Preparation of Cd/Pb Chalcogenide Heterostructured Janus Particles via Controllable Cation Exchange

Abstract

We developed a strategy for producing quasi-spherical nanocrystals of anisotropic heterostructures of Cd/Pb chalcogenides. The nanostructures are fabricated via a controlled cation exchange reaction where the Cd(2+) cation is exchanged for the Pb(2+) cation. The cation exchange reaction is thermally activated and can be controlled by adjusting the reaction temperature or time. We characterized the particles using TEM, XPS, PL, and absorption spectroscopy. With complete exchange, high quality Pb-chalcogenide quantum dots are produced. In addition to Cd(2+), we also find suitable conditions for the exchange of Zn(2+) cations for Pb(2+) cations. The cation exchange is anisotropic starting at one edge of the nanocrystals and proceeds along the ⟨111⟩ direction producing a sharp interface at a (111) crystallographic plane. Instead of spherical core/shell structures, we produced and studied quasi-spherical CdS/PbS and CdSe/PbSe Janus-type heterostructures. Nontrivial PL behavior was observed from the CdS(e)/PbS(e) heterostructures as the Pb:Cd ratio is increased.

Ga for Zn Cation Exchange Allows for Highly Luminescent and Photostable InZnP-Based Quantum Dots

“…Such core–shell structures are often observed in systems with low ion diffusivity where the reaction starts from the QD surface. 35−37 Indeed, the 30–60 min time required for the CE reaction to reach completion (Figure 2c) suggests slow ion diffusion, an observation supported by other reports of slow CE reactions in III–V QD materials. 37,38 …”

Colloidal quantum dot-based surface acoustic wave sensors for NO2-sensing behavior

“…can be indexed as the cubic-lattice PbS (JCPDS 05-0592), which is in a good agreement with the results reported by the Zhang group[34]. The broad peaks were attributed to the small size of the CQDs.…”

Air-Stable and Efficient PbSe Quantum-Dot Solar Cells Based upon ZnSe to PbSe Cation-Exchanged Quantum Dots

“…This is in contrast to the partial cation exchange of CdS to PbS results, which do show features of the residual CdS in the TEM, XRD, and UV-Vis. 33 These observations suggest that after partial exchange residual ZnSe dissolves producing single phase PbSe QDs. We have not attempted to find reaction conditions that would preserve the partially exchanged nanostructures.…”