Three-dimensional Interconnected Porous Structure Research Articles

Synthesis of CaO-CeO2 catalysts by soft template method for biodiesel production

Biodiesel has recently gained extensive attention. Catalysts play an important role in producing biodiesel by transesterification reaction. In this study, CaO-CeO2 catalysts are developed as the solid base catalyst. Using PDMS-PEO as a structure-directing agent, the prepared CaO-CeO2 catalysts have a three-dimensional interconnected porous structure, which benefits the transesterification reaction. While the added Ce slightly decreases the catalytic activity, the stability of the catalyst shows remarkable improvement. Considering the catalytic activity and stability, the best catalyst is determined to be catalyst 0.15-1073 (Ce/Ca molar ratio of 0.15 and calcination temperature of 1073 K). Under optimum reaction conditions, the biodiesel yield reaches to 97.5% and metal leaching is 117.7 ppm. For catalyst 0.15-1073 regenerated after four reaction cycles, the biodiesel yield is 94.1%. The results reveal that the CaO-CeO2 catalyst has good potential for application in large-scale biodiesel production in the future.

Fabrication of amine-functionalized acrylic monoliths via thermally induced phase separation and their application for separation media

This study deals with fabrication of amine-functionalized acrylic monoliths and their application for separation media. Poly(glycidyl methacrylate-co-methyl methacrylate) (PGMA) monoliths with three-dimensional interconnected porous structure were prepared by thermally induced phase separation (TIPS) using cosolvent system, and subsequent aminolysis of oxirane groups produced amine-functionalized acrylic monoliths. The porous structure and specific surface area of the monoliths were dependent on the molecular weight of PGMA. Bovine serum albumin (BSA) was effectively adsorbed on the monoliths by electrostatic interaction, and the binding capacity was enhanced with an increase in the surface area of the monoliths. Furthermore, the amine-functionalized monoliths released BSA by washing with high salt concentration solution. These results demonstrated a potential of the amine-functionalized monoliths prepared by TIPS method for rapid separation and analysis of biomolecules.

Emulsion-templated fully three-dimensional interconnected porous titania ceramics with excellent humidity sensing properties

In this study, a facile emulsion templating method was developed for the preparation of high-performance monolithic porous titania-based humidity-sensing ceramics. High internal phase Pickering emulsions (HIPEs) with internal phase of 70vol%, stabilized by short-chain amphiphilic molecules in situ modified TiO2 solid nanoparticles, were employed as templates. The obtained sensors contain a hierarchically ordered three-dimensional interconnected pore structure and exhibit high sensitivity to water vapors as well as linear response in the wide relative humidity (RH) range between 11% and 95%. The observed sensor impedance variation can be as high as four orders of magnitude, depending on the RH value. In addition, the produced sensors are characterized by the reversible response with relatively small hysteresis and thus can be reversibly operated without repeated high-temperature thermal desorption cleaning.

A facile method to prepare porous graphene with tunable structure as electrode materials for immobilization of glucose oxidase

We first reported a facile method to prepare porous graphene with tunable structure for glucose oxidase (GOD) immobilization based on freeze-drying. The produced porous graphene (PGR) exhibited three-dimensional interconnected porous structure. Moreover, their microstructure was easily tuned by addition of surfactant and oil droplets into the graphene oxide dispersion. Field emission scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy and nitrogen physisorption were used to characterize microstructures, composition and surface area of the produced PGR. The addition of surfactant introduced mesopores in the PGR and the oil droplets can improve the pore volume. It was found that the PGR structure obviously affected the electrochemical behavior of GOD. Electrocatalytical activity towards glucose was also investigated, and the maximum electrocatalytical current reached 6.3 times for 5 mM glucose. The modified electrode was used to detect the glucose, and a low detection limit of 8.7 μM and a high sensitivity of 16.3 μA mM cm−2 were obtained. The good sensing performance was attributed to the good three-dimensional porous structure and conductivity of the PGR.

