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Aiming at the application to photodynamic therapy, natural bacteriochlorophyll‐a was converted to chemically stable free‐base derivatives possessing different kinds of hydrophilic C17‐propionate residues. These semi‐synthetic bacteriochlorins were found to have self‐assembling ability in an aqueous environment and formed stable J‐type aggregates in a cell culture medium containing 0.2% DMSO. The electronic absorption spectra of all the sensitizers showed Qy absorption maxima at 754 nm in DMSO as their monomeric states, while a drastic shift of the red‐most bands to ca. 880 nm was observed in the aqueous medium. The circular dichroism spectra in the medium showed much intense signals compared to those measured in DMSO, supporting the formation of well‐ordered supramolecular structures. By introducing hydrophilic side chains, the bacteriochlorin sensitizers could be dispersed in the aqueous medium as their J‐aggregates without the use of any surfactants. Cellular uptake efficiencies as well as photodynamic activities were evaluated using human cervical adenocarcinoma HeLa cells. Among the 11 photosensitizers investigated, the best result was obtained for a charged derivative possessing trimethylammonium terminal (17‐CH2CH2COOCH2CH2N+(CH3)3I−) and photocytotoxicity of EC50 = 0.09 μM was achieved by far‐red light illumination of 35 J/cm2 from an LED panel (730 nm). [ABSTRACT FROM AUTHOR]

Förster resonance energy transfer (FRET) has been widely applied in fluorescence imaging, sensing and so on, while developing useful strategy of boosting FRET efficiency becomes a key issue that limits the application. Except optimizing spectral properties, promoting orientation factor (κ2) has been well discussed but rarely utilized for boosting FRET. Herein, we constructed binary nano‐assembling of two thermally activated delayed fluorescence (TADF) emitters (2CzPN and DMAC‐DPS) with J‐type aggregate of cyanine dye (C8S4) as doping films by taking advantage of their electrostatic interactions. Time‐resolved spectroscopic measurements indicated that 2CzPN/Cy‐J films exhibit an order of magnitude higher kFRET than DMAC‐DPS/Cy‐J films. Further quantitative analysing on kFRET and kDET indicated higher orientation factor (κ2) in 2CzPN/Cy‐J films play a key role for achieving fast kFRET, which was subsequently confirmed by anisotropic measurements. Corresponding DFT/TDDFT calculation revealed strong "two‐point" electrostatic anchoring in 2CzPN/Cy‐J films that is responsible for highly orientated transitions. We provide a new strategy for boosting FRET in nano‐assemblies, which might be inspired for designing FRET‐based devices of sensing, imaging and information encryption. [ABSTRACT FROM AUTHOR]

An amphiphilic aza‐BODIPY dye (S)‐1 bearing two chiral hydrophilic side chains with S‐stereogenic centers was synthesized. This dye exhibited kinetic‐controlled self‐assembly pathways and supramolecular chiral polymorphism properties in MeOH/H2O (9/1, v/v) mixed solvent. The (S)‐1 monomers first aggregated into a kinetic controlled, off‐pathway species Agg. A, which was spontaneously transformed into an on‐pathway metastable aggregate (Agg. B) and subsequently into the thermodynamic Agg. C. The three aggregate polymorphs of dye (S)‐1 displayed distinct optical properties and nanomorphologies. In particular, chiral J‐aggregation characteristics were observed for both Agg. B and Agg. C, such as Davydov‐split absorption bands (Agg. B), extremely sharp and intense J‐band with large bathochromic shift (Agg. C), non‐diminished fluorescence upon aggregation, as well as strong bisignated Cotton effects. Moreover, the AFM and TEM studies revealed that Agg. A had the morphology of nanoparticle while fibril or rod‐like helical nanostructures with left‐handedness were observed respectively for Agg. B and Agg. C. By controlling the kinetic transformation process from Agg. B to Agg. C, thin films consisting of Agg. B and Agg. C with different ratios were prepared, which displayed tunable CPL with emission maxima at 788–805 nm and g‐factors between −4.2×10−2 and −5.1×10−2. [ABSTRACT FROM AUTHOR]

Zinc methyl 3‐hydroxymethyl‐pyropheophorbides‐a possessing an acylhydrazinylidene group at the 131‐position were prepared by chemically modifying chlorophyll‐a, which were models of bacteriochlorophyll‐d as one of the light‐harvesting pigments in photosynthetic green bacteria. Similar to the self‐aggregation of natural bacteriochlorophyll‐d in the antenna systems called chlorosomes, some of the synthetic models self‐aggregated in an aqueous Triton X‐100 solution to give red‐shifted and broadened visible absorption bands. The newly appeared oligomeric bands were ascribable to the exciton coupling of the chlorin π‐systems along the molecular y‐axis, leading to intense circular dichroism bands in the red‐shifted Qy and Soret regions. The self‐aggregation in the aqueous micelle was dependent on the steric size of the terminal substituent at the 13‐acylhydrazone moiety. An increase in the length of the oligomethylene chain as the terminal moved the red‐shifted Qy maxima to shorter wavelengths, and branched alkyl and benzyl substitutes afforded no more self‐aggregates to leave monomeric species in the hydrophobic environment inside the micelle. These results indicated that the acyl groups on the 13‐hydrazone as the alternative of the natural 13‐ketone regulated the chlorosome‐like self‐aggregation. [ABSTRACT FROM AUTHOR]

To better understand the correlation between molecular structure and optical properties such as aggregation‐induced emission (AIE) and mechanochromic luminescence (MCL) emission, two new pyrene‐based derivatives with substitutions at the 4‐ and 5‐positions (1HH) and at the 4‐, 5‐, 9‐, and 10‐positions (2HH) were designed and synthesized. Cyano groups were introduced at the periphery of the synthesized compounds (1HCN, 1OCN, 1BCN, 2HCN, 2OCN, and 2BCN) to investigate the influence of these groups on the emission properties of the pyrene derivatives both in solution and in the solid state. The fluorescence emission performance of these compounds in water/acetone mixtures was simultaneously studied, revealing outstanding aggregation‐induced emission properties. The typical shift in emission maxima to higher values was attributed to J‐aggregate formation in the aggregate state. Careful investigation of the crystal structures demonstrated abundant and intense intermolecular interactions, such as C−H...π and C−H...N hydrogen bonds, contributing to the remarkable mechanochromic luminescence performance of these compounds. The MCL properties of all the compounds were investigated using powder X‐ray diffraction, and the remarkable mechanochromic properties were attributed to J‐aggregate phenomena in the solid state. These results provide valuable insights into the structure‐property relationship of organic MCL materials, guiding the design of efficient organic MCL materials. [ABSTRACT FROM AUTHOR]

