4 research outputs found

    Isolation of Template Effects That Control the Structure and Function of Nonspherical, Biotemplated Pd Nanomaterials

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    Advances in nanotechnology have indicated that the passivant and the inorganic surface play a pivotal role in controlling the structure/function relationship of materials. Beyond standard materials-based methods, bioligands have recently demonstrated the production of unique nanomaterial morphologies for application under ambient conditions for multiple activities, such as catalysis and biosensing. We have recently demonstrated that a biotemplate technique could be employed to produce spherical and linear Pd nanostructures in water using a self-assembling peptide framework. The materials possessed high catalytic reactivity that was controlled by the three-dimensional structure of the composite materials. To investigate the effect of the peptide template on the reactivity of Pd nanostructures, an in depth analysis of the catalytic activity of Pd nanostructures fabricated via truncated templates is presented. The new templates were designed from portions of the original framework, which demonstrated unique synthetic and functionality control. Two different reactions, Stille C–C coupling and 4-nitrophenol reduction, were employed to ascertain the effect of template structure on the reactivity of synthesized Pd nanomaterials via changes in reagent diffusion through the bioscaffold. The results indicate that the peptide framework plays an important role and could be used to tune and optimize the functionality of the final composite materials for the target application

    Peptide-Modified Dendrimers as Templates for the Production of Highly Reactive Catalytic Nanomaterials

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    Peptide-driven nanomaterials synthesis and assembly has become a significant research thrust due to the capability to generate a range of multifunctional materials with high spatial precision and tunable properties. Despite the extensive amount of available literature, the majority of studies report the use of free peptides to drive synthesis and assembly. Such strategies are not an entirely accurate representation of nature, as many materials binding peptides found in biological systems are sterically constrained to a larger biological motif. Herein we report the synthesis of catalytic Pd nanomaterials using constrained peptides covalently attached to the surface of small, water-soluble dendrimers. Using the R5 peptide conjugated to polyamidoamine dendrimer as a bioconjugate, Pd nanomaterials were generated that displayed altered morphologies compared to nanomaterials templated with free R5. It was discovered that the peptide surface density on the dendrimer affected the resulting nanoscale morphology. Furthermore, the catalytic activities of Pd materials templated with R5/dendrimer are higher as compared to the R5-templated Pd materials for the hydrogenation of allyl alcohol, with an average increase in turnover frequency of ∼1500 mol product (mol Pd × h)<sup>−1</sup>. Small angle X-ray scattering analysis and dynamic light scattering indicate that Pd derived from R5/dendrimer templates remained less aggregated in solution and displayed more available reactive Pd surface area. Such morphological changes in solution are attributed to the constrained peptide binding motifs, which altered the Pd morphology and subsequent properties. Moreover, the results of this study suggest that constrained materials binding peptide systems can be employed as a means to alter morphology and improve resulting properties

    Synthesis and Characterization of Thermoresponsive Hydrogels Based on <i>N</i>‑Isopropylacrylamide Crosslinked with 4,4′-Dihydroxybiphenyl Diacrylate

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    A novel crosslinker [4,4′-dihydroxybiphenyl diacrylate (44BDA)] was developed, and a series of temperature-responsive hydrogels were synthesized through free radical polymerization of <i>N</i>-isopropylacrylamide (NIPAAm) with 44BDA. The temperature-responsive behavior of the resulting gels was characterized by swelling studies, and the lower critical solution temperature (LCST) of the hydrogels was characterized through differential scanning calorimetry. Increased content of 44BDA led to a decreased swelling ratio and shifted the LCST to lower temperatures. These novel hydrogels also displayed resiliency through multiple swelling–deswelling cycles, and their temperature responsiveness was reversible. The successful synthesis of NIPAAm-based hydrogels crosslinked with 44BDA has led to a new class of temperature-responsive hydrogel systems with a variety of potential applications

    Electrochemical Activity of Dendrimer-Stabilized Tin Nanoparticles for Lithium Alloying Reactions

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    The synthesis and characterization of Sn nanoparticles in organic solvents using sixth-generation dendrimers modified on their periphery with hydrophobic groups as stabilizers are reported. Sn<sup>2+</sup>:dendrimer ratios of 147 and 225 were employed for the synthesis, corresponding to formation of Sn<sub>147</sub> and Sn<sub>225</sub> dendrimer-stabilized nanoparticles (DSNs). Transmission electron microscopy analysis indicated the presence of ultrasmall Sn nanoparticles having an average size of 3.0–5.0 nm. X-ray absorption spectroscopy suggested the presence of Sn nanoparticles with only partially oxidized surfaces. Cyclic voltammetry studies of the Sn DSNs for Li alloying/dealloying reactions demonstrated good reversibility. Control experiments carried out in the absence of DSNs clearly indicated that these ultrasmall Sn DSNs react directly with Li to form SnLi alloys
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