Porous Templates Research Articles

Accessibility and Mechanical Stability of Nanoporous Zinc Oxide and Aluminum Oxide Coatings Synthesized via Infiltration of Polymer Templates.

The conformal nanoporous inorganic coatings with accessible pores that are stable under applied thermal and mechanical stresses represent an important class of materials used in the design of sensors, optical coatings, and biomedical systems. Here, we synthesize porous AlOx and ZnO coatings by the sequential infiltration synthesis (SIS) of two types of polymers that enable the design of porous conformal coatings-polymers of intrinsic microporosity (PIM) and block co-polymer (BCP) templates. Using quartz crystal microbalance (QCM), we show that alumina precursors infiltrate both polymer templates four times more efficiently than zinc oxide precursors. Using the quartz crystal microbalance (QCM) technique, we provide a comprehensive study on the room temperature accessibility to water and ethanol of pores in block copolymers (BCPs) and porous polymer templates using polystyrene-block-poly-4-vinyl pyridine (PS75-b-P4VP25) and polymers of intrinsic microporosity (PIM-1), polymer templates modified by swelling, and porous inorganic coatings such as AlOx and ZnO synthesized by SIS using such templates. Importantly, we demonstrate that no structural damage occurs in inorganic nanoporous AlOx and ZnO coatings synthesized via infiltration of the polymer templates during the water freezing/melting cycling tests, suggesting excellent mechanical stability of the coatings, even though the hardness of the inorganic nanoporous coating is affected by the polymer and precursor selections. We show that the hardness of the coatings is further improved by their annealing at 900 °C for 1 h, though for all the cases except ZnO obtained using the BCP template, this annealing has a negligible effect on the porosity of the material, as is confirmed by the consistency in the optical characteristics. These findings unravel new potential for the materials being used across various environment and temperature conditions.

Magnetocaloric effect of nanostructured La0.6Sr0.4CoO3

In this study, we investigate the magnetic and magnetocaloric properties of nanostructured La0.6Sr0.4CoO3 (LSC) samples synthesized under confinement conditions within porous templates. Using this method, we obtained de-agglomerated nanoparticles, which provide us with the feasibility of applying them in nanoparticle films that can be tailored to intricate geometries. We specifically explored the impact of pore size of the template on key parameters including saturation magnetization (MS), Curie temperature (TC), maximum entropy change (ΔS), and relative cooling power (RCP). Our findings reveal enhancements in those quantities, that are likely to be related with the nanostructure of the samples, indicating the potential of nanostructured LSC as an active material for magnetic refrigeration devices. Our alternative approach of synthesizing magnetocaloric materials under confinement conditions presents an exciting prospect for future research and development in the field.

Preparation of cellular SiBOC foams by thermo‐foaming of polymethylvinylborosiloxane–wheat flour dough

AbstractA novel method for the preparation of SiBOC foams from a polymethylvinylborosiloxane (MVBS) solution in ethanol using wheat flour as a foam stabilizer and pore template has been reported. A dough prepared by mixing the MVBS solution and wheat flour undergoes foaming at 180°C due to the stabilization of bubbles created by ethanol vapor by the adsorption of wheat flour particles on their surface. The ceramization of the foamed body at 1500°C followed by burnout of carbon produced from the wheat flour results in SiBOC foams of hierarchical pore structure. The foam density (.68–.44 g cm−3), average cell size (1.81–.58 mm), compressive strength (3.9–1.7 MPa), and thermal conductivity (.33–.21 W m−1 K−1) decrease with an increase in wheat flour to MVBS weight ratio from .25 to 1. The population of smaller pores (∼5–50 μm) created by wheat flour particles on cell walls and struts increases with an increase in wheat flour to MVBS weight ratio. The presence of β‐SiC and turbostratic graphite nanodomains in amorphous SiBOC is evidenced by X‐ray diffraction and transmission electron microscopy analysis.

