Formation Of J-aggregates Research Articles

Concentration-Induced J-Aggregate Formation Causes a Biphasic Change in the Release of trans-Combretastatin A4 Disodium Phosphate from Archaeosomes and the Subsequent Cytotoxicity on Mammary Cancer Cells.

Combretastatin A4 disodium phosphate (CA4P) is a fluorescent, water-soluble prodrug able to induce vascular shutdown within tumors at doses less than one-tenth of the maximum tolerated dose. As a continued effort to develop efficient liposomal CA4P to treat solid tumor, we herein investigate the physical and spectroscopic properties of CA4P in aqueous solution and the mechanism of CA4P release from archaeal tetraether liposomes (archaeosomes). We found that cis-CA4P can be photoisomerized to trans-CA4P. This photoisomerization results in an increase in fluorescence intensity. Both cis- and trans-CA4P undergo fluorescence intensity self-quenching after they reach a critical concentration Cq (∼0.15-0.25 mM). Moreover, both cis- and trans-CA4P in buffer exhibit a red shift in their excitation spectrum and an increase in excitation spectrum band sharpness with increasing concentration, which can be attributed to the formation of J-aggregates. The onset of the dramatic change in excitation maximum occurs at concentrations close to Cq, suggesting that the self-quenching arises from extensive J-aggregate formation and that, when CA4P concentration exceeds Cq, J-aggregate formation begins to increase sharply. Our data also suggest that the extent of J-aggregate formation plays a critical role in CA4P release from tetraether archaeosomes and in the subsequent cytotoxicity on cultured human breast cancer MCF-7 cells. The drug leakage and cytotoxicity rate constants vary with the initial CA4P concentration entrapped inside archaeosomes in a biphasic manner, reaching a local maximum at 0.25-0.50 mM. A mechanism based on the concept of J-aggregate formation has been proposed to explain the biphasic changes in drug release and cytotoxicity with increasing drug concentration. Tetraether archaeosomes are extraordinarily stable and relatively nontoxic to animals; thus, they are promising nano drug carriers. The results obtained from this study pave the way for future development of archaeosomal CA4P to treat solid tumors.

Florescent silica PVA hybrids via sol–gel processing

A cost-effective, one-pot synthesis approach is reported to fabricate Rhodamine 6G (R6G) silica hybrid xerogels. Polyvinyl alcohol (PVA) is used as a non-ionic surfactant to homogeneously trap the dye in silica matrix. Presence of R6G in silica matrix is confirmed through Fourier Transform Infrared (FTIR) spectroscopy and Thermo Gravimetric Analysis (TGA) studies. Hybrids containing larger amount of PVA are found to exhibit better thermal stability than the hybrids with lesser PVA content. Optical properties of the hybrids are analyzed via UV–visible spectroscopy, and it is discovered that hybrids containing larger amounts of PVA do not form aggregates. Uniform distribution of fluorophores in silica matrix helps to minimize formation of J-aggregates in the hybrids, therefore making them ideal candidates for use in dye lasers. The resultant hybrids can be ascribed as stable multicomponent systems that exhibit excellent monodispersity and brightness.

Fluorescence-enhanced gels of D–π–A diphenylacrylonitrile derivatives: Influence of nitro group and alkoxy chain

4-nitrodiphenylacrylonitrile and diphenylacrylonitrile derivatives consisting of methoxy group and alkoxy chain with different lengths were synthesized and their gelation abilities were investigated. It was found that compounds with longer alkoxy chains and a nitro group could gelate some nonpolar and polar organic solvents. On the other hand, diphenylacrylonitrile derivatives without nitro group could not form gels in measured solvents, suggesting that the electron-withdrawing nitro moiety plays an important role in the gel formation. X-ray diffraction showed that gelator molecules stacked together with lamellar packing structures in the gel phases. More importantly, the gelators emitted very weak fluorescence in the solutions because of the twisted conformation in the isolated state. However, the gels had strong fluorescence owing to the suppression of molecular motion, molecular planarization and J-aggregate formation, implying gelation-induced emission enhancement.