J‐aggregates are highly desired dye aggregates but so far there has been no general concept how to accomplish the required slip‐stacked packing arrangement for dipolar merocyanine (MC) dyes whose aggregation commonly affords one‐dimensional aggregates composed of antiparallel, co‐facially stacked MCs with H‐type coupling. Herein we describe a strategy for MC J‐aggregates based on our results for an amphiphilic MC dye bearing alkyl and oligo(ethylene glycol) side chains. In an aqueous solvent mixture, we observe the formation of two supramolecular polymorphs for this MC dye, a metastable off‐pathway nanoparticle showing H‐type coupling and a thermodynamically favored nanosheet showing J‐type coupling. Detailed studies concerning the self‐assembly mechanism by UV‐Vis spectroscopy and the packing structure by atomic force microscopy and wide‐angle X‐ray scattering show how the packing arrangement of such amphiphilic MC dyes can afford slip‐stacked two‐dimensional nanosheets whose macrodipole is compensated by the formation of a bilayer structure. As an additional feature we demonstrate how the size of the nanosheets can be controlled by seeded living supramolecular polymerization. [ABSTRACT FROM AUTHOR]

Contamination of water supplies by polyfluoroalkyl substances, notably perfluorooctanesulfonate (PFOS) and perfluorooctanoic acid (PFOA), has serious health and environmental consequences. Therefore, the development of straightforward and effective means of monitoring and removing PFASs is urgently required. In this study, we report a rapid and sensitive method for the detection of PFOS and PFOA in water that rely on the J‐aggregate formation of meso‐ester‐BODIPY dyes. The dye C10‐mim, which contains a hydrophilic methylimidazolium group and a hydrophobic alkylated BODIPY, self‐assembles in water into weakly green‐emissive micellar assemblies. Upon binding to PFOS or PFOA, a spontaneous disassembly and reorganization forms orange‐emissive J‐aggregates. The rapid formation (≤5 s) of J‐aggregates and the accompanying spectral shifts provide a superior sensing performance, with excellent sensitivity (limit of detection=0.18 ppb for PFOS) and distinct chromogenic and fluorogenic "turn‐on" responses. [ABSTRACT FROM AUTHOR]

The relations for the polarizability of the metallic nanoparticles, coated with the shell of cyanine dyes, are obtained in the article. The frequency dependencies for light absorption and scattering efficiencies, the heating of the composite nanoparticle and the electric field amplification in its neighborhood are studied. It is established that all the dependencies have three maxima which correspond to the frequencies of hybrid plasmon-exciton resonance. It is shown that an increase in content of metal in the nanoparticle causes a blue shift of the maxima from the visible part of the spectrum and a red shift of the maximum from ultraviolet frequency range. The issue of application of metal-organic nanoparticles in nanomedicine, in particular for the photothermal therapy of malignant neoplasms is studied. [ABSTRACT FROM AUTHOR]

Coherent energy exchange between plasmons and excitons has attracted considerable interest from researchers worldwide because of their potential applications in enhanced optical processes, quantum information processing and quantum devices, artificial light harvesting, digital data storage, chemical and biological sensing, and so forth. The energy exchange between a plasmon and an exciton shows a strong dependence on various plasmonic and excitonic parameters. Here, we investigate the role of a subtle change in the chemical structure of an exciton-forming dye in controlling plasmon–exciton interaction at the nanoscale. The only difference between the two exciton-forming dyes used in this study is that one of them (Cy78) has an ethyl group on its polymethine chain, but the other (Cy75) does not. The two plexciton hybrids of the J-aggregates of Cy78 and Cy75 with the same gold nanorod are expected to show very similar plasmon–exciton interactions. However, using ensemble-level extinction as well as single-particle-level scattering spectroscopy, we reveal that, contrary to our expectations, two plexciton systems show drastically different plasmon–exciton coupling strengths. Further investigations into the origin of this unexpected observation using fluorescence spectroscopy and atomic force microscopy, complemented by density functional calculations, reveal that Cy75 exclusively exists in trans-conformation, while the presence of the ethyl substituent in Cy78 gives rise to the coexistence of cis- and trans-conformations. The presence of cis-isomers leads to the enhancement of the overall dipole moment of Cy78 J-aggregates and thereby enhancing the Rabi splitting of its plexciton hybrid by ∼100% compared to Cy75-plexciton. This comprehensive study clearly demonstrates how even an apparently "innocent" and extremely subtle change in the structure of an exciton-forming dye can drive nanoscale plasmon–exciton coupling from one coupling regime to another. [ABSTRACT FROM AUTHOR]

The optical properties of composites consisting of inclusion particles of 'metal core--J-aggregate shell' structure within the dielectric matrix are investigated. Calculations of the frequency dependences of the dielectric functions of layered nanoparticles, the effective dielectric function, and the absorption coefficient of composites are carried out by using the classical and dimensionally adjusted Maxwell-Garnett models of effective medium. As shown, one exciton and two hybrid plasmon--exciton modes are excited in the investigated composite nanoparticles. The nature of oscillations of the real and imaginary parts of the dielectric function of layered particles in the infrared frequency range is explained. The approximate analytical model is constructed to determine the frequencies of hybrid plasmon--exciton resonances. As found out, these frequencies are significantly dependent on the metal content in the nanoparticle. The condition is defined, under which the first maximum of the imaginary part of the dielectric function of a nanoparticle falls into the infrared range of the spectrum. As shown, the frequencies of the hybrid modes of the nanocomposite depend significantly on the dimensions of the core and shell. The third maximum of the imaginary part of the effective dielectric function is located in the ultraviolet frequency range. As proved, the dimensional correction of the Maxwell-Garnett model is used, when the frequency dependences of the absorption coefficient of nanocomposite are studied, and the difference in the results of the calculation of the effective dielectric function is insignificant. The changes of the amplitude, the positions and the numbers of maxima of the imaginary parts of the dielectric functions of particles and composite as well as the absorption coefficient are traced, when the sizes and materials of the core and shell of the inclusion particles are changed. It is represented that, if the metal content is decreased in the inclusion particle, the maxima of the absorption coefficient of the composite are converged, and if the metal content is increased, then the maxima are moved apart. [ABSTRACT FROM AUTHOR]

