J-aggregates Of Dyes Research Articles

Near-Field Electromagnetic Coupling Effects in Dimers of Three-Layer Metalorganic Nanoparticles with a J-Aggregate Dye Outer Shell

Near-Field Electromagnetic Coupling Effects in Dimers of Three-Layer Metalorganic Nanoparticles with a J-Aggregate Dye Outer Shell

J-aggregation strategy of organic dyes for near-infrared bioimaging and fluorescent image-guided phototherapy.

With the continuous development of organic materials for optoelectronic devices and biological applications, J-aggregation has attracted a great deal of interest in both dye chemistry and supramolecular chemistry. Except for the characteristic red-shifted absorption and emission, such ordered head-to-tail stacked structures may be accompanied by special properties such as enhanced absorption, narrowed spectral bandwidth, improved photothermal and photodynamic properties, aggregation-induced emission enhancement (AIEE) phenomenon, and so forth. These excellent properties add great potential to J-aggregates for optical imaging and phototherapy in the near-infrared (NIR) region. Despite decades of development, the challenge of rationally designing the molecular structure to adjust intermolecular forces to induce J-aggregation of organic dyes remains significant. In this review, we discuss the formation of J-aggregates in terms of intermolecular interactions and summarize some recent studies on J-aggregation dyes for NIR imaging and phototherapy, to provide a clear direction and reference for designing J-aggregates of near-infrared organic dyes to better enable biological applications. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Quantum–Classical Mechanics: Nano-Resonance in Polymethine Dyes

It is well known in quantum mechanics that the theory of quantum transitions is based on the convergence of the series of time-dependent perturbation theory. This series converges in atomic and nuclear physics. However, in molecular and chemical physics, this series converges only in the Born–Oppenheimer adiabatic approximation and due to the application of the Franck–Condon principle, and it diverges as a result of going beyond the adiabatic approximation and the Franck–Condon principle. This divergence (singularity) is associated with the incommensurability of the masses of light electrons and heavy nuclei which jointly participate in the full-fledged movement in the transient state of molecular “quantum” transitions. In a new physical theory—quantum–classical mechanics (Egorov, V.V. Heliyon Physics 2019, 5, e02579)—this singularity is damped by introducing chaos into the transient state. This transient chaos is introduced by replacing the infinitely small imaginary additive in the energy denominator of the spectral representation of the total Green’s function of the system with a finite value and is called dozy chaos. In this article, resonance at the nanoscale (nano-resonance) between electron and nuclear reorganization motions in the quantum–classical (dozy-chaos) mechanics of elementary electron transfers in condensed media and their applications to polymethine dyes and J-aggregates in solutions are reviewed. Nano-resonance explains the resonant character of the transformation of the shape of the optical absorption band in a series of polymethine dyes in which the length of the polymethine chain changes, as well as the nature of the red-shifted absorption band of the J-aggregates of polymethine dyes (J-band), which is narrow and intense. The process of dye aggregation in an aqueous solution with an increase in its concentration by the formation of J-aggregates is considered a structural tuning of the “polymethine dye + environment” system into resonance with light absorption. For J-aggregates in Langmuir films, the asymmetry of the luminescence and absorption bands, as well as the small value of their Stokes shifts, are explained. The parasitic transformation of the resonant shape of the optical absorption band of a polymethine dye in solution during the transition from one-photon to two-photon absorption is also explained, and the conditions for the restoration of this nano-resonance shape are predicted.

Photoinduced Charge Transport in Films of Near-Infrared Dye Assisted by Nanoscale Inhomogeneity of Dye Aggregates

To clarify the mechanism of a photoinduced charge transport in films of relatively small organic molecules, i.e., whether it is stimulated by energetic and/or structural disorder, three types of films composed of a specific tricarbocyanine near-infrared dye were prepared, i.e., a polycrystalline film, an amorphous film composed of a mixture of monomers and J- and H-aggregates, and a composite dye film in a polymer matrix composed predominantly of dye J-aggregates. It was found that in most cases the charge transport is governed by trap-limited conduction; however, the suggested driving force for the photoinduced transport of charge carriers can be interpreted to be due to the structural inhomogeneity (i.e., different aggregate types) and energetic disorder in the dye film, where Gaussian and discrete, rather than exponential, trap distributions play a decisive role. It is concluded that intermolecular interactions in J- and H-aggregates of π-conjugated molecules provide fascinating incentives for charge transfer pathways.

