A practical proposal for silver nanoparticles (Ag-NPs) separation by differential centrifugation

The interaction of nanomaterials with biomolecules can be enhanced and amplified when the nanomaterials have specific sizes and shapes; for this reason, a rapid discrimination/separation of the nanoparticles, at least in sizes, is necessary and important. In this work, we show a practical proposal by using centrifugation processes for the separation of silver nanoparticles synthesized by laser ablation. By means of a non-complex differential centrifugation process, varying the rotational speed from 5000 to 25,000 revolutions per minute (rpm), it was possible to separate silver nanoparticles with an average size of 11 nm, from a colloidal solution of nanoparticles with sizes within a range between 8 and 120 nm. Additionally, a simple decay mathematical relationship was determined and proposed, as a first approximation, where the diameter of the nanoparticles is inversely proportional to the exponential function of the centrifugation speed. Here, we have reduced the degree of polydispersity of the silver colloids, in which the nanoparticles were separated by high centrifugation using a Hermle centrifuge, model Z36HK.