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Showing papers on "Excimer published in 2004"


Journal ArticleDOI
TL;DR: The ring flip of a carbohydrate is employed for the tongs-like movable component of a metal ion sensor that is selective for Zn(2+) and Cd(2+).

125 citations


Journal ArticleDOI
TL;DR: In this paper, the photophysical properties of tethered pyrene moieties in homogeneous solution were investigated and the effects of the tether length on photoexcited-state properties of the pyrene species according to a comparison of the results obtained in solution vs in solid-state polymer matrix.
Abstract: Single-walled (SWNTs) and multiple-walled carbon nanotubes (MWNTs) were functionalized with dendra of tethered pyrene species, where the tether length was varied. These functionalized carbon nanotube samples are soluble in common organic solvents, making it possible to characterize the samples and to investigate and compare the photophysical properties of the tethered pyrene moieties in homogeneous solution. In general, the pyrene monomer excited state is significantly quenched by two competing processes of “intramolecular” excimer formation and energy transfer to the nanotube. The excimer formation is dynamic in nature, and the excimer emission is also quenched by the energy transfer, contributing to the overall low fluorescence quantum yields and rapid fluorescence decays. There are effects of the tether length on photoexcited-state properties of the pyrene species according to a comparison of the results obtained in solution vs in solid-state polymer matrix. The structurally more flexible environment f...

76 citations


Journal ArticleDOI
Lining Gao1, Yu Fang1, Xiangpeng Wen1, Yuangang Li1, Daodao Hu1 
TL;DR: In this paper, a photo-induced luminescence film has been prepared by immobilizing pyrene on a quartz plate surface via a flexible long spacer, which shows combined monomer and excimer emission of pyrene both in wet and dry states, and the excimer may be formed mainly by direct excitation of ground state dimers and/or monomers in aggregates.
Abstract: A novel photoinduced luminescence film has been prepared by immobilizing pyrene on a quartz plate surface via a flexible long spacer. The film shows combined monomer and excimer emission of pyrene both in wet and dry states, and the excimer may be formed mainly by direct excitation of ground-state dimers and/or monomers in aggregates. Classical Birks' scheme plays a little role in the formation of the excimers. The emission of the film is sensitive to the presence of dicarboxylic acids, including ethanedioic acid, malonic acid, succinic acid, etc. The emission in the monomer and excimer region increases with addition of the acids. The time needed for the emission to reach equilibrium depends on the nature of the acids. It has been shown that the longer the chains of the acids, the more time is needed. This observation is explained by considering the conformational reorganization of the immobilized pyrene due to insertion of the dicarboxylic acids into the space between neighboring spacers. Experimental re...

75 citations


Journal Article
TL;DR: The excimer lasers are a group of lasers that have found wide application in a variety of medical fields including dermatology, cardiology, ophthalmology, and orthopedics, and of particular interest to dermatology.
Abstract: The excimer lasers are a group of lasers that have found wide application in a variety of medical fields including dermatology, cardiology, ophthalmology, and orthopedics. The word excimer refers to excited dimer. These lasers operate in the ultraviolet range, and examples include the 193 nm argon-fluroide, 248 nm krypton-fluoride, 351 nm xenon-fluoride, and of particular interest to dermatology, the 308 nm xenon-chloride. These lasers utilize a mixture of a noble gas and a halogen as a lasing material. They were first used in medicine for their ability to produce cold tissue ablation, but more recently have been used in dermatology as a method of non-ablative phototherapy.

71 citations


Journal ArticleDOI
TL;DR: In this article, the temporal behavior of a mono-filamentary dielectric barrier discharge in pure argon, from 100 to 700 Torr, was studied, with a sinusoidal voltage supply, its frequency ranging from 10 to 90 kHz.
Abstract: The experimental work reported here is devoted to the temporal behaviour of a mono-filamentary dielectric barrier discharge in pure argon, from 100 to 700 Torr A sinusoidal voltage supply is used, its frequency ranging from 10 to 90 kHz An anode avalanche followed by a cathode streamer as well as the spatial stability of the micro-discharge is clearly seen in successive 3-ns snapshots in the visible range Near the cathode, its diameter is about 02 mm, at 400 Torr The electrical characteristics of the discharge are also evaluated, in particular the breakdown voltage and the energy deposited in the micro-discharge The light output in the vacuum ultraviolet range is essentially due to the second continuum of argon, centred at 130 nm The kinetic study of this continuum shows that primary excitation of the lowest argon atomic 4s and 4s' states is practically achieved after 120 ns since beyond that time the luminescence decay of the second continuum is fairly described by only two exponential terms So collisions between excited states, electronic collisions, and recombination of ionic species do not contribute significantly to this luminescence, after 120 ns Surprisingly, we do not observe the contribution of the Ar(3P1) resonant state in the production of the argon excimers The radiative lifetime of the Ar2[1u(3P2)]low v excimer ((318 ± 003) µs) and the three-body rate constant relative to the decay of the Ar(3P2) metastable state ((132 ± 09) Torr−2 s−1) leading to the formation of Ar2[1u(3P2)], are estimated These results are consistent with those found from the literature A simple kinetic scheme is proposed for times later than 120 ns

