The impact of prolonged irradiation of SPIONs/CdSe/ZnS nanocomposites by visible light on nanocomposite luminescence has been studied. It has been shown that prolonged irradiation of the nanocomposites with 405 nm laser can triple their photoluminescence quantum yield. It has been demonstrated that the efficiency of photoinduced processes on the nanocomposite surface correlates very well with the concentration of the nanocomposite surface ligand in our samples. We have also found that the quantum sized CdSe shell of SPIONs/CdSe/ZnS nanocomposites demonstrates the QD-like dependence of photoluminescence quantum yield on visible light dose and this nanocomposite property can be efficiently used to brighten their photoluminescence.
Magneto-luminescent materials that do not exist in nature, can find a wide application in biomedical and environmental fields. Here we describe magneto-optical properties of core-shell-shell nanocomposites consisting of a Fe3O4 superparamagnetic iron oxide nanoparticle (SPION) covered with quantum-sized brightly luminescent CdSe layer surrounded by ZnS passivating shell. The synthesized nanocomposites demonstrate excitonic bands in their absorption and photoluminescent (PL) spectra centered at 585 nm and 603 nm, respectively. The PL quantum yield of nanocomposites has been increased by 5 times due to their passivation with ZnS shell. The analysis of magneto-optical properties of the synthesized Fe3O4/CdSe/ZnS nanocomposites has shown that their magnetic circular dichroism (MCD) spectrum is characterized with the bands centered at 430 nm, 350 nm and 303 nm corresponding to 6A1 → 4E, 4A1(4G); 6A1 → 4E(4D) and 6A1 → 4T1(4P) electronic transitions, respectively. It has been found that the synthesized core-shell SPIONs demonstrate excellent colloidal stability, magneto-optical properties typical for SPIONs and bright photoluminescence
Carbon dots are promising luminescent nanoparticles which possess unique optical properties together with the simplicity of their synthesis. The revealing of their energy level structure is a crucial for further implementation in various applications from biology to photonics. This work is devoted to the investigation of optical responses of citric acid-based carbon dots with respect to the chemical environment, as solvent polarity. Small spectral shifts of the luminescent and absorption bands for CDs are observed. Assuming the PL is originated from the emission of various luminescent centers in CDs we explain these shifts by their intensity redistribution within PL band in different solvents. The redistribution leads to blue shift of PL band in non-polar solvents, while in polar solvents strong dependence of PL band on polarity value is absent.