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We consider the influence of a resonant control field on weak localization of light in ultracold atomic ensembles. Both steady-state and pulsed light excitation are considered. We show that the presence of a control field essentially changes the type of interference effects which occur under conditions of multiple scattering. For example, for some scattering polarization channels the presence of a control field can cause destructive interference through which the enhancement factor, normally considered to be greater than one, becomes less than one., Comment: Submitted to Journal of Modern Optics, Special Issue: Proceedings of PQE 2011

Investigation of some light-matter interactions in Multi-Interface Novel Devices (MIND) containing a nanoscale Si-layered system have led to a method for predicting free-carrier density dependent nonlinear optical properties as a function of doping, light excitation intensity and carrier injection. The approach is based on the well-known t-matrix approximation. A simplified a few-layer optical model has been constructed that will reproduce the main features/parameters of real systems. The degree of model and simulation self-consistency is discussed using basic physical functions and published experimental data. Near perfect agreement between the simulated model and the corresponding experimental results has been obtained. In this way, the simulation allowed us to determine the main origins/components of the strong optical nonlinearity characteristic of one of the most specific MIND behaviours.

In this work we report on the development of a fluorescence molecular imager based on patterned light excitation operating in the time-domain.

Supramolecular triads were prepared by self-assembly of 4'-pyridyl-2-tetrathiafulvalene axially bound on ZnP-spacer-AuP(+) dyads; the lifetime of the charge separated state ((+)TTF-ZnP-Spacer-AuP ) formed upon light excitation of the triad is greatly increased with respect to that found in the parent dyad.

By the use of dual-wavelength light excitation and bidirectional motor scanning, optical-resolution photoacoustic microscopy images oxygen saturation and blood flow of the mouse ear simultaneously.

9 páginas, 8 figuras.-- El pdf del artículo es el manuscrito de autor., The dynamics of mitochondrial [Ca2+] ([Ca2+]M) plays a key role in a variety of cellular processes. The most important methods available to monitor [Ca2+]M are fluorescent dyes such as rhod-2 and specifically targeted proteins such as aequorin and pericam. However, significant discrepancies, both quantitative and qualitative, exist in the literature between the results obtained with different methods. We have made here a systematic comparison of the response of several fluorescent dyes, rhod-2 and rhod-FF, and two Ca2+-sensitive proteins, aequorin and pericam. Our results show that measurements obtained with aequorin and pericam are consistent in terms of dynamic Ca2+ changes. Instead, fluorescent dyes failed to follow Ca2+ changes adequately, especially during repetitive stimulation. In particular, measures obtained with rhod-2 or rhod-FF evidenced the previously reported Ca2+-dependent inhibition of mitochondrial Ca2+ uptake, but data obtained with aequorin or pericam under the same conditions did not. The reason for the loss of response of fluorescent dyes is unclear. Loading with these dyes produced changes in mitochondrial morphology and membrane potential, which were small and reversible at low concentrations (1–2 μM), but produced large and prolonged damage at higher concentrations. In addition, cells loaded with low concentrations of rhod-2 suffered large changes in mitochondrial morphology after light excitation. Our results suggest that [Ca2+]M data obtained with these dyes should be taken with care., This work was supported by grants from Ministerio de Educación y Ciencia (BFU2008-01871) and from Junta de Castilla y León (VA103A08 and GR105). Sergio de la Fuente holds an FPI (Formación de Personal Investigador) fellowship from the Spanish Ministerio de Ciencia e Innovacion.

A set of conodont samples was analysed optically and chemically with reference to their degree of maturation within CAI ranging from 1 to 4. With increasing maturation there is a slight increase in Ca and P and decrease in Na, Fe and Sr. Other elements show no significant trend as maturation progresses. Under blue-light and u.v. light excitation conodonts exhibit flourescence. In blue light the fluorescent colour progressively shifts from yellow (CAI 1) to yellow-organe (CAI 2) and brown (CAI 3), but there is no substantial shift in the wavelength of peak fluorescent intensity accompanying progressive increase in CAI (maturation). However, there is a distinct difference in relative fluorescence intensity within the CAI range 1–4. A scale of relative fluorescence intensity has been established and correlated to CAI. The relative fluorescence provides a precise method of determining relative level of maturation, particularly at the level corresponding to the oil window.

Thermally stimulated current (TSC) measurements have been performed on samples cut from a PbI2 single crystal. After light excitation, several peaks have been observed in the range 77–320 K. It is demonstrated that excitation by means of a pulsed electron beam can be used to selectively fill either electron or hole traps. The results on PbI2 confirm that most of the observed traps can be identified as hole traps.

