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Semiconductor particles smaller than the bulk exciton radius exhibit strong confinement of the charge carriers. This leads to tunable absorption and photoluminescence (PL). However many of the effects are difficult to quantify due to the inhomogeneous broadening of spectra due to polydispersity. Single nanocrystal spectroscopy of both quantum dots and metal nanoparticles can be used to obtain homogeneous linewidths.
The first image shows single quantum dots deposited onto a cover slip and imaged using a confocal fluorescence microscope. The second image shows photon antibunching histograms from sequences of single photons emitted by one of the emitting sites, which demonstrates that the light is from a single quantum dot. The third image shows a time trace from a single quantum dot, and demonstrates that the fluorescence exhibits blinking. This has been shown to be due to surface states on the NCs, which provide non-radiative recombination pathways for charge carriers.
references:
D. Gomez et al. Feature Review Article PCCP 4989-5011 (2006).
D. Gomez eta l. Appl. Phys Lett. 88, 154106 (2006).
D. Gomez Small, 2, 204-7 (2006).
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