Surface silanols (Si-OH) play a vital role on fused silica surfaces in chromatography. Here, we used an atmospheric-pressure, gas-phase reactor to modify the inner surface of a gas chromatography, fused silica capillary column (0.53 mm ID) with a small, reactive silane (tris(dimethylamino)methylsilane, TDMAMS). The deposition of TDMAMS on planar witness samples around the capillary was confirmed with X-ray photoelectron spectroscopy (XPS), ex situ spectroscopic ellipsometry (SE), and wetting. The number of surface silanols on unmodified and TDMAMS-modified native oxide-terminated silicon were quantified by tagging with dimethylzinc (DMZ) via atomic layer deposition (ALD) and counting the resulting zinc atoms with high sensitivity-low energy ion scattering (HS-LEIS). A bare, clean native oxide - terminated silicon wafer has 3.66 OH/nm2, which agrees with density functional theory (DFT) calculations from the literature. After TDMAMS modification of native oxide-terminated silicon, the number of surface silanols decreases by a factor of ca. 10 (to 0.31 OH/nm2). Intermediate surface testing (IST) was used to characterize the surface activities of functionalized capillaries. It suggested a significant deactivation/passivation of the capillary with some surface silanols remaining; the modified capillary shows significant deactivation compared to the native/unmodified fused silica tubing. We believe that this methodology for determining the number of residual silanols on silanized fused silica will be enabling for chromatography.

Department of Applied Physics Eindhoven University of Technology 5600 MB Eindhoven the Netherlands

Department of Chemical Engineering Brigham Young University Provo UT 84602 USA

Department of Chemistry and Biochemistry Brigham Young University Provo UT 84602 USA

Institute of Physical Engineering Brno University of Technology Technická 2 Brno 616 69 Czech Republic; CEITEC BUT Brno University of Technology Purkyňova 123 612 00 Brno Czech Republic

Materials Group Avery Dennison Corp 8080 Norton Parkway Mentor OH 44060 USA

Restek Corporation 110 Benner Circle Bellefonte PA 16823 USA

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Area-Selective Atomic Layer Deposition of ZnO on Si\SiO2 Modified with Tris(dimethylamino)methylsilane