Background: Gold nanostructures have excellent optical properties, namely localized surface plasmon resonance (LSPR), which makes them suitable for a broad range of applications. The LSPR of Au nanostructures can be manipulated by tuning its shape, size, wall thickness, and other features. Currently, nanoboxes (hollow nanocubes) are limited to wall thicknesses above 5 nm due to process limitations. Nanocages (hollow interiors and porous walls) further extend the tunable LSPR range, but it has been difficult to produce nanocubes with sharp corners and small sizes due to complications inherent to the galvanic replacement, alloying, and dealloying processes required.
Technology: Dong Qin, Xiaojun Sun, and Junki Kim from the School of Materials Science and Engineering at Georgia Tech have developed a simple method of fabricating Au/Pt/Pd-based nanoboxes as small as 20 nm for the outer edge length, together with well-defined openings at the corners and walls with fewer than ten atomic layers (or <2 nm in thickness). The method relies on the selective formation of Ag2O at the corners of Ag nanocubes followed by the conformal deposition of Au/Pt/Pd on the side faces in a layer-by-layer fashion. After the layers are formed on the side faces to generate Ag@Au/Pt/Pd core-shell nanocubes, the Ag2O patches at the corners are selectively removed using ascorbic acid, allowing the removal of the Ag core by H2O2 etching without breaking the ultrathin Au/Pt/Pd shell. This new approach works well for Ag nanocubes 38 nm and 18 nm in edge length, and the wall thickness of the nanoboxes can be readily controlled at 2 nm. Ultrathin Au nanoboxes with controllable openings at the corners exhibit strong optical absorption in the 835 to 1135 nm range, making them ideal for biomedical applications.
Potential Commercial Applications: Due to their strong adsorption in the near infrared region, ultrathin Au nanoboxes would find their uses in biomedical applications, e.g., as contrast agents for optical imaging or as capsules for controlled release. Pt and Pd nanoboxes have potentials uses as catalysts in the automobile industry.
Benefits / Advantages: