Show Photoluminescence Emission Research Articles

Copper-related defects in ZnTe thin films grown by the close space sublimation method

Low-temperature photoluminescence (PL) is used to study defects evolution via immersion technique and annealing in vacuum of ZnTe thin films. In this paper we studied how copper doping from solutions of different molar concentrations affects PL of ZnTe thin films grown by close space sublimation (CSS) method. Undoped ZnTe thin films showed PL emission in the (520-680) nm wavelength region. The incorporation of copper in ZnTe produce a number of broad emission bands that correspond to an electron transition from the conduction band to spin-orbit states of the localized level of Cu2+ ions. All the studied samples had variable concentrations of oxygen and the possibility of the formation of auxiliary oxides is discussed.

Synthesis of Uniform Size Rutile TiO2 Microrods by Simple Molten-Salt Method and Its Photoluminescence Activity.

Uniform-size rutile TiO2 microrods were synthesized by simple molten-salt method with sodium chloride as reacting medium and different kinds of sodium phosphate salts as growth control additives to control the one-dimensional (1-D) crystal growth of particles. The effect of rutile and anatase ratios as a precursor was monitored for rod growth formation. Apart from uniform rod growth study, optical properties of rutile microrods were observed by UV−visible and photoluminescence (PL) spectroscopy. TiO2 materials with anatase and rutile phase show PL emission due to self-trapped exciton. It has been observed that synthesized rutile TiO2 rods show various PL emission peaks in the range of 400 to 900 nm for 355 nm excitation wavelengths. All PL emission appeared due to the oxygen vacancy present inside rutile TiO2 rods. The observed PL near the IR range (785 and 825 nm) was due to the formation of a self-trapped hole near to the surface of (110) which is the preferred orientation plane of synthesized rutile TiO2 microrods.

Regioselective Synthesis of 4-Aryl-1,3-dihydroxy-2-naphthoates through 1,2-Aryl-Migrative Ring Rearrangement Reaction and their Photoluminescence Properties.

4-Aryl-1,3-dihydroxy-2-naphthoates having the less accessible 1,2,3,4-tetrasubstituted naphthalene scaffold and that show photoluminescence emission from solid state as well as in solutions, were selectively synthesized from brominated lactol silyl ethers through the 1,2-aryl-migrative ring rearrangement reaction.

Synthesis and optical properties of innovative degradable black pepper composite material

Widely used as a medicinal plant in Ayurveda black pepper is also a main content of spices. Easily available of such kind of herb is studied the first time as a luminescence point of view. In this paper, we have studied luminescence characteristics of black pepper samples and check their properties for LED applications which are synthesized in four parts 1) Pure powder of black pepper 2) Black Pepper Solution by ethanol 3) Europium (Eu) doped black pepper solution and 4) Black Pepper thin film. The synthesized samples were characterized by Photoluminescence (PL) techniques. The PL characteristics for all four samples showed interesting results. Pure black pepper powder showed PL emission at 471nm under 421nm excitation wavelength. Black pepper solution shows an emission band around 430nm under 397nm excitation. Europium doped black pepper solution shows two emission peaks at 516nm and 658nm under 440nm excitation wavelength. Thin-film of pure black pepper shows an emission band around 454nm under 390nm excitation wavelength. The CIE Chromaticity Coordinates of the Black Pepper and other synthesized samples shows color co-ordinates near the blue and white region in the visible spectrum. These CIE chromaticity co-ordinates demonstrate high spectral characterization of developed materials such as high color purity and excellent chromaticity co-ordinates. The entire photoluminescence results indicated that synthesized samples have promising potential for LED applications.

Rapid and convenient crystallization of quantum dot CsPbBr3 inside a phosphate glass matrix

Although inorganic halide perovskite quantum dots (QDs) have promising photophysical properties and a wide range of applications, they suffer from some issues such as poor water and thermal stabilities. Here, we developed a simple strategy to embedded CsPbBr3 QDs in a glass matrix by adopting conventional melt-quenching technique. We systematically presented the modified glass melting and quenching technique for the direct crystallization of CsPbBr3 QDs inside a glass matrix. Crystallization of the QDs took place during the cooling of the quenched hot glass melt. The effect of the concentration of Cs2CO3, PbBr2 and NaBr on the formation of CsPbBr3 QDs size was also identified. The glasses containing CsPbBr3-embedded QDs showed photoluminescence emission stability without any alteration in their emission peaks and full-width at half-maximum for at least six months under ambient conditions. Our results provide new insights into rapid and convenient crystallization of QDs inside the protective glass matrix. The technique can be utilized to fabricate several rare earth ions co-doped QDs glasses for various color tunable lighting optical devices application.