Metal ions-bridged J-aggregation mediated nanoassembly composition for breast cancer phototherapy

Recently, the highly ordered J-aggregates of organic dyes with intriguing optical properties have received considerable attention in biomedical applications. Herein, binary metal ions Mn(II)/Fe(III) are used to induce the formation of indocyanine green (ICG) J-aggregates. Further, the sheet-like J-aggregates are able to act as "carriers" for loading hydrophobic chemotherapeutic gambogic acid (GA), realizing the effect of "killing two birds with one stone" for both treatment and delivery. The as-designed nanoassembly is formed spontaneously in aqueous environment via π-π stacking, electrostatic interaction, and hydrophobic force, exhibiting enhanced photostability of ICG and outstanding reactive oxygen species (ROS) generation ability. Moreover, significant inhibition of tumor growth by the synergetic effect of phototherapy and chemotherapy is verified in a subcutaneous 4T1 tumors model. In conclusion, this work not only presents a facile and green approach to manufacture carrier-free nanodrugs, but also establishes a universal platform that has potential application in the co-delivery of near-infrared dye and hydrophobic molecules.

J-Aggregates of Multi-Groups Cyanine Dye Under the Assistant of Amphiphilic Polypeptide for Efficient NIR-IIa Phototheranostics Under 1064 nm Irradiation

J-Aggregates of Multi-Groups Cyanine Dye Under the Assistant of Amphiphilic Polypeptide for Efficient NIR-IIa Phototheranostics Under 1064 nm Irradiation

Nano-assemblies from J-aggregated dyes to improve the selectivity of a H2S-activatable photosensitizer.

We report J-aggregates of a boron dipyrromethene derivative (BDP-Nit) as an H2S-activatable nano-photosensitizer. The closely packed BDP-Nit in J-aggregates exhibits high selectivity to H2S over biothiols to produce an active photosensitizer.

Ultralong-Range Polariton-Assisted Energy Transfer in Organic Microcavities.

Non‐radiative energy transfer between spatially‐separated molecules in a microcavity can occur when an excitonic state on both molecules are strongly‐coupled to the same optical mode, forming so‐called “hybrid” polaritons. Such energy transfer has previously been explored when thin‐films of different molecules are relatively closely spaced (≈100 nm). In this manuscript, we explore strong‐coupled microcavities in which thin‐films of two J‐aggregated molecular dyes were separated by a spacer layer having a thickness of up to 2 μm. Here, strong light‐matter coupling and hybridisation between the excitonic transition is identified using white‐light reflectivity and photoluminescence emission. We use steady‐state spectroscopy to demonstrate polariton‐mediated energy transfer between such coupled states over “mesoscopic distances”, with this process being enhanced compared to non‐cavity control structures.

The Kinetics of Dye Encapsulation in Single-Walled Carbon Nanotubes Probed By Statistical Raman Imaging

