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1.
Characterization of rhodamine 6G aggregates intercalated in solid thin films of laponite clay. 2 Fluorescence spectroscopy 总被引:2,自引:0,他引:2
Martínez Martínez V López Arbeloa F Bañuelos Prieto J López Arbeloa I 《The journal of physical chemistry. B》2005,109(15):7443-7450
The photoluminescence response of Rhodamine 6G (R6G) laser dye intercalated into solid thin films of Laponite (Lap) clay is studied as a function of dye loading. Fluorescence spectroscopy (steady-state and time-resolved techniques) was used to characterize the R6G species adsorbed into the solid films. For very diluted R6G loadings (=0.1% CEC, i.e., the percentage of the total cation exchange capacity of Lap) the fluorescence properties of R6G monomer were characterized, which presents an emission band centered at 548 nm, an average lifetime of 4.2 ns, and a fluorescence efficiency higher than that of the R6G monomer in liquid solution. By increasing the loading, dye molecules tend to self-aggregate, and different dimers are formed in moderate dye concentrations (in the 1-25% CEC range): oblique head-to tail J-type dimers, with weak emission bands at around 575 nm; and sandwich H-type dimers, as efficient quenchers of the fluorescent emission. Higher-order aggregates of R6G in Lap films are formed in high loading samples (>40% CEC), with a reminiscent fluorescence band at around 600 nm. 相似文献
2.
The J-aggregation capability of meso-ethylsubstituted thiacarbocyanine (Dye 1 and Dye 2) and oxacarbocyanine (Dye 3) dyes was studied in poly(vinyl alcohol) (PVA) and poly(vinylpyrrolidone) (PVP) films and aqueous solutions, as well as in water. In water, Dye 1 and Dye 3 form J aggregates and dimers, whereas Dye 2 occurs mainly in the dimer form. The addition of PVA to an aqueous solution leads to deaggregation of J aggregates of Dye 1 and Dye 3 and dimers of Dye 1, Dye 2, and Dye 3. Unlike PVA, PVP stimulates the J aggregation of Dye 1 in aqueous solution, with the J aggregate yield depending on the ratio between the PVP monomer unit and dye concentrations. The J aggregation of Dye 1 and Dye 3 takes place in PVA films, whereas the J aggregates of only Dye 1 are formed in PVP films. The photostability of Dye 1 J aggregates in aqueous solutions strongly depends on the spectral region of irradiation and the presence of atmospheric oxygen. The photostability is appreciably lower in aerated solutions and substantially increases in PVA films. 相似文献
3.
This letter reports a novel methodology for the synthesis of dye-containing nanocomposite thin films containing fluorescent rhodamine 6G (Rh6G) laser dye molecules. The nanocomposites are deposited in one step at room temperature in a downstream microwave plasma operating at low pressure and power. By controlling the plasma chemistry, it is possible to reduce the formation of dye dimers and higher aggregates that quench the fluorescence of the dye molecules. The films are intensely absorbent and fluorescent, insoluble in water, mechanically stable, and present good adhesion to the substrate. Besides, the method is compatible with the present silicon technology and therefore particularly interesting for the fabrication of integrated optoelectronic devices. 相似文献
4.
Determination of the dimerization constant of pinacyanol: role of the thermochromic effect 总被引:1,自引:0,他引:1
Sabaté R Estelrich J 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,70(2):471-476
Pinacyanol (PIN), as other cyanine dyes, has demonstrated a unique ability to form associates such as dimers, and H- and J-aggregates. This association is strongly favoured in water, and even at low dye concentrations, dimers and superior order aggregates are present. As a consequence, the determination of the dimerization constant involves sometimes a significant error when these aggregates are neglected. As an increase in temperature shifts the equilibrium among the different species towards the lowest order aggregates, we have obtained the spectra of PIN at several temperatures. By extrapolating some spectral characteristics at high temperatures, a spectrum of the dimer without any contribution of other aggregates was obtained. From this spectrum and that of the monomer, the dimerization constant was calculated, as well as the Gibbs energy change associated to the reaction. The enthalpy and entropy changes of the dimerization were determined from the dependence of the dimerization constants on the temperature. From these results it can be inferred that the driving force of the dimerization is of enthalpic origin. 相似文献
5.