Porous pseudo-substrates for InGaN quantum well growth: Morphology, structure, and strain relaxation

Strain-related piezoelectric polarization is detrimental to the radiative recombination efficiency for InGaN-based long wavelength micro-LEDs. In this paper, partial strain relaxation of InGaN multiple quantum wells (MQWs) on the wafer scale has been demonstrated by adopting a partially relaxed InGaN superlattice (SL) as the pseudo-substrate. Such a pseudo-substrate was obtained through an electro-chemical etching method, in which a sub-surface InGaN/InGaN superlattice was etched via threading dislocations acting as etching channels. The degree of strain relaxation in MQWs was studied by x-ray reciprocal space mapping, which shows an increase of the in-plane lattice constant with the increase of etching voltage used in fabricating the pseudo-substrate. The reduced strain in the InGaN SL pseudo-substrate was demonstrated to be transferable to InGaN MQWs grown on top of it, and the engineering of the degree of strain relaxation via porosification was achieved. The highest relaxation degree of 44.7% was achieved in the sample with the porous InGaN SL template etched under the highest etching voltage. Morphological and structural properties of partially relaxed InGaN MQWs samples were investigated with the combination of atomic force and transmission electron microscopy. The increased porosity of the InGaN SL template and the newly formed small V-pits during QW growth are suggested as possible origins for the increased strain relaxation of InGaN MQWs.

Structure and mechanisms of foam-like bamboo parenchyma tissue

The increased awareness of environmental problems has shifted the attention from synthetic polymer porous materials to natural plant porous materials like bamboo parenchyma tissue to develop functional materials. However, the neglect of the inherent structure and property of plant porous materials leads to insufficient development and utilization of their natural advantages. Here, we investigated the fine structure and mechanisms of bamboo parenchyma tissue, which has multiple high-quality properties like energy-absorbing and toughening, to provide a basis for their wide utilization in porous materials. Results showed that bamboo parenchyma tissue was a foam-like porous material with sufficient strength, high porosity and low density. It was composed of cell walls and four types of three-dimensional polyhedral pores converging in space. The total natural porosity was up to 78.80%. The cell walls exhibited a three-zone strength distribution with an average solid cell wall strength of 75.84 MPa, due to their cocoon-like closed microfibrils patterns, chemical compositions and pits characteristics. The high porosity and weakening of transition zone and cell end wall helped to absorb energy. This study provides ideas for the application of bamboo parenchyma tissue in cushioning energy-absorbing foam materials and porous material templates and for the biomimetic design of environmentally friendly porous materials.

Metal-organic framework and porous polymer monolith as ion-receptor carrier templates for the solid-state naked-eye sensing of ultra-trace Cr(III) from aqueous medium

We report on an effective onsite optical sensor strategy using probe-decorated porous polymer monolith (PPM) and aluminum-based metal-organic framework (MIL-53 (Al) MOF) as a reliable colorimetric sensor for the detection of ultra-trace levels of Cr3+. MOFs and PPMs have attracted considerable interest in environmental applications due to their high surface area, perpetual porosity, and tunable structural network. Here, Al-MOF and PPM materials were used as porous templates for the uniform infusion of a chromoionophoric probe, i.e., (Z)-1,2-diphenyl-2-((4-(E)-phenyldiazenyl)phenyl)imino)ethan-1-ol (DPPE), for the solid-state colorimetric recognition and capturing of Cr3+ from aqueous medium. The structural morphology and surface topography of the sensor materials have been characterized using the transmission/scanning electron microscopy, optical spectroscopy, X-ray/electron diffraction, elemental mapping, surface area/pore volume and thermal analysis to understand the surface properties and stability features of the long-range ordered porous framework. The sensor's superior structural and surface features tender faster ion diffusion to the anchored probe sites within 60 s. The sensor induces a selective ligand-to-metal charge transfer (LMCT) chelation with Cr3+, resulting in a sequence of color transition from pale orange to sepia-brown, with incremental levels of Cr3+. The significance of physicochemical factors, such as pH, probe content, sensor dose, kinetics, temperature, reusability, selectivity, sensitivity, and stability, has been optimized to maximize the ion-sensing performance. The sensors' reusability has been tested by replicating the ion-sensing performance up to eight cycles. The solid-state sensor exhibited a linear range of 1.0–200 ppb for Cr3+, with a detection limit of 0.44 and 0.53 ppb and a quantification limit of 1.39 and 2.22 ppb for DPPE-loaded PPM and Al-MOF sensors, respectively. The practical utility of the sensor materials with industrial/environmental water samples reveals excellent data reliability/reproducibility (recovery ≥99.1 %; RSD ≤2.5 %) for real-time monitoring.

