Synthesis and Luminescence Dynamics of CdSe and CdSe/CdS Quantum Dots

The aim of the study is to analyze the luminescent properties of hexagonal quantum dots and their bridged envelope compounds under constant and temporal spectral analysis conditions. The CdSe nanoparticles were obtained by the hot injection method. To increase the radiation efficiency, CdSe/CdS core-shell structures have been synthesized, ensuring the passivation of surface defects. Steady-state optical measurements have shown that the first absorption maximum is recorded at 546.48 nm (2.26 eV), while the photoluminescence peak falls to 565.89 nm (2.19 eV). The data obtained indicate the presence of a Stokes shift of approximately 70 meV with a quantum radiation power of 21.4%. The time-resolved luminescence has three attenuation components with lifetimes of 7, 25 and 54 nanoseconds, which gives an average value of 26 nanoseconds. For CdSe / CdS nanoparticles, a noticeable increase in the lifetime of excited states is observed — up to 103 nanoseconds, which is probably due to the stabilizing effect of the polymer medium on the surface of the quantum dots. A long-wavelength peak at 742 nm exhibited a prolonged relaxation component of ~1.033 μs, associated with structural defects in the crystal lattice. These findings highlight the critical role of synthesis parameters and surface modifications in optimizing the luminescent properties of quantum dots for various applications