multi-walled carbon nanotubes
single-walled carbon nanotubes
interaction carbon nanotubes with water molecules
influence of carbon nanotubes on growth and reproduction of microorganisms
O. V. Nechaeva, G. V. Torgashov, O. E. Glukhova, N. F. Permyakova, A. N. Kushnarenko, N. P. Konnov, М. V.Samarskiy
In this paper we present the theoretical and experimental study of water-SWNT interaction and the study of the influence of nutrient medium transportation by nanotubes on the growth, morphological and other properties of gram-positive and gram-negative bacteria.
We modelled the interaction of SWNTs with water using molecular mechanics method (MM+) within several picoseconds at 300K. The ability of nanotube for sucking in water molecules until full capsulation can be explained by Van-der-Vaals attraction between edge atoms of nanotube and water molecule. H2O molecules take position only along the symmetry axis of nanotube, what one can explain by its small diameter (0.7 nm). In the larger nanotubes (with diameters about 0.83 nm and 0.96 nm) water molecules draw up along a spiral inside nanotube.
Experimants on bacteria were carried out in nutrient peptide medium. We used multi-wall carbon nanotubes (MWNTs) having diameter between 10 and 20 nm and length of 0.2-0.7 μm. Graphite was used to control the influence of nanotubes on the microorganisms. As test microorganisms we took ones, differing in structure of cellular membrane (gram-negative Escherichia coli and gram-positive Stafylococcus aureus, Bacillus cereus), in cellular morphology (bacillus, coccus) and differing in the shape of colonies which have been grown in nutrient medium.
Our experiments showed that introducing graphite into nutrient medium have no effect on the growth and reproduction of microorganisms. On the contrary, nanotubes introducing intobeef-extract agar with Escherichia coli stimulates growth of the culture, because number of colonies was for sure greater than that of the reference bacterial inoculation. The influence of nanotubes on the morphology of Escherichia coli colonies appeared in their aggregation. The separate colonies had a white tint, they were large (5-6 mm) in comparison with the reference ones, which were semi-transparent, colorless, about 2-3 mm in diameter. Staphilococcus cultivation with MWNTs lead to insignificant increase of the number of colonies, with prevalence of pigmented yellow ones, in contrast with the white reference colonies. It was hard to determine the influence of MWNTs on the growth of bacillus, because bacillus formed a huge number of root-like sprouts. The effect of MWNTs on bacillus, in contrast to reference samples, where they had mostly a M-form with opaque tint, was accompanied their dissociation with subsequent growth in beef-extract agar with more defined R-form.
It was theoretically shown that thin nanotubes of subnanometer diameter able to suck in the water molecules and to hold them inside, what is caused by Van-der-Vaals attraction between edge carbon atoms and water molecules. That means that nanotubes can be used as nanoreserviors. His fact implies the similar effect for thick nanotubes in the water with beef-extract agar.
The influence of MWNTs on dissociation of the microorganisms after their addition to culture medium. We have discovered the stimulation of growth of the gram-negative bacteria in comparison with insignificant increase of growth of the gram-positive coccus and bacillus. However, the further investigations are necessary to explain the effects of colony aggregation and of changing colony structure.