University of Akron

About: University of Akron is a education organization based out in Akron, Ohio, United States. It is known for research contribution in the topics: Polymer & Polymerization. The organization has 17401 authors who have published 29127 publications receiving 702386 citations. The organization is also known as: The University of Akron.

Alginate/graphene double-network nanocomposite hydrogel beads with low-swelling, enhanced mechanical properties, and enhanced adsorption capacity

Abstract: As a novel material, double network hydrogels have attracted great attention in recent years for their excellent mechanical properties; however, several other characteristics are yet to be improved. Here we report the synthesis of a novel alginate/reduced graphene oxide (RGO) double-network (GAD) hydrogel through a facile method, and investigate the GAD's mechanical properties, stability, and adsorption capacity in comparison with those of an alginate/RGO single network hydrogel (GAS). To produce the GAD, the first network of alginate is formed with randomly distributed graphene oxide (GO), resulting in the GAS; then the GAS is treated by a hydrothermal reduction, through which the GO is reduced and self-assembles into a second RGO network interpenetrating with the first, alginate network, forming the double-network GAD. The mechanism of the GAD formation is investigated and the property differences between the GAS and the GAD are examined. The resulting GAD exhibits a higher Young's modulus than the GAS, and the modulus increases with GO concentrations. The GAD also has a lower swelling ratio than the GAS, which leads to improved gel stability in highly concentrated alkali/salt solutions. The GAD beads exhibit an excellent adsorption capacity (Cu2+, 169.5 mg g−1 and Cr2O72−, 72.5 mg g−1) for heavy metal ions, far better than that of the GAS. Even after 10 regeneration cycles, both GAS and GAD can still retain their considerable adsorption capacity for metals. The results of this work are of great significance to double network gel research, especially for environmental applications. With good stability, adsorption capacity, and regeneration ability, the double network gel could be a promising adsorbent nanomaterial for pollutant removal from aqueous solutions.

Adsorption mechanism of single amino acid and surfactant molecules to Au {111} surfaces in aqueous solution: design rules for metal-binding molecules

Abstract: The adsorption mechanism of twenty amino acids and four surfactants was examined on a {111} surface of gold in dilute aqueous solution using molecular dynamics simulation with a broadly applicable intermolecular potential CHARMM–METAL. All molecules are attracted to the surface between −3 and −26 kcal mol−1. The adsorption strength correlates with the degree of coordination of polarizable atoms (O, N, C) to multiple epitaxial sites. Therefore, the molecular size and geometry rather than the specific chemistry determine the adsorption energy. Large molecules with planar sp2 hybridized groups (Arg, Trp, Gln, Tyr, Asn, and PPh3) adsorb most strongly, followed by molecules with polar sp3 hybridized groups, and short molecules with sp3 hybridized alkyl groups exhibit least attraction. Conformationally flexible, extended molecules such as hexadecyltrimethylammonium bromide (CTAB) also showed significant attraction to the metal surface related to accommodation in epitaxial grooves and coordination with numerous epitaxial sites. Computational results are consistent with combinatorial binding experiments, observations in the growth and stabilization of metal nanoparticles, and ab initio data. The mechanism of adsorption conforms to soft epitaxy observed for peptides on metal surfaces (H. Heinz et al., J. Am. Chem. Soc., 2009, 131, 9704) and enables the de novo design of molecules for binding to a given metal surface. In addition to soft epitaxy, contributions to adsorption are possible by covalent bonding and induced charges.