Green Preparation And Application Of Nanosilver Based On Plant Fiber

As abundant and sustainable resources in nature,plant fiber,mainly consisting of different kinds of polysaccharides,are biocompatible,degradable and renewable.In the past,plant fiber was often used as a carrier and weak reductant during the preparation of nanosilver,but the resulting nanosilver with a single morphology and low yield was limited in use,and its preparation process is difficult to control.In this paper,both nanocellulose and pulp fiber were used as reductants to prepare nanosilver,without addition of dispersants and other reductants,for the sake of realizing the high value-added utilization of plant fiber.Then the nanosilver was efficiently synthesized using the green and controlled way.Furthermore,the characteristics and application performance were also investigated.These studies are of great significance for the development of green preparation technology of nanosilver.Then the researches for the above purposes were carried out as following:?1?Under ultraviolet irradiation,the green and controllable synthesis of silver nanoparticles colloids was carried out using TEMPO-oxidized nanocellulose as both a reductant and dispersant,and the reduction rate was up to 96.26%.Then the curve-fitting equation was established for inspecting the preparation process under different conditions,with the absolute value of RSD less than 4.5%.The results indicated that the diameter and length of nanocellulose was 20⁵0 nm and 100³00 nm,respectively.The silver nanoparticles prepared by this method had a good face-centered cubic crystal structure,and their average particle size increased from 14.98 nm to 62.61 nm along with the extension of ultraviolet irradiation time from 2 h to 20 h.The nanocellulose/silver nanoparticles colloids also exhibited good stability and biocompatibility,with the inhibition rate of 100%for E.coli 8099 and S.aureus ATCC 6538,and the total amount of released Ag⁺was only 11.95%after 15 days.?2?Silver nanoparticles were successfully prepared in situ using chemical pulp fiber as a weak reductant and stable carrier,without adding any additional reductants.Then the effect of different synthesis conditions on silver nanoparticles load rates was investigated.The results indicated that the silver nanoparticles load rate was up to 28.12 wt%,and the resulting particles with diameters of 10⁵0 nm held a uniform distribution and face-centered cubic crystal structure.In the reduction of 4-nitrophenol to 4-aminophenol using silver nanoparticles/chemical pulp fiber composites,the catalytic time was only 1.5 mins and the conversion rate was still up to 95.91%after recycling of 50 times.It was also discovered the green preparation method of silver nanoparticles in situ was also applicable to other cellulose fibers,such as tencel fiber,viscose fiber as well as modal fiber,and the resulting silver nanoparticles also had a high load rate and a uniform particle size.?3?Ultra-long silver nanowires were prepared with TEMPO-oxidized nanocellulose as a reductant using hydrothermal method,without any addition of other reductants and protective agents.It was showed that 0.006 g of nanocellulose and 0.01 mmol Ag⁺at 180?for 24 h under argon protection environment were optimal for the preparation of silver nanowires.The length and diameter of the resulting silver nanowires were mainly distributed in a range of 800¹200?m and 100³00 nm separately.The silver nanowires presented a face-centered cubic structure,and their length-diameter ratio could reach more than 5000 and the reduction rate was up to89.36%.Then the silver nanowires were used to fabricate transparent conductive films.When the silver nanowires content was 22.78 mg/m²,the transparent conductive film,with a sheet resistance of 11.90?/sq and a transmittance of more than 75%,displayed a high thermal stability and good electrical conductivity after bending 500 times.?4?Ultra-long silver nanowires with good toughness were synthesized with pulp fibers as reductants using hydrothermal method.It was showed that 0.0075 g pulp fibers and 0.02 mmol Ag⁺at 180?for 24 h under N₂ after adding 0.3⁰.45 mmol HCl were optimal for the preparation of silver nanowires.And the product also possessed face-centered cubic structure.Moreover,the carbonized silver nanowires/pulp fiber composites had a joint,electric and three-dimensional network structure,holding an electromagnetic shielding performance of more than22 dB in the range of 8.2¹2.4 GHz.