Photothermal Microscopy and
Spectroscopy Webinar

A great variety of plasmonic nanoparticle shapes are accessible through synthetic chemistry today. However, the precise positioning of these particles on a substrate or their integration into nanophotonic devices depends on efficient, easy-to-implement strategies for nanoparticle patterning and positioning. In recent years, optical printing with laser light has emerged as a versatile method to achieve this goal. Yet, the optical printing of plasmonic nanoparticles at nanoscale distances, a prerequisite for obtaining plasmonic coupling and forming plasmonic “hot-spots,” often poses an experimental challenge.

In this presentation, I will introduce a strategy for forming and printing gold nanoparticle dimers in a single step through the laser-induced splitting of individual gold nanorods. This approach evades the usual challenges that compromise the accuracy of sequential optical printing of gold nanoparticles, such as the emergence of photothermal forces and convection. TEM and spectral characterization of the dimer structures confirm that the gaps between the two particles are within the sub-nm range. To account for this observation, a nanorod splitting process is discussed that involves a combination of laser-induced differential optical forces, hydrodynamic pressure, plasmonic heating, and surface tension effects.

This method of optical dimer formation and printing by reshaping a single nanorod offers a rapid and precise means of assembling functional plasmonic antennas. It is particularly useful for research areas that depend on high near-field enhancement, such as surface-enhanced Raman scattering (SERS) spectroscopy.