56 citations


Journal ArticleDOI
15 Oct 2004
TL;DR: ESR spectra of 5-doxylstearic acid (5-DSA) showed that the probe location is restricted at SDS concentrations above the cmc, and that the Probe also is highly restricted in motion for BSA-bound SDS micelles.
Abstract: Interactions and characteristics of 0.1% bovine serum albumin (BSA)-sodium dodecyl sulfate (SDS) in 20 mM phosphate buffer solution were investigated by means of fluorescence spectroscopy and electron spin resonance (ESR) spectroscopy. In BSA-SDS system, the intensity ratio, Im3/Im1, of the third vibronic band of the pyrene monomer to the first vibronic band showed a small peak at about 0.1 mM SDS in the phosphate buffer below cmc. In accordance with this Im3/Im1 ratio, the intensity ratio, Ie/Im1, of fluorescence from the pyrene excimer to that from the monomer showed a pseudo-plateau (0.08-0.8 mM) and suggested the existence of micelle-like aggregates below the cmc. Temperature dependence of ln(Ie/Im1) in pyrene fluorescence in the SDS-BSA system was examined as a function of SDS concentration. The activation energy of pyrene diffusion for excimer formation in a micelle was estimated to be 19.2 kJ mol(-1) for the BSA-SDS system. ESR spectra of 5-doxylstearic acid (5-DSA) showed that the probe location is restricted at SDS concentrations above the cmc, and that the probe also is highly restricted in motion for BSA-bound SDS micelles.

49 citations


Journal ArticleDOI
TL;DR: In this article, the excimer emission from direct current glow discharges between a planar cathode and a ring-shaped anode of 0.75 and 1.5 mm diameter, respectively, separated by a gap of 250 μm.
Abstract: The excimer emission from direct current glow discharges between a planar cathode and a ring-shaped anode of 0.75 and 1.5 mm diameter, respectively, separated by a gap of 250 μm, was studied in xenon and argon in a pressure range from 75 to 760 Torr. The thickness of the “cathode boundary layer” plasma, in the 100 μm range, and a discharge sustaining voltage of approximately 200 V, indicates that the discharge is restricted to the cathode fall and the negative glow. The radiant excimer emittance at 172 nm increases with pressure and reaches a value of 4 W/cm2 for atmospheric pressure operation in xenon. The maximum internal efficiency, however, decreases with pressure having highest values of 5% for 75 Torr operation. When the discharge current is reduced below a critical value, the discharge in xenon changes from an abnormal glow into a mode showing self-organization of the plasma. Also, the excimer spectrum changes from one with about equal contributions from the first and second continuum to one that i...

