| Nano-copper exhibits excellent antibacterial properties, but the application of the nanoparticles is restrained due to their agglomeration and low stability. Tetra-needle like ZnO whiskers (T-ZnO) with antibacterial activities are recognized to be good carriers to well-dispersed and stabilized nano-copper. It is expected to obtain an eflficient, long-term and broad-spectrum antibacterial agent by loading nano-copper onto T-ZnO.In this thesis, nano-copper was loaded onto T-ZnO by in situ decomposition of organic copper precursor. By controlling reaction conditions, nano-copper deposited T-ZnO nanohybrid materials (n-Cu@T-ZnO) with different nanoparticle sizes were obtained. The antibacterial properties of the prepared nanohybrid materials were detected, and the antibacterial mechanism was also studied. Furthermore, antibacterial agent with the highest antibacterial activity was added to polypropylene resin by melt blending method to prepare antibacterial plastics. The specific work and main results of this work include:1. Nano-copper were uniformly loaded onto the surface of T-ZnO by in situ decomposition of organic copper precursor. Firstly, the precursor tartaric acid (C4H4O6Cu) was synthesized on the T-ZnO surface by chemical precipitation method. And then, the precursor was decomposed with H2 atmosphere at 250℃ to get n-Cu@T-ZnO nanohybrid materials. By adjusting reaction conditions, n-Cu@T-ZnO nanohybrid materials with different nanoparticle sizes, ranged between 15-45 nm, were obtained. Characterization results of morphology and structure showed that the morphology and structure of T-ZnO did not change during the process. Nano-copper loaded on the surface of T-ZnO was mainly metallic state. However, surface of nano-copper was covered with a layer of CuO since the small-sized nano-copper exposured in the air was very easily to be oxidized.2. The minimal inhibitory concentration (MIC) test showed that, n-Cu@T-ZnO nanohybrid materials exhibited better antibacterial activities against Escherichia coli(E. coli) and Staphylococcus aureus (S. aureus) compared to T-ZnO and nano-copper alone. And its antibacterial properties increased with the decreasing of the nanoparticle size. When the nanoparticle size was 15 nm, the MIC values against E.coli and S.aureus were slightly larger than 400 and 600 mg/L. Study on the antibacterial kinetics of n-Cu@T-ZnO nanohybrid materials showed that the the nanohybrid materials could exert significant inhibitory effect to the bacteria from the logarithmic growth phase.3. The antibacterial mechanism of n-Cu@T-ZnO nanohybrid materials was studied with the dissolution of copper ions (Cu2+) and the release of reactive oxygen species (ROS, such as· OH,· O2-, H2O2). The results showed that n-Cu@T-ZnO nanohybrid material had more ROS produced and Cu2+ released in the suspensions compared with pure T-ZnO and nano-copper. The results showed that the excellent antibacterial properties of n-Cu@T-ZnO was ascribed to the hybrid structure which brought about a lot of dissolution of Cu2+ and the large number of ROS.4. Antibacterial polypropylene (PP) composites were prepared by adding n-Cu@T-ZnO nanohybrid materials with the highest antibacterial activity by melt blending method. Morphology observation showed that the n-Cu@T-ZnO antibacterial agent was well-dispersed in the PP resin matrix. Patch test was used to investigate the antibacterial properties of n-Cu@T-ZnO/PP composites with different antibacterial agent contents. The results showed that when the addition of the antibacterial agent was 1.0 wt%, the antibacterial rate of n-Cu@T-ZnO/PP composite against E.coli could reach 99.98%. In addition, the n-Cu@T-ZnO/PP composite also displayed long-term antibacterial effect. |
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