TY - JOUR
T1 - Organic-to-aqueous phase transfer of cadmium chalcogenide quantum dots using a sulfur-free ligand for enhanced photoluminescence and oxidative stability
AU - Calzada, Raul
AU - Thompson, Christopher M.
AU - Westmoreland, Dana E.
AU - Edme, Kedy
AU - Weiss, Emily A.
N1 - Funding Information:
Research was primarily supported as part of the Argonne- Northwestern Solar Energy Research (ANSER) Center, an Energy Frontier Research Center funded by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), under Award DE-SC0001059 (ligand exchange optimization, electrochemistry, and stability testing), by the Northwestern Materials Research Science and Engineering Center (MRSEC), funded by the National Science Foundation (NSF) under Award DMR-1121262 (ligand exchange development). This work made use of the IMSERC at Northwestern University, which has received support from the NIH (1S10OD012016-01/1S10RR019071-01A1), the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF NNCI-1542205), the State of Illinois, and the International Institute for Nanotechnology (IIN).
PY - 2016/9/27
Y1 - 2016/9/27
N2 - This paper describes a procedure for transferring colloidal CdS and CdSe quantum dots (QDs) from organic solvents to water by exchanging their native hydrophobic ligands for phosphonopropionic acid (PPA) ligands, which bind to the QD surface through the phosphonate group. This method, which uses dimethylformamide as an intermediate transfer solvent, was developed in order to produce high-quality water-soluble QDs with neither a sulfur-containing ligand nor a polymer encapsulation layer, both of which have disadvantages in applications of QDs to photocatalysis and biological imaging. CdS (CdSe) QDs were transferred to water with a 43% (48%) yield using PPA. The photoluminescence (PL) quantum yield for PPA-capped CdSe QDs is larger than that for QDs capped with the analogous sulfur-containing ligand, mercaptopropionic acid (MPA), by a factor of 4 at pH 7, and by up to a factor of 100 under basic conditions. The MPA ligands within MPA-capped QDs oxidize at Eox ∼ +1.7 V versus SCE, whereas cyclic voltammograms of PPA-capped QDs show no discerible oxidation peaks at applied potentials up to +2.5 V versus SCE. The PPA-capped QDs are chemically and colloidally stable for at least 5 days in the dark, even in the presence of O2, and are stable when continuously illuminated for 5 days, when oxygen is excluded and a sacrificial reductant is present to capture photogenerated holes.
AB - This paper describes a procedure for transferring colloidal CdS and CdSe quantum dots (QDs) from organic solvents to water by exchanging their native hydrophobic ligands for phosphonopropionic acid (PPA) ligands, which bind to the QD surface through the phosphonate group. This method, which uses dimethylformamide as an intermediate transfer solvent, was developed in order to produce high-quality water-soluble QDs with neither a sulfur-containing ligand nor a polymer encapsulation layer, both of which have disadvantages in applications of QDs to photocatalysis and biological imaging. CdS (CdSe) QDs were transferred to water with a 43% (48%) yield using PPA. The photoluminescence (PL) quantum yield for PPA-capped CdSe QDs is larger than that for QDs capped with the analogous sulfur-containing ligand, mercaptopropionic acid (MPA), by a factor of 4 at pH 7, and by up to a factor of 100 under basic conditions. The MPA ligands within MPA-capped QDs oxidize at Eox ∼ +1.7 V versus SCE, whereas cyclic voltammograms of PPA-capped QDs show no discerible oxidation peaks at applied potentials up to +2.5 V versus SCE. The PPA-capped QDs are chemically and colloidally stable for at least 5 days in the dark, even in the presence of O2, and are stable when continuously illuminated for 5 days, when oxygen is excluded and a sacrificial reductant is present to capture photogenerated holes.
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U2 - 10.1021/acs.chemmater.6b03106
DO - 10.1021/acs.chemmater.6b03106
M3 - Article
C2 - 28260836
AN - SCOPUS:84989205121
VL - 28
SP - 6716
EP - 6723
JO - Chemistry of Materials
JF - Chemistry of Materials
SN - 0897-4756
IS - 18
ER -