A dimethylaniline (donor)‐indanedione (acceptor) conjugate (sensor 1) with a very low molecular weight of 277 g mol−1 and intramolecular charge transfer (ICT) characteristics was synthesized. Sensor 1 shows weak ICT fluorescence in solution, but strong emission (Φ=16%) in the solid state owing to intramolecular and intermolecular C−H⋅⋅⋅O hydrogen bonds that inhibit the free rotation of the exocyclic C−C single bond. Compared to yellow emitter 1Y, which has a similar donor‐acceptor structure, sensor 1 shows red fluorescence in the solid state owing to J‐aggregate formation. The colorimetric and fluorometric responses of sensor 1 to cyanide in both solution and solid state are due to the nucleophilic addition of cyanide to the β‐conjugated carbon of the indanedione group, which prohibits ICT. Additionally, inexpensive portable paper‐based test kits based on sensor 1 were easily prepared and could be used for fast and quantitative naked‐eye cyanide detection in real time. [ABSTRACT FROM AUTHOR]

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.

The relations for the polarizability of the metallic nanoparticles, coated with the shell of cyanine dyes, are obtained in the article. The frequency dependencies for light absorption and scattering efficiencies, the heating of the composite nanoparticle and the electric field amplification in its neighborhood are studied. It is established that all the dependencies have three maxima which correspond to the frequencies of hybrid plasmon-exciton resonance. It is shown that an increase in content of metal in the nanoparticle causes a blue shift of the maxima from the visible part of the spectrum and a red shift of the maximum from ultraviolet frequency range. The issue of application of metal-organic nanoparticles in nanomedicine, in particular for the photothermal therapy of malignant neoplasms is studied.

We theoretically demonstrate the strong coupling between plasmons and excitons in the plexcitonic circular grating. The J-aggregate molecules, as one of the excitonic materials, have unique optical properties, which is an excellent choice for a wide range of optoelectronic applications. In this hybrid system, the J-aggregate thickness and position has important role in exciton-plasmon coupling. For this reason, we consider two different plasmonic hybrid structures as the Au core@shell, and circular grating. Our results illustrate that, the Rabi splitting values for Au core @ J-aggregate layer is calculated to be 118 meV and for the Au core–J-aggregate layer–Au layer rach to 128 meV which is confimes that plexcitonic circular grating shows stronger couplings than the plexcitonic core@shell structure. [ABSTRACT FROM AUTHOR]

• A way for constructing phthalocyanine J-aggregate nanoparticles (PJN) is developed. • Phthalocyanine J-aggregates are stabilized by a yeast β -D-glucan-based carrier. • PJN possess huge-redshifted (140–165 nm) and strong absorption. • The relationships between phthalocyanine structure and J-aggregation are discussed. • PJN can afford tumor-associated macrophages-targeted multimodal phototheranostics. Phthalocyanines (Pcs) are considered promising in cancer phototherapy. However, their maximum absorption wavelengths are only around 700 nm, which cannot allow deep tissue penetration and leads to poor therapeutic efficacy. To expand their clinical application, significantly shifting their absorption to longer wavelengths is urgently required. Dye J-aggregates exhibit a redshifted absorption relative to its monomer. However, Pc J-aggregates with enormous-redshifted and intense absorption is rarely reported, and little is known about the relationships between Pc structure and J-aggregation. Herein, such Pc J-aggregates are ingeniously conceived. With a yeast β -D-glucan-ursodeoxycholic acid conjugate as a potential tumor-associated macrophages (TAMs)-targeting carrier and 1-(4-carboxyethylphenoxy) zinc (II) phthalocyanine (Pc1) as a model, Pc1 J-aggregate nanoparticle (NanoPc1) is obtained via ultrasonication-aided emulsification-solvent evaporation technique. NanoPc1 displays strong absorption at 830 nm, with a 156 nm redshift. Further investigation on another twenty-four Pcs demonstrates that unsubstituted zinc (II) or magnesium (II) Pc and hydrophobic mono-substituted zinc (II) or magnesium (II) Pcs with mono-substituted phenoxy or phenylthio or naphthoxy as a substituent can readily form desired Pc J-aggregates with significant redshifts (140–165 nm). The other Pcs fail to form expected J-aggregates probably due to absence of central metals, steric hindrance on central metals (atoms), forming axial coordination on central metals, disorder tendency during self-assembly or hydrophilicity. The theoretical calculation indicates that Pc1 in its J-aggregates exhibits a spiral-like arrangement, and the reduction in the energy gap between HOMO and LUMO and variation of intermolecular π-π interaction caused by J-aggregate formation are responsible for the huge redshift. Additionally, using NanoPc1 as an exemplar, such Pc J-aggregate nanoparticles are substantiated to afford TAMs-targeted and efficient tri-modal imaging and photothermal therapy in a H22 mouse model. [ABSTRACT FROM AUTHOR]

Electronics made from biological materials are desirable for use in medical devices, biosensors, and soft robotics because they have properties inaccessible to current inorganic technologies. Here, a series of cationic peptides were developed to self‐assemble with the anionic porphyrin meso‐tetra(4‐sulfonatophenyl)porphine (TPPS4) into supramolecular light‐harvesting wires known as J‐aggregates were developed. In addition to quantifying the binding events between each peptide and TPPS4, we found co‐incubation with mixed peptides allowed TPPS4 to bridge two different peptides at their terminal porphyrin‐binding regions. The J‐aggregates formed on macroscopic scale in near quantitative yield within ~3 h and readily interconverted with the soluble monomers upon cycling the pH; to our knowledge, this is the first report of a peptide‐porphyrin system with such properties. This work has practical and conceptual relevance to the development of new bioelectronic materials. [ABSTRACT FROM AUTHOR]

