Ligand assisted reprecipitation(LARP)is a widely used method for cesium lead halide perovskite nanocrystals(NCs)synthesis.Nevertheless,the ultrafast kinetics of LARP,as well as the inefficient transport properties and...Ligand assisted reprecipitation(LARP)is a widely used method for cesium lead halide perovskite nanocrystals(NCs)synthesis.Nevertheless,the ultrafast kinetics of LARP,as well as the inefficient transport properties and discontinuity of batch reactors,challenge the particle size control and experimental repeatability.To address these issues,an ultrasonic cavitation-enabled microfluidic approach was developed to achieve the continuous synthesis of cesium lead halide perovskite via LARP.It was found that the mixing between the good solvent and antisolvent in the microchannel was greatly enhanced by intensive ultrasonic cavitation.The mixing time could be reduced to below 10 ms under the irradiation of 35 W ultrasound.By modulating the mixing degree,LARP was proved to be a mixing-sensitive process.The effects of ultrasonic power,ultrasonic treatment time,total flow rate,water additive,and reprecipitation temperature on the synthesis of CsPbBr_(3) NCs were systematically investigated.As compared to CsPbBr_(3) NCs synthesized in the batch reactor,the sample synthesized via the ultrasonic cavitation-enabled microfluidic approach possessed stronger photoluminescence intensity and better repeatability.Moreover,the ultrasonic cavitation-enabled microfluidic approach could also realize the continuous synthesis of cesium lead halide perovskite NCs with different halide compositions to cover a wide visible spectrum(426-661 nm).The ultrasonic cavitation-enabled microfluidic approach paved the way for the large-scale of high-quality cesium lead halide perovskite NCs.展开更多
Perovskite nanocrystals(NCs) with high two-photon absorption(TPA) cross-section are of great interest due to their potential applications in three-dimensional optical data storage and multiphoton fluorescence microsco...Perovskite nanocrystals(NCs) with high two-photon absorption(TPA) cross-section are of great interest due to their potential applications in three-dimensional optical data storage and multiphoton fluorescence microscopy. Among various perovskite materials, FAPbBr_(3) NCs show a better development prospect due to their excellent stability. However, there are few reports on their nonlinear optical properties. In this work, the nonlinear optical behavior of FAPbBr_(3) NCs is studied.The methods of multiphoton absorption photoluminescence saturation and open aperture Z-scan technique were applied to determine the TPA cross-section of FAPbBr_(3)NCs, which was around 2.76 × 10^(-45)cm^(4)·s·photon^(-1) at 800 nm. In addition,temperature-dependent photoluminescence induced by TPA was investigated, and the small longitudinal optical phonon energy and electron–phonon coupling strength was obtained, which confirm the weak Pb–Br interaction. Meanwhile, it is found that the exciton binding energy in FAPbBr_(3) NCs was 69.668 me V, which may be ascribed to the strong hydrogen bond interaction. It is expected that our findings will promote the application of FAPbBr_(3) NCs in optoelectronic devices.展开更多
Lutetium oxide nanocrystals codoped with Tm3＋ and Yb3＋ were synthesized by the reverse-like co-precipitation method, using ammonium hydrogen carbonate as precipitant. Effects of the Tm3＋, Yb3＋ molar fractions and ...Lutetium oxide nanocrystals codoped with Tm3＋ and Yb3＋ were synthesized by the reverse-like co-precipitation method, using ammonium hydrogen carbonate as precipitant. Effects of the Tm3＋, Yb3＋ molar fractions and calcination temperature on the structural and upconversion luminescent properties of the Lu2O3 nanocrystals were investigated. The XRD results show that all the prepared nanocrystals can be readily indexed to pure cubic phase of Lu2O3 and indicate good crystallinity. The experimental results show that concentration quenching occurs when the mole fraction of Tm3＋ is above 0.2%. The optimal Tm3＋ and Yb3＋ doped molar fractions are 0.2% and 2%, respectively. The strong blue （490 nm） and the weak red （653 nm） emissions from the prepared nanocrystals were observed under 980 nm laser excitation, and attributed to the 1G4→3H6 and IG4→3F4 transitions of Tm3＋, respectively. Power-dependent study reveals that the 1G4 levels of Tm3＋ can be populated by three-step energy transfer process. The upconversion emission intensities of 490 nm and 653 nm increase gradually with the increase of calcination temperature. The enhancement of the upconversion luminescence is suggested to be the consequence of reducing number of OH- groups and the enlarged nanoerystal size.展开更多
