EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2010
Arshad Aijaz
Abstract A ZnII coordination polymer {[Zn2(cpa)2(bpy)]·3H2O}n (1) (cpa2, = 4-(methoxycarbonyl)benzoate and bpy = 4,4,-bipyridine) has been synthesized under solvothermal condition and structurally characterized. This coordination polymer has nanotubular threefold entangled (2D,3D) structure with embedded water molecules; the water molecules can be partially exchanged in reversible single-crystal-to-single-crystal (SC-SC) fashion by different solvent molecules like methanol, ethanol and acetone giving rise to {[Zn2(cpa)2(bpy)]·(0.5MeOH)·(2.5H2O)}n (2), {[Zn2(cpa)2(bpy)]·(0.5EtOH)·(0.5H2O)}n (3) and {[Zn2(cpa)2(bpy)]·(0.5Me2CO)·(H2O)}n (4). Inclusion of EtOH or MeOH leaves the size of the voids in the framework unaltered. Inclusion of acetone, however, is accompanied by shrinking of the voids in the framework. Heating of 1 at 100 °C under vacuum for 4 h affords the de-solvated compound, {Zn2(cpa)2(bpy)}n (1,). Single-crystal X-ray structure of 1, shows sliding of the individual nanotubular components expanding the overall framework. Thus, the coordination polymer exhibits dynamic motion of the molecular components in SC-SC fashion. All compounds were further characterized via IR spectroscopy, PXRD, elemental and TGA analysis. When 1 is placed in benzene at 100 °C for 2 days, compound {[Zn2(cpa)2(bpy)]·(2.5H2O)}n (5) is formed in a SC-SC fashion where coordination number of ZnII ion increases from four to five. Compound 1 also exhibits reversible guest-dependent photoluminescence properties. [source]

Dual Luminescent Dinuclear Gold(I) Complexes of Terpyridyl-Functionalized Alkyne Ligands and Their Efficient Sensitization of EuIII and YbIII Luminescence

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 22 2010
Xiu-Ling Li
Abstract Reaction of (tpyC6H4C,CAu)n {tpyC6H4C,CH = 4,-(4-ethynylphenyl)-2,2,:6,,2,-terpyridine} with diphosphane ligands Ph2P(CH2)xPPh2 (x = 2 dppe, 3 dppp, 4 dppb, 5 dpppen, 6 dpph) in CH2Cl2 afforded the corresponding dual luminescent binuclear gold(I) complexes [(tpyC6H4C,CAu)2(,-dppe)] (1), [(tpyC6H4C,CAu)2(, - dppp)] (2), [(tpyC6H4C,CAu)2(,-dppb)] (3), [(tpyC6H4C,CAu)2(,-dpppen)] (4), [(tpyC6H4C,CAu)2(,-dpph)] (5). Crystal structural analysis of complexes 1·2CH2Cl2 and 2·2CH2Cl2 show that the terpyridine moieties are free of coordination in these gold(I)-acetylide-phosphane complexes. Spectrophotometric titration between complex 1 and [Eu(tta)3] (Htta = 2-thenoyltrifluoroacetone) or [Yb(hfac)3(H2O)2] (Hhfac = hexafluoroacetylacetone) gave a 2:1 ratio between Ln(,-diketonate)3 (Ln = Eu, Yb) units and the complex 1 moiety, indicating the formation of Au2Ln2 complexes. Both the luminescence titrations and the luminescence quantum yields of Au2Ln2 (Ln = Eu, Yb) solutions show that the energy transfer occurs efficiently from the binuclear gold(I) antennas 1,5 to EuIII and YbIII centers, and all complexes 1,5 are good energy donors for sensitization of visible and NIR luminescence of EuIII and YbIII ions. [source]

Strong Circularly Polarized Luminescence from Highly Emissive Terbium Complexes in Aqueous Solution

