Investigation of the Exchange Kinetics and Surface Recovery of Cd_xHg_1–xTe Quantum Dots during Cation Exchange Using a Microfluidic Flow Reactor

Abstract

Detailed analyses of coupled photoluminescence, emission lifetime, and absorption measurements have been made on the products of cation exchange reactions between CdTe nanocrystals and Hg2+ salt/ligand solutions in a microfluidic flow reactor and capillary measurement cell to probe the reaction kinetics over the seconds to hours time scale and to establish the influence of the reaction conditions on the spatial distribution of the mixed cations within the resulting Cd x Hg1–x Te colloidal quantum dots. The establishment of the evolution of the radiative and nonradiative rates allowed the recovery of the emission quantum yield in Cd x Hg1–x Te quantum dots to be quantified to almost 50% and the necessary time scales to be determined for each set of reaction conditions. The reaction kinetics showed clear indication of a fast surface exchange process followed by a slower internal rearrangement of the cation distribution.

Coupled HgSe Colloidal Quantum Wells through a Tunable Barrier: A Strategy To Uncouple Optical and Transport Band Gap

“…The core/shell structure will be further confirmed by other techniques such as X-ray diffraction (XRD) and optical measurements. Such uncomplete cation exchange has already been observed in other systems such as PbS/CdS 39 and CdTe/HgTe [40][41][42] . It is more likely to happen when the host and replacing cations have the same level of oxidation and comparable sizes.…”

Au@HgxCd1-xTe core@shell nanorods by sequential aqueous cation exchange for near-infrared photodetectors

“…Aspects of the CE reaction between CdTe and Hg x Cd 1-x Te quantum dots, particularly concerning the CE depth from the particle surface and the resulting energy levels, have been reported by many groups. [13,36,58] In order to achieve efficient plasmon-exciton coupling further into the NIR region, we carried out the CE reaction between the CdTe shell and Hg 2+ to realize highly crystalline Au@Hg With the shell transformation from Ag 2 Te to Ag 3 AuTe 2 and subsequently to CdTe, the extinction peaks experience an obvious red shift. Au@CdTe NRs have an extinction peak at 1240 nm, while with the addition of Hg 2+ , the Au@Hg x Cd 1-x Te NRs extinction peak red-shifts to wavelengths between 1563 nm (Au@Hg 0.19 Cd 0.81 Te NRs) and 1817 nm (Au@Hg 0.73 Cd 0.27 Te NRs).…”

“…[3,15,[20][21] With the increase of Hg ratio, Hg x Cd 1-x Te exhibited lower bandgap than pure CdTe, which featured NIR wavelength absorption such as reported QDs or NCs. [13,27,58] When coupling with Au NRs, the as-prepared Au@Hg x Cd 1-x Te NRs exhibited enhanced absorption in NIR region compared to decoupled Hg x Cd 1-x Te NRs with Au cores over etched ( Figure S11). The enhancement is mainly due to the coupling of plasmons from Au cores and excitons from semiconductor shells.…”

Cation/Anion Exchange Reactions toward the Syntheses of Upgraded Nanostructures: Principles and Applications

“…Some recent studies are focusing on improving the scalability of QDs synthesized by the CER strategy. For example, Rogach and colleagues reported a CER in a microfluidic flow reactor to synthesize Cd x Hg 1Àx Te QDs; 79 van Patten and colleagues reported CER-enabled multigram-scale conversions of NCs by applying an air-stable and photostable Ag complex. 95 Inorganic Perovskite NCs Tailoring the composition of inorganic perovskite NCs via AERs and CERs has recently been developed as an efficient strategy for tunable PL and enhanced stability (Figure 3B).…”