Impeding anion exchange to improve composition stability of CsPbX3（X= Cl, Br） nanocrystals through facilely fabricated Cs4Pb6 shell

Inorganic lead halide perovskite nanocrystals(NCs)with superior photoelectric properties are expected to have excellent performance in many fields.However,the anion exchange changes their features and is unfavorable for their applications in many fields.Hence,impeding anion exchange is important for improving the composition stability of inorganic lead halide perovskite NCs.Herein,CsPb X3(X=Cl,Br)NCs are coated with Cs4PbX6 shell to impede anion exchange and reduce anion mobility.The Cs4PbX6 shell is facily fabricated on CsPbX3 NCs through high temperature injection method.Anion exchange experiments demonstrate that the Cs4 PbX6 shell completely encapsulates CsPbX3 NCs and greatly improves the composition stability of CsPbX3 NCs.Moreover,our work also sheds light on the potential design approaches of various heterostructures to expand the application of CsPbM3(M=Cl,Br,I)NCs.

An AEE-active Polymer Containing Tetraphenylethene and 9,10-Distyrylanthracene Moieties with Remarkable Mechanochromism

A polymer （poly（9,10）anthracenevinylene-alt-4,4＇-（9,9-bis（4-（4＇-（1,2,2＇-triphenyviny）phenoxy）butyl）-9H- fluorene-2,7-diyl） dibenzaldehyde）, P1） was successfully synthesized through the Wittig-Horner reaction by employing fluorene and 9,10-distyrylanthracene moieties as building blocks for backbone and tetraphenylethenes as pendant groups. Photophysical and thermal properties of the resulting polymeric emitter were fully characterized by ultraviolet-visible （UV- Vis） absorption and photoluminescence （PL） spectra, thermogravimetric analysis （TGA） and differential scanning calorimetry （DSC）. While P1 emits an orange-light centered at 567 nm in dilute tetrahydrofuran （THF） solution, the solid powder of the polymer exhibits strong yellow emission peaked at 541 nm. It is also found that the as-synthesized polymer shows unique property of aggregation-enhanced emission （AEE）. In addition, P1 possesses high thermal stability with a decomposition temperature （Td,5%） of 430 ℃ and high morphological stability with a glass transition temperature （Tg） of 171℃. Under the stimulus of mechanical force, the emission of P1 can be changed from yellow to red （△λmax = 61 rim）, showing a remarkable mechanochromism. The results from XRD analysis suggest that such mechanochromic phenomenonof PI is probably caused by the destruction of crystalline structure, which leads to the conformational planarization of the distyrylanthracene moieties forming by the polymerization and the increase of molecular conjugation of the backbone.

Electric-field-induced microstructure modulation of carbon nanotubes for high-performance supercapacitors

The growth direction,morphology and microstructure of carbon nano-tubes(CNTs)play key roles for their potential applications in electronic and energy storage devices.However,effective synthesis of CNTs in high crystallinity and desired microstructure still remains a tremendous challenge.Here we introduce an electric field for controlling the microstructure formation of CNTs.It reveals that the electric field not only make CNTs aligned parallel but also improve the density of CNTs.Especially,the microstructures of CNTs gradually change under electrical field.That is,graphite sheets are transformed from the"herringbone"structure to a highly crystalline structure,facilitating the transportation of electrons.Due to the improved aligned growth direction,high density and highly crystalline microstructure,the electrochemical performance of CNTs is greatly improved.When the CNTs are applied in supercapacitors,they present a high specific capacitance of 237 F/g,three times higher than that of the CNTs prepared without electrical field.Such microstructure modulation of CNTs by electric field would help to construct high performance electronic and energy storage devices.