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A conjugated alternating copolymer containing norbornadiene and bis(ethynylene)phenylene units was prepared by the Cassar-Heck-Sonogashira cross-coupling reaction. Its electroluminescence was tested in a device, and its fluorescence colour could be tuned by light-induced norbornadiene-quadricyclane isomerization.

Straightforward synthetic methodologies are reported for the functionalization of oligothiophenes with hydrogen-bonding motifs. Codeposition from a solution of symmetric melamine-terminated electron-donor oligomers with a complementary barbiturate-labeled electron-acceptor fullerene resulted in homogeneous films. Incorporation into photovoltaic devices gave a 2.5-fold enhancement in light energy to electrical energy conversion when compared to analogous systems with the non-hydrogen-bonding parent C(60). [reaction: see text]

This paper reports an analysis of the properties of polymer light-emitting devices (PLEDs) doped with iridium complexes. Devices based on charged and neutral complexes doped into poly(vinylcarbazole) (PVK) are presented, and the role of the ions and the charge-transport properties of the complexes are discussed. In devices with the charged complexes, the concentration of the complex is found to have a profound effect on both the switch-on voltage and the efficiency. At higher doping concentrations the efficiency is increased and the switch-on voltage decreased. The increase in efficiency and decrease in switch-on voltage at higher dopant concentration are found to be due to an alternative charge transport path via the iridium dopant [Ir(bpy)] + (bis(2-phenylpyridine-C 2 ,N')(2.2'-bipyridine)iridium hexafluorophosphate). However, at lower concentrations the complex becomes an electron trap and the efficiency is reduced. The devices are found to be significantly less efficient than those with neutral complexes. This difference is attributed to the ionic content and the charge trapping properties of the charged complexes. The low efficiency of the charged-complex-based devices could be overcome by utilizing a hole-blocking layer; devices with efficiencies as high as 23 cd A - 1 were obtained.

Research on new materials for organic electroluminescence has recently focused strongly on phosphorescent emitters, with the aim of increasing the emission efficiency and stability. Here we report the fabrication of a simple electroluminescent device, based on a semiconducting polymer combined with a phosphorescent complex, that shows fully reversible voltage-dependent switching between green and red light emission. The active material is made of a polyphenylenevinylene (PPV) derivative molecularly doped with a homogeneously dispersed dinuclear ruthenium complex, which fulfils the dual roles of triplet emitter and electron transfer mediator. At forward bias (+4 V), the excited state of the ruthenium compound is populated, and the characteristic red emission of the complex is observed. On reversing the bias (-4 V), the lowest excited singlet state of the polymer host is populated, with subsequent emission of green light. The mechanism for the formation of the excited state of the PPV derivative involves the ruthenium dinuclear complex in a stepwise electron transfer process that finally leads to efficient charge recombination reaction on the polymer.

This paper reports the synthesis and photophysical characterization of heteroleptic mono- and di-nuclear iridium(III) complexes. The complexes contain two ortho-metalating ligands, 2-phenylpyridine, with a bipyridine derivative as the third chelating unit. In the case of the dinuclear complexes the two iridium moieties are connected by a conjugated bridging ligand containing three or four phenyl units. All the complexes emit at room temperature and steady state and time resolved spectroscopy demonstrates that the lowest excited state is a metal-to-ligand charge transfer involving the bipyridine ligand.

By means of fluorescence single molecule spectroscopy, it is shown that the conformation of high molecular weight conjugated polymers in thin films depends on the nature (chemical composition and molecular weight) of the host matrix. When a high molecular weight poly(p-phenylenevinylene) derivative (OC1C10-PPV) is dispersed in a thin polyvinylbutyral-co-vinyl alcohol-co-vinyl acetate (PVB) film, the spectroscopic properties suggest that OC1C10-PPV is in a highly coiled conformation. On the other hand, in a thin polystyrene film (PS) of low molecular weight, the OC1C10-PPV chains adopt a more extended conformation. Increasing the molecular weight of polystyrene leads to increased coiling of the OC1C10-PPV chains, related to poor solvation. The film preparation conditions (spin-coating or drop-casting) have no effect.

The mechanism of excitation energy transfer is studied using host−guest systems consisting of green and yellow emitting poly(phenylene vinylene) (PPV) based polymers into which red emitting dyes are dispersed. The photoluminescence from such polymer−dye systems is studied in the steady-state and time resolved. Furthermore, the electroluminescence from devices containing these polymer−dye systems as emissive layer is measured. It is shown that in such disordered polymers, characterized by dispersive exciton transport, energetic resonance between the polymer and the dye is not the only requisite for efficient energy transfer. In addition, the exciton kinetics of the combined polymer−dye system has to be taken into account. Efficient transfer of excitation energy from a disordered polymer to a dye can only occur if, at a certain energy, the polymer-to-dye exciton transfer rate is higher than the intrapolymer exciton migration rate. A consequence of the mechanism described here is that when a dye is dispersed...

