Research On Synthesis Of Nano-TiO₂ Photosemiconductor Sol As Plant Antibacterial Material And Its Biological Effects

Nowadays, aboard happening and prevalence of plant diseases had a great threaten to modern plant production. The general usage of chemical pesticides is still the most important measures in controlling disaster of plant diseases, but brings problem of serious environmental pollution. Therefore, development of environmental friendly antibacterial materials had great sense to decrease pesticide pollution and increase food safety. Nano-TiO₂ photosemiconductors are new kind of environmental friendly materials, which have been extensively used in environmental cleaning and antibacterial fields. Many researchers reported that TiO₂ photocatalytic killing has been intensively conducted on a wide spectrum of microorganisms, including viruses, bacteria, fungi, algae, and cancer cells.However, there is still no literature concerning about application of nano-TiO₂ photosemiconductor in preventing plant diseases in vivo. Based on above mentioned research findings in other fields, we firstly conducted a study on the nano-TiO₂ photosemiconductor in proventing from plant diseases and promoting plant growth. Nano-TiO₂ photosemiconductor sol (abbr. Nano-TiO₂ sol) was synthesized by sol-gel method, and its properties had been analyzed by the means of SEM, TEM, XRD, UV-spectrophotometer, etc. The photocatalytic activities of nano-TiO₂ sol were investigated by degrading of organic dye, edible oil, etc. The safety evaluation of nano-TiO₂ sol was carried on laboratory mice. And its antibacterial abilities were evaluated by using several species of plant pathogenetic bacteria and fungi. The effects of nano- TiO₂ sol in proventing from plant diseases and promoting plant growth were investigated by cultivating experiments.Nano-TiO₂ sol synthesized in the experiment is a kind of translucence neutral liquid with light yellow colour and having perfectly adhesive and film-forming abilities. TiO₂ particles are mainly anatases and cone-shaped, with a size range of 3.9 - 97.9 nm (mean diameter, 30.6 nm), and having a good stability and dispersion in the sol.The main biological effects of Nano-TiO₂ sol confirmed in the research were as following: (1) safety to mice and no untoward effects to skin; (2) performs a broad-spectrum antibacterial ability to plant pathogenic bacteria with no significant differences among different species and apparently inhibits the mycelium growth, generation and germination of spores; (3) may form successive, transparent antibacterial films on surfaces of leaves, which significantly reduce disease indexes, disease incidences, lesion areas and amounts in cucumber leaves, and effectively inhibited the development of plant diseases of downy mildew (caused by Pseudoperonospora cubensis), bacterial angular spot (caused by Pseudomonos syringae pv. lachrymans) and powdery mildew (caused by Sphaerotheca fuliginea (Schlecht) Poll.); (4) stimulates photosynthetic efficiency, promoting the contents of photosynthetic pigments and the growth of plant heights and leaf areas. (5) promotes germination of cucumber seeds, root systems growth and its physiological activities. These results provide some scientific references for the development of environmetal friendly antibacterial or plant antifungal agents by using nano-TiO₂ photosemiconductor as effective intergradient in preventing prom plant bacterial / fungal diseases, which is will be very useful in conquering pesticides pollution and improving food safety and contolling plant epidemic diseases.