Nanoparticles & Light Energy Experiment: Quantum Dots and Colors
Fluorescent quantum dot solutions illustrate how varying particle sizes release distinct wavelengths of colors. Quantum dot size increases as solutions transition from violet to red (l to r).Copyright 2009 X. Gao. Image reprinted by permission from Macmillan Publishers Ltd: [Nature] Sanderson, Katharine. "Quantum dots go large," Special Report, Nature. Macmillan Publishers Ltd. 459 (11), pp. 760-761; June 2009. http://unanotech.com/wp-content/uploads/2011/06/Nature_Quantum_dots_go_large.pdf
Students are introduced to the physical concept of the colors of rainbows as light energy in the form of waves with distinct wavelengths, but in a different manner than traditional kaleidoscopes. Looking at different quantum dot solutions, they make observations and measurements, and graph their data. They come to understand how nanoparticles interact with absorbing photons to produce colors. They learn the dependence of particle size and color wavelength and learn about real-world applications for using these colorful liquids.
Quantum dots are being used in many real-world applications such as cancer treatments and solar energy generation. Cancer treatments take advantage of the UV absorption ability of different-sized quantum dots to release specific wavelengths of light for detection and monitoring purposes. Traditional polycrystalline solar cells are expensive and limited in efficiency; quantum dots allow engineers to tailor properties to absorb all energy from the Sun (UV-IR) and produce electrical power. The advantages of using quantum dots included enhanced surface area for absorption and particle size-absorption interactions.
After this activity, students should be able to:
- Describe colors in terms of light energy and wavelength.
- Describe how quantum dots work.
- Describe the interplay between quantum dot particle size and color.
- Explain some practical applications for quantum dots.