Quantitation Quantum dots

As briefly mentioned in the previous section, PCS provides quantitative information on the lifetime of the non-radiative state for molecules in solution in the time range from sub-microseconds to seconds. This method can, potentially, be applied to the characterization of the photophysical properties of quantum dots freely diffusing in solution with higher temporal resolution than the previous SPD. 

As mentioned in the introductory part of this section, quantum dots exhibit quite complex non-radiative relaxation dynamics. The non-radiative decay is not reproduced by a single exponential function, in contrast to triplet states of fluorescent organic molecules that exhibit monophasic exponential decay. In order to quantitatively analyze fluorescence correlation signals of quantum dots including such complex non-radiative decay, we adopted a fluorescence autocorrelation function including the decay component of a stretched exponential as represented by Eq. (8.11). 

Xing Y et al (2007) Bioconjugated quantum dots for multiplexed and quantitative immuno-histochemistry. Nat Protoc 2 1152-1165... 

Wu, Y., Campos, S. K., Lopez, G. P., Ozbun, M. A., Sklar, L. A., and Buranda, T. (2007b). The devolpment of quantum dot calibration beads and quantitative multicolor bioassays in flow cytometry and microscopy. Anal. Biochem. 364, 180-192. 

CdTe quantum dots, resulting in polydisperse nanocrystals. Polydispersity was quantitatively assessed from the polydispersity index (PDI) in gel filtration chromatograms. When the MCR values are above 2.0, the excess polymer leads to better monodispersity and colloidal stability, but a reduced fluorescence quantum yield. Between these two limits is the optimal capping ratio (OCR) of approximately 1.5, yielding small, monodisperse nanocrystals (PDI < 1.5) with bright fluorescence ( 50% quantum yield) and exceptional photostability. 

An analysis of RTS in this work quantitatively explains details of hole trapping processes in the tetrahedral-shaped recess quantum dot structure. Noise spectral density is given by superposition of 1/f noise and RTS pulses (Fig. 16) with the activation energy AEke= 190 meV for hole emission and AE),c= 260 meV for hole capture. RTS noise ampUtude has its maximum value at temperature range below 300 K when the quasi Fermi level coincides with the trap energy level. At temperature higher than 300 K the 1/f noise component is dominant and then parameter Cq given by (4) is used as quality and rehabihty indicator. 

Quadrangularin A, 2153, 2162 Quadmpole-linear ion trap (Q-LIT), 1125 Quadmpole time of flight (Q-TOF), 1125 Quantitative electronic structure activity relationship (QESAR), 3352 Quantitative H NMR, 1037 Quantitative structure activity relationship (QSAR), 3351 Quantum dots, 1036 Quassia, 3780 Q. amara, 3781 Q. indica, 3718 Quassin, 3347, 3778... 

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