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

Highly solid-state emissive para-terphenyls laterally substituted with a diphenylamino group

para-Terphenyls laterally substituted with a diphenylamino group show intense solid-state emissions with quantum yields close to unity.

Multicolor tuning of aggregation-induced emission through substituent variation of diphenyl-o-carborane

We demonstrate multicolor tuning of aggregation-induced emission (AIE) derived from o-carborane. Both electron-donating and electron-accepting arylacetylenes underwent efficient palladium coupling reaction with bis(4-bromophenyl)-o-carborane, resulting in moderate yields. The emission spectra of these compounds span almost the entire visible spectrum (λ(max) = 452-662 nm). Study on AIE mechanism indicated that CT-based emission of o-carborane derivatives was enhanced by the restriction of molecular motions. The computational study also suggests the possibility of precise color-control of AIE through substituent variation.

Simple biosensor with high selectivity and sensitivity: thiol-specific biomolecular probing and intracellular imaging by AIE fluorogen on a TLC plate through a thiol-ene click mechanism

A handy, specific, sensitive bioprobe has been developed. Tetraphenylethene (TPE) was functionalized by a maleimide (MI) group, giving a TPE-MI adduct that was nonemissive in both solution and the solid state. It was readily transformed into a fluorogen showing an aggregation-induced emission (AIE) property by the click addition of thiol to its MI pendant. The click reaction and the AIE effect enabled TPE-MI to function as a thiol-specific bioprobe in the solid state. Thus, the spot of TPE-MI on a TLC plate became emissive when it had been exposed to L-cysteine, an amino acid containing a thiol group, but remained nonemissive when exposed to other amino acids that lack free thiol units. The thiol-activated emission was rapid and strong, readily detected by the naked eye at an analyte concentration as low as approximately 1 ppb, thanks to the "lighting up" nature of the bioprobing process. Similarly, the emission of TPE-MI was turned on only by the proteins containing free thiol units, such as glutathione. Clear fluorescence images were taken when living cells were stained by using TPE-MI as a visualization agent, affording a facile fluorescent maker for mapping the distribution of thiol species in cellular systems.

Aggregation-induced emission enhancement of aryl-substituted pyrrole derivatives

The relationship between the structures and light emission properties of five aryl-substituted pyrrole derivatives was studied during aggregation in THF-water mixtures. Only pentaphenylpyrrole clearly shows, however, an aggregation-induced emission enhancement (AIEE) phenomenon. On comparison of the optical properties and single-crystal structures of these pyrrole derivatives, it is suggested that the more twisted configuration which prevented parallel orientation of conjugated chromophores combined with the restricted intramolecular rotation (RIR) effect was the main cause of the AIEE phenomenon.

Polyelectrolyte-assisted formation of molecular nanoparticles exhibiting strongly enhanced fluorescence

A polyelectrolyte-assisted reprecipitation method is developed to fabricate nanoparticles of highly soluble molecules. The approach is demonstrated by using a zwitterionic diaminodicyanoquinodimethane molecule bearing remote ammonium functionalities with high solubility in water as well as organic solvents. Nanoparticles are prepared by injecting aqueous solutions of this compound containing an optimum concentration of sodium poly(styrenesulfonate) into methanol. The strong fluorescence exhibited by the compound in the aggregated state is reflected in the enhanced fluorescence of the polyelectrolyte complex in water. The nanoparticles formed in the colloidal state manifest even stronger fluorescence, which leads to an overall enhancement by about 90 times relative to aqueous solutions of the pure compound. The conditions for achieving the emission enhancement are optimized and a model for the molecular-level interactions and aggregation effects is developed through a range of spectroscopy, microscopy, and calorimetry investigations and control experiments.

Label-free fluorescence detection of mercury(II) and glutathione based on Hg2+-DNA complexes stimulating aggregation-induced emission of a tetraphenylethene derivative

Herein, a sensitive and selective sensor for mercury(II) and glutathione based on the aggregation-induced emission (AIE) of a tetraphenylethene derivative stimulated by Hg(2+)-DNA complexes is reported. Aggregation complexes of AIE probes, quaternized tetraphenylethene salt and anti-Hg(2+) aptamer ssDNA, were formed based on the electrostatic interactions between the ammonium cation of AIE probes and the backbone phosphate anions of DNA. In the presence of target Hg(2+), the aptamer ssDNA with thymine (T)-rich sequences selectively bound with Hg(2+) to form an Hg(2+)-bridged T base pair and the ssDNA changed into a hairpin-like structure. Therefore the AIE probing molecules were brought to be positioned closer. Accordingly, the conformational change of aptamer ssDNA resulted in an obvious enhancement in the fluorescence of the probing complex enabling the sensitive and selective detection of Hg(2+). Furthermore, upon reaction of Hg(2+) with biothiols, the compact structure was destroyed and the fluorescence decreased consequently. Sensitive detection of GSH was realised based on the decrease of fluorescence of the probing complex. The target-aptamer complexes stimulating aggregation-induced emission therefore show great promise for environmental and biological process monitoring and disease diagnosis.

A new label-free continuous fluorometric assay for trypsin and inhibitor screening with tetraphenylethene compounds

A new label-free continuous assay with the ensemble of compound 1 and Arg(6) for trypsin and inhibitor screening was successfully developed by taking advantage of the aggregation-induced emission feature of tetraphenylethene compounds. Both CLSM and DLS studies confirm the formation of the aggregation complex of compound 1 and Arg(6) and disassembly after further addition of trypsin.

High-resolution light microscopy using luminescent nanoparticles

This review presents recent progress in the development of the luminescent nanoparticles for confocal and multiphoton microscopy. Four classes of nanomaterials are discussed: (1) silica-based nanoparticles doped with fluorescent molecules, (2) gold nanoparticles, (3) semiconductor nanocrystals (quantum dots/rods), and (4) nanophosphors. Special considerations are given to recently developed imaging nanoprobes, such as (1) organically modified silica (ORMOSIL) nanoparticles doped with two-photon absorbing fluorophores, which exhibit aggregation-enhanced fluorescence (AEF), and (2) nanophosphors (ceramic nanoparticles containing luminescent lanthanoid ions). Advantages and disadvantages of every class of nanomaterials and their specific applications are briefly discussed.

Fluorescent nanoparticles based on self-assembled pi-conjugated systems

pi-Conjugated molecules are interesting components to prepare fluorescent nanoparticles. From the use of polymer chains that form small aggregates in water to the self-assembly of small chromophoric segments into highly ordered structures, the preparation of these materials allows to develop systems with applications as sensors or biolabels. The potential functionalization of the nanoparticles can lead to specific probing. This progress report describes the recent advances in the preparation of such emittive organic nanoparticles.