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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.


(a) PL spectra of parent CdSe NRs (dashed line) and of product CuInSe2 NRs (solid line) obtained from the parent NCs by sequential CE (NR dimensions: 3 nm diameter, 4 nm long). (b) PL of parent core/shell CdTe/CdSe HNCs (dashed line) and of product CuInTe2/CuInSe2 HNCs (solid line) obtained from the parent HNCs by sequential CE (core diameter: 2.6 nm; HNC length: 4 nm). The fine structure observed in the PL peak of CuInTe2/CuInSe2 HNCs is due to absorption by the solvent used to disperse the HNCs (viz., toluene). (c) PL of parent CdTe QDs (dashed line) and of product CuInTe2 QDs (solid line) obtained from the parent NCs by sequential CE (QD diameter: 2.7 nm). The PL peak energies prior to and after the CE reactions are also given. PL and absorption spectra of parent spherical core/shell CdSe/CdS HNCs (dashed line), intermediate Cu2Se/Cu2S core/shell HNCs, and final product CuInSe2/CuInS2 core/shell HNCs (solid line), obtained by sequential CE reactions, are provided in the Supporting Information, Figure S8.
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fig6: (a) PL spectra of parent CdSe NRs (dashed line) and of product CuInSe2 NRs (solid line) obtained from the parent NCs by sequential CE (NR dimensions: 3 nm diameter, 4 nm long). (b) PL of parent core/shell CdTe/CdSe HNCs (dashed line) and of product CuInTe2/CuInSe2 HNCs (solid line) obtained from the parent HNCs by sequential CE (core diameter: 2.6 nm; HNC length: 4 nm). The fine structure observed in the PL peak of CuInTe2/CuInSe2 HNCs is due to absorption by the solvent used to disperse the HNCs (viz., toluene). (c) PL of parent CdTe QDs (dashed line) and of product CuInTe2 QDs (solid line) obtained from the parent NCs by sequential CE (QD diameter: 2.7 nm). The PL peak energies prior to and after the CE reactions are also given. PL and absorption spectra of parent spherical core/shell CdSe/CdS HNCs (dashed line), intermediate Cu2Se/Cu2S core/shell HNCs, and final product CuInSe2/CuInS2 core/shell HNCs (solid line), obtained by sequential CE reactions, are provided in the Supporting Information, Figure S8.

Mentions: To demonstrate the generality of our approach, we also carried out sequential CE reactions using spherical core/shell CdSe/CdS HNCs, prolate CdTe/CdSe HNCs, CdSe NRs, and different sizes of CdSe and CdTe quantum dots (QDs) as templates. In all these cases, the intermediate Cu-chalcogenide NCs did not show PL, whereas after self-limited partial In3+ for Cu+ exchange, PL in the NIR was observed (Figure 6 and Figure S8, Supporting Information). It is interesting to notice that the NIR PL peak position is clearly correlated with the size, composition, and shape/architecture of the product NC or HNC [e.g., the PL peak is at 1.37 eV for 2.7 nm diameter product CITe QDs and at 1.18 eV for product CITe/CISe core/shell HNCs (see Figure 6) and shifts from 1.22 to 1.17 eV upon increase of the CISe core diameter in product CISe/CIS dot core/rod shell NRs from 2.7 nm ± 0.4 nm to 3.2 nm ± 0.5 nm (see Figure S1, SI)]. This illustrates that the NIR PL of the product NCs (HNCs) can be tuned by a proper choice of the size, shape, composition, and heteroarchitecture of the template NCs (HNCs). Moreover, as discussed above, it may be possible to tailor the carrier localization regime in CuInX2-based HNCs by controlling their composition, size, and heteroarchitecture. It should also be noted that topotactic Cu+ for Cd2+ exchange in template Cd-chalcogenide NCs has already been successfully used by several groups to obtain a variety of Cu-chalcogenide colloidal nanostructures, such as ultrathin Cu2Se/Cu2S nanoplatelets,27 Cu2–xS nanowires,28 and Cu2–xTe QDs, NRs, and tetrapods.29 This, in combination with the results reported in the present work, indicate that our approach is general and can be applied to any CdX (X = S, Se, and Te) 0D,1 1D (nanorods and tetrapods)1 or 2D48 NC or HNC (e.g., CdSe/CdS dot core/rod shell heteronanorods1,2 and heterotetrapods,49 CdSe/CdS concentric core/shell QDs,3 CdTe/CdSe core/shell heteronanorods and heteromultipods,43,44 (Cd,Zn)Te/CdSe heteronanowires50), yielding size-, shape-, and composition-controlled ternary CuInX2 NCs and HNCs that cannot be fabricated by direct synthesis methods.


