Semiempirical Peak Fitting Guided by ab Initio Calculations of X-ray Photoelectron Spectroscopy Narrow Scans of Chemisorbed, Fluorinated Silanes

Abstract

Here, we address the issue of finding correct CF2/CF3 area ratios from X-ray photoelectron spectroscopy (XPS) C 1s narrow scans of materials containing −CH2CH2(CF2) n CF3 (n = 0, 1, 2, ...) moieties. For this work, we modified silicon wafers with four different fluorosilanes. The smallest had a trifluoropropyl (n = 0) moiety, followed by nonafluorohexyl (n = 3), tridecafluoro (n = 5), and finally, heptadecafluoro (n = 7) moieties. Monolayer deposition of the fluorosilanes was confirmed by spectroscopic ellipsometry, wetting, and XPS. Analysis of the trifluoropropyl (n = 0) surface and a sample of polytetrafluoroethylene provided pure-component XPS spectra for −CF3 and −(CF2) n – moieties, respectively. Initial XPS C 1s peak fitting, which follows the literature precedent, was not entirely adequate. To address this issue, six different fitting approaches with increasing complexity and/or input from the Hartree–Fock theory (HF) were considered. Ultimately, we show that by combining HF results with empirical analyses, we obtain more accurate CF2/CF3 area ratios while maintaining high-quality fits.

Improving the hydrophobicity/oleophobicity of polyethylene terephthalate fibrous materials using electron beam‐induced graft polymerization with 2‐(perfluorohexyl)ethyl acrylate monomer and alkyl acrylate monomer

“…Figure 8 shows the results of curve fitting of the bound state on the XPS narrow scan spectra of C1s. Five peaks are observed at about 284.8, 286.3, 288.8, 291.5, and 293.8 eV in the C1s spectrum of the PET fabric in Figure 8, and can be attributed to hydrocarbon group (CC), COC or COH, carbonyl group (CO), CF 2 , and CF 3 , respectively, as reported in several studies 21,22,53,54 . The area ratios of the different chemical bonds were estimated from the curve‐fitting data and are summarized in Table 1.…”

“…CF 2 , and CF 3 , respectively, as reported in several studies. 21,22,53,54 The area ratios of the different chemical bonds were estimated from the curve-fitting data and are summarized in Table 1. For FEA, FEA/BA(C4), and FEA/SA(C18), the CF 2 ratios on the PET fabric surface were 6.2%, 11.1%, and 19.5%, and the CF 3 ratios were 0.5%, 1.8%, and 3.9%, respectively.…”

Thin Organic‐Inorganic Anti‐Fouling Hybrid‐Films for Microreactor Components

“…The presented atomic concentrations are in good agreement with the expected theoretical values according to the perfluorinated surface depicted in Figure 1 and FOTS stoichiometry. However, it is known from the literature [ 55 ] that the CF 2 :CF 3 area ratio from fits is generally below the expected theoretical value.…”

“…The shown C1s core-level spectra exhibit the characteristic shape of a perfluorinated surface both before and after immersion at acidic pH and elevated temperature. [37,38,49,55] The deconvolution divides the recorded spectra into seven main peaks, six of which can clearly be assigned to the organosilan surface modification (Figure 4B,C) with some minor adventitious carbon. As can be seen from the STDRes values, good fits to the C1s envelopes are achieved.…”

Interplay of Hydrophobic Thiol and Polar Epoxy Silicate Groups on Microstructural Development in Low-Alcohol, Crosslinked Sol–Gel Coatings for Corrosion Prevention

“…The nitrogen and fluorine seen in the survey scan are components of the fluorosurfactant used in the coatings. The binding energies at 399.8 eV (N 1s) and 688.8 eV (F 1s) are indicative of nitrogen in amine [26] and the -CF2-CF2-bond [27] , [26] respectively, which are both expected from the surfactant. Figure 4b shows the deconvolution spectra of sulfur 2p for TGST 2:1 typical of spectra for all formulations.…”