Question

With the reduction in particle size, optical absorption spectrum shows:

• A. Blue Shift
• B. Red Shift
• C. Green Shift
• D. Yellow Shift

Hint:

In Quantum Dots the energy gap in these materials becomes inversely proportional to its size. The higher the energy gap, the shorter the wavelength of the emitted light.

Answer 1

The Correct Option is A

When a material's particle size is reduced to the nanoscale, quantum confinement occurs. This makes electron energy levels discrete and further apart, increasing the band gap. The more the particle size decreases, the stronger the quantum confinement effect, which requires more energy for electronic transitions. Consequently, the absorption spectrum shifts towards higher energies and shorter wavelengths, a phenomenon known as a blue shift.