This weekend, I was a “mentor” for KEYs, a program to introduce middle school girls to science and engineering. One of the things they got to see were quantum dots. While these have many applications, the demonstration was of their different colors.
For the demonstration, the scientists mixed quantum dots with a hydrogel, then put little pieces of the hydrogel in vials of water. The hydrogel was invisible in the water under ordinary light. Then, they had the girls put the vials under UV light, and the quantum dots lit up in different colors. (There were 3 vials, one with red, one orange and one green.)
They also had the girls look at some under a microscope. Then, they could see that individual dots blinked on and off, and that the appearance of a steady light was only because there were many many quantum dots. The girls thought this was pretty cool.
I wished I could have been one of them, and not a mentor, because I didn’t get to see and do everything. I just told them what I do, and then followed the group around and helped them fill out their worksheets. And got really tired and useless at the end of the day.
One thing that concerned me a little, was that the scientists were men. The lab we were has a woman PI, (she was the one who started the program for middle school girls), and some of the more junior members of the lab were women, but much of the time it was men explaining things, because they were the ones who knew most about the subjects. However, I hope that the girls got the impression that women and men are equal, since there were plenty of women around the whole time. I worry, however, that we sabotaged ourselves.
But to come back to the science without regard to feminism, quantum dots are cool. To summarize them, they are called dots because they are very small, and they are called quantum because each dot only emits a certain wavelength of light, due to the quantized diffence between electron energy levels. When the dots are hit by UV light, some of their electrons jump to higher energy levels, using the energy from the light. When the electrons jump back down, they must lose energy in the form of a specific wavelength of light.