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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.


Related in: MedlinePlus

Transmission electron microscopy (a–c) and high-resolution HAADF-STEM (d–f) images of CdSe/CdS core/shell NRs (a, d), Cu2Se/Cu2S core/shell NRs (b, e), and CuInSe2/CuInS2 (CISe/CIS) core/shell NRs (c, f). The CISe/CIS NRs shown in c and f were obtained by sequential CE (Cu+ for Cd2+ followed by partial In3+ for Cu+) using the CdSe/CdS NRs shown in a and d as templates and the Cu2Se/Cu2S NRs shown in b and e as intermediates. The squares in panels d–f indicate regions where FFT analysis was performed. The corresponding FFT patterns show characteristic {010} and {002} wurtzite CdS reflections for CdSe/CdS core/shell NRs (inset panel d), characteristic chalcocite Cu2S reflections for Cu2Se/Cu2S core/shell NRs (inset panel e), and characteristic wurtzite CIS reflections for CISe/CIS core/shell NRs (inset panel f). Additional HAADF-STEM images are provided in the Supporting Information (Figures S5–S7).
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fig2: Transmission electron microscopy (a–c) and high-resolution HAADF-STEM (d–f) images of CdSe/CdS core/shell NRs (a, d), Cu2Se/Cu2S core/shell NRs (b, e), and CuInSe2/CuInS2 (CISe/CIS) core/shell NRs (c, f). The CISe/CIS NRs shown in c and f were obtained by sequential CE (Cu+ for Cd2+ followed by partial In3+ for Cu+) using the CdSe/CdS NRs shown in a and d as templates and the Cu2Se/Cu2S NRs shown in b and e as intermediates. The squares in panels d–f indicate regions where FFT analysis was performed. The corresponding FFT patterns show characteristic {010} and {002} wurtzite CdS reflections for CdSe/CdS core/shell NRs (inset panel d), characteristic chalcocite Cu2S reflections for Cu2Se/Cu2S core/shell NRs (inset panel e), and characteristic wurtzite CIS reflections for CISe/CIS core/shell NRs (inset panel f). Additional HAADF-STEM images are provided in the Supporting Information (Figures S5–S7).

Mentions: Transmission electron microscopy (TEM) measurements show that the size and shape of the parent CdSe/CdS NRs are preserved in the product CISe/CIS NRs after the sequential CE reactions (Figure 2). Energy dispersive X-ray spectroscopy (EDS) measurements show a Cd:S ratio of 1:1 for the parent CdSe/CdS NRs, a Cu:S ratio of 2.1:1 for the intermediate Cu-based NRs, and a Cu:In:S ratio of 0.8:1.3:2 for the product CISe/CIS NRs (Figures S2 and S3, Supporting Information). Residual Cd2+ is observed in the intermediate Cu-based NRs (∼2%), but is not detected in the product CISe/CIS NRs. These measurements indicate a successful sequential CE pathway toward CISe/CIS NRs. The product CISe/CIS NRs are accompanied by a byproduct of the CE reaction that was not completely removed by the washing-up procedure (see dark spots in Figure 2c and lighter particles in Figure S7a,b, Supporting Information). This byproduct is probably residual TOP-InCl3 (TOP: trioctylphosphine; see Experimental Methods for details), since it consists only of In (i.e., S and Cu peaks are not observed in the EDS measurements). Therefore, EDS spectra such as the one shown in Figure S2b (Supporting Information), which were collected over large areas containing both nanorods and byproduct, provide a reliable Cu:S ratio (1:2), but overestimate the In content. We corrected for this contribution by measuring EDS spectra on single NRs, which revealed a Cu:In:S ratio that is consistent with the CuInS2 stoichiometry. EDS measurements were also carried out on small groups of isolated NRs, without the byproduct, yielding a Cu:In:S ratio of 0.8:1.3:2 (Figure S3, Supporting Information). We note that the Se signal of the core is not detected since the majority of the volume of the NRs consists of the metal sulfide compositions (CdS, Cu2S, and CIS, respectively).


