Pseudoisocyanine J-aggregates Research Articles

Features of cyanine dyes aggregation on differently charged TiO2 matrices

Changing the polycondensation reaction route, positively and negatively charged TiO2 nanoparticles have been synthesized. On the base of the synthesized TiO2 nanoparticles, porous TiO2 films have been formed with different surface charges. J-aggregates of two anionic dyes were formed on positively charged TiO2 films, while J-aggregates of cationic dye was formed on negatively charged one. Combining J-aggregates with different J-band spectral positions, we have obtained two composites consisting of J-aggregates pairs with an effective excitation energy transfer between them. In both cases, simple mixing of J-aggregate in solution did not result in the composite formation and only sequential deposition of J-aggregate from corresponding solutions was successful. Interesting, not only charge alternating composite of cationic pseudoisocyanine J-aggregates and anionic thiacarbocyanine J-aggregates was realized, but also the same was done in the case of the composite of two anionic carbocyanine J-aggregates.

Features of pseudoisocyanine J-aggregates formation in spin-assisted layer-by-layer assembled films and their interaction with metal nanoparticles

Features of pseudoisocyanine J-aggregates formation in spin-assisted layer-by-layer assembled films and their interaction with metal nanoparticles

Fabrication and Optical Properties of Fiber-Shaped Pseudoisocyanine J-Aggregates Grown Directly on a Glass Substrate

Fabrication and Optical Properties of Fiber-Shaped Pseudoisocyanine J-Aggregates Grown Directly on a Glass Substrate

Nanotube Template-Directed Formation of Strongly Coupled Dye Aggregates with Tunable Exciton Fluorescence Controlled by Switching between J- and H-Type Electronic Coupling.

Strongly coupled dye aggregates with tailored exciton properties may find their use in developing artificial light-harvesting and optoelectronic devices. Here, we report the control of tubular pseudoisocyanine (PIC) dye J- and H-aggregate formation with tunable exciton fluorescence using lithocholic acid (LCA) as a template. The LCA-templated PIC J-aggregate nanotubes formed at a higher LCA/PIC molar ratio (≥5:1) exhibit a sharp, red-shifted absorption band (at 555 nm), intense fluorescence (at 565 nm), and shorter lifetime (200 ps), all indicating their strong superradiance properties. In contrast, the H-aggregate nanotubes formed at a lower LCA/PIC molar ratio (2:1) exhibit a significantly blue-shifted absorption band (at 420 nm) and highly red-shifted fluorescence emission (at 600 nm) with enhanced lifetime (4.40 ns). The controlled switching of the optical properties of the PIC dye aggregates achieved by controlling the LCA/PIC molar ratio could serve as an important guideline for the design of organic photo-functional materials.

A highly sensitive fluorescence “turn on” detection of perrhenate Anion, a non-radioactive surrogate of hazardous pertechnetate anion

Perrhenate oxoanion is a non-radioactive surrogate of the radioactive and hazardous pertechnetate oxoanion. The efficient sensor systems for perrhenate anion in aqueous medium is barely reported and still remains challenging due to low charge density and large size of the anion. In this regard, we have identified a cyanine based molecular rotor probe, pseudoisocyanine, which produces an appreciably larger emission enhancement of ∼60 fold in response to perrhenate anion, which is highest reported, till date, for any turn-on sensor for perrhenate anion leading to a significant improvement in the detection limit (0.17 μM) over existing sensors for perrhenate. Our sensing scheme operates through the ion pairing interaction between perrhenate and pseudoisocyanine which induces the formation of J-aggregates of pseudoisocyanine that yield dramatic changes in its fluorescence properties. The J-aggregate formation of pseudoisocyanine, in the presence of perrhenate anion, also yields significant changes in the absorption properties providing an opportunity of dual sensing of perrhenate, i.e. via fluorimetry and colorimetry. Apart from being sensitive and selective, our probe molecule exhibits a desirable feature of emission and excitation wavelength lying in the red region of the visible specrum which is advantageous for operation of a probe molecule in complex sensing matrix.

Plasmon-Induced Suppression of Exciton Self-Trapping in Polymer-Bound Pseudoisocyanine J-Aggregates

Features of plasmon-enhanced fluorescence in pseudoisocyanine (PIC) J-aggregates formed in polyelectrolyte films at liquid nitrogen temperature have been studied. Due to efficient exciton self-trap...

