Spectroscopy of single metallic nanoparticles using total internal reflection microscopy

We have developed a simple, fast, and flexible technique to measure optical scattering spectra of individual metallic nanoparticles. The particles are placed in an evanescent field produced by total internal reflection of lig ht from a halogen lamp in a glass prism. The light scattered by individual particles is collected using a conventional microscope and is spectrally an alyzed by a nitrogen-cooled charge-coupled-device array coupled to a spectr ometer. This technique is employed to measure the effect of particle diamet er on the dephasing time of the particle plasmon resonance in gold nanopart icles. We also demonstrate the use of this technique for measurements in li quids, which is important for the potential application of particle plasmon s in chemical or biological nanosensors. (C) 2000 American Institute of Phy sics. [S0003-6951(00)01745-9].