Multifunctional Nanocomposite Hydrogels And Graphene Nanocomposite:Synthesis,Properties And Applicaitons

Nanocomposite hydrogels combine the novel properties of nanoparticles with unique properties of hydrogels which lead to new functions originated from the synergic effect or complementary performance of components. Such nanocomposite hydrogels have attracted intensive interests in many fields such as controlled drug delivery, catalysis, sensors and biomaterials. Nowadays, the methods for preparing nanocomposite hydrogels require the mix pre-formed nanoparticles with a hydrogel precursor followed by gelation, or in situ synthesis of metal nanoparticles within polymeric network architectures. The dispersibility and the size of Au nanoparticles in hydrogels are difficult to be controlled by those multi-steps synthesis routes requiring the separate preparation of metal nanoparticles and hydrogels. With the fast development of technologies for synthesis and application of the nanocomposites, it is of great significance to search for a simple and effective method of preparing nanocomposite hydrogel. Herein, based on synthesis of multi-functional nanocomposite hydrogel and novel nanomaterials with unique properties, also combining the advantages of our research group, one-step y-irradiation was used as an effective method to synthesize nanocomposite hydrogel. Moreover, the potential applications for those nanocomposites in the sensor, catalysis, microvalve and heating source are also explored. More details are as follows:1. Thermosensitive poly (N-isopropylacrylamide)/Au nanoparticles (PNIPAM/Au) nanocomposite hydrogels have been synthesized by in situ y-radiation-assisted polymerization. In this reaction, the PNIPAM hydrogels and the Au nanoparticles (NPs) are formed simultaneously, demonstrating an easy and straightforward synthetic strategy for the preparation of a uniform nanocomposite. The results suggest that increasing the monomer content during the preparation of nanocomposite materials can increase the sizes of Au nanoparticles. The effects of irradiation dose and concentration of HAUCI44H2O on the optical and thermal properties of the hydrogel have also been investigated. The PNIPAM/Au nanocomposite hydrogels can act as an excellent catalyst for the conversion of o-nitroaniline to1,2-benzenediamine, and catalytic activity of the composite hydrogel can be tuned by the volume transition of PNIPAM.2. A photo-thermal sensitive PNIPAM/GO nanocomposite hydrogel have been synthesized by in situ y-irradiation-assisted polymerization. The colors and phase transition temperatures of PNIPAM/GO hydrogels change with different GO doping level. Due to the high optical absorbance of GO, the nanocomposite hydrogel shows excellent photo-thermal property where its phase transitions can be controlled remotely by the near-infrared (NIR) laser irradiation and is completely reversible via laser exposure or non exposure. With higher GO loading, the NIR-induced temperature of the nanocomposite hydrogel increases quicker than lower doping level and can be tunable effectively by irradiation time. The nanocomposite hydrogel with excellent photo-thermal property would have great application in biomedical, especially microfluidic device, which have been proved in our experiment as a remote microvalve to control the fluidic flow.3. The PNIPAM hydrogels have been used as reactors for the synthesis of ferroferric oxid, and the excellent laser-induced photo-thermal property of PNIPAM/Fe3O4nanocomposite hydrogel which was ignored in the previous studies was investigated in the application of near-infrared (NIR) laser irradiation. The loading of Fe3O4nanoparticles in the hydrogel can be manipulated to get the desired remote heating on application of NIR laser exposure. The phase transition of the magnetic hydrogel was controlled easily by the laser exposure or non-exposure, and it was completely reversible. The laser-induced temperature was increased quickly with the irradiation time. Based on these excellent magnetic and photo-thermal properties, a valuable heating source with controlled warming position was fabricated.4. A straightforward and facile method for reducing graphite oxide using y-irradiation is explored without using any photocatalysts or reducing agents. The obtained reduced graphene oxide (r-GO) is investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), and fourier transform infrared spectroscopy (FT-IR). Such unique approach not only triggers the deoxygenation reaction of graphite oxide (GO) in water, but also reduces the Au3+simultaneously under the same condition. Various spectroscopic and imaging techniques confirm that most of the chemical functional groups present on GO are removed by irradiation, and Au nanoparticles are deposited on r-GO sheets. The size of nanoparticles increases with increasing Au3+doping level. Moreover, the catalytic activity of the r-GO/Au nanocomposites was investigated.