Abstract
Quantum-dot superlattices (QDSLs) of CdS were grown via a self-organization process with electrostatic interaction between positively- and negatively-charged CdS quantum dots (QDs). The positively- and negatively-charged CdS QDs were prepared separately by modifying a QD surface with cationic and anionic thiol compounds, respectively. The absorption peak of mixed solutions of oppositely charged QDs is red-shifted compared with that of each QD sample: The red-shift is due to a coupling of QDs through the electrostatic interaction. Millimeter-sized QD aggregates were obtained with the elapse of ∼20 hours after the mixing. The peak energies of photoluminescence (PL) and PL excitation spectra of the aggregates correspond well to those of PL and absorption spectra of the mixed solution samples. Furthermore, in x-ray diffraction patterns, a diffraction peak is clearly observed at the low 2θ angle of ∼4°. From the results, we conclude that the obtained aggregates are ordered structures of QDs, that is, QDSLs. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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