| Photosynthesis refers to the process of chloroplasts absorbing sunlight,converting carbon dioxide and water into organics,and releasing oxygen.Among them,photosystem ?(PS?)plays an important role in this complex system,which is the unit for absorbing light energy,separating charge and transferring electrons.Inspired by the principle of light-harvesting and oxygen evolution of PSII,domestic and foreign researchers have designed a variety of light-harvesting materials used for catalysis,such as pigment-semiconductor composites and pigment-protein supermolecular assembly.However,most of the composite system was constructed by multi-step assembling.The design and preparation of such materials are complicated,and the synthesis process still needs to be optimized.Therefore,based on a large number of relevant reports at home and abroad,this paper proposed new ideas to design two different chlorophyll/TiO2 composites.The light-capturing and oxygen-releasing properties of the materials were also studied.In particular,we carried out the research as below:(1)The chloroplast/TiO2 composite coating material was prepared based on the weak interaction between chloroplast and titanium dioxide,and the light-harvesting and oxygen-releasing properties of the material were studied.The results of SEM and TEM showed that the isolated chloroplasts were intact in structure and had a good monodispersity.The EDS element distribution of the composite coating indicated that the Ti02 nanoparticles were uniformly dispersed on the surface of the chloroplast,illustrating good composite effect between them.The results of Zeta potentional analysis certified that the chloroplast interacts with TiO2 nanoparticles by hydrogen bond in the composite system.The analysis of UV-vis spectrum and the monitoring of oxygen-content sensor approved that the composite coating exhibits properties of light-harvesting and oxygen-releasing.(2)The chla-TiO2-liposome was prepared by the synergistic assembly method,the assembly mechanism was studied,and the light-harvesting and oxygen-releasing properties of the material was tested.The hydrophobic organic-titanium source TBOT was confined to the hydrophobic region of phospholipid bilayer,and the chlorophyll molecule was embedded into the phospholipid membrane.The Ti-O-Ti shell was deposited in-situ by sol-gel method and the effective assembly of the three components was realized.The morphology and particle size of the composite microcapsules were characterized by means of SEM,TEM and DLS.The results illustrated that the samples exhibit complete structure,ellipsoidal shape,uniform particle size and good monodispersity.The formation of Ti-O-Ti network shell in the lipid bilayer were confirmed directly or indirectly by means of EDS,TGA,XRD and etc.The position of maximum emission peak of chlorophyll in different polar medium was measured by fluorescence spectrophotometer.It was concluded that chlorophyll molecule was embedded into the bilayer of phospholipid.The results of the monolayer and bilayer of chlorophyll/TBOT/phospholipid both proved that chlorophyll and phospholipid molecules were co-assembled on the bilayer membrane,and TBOT was hydrolyzed-condensed at the lipid/water interface to form TiO2 shell.By analyzing the electrochemical properties of composite liposomes,it was found that the assembly of chlorophyll molecules in the composite liposomes would increase the fluidity of phospholipid bilayer,while the formation of Ti-O-Ti grid would increase the rigidity of the membrane and decrease the lateral fluidity of molecules.The results of UV-vis and Clark oxygen electrode analysis showed that the composite liposomes exhibit properties of light-harvesting and oxygen-releasing. |
PDF Full Text Request