Helical hierarchy found in biomolecules like cellulose,chitin,and collagen underpins the remarkable mechanical strength and vibrant colors observed in living organisms.This study advances the integration of helical/ch...Helical hierarchy found in biomolecules like cellulose,chitin,and collagen underpins the remarkable mechanical strength and vibrant colors observed in living organisms.This study advances the integration of helical/chiral assembly and 3D printing technology,providing precise spatial control over chiral nano/microstructures of rod-shaped colloidal nanoparticles in intricate geometries.We designed reactive chiral inks based on cellulose nanocrystal(CNC)suspensions and acrylamide monomers,enabling the chiral assembly at nano/microscale,beyond the resolution seen in printed materials.We employed a range of complementary techniques including Orthogonal Superposition rheometry and in situ rheo-optic measurements under steady shear rate conditions.These techniques help us to understand the nature of the nonlinear flow behavior of the chiral inks,and directly probe the flow-induced microstructural dynamics and phase transitions at constant shear rates,as well as their post-flow relaxation.Furthermore,we analyzed the photo-curing process to identify key parameters affecting gelation kinetics and structural integrity of the printed object within the supporting bath.These insights into the interplay between the chiral inks self-assembly dynamics,3D printing flow kinematics and photopolymerization kinetics provide a roadmap to direct the out-of-equilibrium arrangement of CNC particles in the 3D printed filaments,ranging from uniform nematic to 3D concentric chiral structures with controlled pitch length,as well as random orientation of chiral domains.Our biomimetic approach can pave the way for the creation of materials with superior mechanical properties or programable photonic responses that arise from 3D nano/microstructure and can be translated into larger scale 3D printed designs.展开更多
基金the financial supports from National Natural Science Foundation of China(22178336 and 21991103).
文摘Ligand assisted reprecipitation(LARP)is a widely used method for cesium lead halide perovskite nanocrystals(NCs)synthesis.Nevertheless,the ultrafast kinetics of LARP,as well as the inefficient transport properties and discontinuity of batch reactors,challenge the particle size control and experimental repeatability.To address these issues,an ultrasonic cavitation-enabled microfluidic approach was developed to achieve the continuous synthesis of cesium lead halide perovskite via LARP.It was found that the mixing between the good solvent and antisolvent in the microchannel was greatly enhanced by intensive ultrasonic cavitation.The mixing time could be reduced to below 10 ms under the irradiation of 35 W ultrasound.By modulating the mixing degree,LARP was proved to be a mixing-sensitive process.The effects of ultrasonic power,ultrasonic treatment time,total flow rate,water additive,and reprecipitation temperature on the synthesis of CsPbBr_(3) NCs were systematically investigated.As compared to CsPbBr_(3) NCs synthesized in the batch reactor,the sample synthesized via the ultrasonic cavitation-enabled microfluidic approach possessed stronger photoluminescence intensity and better repeatability.Moreover,the ultrasonic cavitation-enabled microfluidic approach could also realize the continuous synthesis of cesium lead halide perovskite NCs with different halide compositions to cover a wide visible spectrum(426-661 nm).The ultrasonic cavitation-enabled microfluidic approach paved the way for the large-scale of high-quality cesium lead halide perovskite NCs.
