High-Frequency EPR and ENDOR Spectroscopy of Mn²⁺ Ions in CdSe/CdMnS Nanoplatelets

Abstract

Semiconductor colloidal nanoplatelets based of CdSe have excellent optical properties. Their magneto-optical and spin-dependent properties can be greatly modified by implementing magnetic Mn 2+ ions, using concepts well established for diluted magnetic semiconductors. A variety of magnetic resonance techniques based on high-frequency (94 GHz) electron paramagnetic resonance in continuous wave and pulsed mode were used to get detailed information on the spin structure and spin dynamics of Mn 2+ ions in core/shell CdSe/(Cd,Mn)S nanoplatelets. We observed two sets of resonances assigned to the Mn 2+ ions inside the shell and at the nanoplatelet surface. The surface Mn demonstrates a considerably longer spin dynamics than the inner Mn due to lower amount of surrounding Mn 2+ ions. The interaction between surface Mn 2+ ions and 1 H nuclei belonging to oleic acid ligands is measured by means of electron nuclear double resonance. This allowed us to estimate the distances between the Mn 2+ ions and 1 H nuclei, which equal to 0.31 ± 0.04, 0.44 ± 0.09, and more than 0.53 nm. This study shows that the Mn 2+ ions can serve as atomic-size probes for studying the ligand attachment to the nanoplatelet surface.

Expanding the color palette of bicolor-emitting nanocrystals

“…In this quest for new heterostructures that can exhibit two-color [10][11][12] emission, maintaining confinement is an important step. In this sense, 2D nanoplatelets (NPLs) offer several advantages: (i) their specific growth mechanism 13,14 enables particularly narrow emissions, (ii) their anisotropic shape enables combining both strong confinement within the thickness while presenting a large lateral extension, (iii) their specific colloidal growth allows the design of complex heterostructures involving multiple interfaces [15][16][17][18][19] (iv) the several post-synthetic doping techniques leading toward dopant 20 or trap emissions. [21][22][23][24][25] Thus, NPLs expand the possibilities for emission quantum engineering.…”