Nanosphere lithography: I. Fabrication and characterization of large area silver nanoparticle arrays. II. Electrochemical tuning of silver nanoparticle size. III. Nanoparticle shape as a function of size for silver, gold, cobalt, palladium, and platinum nanoparticle.

摘要

The fabrication and characterization of large metal nanoparticle arrays via nanosphere lithography (NSL) is discussed. Large area (viz., ∼1cm 2) arrays of uniform nanoparticles are required for many applications including nanoparticle optical devices, heterogeneous catalysis, and biosensors. With the NSL approach, the quality of the 2D colloidal crystal mask is the most important factor influencing the uniformity and structural integrity of the final nanoparticle array. Several different self-assembly techniques for the formation of the 2D colloidal crystal mask were evaluated. A horizontal form of convective self-assembly was found to produce large area uniform arrays in a consistent, operator independent manner.; Quantitative evaluation of these large area arrays was achieved with scanning UV-vis extinction spectroscopy. With this technique, the localized surface plasmon resonance (LSPR) is monitored over ∼1 cm2 areas. Three different characteristics of the LSPR spectrum are evaluated to generate spatial maps. From these maps, the locations which possess the largest areas of uniform nanoparticles can be identified.; Electrochemical tuning of nanoparticles is investigated as a post-deposition processing technique to systematically modify the optical properties of silver nanoparticles. In experiments to prove feasibility, silver nanoparticles 122 nm in diameter and 49.2 nm in height were prepared. Electrochemical oxidation was used to alter these nanoparticle dimensions to 119 nm and 45.2 nm, respectively. These changes led to a shift in the plasmon resonance of 19 nm.; The shapes of metal nanoparticles are investigated as a function of their size. It was discovered that for a relatively low temperature melting metal such as silver, the particle morphology was altered due to surface diffusion of silver atoms in small nanoparticles (viz., D 280 nm or dm 7 nm). The nanoparticle diameter as well as the deposition thickness affected the magnitude of these changes. Higher temperature melting metals, such as Pt, did not exhibit any significant morphological changes regardless of nanoparticle size. The influence of substrate choice was also probed to determine its effect on surface melting. The nanoparticles studied exhibited no substantial differences between a variety of substrates.