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- XPS (4) (entfernen)
Pentylcyanobiphenyl was used successfully as a test molecule to show the acid sites upon some commercial nanoscaled titanium dioxide materials. The surface interactions were investigated in detail using methods sensitive to the surface or to the bulk material, e.g., X-ray photoelectron spectroscopy (XPS), infrared spectroscopy, and thermal analysis. Different oxidation states of surface Ti ions were revealed. Several species were found: the majority were bonded through the nitrogen lone pair of the cyano group, but bonding to the surface OH groups by benzene π electrons might also appear. The N 1s lines of adsorbed 5CB were able to distinguish between Lewis acid and relatively weak Brønsted acid sites.
Methods for characterization of epoxy-functionalized substrates used for microarray applications, prepared by silanization with 3-glycidoxypropyltrimethoxysilane, have been developed. Contact angle measurements, X-ray photoelectron spectroscopy, time of flight secondary ion mass spectrometry and fluorescence based methods have been applied to investigate these epoxy-functionalized microarray substrates. The surface density of epoxy-functionalized glass slides was investigated by fluorescence labeling of surface species utilizing Rhodamine 110 as fluorescence probe.
Functionalized organic layers prepared by plasma processes have complex surface chemistries. The problem of elucidating such chemistries is an extensively studied subject. One of the preponderant methods used to acquire information on specific functional groups is chemical derivatization XPS. In this communication, we focus on rather popular chemical derivatization XPS approaches, for instance, the quantification of amines with 4-trifluoromethyl benzaldehyde and of hydroxyl groups with trifluoroacetic anhydride. Although these procedures have been used for a long period by various laboratories, the use of varying protocols is obvious. Comparison of results is therefore difficult. We discuss steps toward a valid experimental procedure, in particular, the calculation of concentrations, the preparation of test samples, the pitfalls, and the shortcomings.
We investigated the ageing of amine-terminated
self-assembled monolayers (amine-SAMs) on different silica
substrates due to exposure to different ambient gases,
pressures, and/or temperatures using time-of-flight secondary
ion mass spectrometry (ToF-SIMS) with principal component
analysis and complementary methods of surface
analysis as X-ray photoelectron spectroscopy (XPS) and
near edge X-ray absorption fine structure (NEXAFS). The
goal of this study is to examine the durability of primary
amine groups of amine-SAMs stored in a user laboratory
prior to being used as supports for biomolecule immobilization
and other applications. We prepared amine-SAMs on
the native oxides of silicon wafers and glass slides using 3-
aminopropyl triethoxysilane, by using optimized conditions
such as anhydrous organic solvent and reaction time scale of
hours to avoid multilayer growth. Selected commercial
amine-SAM slides have been investigated, too. When the
amine-SAMs are exposed to air, oxygen incorporation
occurs, followed by formation of amide groups. The formation
of oxygen species due to ageing was proved by ToFSIMS,
XPS, and NEXAFS findings such as CNO- secondary
ion emission at m/z 42, observation of the N 1s HNC=O
component peak at 400.2400.3 eV in XPS, and, last but not
least, by formation of a π*(HNC=O) resonance at 401 eV in
the N K-edge X-ray absorption spectrum. It is concluded
that the used multi-method approach comprising complementary
ToF-SIMS, XPS, and NEXAFS analyses is well
suited for a thorough study of chemical aspects of ageing
phenomena of amine-SAM surfaces.