The intra- and inter-band relaxation dynamics of CdSe/CdS/ZnS core/shell/shell quantum dots are investigated with the aid of time-resolved nonlinear transmission spectra which are obtained using femtosecond pump-probe...The intra- and inter-band relaxation dynamics of CdSe/CdS/ZnS core/shell/shell quantum dots are investigated with the aid of time-resolved nonlinear transmission spectra which are obtained using femtosecond pump-probe technique. By selectively exciting the core and shell carrier, the dynamics are studied in detail. Carrier relaxation is found faster in the conduction band of the CdS shell （about 130 fs） than that in the conduction band of the CdSe core （about 400 fs）. From the experiments it is distinctly demonstrated the existence of the defect states in the interface between the CdSe core and the CdS shell, indicating that ultrafast spectroscopy might be a suitable tool in studying interface and surface morphology properties in nanosystems.展开更多
CdSe semiconductor nanocrystals capped by CdS were synthesized in the aqueous solution with 2 mercaptoethanol as the stabilizer. The CdS capping with a higher band gap than that of the core crystallite has successfu...CdSe semiconductor nanocrystals capped by CdS were synthesized in the aqueous solution with 2 mercaptoethanol as the stabilizer. The CdS capping with a higher band gap than that of the core crystallite has successfully eliminated the surface traps. Optical absorption and fluorescence emission spectra were used to probe the effect of CdS passivation on the electronic structure of the nanocrystals. The composite CdSe/CdS nanocrystals exhibit strong, narrow(FWHM≤40 nm) and stable band edge photoluminescence. X ray powder diffraction, transmission electron microscopy and X ray photoelectron spectroscopy were used to analyze the composite nanocrystals and determine their average size, size distribution, shape, internal structure and elemental composition.展开更多
A rapid, ultrasensitive and convenient fluorescence measurement technology based on the enhancement of the fluorescence intensity resulting from the interaction of functionalized CdSe/CdS quantum dots （QDs） with bov...A rapid, ultrasensitive and convenient fluorescence measurement technology based on the enhancement of the fluorescence intensity resulting from the interaction of functionalized CdSe/CdS quantum dots （QDs） with bov/ne serum albumin （BSA） was proposed. The citrate-stabilized CdSe/CdS （QDs） were synthesized by using Se powder and Na2S as precursors instead of any pyrophoric organometallic precursors. The modified CdSe/CdS QDs are brighter and more stable against photobleaching in comparison with organic fluorophores. At pH 7.0, the fluorescence signal of CdSe/CdS is enhanced by increasing the concentration of BSA in the range of 0.1-10 μg/mL, and the low detection limit is 0.06 μg/mL. A linear relationship between the enhanced fluorescence peak intensity （△F） and BSA concentration （c） is established using equation △F=50.7c＋16.4 （R=0.996 36）. Results of determination for BSA in three synthetic samples are identical with the true values, and the recovery （98.9%-102.4%） and relative standard deviation （RSD, 1.8%-2.5%） are satisfactory.展开更多
基金This work was supported by the National Natural Science Foundation of China （No.11074003） and the Key Program of Educational Commission of Anhui Province of China （No.KJ2010AI32）. For the help of Prof. J. L. Zhao at Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences in sample preparation is greatly appreciated.
文摘The intra- and inter-band relaxation dynamics of CdSe/CdS/ZnS core/shell/shell quantum dots are investigated with the aid of time-resolved nonlinear transmission spectra which are obtained using femtosecond pump-probe technique. By selectively exciting the core and shell carrier, the dynamics are studied in detail. Carrier relaxation is found faster in the conduction band of the CdS shell （about 130 fs） than that in the conduction band of the CdSe core （about 400 fs）. From the experiments it is distinctly demonstrated the existence of the defect states in the interface between the CdSe core and the CdS shell, indicating that ultrafast spectroscopy might be a suitable tool in studying interface and surface morphology properties in nanosystems.
基金Supported by the National NaturalScience Foundation of China( No. 2 0 0 75 0 0 9)
文摘CdSe semiconductor nanocrystals capped by CdS were synthesized in the aqueous solution with 2 mercaptoethanol as the stabilizer. The CdS capping with a higher band gap than that of the core crystallite has successfully eliminated the surface traps. Optical absorption and fluorescence emission spectra were used to probe the effect of CdS passivation on the electronic structure of the nanocrystals. The composite CdSe/CdS nanocrystals exhibit strong, narrow(FWHM≤40 nm) and stable band edge photoluminescence. X ray powder diffraction, transmission electron microscopy and X ray photoelectron spectroscopy were used to analyze the composite nanocrystals and determine their average size, size distribution, shape, internal structure and elemental composition.
基金Project(50772133) supported by the National Natural Science Foundation of China
文摘A rapid, ultrasensitive and convenient fluorescence measurement technology based on the enhancement of the fluorescence intensity resulting from the interaction of functionalized CdSe/CdS quantum dots （QDs） with bov/ne serum albumin （BSA） was proposed. The citrate-stabilized CdSe/CdS （QDs） were synthesized by using Se powder and Na2S as precursors instead of any pyrophoric organometallic precursors. The modified CdSe/CdS QDs are brighter and more stable against photobleaching in comparison with organic fluorophores. At pH 7.0, the fluorescence signal of CdSe/CdS is enhanced by increasing the concentration of BSA in the range of 0.1-10 μg/mL, and the low detection limit is 0.06 μg/mL. A linear relationship between the enhanced fluorescence peak intensity （△F） and BSA concentration （c） is established using equation △F=50.7c＋16.4 （R=0.996 36）. Results of determination for BSA in three synthetic samples are identical with the true values, and the recovery （98.9%-102.4%） and relative standard deviation （RSD, 1.8%-2.5%） are satisfactory.
