Cobalt–poly(amido amine) superparamagnetic nanocomposites

Atwater, James E.; Akse, James R.; Holtsnider, John T.

doi:10.1016/j.matlet.2008.02.004

Cited by 8 publications

(5 citation statements)

References 19 publications

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“…Quasi-alloy PdAu G 6 -PAMAM DENs rearrange upon oxidation in air to yield core−shell configurations. , Polymer-cored DAB−dendrimer-shelled NPs in 15−20-nm size range could trap more than 900 Cu 2+ ions per NP-DAB16, and external amine groups could be covalently linked to up to 1000−1500 azobenzene chromophores per NP through aza-Michael addition in aqueous suspension . CoNPs were stabilized by G 5 -PAMAM−NH 2 dendrimers (approximately 38 Co atoms per dendrimer), and investigation of the magnetic properties indicated superpamagnetism with a blocking temperature of 50 K …”

Section: Supramolecular Propertiesmentioning

confidence: 99%

“…677,678 Polymer-cored DABdendrimer-shelled NPs in 15-20-nm size range could trap more than 900 Cu 2+ ions per NP-DAB16, and external amine groups could be covalently linked to up to 1000-1500 azobenzene chromophores per NP through aza-Michael addition in aqueous suspension. 679 CoNPs were stabilized by G 5 -PAMAM-NH 2 dendrimers (approximately 38 Co atoms per dendrimer), and investigation of the magnetic properties indicated superpamagnetism with a blocking temperature of 50 K. 680 Similarly, various dendrimers have been used for the stabilization of other NPs, in particular CdS and CdSe, the best characterized semiconductors that are of great interest for the fabrication of nanoelectronic devices. [681][682][683][684][685] Finally, dendrimers, such as PPI dendrimers modified with long alkyl chains, can serve as templates to direct the formation of biominerals such as calcium carbonate, the main constituent of mollusk shells.…”

Section: Dendrimer Encapsulation And/or Stabilization Of Metal Nanopa...mentioning

confidence: 99%

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Dendrimers Designed for Functions: From Physical, Photophysical, and Supramolecular Properties to Applications in Sensing, Catalysis, Molecular Electronics, Photonics, and Nanomedicine

2010

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Section: Supramolecular Propertiesmentioning

confidence: 99%

Section: Dendrimer Encapsulation And/or Stabilization Of Metal Nanopa...mentioning

confidence: 99%

Dendrimers Designed for Functions: From Physical, Photophysical, and Supramolecular Properties to Applications in Sensing, Catalysis, Molecular Electronics, Photonics, and Nanomedicine

2010

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“…The morphology and size of the nanoparticles did not change much even after five cycles, and the reaction was extended to 4-ethynyl-benzaldehyde, 2ethynyl-pyridine, and 1-azidomethyl-4-bromo-benzene, with 100% selectivity and good to excellent yields. 61 ■ DENDRITIC MAGNETICALLY RECYCLABLE CATALYSTS PAMAM dendrimers have been used as templates to encapsulate magnetic zerovalent transition-metal NPs such as Co 62,63 and Ni, 64 but these nanoparticles were not used as magnetic catalysts. After a seminal paper on selective hydroformylation reactions by Alper's group, 65 the area of magnetically recoverable dendritic catalysts has only appeared recently.…”

Section: Catalystsmentioning

confidence: 99%

“…PAMAM dendrimers have been used as templates to encapsulate magnetic zerovalent transition-metal NPs such as Co , and Ni, but these nanoparticles were not used as magnetic catalysts. After a seminal paper on selective hydroformylation reactions by Alper’s group, the area of magnetically recoverable dendritic catalysts has only appeared recently. ,,− Our group has used SPION-cored dendritically encapsulated Pd NPs to efficiently catalyze a variety of reactions and shown that dendritic magnetic NPs are superior to nondendritic magnetic NPs in terms of catalyst loading, catalytic efficiency and catalyst recovery. − …”

Section: Dendritic Magnetically Recyclable Catalystsmentioning

confidence: 99%

Magnetic and Dendritic Catalysts

et al. 2015

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The recovery and reuse of catalysts is a major challenge in the development of sustainable chemical processes. Two methods at the frontier between homogeneous and heterogeneous catalysis have recently emerged for addressing this problem: loading the catalyst onto a dendrimer or onto a magnetic nanoparticle. In this Account, we describe representative examples of these two methods, primarily from our research group, and compare them. We then describe new chemistry that combines the benefits of these two methods of catalysis. Classic dendritic catalysis has involved either attaching the catalyst covalently at the branch termini or within the dendrimer core. We have used chelating pyridyltriazole ligands to insolubilize catalysts at the termini of dendrimers, providing an efficient, recyclable heterogeneous catalysts. With the addition of dendritic unimolecular micelles olefin metathesis reactions catalyzed by commercial Grubbs-type ruthenium-benzylidene complexes in water required unusually low amounts of catalyst. When such dendritic micelles include intradendritic ligands, both the micellar effect and ligand acceleration promote faster catalysis in water. With these types of catalysts, we could carry out azide alkyne cycloaddition ("click") chemistry with only ppm amounts of CuSO4·5H2O and sodium ascorbate under ambient conditions. Alternatively we can attach catalysts to the surface of superparamagnetic iron oxide nanoparticles (SPIONs), essentially magnetite (Fe3O4) or maghemite (γ-Fe2O3), offering the opportunity to recover the catalysts using magnets. Taking advantage of the merits of both of these strategies, we and others have developed a new generation of recyclable catalysts: dendritic magnetically recoverable catalysts. In particular, some of our catalysts with a γ-Fe2O3@SiO2 core and 1,2,3-triazole tethers and loaded with Pd nanoparticles generate strong positive dendritic effects with respect to ligand loading, catalyst loading, catalytic activity and recyclability. In other words, the dendritic catalysts were more efficient and more stable than their nondendritic γ-Fe2O3@SiO2 analogues. The bulk at the dendritic periphery helps to localize the metal nanoparticles at the SPION core surface, which confers these advantages. We could also use sonification as a remarkably simple and efficient method to impregnate the SPIONs with dendrimer-encapsulated PdNPs. Catalysis within the hydrophobic dendrimer pockets that include ligands leads to rapid turnover with or without a γ-Fe2O3@SiO2 core. In addition, catalytically active metal nanoparticles are more robust when they are loaded onto the surface of a γ-Fe2O3@SiO2 dendritic core. Herein, we illustrate this chemistry with examples including olefin metathesis, click chemistry, cross carbon-carbon bond forming reactions, and selective alcohol oxidation.

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“…[3][4][5] In addition, dendrimer can be used as a precise nanoreactor for the synthesis of various nanoparticles such as metals 6 7 semiconductors [8][9][10][11][12] and magnetic oxides. 13 14 Depending on the dendrimer architecture, terminal groups, the loading factor of the metal ions and also ion-ion interaction, nanoparticles (NPs) can grow inside a dendrimer (Internal), outside a dendrimer (External) or in both modes (mixed type). [15][16][17] Dendrimer nanocomposites (DNC) display fascinating physical and chemical properties which are useful in catalysis, sensing, nanoelectronics and cancer treatment.…”

Section: Introductionmentioning

confidence: 99%

Surface Charge Tunability and Size Dependent Luminescence Anisotropy of Aqueous Synthesized ZnS/Dendrimer Nanocomposites

Ghosh¹,

Priyam²,

Saha³

2009

J. Nanosci. Nanotech.

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Highly water-soluble, biocompatible, fluorescent, ZnS/Dendrimer nanocomposites have been synthesized, for the first time, with amino-, carboxyl- or hydroxyl-terminated Polyamidoamine dendrimer. Average size of ZnS nanoparticles within the dendrimer matrix was found to be in the range of 2.2-3.1 nm. ZnS nanoparticles with high monodispersity and photoluminescence efficiency was obtained by tuning various experimental parameters. An eight-fold increase in super-saturation of initial reactants caused a sharp focusing of size distribution by 38% and photoluminescence quantum efficiency also increased from 1.3% to 4.2%. ZnS/Dendrimer nanocomposites display constant positive polarized emission with the anisotropy value of 0.2, which makes it a promising candidate for biophysical probe. The anisotropy value was found to increase with increasing particle size of ZnS nanoparticles and also to depend on nature of surface end groups of the dendrimer molecule. Surface charge being an important biological parameter was tuned by varying pH of the reaction medium. Further, it is demonstrated that photoluminescence and surface charge of these nanocomposites are governed by the surface functionality of the dendrimer molecule.

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Cobalt–poly(amido amine) superparamagnetic nanocomposites

Cited by 8 publications

References 19 publications

Dendrimers Designed for Functions: From Physical, Photophysical, and Supramolecular Properties to Applications in Sensing, Catalysis, Molecular Electronics, Photonics, and Nanomedicine

Dendrimers Designed for Functions: From Physical, Photophysical, and Supramolecular Properties to Applications in Sensing, Catalysis, Molecular Electronics, Photonics, and Nanomedicine

Magnetic and Dendritic Catalysts

Surface Charge Tunability and Size Dependent Luminescence Anisotropy of Aqueous Synthesized ZnS/Dendrimer Nanocomposites

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