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Near-Infrared Emitting CuInSe₂/CuInS₂ Dot Core/Rod Shell Heteronanorods by Sequential Cation Exchange.

van der Stam W, Bladt E, Rabouw FT, Bals S, Donega Cde M - ACS Nano (2015)

Bottom Line: This results in readily available In(3+) ions at the same surface site from which the Cu(+) is extracted, making the process a direct place exchange reaction and shifting the overall energy balance in favor of the CE.The method is very versatile, successfully yielding a variety of luminescent CuInX2 (X = S, Se, and Te) quantum dots, nanorods, and HNCs, by using Cd-chalcogenide NCs and HNCs as templates.The approach reported here thus opens up routes toward materials with unprecedented properties, which would otherwise remain inaccessible.

View Article: PubMed Central - PubMed

Affiliation: Debye Institute for Nanomaterials Science, Utrecht University , P.O. Box 80000, 3508 TA Utrecht, The Netherlands.

ABSTRACT
The direct synthesis of heteronanocrystals (HNCs) combining different ternary semiconductors is challenging and has not yet been successful. Here, we report a sequential topotactic cation exchange (CE) pathway that yields CuInSe2/CuInS2 dot core/rod shell nanorods with near-infrared luminescence. In our approach, the Cu(+) extraction rate is coupled to the In(3+) incorporation rate by the use of a stoichiometric trioctylphosphine-InCl3 complex, which fulfills the roles of both In-source and Cu-extracting agent. In this way, Cu(+) ions can be extracted by trioctylphosphine ligands only when the In-P bond is broken. This results in readily available In(3+) ions at the same surface site from which the Cu(+) is extracted, making the process a direct place exchange reaction and shifting the overall energy balance in favor of the CE. Consequently, controlled cation exchange can occur even in large and anisotropic heterostructured nanocrystals with preservation of the size, shape, and heterostructuring of the template NCs into the product NCs. The cation exchange is self-limited, stopping when the ternary core/shell CuInSe2/CuInS2 composition is reached. The method is very versatile, successfully yielding a variety of luminescent CuInX2 (X = S, Se, and Te) quantum dots, nanorods, and HNCs, by using Cd-chalcogenide NCs and HNCs as templates. The approach reported here thus opens up routes toward materials with unprecedented properties, which would otherwise remain inaccessible.

No MeSH data available.


Visualizations of tomographic 3D reconstructions of (a) the template CdSe/CdS core/shell NRs (yellow, CdS; orange, CdSe), (d) the intermediate Cu2Se/Cu2S core/shell NRs (light brown, Cu2S; dark brown, Cu2Se), and (g) the final product CuInSe2/CuInS2 core/shell NRs (light red, CuInS2; dark red, CuInSe2). Orthoslices at positions marked with b and c for CdSe/CdS NRs, e and f for Cu2Se/Cu2S NRs, and h and i for CuInSe2/CuInS2 NRs show the position of the Se-containing cores, due to the difference in Z-contrast (ZSe = 34 and ZS = 16).
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fig3: Visualizations of tomographic 3D reconstructions of (a) the template CdSe/CdS core/shell NRs (yellow, CdS; orange, CdSe), (d) the intermediate Cu2Se/Cu2S core/shell NRs (light brown, Cu2S; dark brown, Cu2Se), and (g) the final product CuInSe2/CuInS2 core/shell NRs (light red, CuInS2; dark red, CuInSe2). Orthoslices at positions marked with b and c for CdSe/CdS NRs, e and f for Cu2Se/Cu2S NRs, and h and i for CuInSe2/CuInS2 NRs show the position of the Se-containing cores, due to the difference in Z-contrast (ZSe = 34 and ZS = 16).

Mentions: High-resolution (HR) high-angle annular dark field scanning TEM (HAADF-STEM) measurements also confirm the successful sequential cation exchange from parent CdSe/CdS dot core/rod shell NRs into product CISe/CIS dot core/rod shell NRs via intermediate Cu2Se/Cu2S dot core/rod shell NRs (Figure 2d–f). The HAADF-STEM investigation indicates that the parent CdSe/CdS core/shell NRs have the CdS wurtzite structure, since the fast Fourier transform (FFT) analysis of the HRTEM image (inset in Figure 2d) shows the characteristic {002} and {010} wurtzite CdS lattice planes (see also XRD pattern, Figure S4, Supporting Information). The thickness of the NRs varies from 9 to 15 atomic columns. Note that the majority of the volume of the NRs consists of CdS, and therefore the contribution of the CdSe core is not detected. FFT analysis of the HRTEM measurements shows that the product CISe/CIS NRs have the wurtzite CuInS2 crystal structure (inset in Figure 2f; see also XRD pattern, Figure S4, Supporting Information). From high-resolution HAADF-STEM imaging, we could determine that the resulting CISe/CIS NRs have a varying thickness of 8 to 14 atomic columns, consistent with the thickness of the template CdSe/CdS NRs. The position of the core was located by HAADF-STEM electron tomography (Figure 3). Since the intensity in HAADF-STEM images scales with the atomic number Z, this technique can distinguish between parts of the NRs containing Se (ZSe = 34) and S (ZS = 16). The electron tomography reconstruction shows that the cores are slightly elongated and that their shape is preserved in the product HNCs, showing that the anionic sublattice is not affected by the sequential CE reactions. We should note that the acquisition of several images at the same position of interest caused a lot of carbon contamination, due to the ligands covering the NRs. Therefore, the grids were baked at 120 °C for several hours in order to remove the organic ligands from the surface of the NRs. After this treatment, the organic contamination decreased, but also the shell of the CISe/CIS and Cu2Se/Cu2S NRs was slightly altered (Figure 3b,c).


