Facile Synthesis of Size-Controlled Silver Nanoparticles Using Plant Tannin Grafted Collagen Fiber As Reductant and Stabilizer for Microwave Absorption Application in the Whole Ku Band

Size-controlled silver nanoparticles (AgNPs) were facilely synthesized on collagen fiber (CF), in which bayberry tannin (BT), a natural plant polyphenol, was grafted on CF to act as a reductant and stabilizer without any additional reagent (surfactant, template, and capping agent) or treatment (heat and photoirradiation) needed. The as-synthetic AgNPs-BT@CF was well characterized via combined techniques including SEM, HTEM, XRD, XPS, and FT-IR. The particle diameter and size distribution of AgNPs in BT@CF matrix are feasible to adjust by varying the grafting degree of BT on the CF surface. When the grafting degree of BT was 0.4, the particle size of AgNPs is as small as 5.2 ± 1.9 nm. Furthermore, the complex permittivity, and complex permeability of the AgNPs-BT@CF were also investigated in detail. It was found that with the increase of grafting degree of BT on CF the imaginary part (ε″) of complex permittivity was dramatically increased, whereas the real part (μ′) and imaginary part (μ″) of complex permittivity were not obviously changed. The reflection loss (RL) of AgNPs-BT@CF exceeding −10 dB was achieved in the whole Ku band (12.5–18 GHz).