Synthesis Of Micro/Nano Materials By Hydrogel Template Method

Hydrogels are a unique class of macromolecular networks that may contain a large fractionof aqueous solvent within their structure. Their three dimensional network structure formingfrom crosslinking between polymers can provide the space and microenvironment needed for thenucleation and growth of nanoparticles. Hydrogels can be easily assembled in three dimensionswhile displaying multiple functional domains, and their polymerization chemistry allows theincorporation of polar ligands that mimic the acidic matrix proteins regulating mineral growth.So hydrogels are very useful in synthesis of novel advanced functional materials. In this paper,several micro/nano materials, such as hollow calcium carbonate spheres, multi-wall ceria sheresand metal sulfide, were prepared by polyacrylamide hydrogel template method with acurrent-assist approach to promote the migration of ions. The size and morphology of themicro/nano materials could be controlled by varying the current, the content of acrylamide, theconcentration of reactants or adding functional groups. The main content of this paper and theachievement were as following:1. The synthesis of porous CaCO3hollow spheres by polyacrylamide hydrogel templatemethod and the investigation of their propertiesPorous CaCO3hollow spheres were successfully synthesised by polyacrylamide hydrogeltemplate method with a current-assist approach. Firstly, the influence of the content ofacrylamide to the morphology of CaCO3hollow spheres was investigated. The result indicatedthat uniform CaCO3hollow spheres were obtained when the content of acrylamide was5wt%.In addition, CaCO3hollow spheres with various size and morphology were prepared by varyingthe current, adding small biomolecules and β–cyclodextrin. CaCO3/polyacrylamide hydrogelbased drug delivery system (DDS) was prepared. Due to the clathration effect of β–cyclodextrin,ibuprofen molecules were easily loaded into the DDS. This DDS combined the swelling propertyof hydrogel and the pH-sensitive property of CaCO3which resulted in the pH-sensitive propertyof this DDS. In addition, this paper also accounted for the mechanism of the drug release.2. The synthesis of multi-wall CeO2porous spheres by polyacrylamide hydrogel template methodThe porous CeO2hollow spheres were synthesised successfully by polyacrylamide hydrogeltemplate method with a current-assist approach following a thermal treatment. CeO2hollowspheres were transformed from the oxidation of Ce(OH)3which formed inside hydrogel. Aftercalcination, the XRD pattern confirmed that the yellow powders were cubic phase CeO2. PorousCeO2hollow spheres with different number of layers were obtained by varying the content ofacrylamide, the reacting time and the concentration ratio of Ce(NO3)3·6H2O aqueous solution/NaOH aqueous solution. Besides, the formation mechanism of the porous CeO2hollow sphereswas proposed.3. The synthesis of metal sulfide micro/nano materials by polyacrylamide hydrogel templatemethodCopper sulfide and Cadmium sulphide micro/nano materials were synthesised bypolyacrylamide hydrogel template method. The result showed that the current played animportant role in the forming of the metal sulfide. Copper sulfide hollow nanospheres andnanosheets were obtained by varying the current, and then a flower-like copper sulfide structurewas prepared by varying the content of acrylamide. As to cadmium sulphide, different size ofcadmium sulphide spheres were prepared by varying the current in a certain range. Finally, theformation mechanism of metal sulfide micro/nano materials was discussed.