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Semiconductor nanoparticles are often synthesised by reacting two chemicals, one providing cations and the otheranions. The popularity of this approach stems from the tremendous flexibility and the ease of controlling that suchmethods offer in designing the size, shape and various functionalities of resulting nanoparticles in the really small size(typically < 10 nm) limit. Beyond the initial nucleation stage, that consumes the reactants very quickly, further growth ofthese small clusters is supposed to proceed via the ripening process. While some follow the classic Ostwald ripening,1several cases2,3 show marked deviations from this expected behaviour. While touching on some of these aspects, Ishall primarily discuss such cases where the ripening process gives rise to grossly anomalous behaviours, such as adecrease in the particle size among the larger sized particles with time.4 The experimental observations establishingsuch behaviours will be supported by simulations in an attempt to understand the microscopic origin of suchphenomena. We shall show examples of how such understanding of the growth process allows us wonderful controlon the particle size and size distribution,5 leading to our ability to achieve long-range order through self-assembly.6,7
If time permits, I shall also present experimental results on growth of metallic nanoclusters, namely gold, exhibitingqualitatively different behaviour compared to what is encountered in the case of semiconductor nanocrystals.
This work is carried out jointly with Ranjani Viswanatha, Pralay K. Santra, Abhijit Hazarika and Chandan Dasguptafrom IIsc, Bangalore, N. Pradhan, S. Acharya and Niladri S. Karan of IACS, Kolkata, Heinz Amenitsch from AustrianAcademy of Sciences, Graz, Michael Tambasco and Sanat K. Kumar from Columbia University, New York, and YuZhou, Saroj K Nayak from Rensselaer Polytechnic Institute, Troy, K. Ariga and Y. Wada of NIMS, Japan, S. Efrima and Y.Golan of Ben Gurion University, Israel.
References
1. R. Viswanatha, H. Amenitsch, S. Santra, S. Sapra, S. Datar, Y. Zhou, S. Nayak, S. Kumar, D. D. Sarma, J. Phys.Chem. Lett. 1, 304 (2010).
2. R. Viswanatha, Pralay K. Santra, Chandan Dasgupta, and D. D. Sarma, Phys. Rev. Lett. 98, 255501 (2007).
3. R. Viswanatha, Heinz Amenitisch and D. D. Sarma, J. Am. Chem. Soc. 129, 4470 (2007).
4. Unpublished results: R. Viswanatha, P. K. Santra, A. Hazarika S. Nayak, S. Kumar and D. D. Sarma.
5. R. Viswanatha and D. D. Sarma, Chemistry - A European J. 12, 180 (2006).
6. R. Viswanatha, Pralay K. Santra and D. D. Sarma, J. Cluster Sci. 20, 389 (2009).
7. N. Pradhan, S. Acharya, K. Ariga, Niladri S. Karan, D. D. Sarma, Y. Wada, S. Efrima and Y. Golan, J. Am. Chem.Soc., Accepted for publication (2010).
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