Enhancement and Concurrence of Emissions from Multiple Fluorophores in a Single Emitting Layer of Micellar Nanostructures

For concurrent emission of multiple fluorophores from a single emitting layer with a highly efficient energy transfer from antenna molecules to emitting molecules by fluorescence resonance energy transfer (FRET), a paradoxical requirement in an emitting layer is necessary, that is, close placement of an emitting fluorophore and a harvesting molecule, and isolation of emitting fluorophores. Here we demonstrate how to overcome this paradox by full utilization of a micellar nanostructure consisting of a core and a corona, that is, the core is used as a place for FRET between light‐collecting donors and light‐emitting fluorophores, and the corona is used as a barrier for FRET between light‐emitting fluorophores. Enhancement of light emission from fluorophores was achieved by locating emitting fluorophores and light‐harvesting molecules at the same core of micelles. Moreover, with the same micellar nanostructure, concurrent emission of multiple fluorophores with enhanced intensity was induced by isolating them in independent micelles, the corona structure of which worked as an effective blockade for FRET.     

Novel Quercetin Aggregation‐Induced Emission Luminogen (AIEgen) with Excited‐State Intramolecular Proton Transfer for In Vivo Bioimaging

Aggregation‐induced emission luminogens (AIEgens) that undergo excited‐state intramolecular proton transfer (ESIPT) have many applications in bioimaging since they have high quantum efficiency in the aggregated state and a low background signal in aqueous solutions because of their large Stokes shift. One disadvantage of many of the AIEgens with ESIPT that has been described so far is that they require time‐consuming synthesis and the use of toxic reagents. Another disadvantage with most of these materials is that they are only used for bioimaging in cells and are unsuitable for in vivo bioimaging. Herein, a new AIEgen with ESIPT, quercetin (QC) is described, which is easily prepared from Sophora japonica. AIE is attributed to crystallization‐promoted keto emission. The fluorescence is temperature dependent and shows strong resistance to photobleaching. QC AIEgen with ESIPT is shown to have excellent biocompatibility and is successfully used for bioimaging both in cellular cytoplasm and in vivo.     

Control of Solid‐State Dye‐Sensitized Solar Cell Performance by Block‐Copolymer‐Directed TiO2 Synthesis

Hybrid dye‐sensitized solar cells are typically composed of mesoporous titania (TiO₂), light‐harvesting dyes, and organic molecular hole‐transporters. Correctly matching the electronic properties of the materials is critical to ensure efficient device operation. In this study, TiO₂ is synthesized in a well‐defined morphological confinement that arises from the self‐assembly of a diblock copolymer—poly(isoprene‐b‐ethylene oxide) (PI‐b‐PEO). The crystallization environment, tuned by the inorganic (TiO₂ mass) to organic (polymer) ratio, is shown to be a decisive factor in determining the distribution of sub‐bandgap electronic states and the associated electronic function in solid‐state dye‐sensitized solar cells. Interestingly, the tuning of the sub‐bandgap states does not appear to strongly influence the charge transport and recombination in the devices. However, increasing the depth and breadth of the density of sub‐bandgap states correlates well with an increase in photocurrent generation, suggesting that a high density of these sub‐bandgap states is critical for efficient photo‐induced electron transfer and charge separation.     

Perpendicularly Aligned,Size‐and Spacing‐Controlled Nanocylinders by Molecular‐Weight Adjustment of a Homopolymer Blended in an Asymmetric Triblock Copolymer

Perpendicularly arrayed and size‐controlled nanocylinders have been prepared by simply blending an asymmetric polystyrene‐block‐polyisoprene‐block‐polystyrene triblock copolymer with polystyrene (the minority component) homopolymers of different molecular weights. The preference for perpendicular orientation or hexagonal ordering of the nanocylinders over a large area in the asymmetric block copolymer can be controlled by adjusting the molecular weight of the blended homopolymer, and the perfection of hexagonal ordering of the perpendicular cylinders can be tuned by using a substrate whose surface tension is much different from that of the majority component of the block copolymer. Such highly controlled nanostructured block‐copolymer materials, which have been obtained by a simple method independent of film thickness and interfacial tension between the blocks and the substrates, have wide‐ranging commercial potential, e.g., for use in membranes and nanotemplates with size‐tunable pores, bandgap‐controlled photonic crystals, and other nanotechnological fields demanding a specific nanosize and nanomorphology.     

