UV‐Light‐Driven Immobilization of Surface‐Functionalized Oxide Nanocrystals onto Silicon

Abstract

TiO2 nanorods (NRs) and γ‐Fe2O3 nanocrystals (NCs) passivated with unsaturated long‐chain carboxylic acids, namely 10‐undecylenic acid (10UDA) and oleic acid (OLEA), are covalently anchored to Si(100) at room temperature by UV‐light‐driven reaction of hydrogenated silicon with the carbon–carbon double bond (–CC–) moieties of the capping surfactants. The high reactivity of vinyl groups towards Si provides a general tool for attaching particles of both materials via Si–C bonds. Interestingly, TiO2 NRs were efficiently attached to silicon even when capped by OLEA. This latter finding has been explained by a photocatalytic mechanism involving the primary role of hydroxyl radicals that can be generated upon bandgap TiO2 photoexcitation with UV light. The increased oxide coverage achievable on Si opens access to further surface manipulation, as demonstrated by the possibility of depositing an additional film of Au nanoparticles onto TiO2 via TiO2‐catalyzed visible‐light‐driven reduction of aqueous AuCl4– ions. Extensive morphological and chemical characterization of the obtained NC‐functionalized Si substrates is provided to support the effectiveness of proposed photochemical approaches.

Optical and Conductive Properties of As-Synthesized Organic-Capped TiO2 Nanorods Highly Dispersible in Polystyrene-block-poly(methyl methacrylate) Diblock Copolymer

“…TUNA current images (3 × 3 μm) taken at voltages of −6, 0, and 6 V for (a) 30, (b) 40, and (c) 50 wt % TiO 2 /PS-b-PMMA nanocomposites and for (d) 30, (e)40, and (f) 50 wt % TiO 2 /PS-b-PMMA after being exposed to UV light for 24 h. The graphs correspond to horizontal section profiles of each −6 and 6 V images.…”

Surface Functionalization of Epoxy‐Resist‐ Based Microcantilevers with Iron Oxide Nanocrystals

“…Fe 2 O 3 NCs were synthesized by thermal decomposition of iron pentacarbonyl precursor in presence of OLEA, OLAM and DDIOL at 250°C with a mean particle size of 9 nm 16. A surface ligand exchange procedure was applied to the as synthesized NCs to remove the pristine OLEA molecules which can suffer from structural changes caused by the high temperature employed in the synthesis 17…”

Nanocomposite materials for photocatalytic degradation of pollutants

“…Such a modification can occur by a ligand exchange procedure, which in principle replaces the original hydrophobic ligand with specifically designed species. For instance, replacing the pristine capping ligand with double bond terminated carboxylic acid TiO 2 NRs and Fe 2 O 3 NCs were covalently anchored onto active silicon substrates by an UV-driven approach, which exploits the homolytic rupture of the double bond under UV irradiation [109]. Recently, NC surface modification with inorganic salt was successfully developed in order to switch their dispersibility from apolar solvents to polar solvents.…”