Optothermal Formation of Gold “Nano-Lemons” for SERS on Photolipid Bilayer Membranes

Optical printing with laser light is a powerful method for patterning plasmonic nanoparticles on a solid support. However, using particles that display sharp features, such as gold nanostars or bipyramids, can be challenging because plasmonic heating involved in the printing process can lead to tip blunting and melting. This adversely affects the performance of these particles for spectroscopic or catalytic applications. Therefore, strategies need to be implemented to avoid thermal reshaping of complex-shaped nanoparticles either by minimizing plasmonic heating or by dissipating heat away from the particles. Here, an alternative view is proposed. Rather than avoiding plasmonic heating, it is demonstrated that optothermal printing can be leveraged to transform gold nanorods into ellipsoidal or lemon-shaped particles with sharper tips and enhanced local electromagnetic field intensities compared to the initial rods. The potential of these “nano-lemons” for spectroscopic applications is exemplified through surface enhanced Raman scattering measurements of azobenzene photoisomerization within supported photolipid bilayer membranes.