Three-dimensional macroporous cellulose-based bioadsorbents for efficient removal of nickel ions from aqueous solution

We present a simple synthetic method for the preparation of cellulose-g-poly(acrylic acid-co-acrylamide) materials with three-dimensional macroporous structure, which can be used for the environmental application as the reusable bioadsorbents. In the grafting copolymerization process, the acrylic acid and acrylamide are cross-linked with cellulose molecules to form three-dimensional interconnected porous structure. Due to the macropores and the abundant functional groups, the cellulose-based bioadsorbents exhibit excellent adsorption performance for the removal of nickel ions from aqueous solution with a maximum adsorption capacity of 171.8 mg/g. The adsorption of bioadsorbents to Ni2+ is accurately described by a pseudo-second-order kinetic model and the initial concentration-dependent adsorption isotherm suggests a Langmuir isotherm model. Furthermore, the cellulose-based bioadsorbents can be easily separated from the aqueous solution after adsorption and regenerated using 0.2 M HCl solution, which exhibits high adsorption capacity after six adsorption–desorption cycles. Importantly, the biodegradation rate of 53.1 wt% for the bioadsorbents is found after being incubated in the soil extraction solution for 90 days. Therefore, the eco-friendly cellulose-based bioadsorbents could be used for water purification effectively.

Preparation of silicon nitride foam with three-dimensional interconnected pore structure

Silicon nitride (Si3N4) foams with three dimensional (3D) interconnected pore structure were prepared by a combination of protein foaming method and sacrificial template method. Hydrophobic epoxy resin (EP) particles were used as the sacrificial template. The hydrophobic character of EP particles enabled them to absorb on to the air–water interface in the foamed slurry, resulting in the formation of windows on the cell walls after the burn out of EP particles. Pore structures and properties of the Si3N4 foams fabricated with adding different amount of EP powder and different sintering temperature were investigated. It was indicated that the Si3N4 foam fabricated without EP powder exhibited catastrophic failure during the compression test, whereas the Si3N4 foams fabricated with EP powder did not. Moreover, the Si3N4 foams with large numbers of windows on the cell walls exhibited higher compressive strength than the Si3N4 foam without window on its cell walls, even though the open porosities of the former were similar to the latter or even higher than the latter.

Development and Characterization of Acellular Extracellular Matrix Scaffolds from Porcine Menisci for Use in Cartilage Tissue Engineering.

Given the growing number of arthritis patients and the limitations of current treatments, there is great urgency to explore cartilage substitutes by tissue engineering. In this study, we developed a novel decellularization method for menisci to prepare acellular extracellular matrix (ECM) scaffolds with minimal adverse effects on the ECM. Among all the acid treatments, formic acid treatment removed most of the cellular contents and preserved the highest ECM contents in the decellularized porcine menisci. Compared with fresh porcine menisci, the content of DNA decreased to 4.10%±0.03%, and there was no significant damage to glycosaminoglycan (GAG) or collagen. Histological staining also confirmed the presence of ECM and the absence of cellularity. In addition, a highly hydrophilic scaffold with three-dimensional interconnected porous structure was fabricated from decellularized menisci tissue. Human chondrocytes showed enhanced cell proliferation and synthesis of chondrocyte ECM including type II collagen and GAG when cultured in this acellular scaffold. Moreover, the scaffold effectively supported chondrogenesis of human bone marrow-derived mesenchymal stem cells. Finally, in vivo implantation was conducted in rats to assess the biocompatibility of the scaffolds. No significant inflammatory response was observed. The acellular ECM scaffold provided a native environment for cells with diverse physiological functions to promote cell proliferation and new tissue formation. This study reported a novel way to prepare decellularized meniscus tissue and demonstrated the potential as scaffolds to support cartilage repair.

