Research Of Preparation And Sensing Performance Of AgNPs@CNTs Composite Hydrogel

Flexible sensors have a wide range of applications in wearable sensing and electronic skin due to their good adhesion,high sensitivity,light weight and small size,and can be used to monitor human temperature,humidity,deformation,etc.Hydrogels are three-dimensional porous network materials of hydrophilic polymer chains with the advantages of high stretchability,conductivity,biocompatibility and adjustable material composition.Hydrogel-based sensors are expected to have high sensitivity,high linearity and high repeatability at the same time.In this thesis,silver nanoparticle-coated carbon nanotubes（Ag NPs@CNTs）were prepared using a UV irradiation reduction method.A multifunctional hydrogel sensor with high stretchability,anti-freezing and moisture resistance,and antibacterial properties was prepared by compounding Ag NPs@CNTs in a polyvinyl alcohol hydrogel,which can be highly responsive to deformation and to temperature.The main research contents of this paper are as follows:1.A layer of dense and small-sized（5-10 nm）silver nanoparticles was grown in situ on the surface of the acidified carbon nanotubes by UV irradiation of reduced silver ammonia solution.The effect of silver nanoparticles on the electrical conductivity,surface groups and dispersion of carbon nanotubes was investigated.Polyvinyl alcohol/borax/glycerol/Ag NPs@CNTs hydrogels（PBGA）were synthesized by repeated freeze-thawing method through compounding Ag NPs@CNTs in hydrogels.The electrical and mechanical properties of the hydrogels were tested,the role of Ag NPs@CNTs in constructing the three-dimensional network structure of PBGA hydrogels was investigated,and the distribution ratio of each group in the hydrogels was optimised.By replacing the water molecules in the hydrogel with glycerol,the problem of the general hydrogel’s intolerance to low temperature and severe dehydration was solved.The ability of the hydrogel to inhibit Staphylococcus aureus and Pseudomonas aeruginosa was investigated using the antibacterial ability of silver nanoparticles.2.PBGA hydrogels were prepared as sensors and their sensing performance to strain was investigated.The strain sensing capability of PBGA hydrogels was tested at room temperature and the parameters were optimised to obtain a PBGA hydrogel strain sensor with high sensitivity,low lower detection limit,high tensile and high stability.The tensile properties and cyclic stability of PBGA hydrogels were investigated in low temperature,dry environments.The hydrogel was also found to respond equally well to torsion and compression.The mechanism of deformation sensing by the three-dimensional network structure constructed by silver nanoparticles and carbon nanotubes was analysed.PBGA hydrogels can used in human wearable sensing to monitor daily human activities such as finger flexing,swallowing and walking.3.The performance of PBGA hydrogels as temperature sensors was investigated.The temperature responsiveness,response interval,and resolution of PBGA hydrogels were investigated.The analysis suggests that the excellent temperature sensing properties of the hydrogel come from the synergistic effect of silver nanoparticles,carbon nanotubes and polymer molecules.The hydrogel can be used for human body monitoring due to its high resolution,wide testing range,high responsiveness,softness,antimicrobial properties and adherence to the skin.Combining the deformation sensing properties of PBGA hydrogels,we have prepared a bionic sensor with reference to the principle of jellyfish snorkelling in water to achieve real-time monitoring of water temperature and water pressure.