Aggregation-induced emission of 1-methyl-1,2,3,4,5-pentaphenylsilole

Organically modified silica nanoparticles co-encapsulating photosensitizing drug and aggregation-enhanced two-photon absorbing fluorescent dye aggregates for two-photon photodynamic therapy

We report energy-transferring organically modified silica nanoparticles for two-photon photodynamic therapy. These nanoparticles co-encapsulate two-photon fluorescent dye nanoaggregates as an energy up-converting donor and a photosensitizing PDT drug as an acceptor. They combine two features: (i) aggregation-enhanced two-photon absorption and emission properties of a novel two-photon dye and (ii) nanoscopic fluorescence resonance energy transfer between this nanoaggregate and a photosensitizer, 2-devinyl-2-(1-hexyloxyethyl)pyropheophorbide. Stable aqueous dispersions of the co-encapsulating nanoparticles (diameter < or = 30 nm) have been prepared in the nonpolar interior of micelles by coprecipitating an organically modified silica sol with the photosensitizer and an excess amount of the two-photon dye which forms fluorescent aggregates by phase separation from the particle matrix. Using a multidisciplinary nanophotonic approach, we show: (i) indirect excitation of the photosensitizer through efficient two-photon excited intraparticle energy transfer from the dye aggregates in the intracellular environment of tumor cells and (ii) generation of singlet oxygen and in vitro cytotoxic effect in tumor cells by photosensitization under two-photon irradiation.

Switching the light emission of (4-biphenylyl)phenyldibenzofulvene by morphological modulation: crystallization-induced emission enhancement

(4-Biphenylyl)phenyldibenzofulvene is weakly luminescent in the amorphous phase but becomes highly emissive upon crystallization; this unusual crystallization-induced emission enhancement effect allows its emission to be repeatedly switched between dark and bright states by fuming-heating and heating-cooling processes.

Tight intermolecular packing through supramolecular interactions in crystals of cyano substituted oligo(para-phenylene vinylene): a key factor for aggregation-induced emission

Strong supramolecular interactions, which induced tight packing and rigid molecules in crystals of cyano substituent oligo(para-phenylene vinylene) (CN-DPDSB), are the key factor for the high luminescence efficiency of its crystals; opposite to its isolated molecules in solution which have very low luminescence efficiency.

Fluorescence enhancements of benzene-cored luminophors by restricted intramolecular rotations: AIE and AIEE effects

Photoluminescence of simple arylbenzenes with ready synthetic accessibility is enhanced by two orders of magnitude through aggregate formation; viscosity and temperature effects indicate that the emission enhancement is due to the restriction of their intramolecular rotations in the solid state.

A Class of Nonplanar Conjugated Compounds with Aggregation-Induced Emission: Structural and Optical Properties of 2,5-Diphenyl-1,4-distyrylbenzene Derivatives with All Cis Double Bonds

We have studied the structural and optical properties of four 2,5-diphenyl-1,4-distyrylbenzene derivatives with all cis double bonds. These compounds belong to a class of nonplanar conjugated compounds possessing a typical Aggregation-Induced Emission (AIE) property that has no emission in solution but intense emission in crystal. The four molecules are packed in different stacking modes with different intermolecular interactions, resulting in different crystalline state photoluminescence (PL) efficiency. The torsional molecular configuration increases the intermolecular distances effectively in the crystalline state, which decreases the difference of the optical properties from the frozen isolated molecules to the crystalline state. The Stokes shifts of these compounds are very large and the PL spectra have only one broad emission band with poor structure, due to the relatively large configuration difference between the ground state and the first singlet excited state, and the abundant vibration energy levels of the torsional molecule with changeable conformation.