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 21 2010
Amanda P. S. Samuel
Abstract Two luminescent terbium(III) complexes have been prepared from chiral ligands containing 2-hydroxyisophthalamide (IAM) antenna chromophores and their non-polarized and circularly-polarized luminescence properties have been studied. These tetradentate ligands, which form 2:1 ligand/TbIII complexes, utilize diaminocyclohexane (cyLI) and diphenylethylenediamine (dpenLI) backbones, which we reasoned would impart conformational rigidity and result in TbIII complexes that display both large luminescence quantum yield (,) values and strong circularly polarized luminescence (CPL) activities. Both TbIII complexes are highly emissive, with , values of 0.32 (dpenLI-Tb) and 0.60 (cyLI-Tb). Luminescence lifetime measurements in H2O and D2O indicate that while cyLI-Tb exists as a single species in solution, dpenLI-Tb exists as two species: a monohydrate complex with one H2O molecule directly bound to the TbIII ion and a complex with no water molecules in the inner coordination sphere. Both cyLI-Tb and dpenLI-Tb display increased CPL activity compared to previously reported TbIII complexes made with chiral IAM ligands. The CPL measurements also provide additional confirmation of the presence of a single emissive species in solution in the case of cyLI-Tb, and multiple emissive species in the case of dpenLI-Tb. [source]

Synthesis, Upconversion Luminescence and Magnetic Properties of New Lanthanide,Organic Frameworks with (43)2(46,66,83) Topology

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 21 2007
Danfeng Weng
Abstract The synthesis and crystal structures of three new lanthanide,organic frameworks [Ln(pza)(OH)(H2O)]n (Ln = Y(1), Er(2), Yb(3); H2pza = 2,3-pyrazinedicarboxylic acid) with helical chains and novel 2D (43)2(46,66,83) topology are reported. The topology is obtained by simplifying the dinuclear metal core as a six-connected node and the ligand as a three-connected linker. The upconversion property measurement gives green and red emissions coming from two-photon excitation of Y: Er, Yb codoped coordination polymer and arising from ErIII transitions of 4S3/2/2H11/2,4I15/2 and 4F9/2,4I15/2. The magnetic properties of complexes 2 and 3 are also studied.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

Tris(8-hydroxyquinoline-5-sulfonate)aluminum Intercalated Mg,Al Layered Double Hydroxide with Blue Luminescence by Hydrothermal Synthesis

ADVANCED FUNCTIONAL MATERIALS, Issue 17 2010
Shuangde Li
Abstract Blue luminescent hybrid materials (DDS,AQS(x%)/LDH) are successfully prepared by co-intercalating tris(8-hydroxyquinoline-5-sulfonate)aluminum anions (AQS3,) and dodecyl sulfonate (DDS,) with different molar ratios into Mg,Al layered double hydroxides (LDHs) by the hydrothermal and solution co-precipitation methods. A film of the material on a quartz substrate is obtained by the solvent evaporation method. The results show the blue luminescence is remarkably different from the pristine Na3AQS, which has cyan luminescence (ca. 450,470 nm vs. 495 nm). Furthermore, the hydrothermal product of DDS,AQS(66.67%)/LDH exhibits optimal luminous intensity and a significantly enhanced fluorescence lifetime. Nuclear magnetic resonance and Fourier-transform infrared spectroscopy indicate that the cyan,blue luminescence transition is due to the isomerization of meridianal to facial AQS via ligand flip caused by a host,guest electrostatic interaction, in combination with the dispersion and pre-intercalation effect of DDS. The hydrothermal conditions can promote a more ordered alignment of the intercalated fac -AQS compared with alignment in the solution state, and the rigid LDHs environment can confine the internal mobility of AQS to keep the facial configuration stable. This stability allows a facile preparation of large amounts of blue luminous powder/film, which is a new type of inorganic,organic hybrid photofunctional material. [source]

Blue Luminescence of ZnO Nanoparticles Based on Non-Equilibrium Processes: Defect Origins and Emission Controls

