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    In Situ Construction and Characterization of Chlorin-Based Supramolecular Aggregates in Tumor Cells. Liu Wei-Jiao,Zhang Di,Li Li-Li,Qiao Zeng-Ying,Zhang Ju-Chen,Zhao Ying-Xi,Qi Guo-Bin,Wan Dong,Pan Jie,Wang Hao ACS applied materials & interfaces We demonstrate in situ construction and characterization of supramolecular aggregates from chlorin p6 (Cp6) molecules in tumor cells. Fully deprotonated Cp6 molecules in neutral condition were partially protonated inside the acidic lysosomes of cells and significantly increased the hydrophobicity of them that resulted in simultaneous formation of J-type aggregates. Importantly, the formation of J-aggregates was fully characterized in artificial tissues by UV-vis, circular dichroism (CD) and transmission electron microscope (TEM) techniques. Compared to the monomers, the J-aggregates exhibited 55-fold enhanced thermal conversion efficiency (η) at the optimal excitation wavelength (690 nm). The remarkably increased heat effect contributed to the stronger photoacoustic (PA) signals, leading to at least 2 orders of magnitude increase of the tumor-to-normal tissue ratio (T/N), which was defined as the PA signal ratio between tumor site and surrounding normal tissue. We envision that this proof-of-concept study will open a new way to develop tumor environment-induced self-assembly for variable biomedical applications. 10.1021/acsami.6b07049
    Hydrogen-bonded perylene bisimide J-aggregate aqua material. Grande Vincenzo,Soberats Bartolome,Herbst Stefanie,Stepanenko Vladimir,Würthner Frank Chemical science A new twelvefold methoxy-triethyleneglycol-jacketed tetraphenoxy-perylene bisimide () amphiphile was synthesized that self-assembles into two types of supramolecular aggregates in water: red-coloured aggregates of low order and with weak exciton coupling among the PBIs and blue-coloured strongly coupled J-aggregates consisting of a highly ordered hydrogen-bonded triple helix of PBIs. At room temperature this PBI is miscible with water at any proportions which enables the development of robust dye aggregates in solution, in hydrogel states and in lyotropic liquid crystalline states. In the presence of 60-95 wt% water, self-standing coloured hydrogels exhibit colour changes from red to blue accompanied by a fluorescence light-up in the far-red region upon heating in the range of 30-50 °C. This phenomenon is triggered by an entropically driven temperature-induced hydrogen-bond-directed slipped stacking arrangement of the chromophores within structurally well-defined J-aggregates. This versatile aqua material is the first example of a stable PBI J-aggregate in water. We anticipate that this study will open a new avenue for the development of biocompatible functional materials based on self-assembled dyes and inspire the construction of other hydrogen-bonded supramolecular materials in the highly competitive solvent water. 10.1039/c8sc02409j
    Pathway complexity in the self-assembly of a zinc chlorin model system of natural bacteriochlorophyll J-aggregates. Ogi Soichiro,Grzeszkiewicz Charlotte,Würthner Frank Chemical science Whilst bacteriochlorophyll , , and dyes self-assemble into the most efficient light harvesting J-aggregate systems found in nature, their supramolecular packing arrangements are still a matter of debate and a significant number of models have been suggested for their local and long-range ordering. Here we reveal for a synthetic model system based on a zinc chlorin (ZnChl) dye an intriguing interplay of two competing aggregation pathways by kinetic and thermodynamic studies in MeOH/water solvent mixtures: the formation of kinetically controlled off-pathway nanoparticles consisting of excitonically coupled J-dimers the formation of thermodynamically more stable one-dimensional helical fibers consisting of J-coupled extended aggregates. The higher order of the latter is evidenced by atomic force microscopy and a more narrow absorption spectrum of the J-aggregates. Based on a recently developed thermodynamic model that combines the cooperative - growth model with a competing dimerization model, an energy landscape could be derived that describes the pathway complexity of this biomimetic system. Our studies reveal that the kinetic stability of the off-pathway nanoparticles increases with increasing concentration of ZnChl or water content in a MeOH/water solvent mixture. For a water content >90% deeply trapped off-pathway nanoparticle products are formed that do not transform anymore to the more ordered thermodynamic product within reasonable time scales. Based on these observations, we hypothesize that out-of-equilibrium aggregate structures of natural BChl dyes may also exist in the natural chlorosomes of green bacteria. 10.1039/c7sc03725b
    J-aggregates of organic dye molecules complexed with iron oxide nanoparticles for imaging-guided photothermal therapy under 915-nm light. Song Xuejiao,Gong Hua,Liu Teng,Cheng Liang,Wang Chao,Sun Xiaoqi,Liang Chao,Liu Zhuang Small (Weinheim an der Bergstrasse, Germany) Recently, the development of nano-theranostic agents aiming at imaging guided therapy has received great attention. In this work, a near-infrared (NIR) heptamethine indocyanine dye, IR825, in the presence of cationic polymer, polyallylamine hydrochloride (PAH), forms J-aggregates with red-shifted and significantly enhanced absorbance. After further complexing with ultra-small iron oxide nanoparticles (IONPs) and the followed functionalization with polyethylene glycol (PEG), the obtained IR825@PAH-IONP-PEG composite nanoparticles are highly stable in different physiological media. With a sharp absorbance peak, IR825@PAH-IONP-PEG can serve as an effective photothermal agent under laser irradiation at 915 nm, which appears to be optimal in photothermal therapy application considering its improved tissue penetration compared with 808-nm light and much lower water heating in comparison to 980-nm light. As revealed by magnetic resonance (MR) imaging, those nanoparticles after intravenous injection exhibit high tumor accumulation, which is then harnessed for in vivo photothermal ablation of tumors, achieving excellent therapeutic efficacy in a mouse tumor model. This study demonstrates for the first time that J-aggregates of organic dye molecules are an interesting class of photothermal material, which when combined with other imageable nanoprobes could serve as a theranostic agent for imaging-guided photothermal therapy of cancer. 10.1002/smll.201401025
