Fabrication of versatile metal oxide nanostructures using hybrid organic-inorganic materials and their applications

Abstract

A Simple Maskless Top-Down Process for The Fabrication of Vertically Aligned High Density Metal Oxide Nanowires

Vertically aligned metal oxide nanowire arrays were successfully synthesized via a cost-efficient maskless top-down approach. High density nanowires are formed by a simple spin-coating and oxygen plasma process without any artificial mask on the surface of the iron-containing polymer film. Highly crystalline hematite nanowires with a diameter of 38-45 nm and a high aspect ratio of 131 are uniformly produced over large areas after calcination. The high density graphene/megnatite nanostructure created by pyrolyzing organic/iron oxide nanowires with the three-dimensional morphology provided an excellent substrate for highly enhanced Raman scattering with an enhancement factor of up to $7.0 \times 10^4$ due to light trapping effects of the absorbed light in the three-dimensional graphene forest. Our maskless top-down approach to the fabrication of metal oxide nanowires offers unique advantages of a solution-based process to easily overcome the limit in the morphology and substrate-dependent property of the nanowire synthesis. This technique may have great practical potential as a simple, rapid, and reproducible technique for the fabrication of high density and high aspect ratio metal oxide nanowires that are useful in various applications.

Diazoketo-Functionalized POSS Resist for The High-Performance Replica Molds of Ultraviolet-Nanoimprint Lithography

Novel polyhedral oligomeric silsesquioxane (POSS) resists, which are based on a new photo-crosslinking system via Wolff rearrangement, are developed as ideal replica mold materials for ultraviolet-nanoimprint lithography. These POSS resist materials are synthesized by incorporating diazoketo and hydroxyl groups into the POSS core. The resist materials have exhibited a variety of desirable properties as replica molds, such as high modulus, low shrinkage ratio, high transparency, low surface energy, and resistance to organic solvents. The resultant replica molds exhibit a high resolution patterning capacity. These economic fabrication methods of replica molds with high mechanical durability and good releasing properties are potentially useful for versatile applications in the area of mold-based lithography.

Patterned Functionalized Self-assembled Monolayers via Inkless Micro-Contact Printing for Site-Specific Immobilization of Biomolecules

Site-specific immobilization of biomolecules is fundamentally important for a variety of applications in biosensors and biotechnology. Herein, we report a fabrication technique that allows site-specific chemical functionalization followed by biomolecular immobilization through ‘inkless micro-contact printing’ ($I\mu CP$), which utilizes out-diffused and transfer-printed polydimethylsiloxane (PDMS) oligomers from a PDMS stamp possessing pre-defined structural features. Using this technique, oligomeric PDMS-patterned surfaces of multiple length scales on Au substrates were fabricated over large areas with a simple one-step contact printing. The patterned PDMS oligomers and bare Au regions were selectively functionalized with self-assembled monolayers (SAMs) of amine-terminated silane and carboxylic acid-terminated thiol, respectively. The surface functionalization and patterning were systematically characterized using FT-IR, SEM, AFM, XPS, and contact angle measurements. Finally, the potential of this technique for site-specific biomolecular patterning was demonstrated using immobilization of fluorescently-labeled lectin and streptavidin.