Three-monolayer CdSe nanoplatelets having the composition (CdSe) 3 [Cd(OAc) 0.77 (oleate) 1.23 ] 0.78 , large lateral dimensions, minimal strain distortions, and the zinc-blende crystal structure undergo Z-type to L-type ligand exchange with ethylenediamine, affording NPLs of composition (CdSe) 3 [en] 0.67 (en = ethylenediamine). The L-type ligation of the (CdSe) 3 [en] 0.67 (en = ethylenediamine) NPLs is exchanged for Z-type ligation with Cd(oleate) 2 , Cd(OAc) 2 , CdCl 2 , Zn(oleate) 2 , and ZnCl 2 , giving NPLs having near to the ideal compositions of (CdSe) 3 [MX 2 ]. All of the Z-type to L-type and L-type to Z-type ligand exchanges are kinetically slow, requiring several hours to reach completion, suggesting that a considerable surface reconstruction is required. In contrast, three-monolayer NPLs having a significant rolling distortion and four-and five-monolayer NPLs having small lateral dimensions are unstable to ethylenediamine, and Z-type to L-type ligand exchange is not achieved.

The techniques employed in the compositional analysis of semiconductor materials by inductively coupled plasma optical emission spectroscopy (ICP-OES) dramatically influence the accuracy and reproducibility of the results. We describe methods for sample preparation, calibration, standard selection, and data collection. Specific protocols are suggested for the analysis of II−VI compounds and nanocrystals containing the elements Zn, Cd, S, Se, and Te. We expect the methods provided will apply more generally to semiconductor materials from other families, such as to III−V and IV−VI nanocrystals.

Preparations of CdTe quantum platelets, magic-size (CdTe) 13 nanoclusters, and CdTe quantum wires are described using (Me 2 N) 3 PTe (with (Me 2 N) 3 P) as a Te precursor. The (Me 2 N) 3 PTe/(Me 2 N) 3 P precursor mixture is shown to be more reactive than mixtures of trialkylphosphine tellurides and the corresponding trialkylphosphines, R 3 PTe/R 3 P, which are commonly employed in nanocrystal syntheses. For syntheses conducted in primary amine solvents, (Me 2 N) 3 PTe and (Me 2 N) 3 P undergo a transamination reaction, affording (Me 2 N) x (RHN) 3−x PTe and (Me 2 N) x (RHN) 3−x P (R = n-octyl or oleyl). The transaminated (Me 2 N) x (RHN) 3−x PTe derivatives are shown to be the likely Te precursors under those conditions. The enhanced reactivities of the tris(amino)phosphine tellurides are ascribed to increased nucleophilicity due to the amino-N lone pairs.

A lead-free, stable orange-red-emitting material (PEA)4Cu4I4 with a high photoluminescence quantum yield of 68% was successfully prepared by a facile strategy.

CdS and CdSe shells are deposited on wurtzite CdTe quantum platelets (nanoplatelets) by exchanging the initial primary-amine ligation to Cd­(OAc)2 ligation, with subsequent reaction of the Cd­(OAc)2 ligand shell and thiourea or selenourea, respectively. Shell deposition is conducted in a cyclic manner, with 0.21–0.34 monolayers of CdS and 0.99–1.20 monolayers of CdSe being deposited in each cycle. The CdTe quantum platelets having an initial thickness of 1.9 nm are converted to CdTe–CdS and CdTe–CdSe core–shell quantum platelets having maximum thicknesses of 3.0 and 6.3 nm, respectively. The morphologies and wurtzite structure of the initial CdTe quantum platelets are retained upon shell deposition. The absorption spectrum of the CdTe quantum platelets is progressively shifted to lower energy with increasing shell thickness, across the entire visible spectrum. The spectral shifts observed scale with the inverse square of the total core–shell thickness.