Tunable Photocatalytic Activity of PEO‐Stabilized ZnO–Polyoxometalate Nanostructures in Aqueous Solution

Abstract

photocatalysis is of great potential for targeted applications.Due to their unique chemical, electrical, magnetic, mechanical, and optical properties and their catalytic activity, zinc oxide (ZnO) and especially ZnO nanoparticles have received considerable attention in both application fields, solar energy conversion, and catalysis. ZnO is an n-type semiconductor with a wide energy band (3.37 eV) and a high bond energy (60 meV). [1,2] It offers a wide range of properties depending on morphology, size, orientation, and density of the crystals. [3] A good electron mobility, a large volume to surface area ratio, a high UV absorption, and a long life-span are advantageous when used as a photocatalyst in UV-light. [4] The catalytic activity in different model reactions has been examined in dependence on morphology, size and shape, and pH. [3,[5][6][7] As the ZnO properties depend on the structure, numerous nanoparticle synthesis routes have been developed to create different shapes of ZnO structures such as 1D, 2D, and 3D structures including nanorods, nanoneedles, and nanoflowers. [8][9][10][11] A powerful technique to control the morphology is the use of surface-modifying substances, in particular macromole cules. [1] A number of studies have investigated various polymers such as polymethacrylic acid, polyethylene oxide (PEO) and PEO containing copolymers. [11][12][13][14][15] The application of polyethylene oxide-block-polymethacrylic acid (PEO-b-PMAA) copolymers as surface modifiers for ZnO has been thoroughly examined. [16] The photocatalytic activity and selectivity of novel binary and ternary composite nanostructures from polyethylene oxide-stabilized zinc oxide (PEO-ZnO) with and without polyoxometalate (H 4 [Si(W 3 O 10 ) 4 ], POM) are determined in aqueous solution under UV-light. Mono-and di-COOH-end-functionalized PEO polymers are used as surface modifiers, influencing the morphology and stability of the ZnO nanoparticles being synthesized in water. POM acts as an additional versatile photocatalytically active building block resulting in a ternary hybrid structure with tunable photocatalytic activity. Catalytic selectivity is demonstrated by studying photocatalytic dye degradations as model reactions, where the chemical backbone of the dyes and their charge turn out to be the basis for the selectivity. All samples are characterized with dynamic light scattering, transmission electron microscopy, scanning electron microscopy, light microscopy, and ζ-potential measurements. With the functionalized PEOs, large ZnO clusters consisting of leaves are formed while 2-[2-(2-methoxyethoxy) ethoxy] acetic acid (TODA) yields ZnO flower-like structures.

Polyelectrolyte-Microgel-Templated Nickel–Nickel Oxide Nanoparticles for Oxidation Catalysis with o-Phenylenediamine as a Model Substrate

“…The Ni 0 /NiO particles exhibit a diameter of d Ni 0 /NiO = 28 ± 8 nm for the PSS-Ni 0 /NiO l =0.75 sample, d Ni 0 /NiO = 34 ± 12 nm for the PSS-Ni 0 /NiO l =0.9 sample, and d Ni 0 /NiO = 77 ± 15 nm for the PSS-Ni 0 /NiO l =1.0 sample. This proves the successful electrostatic templating effect of the PSS microgel, similar to other electrostatically templated systems. , Increasing Ni 0 /NiO particle sizes were obtained for higher loading ratios, being related to the higher amount of Ni and additionally fewer free charges, reducing the particle stabilization and leading to agglomeration and larger particles.…”

“…This proves the successful electrostatic templating effect of the PSS microgel, similar to other electrostatically templated systems. 5,18 Increasing Ni 0 /NiO particle sizes were obtained for higher loading ratios, being related to the higher amount of Ni and additionally fewer free charges, reducing the particle stabilization and leading to agglomeration and larger particles.…”

“…Although a variety of catalytic nanoparticles are known, the potential of many materials has not yet been exploited. Additionally, multicomponent combinations are possible by fusing organic–inorganic components into hybrid systems, e.g., catalytically active palladium/iron oxide particles entrapped in poly­(aminoethylacrylamide) or polymer-stabilized gold nanoparticles in zinc oxide. − …”

Temperature- and pH-Responsive Hydrogel Nanoparticles with Embedded Au Nanoparticles as Catalysts for the Reduction of Dyes

“…Catalytic reduction, on the other hand, is a reasonably quick process. A range of metal nanoparticles (NPs) and nanocomposite materials has been widely used as catalysts in the reduction of dye molecules. − …”

Efficient dye degradation and THz spectra of {PMo12} based rare earth phosphine oxide complexes

“…POMbased organic-inorganic hybrid materials can also be used as oxidation reaction catalysts, [15][16][17] co-catalysts, 18 condensation reaction catalysts, 19 and photodegradation catalysts for dye molecules. [20][21][22] In the field of catalysis, because this kind of hybrid material has high degradation efficiency to dye molecules, and the cost is relatively low, it has aroused the interest of scientific researchers. 23 In recent years, research on rare earth complexes containing PO groups has not only made progress in basic chemical research, but also these complexes have potential applications in many fields, such as photoluminescence, [24][25][26] extraction, [27][28][29] magnetism, 30,31 catalysis, 32 etc.…”