A molecule featuring two distinct cooperatively grown J‐aggregates is investigated. Interestingly, when cooling a hot monomer solution, the thermodynamically less stable J1 is exclusively formed even at a particularly slowed temperature dropping rate, which transforms to the more stable J2 at room temperature with very slow kinetics. This observation is ascribed to the differed nucleus sizes of J1 and J2. During the cooling process, smaller J1 nuclei are formed first at a higher temperature, favored by the entropy effect. At intermediate temperatures, the elongation of J1 out‐competes the nucleation of J2. Then, below the elongation temperature of J2, the formation of this thermodynamically stable aggregate is hindered kinetically, due to the depletion of monomer by the slow dissociation of J1. Additional evidence proving the larger nucleus size of J2 is also identified with the varied‐temperature spectral analyses and mathematic simulations. [ABSTRACT FROM AUTHOR]

J-aggregate is a promising strategy to enhance second near-infrared window (NIR-II) emission, while the controlled synthesis of J-aggregated NIR-II dyes is a huge challenge because of the lack of molecular design principle. Herein, bulk spiro[fluorene-9,9'-xanthene] functionalized benzobisthiadiazole-based NIR-II dyes (named BSFX-BBT and OSFX-BBT) are synthesized with different alkyl chains. The weak repulsion interaction between the donor and acceptor units and the S…N secondary interactions make the dyes to adopt a co-planar molecular conformation and display a peak absorption >880 nm in solution. Importantly, BSFX-BBT can form a desiring J-aggregate in the condensed state, and femtosecond transient absorption spectra reveal that the excited states of J-aggregate are the radiative states, and J-aggregate can facilitate stimulated emission. Consequently, the J-aggregated nanoparticles (NPs) display a peak emission at 1124 nm with a high relative quantum yield of 0.81%. The efficient NIR-II emission, good photothermal effect, and biocompatibility make the J-aggregated NPs demonstrate efficient antitumor efficacy via fluorescence/photoacoustic imaging-guided phototherapy. The paradigm illustrates that tuning the aggregate states of NIR-II dye via spiro-functionalized strategy is an effective approach to enhance photo-theranostic performance., (© 2024 Wiley‐VCH GmbH.)

Plexcitonic nanoparticles exhibit strong light-matter interactions, mediated by localized surface plasmon resonances, and thereby promise potential applications in fields such as photonics, solar cells, and sensing, among others. Herein, these light-matter interactions are investigated by UV-visible and surface-enhanced Raman scattering (SERS) spectroscopies, supported by finite-difference time-domain (FDTD) calculations. Our results reveal the importance of combining plasmonic nanomaterials and J-aggregates with near-zero-refractive index. As plexcitonic nanostructures nanorattles are employed, based on J-aggregates of the cyanine dye 5,5,6,6-tetrachloro-1,1-diethyl-3,3-bis(4-sulfobutyl)benzimidazolocarbocyanine (TDBC) and plasmonic silver-coated gold nanorods, confined within mesoporous silica shells, which facilitate the adsorption of the J-aggregates onto the metallic nanorod surface, while providing high colloidal stability. Electromagnetic simulations show that the electromagnetic field is strongly confined inside the J-aggregate layer, at wavelengths near the upper plexcitonic mode, but it is damped toward the J-aggregate/water interface at the lower plexcitonic mode. This behavior is ascribed to the sharp variation of dielectric properties of the J-aggregate shell close to the plasmon resonance, which leads to a high opposite refractive index contrast between water and the TDBC shell, at the upper and the lower plexcitonic modes. This behavior is responsible for the high SERS efficiency of the plexcitonic nanorattles under both 633 nm and 532 nm laser illumination. SERS analysis showed a detection sensitivity down to the single-nanoparticle level and, therefore, an exceptionally high average SERS intensity per particle. These findings may open new opportunities for ultrasensitive biosensing and bioimaging, as superbright and highly stable optical labels based on the strong coupling effect., (© 2023 The Authors. Small published by Wiley‐VCH GmbH.)

The present study deals with the design, formation, and photophysical studies on light‐harvesting inorganic‐organic nanohybrid associates comprising a less‐toxic, inorganic core‐shell QD (Cu−In−S/ZnS) and an organic S0041 dye aggregate. One of the main objectives of this study is to understand the interaction between the inorganic and organic excitonic components of the hybrid system and its implication on the photophysical response of the system. The nanohybrid associate have been obtained through the self‐assembly of S0041 dye molecules (organic exciton) onto Cu−In−S/ZnS QD (inorganic exciton). The characterization of as‐synthesized QD have been done by conventional microscopic and spectroscopic measurements. The exciton domain length for the organic dye aggregates is estimated to be 24 nm. Steady‐state absorption, emission, and time‐resolved photoluminescence (PL) intensity decay measurements have been carried out to understand the interaction mechanism between inorganic and organic excitonic components and the overall photophysical behaviour of the hybrid system. The studies have revealed that the formation of hybrid associate is electrostatically driven and thermodynamically feasible. Interestingly, steady‐state and time‐resolved PL decay measurements and their analysis have revealed that the interaction between inorganic QD and organic aggregate is mediated through dipole‐dipole Förster energy transfer (ET) mechanism and the ET efficiency is found to be as high as 95%. The present system is expected to be used in fabrication of less‐toxic nanoscale light‐harvesting system. [ABSTRACT FROM AUTHOR]

