acetonitrile (ACN), dichloromethane (DCM) and dimethylsulfoxide (DMSO)) on luminescent properties of the complexes were examined. The studied Re(I) tricarbonyl complexes assumed distorted octahedral geometry with an N–Re–N bite angle of ca. 75°, and showed possible p–π interactions between the halogen (X) atom and the N-donor ligand (L) ring. Prominent electronic excitations (with high oscillator strengths) are S0→S3, attributed to the hole–electron orbital transition based on the natural transition orbitals analyses, and characterised as MLCT/LMCT. The complexes exhibited prominent Stokes fluorescence with Stokes shifts ranging from 9204 to 19490 cm−1. ReL(CO)3Cl in ACN showed the largest Stokes shift, whereas ReL(CO)3I in ACN displayed the smallest Stokes shift. Fluorescence emission wavelengths varied with X and solvent, though the four complexes emit in the cyan/blue range in DCM. ReL(CO)3F (in ACN) exhibited the highest fluorescence lifetime and quantum yield. The study demonstrates the tunability of photophysical properties and promotes the theoretical probe of optical characteristics of materials as corroborative efforts to experimental findings.

New Multicolor Tungstate-Molybdate Microphosphors as an Alternative to LED Components.

Due to the ongoing need to create phosphors with the appropriate emission color for the production of light emitting diodes, we decided to synthesize a series of multicolour microphosphors with tunable visible emissions, depending on the composition of dopant ions. In this work, we investigated the structure, morphology, and luminescent properties of new molybdate–tungstate phosphors co-doped with Tb3+ and Eu3+ ions. The conventional high temperature solid state method was used to prepare a series of CaMoyW1−yO4:Eu3+x/Tb3+1−x materials. In order to obtain phosphors with the most promising luminescent properties, the experiment was planned by taking into account the different composition of the matrix and the concentration of the particular dopant ions (Eu3+x/Tb3+1−x, x = 0.001, 0.003, 0.005, 0.007, 0.009). As a result, luminescent materials were obtained with a pure tetragonal crystal structure, the space group of I41/a, confirmed by X-ray diffraction (XRD). The size and shape of the particles obtained from the materials were analyzed based on scanning electron microscopy images. Luminescence spectroscopy (excitation and emission spectra, decay lifetimes) was utilized to characterize the luminescence properties of the as-prepared phosphors. The color change of the emission from green-yellow to orange-red was confirmed using the 1931 Comission Internationale de l’Eclairage (CIE) chromaticity coordinates and color correlated temperature (CCT).

Linear tunable NIR emission via selective doping of Ni2+ ion into ZnX2O4 (X=Al, Ga, Cr) spinel matrix

Abstract Adjusted crystal fields can lead to new hybrid materials with promising optical performance. Transition metal ions (TMIs) with d-d electron transitions are sensitive to their surroundings and can be ideal candidates for crystal field research. Herein, we have selected single Ni2+-doped spinel oxide nanocrystals as a model system to systematically explore luminescence mechanisms in different crystal fields. Ni2+-doped ZnAl2O4, ZnGa2O4, and ZnCr2O4 nanospinels with broad near-infrared (NIR) emission bands fully cover the second biological window (1100–1400 nm). We have developed a ZnX2O4 (X = Al, Ga or Cr) (ZXO) spinel framework system using a melting-evaporation procedure, and the whole fabrication period only required 20 min. By changing X ions in the ZXO matrix framework, linear tunable photoluminescence was successfully realized. A sample with a mixed phase of ZnAl2O4 and ZnCr2O4 (ZACO) was also prepared using the same method, and ultrabroadband emissions ranging from 1050-1550 nm were detected. It is valuable to further explore the combinations based on these frameworks to realize tunable emission spectra. Fundamental research on the physical processes will open a new gateway for further research of TMI-doped nanocrystals with promising luminescence properties and broaden the applications to a variety of areas, especially in the biomedical field.

Optically stimulated luminescence decay and dosimetric properties of cerium-doped potassium sulfate phosphor.

Optically stimulated luminescence (OSL) is used for dating in archaeology and geology, and in dosimetry of ionizing radiation. Some crystalline wide band-gap insulators may be used as OSL radiation detectors. Recently it was found that cerium-doped potassium sulfate crystals have promising luminescence properties. This paper presents some OSL properties of K2 SO4 :Ce crystals that were prepared in the form of pellets. The crystals exhibited a strong luminescence signal, good measurement repeatability, and high sensitivity for ionizing radiation. Best results were obtained after annealing at 1000°C. Dose-dependence characteristics were determined in the range 10 mGy to 11.2 Gy. OSL decay curves consisted of several components. Fast and slow OSL components of the phosphor had different properties. The slow component was quite stable and obeyed power law dependence. It decayed in the 55 days after irradiation. Its luminescence properties depended on sample preparation and the storage time after irradiation.

