During the recent decade, an extensive effort has been made to evaluate and investigate the environmental fate of engineered nanomaterials. Excluding carbon nanotubes as an exception, there is currently little known about the environmental implications of highly anisotropic metallic nanoparticles. Within recent decade, new applications have been developed for highly anisotropic gold nanoparticles (i.e. rods and wires) due to their high intensity of surface plasmon resonance at the tips. This characteristic makes these elongated shaped gold nanoparticles good candidates as biosensor, contaminant sensor, imaging contrast, or in drug delivery, and thermal cancer therapy. Shape, aspect ratio, and coating material effects on fate and transport of metallic nanoparticles especially gold within environment is the missing piece of this puzzle. In this research we tried to evaluate these parameters while mimicking real environmental conditions. We investigated gold nanorods with different characteristics such as aspect ratio and surface coating in various ionic strength solutions. Gold nanorods have been synthesized applying well-established methods and the surface coatings of nanoparticles have been changed as targeted. Different ionic strength solutions from very soft to very hard have been prepared according to EPA standards. Additionally effect of each salt such as CaSo4 and MgSO4 has been probed separately. The suspension and aggregates have been characterized by UV-VIS absorbance, DLS (dynamic light scattering), SEM (scanning electron microscopy), and TEM (transmission electron microscopy) techniques. Corresponding aggregation rate and aggregation assembly type (end-to-end or side-by-side) has been derived for each set of experiment by analyzing UV-VIS absorbance graphs.  Results suggest that where the charge repulsion is the dominant mechanism for anti-aggregation, colloidal stability of nanoparticles dramatically reduces as the ionic strength of the solution increases. On the other hand, where steric barrier is the case, stability is almost independent of solution ionic strength.

Colloidal stability of elongated shaped gold nanoparticles in aquatic environment

248th National Meeting (2014)

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