Understanding the formation mechanism of intrinsic and extrinsic defects on colloidal semiconductor quantum dot surfaces could provide a breakthrough in the synthesis and doping of QDs. To study how extrinsic defects are formed during the growth of colloidal QDs we have started an effort using molecular analogs of II-VI QDs as model systems of the QD surfaces. Initial studies have focused on metal ion exchange reactions in molecular clusters with the general formula [M4(EPh)10]2- and [M10E4(EPh)16]4- (M = Zn, Cd, Co, Mn and E = S, Se), which have been used as single-source precursors for producing pure QDs and are smaller than the critical size for QD nucleation. Using a combination of analytical and dopant-specific spectroscopies we confirm incorporation of paramagnetic Co2+ ions into tetrameric metal clusters. The solution chemistries of these doped tetrameric clusters strongly suggests that the [(Zn1-xCox)4(SPh)10]2� and [(Cd1-xCox)4(SPh)10]2- equilibrium favors Co2+ substitution into the Zn cluster compared to the Cd cluster. This result is in agreement with stabilities of Co2+ in ZnS and CdS quantum dots [Radovanovic and Gamelin, J. Am. Chem. Soc., 2001 , 123, 12207]. We will also present recent results on the solution stabilities and cluster formation kinetics as a function of dopant identity and concentration using in situ andstopped-flow spectroscopies.

Molecular clusters as models of quantum dot surfaces

248th National Meeting (2014)

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