Here we point out some parameters, such as substrate roughness, deposition modes, alkyl chain length of the coating agents and solvent used to disperse the nanocrystals, that play a role in the control of nanocrystal ordering in 2D superlattices. The interparticle distances do not follow the rules which imply that they are controlled by the length of the alkyl chain used as coating agent. The solvent in which the nanocrystals are dispersed is a key parameter. From DDA simulations it is observed that collective optical properties of 5 nm noble nanoparticles self-organized in a 2D hexagonal planar array markedly differ with the nanomaterial used (Au and Ag). There is no splitting of the surface plasmon resonance observed for Au nanoparticles, whereas for Ag nanoparticles, with a similar geometry, a splitting is observed when decreasing the interparticle spacing d/(2R) to around one nanoparticle radius due to the strengthening of the dipolar interactions between the nanoparticles. Here it is shown by using AMB-1 magnetostatic bacteria that the change in the hysteresis loop when the nanoparticles are aligned is preferentially due to induced dipolar interactions rather than to the orientation of the easy axes. Intrinsic collective chemical properties due to the nanocrystals ordering are presented.
Source : How to produce 2D self-organizations of inorganic nanocrystals and and how do they affect the chemical and physical properties. M.P.Pileni, Phys. Chem. Chem. Phys., 2010, 12, 11821 – 11835.