Quantum dots fluorescence

[bluejay27]

Quantum dots fluorescence whenever UV light is applied to them. Whenever the UV light is off and visible light hits the quantum dots it posses colors but does not fluorescence. I thought light had to have energy that is equal or greater than the band gap for the quantum dots to emit light. How does emission occur if visible light does not have enough energy to excite the electrons of the quantum dots.

 

[Ygggdrasil]

Color can come from the solution absorbing light. For example, I commonly work with a fluorescent dye that absorbs light in the orange-red end of the visible spectrum (peak absorbance ~ 650 nm). Even though the dye emits red light, solutions of the dye appear blue because when light passes through the solution, the lower wavelengths of light are absorbed, while blue and other higher wavelengths of light are transmitted.