The first actinide polyiodate: a complex multifunctional compound with promising X-ray luminescence properties and proton conductivity.

Herein we report the first example of an actinide polyiodate compound, namely K4[(UO2)2(IO3)6(I4O11)]·(HIO3)4(H2O)6 (UPI-1), which was obtained from slow evaporation of nitric acid with a high I/U ratio. Spectroscopic measurements indicate that UPI-1 possesses X-ray luminescence properties applicable for X-ray scintillation and also exhibits modest protonic conduction.

Synthesis of Luminescent Fused Imidazole Bicyclic Acetic Esters by a Multicomponent Palladium Iodide‐Catalyzed Oxidative Alkoxycarbonylation Approach

AbstractA new multicomponent catalytic approach to important fused imidazole bicyclic acetic esters, whose core is present in many biologically active principles, is presented. It is based on the sequential cyclization‐alkoxycarbonylation‐isomerization of readily available N‐heterocyclic propargylamine derivatives, carried out under oxidative conditions using a simple catalytic system consisting of PdI2 (1 mol%) in conjunction with KI (1 equiv.), in the presence of AcONa as additive (1 equiv.) at 100 °C under 20 bar of a 4 : 1 mixture CO‐air. Under the optimized conditions, several N‐(prop‐2‐yn‐1‐yl)pyridin‐2‐amines were smoothly converted into alkyl 2‐(imidazo[1,2‐a]pyridin‐3‐yl)acetates in fair yields (51–77 %). The method was also applied to the conversion of N‐(prop‐2‐yn‐1‐yl)pyrimidin‐2‐amine into 2‐(imidazo[1,2‐a]pyrimidin‐3‐yl)acetate and of N‐(prop‐2‐yn‐1‐yl)pyrazin‐2‐amine into 2‐(imidazo[1,2‐a]pyrazin‐3‐yl)acetate. Some of the newly synthesized bicyclic derivatives have shown promising luminescence properties.

Luminescence properties of Sm3+ doped Na2B4O7 glasses for lighting application

Sm 3+ ions doped sodium-tetra-borate glasses were developed by melt quenching technique and their physical and luminescence properties were studied. The developed glasses absorbs photons in the UV–Vis–NIR regions. Photoluminescence (excitation and emission) characteristics shows that under 402 nm excitation, strong emission in the orange region owing to the 4 G 5/2 → 6 H 7/2 transition of Sm 3+ ion was observed. Using absorption spectra, Judd–Ofelt (JO) parameters were evaluated. From the JO theory, the radiative properties which includes the radiative transition probabilities, branching ratios and stimulated emission cross section were calculated. Being transparent and a long decay time with an efficient energy transfer from the host matrix to the luminescence center, the developed glasses exhibit promising luminescence properties. The calculated CIE color coordinates and color purity show that the color coordinates of the developed glasses lie in the orange region. The obtained results revealed that the present glasses are promising for the orange light-emitting diodes and solid state laser applications. • Sodium tetra Borate doped with Sm 2 O 3 glasses were synthesized by melt quenching method. • J-O (Ω λ ) parameters for 1.0 mol % of Sm 3+ doped sample were analyzed. • Lifetime of 4 G 5/2 decreases from 2.613 to 0.791 ms with increase in concentration. • NBOSm emit orange luminescence under 402 nm excitation. • The CCT values obtained from CIE for these glass samples shows 1721 K.

Lead-free violet-emitting K2CuCl3 single crystal with high photoluminescence quantum yield

Abstract Lead halide perovskites have attracted great attention on their promising luminescent properties. However, their practical use is hampered by the toxicity of Pb, and also the photoluminescence efficiency in violet region is much lower than green and red emitters. Herein, a new copper (I) halide with nontoxicity and efficient violet emission was synthesized and characterized. The major emission peak locates at 386 nm, the photoluminescence quantum yield reaches 98.8%, and the Stokes shift is as high as 1.15 eV K2CuCl3 crystal consists of one dimensional [CuCl4]3- tetrahedral ribbons, which are isolated by K+ ions. The one dimensional crystal structure and the formation of self-trapped excitons, benefit the large thermal activation energy of 1090 meV, which contributes to the observed efficient emission.