[Display omitted] • Zinc 31-demethyl-bacteriochlorophylls- d with pinacol boronate on B-ring were prepared. • The synthetic analogs self-aggregated in aqueous micelles similar to chlorosome. • The chlorosome-like aggregates exhibited red-shifted and broadened Qy bands. • Exciton-coupled circular dichroism couplets were observed in the red-shifted regions. • The J-aggregation suppressed with an increase in the size of the boron substituents. Zinc 3-hydroxymethyl-131-oxo-bacteriochlorins possessing a variety of pinacol boronates on the B-ring were prepared from chemical modification of naturally occurring chlorophyll- a. The synthetic bacteriochlorophyll- d analogs were dissolved into an aqueous Triton X-100 solution to exhibit red-shifted and broadened electronic absorption bands with reversed S-shape circular dichroism bands, compared with their monomeric bands. The behaviors indicated that most synthetic models possessing a bacteriochlorin π-system self-aggregated inside the aqueous micelles to give similar oligomers as the J-aggregates of bacteriochlorophyll- d bearing a chlorin π-skeleton in major light-harvesting antennas of green photosynthetic bacteria, chlorosomes. The methylboronate self-aggregated more largely than the phenylboroante, and the self-aggregation was suppressed by ortho -substitution on the phenyl ring: phenyl > 1-naphthyl ≫ 9-anthryl and phenyl > 2,6-dimethylphenyl. Along with an increase in the size of the substituents on the boron atom of their boronates, the formation of the chlorosome-like self-aggregates decreased substantially. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbon (PAH) structures with suitable electron‐withdrawing groups are useful building blocks for developing optical and electron‐transporting materials. Here, we report the application of a double benzannulation process to the syntheses of PAH diimides with enlarged π‐frameworks featuring a central anthracene moiety. The preparations are realized by copper‐catalyzed [4+2] cycloaddition of ethynyl‐substituted aromatic dicarboximide to 2,5‐bis(phenylethynyl)terephthalaldehyde, followed by intramolecular photocyclization or direct arylation via Heck cross coupling. A central symmetric benzo[1,2‐k:4,5‐k′]‐bis(fluoranthene)‐3,4,12,13‐tetracarboxyl diimide (BFDI) is acquired, with the single crystal structure revealing its completely planar polycyclic skeleton. Such a shape‐persistent PAH expectedly exhibits a tendency to stack face‐to‐face and forms J‐aggregates. Moreover, BFDI can be difunctionalized site‐selectively at the reactive 9 and 10 positions of the anthracene unit and then applied to prepare conjugated polymers. When coupled with 1,4‐diketopyrrolo[3,4‐c]‐pyrrole (DPP) via thiophene and dithiophene linkers, two polymers with significantly broadened absorption bands extended to the near‐infrared regime are obtained, evidencing the effective π‐conjugative extension ability of BFDI unit. [ABSTRACT FROM AUTHOR]

Issues of molecular weight determination have been central to the development of supramolecular polymer chemistry. Whereas relationships between concentration and optical features are established for well-behaved absorptive and emissive species, for most supramolecular polymeric systems no simple correlation exists between optical performance and number-average molecular weight (Mn). As such, the Mn of supramolecular polymers have to be inferred from various measurements. Herein, we report an anion-responsive supramolecular polymer [M1.Zn(OTf)2]n that exhibits monotonic changes in the fluorescence color as a function of Mn. Based on theoretical estimates, the calculated average degree of polymerization (DPcal) increases from 16.9 to 84.5 as the monomer concentration increases from 0.08 mM to 2.00 mM. Meanwhile, the fluorescent colors of M1 + Zn(OTf)2 solutions were found to pass from green to yellow and to orange, corresponding to a red shift in the maximum emission band (λmax). Therefore, a relationship between DPcal and λmax could be established. Additionally, the anion-responsive nature of the present system meant that the extent of supramolecular polymerization could be regulated by introducing anions, with the resulting change in Mn being readily monitored via changes in the fluorescent emission features. [ABSTRACT FROM AUTHOR]

Power conversion efficiency of organic solar cells increases continuously due the emergence of novel nonfullerene acceptors (NFAs). As solar cell efficiency is governed by photogeneration followed by charge carrier transport toward the electrode, understanding of univocal electron transport properties of NFAs is of great importance. Acceptors from the indacenodithienothiophene‐based family such as ITIC, ITIC‐Th, and ITIC‐4F have been intensively studied in solar cells. Importantly, ITIC‐ and ITIC‐4F‐based films evolve with increasing annealing temperature from 100 °C up to 250 °C into several polymorphs that may impact the electronic transport strongly. Here, for the first time, the effects of temperature‐dependent polymorphism on the charge transport properties of ITIC, ITIC‐Th, and ITIC‐4F are studied. A unipolar, high performance, and high‐temperature stable thin‐film transistor structure is developed first using divinyltetramethyldisiloxane‐bis(benzocyclobutene) as dielectric passivation material to explore the intrinsic charge transport up to 240 °C. It is shown that electron mobility in the three ITIC‐based films is strongly influenced by the molecule specific polymorphism at optimal temperatures. This leads to a strong increase in electron mobility compared to the as‐cast films, which is correlated to changes in molecule aggregation, domain crystallinity, and orientation as well as intermolecular electronic coupling. [ABSTRACT FROM AUTHOR]

We report 1.6 ± 1 μm exciton transport in self-assembled supramolecular light-harvesting nanotubes (LHNs) assembled from amphiphillic cyanine dyes. We stabilize LHNs in a sucrose glass matrix, greatly reducing light and oxidative damage and allowing the observation of exciton-exciton annihilation signatures under weak excitation flux. Fitting to a one-dimensional diffusion model, we find an average exciton diffusion constant of 55 ± 20 cm2/s, among the highest measured for an organic system. We develop a simple model that uses cryogenic measurements of static and dynamic energetic disorder to estimate a diffusion constant of 32 cm2/s, in agreement with experiment. We ascribe large exciton diffusion lengths to low static and dynamic energetic disorder in LHNs. We argue that matrix-stabilized LHNS represent an excellent model system to study coherent excitonic transport.

J-aggregate dyes have been widely used in biomedicine, chemical engineering, etc., due to their structure and photophysical properties. J-aggregation theory describes the nearest-neighbor molecules' transition dipole moments in a sliding stacking arrangement. However, we found that the intervention of polyvalent anions can induce the J-aggregation of dyes via the intermolecular van der Waals and electrostatic interactions, which is an essential way once overlooked. Experimental results and theoretical calculations revealed that the more negatively charged or large size of anions within a specific range, the more efficiently the dye will form J-aggregates. As an application, the content of polyvalent anion salts in a salt-stressed Arabidopsis model was evaluated based on the ratiometric fluorescence emission resulting from the polyvalent anion-induced dye J-aggregation. • A new form of J-aggregation induction, polyvalent anion-induced aggregation was proposed. • Two probes with similar chemical structures to JC-1 were developed. • All three probes can be induced to J-aggregation by polyvalent anions. • The content of polyvalent anions in salt-stressed Arabidopsis model was quantified by JC-OH. [ABSTRACT FROM AUTHOR]

Tunable plasmon-exciton coupling is demonstrated at room temperature in hybrid systems consisting of Ag@Au hollow nanoshells (HNSs) and J-aggregates. The strong coupling depends on the exciton binding energy and the localized surface plasmon resonance strength, which can be tuned by changing the thickness of the Ag@Au HNS. An evident anticrossing dispersion curve in the coupled energy diagram of the hybrid system was observed based on the absorption spectra obtained at room temperature. In this paper, strong coupling was observed twice (first at lower wavelength and then also at a higher wavelength) via a single preparation process of the Ag@Au HNS system. The first Rabi splitting energy (ħΩ) is 225 meV. Then, the extinction spectra of the bare Ag@Au HNS and the Ag@Au HNS-J-aggregate hybrid system were reproduced by numerical simulations using the finite-difference time domain method, which were in good agreement with the experimental observations. We attributed the strong coupling of the new shell hybrid system to the reduced local surface plasmon (LSP) mode volume of the Ag@Au HNS. This volume is about 1021.6 nm3. The features of the Ag@Au HNS nanostructure with a small LSP mode volume enabled strong light-matter interactions to be achieved in single open plasmonic nanocavities. These findings may pave the way toward nanophotonic devices operating at room temperature.

