PS小球自组装三维胶体晶体--来自国外某知名实验室

1. Centrifugation is useful for all kinds of spheres. Spheres are available as 4%, 8% and 10% solution. To get very large grain size we need the concentration of about 20%~35% or more. Centrifugation time should be set experimentally. For our centrifuge it is: 17~20min for 450-600nm spheres, 15-17min for 1000nm spheres, 8-12min for 1700-2000nm spheres, smaller spheres of 200-300nm require 30min centrifugation(because our centrifuge is slow.). 2. You should start with about 1:1 spheres-to-methanol ratio. If you see that spheres do not spread out on the water surface during deposition, it means that you have either a dirty preparation dish or not enough methanol --add one or two droplets methanol, replace water, try again. Add only a few droplets, test it, see how it works, if worked, add more. 3. If you do not have any success and you want to try again always refilling the dish with water, do not try with the same water again, it will not work. 4. Do not touch the water surface before deposition, if you see some dust or a hair remove it with clean tweezers, do not touch the water—it will change the surface tension. 5. Again: if spheres come on water surface too slowly and do not spread out use more methanol, if you have an opposite situation(too much methanol)—you will see probably grains are very small or there will be not any grains at all. 6. Deposition wafer must be hydrophobic—clean it only with methanol or ethanol, if you want to prepare a new one—cut a silicon wafer, put it into soap solution hours and then rinses it with ethanol. 7. For a very large sample—2’’ or 3’’ you will need a larger deposition wafer set the smaller pipette to maximum and apply the spheres on the silicon deposition wafer twice. 8. Do not wait to long between applying the spheres on the deposition wafer and immersing the wafer in the water-methanol evaporates. 9. Add a dilute soap solution from different direction to control the shape of the mask during compression, you can use your finger as well—works very well(because it is always a little grease). 10. Sinking spheres are like a pain in the ass—the best way to clean the mask is first to drain the spheres using a pump(as much as possible)—add soap when doing this! Then use a spoon to gently stir the water which will move the mask on the water surface and because the inner faces these spheres will detach from the mask and then can be easily drain out using a pump. 11. When drying a sample, keep it tilted—this will force the water on the top of the wet sample to evaporate in one direction and it will force the free spheres on the top of monolayer to go to the edge—this way you may expect to have more clean sample (at least on one edge) than keeping the sample lying flat during drying.