ADVANCED FUNCTIONAL MATERIALS, Issue 4 2010
Haibo Zeng
Abstract High concentrations of defects are introduced into nanoscale ZnO through non-equilibrium processes and resultant blue emissions are comprehensively analyzed, focusing on defect origins and broad controls. Some ZnO nanoparticles exhibit very strong blue emissions, the intensity of which first increase and then decrease with annealing. These visible emissions exhibit strong and interesting excitation dependences: 1) the optimal excitation energy for blue emissions is near the bandgap energy, but the effective excitation can obviously be lower, even 420,nm (2.95,eV,<,Eg,=,3.26,eV); in contrast, green emissions can be excited only by energies larger than the bandgap energy; and, 2) there are several fixed emitting wavelengths at 415, 440, 455 and 488,nm in the blue wave band, which exhibit considerable stability in different excitation and annealing conditions. Mechanisms for blue emissions from ZnO are proposed with interstitial-zinc-related defect levels as initial states. EPR spectra reveal the predominance of interstitial zinc in as-prepared samples, and the evolutions of coexisting interstitial zinc and oxygen vacancies with annealing. Furthermore, good controllability of visible emissions is achieved, including the co-emission of blue and green emissions and peak adjustment from blue to yellow. [source]

Upconverting Nanoparticles: The Active-Core/Active-Shell Approach: A Strategy to Enhance the Upconversion Luminescence in Lanthanide-Doped Nanoparticles (Adv. Funct.

ADVANCED FUNCTIONAL MATERIALS, Issue 18 2009
Mater.
Lanthanide-doped nanoparticles capable of (up)converting near-infrared (NIR) light to higher energies via an anti-Stokes process known as upconversion have demonstrated extraordinary potential in biological applications on the virtue that background fluorescence is near-zero. To maximize the intensity of the upconverted luminescence in lanthanide-doped nanoparticles, Vetrone et al. utilize a core/active-shell architecture where the active-shell readily absorbs NIR light and transfers it to the active luminescent core, thereby increasing the upconversion emission, as described on page 2924. [source]

The Active-Core/Active-Shell Approach: A Strategy to Enhance the Upconversion Luminescence in Lanthanide-Doped Nanoparticles

ADVANCED FUNCTIONAL MATERIALS, Issue 18 2009
Fiorenzo Vetrone
Abstract Nanoparticles of NaGdF4 doped with trivalent erbium (Er3+) and ytterbium (Yb3+) are prepared by a modified thermal decomposition synthesis from trifluoroacetate precursors in 1-octadecene and oleic acid. The nanoparticles emit visible upconverted luminescence on excitation with near-infrared light. To minimize quenching of this luminescence by surface defects and surface-associated ligands, the nanoparticles are coated with a shell of NaGdF4. The intensity of the upconversion luminescence is compared for nanoparticles that were coated with an undoped shell (inert shell) and similar particles coated with a Yb3+ -doped shell (active shell). Luminescence is also measured for nanoparticles lacking the shell (core only), and doped with Yb3+ at levels corresponding to the doped and undoped core/shell materials respectively. Upconversion luminescence was more intense for the core/shell materials than for the uncoated nanoparticles, and is greatest for the materials having the "active" doped shell. Increasing the Yb3+ concentration in the "core-only" nanoparticles decreases the upconversion luminescence intensity. The processes responsible for the upconversion are presented and the potential advantages of "active-core"/"active-shell" nanoparticles are discussed. [source]

Comparison of sedimentation and occupation histories inside and outside rock shelters, Keep-River region, northwestern Australia

GEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 1 2006
I.A.K. Ward
This paper compares archaeological evidence of Aboriginal occupation inside rock shelters and outside in adjacent sand sheets, focusing on two locations in the Keep-River region, northwestern Australia. Luminescence and radiocarbon dating reveal that occupation sequences inside rock shelters are generally younger ( < 10,000 yr B.P.) than outside ( < 18,000 yr B.P.). Differences in occupation chronology and artifact assemblages inside and outside rock shelters result from depositional and postdepositional processes and shifts in site function. An increase in regional sedimentation rate from 10 cm/ka , 1 in the Pleistocene to 20 cm/ka , 1 in the Holocene may account for late buildup of sediments within rock shelters, increased artifact accumulation, and reduced postdepositional disturbance in some settings. More intense use of rock shelters in the Late Holocene is indicated from a change in hunting technology and greater production of rock art. The results indicate that some cultural interpretations might be flawed unless archaeological evidence from rock-shelter and open-site excavations is integrated. © 2006 Wiley Periodicals, Inc. [source]

