The aggregation-induced emission (AIE) properties of 1,1,2,3,4,5-hexaphenylsilole (HPS) and poly{11-[(1,2,3,4,5-pentaphenylsilolyl)oxy]-1-phenyl-1-undecyne} (PS9PA) were studied by time-resolved fluorescence technique. The enhanced fluorescence and long fluorescent lifetime were obtained for the sample in an aggregate state as compared to the sample in solution. The time-decay of fluorescence of HPS and PS9PA in high viscosity solvents and low-temperature glasses has also been measured in detail to further investigate the possible mechanism for AIE. Enhanced light emission and long fluorescence lifetime were detected for both HPS and PS9PA in the solution-thickening and -cooling experiments. These results provided direct evidence that the enhanced photoluminescence (PL) efficiency is due to restricted intramolecular motion, which ascribes AIE to the deactivation of nonradiative decay caused by restricted torsional motions of the molecules in the solid state or aggregate form.

We synthesized a group of silole regioisomers 1(x,y), whose photoluminescence varied dramatically with its regiostructure. By internally hindering the intramolecular rotation, we succeeded in creating a novel silole (1(3,4)) that is strongly luminescent in solutions and whose fluorescence quantum yield in acetone is as high as 83%. We revealed that 1(3,4) was a sensitive chemosensor capable of optically discriminating nitroaromatic regioisomers of p-, o-, and m-nitroanilines. Against general belief, crystal formation of 1(2,4) blue-shifted its emission color and boosted its emission efficiency. The light-emitting diode based on the crystal of 1(2,4) emitted a strong blue light (464 nm) in a high current efficiency (5.86 cd/A).

Aggregation induced emission (AIE) is an amazing property for light emitting materials and has attracted much attention. Here, we report a new kind of AIE materials: fluorenone derivates 2,7-dip-tolyl-fluorenone (DTFO) and 2,7-bis(4-(tert-butylthio)phenyl)-fluorenone (DSFO). Strong light emissions with a large Stokes shift and long lifetime in the solid state originate from the formation of excimers. The crystal structure of DSFO shows that every two molecules are bound together even in the ground state by intermolecular hydrogen bonds and form a particular dimer. When this dimer is excited, it turns into an excimer without arrangement adjustment and likewise without repulsive interactions when the excimer decays back to the dimer; so, the nonradiative decay pathways that exist in common excimers are greatly reduced and thus induce a strongly enhanced luminescence in the solid state. OLED devices employing DTFO as light emitting layers are fabricated and evaluated.

On the basis of hybridized target microRNA (miRNA) strand initiated cleavage of hybridized deoxyribonucleic acid (DNA) capture probes (CPs) by a duplex-specific nuclease (DSN), a highly sensitive and selective label-free miRNA biosensor is developed in this article. Briefly, thiolated DNA CPs are immobilized onto a gold electrode through self-assembly. The electrode is then hybridized to a sample solution containing the target miRNA. The hybridized CPs in the miRNA-CP duplexes are simultaneously cleaved by the DSN, releasing the target miRNA strands back to the sample solution. The released target miRNA strands again hybridize with the remaining CPs on the electrode, thus forming an isothermal amplification cycle. The distinct difference in electrochemical impedance between a control and the DSN cleaved biosensor allows label-free detection of miRNA down to femtomolar levels. The mismatch discrimination ability of the DSN permits miRNA expression to be profiled with high selectivity. The exceptional amplification power of the DSN along with the simple assay protocol makes direct miRNA expression profiling possible in real-world samples with minimal or no sample pretreatments. Attempts are made in direct profiling circulating miRNAs in serum and miRNAs in total RNA extracted from cancer cells.

A chiral pyran derivative containing two cholesteryl groups (1) is synthesized, and its optical properties are investigated. Whereas the isolated molecule of 1 is virtually nonluminescent in dilute solutions, it becomes highly emissive with a 2 orders of magnitude increase in fluorescence quantum yield upon aggregation in poor solvents or in solid state, showing a novel phenomenon of aggregation-induced emission (AIE). The color and efficiency of the AIE of 1 can be tuned by varying the morphology of its aggregates: photoluminescence of its aggregates formed in a tetrahydrofuran/water mixture progressively red-shifts (green --> yellow --> red) with increasing water content of the mixture, with the crystalline aggregates emitting bluer lights in higher efficiencies than their amorphous counterparts.

A simple and ultrasensitive label-free microRNA (miRNA) biosensor, based on hybridized miRNA-templated deposition of an insulating polymer film and electrochemical impedance spectroscopic detection, is described in this report. The biosensor is made of a monolayer of charge-neutral morpholino capture probes on an indium tin oxide (ITO)-coated glass slide. Upon hybridization, the neutral surface of the biosensor is converted to anionic by the hybridized miRNA strands. The deposition of the insulating polymer film, poly(3,3'-dimethoxybenzidine) (PDB), is then carried out by the horseradish peroxidase-catalyzed polymerization of 3,3'-dimethoxybenzidine in the presence of H(2)O(2). The cumulative nature of the PDB deposition process significantly enhances the sensitivity of the biosensor. Under optimized conditions, miRNA expression profiling can be performed label-freely from 5.0 fM to 2.0 pM with a detection limit of 2.0 fM. The biosensor is applied to the detection of circulating miRNAs in blood and miRNAs in total RNA extracted from cultured cells.

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