Search results for "Solid"
showing 10 items of 3575 documents
Origin of the Enhanced Photoluminescence Quantum Yield in MAPbBr 3 Perovskite with Reduced Crystal Size
2018
Methylammonium lead bromide perovskite (MAPbBr3) has been widely investigated for applications in visible perovskite light-emitting diodes (LEDs). Fine-tuning of the morphology and of the crystal size, from the microscale down to the quantum confinement regime, has been used to increase the photoluminescence quantum yield (PLQY). However, the physical processes underlying the PL emission of this perovskite remain unclear. Here, we elucidate the origin of the PL emission of polycrystalline MAPbBr3 thin films by different spectroscopic techniques. We estimate the exciton binding energy, the reduced exciton effective mass, and the trap density. Moreover, we confirm the coexistence of free carr…
Excitation and photoluminescence spectra of single- and non-single-phased phosphors based on LaInO3 doped with Dy3+, Ho3+ activators and Sb3+ probabl…
2017
Abstract Single-phased La 0.95 Ln 0.05 InO 3 ( Ln – Dy, Ho), La 0.90 Dy 0.05 Ho 0.05 InO 3 , LaInO 3 ceramic samples as well as the La 0.95 Ln 0.05 In 0.98 Sb 0.02 O 3 ( Ln – Dy, Ho), La 0.90 Dy 0.05 Ho 0.05 In 0.98 Sb 0.02 O 3 , LaIn 0.98 Sb 0.02 O 3 samples with additional impurity LaSbO 3 phase were prepared by solid-state reactions method. Their excitation and photoluminescence (PL) spectra were measured at room temperature. It was established that PL bands intensity of spectra obtained for samples of nominal composition La 0.95 Dy 0.05 In 0.98 Sb 0.02 O 3 , La 0.95 Ho 0.05 In 0.98 Sb 0.02 O 3 , La 0.90 Dy 0.05 Ho 0.05 In 0.98 Sb 0.02 O 3 is much higher than that of single-phase La 0.95…
The evolution of the fraction of Er ions sensitized by Si nanostructures in silicon-rich silicon oxide thin films
2009
Photoluminescence (PL) and time-resolved PL experiments as a function of the elaboration process are performed on Er-doped silicon-rich silicon oxide (SRO:Er) thin films grown under NH(3) atmosphere. These PL measurements of the Er(3+) emission at 1.54 microm under non-resonant pumping with the Er f-f transitions are obtained for different Er(3+) concentrations, ranging from 0.05 to 1.4 at.%, and various post-growth annealing temperatures of the layers. High resolution transmission electron microscopy (HRTEM) and energy-filtered TEM (EFTEM) analysis show a high density of Si nanostructures composed of amorphous and crystalline nanoclusters varying from 2.7 x 10(18) to 10(18) cm(-3) as a fun…
Photoluminescent hybrid nanomaterials from modified halloysite nanotubes
2018
The synthesis of photoluminescent nanomaterials based on halloysite nanotubes is described. The obtained hybrid was characterized by means of TGA, FT-IR, DLS and XPS measurements; in addition its morphology was imaged by TEM and HR-TEM. The HNT hybrid also exhibited photoluminescent properties, both in solution and in the solid state, and white-light emission (0.24, 0.36; CIE coordinates) was observed. This work could be pioneering as a new strategy for manufacturing both LEDs and fluorescent tags based on HNT nanomaterials. © 2018 The Royal Society of Chemistry.
