Showing papers on "Excimer published in 2011"
TL;DR: In this article, pyrene-substituted ethenes, 1,2,2-tripheny-1-pyrenylethene (TPPyE) and 1, 2-diphenyl-1,2dipyrenyl (DPDPyE), are synthesized and characterized.
Abstract: Pyrene-substituted ethenes, 1,2,2-tripheny-1-pyrenylethene (TPPyE) and 1,2-diphenyl-1,2-dipyrenylethene (DPDPyE), are synthesized and characterized. Whereas they are weakly emissive in solution they become strong emitters when aggregated in the condensed phase. In contrast to the general observation that excimer formation quenches the light emission of fluorophores, TPPyE and DPDPyE exhibit efficient excimer emissions in the solid state with high fluorescence quantum yields up to 100%. The π–π intermolecular interactions between the pyrene rings, coupled with multiple C–H⋯π hydrogen bonds, efficiently restrict intramolecular rotations, which block the nonradiative energy decay channel, and hence make the dye molecules highly emissive in the solid state. Non-doped organic light-emitting diodes using TPPyE and DPDPyE as emitters are fabricated, which give green light at low turn-on voltages (down to 3.2 V) with maximum luminance and power, current, and external quantum efficiencies of 49830 cd m−2, 9.2 lm W−1, 10.2 cd A−1 and 3.3%, respectively.
197 citations
TL;DR: In this article, the substituent effects were further examined with a lipid chain replacing polylactide, and the process dependent and reversible mechanochromic fluorescence was discovered for the boron dodecane complex (BF2dbmOC12H25).
Abstract: Difluoroboron β-diketone complexes are versatile light-emitting molecules that exhibit tunable emission in both solution and the solid state. Among this class of dyes, difluoroboron dibenzoylmethane-polylactide (BF2dbmPLA) polymers have been investigated for their molecular weight dependent fluorescence where the polymer chain plays an important role in BF2dbm solid-state emission. Here the substituent effects were further examined with a lipid chain replacing polylactide. Surprising process dependent and reversible mechanochromic fluorescence was discovered for the boron dodecane complex (BF2dbmOC12H25). A thermally annealed spin-cast film of the lipid dye on glass exhibited blue fluorescence under UV light but after shearing or scratching, the mechanically perturbed region turned yellow-green. The blue coloration could be rapidly recovered by thermal treatment of the film. The phenomena were investigated by steady-state fluorescence spectroscopy at room, low, and high temperatures, in situfluorescence microscopy, fluorescence lifetime measurements, and X-ray diffraction. Consistent with previous findings, the ordered-to-amorphous structural change that occurs upon mechanical perturbation may increase molecular rotational freedom, allowing for more efficient excimer emission, which typically occurs at longer wavelengths.
117 citations
TL;DR: In this paper, the trifluoromethyl groups into either the 4- or 5-position of the pyridyl rings of the ligand are shown to lead to a red-shift in the excimer band, moving it into the near infra-red (NIR) region.
Abstract: The Pt(II) complex N^C2^N-1,3-di(2-pyridyl)benzene platinum chloride (PtL1Cl) is known to display efficient triplet luminescence in the green region of the spectrum, and to form an unusually emissive excimer that emits around 690 nm. In this contribution, the introduction of trifluoromethyl groups into either the 4- or 5-position of the pyridyl rings of the ligand is shown to lead to a red-shift in the excimer band, moving it into the near infra-red (NIR) region. The new ligands, synthesised by either Suzuki or Stille cross-coupling methods, are 1,3-bis(4-(trifluoromethyl)pyridin-2-yl)benzene HL27, 1,3-bis(4-(trifluoromethyl)pyridin-2-yl)-4,6-difluorobenzene HL28, and 1,3-bis(5-(trifluoromethyl)pyridin-2-yl)-4,6-difluorobenzene HL29, from which the corresponding Pt(II) complexes PtLnCl have been prepared. The monomer and excimer emission energies in solution are compared with those of PtL1Cl and PtL22Cl {HL22 = 1,3-di(2-pyridyl)-4,6-difluorobenzene}. The order for the monomer can be rationalised in terms of the stabilising effects of the F atoms and the CF3 groups on the HOMO and LUMO respectively. The order of excimer emission proves to be subtly different, but the most red-shifted complex in both cases is PtL27Cl. The electroluminescence of neat films of the complexes as emitting layers in OLEDs displays uniquely excimer-like emission, extending well into the technologically important NIR region.