An efficient J-aggregate based fluorescence turn-on and ratiometric sensor for heparin

Heparin is the second most widely used natural drug and an extensively employed blood anticoagulant worldwide. Construction of fluorescent sensors for Heparin has remained heavily dependent on the complex and time-consuming laborious synthetic efforts. However, reports on the direct usage of in-expensive commercially available probe molecule, for sensitive and selective fluorimetric sensing of Heparin, which can greatly simplify the synthetic efforts, has been limited and remains highly desirable. Herein, we report a very sensitive and selective fluorescence turn-on sensor for Heparin, which utilizes a commercially available organic dye molecule, Pseudoisocyanine. The supramolecular interaction between the Pseudoisocyanine and Heparin leads to the J-aggregate formation of Pseudoisocyanine on the surface of Heparin, with an exceptional fluorescence enhancement of ∼400 fold. The J-aggregates of Pseudoisocyanine also display remarkable changes in the absorption features, in the presence of Heparin, which provides a unique advantageous feature of dual sensing of Heparin, by colorimetry and fluorimetry. Pseudoisocyanine also displays high selectivity towards Heparin over its structurally related analogs Chondroitin sulphate and Hyaluronic acid, and other analytes, with a detection limit of 2 nM. More importantly, our sensor system shows good performance in the serum samples, a complex biological media. We further demonstrate that, the interaction of Heparin with its only medically approved antidote, Protamine can also be monitored using Pseudoisocyanine J-aggregates. Thus, our assay is sensitive and selective, rapid, simple, and inexpensive, which can promote the Heparin related biochemical and biomedical research.

Directed Energy Transfer through DNA-Templated J-Aggregates.

Strongly coupled molecular dye aggregates have unique optoelectronic properties that often resemble those of light harvesting complexes found in Nature. The exciton dynamics in coupled dye aggregates could enhance the long-range transfer of optical excitation energy with high efficiency. In principle, dye aggregates could serve as important components in molecular-scale photonic devices; however, rational design of these coupled dye aggregates with precise control over their organization, interactions, and dynamics remains a challenge. DNA nanotechnology has recently been used to build an excitonic circuit by organizing pseudoisocyanine (PIC) dyes forming J-aggregates on the templates of poly(dA)-poly(dT) DNA duplexes. Here, the excitonic properties of the PIC J-aggregates on DNA are characterized spectroscopically in detail using poly(dA)-poly(dT) tract lengths of 24 and 48 base pairs. The excitonic properties of these DNA templated dye assemblies depend on the length and sequence of the DNA template. The incorporation of a gap of two GC base pairs between two segments of poly(dA)-poly(dT) DNA markedly reduces the delocalization of excitation in the J-aggregates. With a quantum dot (QD) as the light absorber and energy donor and using Alexa Fluor 647 (AF647) as the energy acceptor, with a DNA-templated J-aggregate in between, significant energy transfer from QD to AF647 is observed over a distance far longer than possible without the aggregate bridge. By comparing the efficiency of energy transfer through a continuous J-aggregate with the efficiency when the aggregate has a discontinuity in the middle, the effects of energy transfer within the aggregate bridge between the donor and acceptor are evaluated.

Influence of pseudoisocyanine J-aggregate agglomeration on the optical properties

Influence of pseudoisocyanine J-aggregate agglomeration on the optical properties

Photophysics of J-Aggregate-Mediated Energy Transfer on DNA.

Achieving nanoscale spatial and electronic control over the formation of dye aggregates is a major synthetic challenge due to their typically inhomogeneous self-assembly, which limits control over their higher-order organization. To address these challenges, synthetic DNA-templated pseudoisocyanine (PIC) J-aggregates were recently introduced. However, the dependence of the photophysics of the superradiant exciton on the underlying DNA template length and the impact of static disorder on energy transfer through these PIC J-aggregates remain unknown. We examine the delocalization length progression of superradiant PIC excitons by varying the length of poly-A DNA tracts that template PIC J-aggregates. We then investigate the energy-transfer efficiency from PIC J-aggregates with DNA duplex template length, which we found to be limited by static disorder. Utilizing the self-assembled and selective formation of superradiant excitons on DNA provides a platform to determine the function of delocalized excitons in the context of nanoscale energy transport.

