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 the particle size of a material is reduced to the nanoscale, a phenomenon known as quantum confinement occurs. This means that the energy levels available for electrons within the material become discrete and move further apart from one another. As a result the band gap increases. As particle sizes decrease, the quantum confinement effect becomes more pronounced, leading to an increase in the energy required for electronic transitions. This, in turn, causes a shift in the absorption spectrum towards higher energies, corresponding to shorter wavelengths. This shift toward shorter wavelengths is referred to as a blue shift.