The Application Of Tannic Acid In The Preparation Of Nano-silver Functional Materials

Tannic acid(TA)is a kind of plant polyphenolic compounds which can be widely found in plant roots,stems,leaves and fruits.TA belongs to the family of hydrolysable tannins and has many advantages such as wide source,low cost,environmentally friendly,good biocompatibility and so on.In this,TA-based functional materials were prepared by using TA-Fe as surface modifier.The main researches are as follows:(1)Fabrication of conductive silver microtubes using natural catkin as a template.Catkin,a natural hollow fiber,was used as template to fabricate light,flexible and electrically conductive silver microtubes with high aspect ratio.The template was functionalized by TA-Fe coordination complexes.Then,silver nanoparticles(Ag NPs)can be in situ formed on the fiber surface.The as formed Ag NPs can act as nucleation sites in the subsequent electroless silver plating,leading to the formation of a compact and uniform silver coating on the microtube.The coating was constructed by densely packed Ag NPs of only 15 ± 5 nm in diameter.Because of the tightly accumulation and the small size of the Ag NPs,the resulting silver coated microtubes,without any post-treatments,show a high electrical conductivity.We find that the in situ formed nucleation sites and the stirring speed in the electroless plating play important roles for the formation of perfect silver coating.This method may be extended to fabricate conductive nanocoatings on other substrates.(2)Preparation of Fe3O4@SiO2@(TA-Fe)4@Ag NPs core-shell nanospheres and their catalytic performanceMagnetic core-shell nanospheres were prepared by using Fe3O4 nanospheres as the cores and SiO2 as the shells.An LbL surface modification method by TA-Fe complex was proposed.This method was more suitable for the surface modification of nanospheres with high curvature.After in situ reduction of Ag NPs,a compact Ag NPs layer,constructed by a large number of Ag NPs of only 5-7 nm in diameter,was formed on the surface of core-shell nanospheres.The catalytic performance in the reduction of 4-nitrophenol with NaBH4 as the reducing agent was studied and the reaction rate constant was calculated on the basis of the pseudo-first-order reaction equation.The prepared materials display excellent activities:the rate constant is 0.43 min-1.Furthermore,the magnetic core facilitates the convenient recovery and reuse of the catalyst by applying an external magnet.This method can be extended to the modification of other surfaces with high curvature and guide the development of new and efficient catalytic materials.