Single-Walled Carbon Nanotubes (SWNTs) are nanosystems with a large aspect ratio that have potential in a wide range of optical applications, such as in biomedical imaging [1]. An important advantage of SWNTs in that context is their capability to support two or more functionalities, for instance detection as well as targeting of molecules of interest. The hollowness of SWNTs interior is therefore particularly interesting since SWNTs can act as a template for the creation of new hybrid nanostructures, while leaving the surface free for further functionalization. It was shown that dyes encapsulated inside carbon nanotubes (CNTs) are protected from degradation and present a strong Raman signature with narrow emission peaks, free of background fluorescence, which could enable their use as Raman optical markers [2]. Further, confinement inside SWNTs was found to largely impact molecular organisation [3], tuning the physical and chemical properties of the encapsulated molecules. However, the kinetics of such a system, as well as the precise mechanism of aggregate formation, is still not completely understood. In this study, we explore the encapsulation mechanism of dye molecules in SWNTs. Sexithiophene (6T) molecules were chosen due to their well-conjugated, rod-like structure and giant Raman signal upon encapsulation, at an excitation of 532 nm.Raman imaging (RIMA, Raman Imaging system, Photon etc.) is used to obtain statistical information from a large number of individual SWNTs (>1000 per data point). The encapsulation is carried out using a liquid-phase protocol, allowing the investigation of the impact of various encapsulation parameters (dye concentration and temperature) on the kinetics of the encapsulation process. Spatially resolved Raman imaging allows the comparison of filling and densification speeds for all encapsulation parameters, showing that, in all studied cases, the filling is faster than densification, which occurs over longer time scales. Raman imaging also enables the tailored analysis of different sub-populations, in order to probe the effect of the length or the diameter of the SWNTs on the encapsulation kinetics. Furthermore, Raman intensity distributions are studied, which provide signatures of single and double aggregation that can be correlated to SWNTs characteristics. Finally, a kinetic model and an encapsulation mechanism are proposed. Based on the intensity distributions and the proposed kinetic model, we predict the apparition of double aggregation for all the encapsulation parameters investigated. These results provide much needed insight on aggregate formation in 1D systems, which is crucial to the development of well-behaved and controlled hybrid materials. [1] Kostarelos, K., Bianco, A., & Prato, M. (2009). Promises, facts and challenges for carbon nanotubes in imaging and therapeutics. Nature nanotechnology, 4(10), 627-633.[2] Gaufrès, E., Tang, N. W., Lapointe, F., Cabana, J., Nadon, M. A., Cottenye, N., ... & Martel, R. (2014). Giant Raman scattering from J-aggregated dyes inside carbon nanotubes for multispectral imaging. Nature Photonics, 8(1), 72-78.[3] Almadori, Y., Alvarez, L., Le Parc, R., Aznar, R., Fossard, F., Loiseau, A., ... & Rahmani, A. (2014). Chromophore ordering by confinement into carbon nanotubes. The Journal of Physical Chemistry C, 118(33), 19462-19468.

Observation of photon-mode decoupling in a strongly coupled multimode microcavity.

We have fabricated organic semiconductor microcavities having an extended optical path-length (up to 2 µm) that contain J-aggregates of a cyanine dye. These structures are studied using optical-reflectivity and are found to be characterized by a series of polaritonic modes. By changing the effective oscillator strength of the dye within the cavity, we evidence a transition from "normal" strong coupling in which the photon modes are coupled to one another via the excitonic transition of the molecular dye to a state in which photon-modes become decoupled. We use an eight-level modified Hamiltonian to describe the optical properties of the system and compare the distribution of the confined optical field in coupled and decoupled structures.

Large optical nonlinearity enhancement under electronic strong coupling

Nonlinear optical responses provide a powerful way to understand the microscopic interactions between laser fields and matter. They are critical for plenty of applications, such as in lasers, integrated photonic circuits, biosensing and medical tools. However, most materials exhibit weak optical nonlinearities or long response times when they interact with intense optical fields. Here, we strongly couple the exciton of cyanine dye J-aggregates to an optical mode of a Fabry-Perot (FP) cavity, and achieve an enhancement of the complex nonlinear refractive index by two orders of magnitude compared with that of the uncoupled condition. Moreover, the coupled system shows an ultrafast response of ~120 fs that we extract from optical cross-correlation measurements. The ultrafast and large enhancement of the optical nonlinar coefficients in this work paves the way for exploring strong coupling effects on various third-order nonlinear optical phenomena and for technological applications.

Polymer Composite with J-Aggregates of Polymethine Dye as a Charge-Transport Layer of Organic Light-Emitting Diode

The effect of addition of J-aggregates of polymethine dye into the hole-transport layer of an organic light-emitting diode (OLED) on its characteristics and operational stability was studied. Water-soluble PEDOT:PSS (poly(3,4-ethylenedioxythiophene)) and the interpolymer complex of polyaniline and poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAn-PAMPSA) were used as the matrices of polymer nanocomposites. The highest efficiency characteristics of the OLEDs with the considered structure were achieved using PAn-PAMPSA at a particular component ratio in the interpolymer complex. Additives of J‑aggregates did not significantly affect the efficiency characteristics of the OLEDs; however, an increase in the operational stability of devices was recorded.