Exchange between interstitial oxygen molecules and network oxygen atoms in amorphousSiO2studied byO18isotope labeling and infrared photoluminescence …
2011
Amorphous ${\mathrm{SiO}}_{2}$ ($a$-${\mathrm{SiO}}_{2}$) thermally annealed in an oxygen atmosphere incorporates oxygen molecules (O${}_{2}$) in interstitial voids. When the thermal annealing is performed in $^{18}\mathrm{O}$${}_{2}$ gas, interstitial $^{18}\mathrm{O}$${}_{2}$ as well as interstitial $^{16}\mathrm{O}$$^{18}\mathrm{O}$ and $^{16}\mathrm{O}$${}_{2}$ are formed due to the oxygen exchange with the $a$-${\mathrm{SiO}}_{2}$ network. The ${a}^{1}{\ensuremath{\Delta}}_{g}(v=0)\ensuremath{\rightarrow}{X}^{3}{\ensuremath{\Sigma}}_{g}^{\ensuremath{-}}(v=1)$ infrared photoluminescence band of interstitial ${\mathrm{O}}_{2}$ was utilized to quantitatively analyze the oxygen exchange, t…
Tuning of ZnO 1D nanostructures by atomic layer deposition and electrospinning for optical gas sensor applications
2015
We explored for the first time the ability of a three-dimensional polyacrylonitrile/ZnO material—prepared by a combination of electrospinning and atomic layer deposition (ALD) as a new material with a large surface area—to enhance the performance of optical sensors for volatile organic compound (VOC) detection. The photoluminescence (PL) peak intensity of these one-dimensional nanostructures has been enhanced by a factor of 2000 compared to a flat Si substrate. In addition, a phase transition of the ZnO ALD coating from amorphous to crystalline has been observed due to the properties of a polyacrylonitrile nanofiber template: surface strain, roughness, and an increased number of nucleation …
Luminescence and optical spectroscopy of charge transfer processes in solid solutions Ni Mg1−O and Ni Zn1−O
2016
Abstract In this work photoluminescence spectra for Ni c Mg 1− c O and Ni x Zn 1− x O solid solutions with the rock-salt crystal structure were obtained under synchrotron radiation excitation. Periodical peaks in the photoluminescence excitation spectrum of Ni c Mg 1− c O ( c =0.008) have been discovered for a wide-gap oxide doped with 3d impurities for the first time. They can be considered as LO phonon repetitions of the narrow zero phonon line resulted from the optical transitions into the p–d charge transfer exciton [d 9 h] state. A close coincidence in energy of different peculiarities in the optical absorption and photoluminescence excitation spectra for the Ni c Mg 1− c O and Ni x Zn…
Photoluminescence of Carbon Dots Embedded in a SiO2 Matrix
2016
Abstract We synthetized carbon dots by a pyrolitic method, and studied their photoluminescence in aqueous environment and upon trapping in a solid matrix. To this aim, we devised a facile procedure allowing to embed the dots in amorphous SiO2, without the need of any pre-functionalization of the nanoparticles, and capable of yielding a brightly photoluminescent monolith. Experimental data reveal a remarkable similarity between the emission properties of carbon dots in water and in SiO2, suggesting that the chromophores responsible of the photoluminescence undergo only weak interactions with the environment. Time-resolved photoluminescence data reveal that the typical photoluminescence tunab…
Interstitial O2 distribution in amorphous SiO2 nanoparticles determined by Raman an Photoluminescence spectroscopy
2013
The O2 content and emission properties in silica nanoparticles after thermal treatments in oxygen rich atmosphere have been investigated by Raman and photoluminescence measurements. The nanoparticles have different sizes with average diameter ranging from 7 up to 40 nm. It is found that O2 concentration in nanoparticles monotonically increases with nanoparticles size. This finding is independent on the measurement technique and evidences that oxygen molecules are not present in all the nanoparticles volume. This dependence is interpreted on the basis of a structural model for nanoparticles consisting of a core region able to host the oxygen molecules and a surface shell of fixed size and fr…
Optical properties of ultrathin Al2O3/ZnO nanolaminates
2015
Abstract Because of their high resistance against ultraviolet and high energy particles, ultrathin amorphous nanolaminates can be very attractive for aerospace application. Here we report on the optical and structural properties of ultrathin Al2O3/ZnO nanolaminates deposited by Atomic Layer Deposition. Structural properties of nanolaminates were studied by GIXRD and AFM. Optical characterization was performed by transmittance, spectroscopic ellipsometry and photoluminescence (PL) spectroscopy. Regression analysis of ellipsometric spectra has shown that absorption peak decreases and blue shifted with the decrease of bilayer thickness in the stack. On the basis of the analysis of structural a…