Giaimo JM Lockard JV Sinks LE Scott AM Wilson TM Wasielewski MR 《The journal of physical chemistry. A》2008,112(11):2322-2330
Perylene-3,4:9,10-bis(dicarboximide) (PDI) and its derivatives are robust organic dyes that strongly absorb visible light and display a strong tendency to self-assemble into ordered aggregates, having significant interest as photoactive materials in a wide variety of organic electronics. To better understand the nature of the electronics states produced by photoexcitation of such aggregates, the photophysics of a series of covalent, cofacially oriented, pi-stacked dimers and trimers of PDI and 1,7-bis(3',5'-di-t-butylphenoxy)perylene-3,4:9,10-bis(dicarboximide) (PPDI) were characterized using both time-resolved absorption and fluorescence spectroscopy. The covalent linkage between the chromophores was accomplished using 9,9-dimethylxanthene spacers. Placing n-octyl groups on the imide nitrogen atoms at the end of the PDI chromophores not attached to the xanthene spacer results in PDI dimers having near optimal pi-stacking, leading to formation of a low-energy excimer-like state, while substituting the more sterically demanding 12-tricosanyl group on the imides causes deviations from the optimum that result in slower formation of an excimer-like excited state having somewhat higher energy. By comparison, PPDI dimers having terminal n-octyl imide groups have two isomers, whose photophysical properties depend on the ability of the phenoxy groups at the 1,7-positions to modify the pi stacking of the PPDI molecules. In general, disruption of optimal pi-stacking by steric interactions of the phenoxy side groups results in excimer-like states that are higher in energy. The corresponding lowest excited singlet states of the PDI and PPDI trimers are dimer-like in nature and suggest that structural distortions that accompany formation of the trimers are sufficient to confine the electronic interaction on two chromophores within these systems. This further suggests that it may be useful to build into oligomeric PDI and PPDI systems some degree of flexibility that allows the structural relaxations necessary to promote electronic interactions between multiple chromophores. 相似文献
6.
Langmuir-Blodgett (LB) films of some dichroic dyes, namely derivatives of naphthalenebicarboxylic acid and derivatives of naphthoylenebenzimidazole, and of their mixtures with mesogens: 4-octyl-4'-cyanobiphenyl or 4-pentyl-4'-cyano-p-terphenyl were prepared. Absorption and fluorescence studies using unpolarized and linearly polarized light were carried out. Both absorption and fluorescence spectra indicated the formation of aggregates of dye molecules in monomolecular layers. Moreover, it was found that dye molecules are more tilted to the quartz surface in LB films than to the plane of the air-water interface in Langmuir films. 相似文献
7.
Tani K Ito C Hanawa Y Uchida M Otaguro K Horiuchi H Hiratsuka H 《The journal of physical chemistry. B》2008,112(3):836-844
By use of electrostatic interactions of dye molecules and poly(diallyldimethylammonium chloride) (PDDA), the spin-coating technique has been successfully applied to the preparation of stable J-aggregate thin films of thiacarbocyanine dyes on a polycarbonate or quartz plate. The J-aggregate thin films were prepared by the spin-coating of PDDA aqueous solution on dye thin films prepared on a substrate by the spin-coating of 2,2,3,3-tetrafluoro-1-propanol solution of dyes. Photophysical properties of the dye thin films and J-aggregate thin films were studied by measuring the fluorescence spectra, quantum yields, and lifetimes. Coherent size of the J-aggregates was estimated to be 3-12 by means of the absorption bandwidth (full width at half maximum) or radiative lifetime. Photostability of the J-aggregate thin films was also studied in terms of photodegradation efficiency under argon and oxygen in comparison with the dye thin films, and J-aggregate thin films were found to be more stable than the corresponding dye thin films. 相似文献
8.
