期刊
JOURNAL OF PHYSICAL CHEMISTRY C
卷 114, 期 17, 页码 7793-7805出版社
AMER CHEMICAL SOC
DOI: 10.1021/jp1005023
关键词
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资金
- National Science Foundation [CHE-0453126, CHE-0342912, DBI-0217922]
- National Institutes of Health [CA52955, GM65790]
- Royal Thai Government
- U.S. Department of Energy [DE-FG02-05ER46232-A002]
- U.S. Department of Energy (DOE) [DE-FG02-05ER46232] Funding Source: U.S. Department of Energy (DOE)
Quantum dot (QD) fluorescence is effectively quenched at low concentration by nitroxides bearing amine or carboxylic acid ligands. The association constants and fluorescence quenching of CdSe QDs with these derivatized nitroxides have been examined using electron paramagnetic resonance (EPR) and fluorescence spectroscopy. The EPR spectra in the nonprotic solvent toluene are extremely sensitive to intermolecular and intramolecular hydrogen bonding of the functionalized nitroxides. Fluorescence measurements show that quenching of QD luminescence is nonlinear, with a strong dependence on the distance between the radical and the QD. The quenched fluorescence is restored when the surface-bound nitroxides are converted to hydroxylamines by mild reducing agents or trapped by carbon radicals to form alkoxyamines. EPR studies indicate that photoreduction of the nitroxicle occurs in toluene solution upon photoexcitation at 365 nm. However, photolysis in benzene solution gives no photoreduction, suggesting that photoreduction in toluene is independent of the quenching mechanism. The fluorescence quenching of QDs by nitroxide binding is a reversible process.
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