| Recently, spherical carbon materials with specific size (from nanoscale to micron level) and unique structure have been synthesized by various methods, enriching the research fields of carbon materials. Carbon microspheres (CMSs), with diameters between100nm-1μm, have unusual structures and excellent physical/chemical properties, such as chemical durability, thermal stability and extraordinary thermal conductivity, which are valuable for enhancing composite materials, electrode material for lithium ion battery, catalyst supports, photovoltaic materials, responsive materials and biomedical materials.This dissertation mainly investigated the surface modification of CMSs and their applications. Self-assembled carbon films, molecularly imprinted adsorbents and bulk-heterojunction films for polymer solar cells were fabricated by grafting various polymers. These as-synthesized materials were applied in photonic crystal, solar cells and deep desulfurization from oils.The main results are as follows:1. Self-assembly of carbon films from acidified CMSs. The effects of pH values on the CMSs dispersion and self-assembled films with were discussed. The CMSs film with more ordered and denser structure was obtained using NaOH as solvent under pH=13at deposition temperature of50℃. The sample showed a good reflection to light with uniform color, which indicated the formation of uniform CMSs film and laid a foundation for photonic crystal. 2. The synthesis of molecularly imprinted polymers on the CMSs (MIP/CMSs) and their adsorption property. The MIP/CMSs were prepared using2-vinyl pyridine (2-VP) as monomer and dibenzothiophene (DBT) as template through modifying CMSs surfaces by silanization, grafting and polymeration. Their adsorption to DBT was also investigated.(1) The discussion of silanization process by KH-570. The optimum parameters were:1.0mL of KH-570to0.3g of oxidized CMSs, reaction time of2h at65℃, pH≈5, ethanol=45mL, water=15mL. The dispersion of the silanized CMSs in ethanol was improved and grafting ratio of KH-570reached11%, contributing to the enhanced compatibility of CMSs with various monomers.(2) MIP/CMSs were prepared on the surface of CMSs using DBT as template,2-VP as the functional monomer, chloroform as solvent, azobisisobutyronitrile (AIBN) as initiator and ethylene glycol dimethacrylate (EDMA) as crosslinking agent. The adsorption capacity of DBT on MIP/CMSs was24.6mg/g, higher than that of non-imprinted polymers. Though the adsorption ability was a little lower, the MIP/CMSs using2-VP as monomer exhibited better selectivity towards DBT than similarly structured benzothiophene, as proved by competitive experiment.3. The preparation of porous carbon microspheres (PCMSs) surface molecularly imprinted material (MIP/PCMSs) using methacrylic acid (MAA) as monomer and their adsorption property. PCMSs were synthesized by hydrothermal synthesis method and they showed larger surface area and higher reactivity than the CMSs synthesized by CVD method, which would enhance the desulfurization capability of the MIP/PCMSs.(1) PCMSs with the diameter of160nm and a specific surface area of468.3m2/g were synthesized by hydrothermal method at180℃combined with an annealing process using aqueous glucose solution as raw materials. The optimum parameters were:0.250mol/L glucose solution with reaction time of28h at180℃. The as-obtained PCMSs were abundant in oxygen-containing functional groups on the surfaces, which promoted the surface activation, improved the grafting reactivity and overcame the difficulty of surface modification in the process of MIP/PCMSs preparation.(2) The influence of KH-570and MAA in the coupling and grafting processes were discussed. Based on the optimized parameters, MIP/PCMSs were prepared using DBT as template, chloroform as solvent, AIBN as initiator and EDMA as crosslinking agent. The adsorption results show that the adsorption capacity of DBT on MIP/PCMSs was376mg/g,3.4times that our previous results (109.5mg/g), also higher than that of non-imprinted polymers (240mg/g); the recognition factor was1.57and the adsorption equilibrium time was3h at25℃. The pseudo second order kinetic model provided better correlation for the kinetic adsorption of DBT onto MIP/PCMSs. Selective adsorption experiments suggest that MIP/PCMSs had better selective recognition for DBT and selectivity factor was1.55.4. The synthesis of poly (3-hexylthiophene):CMSs (P3HT:CMSs) composite films as the electron acceptor for polymer solar cells. The relation between energy level structure and photoelectric performance of CMSs was investigated. To prepare P3HT:CMSs bulk heterojunction, acidified and two kinds of aminated CMSs were obtained and three kinds of P3HT:CMSs composite films were prepared by blending and spin-coating using P3HT:A-CMSs (acidified CMSs), P3HT:H-CMSs (1,6-hexanediamine as aminating reagent) and P3HT:D-CMSs (dodecylamine as aminating reagent). The blending volume and conditions of spin-coating and annealing treatment were also investigated.(1) For the three modified CMSs (A-CMSs, H-CMSs and D-CMSs), cyclic voltammetry measurements proved the energy level difference of donor and acceptor was greater than binding energy of exciton (0.3eV), thus it is probable to use the CMSs as acceptor. The sequence of LUMO energy level was D-CMSs>H-CMSs>A-CMSs.(2) Visible region absorption of the P3HT:CMSs composite films was broadened and a red-shift was observed after annealing. Meanwhile, the improved crystallization degree of film led to significant improvement of charge mobility, the open circuit voltage (Voc), short circuit current density (Jsc) and power conversion efficiency (PCE).(3) P3HT:D-CMSs composite films had optimum morphology and optical performance. After annealing, the sequence of performance of cells was P3HT:D-CMSs> P3HT:H-CMSs> P3HT:A-CMSs. Compared with P3HT:A-CMSs, the Voc of P3HT:H-CMSs heterojunction increased from0.690V to0.730V, and the PCE increased by25%. P3HT:D-CMSs composite films showed higher Voc and PCE than P3HT:H-CMSs. In conclusion, amination process not only improved the dispersion of CMSs, but also enhanced the Voc of the solar cells. Amination process and annealing contributed to the improvement of the PCE of the devices. |
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