Biomedical Engineering Reference
In-Depth Information
The existing synthesis technology allows the production of UDD
on an industrial scale (tons per year). UDD powders are produced
commercially in several centers in Russia, Ukraine, Byelorussia,
Bulgaria, China, and Japan. The technology of UDD production
consists of two steps: detonation synthesis of diamond-carbon
soot and post-synthesis chemical purification. The main range of
UDD particle sizes (some nanometers) depends only slightly on
the technological details of production [1, 20, 21]. It is interesting
to note that nanodiamond particles of similar sizes were found in
meteorites [22] and are believed to belong to the family of “presolar
dust grains” formed during star explosions [23]. This “invariance”
of nanodiamond particle size was theoretically investigated using
the model of carbon clustering and diamond/graphite transition in
detonation regime [24].
Due to the small sizes of UDD particles the surface may be covered
by a variety of O-, H-, N-containing functional groups (up to 20% by
weight) with different chemical composition and structure [25]. In
fact, an UDD nanoparticle should be considered as an inert diamond
core covered by the chemically active shell of complex nature.
In contrast to particle size, the surface chemistry of UDD strongly
depends on the details of production technology [26]. The stage of
chemical purification, which can vary from producer to producer,
is the main factor governing the formation of specific chemical
properties of UDD surface [27-30]. The nature and content of
surface functional groups and hence the chemical activity of UDD
are specifically dependent on the production method.
From this point of view, the nanoproducts offered by different
producers sunder the global name “detonation nanodiamonds”
should be considered as different materials. Our experience
indicates that the surface chemistry of UDD samples from even the
same trademark can be different due to uncontrolled variation in
the details of synthesis technology. This difference can lead to the
lack of reproducibility and must be taken into consideration for the
technological applications of as received UDD.
To decrease the polyfunctional character of the surface of as-
received UDD and to obtain predominantly monofunctional surface
layers, the UDD is subjected to chemical treatment (fluorination
[31, 32], chlorination [33, 34], hydrogenation [35, 36], and others
[37]). The key feature of UDD is the possibility to functionalize
the surface by introducing specific chemical groups, including the