In water–DMF at DMF content less than 2.6 mol dm−3, deuteroporphyrin IX dimethyl ester forms both H- and J-aggregates. The J-aggregates are detected as a single type of associated species after binding of the porphyrin with BSA on the surface of the protein IB subdomain. [ABSTRACT FROM AUTHOR]

In this work, manifestations of IR luminescence sensitization of Indocyanine Green during conjugation with colloidal Ag2S quantum dots with an average size of 2.2 and 3.7 nm, passivated with thioglycolic acid molecules (Ag2S/TGA QDs) are studied using absorption and luminescence techniques. The possibility of enhancing luminescence in the dye monomer band (820 nm) under excitation at 660 nm by a factor of 6 in the presence of Ag2S/TGA QDs (2.2 nm) due to a decrease in the polymethine dye chain movement via coordination interaction with QDs was demonstrated. The way to switch-over from the first therapeutic window of biological tissue transparency (NIR-I, 700–950 nm) to the second (NIR-II, 1000–1700 nm), based on sensitization of IR luminescence of Ag2S/TGA QDs with an average size of 3.7 nm in the region of 1040 nm due to of resonance non-radiative transfer of excitation energy from Ag2S/TGA (2.2 nm) QDs at 900 nm to Ag2S/TGA QDs (3.7 nm) via the J-aggregate of ICG dye, which acts as an exciton bridge. [ABSTRACT FROM AUTHOR]

Featured Application: One can generate by irradiation of light an exotic aggregation state of molecules that cannot exist in thermal equilibrium. A highly efficient light-induced aggregation of porphyrin molecules in solution was recently reported for 4-[10,15,20-tris(4-sulfophenyl)-21,24-dihydroporphyrin-5-yl]benzenesulfonic acid (TPPS). Here, we demonstrate that rhodamine 6G (R6G) and pseudoisocyanine (PIC) also show efficient light-induced aggregation in unsaturated aqueous solution, being detected with a multichannel lock-in amplifier as the absorbance decrease/increase in the monomers/aggregates, induced by a laser at 633 nm, which is non-resonant off their main monomer absorption wavelengths. The light-induced aggregation states are H-aggregates that are hardly formed in the thermal equilibrium. The similar absorbance changes are absent in the monomer molecules fixed in polyvinyl alcohol (PVA) films. The aggregation efficiency defined as (Δ A / A) / (U t r a p / k B T) , where A is the absorbance of the monomers, Δ A is the absorbance increase in the aggregates, U t r a p is the optical gradient force potential, and k B T is the thermal energy at room temperature, is approximately 100 for R6G and 500 for PIC, which are much smaller than that of TPPS. [ABSTRACT FROM AUTHOR]

The absorption properties of molecular layer of cyanine dyes and its J-aggregates coated on the island films in the form of an inhomogeneous ensemble of silver or gold nanoparticles were studied. The different overlapping modes of layer absorption and plasmon resonance were obtained by varying the molecular length and the equivalent thickness of the film. It was shown the absorption of hybrid structure was not a simple sum of overlapping bands. Furthermore, the high enhancement of the molecular absorption was observed due to the influence of the near fields of plasmonic silver nanoparticles in comparison with gold island film. Besides, the induced transparency was observed at the absorption maximum of J-aggregates, which could indicate the interaction between the plasmons of metal nanoparticles and the excitons of the J-aggregate of cyanine dye. [ABSTRACT FROM AUTHOR]

It has been reported that when irradiated with laser light non-resonant with the main absorption peaks, porphyrin molecules (4-[10,15,20-tris(4-sulfophenyl)-21,24-dihydroporphyrin-5-yl]benzenesulfonic acid, TPPS) in an aqueous solution become 10,000 to 100,000 times more efficient in light-induced molecular aggregation than expected from the ratio of gradient force potential to the thermal energy of molecules at room temperature. To determine the mechanism of this phenomenon, experiments on the light-induced aggregation of TPPS in alcohol solutions (methanol, ethanol, and butanol) were performed. In these alcohol solutions, the absorbance change was orders of magnitude smaller than in the aqueous solution. Furthermore, it was found that the absorbance change in the aqueous solution tended to be saturated with the increase of the irradiation intensity, but in the ethanol solution, the absorbance change increased linearly. These results can be qualitatively explained by the model in which intermolecular light-induced interactions between molecules within a close distance among randomly distributed molecules in the laser irradiation volume are highly relevant to the signal intensity. However, conventional dipole–dipole interactions, such as the Keesom interaction, are not quantitatively consistent with the results. [ABSTRACT FROM AUTHOR]

A nanoemulsion with a porphyrin shell (NewPS) was created by the self‐assembly of porphyrin salt around an oil core. The NewPS system has excellent colloidal stability, is amenable to different porphyrin salts and oils, and is capable of co‐loading with chemotherapeutics. The porphyrin salt shell enables porphyrin‐dependent optical tunability. The NewPS consisting of pyropheophorbide a mono‐salt has a porphyrin shell of ordered J‐aggregates, which produced a narrow, red‐shifted Q‐band with increased absorbance. Upon nanostructure dissociation, the fluorescence and photodynamic reactivity of the porphyrin monomers are restored. The spectrally distinct photoacoustic imaging (at 715 nm by intact NewPS) and fluorescence increase (at 671 nm by disrupted NewPS) allow the monitoring of NewPS accumulation and disruption in mice bearing KB tumors to guide effective photodynamic therapy. Substituting the oil core with Lipiodol affords additional CT contrast, whereas loading paclitaxel into NewPS facilitates drug delivery. [ABSTRACT FROM AUTHOR]

