Probing the local site environments in Mn:CdSe quantum dots

A quantum dot (QD) contains a well-defined surface passivated by ligands and a bulklike core. The effect of surface passivation and lattice truncation on local structural and electronic microenvironments within a CdSe QD is an area of active research. Selectively probing the local microenvironments that exist at the surface and core of the QD is difficult but can be achieved by use of a Mn(II) impurity ion doped into a CdSe QD using electron paramagnetic resonance (EPR). By use of high frequency EPR (HF-EPR) spectroscopy, the site-dependent perturbation experienced for Mn(II) incorporated as a guest ion into CdSe QDs allows the distinguishing of two unique microenvironments within the QD, namely, an unperturbed core and an electronically distorted surface. Analysis of the Landé g-factor, hyperfine constant (A), and the distribution of g and D (δg, δD) allows the local microenvironments within CdSe to be probed as a function of size, ligand passivation, and site of Mn(II) incorporation.