Preparation Of ZnO-based Bioinspired Nanomaterials And Their Bactericidal And Gas Sensing Properties

Zinc oxide（ZnO）is a widely used inorganic functional material.The wide band gap of 3.37 e V and the high exciton binding energy of 60 me V endow it with excellent optical,electrical and piezoelectric properties,and become one of the hot materials in international frontier research.For the application of biological antibacterial agents,nano-ZnO materials have the advantages of good biocompatibility,non-toxicity and broad-spectrum antibacterial properties,so they have attracted extensive attention in the field of sterilization.For the application of gas sensors,nano-ZnO materials are also widely studied by researchers in the field of gas sensing due to their high electron mobility,mature preparation process and adjustable growth morphology.After hundreds of millions of years of development,nature has evolved many excellent functions and matching structures.Therefore,natural structures provide an important research direction for the construction of high-performance nanocomposite structural materials.In conclusion,inspired by the bionic phenomenon of biological sterilization surfaces in nature and canine olfactory sensitivity,we prepared two ZnO-based bioinspired nanomaterials,and studied the sterilization and gas-sensing properties of the materials respectively:（1）Biological surfaces such as cicada wings and dragonfly wings have evolved fine nano-structured surfaces to kill bacteria by natural selection.The surface of lotus leaf has a multi-level micro/nano structure and is widely available,which brings inspiration for us to design the structure of bactericidal materials.Therefore,fresh lotus leaves are used as raw materials.We sintered fresh lotus leaf modified with Zn（II）at high temperature to load ZnO nanoparticles,and then grew gold nanoparticles through photoreduction to obtain bionics microstructure carbonized lotus leaf/ZnO/Au composite（C-LL/ZnO/Au）.In the period of half an hour,the antibacterial rate of mechanical sterilization for C-LL/ZnO/Au amount to 79.5%,4.7 times of fresh lotus leaf’s figure under the same conditions.In comparison,the antibacterial rate of photocatalytic sterilization for C-LL/ZnO/Au is 93.8%,and the antibacterial rate of synergistic sterilization can reach 100%.We explored the reasons why C-LL/ZnO/Au exhibited excellent synergetic bactericidal properties:on the one hand,the composite retained the papillary structure of lotus leaf and its outstanding mechanical bactericidal properties;on the other hand,the introduction of gold nanoparticles effectively enhanced the photocatalytic sterilization properties of the composites.Due to the synergistic effect and complementary advantages of the mechanical sterilization and photocatalytic sterilization mechanisms,the sterilization rate of C-LL/ZnO/Au can reach 100%in merely half an hour.（2）The high olfactory sensitivity of canines and rodents in nature is closely related to the wrinkled structure of the turbinate in their nasal cavity,which brings inspiration for us to design the structure of gas sensing materials.We first prepared spindle-shaped wrinkled ZnO nanoparticles by one-step hydrothermal method,and then obtained gold nanoparticles with different sizes by sodium citrate reduction method.Subsequently,gold nanoparticles with various loading amounts and sizes were loaded on ZnO nanoparticles to obtain bionic spindle-shaped wrinkled Au/ZnO nanoparticles,which were applied to detect H₂S gas in the environment.Firstly,in the experiments with different concentrations of small-scale Au nanocomposites,the sensor with the gold loading of 0.5 wt%exhibited the most excellent gas sensing properties.Based on the dual effects of electron sensitization and spill-over effect of gold nanoparticles,the sensor had a high response value of 39.23 to 5 ppm H₂S,which was 6.4 times that of pure spindle-shaped wrinkled ZnO under the same test conditions.Secondly,in the experiments loaded with gold nanoparticles of different sizes,the gold nanoparticles with smaller size effectively avoided the agglomeration of Au,and had the best sensing performance.In addition,we also revealed that the sulfurization-desulfurization mechanism resulted in higher reactivity between the composites and H₂S gas,thus enhancing the selectivity of the composites,which provides a new reference for the construction of intelligent,efficient and low-cost H₂S gas sensor.