Nanoobjects microscopy

In situ SEM imaging of self-assembly process of colloidal gold nanorods aggregates
Grzelak D.1, Szustakiewicz P.1, Lewandowski W.1
1 Departament of Chemistry, University of Warsaw
L. Pasteura 1,02-093 Warsaw, Poland. 
E-mail: dgrzelak@chem.uw.edu.pl

Self-assembly of nanoparticles directly from a solution is one of the most promising routes to obtain large-scale, nanoparticle-based materials with unique optical properties. Application of this process revolutionised technologies like  i.e. optics or photovoltaics. Gold nanorods (AuNRs) due to theirs anisotropic shape show unique optical properties, hence they are perfect for application in nanoparticle-based technologies. However, controlling process of AuNRs self-assembly with single nanoparticle precision is almost impossible. In order to achieve this type of control, we need to fully understand the mechanism and forces driving this proces. 
In presented work, we employ in situ scanning electron microscopy to track  movements of single gold nanorods and their vertically oriented aggregates in solution. Together with complementary measurements (UV/Vis spectroscopy and Small Angle X-Ray diffraction) and theoretical modelling it allows us to track and analyse dynamics of self- and disassembly of AuNRs orientally ordered aggregates. Notably, we provide via in situ SEM first direct proof of colloidal stability of such aggregates and significantly expand our understanding on forces governing self-assembly of nanoparticles from solution. 
             
The research is conducted under Reinforce project carried out within the
First Team programme of the Foundation for Polish Science co-financed by
the European Union under the European Regional Development Fund.