Excitation wavelength and intensity dependence of photo-spectral blue shift in single CdSe/ZnS quantum dots

Abstract

The influence of excitation wavelength and intensity on core/shell CdSe/ZnS quantum dots (QDs) photo-spectral blue shift was investigated by spectral imaging. Analysis of the evolution of the distance between the zeroth-order spot and the firstorder spectral streak, we found that the extent of blue shift strongly depends on the excitation wavelength and QDs sizes, but not on the excitation intensity. Converted the extent of blue shift into the decreased QDs volume at a series of time, the core oxidation kinetics of CdSe/ZnS QDs was uncovered that provided a quantitative comparison method for study the excitation wavelength and intensity dependence of single QDs blue shift. The core oxidation rate is almost proportional to the excitation intensity. These results are explained by a fact that higher energy excitation wavelength can accelerate individual exciton formation and higher excitation intensity can induce more amount of exciton formation per a unit time.

Optical levitation of a microdroplet containing a single quantum dot

“…After recording the two-photon coincidence counts and ensuring the single-photon emission, one of the avalanche photo diodes was replaced by a spectrograph and the fluorescence was recorded with a 1 s integration time. The fluorescence line width is similar to the previously reported value [24] and much narrower than that of the QD ensemble (see dotted blue curve in upper right panel of Fig. 4), which indicates that inhomogeneous broadening has been eliminated.…”

Recent progress in nanostructured silver sulfide: from synthesis and nonstoichiometry to properties

“…The well-known Ag 2 S is one of the most requisite semiconducting suldes 1,2,[14][15][16][17][18][19] along with lead, zinc, cadmium and copper suldes. [3][4][5][20][21][22][23][24][25] Ag 2 S is the only semiconducting sulde (except for HgS) having three polymorphous modications (a-Ag 2 S, b-Ag 2 S and g-Ag 2 S) within rather close temperature intervals. 26 These modications of Ag 2 S differ greatly in their structure and properties.…”

Accelerated Photostability Studies of Colloidal Quantum Dots

“…The obtained etching rate results indicate that the etching rate of CdSe QDs is linearly proportional to the incident photon flux, which is in agreement with a previous study on excitation intensity dependence of photo‐oxidation rate in single CdSe QDs. [ 36 ] We postulate that the singlet oxygen generated via TET from CdSe QDs is responsible for photo‐oxidation and etching of the colloidal CdSe QDs excited by photon energies below the solvent's CCTP activation threshold. [ 17 ] The overall photo‐oxidation reaction rate can depend on the generation rate of QDs' excitons, QDs to ground‐state oxygen TET rate (i.e., singlet‐oxygen generation rate), as well as the steps involved in the reaction of singlet oxygen with the QDs' surfaces.…”