Tangential Flow Filtration of Colloidal Silver Nanoparticles: A “Green” Laboratory Experiment for Chemistry and Engineering Students

Abstract

Numerous nanoparticle (NP) fabrication methodologies employ “bottom-up” syntheses, which may result in heterogeneous mixtures of NPs or may require toxic capping agents to reduce NP polydispersity. Tangential flow filtration (TFF) is an alternative “green” technique for the purification, concentration, and size-selection of polydisperse NP suspensions or colloids, in that it allows for real-time analysis and reduces the usage of additional solvent and post-synthetic reagents. Upper-division undergraduate and graduate students in engineering and chemistry successfully applied a three-step TFF process to reduce the polydispersity of Creighton colloidal silver nanoparticles (AgNPs). UV–vis absorption spectroscopy in conjunction with the Lambert–Beer law and Mie’s solutions to the Maxwell equations were employed to rapidly estimate the concentration and size of nanosilver in each TFF-fractionated colloidal sample using the localized surface plasmon resonance (LSPR) of AgNPs. A thorough emphasis on “green” nanochemistry and its underlying principles were also provided to educate the next generation of environmentally conscious nanochemists and nanoengineers for the ever-expanding nanosectors. The overall laboratory experience was perceived as intellectually stimulating and was highly rated in the student evaluations. This interdisciplinary experiment may be implemented in various nanotechnology, physical, or analytical courses.