Daniel Siopa Ricardo Nunes Filomena Martins M. Soledade C. S. Santos Killian Lobato Anabela Gomes 《Journal of Solid State Electrochemistry》2018,22(9):2779-2787
Water plays an important role in N719 sensitization of ZnO films for application as photoanodes in DSC devices. The role of water content in ethanolic N719 sensitization solutions was examined resorting to N719-solvent interaction studies based on Kamlet-Taft solvatochromic parameters. Results show that as the water content increases, solvent’s HBA ability decreases, hindering dye aggregation in solution and increasing the fraction of dye carboxylic groups available for anchorage onto the charged ZnO surface. The impact of dye-dye-solvent equilibria in solution on ZnO nanorod films sensitization and device behavior was evaluated. Devices assembled with films sensitized in N719 solutions containing equal parts of ethanol and water showed a twofold increase in short-circuit current densities when compared to those sensitized in ethanol only, despite exhibiting significantly less stained films. Data indicate that the presence of water in the sensitization solution reduces the amount of dye aggregates in solution and on the ZnO surface. 相似文献
9.
Ray K Nakahara H Sakamoto A 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(1-2):103-107
The fluorescence lifetimes decays and picosecond time-resolved fluorescence spectra were measured to investigate the dynamics of the excited state of sulforhodamine B (SRB) molecules adsorbed in the mono- and multilayered Langmuir-Blodgett (LB) films of octadecylamine. Steady-state and time-resolved fluorescence spectroscopy reveals that the fluorescence lifetimes and contents of the monomer and dimers in the molecular organizates depend upon the concentration of the dye in the solution and the adsorption process. SRB dye molecules adsorbed in LB films have been imaged with scanning near-field optical microscopy (SNOM). This information is exploited to map the distribution with molecular spatial resolution. SNOM provide the visual evidence of the monomers and dimers of SRB in cationic LB films. 相似文献
10.
The photostability of J aggregates of the pseudoisocyanine dye in polyvinylpyrrolidone (PVP) and poly(vinyl alcohol) (PVA) polymer films under continuous irradiation with visible light was investigated. The decay of J aggregates in PVP is predominantly due to the reaction of photooxidation with singlet oxygen generated by triplet-state pseudoisocyanine dimers. Unlike the case of PVP, J aggregates in PVA demonstrate significantly higher photostability because of a lower PVP permeability for oxygen. A significant improvement in the photostability of J aggregates is achieved by the introduction of scavengers of singlet oxygen into the polymer films. 相似文献
11.
Electrophoretic deposition method has been developed for the deposition of TiO(2) nanoparticles modified with organic dyes. Alizarin red, alizarin yellow and pyrocatechol violet dyes were used for the dispersion and charging of TiO(2) in ethanol and anodic electrophoretic deposition of TiO(2) films. The deposition yield was varied by the variation of dye concentration in suspensions and deposition time. Aurintricarboxylic acid dye was used for the deposition of TiO(2) from aqueous suspensions. It was found that thin films of pure aurintricarboxylic acid and composite aurintricarboxylic acid TiO(2) films can be obtained. The deposition yield was studied by quartz crystal microbalance. Dye film thickness was varied in the range of 0.1-2 μm by variation in the deposition time at a constant voltage. The composition of the films and the amount of the deposited material can be varied by the variation of TiO(2) and dye concentration in suspensions and deposition time. The films were studied by Fourier transform infrared spectroscopy, thermogravimetric analysis, differential thermal analysis and electron microscopy. The deposition mechanisms were discussed. The electrophoretic deposition method offers advantages for the fabrication of dye-sensitized TiO(2) films. 相似文献
12.
