Photoluminescence Investigation of Carrier Localization in Colloidal PbS and PbS/MnS Quantum Dots

Abstract

The existence of surface organic capping ligands on quantum dots (QDs) has limited the potential in QDs emission properties and energy band gap structure alteration as well as the carrier localization. This drawback can be addressed via depositing a thin layer of a semiconductor material on the surface of QDs. Herein, we report on the comparative study for photoluminescent (PL) properties of PbS and PbS/MnS QDs. The carrier localization effect due to the alteration of energy band gap structure and carrier recombination mechanism in the QDs were investigated via PL measurements in a temperature range of 10− 300 K with the variation of the excitation power from 10 to 200 mW. For PbS QDs, the gradient of integrated PL intensity (IPL) as a function of excitation power density graph was less than unity. When the MnS shell layer was deposited onto the PbS core, the PL emission exhibited a blue shift, showing dominant carrier recombination. It was also found that the full width half-maximum showed a gradual broadening with the increasing temperature, affirming the electron−phonon interaction.

Size-Dependent Thermal Activation Emissions in Infrared PbS Colloidal Quantum Dots

“…α ≈ 1 indicates the exciton recombination mechanism and α < 1 indicates defect-related emission. 35 Figure 6a−c shows the power-dependent PL spectra. It is easy to find that the emission intensity increases with increasing power density.…”

“…The relationship of the PL integrated intensity with power density is analyzed according to the following formula. I = η I 0 α where I is the spectral integrated intensity, I 0 is the excited optical power density, η is the radiation efficiency, α is the characteristic value, and the value of α can be calculated by curve fitting to determine the specific radiative recombination mechanism. α ≈ 1 indicates the exciton recombination mechanism and α < 1 indicates defect-related emission …”

Study of the Electron-Phonon Coupling in PbS/MnTe Quantum Dots Based on Temperature-Dependent Photoluminescence

“…The Cu peaks observed in Figure 2 a,b correspond to the copper grid used in the HRTEM, whereas the overlapping peaks at 2.3 keV confirm the presence of Pb and S. The atomic percentage ratio between Pb and S is 1:4 is compared to 1:0.3, as mentioned in sample preparation. The higher amount of S, which is four times higher than Pb, might be due to the capping ligands on the surface of PbS QDs (TGL and DTG) that have functional groups of sulfur atoms [ 26 ]. Figure 2 b supports the existence of Mn and Te, which were observed at 5.9 keV and 3.7 keV, respectively, in addition to Pb and S.…”

Drug Release Profiles of Mitomycin C Encapsulated Quantum Dots–Chitosan Nanocarrier System for the Possible Treatment of Non-Muscle Invasive Bladder Cancer

“…Figure 2 b illustrates the normalized PL intensity of ZnS with emission energy of ~3.00 eV. The PL peak for Mn:ZnS was prominently hypsochromic shifted to the blue region and might be due to the cation exchange [ 36 ]. In addition, the shifting of PL intensity from ~400 to 410 nm, in which towards the longer wavelength suggests that the transition of electrons from conduction band to the electron trap centers, the least quantum energy was transmitted to the lattice or Mn states.…”

“…The excellent results of this formulation may provide constructive hints for further developments in this research area of DDS and theranostics. 36.458 g•mol −1 , 37%) was purchased from Friendemann Schmidt (Parkwood, Australia). Other reagents were of analytical grade and used without any further purification.…”