94 citations
TL;DR: Electrochemical characterization and the observation of excimer emission from a series of 9-naphthylanthracene-based dimer- and trimer-bridged high steric hindrance aromatic groups during photoluminescence (PL) measurements in the solid state and in solution electrogenerated chemiluminescent (ECL) measurements are reported.
Abstract: We report the electrochemical characterization and the observation of excimer emission from a series of 9-naphthylanthracene-based dimer- and trimer-bridged high steric hindrance aromatic groups during photoluminescence (PL) measurements in the solid state and in solution electrogenerated chemiluminescence (ECL) measurements. Cyclic voltammetry of 4,4′-bis(9-(1-naphthyl)anthracen-10-yl)biphenyl (4A) and 1,3,5-tris(9-(1-naphthyl)anthracen-10-yl)benzene (4C) showed two or three reversible, closely spaced one-electron transfers on oxidation in dichloromethane. The ECL emission spectra of 4A and 4C resulting from the annihilation reaction in benzonitrile showed two bands: one at the same wavelength as the PL peak in the solution state, and a broad band at longer wavelength. With a coreactant, such as peroxydisulfate, ECL spectra showed a single peak that was less broad in shape. PL measurement in the solid state and measurement of representative time traces of PL intensity, lifetimes, and picosecond time-corr...
81 citations
TL;DR: Two cyclometallated platinum(II) complexes, N^C^N-5-fluoro-1,3-di(2-pyridyl)benzene platinum-II isothiocyanate, MePtNCS, have been synthesized and characterized as discussed by the authors.
Abstract: Two cyclometallated platinum(II) complexes, N^C^N-5-fluoro-1,3-di(2-pyridyl)benzene platinum(II) chloride, FPtCl, and N^C^N-5-methyl-1,3-di(2-pyridyl)benzene platinum(II) isothiocyanate, MePtNCS, have been synthesized and characterized. Both complexes are highly efficient phosphorescent green emitters which can also display excimer emission in the red region. They have been studied as triplet emitters in solution-processed, multilayer organic light-emitting diodes (OLEDs), together with the known complex of 5-methyl-1,3-di(2-pyridyl)benzene, MePtCl, for comparison. The trend in efficiencies of the OLEDs prepared correlates with the charge-trapping properties of the complexes. The most efficiently emitting complex, FPtCl, was used as the dopant in a solution-processed white OLED, employing monomer and excimer emission.
76 citations
TL;DR: In this article, the authors have demonstrated profound influence of solvent in ion selectivity, in acetonitrile-chloroform they formed complexes with Hg 2+, Pb 2+, Cu 2+ and Ni 2+.
62 citations
TL;DR: Through a comparative and detailed study of the (1)H NMR, electrochemical and photophysical properties of DSF-IFs 1 and 2, it is evidenced the intramolecular π-π interactions occurring between the two "aryl-fluorene-aryl" moieties in the ground state and in the excited state.
Abstract: Two series of DiSpiroFluorene-IndenoFluorene (DSF-IF) positional isomers, namely dispiro[2,7-diarylfluorene-9',6,9'',12-indeno[1,2-b]fluorenes], (1,2-b)-DSF-IFs 1 and dispiro[2,7-diarylfluorene-9',6,9'',12-indeno[2,1-a]fluorenes], (2,1-a)-DSF-IFs 2 have been synthesized. These violet-to-blue fluorescent emitters possess a 3π-2spiro architecture, which combines via two spiro links two different indenofluorene cores, that is, (1,2-b)-IF or (2,1-a)-IF and 2,7-substituted-diaryl-fluorene units. Due to their different geometric profiles, the two families of positional isomers present drastically different properties. The marked difference observed between the properties of (1,2-b)-DSF-IF (1) and (2,1-a)-DSF-IF (2) is discussed in terms of intramolecular π-π interactions occurring in (2,1-a)-DSF-IF (2) leading to conformationally-controllable intramolecular excimer formation. Indeed, the original geometry of the (2,1-a)-DSF-IF (2) family, with face-to-face "aryl-fluorene-aryl" moieties, leads to remarkable excimer emission through intramolecular π-π interactions in the excited state. Furthermore, the emission wavelengths can be gradually modulated by the control of the steric hindrance between the adjacent substituted phenyl rings. Thus, through a comparative and detailed study of the (1)H NMR, electrochemical and photophysical properties of DSF-IFs 1 and 2, we have evidenced the intramolecular π-π interactions occurring between the two "aryl-fluorene-aryl" moieties in the ground state and in the excited state. These properties have been finally correlated to the spectacular conformational change modeled by density functional theory (DFT) calculations. Indeed, the two "aryl-fluorene-aryl" moieties switch from a staggered conformation in the ground state to an eclipsed conformation in the first excited state.
