Preparation And Antibacterial Properties Of Nanoparticles Deposited Carbon Nanotubes

Nano-silver and nano-copper have higher antimicrobial activities. But the application of them could be restrained for their agglomeration behavior, bad distribution and low stability. Carbon nanotubes (CNTs) with large specific surface area and some antibacterial activities are recongnized to be good support materials for nanomaterials. Thus, new multi-scale antimicrobial nanomaterials are expected to be get by loading nano-silver and nano-copper onto CNTs.In this dissertation, two methods, namely the gas reduction method and liquid phase reduction method, were employed to deposit nano-silver onto the surface of CNTs. Meanwhile, liquid phase reduction method was used to deposit nano-copper onto the surface of CNTs. In addition, the optimum antimicrobial agent has been added into polypropylene (PP) to prepare antimicrobial plastic by melt blending.According to the gas reduction method, the silver ions were firstly adsorbed onto CNTs to obtain the silver ions grafted CNTs (Ag+-CNTs).Then, the Ag+-CNTs were reducted with H2at lower temperature to get nano-silver deposited CNTs (GR-Ag/CNTs). XRD patterns and TEM images showed that the nanoparticles on the CNTs were nano-silver with the size about32.9nm. The nano-silver had high stability, which was confirmed by the XPS spectra. The minimum inhibitory concentration (MIC) test showed that both Ag+-CNTs and GR-Ag/CNTs had good antimicrobial activity, which is slightly larger than250mg/L and250-500mg/L, respectively.With poly(ethylene imine)(PEI) as surface modification agent of CNTs and chelating agent of silver ion, silver nitrate (AgNO3) as silver source, sodium borohydride (NaBH4as reducing agent, nano-silver deposited carbon nanotubes obtained by liquid phase reduction method (LR-Ag/CNTs) were prepared. The influence of PEI with different molecular weights on the surface structure of nano-silver was explored. It showed that PEI with higher molecular weight (Mw=70000) were prone to tangle, leading to the agglomeration of the nano-silver on the surface of CNTs with the particle size34nm. On the other hand, the uniform particle with size of2.6nm and good dispersion was obtained with the lower molecular weight (Mw=600) PEI. Therefore, PEI with lower molecular weight was used as chelating agent to prepare LR-Ag/CNTs with different silver content. According to the inhibition zone test and minimum inhibitory concentration test, the antimicrobial property of as-prepared composite was better than the silver/carbon aerogels composite reported in literature, and the antimicrobial activity increased with increasing the amount of silver deposited sequentially. In addition, by hiring atomic absorption spectroscopy and antimicrobial properties of AgN03as comparative experiments, the antimicrobial mechanism of LR-Ag/CNTs composite materials was investigated. It showed that the antimicrobial activity of LR-Ag/CNTs was primarily attributed to dissolving silver ion, while there may be other synergistic factors.Similarly, with PEI as coupling agent, copper chloride (CUCl2) as copper source, NaBH4as reducing agent, nano-copper deposited carbon nanotubes obtained by liquid phase reduction method (LR-Cu/CNTs) were prepared. The structure and morphology characterizing results showed that nano-copper was severely oxidized to cuprous oxide and the surface of cuprous oxide was even oxidized to copper oxide. The results of antimicrobial tests showed that the inhibition zone of antimicrobial agent exhibited a large inhibition zone width, but the MIC was larger than1500mg/L.Antimicrobial PP plastic was prepared by melt blending method with4wt%LR-Ag/CNTs as the antimicrobial agent. The antimicrobial property of PP composites with different antibacterial agent content was investigated. The antimicrobial properties results showed that when the addition amount of the antimicrobial agent was0.5wt%, the antimicrobial rate of antimicrobial PP against E. coli could reach99.99%.