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Paul A Alivisatos - One of the best experts on this subject based on the ideXlab platform.
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Cation Exchange a versatile tool for nanomaterials synthesis
Journal of Physical Chemistry C, 2013Co-Authors: Brandon J Beberwyck, Yogesh Surendranath, Paul A AlivisatosAbstract:The development of nanomaterials for next generation photonic, optoelectronic, and catalytic appliCations requires a robust synthetic toolkit for systematically tuning composition, phase, and morphology at nanometer length scales. While de novo synthetic methods for preparing nanomaterials from molecular precursors have advanced considerably in recent years, postsynthetic modifiCations of these preformed nanostructures have enabled the stepwise construction of complex nanomaterials. Among these postsynthetic transformations, Cation Exchange reactions, in which the Cations ligated within a nanocrystal host lattice are substituted with those in solution, have emerged as particularly powerful tools for fine-grained control over nanocrystal composition and phase. In this feature article, we review the fundamental thermodynamic and kinetic basis for Cation Exchange reactions in colloidal semiconductor nanocrystals and highlight its synthetic versatility for accessing nanomaterials intractable by direct synthet...
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nanoheterostructure Cation Exchange anionic framework conservation
Journal of the American Chemical Society, 2010Co-Authors: Prashant K Jain, Lilac Amirav, Shaul Aloni, Paul A AlivisatosAbstract:In ionic nanocrystals the Cationic sublattice can be replaced with a different metal ion via a fast, simple, and reversible place Exchange, allowing postsynthetic modifiCation of the composition of the nanocrystal, while preserving its size and shape. Here, we demonstrate that, during such an Exchange, the anionic framework of the crystal is preserved. When applied to nanoheterostructures, this phenomenon ensures that compositional interfaces within the heterostructure are conserved throughout the transformation. For instance, a morphology composed of a CdSe nanocrystal embedded in a CdS rod (CdSe/CdS) was Exchanged to a PbSe/PbS nanorod via a Cu2Se/Cu2S structure. During every Exchange cycle, the seed size and position within the nanorod were preserved, as evident by excitonic features, Z-contrast imaging, and elemental line scans. Anionic framework conservation extends the domain of Cation Exchange to the design of more complex and unique nanostructures.
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selective facet reactivity during Cation Exchange in cadmium sulfide nanorods
Journal of the American Chemical Society, 2009Co-Authors: Bryce Sadtler, Steven M. Hughes, D O Demchenko, Haimei Zheng, Maxwell G Merkle, U Dahmen, Linwang Wang, Paul A AlivisatosAbstract:The partial transformation of ionic nanocrystals through Cation Exchange has been used to synthesize nanocrystal heterostructures. We demonstrate that the selectivity for Cation Exchange to take place at different facets of the nanocrystal plays an important role in determining the resulting morphology of the binary heterostructure. In the case of copper(I) (Cu+) Cation Exchange in cadmium sulfide (CdS) nanorods, the reaction starts preferentially at the ends of the nanorods such that copper sulfide (Cu2S) grows inward from either end. The resulting morphology is very different from the striped pattern obtained in our previous studies of silver(I) (Ag+) Exchange in CdS nanorods where nonselective nucleation of silver sulfide (Ag2S) occurs (Robinson, R. D.; Sadtler, B.; Demchenko, D. O.; Erdonmez, C. K.; Wang, L.-W.; Alivisatos, A. P. Science 2007, 317, 355−358). From interface formation energies calculated for several models of epitaxial connections between CdS and Cu2S or Ag2S, we infer the relative stab...
