Design Of π-Conjugated Molecules For The Construction Of Optical Functional Nano-materials

π-Conjugated materials have been widelydeveloped as prominent materials for constructing organic electronic devices, solar cell, biological fluorescent probesdue to their photochemical stabilities, goodoptoelectronic property and easy potential flexibility for molecular synthesis. Supramolecular self-assembly has obvious advantages in preparation offunctional nano-materials with long and orderd structure and plays an important role in applying π-conjugated systems for photoswitch, phototherapies and biosensor.Bases oncontrolled self-assembly of supramolecular, a series of π-conjugated molecule were designed and synthesized with functional stuctures. Supramolecular assembly of π-conjugated systemswere through changing the noncovalent forces and investigated the application forproton-conductive material, photothermal therapy and photoswtich.In chapter 1, the knowledge about photo properties of π-conjugatedsystems were briefly summarized. The mechanisms,noncovalent and photoresponsive applications ofsupramolecular self-assembly of π-conjugated molecule have been reviwed.In chapter 2, Hydrogen-bonded supercoilwas self-assembly fromachiral molecular components with light-drivensupramolecular chirality. The twocomponent synthon is a complementary hydrogen-bond pair having one melamine core and threephotoaddressable azobenzene units, which self-assembled into long and helical fibers with intrinsicconformational chirality. Hierarchical self-assembly was presented where one-dimensional helixesbundled into a higher order optically active supercoil structure, leading to spontaneous chiral symmetrybreaking and amplification of chirality. Circular dichroism (CD) spectroscopy, transmission electronmicroscopy (TEM) and atomic force microscopy (AFM), as well as X-ray diffraction (XRD) techniquesreveal the chiral nature of the assembly. Accordingly, a plausible mechanism of a hierarchical selfassembly process has been proposed, which presents a valid approach for constructing supramolecularchirality from achiral molecular building blocks through non-covalent interactions. The morphology andchirality of the supercoils demonstrate photoresponsivity, which is induced from the photoisomerizationof the azobenzene components within the self-assembled nanostructures. Furthermore, the supercoil isa highly proton-conductive material because of its highly ordered structure and the proton transferbetween the H-bonded melamine and azobenzene units within this two-component association.In chapter 3, water-soluble silicananocapsules of perylenediimidewould be as photothermal agents.The strategy was utiliedthat a triblock copolymer (F127)had been used to form micelles tosimultaneously encapsulate perylene diimide (PDI) and template silica growth. In this work, we successfully encapsulated the PDI aggregation into water-solublesillica nanocapsules (PDI@SNCs) with the size of 38.0 nm suitable for biomedical research. UV-vis spectroscopy andfluorescent spectroscopywere showed that the typical π-π intermolecular aggregation of PDI was formedin silicananocapsules witha fine absorption at 808nm.We further demonstrated that the PDI@ SNCs were efficiently used fordetection of photothermal signals with absorption 808 nm.Within 6 min, the temperature of SNCs aqueous solution increased by less than 2℃, while that of PDI@SNCs aqueous solution increased by 11℃. Therefore,π-πaggregated state of PDI encapsulated in silica nanocapsule could efficiently produce fluorescence quenching which was beneficial to transfer the NIR light energy into photothermal signals. Furthermore, wedemonstrated that the PDI@SNCs was efficiently used fordetection of photothermal siganals in mice.In chapter 4, hybrid silica nanocapsules were contructed forvisible photothermal therapy.Two π-conjugated molecules, PDI-6 and PDI-Cl, were encapsulated into water-solublesillica nanocapsules with the size of 38.0 nmsuitable for biomedical research.UV-vis spectroscopy andfluorescent spectroscopywere showed that the typical π-π aggregation of PDI-6 was formedwitha fine absorption at 808nmand the fine fluorescence of PDI-Cl was demonstrated with 480 nm light irradiation in hybrid nanostructure.We furtherinvestigated that the PDI-6&PDI-Cl@SNCs were efficiently used for photothermal signals with absorption 808 nma. Hence, the hybrid silica nanocapsules with two π-conjugated molecules were successfully developed for separating imaging and therapy wavelength channels for imaging-guidedphotothermal therapy.In chapter 5, photocontrolled hybrid silica nanocapsules were synthesis and controlled by visible Light. In this work, four azobenzene derivatives,thephoto-induced E/Z isomerization,were synthesized. Photo-induced core-shell structured nanocapsules release system was designed based on azobenzene derivatives and organosilica. In this system, azobenzene was incorporated into copolymers to form silica shell with switchable property, which provides a novel type of reversible photoregulated release platform.