Synthesis Of Nanomaterials/Chitosan Composite Films And Their Applications

Chitosan,as the only cationic polysaccharide in nature,is characterized by effective cost,wide source,biocompatibility,biodegradability and so on.It has also attracted extensive attention on account of its excellent film-forming feature.Nevertheless,pure chitosan film has issues of acid-alkali resistance and easy expansion in water.Investigators utilize chitosan and nanomaterials to prepare composite films with good stability and acid-alkali resistance which offers a potent and novel route to overcome these problems.Chitosan composite films have been widely used in biological medicine,textile industry,environmental treatment and food processing due to simple operation,low cost and environmentally friendliness.In this thesis,we focus on the construction,properties and applications of nanomaterials/chitosan composite films.It mainly includes the following four parts:Chapter 1 gives a brief introduction of chitosan and nanomaterials and presents the recent research status of nanomaterials/chitosan composite films at home and abroad.Then based on this,the research ideas of this thesis have been proposed.In Chapter 2,Eu-POM/CS films were fabricated from europium-containing polyoxometalates（Eu-POM）and chitosan（CS）.Both observation with the naked eye and characterization with UV-vis spectrometer addresses the high transparency of the as-prepared films.In contrast to pure Eu-POM,the fluorescence intensity and fluorescence lifetime of the Eu-POM/CS films are drastically enhanced.In addition,with the increasing concentration of hydrogen peroxide（H₂O₂）,fluorescence intensity of Eu-POM/CS films decreases gradually.Based on this,the composite films display a high sensitivity and selectivity for H₂O₂ detection.It can be seen that Eu-POM/CS composite films have potential application prospects in the detection of H₂O₂ in biological samples and diagnosis of the related diseases.In Chapter 3,CuO NPs/CS composite films were prepared by CS and copper oxide nanoparticles（CuO NPs）,Firstly,CuO NPs were prepared,and their structure and morphology were characterized by powder X-ray diffraction（XRD）,scanning electron microscope（SEM）and transmission electron microscope（TEM）.Then it was found that the CuO NPs/CS composite films,constructed with CuO NPs and CS,possessed performance of H₂O₂ catalytic decomposition.With the increase of hydrogen peroxide concentration,the color of CuO NPs/CS composite films changed from light blue to dark blue through the naked eye.Therefore,based on the catalytic decomposition performance of CuO NPs/CS composite films,we could detect H₂O₂ utilizing colorimetric method.As shown in UV-vis absorption spectra,with the increasing concentration of H₂O₂,absorption intensity of CuO NPs/CS films at 633 nm enhances gradually.It is noted that CuO NPs/CS films show a good linear relationship（concentration range:0.16～110 M）.Moreover,CuO NPs/CS films display a high selectivity for H₂O₂ detection towards various interfering species in serum.Therefore,strategy of CuO NPs/CS composite films based on colorimetric method for the detection of H₂O₂ is expected to have potential value in the diagnosis of some relevant diseases such as the Parkinson’s disease.In Chapter 4,based on the ISA strategy,pH-responsive supramolecular materials were prepared by cationic azobenzene surfactants,C₂H₅-azobenzene-OC₆H₁₂-N-（CH₃）₃Br^-（ETAB）.and organic dye small molecule,congo red（CR）.UV-vis absorption spectroscopy demonstrates that the length of nano-sheet structures increased gradually when the pH decreased from 6.0 to 3.2.Polarized light microscope（POM）illustrates that the ETAB-CR supramolecular materials have birefringence properties.Additionally,they could act as a fluorescence switch under the regulation of pH.In order to avoid the influence of solvent on fluorescence properties of the supramolecular materials in bulk phase,we prepared（ETAB-CR）/CS composite films with supramolecular materials and chitosan.The fluorescence intensity of as-prepared films exhibits excellent responsive stability and reversibility under the alternate ajustment of NH₃ and HCl.which provides technical support for the applications in some fields（e.g.gas detection and fluorescence switch）.