Surface Functionalization of Porous Nanostructured Metal Oxide Thin Films Fabricated by Glancing Angle Deposition

Abstract

We report the application of solution- and vapor-phase siloxane-based methods for tailoring the surface chemistry/properties of highly porous, nanostructured thin films fabricated using glancing angle deposition (GLAD). The GLAD technique produces high surface area films consisting of isolated columns and provides complete control over the film/column morphology. In the present study, the chemical tunability of a variety of metal oxide GLAD films was investigated using solution-based and vapor-phase surface functionalization methodologies. The surface properties and structures of the treated and untreated films were investigated using scanning electron microscopy (SEM), advancing aqueous contact angle measurements, cyclic voltammetry, and X-ray photoelectron spectroscopy (XPS). Results indicate that the surface chemistry of metal oxide GLAD films could be tailored by either method; however, chemical reactivity depends strongly on the metal oxide film material. Chemical tunability is demonstrated through the covalent tethering of numerous chemical moieties onto the exposed and interior surfaces of metal oxide GLAD films of varied structural motifs. Through careful choice of surface modifier, the present derivatization methods afford a full range of aqueous wettability from hydrophilic to superhydrophobic without compromising film structure. These functionalized, nanoconstructed films demonstrate a high degree of tunability over both structural and surface properties, making them well suited for diverse applications such as optical filters or sensors.

Matrix‐free laser desorption/ionization mass spectrometry using silicon glancing angle deposition (GLAD) films

“…Siuzdak's group has reported yoctomole detection limits for small molecules by functionalizing the surface of porous silicon 10, 13. GLAD films are readily functionalized,44, 45 so their good performance compared to porous silicon surfaces made using other techniques suggests their detection limits could be further improved by similar surface functionalization.…”

Perspectives on oblique angle deposition of thin films: From fundamentals to devices

“…In this way, superhydrophobic WCAs as high as 138°and 160°, respectively, were achieved by controlling the deposition angle, substrate rotation and reactor pressure. Veinot et al [560,566] were responsible for some of the earliest works showing the formation of superhydrophobic surfaces consisting of OAD SiO 2 nanocolumns and 3D nanostructures modified by the chemical grafting of siloxane molecules. More recently, a similar approach involving the molecular vapor deposition of silane onto metal OAD nanocolumns has been proposed as a way of fabricating anti-icing surfaces [558].…”

Combined QCM-D/GE as a tool to characterize stimuli-responsive swelling of and protein adsorption on polymer brushes grafted onto 3D-nanostructures

“…Here, electron-beam evaporation at an oblique angle produces nanostructured morphologies, e.g., slanted or straight columns, helices or chevrons, by an atomic shadowing effect. Additionally, the surface of these structures can be modified to add further functionality [21][22][23]. Recently, we reported on the grafting of poly-(acrylic acid) (PAA) Guiselin brushes onto silicon STFs, which exhibit reversible swelling/deswelling characteristics in response to the pH of the surrounding solution [24].…”