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millisecond kinetics of nanocrystal Cation Exchange using microfluidic x ray absorption spectroscopy
Journal of Physical Chemistry A, 2007Co-Authors: Emory M Chan, Matthew A Marcus, Sirine Fakra, Mariam S Elnaggar, Richard A Mathies, Paul A AlivisatosAbstract:We describe the use of a flow-focusing microfluidic reactor to measure the kinetics of the CdSe-to-Ag2Se nanocrystal Cation Exchange reaction using micro-X-ray absorption spectroscopy (μXAS). The small microreactor dimensions facilitate the millisecond mixing of CdSe nanocrystals and Ag+ reactant solutions, and the transposition of the reaction time onto spatial coordinates enables the in situ observation of the millisecond reaction using μXAS. Selenium K-edge absorption spectra show the progression of CdSe nanocrystals to Ag2Se over the course of 100 ms without the presence of long-lived intermediates. These results, along with supporting stopped-flow absorption experiments, suggest that this nanocrystal Cation Exchange reaction is highly efficient and provide insight into how the reaction progresses in individual particles. This experiment illustrates the value and potential of in situ microfluidic X-ray synchrotron techniques for detailed studies of the millisecond structural transformations of nanopar...
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millisecond kinetics of nanocrystal Cation Exchange using microfluidic x ray absorption spectroscopy
Lawrence Berkeley National Laboratory, 2007Co-Authors: Emory M Chan, Matthew A Marcus, Sirine Fakra, Mariam S Elnaggar, Richard A Mathies, Paul A AlivisatosAbstract:We describe the use of a flow-focusing microfluidic reactor to measure the kinetics of the CdSe-to-Ag2Se nanocrystal Cation Exchange reaction using micro-X-ray absorption spectroscopy (mu XAS). The small microreactor dimensions facilitate the millisecond mixing of CdSe nanocrystal and Ag+ reactant solutions, and the transposition of the reaction time onto spatial coordinates enables the in situ observation of the millisecond reaction with mu XAS. XAS spectra show the progression of CdSe nanocrystals to Ag2Se over the course of 100 ms without the presence of long-lived intermediates. These results, along with supporting stopped flow absorption experiments, suggest that this nanocrystal Cation Exchange reaction is highly efficient and provide insight into how the reaction progresses in individual particles. This experiment illustrates the value and potential of in situ microfluidic X-ray synchrotron techniques for detailed studies of the millisecond structural transformations of nanoparticles and other solution-phase reactions in which diffusive mixing initiates changes in local bond structures or oxidation states.
Celso De Mello Donega - One of the best experts on this subject based on the ideXlab platform.
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highly emissive divalent ion doped colloidal cspb1 xmxbr3 perovskite nanocrystals through Cation Exchange
Journal of the American Chemical Society, 2017Co-Authors: Ward Van Der Stam, Jaco J Geuchies, Thomas Altantzis, Karel H W Van Den Bos, Johannes D Meeldijk, Sandra Van Aert, Sara Bals, Daniel Vanmaekelbergh, Celso De Mello DonegaAbstract:Colloidal CsPbX3 (X = Br, Cl, and I) perovskite nanocrystals (NCs) have emerged as promising phosphors and solar cell materials due to their remarkable optoelectronic properties. These properties can be tailored by not only controlling the size and shape of the NCs but also postsynthetic composition tuning through topotactic anion Exchange. In contrast, property control by Cation Exchange is still underdeveloped for colloidal CsPbX3 NCs. Here, we present a method that allows partial Cation Exchange in colloidal CsPbBr3 NCs, whereby Pb2+ is Exchanged for several isovalent Cations, resulting in doped CsPb1–xMxBr3 NCs (M= Sn2+, Cd2+, and Zn2+; 0 50%), sh...
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luminescent cuins2 quantum dots by partial Cation Exchange in cu2 xs nanocrystals
ChemInform, 2015Co-Authors: Ward Van Der Stam, Johannes D Meeldijk, Sara Bals, Anne C Berends, Freddy T Rabouw, Tom Willhammar, Celso De Mello DonegaAbstract:Luminescent CuInS2 nanocrystals are prepared by partial Cation Exchange in Cu2-xS nanocrystals (NCs) suspended in toluene using a MeOH solution of In(NO3)3 in the molar ratio of In/Cu of ≈1.