The lowest excited singlet states of 4-(dimethylamino)-4‘-cyanostilbene (DCS), 4-(dimethylamino)-4‘-nitrostilbene (DANS), and 4-di(hydroxy-ethyl)amino-4‘-nitrostilbene (DANS-diol) have been investigated by high-resolution fluorescence excitation and dispersed emission spectroscopy on samples seeded in supersonic expansions. Using ab initio calculations of the harmonic force fields of the electronic ground state as a starting point for the analysis of vibrational modes and frequencies, detailed vibrational assignments of the rich line structure of the S1 ← S0 transition in these three push−pull stilbenes are reported. From the experimental and theoretical analysis, it becomes apparent that the excitation spectra are dominated by low-frequency vibrational modes of the stilbene-like backbone, albeit that a characterization in terms of trans-stilbene vibrational terminology is not very appropriate. The fluorescence excitation and emission spectra show significant Franck−Condon factors for transitions involvin...

A series of six dye-functionalized Nd3+ complexes have been synthesized and their photophysical properties have been studied and evaluated. The incorporated dyes dansyl, coumarine, lissamine, and Texas Red possess broad and intense absorption bands in the visible spectral region and therefore are ideally suitable as photosensitizers for near-infrared Nd3+ luminescence, despite their very low intrinsic intersystem crossing quantum yields. The Nd3+ complexes display sensitized near-infrared luminescence upon excitation of the dyes. The enhancement of the intersystem crossing quantum yield of the dyes by the complexed Nd3+ ions plays a crucial role in the sensitization process.

The copolymers of tetrachloroethylacrylate (TeCEA) and pentafluorophenylacrylate (PFPA) and of TeCEA and pentafluorophenylmethacrylate (PFPMA) have been examined with regard to their applicability as core materials for optical waveguides. In particular, their thermal properties as function of polymerisation conditions have been investigated and optimized by addition of crosslinkers. The polymerisation reactions were followed by FT-Raman and FT-IR spectroscopy. Also the optical characteristics like material dispersion and attenuation of the polymers have been studied. The fundamental demands of waveguide polymers are high optical transmission at the near-IR wavelengths windows around 1300 and 1550 nm, respectively, the adjustability of the refractive index of the core polymer versus the cladding polymer, and sufficient thermal stability of at least 70°C. Both the examined copolymers show low absorption at 1300 and 1550 nm of 0.2 and 0.7 dB/cm (best values), respectively. The refractive index (RI) of TeCEA/PFPA copolymer is tunable between 1.464 and 1.518 (1300 nm). TeCEA/PFPMA copolymers are tunable between RI values of 1.469 and 1.518 (1300 nm). Thermal stability as indicated by the glass transition temperature (Tg), which reaches about 81°C for the TeCEA/PFPA copolymer with 5 weight% (wt%) of ethyleneglycoldimethacrylate (EGDMA) crosslinker, whereas for TeCEA/PFPMA copolymer with the same amount of EGDMA a Tg of 105°C is obtained. As determined by quantitative vibrational spectroscopy the conversion in the all-acrylate based copolymer is in the order of 98%. Using also EGDMA as crosslinker and with an additional thermal treatment the unsaturation in photocured TeCEA/PFPMA copolymer can be decreased to values of 4%.

A series of m-terphenyl-based ligands bearing three coordinating oxyacetate and two amido or two sulfonamido groups, (1a-b)H3 and (2)H3, respectively, have been synthesized and characterized. The structures of the corresponding neutral complexes have been studied using 1H-NMR spectroscopy and luminescence experiments. The photophysical properties of the (1a-b)Eu, (2)Eu, (1a)Tb, and (2)Tb complexes have been studied to determine the structure of the first coordination sphere in methanol. The first coordination sphere consists of eight donor atoms provided by the ligand (three chelating oxyacetate groups and two amide or sulfonamide oxygens), and one methanol molecule. The (1a)Dy and (1a)Sm complexes exhibited sensitized luminescence in the visible spectral region, but the luminescence intensity was very sensitive to quenching by C-H groups. The near-infrared emitting (1a)Ln and (2)Ln complexes exhibited sensitized luminescence at wavelengths (at 880, 1060, and 1330 nm for Nd3+, at 980 nm for Yb3+, and at 1550 nm for Er3+) of interest for applications in optical telecommunication devices. The luminescence lifetimes of these complexes in DMSO and [D6]DMSO are in the range of microseconds. The luminescent state of the NIR emitting lanthanide ions is very efficiently quenched by high frequency oscillators (such as C-H groups) in the solvent and the ligand.

