Synthesis And Catalytic Property Of Phosphorus-based Nanocomposites

Enviromnent and energy issues are still the bottleneck for the continuable development of human being. Nowadays, phosphorus-based nanocomposites have been attracted great interest in environmental protection and clean energy field. Solution-based methods have been intensively used in the syntheis of phosphorus-based nanomaterials, owing to its simplicity, effective, feasible, and versatility. Still, it remains a significant challenge to access micro-/nanomaterials with the controllable size, morphology, especially, the crystal factes or growth orientation. In this work, we developed some novel and easy solution-based mehods for the controlled-synthesis of phosphorus-based nanocomposites, such as F-substituted hydroxyapatite (FHAp), Ag/FHAp, and Ag@Ag3PO4. The details are as follows:(1) A facile strategy for the shape-controlled synthesis of FHAp microcrystals based upon using a combination of EDTA and citric acid (CA) was demonstrated. Novel, well-defined FHAp microcrystals of various shapes, such as hexagonal disks with predominant (0001) faces, hexagonal shuttles, hexagonal prisms, icosahedrons, and hexagonal microrods, were fabricated. The effects of the solution pH value, amount of chelating reagents and fluride ions and hydrothermal time and temperature were investigated in detail. It was found that the acidic medium is benifical for the formation of one-dimensional FHAp microstructures, while the basic reaction soluition favors the yield of three-dimensional (3D) FHAp microstructures. In this double-chelating-agent system, careful control over the Ca/EDTA molar ratio enabled a fine control over the morphology of FHAp particles from 3D polycrystalline microstructures to ID well-faceted single-crystal microrods. Based on this result, simply varying the concentration of CA and/or fluoride ions could allowe the shape-and size-control over 1D well-faceted FHAp microcrystals. F- ions were found to play a critical role in the formation of well-defined hexagonal microcrystals.(2) A facile single-step hydrothermal method was developed for the synthesis of FHAp hollow micro-/nanostructures. By using EDTA and CA as mixed chelating reagents and simple variation of F- ions addition order, FHAp hollow micro-/nanostructures with well-defined morphologies, including hollow hexagonal rods, hexagonal prisms, and hierarchical microstructures were synthesized in single step. It was found that CaF2 particles formed most likely acted as the in situ template for the formation of hollow FHAp crystals. Time-dependent experimental results indicated that Ostwald ripening process could be used to explain the formation mechanism of the hierarchical hollow FHAp microparticles. In addition, it is believed that other factors, for example, hydrothermal condition and chelating reagent, may promote the formation of hollow FHAp particles.(3) Silver-fluorapatite composite which consists of fluorapatite microcrystals (FHAp MPs) decorated with silver nanoparticles (Ag NPs) were prepared through a facile single-step hydrothermal method. The synthesis process involves the use of EDTA as both a chelating agent and a reducing agent, allowing the one-pot formation of Ag/FHAp composites. The Ag NPs prepared via this method exhibit monodispersed size distribution, around 30 nm, and essentially uniform dispersion on FHAp MPs supports with sizes of 1-2μm. We demonstrated that the population and size of Ag NPs in the Ag/FHAp composites can be tuned easily by varying the concentration of silver nitrate in the starting reaction solution, as well as by varying the pH value of solution. Additionally we also demonstrated that the resulting Ag/FHAp composites with different Ag loadings possess tunable surface plasmon resonance properties.(4) A facile, efficient, and environmentally friendly synthetic route was developed to fabricate silver submicron-sized particles by reducing silver nitrate with EDTA in aqueous solution. It was found that by varying the amount of EDTA utilized in the reaction medium and/or hydrothermal reaction time, the size of prepared silver particles can be readily controlled from 200 to 500 nm. Compared with silver nanoparticles, the as-synthesized submicron-sized silver particles were found to show a comparable catalytic activity towards the reduction of 4-nitrophenol to 4-aminophenol in the presence of an excess amount of NaBH4.(5) Novel Ag@Ag3PO4 composite photocatalysts were prepared by a simple precipitation and photoreduction methods. The as-prepared photocatalysts can absorb solar energy with a wavelength shorter than 550 nm. The photocatalytic activity of as-prepared samples was evaluated by photocatalytic decolorization of Rhodamine B (RhB) aqueous solution at ambient temperature under visible-light irradiation. The prepared Ag@Ag3PO4 composite photocatalysts exhibits an excellent visible-light photocatalytic activity for photocatalytic degradation of RhB in water, and their photocatalytic activity exceeds that of nitrogen-doped TiO2 by a factor of more than 10. The mechanism suggests that the high photocatalytic activity and excellent stability may result from the super sensitivity of Ag3PO4 to light and the surface plasmon resonance of Ag nanoparticles in the region of visible light. The composite photocatalysts maintain a high level even though used for five times.