Preparation of Oxygen-enriched Activated Carbons from Coal-based Humic Acids by Zinc Chloride Activation

Oxygen-enriched activated carbons (ACs) for electrochemical capacitors (ECs) were prepared from coal-based humic acids (HAs) by zinc chloride (ZnCl2) activation. The effects of ZnCl2/HAs ratio and activation temperature on the characteristics of ACs were investigated by nitrogen adsorption at 77K, scanning electron microscope, transmission electron microscope and X-ray photoelectron spectroscopy. The electrochemical performances of ECs with ACs as electrode in a 3M KOH aqueous solution were evaluated by galvanostatic charge-discharge, cyclic voltammetry and Nyquist impedance spectroscopy. The results indicate that the optimum conditions for preparing ACs from coal-based HAs are ZnCl2/HAs ratio of 2.0 and activation temperature of 500 °C. The AC as electrode for ECs prepared under these conditions presents a high specific capacitance of 226 F/g at a high current density of 5 A/g, and exhibits good cycling stability and minimal resistance. The excellent electrochemical performances of ACs are attributed to three aspects: the well-developed porosity with moderate specific surface area, three-dimensional interconnected pore structure and the oxygen-enriched functional groups in carbon network.

Facile synthesis of functionalized porous carbon with three-dimensional interconnected pore structure for high volumetric performance supercapacitors

Functionalized porous carbon with three-dimensional (3D) interconnected pore structure has been successfully synthesized through direct heat-treatment of KOH-soaked soybeans. Benefiting from heteroatoms (N, O) doping, interconnected porous carbon framework with high surface area as well as high packing density (up to 1.1gcm−3), the as-obtained porous carbon material exhibits high volumetric capacitance of 468Fcm−3, good rate capability and excellent cycling stability (91% of capacitance retention after 10,000 cycles) in 6M KOH electolyte. More importantly, the as-assembled symmetric supercapacitor delivers high volumetric energy density of 28.6WhL−1 in 1M Na2SO4 aqueous solution.

Characterization and Adsorption Performance of Polyurethane Foam Synthesized From Guluronic Acid Rich Sodium Alginate

Polyurethane foams based on guluronic acid(G)-rich sodium alginate(PF-SA) were synthesized by using cross-linking low molecular weight G-rich alginic acid(LG-HA)with hexamethylene diisocyanate(HDI). The prepared PF-SA was characterized and its adsorption performance of methylene blue(MB) in aqueous solution was investigated by XRD, FTIR, SEM, BET. The results show that the dosage of HDI and the concentration of LG-HA have a significant impact on the morphology and the microstructure of PF-SA; PF-SA with three-dimensional interconnected pore structure may be prepared when the molar ratio of HDI to the monomer unit of LG-HA was in the range of 1: 4 to1: 3, the concentration of LGHA was in the range of 0.08-0.1 g/m L; this PF-SA is effective for the adsorption of MB: for a solution with concentration of 100 mg/L MB, the adsorption equilibrium can be reached in 30-160 min at room temperature. The removal efficiency of MB was as high as 99%.

Hyaluronic acid/poly(lactic-co-glycolic acid) core/shell fiber meshes loaded with epigallocatechin-3-O-gallate as skin tissue engineering scaffolds.

In this study, hyaluronic acid (HA)/poly(lactic-co-glycolic acid, PLGA) core/shell fiber meshes loaded with epigallocatechin-3-O-gallate (EGCG) (HA/PLGA-E) for application to tissue engineering scaffolds for skin regeneration were prepared via coaxial electrospinning. Physicochemical properties of HA/PLGA-E core/shell fiber meshes were characterized by SEM, Raman spectroscopy, contact angle, EGCG release profiling and in vitro degradation. Biomechanical properties of HA/PLGA-E meshes were also investigated by a tensile strength test. SEM images showed that HA/PLGA-E fiber meshes had a three-dimensional interconnected pore structure with an average fiber diameter of about 1270 nm. Raman spectra revealed that EGCG was uniformly dispersed in the PLGA shell of meshes. HA/PLGA-E meshes showed sustained EGCG release patterns by controlled diffusion and PLGA degradation over 4 weeks. EGCG loading did not adversely affect the tensile strength and elastic modulus of HA/PLGA meshes, while increased their hydrophilicity and surface energy. Attachment of human dermal fibroblasts on HA/PLGA-E meshes was appreciably increased and their proliferation was steadily retained during the culture period. These results suggest that HA/PLGA-E core/shell fiber meshes can be potentially used as scaffolds supporting skin regeneration.