Recent progress in utilizing near-infrared J-aggregates for imaging and cancer therapy

Schematic diagram of NIR J-aggregates of various organic dyes as effective bioimaging (fluorescence (FL) or photoacoustic (PA)) and therapeutic agents (PDT or PTT).

Strong coupling with absorption and emission features of Ag@Au hollow nanoshells interacting with J-aggregated dye molecules

We investigate the strong coupling from 5,5’,6,6’-tetrachloro-1,1’-diethyl-3,3’-di(4-sulfobutyl)-benzimidazolocarbocyanine (TDBC) molecules near pure nano-triangular Ag prisms or Ag@Au hollow nanoshells. When TDBC molecules are deposited on pure Ag nanoprisms or Ag@Au hollow nanoshells with the plasmonic resonance peak, matching very closely with the absorption band of TDBC J-aggregates, obvious Rabi splitting can be observed due to the strong coupling regime. Meanwhile, the photoluminescence intensity decreased with the increasing of the temperature, verifying the decreasing plasmon–exciton coupling interaction in the higher temperature. Our experimental results are coincident with the simulation results calculated by finite-difference time-domain method.

Switching resonance character within merocyanine stacks and its impact on excited-state dynamics

Summary In this study, the optical properties and excited-state dynamics of the unique self-assembled donor-acceptor (DA) merocyanine dye stacks from dimer up to octamer, prepared via dipole-dipole interactions, are reported in terms of coherent exciton dynamics and formation of an excimer-like state. Our findings are based on the steady-state absorption/emission, time-resolved fluorescence, and transient absorption (anisotropy) measurements, including wavepacket analysis and quantum mechanical calculations. Coherent exciton of torsional motions-restricted dye stacks rapidly localizes into the weakly emissive excimer-like state, by shortening the inter-moiety distance and changing the bond-length alternation pattern. The inner merocyanine moiety, having two neighboring units, has a reversed resonance character (non-polar (N) Z) in the ground state. This difference has led to two conclusions: (1) tetramers and octamers exhibit different features of excimer-like state than the dimer, and (2) octamers exhibit slower localization dynamics due to the enhanced homogeneity (six inner-moieties) compared with tetramers (two inner moieties).

Development of a highly efficient, strongly coupled organic light-emitting diode based on intracavity pumping architecture.

We report a highly efficient polariton organic light-emitting diode (POLED) based on an intracavity pumping architecture, where an absorbing J-aggregate dye film is used to generate polariton modes and a red fluorescent OLED is used for radiative pumping of emission from the lower polariton (LP) branch. To realize the device with large-area uniformity and adjustable coupling strength, we develop a spin-coating method to achieve high-quality J-aggregate thin films with controlled thickness and absorption. From systematic studies of the devices with different J-aggregate film thicknesses and OLED injection layers, we show that the J-aggregate film and the pump OLED play separate roles in determining the coupling strength and electroluminescence efficiency, and can be simultaneously optimized under a cavity design with a good LP-OLED emission overlap for effective radiative pumping. By increasing the absorption with thick J-aggregate film and improving the electron injection of pump OLED with Li2CO3 interlayer, we demonstrate the POLED with a large Rabi splitting energy of 192 meV and a maximum external quantum efficiency of 1.2%, a record efficiency of POLEDs reported so far. This POLED architecture can be generally applied for exploration of various organic materials to realize novel polariton devices and electrically pumped lasers.

Concurrent formation of H- and J-aggregates of dyes with chiralities individually determined by G-quadruplex handedness

DNA templated dye assemblies pave an easy way to regulate the optical properties of molecular aggregates. G-quadruplexes (G4s) provide versatile DNA platforms for the dye assemblies since their foldings can be easily tuned by cation ions and sequences. In this work, we found that the G4 handedness can be used to control the aggregate chirality of a dye of 3,3′-diethylthiacarbocyanine (DiSC2(3)). The left-handed and right-handed G4s can template the concurrent formation of the J- and H-aggregates of DiSC2(3) with emergence of the featured absorption spectra. However, the chiral J-aggregate of DiSC2(3) can be formed only on the left-handed G4s, while the chiral H-aggregate is otherwise grown only on the right-handed G4s, as confirmed by the induced circular dichroism (ICD) spectra with the characteristic splitting bands. Additionally, these G4s even at tens of nM level are efficient to produce these chiral aggregates, demonstrating the high sensitivity of G4s in creating these optically active dye assemblies. The possible growth sites of the aggregates are proposed by the sequence length-dependent assemblies. Our work will provide a new way to control the chiral assemblies of dye aggregates via the G4 handedness.

