Flexible Polymer Composites Based On Silver Nanofillers And Their Properties

With the rapid development of science and techonolgy,flexible polymer composite materials have been widely used in flexible sensing,environmental monitoring,electromagnetic shielding,self-energy,biomedicine and other fields.These fields not only need different shapes and properties of flexible substrates,and the filler is also an important factor affecting the application.At present,high-quality fillers include carbon-based nanomaterials,intrinsically conductive polymers,and noble metal nanofillers.In this paper,we synthesized silver nanowires（AgNWs）by hydrothermal method and silver nanotriangular plates（AgNTs）by seed growth method,respectively.Afterwards,we added AgNWs as conductive fillers into polyacrylamide（PAAm）-gelatin double-network hydrogels,and studied the internal structure,morphology and electrical sensing response performance of the prepared conductive composite hydrogels in depth.In addition,we adsorbed high concentrations of AgNTs on the filter paper in the manner of face-to-face self-assembly.The theoretical simulations have been carried out to verify the high density of hot spots with huge localized EF near the corners of the assembled structures and Raman spectroscopy was used to study the substrates for trace detection of rhodamine 6G（R6G）and thiram bimolecules.1.Preparation and properties of PAAm-Gelatin-AgNWs double-network conductive composite hydrogels（1）First,we synthesized the AgNWs with ultra-high aspect ratio as conductive fillers by hydrothermal method.The double-network hydrogel that formed by acrylamide（chemical cross-linked network）and gelatin（physical cross-linked network）were used as the flexible polymer substrates.The morphological characterization reveals AgNWs with extremely high aspect ratio and uniform size distribution（150nm）.By adjusting the experimental parameters（content of gelatin and AgNWs）,we achieved the regulation of the mechanical properties.（2）The strain response performance experiment showed that the PGA conductive hydrogel exhibits an ultra-wide strain sensing range（0-1649%）and good sensitivity（gauge factor,GF=1.36）when the AgNWs content is 10 mg.Furthermore,the PGA hydrogel exhibited remarkable durability（800 stretch-release cycles）during the cycling response.The practical application of the hydrogel can effectively realize the motion detection of various parts of human bodys,and the research provides a new idea for designing a flexible wearable strain sensor with a large strain range and sensitivity.（3）Furthermore,the hydrogels treated using the solvent displacement method exhibited excellent environmental tolerance.It was found to have good sensitivity（GF=5.92）and cycle stability.And we used it to monitor various movements of the human body using wireless sensor equipment.2.Preparation and properties of filter paper-based self-assembled AgNTs（1）We synthesized AgNTs by seed growth method.Transmission electron microscopy（TEM）showed that the synthesized nanoplates had uniform size distribution（52.7±4.6 nm）and stable morphology.The ultraviolet-visible absorption spectroscopy（UV-vis）indicated that the AgNTs had a tunable absorption spectrum,which would blue-shift from 620 nm to 556 nm as the added seed volume changed from 250μL to 700μL.Theoretical simulation proves that the size of the triangular sheet has an important influence on the UV-vis spectrum.（2）Subsequently,the high concentration AgNTs solution self-assembled on the cellulose filter paper to form a face-to-face structure.By simulating the plasmonic response and local electromagnetic field（EF）enhancement of the AgNTs,we verified the high-density hot spots with huge local EF near the corners of the assembled structure.We calculated the SERS enhancement signal under different laser irradiations up to（E/E₀）⁴=10⁸（633 nm）,10¹⁰（954 nm）,10¹²（994 nm）,respectively.（3）Based on the self-assembled structure,we developed a cost-effective and efficient flexible SERS substrate.The experimental results showed that the self-assembled SERS substrates can detect ultra-low concentrations of R6G dye and thiram.This composites with excellent sensitivity,stability and selectivity shows potential applications in food safety and environmental monitoring.