The Experts below are selected from a list of 504 Experts worldwide ranked by ideXlab platform

Pengfei Duan - One of the best experts on this subject based on the ideXlab platform.

  • toward large Dissymmetry Factor of circularly polarized luminescence in donor acceptor hybrid systems
    Journal of Physical Chemistry Letters, 2021
    Co-Authors: Xue Jin, Tonghan Zhao, Jianlei Han, Pengfei Duan
    Abstract:

    Chiroptical materials with circularly polarized luminescence (CPL) activity have aroused a lot of interest. One essential Factor for evaluating the features of CPL-active materials is the Dissymmetry Factor (glum), which represents the circular polarization of emitted light. Essentially, for the practical application of CPL, the most important issue is to greatly improve the glum value. Recently, benefiting from the flexible and efficient design in hybrid donor-acceptor systems, more and more examples involving glum value amplification have been reported. In this Perspective, we highlight the proposed mechanism for the generation and amplification of CPL in these hybrid systems. We also present the corresponding design principles and potential pitfalls in experimental processes. We hope that this Perspective can shed light on the development of highly efficient CPL-active materials.

  • electric field regulated energy transfer in chiral liquid crystals for enhancing upconverted circularly polarized luminescence through steering the photonic bandgap
    Advanced Materials, 2020
    Co-Authors: Minghao Zhou, Pengfei Duan, Xuefeng Yang, Yafei Wang
    Abstract:

    Circularly polarized luminescent materials with high Dissymmetry Factor (glum ) have been attracting increasing attention due to their distinctive photonic properties. In this work, by incorporating upconversion nanoparticles (UCNPs) and CsPbBr3 perovskite nanocrystals (PKNCs) into a chiral nematic liquid crystal (N*LC), enhanced upconverted circularly polarized luminescence (UC-CPL) based on a radiative energy transfer (RET) process from UCNPs to CsPbBr3 PKNCs is successfully implemented. By locating the emission peak of CsPbBr3 PKNCs at the center of the photonic bandgap of N*LC, the maximum glum value of UC-CPL can be amplified to an extremely large value of 1.1. Meanwhile, upconverted emission of UCNPs can be significantly enhanced due to the band edge enhancement effect of the N*LC, subsequently enhancing the emission of the CsPbBr3 PKNCs through the RET process. In addition, an applied electric field can switch the upconverted emission of the UCNPs, as well as the RET process, enabling an electric-field-controlled UC-CPL switch.

  • circularly polarized luminescence from gelator molecules from isolated molecules to assemblies
    2020
    Co-Authors: Tonghan Zhao, Pengfei Duan
    Abstract:

    Currently, molecular gels have become one kind of the fascinating candidates for fabricating chiroptical materials with circularly polarized luminescence (CPL) properties, due to the tunable and modifiable structure, simple yet facile synthesis, controlled and reversible assembly, and so on. Since self-assembly approach has been regarded as an efficient way for amplifying the chirality, supramolecular gelation provides a remarkable method for fabricating CPL materials with high Dissymmetry Factor (glum). Various gel systems, including chiral-, achiral-, organic-inorganic hybrid systems can be endowed with CPL activities through supramolecular gelatinization, possessing excellent luminescence circular polarization. This chapter summarizes and reviews the present status and progress of supramolecular gel systems with CPL activity.

  • Amplifying Dissymmetry Factor of Upconverted Circularly Polarized Luminescence through Chirality-Induced Spin Polarization in the Photon Upconversion Process.
    The Journal of Physical Chemistry Letters, 2019
    Co-Authors: Tonghan Zhao, Jianlei Han, Xujin Qin, Minghao Zhou, Pengfei Duan
    Abstract:

    A general phenomenon about upconverted circularly polarized luminescence (UC-CPL) based on triplet-triplet annihilation (TTA) was realized in an ambient environment by coupling three kinds of chiral acceptors with corresponding achiral sensitizers. All of the Dissymmetry Factors of UC-CPL exhibited significant amplification compared with the prompt CPL of the used chiral acceptors. Chirality-induced spin polarization during the TTA-UC process was in charge of the amplified Dissymmetry Factor of UC-CPL. Chirality-induced spin-polarized triplet excitons will suppress the TTA efficiency because the spin-polarized electrons go against the electron exchange within triplet excitons. However, the chirality-induced spin-polarized singlet excitons resulting from the TTA process can be promoted, enabling a large Dissymmetry Factor of UC-CPL.

