CRYSTAL RESEARCH AND TECHNOLOGY, Issue 10 2010
Changhyun Jin
Abstract It is essential to passivate one-dimensional (1D) nanostructures with insulating materials to avoid crosstalking as well as to protect them from contamination and oxidation. The structure and influence of thermal annealing on the photoluminescence properties of ZnS-core/SiO2 -shell nanowires synthesized by the thermal evaporation of ZnS powders followed by the sputter deposition of SiO2 were investigated. Transmission electron microscopy and X-ray diffraction analyses revealed that the cores and shells of the core-shell nanowires were single crystal zinc blende-type ZnO and amorphous SiO2, respectively. Photoluminescence (PL) measurement showed that the core-shell nanowires had a green emission band centered at around 525 nm with a shoulder at around 385 nm. The PL emission of the core-shell nanowires was enhanced in intensity by annealing in an oxidative atmosphere and further enhanced by subsequently annealing in a reducing atmosphere. Also the origin of the enhancement of the green emission by annealing is discussed based on the energy-dispersive X-ray spectroscopy analysis results. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Characterization of reactive DC magnetron sputtered TiAlN thin films

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 10 2008
B. Subramanian
Abstract Thin films of about 1,m Titanium Aluminum Nitride (TiAlN) were deposited onto mild steel substrates by reactive direct current (DC) magnetron sputtering using a target consisting of equal segments of titanium and aluminum. X-ray diffraction (XRD) analysis showed that the TiAlN phase had preferred orientations along 111 and 200 with the face-centered cubic structure. Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM) analyses indicated that the films were uniform and compact. Photoluminescence (PL) spectra reveal that TiAlN thin films are of good optical quality. Laser Raman studies revealed the presence of characteristic peaks of TiAlN at 312.5, 675, and 1187.5 cm,1. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Dewetted growth of CdTe in microgravity (STS-95)

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 6 2004
M. Fiederle
Abstract Two CdTe crystals had been grown in microgravity during the STS-95 mission. The growth configuration was dedicated to obtain dewetting of the crystals and to achieve high quality material. Background for the performed experiments was based on the theory of the dewetting and previous experience. The after flight characterization of the crystals has demonstrated existance of the dewetting areas of the crystals and their improved quality regarding the earth grown reference sample. The samples had been characterized by EDAX, Synchrotron X-ray topography, Photoluminescence and Optical and IR microscopy. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Designed Assembly and Structures and Photoluminescence of a New Class of Discrete ZnII Complexes of 1H -1,10-Phenanthroline-2-one

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 17 2006
Jie-Peng Zhang
Abstract The hydrothermal reaction of 1H -1,10-phenanthroline-2-one (Hophen), zinc acetate, benzoic acid (Hba), and triethylamine (3.0 mL) yields the tetranuclear complex [Zn4(,3 -OH)2(ophen)4(ba)2] (2), which features a chair-like Zn4(,3 -OH)2 cluster with two ba ligands centrosymmetrically oriented. [(OAc){Zn3(,3 -OH)(ophen)3}(ox){Zn3(,3 -OH)(ophen)3}(OAc)] (3; ox = oxalate) was isolated when less triethylamine (1.0 mL) was used. Two Zn3(,3 -OH)(ophen)3 clusters in 3 are linked together by an oxalate to form a dumbbell-like structure in which the acetate and oxalate ligands point outward from the Zn3(,3 -OH)(ophen)3 cluster with an acute bending angle. A geometric analysis reveals that Zn3(,3 -OH)(ophen)3 and dicarboxylate with an obtuse bending angle cannot form an infinite zigzag chain, whereas the ring isomer can. With isophthalate (ipa), thiophene-2,5-dicarboxylate (tda), and 4,4,-oxybis(benzoate) (oba) instead of the acetate of 3 three new complexes, namely [{Zn3(,3 -OH)(ophen)3}(ipa)2{Zn3(,3 -OH)(ophen)3}]·0.5H2O (4), [{Zn3(,3 -OH)(ophen)3}(tda)2{Zn3(,3 -OH)(ophen)3}] (5), and [{Zn3(,3 -OH)(ophen)3}(oba)2{Zn3(,3 -OH)(ophen)3}] (6), were obtained in which two Zn3(,3 -OH)(ophen)3 clusters are linked by a pair of ipa, tda, or oba ligands to form isostructural, cluster-based 2:2 metallomacrocycles. Photoluminescence studies of 2,6 revealed that their luminescent properties are derived from ophen-based ,-,* excited states. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

