We present low-temperature studies of the optical properties of single CdS nanorods in relation to their morphology. Keeping track of the same nanorods in the photoluminescence (PL) study and during scanning electron microscope imaging, we were able to distinguish intrinsic spectral features of the nanorods from those of nanocluster aggregates. We observed strong PL polarization in the direction perpendicular to the nanorod axis. The sharp peaks in the "blue" region of the PL spectra are redshifted relative to those of bulk CdS and of CdS microparticles in a glass matrix. Finally, we observe a very interesting "spectral diffusion" of the main emission peaks with the following characteristics: (a) Energy-energy correlation of the two main peaks, and (b) correlation and anticorrelation between energy and intensity for the two peaks. Possible mechanisms behind this phenomenon are discussed.
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