Intense blue emission of perovskite-type fluoride phosphor Cs4Mg3CaF12: Eu2+ as a promising pc-WLEDs material

Abstract An intriguing novel perovskite-type Cs4Mg3CaF12: Eu2+ phosphor with desirable properties for potential application in the field of white light-emitting diodes was first time synthesized. The Rietveld structural refinement, scanning electron microscopy and high resolution transmission electron microscopy were used to determine the crystallographic parameters, morphology and microstructure of Cs4Mg3CaF12: Eu2+ phosphor. The first principle calculation based on the density functional theory further provided a theoretical understanding of the band structure for the undoped Cs4Mg3CaF12 and indicated that it has a large direct band gap of 7.1 eV. Upon the excitation of Cs4Mg3CaF12: Eu2+ phosphor in the broad range of 250–450 nm, the bright blue light emission was observed with the maximum at 474 nm and a full width at half-maximum of 2808 cm−1 that was attributed to the electric-dipole allowed 4f65 d1→4f7 transition of Eu2+ ions. Based on the Dexter’s theory, the concentration quenching mechanism among Eu2+ in the Cs4Mg3CaF12: Eu2+ phosphor was validated to be the dipole-dipole interaction, and the critical distance was determined to be 23.34 A. On the basis of temperature-dependent luminescence measurement, an analysis of the origins of thermal quenching behavior was presented. The Cs4Mg3CaF12: Eu2+ phosphor not only has favorable thermal stability with emission intensity reduction by 20% at T = 473 K in reference to the room temperature level, but also shows the integrated PL intensity 95% as high as that of BaMgAl10O17: Eu2+, internal quantum efficiency of 64% and color purity of 85%. The results of this work indicate that the blue-emitting Cs4Mg3CaF12: Eu2+ phosphor with promising luminescence properties has a capacity for incorporation as a component to the near-UV based phosphor-converted WLEDs.

TL, OSL and RL emission spectra of RE-doped LiMgPO4 crystals

Abstract In this work the spectral properties of emission of differently doped lithium magnesium phosphate (LiMgPO4, LMP) compound were investigated by thermoluminescence (TL), optically stimulated luminescence (OSL) and radio-luminescence (RL) methods. The samples were prepared in the form of crystals, which were grown from the melt by micro-pulling-down technique. Different rare-earth (RE) dopants have been studied regarding the influence on luminescence properties. It was found that the presence of boron ions together with the RE dopant seems to have an impact mainly on the TL emission spectra of the studied LMP crystals. TL, OSL, RL and after-glow emission spectra are comparable for the LMP crystals of the same dopants concentrations. The OSL emission spectra were obtained over a whole available wavelength range by the measurements of the after-glow spectra after the sample stimulation has ended. The obtained results tend to suggest that the investigated RE-doped LMP crystals exhibit promising luminescent properties and could be considered as appropriate candidates for real-time detectors.

Highly Stretchable and Transparent Double-Network Hydrogel Ionic Conductors as Flexible Thermal-Mechanical Dual Sensors and Electroluminescent Devices.

The latest generation flexible devices feature materials that are conductive, highly stretchable, and transparent to meet the requirements of a reliable performance. However, the existing conductors are mostly electronic conductors, which cannot satisfy these high-performance challenges. A robust hydrogel ionic conductor was rapidly fabricated with a facile one-pot approach by employing bioinspired agar with a physically cross-linked network, polyacrylamide (PAM) with a photoinitiated cross-linked network under appropriate UV intensity, and Li+ as conductive ions. The resulting Li+/agar/PAM ionic double-network hydrogels could be fabricated into various shapes through injection. The unique ionic hydrogel showed a remarkable stretchability with over 1600% extension, high tension/compression strength (0.22 MPa/3.5 MPa), and toughness (2.2 MJ/m3). Furthermore, it was demonstrated to possess dual sensory capabilities through the combination of both temperature and mechanical deformation. This hydrogel ionic conductor exhibited high stretching sensitivity with a gauge factor of 1.8 at strain 1100% and bending sensitivity in a broad angle range of 30-150°, respectively. Such highly optical transparency and elasticity endow the hydrogel-phosphor composites with promising luminescent properties. The multifunctional ionic hydrogel can be used as soft conductors for application in flexible devices such as ionic skin for wearable sensors and luminescence display.

