Core–Shell Cadmium Telluride Quantum Platelets with Absorptions Spanning the Visible Spectrum

Abstract

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.

Dielectric Screening Modulates Semiconductor Nanoplatelet Excitons

“…In this work, we measure the absorption spectra of zinc-blende II–VI NPLs, which consist of alternating M–X atomic layers (M = Cd, Hg and X = Se, Te), as shown in Figure a. The NPLs have thicknesses of 0.7–1.9 nm and lateral dimensions of 50–200 nm (Figure b). − The synthesis procedures for individual NPLs and material characterization can be found in the Supporting Information (Supporting Information Sections I and II; EDS in Table S1, FTIR in Figures S1 and S2, and TEM in Figures S3 and S4). Motivated by their similarity to other 2D excitonic semiconductors, such as quantum wells and transition metal dichalcogenides (TMDCs), we use the distinct room temperature features of the absorption spectra (Figure c) to understand bandgap and excitonic properties.…”

CdSe/CdS/CdTe Core/Barrier/Crown Nanoplatelets: Synthesis, Optoelectronic Properties, and Multiphoton Fluorescence Upconversion

“…19 Recently, a variety of Cd-based NPL heterostructures have been synthesized, which can further shape the electron and hole wave functions. [20][21][22][23][24] In the case of concentric hetero-NPLs, type-I CdSe/ZnS NPLs yield fast photoluminescence (PL) lifetime, 25 in combination with a red shift of the band edge, while quasi-type-II CdSe/CdS core/shell NPLs combine an even larger red shifted emission with a reduced PL decay rate. 26 One can also laterally extend the NPLs by growing a second material around the NPL edges.…”

CdS Nanoplates Modification as a Platform for Synthesis of Blue-Emitting Nanoparticles

“…Sample S2-1A showed mainly flat structures, similar to the original S2 sample, however, with an apparent increase of NPLs lateral size, and with a predisposition to aggregate. This may prove that 3-MPA as a ligand incorporated into the structure of NPLs, creating an additional monolayer (421 nm corresponding to 2.9 eV, characterized by 7 monolayers) [ 14 ]. The constituents of the NPs surface can undergo exchange to a certain extent and during this process up to one new monolayer may be formed [ 15 ].…”