Preparation, Antibacterial Activity And Photocatalytic Properties Of TiO₂-based Nanomaterials

TiO₂ is an n-type semiconductor having wide band gap, Quantum size effect increases both the band gap and the redox potential. Therefore, it has characteristics of high specific surface area, high density of surface lattice defects and high surface energy, leading the photocatalytic activity increase directly. TiO₂ is a promising technique for decontamination, purification, deodorization of air and wastewater, as well as inactivating bacteria. Besides, More and more research scholars study TiO₂ nanomaterials because of its high chemical stability, non-toxicity, high photo-reactivity, broad-spectrum activation, antibiosis and cheapness; it has been used extensively as biocide against various microorganisms: bacteria, fungi and viruses.In this paper, In order to investigate the photocatalytisis and water dispersion stability of the TiO₂-TDA-2# nanoparticles, We used methylene blue and methyl orange as the model compound for the research of photoreactions. As a reference, the photocatalytic activity for P25 TiO₂ has also been study for comparison. The results demonstrated TiO₂-TDA-2# on the degradation rate and removal rate of methylene blue were 182.3733 μg /（min?g） and 87.4013%; while TiO₂-TDA-2# on the degradation rate and removal rate of methyl orange were 146.9539 μg/（min?g） and 71.0530 %, Which showed that the photocatalytic performances of TiO₂-TDA-2# were relatively well. Settlement testing and spectrophotometer detection were also used to confirm the water dispersion stability of TiO₂-TDA-2# nanoparticles. It was found that the aqueous solution of TiO₂-TDA-2# nanoparticles was still clear and transparent after 20 days; Furthermore, the absorbance of the aqueous solution of TiO₂-TDA-2# has unchanged within 15 days. Thus, the TiO₂-TDA-2# has good aqueous solution dispersion and stability.By choosing TiO₂-TDA-2# which has well photocatalytisis and good aqueous solution dispersion and stability as the composite catalyst support, Water solubility Ag/TiO₂（ATA） antibacterial agent was successfully synthesized by photocatalytic reduction. Structure, surface morphology and average particle size of ATA were characterized and confirmed by UV-visible spectrophotometer（UV-vis）, transmission electron microscopy（TEM）, X-ray diffraction（XRD）, energy X-ray analysis（EDS） dispersion, Fourier transform infrared spectroscopy（FTIR） and High Resolution transmission electron microscopy（HR-TEM）.The antibacterial activities of ATA nanoparticles against Escherichia coli（E.coli, ATCC 25922） and Staphylococcus aureus（S.aureus ATCC 6538） were studied by measuring the effect of the ATA nanoparticles on the bacterial growth kinetics in LB Lennox liquid media in the absence of light. The results demonstrated that the minimum inhibit concentration（MIC） of ATA against E.coli and S.aureus were 5.0 μg/mL（the concentration of TiO₂ was 3.95μg/mL,the concentration of Ag was 1.05 μg/m L）and 25.0 μg/mL（the concentration of TiO₂ was 17.74 μg/m L,the concentration of Ag was 5.26 μg/mL）, which was significantly higher than the antimicrobial activity of TiO₂ and Ag. The excellent antibacterial activities of ATA may result from the synergistic effect of Ag and Ti O2. However, Reasons need to carry out follow-up study. Besides, The minimum inhibit concentration（MIC） of ATA against Acinetobacter baumannii（A.baumannii） and Klebsiella pneumonia（K.peneumoniae） were 1.26 μg/mL and 6.25 μg/m L, While the minimum inhibit concentration（MIC） of ATA against Streptococcus epidermidis（S.epidermidis）,Hemolytic streptococcus（H.streptococcus） and Pseudomonas aeruginosa（P.Aeruginosa） were 3.13 μg/m L. Therefore, ATA is a composite material having excellent broad-spectrum antimicrobial activity.The biocompatibility of ATA composite antibacterial agent was analysised by hemolysis assay. Studies have shown that the ATA was non-hemolytic material when it was at the normal used concentration. Morever, ATA composite antibacterial agent is more secure than nano silver that has antibacterial.In order to illustrate the antimicrobial mechanism of ATA, We use isobaric tags for relative and absolute quantitation proteomics technology to study differences between the proteins interaction with ATA and the control. The results demonstrated that the antibacterial mechanism of ATA might be the synergistic effect.ATA nanomaterials will bind together with polymer including nucleic acid after entering into the bacterial, and regulate the target genes, resulting in the loss of normal function; Morever, ATA nanomaterials will affected the ativity of various kinds of transport proteins, leading the imbalance of ion concentration inside the cells, and thus kill the cells.TiO₂ nanotubes were prepared via hydrothermal synthesis using different titanium dioxide as raw material. The results showed that the nanotubes synthesised by TiO₂-TDA-1#,TiO₂-TDA-2# and porous TiO₂ have a clear tubular structure; but the structure of nanotubes using rutile TiO₂ and Degussa P25 TiO₂ were not clear. This could be because the reactions require a higher pressure for rutile titanium dioxide. What’s more, In spite of TiO₂-NT can not degrade methylene blue effectively, It has a strong adsorption capacity on methylene blue.