Thermal Stability of Oleate‐Stabilized Gd2O2S Nanoplates in Inert and Oxidizing Atmospheres

AbstractCapping ligands play an important role in the chemistry of nanoparticles synthesized with organic surfactants. This is relevant to a number of device applications where heating may cause major modifications of crystalline nanoparticles including amorphization, surface rearrangements or sintering. Ultrathin monodisperse Ln2O2Sx oxysulfide nanoparticles (Ln=lanthanide) obtained in a mixture of oleylamine, oleic acid and 1‐octadecene show promising luminescence and light absorption properties. In view of applications, one open question concerns the thermal behavior and the role of the ligands on the thermal reactivity of the nanoparticles. In this report, we show that the thermal stability of Gd2O2Sx nanocrystals is limited because of their non‐stoichiometric composition and strongly depends on the annealing atmosphere. The sintering temperature of the nanoparticles is lower in air than in inert atmosphere because of a rapid degradation of the ligands. Annealing the nanoparticles in air enables removing the ligands without altering the nanocrystals structure. The decomposition of the Gd2O2Sx nanocrystals in inert atmosphere exhibits a complex multi‐step behavior that was precisely modeled. This work gives a comprehensive description of the stability conditions of lanthanide oxysulfide nanoparticles. It establishes the conditions for their practical use and opens the way to major improvements of the surface activity of Ln2O2S nanoparticles and related nanocrystals.

Syntheses, Experimental and Theoretical Studies on Absorption/Emission Properties of Pyrazoline-Containing Aryl/Methoxynaphthyl Substituents

5-Aryl-3-(2-methoxynaphthalen-6-yl)-1-phenylpyrazoline derivatives were synthesized starting from (E)-1-(3-aryl)-(2-methoxynaphthalen-6-yl)-prop-2-en-1-one and phenylhydrazine. The compounds were characterized by 1H and 13C nuclear magnetic resonance (NMR), elemental analyses and mass spectrometry. Some compounds showed promising luminescence properties in solution and in solid state; the absorption and emission characteristics were measured and the fluorescence quantum yield of two of the derivatives [4,5-dihydro-3-(2-methoxynaphthalen-6-yl)-5-(3,4,5-trimethoxyphenyl)-1-phenyl-1 H -pyrazoline and 5-(4-chlorophenyl)-4,5-dihydro-3-(2-methoxynaphthalen-6-yl)-1-phenyl-1 H -pyrazoline] were found to have excellent values compared to rhodamine B standard. Theoretical calculations at time-dependent density functional theory (TD-DFT) level are in agreement with the experimental measurements and are helpful to explain the electronic behavior.

Niobium oxide influence on the structural properties and NIR luminescence of Er3+/Yb3+ co-doped and single-doped 1−xSiO2−xNb2O5 nanocomposites prepared by an alternative sol–gel route

Abstract We have investigated how the Nb content influences the structural and luminescence properties of Er 3+ /Yb 3+ co-doped SiO 2 –Nb 2 O 5 nanocomposites prepared by an alternative sol-gel process at different Si/Nb molar ratios of 90:10 up to 20:80. X-ray diffraction (XRD), Transmission electron microscopy (TEM), Diffuse reflectance spectroscopy (DRS), Fourier transform infrared spectroscopy (FTIR), and Photoluminescence spectroscopy (PL) provided a detailed structural and spectroscopic analysis of the composites. Formation of the Nb 2 O 5 crystalline phases depended on the Si/Nb ratio. Nanocomposites with 20 up to 40 and 80 mol% of Nb contained the T crystalline phase, whereas nanocomposites with 50 mol% of Nb presented both the T and M crystalline phases. The average crystallite size increased from 5.9 nm to 33.8 nm as the niobium content, as revealed by XRD. The λ cutoff increased with the Nb content, and the band gap energy ranged from 4.27 eV to 3.54 eV. Full elimination of OH groups was suitable for the highest Nb concentrations, which influenced the luminescence properties. Efficient Yb 3+ → Er 3+ energy transfer occurred under 977-nm excitation, leading to broad and intense 1.5-µm emission for Nb30 and Nb40, with FWHM of 67 nm and 69 nm, respectively. Under 520-nm and host excitations, Er 3+ and Yb 3+ emissions at 1.0 µm took place. The different Nb 2 O 5 crystalline phases influenced the energy transfer processes between Er 3+ and Yb 3+ ions, which affected the relative intensity of the 1.0/1.5-μm emissions. Tuning of this relative intensity is possible depending on the Nb content, which paves the way for the application of these nanocomposites as optical amplifiers at 1.5 μm, solid-state lasers and energy converters. The Er 3+ /Yb 3+ co-doped nanocomposites with 30 and 40 mol% of Nb amount displayed the most promising luminescence properties for photonic applications.