61 citations
TL;DR: A detailed spectroscopic investigation supported by density functional theory (DFT) calculations on two series of CBP derivatives finds that the resulting poor coupling between the two halves of the molecules leads to an electronic structure similar to that of N-phenyl-3,6-dimethylcarbazole, with a high triplet-state energy.
Abstract: Carbazole-based materials such as 4,4'-bis(N-carbazolyl)-2,2'-biphenyl (CBP) and its derivatives are frequently used as matrix materials for phosphorescent emitters in organic light emitting diodes (OLED)s. An essential requirement for such matrix materials is a high energy of their first triplet excited state. Here we present a detailed spectroscopic investigation supported by density functional theory (DFT) calculations on two series of CBP derivatives, where CH(3) and CF(3) substituents on the 2- and 2'-position of the biphenyl introduce strong torsion into the molecular structure. We find that the resulting poor coupling between the two halves of the molecules leads to an electronic structure similar to that of N-phenyl-3,6-dimethylcarbazole, with a high triplet-state energy of 2.95 eV. However, we also observe a triplet excimer emission centered at about 2.5-2.6 eV in all compounds. We associate this triplet excimer with a sandwich geometry of neighboring carbazole moieties. For compounds with the more polar CF(3) substituents, the lifetime of the intermolecular triplet excited state extends into the millisecond range for neat films at room temperature. We attribute this to an increased charge-transfer character of the intermolecular excited state for the more polar substituents.
57 citations
TL;DR: An unexpected result was found that the framework of the fluorescence blob model (FBM) which predicts that quenching takes place inside a blob, which is the finite volume probed by an excited chromophore during its lifetime, is found to describe satisfyingly the data obtained with the longer PEO(X)-Py(2) samples.
Abstract: A series of poly(ethylene oxide)s labeled at both ends with pyrene, (PEO(X)−Py2, where X represents the number average molecular weight (Mn) of the PEO chains and equals 2, 5, 10, and 16.5 K) was prepared together with one-pyrene-monolabeled PEO (PEO(2K)−Py). The process of end-to-end cyclization (EEC) was investigated by monitoring intramolecular excimer formation in seven organic solvents with viscosities (η) ranging from 0.32 to 1.92 mPa·s. The steady-state fluorescence spectra showed that excimer formation of PEO(X)−Py2 decreased strongly with increasing η and Mn. The monomer and excimer time-resolved fluorescence decays were analyzed according to the traditional Birks’ scheme. Birks’ scheme analysis indicated that the decrease in excimer formation with increasing Mn and η was due partly to a decrease in the rate constant of EEC, but most importantly, to a large increase in the fraction of pyrenes that did not form excimer (fMfree). This result is in itself incompatible with Birks’ scheme analysis whi...
49 citations
TL;DR: In this article, the authors present an experimental study on the lifetimes of the σ-Sigma (5s-35s) molecule in its vibrational ground state and in an excited state.
