Core-shell structures of nanoparticles have wide applications in areas of catalyst synthesis, drug delivery, bio-imaging, environmental remediation, etc. The structure and the size of the core-shell play important roles in governing the physical and chemical properties of the formed nanohybrids. In this study, the core-shell structure was formed through spontaneous heteroaggregation between neutral nanoparticles (i.e. hematite nanoparticles or HemNPs) and charged nanoparticles (i.e., polystyrene nanoparticles or PSNPs). The pH of the 1 mM NaCl dispersant solution was adjusted to 6.34 so that HemNPs were neutral and underwent favorable homoaggregation whereas PSNPs were negatively charged and underwent no homoaggregation. When the two types of particles were mixed, homoaggregation of HemNPs and heteroaggregation between HemNPs and PSNPs took place simultaneously, forming HemNPs-PSNPs heteroaggregates. The size of heteroaggregates increased initially and became stable afterwards, as shown by the hydrodynamic diameter measurement using dynamic light scattering (DLS). The transmission electron microscopy (TEM) images of heteroaggregates at the stable stage show that HemNPs and PSNPs formed core-shell structure in which HemNPs are the cores and PSNPs are the shells. The size of the core-shell nanohybrids can be controlled by varying the concentration ratio of PSNPs to HemNPs. The elevated concentration of PSNPs reduced the size of the colloidally stable nanohybrids due to that PSNPs could quickly surround HemNPs before the HemNP had the chance to attach to other HemNPs. Decreasing the concentration of the PSNPs resulted in larger size of stable nanohybrids because HemNPs could attach to each other through direct contact or bridging by an intermediate PSNP. The influence of size of charged nanoparticles on the formation of core-shell nanohybrids will be discussed as well.

Self-assembling of neutral and charged nanoparticles into core-shell nanohybrids with size control

2019 Spring National Meeting

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