Quantum Dots

## General Information (more on wikipedia)

 Molecular Weight Density Radius @Temperature Reference Species QD655 MW D 35 nm 37 celcius [1]

A quantum dot is a semiconductor nanostructure that confines the motion of conduction band electrons, valence band holes, or excitons (bound pairs of conduction band electrons and valence band holes) in all three spatial directions. The confinement can be due to electrostatic potentials (generated by external electrodes, doping, strain, impurities), the presence of an interface between different semiconductor materials (e.g. in core-shell nanocrystal systems), the presence of the semiconductor surface (e.g. semiconductor nanocrystal), or a combination of these. A quantum dot has a discrete quantized energy spectrum. The corresponding wave functions are spatially localized within the quantum dot, but extend over many periods of the crystal lattice. A quantum dot contains a small finite number (of the order of 1-100) of conduction band electrons, valence band holes, or excitons, i.e., a finite number of elementary electric charges.

## Diffusion of in water:

• $D = \ \mu m^{2} s^{-1}$

## Diffusion of QD655 in dilute agarose medium (close to cell culture medium):

• polyethylene glycol-coated QD655 at 37 degrees: $D = 18.6\ \mu m^{2} s^{-1}$ [1]

## Diffusion of QD655 in below the pial surface of ECS brain cells :

• polyethylene glycol-coated QD655 at 37 degrees: $D = 0.167\ \mu m^{2} s^{-1}$ [1]
Bibliography
1. PNAS ; April 4, 2006 ; vol. 103 ; no. 14 ; 5567-5572