We use molecular dynamics simulations to examine the possibility of rolling nanorods on the surfaces of polar liquids. Asymmetric charging of nanorod surfaces, generated by light excitation of its photoactive hydrophobic surfactants, can induce asymmetric Coulombic coupling to the polar liquid surfaces. We demonstrate that under this driving nanorods with diameters of 3-10 nm can roll on water with translational velocities of 1-5 nm/ns. The efficiency of this motion is controlled by the chemistry and dynamical phenomena at the nanorod-water interface.

The understanding of interactions between nanomaterials and biological entities is fundamental to develop nanoproducts in oncology. NBTXR3 (hafnium oxide inert nanoparticle) and protoporphyrin IX (Pp IX) nanocarrier (silica nanoparticle encapsulating Pp IX, the monomer of Photofrin®) are nanoproducts, issued from Nanobiotix platforms, aim to enlarge the therapeutic window of oncology treatment, using external energy sources to carry out "on" / "off" activation. In the first part of this work, we have studied interaction between NBTXR3 and human colon cancer cells. NBTXR3 penetrates by endocytosis and presents long residence within endo-lysosomal compartment. Significantly enhance of tumour cell radiation response is demonstrated after NBTXR3 activation with ionizing radiation. Compared to controls, irradiated cells having internalized NBTXR3, offer a particular morphology which is described. In the second part, we present the synthesis of a new hybrid nanoproduct for photodynamic therapy (PDT), the Pp IX nanocarrier, and the study of its interaction in vitro on six human cancer cell lines and in vivo on nude mice model xenografted with three different cancer types. In vitro, Pp IX nanocarrier activated at 630 nm is more efficient than free Pp IX. Further, this new hybrid nanoproduct enhances biodistribution of Pp IX, with different kinetic of tumour accumulation between models. Ultimately, based on these new understanding of interactions between nanoparticles and cancer cells, both NBTXR3 nanoparticle and Pp IX nanocarrier, offer a breakthrough approach to create efficient pathways to cancer therapy., La compréhension des interactions entre les nanomatériaux et les entités biologiques est fondamentale pour développer des nanoproduits en oncologie. NBTXR3 (nanoparticule inerte d'oxyde d'hafnium) et protoporphyrine IX (Pp IX) nanotransporteur (nanoparticule de silice encapsulant le Pp IX, le monomère du Photofrin®) sont des nanoproduits, issus des plateformes Nanobiotix, développés pour élargir la fenêtre thérapeutique des traitements du cancer en utilisant des sources d'activation externe de type " on " / " off ". La première partie de ce travail présente l'étude de l'interaction de NBTXR3 avec des cellules tumorales coliques humaines. NBTXR3 pénètre par endocytose et persiste dans le compartiment endolysosomial. Une augmentation significative de la réponse cellulaire à la radiothérapie est démontrée après activation de NBTXR3 par des radiations ionisantes. L'irradiation des cellules traitées par NBTXR3 entraîne des modifications spécifiques de leur morphologie par rapport aux contrôles; elles sont décrites ici. Une deuxième partie présente la synthèse d'un nouvel hybride pour la thérapie photodynamique, le Pp IX nanotransporteur, et étudie son interaction in vitro avec six lignées de cellules tumorales humaines et in vivo dans un modèle de souris nude xénogreffée avec trois types tumoraux. In vitro, le Pp IX nanotransporteur activé à 630 nm est plus efficace que le Pp IX libre. De plus, ce nouvel hybride favorise la biodistribution du Pp IX, avec une cinétique d'accumulation tumorale différente entre les modèles. La compréhension des interactions entre nanoparticules et cellules cancéreuses, apportée par ce travail, contribue à la création de nanothérapies innovantes.