  • photon upconverted circularly polarized luminescence via triplet triplet annihilation
    Advanced Materials, 2019
    Co-Authors: Dong Yang, Jianlei Han, Minghua Liu, Pengfei Duan
    Abstract:

    Circularly polarized luminescent materials are of increasing attention due to their potential applications in advanced optical technologies, such as chiroptical devices and optical sensing. Recently, in all reported circularly polarized luminescent materials, high-energy excitation results in low-energy or downconverted circularly polarized luminescence (CPL) emission. Although photon upconversion-i.e., the conversion of low-energy light into higher-energy emission, with a wide variety of applications-has been widely reported, the integration of photon upconversion and CPL in one chiral system to achieve higher-energy CPL emission has never been reported. Herein, a brief review is provided of recent achievements in photon-upconverted CPL via the triplet-triplet annihilation mechanism, focusing on the amplified Dissymmetry Factor glum through energy transfer process and dual upconverted and downconverted CPL emission through chirality and energy transfer process.

Minghua Liu - One of the best experts on this subject based on the ideXlab platform.

  • circularly polarized luminescence from solvent free chiral organic π liquids
    Angewandte Chemie, 2021
    Co-Authors: Minghua Liu, Yuqian Jiang, Xue Bai, Yimeng Sun, Guangjiu Zhao, Jian Jiang, Chenhuan Yuan
    Abstract:

    The solvent-free organic π-liquids have been attracting increasing attentions owing to the inherent optoelectronic properties accompanied by the advantages of non-volatility and high processability. Herein, we reported a series of naphthalene derivatives substituted with chiral branched alkyl chains, which are present as liquids (Nap1-3) or solid (Nap4) at room temperature, depending on the substitution positions. Circular dichroism (CD) and circularly polarized luminescence (CPL) were only observed for enantiomeric Nap2 (2,3-substituted) liquid. It is suggested that the chiral aggregation in the π-liquid leads to the CD signal and the chiral excimer resulting in the CPL performance. When achiral anthracene or pyrene was dissolved in Nap2, the π-liquid could serve as chirality and energy transfer media in which both CD and CPL emerged from the achiral anthracene. A CPL Dissymmetry Factor (|glum |) of anthracene reached to 5.2×10-2 when dissolved in chiral Nap2 liquid, which is nearly two orders of magnitude higher than that of the pure Nap2 π-liquid.

  • multi color tunable circularly polarized luminescence in one single aie system
    Chemical Science, 2020
    Co-Authors: Hongxing Shang, Minghua Liu, Zeyang Ding, Yue Shen, Bing Yang, Shimei Jiang
    Abstract:

    Circularly polarized luminescence (CPL) materials with a large luminescence Dissymmetry Factor (glum) and multi-color properties are very attractive. While multi-color tunable CPL can be realized by different organic dyes, the challenge of realizing both a higher glum and multiple colors using a single component remains. Here, we design an aggregation-induced emission (AIE) fluorophore, which is a pyridine functionalized cyanostilbene attached to a chiral unit, and realize multi-color tunable CPL with a high glum. The compound can self-assemble into a nanohelix and form both gel and xerogel films, exhibiting blue CPL with large glum values of −3.0 × 10−2 and −1.7 × 10−2, respectively. With the assistance of pyridine protonation, the xerogel films exhibit red-shifted CPL signals from 480 nm to 530 nm, covering from blue via green and yellow to orange. Additionally, the glum remains constant during the process. This work paves a simple and convenient way to construct multi-color tunable CPL materials using a single molecule.

