![]() ![]() 23–25ĭoping, i.e., the intentional incorporation of impurities into a crystal lattice, has been employed as a powerful strategy to tune optical, electrical, and magnetic properties of II–VI based zero-dimensional colloidal nanostructures, 26–35 even down to the level of magic-sized or molecular nanocluster. 20–22 Even lasing after optical pumping has been demonstrated. 16–18 Additionally, compared to core-only NPLs, 2D heterostructures exhibit reduced photoluminescence blinking and enhanced photoluminescence quantum yields, 14,19 thus triggering their implementation in optoelectronic devices such as light emitting diodes. Colloidal atomic layer deposition (c-ALD) has been applied in the synthesis of complex core/shell (shell grown on top of a NPL core) 12,13 and core/crown (crown grown laterally around a NPL core) 14,15 heterostructures, finally enabling absorption and emission energies to be tuned via the delocalization of charge carrier wave functions. 2–8 In contrast to quantum dots, where absorption and/or emission energies can be continuously tuned, 9–11 the discrete change in ML thickness and thus in quantum confinement allows for a stepwise shift of the optical resonances. 1 Compared to 0D systems, two-dimensional (2D) NPLs offer great advantages such as the control of the quantum confinement at the monolayer (ML) level, narrower emission linewidths, shorter recombination lifetimes, directed emission, and larger absorption cross sections and coefficients. The development of colloidal nanoplatelets (NPLs) started more than a decade ago when researchers adapted and expanded the protocols used for the fabrication of zero-dimensional (0D) II–VI nanocrystals. Thus, our study not only demonstrates magneto-optical functionality in 2D nanocrystals by Co 2+ doping but also shows that a careful choice of the dopant type paves the way for a more detailed understanding of the impurity incorporation process into these novel 2D colloidal materials. Taking advantage of the absorption-based technique of magnetic circular dichroism, we directly prove the presence of sp- d exchange interactions between the dopants and the band charge carriers in CdSe/Co 2+:CdS heteronanoplatelets. Analyzing interatomic Co 2+ ligand field transitions, we conclude that Co 2+ is incorporated into lattice sites of the CdS shell, and effects such as diffusion of dopants into the CdSe core or diffusion of the dopants out of the heterostructure causing self-purification play a minor role. Here, we demonstrate the successful incorporation of Co 2+ ions into the shell of CdSe/CdS core/shell nanoplatelets, using these ions (i) as microscopic probes for gaining distinct structural insights and (ii) to enhance the magneto-optical functionality of the host material. While dopant incorporation has been extensively investigated in zero-dimensional quantum dots, the substitutional replacement of atoms in two-dimensional (2D) nanostructures by magnetic dopants has been reported only recently. The intentional incorporation of transition metal impurities into colloidal semiconductor nanocrystals allows an extension of the host material’s functionality.
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