Systematic Studies on Photoluminescence of Oligo(arylene-ethynylene)s: Tunability of Excited States and Derivatization as Luminescent Labeling Probes for Proteins

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 14 2006
Yong-Gang Zhi
Abstract Functionalized oligo(phenylene-ethynylene)s (OPEs) with different conjugation lengths, p -X(C6H4C,C)nSiMe3 (n = 1,4; X = NH2, NMe2, H) were synthesized by Sonogashira coupling of (phenylene-ethynylene)s and 1-iodo-4-(trimethylsilylethynyl)benzene, followed by desilylation of the p -substituted (trimethylsilylethynyl)benzenes with potassium hydroxide. The photoluminescent properties for the OPE series with different chain lengths and their solvatochromic responses were examined. The absorption maxima were red-shifted with increasing numbers of ,(C6H4C,C), units (n), and a linear plot of the absorption energy maxima vs. 1/n was obtained for each series. The emission spectra in dichloromethane showed a broad and structureless band, the energies of which (in wavenumbers) also fit linearly with 1/n. Both the absorption and emission wavelength maxima of the NH2 - and NMe2 -substituted OPEs exhibited significant solvent dependence, whereas the parent OPEs (X = H) showed only minor shifts of the ,max values in different solvents. Substituent effects upon the photoluminescent characteristics of the OPEs and the tunability of the excited states were examined with the p -X(C6H4C,C)nSiMe3 (n = 2, 3; X = NH2, NMe2, H, SMe, OMe, OH, and F) series. The H- and F-substituted counterparts exhibited high-energy vibronically structured emissions attributed to the 3(,,*) excited states of the (arylene-ethynylene) backbone. For compounds bearing NH2 and NMe2 groups, a broad red-shifted emission with a remarkable Stokes shift from the respective absorption maximum was observed, which can be assigned to an n , ,* transition. The n , ,* assignment was supported by MO calculations on the model compounds p -X(C6H4C,C)2SiH3 (X = NH2, H). Functionalization of the oligo(arylene-ethynylene)s with the N -hydroxysuccinimidyl (NHS) moiety enabled covalent attachment of the fluorophore to HSA protein molecules. A series of fluorescent labels, namely p -X(C6H4C,C)nC6H4NHS, (n = 1, X = NH2, NMe2, SMe, OMe, OH, F; n = 2, X = NH2, NMe2) and p -Me2NC6H4C,C(C4H2S)C,CC6H4NHS were synthesized, and their conjugates with HSA (human serum albumin) were characterized by MALDI-TOF mass spectrometry, UV/Vis absorption spectroscopy, and gel electrophoresis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

Preparation-Condition Dependence of Hybrid SiO2 -Coated CdTe Nanocrystals with Intense and Tunable Photoluminescence

ADVANCED FUNCTIONAL MATERIALS, Issue 8 2010
Ping Yang
Abstract When aqueously prepared CdTe nanocrystals (NCs) are coated with a SiO2 shell containing Cd ions and a sulfur source, they show a drastic increase in photoluminescence (PL) efficiency with a significant red shift and spectral narrowing after reflux. This is ascribed to the creation of a hybrid structure characterized by the formation of CdS-like clusters in the vicinity of the NCs in the SiO2 shell. Since these clusters are close to the NCs, their effective size increases to reduce the quantum size effect. The dependences of the PL properties on the preparation conditions are systematically investigated. The PL efficiency increases from 28% to 80% in the best case with a red shift of 80,nm. The PL behaviors differ from those of normal CdTe NCs and include less temperature quenching and longer PL lifetime. The SiO2 coating enables bioconjugation with IgG without deterioration of PL efficiency, making hybrid NCs amenable for bioapplication. [source]

