Question

What is the observed variation in volors and what is the realtionship between these colors and the electtonic structure of the material?

GO FIGURE As the size of the quantum dots decreases, does the wavelength of the emitted light increase or decrease? Size of CdSe quantum dots 2 nm →7 nm 2.7 eV 2.0 eV Band gap energy, Eg A FIGURE 12.44 Photoluminescence. When illuminated with ultraviolet light, these solutions, each containing nanoparticles of the semiconductor CdSe, emit light that corresponds to their respective band gap energies. The light emitted depends on the size of the CdSe nanoparticles.

Answer 1

Quantum dots( from figure 12.44)

As the band gap energy and wavelength increases the colour changed violet to red. From 2nm to 7nm the colour varies from violet to red and correspondingly size of electronic structure of quantum dot will increases from small to larger one. Larger Quantum Dots of 5–6 nm diameter emit longer wavelengths, with colours such as orange or red. Smaller Quantum Dots (2–3 nm) emit shorter wavelengths, yielding colors like blue and green. As the size of the Quantum Dots decreases wavelength of emitted light decreases.