So I have made progress in creating monolayers of polystyrene microspheres on glass. Because I have been using glass slides as practice I am a little nervous about how changing to the silica substrate will affect the monolayer formation. Using previous literature I have performed 7 trials with various sphere sizes in either water or a water/methanol mixture to improve formation and film continuity. Using an optical microscope I can see the formation of these layers with 2 micron sized spheres but am unable to say with certainty about the 500 and 200 nm sized spheres. The glass coverage is greater with decreasing sphere size and when using methanol and 2 micron spheres the coverage was greater but from what I can tell using a microscope it appears that a multilayer may have formed over most of the surface with small patches of monolayers scattered throughout. I have repeated the trial and the sample is being dried overnight and observations will be made again tomorrow. I will begin using silica next week and hopefully will be able to begin taking SEM images of these in order to determine with certainty the formation of this monolayer. The literature that I'm using was performing these trials on highly ordered pyrolytic graphite and saw the best film coverage on this so I may have to see what I with silica and consider other options.
Thursday, January 26, 2012
Tuesday, January 10, 2012
Multiple Day Update
Have been working in the lab but forgot to update the blog on my progress.
Last week I mixed a 6 mL solution of 2 micron latex spheres (1% wt, 2.4 mL latex solution, 3.6 mL nanopure water) and added SDS as a spreading agent (31.093 mM). The solution was then sonicated fo 10 min and a piece of glass (microscope slide cover) was lowered about 4 mm into the solution and withdrawn at roughly 1 micron/second for 1 hour and 12.5 minutes. The glass was allowed to dry for 140 min and then viewed under an optical microscope. The film appeared to be a monolayer of latex spheres but was was patchy. To help fix this I will be performing this again with a modified version of a Langmuir-Blodgett trough to keep an effective concentration of spheres near the surface of the glass as it's withdrawn. Will add an update of this shortly.
I have also cleaned a silicon wafer using a plasma cleaner and ammonium hydroxide/hydrogen peroxide solution and cleaved a small area for AFM. The RMS roughness of the silicon piece was determined to be 0.268 nm.
Last week I mixed a 6 mL solution of 2 micron latex spheres (1% wt, 2.4 mL latex solution, 3.6 mL nanopure water) and added SDS as a spreading agent (31.093 mM). The solution was then sonicated fo 10 min and a piece of glass (microscope slide cover) was lowered about 4 mm into the solution and withdrawn at roughly 1 micron/second for 1 hour and 12.5 minutes. The glass was allowed to dry for 140 min and then viewed under an optical microscope. The film appeared to be a monolayer of latex spheres but was was patchy. To help fix this I will be performing this again with a modified version of a Langmuir-Blodgett trough to keep an effective concentration of spheres near the surface of the glass as it's withdrawn. Will add an update of this shortly.
I have also cleaned a silicon wafer using a plasma cleaner and ammonium hydroxide/hydrogen peroxide solution and cleaved a small area for AFM. The RMS roughness of the silicon piece was determined to be 0.268 nm.
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