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Graphite and multiwall carbon nanotube surfaces were functionalized by vacuum-ultraviolet induced photochemistry in NH3 or O2, in order to introduce amino- (NH2) or hydroxyl (OH) functionalities, respectively. Modified surfaces were characterized by X-ray photoelectron spectroscopy (XPS), which showed significant incorporation of nitrogen (N) and oxygen (O) at the materials surface. While high-resolution XP spectra did not yield much specific information about the incorporated functional groups, chemical derivatization with 4-trifluoromethyl benzaldehyde and trifluoroacetic anhydride accompanied by XPS enabled quantification of NH2 and OH groups, respectively. Using near edge X-ray absorption fine structure spectroscopy, we assessed the conservation of the aromatic structure following functionalization treatments.
Fluorinated Boron-Dipyrromethene (BODIPY) dyes: bright and versatile probes for surface analysis
(2013)
A family of bright boron-dipyrromethene-type fluorophores with a high number of fluorine atoms (F-BODIPYs) has been developed and characterized by X-ray crystallography and optical spectroscopy. The introduction of 3,5-bis(trifluoromethyl)phenyl and pentafluorophenyl moieties significantly enhances the photostability of such dyes, yielding for instance photostable near-infrared (NIR) fluorophores that show emission maxima>750 nm, when the BODIPY's π system is extended with two (dimethylamino)styryl and (dimethylamino)naphthastyryl moieties, or green-emitting BODIPYs with fluorescence quantum yields of unity. When equipped with a suitable group that selectively reacts for instance with amines, F-BODIPYs can be used as potent dual labels for the quantification of primary amino groups on surfaces by X-ray photoelectron spectroscopy (XPS) and fluorescence, two powerful yet complementary tools for the analysis of organic surface functional groups. The advantage of reactive F-BODIPYs is that they allow a fast and non-destructive mapping of the labelled supports with conventional fluorescence scanners and a subsequent quantification of selected areas of the same sample by the potentially traceable XPS technique. The performance is exemplarily shown here for the assessment of the amino group density on SiO2 supports, one of the most common reactive silica supports, in particular, for standard microarray applications.
A toluene solution of 4,4´-methylenebis(2,6-diethylaniline) was spin coated on Si wafers. The samples were derivatized with pentafluorobenzaldehyde (PFB) in order to determine the primary amino groups on the surface. XPS C 1s and N 1s and C and N K-edge NEXAFS of underivatized and derivatized films were carefully analyzed. The result was that after 10 min of exposure the gas-surface reaction was already completed. A reasonable derivatization reaction yield in the order of 90% is derived from the experiments. This number correlates well to a reaction yield obtained by a wet chemical approach.