Self-cleaning, photocatalytic films on aluminum plates for multi-pollutant air remediation: promoting adhesion and activity by SiO₂ interlayers

Abstract

In recent years, nanoparticles have come under close scrutiny for their possible health and environmental issues, making them less attractive for photocatalytic applications in air or water purification. Replacing free nano-powders with active and stable films is thus a fundamental step towards developing effective photocatalytic devices. Aluminum represents a cheap and technologically-relevant substrate, but its photocatalytic applications have been hampered by adhesion issues and metal ion diffusion within the photocatalytic layer. In this work, the use of silica interlayers is investigated as a strategy to promote adhesion, efficiency and reusability of TiO 2 films deposited on aluminum plates. Films were prepared from stable titania sols to avoid the use of nano-powders. Aluminum substrates with different surface morphology were investigated and the role of the silica interlayer thickness was studied. Films were extensively characterized, studying their structure, morphology, optical properties, adhesion and hardness. Self-cleaning properties were studied with respect to their superhydrophilicity and ability to resist fouling via alkylsilanes.Photocatalytic degradation tests were carried out using both volatile organic compounds (VOC) and NOx, also in recycle tests. The presence of the silica interlayer proved crucial to promote the film

Mimicking Stained Glass: A Hands-On Activity for the Preparation and Characterization of Silica Films Colored with Noble Metal Ions and Nanoparticles

“…The silica sol was prepared at room temperature, following a procedure previously reported: 29 25.4 mL of ethanol was mixed with 2.2 mL of a 1 M HCl aqueous solution and 4.9 mL of tetraethyl orthosilicate (TEOS) and stirred for 1 h. Table 1 summarizes the reagent amounts used for sol preparation.…”

“…In this activity, colored glass was obtained by deposition of a surface coating composed of a silica matrix with embedded color-inducing metal ions and nanoparticles. The silica layer was deposited by spin coating of a colloidal solution (or sol) of silica prepared by a sol–gel method. , The silica colloidal particles contained in the ethanol-based sol can form a uniform silica coating at the surface upon solvent removal, without the need for high temperature heat treatments. This colorless, transparent surface coating is then colored by the deposition of a few drops of a solution of a metal salt on top of the freshly deposited silica layer.…”