Photoluminescence-Based Sensing With Porous Silicon Films, Microparticles, and Nanoparticles

ADVANCED FUNCTIONAL MATERIALS, Issue 20 2009
Michael J. Sailor
Abstract Here, chemical sensors made from porous Si are reviewed, with an emphasis on systems that harness photoluminescence and related energy- and charge-transfer mechanisms available to porous Si-derived nanocrystallites. Quenching of luminescence by molecular adsorbates involves the harvesting of energy from a delocalized nanostructure that can be much larger than the molecule being sensed, providing a means to amplify the sensory event. The interaction of chemical species on the surface of porous Si can exert a pronounced influence on this process, and examples of some of the key chemical reactions that modify either the surface or the bulk properties of porous Si are presented. Sensors based on micron-scale and smaller porous Si particles are also discussed. Miniaturization to this size regime enables new applications, including imaging of cancerous tissues, indirect detection of reactive oxygen species (ROS), and controlled drug release. Examples of environmental and in vivo sensing systems enabled by porous Si are provided. [source]

Observation of a Charge Transfer State in Low-Bandgap Polymer/Fullerene Blend Systems by Photoluminescence and Electroluminescence Studies

ADVANCED FUNCTIONAL MATERIALS, Issue 20 2009
Yi Zhou
Abstract The presence of charge transfer states generated by the interaction between the fullerene acceptor PCBM and two alternating copolymers of fluorene with donor,acceptor,donor comonomers are reported; the generation leads to modifications in the polymer bandgap and electronic structure. In one of polymer/fullerene blends, the driving force for photocurrent generation, i.e., the gap between the lowest unoccupied molecular orbitals of the donor and acceptor, is only 0.1,eV, but photocurrent is generated. It is shown that the presence of a charge transfer state is more important than the driving force. The charge transfer states are visible through new emission peaks in the photoluminescence spectra and through electroluminescence at a forward bias. The photoluminescence can be quenched under reverse bias, and can be directly correlated to the mechanism of photocurrent generation. The excited charge transfer state is easily dissociated into free charge carriers, and is an important intermediate state through which free charge carriers are generated. [source]

Tuning and Enhancing Photoluminescence of Light-Emitting Polymer Nanotubes through Electron-Beam Irradiation

ADVANCED FUNCTIONAL MATERIALS, Issue 4 2009
Young Ki Hong
A new method for the tuning and enhancing photoluminescence (PL) characteristics of light emitting poly (3-methylthiopnehe) (P3MT) nanotubes through E-beam irradiation under atmospheric environments is reported. An E-beam generated from a linear electron accelerator (1 MeV, 1.6,×,1013,8.0,×,1016 electrons cm,2) is irradiated onto P3MT nanotubes including an Al2O3 template. From laser confocal microscope (LCM) PL experiments, significant enhancements in the PL intensity,up to about 90 times of an isolated single strand of the E-beam irradiated P3MT nanotubes,are observed. The luminescent color of the P3MT nanotubes changes from green to red color depending on the variation of E-beam dosage. These results might originate from the de-doping effect and the conformational modification through E-beam irradiations. Conformational changes of the E-beam irradiated P3MT nanotubes are confirmed by LCM single Raman and ultraviolet-visible (UV/Vis) absorption spectra. From UV/Vis absorption spectra, it is observed that the ,,,* transition peak and the doping induced bipolaron peaks of the P3MT nanotubes dramatically vary with E-beam irradiating conditions. [source]