Effects of synthesis temperature and Eu2O3 concentration on the crystalline phases and photoluminescence properties of SrAl2O4 phosphors

Phosphors with the compositions of x% Eu2O3-doped SrAl2O4 (x = 0.25, 0.5, 0.75, and 1.0, in mole ratio) were synthesized in air using solid state reaction method. From the SEM observations, we had found that the nano-cotton-filament-structured crystals were formed on the particle surfaces of all synthesized x% Eu2O3-doped SrAl2O4 powders, and their volume decreased with raising synthesis temperature. XRD patterns, TEM observations, and EDS analyses were used to analyze and confirm the compositions of the formed nano-cotton-filament-structured crystals, and the reaction sequences of Eu2O3-doped SrAl2O4 were well presented and proven in this study. When 260–265 nm were used as excitation wavelength, all the synthesized x% Eu2O3-doped SrAl2O4 phosphors would show photoluminescence emission intensity at three emission peaks with wavelengths of 590–592, 610–612, and 658 nm, which are respective corresponding to 5D0 → 7F1, 5D0 → 7F2, and 5D0 → 7F3 transitions of Eu3+ ions. The emission intensities of those characteristic peaks were apparently affected by the Eu2O3 concentration and synthesis temperature, and the concentration quench effect was also observed. The dominated emission light of all x% Eu2O3-doped SrAl2O4 phosphors was the transition of 5D0 → 7F1 (590–592 nm) peak, which was different from before research, and we would well discuss and explain the reason to cause this result.

Dual‐Function HKUST‐1: Templating and Catalyzing Formation of Graphitic Carbon Nitride Quantum Dots Under Mild Conditions

AbstractGraphitic carbon nitride quantum dots (g‐CNQDs) are highly promising photoresponsive materials. However, synthesis of monodispersed g‐CNQDs remains challenging. Here we report the dual function of MOF [Cu3BTC2] (HKUST‐1) as a catalyst and template simultaneously to prepare g‐CNQDs under mild conditions. Cyanamide (CA), a graphitic carbon nitride precursor, catalytically dimerized inside the larger MOF cavities at 90 °C and condensed into g‐CNQDs at 120 °C in a controlled fashion. The HKUST‐1 template was stable under the reaction conditions, leading to uniform g‐CNQDs with a particle size of 2.22±0.68 nm. The as prepared g‐CNQDs showed photoluminescence emission with a quantum yield of 3.1 %. This concept (MOF dual functionality) for catalyzing CA polycondensation (open metal sites (OMSs) effect) and controlling the produced particle size (pore‐templating effect), together with the tunable MOF porosity, is expected to produce unique g‐CNQDs with controllable size, morphology, and surface functionality.

Dual-Function HKUST-1: Templating and Catalyzing Formation of Graphitic Carbon Nitride Quantum Dots Under Mild Conditions.

Graphitic carbon nitride quantum dots (g‐CNQDs) are highly promising photoresponsive materials. However, synthesis of monodispersed g‐CNQDs remains challenging. Here we report the dual function of MOF [Cu3BTC2] (HKUST‐1) as a catalyst and template simultaneously to prepare g‐CNQDs under mild conditions. Cyanamide (CA), a graphitic carbon nitride precursor, catalytically dimerized inside the larger MOF cavities at 90 °C and condensed into g‐CNQDs at 120 °C in a controlled fashion. The HKUST‐1 template was stable under the reaction conditions, leading to uniform g‐CNQDs with a particle size of 2.22±0.68 nm. The as prepared g‐CNQDs showed photoluminescence emission with a quantum yield of 3.1 %. This concept (MOF dual functionality) for catalyzing CA polycondensation (open metal sites (OMSs) effect) and controlling the produced particle size (pore‐templating effect), together with the tunable MOF porosity, is expected to produce unique g‐CNQDs with controllable size, morphology, and surface functionality.

