The viscoelastic properties of human kidney cell lines from different tumor types (carcinoma (A-498) and adenocarcinoma (ACHN)) are compared to a non-tumorigenic cell line (RC-124). Our methodology is based on the mapping of viscoelastic properties (elasticity modulus E and apparent viscosity η) over the surface of tens of individual cells with atomic force microscopy (AFM). The viscoelastic properties are averaged over datasets as large as 15000 data points per cell line. We also propose a model to estimate the apparent viscosity of soft materials using the hysteresis observed in conventional AFM deflection-displacement curves, without any modification to the standard AFM apparatus. The comparison of the three cell lines show that the non-tumorigenic cells are less deformable and more viscous than cancerous cells, and that cancer cell lines have distinctive viscoelastic properties. In particular, we obtained that E(RC-124) > E(A-498) > E(ACHN) and η(RC-124) > η(A-498) > η(ACHN).

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The vibrational properties of double-walled carbon nanotubes (DWNTs) is investigated by high-pressure resonance Raman scattering up to 30 GPa in two different pressure-transmitting media (PTM): paraffin oil and NaCl. The protection effect on the outer tube during compression is verified .The collapse of DWNTs is experimentally observed for the first time, showing to be two-step: the onset of the outer 1.56 nm diameter tube collapse at ∼21 GPa is followed by the collapse of the inner 0.86 nm diameter tube at a higher pressure of ∼25 GPa. This observation is supported by calculations. We show that filling a tube with another tube leads to a pressure stabilization against collapse, in strong opposition to what is observed when filling a tube with fullerenes or iodine. The collapse pressure in DWNTs appears to follow a 1/d tav 3 law, where d tav is the average diameter from the inner and outer tubes, in agreement with predictions [ Yang X. Yang X. Appl. Phys. Lett.200689113101]. Contrary to SWNTs and peapods, for DWNTs, the observed collapse pressure is independent of the PTM nature. Those differences are discussed in terms of tube filling homogeneity and of the separate roles of inner and outer tubes: the outer tube offers chemical screening to the inner tube, whereas the inner tube guarantees mechanical support to the outer one. This leads to high collapse pressure independent of the DWNT environnment: a characteristic that makes DWNTs ideal fillers for composite nanomaterials for high load mechanical support.

Neste trabalho reportamos reações de troca iônica e decomposição térmica em nanotubos de óxido de titânio, obtidos pelo tratamento hidrotérmico de TiO 2 e NaOH. Considerando os resultados obtidos, sugerimos uma nova composição química para os nanotubos: Na 2 Ti 3 O 7 ·nH 2 O. Os resultados também indicam que a estrutura da parede dos nanotubos seria isoestrutural às lamelas observadas para o Na 2 Ti 3 O 7 bulk. Dependendo da natureza da lavagem (água deionizada ou solução ácida) executada no nanotubo após o tratamento hidrotérmico a concentração de íons Na + pode ser modificada através de um processo de troca iônica do Na + por H + . Tais resultados permitem sugerir a seguinte fórmula química geral para os nanotubos obtidos: Na 2-x H x Ti 3 O 7 ·nH 2 O (0≤ x ≤2), sendo x dependente das condições de lavagens.In this paper we report the ion exchange reactions and the thermal decomposition of titanium oxide nanotubes, obtained by hydrothermal treatment of TiO 2 and NaOH. Based on these results we propose a new composition for the as-prepared nanotubes as Na 2 Ti 3 O 7 ·nH 2 O. Our results also suggest that nanotube walls have structure similar to those observed in the layer of the bulk Na 2 Ti 3 O 7 . Depending on how the washing process is performed on the nanotubes (water or acid solutions) the Na + content can be modified via the exchange reaction of Na + by H + . Thus, a general chemical formula was also proposed: Na 2-x H x Ti 3 O 7 ·nH 2 O (0≤ x ≤2), x being dependent on the washing process.Keywords: titanate nanotubes, nanorods, TiO 2 , photocatalysis, hydrothermal treatment IntroductionThe discovery of carbon nanotubes in early 90's opened a new research area in materials science. 1 Since then, much attention has been given to the study and search for new materials with tubular structures. The understanding of nanotube formation mechanisms has significantly improved but a clear picture of this process is still an open subject. Since carbon nanotubes originate from graphite layers (graphene) a lot of effort has been devoted to prepare nanotubes from other layered materials. After carbon nanotubes the first studied inorganic nanotubes were WS 2 , MoS 2 , BN and NbS 2 . [2][3][4][5] The preparation of these nanotubes from layered materials leads to the thought that is possible to prepare nanotubes from all materials whose bulk counterpart is a layered compound. Nowadays, a considerable list of inorganic nanotubes is known and it is increasing at an amazing rate. Among the inorganic nanotubes, titanium oxide nanotubes are very attractive because these nanostructures are promising for applications as photocatalysts, UV absorbers, dye-sensitizing solar cells, self-cleaning devices, and catalyst supports. 6,7 Kasuga et al. 8 reported the preparation of titanium oxide nanotubes through hydrothermal treatment of TiO 2 -SiO 2 powders in aqueous NaOH solutions. This preparation method is very simple and inexpensive. However, a great debate has been established in the literature regarding the formation mechanism, compo...

By using first principles calculations we report a chemical doping induced gap in graphene.The structural and electronic properties of CrO 3 interacting with graphene layer are calculated using ab initio methods based on the density functional theory. The CrO 3 acts as an electron acceptor modifying the original electronic and magnetic properties of the graphene surface through a chemical adsorption. The changes induced in the electronic properties are strongly dependent of the CrO 3 adsorption site and for some sites it is possible to open a gap in the electronic band structure. Spin polarization effects are also predicted for some adsorption configurations.

The interaction of 1,2-dichlorobenzene (DCB) with carbon nanotubes is analyzed by experimental and theoretical methods. Using first-principles calculations we studied the structural and electronic behavior of DCB interacting with a semiconductor (8,0) single-wall carbon nanotube (SWNT). We have found that the DCB weakly interacts with a perfect SWNT surface, but this interaction is slightly stronger when the SWNT surface has structural vacancies. Resonant Raman experiments performed on DCB-adsorbed SWNTs confirm the weak DCB−SWNT interaction, as suggested by the ab initio simulations.

Bi 2 W O 6 ferroelectric single crystal was investigated by micro-Raman scattering and infrared spectroscopies. Symmetry of modes was established and the mode assignment was proposed.

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