Fluorene pendant-functionalization of poly(N-vinylcarbazole)as deep-blue fluorescent and host materials for polymer light-emitting diodes

π-Electron coupling of pendant conjugated segment inπ-stacked semiconducting polymers always causes the formation of defect trapped sites and further quenched high-band excitons,which is harmful to the performance and stability of deep-blue polymer light-emitting diodes(PLEDs).Herein,considerate of“defect”carbazole(Cz)electromers in poly(N-vinylcarbazole)(PVK),a series of fluorene units are introduced into pendant segments(PVCz-DMeF,PVCz-FMeNPh and PVCz-DFMeNPh)to suppress the strongπ-electron coupling of pendant Cz units and enhance radiative transition toward fabricating sable PLEDs.Compared to PVCz-FMeNPh and PVCz-DFMeNPh,PVCz-DMeF spin-coated films show a relatively efficient deep-blue emission,completely similar to its single pendant chromophore,confirmed an extremely weak charge-transfer and electron coupling between adjacent pendant segments.Therefore,PLEDs based on PVCz-DMeF present stable and deep-blue emission with a high color purity(0.17,0.08),associated with extremely weak defect emission at 600∼700nm(induced by carbazole electromers).Finally,PLEDs based on PVCz-DMeF/F8BT blended films(1:1)also present the high maximum luminance(Lmax)of 6261 cd/m2 and current efficiency(CE_(max))of 2.03 cd/A,confirmed slightly trapped sites formation.Therefore,precisely control the arrangement and packing model of pendant units inπ-stacked polymer is an essential prerequisite for building efficient and stable emitter for optoelectronic devices.

Mitochondria-targeting NIR fluorescent probe for rapid,highly sensitive and selective visualization of nitroxyl in live cells,tissues and mice

Nitroxyl(HNO)has been reported to possess unique biological and pharmacological performances,and emerged as a novel therapy for congestive heart failure.Recent studies also suggest that HNO may be produced and involved in important metabolisms in mitochondria.However,due to its high reactivity and short life properties,fast,sensitive and selective observation and monitoring of HNO related dynamic changes in mitochondria still remains a great challenge.Herein,we synthesized a mitochondria-targeting near-infrared(NIR)fluorescent probe(DCMHNO)for rapid detection of HNO with remarkably high sensitivity,selectivity and photostability.DCMHNO shows fast response(about 4 min)towards HNO via 2-(diphenylphosphino)benzoyl group through the Staudinger reaction to boost the bright NIR emission(700 nm)with excellent sensitivity(detection limit of 13 nM),high p H stability and very low interference from other species.DCMHNO can selectively locate in mitochondria and visualize exogenous and endogenous HNO in live He La cells with high biocompatibility and photostability.The probe could also monitor the interaction between NO and H2 S that gives rise to the generation of HNO in live He La cells.In addition,DCMHNO was further utilized in ex vivo NIR imaging of HNO in live mouse liver tissues at the depth of about 50μm.In vivo imaging of HNO with high signal-to-noise ratio in live mice was also realized by using DCMHNO.These remarkable imaging performances could render NIR DCMNHNO as a useful tool to reveal HNO related dynamic changes in live samples.