    Nano-assemblies of J-aggregates based on a NIR dye as a multifunctional drug carrier for combination cancer therapy. Song Xuejiao,Zhang Rui,Liang Chao,Chen Qian,Gong Hua,Liu Zhuang Biomaterials The combination of chemotherapy with photothermal therapy, which may lead to improved therapeutic efficacies and reduced side effects of conventional chemotherapy, would require safe drug delivery systems (DDSs) with strong near-infrared (NIR) absorbance, efficient drug loading, and effective tumor homing ability. Herein, we fabricate nano-assemblies containing J-aggregates of a NIR dye, IR825, for drug delivery and combined photothermal & chemotherapy of cancer. It is found that IR825 could be complexed with a low-molecular-weight cationic polymer polyethylenimine (PEI), forming IR825@PEI J-aggregates with greatly enhanced NIR absorbance red-shifted to 915 nm. Those nano-assemblies of J-aggregates are further modified with polyethylene glycol (PEG), obtaining IR825@PEI-PEG nano-complex which exhibits great dispersity in physiological solutions, excellent photostability, and is able to efficiently load chemotherapeutic drug doxorubicin (DOX) via a unique strategy different from drug loading in conventional amphiphilic polymer-based DDSs. In vivo animal experiments uncover that IR825@PEI-PEG/DOX upon intravenous injection into tumor-bearing mice shows rather high tumor uptake as illustrated by photoacoustic imaging. In vivo combined photothermal & chemotherapy is then carried out, demonstrating great synergistic anti-tumor therapeutic effect remarkably superior to those achieved by the respective mono-therapies. Hence, we present a novel type of nanoscale DDSs based on nano-assemblies of small molecules without involving amphiphilic polymers, promising for imaging-guided combination cancer therapy. 10.1016/j.biomaterials.2015.04.001
    Indocyanine Green J Aggregates in Polymersomes for Near-Infrared Photoacoustic Imaging. Changalvaie Behzad,Han Sangheon,Moaseri Ehsan,Scaletti Federica,Truong Lauren,Caplan Rosalie,Cao Alice,Bouchard Richard,Truskett Thomas M,Sokolov Konstantin V,Johnston Keith P ACS applied materials & interfaces Clinical translation of photoacoustic imaging (PAI) has been limited by the lack of near-infrared (NIR) contrast agents with low toxicity required for regulatory approval. Herein, J aggregates of indocyanine green (ICG) with strong NIR absorbance were encapsulated at high loadings within small 77 nm polymersomes (nanocapsules) composed of poly(lactide--glycolide--poly(ethylene glycol)) (PLGA--PEG) bilayers, thus enabling PAI of of breast and ovarian cancer cells with high specificity and a sensitivity at the level of ∼100 total cells. All of the major components of the polymersomes are FDA approved and used in the clinic. During formation of polymersomes with a water-in-oil-in-water double emulsion process, loss of ICG from the ICG J aggregates was minimized by coating them with a layer of branched polyethylenimine and by providing excess "sacrificial" ICG to adsorb at the oil-water interfaces. The encapsulated J aggregates were protected against dissociation by the polymersome shell for 24 h in 100% fetal bovine serum, after which the polymersomes biodegraded and the J aggregates dissociated to ICG monomers. 10.1021/acsami.9b14519
    Highly-Soluble Cyanine J-aggregates Entrapped by Liposomes for Optical Imaging around 930 nm. Miranda Dyego,Huang Haoyuan,Kang Homan,Zhan Ye,Wang Depeng,Zhou Yang,Geng Jumin,Kilian Hailey I,Stiles Wesley,Razi Aida,Ortega Joaquin,Xia Jun,Choi Hak Soo,Lovell Jonathan F Theranostics Near infrared (NIR) dyes are useful for optical imaging. Liposomes have been used extensively for delivery of diverse cargos, including hydrophilic cargos which are passively loaded in the aqueous core. However, most currently available NIR dyes are only slightly soluble in water, making passive entrapment in liposomes challenging for achieving high optical contrast. : We modified a commercially-available NIR dye (IR-820) via one-step Suzuki coupling with dicarboxyphenylboronic acid, generating a disulfonated heptamethine; dicarboxyphenyl cyanine (DCP-Cy). DCP-Cy was loaded in liposomes and used for optical imaging. Owing to increased charge in mildly basic aqueous solution, DCP-Cy had substantially higher water solubility than indocyanine green (by an order of magnitude), resulting in higher NIR absorption. Unexpectedly, DCP-Cy tended to form J-aggregates with pronounced spectral red-shifting to 934 nm (from 789 nm in monomeric form). J-aggregate formation was dependent on salt and DCP-Cy concentration. Dissolved at 20 mg/mL, DCP-Cy J-aggregates could be entrapped in liposomes. Full width at half maximum absorption of the liposome-entrapped dye was just 25 nm. The entrapped DCP-Cy was readily detectable by fluorescence and photoacoustic NIR imaging. Upon intravenous administration to mice, liposomal DCP-Cy circulated substantially longer than the free dye. Accumulation was largely in the spleen, which was visualized with fluorescence and photoacoustic imaging. DCP-Cy is simple to synthesize and exhibits high aqueous solubility and red-shifted absorption from J-aggregate formation. Liposomal dye entrapment is possible, which facilitates photoacoustic and fluorescence imaging around 930 nm. 10.7150/thno.28376
    Integration of individual nanoscale structures into devices using dynamic nanostenciling. Egger Stefan,Ilie Adelina,Machida Shinichi,Nakayama Tomonobu Nano letters We succeeded in integrating individual, pre-existing nanostructures into functional devices using ultrahigh vacuum dynamic nanostenciling and show working devices based on single-walled carbon nanotubes, a benchmark nanomaterial, and porphyrin J-aggregates, a "soft" supramolecular nanomaterial. Nanostructures are first located via atomic force microscopy, while device elements are added step by step, with an achieved positional accuracy of 20 nm, using a shadow mask assembly that moves while being exposed to evaporated material. Electronic transport, potentiometry, and scanning Kelvin probe were used for control at any fabrication stage and were available in situ. Such complex fabrication/characterization capabilities, applicable repeatedly, reliably, and nondestructively, pave the way for dynamic nanostenciling instrumentation to establish itself as a viable tool for easy integration and prototyping of fragile nanostructures synthesized through a wide range of processes. 10.1021/nl071778m
