Iron oxide is a unique semiconductor material, either as a single nanoparticle, or as a component of multifunctional nanoparticles. Its desirable properties, abundance, non-toxicity, and excellent magnetic properties make it a valuable for many applications. Porous iron oxide nanorods are able to transduce light into heat through the photothermal effect. Photothermal heating arises from the energy dissipated during light absorption leading to rapid temperature rise in close
proximity to the surface of the nanoparticle. The heating effect can be efficiently harnessed to drive/promote different physical phenomena. In this report, we describe the synthesis and properties of porous Fe<sub>3</sub>O<sub>4</sub> for photothermal applications. We then demonstrate their use as photothermally enhanced and recyclable materials for environmental remediation through sorption processes.
This study describes a simple two-step approach to coat gold nanorods with a silica/titania shell. Gold nanorods with an
aspect ratio of 2.5 (L=48±2 and d=19±1) are synthesized by a silver-seed mediated growth approach according to our
previously reported procedure (Hunyadi Murph ACS Symposium Series, Volume 1064, Chapter 8, 2011, 127-163 and
reference herein). Gold nanorods are grown on pre-formed gold nano-seeds in the presence of surfactant,
cetyltrimethylammonium bromide (CTAB), and a small amount of silver ions. A bifunctional linker molecule which has
a thiol group at one end and a silane group at the other is used to derivatize gold nanorods. The silane group is
subsequently reacted with both sodium silicate and titanium isopropoxide to a silica/titania shell around the gold
nanorods. By fine tuning the reaction conditions, the silica/titania shell thickness can be controlled from ~5 to ~40nm.
The resulting nanomaterials are stable, amenable to scale up and can be isolated without core aggregation or
decomposition. These new materials have been characterized by scanning electron microscopy, energy dispersive X-ray
analysis, UV-Vis spectroscopy and dynamic light scattering analysis. Photocatalytic activity of Au-silica/titania
nanomaterials under visible and UV illumination is measured via degradation of a model dye, methyl orange (MO)
under visible and UV illumination. The results indicate a 3 fold improvement in the photocatalytic decomposition rate of
MO under visible illumination vs. UV illumination.