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luminescent cuins2 quantum dots by partial Cation Exchange in cu2 xs nanocrystals
Chemistry of Materials, 2015Co-Authors: Ward Van Der Stam, Johannes D Meeldijk, Sara Bals, Anne C Berends, Freddy T Rabouw, Tom Willhammar, Celso De Mello DonegaAbstract:Here, we show successful partial Cation Exchange reactions in Cu2–xS nanocrystals (NCs) yielding luminescent CuInS2 (CIS) NCs. Our approach of mild reaction conditions ensures slow Cu extraction rates, which results in a balance with the slow In incorporation rate. With this method, we obtain CIS NCs with photoluminescence (PL) far in the near-infrared (NIR), which cannot be directly synthesized by currently available synthesis protocols. We discuss the factors that favor partial, self-limited Cation Exchange from Cu2–xS to CIS NCs, rather than complete Cation Exchange to In2S3. The product CIS NCs have the wurtzite crystal structure, which is understood in terms of conservation of the hexagonal close packing of the anionic sublattice of the parent NCs into the product NCs. These results are an important step toward the design of CIS NCs with sizes and shapes that are not attainable by direct synthesis protocols and may thus impact a number of potential appliCations.
Kazuhiko Tanaka - One of the best experts on this subject based on the ideXlab platform.
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high speed simultaneous ion exclusion Cation Exchange chromatography of anions and Cations on a weakly acidic Cation Exchange resin column
Journal of Chromatography A, 2003Co-Authors: Masanobu Mori, Kazuhiko Tanaka, Murad I H Helaleh, Qun Xu, Mikaru Ikedo, Yutaka Ogura, Shinji Sato, Wenzhi Hu, Kiyoshi Hasebe, Paul R HaddadAbstract:The simultaneous ion-exclusion/Cation-Exchange separation column packed with a polymethacrylate-based weakly acidic Cation-Exchange resin of 3 μm particle size was used to achieve the simultaneous high-speed separation of anions and Cations (Cl−, NO3−, SO42−, Na+, K+, NH4+, Ca2+ and Mg2+) commonly found in environmental samples. The high-speed simultaneous separation is based on a combination of the ion-exclusion mechanism for the anions and the Cation-Exchange mechanism for Cations. The complete separation of the anions and Cations was achieved in 5 min by elution with 15 mM tartaric acid–2.5 mM 18-crown-6 at a flow-rate of 1.5 ml/min. Detection limits at S/N=3 ranged from 0.36 to 0.68 μM for anions and 0.63–0.99 μM for Cations. This method has been applied to the simultaneous determination of anions and Cations in several environmental waters with satisfactory results.
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simultaneous determination of anions and Cations by ion exclusion chromatography Cation Exchange chromatography with tartaric acid 18 crown 6 as eluent
Journal of Chromatography A, 1999Co-Authors: Semog Kwon, Kazuhiko Tanaka, Kwangpill Lee, Kazutoku OhtaAbstract:Ion-exclusion chromatography–Cation-Exchange chromatography was developed for the simultaneous separation of common inorganic anions and Cations (Cl−, NO3− and SO42−; Na+, NH4+, K+, Mg2+ and Ca2+) on a weakly acidic Cation-Exchange column by elution with weak acid. Generally, the resolution among these monovalent Cations was only moderate, thereby hindering the determination of these analytes in natural-water samples. Therefore, 18-crown-6 was added to the eluent to improve the resolution. A good separation of these anions and Cations on a weakly acidic Cation-Exchange column was achieved in 30 min by elution with 5 mM tartaric acid/6 mM 18-crown-6/methanol–water (7.5:92.5). The ion-exclusion chromatography–Cation-Exchange chromatography method developed here was successfully applied to the separation of major anions and Cations in an environmental water sample.
