Lanthanide-doped CdS quantum dots: luminescence and paramagnetic properties

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Lanthanide-doped CdS quantum dots: luminescence and paramagnetic properties* D. O. Sagdeev,a R. R. Shamilov,a V. K. Voronkova,b A. A. Sukhanov ,b and Yu. G. Galyametdinova,b aKazan

National Research Technological University, 68 ul. Karla Marksa, 420015 Kazan, Russian Federation. Fax: +7 (843) 238 5694. E-mail: [email protected] bZavoisky Physical-Technical Institute, Kazan Scientific Center of the Russian Academy of Sciences, 10/7 Sibirsky Trakt, 420029 Kazan, Russian Federation. Fax: +7 (843) 272 5075. E-mail: [email protected] Optical and magnetic properties of CdS quantum dots (QDs) doped with europium(II) and gadolinium(III) ions were studied. L-Cysteine stabilized nanoparticles were synthesized by the colloidal method in aqueous media. The QDs obtained have a hexagonal crystal lattice. The nanoparticle size varies from 3 to 14 nm. The EPR spectra of nanoparticles prepared in different conditions were measured and analyzed. Dependences of the optical properties of nanoparticles on the reaction time and pH values were studied. The dependence of the luminescence properties of CdS QDs on the dopant ion type was established. It was shown that the increase in the reaction time and medium pH values favors a bathochromic shift of maxima in the luminescence spectra of nanoparticles. Key words: quantum dots, cadmium sulfide, paramagnetic ions, europium, gadolinium, colloidal synthesis, photoluminescence, EPR spectroscopy.

Semiconductor nanoparticles, viz., quantum dots (QDs) and lanthanide ions, are promising luminescent materials, each having its own advantages.1,2 Adducts of lanthanide ions with organic ligands exhibit highly efficient, narrow-band luminescence, which makes them in-demand materials for the design of various optoelectronic devices including organic light-emitting diodes, lasers, and luminescent labels.3,4 Semiconductor QDs are characterized by broader-band luminescence, the emission wavelength and the quantum yield of luminescence being dependent on the particle size and ligand environment. This allows one to fabricate luminescent materials characterized by different emission wavelengths using the same reactants by properly choosing the synthesis conditions.1,5 Doping nanoparticles with various impurity ions is a topical avenue of recent scientific research into the properties of QDs with emphasis placed on the effect of dopant ions on the optical and magnetic properties of QDs to obtain multifunctional materials.6,7 Doping QDs with Mn2+ and Gd3+ ions and the design of combined biolabels based on them for medical applications (visualization using luminescence and MRI) has been reported.8,9 Extension of QD functionality can significantly improve * Based on the materials of the XXI Mendeleev Congress on General and Applied Chemistry (September 9—13, 2019, St. Petersburg, Russia).

the efficiency of their application in proteomics and medical diagnostics.10 Publications on the synthesis of nanostructures doped with europium(III) ions as well as individual europium(II) chalcogenides are available. However