Abstract: Since their first experimental observation, ultralong-range Rydberg molecules consisting of a highly excited Rydberg atom and a ground state atom have attracted the interest in the field of ultracold chemistry. Especially the intriguing properties like size, polarizability and type of binding they inherit from the Rydberg atom are of interest. An open question in the field is the reduced lifetime of the molecules compared to the corresponding atomic Rydberg states. In this letter we present an experimental study on the lifetimes of the ^3\Sigma (5s-35s) molecule in its vibrational ground state and in an excited state. We show that the lifetimes depends on the density of ground state atoms and that this can be described in the frame of a classical scattering between the molecules and ground state atoms. We also find that the excited molecular state has an even more reduced lifetime compared to the ground state which can be attributed to an inward penetration of the bound atomic pair due to imperfect quantum reflection that takes place in the special shape of the molecular potential.
48 citations
TL;DR: It is shown that pyrene-modified PAMAM dendrimers can be effectively utilized to generate wavelength-tunable emitting systems displaying bluish green, greenish yellow, and orange-red colors at room temperatures, and that general and specific solvent effects play a crucial role in the positive solvatochromism exhibited by the system.
Abstract: Significant aggregation is observed in pyrene-modified zero- and first-generation polyamidoamine (PAMAM) dendrimers above their critical aggregation concentration (CAC, >10(-6) M). The pyrene units are attached to the dendrimer skeleton through imine bonds, which play a pivotal role in enhancing the aggregation propensity of the PAMAM dendrimers. Scanning electron microscopy studies suggest that pyrene-modified PAMAM dendrimers aggregate into doughnut-shaped assemblies. As a result of aggregation, the pyrene chromophores are pre-arranged in a face-to-face geometry in the ground state, and readily generate pyrene "static excimer" on photoexcitation. The static pyrene excimer emits with an unprecedented quantum yield of 0.62 ± 0.01 in dichloromethane, and also exhibits remarkable positive solvatochromism from 498 to 638 nm, which leads to the highest bathochromic shift for pyrene excimer emission in solution reported so far. Lippert-Mataga analysis of the system suggests that general and specific solvent effects play a crucial role in the positive solvatochromism exhibited by the system. Luminescence quenching studies on both monomer and aggregate systems were carried out in the presence of various metal ions, and the results imply that pyrene-modified PAMAM dendrimer can be utilized for selective detection of Hg ions in the presence of a wide variety of transition, alkali, and alkaline earth metal ions. This report presents the first dendrimer-based chromophoric system exhibiting positive solvatochromism over a range of 140 nm, and shows that pyrene-modified PAMAM dendrimers can be effectively utilized to generate wavelength-tunable emitting systems displaying bluish green, greenish yellow, and orange-red colors at room temperatures.
TL;DR: The calculations of excited states of monomer and associated moieties suggested that a parallel-displaced arrangement is responsible for the excimer emission observed experimentally, although some other associations, such as T-shape dimer structures, can still be relatively abundant at this surface concentration.
Abstract: A combined experimental-computational approach was used to study the self-organization and microenvironment of 1-methylnaphthalene (1MN) deposited on the surface of artificial snow grains from vapors at 238 K. The specific surface area of this snow (1.1 × 10(4) cm(2) g(-1)), produced by spraying very fine droplets of pure water from a nebulizer into liquid nitrogen, was determined using valerophenone photochemistry to estimate the surface coverage by 1MN. Fluorescence spectroscopy at 77 K, in combination with molecular dynamics simulations, and density functional theory (DFT) and second-order coupled cluster (CC2) calculations, provided evidence for the occurrence of ground- and excited-state complexes (excimers) and other associates of 1MN on the snow grains' surface. Only weak excimer fluorescence was observed for a loading of 5 × 10(-6) mol kg(-1), which is ∼2-3 orders of magnitude below monolayer coverage. However, the results indicate that the formation of excimers is favored at higher surface loadings (>5 × 10(-5) mol kg(-1)), albeit still being below monolayer coverage. The calculations of excited states of monomer and associated moieties suggested that a parallel-displaced arrangement is responsible for the excimer emission observed experimentally, although some other associations, such as T-shape dimer structures, which do not provide excimer emission, can still be relatively abundant at this surface concentration. The hydrophobic 1MN molecules, deposited on the ice surface, which is covered by a relatively flexible quasi-liquid layer at 238 K, are then assumed to be capable of dynamic motion resulting in the formation of energetically preferred associations to some extent. The environmental implications of organic compounds' deposition on snow grains and ice are discussed.
