Fullerenols are polyhydroxylated, water soluble derivatives of fullerene C60, with potential application in medicine as diagnostic agents, antioxidants or nano drug carriers. This paper describes synthesis and physical characterization of a new nanocomposite hydroxyapatite/fullerenol. Surface of the nanocomposite hydroxyapatite/fullerenol is inhomogeneous with the diameter of the particles in the range from 100 nm to 350 nm. The ζ potential of this nanocomposite is ten times lower when compared to hydroxyapatite. Surface phosphate groups of hydroxyapatite are prone to forming hydrogen bonds, when in close contact with hydroxyl groups, which could lead to formation of hydrogen bonds between hydroxyapatite and hydroxyl groups of fullerenol. The surface of hydroxyapatite particles (-2.5 mV) was modified by fullerenol particles, as confirmed by the obtained ζ potential value of the nanocomposite biomaterial hydroxyapatite/fullerenol (-25.0 mV). Keywords: Hydroxyapatite, Fullerenol, Nanocomposite, Surface Analysis.
The role of defects on a substrate surface during the initial stages of
nucleation and growth ofAg deposited electrochemically and physically on
highly oriented pyrolytic graphite (HOPG) has been observed ex situ by
scanning tunneling microscopy (STM). The silver was electrodeposited under
current controlled electrochemical conditions at 26?A/cm2, which
corresponded to a deposition rate of 0.1 monolayers (ML) per second. For
comparison, physical deposition of Ag on HOPG was performed by DC Ar + ion
sputtering, at the same deposition rate and for the same deposition times.
In both cases, Ag grows in an island growth mode, but the distribution of
the islands appears to be quite different. In physical deposition, the Ag
islands are almost homogeneously distributed over the substrate surface and
a slight accumulation of islands on steps does not contribut e significantly
to the overallmorphology. This indicates the crucial role of point defects on the substrate in the initial stages of nucleation. In electrochemical
deposition, more line d defects are observed after a flow of current,
andtheir role in the beginning of the nucleat ion is more pronounced. Lined
defects are responsible for the string-like shaped domains of deposited
atoms. Also, the existence of string-like shaped nucleation exclusion zones
is indicated. The problem of the formation of nucleation exclusion
zones,which appear only in electrochemical deposition, has been reconsidered
and a new explanaton of their formation is given. A mathematical model for the
calculation of the radius of the nucleati on exclusion zone has been
developed.
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