Hi Jianqian and Jessica,
We’ve finished doing some measurements on the Mn doped ZnSe quantum dots. After playing around with the excitation wavelength we measured about a 75% modulation depth for both the quantum dots in water and the quantum dots in micelles. This is for a laser intensity of about 1MW/cm2 for the 660nm red laser, and we excited the dots with a 470nm LED. Exciting with a 405LED we saw very little modulation – I’m not sure if this is because of the overall excitation power or the wavelength. This is close to the modulation reported in the Hell paper. Although the modulation depth is not quite as high and didn’t show a strong dependence on power. The dots had a tendency to clump up even after sonicating – so it’s possible that out-of-focus dots contributed to the signal reducing the modulation depth. Andrew just posted some images.
The dots in chloroform were bad by the time we tried to measure them. All the chloroform had evaporated. We put them in hexane, but they weren’t that bright and were more green than yellow. Do you think quantum dots in solvent would disperse better on the coverslip?
Let us know what you think,