ABSTRACT
Self-assembling Au mesoflower arrays are prepared using a polymethylmethacrylate (PMMA) template on an iron substrate via a combined top-down/bottom-up nanofabrication strategy. The PMMA template with the holes around 300-500 nm in diameter is first fabricated by using polymer blend lithography on iron substrates, and the highly homogeneous Au mesoflower arrays with less than 10 nm intraparticle gaps are subsequently obtained by an in situ galvanic reaction between HAuCl4 solution and the iron substrate under optimal stirring of the solution as well as reaction time. Owing to the unique mesostructures and uniformity, Raman measurements show that the gold mesoflower arrays obtained demonstrated a strong and reproducible surface enhanced Raman scattering (SERS) enhancement on the order of â¼10(7)-10(8). The development of a SERS substrate based on the Au mesoflowers with high spatial density of hot spots, relatively low cost and facial synthesis provides a novel strategy for applications in chemical and biomolecular sensing.
Subject(s)
Crystallization/methods , Gold/chemistry , Nanostructures/chemistry , Nanostructures/ultrastructure , Spectrum Analysis, Raman/methods , Surface Plasmon Resonance/methods , Light , Macromolecular Substances/chemistry , Materials Testing , Molecular Conformation , Particle Size , Scattering, Radiation , Surface PropertiesABSTRACT
A major challenge in constructive nanolithography is the preservation of the lateral resolution of a monolayer-thick template pattern while amplifying it to a structure with a thickness above 10 nm. So far, the most successful approach to achieve this is surface-initiated polymerization (SIP) from e-beam structured monolayer templates in a multistep process. However, spreading of the polymer on the substrate leads to a rapid line-widening. Therefore, structures with lateral resolutions well below 100 nm and thicknesses above 10 nm (aspect ratio: 0.1) were not reported yet. Our approach of photoinduced, constructive, reversible nanolithography, is based on nanografting within a coumarin-derivative thiol (CDT) solution using the tip of an atomic force microscope (AFM). By photodimerization and the formation of disulfide bonds, the CDT polymerizes in a single-step process. We demonstrate the highest lateral resolution in constructive nanolithography at thicknesses above 10 nm (40 nm lateral resolution at 12 nm thickness, aspect ratio: 0.3).
