Ensemble photoluminescence measurements (steady state measurements) give the average behavior of all the individual particles in the sample under study. The inhomogeneous broadening effect due to different factors can be known only if the nanocrystals can be probed at the single particle level. Single Molecule Fluorescence Microscopy is a powerful tool for imaging and probing the dynamics of individual fluorescent molecules and luminescent semiconductor nanocrystals (Quantum Dots). Cadmium Sulphide (CdS) Quantum Dots (QDs) have been synthesized in reverse micelle method; characterized, imaged and single particle level spectral studies have been carried out to understand the reason for spectral broadening. Nikon Eclipse 2000U (inverted) epi-fluorescence microscope was used to image the individual CdS nanocrystals. Imaging and spectroscopy of individual CdS QDs were done by spin coating suitable concentration of sample on the microscope cover slip. 405nm Diode laser was used to excite the sample. The emitted light from the sample was allowed to pass through a CCD camera and collected movies with an exposure time of 200 ms. Movies collected show blinking spots of diffraction limited particles. Spectrally resolved PL imaging of individual spatially isolated CdS NCs is done using a combination of slit and transmission grating (70groves/mm) with an exposure time of 12s on each frame. Each spectrum was calibrated with 3 different laser lines and analyzed using ImageJ and Origin 8 softwares. Broadening can happen both because of the size variation of particles in the sample and due to the inherent spectral broadening of individual CdS NCs. The result of the analyzed spectra of more than 100 particles will be used to explain the reason for broadening. References [1] Layek, A; De,S; Thorat,R; Chowdhury,A. J.Phys.Chem.Lett. 2011,2,1241-1247 [2].Ethayaraja,M; Ravikumar,C; Muthukumaran,D; Dutta,K; Bandyopadhyaya,R.J.Phys.Chem.C. 2007,111,3246-3252. [3] Smith,A.M.; Nie,S.M. Acc. Chem.Res. 2010, 43,190-200.

Synthesis and spectrally resolved single particle photoluminescence imaging of CdS quantum dots

250th National Meeting (2015)

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