Copper oxide nanorods assembly and their whisker transformation at liquid–liquid interface and on solid surfaces

•Copper oxide nanorods assembly and their whisker transformation.•Dynamics assembly of colloidal nanoparticles at liquid–liquid interfaces.•π electrons and breath figure assisted CuO assembly.•Real time dynamic monitoring of CuO by an atmospheric scanning electron microscope (ASEM).

We report on real time fluctuations and chain-like assemblies of copper oxide (CuO) nanorods at the liquid–liquid interface. The rods were found to transform into whiskers and 3D structures upon spin-casting on silicon substrates. The results of atmospheric scanning electron microscope (ASEM) and atomic force microscopy (AFM) provide compelling evidence that both the transformation and the assembly are driven by interaction between the π electrons of toluene and CuO nanorods, and to a smaller extent by breath figure dynamics rather than the solution-liquid–solid mechanism that was previously believed to account for whisker formation. These results open up a way for studying and understanding the dynamics of nanoparticles at liquid–liquid interfaces.