Oil/water interfacial self-assembly for the organization of hydrophobic NaYF4:Yb, Er nanoplatelets into closely-packed fluorescent nanofilms

This paper presents an oil/water interface self-assembly strategy for the fabrication of hydrophobic nanoparticles into mono- and multi-layered nanofilms with NaYF4:Yb,Er nanoplatelets as a prototype. In this approach, hydrophobic β-NaYF4:Yb,Er nanoplatelets dispersed in chloroform solvent are used as the sub-phase, then a certain amount of water is added to produce a chloroform/water interface. When ethanol is added, the up-conversion NaYF4:Yb,Er nanoplatelets are found to readily self-assemble at the oil/water interface into a closely-packed mono- or multi-layer nanofilm with a preferred [001] orientation. Compared with the previous water/oil interface self-assembly strategy, the present method is not only used for fabrication of hydrophobic nanoparticles into high quality nanofilms, but also is environmentally friendly and is safe to the operator.