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Selective cation exchange in the core region of Cu2-xSe/Cu2-xS core/shell nanocrystals.

Miszta K, Gariano G, Brescia R, Marras S, De Donato F, Ghosh S, De Trizio L, Manna L - J. Am. Chem. Soc. (2015)

Bottom Line: We studied cation exchange (CE) in core/shell Cu2-xSe/Cu2-xS nanorods with two cations, Ag(+) and Hg(2+), which are known to induce rapid exchange within metal chalcogenide nanocrystals (NCs) at room temperature.These experiments prove that CE in copper chalcogenide NCs is facilitated by the high diffusivity of guest cations in the lattice, such that they can probe the whole host structure and identify the preferred regions where to initiate the exchange.For both guest ions, CE is thermodynamically driven as it aims for the formation of the chalcogen phase characterized by the lower solubility under the specific reaction conditions.

View Article: PubMed Central - PubMed

Affiliation: Department of Nanochemistry, Istituto Italiano di Tecnologia (IIT) , via Morego, 30, 16163 Genova, Italy.

ABSTRACT
We studied cation exchange (CE) in core/shell Cu2-xSe/Cu2-xS nanorods with two cations, Ag(+) and Hg(2+), which are known to induce rapid exchange within metal chalcogenide nanocrystals (NCs) at room temperature. At the initial stage of the reaction, the guest ions diffused through the Cu2-xS shell and reached the Cu2-xSe core, replacing first Cu(+) ions within the latter region. These experiments prove that CE in copper chalcogenide NCs is facilitated by the high diffusivity of guest cations in the lattice, such that they can probe the whole host structure and identify the preferred regions where to initiate the exchange. For both guest ions, CE is thermodynamically driven as it aims for the formation of the chalcogen phase characterized by the lower solubility under the specific reaction conditions.

No MeSH data available.


CE in Cu2–xSe/Cu2–xS NRs with Ag+ and Hg2+ ions.HAADF-STEM images of groups of (a) pristine, (b) Ag+, and(c) Hg2+ partially exchanged Cu2–xSe/Cu2–xS NRs with the correspondingSTEM-EDS elemental maps. Scale bars are 20 nm.
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fig2: CE in Cu2–xSe/Cu2–xS NRs with Ag+ and Hg2+ ions.HAADF-STEM images of groups of (a) pristine, (b) Ag+, and(c) Hg2+ partially exchanged Cu2–xSe/Cu2–xS NRs with the correspondingSTEM-EDS elemental maps. Scale bars are 20 nm.

Mentions: When Cu+ cations in Cu2–xS nanorods (NRs)were partially replaced by Hg2+ ions, the NRs evolved intomultidomain structures, similar to whatwas observed by other groups when exposing CdS NRs or Cu2S nanowires to Cu+ or Ag+ ions, respectively.2e,6,7b This is seen in the high-angleannular dark-field (HAADF) scanning transmission electron microscopy(STEM) images of Figure 1a,c, and in the compositional maps acquired via energy dispersiveX-ray spectroscopy (EDS). In the Ag+ case, the NRs wereconverted into a mixture of rods with a segmented structure and rodswith ternary composition (see Figure 1b and selected area electron diffraction analyses in Figure S2). In some of the partially exchangedNRs, a slightly Ag-rich shell was also visible. The two cations, despitehaving similar ionic radii (Ag+ = 1.0 Å and Hg2+ = 0.96 Å in tetrahedral coordination),9 seemed to behave differently: the Ag+ ions appearedto probe the entire NR volume, while the Hg2+ ions weremainly engaged in reactions that started at the tips of the rods.We then extended this reaction scheme to core/shell Cu2–xSe/Cu2–xS NRs.A comparison of HAADF-STEM and EDS analyses of the initial samplewith those after partial exchange indicated a selective replacementof Cu+ ions in the selenide core region (see Figures 2 and S3, S4).


Selective cation exchange in the core region of Cu2-xSe/Cu2-xS core/shell nanocrystals.

Miszta K, Gariano G, Brescia R, Marras S, De Donato F, Ghosh S, De Trizio L, Manna L - J. Am. Chem. Soc. (2015)

CE in Cu2–xSe/Cu2–xS NRs with Ag+ and Hg2+ ions.HAADF-STEM images of groups of (a) pristine, (b) Ag+, and(c) Hg2+ partially exchanged Cu2–xSe/Cu2–xS NRs with the correspondingSTEM-EDS elemental maps. Scale bars are 20 nm.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4591528&req=5

fig2: CE in Cu2–xSe/Cu2–xS NRs with Ag+ and Hg2+ ions.HAADF-STEM images of groups of (a) pristine, (b) Ag+, and(c) Hg2+ partially exchanged Cu2–xSe/Cu2–xS NRs with the correspondingSTEM-EDS elemental maps. Scale bars are 20 nm.
Mentions: When Cu+ cations in Cu2–xS nanorods (NRs)were partially replaced by Hg2+ ions, the NRs evolved intomultidomain structures, similar to whatwas observed by other groups when exposing CdS NRs or Cu2S nanowires to Cu+ or Ag+ ions, respectively.2e,6,7b This is seen in the high-angleannular dark-field (HAADF) scanning transmission electron microscopy(STEM) images of Figure 1a,c, and in the compositional maps acquired via energy dispersiveX-ray spectroscopy (EDS). In the Ag+ case, the NRs wereconverted into a mixture of rods with a segmented structure and rodswith ternary composition (see Figure 1b and selected area electron diffraction analyses in Figure S2). In some of the partially exchangedNRs, a slightly Ag-rich shell was also visible. The two cations, despitehaving similar ionic radii (Ag+ = 1.0 Å and Hg2+ = 0.96 Å in tetrahedral coordination),9 seemed to behave differently: the Ag+ ions appearedto probe the entire NR volume, while the Hg2+ ions weremainly engaged in reactions that started at the tips of the rods.We then extended this reaction scheme to core/shell Cu2–xSe/Cu2–xS NRs.A comparison of HAADF-STEM and EDS analyses of the initial samplewith those after partial exchange indicated a selective replacementof Cu+ ions in the selenide core region (see Figures 2 and S3, S4).

Bottom Line: We studied cation exchange (CE) in core/shell Cu2-xSe/Cu2-xS nanorods with two cations, Ag(+) and Hg(2+), which are known to induce rapid exchange within metal chalcogenide nanocrystals (NCs) at room temperature.These experiments prove that CE in copper chalcogenide NCs is facilitated by the high diffusivity of guest cations in the lattice, such that they can probe the whole host structure and identify the preferred regions where to initiate the exchange.For both guest ions, CE is thermodynamically driven as it aims for the formation of the chalcogen phase characterized by the lower solubility under the specific reaction conditions.

View Article: PubMed Central - PubMed

Affiliation: Department of Nanochemistry, Istituto Italiano di Tecnologia (IIT) , via Morego, 30, 16163 Genova, Italy.

ABSTRACT
We studied cation exchange (CE) in core/shell Cu2-xSe/Cu2-xS nanorods with two cations, Ag(+) and Hg(2+), which are known to induce rapid exchange within metal chalcogenide nanocrystals (NCs) at room temperature. At the initial stage of the reaction, the guest ions diffused through the Cu2-xS shell and reached the Cu2-xSe core, replacing first Cu(+) ions within the latter region. These experiments prove that CE in copper chalcogenide NCs is facilitated by the high diffusivity of guest cations in the lattice, such that they can probe the whole host structure and identify the preferred regions where to initiate the exchange. For both guest ions, CE is thermodynamically driven as it aims for the formation of the chalcogen phase characterized by the lower solubility under the specific reaction conditions.

No MeSH data available.