Perhalogenoaryl and pyridyl acrylates were prepared and their bulk polymerization was studied. Thermal and optical properties of the homo and some copolymers are described. The lightlosses of poly(pentafluorophenyl) acrylate at 1300 and 1500 nm were found to be

The photo-polymerization of tetrachloroethylacrylate (TeCEA), pentafluorophenylacrylate (PFPA) and pentafluorophenylmethacrylate (PFPMA) was examined by quantitative FT-IR and FT-Raman spectroscopy and by thermal analysis. The agreement between the FT-Raman results and thermal analysis was good for all monomers. The FT-IR measurement yielded higher percentages of unsaturation than the two other techniques in the slowly reacting PFPMA polymer, which can be attributed to oxygen quenching effects. Calculations of unsaturation based on spectroscopic measurements were carried out using the relative band ratio method. The influence of the choice of the internal reference band on the unsaturation calculation was examined. The photo-polymerization of the acrylates reached conversions of 95%–99% after irradiation of only a few minutes, samples which contained PFPMA reached conversions of about 85% after 1.5 h of irradiation. Volatile compounds in the resulting polymers were quantified and identified by thermogravimetic analysis (TGA) and thermal desorption followed by gas chromatography with mass spectrometric detection (TD-GC-MS), respectively. Glass transition temperatures of the resulting polymers as determined by differential scanning calorimetry (DSC) vary from 70°C to 125°C.

Several non-iterative algorithms for the analysis of stretched exponential decay are proposed. Decay parameters are obtained by standard linear optimization methods, providing reasonable accuracy, high speed of processing and independence of the initial guesses. The latter feature ensures an excellent possibility to use them for generating initial guesses for iterative procedures, rendering the minimum search more reliable and faster. Proposed algorithms were investigated by fitting simulated data and then used for the analysis of fluorescence and anisotropy decays of dimethylaminonitrostilbene molecules dissolved in polymethyl methacrylate films.

Latex particles of various sizes, containing a fluorescent dye and dispersed at low density in a poly(vinyl alcohol) matrix, were imaged by near-field scanning optical microscopy. The fluorescence intensity of the latex particles was studied quantitatively, by integrating the total intensity measured per particle. For all the samples, a high accuracy in determination of the fluorescence intensity could be achieved. The noticed difference in fluorescence intensity for particles of a similar size is mainly affected by the size distribution of the particles and by sample preparation. Particularly, the smaller particles (50−100 nm) show a significant difference in fluorescence intensity. This was confirmed by further study of the distribution of particle sizes by transmission electron microscopy and by examination of the correlation between the fluorescence intensity of the latex particles and their size. When the size difference is significant (e.g., when particles of 100 and 200 nm, which show a narrow size...

Rare earth ions, with relatively long luminescence lifetimes, have significant advantages for application in fields as varied as diagnostics and optical amplification. In diagnostics the long luminescence lifetimes allow for extremely sensitive time-gated detection, where the difference in temporal behavior of scatter and background fluorescence and the long-lived rare earth luminescence is utilized. In optical amplification the long excited-state lifetime makes it easier to obtain population inversion, a requirement for effective stimulated emission. Unfortunately the absorption cross section of rare earth ion transitions is extremely low. However, via sensitized excitation by means of a suitable organic molecule, efficient excitation is obtained. It is shown that excitation in the visible part of the spectrum can be used to excite rare earth ions which luminesce in the near-IR, such as ytterbium, neodymium, and erbium, via a fluorescein-derivative as sensitizer. The advantages of this approach are manifold. Low-cost light sources are available for the visible part of the spectrum, and interferences from the matrix (scatter, absorption) are minimal. Detection in the near-IR is almost interference-free. For optical amplification the wavelength regions around 1300 and 1550 nm, which can be covered with the neodymium and erbium complexes, respectively, are the most important for applications in optical telecommunication.

Charge-transfer fluorescence probes show a strong response of the intensity and wavelength positions of their spectra to solvent polarity and mobility. Such properties have been applied in the past to follow polymerization kinetics and solvent-induced effects (e.g., swelling) in polymeric materials. An important advantage of charge-transfer fluorescence probes is that they can be measured at extremely low concentrations, hence interference with the polymeric system is limited. Furthermore they report from “within,” since they are only sensitive to phenomena which occur in their immediate surroundings. In this paper it is shown that charge-transfer fluorescence probes can also be applied to study mechanical and thermal properties of polymers. The charge-transfer fluorescence probe Fluoroprobe (1-phenyl-4-[(4-cyano-1-naphthyl)methylene]piperidine) was doped into a polyether–polyester block copolymer, which was submitted to thermal and mechanical stress. The effect of strain applied to the polymers in various forms (fibers, sheets) and the effect of thermal processes (glass transition temperatures, phase transitions, melting points) are clearly reported by the changes in fluorescence intensity and wavelength of the Fluoroprobe molecule.