Aggregation behavior of tetraphenylporphyrin in aqueous surfactant solutions: Chiral premicellar J-aggregate formation

Porphyrin-surfactant interactions in aqueous solutions are known to result in the selfassembly of various supramolecular structures, including pigment-surfactant complexes, J- and H-aggregates, and solubilized dye species. Detailed studies on the mechanisms of the intermolecular interactions governing the above self-assembly processes allow to predict the aggregation state and hence, the photophysical properties of the dye-surfactant assemblies in order to perform a direct synthesis of the desired porphyrin-based nanostructures at the appropriate experimental conditions. This paper describes a novel example of the surfactant-induced J-aggregate formation from the diprotonated hydrophobic tetraphenylporphyrin species in submicellar aqueous anionic surfactant solutions. The above assemblies are characterized by a rod-like morphology and possess supramolecular chirality according to the CD measurements.

Fluorescence tuning of 2D montmorillonite optically active layers with beta-cyclodextrine/dye supramolecular complexes

Montmorillonite 2D-optically active layers were investigated using non-ionic Coumarine and cationic Pyronine dyes. The modification of thin montmorillonite films (MF) was done by single dye species and/or with β-cyclodextrine (CD) supramolecular complexes (SC). Equilibrium constants for SC formation were determined in the range 0.1·103 −6.0·103 for temperatures 283–323K. Thus amounts of dye incorporated in the SC with CD prepared at temperature 293K is more than 96% for Coumarine and more than 81% for Pyronine dye. Adsorption of SC in MF was proved by detection of increased first basal reflections using X-ray diffraction. The molecular transition moments for monomeric dye species in 2D MF of SC for Pyronine absorbing at 560nm were inclined 60° and co-adsorbed dimers or higher aggregates of molecules tilted around 33° towards montmorillonite surface. Coumarine absorption in the whole investigated spectral range indicated average molecule inclination around 28°. The angle of the Coumarine dye is favourable for the formation of J-aggregates with sufficient fluorescence intensity detected at 478nm for solid state applications.

J-aggregate formation behavior of a cationic cyanine dye on inorganic layered material

Adsorption, aggregation, and photochemical behavior of a cationic cyanine dye (5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethylbenzimidazolylcarbo-cyanine chloride (JC-1)) on an inorganic layered material were examined. JC-1 formed J-aggregates on the clay surface even at a low loading level. The structure of the J-aggregate was determined through analysis using the extended dipole model proposed by Kuhn et al. Aggregation number and slip angle of the J-aggregate on the clay surface were calculated as more than 8 molecules and 20–22°, respectively. The J-aggregate on the clay sheet exhibited high fluorescence quantum yield (0.4), thus, this complex will be promising to construct photochemical reaction systems such as artificial light harvesting systems.

Aggregation state of amphiphilic cationic tetraphenylporphyrin derivatives in aqueous microheterogeneous systems

The conditions for the formation of ionic associates and J- and H-aggregates from amphiphilic cationic tetraphenylporphyrin derivatives in aqueous solutions of anionic surfactants and polyelectrolytes in a wide range of concentrations and pH are considered. The aggregation behaviors of tetraphenylporphyrin and its cationic derivatives in aqueous microheterogeneous systems are compared illustrating the influence of the porphyrin molecular structure on its ability to form supramolecular aggregates of a certain structure. The mechanism of the promoting action of premicellar solutions of anionic surfactants on the formation of J-aggregates of the diprotonated form of cationic porphyrins was proposed. The acid-base properties of a number of new synthetic meso-aryl-substituted porphyrins in aqueous microheterogeneous systems were characterized.

Interplay of monomers, dimers and J-aggregates of thiamonomethinecyanine dye with PEDOT and PSS in the dye–PEDOT:PSS composite system

Mutual influence of thiamonomethinecyanine dye and PEDOT:PSS in the dye–polymer composite solutions and films was studied. It was found that PSS tends to suppress formation of J-aggregates of the dye molecules in the solution, while there is a competition between sulfonic groups of dye and PSS for binding with the PEDOT backbone. Interaction of dye monomers with PEDOT:PSS at relatively small dye concentration in the composite film was found to suppress film conductivity, while dimerization of the dye molecules at higher concentration resumes conductivity of the composite film. Suppressed conductivity upon interaction of the dye and PEDOT backbone was explained by steric disparity of the distance between sulfonic groups of the dye molecule and the distance between positive sites of the planar PEDOT backbone which induces deformation of the latter.

