Ambient-ageing processes in amine self-assembled monolayers on microarray slides as studied by ToF-SIMS with principal component analysis, XPS, and NEXAFS spectroscopy

Abstract

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 ToF-SIMS, XPS, and NEXAFS findings such as CNO(-) secondary ion emission at m/z 42, observation of the N 1s HNC=O component peak at 400.2-400.3 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.

Role of molecular properties of ulvans on their ability to elaborate antiadhesive surfaces

“…Three components corresponding to primary amino function at 399 eV, nitrogen from amide bonds at 400.2 eV and primary ammonium function (NH 3 + ) and nitrogen from residual activated ester at 401.9 eV were observed . An increase in the contribution from NH 3 + and nitrogen from residual activated ester, was found, compared to those made in normal activation condition (about 1.5–2 for polysaccharides immobilized by an excess of activation reagents).…”

IR‐ and NEXAFS‐spectroscopic characterization of plasma‐nitrogenated polyolefin surfaces

“…Amides are often observed as aging products of nitrogen containing organic molecules. They are typically formed by oxidation when the samples were exposed to ambient air for a while . In the given case, while the origin of amide species is probably not an amide contamination of educt amines which should be visible in IR spectra shown as supplementary material (Figure S2), oxidation of amines re‐formed by partial hydrolysis of the product imines could possibly play a role.…”

Coupling of kenaf Biochar and Magnetic BiFeO3 onto Cross-Linked Chitosan for Enhancing Separation Performance and Cr(VI) Ions Removal Efficiency

“…From Figure 2b, the main peaks of the C 1s spectrum of CKB at binding energies of 284.8, 285.3, 286.98, and 288.58 eV can be assigned to C-C, C-N, C-O-C, and C=O groups [28], respectively, which belong to both chitosan and kenaf biochar. N 1s spectrum in Figure 2c shows three peaks at 399.9, 400.4, and 402.5 eV, referring to -NH2, -NHCO-, and C-N, respectively [29,30]. Figure 2d shows XPS peak deconvolution for O1s spectrum of CKB.…”