    Biological Photothermal Nanodots Based on Self-Assembly of Peptide-Porphyrin Conjugates for Antitumor Therapy. Zou Qianli,Abbas Manzar,Zhao Luyang,Li Shukun,Shen Guizhi,Yan Xuehai Journal of the American Chemical Society Photothermal agents can harvest light energy and convert it into heat, offering a targeted and remote-controlled way to destroy carcinomatous cells and tissues. Inspired by the biological organization of polypeptides and porphyrins in living systems, here we have developed a supramolecular strategy to fabricate photothermal nanodots through peptide-modulated self-assembly of photoactive porphyrins. The self-assembling nature of porphyrins induces the formation of J-aggregates as substructures of the nanodots, and thus enables the fabrication of nanodots with totally inhibited fluorescence emission and singlet oxygen production, leading to a high light-to-heat conversion efficiency of the nanodots. The peptide moieties not only provide aqueous stability for the nanodots through hydrophilic interactions, but also provide a spatial barrier between porphyrin groups to inhibit the further growth of nanodots through the strong π-stacking interactions. Thermographic imaging reveals that the conversion of light to heat based on the nanodots is efficient in vitro and in vivo, enabling the nanodots to be applied for photothermal acoustic imaging and antitumor therapy. Antitumor therapy results show that these nanodots are highly biocompatible photothermal agents for tumor ablation, demonstrating the feasibility of using bioinspired nanostructures of self-assembling biomaterials for biomedical photoactive applications. 10.1021/jacs.6b11382
    Control of H- and J-aggregate formation via host-guest complexation using cucurbituril hosts. Gadde Suresh,Batchelor Elizabeth K,Weiss Joshua P,Ling Yonghua,Kaifer Angel E Journal of the American Chemical Society The binding interactions between two cyanine dyes, pseudoisocyanine (PIC) and pinacyanol (PIN), and the cucurbit[n]uril hosts, cucurbit[7]uril (CB7) and cucurbit[6]uril (CB6), were investigated by electronic absorption spectroscopy and DFT computational methods. The CB7 host forms more stable complexes with both dyes than CB6 and the computational studies suggest that the cavity of the smaller host CB6 is not threaded by the dyes. The equilibrium association constants (K) for complexation by CB7 were measured and found to be 2.05 x 10(4) and 3.84 x 10(5) M(-1) for PIC and PIN, respectively, in aqueous media at 23 degrees C. CB7 complexation was found to effectively disrupt the intermolecular forces responsible for the aggregation of both dyes. Thus, CB7 completely disrupts the J-aggregates formed by PIC and the H-aggregates (as well as lower concentrations of J-aggregates) formed by PIN. In both cases a competing guest, 1-aminoadamantane (AD), could be used to adjust the extent of aggregation of the cyanine dye. AD regulates aggregate formation because it forms an extremely stable complex with CB7 (K approximately = 10(12) M(-1)) and exerts a tight control on the CB7 concentration available to interact and bind with the dye. 10.1021/ja807197c
    Selective Monitoring and Imaging of Eosinophil Peroxidase Activity with a J-Aggregating Probe. Kim Tae-Il,Hwang Byunghee,Lee Boeun,Bae Jeehyeon,Kim Youngmi Journal of the American Chemical Society The specific detection of eosinophil peroxidase (EPO) activity requires the difficult distinction between hypobromous acid generated by EPO and hypochlorous acid generated by other haloperoxidases. Here we report a fluorogenic probe that is halogenated with high kinetic selectivity (≥1200:1) for HOBr over HOCl. Heavy-atom effects do not quench the dibrominated product because of its self-assembly into emissive J-aggregates that provide a turn-on signal. Applications of this fluorogen to EPO activity assays, dipstick sensors, fluorescence imaging of EPO activity, assays of oxidative stress in cancer cells, and immune response detection in live mice are reported. 10.1021/jacs.8b07073
    Quantum dot/J-aggregate blended films for light harvesting and energy transfer. Walker Brian J,Bulović Vladimir,Bawendi Moungi G Nano letters This paper describes the solution preparation of thin films composed of quantum dots and thiacyanine J-aggregates, making use of the size tunable emission of quantum dots and the narrow, intense absorption of J-aggregates in the solid state. These blended films exhibit 90% energy transfer efficiency from J-aggregates to quantum dots and can uniformly cover a large area. Because the presence of the J-aggregates enhances the QD photoluminescence intensity by 2.5-fold over QDs alone, these solid state materials may be useful in downconversion applications or in fundamental investigations of light harvesting. 10.1021/nl1018639
    Color-selective photocurrent enhancement in coupled J-aggregate/nanowires formed in solution. Walker Brian J,Dorn August,Bulović Vladimir,Bawendi Moungi G Nano letters J-aggregates are ordered clusters of coherently coupled molecular dyes, (1) and they have been used as light sensitizers in film photography due to their intense absorptions. Hybrid structures containing J-aggregates may also have applications in devices that require spectral specificity, such as color imaging or optical signaling. (2) However the use of J-aggregates in optoelectronic devices has posed a long-standing challenge (3, 4) due to the difficulty of controlling aggregate formation and the low charge carrier mobility of many J-aggregates in solid state. In this paper, we demonstrate a modular method to assemble three different cyanine J-aggregates onto CdSe nanowires, resulting in a photodetector that is color-sensitized in three specific, narrow absorption bands. Both the J-aggregate and nanowire device components are fabricated from solution and the sensitizing wavelength is switched from blue to red to green, using only solution-phase exchange of the J-aggregates on the same underlying device. 10.1021/nl200679n
    Substituent-control exciton in J-aggregates of protonated water-insoluble porphyrins. Okada Shinsuke,Segawa Hiroshi Journal of the American Chemical Society A series of protonated porphyrin J-aggregates of various water-insoluble tetraphenylporphyrin derivatives was prepared by aggregation at the liquid-liquid or gas-liquid interface. Using atomic force microscopy, we observed microcrystalline porphyrin J-aggregates. The J-aggregates have two strong exciton bands corresponding to the B (Soret)- and Q-bands of the protonated porphyrin. Interestingly, the excitation energy of the lower exciton (denoted by S1) markedly depends on the meso-substituents, whereas that of the higher exciton (denoted by S2) does not depend on them. These results indicate that the nature of the exciton coupling of the S1 transition dipole moment can be systematically changed by the substituents. 10.1021/ja017768j
