Preparation Of High Antibacterial Activity Zno Crystal By Controlling Facets Exposure And Its Application

Nanosized zinc oxide（ZnO）displays antibacterial activity.However,its performance is severely hindered by the agglomeration and instability of the nanostructure during processing and application.Low-dimensional ZnO at micro/nano-scale possesses specific morphologies and different exposed crystal facets,and the sub-micron Zn O crystal with highly active exposed crystal facets is expected to exhibit considerably high antibacterial activity as that of the nanosized ZnO,making it promising for a wide range of applications in antibacterial field.This thesis aimed at the crystal facets regulation and performance enhancement of low-dimensional ZnO.ZnO crystals with different morphological structures and exposed facets were synthesized using hydrothermal method under the atmospheric pressure.On this basis,the relationships between the exposed crystal facets and their antibacterial activity were investigated.Furthermore,the preparation conditions of high-activity ZnO were optimized,and large-scale preparation of flower-like Zn O was achieved at room temperature.ZnO with the high antibacterial activity was then added to the polypropylene（PP）matrix to obtain antibacterial composite.1.Low-dimensional ZnO with different morphological structures and exposed facets was regulated by controlling the reaction conditions in the hydrothermal system under the atmospheric pressure,which was induced by polar surfaces of ZnO crystals.The low-dimensional Zn Os with different exposed crystal facets,such as{21?1?0}-faceted flower-like,{101?1}-,{101?0}-and（0001）-faceted urchin-like or{101?0}-and（0001）-faceted rod-like ZnOs were obtained.2.The antibacterial activity of low-dimensional ZnO with different exposed facets was evaluated by antibacterial ratio detection methods（GB/T 21510-2008）and minimal inhibitory concentration（MIC）test（Disinfection technical specifications 2008）.The results showed that the antibacterial ratio of flower-like ZnO against Escherichia coli（E.coli）and Staphylococcus aureus（S.aureus）were both up to 99.99%at the concentration of 0.5 g/L.Compared to urchin-like Zn O（The MIC values were 600 and 800 mg/L against E.coli and S.aureus,respectively）and rod-like ZnO（The MIC values were both beyond 1000 mg/L against E.coli and S.aureus）,the MIC values of flower-like ZnO were as low as 200 and 300 mg/L against E.coli and S.aureus,respectively.3.The antibacterial mechanism of low-dimensional Zn O was studied considering the influence of exposed crystals on the dissolution of zinc ions,the release of active substances H₂O₂,and the formation of surface oxygen vacancies in ZnO systems.It was found that the different active exposed facets of ZnO crystals could be used to regulate the oxygen vacancy concentration in the surface layer of ZnO and the H₂O₂ produced in the absence of light irradiation,which led to the diverse catalytic antibacterial activity of the low-dimensional ZnO with different exposed facets.4.Low-dimensional Zn O with high activity was produced in magnifying experiment.Nanosheet flower-like ZnO with controlled exposed crystal facets and excellent antibacterial activity could be produced with good reproducibility by optimizing the process conditions.The produced ZnO antibacterial agent can be well dispersed in the PP matrix to prepare an antibacterial composite using extrusion melt-blending method.When the addition of the antibacterial agent was 0.5 wt%,the antibacterial ratio of the composite was higher than 95%,and the long-term antibacterial property was reflected in the natural aging process of the composites.The experimental results suggest that the as-prepared composites not only exhibited excellent antibacterial properties,but also good long-term antibacterial effect.