Photochemical instability of thiol-capped CdTe quantum dots in aqueous solution and living cells: process and mechanism.
The process and mechanism of photochemical instability of thiol-capped CdTe quantum dots (QDs) in aqueous solution were experimentally studied. After laser irradiation, the corresponding Raman bands of the Cd-S bond decreased obviously, indicating bond breaking and thiol detachment from the QD surfaces. Meanwhile, a photoinduced aggregation of QDs occurred with the hydrodynamic diameter <Dh> increased to hundreds of nanometers from an initial 20 nm, as detected with dynamic light scattering measurements. The bleaching of the photoluminescence of QDs under laser irradiation could be attributed to the enhanced nonradiative transfer in excited QDs caused by increased surface defects due to the losing of thiol ligands. Singlet oxygen (1O2) was involved in the photooxidation of QDs, as revealed by the inhibiting effects of 1O2 quenchers of histidine or sodium azide (NaN3) on the photobleaching of QDs. The linear relationship in Stern-Volmer measurements between the terminal product and the concentration of NaN3 demonstrated that 1O2 was the main pathway of the photobleaching in QD solutions. By comparing the photostability of QDs in C2C12 cells with and without NaN3 treatment, the photooxidation effect of 1O2 on photobleaching of cellular QDs was confirmed.
Ma
Jiong
J
Surface Physics Laboratory (National Key Laboratory), Physics Department, State Key Laboratory for Advanced Photonic Materials and Devices, Fudan University, Shanghai, PR China.
Chen
Ji-Yao
JY
Zhang
Yu
Y
Wang
Pei-Nan
PN
Guo
Jia
J
Yang
Wu-Li
WL
Wang
Chang-Chun
CC
D000818:Animals; D019187:Cadmium Compounds / Q000737:chemistry*; D002460:Cell Line; D002470:Cell Survival; D002850:Chromatography, Gel; D051379:Mice; D038761:Photobleaching; D045663:Quantum Dots; D012996:Solutions; D013059:Spectrum Analysis, Raman; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013691:Tellurium / Q000737:chemistry*
D019187:Cadmium Compounds; D012996:Solutions; D013438:Sulfhydryl Compounds; D013691:Tellurium; C028337:cadmium telluride