When the size of noble metal nanoparticles is reduced to less than the wavelength of light, the particles intensely absorb and scatter light at wavelengths that depends on the particle size, shape, and local dielectric environment due to Localized Surface Plasmon Resonance (LSPR) modes. Plasmonic particles have been used in a wide variety of sensor and optical device applications including tracers for intracellular transport, immunoassays, and surface enhanced Raman spectroscopy substrates. Controlling nanoparticle shape is essential for tuning these nanoparticles for a given application; however, controlling shape without affecting the particle volume is challenging. Reported here is a simple technique to mechanically alter the shape of silver nanoparticles by mechanically rolling a glass tube over them. This shape change in turn induces a red-shift in the LSPR wavelength of silver nanoparticles. The flattened particles were characterized by both optical and electron microscopy, single nanoparticle scattering spectroscopy, and surface enhanced Raman spectroscopy. AFM and SEM results consistently demonstrate the effect of applied load on silver nanospheres into discs; deformation increases with applied load (0-100 N). Increase in applied load from 0 to 100 N increases the silver nanoparticle diameter and decreases the height. This deformation caused a dramatic redshift in the nanoparticle scattering spectrum and also generated new surface area to which thiolated molecules could attach as evident from the SERS spectrum. The simple technique employed here requires no lithographic templates and has potential for rapid, reproducible, inexpensive and scalable tuning of nanoparticle shape, surface area, and resonance while preserving particle volume. This work was supported by <i>NIBIB </i>of the National Institutes of Health under award number R15EB014560-01A1 and <i>NIGMS </i>of the National Institutes of Health under award number 5P20GM103444-07.

Tuning localized surface plasmon resonance wavelengths of nanoparticles by mechanical deformation

251st National Meeting (2016)

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