    Self-organizing functional materials via ionic self assembly: porphyrins H- and J-aggregates on synthetic chrysotile nanotubes. De Luca Giovanna,Romeo Andrea,Villari Valentina,Micali Norberto,Foltran Ismaela,Foresti Elisabetta,Lesci Isidoro G,Roveri Norberto,Zuccheri Tommaso,Scolaro Luigi Monsù Journal of the American Chemical Society Positively charged, synthetic chrysotile nanotubes act as inorganic tectons supporting H- and J-type aggregates of anionic porphyrins with markedly different optical properties, making these nanohybrid materials of interest for application in nanotechnology. 10.1021/ja901273h
    Nanostructuration of phenylenevinylenediimide-bridged silsesquioxane: from electroluminescent molecular J-aggregates to photoresponsive polymeric H-aggregates. Dautel Olivier J,Wantz Guillaume,Almairac Robert,Flot David,Hirsch Lionel,Lere-Porte Jean-Pierre,Parneix Jean-Paul,Serein-Spirau Françoise,Vignau Laurence,Moreau Joël J E Journal of the American Chemical Society A new approach to control molecular aggregation of pi-conjugated chromophores in the solid state has been investigated. Our strategy was to use a modifiable bulky fragment which should induce a J-aggregation and offer the possibility to reach an H-aggregation upon its chemical modification by lateral slip of pi-conjugated molecules. The chosen fragment for that purpose was the hydrolyzable triethoxysilane function (Si(OEt)3). Our objective was to design and synthesize electroluminescent or solar cell hybrid organic-inorganic materials by the sol-gel process applied to a bifunctionalized silane. With this intention, the synthesis of the sol-gel processable phenylenevinylenediimide silsesquioxane 6 was accomplished and the study of spin-coated thin films of the pure silane precursor subjected or not to the sol-gel process has been carried out. Optical properties of 6 are consistent with the formation of J-aggregates in the solid state due to the steric hindrance introduced by the triethoxysilane units. Conversely, the spectroscopic behavior observed for the hybrid film 6F is attributed to an H-aggregation corresponding to a "card pack" orientation of the distyrylbenzeneimide chromophores in the compressed silicate network. Morevover, 6 and 6F also exhibited different electronic behaviors: light-emitting diodes exhibited high brightness with the native precursor 6 and almost no light output with the sol-gel processed silsesquioxane 6F. Photovoltaic cells showed the opposite behavior with low photocurrent generation in the precursor case and higher photocurrents with the sol-gel processed layers. These results provide a deeper understanding of the present self-assembly process that is strongly governed by the molecular packing of the oligosiloxane precursor. 10.1021/ja058680z
    Hybrid-state dynamics of gold nanorods/dye J-aggregates under strong coupling. Hao Ya-Wei,Wang Hai-Yu,Jiang Ying,Chen Qi-Dai,Ueno Kosei,Wang Wen-Quan,Misawa Hiroaki,Sun Hong-Bo Angewandte Chemie (International ed. in English) 10.1002/anie.201101699
    Magnetochiral effects in amphiphilic porphyrin J-aggregates. Ribó Josep M Angewandte Chemie (International ed. in English) The detection of magnetochiral dichroism (MChD; CD: circular dichroism) in a suspension of J-aggregate particles of an achiral amphiphilic nonmetalated porphyrin renews the interest for porphyrins in supramolecular chemistry and reinforces the concept that novel advanced materials can be obtained through self-assembly and auto-organization processes (see picture). 10.1002/anie.201105031
    Super-helix formation induced by cyanine J-aggregates onto random-coil carboxymethyl amylose as template. Kim Oh-Kil,Je Jongtae,Jernigan Glenn,Buckley Leonard,Whitten David Journal of the American Chemical Society The J-aggregation of Cyanine-1dye in the presence of carboxymethyl amylose (CMA) is described. The J-aggregation requires a large excess CMA concentration; the J-band maximum appears in the concentration range, [CMA]/[dye] = 10-50, depending on the degree of substitution (DS) of carboxylation, where [CMA] is the concentration of polymer repeat units. An extraordinarily large induced circular dichroism (CD) is observed from J-aggregates of the achiral cyanine dye in association with a random coil CMA, suggesting that the CMA is transformed into a helix. The magnitude of CD intensity increases with increasing DS of CMA and pH up to neutral (where a maximum J-aggregation occurs), while the CMA-bound dye monomer and H-aggregates (occurring at pH > or = 9) exhibit no induced CD. The trend in the CD intensity (of the J-aggregates) is in parallel with the fluorescence intensity of the J-aggregates. This suggests that binding of the J-aggregates onto the template CMA is sterically controlled by the asymmetric environment of glucose residues (of CMA) so that more twisting power is exerted with increasing DS (of CMA), rendering the cyanine dye/CMA complex a more rigid (a high fluorescence intensity) super-helix. This is also revealed by the AFM image of a long strand. 10.1021/ja0533141
    Near-Infrared Quantum Dot Emission Enhanced by Stabilized Self-Assembled J-Aggregate Antennas. Freyria Francesca S,Cordero José M,Caram Justin R,Doria Sandra,Dodin Amro,Chen Yue,Willard Adam P,Bawendi Moungi G Nano letters Enhancing photoluminescent emission (PL) in the near-infrared-infrared (NIR-IR) spectral region has broad applications from solar energy conversion to biological imaging. We show that self-assembled molecular dye J-aggregates (light-harvesting nanotubes, LHNs) can increase the PL emission of NIR PbS quantum dots (QDs) in both liquid and solid media more than 8-fold, promoted primarily by a long-range antenna effect and efficient Förster resonance energy transfer (FRET) from donor to acceptor. To create this composite material and preserve the optical properties of the nanocrystals, we performed an in situ ligand substitution followed by a functionalization reaction using click-chemistry. This resulted in PbS QDs soluble in an aqueous environment compatible with the molecular J-aggregates (LHNs). Theoretical and experimental results demonstrate that long-range diffusive exciton transport in LHNs enables efficient energy transfer to low concentrations of QDs despite there being no direct binding between molecular donors and QD acceptors. This suggests a broad application space for mixed light harvesting and photophysically active nanocomposite materials based on self-assembling molecular aggregates. 10.1021/acs.nanolett.7b03735
    NIR J-aggregates of hydroazaheptacene tetraimides. Cai Kang,Xie Jiajun,Zhao Dahui Journal of the American Chemical Society Hydroazaacene dicarboximide derivatives with red to NIR absorptions are designed and synthesized, which exhibit well-defined J-aggregation behaviors in both solution and thin films. The absorption and emission of an aggregate extend well into the NIR regime (λ(max) = 902 nm), manifesting particularly narrow bandwidth (fwhm = 152 cm(-1)) and is nearly transparent in the visible region. 10.1021/ja410265n
