Colloidal Mercury-Doped CdSe Nanoplatelets with Dual\nFluorescence

Abstract

Quasi-two-dimensional\n(2D) CdSe nanoplatelets (NPLs) are distinguished\nby their unique optical properties in comparison to classical semiconductor\nnanocrystals, such as extremely narrow emission line widths, reduced\nAuger recombination, and relatively high absorption cross sections.\nInherent to their anisotropic 2D structure, however, is the loss of\ncontinuous tunability of their photoluminescence (PL) properties due\nto stepwise growth. On top of that, limited experimental availability\nof NPLs of different thicknesses and ultimately the bulk band gap\nof CdSe constrain the achievable PL wavelengths. Here, we report on\nthe doping of CdSe NPLs with mercury, which gives rise to additional\nPL in the red region of the visible spectrum and in the near-infrared\nregion. We employ a seeded-growth method with injection solutions\ncontaining cadmium, selenium, and mercury. The resulting NPLs retain\ntheir anisotropic structure, are uniform in size and shape, and present\nsignificantly altered spectroscopic characteristics due to the existence\nof additional energetic states. We conclude that doping takes place\nby employing elemental analysis in combination with PL excitation\nspectroscopy, X-ray photoelectron spectroscopy, and single-particle\nfluorescence spectroscopy, confirming single emitters being responsible\nfor multiple distinct emission signals.