Precise tuning of silica pore length and pore diameter on silica-encapsulated gold core–shell nanoparticles and catalytic impact

The ability to individually tune the pore length and pore diameter of silica-encapsulated gold core–shell nanoparticles (CSNPs) via a seeded encapsulation method is demonstrated and their impact on catalysis determined. Reducing the solvent volume during the shell growth phase resulted in CSNPs with shells of increasing thickness from 75 nm to 202 nm, following a linear relationship. The addition of 1, 3, 5-triisopropylbenzene (TIB) during synthesis increased the average pore diameter from 25 Å to 32 Å by swelling the pore template, swelling further to 38 Å when adding both TIB and n-decane. By decoupling the gold core reduction and silica condensation stages, gold core diameters were largely unaffected by silica growth reaction conditions. This was achieved by encapsulating CTAB-stabilized nanoparticles rather than reducing and stabilizing the nanoparticles during silica condensation. When used to catalyze solvent-free benzyl alcohol oxidation, it was found that CSNPs with increasing shell thicknesses demonstrated increased formation of the desirable aldehyde product, holding the undesired ester product yield constant. In contrast, CSNPs with increasing pore diameter exhibit increased formation of both aldehyde and ester products unselectively. These results—uniquely observed through the parametric isolation of pore length and diameter—suggest the reactant concentration at the pore wall due to hydrogen bonding, forming concentric “microphases” within the pores.

Versatile Synthesis of Hollow-structured Mesoporous Carbons by Enhanced Surface Interaction for High-performance Lithium-ion Batteries.

Nanoporous carbons are very attractive for various applications including energy storage. Templating methods with assembled amphiphilic molecules or porous inorganic templates are typically used for the synthesis. Amongst the different members of this family, CMK-5-like structures that are constructed to consist of sub-10nm amorphous carbon nanotubes and ultrahigh specific surface area due to their thin pore walls, have the best properties in various respects. However, the fabrication of such hollow-structured mesoporous carbons entails elaborately tailoring the surface properties of template pore walls and selecting specific carbon precursors. Thus, very limited cases are successful. Herein, wereport a versatile and general silanol-assisted surface-casting method to create hollow-structured mesoporous carbons and heteroatom-doped derivatives with numerous organic molecules (e.g., furfuryl alcohol, resol, 2-thiophene methanol, dopamine, tyrosine) and different structural templates. These carbon materials exhibit ultrahigh surface area (2400 m2 g-1 ), large pore volume (4.0 cm3 g-1 ), as well as satisfactory lithium-storage capacity (1460 mAh g-1 at 0.1 A g-1 ), excellent rate capability (320 mAh g-1 at 5 A g-1 ), and very outstanding cycling performance (2000 cycles at 5 A g-1 ). This article is protected by copyright. All rights reserved.