Self‐Assembly of Diblock‐Copolymer Micelles for Template‐Based Preparation of PbTiO3 Nanograins

A bottom‐up fabrication route for PbTiO₃ nanograins grown on predefined TiO₂ nanostructures used as seeds is presented. The structuring of the TiO₂ seeds is performed using a self‐organized template constructed from a gold‐loaded micellar monofilm. With this fabrication process, TiO₂ seeds and PbTiO₃ grains with diameters of 12 and 30 nm, respectively, are prepared without the need for electron‐beam lithography. The dimensions of the structure imposed by the micellar template are transferred through all the processing steps to the final PbTiO₃ grains. Furthermore, it is shown that the intermicelle distance and the degree of order in the dried monofilm is mainly determined by the preparation conditions, such as the pulling velocity in the dipping process and the strength of the surface–micelle interaction, and not necessarily by the architectural properties (block length and ratio) of the diblock copolymers that build the micelles. The intermicelle spacing in the dried film is much smaller than the micelle dimensions in solution, and approaches the dimensions of a fully collapsed micelle when the dipping process is performed slowly enough.     

Self‐Assembled Dual Dye‐Doped Nanosized Micelles for High‐Contrast Up‐Conversion Bioimaging

Sensitized triplet–triplet annihilation based photon up‐conversion (TTA‐UC) greatly improves the scope and applicability of fluorescence bioimaging by enabling anti‐Stokes detection at low powers, thus eliminating the background autofluorescence and limiting the potential damage of the living tissues. Here the authors present a facile, one‐step protocol to prepare dual dye‐doped, TTA‐UC active nanomicelles starting from the commercially available surfactant Kolliphor EL, a component of several FDA approved preparations. These nanosized micelles show an unprecedented up‐conversion yield of 6.5% under 0.1 W cm^?2 excitation intensity in an aqueous, nondeaerated dispersion. The supramolecular architecture obtained preserves the embedded dyes from oxygen quenching, allowing satisfactory anti‐Stokes fluorescence imaging of 3T3 cells. This is the first example of efficient multicomponent up‐converters prepared using highly biocompatible materials approved by the international authority, paving the way for the development of new complex and multifunctional materials for advanced theranostics.     

Cationic Conjugated Polyelectrolytes with Molecular Spacers for Efficient Fluorescence Energy Transfer to Dye‐Labeled DNA

Two water‐soluble conjugated polyelectrolytes, poly(9,9′‐bis(6‐N,N,N‐trimethylammoniumhexyl)fluorene‐alt‐1,4‐(2,5‐bis(6‐N,N,N‐trimethylammoniumhexyloxy))phenylene) tetrabromide ( P1i ) and poly((10,10′‐bis(6‐N,N,N‐trimethylammoniumhexyl)‐10H‐spiro(anthracene‐9,9′‐fluorene))‐alt‐1,4‐(2,5‐bis(6‐N,N,N‐trimethylammoniumhexyloxy))phenylene) tetrabromide ( P2i ) are synthesized, characterized, and used in fluorescence resonance energy transfer (FRET) experiments with fluorescein‐labeled single‐stranded DNA (ssDNA‐Fl). P1i and P2i have nearly identical π‐conjugated backbones, as determined by cyclic voltammetry and UV‐vis spectroscopy. The main structural difference is the presence of an anthracenyl substituent, orthogonal to the main chain in each of the P2i repeat units, which increases the average interchain separation in aggregated phases. It is possible to observe emission from ssDNA‐Fl via FRET upon excitation of P2i . Fluorescein is not emissive within the ssDNA‐Fl/ P1i electrostatic complex, suggesting Fl emission quenching through photoinduced charge transfer (PCT). We propose that the presence of the anthracenyl “molecular bumper” in P2i increases the distance between optical partners, which decreases PCT more acutely relative to FRET.     

