Coating glass with two-component metal colloids via Marangoni Flow
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Microfluidics, the study of physics at nanoliter volumes, has burgeoned due to the myriad of practical applications in biology, chemistry and medicine. Borosilicate glass can be spontaneously coated with a film of passivated Ag nanoparticles via a process known as Marangoni flow. Silver nanoparticles suspended in chloroform are mixed with a water/ethanol (v/v) mixture containing acidified 11-mercaptoundecanoic acid. Following mechanical agitation, Ag nanoparticles embedded in a film are driven from the organic?aqueous interface. A reddish-brown colored film, verified by transmission electron microscopy to contain uniformly dispersed Ag nanoparticles, is observed to spontaneously climb the interior surface of an ordinary, laboratory glass vial. To test the general applicability of this method, Marangoni flow with two nanostructures composed of different elements and morphologies was tested. When passivated gold nanoparticles in toluene are added to this system, the rate of Marangoni flow increases. To test that both nanostructures are present in the transferred film, optical spectroscopic detection was employed. While optical detection can distinguish Ag and Au nanoparticles in suspension, on a surface they can?t easily be distinguished because of lateral interactions among the nanoparticles. Therefore, gold nanorods with an extinction spectral features located to the red of the Ag spherical nanoparticles were synthesized and added to our Marangoni flow system. Preliminary results are presented.