Characterization of chitosan microparticles reinforced cellulose biocomposite sponges regenerated from ionic liquid

The chitosan-microparticles reinforced cellulose biocomposite sponges regenerated from ionic liquid were prepared and characterized. Fourier transform infrared (FTIR) spectroscopy confirmed that the cellulose dissolved in 1-allyl-3-methylimidazolium chloride without derivatization. Chitosan particles as reinforcement were incorporated into the cellulose matrix. FTIR spectra indicated hydrogen bonding between hydroxyl groups of cellulose and chitosan. The biocomposite sponges showed uniform three-dimensional interconnected porous structures. The breaking strength of the sponges increased significantly, from 0.09 to 0.32 MPa with the addition of 1.0 wt% chitosan. The sponges also demonstrated excellent antibacterial activity against S. aureus and E. coli with the average inhibition zone diameters >2 mm and the inhibition rate higher than 80 %. Furthermore, the biocomposite sponges exhibited good moisture penetrability and high porosity. The water uptake ability of the sponge was >25 times of its weight in water with a fast swelling. The chitosan/cellulose composite sponge is expected to be a promising material for potential applications as wound dressing.

Morphology and properties of poly vinyl alcohol (PVA) scaffolds: Impact of process variables

Successful engineering of functional biological substitutes requires scaffolds with three-dimensional interconnected porous structure, controllable rate of biodegradation, and ideal mechanical strength. In this study, we report the development and characterization of micro-porous PVA scaffolds fabricated by freeze drying method. The impact of molecular weight of PVA, surfactant concentration, foaming time, and stirring speed on pore characteristics, mechanical properties, swelling ratio, and rate of degradation of the scaffolds was characterized. Results show that a foaming time of 60s, a stirring speed of 1000rpm, and a surfactant concentration of 5% yielded scaffolds with rigid structure but with interconnected pores. Study also demonstrated that increased foaming time increased porosity and swelling ratio and reduced the rigidity of the samples.

Facile fabrication of poly(methyl methacrylate) monolith via thermally induced phase separation by utilizing unique cosolvency

Poly(methyl methacrylate) (PMMA) monoliths with a three-dimensional continuous interconnected porous structure in a single piece were fabricated via thermally induced phase separation (TIPS) by utilizing unique cosolvency toward PMMA. We found that PMMA was soluble in a mixture of non-solvents (ethanol and water) at 60 °C. Cooling the solution resulted in formation of a monolith having interconnected pores. Cross-sectional analysis using scanning electron microscopy (SEM) showed a continuous porous network with submicron-sized skeleton. The pore size of the monolith was readily controlled by varying the fabrication parameters such as the polymer concentration and molecular weight, the cooling temperature and the solvent composition. The cross-section of the monolith showed high water repellency. The PMMA monolith was also obtained in a mixture of isopropanol and water with an appropriate solvent ratio.

Fabrication of Polycarbonate and Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) Blend Monolith via Non-solvent-induced Phase Separation Method

Abstract A blend monolith of polycarbonate and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with a three-dimensional continuous interconnected porous structure is fabricated through a non-solvent-induced phase separation (NIPS) method. By tuning the solvent composition for NIPS, the monolith of the two immiscible polymers is obtained successfully. The blend monolith, with its large surface area and high thermal stability, may find use in various potential applications of porous materials.

Facile fabrication of polycarbonate monolith by non-solvent induced phase separation method

Polycarbonate (PC) monoliths with three-dimensional continuous interconnected porous structure in a single piece are fabricated via non-solvent induced phase separation (NIPS) for the first time. The morphology of fabricated monolith is observed through SEM, the surface area is determined by BET method and the thermal property is measured via DSC. The pore and skeleton sizes of the monolith are readily controlled by varying the fabrication parameters such as the polymer concentration and molecular weight, the standing temperature and the solvent composition. The PC monolith possesses relatively large surface area and sharp melting point at 232 °C. These monoliths with high thermal stability can offer various potential applications of functional materials.