Size Dependence of Non-Radiative Decay Rates in J-Aggregates.

Fluorophores that emit in the near-infrared (NIR, 700-1700 nm) and have high quantum yields are urgently needed for many technical applications such as organic light-emitting diodes or bioimaging. The design of such chromophores is hampered by the energy gap law, which states that shifting the emission to lower wavelengths is accompanied by a dramatic increase in the nonradiative decay rate. In this article we argue that linear oligomers with J-type excitonic coupling are ideal NIR fluorophores because of the advantageous dependence of the emission energy and the radiative and nonradiative rates on the length N over which the excitation is delocalized. The lowering of the emission energy due to exciton splitting and the linear increase of the radiative rate with length (super-radiance) are well understood. However, less attention has been paid to the decrease of the nonradiative rate with length, which can compensate for the exponential increase due to the energy gap law. According to the exciton model, the Huang-Rhys factors decrease like N-2 while the strength of the nonadiabatic coupling remains approximately constant. Plugging these relations into the Englman-Jortner's energy gap law, we show that for excitonic coupling that is not too strong the nonradiative rate decreases quickly with N. This phenomenon explains the decrease of the nonradiative rate with length in J-aggregates of carbocyanine dyes and the exceptionally high fluorescence quantum yields of linear ethyne-linked zinc-porphyrin arrays, which seemed to defy the energy gap law.

Fluorescence properties of hybridized thin films consisting of organic dye J-aggregates and titanium oxide nanoparticles

Aiming at a highly bright emitter, hybridized thin films consisting of organic dye TDBC J-aggregates (JA) and titanium oxide (TO) nanoparticles (NPs) have been fabricated successfully. The fluorescence intensity and the corresponding fluorescence quantum yield multiplied ca. 10 times and ca. twice, respectively. TO NPs have a high refractive index, and have no absorption loss like metal NPs. On the other hand, extinction (absorption) and fluorescence spectra are in general overlapped in organic dye JA, that is, so a small Stokes’ shift. Namely, the present phenomenon could be qualitatively explained by the simultaneously optical processes of both “excitation enhancement” induced directly by near-field effect from TO NPs and “emission enhancement” as a radiation of scattering field from TO NPs, which were polarized by the excitation energy from TDBC JA to TO NPs. In other words, the definite scattering peak in the extinction spectrum of TO NPs should be tuned efficiently with extinction (absorption) and fluorescence peak bands of TDBC JA.

Spectral Properties of Indotricarbocyanine Dye during Self-Assembly of Its H*- and J-Aggregates

The results of studying the self-assembly of H*- and J-aggregates of indotricarbocyanine dye in a phosphate-buffered saline are given. The formation of nonluminescent H*-aggregates with an absorption band at 516 nm and a full width at half maximum of 35 nm (1303 cm–1) is observed for the dye under study at pH 7.0, while J-aggregates are practically absent. At pH 7.4, H*-aggregates of the dye are not formed, but the self-assembly of J-aggregates with an absorption band at 777 nm and a full width at half maximum (FWHM) of 30 nm (497 cm–1) is observed; their photoluminescence quantum yield does not exceed 10–6. It was found that a change in the solution temperature from 20 to 31°C reduces the time of self-assembly of H*‑aggregates by a factor of 25. An increase in the solution temperature from 20 to 80°C leads to the decomposition of both H*- and J-aggregates; the temperature, at which the absorbance at the band maximum decreases by half, is 37°C for the bands of H*-aggregates and 32°C for the band of J-aggregates. It is shown that the absorption bands that appear in the spectral range of 400–480 nm are attributed to electronic transitions to high excited states of dye aggregates.