Synthesis of Janus Nanoparticles using a Packed Column and their Applications

Abstract

Janus nanoparticles, nanoparticles with two regions of differing properties, have been of interest to researchers for the last 30 years. Differing surface regions of Janus nanoparticles allows for self-assembly into larger structures, giving these nanoparticles potential applications in coatings, targeted drug delivery, and emulsion stability to name a few. Three main challenges exist when developing Janus nanoparticles: size control, scalability of the synthesis method, and versatility of the method. Versatility refers to the ability to make different Janus nanoparticles without changing the synthesis method. Even with increased interest into Janus nanoparticles, synthesis methods that overcome all three challenges are scarce. Considering the large number of possible applications, it is crucial that new synthesis methods are developed that can overcome these challenges. In this work, a novel synthesis method was presented that produces Janus nanoparticles in a packed column. Nanoparticles were masked onto the column’s packing material and selectively modified with different compounds to developed dual-sided nanoparticles. This method allowed development of multiple anisotropic Janus nanoparticle configurations without making changes to the synthesis method or equipment. Nanoparticles were characterized using dynamic light scattering, Fourier-transform infrared spectroscopy, and fluorescent spectroscopy. Fluorescent optical microscopy and transmission electron microscopy were utilized to visualize these nanoparticles and confirmed the existence of two different surface modifications based on the location of different fluorescent dyes or location of nanostructures of varied size.. Self-assembling abilities and potential applications for Janus nanoparticles were also examined. The effect of Janus nanoparticles on interfacial tension of an immiscible fluid interface was investigated, and self-assembled monolayers of Janus nanoparticles were formed on hydrophobic surfaces and examined using optical microscopy. Results showed that Janus nanoparticles reduced interfacial tension between immiscible fluids and uniformly assembled on hydrophobic surfaces, further confirming the creation of two-sided nanoparticles. With regards to potential applications, investigation into the use of Janus nanoparticles for improved emulsion iii stability and pore size control was done using liquid-liquid and liquid-gas interfaces. Finally, stationary phase surface area was increased to determine if this method can produce larger quantities of Janus nanoparticles as the first step to determining scalability. Initial results from scaled-up packed column synthesis runs looked promising and indicated that the packed column method has the potential to be scaled-up to produce nanoparticles at industrial level quantities.