Plasmon-Assisted Delivery of Single Nano-Objects in an Optical Hot Spot

Fully exploiting the capability of nano-optics to enhance light. matter interaction on the nanoscale is conditioned by bringing the nano-object to interrogate within the minuscule volume where the field is concentrated. There currently exists several approaches to control the immobilization of nano-objects but they all involve a cumbersome delivery step and require prior knowledge of the "hot spot" location.(1-6) Herein, we present a novel technique in which the enhanced local field in the hot spot is the driving mechanism that triggers the binding of proteins via three-photon absorption. This way, we demonstrate exclusive immobilization of nanoscale amounts of bovine serum albumin molecules into the nanometer-sized gap of plasmonic dimers. The immobilized proteins can then act as a scaffold to subsequently attach an additional nanoscale object such as a molecule or a nanocrystal. This universal technique is envisioned to benefit a wide range of nano-Optical functionalities including biosensing,(7-12) enhanced spectroscopy like surface-enhanced Raman spectroscopy(13,14) or surface-enhanced infrared absorption spectroscopy,(15) as well as quantum optics.(1,2,6)