Tuning the Dimensions and Periodicities of Nanostructures Starting from the Same Polystyrene‐block‐poly(2‐vinylpyridine) Diblock Copolymer

The controlled tuning of the characteristic dimensions of two‐dimensional arrays of block‐copolymer reverse micelles deposited on silicon surfaces is demonstrated. The polymer used is polystyrene‐block‐poly(2‐vinylpyridine) (91 500‐b‐105 000 g mol^–1). Reverse micelles of this polymer with different aggregation numbers have been obtained from different solvents. The periodicity of the micellar array can be systematically varied by changing copolymer concentration, spin‐coating speeds, and by using solvent mixtures. The profound influence of humidity on the micellar film structure and the tuning of the film topography through control of humidity are presented. Light scattering, atomic force microscopy, scanning electron microscopy, transmission electron microscopy, and X‐ray photoelectron spectroscopy were used for characterization. As possible applications, replication of micellar array topography with polydimethylsiloxane and post‐loading of the micelles to form iron oxide nanoparticle arrays are presented.     

Engineering Sensor Arrays Using Aggregation‐Induced Emission Luminogens for Pathogen Identification

Lacking rapid and reliable pathogen diagnostic platforms, inadequate or delayed antimicrobial therapy could be made, which greatly threatens human life and accelerates the emergence of antibiotic‐resistant pathogens. In this contribution, a series of simple and reliable sensor arrays based on tetraphenylethylene (TPE) derivatives are successfully developed for detection and discrimination of pathogens. Each sensor array consists of three TPE‐based aggregation‐induced emission luminogens (AIEgens) that bear cationic ammonium group and different hydrophobic substitutions, providing tunable logP (n‐octanol/water partition coefficient) values to enable the different multivalent interactions with pathogens. On the basis of the distinctive fluorescence response produced by the diverse interaction of AIEgens with pathogens, these sensor arrays can identify different kinds of pathogens, even normal and drug‐resistant bacteria, with nearly 100% accuracy. Furthermore, blends of pathogens can also be identified accurately. The sensor arrays exhibit rapid response (about 0.5 h), high‐throughput, and easy‐to‐operate without washing steps.     

Functionalized Siloles: Versatile Synthesis,Aggregation‐Induced Emission,and Sensory and Device Applications

The synthesis of functionalized siloles has been a challenge because of the incompatibility of polar functional groups with the reactive intermediates in the conventional protocols for silole synthesis. In this work, a synthetic route for silole functionalization is elaborated, through which a series of functionalized siloles are successfully prepared. Whereas light emissions of traditional luminophores are often quenched by aggregation, most of the functionalized siloles show an exactly opposite phenomenon of aggregation‐induced emission (AIE). The siloles are nonemissive when dissolved in their good solvents but become highly luminescent when aggregated in their poor solvents or in the solid state. Manipulation of the aggregation–deaggregation processes of the siloles enables them to play two seemly antagonistic roles and work as both excellent quenchers and efficient emitters. The AIE effect endows the siloles with multifaceted functionalities, including fluorescence quenching, pH sensing, explosive detection, and biological probing. The sensing processes are very sensitive (with detection limit down to 0.1 ppm) and highly selective (with capability of discriminating among different kinds of ions, explosives, proteins, DNAs, and RNAs). The siloles also serve as active layers in the fabrication of electroluminescent devices and as photosensitive films in the generation of fluorescence patterns.     