Direct 355 or 532 nm light excitation of TBAI(3), where TBA is tetrabutyl ammonium, in CH(3)CN at room temperature yields an iodine atom, I(*), and an iodine radical anion, I(2)(-*). In the presence of excess iodide, the iodine atom reacts quantitatively to yield a second equivalent of I(2)(-*) with a rate constant of k = 2.5 +/- 0.4 x 10(10) M(-1) s(-1). The I(2)(-*) intermediates are unstable with respect to disproportionation and yield initial reactants, k = 3.3 +/- 0.1 x 10(9) M(-1) s(-1). The coordination compound Ru(bpz)(2)(deeb)(PF(6))(2), where bpz is 2,2'-bipyrazine and deeb is 4,4'-(C(2)H(5)CO(2))(2)-2,2'-bipyridine, was prepared and characterized for mechanistic studies of iodide photo-oxidation in acetonitrile at room temperature. Ru(bpz)(2)(deeb)(2+) displayed a broad metal-to-ligand charge transfer (MLCT) absorption band at 450 nm with epsilon = 1.7 x 10(4) M(-1) cm(-1). Visible light excitation resulted in photoluminescence with a corrected maximum at 620 nm, a quantum yield phi = 0.14, and an excited state lifetime tau = 1.75 micros from which k(r) = 8.36 x 10(4) s(-1) and k(nr) = 5.01 x 10(5) s(-1) were abstracted. Arrhenius analysis of the temperature dependent excited state lifetime revealed an activation energy of approximately 2500 cm(-1) and a pre-exponential factor of 10(10) s(-1), assigned to activated surface crossing to a ligand field or MLCT excited state. Steady state light excitation of Ru(bpz)(2)(deeb)(2+) in a 20 mM TBAI acetonitrile solution resulted in ligand loss photochemistry with a quantum yield of 5 x 10(-5). The MLCT excited state was dynamically quenched by iodide with K(sv) = 1.1 x 10(5) M(-1) and k(q) = 6.6 +/- 0.3 x 10(10) M(-1) s(-1), a value consistent with diffusion-limited electron transfer. Excited state hole transfer to iodide was quantitative but the product yield was low due to poor cage escape yields, phi(CE) = 0.042 +/- 0.001. Nanosecond transient absorption was used to quantify the appearance of two photoproducts [Ru(bpz(-))(bpz)(deeb)](+) and I(2)(-*). The coincidence of the rate constants for [Ru(bpz(-))(bpz)(deeb)](+) formation and for excited state decay indicated reductive quenching by iodide. The rate constant for the appearance of I(2)(-*) was about a factor of 3 slower than excited state decay, k = 2.4 +/- 0.2 x 10(10) M(-1) s(-1), indicating that I(2)(-*) was not a primary photoproduct of excited state electron transfer. A mechanism was proposed where an iodine atom was the primary photoproduct that subsequently reacted with iodide, I(*) + I(-) --I(2)(-*). Charge recombination Ru(bpz(-))(bpz)(deeb)(+) + I(2)(-*) --Ru(bpz)(2)(deeb)(2+) + 2I(-) was highly favored, DeltaG(o) = -1.64 eV, and well described by a second-order equal concentration kinetic model, k(cr) = 2.1 +/- 0.3 x 10(10) M(-1) s(-1).

Two calix[4]arenes with four 2-pyridyhnethyl-l-oxide pendant groups at the lower rim have been synthesized, and their Tb(III) and Eu(III) complexes are fluorescent upon UV light excitation at 312 nm. The complexes are not stable in aqueous solution, completely losing their luminescent properties.

Point contact current measurements with high spatial resolution were performed on undoped high-resistivity (up to semi-insulating) LEC GaAs samples under IR light excitation. Mesoscopic electrical non-uniformities, existing in the samples and strongly related to the cellular structure of dislocations, show different reactions to the light excitation depending on the dark carrier concentration of the samples. Especially, in samples with a Hall mobility strongly reduced by such non-uniformities the amplitude of the fluctuations of the point contact current, respectively of the resistivity between cell walls and cell centres, is clearly reduced by light excitation. This homogenization is connected with an enhancement of the photo Hall mobility in these samples compared to the dark Hall mobility.

Photoacoustic spectroscopy is a new analytical technique which allows the detection of light-induced heat production due to non-radiative deactivation of light excitation. This paper gives an overview of the theory of photoacoustics and its application in photosynthesis research to measure energy conversion and storage, and for molecular structure and interaction studies as well as oxygen evolution in photosynthetic systems.

Molecular machines—(supra)molecular systems in which large-amplitude motions of some components can be controlled by appropriate stimuli can be operated by means of chemical, electrochemical, or photochemical processes. However, the use of light stimulation has several advantages. For example, photons can be used to supply energy to the system and to gather information about its state without physically touching it. Light excitation can be carried out by a variety of sources (including the sun), with the possibility of a fine resolution in space and time.

