Investigation of band parameters and electrochemical analysis of multi core-shell CdSe/CdS/ZnS quantum dots

Highly emissive core-multi-shell (CdSe/CdS/ZnS) quantum dots (QDs) within size range of 2 nm-5 nm were prepared via hot injection method. Capping agent (polymers) were used to increase the lifetime of QDs, without a protective atmosphere. Red shift was observed in an absorption spectrum of QDs peaks at 362 nm, 365 nm, 558 nm, and 556 nm for CdSe/CdS and CdSe/CdS/ZnS with respect to CdSe core. Voltammetry measurements (Eg 2. 09 eV) for band gaps were in good agreement with the UV-visible spectroscopic data (Eg 2.65 eV). QDs exhibited three distinguished peaks comparing to (111), (220), and (311) planes of cubic structures of CdSe, CdSe/CdS and CdSe/CdS/ZnS within crystallite size of 20-27 nm as observed by XRD spectra. A larger active surface area 0.06 cm-2, computed by CV increased the catalytic activity of sensors by exposing the electroactive sites. Linear, nonlinear optical susceptibility and absorption coefficients were computed by an effective mass model. Quantum confinement was confirmed by taking electron probability density as function of radial distance of quantum dots.

Automated summary

Highly emissive core-multi-shell (CdSe/CdS/ZnS) quantum dots (QDs) with sizes ranging from 2 nm to 5 nm were synthesized using the hot injection method. Polymer capping agents were employed to enhance the QDs' lifetime without the need for a protective atmosphere. The absorption spectra of CdSe/CdS and CdSe/CdS/ZnS displayed a red shift compared to CdSe core, with peaks at 362 nm, 365 nm, 558 nm, and 556 nm. The band gaps measured by voltammetry (Eg 2.09 eV) were in good agreement with the UV-visible spectroscopic data (Eg 2.65 eV). XRD spectra confirmed the quantum confinement effect, showing distinct peaks corresponding to the (111), (220), and (311) planes of cubic structures for CdSe, CdSe/CdS, and CdSe/CdS/ZnS, respectively. The effective mass model was used to calculate the linear and nonlinear optical susceptibilities and absorption coefficients.