Size-Dependent Optical Properties of Colloidal PbS Quantum Dots

We quantitatively investigate the size-dependent optical properties of colloidal PbS nanocrystals or quantum dots (Qdots), by combining the Qdot absorbance spectra with detailed elemental analysis of the Qdot suspensions. At high energies, the molar extinction coefficient epsilon increases with the Qdot volume d(3) and agrees with theoretical calculations using the Maxwell-Garnett effective medium theory and bulk values for the Qdot dielectric function. This demonstrates that quantum confinement has no influence on epsilon in this spectral range, and it provides an accurate method to calculate the Qdot concentration. Around the band gap, epsilon only increases with d(1.3), and values are comparable to the…

• BF
  Belgian Federal Science Policy Office
• FW
  Fonds Wetenschappelijk Onderzoek
• UG
  Universiteit Gent
• VR
  Vlaamse regering