ABSTRACT
A one-step method to produce ≈12 nm hydrodynamic diameter water-soluble CdSe/ZnS quantum dots (QDs), as well as CdS/ZnS, ZnSe/ZnMnS/ZnS, AgInS2 /ZnS, and CuInS2 /ZnS QDs, by ligand exchange with a near-monolayer of organosilane caps is reported. The method cross-links the surface-bound silane ligands such that the samples are stable on the order of months under ambient conditions. Furthermore, the samples may retain a high quantum yield (60%) over this time. Several methods to functionalize aqueous QD dispersions with proteins and fluorescent dyes have been developed with reaction yields as high as 97%.
Subject(s)
Quantum Dots/chemistry , Silanes/chemistry , Water/chemistry , Biotinylation , Cadmium Compounds/chemistry , Cellulose/chemistry , Dynamic Light Scattering , Hydrodynamics , Rhodamines/chemistry , Selenium Compounds/chemistry , Solubility , Sulfides/chemistry , Zinc Compounds/chemistryABSTRACT
We report here a method for synthesizing CdSe quantum dots (QDs) containing copper such that each QD is doped with four copper ions. The synthesis is a derivative of the cluster-seed method, whereby organometallic clusters act as nucleation centers for quantum dots. The method is tolerant of the chemical identity of the seed; as such, we have doped four copper ions into CdSe QDs using [Na(H2O)3]2[Cu4(SPh)6] as a cluster seed. The controlled doping allows us to monitor the photophysical properties of guest ions with X-ray spectroscopy, specifically XANES and EXAFS at the copper K-edge. These data reveal that copper can capture both electrons and holes from photoexcited CdSe QDs. When the dopant is oxidized, photoluminescence is quenched and the copper ions translocate within the CdSe matrix, which slows the return to an emissive state.
Subject(s)
Cadmium Compounds/chemistry , Copper/chemistry , Crystallization/methods , Nanostructures/chemistry , Nanostructures/ultrastructure , Quantum Dots , Selenium Compounds/chemistry , Materials Testing , Particle SizeABSTRACT
We have developed a strategy for the ratiometric detection of toxic Hg(2+) ions using a semiconductor nanocrystal energy-transfer donor coupled to a mercury-sensitive "turn-on" dye acceptor. The results demonstrate a new paradigm of toxic metal sensing that resolves the difficulties with the use of semiconductor nanotechnology for this purpose.