Platform Synthesis: A Useful Strategy for Rapid and Systematic Generation of Molecular Diversity

Emergence of library-based approaches have changed the way of developing new functional molecules in materials science and pharmaceutical science. Therefore, reliable methods for rapid and systematic generation of functional molecules are highly called for in this field. We herein describe our concept of "platform synthesis" as a useful strategy for generating molecular diversity. This simple yet powerful strategy realizes the synthesis of a number of interesting multifunctional molecules, such as multisubstituted olefins, in a programmable and diversity-oriented format. As well as applications to the synthesis of pharmaceutically important molecules, such as tamoxifen and CDP840, applications to materials science, which have led to the discovery of interesting fluorescent materials and properties, are also described.

Balanced Carrier Transports of Electrons and Holes in Silole-Based CompoundsA Theoretical Study

By employing a diabatic model and a first-principle direct method, we have investigated the carrier transport properties of the highly efficient organic light-emitting materials 1,1,2,3,4,5-hexaphenylsilole (HPS) and 1-methyl-1,2,3,4,5-pentaphenylsilole (MPPS). The electronic coupling constants and reorganization energies are calculated for a wide variety of nearest-neighbor charge transfer pathways. The theoretical calculations show that (i) the electron mobility is very close to that of the hole, which indicates a balanced carrier transport in these materials, and (ii) the carrier mobilities for MPPS are larger than those for HPS. These results help explain the underlying microscopic mechanism for the high electroluminescence efficiency.

Helical Stacking Tuned by Alkoxy Side Chains in π-Conjugated Triphenylbenzene Discotic Derivatives

We report on the synthesis and self-assembly of a new series of discotic molecules containing triphenylbenzene as the core and alkoxy side chain with varying length. It was found that compounds 3 a-c, 4 b and 5 b could form stable gels in several apolar solvents. Transmission electron microscopy (TEM) images revealed that their morphologies were very different for the different alkoxy-substituted organogels. In toluene or hexane, 3 b and 3 c resulted in both left- and right-handed helical fibers, whereas 3 a resulted in straight rigid fibers; 4 b and 5 b resulted in most straight fibers with a few twisted fibers. The results from FT-IR and UV/Vis absorption spectroscopy indicated that the hydrogen bonding and pi-pi interactions were the main driving forces for the formation of the self-assembled gels. Further detailed analysis of their aggregation modes were conducted by UV-visible absorption spectra and X-ray diffraction (XRD) measurements. Based on these findings, the influence of these peripheral alkoxy substituents on the gel formation and the aggregation mode were discussed. The special enhanced fluorescent emissions, which resulted from aggregation, were also found in the gel phase.

Synthesis of, Light Emission from, and Optical Power Limiting in Soluble Single-Walled Carbon Nanotubes Functionalized by Disubstituted Polyacetylenes

Single-walled carbon nanotubes are covalently functionalized by conjugated polyacetylenes through their cyclization reactions with poly(1-phenyl-1-alkyne) and poly(diphenylacetylene) derivatives carrying azido functional groups at the ends of their alkyl pendants. The resultant polyene nanotube addends are soluble in common solvents, emit intense visible lights and strongly attenuate the power of harsh laser pulses.

Tunable aggregation-induced emission of diphenyldibenzofulvenes

Nonemissive fulvenes can be induced to luminesce by aggregate formation, with the crystalline aggregates emitting bluer lights more intensely than their amorphous counterparts.

Fluorescent “light-up” bioprobes based on tetraphenylethylene derivatives with aggregation-induced emission characteristics

Aggregation in poor solvents and complexation with calf thymus DNA and bovine serum albumin turn "on" the fluorescence of tetraphenylethylene derivatives, due to the restriction of intra-molecular rotations of the dyes in the aggregates and complexes.

Dibenzosuberenylidene-Ended Fluorophores: Rapid and Efficient Synthesis, Characterization, and Aggregation-Induced Emissions

A series of pi-conjugated compounds ending with dibenzosuberenylidene were synthesized efficiently. Their luminescence efficiencies were well-tuned by structural modification. Moreover, relative emission intensities were strongly affected by their existing appearances and exhibited aggregation-induced emission (AIE) behavior. Thus, emissions from nanoparticles, films, or powders were found to be more efficient than those from solutions. It demonstrated that these synthesized compounds might be practically used as fluorescent materials for potential optoelectronic applications.