TL;DR: Intramolecular excimer formation with 1,5-bis(1-pyrenylcarboxy)pentane, (1PC(5)1PC) is studied as a function of temperature in a series of alkane solvents and in toluene, covering a wide range of solvent viscosities η, from 0.2 to 125 cP.
Abstract: Intramolecular excimer formation with 1,5-bis(1-pyrenylcarboxy)pentane, (1PC(5)1PC) is studied as a function of temperature in a series of alkane solvents and in toluene, covering a wide range of s...
TL;DR: Time-resolved fluorescence was applied to characterize the behavior in solution of a gemini surfactant substituted with pyrene, and it was found that the pyrene excimer is formed mostly by diffusion within the Py-3-12 micelles, which suggests that thepyrene microenvironment is fluid, an important feature for future studies on the interactions of Py- 3-12 with DNA.
Abstract: Time-resolved fluorescence was applied to characterize the behavior in solution of a gemini surfactant substituted with pyrene (Py-3-12). Upon association in water, excimer formation by Py-3-12 can be probed by acquiring pyrene monomer and excimer fluorescence decays which can be fitted globally according to the model free (MF) analysis to yield quantitative information about the internal dynamics of the Py-3-12 surfactant micelles as well as a complete description of the distribution of the different pyrene species in solution either incorporated inside the micelles or free in solution. A proof of procedure for the MF analysis was established by noting that the concentrations of free surfactant in solution, [Py-3-12]free, was found to equal the critical micelle concentration (CMC) for surfactant concentrations larger than the CMC. (IE/IM)SPC, the ratio of pyrene monomer to excimer fluorescence intensities, was calculated from parameters retrieved from the MF analysis of the fluorescence decays and was fo...
TL;DR: The fluorescence properties of two bis(1,8-naphthalimides) with amino-containing spacers are investigated, giving special emphasis to the observation of excimer emission, and the occurrence of homo-Förster resonance energy transfer is established by fluorescence polarization measurements and calculation of the corresponding critical Förster radius.
Abstract: The fluorescence properties of two bis(1,8-naphthalimides) with amino-containing spacers are investigated, giving special emphasis to the observation of excimer emission. It is found that a minor elongation of the spacer by two methylene units gives rise to a quantitative shut-down of the broad and red-shifted excimer emission. Furthermore, a switching of this emission is established through manipulation of a photoinduced electron transfer process, which involves the amino spacer. Protons as well as protic solvents lead to substantial excimer emission with lifetimes of 12 to 27 ns. The excimer quantum yield takes a maximum value of Φ(f) = 0.07 (acetonitrile with 1 equiv trifluoroacetic acid). The increased virtual Stokes shifts (ca. 150 nm) as compared to the fluorescence of monomeric 1,8-naphthalimides are an alternative approach to obtain colored, significant, and long-lived fluorescence from these chromophores. As an additional excited state pathway, the occurrence of homo-Forster resonance energy transfer (homo-FRET) is established by fluorescence polarization measurements and calculation of the corresponding critical Forster radius (R(0) ca. 13 A). The average interchromophore distance between the naphthalimides is estimated as 7.5 A and 9.5 A for the dyad with the shorter and the longer spacer, respectively. These observations and the absence of a rise time component for excimer emission are in agreement with the formation of a "loose" ground state dimer, which upon excitation undergoes a fast geometrical adjustment to the excimer structure where the chromophores are at contact distance.
TL;DR: In this article, a pair of supramolecular pseudo-isomers, namely, (Cu3I3)(Cu3L3)2·H2O (1) and (Cu 3Pz3)(Pz = pyrazolate), were reported, which incorporate the same or different copper(I)-cluster-based luminophores.
Abstract: Reported herein are a pair of supramolecular pseudo-isomers, namely, (Cu3I3)(Cu3L3)2·H2O (1) and (Cu3I3)(Cu3L3)2 (2) (L = 3-(4-pyridyl)-5-isobutyl-pyrazolate), both of which incorporate Cu3Pz3 (Pz = pyrazolate) and Cu3I3 clusters as luminophores. The two complexes show distinct yellow (570 nm) and orange (638 nm) emissions, which are ascribed to the formation of the excimer and exciplex involving the same or different copper(I)-cluster-based luminophores.