Organized Nanostructured Complexes of Polyoxometalates and Surfactants that Exhibit Photoluminescence and Electrochromism

ADVANCED FUNCTIONAL MATERIALS, Issue 4 2009
Tierui Zhang
Abstract A variety of functional nanostructured organic/inorganic hybrid materials from the europium-exchanged derivative of a Preyssler-type polyoxometalate (POM), [EuP5W30O110]12,, and functional organic surfactants were prepared by the ionic self-assembly (ISA) route. The effect of organic surfactants on the structure, photoluminescent, electrochemical and electrochromic properties of the POM anions was investigated in detail. All obtained hybrid materials are amphotropic, i.e., exhibit both thermotropic and lyotropic liquid-crystalline phase behaviour. Investigations of their photophysical properties have shown that the interactions of the various surfactants with the polyanions influence the coordination environments and site symmetry of Eu3+ in different ways. The functional groups in the organic surfactants significantly influence the electrochromic properties and photoluminescence of POMs. Different from normal and pyridine-containing complexes, no photoluminescence and no electrochromism were observed from the ferrocene-containing complexes. This may be explained in view of charge transfer between the POM anion and the ferrocenyl group. [source]

Hybrid Solar Cells from Regioregular Polythiophene and ZnO Nanoparticles,

ADVANCED FUNCTIONAL MATERIALS, Issue 8 2006

Abstract Blends of nanocrystalline zinc oxide nanoparticles (nc-ZnO) and regioregular poly(3-hexylthiophene) (P3HT) processed from solution have been used to construct hybrid polymer,metal oxide bulk-heterojunction solar cells. Thermal annealing of the spin-cast films significantly improves the solar-energy conversion efficiency of these hybrid solar cells to ,,0.9,%. Photoluminescence and photoinduced absorption spectroscopy demonstrate that charge-carrier generation is not quantitative, because a fraction of P3HT appears not to be in contact with or in close proximity to ZnO. The coarse morphology of the films, also identified by tapping-mode atomic force microscopy, likely limits the device performance. [source]

Stable Blue Emission from a Polyfluorene/Layered-Compound Guest/Host Nanocomposite,

ADVANCED FUNCTIONAL MATERIALS, Issue 7 2006
E. Aharon
Abstract In this study a blue-light-emitting conjugated polymer, poly(9,9-dioctylfluorene), is confined to the interlayer space of inorganic, layered metal dichalcogenide materials, metallic MoS2, and semiconducting SnS2. The nanocomposites are prepared through Li intercalation into the inorganic compound, exfoliation, and restacking in the presence of the polymer. X-ray diffraction and optical absorption measurements indicate that a single conjugated polymer monolayer, with an overall extended planar morphology conformation, is isolated between the inorganic sheets, so that polymer aggregation or ,,, interchain interactions are significantly reduced. Photoluminescence (PL) measurements show that the appearance of the undesirable green emission observed in pristine polymer films is suppressed by incorporating the polymer into the inorganic matrix. The blue emission of the intercalated polymer is stable for extended periods of time, over two years, under ambient conditions. Furthermore, the green emission is absent in the PL spectra of nanocomposite films heated at 100,°C for 7,h in air with direct excitation of the keto defect. Finally, no green emission was observed in the electroluminescence spectrum of light-emitting devices fabricated with a polymer-intercalated SnS2 nanocomposite film. These results support the proposed hypothesis that fluorenone defects alone are insufficient to generate the green emission and that interchain interactions are also required. [source]

