Synthesis,Crystal Structure and Photophysical Property of 2-(9H-carbazol-9-yl)-3-(2-(2,4,5-tri-(9H-carbazol-9-yl)-3,6-dicyanophenoxy)phenoxy)dibenzo[b,e][1,4]dioxine-1,4-dicarbonitrile

A purely organic compound 2-（9 H-carbazol-9-yl）-3-（2-（2,4,5-tri-（9 H-carbazol-9-yl）-3,6-dicyanophenoxy）phenoxy）dibenzo[b,e][1,4]dioxine-1,4-dicarbonitrile, C76 H40 N8 O4, was synthesized and characterized by NMR, UV-Vis, photoluminescenceand X-ray single-crystal structure analysis. The compound crystallizes in monoclinic system, space group P21/n with a = 11.6537（3）, b = 34.9738（8）, c = 15.5053（3） ？, β =101.992（2）°, V = 6181.6（2）？3, Z = 4, Mr= 1129.18 g/mol, Dc =1.396 g/cm3, F（000） =2672, μ = 2.239 mm–1, GOOF = 1.019, the final R = 0.0577 and wR= 0.1559 for 11925 observed reflections with I 〉2σ（I）. The UV-vis absorption and fluorescence of the compound were discussed. The compound exhibitsyellow-green luminescence with maximum emission peak at 538 nm, and quantum yields of ф = 0.25 and 0.48 in air-equilibrated and degassed toluene at room temperature. Transient decay spectral studies show that compound 1 displays two component decay fashions with a short decay lifetime of 23 ns for the prompt fluoresce anda long decay lifetime of 3.8ms for thermally activated delayed fluorescence. In air-equilibrated toluene, only a short decay lifetime of 17 ns was observed.The experimental and computational results show thatthe emission of the compound originates from the CT excited states.

Ratiometric hypoxia detection by bright organic room temperature phosphorescence of uniformed silica nanoparticles in water

Organic room temperature phosphorescence(RTP)in water has attracted much attention recently for its potential biological applications.However,it remains a formidable challenge to achieve efficient RTP from pure organic compounds in aqueous phase due to the dramatic deactivation of triplet excited states in water and the poor water dispersibility of large organic particles/crystals.Represented herein is covalent incorporation of a pure organic monochromophore in silica nanoparticles(SiNPs)featuring fluorescence and bright phosphorescence in aqueous solution.The covalent bonding of organic phosphors in polysiloxane framework was found to show excellent water dispersibility,at the same time suppress the nonradiative deactivation of triplet excited states especially from water,thus leading to high phosphorescence quantum yields(up to 22%)and long lifetimes(up to 3.5 ms)in aqueous phase.More strikingly,oxygen-insensitive fluorescence as internal reference and oxygen-dependent phosphorescence as oxygen indicator from the organic chromophore in the porous SiNPs realized ratiometric hypoxia detection with ultrasensitivity(K_(SV)=449.3 bar^(-1)).