Background: Photodynamic therapy (PDT) is based on the principle of using light excitation of a wavelength-specific endogenous or exogenous photosensitizer to destroy the target tissue, and has shown efficacy in the treatment of certain non-melanoma skin cancers. PDT using aminolevulinic acid (5-ALA) has attracted attention in the treatment of acne vulgaris. Method: Twenty patients with moderate to severe acne vulgaris on the face were treated with four sessions of topical ALA-PDT with blue light (415 nm) on the right side of the face compared with blue light alone on the left side of the face, each treatment being 1 week apart. Ten percent of topical ALA was applied to acne spots on the right side of the face with a 1-h incubation period and the entire face was treated with 48 J/cm2 of 415±5 nm light from an articulated LED planar array. Evaluation was performed by counting acne lesions at baseline, 4, 8, 12 and 16 weeks after the beginning of the treatment. Biophysical measurements included sebum levels and the erythema, and melanin indices. Result: At the given assessment times 4, 8, 12 and 16 weeks after the beginning of the treatment, the mean percent reduction in inflamed lesions counts tended to be higher in the ALA-PDT areas; it was 32%, 50.9%, 65.9% and 71.1%, respectively, compared with the blue-light-alone treatment, which was 20.7%, 27%, 57.7% and 56.7%, respectively, but without any statistical significance (P=0.092). There was no demonstrable significant change in sebum excretion, erythema or the melanin index after treatment. The side effects were pain, stinging, peeling, erythema, pruritus, oozing and pustules. These side effects were stronger on the ALA-PDT-treated side. Conclusion: From this study, the trend for ALA-PDT with blue light to be superior to blue light alone was observed, but it did not reach statistical significance. ALA-PDT had more side effects.

We compared methylene blue (MB)-mediated photobactericidal efficacies against Pseudomonas aeruginosa when using nanosecond pulsed light and CW light. In the intensity range of 10-200 mW/cm 2 , there was no significant difference between two cases, while photobactericidal efficacy with nanosecond pulsed light was significantly lower than that with CW light at an intensity of 250 mW/cm 2 . This is attributable to the saturated absorption of MB molecules due to high peak intensity of nanosecond pulsed light. On the basis of these results, we estimated the depth dependence of bacterial killing, showing that in the skin tissue region deeper than 1.5 mm, photobactericidal efficacy with nanosecond pulsed light was higher than that with CW light. This suggests that the advantage of using high-peak-intensity pulsed light for deep tissue treatment.

We report the investigation of the steady-state Hall mobility behavior upon extrinsic light excitation in n-type liquid-encapsulated Czochralski GaAs crystals. The carrier concentration of the samples measured in the dark ranged from 108 to 3×1011 cm−3. The Hall mobility demonstrated a pronounced minimum in the concentration region 109–1011 cm−3. In samples of this region a significant increase of the Hall mobility from ⩾1460 to 6300–7800 cm2 V s could be induced by light, in some cases without an increase of the measured carrier concentration. Such behavior was explained by reduction of the mesoscopic nonuniformities related to the cellular structure of dislocations by the carriers generated from defect levels in the band gap.

Novel one-component phosphors, Cd1-xDyxSiO3, which emit white color long-lasting phosphorescence upon UV light excitation, are prepared by the conventional high-temperature solid-state method and t...

The dynamics of electronic carriers after a light excitation pulse in Fe-doped LiNbO3 crystals is discussed under two alternative theoretical schemes. One considers thermally-activated diffusive transport of electrons (hopping) and uses a MonteCarlo approach. Simulations of the temporal evolution of the small polarons (Nb+4/Nb+5) and iron-impurity (Fe+2/Fe+3) centers during and after the light pulse has been obtained for different light intensities and antisite concentrations. On the other hand, the kinetics has been also described by using a standard two-center model and coherent band transport. The results of the two approaches have been compared on the light of the available experimental data.

This issue is a collection of papers presented at the 2nd International Conference on Photo-Induced Phase Transitions; Cooperative, non-linear and functional properties (PIPT'05), which was held in Rennes (France) on 24–28 May 2005 and chaired by Herve Cailleau and Tadeusz Luty. The first PIPT conference was organized by Professor Keiichiro Nasu in Tsukuba, Japan, in 2001. During 5 days, PIPT'05 provided an interdisciplinary forum for research communications between solid state physicists, photophysicists, photochemists and photobiologists, as well as material scientists. Scientists came from all around the world (Europe, Japan, USA, Canada, ...). The fascinating scientific challenge of the possibility of triggering physical properties of a material by light excitation was at the heart of the exchange of ideas between scientists of the different fields. The topics of the conference were about light-induced phenomena in functional materials, nano-particles and devices, photo-induced structural, magnetic and/or electronic phase transitions, photo-induced gauge type phase transitions, photo-induced cooperative molecular switching and chemical reactions in solids, dynamics of out-of-equilibrium processes, light-driven non-thermal processes such as coherent phonons, shock waves, surface melting and femtomagnetism, precursor phenomena, coherent, co-operative and non-linear processes in excited states and new investigations by light, x-ray and electron probes. As you will see, the collection of papers presented here cover many of the fields mentioned above. The PIPT conferences, encompassing different areas of light-induced phenomena are also meant to bridge the gap between experimentalists and theoreticians, and to promote communication between scientists working on different continents. The present conference was attended by 148 participants from 17 countries, with the total number of 87 presentations (16 invited, 27 contributed talks and 44 posters). It is encouraging to note that, in addition to the unwavering participation of the established members of the PIPT community, numerous young researchers could also participate in the conference. This has been possible thanks to the generous sponsorship from the University of Rennes 1, Rennes Metropole, Conseil General d'Ille et Vilaine, Region Bretagne, CNRS (France) and JST/ERATO (Japan) and the organizers would like to express their enormous gratitude to these organizations. The present conference benefited also from substantial logistic support from the University of Rennes 1, which is gratefully acknowledged here. The papers published in this issue were refereed and accepted papers, according to the normal rules of the Journal of Physics: Conference Series. This proceedings issue comprises 40 papers. Thanks are due to IOP Publishing Ltd, of Dirac House, Temple Back, Bristol BS1 6BE, UK for their willingness to publish these proceedings. The Guest Editors express their gratitude to all the authors and the referees, while the organizers of PIPT'05 would like to take this opportunity to thank the members of the International Advisory Committee and of the Local Organization Committee, the invited speakers, the session chairmen and all the attendees (see photo below) for their contribution to the conference. At the website http://www.gmcm.univ-rennes1.fr/pipt additional information and some photographs can be found. It is also a pleasure to announce that the next conference of the PIPT series will be held in 2007 in Japan, and will be chaired by Shin-ya Koshihara.