Well-Aligned ZnO Nanowire Arrays Fabricated on Silicon Substrates ,

ADVANCED FUNCTIONAL MATERIALS, Issue 6 2004
C. Geng
Abstract Arrays of well-aligned single-crystal zinc oxide (ZnO) nanowires of uniform diameter and length have been synthesized on a (100) silicon substrate via a simple horizontal double-tube system using chemical vapor transport and condensation method. X-ray diffraction and transmission electron microscopy (TEM) characterizations showed that the as-grown nanowires had the single-crystal hexagonal wurtzite structure with detectable defects and a <0002> growth direction. Raman spectra revealed phonon confinement effect when compared with those of ZnO bulk powder, nanoribbons, and nanoparticles. Photoluminescence exhibited strong ultraviolet emission at 3.29,eV under 355,nm excitation and green emission at 2.21,eV under 514.5,nm excitation. No catalyst particles were found at the tip of the nanowires, suggesting that the growth mechanism followed a self-catalyzed and saturated vapor,liquid,solid (VLS) model. Self-alignment of nanowires was attributed to the local balance and steady state of vapor flow at the substrate. The growth technique would be of particular interest for direct integration in the current silicon-technology-based optoelectronic devices. [source]

Blue Photoluminescence from Chemically Derived Graphene Oxide

ADVANCED MATERIALS, Issue 4 2010
Goki Eda
Blue photoluminescene (PL) from chemically derived graphene oxide has been observed. The PL is attributed to radiative recombination of electron,hole pairs in isolated "molecular" sp2 domains, which are present within the carbon,oxygen sp3 matrix in chemically derived graphene oxide. The PL intensity is correlated to the evolution of sp2 domains during reduction. [source]

Strong Ultra-Broadband Near-Infrared Photoluminescence from Bismuth-Embedded Zeolites and Their Derivatives

ADVANCED MATERIALS, Issue 36 2009
Hong-Tao Sun
Zeolites with embedded bismuth compounds display strong, air-stable, long-lived, ultrabroadband, and tunable near-infrared photoluminescence (see picture). Bismuth ions not only act as luminescence-active centers, but also as blocks for selectively closing the "in,out windows" of water molecules. Bismuth active centers can be sealed in a low-vibrational environment by bismuth agglomerates even when the sample still contains a large amount of water. [source]

Water-Soluble Silicon Quantum Dots with Wavelength-Tunable Photoluminescence

ADVANCED MATERIALS, Issue 6 2009
Zhenhui Kang
H-terminated Si quantum dots (Si QDs) with 3,nm diameter are converted to water-soluble uniform-sized Si QDs after controlled oxidation in an EtOH/H2O2 solution. These dots present Si/SiOxHy core/shell nanostructures, and can be finely tuned to emit light in seven different colors due to the quantum size effect in the Si cores, exhibiting excellent photocatalytic activity in the visible range. [source]

Spatially Localized Photoluminescence at 1.5 Micrometers Wavelength in Direct Laser Written Optical Nanostructures

ADVANCED MATERIALS, Issue 23 2008
Sean Wong
No abstract is available for this article. [source]

Self-Assembled Highly Faceted Wurtzite-Type ZnS Single-Crystalline Nanotubes with Hexagonal Cross-Sections,

ADVANCED MATERIALS, Issue 16 2005
L.-W. Yin
Highly faceted wurtzite-type ZnS nanotubes with hexagonal cross-sections have been self-assembled via a thermochemistry process. The self-assembled growth along the c -axis is associated with the non-central and polar surfaces of the ZnS structure (see Figure and inside cover). Photoluminescence at room temperature shows a weak blue and a strong green emission band. [source]

Up-Conversion Photoluminescence in Polyfluorene Doped with Metal(II),Octaethyl Porphyrins

ADVANCED MATERIALS, Issue 24 2003
P.E. Keivanidis
The up-conversion photoluminescence (PL) in films of polyfluorene (PF) doped with metallated porphyrins is reported for the first time. The dependence of the up-conversion process on the pump laser intensity and wavelength, the central metal moiety of the dopants, and the temperature is presented. Up-conversion emission is observed at pump intensities as low as 2 kW,cm,2. Comparison of the PF integral PL intensities after laser excitation by 532, 543, and 405 nm enables the discussion of the energy-transfer mechanism and the efficiency of the process. [source]