Cyanine-based near-i.r. fluorescent probes have been applied as labels to determine functional groups in polymeric materials. The advantage of such probes is that they can be applied to polymers which are autofluorescent or strongly coloured or to strongly scattering polymer emulsions. Two examples are discussed: the labelling of a polymer latex with aldehyde functional groups, by application of a cyanine with a hydrazide functionality, and the labelling of amino functional groups in a polyamide utilizing a cyanine label with an isothiocyanate functionality. The cyanines which have been applied absorb and fluoresce in the 650–700 nm range and in the 750–800 nm range, respectively. In addition to near-i.r. fluorescence, the cyanine dyes have strong absorption (with extinction coefficients in the order of 2 × 10 5 lmol −1 cm −1 ). It is shown that by application of reflection absorption measurements also sensitive detection of labelled functional groups can be realized. The combined application of fluorescence and reflection measurements allows for the detection of concentration and distribution of functional groups in polymeric systems down to very low levels.

A donor-bridge-acceptor fluorophore with extreme sensitivity to environmental influences has been attached covalently to a polyamino crosslinker. It was found that the progress of the crosslinking reaction with an aceto-acetate functionalized polyacrylate dispersion can be monitored from the fluorescence wavelength shift of the fluorophore. Also formation and drying of films applied from the resulting labelled dispersion induces a significant wavelength shift of the fluorescence of the incorporated label.

Maleimido-fluoroprobe (MFP) is a derivative of “fluoroprobe” (FP), the most sensitive known fluorescent polarity probe. MFP differs from FP in that it is completely nonfluorescent. The characteristic strong FP-type fluorescence is however switched on when the CC bond of the maleimide group becomes saturated forming the succinimide derivative, SFP. This fluorogenic behavior is shown to be induced by copolymerization of MFP into growing polyacrylate chains. The increase in the intensity of the fluorescence, which is observable even in the early, low-viscosity stage of polymerization, provides therefore a measure of the degree of polymerization. The strong blue shift of the fluorescence of chain-incorporated SFP moieties fulfills the usual polarity probe function of monitoring changes in the microscopic dielectric environment of the polymer as vitrification takes place. This duality in the probe characteristics of MFP is illustrated by results on the radiation-induced bulk polymerization of methyl methacrylate.

A charge-transfer fluorescence molecule has been applied to study the structure of polystyrene latices and polystyrene—glycidylmethacrylate core—shell latices. Information on the composition of the latex could be obtained on the basis of the combined application of steady state and time-resolved fluorescence measurements. Time-resolved measurements were done using a frequency-domain approach; the time-resolved data were interpreted using the maximum entropy method of analysis.

Two novel m-terphenyl-based organic ligands (2 and 3) have been synthesized. Photophysical studies show that the ligands form stable complexes with Eu3+, since typical Eu3+ luminescence is observed upon excitation of the ligand. The acyclic complex 2·Eu3+ shows relatively long lifetimes in methanol (e.g. = 0.72 ms in CH3OH). The acylic ligand 2 allows the additional coordination of two solvent molecules and their high-energy vibrational modes form the main quenching pathway for the Eu3+ luminescence. In comparison with 1·Eu3+, the more rigid dioxolane-containing complex 3·Eu3+ provides an additional donor atom, which reduces the solvent coordination of 3·Eu3+ (3·Eu3+ = 1.42 ms compared to 1·Eu3+ = 0.75 ms in CH3OH). The high-energy vibrational modes of the organic ligand 3 are the most important quenchers. Typical near-infrared Nd3+ emission at 1060 and 1350 nm resulting from 3·Nd3+ has been observed. Quenching by the solvent is still operative for 3·Nd3+, because of the larger ionic radius of the Nd3+ ion.

A probe molecule, which shows an unusually large change in fluorescent properties in response to changes in its environment, was introduced into a monodisperse polystyrene latex. Upon addition of low-molecular-weight compounds, the ensuing swelling process of the latex could be followed via the changes in the fluorescence spectrum of the probe molecule. Polymerization reactions of monomers, introduced into the particles, could also be monitored by means of this approach. Using glycidylmethacrylate as the monomer led to the formation of particles in which two distinctly different surroundings could be detected after such a polymerization. © 1995 John Wiley & Sons, Inc.