Structural templating of J-aggregates: Visualizing bis(monoacylglycero)phosphate domains in live cells

Identifying the key structural and dynamical determinants that drive the association of biomolecules, whether in solution, or perhaps more importantly in a membrane environment, has critical implications for our understanding of cellular dynamics, processes, and signaling. With recent advances in high-resolution imaging techniques, from the development of new molecular labels to technical advances in imaging methodologies and platforms, researchers are now reaping the benefits of being able to directly characterize and quantify local dynamics, structures, and conformations in live cells and tissues. These capabilities are providing unique insights into association stoichiometries, interactions, and structures on sub-micron length scales. We previously examined the role of lipid headgroup chemistry and phase state in guiding the formation of pseudoisocyanine (PIC) dye J-aggregates on supported planar bilayers [Langmuir, 25, 10719]. We describe here how these same J-aggregates can report on the in situ formation of organellar membrane domains in live cells. Live cell hyperspectral confocal microscopy using GFP-conjugated GTPase markers of early (Rab5) and late (Rab7) endosomes revealed that the PIC J-aggregates were confined to domains on either the limiting membrane or intralumenal vesicles (ILV) of late endosomes, known to be enriched in the anionic lipid bis(monoacylglycero)phosphate (BMP). Correlated confocal fluorescence - atomic force microscopy performed on endosomal membrane-mimetic supported planar lipid bilayers confirmed BMP-specific templating of the PIC J-aggregates. These data provide strong evidence for the formation of BMP-rich lipid domains during multivesicular body formation and portend the application of structured dye aggregates as markers of cellular membrane domain structure, size, and formation.

Controlled formation of pseudoisocyanine J-aggregates in the interlayer space of synthetic saponite

In presented work dye assemblies with J-type intermolecular coupling, which are well recognized not only for their exciton transport but also for hole and electron transport properties were investigated. The use of materials consisting of J-type dye assemblies can be significantly enhanced if their photonic properties can be controlled by some external stimuli. For these reasons the switching abilities between J-type aggregated and non-aggregated states of a cationic cyanine dye, 1,1′-diethyl-2,2′-cyanine (pseudoisocyanine, PIC) intercalated in the interlayer space of synthetic saponite (Sap) were compared. The switching was performed by adding and removing of dimethyl sulfoxide (DMSO) from the interlayer space. The PIC/Sap hybrid film prepared at 70% CEC loading level has shown excellent stability within 20cycles of photophysical response after adding and removing of DMSO from the interlayer space, indicating that presented experimental approach can be useful in the future development of artificial light harvesting or semiconductor systems with controllable properties.

Evidence of Exciton Self-Trapping in Pseudoisocyanine J-Aggregates Formed in Layered Polymer Films

At low temperatures in the luminescence spectrum of pseudoisocyanine (PIC) J-aggregates formed in a layered polymer film an unusual broad red-shifted band appears. The analysis of spectral properties of PIC J-aggregates allowed us to ascribe the additional red band to the exciton self-trapped state. In a layered polymer film, PIC J-aggregates are found to possess a 2D island-like structure, which results in a barrier type of the exciton self-trapping with coexisting free and self-trapped excitons. Both the strong topological disorder and exciton–phonon coupling are suggested to be the reason for the exciton self-trapping in J-aggregates. Nonradiative relaxation of self-trapped excitons at room temperature has been proposed to be responsible for a very low luminescence quantum yield and giant nonradiative rate constant for PIC J-aggregates formed in a layered film.

Metal-Enhanced Fluorescence of Pseudoisocyanine J-Aggregates Formed in Layer-by-Layer Assembled Films

A formation of pseudoisocyanine (PIC) dye J-aggregates in the polyelectrolyte film by the layer-by-layer (LbL) assembly method has been studied. It has been shown that this process leads to significant J-band widening and fluorescence quenching as a result of increasing static disorder. To enhance the J-aggregate fluorescence properties, the effect of J-aggregate interaction with plasmon resonances of gold nanoparticles has been used. It is found that the maximal 8-fold fluorescence enhancement for PIC J-aggregates in the LbL films could be achieved at 16 nm distance between Au nanoparticles (NPs) and the J-aggregates. Plasmon influence on the J-aggregate fluorescence has been analyzed using a two-level system in the local plasmon field approximation. The model gives a good correlation with the experimental results and could be used for further studying the exciton–plasmon interaction in J-aggregates.

First-principles simulations of the initial phase of self-aggregation of a cyanine dye: structure and optical spectra.

Using first-principles simulations, we investigated the initial steps of the self-aggregation of the dye pseudoisocyanine (PIC) in water. First, we performed molecular dynamics (MD) simulations of the self-aggregation process, in which pile-of-coins oligomers ranging from dimers to stacks of about 20 molecules formed. The oligomer structures were found to be very flexible, with the dimers entering a weakly coupled state and then returning to a stable π-π stacked conformation on a nanosecond time scale. The structural information from the MD simulations was combined with quantum chemical calculations to generate a time-dependent Frenkel exciton Hamiltonian for monomers, dimers, and trimers, which included vibronic coupling. This Hamiltonian, in turn, was used to calculate the absorption spectra for these systems. The simulated dimer spectrum compared well to experiment, validating the face-to-face stacked dimer arrangement found in our MD simulations. Comparison of the simulated trimer spectrum to experiment suggested that oligomers larger than the dimer cannot be abundant at the onset of J-aggregation. Finally, the conformation of the PIC J-aggregate was investigated by testing the stability of several possible conformations in our MD simulations; none of the tested structures was found to be stable.