    Supramolecular Assembly of Complementary Cyanine Salt J-Aggregates. Li Zhong'an,Mukhopadhyay Sukrit,Jang Sei-Hum,Brédas Jean-Luc,Jen Alex K-Y Journal of the American Chemical Society An understanding of structure-property relationships in cyanine dyes is critical for their design and application. Anionic and cationic cyanines can be organized into complementary cyanine salts, offering potential building blocks to modulate their intra/intermolecular interactions in the solid state. Here, we demonstrate how the structures of these complementary salts can be tuned to achieve highly ordered J-type supramolecular aggregate structures of heptamethine dyes in crystalline solids. 10.1021/jacs.5b08072
    Chlorophyll J-aggregates: from bioinspired dye stacks to nanotubes, liquid crystals, and biosupramolecular electronics. Sengupta Sanchita,Würthner Frank Accounts of chemical research Among the natural light-harvesting (LH) systems, those of green sulfur and nonsulfur photosynthetic bacteria are exceptional because they lack the support of a protein matrix. Instead, these so-called chlorosomes are based solely on "pigments". These are self-assembled bacteriochlorophyll c, d, and e derivatives, which consist of a chlorophyll skeleton bearing a 3(1)-hydroxy functional group. Chemists consider the latter as an essential structural unit to direct the formation of light-harvesting self-assembled dye aggregates with J-type excitonic coupling. The intriguing properties of chlorosomal J-type aggregates, particularly narrow red-shifted absorption bands, compared with monomers and their ability to delocalize and migrate excitons, have inspired intense research activities toward synthetic analogues in this field. The ultimate goal of this research field is the development of (opto-)electronic devices based on the architectural principle of chlorosomal LH systems. In this regard, the challenge is to develop small, functional building blocks with appropriate substituents that are preprogrammed to self-assemble across different length scales and to emulate functions of natural LH systems or to realize entirely new functions beyond those found in nature. In this Account, we highlight our achievements in the past decade with semisynthetic zinc chlorins (ZnChls) as model compounds of bacteriochlorophylls obtained from the naturally most abundant chlorin precursor: chlorophyll a. To begin, we explore how supramolecular strategies involving π-stacking, hydrogen bonding, and metal-oxygen coordination can be used to design ZnChl-based molecular stack, tube, and liquid crystalline assemblies conducive to charge and energy transport. Our design principle is based on the bioinspired functionalization of the 3(1)-position of ZnChl with a hydroxy or methoxy group; the former gives rise to tubular assemblies, whereas the latter induces stack assemblies. Functionalization of the 17(2)-position with esterified hydrophilic or hydrophobic chains, dendron-wedge substituents, and chromophores having complementary optical properties such as naphthalene bisimides (NBIs) is used to modulate the self-assembly of ZnChl dyes. The resulting assemblies exhibit enhanced charge transport and energy transfer abilities. We have used UV/vis, circular dichroism (CD), fluorescence spectroscopy, and dynamic light scattering (DLS) for the characterization of these assemblies in solution. In addition, we have studied assembly morphologies by atomic force microscopy (AFM), scanning tunneling microscopy (STM), transmission electron microscopy (TEM), and cryogenic-TEM. Crystallographic techniques such as powder X-ray and solid-state NMR have been used to explain the precise long- and short-range packing of dyes in these assemblies. Finally, functional properties such as charge and energy transport have been explored by pulse radiolysis time-resolved microwave conductivity (PR-TRMC), conductive AFM, and time-resolved fluorescence spectroscopy. The design principles discussed in this Account are important steps toward the utilization of these materials in biosupramolecular electronics and photonics in the future. 10.1021/ar400017u
    Fluorescent J-aggregates of core-substituted perylene bisimides: studies on structure-property relationship, nucleation-elongation mechanism, and sergeants-and-soldiers principle. Kaiser Theo E,Stepanenko Vladimir,Würthner Frank Journal of the American Chemical Society A series of highly soluble and fluorescent, at core tetraaryloxy-substituted and in imide positions hydrogen atom containing perylene bisimide (PBI) dyes 1a-e with varying peripheral side chains have been synthesized and thoroughly characterized. The self-assembly of these PBIs has been studied in detail by UV/vis, linear dichroism (LD) and circular dichroism (CD) spectroscopy, and scanning probe microscopy (AFM, STM). These studies revealed that the present PBIs self-assemble into extended double string cables, which consist of two hydrogen-bonded supramolecular polymeric chains of densely packed and strongly excitonically coupled PBI chromophores, providing highly fluorescent J-aggregates. The aggregation strength ("melting" temperature) and the fluorescence properties of these J-aggregates are dependent on the number and chain length of the peripheral alkoxy substituents, thus revealing a structure-property relationship. In contrast to previously reported assemblies of PBIs, for which the aggregation process is described by the isodesmic (or equal K) model, a cooperative nucleation-elongation mechanism applies for the aggregation of the present assemblies as revealed by concentration-dependent UV/vis absorption studies with the chiral PBI 1e, providing equilibrium constants for dimerization (= nucleation) of K(2) = 13 +/- 11 L mol(-1) and for elongation of K = 2.3 +/- 0.1 x 10(6) L mol(-1) in methylcyclohexane (MCH). LD spectroscopic measurements have been performed to analyze the orientation of the monomers within the aggregates. The nonlinearity of chiral amplification in PBI aggregates directed by sergeants-and-soldiers principle has been elucidated by coaggregation experiments of different PBI dyes using CD spectroscopy. The dimensions as well as the molecular arrangement of the monomeric units in assemblies have been explored by atomic force microscopy (AFM) and scanning tunneling microscopy (STM). 10.1021/ja900684h