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)

Transmission electron microscopy (a–c) and high-resolution HAADF-STEM (d–f) images of CdSe/CdS core/shell NRs (a, d), Cu2Se/Cu2S core/shell NRs (b, e), and CuInSe2/CuInS2 (CISe/CIS) core/shell NRs (c, f). The CISe/CIS NRs shown in c and f were obtained by sequential CE (Cu+ for Cd2+ followed by partial In3+ for Cu+) using the CdSe/CdS NRs shown in a and d as templates and the Cu2Se/Cu2S NRs shown in b and e as intermediates. The squares in panels d–f indicate regions where FFT analysis was performed. The corresponding FFT patterns show characteristic {010} and {002} wurtzite CdS reflections for CdSe/CdS core/shell NRs (inset panel d), characteristic chalcocite Cu2S reflections for Cu2Se/Cu2S core/shell NRs (inset panel e), and characteristic wurtzite CIS reflections for CISe/CIS core/shell NRs (inset panel f). Additional HAADF-STEM images are provided in the Supporting Information (Figures S5–S7).
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fig2: Transmission electron microscopy (a–c) and high-resolution HAADF-STEM (d–f) images of CdSe/CdS core/shell NRs (a, d), Cu2Se/Cu2S core/shell NRs (b, e), and CuInSe2/CuInS2 (CISe/CIS) core/shell NRs (c, f). The CISe/CIS NRs shown in c and f were obtained by sequential CE (Cu+ for Cd2+ followed by partial In3+ for Cu+) using the CdSe/CdS NRs shown in a and d as templates and the Cu2Se/Cu2S NRs shown in b and e as intermediates. The squares in panels d–f indicate regions where FFT analysis was performed. The corresponding FFT patterns show characteristic {010} and {002} wurtzite CdS reflections for CdSe/CdS core/shell NRs (inset panel d), characteristic chalcocite Cu2S reflections for Cu2Se/Cu2S core/shell NRs (inset panel e), and characteristic wurtzite CIS reflections for CISe/CIS core/shell NRs (inset panel f). Additional HAADF-STEM images are provided in the Supporting Information (Figures S5–S7).
Mentions: Transmission electron microscopy (TEM) measurements show that the size and shape of the parent CdSe/CdS NRs are preserved in the product CISe/CIS NRs after the sequential CE reactions (Figure 2). Energy dispersive X-ray spectroscopy (EDS) measurements show a Cd:S ratio of 1:1 for the parent CdSe/CdS NRs, a Cu:S ratio of 2.1:1 for the intermediate Cu-based NRs, and a Cu:In:S ratio of 0.8:1.3:2 for the product CISe/CIS NRs (Figures S2 and S3, Supporting Information). Residual Cd2+ is observed in the intermediate Cu-based NRs (∼2%), but is not detected in the product CISe/CIS NRs. These measurements indicate a successful sequential CE pathway toward CISe/CIS NRs. The product CISe/CIS NRs are accompanied by a byproduct of the CE reaction that was not completely removed by the washing-up procedure (see dark spots in Figure 2c and lighter particles in Figure S7a,b, Supporting Information). This byproduct is probably residual TOP-InCl3 (TOP: trioctylphosphine; see Experimental Methods for details), since it consists only of In (i.e., S and Cu peaks are not observed in the EDS measurements). Therefore, EDS spectra such as the one shown in Figure S2b (Supporting Information), which were collected over large areas containing both nanorods and byproduct, provide a reliable Cu:S ratio (1:2), but overestimate the In content. We corrected for this contribution by measuring EDS spectra on single NRs, which revealed a Cu:In:S ratio that is consistent with the CuInS2 stoichiometry. EDS measurements were also carried out on small groups of isolated NRs, without the byproduct, yielding a Cu:In:S ratio of 0.8:1.3:2 (Figure S3, Supporting Information). We note that the Se signal of the core is not detected since the majority of the volume of the NRs consists of the metal sulfide compositions (CdS, Cu2S, and CIS, respectively).

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.


Related in: MedlinePlus