Study of spatial organisation of magnetic field directed gold-pickering-ferrofluid-nanoemulsion in spin coated film

Abstract

The magnetic field directed self-assembly of the nanoparticles is cheap, fast and easy method to prepare the patterned thin film useful for various applications. However, the dipole-dipole interaction between nanoparticles at the interface generates the rough-edged patterns even at microscale causing the excess optical scattering making it unsuitable for the optical applications. In this work, the magnetic field was applied during the spin coating of the Polyethylene glycol 40S (PEG) capped Gold-Pickering ferrofluid nanoemulsion (PEG-C-GM-FF) dispersed in aqueous Polyvinyl alcohol (PVA) solution with different viscosities. Optimised combination of spinning speed and magnetic field strength was achieved to prepare the film with the straight chains of PEG-C-GM-FF required for the optical applications. It is a quick, cost-effective, non-intrusive and simple method for achieving a thin layered array of chains with tuneable gaps between them. The image analysis revealed that the Full Width Half Maximum (FWHM) representing the PEG-C-GM-FF chain spatial density across the substrate for each aqueous phase viscosity decreases with the increase in the spin speeds at constant magnetic field strength. The FTIR (Fourier Transformed Infrared Spectroscopy) of the patterned thin film showed that the intensity of the 2927 ​cm−1 vibrational band corresponding to CH bond in PVA was seen to be linearly increasing with the spatial density of the PEG-C-GM-FF chains. In comparison to the gold strip patterns printed with the nanolithography technique; the magnetically aligned array of PEG-C-GM-FF showed a potential for preparing photonic antenna suitable for enhancing the optical absorption and detect low concentration analyte.

Keywords

• Nanofabrication
• Spin coating
• FTIR
• Magnetic field
• Plasmonic antenna
• Image analysis