Gold nanorods excited at 830 nm on a far-field laser-scanning microscope produced strong two-photon luminescence (TPL) intensities, with a cos(4) dependence on the incident polarization. The TPL excitation spectrum can be superimposed onto the longitudinal plasmon band, indicating a plasmon-enhanced two-photon absorption cross section. The TPL signal from a single nanorod is 58 times that of the two-photon fluorescence signal from a single rhodamine molecule. The application of gold nanorods as TPL imaging agents is demonstrated by in vivo imaging of single nanorods flowing in mouse ear blood vessels.
in vivo imaging; plasmon resonance; multiphoton; nonlinear optics, FLUORESCENCE CORRELATION SPECTROSCOPY; 2ND-HARMONIC GENERATION; ENHANCEMENT; MICROSCOPY; METALS; PHOTOLUMINESCENCE; GROWTH; NANOPARTICLES; EXCITATION; MECHANISM
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