Large-area customizable honeycomb patterned polycarbonate derived from roofing sheet waste for a slippery liquid-infused porous surface

Polycarbonate (PC) is widely recognized for its exceptional ductility, high heat resistance, and impressive transparency, making it a material of great importance and extensive use. However, the increasing accumulation of PC-based solid waste, particularly discarded roofing sheets, has raised significant environmental concerns worldwide. The incineration or incomplete decomposition of polycarbonate waste in landfills generates hazardous by-products such as microplastics and Bisphenol-A (BPA). In this study, we propose an innovative recycling approach that converts low-grade roofing sheets waste into large-area customizable honeycomb-patterned PC, offering great potential for the development of slippery liquid-infused porous surfaces (SLIPs). The achievement of a highly ordered honeycomb pattern array is facilitated through the implementation of an improved phase separation (IPS) method, employing methanol as a pore inducer and template droplet stabilizer, thereby eliminating the necessity for surfactants or specially engineered polymers. This approach enables the formation of a monolayered pattern array with uniform closed dead-end pores shaped like round flowerpots, holding immense promise for creating SLIPs with self-cleaning, anti-fouling and electrification properties due to the reduction in surface-contaminant adhesion and friction, rendering them suitable for various applications, including smart coatings for rain corrosion protection and falling raindrop energy harvesting.

Analysis of Effect of Concentration Dependence of Exchange Current on the Metal Electrodeposition into Template Nanopores

Metal electrodeposition into the nanopores of template of porous anodic alumina type under the conditions of mixed kinetics is studied theoretically using analytical and numerical methods. Two main stages of the process are studied: the non-steady-state formation of diffusion layer in the template pores and much longer process of pore filling with metal. The effect of nonlinearity of the concentration dependence of exchange current density of metal electrodeposition on the current density of the diffusion layer formation and pore filling with metal is studied.

Porous Carbon Template Decorated with MOF-Driven Bimetallic Phosphide: A Suitable Heterostructure for the Production of Uninterrupted Green Hydrogen via Renewable Energy Storage Device.

Water splitting via an uninterrupted electrochemical process through hybrid energy storage devices generating continuous hydrogen is cost-effective and green approach to address the looming energy and environmental crisis toward constant supply of hydrogen fuel in fuel cell driven automobile sector. The high surface area metal-organic framework (MOF) driven bimetallic phosphides (ZnP2 @CoP) on top of CNT-carbon cloth matrix is utilized as positive and negative electrodes in energy storage devices and overall water splitting. The as-prepared positive electrode exhibits excellent specific capacitances/capacity of 1600 F g-1 /800 C g-1 @ 1A g-1 and the corresponding hybrid device reveals an energy density of 83.03Wh kg-1 at power density of 749.9W kg-1 . Simultaneously, the electrocatalytic performance of heterostructure shows overpotentials of 90 mV@HER and 204 mV@OER at current density of 10 and 20mA cm-2 , respectively in alkaline electrocatalyzer. Undoubtedly, it shows overall water splitting with low cell voltage of 1.53 V@10mA cm-2 having faradic and solar-to-hydrogen conversion efficiency of 98.81% and 9.94%, respectively. In addition, the real phase demonstration of the overall water-splitting is performed where the electrocatalyzer is connected with a series of hybrid supercapacitor devices powered up by the 6V standard silicon solar panel to produce uninterrupted green H2 .

An injectable macroporous hydrogel templated by gasification reaction for enhanced tissue regeneration

Owing to excellent biocompatibility, tunable modulus to match biological tissues, full of water environment, and wide range of constituents, injectable hydrogels have always been preferred as superior performers of regenerative medicine. In principle, the inclusion of macroporous structures in hydrogels facilitates the diffusion of oxygen and nutrients for cell survival and the removal of the metabolic waste, thus strengthening the integration between materials and host tissues. So far, it is still a challenge to construct macroporous structure in hydrogels in situ with preservation of mechanical strength after injecting hydrogel precursors into the biological tissues. In this study, we propose an innovative in situ gas-forming strategy for preparing a kind of bioactive injectable macroporous hydrogel with the assistance of Mg microparticles (MgMPs). Hydrogen gas as a product of MgMPs reacting with water acts as porous template during the gelation process. So the porosity is closely related to the amount of MgMPs, which is a crucial factor for improving cell viability and proliferation throughout the macroporous hydrogel. Referring to the in vivo wound care experiments, regenerated epidermis and extensive blood vessels are found in the macroporous hydrogel, indicating enhanced tissue regeneration. This in situ gas-templating strategy for preparing injectable macroporous hydrogels holds promise as a technique for providing improved biological scaffolds.

Structured Cs3Cu2I5 scintillation screen based on oxidized silicon micropore array template for high-resolution X-ray imaging

Improving the spatial resolution of X-ray imaging is one of the main directions of scintillation screen research. Herein, a structured Cs3Cu2I5 scintillation screen based on oxidized silicon micropore array template was developed. A feasible method was explored to solve the problems such as the preparation of oxidized silicon micropore array template with micron-period structure and the compact filling of Cs3Cu2I5 scintillator into the template. The X-ray imaging resolution using the structured Cs3Cu2I5 scintillation screen reaches 113 lp/mm attributing to the light guide and optical isolation of the template pore walls. The results of detective quantum efficiency, the X-ray imaging photographs of a micro-resolution plate and a small zebrafish show that the image quality using the structured screen is excellent. Meanwhile, the developed Cs3Cu2I5 scintillation screen exhibits good radiation resistance, which can keep the light output basically unchanged when the radiation dose is up to 43.2 Gy. The screen also exhibits good luminescence stability compared to Cs3Cu2I5 itself due to the protection of the template. These indicate that the structured Cs3Cu2I5 scintillation screen has a good application prospect in high-resolution X-ray imaging.

Facile transformation of graphene oxide nanospheres based on AAO template

In this paper, a facile one-step drop method is developed to convert reduced graphene oxide into graphene oxide nanoparticles. An aqueous solution of reduced graphene oxide is poured through the pores of anodic aluminum oxide templates to form graphene oxide nanospheres at low temperature (120 ​°C) and low pressure (0.8 ​bar) preparation conditions. Electrochemical exfoliation of graphite and reduced graphene oxide nanospheres (not hollow) were adopted to fabricate reduced graphene oxide within the pores of an anodic aluminum oxide template. The prepared reduced graphene oxide nanospheres show uniform diameters (∼42.5 ​nm) and a low O/C ratio (8%). Graphene nanospheres achieve higher sensitivity to CO2 gas in air (at room temperature) compared to graphene oxide nanosheets (i.e., in contrast to carbon dioxide gas sensors in graphene sheets). Its sensitivity increased to 35% by shaping the nanosheets to nanospheres of reduced graphene oxide which is attributed to a surface area expansion of 7.4 ​× ​105 times. Moreover, graphene oxide, reduced graphene oxide, and reduced graphene oxide nanospheres show a fast response time of 0.19 ​s, 0.24 ​s, and 0.31 ​s, and short recovery times of 1.14 ​s, 1.17 ​s, and 1.22 ​s, respectively, with higher sensitivity of reduced graphene oxide nanospheres.

Magnetic saturation enhancement of gold-capped nickel nanorods

Nickel nanorods (NRs) capped with gold (Au/Ni) were grown into porous anodic aluminum oxide templates and subsequently transferred onto Au/Si (100) substrates. A high dense 2D array of Ni and Au/Ni nanorods was analyzed by vibrating sample magnetometry; it was found that an increase in 14.8% of the magnetic moment following the deposition of Au caps. In order to further investigate this phenomenon, the magnetic distribution of Au/Ni nanorods was studied by off-axis electron holography. The magnetization and induction strengths were evaluated to be 4.7 × 105 A/m and 0.62 T, respectively, which is equivalent to magnetometry measurements of the Ni NR arrays. Remarkably, a vortex state configuration was imaged in the Au segment by the retrieved magnetic phase of the electron holograms under free lens conditions of the transmission electron microscope column. It was concluded that the magnetic distribution in the Au segment is associated with a ferromagnetic coupling with Ni and correlated with the magnetometry measurements.

Tailoring the Morphology of Monodisperse Mesoporous Silica Particles Using Different Alkoxysilanes as Silica Precursors.

The hard template method for the preparation of monodisperse mesoporous silica microspheres (MPSMs) has been established in recent years. In this process, in situ-generated silica nanoparticles (SNPs) enter the porous organic template and control the size and pore parameters of the final MPSMs. Here, the sizes of the deposited SNPs are determined by the hydrolysis and condensation rates of different alkoxysilanes in a base catalyzed sol-gel process. Thus, tetramethyl orthosilicate (TMOS), tetraethyl orthosilicate (TEOS), tetrapropyl orthosilicate (TPOS) and tetrabutyl orthosilicate (TBOS) were sol-gel processed in the presence of amino-functionalized poly (glycidyl methacrylate-co-ethylene glycol dimethacrylate) (p(GMA-co-EDMA)) templates. The size of the final MPSMs covers a broad range of 0.5-7.3 µm and a median pore size distribution from 4.0 to 24.9 nm. Moreover, the specific surface area can be adjusted between 271 and 637 m2 g-1. Also, the properties and morphology of the MPSMs differ according to the SNPs. Furthermore, the combination of different alkoxysilanes allows the individual design of the morphology and pore parameters of the silica particles. Selected MPSMs were packed into columns and successfully applied as stationary phases in high-performance liquid chromatography (HPLC) in the separation of various water-soluble vitamins.

The Morphology-Controllable Synthesis of Ni–Co–O Nanosheets on a 3D Porous Ni Template as a Binder-Free Electrode for a Solid-State Symmetric Supercapacitor

In this work, a porous Ni template (Ni–Co–O@3D Ni) with Ni–Co oxide nanosheets (Ni–Co–O)@3D was synthesized by incorporating Ni–Co oxide nanosheets within a 3D porous Ni template as a binder-free electrode for a supercapacitor. The 3D Ni template was synthesized with hydrogen bubble templates that possessed different applied voltages that marked differences in terms of physicochemical properties, as well as factors that affect the subsequent growth of Ni–Co–O nanosheets. Then, Ni and Co metal ion sources were introduced to produce the morphology adjustment of Ni–Co–O@3D Ni with a multiple hierarchical architecture with a hydrothermal process. Field emission scanning electron microscopy (FESEM), X-ray absorption spectroscopy (XAS), and an electrochemical analysis were employed to investigate the morphological, structural, and electrochemical characteristics. FESEM and XAS results evidenced that Ni–Co–O@3D Ni consists of a 3D, well-designed hierarchical interconnected network, and the local electronic structure change has a great influence on the capacitive performance. The electrochemical results of Ni–Co–O@3D Ni displayed an excellent electrochemical performance due to the synergistic effect of Ni and Co on Ni–Co–O@3D Ni, which possessed multiple oxidation states to enable various reversible Faradaic redox reactions. Remarkably, the solid-state symmetric supercapacitor fabricated with Ni–Co–O@3D Ni exhibited excellent capacitive behaviour at a wide operating voltage window and cycling performance. Also, the as-assembled solid-state symmetric supercapacitor (two devices in series) can successfully illuminate a desired parallel pattern consisting of 36 red LED lights, demonstrating its practical application as a supercapacitor.

Gold nanoparticles embedded Fe-BTC (AuNPs@Fe-BTC) metal-organic framework as a fluorescence sensor for the selective detection of As(III) in contaminated waters

In this article, a new off-mode fluorescent platform based on the metal-organic framework (MOF) is introduced as a highly selective and rapid chemical sensor for the detection of As(III) in water and wastewater samples. A typical Fe-BTC (BTC = 1,3,5-benzenetricarboxylate or trimesic acid) MOF was used as a porous template for loading gold nanoparticles (AuNPs@Fe-BTC MOF). The physicochemical properties of AuNPs@Fe-BTC MOF were characterized by Fourier-transform infrared spectroscopy (FT-IR), Field emission scanning electron microscopy (FESEM), Energy-dispersive X-ray spectroscopy (EAX), element mapping (MAP) and X-ray diffraction (XRD) analysis. This sensing method for As(III) ions is based on the fact that the fluorescence intensity of AuNPs@Fe-BTC MOF sensor decreases in proportion to the increase in As(III) concentration. The main effective factors on the performance of the sensor signal such as MOF dosage, sonication time, pH and reaction time were optimized. Under optimized conditions, the calibration graph was linear in the concentration range of 0.5–380 ng mL−1 of As(III) and the limit of detection was 0.2 ng mL−1. The proposed method was successfully validated by addition/recovery experiments by the determination of As(III) in four river water and two wastewater effluent samples.

Effects of structure, size and non-magnetic Cu layer thickness on magnetization switching behavior in Ni/Cu/M (M [formula omitted] Ni, Co) cylindrical nanowires

We have investigated the dependence of the magnetization switching behavior on the structure, size and nonmagnetic Cu layer thickness (tCu) in Ni/Cu/M (M = Ni, Co) cylindrical nanowires fabricated by electrodeposition using porous polycarbonate templates. The crystal structure of the Ni nanowires was (111)- or (200)-oriented polycrystalline fcc, while that of Co nanowires was (100)- or (101)-oriented hcp and/or (111)-oriented polycrystalline fcc. When the wire diameter (d) was 50 nm, the squareness ratio (Mr/Ms) for M = Ni, as estimated from the magnetization curve, is almost constant at Mr/Ms∼0.79 (Mr/Ms∼0.64 for M = Co) when tCu increases from 0 to 500 nm. When d=100nm, Mr/Ms decreases by 41% from 0.71 to 0.42 with increasing tCu from 0 to 700 nm for M = Ni, while Mr/Ms decreases by 25% from 0.53 to 0.40 with varying tCu from 0 to 500 nm for M = Co. The threshold Cu layer thickness (tCuth) beyond which Mr/Ms becomes constant at d=100nm is ∼500 nm for M = Ni and ∼300 nm for M = Co. The results are qualitatively consistent with those obtained from our micromagnetic simulation and analysis. The observed difference in the tCuth dependence of Mr/Ms between M = Ni and Co is attributed to the change in the magnetic domain structure of the nanowires as it sensitively varies with the magnetocrystalline anisotropy. On the other hand, the coercive force of the nanowires shows a small tCu dependence for both d=50 and 100 nm. These results indicate that the layered structure in the nanowires governs the magnetic domain structure, though the effect on the magnetization switching behavior is indeed relatively small.

Incorporation of silica nanoparticles into porous templates to fabricate mesoporous silica microspheres for high performance liquid chromatography applications

High-performance liquid chromatography is one of the most important analytical tools for the identification and separation of substances. The efficiency of this method is largely determined by the stationary phase of the columns. Although monodisperse mesoporous silica microspheres (MPSM) represent a commonly used material as stationary phase their tailored preparation remains challenging. Here we report on the synthesis of four MPSMs via the hard template method. Silica nanoparticles (SNPs) which form the silica network of the final MPSMs were generated in situ from tetraethyl orthosilicate (TEOS) in the presence of (3-aminopropyl) triethoxysilane (APTES) functionalized p(GMA-co-EDMA) as hard template. Methanol, ethanol, 2-propanol, and 1-butanol were applied as solvents to control the size of the SNPs in the hybrid beads (HB). After calcination, MPSMs with different sizes, morphology and pore properties were obtained and characterized by scanning electron microscopy, nitrogen adsorption and desorption measurements, thermogravimetric analysis, solid state NMR and DRIFT IR spectroscopy. Interestingly, the 29Si NMR spectra of the HBs show T and Q group species which suggests that there is no covalent linkage between the SNPs and the template. The MPSMs were functionalized with trimethoxy (octadecyl) silane and used as stationary phases in reversed-phase chromatography to separate a mixture of eleven different amino acids. The separation characteristics of the MPSMs strongly depend on their morphology and pore properties which are controlled by the solvent during the preparation of the MPSMs. Overall, the separation behavior of the best phases is comparable with those of commercially available columns. The phases even achieve faster separation of the amino acids without loss of quality.