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)

(a) PL spectra of parent CdSe NRs (dashed line) and of product CuInSe2 NRs (solid line) obtained from the parent NCs by sequential CE (NR dimensions: 3 nm diameter, 4 nm long). (b) PL of parent core/shell CdTe/CdSe HNCs (dashed line) and of product CuInTe2/CuInSe2 HNCs (solid line) obtained from the parent HNCs by sequential CE (core diameter: 2.6 nm; HNC length: 4 nm). The fine structure observed in the PL peak of CuInTe2/CuInSe2 HNCs is due to absorption by the solvent used to disperse the HNCs (viz., toluene). (c) PL of parent CdTe QDs (dashed line) and of product CuInTe2 QDs (solid line) obtained from the parent NCs by sequential CE (QD diameter: 2.7 nm). The PL peak energies prior to and after the CE reactions are also given. PL and absorption spectra of parent spherical core/shell CdSe/CdS HNCs (dashed line), intermediate Cu2Se/Cu2S core/shell HNCs, and final product CuInSe2/CuInS2 core/shell HNCs (solid line), obtained by sequential CE reactions, are provided in the Supporting Information, Figure S8.
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fig6: (a) PL spectra of parent CdSe NRs (dashed line) and of product CuInSe2 NRs (solid line) obtained from the parent NCs by sequential CE (NR dimensions: 3 nm diameter, 4 nm long). (b) PL of parent core/shell CdTe/CdSe HNCs (dashed line) and of product CuInTe2/CuInSe2 HNCs (solid line) obtained from the parent HNCs by sequential CE (core diameter: 2.6 nm; HNC length: 4 nm). The fine structure observed in the PL peak of CuInTe2/CuInSe2 HNCs is due to absorption by the solvent used to disperse the HNCs (viz., toluene). (c) PL of parent CdTe QDs (dashed line) and of product CuInTe2 QDs (solid line) obtained from the parent NCs by sequential CE (QD diameter: 2.7 nm). The PL peak energies prior to and after the CE reactions are also given. PL and absorption spectra of parent spherical core/shell CdSe/CdS HNCs (dashed line), intermediate Cu2Se/Cu2S core/shell HNCs, and final product CuInSe2/CuInS2 core/shell HNCs (solid line), obtained by sequential CE reactions, are provided in the Supporting Information, Figure S8.
Mentions: To demonstrate the generality of our approach, we also carried out sequential CE reactions using spherical core/shell CdSe/CdS HNCs, prolate CdTe/CdSe HNCs, CdSe NRs, and different sizes of CdSe and CdTe quantum dots (QDs) as templates. In all these cases, the intermediate Cu-chalcogenide NCs did not show PL, whereas after self-limited partial In3+ for Cu+ exchange, PL in the NIR was observed (Figure 6 and Figure S8, Supporting Information). It is interesting to notice that the NIR PL peak position is clearly correlated with the size, composition, and shape/architecture of the product NC or HNC [e.g., the PL peak is at 1.37 eV for 2.7 nm diameter product CITe QDs and at 1.18 eV for product CITe/CISe core/shell HNCs (see Figure 6) and shifts from 1.22 to 1.17 eV upon increase of the CISe core diameter in product CISe/CIS dot core/rod shell NRs from 2.7 nm ± 0.4 nm to 3.2 nm ± 0.5 nm (see Figure S1, SI)]. This illustrates that the NIR PL of the product NCs (HNCs) can be tuned by a proper choice of the size, shape, composition, and heteroarchitecture of the template NCs (HNCs). Moreover, as discussed above, it may be possible to tailor the carrier localization regime in CuInX2-based HNCs by controlling their composition, size, and heteroarchitecture. It should also be noted that topotactic Cu+ for Cd2+ exchange in template Cd-chalcogenide NCs has already been successfully used by several groups to obtain a variety of Cu-chalcogenide colloidal nanostructures, such as ultrathin Cu2Se/Cu2S nanoplatelets,27 Cu2–xS nanowires,28 and Cu2–xTe QDs, NRs, and tetrapods.29 This, in combination with the results reported in the present work, indicate that our approach is general and can be applied to any CdX (X = S, Se, and Te) 0D,1 1D (nanorods and tetrapods)1 or 2D48 NC or HNC (e.g., CdSe/CdS dot core/rod shell heteronanorods1,2 and heterotetrapods,49 CdSe/CdS concentric core/shell QDs,3 CdTe/CdSe core/shell heteronanorods and heteromultipods,43,44 (Cd,Zn)Te/CdSe heteronanowires50), yielding size-, shape-, and composition-controlled ternary CuInX2 NCs and HNCs that cannot be fabricated by direct synthesis methods.

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.