Yaser Acikbas Cansu Özkaya Selahattin Bozkurt Rifat Çapan Matem Erdoğan Gamze D. Tetik 《高分子科学杂志,A辑:纯化学与应用化学》2019,56(9):845-853
Determination of organic vapor sensing properties of α-Naphthylmethacrylate (α-NMA) monomer based Langmuir-Blodgett (LB) thin films was aimed in this study. LB thin film fabrication was performed on quartz glass and quartz crystal substrates in order to investigate the characterization and organic vapor properties of α-NMA materials by using UV-Visible, Atomic Force Microscopy (AFM) and Quartz Crystal Microbalance (QCM) techniques. π-A isotherm graph was taken and a suitable surface pressure value were primarily determined as 13?mN m?1 for successful α-NMA LB thin film fabrication. Transfer ratio value was found to be ≥ 0.93 for quartz glass and quartz crystal substrates. The typical frequency shift per layer was obtained as 16.93?Hz/layer and the deposited mass onto a quartz crystal was calculated as 271.30?ng/layer (1.02?ng mm?2). The sensing responses of α-NMA LB films against dichloromethane, chloroform, toluene and m-xylene were measured by QCM system. Dichloromethane created the maximum shift in the resonance frequency than other organic vapors used in this study. Results exhibited that α-NMA LB thin films were potential candidates for organic vapor sensing applications, especially high sensitive detection of dichloromethane at room temperature. 相似文献
13.
Jin Wang Mitsuru Ueda Tomoya Higashihara 《Journal of polymer science. Part A, Polymer chemistry》2014,52(8):1139-1148
A series of all‐conjugated diblock and triblock copolymers comprised of poly(naphthalene diimide) (PNDI)‐based n‐type and the poly(3‐hexylthiophene) (P3HT) segments could be synthesized via the Kumada catalyst‐transfer polycondensation process. The crystalline structures and chain orientation of the block copolymer thin films were systematically studied by grazing incident wide‐angle X‐ray scattering (GIWAXS). The GIWAXS results indicated that both the P3HT and PNDI segments in the block copolymers form exclusive crystalline domains in which the P3HT domain aligns with an edge‐on rich orientation, and the PNDI domain aligns with a face‐on rich orientation. In contrast, the blend films of the P3HT and PNDI homopolymers also show two distinguished crystalline domains in which the P3HT domain aligns with an edge‐on rich orientation, and the PNDI domains align in different ways depending on the chemical structure of n‐type polymers, that is, PNDI1Th is isotropically dispersed, while PNDI2Th aligns with a face‐on rich orientation. In addition, the effect of thermal annealing on the crystalline behavior of the block copolymers is reported. The GIWAXS results indicated that thermal annealing increases the crystallinity of both segments without affecting their chain orientation. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1139–1148 相似文献
14.
Vogt BD Soles CL Lee HJ Lin EK Wu WL 《Langmuir : the ACS journal of surfaces and colloids》2004,20(4):1453-1458
Specular X-ray reflectivity (XR) and quartz crystal microbalance (QCM) measurements were used to determine the absorption of water into thin poly(4-ammonium styrenesulfonic acid) films from saturated vapor at 25 degrees C. The effect of film thickness on the absorption kinetics and overall absorption was investigated in the range of thickness from (3 to 200) nm. The equilibrium swelling of all the films irrespective of film thickness was (0.57+/-0.03) volume fraction. Although the equilibrium absorption is independent ofthickness, the absorption rate substantially decreases for film thickness < 100 nm. For the thinnest film (3 nm), there is a 5 orders of magnitude decrease in the diffusion coefficient for water. 相似文献
15.
