Effect Of Solvent On Fullerene C₆₀ Micro/Nanocrystals

Fullerene C₆₀ has raised extensive concerns because of its caged symmetrical shape and highly delocalized conjugated system of?electrons.But its zero-dimensional structure makes it show isotropic in some physical properties such as optics,electricity,magnetism,which leads to the limited applications.At present,through molecular self-assembly,fullerene molecules can form well-defined fullerene micro/nanocrystals?FMNCs?including fibrous one-dimensional fullerene micro/nanocrystals?1DFMNCs?,flake-liketwo-dimensionalfullerene micro/nanocrystals?2D FMNCs?and cubic-like three-dimensional fullerene micro/nanocrystals?3D FMNCs?,which can not only reserve the unique physicochemical properties of fullerene but also endow the material with new functions due to its size and dimensional effect.Therefore,the controllable fabrication of FMNCs is of great importance.In this thesis,the effect of good and poor solvents on the morphologies and crystal structures of the prepared C₆₀ FMNCs were studied systematically and the possible mechanism involved was also proposed.The specific content are as follows:1.Three types of xylene with totally different solubility to C₆₀ were first used as the good solvents to realize the growth control of FMNCs by solvent evaporation method.By optical microscopy?OM?,scanning electron microscopy?SEM?and X-ray diffraction pattern?XRD?,it was concluded that the crystal morphologies and patterns of products depended on the saturated solubility of C₆₀ in the used good solvents.When using o-xylene of high solubility,3D micro/nanocuboids with both FCC and HCP structures were synthesized,2D micro/nanoflakes with FCC structure were formed by the use of p-xylene of medium solubility.And 1D micro/nanowhiskers with HCP structure were prepared with m-xylene of low solubility.The results were also similar under different methods.Besides,Fouriertransforminfraredspectra?FT-IR?,Ramanspectra,thermogravimetric analyses?TGA?and differential scanning calorimetry?DSC?were carried out to analyze the composition of these final products.Meanwhile,Material Studio software was utilized for the geometric optimization and energy simulation of the above mentioned three systems to provide a reasonable explanation to the growth mechanism of FMNCs.The results indicated that the solubility of C₆₀ in the aromatic solvents could ultimately affect the growth degree in different directions as well as the minimum energy required for the formation of solvated HCP structure stably,which offered the experiment data and theory basis for the selective control of the preparation of fullerene C₆₀micro/nanomaterials.2.The poor solvents with declined polarity parameters and the C₆₀ saturated solution of toluene were used to prepare FMNCs by the liquid-liquid interface precipitation?LLIP?method for the first time.The persistance of optical anisotropy and the stability of crystal structures of the grown FMNCs were studied by the characterizations of polarizing optical microscopy?POM?and XRD.As a result,when choosing methanol,ethanol,n-propanol and n-butanol as the poor solvent respectively,it was found that the stability of the products on optical anisotropy and solvated structure would be prolonged by the decrease of solvent polarity.While for less polar alcohols?n-pentanol,n-hexanol and n-octanol?,the properties could only keep for 2 d among these solvates,the optical anisotropic durability of 1D FMNCs prepared by C₆₀/toluene/n-butanol system could be increased to 5 d,and its solvated orthorhombic and hexagonal structures could also maintain up to 7 d.3.As the control group,the above mentioned poor solvents and the more volatile m-xylene were used as the poor solvent and the good solvent respectively to prepare C₆₀ FMNCs.Following the preceding steps,the results were basically the same as the toluene system,whichthe optical anisotropic durability and solvated structural stability of the products increased first and then decreased by using the poor solvents with declined polarities.Especially for the 1D FMNCs grown by C₆₀/m-xylene/n-butanol system,its solvated HCP structure and optical anisotropy could last up to more than half a month,which were more stable than any other reported C₆₀ solvates by selecting m-xylene as good solvent.This is of great significance for obtaining 1D FMNCs with lasting optical anisotropy and expanding their development in the field of optical equipments such as optical polarizers and linear polarized light emitting devices.