Carbon nanotube sponge filters for trapping nanoparticles and dye molecules from water

Carbon nanotube sponges show effective filtration for nanoparticles and dye molecules with different sizes and concentrations from water. The three-dimensional interconnected porous structure formed by entangled nanotubes can trap nanoparticles and molecules by physisorption without the need for chemical functionalization. The sponge filters are potential environmental materials for water treatment.

Conversion of sea urchin spines to Mg-substituted tricalcium phosphate for bone implants

The skeleton of sea urchin spines is composed of large single crystals of Mg-rich calcite, which have smooth, continuously curved surfaces and form a three-dimensional fenestrated mineral network. Spines of the echinoids Heterocentrotus trigonarius and Heterocentrotus mammillatus were converted by the hydrothermal reaction at 180 °C to bioresorbable Mg-substituted tricalcium phosphate (β-TCMP). Due to the presence of Mg in the calcite lattice, conversion to β-TCMP occurs preferentially to hydroxyapatite formation. The converted β-TCMP still maintains the three-dimensional interconnected porous structures of the original spine. The main conversion mechanism is the ion-exchange reaction, although there is also a dissolution–reprecipitation process that forms some calcium phosphate precipitates on the surfaces of the spine network. The average fracture strength of urchin spines and converted spines (β-TCMP) in the compression tests are 42 and 23 MPa, respectively. In vivo studies using a rat model demonstrated new bone growth up to and around the β-TCMP implants after implantation in rat femoral defects for 6 weeks. Some new bone was found to migrate through the spine structural pores, starting from the outside of the implant through the pores at the edge of the implants. These results indicate good bioactivity and osteoconductivity of the porous β-TCMP implants.

Synthesis of Graphitic Ordered Macroporous Carbon with a Three-Dimensional Interconnected Pore Structure for Electrochemical Applications

In this study, ordered macroporous carbon with a three-dimensional (3D) interconnected pore structure and a graphitic pore wall was prepared by chemical vapor deposition (CVD) of benzene using inverse silica opal as the template. Field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectrometry, nitrogen adsorption, and thermogravimetric analysis techniques were used to characterize the carbon samples. The electrochemical properties of the carbon materials as a carbon-based anode for lithium-ion batteries and as a Pt catalyst support for room-temperature methanol electrochemical oxidation were examined. It was observed that the CVD method is a simple route to fabrication of desired carbon nanostructures, affording a carbon with graphitic pore walls and uniform pores. The graphitic nature of the carbon enhances the rate performance and cyclability in lithium-ion batteries. The specific capacity was found to be further improved when SnO(2) nanoparticles were supported on the carbon. The specific activity of Pt catalyst supported on the carbon materials for room-temperature methanol electrochemical oxidation was observed to be higher than that of a commercial Pt catalyst (E-TEK).

Pore structure analysis of particle beds for fluid transport simulation during filtration

Accurate assessment of the transport properties of porous media (in our case, filter cake) is of major importance in the development of improved filtration processes. Implications from these studies are important in the design and operation of filtration equipment in order to enhance the efficiency of this important solid–liquid separation process. The microstructure and connectivity of pore space are important features to describe detailed fluid flow phenomena in filter cake during fine particle filtration. In this regard, 3D characterization of pore structure is essential. The pore structure has to be described by parameters which are of special relevance to the interpretation of fluid transport phenomena. These parameters should be based on directly measured variables of the pore system and not inferred from indirect variables (such as those determined empirically from transport processes) valid only for a particular pore structure. In this way, fundamental relationships between pore structure and fluid transport at the microstructure level can be described. In order to achieve this level of sophistication, the three-dimensional interconnected pore structure of filter cake must be determined. Study of fluid transport phenomena in filter cake using X-ray microtomography (XMT) to characterize the complex three-dimensional pore geometry is discussed. On this basis, the lattice Boltzmann (LB) method is used to simulate fluid flow and to begin to establish a fundamental relationship between pore microstructure and effective transport coefficients. For example, can network analysis using skeletonization procedures be used to confirm fundamental relationships that might be developed? Eventually then, with this detailed model, design and operating variables could be optimized for improved filtration efficiency.