Bhaskar. M. Murari Sneh. Anand Nivedita. K. Gohil Nabo. K. Chaudhury 《Journal of Sol-Gel Science and Technology》2007,41(2):147-155
The characterization of physicochemical properties of the internal environment of sol-gel thin films is required for understanding
and designing applications in optical biosensors. We have investigated the dip coated tetraethyl-orthosilicate (TEOS) derived
sol-gel thin films deposited on microscopic glass cover slips using molar ratio (water or ethanol / TEOS) R=32 using fluorescence spectroscopic measurements (emission, lifetime and anisotropy) on entrapped fluorescent probes. The
effect of water and/or ethanol was studied as a function of storage (60 days) using fluorescent probes Hoechst 33258 (H258)
and Pyranine (PY). Distribution of fluorescent probes in thin film was studied using confocal microscope. Emission maxima
of H258 entrapped thin films from sol prepared using water as solvent showed emission maximum at 503 nm indicating the presence
of water like environment which did not change during storage. On the contrary, PY entrapped thin films depicted emission
bands at 434 nm and 513 nm, characteristics of ethanol and water respectively, up to the first few weeks and then the band
at 434 nm prevailed (60 days), suggesting heterogeneous internal environment. Thin films from sol prepared using ethanol as
solvent showed presence of ethanol through out storage. Fluorescence lifetime data of these probes in both sol-gel and thin
films also suggested presence of heterogeneous internal environment. Thin films prepared from sol-gel using water as solvent
suggested release of ethanol in the pores during hydrolysis and condensation reaction, which were clearly indicated by PY.
The effect of sodium phosphate buffer was also studied in sol-gel and thin films. The results of these measurements showed
that both the probes H258 and PY could be used effectively in monitoring the physicochemical properties of internal environment
of thin films and sol-gel as a function of storage. 相似文献
16.
Klika Z Capková P Horáková P Valásková M Malý P Machán R Pospísil M 《Journal of colloid and interface science》2007,311(1):14-23
The distribution of various aggregates (dimers, trimers, and tetramers) of methylene blue (MB) formed in aqueous solution at various concentrations of dye has been calculated using the equilibrium aggregation constants betaq. Two montmorillonite samples with different cation exchange capacities, surface areas, and interlayer distances d001, Na-SWy, and Ca-Cheto, were saturated with methylene blue (MB) solutions with various ratios between monomers and higher aggregates of dye. The total amount of MB in the intercalated montmorillonite samples (MB-SWy and MB-Cheto) increases with increasing concentration of dye in water solutions, i.e., with increasing aggregates/monomers ratio of MB in water solution. In all intercalated montmorillonite samples with methylene blue except guest qth aggregate cations [MBqq+] low contents of Na+ (in MB-SWy) and Ca2+ (in MB-Cheto) cations were also determined. A very good positive correlation between the basal spacing d001 and the MB/montmorillonite molar ratio was revealed for saturated MB-montmorillonite samples. Structural analysis using a combination of diffraction data with molecular modeling revealed the differences in the interlayer arrangement of MB guests in MB-SWy and MB-Cheto intercalates. Also, fluorescence measurements showed the strong effect of the silicate layer charge on the spectroscopic behavior of MB guests intercalated in montmorillonite. Methylene blue exhibits a certain luminescence in MB-SWy samples with cation exchange capacity 0.80 meq g-1 and almost no luminescence in MB-Cheto samples with higher cation exchange capacity 1.50 meq g-1. 相似文献
17.
I. Yilgor E. Yilgor S. Das G. L. Wilkes 《Journal of Polymer Science.Polymer Physics》2009,47(5):471-483
Time‐dependent morphology development in segmented polyureas obtained by the stoichiometric reactions between amine terminated poly(tetramethylene oxide) (PTMO) and aromatic diisocyanates were investigated. Polyureas were prepared by reacting aminopropyl terminated PTMO oligomer (Mn = 1100 g/mol) and various aromatic diisocyanates, such as 1,4‐phenylene diisocyanate (PPDI), 1,3‐phenylene diisocyanate (MPDI), diphenylmethane diisocyanate (MDI), and tolylene diisocyanate (TDI). Time‐dependent FTIR studies were conducted on thin films cast onto KBr discs, which were annealed at 200 °C for 10 min in an air oven. After removing from the oven, samples were placed into the FTIR spectrometer at room temperature, where time‐dependent spectra were recorded until equilibrium was reached. Time‐dependent peak reorganization in 3500–3100 cm?1 (N? H region), 1750–1450 cm?1 (C?O region or amide I and amide II regions), and 1180–1020 cm?1 (C? O? C) were monitored. Depending on the chemical structure and the symmetry of the diisocyanate, major differences were observed in the time needed to reach an equilibrium morphology in these homologous poly(ether urea) copolymers. Symmetric PPDI‐based polyurea reached equilibrium in about 1 h compared with its asymmetric MPDI‐based counterpart, which needed about 150 h. Microphase development of the MPDI urea was also characterized by AFM, which gave similar results. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 471–483, 2009 相似文献
18.