Optical and structural properties of In-rich InxGa1−xAs epitaxial layers on (1 0 0) InP for SWIR detectors

In-rich InxGa1−xAs epitaxial layers were grown on InP (100) substrates by a metalorganic vapor phase epitaxy (MOVPE) technique. The effect of Indium (In) composition on the crystalline quality and optical properties are investigated. High resolution X-ray diffraction (HR-XRD) measurement and Raman scattering spectrum are used to evaluate the crystalline quality, the residual strain and dislocation density property. The number of dislocations in the epitaxial layers is found to increase by increasing the Indium content in order to release the stresses due to the epitaxial clamping. Photoluminescence (PL) measurement is used to characterize the optical properties. At 10 K, PL measurements show that the InGaAs band gap redshifts with the indium content. Moreover, the asymmetry at the low-energy side of the PL peak has been attributed to the presence of localized excitons. In all samples, a blue shift of PL peaks is evidenced by increasing the excitation power density, which is in line with the presence of carrier’s localization and non-idealities in this system. Moreover, the temperature-dependence of the PL peak energy displays an unusual red-blue-red shift (S-shaped) behavior when raising the temperature. These observations can be related to the inhomogeneous distribution of indium which gives rise to the appearance of dislocations and other defects which serve as traps for charge carriers. Interestingly, those highly In-content InxGa1−xAs epitaxial layers show PL emission located between 1637 and 1811 nm (depending on In content) and thus might be suitable for in the design of novel heterostructure devices such as short wave infrared (SWIR) detectors.

Scintillation and dosimetric properties of Ce-doped MgAl2O4 single crystals

The undoped and Ce-doped MgAl2O4 single crystals were synthesized by the floating zone method equipped with four xenon arc lamps, and the photoluminescence (PL), scintillation, and dosimetric properties were investigated. The Ce-doped crystals showed PL emission peaks at around 420 and 720 nm. The former was ascribed to the 5 d-4f transition of Ce3+ ion, and the latter was ascribed Mg deficiency. The PL decay time profiles of the Ce-doped crystals exhibited the fast decay, and the decay time constants were the typical value of others Ce-doped materials. Thus, the decay time constants were attributed to the 5 d-4f transitions of Ce3+ ion. In addition, optically-stimulated luminescence (OSL) signals could be detected in all the crystals when the stimulation wavelength was 470 nm. The OSL dose response functions showed linearly proportional relationship from 10 to 1000 mGy in all the Ce-doped crystals. The thermally-stimulated luminescence (TSL) glow curves exhibit three peaks due to antisite of Al3+ ion, V center and antisite of Mg2+ ion. All the Ce-doped crystals showed improved TSL intensity and dose response sensitivity compared the undoped crystal. The 0.2 and 1% Ce-doped crystals showed linearly response at the dose range of the 0.1–1000 mGy.

Study of energy transfer from Bi3+ to Tb3+ in Y2O3 phosphor and its application for W-LED

Y2O3 activated with different activators were prepared by co-precipitation method. The prepared phosphors were characterized by XRD, SEM and photoluminescence (PL) techniques. The Tb3+ doped Y2O3 phosphor shows characteristic green emission due to 5D4 to 7Fj transitions of Tb3+ ion. The Bi3+ doped Y2O3 phosphor shows PL emission in blue region due to the transition between excited 3P1 state and ground state 1S0 of Bi3+ ion. The multiple systems of Tb3+emission lines in Y2O3:Tb3+ and two types of excitation and emission spectra of Y2O3:Bi3+ phosphors are due to two Y3+ sites in the host structure with C2 and S6 symmetries. Due to the addition of transition metal ion Bi3+ in Y2O3:Tb3+ lattice, the excitation efficiency is enhanced throughout the spectral range from 300 nm to 400 nm. Bi3+ ions absorb N-UV radiation and, subsequently, the energy is transferred from the sensitizer Bi3+ to activator Tb3+ and emitted via 5D4 to 7Fj transitions of Tb3+ ion. From the spectral properties of Y2O3:Bi3+ and Y2O3:Tb3+, Bi3+, it is established that the prepared phosphors are useful in near UV excited LED (solid state lighting) application.

Tunable emission of cadmium-free transition metal (Cu, Mn, Ag) co-doped ZnInS/ZnS core-shell quantum dots

Abstract Color tunable quantum dots (QDs) based on the Cu, Mn, Ag co-doped ZnInS core and ZnS outer-shell were synthesized by using an eco-friendly method. Core-shell doped QDs with the average size of 3.85 nm were obtained by using a one-pot synthesis followed by a hot injection with n-dodecanethiol (DDT) and oleylamine (OLA) as stabilizers in oil phase. Cu, Mn and Ag ions were introduced as single-dopant or co-dopants during the synthesis, providing an effective means to control the emission color of the QDs. The as-synthesized QDs showed photoluminescence emission ranging from green (530 nm) to near-red (613 nm), adjusted by doping components, dopant concentration, and Zn/In ratio. Importantly, quasi-white emission has been achieved by controlling the concentration of co-doped metal ions (Mn, Cu and Ag). The primary results demonstrated the promising potential of co-doped QDs as alternative materials for future high quality white LED applications.