We propose a novel microscopic arrangement that allows highly multiplexed nanoscopic imaging. We use a laser-trapped microparticles to concentrate light in a nanoscopic volume in a close vicinity of a particle. By arranging these microparticles in a close-packed two-dimensional array, parallel multiplexing can be achieved both for light excitation and signal collection.

Amorphous Si and a-Si1-xGex (0 ≤= x ≤= 0.38) films illuminated by above bandgap light, and heated between 110 and 180°C, undergoes an ordering transition, which is reversed to the amorphous phase by either heating up above 180°C or cooling down below 110°C. This structural change is investigated by Raman spectroscopy. The changes observed in the Raman spectra reveal the formation of small ordered clusters (only a few lattice parameters in diameter). The ordered state was not observed by the only effect of either light or temperature, suggesting that specific temperature and light excitation conditions are necessary to generate and support the ordered state, that appears as a nano-crystalline structure.

Simultaneous bidirectional forward and backward electron transfers take place on a light-exited semiconductor particle, even at the same geometric site. The potentials of the electron pathways are different, giving rise to two independent molecular conversion reactions. This type of multi-electron transfer reactions is overviewed and the stepwise unidirectional multi-electron transfer on the excited semiconductor particle is also described.

This contribution reports on a novel self-assembled monolayer (SAM) on a gold surface, able to immobilize double-strand DNA and to induce its cleavage upon light excitation. DNA binding with the SAM is mainly driven by a highly favored electrostatic interaction, and it is shown that DNA immobilization takes place without impairing its intrinsic high order. SAM irradiation leads to an uncommon defluorination reaction, and it is unambiguously demonstrated that DNA breakage is strictly interrelated to this photochemical pathway. The photocleavage process is very efficient, is exclusively controlled by illumination conditions, seems to be non-base-specific, and does not require external additives. These features, together with the low excitation energy required, the prolonged thermal stability under physiological conditions, and the ease of preparation, make the SAM presented herein an appealing model system for designing nanodevices for applications where efficient, non-base-specific, and externally tunable ...

The existing and potential technological importance of nanocrystalline semiconductor thin films sensitized to visible light by molecular chromophores have initiated considerable efforts toward understanding the detailed mechanisms of photoprocesses occurring at the interface. However, such studies are made difficult by the complex nature of kinetic processes observed following light excitation. In this paper, we review literature reports of excited-state processes in these materials and attempt to clarify the underlying mechanisms responsible for the complex kinetic behavior typically observed.

New dinuclear asymmetric complexes of ruthenium and rhenium, of formula [(bpy)(CO)3 ReI(4,4′bpy)RunII/III (NH3)5]3+/4+ have been prepared and characterized by spectroscopic and electrochemical techniques. In the mixed-valent species [ReI, RuIII], the back electron transfer reaction RunII → ReII, that occurs after light excitation, is predicted to be in the Marcus inverted region. This fact is consistent with the observed quenching of the luminiscence of the Re chromophore in [(bpy)(CO)3ReI(4,4′-bpy)RuIII (NH3)5]4+, when compared to the parent complex [(bpy)(CO)3ReI(4,4′-bpy)]+. A theoretical treatment due to Creutz, Newton and Sutin has been successfully applied to predict the electronic coupling element in the mixed-valent complex. Fil: Fagalde, Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Química del Noroeste. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química del Noroeste; Argentina. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química Física; Argentina Fil: Katz, Néstor Eduardo. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Química del Noroeste. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química del Noroeste; Argentina

