A new approach for the achievement of stable aqueous dispersions of carbon nanotubes.

A novel methodology to prepare stable aqueous dispersions of raw single- and multi-walled carbon nanotubes is reported, based on dispersions previously prepared in tetrahydrofuran containing a phenol that donates electrons to nanotubes and provides colloidal stability through electrostatic repulsion. A proposed mechanism for the stabilization of the dispersions is presented. Conductive and transparent thin films are prepared through a liquid/liquid interfacial route starting from these dispersions.

Electrostatic stabilization of multi-walled carbon nanotubes dispersed in nonaqueous media.

Dispersing carbon nanotubes is an easy and low-cost way to manipulate these solids and allows the preparation of more complex materials or devices, so it is fundamental for further uses that these dispersions have controlled properties and high colloidal stability. In this work we report the spontaneous electrical charge build-up in pristine multi-walled carbon nanotubes dispersed in common organic solvents such as chloroform and tetrahydrofuran and the achievement of dispersions stable for long periods without adding passivant agents or functional groups on nanotubes surface. Results from electrokinetics, homo- and heterocoagulation provided macroscopic evidences that carbon nanotubes acquire electric charges after dispersion in some organic liquids and we confirmed this process by measuring in situ Raman spectra of the nanotubes dispersions with higher surface electric potentials. We also show that the signal of electric potential of the dispersions can be predicted by the acid-base behaviour of the dispersing medium, corroborating previously reports for other dispersions of carbon nanomaterials.

Structural aspects of graphitic carbon modified SBA-15 mesoporous silica and biological interactions with red blood cells and plasma proteins.

Functional mesoporous materials have been worldwide studied for different applications. Mesoporous silicas are highlighted due to the synthetic possibilities for the preparation of such materials with different particle sizes and morphologies, and controlled pores sizes and structures. Moreover, the silica superficial silanol groups are explored in several chemical modifications, leading to functional materials with tuned functionalities and properties. In this work, an organo-functionalization and pyrolysis synthetic procedure is used to obtain graphitic carbon modified mesoporous SBA-15 silica. The carbon content was tuned during the functionalization step, and the graphitic nanodomains were formed in the pores surface and particles outer surface. Textural and small angle X-ray diffraction analysis accessed the presence of the carbon nanostructures inside the SBA-15 mesopores. Advanced microanalysis using electron energy loss spectroscopy coupled to a transmission electron microscope had confirmed the carbon distribution along the silica pores, which gives higher hydrophobicity and changed the interaction of the mesoporous material with biological systems. Finally, the influence of the surface modification with graphitic carbon species over the interaction with human red blood cells (hemolysis) and human blood plasma (protein corona formation) was elucidated for the very first time for this kind of functional materials. It was observed that the graphitic carbon species considerably reduced the hemolytic effect of the silica particles, and was responsible for modulating the loading and composition of the hard corona plasma proteins. This work deepness the fundamental knowledge on the interaction between such nanomaterials and biological systems, one step further the use of these modified silicas in biomedical applications.