In Situ Preparation Of Silver Nanoparticles/Alginate Fibers And Performance Investigation

Alginate fiber is a type of new bio-polymer material, which is prepared by wet-spinning with Brown seaweed polysaccharide(primarily sodium alginate) as material. It has been widely applied in medical industry as medical gauze and dressings due to its high moisture absorption, oxygen permeation, biocompatibility and biological degradation properties. In recent years, in addition to the traditional application areas, such as medical dressings, the application of alginate fiber in textiles has received extensive attention. It is significant to further enhance the functionality of alginate fiber, extend its application scope and enhance its value via combining nano materials with alginate fiber. In this work, we firstly investigate the Green preparation methods of silver nanoparticles(AgNPs) via the water-bath heating and microwave heating, discuss the role of alginate in synthesis of AgNPs and the stable mechanism of sodium alginate-based AgNPs. Then, we study on the preparation of AgNPs/alginate fiber by in-situ blending and in situ reduction method, explore the antimicrobial properties and catalytic performance of the as-prepared AgNPs/Alginate fiber. The specific work includes following sections:1.Sodium alginate-based silver nanoparticles were synthesized in an aqueous medium with sodium alginate as stabilizer and reducer, via ordinary water bath heating and microwave heating methods. Water-bath heating method, we investigated the effect of reaction conditions on the synthesis of AgNPs. The prepared AgNPs were characterized by UV-vis spectroscopy, transmission electron microscopy(TEM), X-ray diffraction(XRD). The results indicated low concentrations of sodium alginate(0.25-0.5 wt%) is conducive to synthesize smaller particle size, uniform and stable AgNPs, When the concentration of silver ions in 0.5-5.0 mmol/L, the synthesized AgNPs are well dispersed, however, increased to 7.0 mmol/l, resulting in higher aggregation of AgNPs. Along with the extended reaction time(5-60 min), generate increased amounts of AgNPs, but little change in the diameter of AgNPs, further indicating the good stability of sodium alginate to AgNPs. Microwave heating method, it is possible that a large amount of AgNPs with small particles size can be achieved using sodium alginate as the reducing and stabilizing agent. Reactions can be carried out within a short time(<10 min), the size of AgNPs could be controlled by changing the concentration of sodium alginate. The antimicrobial properties were investigated by S. aureus and E. coli, and the results indicated that the prepared AgNPs showed strong antibacterial activity. The minimum inhibitory concentration(MIC) of AgNPs is 0.15 mmol/L(water bath heating) and 0.1 mmol/l(microwave heating), the minimum bactericidal concentration(MBC) of AgNPs is 0.3 mmol/L(water bath heating) and 0.25 mmol/L(microwave heating). Finally, synthesis and stabilization mechanism of AgNPs was explored. The hydroxyl and carboxyl groups on the molecular chain of Sodium alginate are associated with the synthesis and stability of AgNPs, AgNPs are stable with negative charge due to package of sodium alginate.2.Sodium alginate- silver nanoparticles colloid solution was obtained with alginate as stabilizing and reducing agent. Then, sodium alginate powder was directly added to the above solution and the resultant sodium alginate-AgNPs spinning solution was spun to prepare AgNPs/alginate fibers. The fibers were characterized by SEM, TEM and XRD. The results showed that the AgNPs were stable and dispersed well without aggregation in the prepared fibers. Mechanical properties of the fibers were also measured, the prepared fibers still had a relatively high strength and modulus. The antimicrobial properties were investigated by S. aureus and E.coli, and the results indicated that the composite fibers showed strong antibacterial activity.3.The preparation of AgNPs/alginate fibers by in-situ reduction, namely, silver ions complex with carboxyl or hydroxyl of alginate fiber, then,silver ions were in situ reduced and grow onto the alginate fibers. The prepared fibers were characterized by SEM, TEM, XRD, etc. The results indicated that AgNPs occupied not only on the surface but also the interior of the fibers without aggregation and the distribution of AgNPs was graded from the surface toward the center in the fibers. The alginate-AgNPs composite fibers showed strong antibacterial activity on both Gram classes of bacteria and excellent catalytic capability of 4-nitrophenol reduction and methylene blue degradation. The as-prepared AgNPs/alginate fibers are expected to have potential for functional textile and biomedical material. The fiber can also be used for catalyst of ion transfer reaction or dye wastewater treatment.