Determination of benzo[a]pyrene (BaP) metabolites in urine can provide direct insight into recent exposure to BaP integrated from all uptake routes. In order to detect 3-OH BaP in human urine after exposure to BaP at the workplace, extremely sensitive methods need to be developed. In this paper, a new extraction method is presented, and two laserbased fluorescence techniques are evaluated. Using HPLC with laser-induced fluorescence detection, a detection limit of 8 ng/L was obtained. With laser-excited Shpol'skii spectrometry after chemical derivatization, 3-OH BaP could be detected at even a 0.5-ng/L concentration. In a pilot study, urine samples from coke-oven workers and from occupationally nonexposed control persons were analyzed. In the control samples, the average 3-OH BaP concentration was 8.3 ng/L; the 3-OH BaP concentrations were found to be highly correlated (r2 = 0.89) with urinary 1-OH pyrene, a widely used biomarker for polycyclic aromatic hydrocarbon (PAH) exposure. Significantly elevated 1-OH pyrene concentrations were measured in urine samples from coke-oven workers, but in most samples a corresponding increase of 3-OH BaP was not observed. Possible explanations for this discrepancy are discussed.

The practical applicability and analytical performance of laser-excited Shpol'skill spectroscopy (LESS) for the determination of benzo[a]pyrene (BaP) metabolites was studied. Quantitation of these compounds in fish bile can provide insight into the BaP uptake from a contaminated aquatic environment (blomonitoring). Chemical derivatization of hydroxylates BaP metabolites with methyl iodide (to improve the compatibility with the Shpol'skii matrix) was tested. The methylation of phenolic metabolites was rapid and quantitative, but with BaP-dihydro diol metabolites, mixtures and methylation and elimination products were formed

Acylation of perhalogenophenols and pyridinols by acryloyl chloride in the presence of hindered pyridines, such as 2,6-lutidine, afforded the corresponding acrylates which were isolated in a pure form by chromatography on a Florisil® column. This was performed without in situ polymerization of the corresponding acrylates.

An accurate extraction and measurement procedure to determine chlorinated biphenyls (CBs) in surface waters was developed, and sampling techniques for removing suspended matter (SPM) were investigated. The procedure involved a 10-L batch liquid-liquid extraction directly from the sample bottle to prevent loss due to adsorption to the wall. Exhaustive extraction for recovery measurements was proposed, next to spikes, resulting in an extraction time of 10-45 h. A detection limit lower than 10 pg/kg and a coefficient of variation of 3-9% were obtained. Two sampling techniques to remove SPM were investigated: filtration and continuous-flow centrifugation. Filter clogging and adsorption affected the accuracy of the filtration technique. Insufficient separation of low-density particulate organic matter in continuous-flow centrifuge determined the CB contents measured in centrifugates. Results using these techniques for distribution or bioavailability studies are questionable because freely dissolved CBs and dissolved organic matter-bound CBs cannot be distinguished. Centrifugation may be applicable to transport studies. 53 refs., 5 figs., 3 tabs.

The ataxonomic discrimination of phytoplankton species on the basis of fluorescence data obtained by multiwavelength excitation in combination with wavelength selective detection in flow cytometry is demonstrated. The discrimination is based on differences in pigment composition between the species, which are reflected in their spectral characteristics. Classification can be done both by making use of the absolute fluorescence intensities and with fluorescence parameter ratios. The latter approach has the advantage that size-related effects and instrument fluctuations are reduced to a large extent. Photoadaptation does influence the absolute as well as the ratioed parameters that are obtained but does not impede the classification into major ataxonomic groups.

A new technique for solid-phase preconcentration of contaminants dissolved in surface waters is presented. The method is based on application of extraction material that is not packed, as in conventional solid-phase extraction systems, but instead is present in a freely floating form, as in a fluidized-bed reactor. The feasibility of the fluidized-bed extraction approach is demonstrated for the determination of heavy metals in surface waters using 8-hydroxyquinoline attached to solid supports as complexing agent. Recoveries, repeatability, and sensitivity appear satisfactory for this application, even when no filtration of the sample is done. As fluidized-bed extraction is based on free-floating, unpacked, extraction material, the pressure drop over the column is minimal and filtration is not required. Hence the technique seems eminently suited for deployment as an in situ, long-term, sampling method. As such it will provide time-integrated contamination levels that are not biased by biological variability or filtration artifacts, disadvantages of the commonly used methods for monitoring of contaminants in surface water.

Acylation of perhalogenophenols and pyridinols by acryloyl chloride in the presence of hindered pyridines, such as 2,6-lutidine, afforded the corresponding acrylates which were isolated in a pure form by chromatography on a Florisil® column. This was performed without in situ polymerization of the corresponding acrylates.

