ARTICLE
Spectroscopy of Single CdSe Nanoplatelets Mickae¨l D. Tessier, Cle´mentine Javaux, Ivan Maksimovic, Vincent Loriette, and Benoit Dubertret* Laboratoire de Physique et d'Etude des Matériaux, CNRS, Université Pierre et Marie Curie, ESPCI, 10 rue Vauquelin, 75005 Paris, France
T
he spectroscopy of a single molecule has led to the observation of new effects13 and to direct measurements of the influence of the molecule's environments.4 Semiconductor single nanoparticle spectroscopy is limited because the nanoparticles observed so far, as quantum dots or nanorods, have slightly different composition, shape, or surface atoms. These differences prevent a complete decoupling between fluctuations due to the nanoparticle composition from the ones due to the environment. Recently, semiconductor nanoplatelets (NPLs) with a thickness controlled to atomic precision have been synthesized.57 These colloidal objects have 1D confinement, and they show identical thickness and composition at least in the direction of highest confinement. These NPLs thus offer an interesting opportunity to study the effect of the environment on the nanoparticle fluorescence emission, independently of the particle composition. The 1D confined nanoparticles with two different crystal structures, wurtzite and zinc blende, have been synthesized. Wurtzite crystal type structures have the shape of nanoribbons and have been obtained by an amine-rich reaction pathway through a lamellar assembly growth mechanism.8,9 The top and bottom faces of these wurtzite nanoribbons are terminated with a mixture of anions and cations. These structures have, in general, large lateral dimensions (∼100 nm), tend to aggregate in solution, and single ribbon spectroscopy is a difficult task.10 On the other hand, zinc blende crystal type structures have their thickness in the 100 direction, and their top and bottom surfaces are uniformly terminated with cadmium atoms, passivated with carboxylate alkyl groups. These NPLs have tunable lateral dimensions from a few nanometers to a few tens of nanometers,11 and they can be dispersed in hexane in low concentration without noticeable aggregation. These NPLs have recently been synthesized in CdSe, CdS, and CdTe with different thicknesses for TESSIER ET AL.
ABSTRACT
We collect and resolve spectrally and temporally the photoluminescence of single CdSe nanoplatelets. The emission intensity of single nanoplatelets at room temperature shows ON and OFF periods with a usual blinking statistics, while at 20 K, their emission intensity can be extremely stable in time. At room temperature, the emission spectra of single nanoplatelets are similar to ensemble measurements with a full width at half-maximum of 40 meV. At 20 K, we obtain a resolution-limited spectral line width (
