Surface Enhanced DNP Assisted Solid-State NMR of Functionalized SiO₂ Coated Polycarbonate Membranes

Abstract

Surface enhanced solid-state NMR by dynamic nuclear polarization (DNP SENS) enables the characterization of the inner-pore surface functionalization of porous etched ion-track membranes exhibiting low specific surface areas compared to typical SBA- or MCM-type mesoporous silica materials. The membranes were conformally coated with a 5 nm thin SiO2 layer by atomic layer deposition. This layer was subsequently modified by aminopropyl silane linkers that allow further functionalization via the terminal amine group. The results evidence that in principle DNP SENS is a capable tool to analyze more complex porous systems, e.g. bioinspired functional etched ion-track membranes down to the molecular level. These results are relevant also for single nanopore systems, for which a direct analysis of the channel surface functionalization is not feasible by classical characterization methods. The applicability of DNP SENS to complex porous systems requires the optimization of the sample preparation and measurement parameters.

Small Molecules, Non-Covalent Interactions, and Confinement

“…60-75 ppm proves the formation of the characteristic Tn-groups, which result from the binding of APTES to the silica inside the channels. 29 Si CPMAS spectra (i) revealing the characteristic Tn-groups in the tenfold magnefication (i) (adapted from [196])).…”

“…In the remainder of this section, some characteristic examples of single component liquids, such as small polar, nonpolar, and aromatic molecules, confined in mesoporous silica are discussed. The competition of these interactions leads to pronounced changes of their phase behavior, in 29 Si CPMAS spectra (i) revealing the characteristic T n -groups in the tenfold magnefication (ii) (adapted from [196])).…”

“…Figure 3. a): Sketch of the three-step process to synthesize amine functionalized silica coated porous polycarbonate-membranes (see text for details). b): DNP enhanced29 Si CPMAS spectra (i) revealing the characteristic Tn-groups in the tenfold magnefication (i) (adapted from[196])).…”

Chemically Modified Silica Materials as Model Systems for the Characterization of Water-Surface Interactions

“…or polyethylene terephthalate (PET) are typical examples where this problem is grave. In a recent study we applied the DNP enhanced NMR technique [70] to investigate the functionalization of the inner-pore surfaces of porous etched iontrack membranes conformally coated with a 5 nm thin SiO 2 layer by atomic layer deposition (ALD) and subsequently modified by aminopropyl silane linkers. The functionalization of these membranes is monitored by DNP enhanced 13 C-and 29 Si-solid state NMR.…”

“…The signals of the T n -groups are clearly visible in the DNP enhanced spectrum, showing the successful functionalization of the silica coated ion-tracks. For further details see the paper by Kumari et al [70].…”