Lissamine functionalized terphenyl-based Nd complexes are synthesized, and incorporated in deuterated dimethylsulfoxide solutions and partially fluorinated planar polymer waveguides. Optical excitation of the lissamine sensitizer around 500 nm, followed by intramolecular energy transfer to the Nd3+ ion, causes near-infrared photoluminescence (890, 1060, 1340 nm) due to intra-4f transitions in the Nd3+ ion. The intramolecular energy transfer rate is larger than 107 s−1. Due to the large absorption cross-section of the sensitizer (>10−17 cm2 around 500 nm), the Nd3+ is excited 104 times more efficiently than in a pure complex, without sensitizer. The Nd3+ luminescence lifetime is relatively short, both in solution (2.2 μs) and in a polymer host (0.8 μs), which is attributed to coupling to vibrational states of nearby C–H and O–H groups. Spincoated fluorinated polymer planar waveguides, doped with these sensitized organic Nd complexes show excellent waveguide properties. Upon continued illumination, photodegradation is observed in the doped polymer films.

International audience; It is shown that the successful sensitization of lanthanide luminescence by azatriphenylenes can be expanded from sensitization in non-hydroxylic solvents to aqueous media by the addition of two or more carboxylate functionalities on the triphenylene skeleton. Furthermore, it is reported that a fluorescent donor– bridge– acceptor system incorporated in a thin polymer film allows the production of blue electroluminescence that can be tuned from blue to yellow by exposure to solvent vapours.

Fluorescence methods are increasingly applied for the characterization of polymeric materials. In the present chapter, a number of applications of fluorescence spectroscopy are presented in an effort to illustrate the potential of this technique to study structure and properties of polymeric materials. In analytical chemistry fluorescence, methods to date are widely applied to determine trace constituents in environmental and bioanalysis. The technique can be applied to the determination of autofluorescent compounds, or—since fluorescence, by no means, is a universal phenomenon—nonfluorescent compounds may be measured by making use of suitable fluorescent labels. Because fluorescence emission involves the measurement of light against a dark background, and is not based on difference measurements like most absorption techniques, detection may be achieved on a very low level. Recently, even fluorescent measurements of single molecules are reported which are covered in this chapter. By application of fluorescent labels even more areas of research come within reach. In situ morphological characteristics of polymers as such and polymers in interaction with solvents or undergoing some sort of physical or chemical action may be studied.

m-Terphenyl-based lanthanide complexes functionalized with a triphenylene antenna chromophore ((Ln)1) exhibit sensitized visible and near-infrared emission upon photoexcitation of the triphenylene antenna at 310 nm. Luminescence lifetime measurements of the (Eu)1 and (Tb)1 complexes in methanol-h1 and methanol-d1 revealed that one methanol molecule is coordinated to the lanthanide ion, indicating that all eight donor atoms provided by the ligand are involved in the encapsulation of the lanthanide ion. The luminescence lifetimes of the near-IR-emitting complexes (Er)1, (Nd)1, and (Yb)1 in DMSO-h6 and DMSO-d6 are in the microsecond range, and are dominated by nonradiative deactivation of the luminescent state. The processes preceding the lanthanide luminescence in the sensitization process have been studied in detail. The complexed lanthanide ion reduces the antenna fluorescence and increases the intersystem crossing rate via an external heavy atom effect. The subsequent energy-transfer process was found to take place via the antenna triplet state in all complexes. Luminescence quantum yield measurements and transient absorption spectroscopy indicated that in solution two conformational isomers of the complexes exist: one in which no energy transfer takes place, and one in which the energy transfer does take place, resulting in the lanthanide luminescence. The intramolecular energy-transfer rate is higher in the (Eu)1 and (Tb)1 complexes than in the near-infrared-emitting complexes. In methanol the energy-transfer rate is 3.8 × 107 s-1 for (Eu)1 and (Tb)1. In DMSO-d6 the intramolecular energy-transfer rate is higher in the (Nd)1 complex (1.3 × 107 s-1) than in the (Er)1 (3.8 × 106 s-1) and (Yb)1 (4.9 × 106 s-1) complexes.

International audience; Fluorexon (4′,5′-bis[N,N-bis(carboxymethyl)aminomethyl]fluorescein) forms stable, water-soluble complexes with lanthanide ions. The complexes with neodymium(III), erbium(III) and ytterbium(III) display sensitised near-infrared lanthanide luminescence upon excitation of the fluorexon with visible light. The photosensitisation efficiency is very high (0.5–1.0) as a result of lanthanide-enhanced intersystem crossing in the sensitising chromophore and rapid intracomplex energy transfer. The overall luminescence quantum yields, however, are low (2E-4 – 5E-3) due to nonradiative deactivation of the excited lanthanide ion.