Three perylenetetracarboxylic diimide (PDI) dimers linked with a conjugated chain of different lengths have been designed and prepared. The UV-Vis absorption and fluorescence spectra of these three dimers revealed different photophysical properties owing to the different length of the linkage. The intermolecular π-π interactions were found to be enhanced significantly with the increase in the length of the linkage and therefore induced different aggregation behaviors of these molecules. The structure of the molecular aggregates was investigated by X-ray diffraction (XRD), and the morphology of the aggregates was examined by atomic force microscopy (AFM). One-dimensional fibers were observed for the aggregates of compounds 2 and 3, and thin solid films were observed for the aggregates of compound 1. 相似文献
19.
This study reports the synthesis, characterization and gas sensing applications of N-cyclohexylmethacrylamide (NCMA) monomer material using FT-IR, 1H and 13C NMR, UV-visible spectroscopy, Quartz Crystal Microbalance (QCM) and Langmuir-Blodgett (LB) thin film deposition techniques. The thin film deposition conditions of NCMA monomer material, which are prepared by LB film technique, are characterized by UV-visible spectroscopy and QCM system. The sensing behaviors of the LB film with respect to volatile organic compounds (VOCs) at room temperature are investigated. Surface pressure change as a function of surface area of NCMA molecule at the water surface shows a well-organized and stable monolayer at 18 mN m?1 surface pressure value for LB film deposition. Transfer ratio values are found to be ≥ 0.94 for quartz glass and ≥ 0.93 for quartz crystal substrate. The typical frequency shift per layer is obtained 20.10 Hz/layer and the deposited mass onto a quartz crystal is calculated as 824.62 ng/layer. The sensing responses of the LB films against chloroform, dichloromethane, acetone, toluene, benzene and ethanol are measured by QCM system. The sensitivities of the NCMA LB film sensor are determined between 0.085 and 0.029 Hz ppm?1. Sensitivities with detection limits are between 35.29 and 100.33 ppm against organic vapors. These results can be concluded that the monomer LB film sample is found to be significantly more sensitive to chloroform and dichloromethane vapors than others organic vapors used in this work. This material may find potential applications in the development of room temperature organic vapor sensing. 相似文献
20.
Pereira RV Gehlen MH 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(13-14):2926-2932
The interaction of the cationic dyes acridine, 9-aminoacridine (9AA), and proflavine, with sodium dodecyl sulfate (SDS) was studied by electronic absorption, steady-state and time-resolved fluorescence spectroscopies. The dyes interact with SDS in the pre-micellar region leading in two cases to dimerization in dye-surfactant aggregates, but with distinct molecular arrangements. For proflavine, the observed red shift of the electronic absorption band indicates the presence of J-aggregate, which are nonfluorescent. In the case of 9AA, the aggregates were characterized as nonspecific (neither J- nor H-type is spectroscopically observed). The time-resolved emission spectra gives evidences of the presence of weakly bound dimers by the recovery of three defined decay times by global analysis: dye monomer (tau1 = 16.4 ns), dimer (tau2 = 7.1 ns), and a faster component (tau3 = 2.1 ns) ascribed to intracluster energy migration between monomer and dimer. Acridine has a weak interaction with SDS forming only an ion pair without further self-aggregation of the dye. 相似文献