Fluorescent Aggregates of 1-(p-Butyloxyphenyl)-4-(p-cyanophenyl)Buta-1E,3E-Diene: Temperature Sensing and Photoimaging Applications

The use of fluorescent solid films of a 1-(p-butyloxyphenyl)-4-(p-cyanophenyl)buta-1E, 3E-diene as an efficient temperature sensor is described. The fluorescence changes in these films are proposed to occur due to a reversible temperature-dependent variation in its monomer-aggregate ratio. Photoisomerization of the butadiene chromophore in solid films was observed to occur only at elevated temperatures (>120 degrees C), making the material also useful for reversible photochemical generation of fluorescence patterns with nondestructive readout properties.

Reproducible on-off switching of solid-state luminescence by controlling molecular packing through heat-mode interconversion

Organic luminescent solids are attracting increasing interest in various fields of application. Modification or alteration of the chemical structures of their component molecules is the most common approach for tuning their luminescence properties. However, for dynamic tuning or switching of solid-state luminescence with high efficiency and reproducibility successful examples are limited as chemical reactions in the solid state frequently encounter insufficient conversion, one-way reactions or loss of their luminescence properties. One promising approach is to control the luminescence properties by altering the mode of solid-state molecular packing without chemical reactions. Here, we show that 2,2':6',2''-terpyridine, practically non-luminescent in the form of amorphous solid or needle crystal, shows strong blue luminescence upon formation of a plate crystal. Efficient and reproducible on-off switching of solid-state luminescence is demonstrated by heat-mode interconversion between the plate and needle crystals. Because alteration of the mode of molecular packing does not require chemical reactions, the present findings would open the way for the development of novel organic luminescent solids that can be switched on and off by external thermal stimuli.

Making silole photovoltaically active by attaching carbazolyl donor groups to the silolyl acceptor core

Appending carbazolyl groups to a hexaphenylsilole core yielded thermally and morphologically stable carbazolylsiloles; the silole carrying two carbazolyl peripheral groups showed photovoltaic activity.

Triarylethene-Based Extended π-Systems: Programmable Synthesis and Photophysical Properties

[reaction: see text] On the basis of an efficient Pd-catalyzed triarylation to a vinylsilane platform, four types of structurally well-defined triarylethene-based extended pi-systems have been prepared very rapidly. From a compound library constructed by the present method, it was possible to find a number of interesting fluorescent materials, as well as interesting fluorescent properties such as aggregation-induced enhanced emission. A useful method for the rapid synthesis and property evaluation has also been developed.

Luminescent oligo(tetraphenyl)silole nanoparticles as chemical sensors for aqueous TNT

Colloidal oligo(tetraphenyl)silole nanoparticles in THF/H2O suspensions show increased luminescence and offer a method to detect TNT in an aqueous environment.

Ultraviolet-emitting conjugated polymer poly(9,9′-alkyl-3,6-silafluorene) with a wide band gap of 4.0 eV

An ultraviolet-emitting conjugated polymer, poly(9,9'-alkyl-3,6-silafluorene) with a wide band gap of 4.0 eV, has been synthesized and characterized.

Silole nanocrystals as novel biolabels

A novel class of biofunctional silole nanocrystals with the potential to create highly sensitive immunoassay was firstly demonstrated. Biolabels were constructed by encapsulating nanocrystalline hexaphenylsilole [Ph2Si(CPh)4HPS] within ultrathin polyelectrolyte layers via the layer-by-layer (LbL) technique that provided an "interface" for the attachment of antibodies. A high ratio of fluorescent dyes to biomolecules (F/P ratio; 2.4 x 10(3)) was achieved without self-quenching problem. The aggregation-induced emission (AIE) feature offered silole biolabels the sensitivity 40- to 140-fold higher than that of a start-of-the-art immunoassay using directly fluorescent-labeled antibodies.