Size-controlled ex-nihilo ferromagnetism in capped CdSe quantum dots

The observation of RTEM in CdSe quantum dots (QD) capped with TOPO was investigated. XPS and EXAFS studies on TOPO passivated CdSe QDs have shown that TOPO binds only at the Cd site and that the surface coverage on the Cd sites varies from a high of about 60% for D=2 nm to about 35% for D>3 nm. The mechanism of charge transfer from Cd to TOPO invoked in the interpretation was measured in some of the samples using XANES (X-ray absorption near-edge structure) and EXAFS (extended X-ray absorption fine structure) spectra of TOPO-capped CdSe QDs. It was observed that with the reduction in size D of the CdSe QDs, an increase in the d-hole population of the Cd 4d band is possible as a result of the charge redistribution with the capping agent TOPO.