45 citations


Journal ArticleDOI
TL;DR: In this paper, the stability constants of the macrocyclic phenanthrolinophane 2,9-[2,5,8-triaza-5-(N-anthracene-9-methylamino)ethyl]-[9]-1,10-phenanthropoietinophane (L) bearing a pendant arm containing a coordinating amine and an anthracene group were determined in 0.10 mol dm−3 NMe4Cl H2O-MeCN (1 ∶ 1, v/v) solution at
Abstract: The macrocyclic phenanthrolinophane 2,9-[2,5,8-triaza-5-(N-anthracene-9-methylamino)ethyl]-[9]-1,10-phenanthrolinophane (L) bearing a pendant arm containing a coordinating amine and an anthracene group forms stable complexes with Zn(II), Cd(II) and Hg(II) in solution. Stability constants of these complexes were determined in 0.10 mol dm−3 NMe4Cl H2O–MeCN (1 ∶ 1, v/v) solution at 298.1 ± 0.1 K by means of potentiometric (pH metric) titration. The fluorescence emission properties of these complexes were studied in this solvent. For the Zn(II) complex, steady-state and time-resolved fluorescence studies were performed in ethanol solution and in the solid state. In solution, intramolecular π-stacking interaction between phenanthroline and anthracene in the ground state and exciplex emission in the excited state were observed. From the temperature dependence of the photostationary ratio (IExc/IM), the activation energy for the exciplex formation (Ea) and the binding energy of the exciplex (−ΔH) were determined. The crystal structure of the [ZnLBr](ClO4)·H2O compound was resolved, showing that in the solid state both intra- and inter-molecular π-stacking interactions are present. Such interactions were also evidenced by UV-vis absorption and emission spectra in the solid state. The absorption spectrum of a thin film of the solid complex is red-shifted compared with the solution spectra, whereas its emission spectrum reveals the unique featureless exciplex band, blue shifted compared with the solution. In conjunction with X-ray data the solid-state data was interpreted as being due to a new exciplex where no π-stacking (full overlap of the π-electron cloud of the two chromophores – anthracene and phenanthroline) is observed. L is a fluorescent chemosensor able to signal Zn(II) in presence of Cd(II) and Hg(II), since the last two metal ions do not give rise either to the formation of π-stacking complexes or to exciplex emission in solution.

45 citations


Journal ArticleDOI
TL;DR: In this article, the crystal structures and spectral-luminescence properties of anisoylbenzoylmethanatoboron difluoride (1) and dianisoylsoyl-methane-naphthane (DMD) were studied in the solid state and in solution, and the structural features of compounds 1 and 2 are responsible for the occurrence of a new type of excimers in solutions.
Abstract: The crystal structures and spectral-luminescence properties of anisoylbenzoylmethanatoboron difluoride (1) and dianisoylmethanatoboron difluoride (2) were studied in the solid state and in solution. The structural features of compounds 1 and 2 are responsible for the occurrence of a new type of excimers in solutions, which differs from that observed in the crystalline state.

44 citations


Journal ArticleDOI
TL;DR: Iradiation of 5,12-didecyloxytetracene leads to photodimers P(1) (planosymmetric) and P(2) (centrosymmetric) which are characterized by naphthalene excimer fluorescence, whereas P( 2) emits naphthaene monomer fluorescence.

40 citations


Journal ArticleDOI
TL;DR: The absorption and fluorescence spectral characteristics of dibenzofuran-2-carboxylic acid (DBFCA) have been studied in aqueous solutions and in several organic solvents.
Abstract: The absorption and fluorescence spectral characteristics of dibenzofuran-2-carboxylic acid (DBFCA) have been studied in aqueous solutions and in several organic solvents. The fluorescence emission is structured both at basic pH and in nonaqueous media, whereas at acidic pH it is broad and largely Stokes-shifted. The red-shifted emission emerges solely as a consequence of an intramolecular charge-transfer (ICT) state, stabilized by hydrogen bonding with the solvent, and is not due to changes in the molecular structure upon excitation, to excimer emission, or to any other multimolecular processes. The pK's in the ground and first electronic excited states are pK = 4.19 and pK* = 8.5, as calculated by the Forster cycle from the absorptometric and fluorimetric data. DBFCA forms inclusion complexes with α-, β-, and γ-cyclodextrins (CDs), with the spectral behavior being very dependent on the type of CD and pH. At alkaline pH, only the β- and γ-CDs form complexes, with a 1:1 stoichiometry. 1 H NMR spectra point to the most likely structure of the complex in solution, with the carboxylate group located at the narrower end of the CD. The observed fluorescence quenching is static in nature, as deduced from the temperature dependence of the emission and from the absorption spectra. The decrease in fluorescence has been used to assess the formation constants by nonlinear regression analysis, and from their dependence on the temperature, the thermodynamic parameters of the binding, enthalpy, and entropy have been deduced. At acidic pH, fluorescence enhancement occurs with α-and β-CDs, and DBFCA forms complexes more stable than those at alkaline conditions with all the CDs. γ-CD induces the formation of an excimer of 2:1 stoichiometry, DBFCA 2 :γ-CD. The effect of the -COOH group on the stability is analyzed by comparing the DBFCA complexes with those formed with the nonsubstituted dibenzofuran (DBF).