The characterisation of monomode passive polymer optical devices fabricated according to the POPCORN technology bymethods originated from electron, ion and optical spectroscopy is summarized. Impacts of observed waveguide perturbationson the optical characteristics ofthe waveguide are evaluated.In the POPCORN approach optical components for telecommunication applications are fabricated by photo-curing of liquidhalogenated (meth)acrylates which have been applied on moulded thermoplastic substrates. For tuning of waveguidematerial refractive indices with respect to the substrate refractive index frequently comonomer mixtures are used. Thepolymerisation characteristics, especially the polymerisation kinetics of individual monomers, determine the formation ofcopolymers. Therefore the unsaturation as function of UV-illumination time in the formation of halogenated homo- andcopolymers has been examined. From different suitable copolymer systems, after characterisation of their glass transitiontemperatures, their curing behaviour and their refractive indices as function of the monomer ratios, monomode waveguidesapplying PMMA substrates have been fabricated. To examine the material composition also in the 6 x 6 jtm2 waveguidesthey have been visualised by transmission electron microscopy. With this method e.g. segregation phenomena could beobserved in the waveguiding copolymer with features in the 100 nm range. Secondary ion mass spectrometry has been usedfor waveguide cross section characterisation as well. The optical losses in monomode waveguides caused by segregation andother material induced defects like micro bubbles formed as a result of shrinkage have been quantisized by return lossmeasurements. Defects causing scattering could be observed by convocal laser scanning microscopy and by conventionallight microscopy.Keywords: integrated optics, polymer waveguide, halogenated acrylates, halogenated methacrylates, convocal scanninglaser microscopy, transmission electron microscopy, SIGA, POPCORN

International audience

Rare-earth ions, with relatively long luminescence lifetimes, have significant advantages for diagnostic application. In diagnostics the long luminescence lifetimes allow for extremely sensitive time-gated detection, where the difference in temporal behavior of scatter and background fluorescence and the long-lived rare earth luminescence is utilized. Unfortunately the absorption cross-section of rare earth ion transitions is extremely low. However, via sensitized excitation by means of a suitable organic molecule efficient excitation is obtained. It is shown that excitation in the visible part of the spectrum can be used to excite rare-earth ions which luminescent in the near-IR, such as ytterbium, neodymium and erbium, via a fluorescein-derivative as sensitizer. The advantages of this approach are manifold. Low cost light source are available for the visible part of the spectrum and interference's from the matrix are minimal. Detection in the near-IR is almost interference-free.

Efficient intramolecular energy transfer (ET) from an excited chromophore to Nd3+ and Er3+ ions with subsequent emission in the near-infrared (h2) is possible in novel compounds (1). These are made by covalent attachment of fluorescein to a calix[4]arene possessing a cavity at the lower rim in which the trivalent lanthanoid ions are complexed.

The existence of polythiocar- bamatozinc complexes, species pre- sumed to be involved in catalyzing sulfur vulcanization, has been studied by com- putational and mass-spectrometric tech- niques. Density functional calculations reveal that the sulfuration energy of bis(trithiocarbamato)zinc(ii) is compara- ble to that of bis(phenyltrithiolato)- zinc(ii), a stable sulfurated complex. Interestingly, the analogous nonsym- metrically sulfurated complex (dithio- carbamato)(tetrathiocarbamato)zinc(ii) is energetically slightly more favorable. The calculations indicate that polythio- carbamatozinc complexes may indeed be involved in the sulfur vulcanization cascade, a conclusion corroborated by ensuing laser-desorption ionization (LDI) mass-spectrometric measure- ments on mixtures of dithiocarbamato- zinc(ii) complexes and elemental sulfur. These demonstrate the presence of poly- thiocarbamatozinc ions that are sulfu- rated with up to eight additional sulfur atoms.

