The use of multifunctional branched amphiphilic molecules for the formation of silver nanoparticles

Abstract

Many areas of technology continue to place a high demand on the miniaturization of critical components for a new generation of optical, magnetic, and electrical sensors, and actuators. This push leads scientists to seek new techniques to use in the fabricate devices. Because of their shape and size, nanoparticles exhibit a unique array of physical, optical and electrical properties that are not present in bulk form. Furthermore, these properties may be enhanced by their specific ordering. The formation of nanoparticles and their incorporation into polymer thin films has received increased attention for their potential use as nanodevices. The goal of the research presented here was to fabricate a polymer-nanoparticle assembly in which the polymer controlled the size, shape and exact placement of the nanoparticles created. In this work, Langmuir monolayers of a multifunctional branched amphiphilic molecule were utilized due the novel behavior the molecule exhibited at the air-water interface. The molecules possessed the ability to form semi-cylindrical polymer fibers at the air-solid interface when transferred to silicon wafers. The functionality of the hyperbranched molecule, coupled with the constraints of the air-liquid interface, proved to be key elements in the nanoparticle formation. The presence of reduced silver in the monolayer was confirmed using synchrotron X-ray studies and X-ray photospectroscopy. Morphological studies of the polymer-nanoparticle assembly at the air-solid interface were analyzed using atomic force microscopy. The size of the silver nanoparticles in the monolayer at the air-liquid interface remained stable for a minimal period of 24 hours, indicating that the polymer played a crucial capping role in the formation of the nanoparticles and prevented their further aggregation. The formation of size-limited, stable nanoparticles, combined with the polymer's efficiency to directly induce the reduction of silver ions, resulted in a beautiful display of the biomimetic capabilities of polymers.