The proposal to use active thermography in medical diagnostics is promising in some applications concerning investigation of directly accessible parts of the human body. The combination of dynamic thermograms with thermal models of investigated structures gives attractive possibility to make internal structure reconstruction basing on different thermal properties of biological tissues. Measurements of temperature distribution synchronized with external light excitation allow registration of dynamic changes of local temperature dependent on heat exchange conditions. Preliminary results of active thermography applications in medicine are discussed. For skin and under- skin tissues an equivalent thermal model may be determined. For the assumed model its effective parameters may be reconstructed basing on the results of transient thermal processes. For known thermal diffusivity and conductivity of specific tissues the local thickness of a two or three layer structure may be calculated. Results of some medical cases as well as reference data of in vivo study on animals are presented. The method was also applied to evaluate the state of the human heart during the open chest cardio-surgical interventions. Reference studies of evoked heart infarct in pigs are referred, too. We see the proposed new in medical applications technique as a promising diagnostic tool. It is a fully non-invasive, clean, handy, fast and affordable method giving not only qualitative view of investigated surfaces but also an objective quantitative measurement result, accurate enough for many applications including fast screening of affected tissues.

In the same way as combination of atoms leads to molecules, combination of molecular components leads to supramolecular species (supermolecules).[1–3] Because of the extraordinary progress made by synthetic methods, it is now possible to say that almost any desired supramolecular species can be prepared, provided that sufficient resources are applied to the problem. Several supramolecular species are very appealing from an aesthetic viewpoint. [4] More important, by assembling in an appropriate way suitably chosen molecular components it is now possible to design and construct supramolecular species capable of performing useful functions (molecular-level devices).[2, 3, 5, 6]

In recent years several spectroscopic methods based on deep level photoionization have been developed because of the demand to investigate materials spreading over a wide range of resistivities. This paper deals with some capacitance- and current-based analyses, that are mature techniques for the characterization of semiconducting as well as semi-insulating materials with respect of deep level identification as well as spatial distribution. Results relevant to novel materials are also reported.

We report an effective method to the high quality fabrication of the AlQ 3 /SiO 2 organic-inorganic hybrid film with a blue luminescent under a UV light excitation. The high quality AlQ 3 /SiO 2 film preparation makes the hybrid material a key step forward to the applications in OLEDs.

application/pdf, Excitonic lasing from single ZnO nanobelts was observed at room temperature, which was due to the exciton-exciton scattering processes appearing under intense light excitation. Morphologies of the nanobelts are rectangular shapes, so that crystalline facets of the nanobelts acted as the lasing cavity mirrors. We demonstrated that mode spacings correspond to cavity lengths of the respective nanobelts, and directly observed the lasing from single ZnO nanobelts by mapping of the luminescence intensity.

A novel near-infrared (NIR) downconversion (DC) phosphor KSrPO4:Eu2+, Pr3+ is synthesized by the conventional high temperature solid-state reaction. The Eu2+ acts as an efficient sensitizer for Pr3+ in the KSrPO4 host. With broadband near-ultraviolet light excitation induced by the 4f→5d transition of Eu2+, the characteristic NIR emission of Pr3+, peaking at 974 nm and 1019 nm due to 3P0→1G4 and 1G4→3H4 transitions, is generated as a result of the energy transfer from Eu2+ to Pr3+. The luminescence spectra in both the visible and the NIR regions and the decay lifetime curves of Eu2+ prove the energy transfer from Eu2+ to Pr3+. This Eu2+ and Pr3+ co-doped KSrPO4 phosphor may be a promising candidate to modify the spectral mismatch behavior of crystalline solar cells and sunlight.

Two neutral cyclometalated platinum(II) complexes, Pt(DPP)(acac) and Pt(BPP)(acac) (DPP = 2,4-diphenylpyridine, BPP = 2-(4-tert-butylphenyl)-4-phenylpyridine, acac = acetylacetone), have been synthesized and characterized by (1)H NMR spectroscopy, mass spectrometry, elemental analyses and by X-ray crystallography for Pt(DPP)(acac). Electrogenerated chemiluminescence (ECL) of the two complexes in the absence or presence of coreactant tri-n-propylamine (TPrA) in different solvents (CH(3)CN, CH(2)Cl(2), DMF, CH(3)CN/H(2)O (V, 50 : 50)) has been studied. The ECL spectra are identical to their own PL spectra, indicating that ECL processes lead to the same metal-to-ligand charge-transfer ((3)MLCT) excited state that is generated by light excitation. The ECL potentials of Pt(DPP)(acac) and Pt(BPP)(acac)/TPrA in CH(3)CN and CH(3)CN/H(2)O solution were at ~0.75 V vs. SCE, and significantly negatively shifted by about 0.6 V compared to that of the Ru(bpy)(3)(2+)/TPrA system. The ECL quantum efficiencies of the complexes are comparable to that of the Ru(bpy)(3)(2+)/TPrA system. The significant increase of the ECL signal in the coreactant system is due to the formation of the strongly reducing intermediate TPrA˙. It is noteworthy that the ECL efficiencies of the synthesized compounds are much higher than that of the tridentate polypyridyl ligands.