Cyanine-based near-IR fluorescent probes have been applied as labels to determine aldehyde-groups in polymeric materials. The advantage of such probes is that they can be applied to polymers which are autofluorescent or strongly colored or to strongly scattering polymer emissions. The example which is discussed in this paper is the labelling of a polymeric core-shell latex, comprising a polystyrene core and a glycidylmethacrylate shell, which has been hydrolyzed and subsequently oxidized to form aldehyde functional groups, by application of a Cyanine with a hydrazide functionality. The Cyanine which has been applied absorbs and fluoresces in the 650 - 700 nm range. In addition to near-IR fluorescence, the Cyanine dyes have strong absorption (with extinction coefficients in the order of 2 X 105 I/mol.cm). It is shown that by application of reflection absorption measurements also sensitive detection of labelled functional groups can be realized. The combined application of fluorescence and reflection measurements allows for the detection of concentration and distribution of functional groups in polymeric systems down to very low levels.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Three types of lower-lower rim linked biscalix[4]arenes that contain carboxylic ester (1) and/or amide functions (2 and 3) at their remaining phenolic oxygen atoms were synthesized. The homo- and heterodinuclear lanthanide ion complexes based on these ligands were used to study the energy transfer between different lanthanide ions. Photophysical studies comparing the luminescence properties of the homodinuclear Eu3+ complex and the heterodinuclear Eu3+-Nd3+ complex of 2 indicated that energy transfer is likely to occur from Eu3+ to Nd3+ with an efficiency of > 50%. The luminescence properties turned out to be strongly solvent dependent, which is attributed to structural changes leading to different positions of the lanthanide ions in the cavities provided by the biscalix[4]arene.

International audience; Near-infrared luminescent ytterbium(III), neodymium(III) and erbium(III) chelates containing organic chromophores derived from fluorescein and eosin have been synthesized and studied spectroscopically. The complexes can be efficiently excited with visible light and show intense lanthanide luminescence at low concentrations (2≈ 10−6 mol l−1) in D2O as a result of energy transfer from the dye moiety to the rare earth ion. Quenching of the luminescence of the complexes by molecular oxygen reveals information on the rate of energy transfer from the “antenna” chromophore to the lanthanide ion.

Time-resolved fluorescence measurements have been carried out on charge-transfer fluorescent molecules incorporated in polymeric lattices, consisting of polystyrene cores and polyglycidylmethacrylate shells, and in polymethylmethacrylate thin films. New approaches to the analysis of fluorescence lifetime data obtained for molecules in polymer matrices had to be applied, since conventional analysis methods appeared not suitable for such strongly heterogeneous systems. The polymer lattices could be characterized by application of phase- resolved fluorescence lifetime measurements followed by maximum-entropy methods for data analysis. The thin films were studied using time-correlated single photon counting fluorescence lifetime measurements and data analysis with a home-built program based on stretched exponential decays. Interactions of the fluorescent guest molecules could be established by combined fluorescence lifetime and depolarization measurements. Suggestions for further improvements in fluorescence lifetime methods for characterization of polymeric materials have been made.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Recently developed photobleachable polymers show a loss of < 0.1 dB/cm at 1300 nm and < 0.15 dB/cm at 1550 nm. Nonchromophore containing polymers show film waveguide losses of < dB/cm at 1300 nm and 1550 nm. Refractive indices in these materials can be tuned within a range of 0.05 by changing the polymer composition. Multilayers of cross-linked (solvent resistant) layers, each 2-10 microns have been deposited by multiple spinning steps. Using these multilayers, fully embedded, fiber-compatible strip waveguide structures have been created by masked bleaching of multilayers with chromophore containing corelayers. The lateral refractive index contrast is thereby tuned by changing the chromophore content of the corepolymer. Poling-induced loss has been investigated by wavelength and polarization dependent measurements of losses in films. The results indicate that this loss is due to increased scattering. Bleached channel waveguides in a poled (at 125 V/micrometers ) nonlinear optical polymer have been made showing losses of < dB/cm at 1300 nm. Rapid photodegradation at 1300 nm has been observed in stilbene containing channel waveguides. In a nitrogen atmosphere no degradation was seen. The same is true for waveguides in air at 1550 nm. This suggests the attack of the stilbene chromophores by singlet oxygen. Therefore a new generation of low-loss, linear, and nonlinear optical polymers based on singlet oxygen resistant molecules has been developed. The linear optical polymers are used for the realization of low-insertion loss (< 2 dB), digital (switch voltage 3-6 V) and efficient (switching power < mW, cross talk - 20 dB) pigtailed and packaged 1 X 2 switches. They utilize the strong thermo-optic effect in polymers. Their switching time is therefore limited to 1 ms whereas their polarization dependence is < 0.3 dB.

A new hydrazide derivative of a cyanine dye is synthesized for the chemical derivatization of aldehydes. With this red absorbing fluorophore it is possible to apply visible diode laser induced fluorescence (DIO-LIF) detection in conventional-size liquid chromatography (LC). The dye is based on CY5.3a-IA, a sulfonated dicarbocyanine with a iodoacetamido reactive group. The detection limit of n-octylaldehyde is 7 × 10−8 M, limited by the reactivity of the label. Mixtures comprised of strongly resembling aldehydes were derivatized with the label and analyzed by LC-DIO-LIF. The potential applicability in biological problems is shown by the derivatization of 4-hydroxy-2-nonenal (HNE).