    Ethylene-Bridged Oligo-BODIPYs: Access to Intramolecular J-Aggregates and Superfluorophores. Patalag Lukas J,Ho Luong Phong,Jones Peter G,Werz Daniel B Journal of the American Chemical Society A versatile and rapid access to various chain lengths of ethylene-bridged BODIPY motifs was discovered. Corresponding oligomers comprising up to eight monomeric units were studied with respect to their microstructures by photophysical, X-ray crystallographic, and computational means. The investigation of three different dipyrrin cores revealed a crucial dependence on the substitution pattern of the core, whereas the nature of the meso-periphery is less critical. The impact of substituent effects on the conformational space was investigated by Monte Carlo simulations and a set of DFT methods (B3LYP, PBEh-3c, TPSS/PWPB95), including dispersion effects. Cryptopyrrole-derived oligo-BODIPYs are characterized by a tight intramolecular arrangement triggering a dominant J-type excitonic coupling with red-shifts up to 45 nm, exceptionally small line widths of the absorption and emission event (up to 286 cm), outstandingly high attenuation coefficients (up to 1 042 000 M cm), and quantum yields of up to unity. 10.1021/jacs.7b08176
    Collective fluorescence blinking in linear J-aggregates assisted by long-distance exciton migration. Lin Hongzhen,Camacho Rafael,Tian Yuxi,Kaiser Theo E,Würthner Frank,Scheblykin Ivan G Nano letters Fluorescence blinking corresponding to collective quenching of up to 100 dye monomers is reported for individual J-aggregates of a perylene bisimide (PBI) dye. This implies an exciton diffusion length up to 70 nm in these one-dimensional assemblies. The number of quenched monomers was directly measured by comparing the fluorescence brightness of the J-aggregates with that of noncoupled PBI molecules. This brightness analysis technique is useful for unraveling photophysical parameters of any individual fluorescent nanosystem. 10.1021/nl9036559
    Kinetic control of chirality in porphyrin J-aggregates. Romeo Andrea,Castriciano Maria Angela,Occhiuto Ilaria,Zagami Roberto,Pasternack Robert F,Scolaro Luigi Monsù Journal of the American Chemical Society Detailed kinetic investigations demonstrate the fundamental role of kinetic parameters in the expression and transmission of chirality in supramolecular systems. The rate of the aggregation process leading to the formation of J-aggregates strongly affects the size of these nanoassemblies and the chiral induction. 10.1021/ja410514k
    J-aggregates: from serendipitous discovery to supramolecular engineering of functional dye materials. Würthner Frank,Kaiser Theo E,Saha-Möller Chantu R Angewandte Chemie (International ed. in English) J-aggregates are of significant interest for organic materials conceived by supramolecular approaches. Their discovery in the 1930s represents one of the most important milestones in dye chemistry as well as the germination of supramolecular chemistry. The intriguing optical properties of J-aggregates (in particular, very narrow red-shifted absorption bands with respect to those of the monomer and their ability to delocalize and migrate excitons) as well as their prospect for applications have motivated scientists to become involved in this field, and numerous contributions have been published. This Review provides an overview on the J-aggregates of a broad variety of dyes (including cyanines, porphyrins, phthalocyanines, and perylene bisimides) created by using supramolecular construction principles, and discusses their optical and photophysical properties as well as their potential applications. Thus, this Review is intended to be of interest to the supramolecular, photochemistry, and materials science communities. 10.1002/anie.201002307
    The spectral signatures of Frenkel polarons in H- and J-aggregates. Spano Frank C Accounts of chemical research Electronic excitations in small aggregates, thin films, and crystals of conjugated organic molecules play a fundamental role in the operation of a wide array of organic-based devices including solar cells, transistors, and light-emitting diodes. Such excitations, or excitons, are generally spread out over several molecules: a balance between the delocalizing influence of resonant intermolecular coupling and the localizing influence of static and dynamic disorder determines the coherence range of the exciton. Because of the "soft" nature of organic materials, significant nuclear relaxation in the participating molecules also accompanies the electronic excitations. To properly understand energy or charge transport, one must treat intermolecular (excitonic) coupling, electron-vibrational coupling, and disorder on equal footing. In this Account, we review the key elements of a theoretical approach based on a multiparticle representation that describes electronic excitations in organic materials as vibronic excitations surrounded by a field of vibrational excitations. Such composite excitations are appropriately called Frenkel excitonic polarons. For many conjugated molecules, the bulk of the nuclear reorganization energy following electronic excitation arises from the elongation of a symmetric vinyl stretching mode with energy approximately 1400 cm(-1). To appreciate the impact of aggregation, we study how the vibronic progression of this mode, which dominates the isolated (solvated) molecule absorption and emission spectra, is distorted when molecules are close enough to interact with each other. As we demonstrate in this Account, the nature of the distortion provides a wealth of information about how the molecules are packed, the strength of the excitonic interactions between molecules, the number of molecules that are coherently coupled, and the nature of the disorder. We show that the aggregation-induced deviations from the Poissonian distribution of vibronic peak intensities take on two extremes identified with ideal H- and J-aggregates. The sign of the nearest neighbor electronic coupling, positive for H and negative for J, distinguishes the two basic aggregate forms. For several decades, researchers have known that H-aggregates exhibit blue-shifted absorption spectra and are subradiant while J-aggregates exhibit the opposite behavior (red-shifted absorption and superradiance). However, the exact inclusion of exciton-vibrational coupling reveals several more distinguishing traits between the two aggregate types: in H(J)-aggregates the ratio of the first two vibronic peak intensities in the absorption spectrum decreases (increases) with increasing excitonic coupling, while the ratio of the 0-0 to 0-1 emission intensities increases (decreases) with disorder and increases (decreases) with increasing temperature. These two extreme behaviors provide the framework for understanding absorption and emission in more complex morphologies, such as herringbone packing in oligo(phenylene vinylene)s, oligothiophenes and polyacene crystals, as well as the polymorphic packing arrangements observed in carotenoids. 10.1021/ar900233v
