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Growth Mechanisms of CdS Nanocrystals in Aqueous Media
Department of Chemistry, Center of Excellence for Nanostructured and Innovative Materials (CEMIN), University of Perugia, Via Elce di Sotto 8, 06123 Perugia, Italy
Present address: European Laboratory for Non Linear Spectroscopy (LENS), University of Florence, via Nello Carrara 1, 50019 Sesto Fiorentino, Firenze, Italy.
* Author to whom correspondence should be addressed.
Received: 7 December 2011; in revised form: 16 May 2012 / Accepted: 23 May 2012 / Published: 6 June 2012
Abstract: CdS nanocrystals were prepared in water-in-oil microemulsions. The nanocrystal properties, absorption and luminescence spectra and size distributions, were monitored at different times after mixing the microemulsions of the two precursors to obtain information on their growth mechanism. In particular, CdS nanocrystals were prepared using water-in-heptane or water-in-nonane microemulsions. The results obtained from the investigation of nanocrystals prepared using heptane as the organic phase, confirmed that nanocrystal nucleation is fast while their growth is determined by droplet exchange content rate. Size distribution histograms obtained from the sample at early time points after mixing presented a bimodal population having average sizes of 3.0 ± 0.1 and 5.8 ± 0.1 nm, thus indicating that surface process controls the nanocrystal growth. With longer reaction times the occurrence of water droplet coalescence is likely responsible for the formation of nanocrystal agglomerates. Using a water-in-nonane microemulsion, the droplet exchange rate can be modified, thus leading to smaller CdS nanocrystals. However, the development of structural defects cannot be excluded, as evidenced by the luminescence spectra of the suspension. In general, aging of the nanocrystal in the pristine microemulsion resulted in the development of cubic semiconductor nanostructures.
Keywords: CdS nanocrystal; microemulsion; luminescence; dimension distributions; TEM; growth mechanism
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MDPI and ACS Style
Latterini, L.; Iagatti, A. Growth Mechanisms of CdS Nanocrystals in Aqueous Media. Crystals 2012, 2, 618-626.
Latterini L, Iagatti A. Growth Mechanisms of CdS Nanocrystals in Aqueous Media. Crystals. 2012; 2(2):618-626.
Latterini, Loredana; Iagatti, Alessandro. 2012. "Growth Mechanisms of CdS Nanocrystals in Aqueous Media." Crystals 2, no. 2: 618-626.