Recent Research Projects

Nanocrystals in Molten Salts

Our group recently reported on the formation of colloidal solutions of NCs  dispersed in molten inorganic saltsMolten inorganic salts represent a very attractive class of solvents for the synthesis and processing of nanomaterials due to their high temperature stability, wide electrochemical window, stability in the presence of highly reactive species, the ability to dissolve many ionic solids not soluble in traditional solvents, and transparency in a broad range of the electromagnetic spectrum. Currently we explore both fundamental and applied aspects of these unusual colloidal media.

(a) Phase transfer of Pt NCs from decane phase n-decane to molten inorganic salt. (b) Small angle X-ray scattering for 4.0 nm Pt NCs in toluene solution and the same NCs in molten inorganic salt. Both curves show I(q) characteristic of a stable colloidal solution. (c) NC surface induces a solvent restructuring with electrostatic correlations extending an order of magnitude beyond the Debye screening length. These strong oscillatory ion–ion correlations, which are not accounted by the traditional mechanisms of steric and electrostatic stabilization of colloids, enable apparently “impossible” colloidal stabilization in highly ionized media. 

Molten inorganic salts can be applied to the synthesis of ternary III-V semiconductor colloidal QDs.
Molten inorganic salts can be applied to annealing structural defects in colloidal GaAs NCs.

State-Resolved Charge Transport in Colloidal Quantum Dots

The novel hybrid surface passivation process efficiently eliminates surface states of HgTe QDs, enabling reversible filling of quantum-confined orbitals, switching between n-type and p-type transport, and air-stable tunable doping. The striking observations of well-resolved conductance peaks for the HgTe QD FETs and unprecedentedly high electron mobility for QD devices showing transport through discrete electronic states, represent a new level of control and performance in the application of QD solids.

Direct Optical Patterning of Inorganic Materials

We introduced a general chemical approach for photoresist-free, direct optical lithography of functional inorganic nanomaterials (DOLFIN). The patterned materials can be metals, semiconductors, oxides, magnetic, or rare earth compositions. No organic impurities are present in the patterned layers, which helps achieve good electronic and optical properties.