Spectrophotometric observations of thiacyanine dye J-aggregation on citrate capped silver nanoparticles

AbstractThe J-aggregation of anionic cyanine dye, 5,5’ – disulfopropyl-3,3’ – dichloro - thiacyanine sodium salt (TC) in the presence of 2x10-3 M KCl and citrate capped silver nanoparticles (AgNPs, diameter ~10nm) was investigated. The influence of added salt (KCl), as well as AgNPs and TC concentration on the intensity of the absorption bands with the maxima at 464 and 481 nm, characteristic of the J-aggregation of the dye in solution and on AgNPs surface, respectively, was studied. The spectrophotometric and fluorescence spectra confirmed that AgNPs induced the decomposition of J-aggregates formed in solution on the account of their formation on NPs surface. The obtained results enabled the evaluation of number of TC molecules per AgNPs participating in J-aggregate formation. The experimental results yielded about 320 molecules of TC per AgNPs in at least three layers in a slanted orientation.

Fano resonance in a gold nanosphere with a J-aggregate coating.

We present a facile method to induce J-aggregate formation on gold nanospheres in colloidal solution using polyvinylsulfate. The nanoparticle J-aggregate complex results in an absorption spectrum with a split lineshape due to plasmon-exciton coupling, i.e. via the formation of upper and lower plexcitonic branches. The use of nanoparticles with different plasmon resonances alters the position of the upper plexcitonic band while the lower band remains at the same wavelength. This splitting is investigated theoretically, and shown analytically to arise from Fano resonance between the plasmon of the gold nanoparticles and exciton of the J-aggregates. A theoretical simulation of a J-aggregate coated and uncoated gold nanosphere produces an absorption spectrum that shows good agreement with the experimentally measured spectra.

The unprecedented J-aggregate formation of rhodamine moieties induced by 9-phenylanthracenyl substitution.

We report a substitution of 9-phenylanthracenyl group into rhodamine derivatives that can induce the J-aggregate formation of rhodamine moieties in the aqueous solution upon the addition of a halide ion. From X-ray crystallographic analysis, the dramatic red-shift in the absorption band (i.e. app. 100 nm) originates from the cooperative slipped-stacking of rhodamine and anthracene molecules.

Temperature and concentration dependence of J-aggregate of a cyanine dye in a Laponite film fabricated by Langmuir–Blodgett technique

In this communication, we report the temperature and concentration dependence of J-aggregate of a cyanine dye N,N′-dioctadecylthiacyanine perchlorate (NK) in the Laponite film fabricated by Langmuir–Blodgett technique. Surface pressure area per molecule isotherm revealed the formation of stable Langmuir monolayer at the air–water interface. Spectroscopic characterization confirmed the formation of J-aggregates in the NK LB film without Laponite. In the hybrid film, J-aggregate forms at lower Laponite concentration (1ppm), higher deposited surface pressure and at lower subphase temperature. Both the J-aggregated films were found to be optical second harmonic generation (SHG) active and mechanically very stable, although intrinsically NK is SHG inactive.

H- and J-aggregation of fluorene-based chromophores.

Understanding of H- and J-aggregation behaviors in fluorene-based polymers is significant both for determining the origin of various red-shifted emissions occurring in blue-emitting polyfluorenes and for developing polyfluorene-based device performance. In this contribution, we demonstrate a new theory of the H- and J-aggregation of polyfluorenes and oligofluorenes, and understand the influence of chromosphere aggregation on their photoluminescent properties. H- and J-aggregates are induced by a continuous increasing concentration of the oligofluorene or polyfluorene solution. A relaxed molecular configuration is simulated to illustrate the spatial arrangement of the bonding of fluorenes. It is indicated that the relaxed state adopts a 21 helical backbone conformation with a torsion angle of 18° between two connected repeat units. This configuration makes the formation of H- and J-aggregates through the strong π-π interaction between the backbone rings. A critical aggregation concentration is observed to form H- and J-aggregates for both polyfluorenes and oligofluorenes. These aggregates show large spectral shifts and distinct shape changes in photoluminescent excitation (PLE) and emission (PL) spectroscopy. Compared with "isolated" chromophores, H-aggregates induce absorption spectral blue-shift and fluorescence spectral red-shift but largely reduce fluorescence efficiency. "Isolated" chromophores not only refer to "isolated molecules" but also include those associated molecules if their conjugated backbones are not compact enough to exhibit perturbed absorption and emission. J-aggregates induce absorption spectral red-shift and fluorescence spectral red-shift but largely enhance fluorescence efficiency. The PLE and PL spectra also show that J-aggregates dominate in concentrated solutions. Different from the excimers, the H- and J-aggregate formation changes the ground-state absorption of fluorene-based chromophores. H- and J-aggregates show changeable absorption and emission derived from various interchain interactions, unlike the β phase, which has relatively fixed absorption and emission derived from an intrachain interaction.