X-ray diffraction analysis of GaInNAs double-quantum-well structures

JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 1 2004
Kiichi Nakashima
The structures of GaInNAs/GaAs double-quantum-well (DQW) samples with various well-layer thicknesses were analysed by X-ray diffraction measurements. Two types of rocking-curve analysis were applied with different scanning configurations: a conventional configuration without a receiving slit and one with an analyser crystal placed in front of the receiving detector (the latter is the same as that usually used in reciprocal-space mapping measurements). It was found that systematic combination of both types of analysis is essential for the characterization of the sample structures. The two types of X-ray profiles obtained using the different scanning configurations exhibit a considerable difference in intensity as the thickness of the well layers increases. The increasing difference clearly indicates deterioration of the DQW structures. The two profiles exhibit little difference in terms of shape, merely showing that the DQW layers are coherently strained relative to the substrate. This implies that measurement in only one of the configurations is insensitive to the deterioration and leads to the wrong conclusion that a sample has a perfect structure without dislocations and defects. Photoluminescence and transmission electron microscope analyses both reveal that defects really do exist in the DQW structures, which is consistent with the difference in intensity observed in the X-ray measurements. From these results, a clear picture that consistently explains the sensitivity of X-ray diffraction analysis to the deterioration of samples is presented. In addition, based on this picture, it is proposed that the procedure of comparing the two types of profiles represents a new type of analysis method for the precise characterization of samples. [source]

Synthesis and characterizations of nanosized iron(II) hydroxide and iron(II) hydroxide/poly(vinyl alcohol) nanocomposite

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2010
M. Fathima Parveen
Abstract Nanosized Fe(OH)2 was synthesized by a coprecipitation method. Peaks between 500 and 1250 cm,1 in Fourier transform infrared (FTIR) spectroscopy confirmed the presence of metal hydroxide stretching. X-ray diffraction showed the suppressed crystalline system of Fe(OH)2/aniline (ANI) due to the presence of a higher weight percentage of the dispersing agent, ANI. Thermogravimetric analysis implied that 75.5 wt % of residue remained up to 800°C. High resolution transmission electron microscope (HRTEM) analysis of Fe(OH)2/ANI revealed that its size ranged from 10 to 50 nm with a rodlike morphology. Scanning electron microscopy implied that pristine Fe(OH)2 had a nanotriangular platelet morphology, and a higher weight percentage of dispersing agent intercalated with Fe(OH)2 had a spheroid with an agglomerated structure. The (UV,visible) spectrum implied the presence of Fe2+ ions at 326 nm and the existence of an amino group intercalated with Fe(OH)2 showed a sharp peak at 195 nm, the intensity of which increased with increasing intercalated dispersing agent weight percentage. Photoluminescence showed that ANI-intercalated Fe(OH)2 showed a lesser intensity than the pristine Fe(OH)2. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

Synthesis and characterization of copolythiophene

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007
Jie He
Abstract Copolythiophenes (Co-PTs), poly(3-hexylthiophene- co -3-thiophene carboxylic acid) (P3HT-TCa), poly(3-hexyloxylthiophene- co -3-thiophene carboxylic acid) (P3HOT-TCa), and poly(3-phenylthiophene- co -3-thiophene carboxylic acid) (P3PhT-TCa), were synthesized by chemical oxidized polymerization to investigate the effect of copolymerization on the properties of polythiophenes (PTs). Gel permeation chromatography showed that the molecular weight (MW) of Co-PT was lower than that of homopolythiophene. Fourier transform infrared (FTIR) spectra indicated that the copolymerization was successful between the monomers. The ,max of Co-PTs gave a "blue shift" in ultraviolet-visible (UV-VIS) spectra. Photoluminescence (PL) spectra showed that the PL intensity of Co-PT became weaker than that of homopolythiophene and the disappearance of PL had been observed in P3HOT-TCa. The thermal stability of Co-PT was influenced by the carboxyl for its low decomposition temperature. Furthermore, the copolymerization between multi-wall carbon nanotube containing thiophene ring (MWNT-Th) and 3-hexyloxylthiphene could also take place successfully. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source]