TL;DR: In this article, a dipyrene ligand was designed which shows intramolecular excimer formation in solution and its specific interaction with Cu 2+ or Hg 2+ leads to the disruption of the excimer and results in a fluorescence-mediated sensing of these ions in a mixed organic-aqueous solution.
TL;DR: The results support the conclusions of a previous investigation proposing that pressure-induced reactivity of pyridine is limited to crystal defects and agrees with the present knowledge of the solid-state chemistry of aromatic crystals.
Abstract: Two-photon excitation profiles and fluorescence spectra have been measured as a function of pressure in a diamond anvil cell up to 15.5 GPa in crystal phases I and II and in the glassy form of pyridine. The fluorescence emission intensity increases by about 6 orders of magnitude in going from the liquid to the crystalline phases at 3 GPa and further increases with pressure. This is explained by an energy inversion of the lowest 1B1 (nπ*) and 1B2 (ππ*) excited states likely due to the involvement of the lone pair of the N atom in intermolecular CH···N bonds. These interactions characterize the crystal phases and are stabilized by pressure. The glassy form, accordingly, is characterized by a much weaker fluorescence. Excimer emission is also observed. Comparison of the emission of several samples with different compression and annealing histories, the lack of reversibility in the excimer emission with decompression, and the larger relative intensity of the excimer band in the glassy form suggest that excime...
TL;DR: In this article, a series of pyrene-labeled polymers have been synthesized for optical recording, and the manipulation of polymer chain mobility, resulting in the control of intermolecular distance between pyrene molecules so as to produce static excimers useful for emission contrast formation, can be well defined.
Abstract: A series of pyrene-labeled polymers have been synthesized for optical recording. Through the manipulation of polymer chain mobility, resulting in the control of intermolecular distance between pyrene molecules so as to produce static excimers useful for emission contrast formation, the optical recording of PLPs can be well defined.
TL;DR: The excited state characteristics of phenylene (Ph)-bridged periodic mesoporous organosilica (PMO) powders with crystal-like and amorphous wall structures are investigated and the existence of excited states with various conformations including ground state dimers or aggregates of the Ph moieties was suggested.
Abstract: The excited state characteristics of phenylene (Ph)-bridged periodic mesoporous organosilica (PMO) powders with crystal-like and amorphous wall structures are investigated Crystal-like Ph–PMO has a molecular ordering of the bridging organic moieties with intervals of 076 and 044 nm parallel and perpendicular to the mesochannel direction, respectively, whereas amorphous Ph–PMO has no molecular-level periodicity in the wall Fluorescence from the exciton and excimer of the Ph moieties and the defect center in the silicate network were detected at room temperature, but fluorescence from the excimer and the defect center were not detected at 77 K for crystal-like Ph–PMO dispersed in a methanol/ethanol mixed solvent The decay curve of the exciton fluorescence of crystal-like Ph–PMO at room temperature was analyzed successfully using a one-dimensional diffusion model quenched by the defect center and the excimer site The results were discussed in comparison with those for the crystal-like biphenylene-bridged PMO reported in the preceding paper (Yamanaka et al, Phys Chem Chem Phys, 2010, 12, 11688–11696) The existence of excited states with various conformations including ground state dimers or aggregates of the Ph moieties was suggested for amorphous Ph–PMO It was clearly apparent that the differences in the excited state dynamics reflected the differences in the molecular-level structure in the wall
TL;DR: In this paper, the excitation of two π-stacked adenines by a 25-fs fwhm laser pulse was found to lead to the formation of a long-lived excimer, with an average C 2 − C 2 ) distance of 2.2
TL;DR: In this article, a chromatically stable white phosphorescent organic light-emitting diode using platinum [1,3-difluoro-4,6-di(2-pyridinyl)benzene]chloride (Pt-4) dye as the emitting layer, producing both light blue-monomer and red-excimer emission, is obtained.