    Sub-Nanosecond Resonance Energy Transfer in the Near-Infrared within Self-Assembled Conjugates of PbS Quantum Dots and Cyanine Dye J-Aggregates. Wang Chen,Weiss Emily A Journal of the American Chemical Society Energy transfer (EnT) of near-infrared (NIR) excitons enables applications in harvesting of solar energy and biological imaging. Fast exciton extraction from NIR-absorbing Pb-chalcogenide quantum dots (QDs) may allow utilization of the photon downconversion (multiple exciton generation) process that occurs in those QDs to amplify signal in QD-based sensors or photocurrent in QD-based photovoltaics. This paper describes subnanosecond extraction of NIR excitons from PbS QDs by adsorbed J-aggregates of cyanine dye in aqueous dispersions. The QD/J-aggregate complexes form through electrostatic self-assembly, and the rate and yield of EnT within the complexes can be optimized by adjusting spectral overlap between QD emission and the J-aggregate absorption, which are controlled by density of charged ligands on the QD surface and the pH. The primary EnT pathways have rate constants ranging from (800 ps)(-1) to (2.2 ns)(-1), which are 1-2 orders of magnitude faster than previously reported examples with PbS QDs as exciton donors. The fastest EnT process occurs in 90 ps and is potentially competitive with Auger recombination of biexcitonic states in PbS QDs. 10.1021/jacs.6b04087
    Self-assembly of multi-stranded perylene dye J-aggregates in columnar liquid-crystalline phases. Herbst Stefanie,Soberats Bartolome,Leowanawat Pawaret,Stolte Matthias,Lehmann Matthias,Würthner Frank Nature communications Many discoid dyes self-assemble into columnar liquid-crystalline (LC) phases with packing arrangements that are undesired for photonic applications due to H-type exciton coupling. Here, we report a series of crystalline and LC perylene bisimides (PBIs) self-assembling into single or multi-stranded (two, three, and four strands) aggregates with predominant J-type exciton coupling. These differences in the supramolecular packing and optical properties are achieved by molecular design variations of tetra-bay phenoxy-dendronized PBIs with two N-H groups at the imide positions. The self-assembly is driven by hydrogen bonding, slipped π-π stacking, nanosegregation, and steric requirements of the peripheral building blocks. We could determine the impact of the packing motifs on the spectroscopic properties and demonstrate different J- and H-type coupling contributions between the chromophores. Our findings on structure-property relationships and strong J-couplings in bulk LC materials open a new avenue in the molecular engineering of PBI J-aggregates with prospective applications in photonics. 10.1038/s41467-018-05018-6
    Nanotubular J-aggregates and quantum dots coupled for efficient resonance excitation energy transfer. Qiao Yan,Polzer Frank,Kirmse Holm,Steeg Egon,Kühn Sergei,Friede Sebastian,Kirstein Stefan,Rabe Jürgen P ACS nano Resonant coupling between distinct excitons in organic supramolecular assemblies and inorganic semiconductors is supposed to offer an approach to optoelectronic devices. Here, we report on colloidal nanohybrids consisting of self-assembled tubular J-aggregates decorated with semiconductor quantum dots (QDs) via electrostatic self-assembly. The role of QDs in the energy transfer process can be switched from a donor to an acceptor by tuning its size and thereby the excitonic transition energy while keeping the chemistry unaltered. QDs are located within a close distance (<4 nm) to the J-aggregate surface, without harming the tubular structures and optical properties of J-aggregates. The close proximity of J-aggregates and QDs allows the strong excitation energy transfer coupling, which is around 92% in the case of energy transfer from the QD donor to the J-aggregate acceptor and approximately 20% in the reverse case. This system provides a model of an organic-inorganic light-harvesting complex using methods of self-assembly in aqueous solution, and it highlights a route toward hierarchical synthesis of structurally well-defined supramolecular objects with advanced functionality. 10.1021/nn506095g
    Fluorescent Cyanine Dye J-Aggregates in the Fluorous Phase. Cao Wei,Sletten Ellen M Journal of the American Chemical Society We present a perfluorocarbon-hydrocarbon amphiphilic cyanine dye that J-aggregates in fluorous solvent. J-Aggregation is a special type of fluorophore aggregation, affording enhanced photophysical properties. Cyanine dyes are excellent J-aggregators in water but, until now, cyanine J-aggregates have not been translated to nonaqueous media. The fluorous phase J-aggregate displays enhanced photostability and processability compared to analogous aqueous aggregates. 10.1021/jacs.7b11925
    A Columnar Liquid-Crystal Phase Formed by Hydrogen-Bonded Perylene Bisimide J-Aggregates. Herbst Stefanie,Soberats Bartolome,Leowanawat Pawaret,Lehmann Matthias,Würthner Frank Angewandte Chemie (International ed. in English) A new perylene bisimide (PBI) dye self-assembles through hydrogen bonds and π-π interactions into J-aggregates that in turn self-organize into liquid-crystalline (LC) columnar hexagonal domains. The PBI cores are organized with the transition dipole moments parallel to the columnar axis, which is an unprecedented structural organization in π-conjugated columnar liquid crystals. Middle and wide-angle X-ray analyses reveal a helical structure consisting of three self-assembled hydrogen-bonded PBI strands that constitute a single column of the columnar hexagonal phase. This remarkable assembly mode for columnar liquid crystals may afford new anisotropic LC materials for applications in photonics. 10.1002/anie.201612047