Near-Infrared Emitting CuInSe₂/CuInS₂ Dot Core/Rod Shell Heteronanorods by Sequential Cation Exchange.

van der Stam W, Bladt E, Rabouw FT, Bals S, Donega Cde M - ACS Nano (2015)

Visualizations of tomographic 3D reconstructions of (a) the template CdSe/CdS core/shell NRs (yellow, CdS; orange, CdSe), (d) the intermediate Cu2Se/Cu2S core/shell NRs (light brown, Cu2S; dark brown, Cu2Se), and (g) the final product CuInSe2/CuInS2 core/shell NRs (light red, CuInS2; dark red, CuInSe2). Orthoslices at positions marked with b and c for CdSe/CdS NRs, e and f for Cu2Se/Cu2S NRs, and h and i for CuInSe2/CuInS2 NRs show the position of the Se-containing cores, due to the difference in Z-contrast (ZSe = 34 and ZS = 16).
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fig3: Visualizations of tomographic 3D reconstructions of (a) the template CdSe/CdS core/shell NRs (yellow, CdS; orange, CdSe), (d) the intermediate Cu2Se/Cu2S core/shell NRs (light brown, Cu2S; dark brown, Cu2Se), and (g) the final product CuInSe2/CuInS2 core/shell NRs (light red, CuInS2; dark red, CuInSe2). Orthoslices at positions marked with b and c for CdSe/CdS NRs, e and f for Cu2Se/Cu2S NRs, and h and i for CuInSe2/CuInS2 NRs show the position of the Se-containing cores, due to the difference in Z-contrast (ZSe = 34 and ZS = 16).
Mentions: High-resolution (HR) high-angle annular dark field scanning TEM (HAADF-STEM) measurements also confirm the successful sequential cation exchange from parent CdSe/CdS dot core/rod shell NRs into product CISe/CIS dot core/rod shell NRs via intermediate Cu2Se/Cu2S dot core/rod shell NRs (Figure 2d–f). The HAADF-STEM investigation indicates that the parent CdSe/CdS core/shell NRs have the CdS wurtzite structure, since the fast Fourier transform (FFT) analysis of the HRTEM image (inset in Figure 2d) shows the characteristic {002} and {010} wurtzite CdS lattice planes (see also XRD pattern, Figure S4, Supporting Information). The thickness of the NRs varies from 9 to 15 atomic columns. Note that the majority of the volume of the NRs consists of CdS, and therefore the contribution of the CdSe core is not detected. FFT analysis of the HRTEM measurements shows that the product CISe/CIS NRs have the wurtzite CuInS2 crystal structure (inset in Figure 2f; see also XRD pattern, Figure S4, Supporting Information). From high-resolution HAADF-STEM imaging, we could determine that the resulting CISe/CIS NRs have a varying thickness of 8 to 14 atomic columns, consistent with the thickness of the template CdSe/CdS NRs. The position of the core was located by HAADF-STEM electron tomography (Figure 3). Since the intensity in HAADF-STEM images scales with the atomic number Z, this technique can distinguish between parts of the NRs containing Se (ZSe = 34) and S (ZS = 16). The electron tomography reconstruction shows that the cores are slightly elongated and that their shape is preserved in the product HNCs, showing that the anionic sublattice is not affected by the sequential CE reactions. We should note that the acquisition of several images at the same position of interest caused a lot of carbon contamination, due to the ligands covering the NRs. Therefore, the grids were baked at 120 °C for several hours in order to remove the organic ligands from the surface of the NRs. After this treatment, the organic contamination decreased, but also the shell of the CISe/CIS and Cu2Se/Cu2S NRs was slightly altered (Figure 3b,c).

Bottom Line: This results in readily available In(3+) ions at the same surface site from which the Cu(+) is extracted, making the process a direct place exchange reaction and shifting the overall energy balance in favor of the CE.The method is very versatile, successfully yielding a variety of luminescent CuInX2 (X = S, Se, and Te) quantum dots, nanorods, and HNCs, by using Cd-chalcogenide NCs and HNCs as templates.The approach reported here thus opens up routes toward materials with unprecedented properties, which would otherwise remain inaccessible.

View Article: PubMed Central - PubMed

Affiliation: Debye Institute for Nanomaterials Science, Utrecht University , P.O. Box 80000, 3508 TA Utrecht, The Netherlands.

ABSTRACT
The direct synthesis of heteronanocrystals (HNCs) combining different ternary semiconductors is challenging and has not yet been successful. Here, we report a sequential topotactic cation exchange (CE) pathway that yields CuInSe2/CuInS2 dot core/rod shell nanorods with near-infrared luminescence. In our approach, the Cu(+) extraction rate is coupled to the In(3+) incorporation rate by the use of a stoichiometric trioctylphosphine-InCl3 complex, which fulfills the roles of both In-source and Cu-extracting agent. In this way, Cu(+) ions can be extracted by trioctylphosphine ligands only when the In-P bond is broken. This results in readily available In(3+) ions at the same surface site from which the Cu(+) is extracted, making the process a direct place exchange reaction and shifting the overall energy balance in favor of the CE. Consequently, controlled cation exchange can occur even in large and anisotropic heterostructured nanocrystals with preservation of the size, shape, and heterostructuring of the template NCs into the product NCs. The cation exchange is self-limited, stopping when the ternary core/shell CuInSe2/CuInS2 composition is reached. The method is very versatile, successfully yielding a variety of luminescent CuInX2 (X = S, Se, and Te) quantum dots, nanorods, and HNCs, by using Cd-chalcogenide NCs and HNCs as templates. The approach reported here thus opens up routes toward materials with unprecedented properties, which would otherwise remain inaccessible.

No MeSH data available.