Journal ArticleDOI
TL;DR: The results from these two simple systems clearly demonstrate that the radical ion annihilation pathway of ECL can generate different emissive states than those formed following photoexcitation.
Abstract: Electrogenerated chemiluminescence (ECL) arising from the reaction of radical ions has previously be shown to arise from a variety of states including excited singlets, triplets, excimers, and exciplexes. In this work we describe two systems that form emissive states in ECL with different properties than those when formed with photoluminescence. The first system involves the reaction of the anthracene radical anion with the radical cation of 4,N,N-trimethylaniline. ECL from this system exhibited an exciplex whose energy and intensity relative to the emission from the anthracene singlet could be tuned by adjusting the solvent permittivity and ionic strength. Under conditions considered extreme for electrochemical experiments, no added electrolyte in dimethoxyethane, the relative intensity of the anthracene-related exciplex, formed from the encounter complex, was 8 times greater and red-shifted from that generated by photoluminescence in the same solution with 100-fold exciplex partner added. In the second system examined, the benzophenone radical anion reacted with the radical cation of either phenoxathiin or 4-methoxythioanisole; the ECL emission was from the benzophenone triplet state and an excimer. The excimer, a species not seen with photoluminescence, predominated as the benzophenone concentration was elevated into the low millimolar range. The results from these two simple systems clearly demonstrate that the radical ion annihilation pathway of ECL can generate different emissive states than those formed following photoexcitation.

Journal ArticleDOI
TL;DR: Oligodeoxyribonucleotides carrying multi-pyrene clusters were chemically prepared by introducing a novel nucleoside–pyrene conjugate into ODNs and the excimer fluorescence of the arrays was stable and was not quenched by duplex formation.

Journal ArticleDOI
TL;DR: A pyrene functional fluoroionophore was used to construct a supramolecular 1 /γ-CD complex for detection of Cu 2+ in water as discussed by the authors, and the response characteristics of the complex were used for the determination of the Cu 2 + concentration in water.

Journal ArticleDOI
19 Apr 2004
TL;DR: In this paper, the triplet excited structures of Cu(II) octaethylporphyrin (CuOEP) in toluene and in 1:1 mixture of tetrahydrofuran (THF) were investigated by time-domain laser pulse pump, X-ray pulse probe Xray absorption spectroscopy (pump-probe XAS) using X-rays from a third generation synchrotron source with 100-ps time resolution.
Abstract: The triplet excited structures of Cu(II) octaethylporphyrin (CuOEP) in toluene and in 1:1 mixture of toluene and tetrahydrofuran (THF) were investigated by time-domain laser pulse pump, X-ray pulse probe X-ray absorption spectroscopy (pump–probe XAS) at room temperature using X-rays from a third generation synchrotron source with 100-ps time resolution. The transient optical absorption measurements indicate a strong solvent dependency of the triplet excited state lifetime due to the presence of oxygen-containing solvent molecules. While the ground state CuOEP molecules remain square-planar in both solvents, the attenuation of a peak attributed to the 1s → 4p z transition at the Cu K-edge for the laser excited CuOEP in the THF/toluene mixture revealed the penta-coordinated exciplex formation which is responsible for the shortening of the triplet excited state lifetime. Meanwhile, the average Cu–N distance in the triplet excited state is lengthened by 0.03 A due to ligation with a THF solvent molecule, which agrees with a domed coordination structure for copper in the penta-coordinated exciplex.

Journal ArticleDOI
TL;DR: The dimer and excimer formation mechanisms of anthracene in NaY zeolitic nanocavities have been studied by using various spectroscopic techniques of 129Xe NMR, diffuse reflectance, and emission as well as time-resolved fluorescence as mentioned in this paper.
Abstract: The dimer and the excimer formation mechanisms of anthracene in NaY zeolitic nanocavities have been studied by using various spectroscopic techniques of 129Xe NMR, diffuse reflectance, and emission as well as time-resolved fluorescence. Two anthracene molecules adsorb concertedly into a zeolitic supercage to form a ground-state stable dimer. An excited monomer in a singly occupied supercage gives birth to an excimer if another monomer exists in a tetrahedrally connected nearest supercage. An excited monomer forms a nonluminescent ion pair with a monomer in a nearest supercage by transferring an electron within 100 ps. The dark intermediate rearranges to transform into an excimer on the time scale of 400 ps.

Journal ArticleDOI
TL;DR: For example, 1,2-Bis(1,10-phenanthrolin-2-yl)ethylenediamine (1) exhibited a unique long-life time excimer fluorescence at 528 nm by binding with calf thymus DNA as mentioned in this paper.