    Concurrent Cooperative J-Aggregates and Anticooperative H-Aggregates. Cai Kang,Xie Jiajun,Zhang Di,Shi Wenjing,Yan Qifan,Zhao Dahui Journal of the American Chemical Society Completely understanding the working mechanisms of sophisticated supramolecular self-assembly exhibiting competing paths is very important for chemists en route to acquiring the ability of constructing supramolecular systems with controlled structures and designed functions. Here, the self-aggregation behaviors of an N-heterocyclic aromatic dicarboximide molecule 1, boasting two competing paths that give rise to different supramolecular structures and exhibit distinct thermodynamic features, are carefully examined. First, a group of H-aggregates are observed when providing a medium driving force for aromatic stacking, and their formation is manifested as an anticooperative process. When exposed to enhanced strength of aromatic interactions, these H-aggregates are found to transform into J-aggregates via a cooperative assembly mechanism. With the assistance of a mathematic model accommodating two competing polymerization pathways, calculations are conducted to simulate and explain the thermodynamic equilibria of such a unique supramolecular system. The calculation results are highly consistent with the experimental observations, and some important properties are elucidated. Specifically, the anticooperative assembly mechanism generally promotes the formation of low to medium oligomers, whereas the cooperative path is more competent at producing high polymers. If the anticooperative and cooperative routes coexist and compete for the same molecule, the cooperative formations of high polymers are significantly suppressed unless a very high degree of polymerization can be achieved. Such a unique feature of concurring anticooperative and cooperative paths emerges to the H- and J-aggregates of molecule 1 and thus brings about the interesting sequential appearances of the two types of aggregates under conditions of continuously enlarged driving force for self-aggregation. Finally, based on the knowledge acquired from this study and by analyzing the steric features of 1 that influence its supramolecular packing motifs, a slightly modified molecular structure is designed, with which the intermediate H-aggregation state was successfully suppressed, and a single cooperative J-aggregation path is manifested. 10.1021/jacs.8b01463
    Living Supramolecular Polymerization of a Perylene Bisimide Dye into Fluorescent J-Aggregates. Wagner Wolfgang,Wehner Marius,Stepanenko Vladimir,Ogi Soichiro,Würthner Frank Angewandte Chemie (International ed. in English) The self-assembly of a new perylene bisimide (PBI) organogelator with 1,7-dimethoxy substituents in the bay position affords non-fluorescent H-aggregates at high cooling rates and fluorescent J-aggregates at low cooling rates. Under properly adjusted conditions, the kinetically trapped "off-pathway" H-aggregates are transformed into the thermodynamically favored J-aggregates, a process that can be accelerated by the addition of J-aggregate seeds. Spectroscopic studies revealed a subtle interplay of π-π interactions and intra- and intermolecular hydrogen bonding for monomeric, H-, and J-aggregated PBIs. Multiple polymerization cycles initiated from the seed termini demonstrate the living character of this chain-growth supramolecular polymerization process. 10.1002/anie.201709307
    Shortwave Infrared Imaging with J-Aggregates Stabilized in Hollow Mesoporous Silica Nanoparticles. Chen Wei,Cheng Chi-An,Cosco Emily D,Ramakrishnan Shyam,Lingg Jakob G P,Bruns Oliver T,Zink Jeffrey I,Sletten Ellen M Journal of the American Chemical Society Tissue is translucent to shortwave infrared (SWIR) light, rendering optical imaging superior in this region. However, the widespread use of optical SWIR imaging has been limited, in part, by the lack of bright, biocompatible contrast agents that absorb and emit light above 1000 nm. J-Aggregation offers a means to transform stable, near-infrared (NIR) fluorophores into red-shifted SWIR contrast agents. Here we demonstrate that J-aggregates of NIR fluorophore IR-140 can be prepared inside hollow mesoporous silica nanoparticles (HMSNs) to result in nanomaterials that absorb and emit SWIR light. The J-aggregates inside PEGylated HMSNs are stable for multiple weeks in buffer and enable high resolution imaging with 980 nm excitation. 10.1021/jacs.9b05195
    -Aggregates of Cyanine Dye for NIR-II Dynamic Vascular Imaging beyond 1500 nm. Sun Caixia,Li Benhao,Zhao Mengyao,Wang Shangfeng,Lei Zuhai,Lu Lingfei,Zhang Hongxin,Feng Lishuai,Dou Chaoran,Yin Dongrui,Xu Huixiong,Cheng Yingsheng,Zhang Fan Journal of the American Chemical Society Light in the second near-infrared window, especially beyond 1500 nm, shows enhanced tissue transparency for high-resolution optical bioimaging due to decreased tissue scattering, absorption, and autofluorescence. Despite some inorganic luminescent nanoparticles have been developed to improve the bioimaging around 1500 nm, it is still a great challenge to synthesize organic molecules with the absorption and emission toward this region. Here, we present -aggregates with 1360 nm absorption and 1370 nm emission formed by self-assembly of amphiphilic cyanine dye FD-1080 and 1,2-dimyristoyl--glycero-3-phosphocholine. Molecular dynamics simulations were further employed to illustrate the self-assembly process. Superior spatial resolution and high signal-to-background ratio of -aggregates were demonstrated for noninvasive brain and hindlimb vasculature bioimaging beyond 1500 nm. The efficacy evaluation of the clinically used hypotensor is successfully achieved by high-resolution dynamic vascular imaging with -aggregates. 10.1021/jacs.9b10043
    Highly Efficient Thermally Activated Delayed Fluorescence via J-Aggregates with Strong Intermolecular Charge Transfer. Xue Jie,Liang Qingxin,Wang Rui,Hou Jiayue,Li Wenqiang,Peng Qian,Shuai Zhigang,Qiao Juan Advanced materials (Deerfield Beach, Fla.) The development of high-efficiency and low-cost organic emissive materials and devices is intrinsically limited by the energy-gap law and spin statistics, especially in the near-infrared (NIR) region. A novel design strategy is reported for realizing highly efficient thermally activated delayed fluorescence (TADF) materials via J-aggregates with strong intermolecular charge transfer (CT). Two organic donor-acceptor molecules with strong and planar acceptor are designed and synthesized, which can readily form J-aggregates with strong intermolecular CT in solid states and exhibit wide-tuning emissions from yellow to NIR. Experimental and theoretical investigations expose that the formation of such J-aggregates mixes Frenkel excitons and CT excitons, which not only contributes to a fast radiative decay rate and a slow nonradiative decay rate for achieving nearly unity photoluminescence efficiency in solid films, but significantly decreases the energy gap between the lowest singlet and triplet excited states (≈0.3 eV) to induce high-efficiency TADF even in the NIR region. These organic light-emitting diodes exhibit external quantum efficiencies of 15.8% for red emission and 14.1% for NIR emission, which represent the best result for NIR organic light-emitting diodes (OLEDs) based on TADF materials. These findings open a new avenue for the development of high-efficiency organic emissive materials and devices based on molecular aggregates. 10.1002/adma.201808242