An effective strategy to enhance the performance of inorganic semiconductors is moving towards organic-inorganic hybrid materials. Here, we report the design of core–shell hybrid materials based on a TiO2 core functionalized with a polyampholytic (poly(dehydroalanine)-graft-(n-propyl phosphonic acid acrylamide) shell (PDha-g-PAA@TiO2). The PDha-g-PAA shell facilitates the efficient immobilization of the photosensitizer Eosin Y (EY) and enables electronic interactions between EY and the TiO2 core. This resulted in high visible-light-driven H2 generation. The enhanced light-driven catalytic activity is attributed to the unique core–shell design with the graft copolymer acting as bridge and facilitating electron and proton transfer, thereby also preventing the degradation of EY. Further catalytic enhancement of PDha-g-PAA@TiO2 was possible by introducing [Mo3S13]2− cluster anions as hydrogen-evolution cocatalyst. This novel design approach is an example for a multi-component system in which reactivity can in future be independently tuned by selection of the desired molecular or polymeric species. 相似文献
Acrylamide was grafted onto starch using ceric(IV) ion as initiator. Starch–graft-polyacrylamide was then modified through Mannich reaction using formaldehyde and diethylamine to give poly(N, N′-[(diethylamino) methyl]-acrylamide). The modified-graft copolymer was quaternized using different reagents; methyl iodide, n-butylbromide, sodium chloroacetate and propane sultone to give cationic and ampholytic graft materials. The absorbing properties of the produced materials toward deionized water and aqueous salt solutions were investigated. Studies of the absorbing properties of polyampholytes have revealed that these materials do not shrink upon increasing salt concentration. Kinetics of swelling in deionized water is also discussed. 相似文献
Purely ionic interactions in natural and synthetic macromolecules involve the mutual interaction of fixed charges and their interaction with mobile ions. Such charge‐dependent interactions lead to well‐documented effects, including chain expansion of polyelectrolytes, globularization of polyampholytes, distributions of mobile ions according to charge screening, or ion condensation models. A variety of structural features, functions, and applications of these systems is amplified by the superimposition of charge‐independent effects associated with the occurrence of less polar or hydrophobic groups, special salts, surfactants, or complementary protein assemblies. For instance, ionic and hydrophobic attractive interactions stabilize pearls (or rings)‐on‐a‐string conformations, possibly a model for the formation of the chromatin assembly. The attractive interactions due to hydrophobic fatty acid groups attached to polysaccharides promote the formation of vesicles that entrap and slowly release water‐soluble drugs. Intra‐ and intermolecular associations based on ion‐pairing mixed interactions also control the formation of host–guest compounds, protein conformation, and the assembly of layered polyelectrolytes. Metallo‐supramolecular polymers and networks are formed due to the coordination of multivalent cations with bi‐ and trifunctional organic ligands. The association of lithium salts to polymers in the absence of water allows the formation of highly efficient energy sources. It also allows the identification of the ionic species that control charge‐independent contributions to Hofmeister effects. This critical review presents a synthetic classification of systems displaying ionic mixed interactions, and a discussion of underlying molecular mechanisms. 相似文献
This paper reports a novel amphoteric aliphatic polycarbonate bearing both amine and carboxyl groups. In the absence of protection‐deprotection chemistry, the multi‐functionalized copolymer is synthesized by one‐step enzymatic copolymerization. The influences of the reaction conditions including monomer feed ratio and polymerization time are explored. The simultaneous incorporation of amine and carboxyl functionalities provides the copolymer with a pH‐tunable self‐aggregation feature, leading to various aggregation states including precipitated agglomerate, well‐dispersed positively or negatively charged nanoparticles in a controlled manner. The copolymer displays minimal cytotoxicity to 293T and HeLa cells.
A novel amphoteric poly(amino acid) is synthesized by grafting a cationic amino acid (L ‐Arg) to γ‐PGA to prepare charged NPs. γ‐PGA‐Arg NPs can be prepared by the self‐complexation of a single polymer by intra‐/inter‐molecular electrostatic interactions when the polymer is dispersed in water. The size and surface charge of the NPs can be regulated by the grafting degree of Arg (41, 56, and 83%). The smallest NPs are obtained at 56% grafting degree of the γ‐PGA‐Arg copolymer. The 56 and 83% grafting degree NPs are stable for at least 1 week. Depending on their surface charge, these NPs can selectively adsorb anionically or cationically charged proteins.
This paper is focused on the temperature-dependent synthesis of gold nanotriangles in a vesicular template phase, containing phosphatidylcholine and AOT, by adding the strongly alternating polyampholyte PalPhBisCarb.UV-vis absorption spectra in combination with TEM micrographs show that flat gold nanoplatelets are formed predominantly in the presence of the polyampholyte at 45°C. The formation of triangular and hexagonal nanoplatelets can be directly influenced by the kinetic approach, i.e., by varying the polyampholyte dosage rate at 45°C. Corresponding zeta potential measurements indicate that a temperature-dependent adsorption of the polyampholyte on the {111} faces will induce the symmetry breaking effect, which is responsible for the kinetically controlled hindered vertical and preferred lateral growth of the nanoplatelets. 相似文献