Abstract: A chromatically stable white phosphorescent organic light-emitting diode using platinum [1,3-difluoro-4,6-di(2-pyridinyl)benzene]chloride (Pt-4) dye as the emitting layer, producing both light blue-monomer and red-excimer emission, is obtained. We have investigated both photoluminescence (PL) and electroluminescence (EL) of Pt-4 dye, which appear to be very different. Whereas the PL spectra reveal monomer and excimer peaks at around 480 nm and 610 nm, the 480 nm monomer and 660 nm excimer emission are characteristic of the EL spectra. It is shown that in contrast to PL, which is ascribed to an energy transfer process, EL emission can be explained by direct hole trapping, which is deduced from the energy levels of Pt-4 dye and 1, 3-bis(9-carbazolyl) benzene host and demonstrated by current density–voltage characteristics of various concentrations.
TL;DR: The first clear report of the observations of the excimer emission of anthracene in very low fluid solutions in which appropriate substituents were introduced was given in this paper, showing that these dendrimers could form aggregates under highly diluted conditions.
Abstract: We prepared water-soluble anthracene-cored poly(aryl ether) dendrimers wG1 and wG2 , together with lipophilic dendrimers G1 and G2 , and examined their photochemical properties. Water-soluble dendrimers wG1 and wG2 produced excimer emissions peaking at 463 nm and 447 nm, respectively, in water at a concentration of 10 −5 M, indicating that these dendrimers could form aggregates under highly diluted conditions. The results presented here are the first clear report of the observations of the excimer emission of anthracene in very low fluid solutions in which appropriate substituents were introduced.
TL;DR: In this paper, the time-resolved emission spectra (TRES) and area normalized emission spectras (TRANES) were exploited to characterize the excimers of poly(N-vinyl carbazole) (PNVC) in toluene and water.
TL;DR: In this paper, the surface change properties of the exposed fabrics were characterized by surface analysis methods such as wettability, atomic force microscopy, and X-ray photoelectron spectroscopy.
Abstract: Durable curcumin-treated antibacterial polyethylene terephthalate (PET) fabrics (against Staphylococcus aureus) were produced by dyeing with curcumin after surface activation using vacuum ultraviolet excimer lamp at 172 nm. Surface change properties of the exposed fabrics were characterized by surface analysis methods such as wettability, atomic force microscopy, and X-ray photoelectron spectroscopy. Results show an increase in surface hydrophilicity with a water contact angle of the PET fabric reaching 24° after 10 min excimer irradiation, which could be attributed to an increase in carboxyl group formation as confirmed by X-ray photoelectron spectroscopy measurements. Varying concentrations of curcumin were immobilized onto untreated and vacuum ultraviolet-irradiated PET samples using diffusion method at 90°C, and the treated fabrics characterized using K/S (color strength) values at 440 nm. K/S values increased when the PET surface was subjected to a prior excimer irradiation, because of grafting of curcumin at the PET surface. Increased excimer irradiation time increased grafting of curcumin because the inner fabric fiber surfaces were also more thoroughly treated. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
TL;DR: A dielectric barrier discharge excited neutral argon (Ar I) excimer lamp has been developed and characterised in this article, where the effects of discharge gas pressure, flow rate, excitation frequency and pulse width on the intensity of the Ar I vacuum ultraviolet (VUV) emission at 126 nm and near infrared (NIR) lines at 750.4 nm and 811.5 nm have been investigated.
Abstract: A dielectric barrier discharge excited neutral argon (Ar I) excimer lamp has been developed and characterised. The aim of this study was to develop an excimer lamp operating at atmospheric pressure that can replace mercury lamps and vacuum equipment used in the sterilisation of medical equipment and in the food industry. The effects of discharge gas pressure, flow rate, excitation frequency and pulse width on the intensity of the Ar I vacuum ultraviolet (VUV) emission at 126 nm and near infrared (NIR) lines at 750.4 nm and 811.5 nm have been investigated. These three lines were chosen as they represent emissions resulting from de-excitation of excimer states that emit energetic photons with an energy of 9.8 eV. We observed that the intensity of the VUV Ar 2 * excimer emission at 126 nm increased with increasing gas pressure, but decreased with increasing excitation pulse frequency and pulse width. In contrast, the intensities of the NIR lines decreased with increasing gas pressure and increased with increasing pulse frequency and pulse width. We have demonstrated that energetic VUV photons of 9.8 eV can be efficiently generated in a dielectric barrier discharge in Ar.
