Multilayer Langmuir–Blodgett assemblies of hydrophobized CdS nanoparticles by organization at the air–water interface

Abstract

The formation of multilayer Langmuir–Blodgett (LB) films of hydrophobized CdS nanoparticles by organization at the air–water interface is described. The hydrophobization of CdS nanoparticles (60 A diameter) synthesized in an aqueous medium is accomplished by extraction of the particles from solution into thermally evaporated octadecylamine (ODA) films. Vigorous stirring of the ODA–CdS nanocomposite films in organic solvents resulted in dispersion of the CdS particles in the organic phase. The hydrophobic CdS nanoparticles were dispersed on the surface of water, organized into a fairly closely packed monolayer and multilayer films formed on different substrates by the versatile Langmuir–Blodgett technique. The organization of the particles and formation of multilayer films by the Langmuir–Blodgett technique was followed by surface pressure–area isotherm measurements of the nanoparticle Langmuir monolayer, quartz crystal microgravimetry, contact angle measurements, UV–vis spectroscopy and Fourier transform infrared spectroscopy studies. It is observed that a reasonably close-packed monolayer of the CdS nanoparticles forms on the surface of water and that excellent multilayer films of the particles can be grown on different supports via sequential transfer by the LB technique.