Journal ArticleDOI
01 May 2004-Polymer
TL;DR: Aqueous solutions of poly(methacrylic acid)- b -polydimethylsiloxane copolymer (PMA- b -PDMS), and reference solutions of PMA homopolymer, were studied as a function of pH using fluorescent probes: pyrene (P) and 1,3-bis(1-pyrenyl)propane (P3P).

Journal ArticleDOI
TL;DR: Thermal characterization of these systems showed that an increase in the temperature resulted in changes in the properties of excimer fluorescence, an occurrence attributed to a higher mobility of the otherwise glassy PDLLA.

Journal ArticleDOI
TL;DR: A matter-wave amplifier for vibrational ground-state molecules which uses a Feshbach resonance to first form quasibound molecules starting from an atomic Bose-Einstein condensate and amplification of ground state molecules is achieved by using a strongly damped cavity mode for the transition from the electronically excited molecules to the molecular ground state.
Abstract: We describe a matter-wave amplifier for vibrational ground-state molecules which uses a Feshbach resonance to first form quasibound molecules starting from an atomic Bose-Einstein condensate. The quasibound molecules are then driven into their stable vibrational ground state via a two-photon Raman transition inside an optical cavity. The transition from the quasibound state to the electronically excited state is driven by a classical field. Amplification of ground state molecules is then achieved by using a strongly damped cavity mode for the transition from the electronically excited molecules to the molecular ground state.

Journal ArticleDOI
TL;DR: It is shown that a few coumarin dye solutions exhibit dual amplified spontaneous emission (ASE) spectra under pulsed laser excitation, though all these solutions exhibit only one fluorescence band under steady-state conditions.

Journal ArticleDOI
TL;DR: In this article, the photophysical properties of two derivatives of N-(β-methylnaphthalene) aza-crown systems having different cavity dimensions were investigated and the cavity size is found to have a pronounced effect on exciplex formation as well as energy transfer in the systems at room temperature and low temperature.

Journal ArticleDOI
TL;DR: In this article, the self-assembled monolayers (SAMs) of CH3−(CH2)17−Si(OMe)3 (1), HS−( CH2)10−Si (OEt)3(2), and NC−(Ch2)11− Si(OEt)-3 (3) were used for surface modification of 4-cyano-4-pentylbiphenyl (5CB) films.
Abstract: Polymer-dispersed liquid crystal (PDLC) films of 4-cyano-4‘-pentylbiphenyl (5CB) were fabricated between two quartz substrates, the surfaces of which had been modified with the self-assembled monolayers (SAMs) of CH3−(CH2)17−Si(OMe)3 (1), HS−(CH2)10−Si(OEt)3 (2), and NC−(CH2)11−Si(OEt)3 (3). The SAM-modification effects on the molecular aggregation of 5CB were investigated by steady-state and time-resolved fluorescence analysis for the PDLC films. Remarkably, it was found that selective excitation of the interface layer with the substrate surface gave both the monomer and excimer emissions of 5CB in relative intensities, depending on the chemical nature of the SAM surfaces. While the monomer and excimer emissions appeared in comparative intensities in the case of the unmodified quartz surface, the surface modification with the SAM of 1 resulted in a dominant contribution of the excimer emission. By contrast, the monomer emission was much stronger than the excimer emission in the case of the surface modifi...

Journal ArticleDOI
TL;DR: In this paper, a series of acenaphthyl-containing compounds comprising dimers, higher oligomers, and a poly(acenAPHthylene) (PAcN) homopolymer were investigated for excimer formation in solution.
Abstract: Excimer (excited state dimer) formation mechanisms in solution have been investigated for a series of acenaphthyl-containing compounds comprising dimers, higher oligomers, and a poly(acenaphthylene) (PAcN) homopolymer Excimer fluorescence is observed only for dimers with a threo-diisotactic arrangement of the acenaphthyl groups indicating that interactions between nearest-neighbour chromophores are able to play a role in excimer formation in PAcN An increase in excimer emission is observed with increasing chain length and attributed to additional excimer formation and energy migration processes

Journal ArticleDOI
TL;DR: In this article, the relative emission intensity of the Ne resonance lines and the Ne 2 ∗ excimer continua in pure neon were studied as a function of pressure, rf power, and gas flow rate.

