Synthesis of surfactant encapsulated nickel hexacyanoferrate nanoparticles and deposition of their Langmuir–Blodgett film

Abstract

Sodium hexametaphosphate (HMP) stabilized nickel hexacyanoferrate (NiHCF) nanoparticles were prepared in aqueous solution and were successfully extracted into an organic phase using cetyltrimethylammonium bromide (CTAB) as the surfactant. Dynamic Light Scattering (DLS) studies suggest that the average size of the nanoparticles is retained during the extraction process from the aqueous to the organic phase. X-Ray diffraction, cyclic voltammetry, IR spectroscopy and magnetic measurements carried on the organic phase shows specific signatures of the presence of the surfactant encapsulated NiHCF nanoparticles. Transmission Electron Microscopy (TEM) measurements show that the average size of these surfactant encapsulated nanoparticles in the organic phase is about 22 nm, and as has been suggested by DLS studies, it does not change with respect to repeated evaporation and re-extraction processes of the organic phase. Pressure–area isotherms of the organic phase in a Langmuir–Blodgett (LB) trough, with water as subphase, indicate stable monolayer formation of the surfactant-encapsulated NiHCF nanoparticles at the air–water interface. Multi-layered deposition of the surfactant-encapsulated nanoparticles onto an indium tin oxide (ITO) coated glass slide could also be carried out using the LB technique. Cyclic voltammetry studies on these LB multilayers confirm regular and systematic transfer of the NiHCF nanoparticles on the ITO substrate. The method described here is the first of its kind with respect to the synthesis of surfactant encapsulated molecular magnetic nanoparticles and subsequent deposition of their LB films.