Lithographied nanostructures as nanosensors

Abstract

Major improvements in fabrication techniques at the nanoscale during the last two decades enable us to exploit and control nanoscale phenomena such as the localized surface plasmons (LSP) provided by metallic nanoparticles (MNP). The large enhancement of the elec- tromagnetic field due to plasmonic effects increases drastically the response of any analyte located close to or adsorbed onMNPs, which opens ways for detection of very lowconcentration of analytes and sensor miniaturization. However, the efficiency of such nanosensors requires a precise control of the optical properties of the MNPs since it strongly depends on their geome- trical properties. Such precision can be reached by nanolithography techniques. The parameters that govern the near field enhancement include the geometrical parameters of the MNPs (size, shape, and gap), the LSP characteristics (near field decay length and resonance position) and the excitation parameters (excitation wavelength and associated electric field polarization). Nano- lithography techniques used for surface nanostructuring include optical, focused electron and ion beams, nanoimprint and nanosphere lithographies. Nanosensor fabricated lithographically exploit localized surface plasmon resonance, surface enhanced Raman scattering, and surface enhanced fluorescence.