Quantification of Silane Molecules on Oxidized Silicon: Are there Options for a Traceable and Absolute Determination?

Abstract

Organosilanes are used routinely to functionalize various support materials for further modifications. Nevertheless, reliable quantitative information about surface functional group densities after layer formation is rarely available. Here, we present the analysis of thin organic nanolayers made from nitrogen containing silane molecules on naturally oxidized silicon wafers with reference-free total reflection X-ray fluorescence (TXRF) and X-ray photoelectron spectroscopy (XPS). An areic density of 2-4 silane molecules per nm(2) was calculated from the layer's nitrogen mass deposition per area unit obtained by reference-free TXRF. Complementary energy and angle-resolved XPS (ER/AR-XPS) in the Si 2p core-level region was used to analyze the outermost surface region of the organic (silane layer)-inorganic (silicon wafer) interface. Different coexisting silicon species as silicon, native silicon oxide, and silane were identified and quantified. As a result of the presented proof-of-concept, absolute and traceable values for the areic density of silanes containing nitrogen as intrinsic marker are obtained by calibration of the XPS methods with reference-free TXRF. Furthermore, ER/AR-XPS is shown to facilitate the determination of areic densities in (mono)layers made from silanes having no heteroatomic marker other than silicon. After calibration with reference-free TXRF, these areic densities of silane molecules can be determined when using the XPS component intensity of the silane's silicon atom.

Quantification of amine functional groups on silica nanoparticles: a multi-method approach

“…Studies of amine and carboxylic acid functionalized polymer and clay NPS have determined that anywhere from a few percent to approximately all of the functional groups can be covalently modied. 2,7,18,43,44 With the exception of an assay based on reaction of maleimide with cysteine, 45 most studies have reported covalent modication of low fractions of total amine with larger probes or reagents generally having lower coupling efficiency. The results in Table 1 demonstrate that a minimum of 50% of total amines react with the reagents used for the two colorimetric assays for silica NPs, with over 70% modication achieved for most samples.…”

Dimethylimidazolium-Functionalized Polybenzimidazole and Its Organic–Inorganic Hybrid Membranes for Anion Exchange Membrane Fuel Cells

“…Moreover, Figures 5b and 5c show the XPS full spectrum and high-resolution spectrum of Si 2p core-level peak for the PBI-DIm-Si hybrid membrane. The Si 2p peak can be deconvoluted into two sub-peaks at 101.7 eV for silane and 103.3 eV for silica [51], revealing that the partial silicon element was converted from organic silane to inorganic silica. This result confirmed the formation of the silica-based component in the hybrid membrane.…”

Probing Lithium-Ion Battery Electrolytes with Laboratory Near-Ambient Pressure XPS

“…was referenced to main O 1s peak component of molecular O 2 located at 539.3 eV[25,26] 2. A relative uncertainty of 20% has to be considered for the relative peak component areas[31,32] 3. B.E.…”