Pixis 100bx

The plasmon resonance scattering measurements were carried out on an inverted dark-field microscope (eclipse Ti-U, Nikon) using a ×40 objective lens (numerical aperture, 0.6) and a dark-field condenser (0.8 < numerical aperture < 0.95). A halogen lamp (100 W) was used as a source of white light to generate plasmon resonance scattering light. The dark-field images were captured by a true-colour digital camera (Nikon DS-fi). The light scattered from the bifunctionalized nanoantennae was split by a monochromator (grating density, 300 lines mm^–1; blazed wavelength, 500 nm; Acton SP2300i, Princeton Instruments). An IsoPlane-320 spectrometer was used, and the split light was collected by a charge-coupled device (Pixis 100BX, Princeton Instruments). An a.c. EF of 3 MHz at 0.65 V was applied for 10 min, and scattering spectra were monitored (1,000 frames recorded). The exposure time was 500 ms. The samples for plasmon resonance scattering were prepared by immobilizing nanoantennae on ITO. First, ITO slides were treatment with ethanol, acetone and water under sonication. Next, 50 µl nanoantennae solution was drop-casted on the ITO slides for 10 min, followed by a single-step washing and rinsing with water. Finally, the slides were dried with N₂ gas.