Preparation And Properties Of Photocatalytic Nanocomposites Based On Cotton Cellulose Nanofibers

Nanomaterials have some special properties due to their unique structure, which can be applied to various fields. Many methods have been developed to prepare nanomaterials, specially ectrospinning is a simple and effective method for the preparation of one-dimensional nanomaterials. Currently, spinnable synthetic polymers have been up to over one hundred kinds,but the most of those polymers is difficult to be degraded, which is serious for environmental.However, the natural cotton cellulose, as an abundant, cheap, renewable, biodegradable natural polymer materials, which can also be prepared as superfine cotton nanofibers by electrospinning.Then, we make the inorganic nanomaterials load on the surface of the cotton nanofibers by chemical or physical means to get cotton fibers nanocomposite that have better performance than a single material. Based on the above ideas background, the main works and results of this paper are as follows:1. Preparation and photocatalytic properties of the cotton nanofibers/Zn O/Cd S nanocompositesFirstly, cotton nanofibers were prepared by electrospinning, which have a large specific surface area, its diameter between 100²00nm and there are rich hydroxyl on the surface, so it is easy to modified. Then, Zn O nanorods were successfully prepared on the cotton nanofibers surface by a hydrothermal method. Zn O has a response only under ultraviolet light duo to its wide band gap. In order to expand its light response range to the visible light region, we have deposited the Cd S nanoparticles on the Zn O nanorods sureface by the co-precipitation method to obtain the cotton nanofibers/Zn O/Cd S nanocomposites. The structure, morphology, and properties of the composite nanofiber were characterized by XRD、SEM、TEM、EDS、UV technique. The experiments results show that the degradation rate of cotton nanofibers/Zn O/Cd S nanocomposites for Rhodamine B can up to 75% in 180 min under visible light irradiation.2. Preparation and formation mechanism of the cotton nanofibers/In₂S₃ nanocompositesThe electrospun cotton nanofibers were used as substrates for preparing thin curly In₂S₃ nanosheets on the nanofiber surfaces by a hydrothermal reaction. The thin curly In₂S₃ nanosheets between 10¹5nm in thickness are interconnected to form a porous structure, which effectively increasing the specific surface area of cotton nanofibers/In₂S₃. Its structure is determined to be tetragonal by XRD, SEM and XPS characterization. Besides, in order to explore the formation mechanism for thin curly In₂S₃ nanosheets, the addition amount of reduced glutathione（GSH）and urea, the reaction time during the reaction were studied, which have an influence on the morphology of product. The changes in morphology of the sample can be observed by means of SEM under different reaction condition. The possible formation mechanism of the cotton nanofibers/In₂S₃ nanocomposites were inferred. The results showed that when the concentration of GSH and urea was 12.5m M, the concentration of In（NO3）3 ? x H2 O was 6.25 m M, the reaction was carried out at 180°C for 10 h, the uniform morphology and structure CCNFs/In₂S₃ nanocomposites can be obtained.An optimum ratio for the precursor reaction solution was obtained. The addition amount of urea plays a very important role on In₂S₃ seed formation. Moreover, the addition of GSH and reaction time have an important impact for the curling In₂S₃ sheets structure.3. Preparation and photocatalytic properties of the cotton nanofibers/In₂S₃/Ag-CdS nanocompositesCotton nanofibers/In₂S₃ nanocomposites show a great potential in visible light catalysis,hydrolysis produce hydrogen and solar cells, because of its advantages of suitable band gap,large specific surface area and facilitate recycling. So as to optimize cotton nanofiber/In₂S₃ nanocomposites catalytic efficiency in visible light, Ag nanoparticles on the cotton nanofibers/In₂S₃ surface were deposited by UV reduction, and then load a certain amount of Cd S nanoparticles by the successive ion layer adsorption reaction to prepared finally product cotton nanofibers/In₂S₃/Ag-Cd S nanocomposites. Ag and Cd S nanoparticles stably dispersed on In₂S₃ nanosheets, which effectively improve its ability to absorb visible light. The photocatalytic activities of cotton nanofibers/In₂S₃, cotton nanofibers/In₂S₃/Ag and cotton nanofibers/In₂S₃/Ag-Cd S nanocomposites also were investigatived. The experiments results show that the degradation rate of cotton nanofibers/In₂S₃/Ag-Cd S nanocomposites for Rhodamine B can up to 95% in 40 min under visible light irradiation. Its also exhibit stable cyclability.