Novel Conjugated Organic Dyes for Efficient Dye‐Sensitized Solar Cells

Novel conjugated organic dyes that have N,N‐dimethylaniline (DMA) moieties as the electron donor and a cyanoacetic acid (CAA) moiety as the electron acceptor were developed for use in dye‐sensitized nanocrystalline‐TiO₂ solar cells (DSSCs). We attained a maximum solar‐energy‐to‐electricity conversion efficiency (η) of 6.8 % under AM 1.5 irradiation (100 mW cm^–2) with a DSSC based on 2‐cyano‐7,7‐bis(4‐dimethylamino‐phenyl)hepta‐2,4,6‐trienoic acid (NKX‐2569): short‐circuit photocurrent density (J_sc) = 12.9 mA cm^–2, open‐circuit voltage (V_oc) = 0.71 V, and fill factor (ff) = 0.74. The high performance of the solar cells indicated that highly efficient electron injection from the excited dyes to the conduction band of TiO₂ occurred. The experimental and calculated Fourier‐transform infrared (FT‐IR) absorption spectra clearly showed that these dyes were adsorbed on the TiO₂ surface with the carboxylate coordination form. A molecular‐orbital calculation indicated that the electron distribution moved from the DMA moiety to the CAA moiety by photoexcitation of the dye.     

Nanoporous Ultra‐Low‐Dielectric‐Constant Fluoropolymer Films via Selective UV Decomposition of Poly(pentafluorostyrene)‐block‐Poly(methyl methacrylate) Copolymers Prepared Using Atom Transfer Radical Polymerization

Block copolymers of poly(pentafluorostyrene) (PFS) and poly(methyl methacrylate) (PMMA) (PFS‐b‐PMMA) have been synthesized using atom transfer radical polymerization (ATRP). Then, nanoporous fluoropolymer films have been prepared via selective UV decomposition of the PMMA blocks in the PFS‐b‐PMMA copolymer films. The chemical composition and structure of the PFS homopolymers and copolymers have been characterized using nuclear magnetic resonance (NMR) spectroscopy, thermogravimetric analysis (TGA), X‐ray photoelectron spectroscopy (XPS), time‐of‐flight secondary‐ion mass spectrometry (ToF‐SIMS), and molecular‐weight measurements. The cross‐sectional and surface morphologies of the PFS‐b‐PMMA copolymer films before and after selective UV decomposition of the PMMA blocks have been studied using field‐emission scanning electron microscopy (FESEM). The nanoporous fluoropolymer films with pore sizes in the range 30–50 nm and porosity in the range 15–40 % have been obtained from the PFS‐b‐PMMA copolymers of different PMMA content. Dielectric constants approaching 1.8 have been achieved in the nanoporous fluoropolymer films which contain almost completely decomposed PMMA blocks.     

Dye‐Doped Polyhedral Oligomeric Silsesquioxane (POSS)‐Modified Polymeric Matrices for Highly Efficient and Photostable Solid‐State Lasers

Here, the design, synthesis, and characterization of laser nanomaterials based on dye‐doped methyl methacrylate (MMA) crosslinked with octa(propyl‐methacrylate) polyhedral oligomeric silsesquioxane (8MMAPOSS) is reported in relation to their composition and structure. The influence of the silicon content on the laser action of the dye pyrromethene 567 (PM567) is analyzed in a systematic way by increasing the weight proportion of POSS from 1 to 50%. The influence of the inorganic network structure is studied by replacing the 8MMAPOSS comonomer by both the monofunctionalized heptaisobutyl‐methacryl‐POSS (1MMAPOSS), which defines the nanostructured linear network with the POSS cages appearing as pendant groups of the polymeric chains, and also by a new 8‐hydrogenated POSS incorporated as additive to the polymeric matrices. The new materials exhibit enhanced thermal, optical, and mechanical properties with respect to the pure organic polymers. The organization of the molecular units in these nanomaterials is studied through a structural analysis by solid‐state NMR. The domain size of the dispersed phase assures a homogeneous distribution of POSS into the polymer, thus, a continuous phase corresponding to the organic matrix incorporates these nanometer‐sized POSS crosslinkers at a molecular level, in agreement with the transparency of the samples. The silicon–oxygen core framework has to be covalently bonded into the polymer backbone instead of being a simple additive and both the silica content and crosslinked degree exhibit a critical influence on the laser action.     