  • The largest CPL enhancement by further assembly of self-assembled superhelices based on the helical TPE macrocycle
    Materials Horizons, 2020
    Co-Authors: Ying-xue Yuan, Minghua Liu, Kai-ran Zhang, Ting-ting Zhou, Song Wang, Yan-song Zheng
    Abstract:

    Helical self-assemblies from organic luminophores generally display significant enhancement of circularly-polarized luminescence (CPL) activity, but their CPL Dissymmetry Factor (glum) is still small. Whether further assembly of helical self-assemblies can further boost the CPL glum value is not known. In this paper, helical tetraphenylethylene (TPE) tetracycle tetramine enantiomers were synthesized and showed CPL activity with glum at the 10−3 level. After the helical enantiomer self-assembled into superhelices together with 4-dodecylbenzenesulfonic acid, the CPL signal was enhanced by more than 60-fold both in solution and in the solid state. Unprecedentedly, the superhelices could further self-assemble together with one enantiomer of tartaric acid (TA) to become longer and wider bundles, which showed a CPL |glum| of up to 0.61 and gave the largest CPL enhancement (more than 200-fold) among CPL active materials. But another TA enantiomer aroused no CPL change, showing great potential for chiral recognition of conventional chiral molecules through the CPL spectrum. Moreover, due to the phenyl tilt of the TPE unit, the helical sense of the superhelices is opposite to that of the helical monomer, which was confirmed by theoretical calculations. Meanwhile, thanks to the AIE character of the TPE unit and complete immobilization of its propeller-like conformation, the helical nanofibers displayed a Φf of 95%. This finding demonstrates that the CPL Dissymmetry Factor can be consecutively magnified by formation of superhelices and further assembly of helical self-assemblies, providing a new method for preparing highly active CPL materials.

  • photon upconverted circularly polarized luminescence via triplet triplet annihilation
    Advanced Materials, 2019
    Co-Authors: Dong Yang, Jianlei Han, Minghua Liu, Pengfei Duan
    Abstract:

    Circularly polarized luminescent materials are of increasing attention due to their potential applications in advanced optical technologies, such as chiroptical devices and optical sensing. Recently, in all reported circularly polarized luminescent materials, high-energy excitation results in low-energy or downconverted circularly polarized luminescence (CPL) emission. Although photon upconversion-i.e., the conversion of low-energy light into higher-energy emission, with a wide variety of applications-has been widely reported, the integration of photon upconversion and CPL in one chiral system to achieve higher-energy CPL emission has never been reported. Herein, a brief review is provided of recent achievements in photon-upconverted CPL via the triplet-triplet annihilation mechanism, focusing on the amplified Dissymmetry Factor glum through energy transfer process and dual upconverted and downconverted CPL emission through chirality and energy transfer process.

  • significantly boosted and inversed circularly polarized luminescence from photogenerated radical anions in dipeptide naphthalenediimide assemblies
    Journal of Physical Chemistry Letters, 2019
    Co-Authors: Yuan Wang, Yuqian Jiang, Xuefeng Zhu, Minghua Liu
    Abstract:

    Circularly polarized luminescence (CPL) reflects the excited-state properties of the chiral system. However, compared to the singlet and triplet excited states, there are still many unknowns about CPL from the double excited state. Here, using the self-assembly strategy of a dipeptide substituted naphthalenediimide (NDI-GE) and the photogenerated radical anions, we have explored the ground-state (CD) and excited-state (CPL) chiral characteristics of neutral NDI and NDI•- radical anion assemblies. The neutral gelator assemblies showed CPL with the Dissymmetry Factor glum on the order of 10-3; the radical anion exhibited an inversed CPL signal with a significantly enhanced glum of 10-1. Time-dependent density functional theory calculation revealed that upon formation of the radical anions, the direction of the dipole moment changed, thus leading to the inversion of CD and CPL. The present work reveals a new platform for developing CPL materials based on the doublet excited state.

Jianlei Han - One of the best experts on this subject based on the ideXlab platform.

  • toward large Dissymmetry Factor of circularly polarized luminescence in donor acceptor hybrid systems
    Journal of Physical Chemistry Letters, 2021
    Co-Authors: Xue Jin, Tonghan Zhao, Jianlei Han, Pengfei Duan
    Abstract:

    Chiroptical materials with circularly polarized luminescence (CPL) activity have aroused a lot of interest. One essential Factor for evaluating the features of CPL-active materials is the Dissymmetry Factor (glum), which represents the circular polarization of emitted light. Essentially, for the practical application of CPL, the most important issue is to greatly improve the glum value. Recently, benefiting from the flexible and efficient design in hybrid donor-acceptor systems, more and more examples involving glum value amplification have been reported. In this Perspective, we highlight the proposed mechanism for the generation and amplification of CPL in these hybrid systems. We also present the corresponding design principles and potential pitfalls in experimental processes. We hope that this Perspective can shed light on the development of highly efficient CPL-active materials.

