Templated Synthesis And Characterizations Of High Moment Magnetic Nanoparticles For Bioapplications

Magnetic nanoparticles have been widely used for biomedical applications such as drug and gene delivery, hyperthermia treatment of cancer, MRI contrast enhancement, cell labeling and magnetic separation. We present two new types of magnetic nanoparticles for bioapplications; granular superparamagnetic gold nanoparticles and multilayered nanodisks. Granular superparamagnetic gold nanoparticles consist of superparamagnetic islands embedded in a gold matrix. Multilayered nanodisks consist of two magnetic layers separated by a non-magnetic layer with two capping layers. Capping layers such as gold provide functionalization sites for biomolecule attachment. These nanoparticles possess two key magnetic requirements for bioapplications, a high saturation magnetic moment and a near-zero remanence, and have a great potential of combining both magnetic and gold nanoparticle into one nanoentity to provide multifunctionality. A scalable, inexpensive, and simple template-based synthesis process to produce nanoparticles in large quantity has been developed. Anodic aluminum oxide (AAO) has been utilized to generate very large area templates with feature size ranging from 20 nm to 100 nm. Thick and ultra thin (< 200 nm) AAO templates have been successfully fabricated by anodization. The anodization process of ultra thin AAO has been studied. Using such template, a new type of nanoparticle, truncated hollow cones, can be produced. Multilayered and granular nanodisks have been fabricated by evaporation and electrodeposition into the AAO templates and their magnetic properties have been characterized. Using thick AAO template, multilayered or granular nanodisks are deposited through electrodeposition. A one-bath electrolyte has been developed to deposit both gold and magnetic materials (Co and Fe). The designed properties have been achieved for such nanodisks, including high moment, low remanence and tunable saturation field. Pillar-template has been generated using the thick AAO template, and has also been explored to fabricate nanodisks in large quantity.