Bright Aggregation‐Induced Emission Dots for Dynamic Tracking and Grading of Patient‐Derived Xenografts in Zebrafish

Cancer prognosis will benefit from a scoring system that could grade malignant traits of patient‐derived cells by assessing their growth and metastasis in a living system. Specific tracking of patient‐derived cells requires labeling by contrast agents with good signal‐to‐noise ratio and no specific stain of host tissues. Towards this aim, aggregation‐induced emission (AIE) dots are developed for in vivo cancer tracking with emphasis on reproducible optimized formulation and specific fluorescent labeling of cells that enable enhanced spatial temporal resolution in vivo. The importance of energy‐dependent AIE dots uptake for patient‐derived cell labeling is emphasized to reveal their specific uptake by viable cancer cells. Using optically transparent zebrafish embryo, the ability is demonstrated to follow the engraftment of transplanted AIE dot labeled cells in zebrafish brains over one week. Cells detected outside the brain after 7 d are quantified as metastatic cells. Results from seven clinical samples demonstrate the utility of this methodology to differentiate low engraftment level of benign neoplasms from higher engraftment level and metastasis detected in malignant ovarian cancer specimens. Achieving clinically validated results supports the use of AIE dot labeled patient derived cells in zebrafish xenografts for future cancer prognosis.     

Layer‐By‐Layer Dendritic Growth of Hyperbranched Thin Films for Surface Sol–Gel Syntheses of Conformal,Functional, Nanocrystalline Oxide Coatings on Complex 3D (Bio)silica Templates

Here, a straightforward and general method for the rapid dendritic amplification of accessible surface functional groups on hydroxylated surfaces is described, with focus on its application to 3D biomineral surfaces. Reaction of hydroxyl‐bearing silica surfaces with an aminosilane, followed by alternating exposure to a dipentaerythritol‐derived polyacrylate solution and a polyamine solution, allows the rapid, layer‐by‐layer (LBL) build‐up of hyperbranched polyamine/polyacrylate thin films. Characterization of such LBL‐grown thin films by AFM, ellipsometry, XPS, and contact angle analyses reveals a stepwise and spatially homogeneous increase in film thickness with the number of applied layers. UV–Vis absorption analyses after fluorescein isothiocyanate labeling indicate that significant amine amplification is achieved after the deposition of only 2 layers with saturation achieved after 3–5 layers. Use of this thin‐film surface amplification technique for hydroxyl‐enrichment of biosilica templates facilitates the conformal surface sol–gel deposition of iron oxide that, upon controlled thermal treatment, is converted into a nanocrystalline (～9.5 nm) magnetite (Fe₃O₄) coating. The specific adsorption of arsenic onto such magnetite‐coated frustules from flowing, arsenic‐bearing aqueous solutions is significantly higher than for commercial magnetite nanoparticles (≤50 nm in diameter).     

Facile Synthesis of Nanostructured Carbon through Self‐Assembly between Block Copolymers and Carbohydrates

A simple and direct wet chemistry method is reported to simultaneously synthesize nanostructured carbon films and particles through self‐assembly of poly(styrene)‐poly(4‐vinylpyridine) (PS‐P4VP) and carbohydrate precursors (turanose, raffinose, glucose, etc.) in two fabrication processes—spin‐coating and aerosol processing. Starting with a homogeneous solution containing PS‐P4VP and carbohydrates, evaporation of solvent during either spin‐coating or an aerosol process leads to the formation of ordered mesostructured films and particles. High temperature treatment in argon atmosphere removes PS fragments, carbonizes carbohydrates and partial PVP fragments, and results in ordered nanoporous carbon films and particles. SEM, TEM, and GISAXS characterization indicates that these nanostructured carbon materials exhibit large nanopores (> 20 nm), controlled 1–3 dimensional structures, and controlled surface chemistry. Nitrogen sorption isotherms and electrochemistry characterization indicates the accessibility of the carbon nanopores to both gas phase and aqueous phase. Results suggest that the nanostructured carbon films and particles can be tuned through solvent annealing, precursor concentration, and choice of block copolymers used. These carbon materials present varied practical applications for sorption and separation, sensors, electrode materials, etc.