| The application of nanomaterials is increasing rapidly in recent years. More importantly, the application in biomedicine and environmental science has been receiving greater attention and has now become an important research field. In biomedicine research, nanomaterials (NMs) provide strategies for the diagnosis and treatment of cancer. Dedicated NMs can be used to monitor the progress of a therapy or disease, for cell imaging and drug delivery, or for tissue engineering.In the environment protection, NMs was used for the degradation of pollutants in waste water and air. Hydroxyapatite (HA) and TiO2are widely studied inorganic materials because of their biocompatibility and stability. In this study, we focous on the synthesis and application of HA and TiO2based nanocomposite. Firstly, we demonstrated the application of HA-composite in cell imaging and biomineralization. Secondly, TiO2hollow shells with controllable crystallinity were synthesized. We also futher discussed the application of TiO2hollow shells as photocatalysts in dye degragation.In chapter1, we provide a brief description of the synthesis of nanomaterial and their application in biomedicine, environment protection, and energy science. Furthermore, we introduce two kinds of inorganic nanomaterials, hydroxyapatite (HA) and titanium dioxide (TiO2), focous on the sythesis and applications of HA and TiO2.In chapter2, we present the synthesis of reduced graphene oxide/hydroxyapatite (RGO/HA) hybrid materials by an environmental-friendly route. Graphene oxide (GO) was first simultaneously reduced and surface functionalized by one-step oxidative polymerization of dopamine (PDA). The bioinspired surface was further used for biomimetic mineralization of hydroxyapatite. When incubated in a simulated body fluid (SBF), the PDA layer enabled efficient interaction between the RGO surface and the mineral ions to improve the bioactivity, promoted the formation of the HA nanoparticles. A detailed structural and morphological characterization of the mineralized composite was performed. The HA-based hybrid materials exhibited no cytotoxic effect on L929fibroblast cells, showing potential capacity of being a scaffold material for bone tissue regeneration and implantation. This facile strategy also can be a useful platform for other RGO-based nanocomposite.In bone tissue engineering, it is imperative to design multifunctional biomaterials which can induce and assemble bonelike apatite that is close to natural bone. In chapter3, GO was functionalized by carrageenan (Car). The resulting GO-Car composite was further used as a substrate for biomimetic and cell-mediated mineralization HA. It was confirmed that carrageenan on the GO surface facilitated the nucleation of HA. The observation of the effect of the GO-Car on the adhesion, morphology, and proliferation of MC3T3-E1cells was investigated. In vitro studies clearly show the effectiveness of GO-Car in promoting HA mineralization and cell differentiation.In chapter4, we report a facile modification of GO by gelatin (Gel) to mimic charged proteins present in the extracellular matrix during bone formation. The bioinspired surface of GO-Gel composite was used for biomimetic mineralization of HA. MC3T3-E1cells were cultured on the GO-Gel surfaces to observe various cellular activities and HA mineralization. Higher cellular activities such as cell adhesion, cell proliferation, and alkaline phosphatase activity (ALP) were observed on the GO-Gel surface comparing with the GO or glass surface. The increase of ALP confirms that the proposed GO-Gel promote the osteogenic differentiation of MC3T3-E1cells. Moreover, the evidence of mineralization evaluated by scanning electron microscope (SEM) and alizarin red staining (ARS) corroborate the idea that native osteoid matrix is ultimately deposited. All the data suggest that the GO-Gel hybrid have great potential as osteogenesis promoting scaffolds for successful application in bone surgery.In chapter5, a redox luminescence switch was prepared by doping CePO4:Tb in hydroxyapatite nanoparticles. The resulting multifuncational material exhibits good biocompatibility, biological affinity and potential drug-carrying capability. The luminescent hydroxyapatite nanoparticles may find important applications in biomedical diagnostics, drug delivery, and biological sensors.In chapter6, a simple, template-based route for the synthesis of fluorescent HA nanoparticle has been developed. Well-dispersed HA nanoparticles prepared by using SiO2as templates (THA) were surface-functionalized with fluorescein isothiocyanate (FITC), resulting in bright and stable fluorescent particles (THA-FITC). These fluorescent nanoparticles were demonstrated to be internalized into Hela cells and have no apparent cytotoxic effects on fibroblast cells, which confirmed the biocompatibility and cell labeling capability of the nanoparticles. Due to the large surface areas, porous nature, and visible lights excited luminescence characters, THA-FITC nanoparticles will have applications in fields such as cell labeling, whole animal imaging and therapy, and drug delivery and release. In chapter7, a novel resorcinol-formaldehyde (RF)-protected calcination process was explored for preparing hollow TiO2nanostructures with a controllable crystallinity and phase. A systematic study on the crystallization behavior of TiO2hollow shell with different core template and different outer protection layer is also investigated. It has been found that the grain growth and phase transformation of TiO2was determined by several parameters such as shell materials, core materials, calcination conditions and calcination environments. In order to enhance photocatalytic activity by improving water dispersity of TiO2samples, we also carried out base treatment. By controlling the synthesis and calcination conditions, and optimizing crystalline properties of TiO2hollow shell, we have been able to achieve enhanced photocatalytic performance toward RhB degradation under UV irradiation. In particular, TiO2hollow shells with optimal crystalline properties and improved water dispersity show significantly high photocatalytic activity comparable to commercial P25TiO2.The structure-enhanced light utilization of semiconductor materials is very important for the design of the photocatalyst. In chapter8, we discuss the relationship between hollow structure-induced light harvesting and photocatalytic properties of TiO2, through comparing the photocatalytic activity of the TiO2hollow spheres and the broken ones. UV-driven degradation of RhB as well as calculations based on the Mie scattering theory was employed to investigate the multiple reflections phenomenon. We demonstrate that in the submicron-scale TiO2hollow shells, there is no multiple reflections of the incident light within the interior cavity. The photocatalytic performance of TiO2hollow structures may be enhanced by the multiple scattering only when the size of the TiO2shell was match with the wavelength of incident light to show resonance. However, the activity enhancement from the multiple scattering is also minor (17%). Both of the experimental evidence and theoretical calculations warrant in-depth investigation with a view to acquiring a better understanding of the actual effect of multiple reflections on catalytic activity, which is also helpful for design of the structure of other semiconductor materials. |
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