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simultaneous ion exclusion chromatography Cation Exchange chromatography with conductimetric detection of anions and Cations in acid rain waters
Journal of Chromatography A, 1994Co-Authors: Kazuhiko Tanaka, Kazutoku Ohta, James S Fritz, Susumu Matsushita, Akiyoshi MiyanagaAbstract:Abstract A simple, selective and sensitive method was investigated for simultaneously determining anions (Cl−, NO3−, SO42−) and Cations (Na+, NH4+, K+, Mg2+, Ca2+) in acid rain and related environmental waters in central Japan. The method involves simultaneous ion-exclusion-Cation-Exchange chromatography with conductimetric detection on a polyacrylate weakly acidic Cation-Exchange resin column with a weak-acid eluent. With the weak-acid eluent (tartaric acid) both anions and Cations were separated simultaneously, based on ion-exclusion and Cation-Exchange mechanism. Owing to the presence of H+ ions in the tartaric acid eluent, the detector response was positive for the anions and negative for the Cations. Using a 5 mM tartaric acid-7.5% methanol-water eluent, good simultaneous separation and detection were achieved in about 30 min. The results indicated an ionic balance of about 100% between the anions (including HCO3−) and the Cations (including H+).
Kazutoku Ohta - One of the best experts on this subject based on the ideXlab platform.
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simultaneous determination of anions and Cations by ion exclusion chromatography Cation Exchange chromatography with tartaric acid 18 crown 6 as eluent
Journal of Chromatography A, 1999Co-Authors: Semog Kwon, Kazuhiko Tanaka, Kwangpill Lee, Kazutoku OhtaAbstract:Ion-exclusion chromatography–Cation-Exchange chromatography was developed for the simultaneous separation of common inorganic anions and Cations (Cl−, NO3− and SO42−; Na+, NH4+, K+, Mg2+ and Ca2+) on a weakly acidic Cation-Exchange column by elution with weak acid. Generally, the resolution among these monovalent Cations was only moderate, thereby hindering the determination of these analytes in natural-water samples. Therefore, 18-crown-6 was added to the eluent to improve the resolution. A good separation of these anions and Cations on a weakly acidic Cation-Exchange column was achieved in 30 min by elution with 5 mM tartaric acid/6 mM 18-crown-6/methanol–water (7.5:92.5). The ion-exclusion chromatography–Cation-Exchange chromatography method developed here was successfully applied to the separation of major anions and Cations in an environmental water sample.
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simultaneous ion exclusion chromatography Cation Exchange chromatography with conductimetric detection of anions and Cations in acid rain waters
Journal of Chromatography A, 1994Co-Authors: Kazuhiko Tanaka, Kazutoku Ohta, James S Fritz, Susumu Matsushita, Akiyoshi MiyanagaAbstract:Abstract A simple, selective and sensitive method was investigated for simultaneously determining anions (Cl−, NO3−, SO42−) and Cations (Na+, NH4+, K+, Mg2+, Ca2+) in acid rain and related environmental waters in central Japan. The method involves simultaneous ion-exclusion-Cation-Exchange chromatography with conductimetric detection on a polyacrylate weakly acidic Cation-Exchange resin column with a weak-acid eluent. With the weak-acid eluent (tartaric acid) both anions and Cations were separated simultaneously, based on ion-exclusion and Cation-Exchange mechanism. Owing to the presence of H+ ions in the tartaric acid eluent, the detector response was positive for the anions and negative for the Cations. Using a 5 mM tartaric acid-7.5% methanol-water eluent, good simultaneous separation and detection were achieved in about 30 min. The results indicated an ionic balance of about 100% between the anions (including HCO3−) and the Cations (including H+).
Sara Bals - One of the best experts on this subject based on the ideXlab platform.
