Rui Filipe Araújo

Efficient dispersion of multi-walled carbon nanotubes in aqueous solution by non-covalent interaction with perylene bisimides

A selection of bolaamphiphilic perylene bisimides (PBI) were prepared from the reaction of perylenetetracarboxylic dianhydride with α-amino acids. These molecules were obtained in good yield using a simple synthetic protocol and avoiding the need for complex purification methods, a major advantage for future applications. Carbon nanotubes (CNT) were dispersed in an aqueous solution of the PBI, buffered at pH 7, and the suspension was studied by absorption and emission spectroscopy. PBI functionalized with Boc-lysine and phenylalanine led to an excellent suspension of CNT in water, stable for at least 24 h at room temperature. Theoretical calculations were used to support and explain the experimental observations.

Processing strategies for smart electroconductive carbon nanotube-based bioceramic bone grafts

Electroconductive bone grafts have been designed to control bone regeneration. Contrary to polymeric matrices, the translation of the carbon nanotube (CNT) electroconductivity into oxide ceramics is challenging due to the CNT oxidation during sintering. Sintering strategies involving reactive-bed pressureless sintering (RB + P) and hot-pressing (HP) were optimized towards prevention of CNT oxidation in glass/hydroxyapatite (HA) matrices. Both showed CNT retentions up to 80%, even at 1300 °C, yielding an increase of the electroconductivity in ten orders of magnitude relative to the matrix. The RB + P CNT compacts showed higher electroconductivity by ∼170% than the HP ones due to the lower damage to CNTs of the former route. Even so, highly reproducible conductivities with statistical variation below 5% and dense compacts up to 96% were only obtained by HP. The hot-pressed CNT compacts possessed no acute toxicity in a human osteoblastic cell line. A normal cellular adhesion and a marked orientation of the cell growth were observed over the CNT composites, with a proliferation/differentiation relationship favouring osteoblastic functional activity. These sintering strategies offer new insights into the sintering of electroconductive CNT containing bioactive ceramics with unlimited geometries for electrotherapy of the bone tissue.