Brewster angle optical reflection observation of self-limiting nanoparticle monolayer self-assembly at a liquid/liquid interface

• Published in: AIP advances Vol. 9; no. 6; pp. 065022 - 065022-6
• Main Authors: Hu, Jiayang, Pan, Brady, Makihara, Takuma, Garcia, Roy D. J., Herman, Irving P.
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 01-06-2019; AIP Publishing LLC
• Subjects: Angle of reflection; Brewster angle; Die casting; Heptanes; Iron oxides; Light reflection; Monolayers; Nanoparticles; Optical reflection; Polarized light; Reflectance; Self-assembly; Substrates
• ISSN: 2158-3226; 2158-3226
• DOI: 10.1063/1.5099487

Real-time optical reflection of incident p-polarized light near Brewster’s angle shows that after drop-casting iron oxide nanoparticles (NPs) in heptane on top of a diethylene glycol (DEG) liquid substrate, an iron oxide NP layer forms at the DEG/heptane interface, and it self-limits to a monolayer even when there are excess NPs dispersed in the upper heptane phase. Most modes of NP self-assembly do not self-limit growth after the formation of a single monolayer. Observations are compared to a reflection model incorporating the reflectances expected at each interface. An effective medium model of the dielectric constant is used to model the reflectance of the NP layer at the DEG/heptane interface.