Group IV nanocrystals with ion-exchangeable surface ligands and methods of making the same
Methods are described that include reacting a starting nanocrystal that includes a starting nanocrystal core and a covalently bound surface species to create an ion-exchangeable (IE) nanocrystal that includes a surface charge and a first ion-exchangeable (IE) surface ligand ionically bound to the surface charge, where the starting nanocrystal core includes a group IV element.
1. A method comprising:
contacting a starting nanocrystal with a precursor of a first ligand and at least one of an oxidizing agent or a reducing agent, wherein:
the starting nanocrystal comprises a core having an outer surface and a starting ligand covalently bound to the outer surface,
the contacting results in a removal of at least a portion of the starting ligand from the core and the formation of a first charge on the outer surface,
the contacting results in the formation of the first ligand having a second charge opposite to the first charge,
the second charge associates with the first charge to form a first nanocrystal comprising the first ligand ionically bound to the core, and
the first ligand is capable of being reversibly exchanged with a second ligand to form a second nanocrystal comprising the second ligand ionically bound to the core.
2. The method of claim 1 , wherein the core comprises a group IV element.
3. The method of claim 2 , wherein the group IV element comprises germanium.
4. The method of claim 1 , wherein the starting ligand comprises at least one of hydrogen, a saturated hydrocarbon, an unsaturated hydrocarbon, a halogen, or a chalcogen.
5. The method of claim 1 , wherein the first charge is negative.
6. The method of claim 5 , wherein the first ligand comprises at least one of an alkylammonium, a phosphonium, a hydrazinium, or an alkali metal.
7. The method of claim 6 , wherein the first ligand comprises at least one of oleylammonium, CH 3 (CH 2 ) 11 NH 3 + , CH 3 NH 3 + , N 2 H 5 + , or Na + .
8. The method of claim 1 , wherein the first charge is positive.
9. The method of claim 8 , wherein the first ligand comprises at least one of BF 4 − , ClO 4 − , PF 6 − , (C 6 H 5 ) 4 B − , or (C 6 F 5 ) 4 B − .
10. The method of claim 1 , wherein the contacting removes substantially all of the starting ligand.
11. The method of claim 1 , wherein the reducing agent comprises at least one of a sulfide, an alkali metal, an alkaline earth metal, an alkyllithium reagent, a Grignard reagent, a metal hydride, sodium borohydride, or dihydrogen.
12. The method of claim 1 , wherein the oxidizing agent comprises at least one of NOBF 4 , [(CH 3 CH 2 ) 3 O][BF 4 ], an elemental halide, or an elemental chalcogen.
13. The method of claim 1 , wherein the precursor of the first ligand comprises at least one of an alkali metal salt, oleylamine, hydrazine, ammonia, an amine, or a phosphine.
14. The method of claim 1 , further comprising:
an additional contacting of the first nanocrystal with a precursor of the second ligand, wherein:
the additional contacting results in the forming of the second nanocrystal, and
the second ligand is different from the first ligand.
15. A nanoparticle comprising:
a core comprising a group IV element and an outer surface having a surface charge; and
a first ligand comprising a charge opposite of the surface charge, wherein:
the first ligand is ionically bound to the core, and
at least a portion of the first ligand is capable of being reversibly exchanged with a second ligand.
16. The nanoparticle of claim 15 , wherein the group IV element comprises germanium.
17. The nanoparticle of claim 15 , wherein:
the first ligand comprises at least one of oleylammonium, Na + , NR x H y + , or PR' v H w + , and
R is a first organic group, R' is a second organic group, y=4−x, and w=4−v.
18. The nanoparticle of claim 15 , wherein the first ligand comprises at least one of BF 4 − , ClO 4 − , PF 6 − , (C 6 H 5 ) 4 B − , or (C 6 F 5 ) 4 B − .