Quantum dot nanoparticles having enhanced stability and luminescence efficiency
Certain dithio-compounds have been found to be superior capping ligands for quantum dot (QD) nanoparticles. Example dithio-ligands include dithiocarbamate ligands. These strongly binding ligands are capable of coordinating to both positive and negative atoms on the surface of the nanoparticle. The ligands are bi-dentate and thus their approach to the QD surface is not as sterically hindered as is the approach of mono-dentate ligands. These ligands can therefore completely saturate the QD surface.
1. A quantum dot (QD) nanoparticle comprising:
a plurality of first dithiocarbamate capping ligands having a formula selected from the group consisting of
wherein each R 1 is a functional group; and
a plurality of second dithiocarbamate capping ligands having the formula
wherein R 2 is an alkyl group and R 3 is a functional group.
2. The QD nanoparticle recited in claim 1 , wherein R 1 comprises a hydrophilic group.
3. The QD nanoparticle recited in claim 1 , wherein R 1 comprises an amphiphilic moiety.
4. The QD nanoparticle recited in claim 1 ,
wherein each R 3 is selected from the group consisting of functional groups comprising a hydrophilic group and functional groups comprising an amphiphilic moiety.
5. The QD nanoparticle recited in claim 1 , wherein R 2 is an ethyl group.
6. A quantum dot (QD) nanoparticle comprising a plurality of first dithiocarbonate capping ligands having the general structure
wherein at least one of R and R′ is a C12 hydrocarbon chain with a carboxylic acid functionality on the C12 position.
7. The QD nanoparticle recited in claim 6 wherein one of R and R′ is an alkyl or aryl hydrocarbon.
8. The QD nanoparticle recited in claim 6 wherein one of R and R′ is an amphiphilic group.
9. The QD nanoparticle recited in claim 8 , wherein the amphiphilic group is a polyethyleneglycol (PEG).