A novel core–shell structured columnar liquid crystal composed of a donor‐acceptor dyad of tetraphenoxy perylene bisimide (PBI), decorated with four bithiophene units on the periphery, was synthesized. This molecule self‐assembles in solution into helical J‐aggregates guided by π–π interactions and hydrogen bonds which organize into a liquid‐crystalline (LC) columnar hexagonal domain in the solid state. Donor and acceptor moieties exhibit contrasting exciton coupling behavior with the PBIs' (J‐type) transition dipole moment parallel and the bithiophene side arms' (H‐type) perpendicular to the columnar axis. The dyad shows efficient energy and electron transfer in solution as well as in the solid state. The synergy of photoinduced electron transfer (PET) and charge transport along the narcissistically self‐assembled core–shell structure enables the implementation of the dye in two‐contact photoconductivity devices giving rise to a 20‐fold increased photoresponse compared to a reference dye without bithiophene donor moieties. [ABSTRACT FROM AUTHOR]

A novel fluorescent probe L was designed for rapid detection of Al3+ with high selectivity in water-acetonitrile medium based on aggregation-induced emission (AIE). The recognition mechanism was investigated by fluorescence spectra, SEM, FI-IR, 1H NMR, and mass spectra. The detection limit of Al3+ was 5.3 × 10−8 M. The recoveries were within the range of 84.5–103.3% and the relative standard deviation (RSD) values were within the range of 1.7–6.4%. The AIE behavior could be attributed to the J-aggregates formation and the chelation-enhanced fluorescence (CHEF) in water-acetonitrile medium. The probe L can be used to detect Al3+ in food and environmental samples. What's more interesting is that the L could detect intracellular Al3+ in live cells by bioimaging. [ABSTRACT FROM AUTHOR]

The adsorption of three different polycations at the negatively charged surface of tubular J-aggregates of the amphiphilic cyanine dye 3,3′-bis(2-sulfopropyl)-5,5′,6,6′-tetrachloro-1,1′-dioctylbenzimidacarbocyanine (C8S3) is investigated by means of cryogenic electron microscopy and optical absorption spectroscopy. All three polycations could be adsorbed at the tubular aggregates without flocculation or precipitation when added in molar amounts of monomers sufficiently smaller than that of the dye molecules. It is found that preferably, a minority of aggregates is coated by the polycations while a majority of aggregates is left uncoated. For the coated aggregates, the adsorption leads to charge reversal of the aggregate surface as supported by zeta potential measurements. The morphology of the coating differs significantly for the three polycations: The branched polycation polyethylenimine (PEI) attaches to the tubular aggregate by hit-and-stick adsorption of the coiled state in solution forming irregular clot-like coatings; the flexible and weakly cationic poly (allylamine hydrochloride) (PAH) forms a more homogeneous coating but destroys the integrity of the dye aggregate; the more hydrophobic and strong polycation poly (diallyldimethylammonium chloride) (PDADMAC) forms a thin and homogeneous layer, supposedly by wrapping around the tubular aggregate. For the latter growth of a second double layer of dyes is observed for the aggregates. The different morphologies of the coating layers are explained by the details of the chemical structure of the polycations. The possible adsorption of polyelectrolytes at these amphiphilic tubular structures, stabilized by means of hydrophobic forces, is far from obvious and demonstrates an applicable route to the build-up of more complex nanostructures in solution by means of a self-assembly process. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Chlorophyll a was incorporated into DMPC/DHPC assemblies. • J-aggregate of chlorophyll a was induced in DMPC/DHPC = 3:2 (q = 1.5). • Local hydrophobicity around chlorophyll a was analyzed based on the deconvolution of Soret band spectrum. • Photo-reduction of methyl viologen can be catalyzed by aggregated chlorophyll a. Abstract The J-aggregate of chlorophyll a (Chl a) functions as a light-harvesting antenna in natural systems. In this study, we employed the phospholipid membranes composed of longer-chain 1,2-dimyristoyl- sn -glycero-3-phosphocholine (DMPC) and shorter-chain 1,2-dihexanoyl- sn -glycero-3-phosphocholine (DHPC), as a platform to induce Chl a aggregates. The DMPC/DHPC assembly at the mixing ratio (q) = 1.5 induced J-aggregates of Chl a at 20 °C with a total lipid concentration of 20 mM. While, Chl a aggregates were not observed in the membranes at q = ∞ (DMPC vesicles) and q = 0 (DHPC micelles). The surroundings Chl a molecules in DMPC/DHPC at q = 1.5 were estimated to comprise a less polar environment, based on the deconvolution analysis of Soret band spectrum (400–440 nm). The photo-reduction activity of Chl a J-aggregates was investigated in lower lipid concentration conditions. [ABSTRACT FROM AUTHOR]

Photothermal therapy (PTT) represents a promising noninvasive tumor therapeutic modality, but the current strategies for enhancing photothermal effect have been mainly based on promoting thermal relaxation or suppressing radiative dissipation process of excited energy, leaving little room for further improvement in photothermal effect. Herein, as a proof of concept, we report the thermophoresis-enhanced photothermal effect with pure organic Janus-like nanoparticles (Janus-like NPs) for PTT. The Janus-like NPs are eccentrically loaded with compactly J-aggregated photothermal molecules (DMA-BDTO), which show red-shifted absorption wavelength and inhibited radiative decay as compared to individual molecules. Under NIR irradiation, the asymmetric heat generation at particle surface endows Janus-like NPs the active thermophoresis, which further increases collisions and converts kinetic energy into thermal energy, and Janus-like NPs exhibit significantly elevated temperature as compared to conventional NPs with homogenously distributed DMA-BDTO. Both in vitro and in vivo results confirm such thermophoresis-enhanced photothermal effect for improved PTT. Our new strategy of thermophoresis-enhanced photothermal effect shall open new insights for improving photothermal-related tumor therapy. [Display omitted] [ABSTRACT FROM AUTHOR]

A highly efficient light-induced aggregation of porphyrin molecules in solution was recently reported for 4-[10,15,20-tris(4-sulfophenyl)-21,24-dihydroporphyrin-5-yl]benzenesulfonic acid (TPPS). Here, we demonstrate that rhodamine 6G (R6G) and pseudoisocyanine (PIC) also show efficient light-induced aggregation in unsaturated aqueous solution, being detected with a multichannel lock-in amplifier as the absorbance decrease/increase in the monomers/aggregates, induced by a laser at 633 nm, which is non-resonant off their main monomer absorption wavelengths. The light-induced aggregation states are H-aggregates that are hardly formed in the thermal equilibrium. The similar absorbance changes are absent in the monomer molecules fixed in polyvinyl alcohol (PVA) films. The aggregation efficiency defined as ( Δ A / A ) / ( U t r a p / k B T ) , where A is the absorbance of the monomers, Δ A is the absorbance increase in the aggregates, U t r a p is the optical gradient force potential, and k B T is the thermal energy at room temperature, is approximately 100 for R6G and 500 for PIC, which are much smaller than that of TPPS.