  • Amplifying Dissymmetry Factor of Upconverted Circularly Polarized Luminescence through Chirality-Induced Spin Polarization in the Photon Upconversion Process.
    The Journal of Physical Chemistry Letters, 2019
    Co-Authors: Tonghan Zhao, Jianlei Han, Xujin Qin, Minghao Zhou, Pengfei Duan
    Abstract:

    A general phenomenon about upconverted circularly polarized luminescence (UC-CPL) based on triplet-triplet annihilation (TTA) was realized in an ambient environment by coupling three kinds of chiral acceptors with corresponding achiral sensitizers. All of the Dissymmetry Factors of UC-CPL exhibited significant amplification compared with the prompt CPL of the used chiral acceptors. Chirality-induced spin polarization during the TTA-UC process was in charge of the amplified Dissymmetry Factor of UC-CPL. Chirality-induced spin-polarized triplet excitons will suppress the TTA efficiency because the spin-polarized electrons go against the electron exchange within triplet excitons. However, the chirality-induced spin-polarized singlet excitons resulting from the TTA process can be promoted, enabling a large Dissymmetry Factor of UC-CPL.

  • photon upconverted circularly polarized luminescence via triplet triplet annihilation
    Advanced Materials, 2019
    Co-Authors: Dong Yang, Jianlei Han, Minghua Liu, Pengfei Duan
    Abstract:

    Circularly polarized luminescent materials are of increasing attention due to their potential applications in advanced optical technologies, such as chiroptical devices and optical sensing. Recently, in all reported circularly polarized luminescent materials, high-energy excitation results in low-energy or downconverted circularly polarized luminescence (CPL) emission. Although photon upconversion-i.e., the conversion of low-energy light into higher-energy emission, with a wide variety of applications-has been widely reported, the integration of photon upconversion and CPL in one chiral system to achieve higher-energy CPL emission has never been reported. Herein, a brief review is provided of recent achievements in photon-upconverted CPL via the triplet-triplet annihilation mechanism, focusing on the amplified Dissymmetry Factor glum through energy transfer process and dual upconverted and downconverted CPL emission through chirality and energy transfer process.

  • circularly polarized luminescence in nanoassemblies generation amplification and application
    Advanced Materials, 2019
    Co-Authors: Yutao Sang, Tonghan Zhao, Jianlei Han, Pengfei Duan, Minghua Liu
    Abstract:

    Currently, the development of circularly polarized luminescent (CPL) materials has drawn extensive attention due to the numerous potential applications in optical data storage, displays, backlights in 3D displays, and so on. While the fabrication of CPL-active materials generally requires chiral luminescent molecules, the introduction of the "self-assembly" concept offers a new perspective in obtaining the CPL-active materials. Following this approach, various self-assembled materials, including organic-, inorganic-, and hybrid systems can be endowed with CPL properties. Benefiting from the advantages of self-assembly, not only chiral molecules, but also achiral species, as well as inorganic nanoparticles have potential to be self-assembled into chiral nanoassemblies showing CPL activity. In addition, the Dissymmetry Factor, an important parameter of CPL materials, can be enhanced through various pathways of self-assembly. Here, the present status and progress of self-assembled nanomaterials with CPL activity are reviewed. An overview of the key Factors in regulating chiral emission materials at the supramolecular level will largely boost their application in multidisciplinary fields.

  • enhanced circularly polarized luminescence in emissive charge transfer complexes
    Angewandte Chemie, 2019
    Co-Authors: Jianlei Han, Pengfei Duan, Xue Jin, Dong Yang, Minghua Liu, Yuqian Jiang
    Abstract:

    Achieving a large Dissymmetry Factor (glum ) is a challenge in the field of circularly polarized luminescence (CPL). A chiral charge-transfer (CT) system consisting of chiral electron donor and achiral electron acceptor shows bright circularly polarized emission with large glum value. The chiral emissive CT complexes could be fabricated through various approaches, such as grinding, crystallization, spin coating, and gelatinization, by simply blending chiral donor and achiral acceptor. The structural synergy originating from π-π stacking and strong CT interactions resulted in the long-range ordered self-assembly, enabling the formation of supramolecular gels. Benefiting from the large magnetic dipole transition moment in the CT state, the CPL activity of CT complexes exhibited large circular polarization. Our design strategy of the chiral emissive CT complexes is expected to help the development of new molecular engineering strategies for designing highly efficient CPL-active materials.