Simple and Versatile Molecular Donors for Organic Photovoltaics Prepared by Metal-Free Synthesis

Donor-acceptor molecules (D-π-A) built by connecting a diphenylhydrazone block to a dicyanovinyl acceptor group via various thiophene-based π-conjugating spacers (1-5) were synthesized from mono- or dialdehydes by a simple metal-free procedure. Cyclic voltammetry and UV/Vis absorption spectroscopy show that the extension and/or increase of the donor strength of the spacer produces a decrease of the HOMO and LUMO energy level, a red shift of the absorption spectrum and an increase of the molecular absorption coefficient. Compared to solutions, the optical spectra of spin-cast thin films of compounds 1-3 show a broadening and red shift of the absorption bands, consistent with the formation of J-aggregates. In contrast the blue shift observed for the EDOT-containing compounds 4 and 5 suggests the presence of H-aggregates. Solution-cast and vacuum-deposited films of donors 1-5 were evaluated in solar cells with fullerene C60 as acceptor. A power-conversion efficiency among the highest reported for bilayer devices of basic configuration was obtained with compound 2. On the other hand, the results obtained with 4 and 5 suggest that the presence of EDOT in the structure can have deleterious effects on the organization and performances of the donor material.

Cation-induced self-assembly of an amphiphilic perylene diimide derivative in solution and Langmuir–Blodgett films

A novel amphiphilic perylenetetracarboxylic diimide (PDI) derivative, N-(4′-benzo-15-crown-5-ether)-N-hexyl-1,7-di(4-tert-butyl-phenoxy)perylen-3,4,9,10-tetracarboxylic diimide (15C5PDI), has been synthesized and characterized. Dimerization of 15C5PDI is induced in CHCl3 solution with the present of K+, resulting in the formation of the slipped co-facial J-aggregates, as revealed by absorption and fluorescence spectroscopies. Analysis of the surface pressure–area (π–A) isotherms and spectral change for the monolayer formed at the air/water interface, disclosed that 15C5PDI molecules adopted the H-type aggregation mode with a face-to-face configuration and edge-on orientation on both the surface of pure water and K+ aqueous solution. Consequently, a particularly interesting fluorescence emission change from “switch-on” to “switch-off” could be observed upon aggregation that was accompanied by a transformation from strongly fluorescent J-type into non-fluorescent H-type packing of the 15C5PDI dyes. Depending mainly on the coordination bonding between 15-crown-5-ether groups and K+ ions, one dimensional nanofibrils formed on the surface of the K+ aqueous solution with a more closely arrangement of 15C5PDI molecules relative to those on pure water subphase revealed by the π–A isotherms and atomic force microscopy (AFM) images. X-ray diffraction studies indicate that the film crystallinity and general molecular order in the Langmuir–Blodgett (LB) films deposited from the KCl solution are improved effectively in comparison with those from pure water subphase. Furthermore, the conductivity of the LB films prepared in K+ solution is more than ca. 1 order of magnitude higher than those from water.

Mechanism and Kinetics of J-Aggregation of Thiacyanine Dye in the Presence of Silver Nanoparticles

The aim of the present work was to elucidate the binding mechanism and kinetics of anionic cyanine dye 3,3′-disulfopropyl-5,5′-dichlorothiacyanine sodium salt (TC) J-aggregation on the surface of silver nanoparticles (AgNPs, particle size ∼6 nm). The hybrid J-aggregate–AgNPs assembly was characterized by TEM analysis, UV–vis spectrophotometry, and fluorescence measurements. In the elucidation of TC binding on the surface of AgNPs, they were considered as macromolecules with several binding sites and TC dye was considered as a ligand. Scatchard and Hill analysis revealed that TC binding was a random process rather than cooperative, with ∼200 bonded TC molecules per AgNP and a binding constant Ka = 4.8 × 107 M. The TC–AgNP assembly exerted concentration-dependent fluorescence quenching properties. The linearity of the Stern–Volmer relation, accounting for both static and dynamic quenching, indicated that only one type of quenching occurred, suggesting that AgNPs quenched the fluorescence of TC with an extraordinarily high Stern–Volmer constant (KSV) in the range of 108 M–1. Additionally, the kinetics of J-aggregation of TC in the presence of AgNPs was studied using a stopped–flow technique. Kinetic measurements were performed as a function of the TC and AgNP concentration, yielding sigmoidal kinetic curves. The concentration dependence of the parameters of the kinetic curves indicated that J-aggregate formation on the AgNP surface occurred via a two-step process; the first was adsorption of the initial dye layer, followed by the growth of consecutive layers.