Plasmon Controlled Exciton Fluorescence of Molecular Aggregates

In the present work controlled plasmon enhanced fluorescence of thiacyanine dye J-aggregates in water solution has been demonstrated. To control a distance between J-aggregates and silver nanoparticles the latter have been covered by a polymer shell of variable thickness using the layer-by-layer assembly method. The best 2-fold fluorescence enhancement has been observed for the 16 nm thick polymer shell. Transmission electron microscopy (TEM) images have revealed an insufficient contact between J-aggregates and NPs that could be the main reason for the small fluorescence enhancement. Experimental results have been described using a model of two-level system affected by the local plasmon resonances field. According to the model more than 20-fold enhancement of J-aggregates fluorescence could be expected under optimal conditions. Besides, strong fluorescence enhancement dependence on an exciton coherence length has been predicted. According to it, significant fluorescence response should be observed for metal nanoparticles interacting J-aggregates with large exciton coherence length such as pseudoisocyanine J-aggregates and some others.

Layer-by-Layer Assemblies Composed of Polycationic Electrolyte, Organic Dyes, and Layered Silicates

The formation of layer-by-layer (LBL) assemblies is a simple procedure, suitable for the construction of thin films with well-defined structures and compositions. LBL assemblies based on layered silicates, cationic organic dyes, and polycationic electrolyte were investigated by absorption and fluorescence spectroscopies. The formations of two simple films were investigated: one film bearing a laser dye, oxazine 1, and the second based on J-aggregates of pseudoisocyanine. A detailed study based on chemometric methods (principal component analysis, multivariate curve resolution-alternating least squares) confirmed the very complex nature of the LBL assembly formation. During the assembly deposition, the outer surface with the adsorbed dye often exhibited significant changes upon the formation of a new layer. These changes mainly included a partial desorption of the dye and structural rearrangement of the adsorbed dye species, including molecular aggregation. A complex film composed of alternating layers of the two dyes was made mainly for the purpose of investigating photophysical phenomena, such as fluorescence quenching and intermolecular resonance energy transfer. The results obtained can be useful for further studies leading to the development of functional materials based on photoactive dyes, inorganic layered carriers, and polyelectrolytes.

Ultrafast transition between polariton doublet and alternating current Stark triplet in organic one-dimensional photonic crystal microcavity

This work investigates nonlinear transmission properties of cavity polaritons in a one-dimensional photonic crystal microcavity containing pseudoisocyanine J-aggregates. It was observed that an unexpected transmission peak appeared between the two peaks of cavity polaritons, when the incident light intensity was high. The decay time of this third peak, determined by the pump-probe transient transmission spectroscopy, was less than 1 ps. We observed ultrafast transition between the cavity polariton doublet and AC Stark triplet in an organic system.

Antenna size effect: The influence on energy transfer in the CdTe–pseudoisocyanine nanocomposite system

A 30-fold increase in the quantum yield of fluorescence of pseudoisocyanine (PIC) J-aggregates in the vicinity of CdTe nanocrystals has been revealed as a result of the resonant energy transfer from the nanocrystals to PIC J-aggregates in aqueous solutions. This enormous effect was accompanied by rather modest (∼30%) energy transfer efficiency and was assigned to rearrangement in the J-aggregate structure where the increased number of participating molecules in the J-aggregate coherence domain was calculated. No energy transfer was observed when the J-aggregate antenna size was small. The antenna size was found to be controlled by pH of the solution.

Effects of DNA on the Formation of J-Aggregates of Pseudo-Isocyanine

We prepared the solution and film samples including pseudo-isocyanine (PIC), DNA and polyvinylalcohol (PVA) and conducted the absorption and circular dichrosim spectroscopies. The effects of DNA on the formation of J-aggregates were investigated by the dependence of optical spectra on the concentration of the dye and DNA. From the results, we found that small amount of DNA promotes the formation of J-aggregates in solution, and the maximum J-aggregate peak was obtained with the PIC iodide concentration of 1.31 × 10−3 mol/l, which is less concentrated than usual conditions. We also succeeded to fabricate PVA films including 1.2% dye and 0.5% DNA by a spin coating method from the solution, demonstrating the J-aggregate peak and a circular dichroism signal.