Study On Nano-Silver And Silver Loaded Nano-antimicrobial

Rarely has an eternal topic had an impact on human life as great as the healthy problem which is hotly pursued by scientists in recent years. Germs are absent nowhere, and many of them could cause the diseases and menace the health of mankind. To sterilize and inhibit the propagation of bacteria by antibacterial materials is an important way to improve the health level of people.The preparation of nano-silver and silver loaded antimicrobials and their antibacterial activities were studied in this thesis. The morphologies of the antimicrobials were characterized by Transmission Electron Microscope (TEM) and Scanning Electron Microscope (SEM). The optical characteristics were analyzed by Ultraviolet-visible Spectrometer(UV-VIS) and Fourier Transform Infrared Spectrometry(FTIRs). The structures of antimicrobials were analyzed by X-Ray Diffractionmeter(XRD). The stabilization and phase transformation temperature of antimicrobials were analyzed by thermal analyzer. The antibacterial activities of the antimicrobials and antibacterial products were characterized by Minimum Inhabitation Concentration (MIC) and 24 hour Sterilizing efficiency (SE) Test.Silver colloids were prepared by chemical reduction method, and the silver concentration was 3.6×105ppm. Silver nanoparticles were separated from the colloids, and their diameters were distributed in 10nm to 50nm. It shows that the growth behavior of the particles relates with pH value of the solution. At a lower pH, the increase of reaction velocity mainly represents the growth of particles, while it represents the increase of the nucleation rate at a higher pH. The added dispersant (PVP) could promote the reaction of glucose and silver nitrate because of the coordination of PVP with H+.PVP protected the silver particles from agglomeration and growth, resulted in a good stability of the colloids, when the weight ratio of PVP to AgNO3 is in the range of 1.2 to 1.3. Different from the reported result, it was concluded that the PVP protected silver particles with diameters of 10 to 50nm by coordinating N with the silver. According to the studies on the antibacterial activity of silver particles, the activity dramatically advanced with the diameter decrease from 500nm to 50nm and 5nm, and the nanometer effect appeared obviously.Silver loaded 4A zeolites were prepared by ion exchange method, whose antibacterial activity and thermal stability were also studied. With the increase of Ag+ content, the stability of zeolite first increased and then decreased, and it was caused by the decrease of specific area and the instability of the Ag-O bond after Ag+ exchanged. The stability was decreased with the decrease of pH. At a low pH, H+ would be loaded in zeolite, and it caused the increase of specific area. The concentration of Ag+ which released into antibacterial solution increased with the increase of silver content in zeolite, so the antibacterial activities were improved. When it was 3%wt, the MIC for Escherichia coliform (E-coli) and Staphylococcus aureus (S-aureus) were 62.5ppm. The antibacterial activity decreased with the increase of heat treatment temperature, because Ag+ diffused to the surface of zeolite, reduced and assembled as clusters; when it was treated at 800℃, almost all silver ions were reduced, and the cavity structure of zeolite was destroyed, touches between silver and bacterial were destroyed, which made the dramatic decrease of the antibacterial activity.Silver doped TiO2 (Ag-TiO2) was prepared by Sol-Gel method, and the influences of silver on the phase transformation, photocatalysis and antibacterial activities of TiO2 were studied. The phase transformation was inhibited at a lower calcination temperature, owing to the distortion of lattice caused by silver and the formation of the bond Ti-O-Ag. When silver doped TiO2 powders were calcined at a higher temperature, the distortion was erased and vacancies were left because Ag+ has migrated to the surface of TiO2, which improved the phase transformation. The TiO2 got a better photocatalysis and antibacterial activities when it treated at 500℃. The silver can improve the photocatalysis and antibacterial activities dramatically. When the content of silver is 1%mol, the photocatalysis activity is best, and antibacterial activity increases continuously with the increase of silver content.Antibacterial polypropylene (PP) resin was prepared with the as prepared antimicrobials, and their antibacterial activities were studied. The resin with silver nanoparticles got a good antibacterial activity, and the 24h SE to S-aureus was over 90% when the silver content was 600ppm(500nm), 150ppm(50nm) and 100ppm(5nm) respectively; the 24h SE of resin with 1%wt silver loaded zeolite for E-coli and S-aureus was over 98%; the 24h SE of resin with 1%wt silver doped TiO2(0.5%mol silver) for E-coli and S-aureus was over 90%, under a violet light illuminated circumstance.