Ligand-Driven Wavelength-Tunable and Ultra-Broadband Infrared Luminescence in Single-Ion-Doped Transparent Hybrid Materials

ADVANCED FUNCTIONAL MATERIALS, Issue 13 2009
Shifeng Zhou
Abstract Here, tuning of the optical properties of emission centers by tailoring the ligand fields is investigated. Experimentally, it is demonstrated that Ni2+ can act as a single emission species in multiple octahedral local environments. Nanocrystal-embedded hybrid materials are employed as hosts in order to take advantage of their convenience in local environment design for practical applications. Novel composite gain materials with high transparence are successfully made, and show interesting wavelength-tunable and ultra-broadband infrared luminescence covering the whole near-infrared region from 1,100 to 1,800,nm. The infrared luminescence peak positions can be finely tuned from 1,300 to 1,450 and to 1,570,nm, with the largest full width at half maximum being about 400,nm and covering the telecommunication bands at 1,200,1,500,nm. According to the results of characterization, the unusual luminescence, interestingly, originates from Ni2+ in nanocrystals and the doping efficiency of Ni2+ is surprisingly high. The results demonstrate that the method presented may be an effective way to fabricate multifunctional light sources with various fundamental multifunctional applications from efficient broadband optical amplifiers to bio-imaging. [source]

Luminescence of Nanocrystalline Erbium-Doped Yttria

ADVANCED FUNCTIONAL MATERIALS, Issue 5 2009
Yuanbing Mao
Abstract In this paper, the luminescence, including photoluminescence, upconversion and cathodoluminescence, from single-crystalline erbium-doped yttria nanoparticles with an average diameter of 80,nm, synthesized by a molten salt method, is reported. Outstanding luminescent properties, including sharp and well-resolved photoluminescent lines in the infrared region, outstanding green and red upconversion emissions, and excellent cathodoluminescence, are observed from the nanocrystalline erbium-doped yttria. Moreover, annealing by the high power laser results in a relatively large increase in photoluminescent emission intensity without causing spectral line shift. These desirable properties make these nanocrystals promising for applications in display, bioanalysis and telecommunications. [source]

Efficient Luminescence from Rare-Earth Fluoride Nanoparticles with Optically Functional Shells,

ADVANCED FUNCTIONAL MATERIALS, Issue 7 2006
M. Lezhnina
Abstract Rare-earth fluorides are a class of materials with considerable potential in optical applications. Fluoride lattices typically permit high coordination numbers for the hosted rare-earth ions, and the high ionicity of the rare-earth-to-fluorine bond leads to a wide bandgap and very low vibrational energies. These factors make rare-earth fluorides very useful in optical applications employing vacuum ultraviolet and near-infrared excitation. The preparation of nanometer-sized particles has opened the door for new properties and devices if the performance of their macroscopic counterparts can be conserved in the nanometer regime. However, at small particle sizes, defect surface states and adhering water reduce the optical efficiency. These shortcomings can be reduced by applying protective shells around the luminescent cores, which can also be involved in the luminescent process. [source]

Sensitized Lanthanide-Ion Luminescence with Aryl-Substituted N -(2-Nitrophenyl)acetamide-Derived Chromophores

HELVETICA CHIMICA ACTA, Issue 11 2009
Michael Andrews
Abstract The syntheses of the two tetraazamacrocyclic ligands L1 and L2 bearing a [(methoxy-2-nitrophenyl)amino]carbonyl chromophore, i.e., an N -(methoxy-2-nitrophenyl)acetamide moiety, together with their corresponding lanthanide-ion complexes are described. A combined spectroscopic (UV/VIS, 1H-NMR), structural (X-ray), and theoretical (DFT) investigation revealed that the absorption properties of the chromophores were dictated by the extent of electronic delocalisation, which in turn was determined by the position of the MeO substituent at the aromatic ring. X-Ray crystallographic studies showed that when attached to the macrocycle, both isomeric forms of the N -(methoxy-2-nitrophenyl)acetamide unit can participate in coordination, via the CO, to an encapsulated potassium cation. Luminescence measurements confirmed that such a binding mode also exists in solution for the corresponding lanthanide complexes (q ca. ,1), with the para -MeO derivative allowing longer wavelength sensitization (,ex 330,nm). [source]

