Time-Resolved Fluorescence of Carbon Nanotubes and Its Implication for Radiative Lifetimes

The temporal evolution of fluorescence from isolated single-wall carbon nanotubes (SWNTs) has been investigated using optical Kerr gating. The fluorescence emission is found to decay on a time scale of 10 ps. This fast relaxation arises from nonradiative processes, the existence of which explains the relatively low observed fluorescence efficiency in isolated SWNTs. From the measured decay rate and a determination of fluorescence quantum efficiency, we deduce a radiative lifetime of 110 ns.

Figure 1

AFM image of isolated nanotubes deposited on mica. The nanotubes are $\sim 1\mathrm{nm}$ in height, as expected for isolated SWNTs.

Figure 2

Absorption (dotted curve) and fluorescence (solid curve; excitation wavelength 785 nm) spectra of isolated SWNTs suspended in PAA micelles in water.

Figure 3

Fluorescence decay of SWNTs (solid curve) as measured by the Kerr gating technique. The smooth solid line is a fit to a 7-ps exponential decay, with a weaker and slower tail. The dashed curve shows the response function of Kerr medium, as characterized by a spectrally filtered fs white light pulse introduced at time $t=0$.