Nature Nanotechnology 6, 580–587 (2011); published online 21 August 2011; corrected online 26 August 2011; corrected after print 25 May 2012.
In this Article we should have mentioned previous works on the competition between van der Waals forces and/or other attractive short-range forces and electrostatic long-range interactions in the assembly of different types of aggregates. To our knowledge this issue was first studied by Zeleny in 1914 in experiments on the instability of charged droplets, with the competing forces being electrical repulsion and surface tension1,2, and it was later discussed by Taylor in 19643. The idea that negatively charged nanoparticles can agglomerate to form larger particles via magic-number progression was proposed in ref. 4 in 1984. In 1985 Ramsden reported that CdS nanoparticles formed aggregates of limited dimensions5, and in 1987 he explained the stability of polydisperse superspheres containing a few tens of nanoscale particles in terms of the balance between long-range electrostatic repulsion and short-range attractive dispersion forces6. In the early 1990s Zukoski and co-workers also explored how equilibrium between long- and short-range forces influenced the size of nanoparticle clusters7,8.
The clear difference between our work and that reported in Refs 1,2,3,4,5,6 is that the supraparticles (superspheres) in our experiments are much more uniform in size and shape. This has allowed us to develop a new phenomenological model of supraparticle formation that, in turn, has led to the observation of a number of nanoparticle structures that had not been observed before, including colloidal crystals made of supraparticles and various core–shell systems (including some that resemble viruses). The main difference between our work and that reported in Refs 7,8 is that the clusters observed in those experiments were transient in nature and their self-limiting properties were less obvious. We also demonstrate the generality of the phenomenon by making supraparticles from combinations of two materials.
About this article
Search for Yunsheng Xia in:
Search for Trung Dac Nguyen in:
Search for Ming Yang in:
Search for Byeongdu Lee in:
Search for Aaron Santos in:
Search for Paul Podsiadlo in:
Search for Zhiyong Tang in:
Search for Sharon C. Glotzer in:
Search for Nicholas A. Kotov in: