Anisotropic Surface Modification Research Articles

Tailored Catalytic Nanoframes from Metal–Organic Frameworks by Anisotropic Surface Modification and Etching for the Hydrogen Evolution Reaction

AbstractA facile anisotropic surface modification and etching strategy is presented for the synthesis of hollow structured ZIF‐67 nanoframes. The strategy uses structural and compositional distinctions between each crystallographic facet of truncated rhombic dodecahedrons ZIF‐67 (tZIF‐67 RDs) and the moderate coordinating and etching effects of cyanuric acid (CA). The CA can anisotropically modify and protect the {110} facets from etching, causing the six {100} facets be selectively etched via an inside‐out manner, and finally forming the hollow nanoframes. The surface‐modified hollow tZIF‐67 RDs can be facet‐selectively etched by metal salts in an outside‐in manner to give metal‐doped tZIF‐67 nanoframes. After calcination, the metal‐tZIF‐67 hybrids are converted into metal‐Co alloy/C composite catalysts with hollow nanoframed structures. The PtCo/C catalyst with only 5.9 wt % Pt exhibits high catalytic activities and stabilities in the hydrogen evolution reaction (HER) in acidic solutions.

Tailored Catalytic Nanoframes from Metal-Organic Frameworks by Anisotropic Surface Modification and Etching for the Hydrogen Evolution Reaction.

A facile anisotropic surface modification and etching strategy is presented for the synthesis of hollow structured ZIF-67 nanoframes. The strategy uses structural and compositional distinctions between each crystallographic facet of truncated rhombic dodecahedrons ZIF-67 (tZIF-67 RDs) and the moderate coordinating and etching effects of cyanuric acid (CA). The CA can anisotropically modify and protect the {110} facets from etching, causing the six {100} facets be selectively etched via an inside-out manner, and finally forming the hollow nanoframes. The surface-modified hollow tZIF-67 RDs can be facet-selectively etched by metal salts in an outside-in manner to give metal-doped tZIF-67 nanoframes. After calcination, the metal-tZIF-67 hybrids are converted into metal-Co alloy/C composite catalysts with hollow nanoframed structures. The PtCo/C catalyst with only 5.9 wt % Pt exhibits high catalytic activities and stabilities in the hydrogen evolution reaction (HER) in acidic solutions.

Plasmon-triggered living photopolymerization for elaboration of hybrid polymer/metal nanoparticles

Surface plasmon resonance can be used to manipulate light at the nanoscale. It was used here to trigger photopolymerization of an atom transfer radical polymerization (ATRP) molecular system, leading to a thin polymer shell at the surface of the metal nanostructure. The polymerization can be reactivated from the first polymer shell to covalently graft a second monomer layer with precise control over the thickness at the nanometric scale, depending on the photonic parameters. This route can be applied to different nanoobjects and allows an anisotropic surface modification in agreement with the spatial localization of the enhanced electromagnetic field near the nanostructure. This new route opens the door towards the preparation of multifunctional hybrid metal/polymer nanostructures.

Anisotropic modification of SPIONs surface with thiol and alkyne groups for fabrication of poly (2-hydroxyethyl methacrylate)/polydopamine amphiphilic Janus nanoparticles via double-click reaction

The Janus nanoparticles (JNPs) have been considered as dual-functionalized devices. One of the materials which can be used in the hybrid Janus nanoparticles is superparamagnetic iron oxide nanoparticles (SPIONs). In this work, a novel procedure based on anisotropic surface modification of SPIONs through Pickering Emulsion was utilized to obtain bi-functional SPIONs with thiol and triple bond functional groups. These surface-modified nanoparticles have a great potential to graft a variety of polymers with different molecular weights to its surface. Low molecular ATRP-synthesized poly (2-hydroxyethyl methacrylate) (PHEMA) as a hydrophilic polymer and polydopamine (PDA) as a hydrophobic one were synthesized and were covalently anchored to the surface of bi-functional SPIONs through double click reaction, i.e. [2 + 3] cycloaddition and thiol-ene reaction. As a result, polymeric Janus nanoparticles with amphiphilic and magnetic properties were obtained. The prepared polymers and SPIONs were fully characterized by various methods, as well as final polymeric Janus nanoparticles.

Out-of-Equilibrium Assembly of Colloidal Particles at Air/Water Interface Tuned by Their Chemical Modification

Assemblies of monolayers made of colloidal silica particles trapped at the air/water interface are prepared to have an increasing capillary interaction. Fine-tuning of the strength of interaction and its orientational specificity is achieved through isotropic or anisotropic colloid surface chemical modification or by adjusting the subphase surface tension. The capillary attraction between colloids is strong and specific enough to drive the particle organization out of equilibrium toward kinetically arrested assemblies. For isotropic particles, the square order competes with the hexagonal one at low area densities, which leads to their mutual frustration resulting in a polycrystalline solid at high densities. Anisotropic Janus particles attract so strongly and with such an orientational specificity that the resulting assemblies are the most dynamically arrested, although the crystal grains are highly ordered on the short length scale. We show that the particle anisotropic surface modification does not alwa...

One-pot synthesis of long twin gold nanorods in a gelled surfactant solution

A new one-pot synthesis method was developed for producing long twin gold nanorods with lengths of ca. 1755 nm, which have the potential to be arranged on a substrate using anisotropic surface modification.

金属酸化物ナノ結晶粒子の異方的表面修飾法

This research aims to develop a method to realize anisotropic surface modification of metal oxide nanoparticles. The anisotropic surface modification can be realized under the condition that the interaction with organic molecules largely depends on the crystal faces. In order to evaluate the interaction between organic molecules and crystal faces of metal oxide nanoparticles, we placed rutile and anatase phases of TiO2 single crystal substrate in high-temperature and high-pressure water with various organic molecules. After this hydrothermal treatment, substrates were rinsed and analyzed by contact angle measurement and X-ray photoelectron spectroscopy. The results showed that rutile (110) face had higher affinity with phosphoric acid and anatase (101) also had higher affinity with amines. These results are indispensable to realize anisotropic surface modification of metal oxide nanoparticles during their synthesis.

Formation of Janus TiO<SUB>2</SUB> Nanoparticles by a Pickering Emulsion Approach Applying Phosphonate Coupling Agents

Anisotropic surface modification of TiO2 nanoparticles was achieved applying a Pickering emulsion approach. TiO2 nanoparticles were prepared by sol-gel routes which allowed an excellent control over their size and morphology. The obtained colloids were further used as stabilizers in the formation of oil-in-water Pickering emulsion. For reasons of comparison, also commercially available titanium dioxide nanoparticles (Evonik AEROXIDE TiO2 P25) were used in the functionalization experiments. An organophosphorus coupling agent present in the oil phase coordinated to the surface of the anatase nanoparticles. In such a way an anisotropic surface modification of the particles was achieved which increased the stability of the Pickering emulsion. Spectroscopic studies revealed the presence of organophosphorus coupling agents which exhibited a covalent bonding to the surface of the particles. Thermogravimetric analyses confirmed a lower surface coverage of the particles modified in emulsion compared to those modified in suspension. Reactions of organophosphorus coupling agents containing an additional methacrylate group applying an organic monomer (methyl methacrylate) as the oil phase of the Pickering emulsion resulted in hybrid TiO2@polymer spheres. Spectroscopic characterization of the resulting particles revealed that the phosphonates were coordinated to the TiO2 surface and at the same time copolymerized with the MMA within the oil droplet. Morphological investigations of the isolated final product showed that the material was composed of polymer spheres with the stabilizing TiO2 nanoparticles on their surface.

Effect of Anisotropic Membrane Surface Modification of Nafion Based Ionic Polymer-Metal Composites

In order to enhance the electromechanical characteristics of IPMCs actuators under low voltage, a set of anisotropic membrane surface modification techniques, including roughness along, roughness across and roughness across both directions, is proposed in this paper. Three groups of IPMCs samples based on corresponding roughness direction have been prepared to validate the these surface modification. Experiments have been made to measure the electromechanical characteristics of the samples. The results show that the IPMCs actuator with micro-grooves being across the length of the IPMCs actuator could improve the IPMCs’ tip blocking force and deflection, and it exhibits blocking forces by 10% larger than the conventional IPMCs while its displacement is approximately 8% larger. We can conclude that an appropriate anisotropic surface modification could be an effective method to create a preferred bending force and to enhance the bending margin of IPMCs actuators.