Size-dependent properties of CdSe quantum dots

Temperature dependences of the magnetic susceptibility and heat capacity C₏ of CdSe quantum dots with size d=2. 8, 4. 1, and 5. 6 nm are compared to those of bulk CdSe to determine the size-dependent effects. With decreasing size d, the following effects are observed: (i) room temperature optical absorption shows a blueshift of the band gap; (ii) room temperature x-ray diffraction show wurtzite structure but with smaller lattice constants; (iii) magnetic susceptibility changes from negative (diamagnetic) for the bulk to positive with magnitude increasing with decreasing d; and (iv) the Sommerfeld constant determined from the C₏∕T vs T^2 data increases. Possible explanations for these size-dependent properties are presented.