Cody L Covington - One of the best experts on this subject based on the ideXlab platform.

  • Atropoisomerism in Biflavones: The Absolute Configuration of (-)-Agathisflavone via Chiroptical Spectroscopy.
    Journal of Natural Products, 2016
    Co-Authors: Cody L Covington, Fernando Martins Dos Santos Junior, Jessica H. S. Da Silva, Ricardo M. Kuster, Mauro Barbosa De Amorim
    Abstract:

    The first natural occurrence in optically active form of the dimeric flavonoid agathisflavone and definition of its axial chirality using chiroptical spectroscopic methods are described. The experimental electronic circular dichroism, electronic Dissymmetry Factor, optical rotatory dispersion, vibrational circular dichroism (VCD), and vibrational Dissymmetry Factor spectra of agathisflavone are presented and analyzed with their corresponding quantum chemical predictions to definitively assign the axial chirality of (−)-agathisflavone as (aS).

  • Solvation dependence observed in the electronic Dissymmetry Factor spectra: how much information are we missing by analyzing the circular dichroism spectra alone?
    Physical Chemistry Chemical Physics, 2016
    Co-Authors: Cody L Covington
    Abstract:

    A study utilizing the newly developed electronic Dissymmetry Factor (EDF) spectral analysis reveals that for [1,1'-binaphthalene]-2,2'-diol (BN) the experimental EDF spectra show differences due to solvent complexation following the trend in solvent polarity, that are not apparent in the electronic circular dichroism (ECD) or corresponding electronic absorption (EA) spectra. Large experimental EDF spectral magnitudes for BN are seen to peak in regions with no corresponding peaks in the EA spectrum and only a shoulder in the ECD spectrum. This observation indicates that EDF analysis is a new complementary method to conventional ECD analysis of chiral molecules. TD-DFT calculations predict similar EDF peaks as in the experimental EDF spectra, however, the experimentally observed solvation dependent behaviour of the EDF peaks was not reproduced in the calculations. Studies on 6,6'-dibromo-[1,1'-binaphthalene]-2,2'-diol also show similar characteristics in the EDF spectra, though not as pronounced and with different solvent effects. This report thus identifies a new means of chiral molecular structural analysis, hitherto unnoticed, and establishes the use of the Dissymmetry Factor spectrum as yielding new insight, but at no added cost.

  • Atropoisomerism in Biflavones: The Absolute Configuration of (−)-Agathisflavone via Chiroptical Spectroscopy
    2016
    Co-Authors: Cody L Covington, Jessica H. S. Da Silva, Ricardo M. Kuster, Fernando M. S., Mauro Barbosa De Amorim
    Abstract:

    The first natural occurrence in optically active form of the dimeric flavonoid agathisflavone and definition of its axial chirality using chiroptical spectroscopic methods are described. The experimental electronic circular dichroism, electronic Dissymmetry Factor, optical rotatory dispersion, vibrational circular dichroism (VCD), and vibrational Dissymmetry Factor spectra of agathisflavone are presented and analyzed with their corresponding quantum chemical predictions to definitively assign the axial chirality of (−)-agathisflavone as (aS)

  • Absolute Configuration of (-)-Centratherin, a Sesquiterpenoid Lactone, Defined by Means of Chiroptical Spectroscopy.
    Journal of Natural Products, 2015
    Co-Authors: Fernando Martins Dos Santos Junior, Cody L Covington, Ana Carolina Ferreira De Albuquerque, Jonathas Felipe Revoredo Lobo, Ricardo Moreira Borges, Mauro Barbosa De Amorim
    Abstract:

    (-)-Centratherin is a bioactive sesquiterpenoid lactone, whose absolute configuration (AC) was not established, but has been proposed based on those of germacrane precursors. To verify this proposal, the experimental electronic circular dichroism (ECD), electronic Dissymmetry Factor (EDF), optical rotatory dispersion (ORD), vibrational circular dichroism (VCD), and vibrational Dissymmetry Factor (VDF) spectra of (-)-centratherin have been analyzed with the corresponding density functional theoretical predictions. These analyses suggest the AC of naturally occurring (-)-centratherin to be (6R,7R,8S,10R,2'Z).

