Orbit Effect In Chiral Organic Polymer Crystals

As one of the most important structures in nature,chiral nanostructures have very important relationship to the origin of life and gene transmission.Chiral phenomena exist in varietyies structures with different sizes,from nanoscale to the galactic scale.Controllable and stable organic nanostructures can be formed by the supramolecular chiral self-assembly process.Various chiral and chiral molecules can be used to form chiral nanostructures through non-covalent bonds between molecules.At present,chiral supramolecular structures with long range order can be obtained by introducing chiral groups into organic structures or self-assembly of chiral and acchiral molecules.The electron vortex beams in organic spiral structure could generate pronounced significant orbital angular momentum.Due to the orbital angular momentum generated by chiral helical structures,chiral supramolecular materials have the chiral-induced spin selectivity.These special properties provide the foundation for the application of chiral materials in the field of spintronic devices.In general,strong magneto-optical coupling effects can be observed in magnetic materials.Due to the spontaneous magnetization in the magnetic material or external magnetic field,the energy bands of the material are split,while the spin-orbit coupling could further enhance the split of energy bands.These mechanisms allow the spin of electron to be coupled with photons,resulting in a series of magneto-optical phenomena Generally,Polarized light and electric field possess tunability of orbital angular momentum and spin momentum of electron to result in optomagnetic effects in the chiral materials with the helix sturcture.Magnetic circular dichroism and magneto-chiral dichroism can be observed in chiral materials due to the interaction between light and spin of electron.Magneto-optic coupling in chiral organic materials provide a new way for the research of light dependent spin mechanics and spin dependent polarization photonics.Spin-orbit coupling plays a key factor in the magneto-optical coupling effect of organic materials.At present,magneto-optical coupling effect can be enhanced by adding heavy metal elements in organic materials to enhance spin-orbit coupling effect.In general,pure organic materials are consisted of low masse lements,thus orbital angular momentum in pure organic materials have the very low value.The interactions related to orbital angular momentum in pure organic materials can generally be ignored.It is difficult to observe similar magneto-optical coupling effects in pure organic materials.Due to helical structure of chiral materials,strong chirality induced orbital angular momentum can not be ignored,and many magneto-optical coupling phenomena in chiral materials are related to chirality induced orbital angular momentum.Therefore,chiral supramolecular nanostructures with strong chirality induced orbital angular momentum were prepared by using chiral solvent.Based on supramolecular chiral nanostructures,we further investigate the dominant role of chirality induced orbital angular momentum in spin polarization controlled by light in organic charge transfer ferromagnetic materials,circularly polarized light emission and circularly polarized light detection.Our research work mainly consists of the following three parts.(1)We have prepared chiral P3HT nanowires with strong chirality induced orbital angular momentum by using chiral solvation-induced supramolecular self-assembly method.Then,C60 was introduced into the chiral P3HT nanowires as acceptor to prepare one type of room-temperature chiral ferromagnet without any transition metal,and this organic chiral charge transfer possess excellent thermostability.The chiral structure is confirmed through both TEM and CD spectrometer.The magnetization and magnetoelectric coupling effect of this chiral charge transfer magnet can be tuned by changing the type of polarized light.Compared with linearly polarized light,circularly polarized light can enhance the magnetization of chiral charge transfer magnets by tuning chirality induced orbital angular momentum.We reveal that chirality induced orbital angular momentum plays a key factor in spin polarization controlled by light in this chiral charge transfer magnets.Polarization of light through chiral charge transfer magnets is effectively tuned by an external magnetic field.This opto-magnetic effects will enhance the function of organic chiral magnet.It lays a foundation for its practical application in low energy consumption multiferroic recording and biological detection in the future.(2)We use the chiral P3HT nanowires with strong orbital angular momentum to study the relationship between chirality induced orbital angular momentum and circularly polarized light emission.Due to chirality induced orbital angular momentum,the spin relaxation time in chiral P3HT nanowires is significantly decressed,which is equivalent to recombination time.Thus,circularly polarized light emission was observed in chiral P3HT nanowires.By using external magnetic field and electric field,we further change the energy level splitting caused by chirality induced orbital angular momentum and circularly polarized light emission was tuned by external magnetization and electric field in chiral P3HT nanowires.We also prevent helical electron transport by introducing electron acceptors,thus suppressing the effect of chirality induced orbital angular momentum.Therefore,circularly polarized light emission disappeared in the charge transfer complex.We not only reveal that chirality induced orbital angular momentum play a decisive role in circularly polarized light emission of chiral P3HT nanowires,but also achieve circularly polarized light emission tuned by external magnetic field.The opto-magnetic coupling of chiral P3HT nanowires plays a key role in their future applications in optoelectronic devices,and provides a broad space for their further applications in optical enhanced imaging and optical sensors.(3)Chiral P3HT nanowires and chiral TPPS nanowires were used to fabricate circularly polarized light detectors with visible and ultraviolet wavelengths,respectively.These two kinds of circularly polarized light detectors show excellent reversibility and stability.The photodetectivity of chiral P3HT nanowire CPL detector is 1.25 ×1011 Jones,and photodetectivity of TPPS nanowires CPL detector is 2.5 × 1012 Jones.We reveal that the detection of circularly polarized light in these two kinds of chiral supramolecular CPL detectors is not because of absorption difference of left-handed and right-handed circularly polarized light,but the chirality induced orbital angular momentum in chiral materials.The orbital angular momentum induced by the chiral helical structure can split the energy levels by enhancing the spin-orbit coupling effect,so that the photocurrent generated by left-handed and right-handed CPL excitation is different.It also provides a new way for design of CPL detectors based on chiral supramolecular materials in the furture.