Abstract

Recent advances in two-photon excited photoluminescence of plasmonic gold nanorods have greatly expanded their application. Shape-controlling of nanorods can enhance a particular photophysical process to tailor needs but its application to two-photon luminescence is yet to be fully developed despite its importance in biolabelling. In particular, bipyramidal gold nanorods have received a large amount of interest as a biolabelling due to highly localised field at their tips, which provide enhancement for emission processes. However, no proper evaluation of geometrical properties of bipyramids such as tip shape, curvature, pentagonal cross section or the waist have been conducted on the field enhancement and peak evolution. Numerical simulations using finite element analysis show that small change in tip radius of curvature can change nonlinear process such as two-photon luminescence (TPL) two to four-fold increase. However, such large increase is not observed in experimental measurement of TPL with respect to tip curvature, indicating that there is fundamental limit to how the field enhancement can influence emission processes.

© 2017 Japan Society of Applied Physics, Optical Society of America