Reproducible Solvent,Thermal Synthesis, Controlled Microstructure, and Photoluminescence of REPO4:Eu3+, Tb3+ (RE=Y, La, and Gd) Nanophosphors

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2010
Xiuzhen Xiao
By altering the temperature and solvents, we have synthesized hydrated and dehydrated Eu3+/Tb3+ -doped REPO4 (RE=Y, La, and Gd) nanophosphors via a solvo-thermal technology. X-ray powder diffraction and scanning electronic microscopy reveal that they have different structures and different morphologies. REPO4 prepared under subsequent heating at 80°, 120°, and 160°C for 1 day, respectively, present larger particle size than that formed by heating at 160°C for 3 days. Moreover, at the same temperature of 160°C and pH 3, three different solvents (ethanol, N,N -dimethylformamide (DMF), and water) were used, whose influence on the microstructure of LaPO4 has been examined. As a result, LaPO4 samples from anhydrous ethanol solvent show a pure hexagonal phase and nanowire morphology, just like that prepared from the water solvent. On the other hand, the microstructure of LaPO4 samples from DMF,H2O-mixed solvents have been changed: with the increasing volume ratio of DMF to H2O, the crystal phase of LaPO4 has been changed from hexagonal phase to monoclinic phase and the morphology from nanowires to nanoparticles. Finally, the photoluminescence properties of these Eu3+ (Tb3+)-activated rare earth phosphates have been investigated, indicating that the photoluminescent behavior are related to their crystal phases and microstructures. [source]

Electron Field Emission and Photoluminescence of Anatase Nanotube Arrays

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2008
Yang Yang
TiO2 nanotube arrays with a high aspect ratio were grown on conductive Ti substrates by anodization in an organic electrolyte. The as-prepared TiO2 nanotubes were vertically grown and adhered well to the substrates. The photoluminescence spectrum and X-ray diffraction showed that the crystal structure of the postannealed TiO2 nanotube arrays was oxygen-defective anatase. This kind of anatase nanotube arrays exhibited efficient electron field emission even at room temperature with a low applied electric field of ,9 V/,m. The emission current exceeded 70 ,A/cm2 at an extraction voltage of 700 V. [source]

Photoluminescence of High-Aspect-Ratio PbTiO3 Nanotube Arrays

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2008
Yang Yang
High-aspect-ratio PbTiO3 nanotube arrays have been synthesized by the hydrothermal method. X-ray diffraction result shows that PbTiO3 nanotube arrays have a tetragonal perovskite structure without any other impurity. The photoluminescence property of PbTiO3 nanotube arrays studied at room temperature reveals a strong green emission band peaking at 550 nm (2.25 eV). Both Raman spectroscopy and X-ray photoelectron spectroscopy demonstrate the existence of local defects in PbTiO3 nanotube arrays, which act as emission source and result in the photoluminescence behavior of PbTiO3 nanotube arrays. [source]

Energy Transfer Enables 1.53 ,m Photoluminescence from Erbium-Doped TiO2 Semiconductor Nanocrystals Synthesized by Ar/O2 Radio-Frequency Thermal Plasma

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2008
Ji-Guang Li
Highly crystalline, highly luminescent nanopowders of Er3+ -doped TiO2 have been successfully synthesized via one-step Ar/O2 radio-frequency thermal plasma processing. Energy transfer from the TiO2 host to Er3+ activators has been confirmed by combined means of UV-vis, excitation, and photoluminescence spectroscopies. As a consequence, bright photoluminescence at ,1.53 ,m was observed from the nanopowders either by directly exciting the Er3+ activator or by exciting the TiO2 host lattice. A comparative study shows that the nanopowder of the same system made via coprecipitation lacks the energy transfer. The plasma-generated nanopowders may thus find applications in optoelectronic devices. [source]