We report a novel method to synthesize Y2O3:Eu3+ nanoscrolls by hydrothermal and post-heat treatments. In the hydrothermal process, a precursor compound with well-defined urchinlike morphology has been obtained with the aid of BO33− and L-glutamic acid. The formed micro-urchins consist of numerous nanoscrolls rolled up from nanosheets. Condition experiments and analysis reveal that BO33− anions and L-glutamic acid were vital for the rolling process of the nanoscrolls. Under ultrasound treatment, the micro-urchins can break into separated nanoscrolls. In a subsequent calcination process, the as-prepared precursors can transform into Y2O3:Eu3+ with the same morphology. The resultant Y2O3:Eu3+ micro-urchins exhibit a strong red emission corresponding to the 5D0 →7F2 transition of the Eu3+ ions under UV light excitation. Moreover, our method may provide a new way to realize the “rolling-up” process of other compounds.

β-NaYF(4) : Yb,Er upconversion nanoparticles (UCNPs) can emit bright green fluorescence under near-infrared (NIR) light excitation which is safe to the body and can penetrate deeply into tissues. The application of UCNPs in biolabeling and imaging has received great attention recently. In this work, β-NaYF(4) : Yb,Er UCNPs with an average size of 35 nm, uniformly spherical shape, and surface modified with amino groups were synthesized by a one-step green solvothermal approach through the use of room-temperature ionic liquids as the reactant, co-solvent and template. The as-prepared UCNPs were introduced into Caenorhabditis elegans (C. elegans) to achieve successful in vivo imaging. We found that longer incubation time, higher UCNP concentration and smaller UCNP size can make the in vivo fluorescence of C. elegans much brighter and more continuous along their body. The worms have no apparent selectivity on ingestion of the UCNPs capped with different capping ligands while having similar size and shape. The next generation of worms did not show fluorescence under excitation. In addition, low toxicity of the nanoparticles was demonstrated by investigating the survival rates of the worms in the presence of the UCNPs. Our work demonstrates the potential application of the UCNPs in studying the biological behavior of organisms, and lays the foundation for further development of the UCNPs in the detection and diagnosis of diseases.

A series of Ce 3+ and Mn 2+ co-doped LiCaBO 3 single composition phosphors were synthesized by a solid-state reaction method, and their luminescent properties had also been investigated. Ce 3+ and Mn 2+ co-doped LiCaBO 3 phosphors showed a blue and orange dual emission under the near-UV light excitation within the wavelength range of 325-375 nm, resulting from the 5d-4f transitions of Ce 3+ and the d-d forbidden transition of Mn 2+ , respectively. The energy transfer from Ce 3+ to Mn 2+ was investigated and demonstrated to be a resonance-type via a dipole-dipole mechanism with the critical distance of about 4.1 A. The photoluminescence intensity ratio of blue and orange emission could be tuned by adjusting the concentration of Ce 3+ and Mn 2+ . The potential applications of these dual-emitting phosphors are the alternative blue and orange-emitting light emitting diode (LED) conversion phosphors due to their strong excitation bands in the wavelength range of 325-375 nm.

A photostable dicyanomethylenedihydrofuran fluorophore which contains electron-donating alkoxy groups is described. This chromophore is highly environmentally-sensitive, which is a remarkable property for a fluorescent reporter. Its light excitation also enables, in low viscous solvents, the formation of dark states whose radical or triplet nature is ruled out.

Undoped and Eu3+-doped Sr2Mg1-xZnxSi2O7 (0≤x≤1) powder crystal samples were obtained via a conventional solid-state reaction method. The XRD result and FT-IR spectra demonstrated the complete solid-solution as well as lattice distortion between Sr2MgSi2O7 and Sr2ZnSi2O7. The UV emission spectra showed the main emission around 616nm, which implied the non-inversion symmetry around Eu3+ in Sr2Mg1-xZnxSi2O7:Eu3+ (0≤x≤1). The UV excitation spectra exhibited the Eu3+-O2- CT transitions centered at 250nm and 258nm in Sr2MgSi2O7:Eu3+ and Sr2ZnSi2O7:Eu3+, respectively. The emission of Sr2(Mg, Zn)Si2O7:Eu3+ under 147nm light excitation is very weak, which suggests that energy transfer from the host to the activator is not so efficient in Sr2Mg1-xZnxSi2O7:Eu3+ (0≤x≤1) system.