Highly efficient deep-red emitting methyl substituted thiophenylquinoline based Ir(III) complexes for solution-processed organic light-emitting diodes

ABSTRACTHerein, we synthesized two new methyl substituted thiophenyl-quinoline based heteroleptic Ir(III) complexes as guest molecules for deep-red emitting solution-processed phosphorescent organic light-emitting diodes (PhOLEDs). Their thermal stabilities, photophysical properties and electroluminescence (EL) properties are systematically investigated. (MTPQ)2Ir(pic) and (MTPQ)2Ir(acac) showed photoluminescence emission of 614 and 629 nm and a photoluminescence quantum yield of 21% and 15%, respectively. Solution-processed deep-red emitting PhOLEDs were fabricated using standard structure with PEDOT:PSS and TPBi as hole and electron transport layers, respectively and, a mixed host of TCTA:TPBi (1:1) doped with the guest Ir(III) molecules. The emission electroluminescence wavelength was slightly red shifted by 11 nm for both (MTPQ)2Ir(pic) (625 nm) and (MTPQ)2Ir(acac) (640 nm). A maximum external quantum efficiency of 8.46% and maximum current efficiency of 7.37 cd/A was achieved for (MTPQ)2Ir(pic) with a deep-red CIE coordinates of (0.679, 0.318).

Synthesis and photoluminescence properties of red, green and blue emitting LaYO3:M (M = Eu3+, Tb3+, Sm3+,Bi3+, Pb2+) phosphors

Red, green and blue light emitting Eu3+, Sm3+, Tb3+, Bi3+ and Pb2+ ions doped LaYO3 phosphors were synthesized by co-precipitation method and their photoluminescence (PL) properties were studied. The Eu3+-doped LaYO3 compound exhibited characteristic emissions of Eu3+. The intensity of PL emission peak found to be more at 614nm than 595nm. LaYO3:Sm3+ phosphor showed PL emission at 570nm, 608nm and 660nm which is characteristic emission of Sm3+. Tb3+ doped LaYO3 compound show intense emission at 545nm which again characteristic emission of Tb3+ in LaYO3 host. Eu3+, Tb3+ and Sm3+ doped LaYO3 phosphors displayed charge transfer band in UV region which is responsible for intense emission in red, orange and green region. Transition metal ions such as Pb2+ and Bi3+ doped LaYO3 phosphor exhibited PL emission in blue region. Prepared phosphors are useful to be used in display devices and related applications.

Unveiling the correlation between structural order–disorder character and photoluminescence emissions of NaNbO3

Orthorhombic NaNbO3 particles obtained via the MAH route show photoluminescence emission related to the structural disorder effect at the medium-range.

Synthesis of porphyrin-appended poly(fluorene-alt-carbazole): photoluminescent and electrochemical studies

Poly(fluorene-alt-carbazole) appended with meso-tetraphenylporphyrin (MTPPC) linked through oxyethylene spacer and the parent poly(N-hexyl-2,7-carbazole-alt-9,9-di-n-hexyl fluorene) (P1) were synthesized and characterized. Optical absorption properties of the polymers containing 5% of MTPPC (P2) and 10% of MTPPC (P3) in the polymer backbone show extended optical absorption toward long wavelength compared to the parent polymer P1. Optical absorption studies of the polymers showed that polymer P1 has absorption at 384 nm in solution, whereas polymers P2 and P3 have absorption at 384 nm corresponding to polymer backbone and soret band at 421 nm with Q bands at around 518 and 554 nm in solution. P1 shows photoluminescence emission around 417 nm, whereas P2 and P3 fall around 656 nm. Thermal, electrochemical, and quenching studies of the polymers have been studied and the details are reported.