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highly emissive divalent ion doped colloidal cspb1 xmxbr3 perovskite nanocrystals through Cation Exchange
Journal of the American Chemical Society, 2017Co-Authors: Ward Van Der Stam, Jaco J Geuchies, Thomas Altantzis, Karel H W Van Den Bos, Johannes D Meeldijk, Sandra Van Aert, Sara Bals, Daniel Vanmaekelbergh, Celso De Mello DonegaAbstract:Colloidal CsPbX3 (X = Br, Cl, and I) perovskite nanocrystals (NCs) have emerged as promising phosphors and solar cell materials due to their remarkable optoelectronic properties. These properties can be tailored by not only controlling the size and shape of the NCs but also postsynthetic composition tuning through topotactic anion Exchange. In contrast, property control by Cation Exchange is still underdeveloped for colloidal CsPbX3 NCs. Here, we present a method that allows partial Cation Exchange in colloidal CsPbBr3 NCs, whereby Pb2+ is Exchanged for several isovalent Cations, resulting in doped CsPb1–xMxBr3 NCs (M= Sn2+, Cd2+, and Zn2+; 0 50%), sh...
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luminescent cuins2 quantum dots by partial Cation Exchange in cu2 xs nanocrystals
ChemInform, 2015Co-Authors: Ward Van Der Stam, Johannes D Meeldijk, Sara Bals, Anne C Berends, Freddy T Rabouw, Tom Willhammar, Celso De Mello DonegaAbstract:Luminescent CuInS2 nanocrystals are prepared by partial Cation Exchange in Cu2-xS nanocrystals (NCs) suspended in toluene using a MeOH solution of In(NO3)3 in the molar ratio of In/Cu of ≈1.
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luminescent cuins2 quantum dots by partial Cation Exchange in cu2 xs nanocrystals
Chemistry of Materials, 2015Co-Authors: Ward Van Der Stam, Johannes D Meeldijk, Sara Bals, Anne C Berends, Freddy T Rabouw, Tom Willhammar, Celso De Mello DonegaAbstract:Here, we show successful partial Cation Exchange reactions in Cu2–xS nanocrystals (NCs) yielding luminescent CuInS2 (CIS) NCs. Our approach of mild reaction conditions ensures slow Cu extraction rates, which results in a balance with the slow In incorporation rate. With this method, we obtain CIS NCs with photoluminescence (PL) far in the near-infrared (NIR), which cannot be directly synthesized by currently available synthesis protocols. We discuss the factors that favor partial, self-limited Cation Exchange from Cu2–xS to CIS NCs, rather than complete Cation Exchange to In2S3. The product CIS NCs have the wurtzite crystal structure, which is understood in terms of conservation of the hexagonal close packing of the anionic sublattice of the parent NCs into the product NCs. These results are an important step toward the design of CIS NCs with sizes and shapes that are not attainable by direct synthesis protocols and may thus impact a number of potential appliCations.
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anisotropic Cation Exchange in pbse cdse core shell nanocrystals of different geometry
Chemistry of Materials, 2012Co-Authors: Marianna Casavola, Sara Bals, Marijn A Van Huis, Karel Lambert, Zeger Hens, Daniel VanmaekelberghAbstract:We present a study of Cd2+-for-Pb2+ Exchange in PbSe nanocrystals (NCs) with cube, star, and rod shapes. Prolonged temperature-activated Cation Exchange results in PbSe/CdSe heterostructured nanocrystals (HNCs) that preserve their specific overall shape, whereas the PbSe core is strongly faceted with dominance of {111} facets. Hence, Cation Exchange proceeds while the Se anion lattice is preserved, and well-defined {111}/{111} PbSe/CdSe interfaces develop. Interestingly, by quenching the reaction at different stages of the Cation Exchange new structures have been isolated, such as core–shell nanorods, CdSe rods that contain one or two separated PbSe dots and fully zinc blende CdSe nanorods. The crystallographically anisotropic Cation Exchange has been characterized by a combined HRTEM/HAADF-STEM study of heterointerface evolution over reaction time and temperature. Strikingly, Pb and Cd are only intermixed at the PbSe/CdSe interface. We propose a plausible model for the Cation Exchange based on a layer-by...