Copyright 2004 by Marcel Dekker, Inc. All Rights Reserved.

levels (fV1 Mn per NQD). Despite input concentrations of f0.5–5% dopantprecursor, dopant incorporation is only f0.025–0.125%. In the Cd(Mn)Sesystem, for example, Mn 2+ incorporation into CdSe was limited to nearsurfacelattice sites, and the remaining Mn 2+ was present merely as ‘‘surfaceassociated’’ions. The location of the dopant ions following DMS NQDpreparation was elucidated using a combination of chemical surface treatmentsand EPR measurements. Surface-exchange reactions, involving thoroughreplacement of TOPO/TOP capping ligands for pyridine, revealed thatmuch of the dopant cations were only loosely associated with the NQDsurface. EPR spectra following surface exchange showed a dramatic decreasein intensity following surface exchange (Fig. 24), indicating that the majorityof dopant ions were not successfully incorporated into the CdSe crystallattice. Further, even limited incorporation of Mn into the CdSe latticerequired the use of a single-source Mn–Se precursor [Mn 2 (A-SeMe) 2 (CO) 8 ],rather than a simple Mn-only precursor [e.g., MnMe 2 , Mn(CO) 5 Me, (MnTe(CO) 3 (PEt 3 ) 2 ) 2 ]. In the absence of the single-source dopant precursor, whichFigure 24 Low-temperature (5 K) EPR spectra of 4.0-nm-diameter Mn-dopedCdSe NQDs prepared using (a,b) a Mn-only precursor and (c,d) the Mn 2 (A-SeMe) 2 (CO) 8 single-source precursor. Before purification (a,c), both samples displaythe six-line pattern characteristic of Mn. After pyridine cap exchange (b,d), only thesample prepared with the single-source precursor retains the Mn signal. (From Ref.64, reprinted with permission.)Copyright 2004 by Marcel Dekker, Inc. All Rights Reserved.