基金Project supported by the National Natural Science Foundation of China (Grant No. 62174079)the Fund from the Science, Technology, and Innovation Commission of Shenzhen Municipality (Grant Nos. JCYJ20220530113015035, JCYJ20210324120204011, JCYJ20190808121211510, and KQTD2015071710313656)。
文摘Perovskite nanocrystals(NCs) with high two-photon absorption(TPA) cross-section are of great interest due to their potential applications in three-dimensional optical data storage and multiphoton fluorescence microscopy. Among various perovskite materials, FAPbBr_(3) NCs show a better development prospect due to their excellent stability. However, there are few reports on their nonlinear optical properties. In this work, the nonlinear optical behavior of FAPbBr_(3) NCs is studied.The methods of multiphoton absorption photoluminescence saturation and open aperture Z-scan technique were applied to determine the TPA cross-section of FAPbBr_(3)NCs, which was around 2.76 × 10^(-45)cm^(4)·s·photon^(-1) at 800 nm. In addition,temperature-dependent photoluminescence induced by TPA was investigated, and the small longitudinal optical phonon energy and electron–phonon coupling strength was obtained, which confirm the weak Pb–Br interaction. Meanwhile, it is found that the exciton binding energy in FAPbBr_(3) NCs was 69.668 me V, which may be ascribed to the strong hydrogen bond interaction. It is expected that our findings will promote the application of FAPbBr_(3) NCs in optoelectronic devices.
基金Foundation item: Projects (10704090,10774140,11047147)supported by the National Natural Science Foundation of ChinaProjects (KJ090514,KJTD201016)supported by the Natural Science Foundation of Chongqing Municipal Education Commission,China
文摘Lutetium oxide nanocrystals codoped with Tm3＋ and Yb3＋ were synthesized by the reverse-like co-precipitation method, using ammonium hydrogen carbonate as precipitant. Effects of the Tm3＋, Yb3＋ molar fractions and calcination temperature on the structural and upconversion luminescent properties of the Lu2O3 nanocrystals were investigated. The XRD results show that all the prepared nanocrystals can be readily indexed to pure cubic phase of Lu2O3 and indicate good crystallinity. The experimental results show that concentration quenching occurs when the mole fraction of Tm3＋ is above 0.2%. The optimal Tm3＋ and Yb3＋ doped molar fractions are 0.2% and 2%, respectively. The strong blue （490 nm） and the weak red （653 nm） emissions from the prepared nanocrystals were observed under 980 nm laser excitation, and attributed to the 1G4→3H6 and IG4→3F4 transitions of Tm3＋, respectively. Power-dependent study reveals that the 1G4 levels of Tm3＋ can be populated by three-step energy transfer process. The upconversion emission intensities of 490 nm and 653 nm increase gradually with the increase of calcination temperature. The enhancement of the upconversion luminescence is suggested to be the consequence of reducing number of OH- groups and the enlarged nanoerystal size.
基金the support from the University of South Carolina
文摘Helical hierarchy found in biomolecules like cellulose,chitin,and collagen underpins the remarkable mechanical strength and vibrant colors observed in living organisms.This study advances the integration of helical/chiral assembly and 3D printing technology,providing precise spatial control over chiral nano/microstructures of rod-shaped colloidal nanoparticles in intricate geometries.We designed reactive chiral inks based on cellulose nanocrystal(CNC)suspensions and acrylamide monomers,enabling the chiral assembly at nano/microscale,beyond the resolution seen in printed materials.We employed a range of complementary techniques including Orthogonal Superposition rheometry and in situ rheo-optic measurements under steady shear rate conditions.These techniques help us to understand the nature of the nonlinear flow behavior of the chiral inks,and directly probe the flow-induced microstructural dynamics and phase transitions at constant shear rates,as well as their post-flow relaxation.Furthermore,we analyzed the photo-curing process to identify key parameters affecting gelation kinetics and structural integrity of the printed object within the supporting bath.These insights into the interplay between the chiral inks self-assembly dynamics,3D printing flow kinematics and photopolymerization kinetics provide a roadmap to direct the out-of-equilibrium arrangement of CNC particles in the 3D printed filaments,ranging from uniform nematic to 3D concentric chiral structures with controlled pitch length,as well as random orientation of chiral domains.Our biomimetic approach can pave the way for the creation of materials with superior mechanical properties or programable photonic responses that arise from 3D nano/microstructure and can be translated into larger scale 3D printed designs.