Blue-green CaSc2O4:Tb3+ phosphors have been prepared by solid-state reaction. Under 254 or 276 nm light excitation, both blue and green emissions are observed, which are attributed to the characteristic 4f-4f transitions (D-5(3,4)-F-7(J), J = 6, 5, 4, 3) of Tb3+. The cross-relaxation from D-5(3) to D-5(4) states are investigated by spectroscopic and dynamic measurements. The luminescent color of CaSc2O4:Tb3+ can be tuned from blue to green by manipulating the cross-relaxation. Moreover, efficient white light is generated for fluorescence lamps by blending the blue-green CaSc2O4:Tb3+ with a red CaSc2O4:Eu3+ phosphor. (c) 2009 The Electrochemical Society. [DOI: 10.1149/1.3060382] All rights reserved.

Photoluminescence (PL) properties of Ba 3 MgSi 2 O 8 :Eu 2+ (BMS-E) blue phosphor and Ba 3 MgSi 2 O 8 :Eu 2+ ,Mn 2+ (BMS-EM) blue-red phosphor under near-UV-light excitation were investigated. BMS-E shows efficient blue-violet emission at 437 nm under 405 nm light excitation. The sample doped with 0.05 mol/mol Eu 2+ shows PL peak intensity about twice higher than a commercial BaMgAl 10 O 17 :Eu 2+ (BAM) for low-pressure Hg lamps. The PL integrated intensity of BMS-E below 0.2 mol/mol of Eu content is similar to that of BAM in magnitude of thermal quenching. BMS-EM shows strong red emission under 405 nm light excitation because of the efficient energy transfer from Eu 2+ to Mn 2+ . The sample doped with 0.10 mol/mol Eu 2+ and 0.10 mol/mol Mn 2+ shows luminance about 12 and 3 times larger than Y 2 O 2 S:Eu 3+ and La 2 O 2 S:Eu 3+ , respectively. Moreover, the PL integrated intensity of the BMS-EM shows less thermal quenching than that of La 2 O 2 S:Eu 3+ and (Y,Gd)3(Al,Ga) 5 O 12 :Ce 3+ (YAG:Ce 3+ ). These results indicate that BMS-E and BMS-EM are promising phosphors for white light-emitting diodes (LEDs) fabricated with near-UV LEDs.

Various characteristics of frequency-integrated intensities of secondary radiation components near the resonance excitation region have been calculated for a three-level system coupled with a reservoir using a stochastic model. It has been found that the spectral and temporal characteristics of the resonant second-order optical processes can be understood consistently by considering that Raman scattering results from the average value of the induced-dipole moment with respect to the energy fluctuation due to the system-reservoir interaction, while luminescence results from its deviation from the average value. A simple method to determine parameter values that characterize the excited-state dynamics in condensed phases from the secondary radiation data is also discussed.

The new mononuclear complex [(DEAS-bpy)Re(CO) 3 (BPP)] + is prepared {DEAS-bpy = 4,4′-bis[p-(diethylamino)-α-styryl]-2,2′-bipyr idine, BPP = 1,10-bis(4-pyridyl)-3,8-dimethyl-1,3,5,7,9-decapentaene} in which electrochemical and photophysical properties clearly indicate the presence of a long-lived charge-separated excited state at room temperature upon light excitation.

It is shown by optical electroabsorption (EAB) measurements, that photostimulated long time metastability of energy spectrum in vitreous GeS 2.2 arises as result of the formation of the low energy quasi-molecular structures under intensive light excitation. These structures oscillate in time and change the energy spectrum. The dynamics of the phenomena testifies that the formation of atomic superclusters takes place. The results of measurements of dynamics of photostimulated structure formation coincide with earlier EAB measurements of photostimulated structure dissociation.

Currently, the intrinsic fiber-optic immunosensors in common use are usually based on polychromatic light excitation of the surface plasmon resonance, such as the BIACORE Probe developed by Biacore company (Sweden). We propose in this paper a novel fiber-optic immunosensor, simpler and cheaper, which is illuminated by a monochromatic light at 658 nm wavelength emitted from a commercially available laser diode. The application of detecting the rabbit IgG affinity reaction proves its feasibility. This work provides a starting step towards the development of a portable immunoprobe for non-labeling immunoassay.