Journal ArticleDOI
TL;DR: In this paper, pyrene excimer emission in alkali-metal-exchanged zeolites is readily observed to grow in using an ultrafast streak camera with 3.3 ps time-resolution.
Abstract: Pyrene excimer emission in alkali-metal-exchanged zeolites is readily observed to grow in using an ultrafast streak camera with 3.3 ps time-resolution. Rise-time constants range from 7 to 14 ps depending on the composition of the zeolite. These results show that two pyrene molecules in doubly occupied cavities must move from their pre-excitation orientation into the face-to-face orientation required for the excimer.

Journal ArticleDOI
TL;DR: In this article, it is shown that the formation of molecular centers of the nature of highly excited diatomic excimer molecules in clusters in the process of self-trapping of high-energy p excitons (n=1) is the main stages of this mechanism, followed by nonradiative dissociation of these molecules to excited atoms and atoms in the ground state with large kinetic energies.
Abstract: New channels of desorption of excited atoms and molecules from clusters of argon, krypton, and xenon under electron bombardment are found by the method of vacuum ultraviolet emission spectroscopy. The maximum yield of particles is registered in the interval of average sizes of 50–100 atoms/cluster. The regularities and features of the desorption of excited particles are revealed, making it possible to establish a new desorption mechanism called nonradiative excimeric dissociation. It is shown that the main stages of this mechanism are: the formation of molecular centers of the nature of highly excited diatomic excimer molecules in clusters in the process of self-trapping of high-energy p excitons (n=1); the nonradiative dissociation of these molecules to excited atoms and atoms in the ground state with large kinetic energies. It is established that the appearance of new channels of desorption of excited atoms and molecules from clusters under bombardment by electrons is due to features of the physical pro...

Journal ArticleDOI
TL;DR: The fluorescence spectra of the intramolecular electron transfer compound, N-(1-pyrenylmethyl)-N-methyl-4-methoxyniline (Py-Am), have been studied at different pressures as mentioned in this paper.
Abstract: The fluorescence spectra of the intramolecular electron-transfer compound, N-(1-pyrenylmethyl)-N-methyl-4-methoxyniline (Py-Am), have been studied at different pressures There are three emitting species in the excited molecules of Py-Am for the neat sample, local excited state of pyrene group for monomer emission, intermolecular exciplex, and intramolecular exciplex The exciplexes are difficult to characterize at ambient pressure Pressure tuning for the electronic states shows its powerful ability to distinguish the different properties of the states Under the effect of pressure, the intermolecular and intramolecular exciplexes are observed clearly with different tendencies to change their emission intensity at significantly different wavelengths

Journal ArticleDOI
TL;DR: A photo-induced luminescence film has been prepared by immobilizing pyrene on quartz plate surface via a flexible long spacer, 1,3-diaminopropane and 3-glycidoxypropyl trimethoxysilane as mentioned in this paper.
Abstract: A novel photo-induced luminescence film has been prepared by immobilizing pyrene on quartz plate surface via a flexible long spacer, 1,3-diaminopropane and 3-glycidoxypropyl trimethoxysilane. The film shows combined monomer and excimer emission of pyrene in both wet and dry states. Steady-state and time-resolved fluorescence emission measurements demonstrated that the excimer emission mainly came from direct excitation of ground state dimers, and/or monomers in aggregated state. Classical Birks’ scheme plays little role in the formation of the excimers. The structures of the excimers formed during the excitation are complex. Both “standard excimer” of sandwich-like fully overlapped structure and ‘distorted excimer” of partially overlapped structure exist in the excited state of the fluorophore. The emission of the film is sensitive to the presence of dicarboxylic acids, including ethanedioic acid, malonic acid, succinic acid, etc. The emission in the monomer and excimer region increases along with increasing the concentration of the dicarboxylic acids. The time needed for the emission to reach equilibrium depends on the nature of the acids. It has been shown that the longer the chain length of the acids, the more the time needed. This observation is explained by considering the conformational reorganization of the immobilized pyrene due to insertion of the dicarboxylic acids into the space between neighboring spacers. Experimental results from similar studies using formic acid and acetic acid are in support of this explanation. Furthermore, the response of the film to dicarboxylic acids is reversible.

Journal ArticleDOI
TL;DR: In this article, the structure of p-nitroaniline in the ground and first excited state were studied using ab initio quantum chemical methods and the calculated parameters were compared to available experimental data and the amino group nonplanarity was analyzed.
Abstract: The structure of p-nitroaniline in the ground and first excited state were studied using ab initio quantum chemical methods. The calculated parameters were compared to available experimental data and the amino group non-planarity was analyzed. The changes in geometry due to excitation from the ground to the excited state are also discussed.