Preparation Of Functional Nanocomposite Materials And Investigations On Their Properties

The rapid development of modern technology has brought higher and higher demand fornanomaterials. New materials need to have better performance in some property than othermaterials, but also have several functionalities. Therefore, investigation on one material aboutits structure and composition is difficult to meet the actual needs. In this situation, compositenanomaterials emerge, which provide possibility for the preparation of high-endmultifunctional materials. In recent years, investigations on the composition, method andstructure of composite nanomaterials have flourished. Although each method and structurehave their own characteristics, but generally speaking, composite nanomaterials developtowards the direction of simple, size and composition controllable preparation of compositematerials with better performance and more functionalities.As noble metal nanoparticles have high specific surface area and high catalytic activity,they have wide application prospects in chemical catalysis, electrocatalysis and many otherfields. However, as their prices are expensive, how to effectively increase their catalytic andrenewable catalytic activity are the two key factors to promote its wide application. Toachieve these two goals, it must be achieved that the size of nanoparticles could be wellcontrolled and the aggregation and leaching problems should be resolved. Finally, recyclablecomposite catalyst which could be recycled rapidly needs to be prepared.On the other hand, as hierarchically porous siliceous nanomaterials have high specificsurface area, and their unique pore structure favors the diffusion of loading substances, thereby increasing the loading amount, they are more and more used for catalyst or drugloading. However, up to now, few reported drug loading capacity of mesoporous siliceousmaterials were more than20%, so how to increase the drug loading capacity by adjusting thestructure and composition of mesoporous siliceous materials is most concerned by theresearchers.This paper stands from the view of investigating high performance compositenanomaterials. Firstly, by using electrospinning, hydrothermal, self-assembly and many othermethods, we prepared several Pd nanoparticles based composite catalysts, solved the particleaggregation or leaching problem by structural design. We carefully investigated the factorswhich may affect the noble metal particle size distribution in the reaction and tested thecatalytic or electrocatalytic activity of the obtained products. Secondly, we prepared threemagnetic catalyst supports by composing magnetic nanoparticles or microspheres into them.By structural design, the acidic corrosion and leaching problems of magnetic materials wereresolved. In addition, we used the obtained magnetic composite materials as supports fornoble metal nanoparticles and their catalytic and recycling activities were investigated.Finally, by using surfactant-polyelectrolyte two-component template, we preparedhierarchically porous silica nanocubes and Fe3+doped silica hollow microspheres, and theirdrug loading properties were investigated. The conclusions are as follows:1. By using sulfonated electrospun polystyrene nanofibers as template, polyanilinenanotube with Pd nanoparticles attached to their inner walls were prepared. The big sterichindrance of sulfuric groups on fiber surfaces could well control the size of Pd nanoparticles(d=3.411nm, σ=0.687nm). Moreover, by loading Pd nanoparticles on the inner walls ofpolyaniline nanotubes, the leaching extent was alleviated. According to the experimentalresults, the catalytic activity of the product towards the reduction of p-nitroaniline is not onlysuperior to Pd/C catalyst, but also much stronger than Pd/carbon nanotube composite catalyst.By using one-step solvothermal method, hierarchically porous TiO2hollow spheres withPd nanoparticles (2-5nm) distributed in their pores were prepared. Forming the Pdnanoparticles in the hierarchically pores, not only effectively limits their growth and controlstheir diameter to a small value, but also effectively avoids their aggregation and leachingphenomena. When using the composite catalyst modified electrode to determine the content of H2O2, current response is very stable and the sensitivity,226.72μA mM-1cm-2, is relativelyhigh. Moreover, the current response and the concentration of H2O2are in good linearrelationship (in the concentration range of0.01mM to0.86mM, R2=0.99722). The lowerdetection limit (3.81μM) also confirms that the as-synthesized TiO2/Pd hollow spherespossessed efficient electrocatalytic activity towards the reduction of H2O2, which havepotential applications as a nonenzymic sensor for detecting H2O2.By using environmental friendly glucose based carbon spheres as carrier for Pdnanoparticles and polyaniline layer, a three-component composite material was obtained. Thekey factor to influence the morphology of carbon/Pd nanoparticles is the aggregation degreeof Pd nanoparticles. The large amount of surface group on carbon spheres could well stabilizethe Pd nanoparticles and the outside polyaniline layer could effectively protect them fromaggregation or leaching. The composite catalyst has good catalytic activity towards thereduction of H2O2, as the sensitivity is high up to656.07mA M-1cm-2. Moreover, the currentresponse and the concentration of H2O2are in good linear relationship (R2=0.99417) and thedetection limit (5.48μM) is low, indicating that the material is a good candidate for electrodematerials.2. Firstly, by using the solution based preparative method and the self assembly methodunder low temperature, carbon nanotubes/Fe3O4nanoparticles/polyaniline compositenanomaterials, with well one-dimensional tubular morphology were obtained. Secondly, byusing one-step method to prepare Fe3O4nanoparticles contained polyaniline layer on thesurface of polystyrene template microspheres, the composite polyaniline hollow spheres withFe3O4nanoparticles distributed in their matrix could be obtained after the removal oftemplate spheres. In this way, the Fe3O4nanoparticles are effectively prevented fromaggregation and leaching. Further loading noble metal nanoparticles on the magnetic supportby pre-growth or post-adsorption method, magnetic catalysts containing different noble metalnanoparticles could be obtained. It is found that Pd nanoparticles contained compositecatalyst exhibits higher catalytic activity towards the reduction of p-nitroaniline than Pd/Ccatalyst, and gold nanoparticle contained catalyst has higher electrocatalytic activity towardsthe oxidation of dopamine, providing a new kind of effective electrode material forelectrochemical sensing of dopamine. By hydrothermally coating a carbon layer on magnetic Fe3O4microspheres, a kind ofmagnetic composite nanomaterials was obtained, and then it was used as the support for Pdnanoparticles. The dense structure of glucose based carbon layer can effectively protect theFe3O4microspheres form being corroded by acid, and the abundant surface functional groupssuch as hydroxyl groups, can effectively stabilize Pd nanoparticles, preventing them fromleaching and aggregation. Moreover, their catalytic activity and recycling activity towards thereduction of methyl orange are much higher than those of Pd/C catalyst.3. By using a kind of two-component template, silica nanocubes with hierarchicallyporous structure were prepared. By tuning the used amount of CTAB, the shape of suchhierarchically porous silica nanocubes can be well transformed from solid particles to hollowparticles. The obtained products exhibit high drug loading capacities for IBU, which are362mg/g for solid particles, and509mg/g for hollow ones. However, their drug release speedsare too fast. In addition, when hollow silica nanocubes are used for drug loading and release,concentration controlled drug release could be realized, which is determined by its uniquehollow and porous structure. By adding Fe3+ions during the preparative process ofhierarchically porous silica materials, Fe3+doped silica hollow spheres could be obtained.Fe3+ions played a big role in shaping the template, and thus determined the morphology ofthe final products. Other reaction parameters, such as reaction time, could also influence themorphology of the product. For drug loading and release, Fe3+ions doping significantly slowdown the rate of drug release, but cause little change to the drug loading capacity. In addition,as the pore diameters in Fe3+doped silica hollow spheres are much larger, they do not exhibitconcentration controlled drug release.