  • Absolute Configuration of (−)-Centratherin, a Sesquiterpenoid Lactone, Defined by Means of Chiroptical Spectroscopy
    2015
    Co-Authors: Fernando M. S., Cody L Covington, Ricardo Moreira Borges, Ana Carolina F. De Albuquerque, Jonathas F. R. Lobo, Mauro B. De Amorim, Prasad L Polavarapu
    Abstract:

    (−)-Centratherin is a bioactive sesquiterpenoid lactone, whose absolute configuration (AC) was not established, but has been proposed based on those of germacrane precursors. To verify this proposal, the experimental electronic circular dichroism (ECD), electronic Dissymmetry Factor (EDF), optical rotatory dispersion (ORD), vibrational circular dichroism (VCD), and vibrational Dissymmetry Factor (VDF) spectra of (−)-centratherin have been analyzed with the corresponding density functional theoretical predictions. These analyses suggest the AC of naturally occurring (−)-centratherin to be (6R,7R,8S,10R,2′Z)

Kenji Matsuda - One of the best experts on this subject based on the ideXlab platform.

  • hexa peri hexabenzo 7 helicene homogeneously π extended helicene as a primary substructure of helically twisted chiral graphenes
    Journal of the American Chemical Society, 2018
    Co-Authors: Yusuke Nakakuki, Takashi Hirose, Hikaru Sotome, Hiroshi Miyasaka, Kenji Matsuda
    Abstract:

    Helically twisted graphenes can be considered as a promising candidate for the nanometer-sized molecular inductors in molecular electronics and molecular spring materials in nanomechanics. Here, we report the synthesis of hexa-peri-hexabenzo[7]helicene, which represents a primary substructure of the helical graphenes. The helically twisted polycyclic aromatic hydrocarbon was synthesized by a tetrasubstituted alkene formation using McMurry coupling followed by stepwise photocyclodehydrogenation and aromatization reactions. The π-extended helicoid structure with a noticeable intramolecular π–π interaction was unambiguously determined by X-ray crystallography. The primary helical nanographene molecule has a small HOMO–LUMO band gap evidenced by the absorption edge that appeared at ca. 800 nm, which exhibits an excellent chiroptical property with a Dissymmetry Factor of circular dichroism of |gCD| = 0.016 at 680 nm. The femtosecond transient absorption spectroscopy revealed the ultrafast excited-state dynamic...

  • Hexa-peri-hexabenzo[7]helicene: Homogeneously π‑Extended Helicene as a Primary Substructure of Helically Twisted Chiral Graphenes
    2018
    Co-Authors: Yusuke Nakakuki, Takashi Hirose, Hikaru Sotome, Hiroshi Miyasaka, Kenji Matsuda
    Abstract:

    Helically twisted graphenes can be considered as a promising candidate for the nanometer-sized molecular inductors in molecular electronics and molecular spring materials in nanomechanics. Here, we report the synthesis of hexa-peri-hexabenzo­[7]­helicene, which represents a primary substructure of the helical graphenes. The helically twisted polycyclic aromatic hydrocarbon was synthesized by a tetrasubstituted alkene formation using McMurry coupling followed by stepwise photocyclodehydrogenation and aromatization reactions. The π-extended helicoid structure with a noticeable intramolecular π–π interaction was unambiguously determined by X-ray crystallography. The primary helical nanographene molecule has a small HOMO–LUMO band gap evidenced by the absorption edge that appeared at ca. 800 nm, which exhibits an excellent chiroptical property with a Dissymmetry Factor of circular dichroism of |gCD| = 0.016 at 680 nm. The femtosecond transient absorption spectroscopy revealed the ultrafast excited-state dynamics of the helical nanographene molecule, with a lifetime of only few picoseconds in the lowest-energy excited (S1) state