Tuning Eu3+ emission in europium sesquioxide films by changing the crystalline phase

We report the growth of europium sesquioxide (Eu2O3) thin films by pulsed laser deposition (PLD) in vacuum at room temperature from a pure Eu2O3 ceramic bulk target. The films were deposited in different configurations formed by adding capping and/or buffer layers of amorphous aluminum oxide (a-Al2O3). The optical properties, refractive index and extinction coefficient of the as deposited Eu2O3 layers were obtained. X-ray photoelectron spectroscopy (XPS) measurements were done to assess its chemical composition. Post-deposition annealing was performed at 500°C and 850°C in air in order to achieve the formation of crystalline films and to accomplish photoluminescence emission. According to the analysis of X-ray diffraction (XRD) spectra, cubic and monoclinic phases were formed. It is found that the relative amount of the phases is related to the different film configurations, showing that the control over the crystallization phase can be realized by adequately designing the structures. All the films showed photoluminescence emission peaks (under excitation at 355nm) that are attributed to the intra 4f-transitions of Eu3+ ions. The emission spectral shape depends on the crystalline phase of the Eu2O3 layer. Specifically, changes in the hypersensitive 5D0→7F2 emission confirm the strong influence of the crystal field effect on the Eu3+ energy levels.

Enhanced radiation hardness of InAs/InP quantum wires

We report the influence of 2.4 MeV proton irradiation on the photoluminescence (PL) of self-assembled InAs/InP quantum wires (QWRs) and quantum wells (QWs), which show PL emission at similar wavelengths. The proton irradiation leads to an extinction of the PL intensity and to a deterioration of the thermal stability of the PL both in QWR and QW samples. However, the QWRs tend to exhibit higher radiation hardness, especially at low temperatures and upon just above-bandgap excitation.

Synthesis and luminescence of graphene-nano calcium sulphide composite

Graphene-nanocrystalline calcium sulphide has been synthesized using in-situ reduction of calcium salt and graphene oxide. Graphene oxide was prepared using Hummer's method.Surface morphology and crystal structure of samples were observed by transmission electron microscopy (TEM) and X-Ray diffraction (XRD). Ultra thin graphene and graphene oxide sheets with size ranging between tens to several hundreds of square nanometers are observed in TEM images. The TEM micrographs of G-CaS show that CaS particles are embedded in graphene sheets and the average particle size of CaS particles in the composite is less than 50 nm. The reduction in the intensity of various functional groups in FTIR spectrum also confirms the formation of graphene. The UV-Visible spectra of CaS shows absorption peak at 220 nm with a small shoulder at 250 nm whereas in G-CaS 220 nm absorption peak has reduced intensity and the shoulder at 250 nm has now shifted to 270 nm due to modification in the defect structure of CaS by graphene. CaS and G-CaS shows photoluminescence emission at 470 nm (λexc. = 375 nm) and 440 nm (λexc. = 350 nm) respectively, however emission intensity of G-CaS is relatively lower than CaS. Although the emission intensity is found to be lower than CaS, addition of CaS to graphene in G-CaS complex has made graphene luminescent. XPS spectra also indicate reduction of various oxygen containing functional groups in highly reduced graphene oxide and G-CaS.

Samarium‐Doped Oxyfluoride Glass‐Ceramic as a New Fast Erasable Dosimetric Detector Material for Microbeam Radiation Cancer Therapy Applications at the Canadian Synchrotron

There is a special need to develop a dosimetry technique with a large‐dynamic range and high‐spatial resolution to characterize the microstructured X‐ray beams used in microbeam radiation therapy (MRT) for cancer. We report the synthesis and characterization of oxyfluoride glass‐ceramic (SiO2–Al2O3–CaF2–CaO–SmF3) plates, which contain trivalent‐samarium‐doped calcium fluoride (CaF2:Sm3+) nanocrystals, for use as a dosimetric detector material, particularly for MRT applications. Our approach utilizes the extent of Sm3+→Sm2+ valence reduction caused by X‐ray irradiation as a probe of the X‐ray dose delivered; and confocal fluorescent microscopy is used to read out the distribution of valence reduction through the photoluminescence (PL) signal. Our study showed that the Sm3+→Sm2+ valence reduction takes place in CaF2 nanocrystals, but not in the glass matrix. The Sm2+ shows PL emission predominantly due to the fast 4f55d1→7F0 transition, which allows us to read out the detector plate at a high scanning speed. Further, our experiments showed that the detection dose range reaches several thousands of grays, and X‐ray dose distribution is detected at a micrometer scale. In addition, the Sm2+ signal can be erased either by heating the irradiated sample at a suitable high temperature or by exposing it to UV light; and the erased glass‐ceramic plate is reusable. The new Sm‐doped oxyfluoride glass‐ceramic with CaF2 nanocrystals reported in this work shows potential for practical use in high‐dose and high‐resolution dosimetry for MRT.