Nanoparticle cluster arrays (NCAs) are a novel class of electromagnetic materials which utilize near- and far-field interactions between nanoparticles in the array to generate high electric (E)-field enhancements. A rational design of NCAs with defined optical properties requires a thorough understanding of the geometry-dependent optical response of the building blocks. We systematically investigated the near- and far-field responses of clusters of closely packed 60 nm gold nanoparticles (n = 7) as a function of size and cluster geometry through a combination of experimental spectroscopy and generalized Mie theory calculations. From all of the investigated cluster configurations, nanoparticle trimers with D3h geometry and heptamers in D6h geometry stand out due to their polarization-insensitive responses and high E-field intensity enhancements, making them building blocks of choice in this size range. NCAs are enabling substrates in Surface Enhanced Raman Spectroscopy (SERS). We demonstrate that NCAs enable to detect ultra-traces of aromatic vapors. NCAs functionalized with a thin film of an aqueous NaOH solution facilitated the detection of 2,4-dinitrotoluene vapor at concentrations of at least 10 ppt even in the presence of different interferents (Diesel, fertilizer, pesticide vapors).

Rationally designed nanoparticle cluster array for surface enhanced Raman spectroscopy

242nd National Meeting (2011)

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