Electrical Detection of Surface Plasmon Resonance in Individual Gold Nanowires

Plasmon absorption in individual gold nanowires has been detected electrically.~ Gold nanowires, electrochemically synthesized in polycarbonate templates with diameters of 40 nm and lengths of 5 $\mu $m, are connected under an optical microscope using multiphoton absorption polymerization (MAP).~ MAP uses a prepolymer acrylic based resin and a focused ultrafast laser to stereolithographically pattern with sub-micron resolution.~ For this experiment, nonconducting acrylate leads are made by MAP to connect to a single gold nanowire.~ These polymer leads can then be made conductive by surface modification followed by electroless copper enhancement.~ In this way the resistance of a single nanowire can be measured in a four-probe scheme.~ The gold rod can then be optically excited near its plasmon absorption peak.~ The excitation is quickly converted to heat, which is observed as an increase in resistance.~ This electrically detected plasmon absorption has been found to be linearly dependent on light intensity and is also sensitive to the direction of the polarization with respect to the rod.~ This non-optical plasmon detection is of basic interest but may be applicable for intrabeam polarization detection or electrical detection of biomolecules.