Water Stability and Luminescence of Lanthanide Complexes of Tripodal Ligands Derived from 1,4,7-Triazacyclononane: Pyridinecarboxamide versus Pyridinecarboxylate Donors

HELVETICA CHIMICA ACTA, Issue 11 2009
Grégory Nocton
Abstract A series of europium(III) and terbium(III) complexes of three 1,4,7-triazacyclononane-based pyridine containing ligands were synthesized. The three ligands differ from each other in the substitution of the pyridine pendant arm, namely they have a carboxylic acid, an ethylamide, or an ethyl ester substituent, i.e., these ligands are 6,6,,6,-[1,4,7-triazacyclononane-1,4,7-triyltris(methylene)]tris[pyridine-2-carboxylic acid] (H3tpatcn), -tris[pyridine-2-carboxamide] (tpatcnam), and -tris[pyridine-2-carboxylic acid] triethyl ester (tpatcnes) respectively. The quantum yields of both the europium(III) and terbium(III) emission, upon ligand excitation, were highly dependent upon ligand substitution, with a ca. 50-fold decrease for the carboxamide derivative in comparison to the picolinic acid (=pyridine-2-carboxylic acid) based ligand. Detailed analysis of the radiative rate constants and the energy of the triplet states for the three ligand systems revealed a less efficient energy transfer for the carboxamide-based systems. The stability of the three ligand systems in H2O was investigated. Although hydrolysis of the ethyl ester occurred in H2O for the [Ln(tpatcnes)](OTf)3 complexes, the tripositive [Ln(tpatcnam)](OTf)3 complexes and the neutral [Ln(tpatcn)] complexes showed high stability in H2O which makes them suitable for application in biological media. The [Tb(tpatcn)] complex formed easily in H2O and was thermodynamically stable at physiological pH (pTb 14.9), whereas the [Ln(tpatcnam)](OTf)3 complexes showed a very high kinetic stability in H2O, and once prepared in organic solvents, remained undissociated in H2O. [source]

Effects of Zinc(II) on the Luminescence of Europium(III) in Complexes Containing , -Diketone and Schiff Bases

HELVETICA CHIMICA ACTA, Issue 11 2009
Yuko Hasegawa
Abstract The UV, excitation, and luminescence spectra of tris(pivaloyltrifluoroacetonato)europium(III) ([Eu(pta)3]; Hpta=1,1,1-trifluoro-5,5-dimethylhexane-2,4-dione=HA) were measured in the presence of bis(salicylidene)trimethylenediamine (H2saltn), bis[5-(tert- butyl)salicylidene]trimethylenediamine (H2(tBu)saltn), or bis(salicylidene)cyclohexane-1,2-diyldiamine (H2salchn), and the corresponding ZnII complexes [ZnB] (B=Schiff base). The excitation and luminescence spectra of the solution containing [Eu(pta)3] and [Zn(salchn)] exhibited much stronger intensities than those of solutions containing the other [ZnB] complexes. The introduction of a tBu group into the Schiff base was not effective in sensitizing the luminescence of [Eu(pta)3]. The luminescence spectrum of [ZnB] showed a band around 450,nm. The intensity decreased in the presence of [Eu(pta)3], reflecting complexation between [Eu(pta)3] and [ZnB]. On the basis of the change in intensity against the concentration of [ZnB], stability constants were determined for [Eu(pta)3Zn(saltn)], [Eu(pta)3Zn{(tBu)saltn}], and [Eu(pta)3Zn(salchn)] as 4.13, 4.9 and 5.56, respectively (log,, where =[[Eu(pta)3ZnB]]([[Eu(pta)3]][[ZnB]]),1). The quantum yields of these binuclear complexes were determined as 0.15, 0.11, and 0.035, although [Eu(pta)3Zn(salchn)] revealed the strongest luminescence at 613,nm. The results of X-ray diffraction analysis for [Eu(pta)3Zn(saltn)] showed that ZnII had a coordination number of five and was bridged with EuIII by three donor O-atoms, i.e., two from the salicylidene moieties and one from the ketonato group pta. [source]

