The Preparation And Bacteriostatic Activities Of Silver Loaded Inorganic Oxide Nanocomposites

Health has always been the major concern of our country. With the increase of people's life standard, how to control and restrain the growth and reproduction of harmful bacteria becomes an important topic and has attracted a great deal of attention in recent years. Inorganic antimicrobial agents have many advantages in commercial potentials; it became a focus in antibacterial research. However, the inorganic antmicrobial agents also have disadvantages such as stability, the establishment of antibiosis indicator and so on. How to synthesis the agents which not only have good stability and antibacterial property but also can satisfy the practical application became very urgent.This study aims to exploit inorganic agents with good antibacterial properties. The reduction in situ method, adsorbtion and chemical reduction method and calcintion method were adopted to prepare nanoscale-CaCO3/Ag, SiO₂/Ag and ZnO/Ag, respectively. 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 (FT-IR). The structures of antimicrobials were analyzed by X-Ray Diffractionmeter (XRD). The composition was investigated by X-ray photoelectron spectrum (E-max). Furthermore, the antibacterial activities of the antimicrobials and antibacterial products were characterized by detection of inhibition zone. The results are as follows:1. Different sizes of silver colloids were prepared by chemical reduction method and silver nanoparticles were separated from the colloids, diameters of which ranged from 5-50 nm. By employing different reaction conditions,various sizes of silver colloids were grown in a controlled manner. The effect of various factors has been investigated.It was found that different reduction agents have the significant influence on the size of silver colloids. When NaBH4 is employed as the reduction agent, the silver colloids obtained are the smallest particles with an average nanometer of 5-10 nm. It also shows good dispersibility. 2. The surface modification of nanoscale calcium carbonate was achieved through chemical coupling with the coupling agents of APTES, MPTES and KH570, respectively. The nanoscale-calcium carbonate shown perfect hydrophobicity with the contact angle of 107°. On the base of surface modification, calcium carbonate loaded silver nanocomposties were prepared by chemical reduction which showed excellent antibacterial activities. The technological process and the bacteria restraint of the agent were thoroughly studied and the inhibition zone to golden brown staphylococcus and Escherichia coli is 23.4 mm and 21.8 mm respectively.3. The conventional Stober method was adopted to prepared silica microsphere in different alcohol solution. The influence of different alcohols solvent on the size of silica was discussed. The results indicated that the diameter of silica is gradually increased with the molecular weight of methanol, ethanol, propyl alcohol and buthanol and the mechanism was also discussed subsequently. Taking the silica prepared as a carrier, we obtained SiO₂/Ag composites by adsorption and chemical reduction. The SiO₂/Ag composites are very sensitive to golden brown staphylococcus and Escherichia coli with the inhibition zone diameter of 15.3 mm and 10.4 mm respectively.4. The synthesis of nanoscale-zinc oxide by calcination and precipitation approach has been investigated. The synthesis methods'influence on the size of nano-zinc oxide was studied. The results revealed that the diameters of nanoparticles obtained by calcination and precipitation approach are about 25 nm and 168 nm respectively. Comparatively speaking, the precipitation approach is more easily to obtain regular and good dispersity nanoparticles. On the base of nano-zinc oxide obtained by precipitation method, ZnO/Ag composites have been prepared by pyrolysis method. The detection of inhibition zone shown that the diameter of inhibition zone to golden brown staphylococcus and Escherichia coli is 20.8 mm and 15.2 mm, respectively.In conclusion, three kinds of inorganic oxide loaded Ag nanocomposites antibacterial agents with high antibacterial activities were prepared by different methods in this paper. The data provided by the present study are valuable to the exploitation of inorganic nanoscale-antibacterial agents.