Light-Harvesting in the Near-Infrared Region: Dye-Sensitized Solar Cells Sensitized with Asymmetric Ring-Expanded Zinc(II) Phthalocyanines

A near-IR absorbing dye (FcS1), in which three fluorene rings were fused with a porphyrazine ring, has been designed and synthesized as a photosensitizer for dye-sensitized solar cells (DSSCs). The fusion of the fluorene rings led to tailoring of the HOMO and LUMO energy levels as well as an expansion of the π-system. The absorption spectrum of FcS1 adsorbed onto a nanocrystalline TiO2 film suggested the formation of J-aggregates with tilted orientation of the macrocyclic ligands. While the power conversion efficiency of DSSCs sensitized with FcS1 was a modest 3.2 % under simulated air mass 1.5 global sunlight, FcS1 can convert the red and near-IR light regions between 600 and 860 nm into electricity.

Features of J-aggregates formation in pores of nanostructured anodic aluminum oxide

Features of J-aggregates formation in pores of nanostructured anodic aluminum oxide

Highly ordered arrangement of meso-tetrakis(4-aminophenyl)porphyrin in self-assembled nanoaggregates via hydrogen bonding

meso-Tetrakis(4-aminophenyl)porphyrin (TAPP) can self-assemble into nanostructures with different morphologies by a phase-transfer method. The morphologies (nanospheres, nanorods and nanothorns) of porphyrin nanoaggregates could be easily tuned just by changing the concentration of porphyrin in a proper solvent at room temperature. HRTEM images revealed the formation of highly ordered supramolecular arrays of TAPP, i.e., superlattice of TAPP molecules in nanoaggregates, which agreed well with the size of one molecule of TAPP. UV–vis absorption spectra showed an obvious red shift of the Soret band of TAPP, indicating the formation of J-aggregates of TAPP in nanoaggregates.

Use of JC-1 to assess mitochondrial membrane potential in sea urchin sperm

There is a need within marine research areas for more rapid techniques to assess the health of sperm from marine invertebrates. Originating in medical research, flow cytometry has been applied to rapidly measure a range of cellular processes within a plethora of different cell types. To date, the transfer of that knowledge to marine research has been limited. A method has been developed to assess mitochondrial membrane potential (MMP) in sea urchin (Centrostephanus rodgersii) sperm using the stain 5,5′,6,6′-tetrachloro-1,1′3,3′-tetrathylbenzimidazolyl-carbocyanine iodide (JC-1) and flow cytometry. MMP is a useful indicator of sperm health as the mitochondrion is the single source of ATP production, and the driver of apoptosis. The method was carefully optimised and validated with the use of positive controls. There were strong correlations between MMP measurements and sperm swimming speed and motility (R values of 0.8–0.9, p<0.001). JC-1 successfully differentiated between sperm with low and high MMP. However, in sperm that were treated with the mitochondrial inhibitor, carbonyl cyanide 3-chlorophenylhydrazone (CCCP), JC-1 fluorescence in stained sperm did not conform to that usually seen for other cell types. Using fluorescence microscopy, it was confirmed that this was due to the formation of J-aggregates in the acrosome vesicle following MMP collapse. To our best knowledge, this is the first report of J-aggregates forming in an organelle other than the mitochondria. This unexpected fluorescence response necessitated the use of a quadrant approach (% high MMP) instead of the usual ratiometric approach (FL2/FL1) to quantify MMP changes. Difficulties overcome during method development are described, many of which were likely related to the required use of seawater as a test medium. The developed method will enable rapid measurement of mitochondrial membrane potential of sea urchin sperm for application in reproductive biology, aquaculture research, and the impact of environmental stressors such as ocean acidification and pollution on sperm development and function.