A Strategy to Achieve Efficient Dual-Mode Luminescence of Eu3+ in Lanthanides Doped Multifunctional NaGdF4 Nanocrystals

ADVANCED MATERIALS, Issue 30 2010
Yongsheng Liu
A strategy is proposed to fabricate dual-mode luminescent NaGdF4 nanocrystals that are composed of NaGdF4:Yb3+,Tm3+ core and NaGdF4:Eu3+ shell. Intense downconversion via the sensitization of Gd3+ and upconversion luminescence of Eu3+ that is one order of magnitude higher than the triply-doped core only counterparts have been achieved by employing the distinct core/shell nanostructures and double sensitizations of Yb3+ and Tm3+. [source]

Bioimaging with Two-Photon-Induced Luminescence from Triangular Nanoplates and Nanoparticle Aggregates of Gold

ADVANCED MATERIALS, Issue 22 2009
Yuqiang Jiang
Cell imaging with two-photon-induced photoluminescence is demonstrated using gold nanoparticles (either triangular nanoplates or nanosphere aggregates) as imaging agents. On being conjugated to yeast cells, gold nanoplates exhibit visible two-photon excited luminescence that can be detected by two-photon laser scanning microscopy. The cells can be either dried (in the air) or alive (in water). [source]

Nanodiamond Photoemitters Based on Strong Narrow-Band Luminescence from Silicon-Vacancy Defects

ADVANCED MATERIALS, Issue 7 2009
Igor I. Vlasov
The formation and thermodynamic stability of silicon-vacancy (Si-V) color centers, intensively emitting at a wavelength of 738,nm, are demonstrated for the first time in nanodiamonds less than 10,nm in size. These findings open prospects for the production of stable and efficient optical nanoemitters (single-photon emitters) based on nanodiamond. [source]

Enhanced Solid-State Luminescence and Low-Threshold Lasing from Starburst Macromolecular Materials,

ADVANCED MATERIALS, Issue 3 2009
Wen-Yong Lai
High solid-state quantum efficiency (,PL,,,0.90) materials with attractive properties for OLED and laser applications are reported. Our results show that long fluorene chain-lengths are not a necessary prerequisite for efficient solid-state luminescence. Isolated-molecule-like solid-state emission, stable pure-deep-blue electroluminescence, and low-threshold lasing (,laser,=,437,nm, Ethlaser,,,0.4,nJ/pulse, 1.3,µJ cm,2) are demonstrated. [source]

White Luminescence from Sol,Gel-Derived SiOC Thin Films

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2009
Aylin Karakuscu
A new approach to obtain visible luminescence from sol,gel-derived SiOC films is proposed. In order to investigate the influence of Si and C content, Si- and C-rich SiOC films were prepared as well as stoichiometric SiOC films. High intense white luminescence is obtained where the emission color can be controlled by the experimental parameters such as the starting sol,gel-composition and the pyrolysis temperature. In stoichiometric SiOC films, low pyrolysis temperature yields UV-blue luminescence, whereas high temperatures favor green-yellow luminescence. On the contrary, in Si-rich SiOC films, intense white luminescence is obtained with a broad emission from 430 to 900 nm and an external quantum efficiency (EQE) of 11.5%. Relatively, stoichiometric SiOC films showed an EQE of 5%. Finally, C-rich SiOC films did not show noticeable luminescence due to absorption by carbon clusters. [source]