Photoluminescence from Boron-Doped Titanium Nitride Nanocomposite Thin Films Prepared by the Magnetron Sputtering Method

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2007
Sheng-Guo Lu
Boron-doped titanium nitride (TiBN) thin films with nanosized grains were prepared by a magnetron sputtering method. X-ray diffraction and transmission electron microscopy observation indicated that TiBN thin films have a cubic structure with grains ,5 nm in size. The photoluminescence (PL) of the films was investigated as a function of temperature over a wavelength range of 350,900 nm. Two PL peaks near 3.20 and 2.38 eV were conisdered to have resulted from the recombination of the donor-bound excitons and deep-trap defects with the holes in the valence band, respectively. An energy transfer from bound electrons to deep-trap defects was observed in the nanocomposite thin film. [source]

Photoluminescence of Cerium-Doped ,-SiAlON Materials

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2004
Rong-Jun Xie
Cerium-doped ,-SiAlON (MxSi12,(m+n)Alm+nOnN16,n) materials have been prepared by gas-pressure sintering and post-hot-isostatic-press (HIP) annealing, using four powder mixtures of ,-Si3N4, AlN, and either (i) CeO2, (ii) CeO2+ Y-,-SiAlON seed, (iii) CeO2+ Y2O3, or (iv) CeO2+ CaO. Cerium-containing CeAl(Si6,zAlz)(N10,zOz) (JEM) phase, rather than Ce-,-SiAlON phase, forms in the sample with only CeO2, whereas a single-phase ,-SiAlON generates in samples with dual doping (CeO2+ Y2O3 and CeO2+ CaO). On ultraviolet-light excitation, JEM gives one broad emission band with maximum at 465 nm and a shoulder at 498 nm; ,-SiAlON shows an intense and broad emission band that peaks at 500 nm. The unusual long-wavelength emissions in JEM and ,-SiAlON are due to increases in the nephelauxetic effect and the ligand-field splitting of the 5d band, because the coordination of Ce3+ in JEM and ,-SiAlON is nitrogen enriched. [source]

Tuning the Photoluminescence of Silsesquioxanes with Short Substituted Urea Bridges

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 6 2008
María L. Gómez
Abstract The polycondensation of a precursor synthesized by the reaction of 3-(anilinepropyl)trimethoxysilane with 3-(isocyanatopropyl)triethoxysilane led to a silsesquioxane bearing a substituted urea group in the short organic bridge. The self-assembly of organic bridges, analyzed by SAXS and FTIR spectra, could be controlled by varying the conditions of the synthesis. Depending on the size of organic clusters, the silsesquioxane exhibited photoluminescence either in the green or red regions of the spectra, or an emission that could be tuned in the whole visible region by the excitation wavelength. [source]

Photoluminescence of Self-organized Perylene Bisimide Polymers

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 2 2004
Edda E. Neuteboom
Abstract Summary: Three polymers consisting of alternating perylene bisimide chromophores and flexible polytetrahydrofuran segments of different length have been studied using absorption and (time-resolved) photoluminescence spectroscopy. In o -dichlorobenzene, the chromophores self organize to form H-like aggregates. The photoluminescence spectra of the self-organized polymers consist of vibronically resolved monomeric perylene bisimde fluorescence (,max,=,538 nm, ,,=,3.9 ns) and unstructured excimer-type emission (,max,=,635 nm, ,,=,17 ns). An additional short-lived (,,,,2 ns) luminescence component is observed and ascribed to the dynamic deactivation of the monomeric photoexcited state via excimer formation or energy transfer. Structure of alternating perylene bisimide , polyTHF copolymers. [source]