Astaxanthin is an excellent antioxidant that can form unstable aggregates in biological or artificial systems. The changes of astaxanthin properties caused by molecular aggregation have gained much attention recently. Here, water-dispersible astaxanthin H- and J-aggregates were fabricated and stabilized by a natural DNA/chitosan nanocomplex (respectively noted as H-ADC and J-ADC), as evidenced by ultraviolet and visible spectrophotometry, Fourier transform infrared spectroscopy, and Raman spectroscopy. Compared with J-ADC, H-ADC with equivalent astaxanthin loading capacity and encapsulation efficiency showed smaller particle size and similar zeta potential. To explore the antioxidant differences between astaxanthin H- and J-aggregates, H-ADC and J-ADC were subjected to H2O2-pretreated Caco-2 cells. Compared with astaxanthin monomers and J-aggregates, H-aggregates showed a better cytoprotective effect by promoting scavenging of intracellular reactive oxygen species. Furthermore, in vitro 1,1-diphenyl-2-picrylhydrazyl and hydroxyl free radical scavenging studies confirmed a higher efficiency of H-aggregates than J-aggregates or astaxanthin monomers. These findings give inspiration to the precise design of carotenoid aggregates for efficient utilization.

In this report, we investigated the impact of adding a large π-extended squaraine dye to the classic bulk heterojunction P3HT:PC61BM system. The compound, SQIQ-A, is a bis-indole squaraine dye appended with acetylene-indoloquinoxaline end-capping units that exhibits strong optical absorption in thin film from 650 to 750 nm, beyond the absorption wavelength cut-off for P3HT:PC61BM films (ca. ∼650 nm). The dye SQIQ-A can form H- or J-aggregates (blue or red shifting the optical absorption profiles) via solvent vapour annealing with CHCl3 or THF, respectively, thus providing a simple method to control the morphology and optical properties of the molecule. Ternary blended films composed of P3HT:PC61BM:SQIQ-A (1:1:0.3 mass ratio) were investigated as-cast, after solvent vapour annealing, and after thermal annealing. Films were characterized using optical absorption spectroscopy, X-ray diffraction, atomic force microscopy, and polarized light microscopy. Solar cells were fabricated using an inverted architecture in air and analysed using current-voltage and external quantum efficiency measurements. It was found that solar cells thermally annealed at 130 °C for 10 min gave good power conversion efficiencies of 3%, similar to the control P3HT:PC61BM but with improved fill factors and noticeable photocurrent generation from 650 to 760 nm where the SQIQ-A molecule absorbs. Exposure to solvent vapour (CHCl3 or THF) results in aggregation of all components but specifically leads to the formation of micron-sized domains, lowering the overall photovoltaic performance. [ABSTRACT FROM AUTHOR]

Abstract: This Communication reports photo‐triggered supramolecular assembly of a naphthalene‐diimide (NDI) derivative, appended with a photo‐labile ortho‐nitrobenzyl (ONB)‐ester protected carboxylic acid. Photo‐irradiation produces the free COOH group which facilitates H‐bonding‐driven face‐to‐face stacking of the NDI chromophores producing an ultra‐thin (height <2.0 nm) two‐dimensional (2D) nanosheet. In contrast, spontaneous supramolecular assembly of the same active monomer exhibits entirely different features such as uncontrolled growth, J‐aggregation and fibrillar morphology. A completely different pathway for photo‐triggered assembly is attributed to the dual function of the photo‐caged pro‐monomer in i) producing the carboxylic acid in controlled manner and ii) simultaneously inhibiting the spontaneous J‐aggregation of the photo‐generated monomers by ester‐carboxylic acid H‐bonding and in turn directing a distinct growth mechanism. [ABSTRACT FROM AUTHOR]

Optical properties and morphologies of molecular aggregates of two similar cyanine dyes (BIC and TDBC) have been studied. The dyes have the same 5,5′,6,6′-tetrachlorobenzimidacarbocyanine chromophore part and differ just in one methyl group in alkyl chains. Due to such a similarity of the dye molecular structures, their aggregates are often supposed to have similar structure. However the difference in optical properties was reported in some publications assuming different structures of the J-aggregates. Indeed, we have found distinct morphologies for BIC and TDBC J-aggregates: spherical species for BIC J-aggregates and rod-like ones for TDBC J-aggregates. The difference in morphologies and, hence, structures is the reason of unlike optical properties of these J-aggregates. [ABSTRACT FROM AUTHOR]

Four cyanostyryl-substituted carbazole derivatives (CN-ODEC1, CN-ODEC2, CN-DDEC1, and CN-DDEC) were synthesized and their self-assembly properties have been studied. It was found that they could form organogels especially in aromatic solvents. Scanning electron microscopy and light microscopy images show that the xerogels formed from monosubstituted derivatives (CN-O/DDEC1) gave well-organized tapes, and those from disubstituted derivatives (CN-O/DDEC2) exhibited heavy entangled three-dimensional structures. The UV–vis absorption and fluorescence emission spectra, as well as X-ray diffraction patterns, suggest that carbazole derivatives underwent J-type π-stacking. Meanwhile, we suggested that strong H-bonding and moderate π–π interactions were the key driving force for the gelation of the monosubstituted derivatives, and head-to-tail “ladder-type” J-aggregates were formed in the gel state. On the other hand, strong π–π interaction might be considered as the main driving force for the gelation of disubstituted derivatives, and J-aggregates with no well-organized packing mode of molecules were obtained in the gel phase. It should be noticed that aggregation-induced emission was observed during the gelation processes. [ABSTRACT FROM AUTHOR]