Upconversion Luminescence in ,-AlON:Yb3+,Tm3+ Ceramic Phosphors

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2009
Fang Zhang
Upconversion emission properties of ,-AlON:Yb3+,Tm3+ phosphors were investigated under single-wavelength diode laser excitation of 980 nm. Blue (479 nm) and red (653 nm) emission bands were observed which correspond to the transitions of 1G4,3H6 and 1G4,3F4 of Tm3+ ions, respectively. The upconversion spectra show a concentration-dependent luminescence intensity, reaching its peak at a concentration of 1.2 mol% Yb and 0.5 mol% Tm. Pump power dependence of the upconversion emission intensity (P,I) revealed that a two-photon process was involved in the blue and red emissions. [source]

Expression of ,re,y luciferase gene in Erwinia amylovora

LUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 4 2003
Giovanna Gentilomi
Abstract In this study we describe an ef,cient stable genetic transformation of the phytopathogenic bacterium Erwinia amylovora using a recombinant expression vector encoding the ,re,y luciferase gene of Photinus pyralis, which is further controlled by IPTG-inducible promoter. Stably transformed E. amylovora cells maintain the same infectivity as the wild-type strain and, after induction with IPTG, produce luciferase. Luminescence produced by the action of luciferase on an exogenous substrate was easily detectable by a simple and rapid bioluminescent assay (BL). The transformed E. amylovora strain maintains the same high emission level, even after passage in pears, until about 15 days post-infection. Our ,ndings therefore show that the luciferase assay can be conveniently used to follow the bacterial movement in plant tissue and its dissemination in controlled environments. [source]

Spectral properties and thermoluminescence of codoped PbWO4:(Mo,Y) and PbWO4:(F,Y) crystals

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2009
Jian-jun Xie
Abstract Lead tungstate, PbWO4 single crystals codoped with Mo6+/F, and Y3+ ions were grown using the modified Bridgman method. Optical transmission, X-ray excited luminescence, photoluminescence, ultrashort pulsed X-ray excited fluorescent lifetime and thermoluminescence have been investigated. Compared to pure PbWO4, the codoped PbWO4:(Mo,Y) and PbWO4:(F,Y) crystals exhibit improved transmittance in the short-wavelength region. Luminescence and light-yield measurements demonstrated that Mo6+/F, and Y3+ codoping could enhance the luminescence of PbWO4 and reduce slow decay components. Doped Mo6+ and F, ions in PbWO4 were tentatively considered to occupy W and O sites, while Y3+ ions codoped in PbWO4:Mo/F mostly occupy Pb sublattice sites. The second excitation peak at 335 nm, which is the second effective excitation for the enhanced blue-green emission in as-grown PbWO4:(Mo,Y) and PbWO4:(F,Y) crystals, should be related to MoO42, groups and O vacancies (VO). Thermoluminescence glow curve measurement between RT and 400 °C provides complementary information about trapping states and the effect of Y3+ ion codoping resulting in the reduction of stable and temporary hole centers. Further work is needed to explain the doping and energy-transfer mechanism. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Enhanced luminescence and two-photon absorption of silver nano-clusters

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S1 2009
A. V. Aiboushev
Abstract Luminescence of silver nanoparticles photo-deposited on titan dioxide nanoparticles of mesoporous film is studied. Luminescence was registered under the two-photon excitation by femto-second laser pulses of Ti:sapphire laser. It was observed that Ag/ TiO2 mesoporous films have high concentration of bright luminescence spots which reveal stability to degradation under long illumination. Various configurations of silver nanoparticles are analyzed to explain the physics of bright luminescence spots ("hot spots"). Luminescence intensity reveals "hot spots" dependence on the polarization of excitation laser pulse. Properties of Ag/TiO2 system can be useful for single molecule spectroscopy and visualization of biological objects. Aapplication of Ag/ TiO2 mesoporous films for Raman scattering spectroscopy de-menstruated for the case of Rhodamine B. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Luminescence and energy structure of ultrathin InAs/AlAs quantum wells

