Biomedical Engineering Reference
In-Depth Information
grafting of different organic functionalities, in order to modify the
chemical activity of UDD in a way suitable for their subsequent
practical applications (see reviews [19, 38]).
The great importance of surface chemistry of UDD requires a
deep investigation of the properties of functional groups, both at
the stage of production and after subsequent chemical modification.
Characterization of surface groups on UDD is usually achieved by
Fourier transform infrared (FTIR) spectroscopy [25, 27, 29, 30, 34,
35], because diamond is transparent in IR-region and the IR-spectra
of UDD are mainly produced by surface species. X-ray photoelectron
spectroscopy (XPS) was also used for this purpose [31, 39, 40].
The main disadvantages of these methods are the relatively low
sensitivity and difficulties in data interpretation to obtain direct
information on the chemical composition of surface groups.
The mass spectrometry analysis of chemical composition of
gases evolved from the solid sample during programmed heating
in vacuum or in inert atmosphere, so-called thermal desorption
mass spectrometry (TDMS), is a technique providing information
on the chemical composition and the thermal stability of surface
species. TDMS was widely used to study the surface chemistry of
dispersed carbon materials [41, 42], diamond monocrystals [43] and
diamond powders [44]. TDMS seems to be a promising technique for
characterization of UDD surface as well [26].
6.2 A Short Survey of Applications of Thermal
Desorption Mass Spectrometry to the Study
of the Surface of Diamond Materials
TDMS is a method of characterizing the surface species by pro-
grammed heating of the sample under vacuum and simultaneously
detecting of the evolved gas by means of a mass spectrometer. During
the temperature increase some adsorbed species and decomposition
products of surface functional groups escape from the surface at
different temperatures causing a rise in the pressure of a specific mass
component. The results of measurements usually are represented in
the form of temperature profiles (spectra of thermal desorption) of
ionic fragments with different masses in the mass spectrum. This
method is characterized by high sensitivity and high information
content. Besides the information about the chemical composition of
