Quantum Dot Surfaces

Quantum dot surfaces are redox active and are known to influence the electronic properties of nanocrystals, yet the molecular-level changes in surface chemistry that occur upon addition of charge are not well understood.

In a paper, published in Nano Letters, Ph.D. Student Carolyn Hartley and Professor Jillian Dempsey of the Dempsey Research Group, report a systematic study monitoring changes in surface coordination chemistry in 3.4 nm CdSe quantum dots upon remote chemical doping by the radical anion reductant sodium naphthalenide (Na[C10H8]). These studies reveal a new mechanism for charge-balancing the added electrons that localize on surface states through loss of up to circa 5% of the native anionic carboxylate ligands, as quantified through a combination of UV–vis absorption, 1H NMR, and FTIR spectroscopies.

This work introduces a new new method for distinguishing between reduction of surface metal and chalcogenide ions by monitoring ligand loss and optical changes upon doping, and work emphasizes the importance of studying changes in surface chemistry with remote chemical doping and is more broadly contextualized within the redox reactivity of the QD surface.