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2008
T. S. Shamirzaev
Abstract The energy spectrum of thin InAs/AlAs quantum wells (QWs) has been studied by photoluminescence (PL). It has been found that the PL spectra of the QWs consist of intense lines related to a no-phonon excitonic transition accompanied with its phonon replicas. The band alignment in the QWs with the lowest conduction band states belonging to the indirect minimum is shown to be of type I. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Luminescence and vibrational properties of erbium-implanted nanoporous GaN

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008
C. B. Soh
Abstract Implantation of erbium (Er) into GaN is useful in creating selected areas to emit at the green, yellow and infrared wavelengths. Enhanced erbium activation is obtained when erbium is implanted into porous GaN formed by electrochemical etching than into as-grown GaN. This is due to the increase in surface areas for light extraction and the availability of more free surfaces to accommodate strain when it is annealed. Furnace annealing at 1100 °C for 30 mins in nitrogen gives rise to higher band-edge photoluminescence intensity. Apart from the host GaN phonon modes, we have also observed disorder-induced lattice vibrations at 170, 200 and 350-365 cm,1 from Er-implanted porous GaN. The E2 (high) mode of GaN also shifts towards higher energy at higher annealing temperatures, indicative of more erbium occupying the VGa site (ionic radii of Er > Ga) and hence increasing the compressive stress in the GaN crystal lattice. The prominent defect-induced local vibrational modes in Er-doped nanoporous GaN are also observed in ultraviolet resonant Raman scattering. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Luminescence of Ce-doped borate-oxyfluoride glass ceramics

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3 2007
L. Dimitrocenko
Abstract In the present work we studied the possibility to obtain oxyfluoride glass ceramics based on a lithium and potassium borate glasses with addition of fluorides. Lithium-borate glasses without lanthanum fluoride are transparent up to 275 nm. In samples with LaF3 doped with Ce-activator, an additional absorption at about 300 nm and intense photoluminescence could be observed. Ce-doped potassium-borate glass with addition of fluorides LaF3, LiF and GdF3 was milky and not transparent, an intense photoluminescence has been observed, X-ray diffraction measurements showed a presence of well-pronounced crystalline phases of LiF as well as of GdBO3. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

The role of breathers in the anomalous decay of luminescence

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2006
Eva Mihóková
Abstract Luminescence of alkali halides doped by heavy ns2 ions exhibits an anomaly in the slow component emission decay. The anomaly is explained by the formation of a discrete breather in the immediate neighborhood of the impurity. We study properties of these breathers, their phase space structure, robustness, and propensity for formation. Under a wide range of parameters and interionic potentials they form 2-dimensional Kolmogorov-Arnold-Moser tori (less than generic) in phase space. We show strobed views of these tori, useful in quantization. All features support the thesis of breather formation as the explanation for the luminescence decay anomaly that first motivated our breather proposal. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Luminescence of anthracene molecules in single crystal matrices

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2006
T. Aoki-Matsumoto
Abstract Optical properties of single fluorene/phenanthrene crystals doped with various mole fraction of anthracene, 10,5 to a few %, were investigated at 10 K. In low concentration samples, sharp structures attributed to isolated anthracene molecules were observed. Inhomogeneous width in their 0-0 energy were found to be ,20 cm,1. When concentration is higher, spectral species, which are distinctly different from the isolated molecule spectrum, were observed and their origins are discussed. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Integration of CdSe quantum dots with GaN optoelectronic materials

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2005
J. G. Pagan
Abstract Material structures on the nanoscale can enable enhancement of optoelectronic device performance. For example, in the InGaN active layers of MOCVD grown blue light emitting diodes, indium segregation plays a critical role in the interplay between blue luminescent channels and non-radiative recombination centers such as crystal defects. Unfortunately, high efficiency luminescence of InGaN does not extend into the "deep green" spectral region, around the wavelength of peak human eye response. We are investigating whether commercially available luminescent nanostructures such as CdSe quantum dots can be incorporated into III-nitride devices to extend their high-efficiency performance into the "deep green". Surfactant stabilized CdSe particles in liquid dispersions are drop-cast onto HVPE grown GaN. Physical properties of resultant CdSe surface structures are examined. Luminescence is reported before and after subsequent growth of GaN. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]