I apologize to my readers for the length of time that has passed between this post and my last. It is funny how time can get away from you when you are always doing something. I want to begin this update with a little more in depth explanation regarding some of the backtracking with the "terrace" phase of the project. Below I have added images of spheres which have been deposited on silica using two different methods. The pictures are slightly out of order due to a difficult image adding process but the captions for each are correct and should help with any confusion. What you see are the Langmuir-Blodgett technique and the drop evaporation technique. The LB technique is done using 200 nm spheres whereas the drop technique is done using 100 nm spheres. For the LB technique, extra surfactant must be added to help drive the spheres to the silica surface during the withdrawal step, which is crucial to keeping the amount of spheres at the liquid solid interface roughly constant and facilitate the formation of the mono-layer This extra surfactant is what you see crammed in between the spheres in the middle two images below, and as you might notice it is quite thick. The formation of the desired pillars is dependent on etching in the spaces between the beads and if it is clogged with the extra surfactant the etching is not able to be done correctly. To correct this a different approach had to be taken which is where the drop evaporation method comes in. This technique does not require the use of any extra surfactant and actually allows for a cleaning step where the beads are centrifuged to try and remove as much surfactant as possible. I made several different concentrations of 100 nm beads and deposited them onto silica in order to determine what the best concentration of beads was for forming the best mono-layer I determined it was 0.5 wt % and made a few more samples, the results of which can be seen in the first and 4th images below. As you can see they are still a mono-layer (with more interruptions that the LB method but a good amount of coverage comparatively and they are much cleaner. The only surfactant observed exists as the connections between the spheres which is essential for their forming a layer. Etching has finally begun again and although due to an already hectic schedule I have not yet been able to properly observe the results of the etching yet I am excited to see what kind of progress this has made!
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| 100 nm spheres-Drop evaporation Technique |
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| 200 nm spheres-Langmuir-Blodgett Technique |
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| 200 nm spheres-Langmuir-Blodgett Technique |
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| 100 nm spheres-Drop evaporation Technique |
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