Patent•
30 Jul 2011
TL;DR: In this article, a serigraphic template is provided with areas (6a) permeable for excimer radiations and (6b) impermeable for the excimer radiation radiations.
Abstract: The method involves applying an UV lacquer coating (4) on a carrier substrate (1), and treating the coating in the substrate using an excimer radiator (7), where the radiator is formed with a serigraphic template (6) provided with areas (6a) permeable for excimer radiations and areas (6b) impermeable for the excimer radiations. The coating is illuminated by the template, where the template has a cylindrical net- or web-like frame that is sealed by an excimer radiation impermeable layer i.e. plastic layer. A cylinder made of quartz or magnesium fluoride is provided in the template.
TL;DR: It is suggested that pyrene-4-maleimide is an excellent probe to assess proximities between cysteines in proteins and thiols in other macromolecules, as well as to follow conformational changes.
Abstract: Pyrene-containing compounds are commonly used in a number of fluorescence-based applications because they can form excited-state dimers (excimers) by stacking interaction between excited-state and ground-state monomers. Their usefulness arises from the facts that excimer formation requires close proximity between the pyrenes and that the excimer emission spectrum is very different from that of the monomers. One of many applications is to assess proximity between specific sites of macromolecules labeled with pyrenes. This has been done using pyrene maleimide, a reagent that reacts with reduced thiols of cysteines, but its use for structural studies of proteins has been rather limited. This is because the introduction of two cysteines at sufficiently close distance from each other to obtain excimer fluorescence upon labeling with pyrene maleimide requires detailed knowledge of the protein structure or extensive site-directed mutagenesis trials. We synthesized and tested a new compound with a 4-carbon methylene linker placed between the maleimide and the pyrene (pyrene-4-maleimide), with the aim of increasing the sampling distance for excimer formation and making the use of excimer fluorescence simpler and more widespread. We tested the new compound on thiol-modified oligonucleotides and showed that it can detect proximity between thiols beyond the reach of pyrene maleimide. Based on its spectroscopic and chemical properties, we suggest that pyrene-4-maleimide is an excellent probe to assess proximities between cysteines in proteins and thiols in other macromolecules, as well as to follow conformational changes.
01 Jan 2011
TL;DR: In this article, a model of excimer laser-annealing of amorphous silicon layers which are irradiated with a pulsed KrF excimers laser is presented.
Abstract: This paper describes a one-dimen- sional model of excimer laser-annealing of amorphous silicon layers which are irradiated with a pulsed KrF excimer laser. For realisa- tion of the model in COMSOL Multiphysics, the application mode heat transfer in solids is used. The model predicts a melt threshold for the energy density of the laser of Eth = 88.5 mJ/cm 2 . It also predicts a linear increase of the melt duration with a slope of approximately ∂tm/∂E = 625 ns cm 2 J -1 and a decrease of the onset time to melt from ton = 28 ns down to some nanoseconds with en- hanced energy density of the laser. Concerning the melt depth, the simulations return a linear slope of ∂dm/∂E = 43 µm cm 2 J -1 with incre- asing energy density. All these results are in excellent agreement with the results of our experiments and therefore, the validity of our model is confirmed.
TL;DR: In this paper, a table-top electron-beam-sustained 2.45 GHz RF discharge in rare gases into a self-burning discharge has been observed for increasing RF amplitude.
Abstract: Transformation of a table-top electron-beam–sustained 2.45 GHz RF discharge in rare gases into a self-burning discharge has been observed for increasing RF amplitude. Thereby, the emission spectrum undergoes significant changes in a wide spectral range from the vacuum ultraviolet (VUV) to the near infrared. A strong increase of VUV excimer emission is observed for the self-burning discharge. The so-called first excimer continuum, in particular, shows a drastic increase in intensity. For argon this effect results in a brilliant light source emitting near the 105 nm short-wavelength cutoff of LiF windows. The appearance of a broad-band continuum in the UV and visible range as well as effects of RF excitation on the atomic line radiation and the so-called third excimer continuum are briefly described.