Power and Wavelength Dependence of Photoenhancement in (CdSe)ZnS-Dopamine in Aqueous Solution and Live Cells

(CdSe)ZnS-Dopamine. Photoluminescence. Photoenhancement. Living Cell CdSe(ZnS) quantum dots conjugated to the electron donor dopamine show enhancement of photoluminescence over a time course of seconds to minutes when exposed to ultraviolet or blue irradiation. This phenomenon is observed when the dots are in aqueous solution as well as after endocytosis by living cells. The rate of enhancement is directly related to the number of dopamine conjugates per quantum dot, and can be semi-quantitatively adjusted over a wide range. Uptake of the particles by cells is also dependent upon surface coverage, with moderate coverages proving ideal for both uptake and relative signal enhancement. The enhancement is strongly power-dependent and may also show dependence upon wavelength; however, direct excitation of the dopamine molecule is not necessary for the enhancement effect.