Nanoporous Scaffolds Research Articles

Electrophoretic Deposition of Nanoporous Oxide Coatings from Concentrated CuO Nanoparticle Dispersions.

Electrophoretic deposition (EPD) of nanoporous oxide coatings is an interesting research avenue owing to the experimental simplicity and broad scope of applications and materials. In this study, the properties of concentrated (up to 5000 mg/L), nonaqueous CuO nanoparticle (NP) dispersions were tailored to produce micrometer-thick, nanoporous CuO films by EPD. In particular, we performed a systematic investigation of the electrophoretic mobilities and size distributions of dispersed CuO aggregates and developing agglomerates in different organic solvents for concentrations ranging from 50 to 5000 mg/L with and without surfactant addition. Time-resolved dynamic light scattering analyses showed that aggregate mobilities and agglomeration rates decrease with increasing hydrocarbon chain length of the organic solvent (from ethanol to hexanol) and thus with increasing viscosity. The highest electrophoretic mobility was obtained for CuO NP aggregates and agglomerates dispersed in ethanol as a solvent. However, the addition of ≥0.5 wt % acetylacetone as a surfactant is required to stabilize these dispersions for subsequent EPD and at the same time introduce a net attractive (electrostatic) interaction between neighboring agglomerates on the substrate to promote layer formation during the EPD step. The produced micrometer-thick nanoporous CuO coatings can serve as high surface area nanostructured materials or nanoporous scaffolds in catalysis, combustion, propellants, and nanojoining.

N-Doped Nanoporous Carbon Scaffold As an Electrocatalyst for CO2 Reduction

The rising level of CO2 in the atmosphere poses a major threat to our global climate [1]. Renewable energy are promising alternatives but the utilization of renewable energy is challenging because of its intermittency. The key solution is to develop an energy storage system that can store energy and then release it as needed. CO2 reduction reaction (CO2RR) uses abundant CO2 present in the atmosphere and renewable energy as the input power. Therefore, increasing interest has been focused on electrochemical routes to transform CO2 into useful products. However, the reduction of CO2 is thermodynamically and kinetically unfavorable. To overcome the energy barrier of CO2RR, the development of high efficiency and high selectivity catalysts is a key goal of CO2RR research.Metallic catalysts have attracted much attention for CO2RR and have achieved some successes. However, most metallic catalysts exhibit large CO2RR overpotentials and insufficient selectivity. Also, the high price of noble metals is a key obstacle to scale-up and commercialization of these materials for CO2RR.Carbon is a very promising candidate to advance CO2RR due to its high specific surface areas and good conductivity. However, carbon atoms are electrically neutral and therefore it is difficult to activate the CO2 molecules and adsorb the intermediate. Therefore, it is necessary to develop novel carbon catalysts to enhance their catalytic activity for CO2RR. Nitrogen is the most commonly used carbon doping atom due to its high electronegativity, which leads to polarization of the adjacent carbon atoms, thus enhancing the electronic/ionic conductivity [2]. Many carbon materials, such as carbon nanotubes and graphene, have been doped with N and investigated as CO2RR catalysts [3][4], with some N-doped materials exhibiting a 85% Faradaic efficiency towards CO production[5].In this work, a nitrogen-doped templated nanoporous carbon scaffold (N-doped NCS) was investigated as a catalyst material for electrochemical CO2 reduction. The NCS is a novel, templated, binder-free, self-supported, fully tunable mesoporous carbon material[6] that gives a high active site density and good conductivity.NCS material, having a pore size of either 12, 50 or 85 nm, was heated in NH3 gas at 700 °C for 7 hours to prepare N-doped NCS. SEM and TEM were used to confirm the NCS morphology, while XPS, EDX and elemental analysis were used to determine the N content of the NCS material. The electrochemical performance of the N-doped NCS was carried out first using CV in CO2 sat. 0.1 M KHCO3 in a glass cell. After that, a membrane electrode assembly (MEA) CO2 electrolyzer was used to determine the CO2 reduction activity. An N-doped NCS (IrO2-coated) was used as the anode and an anion exchange membrane (AEM) was used as the separator during CO2 electrolysis, with humidified CO2 gas used at the cathode side. The gas products were collected from the cathode outlet and injected into a gas chromatography system for analysis. No liquid products were observed in the solution that was released to the cell outlet.The performance of N-doped NCS will be presented based on the results obtained in various solution-flow cell configurations. Effect of N-doped NCS preparation optimization will also be discussed. Based on both the CV results and the MEA CO2 electrolyzer data, the onset potential of CO2RR was comparable to what has been reported by others for N-doped carbons, but the high internal surface area of the NCS, combined with its high extent of N doping, may give the N-doped NCS some advantages. A maximum 90% FECO was achieved and the stability of the catalytic material was also studied in the flow cell systems.

Pt/Nanoporous Carbon Scaffold Catalyst Layer for Use in Symmetrical Proton Exchange Membrane Fuel Cells

Carbon microstructures are an essential component of both the cathode and anode catalyst layer in PEMFCs, typically serving as the catalyst support [1], and it is known that the carbon porosity, surface area, and its hydrophobicity/hydrophilicity have a significant effect on electrocatalytic activity and transport issues. This is due to the impact of the carbon on catalyst dispersion, Nafion distribution, electronic conduction, and mass transport limitations [2-4]. Typically, carbon black is used as the catalyst support because of its high surface area, low cost, good electrical conductivity [4,5], but it is susceptible to corrosion and does not pack uniformly, thus resulting in uncontrolled pathways for reactants/products through the catalyst layer [6,7]. Recently, there has been an increasing interest in using mesoporous carbons as catalyst supports for fuel cell application, due to the better accessibility of the internal carbon surfaces, and the tethered Pt nanoparticles, to the reactants, and better mass transport of reactants and products during fuel cell operation [8,9].Our team has recently developed a novel nanoporous carbon scaffold (NCS), which is self-supported, scalable, and highly tunable (its monodisperse pore size can be controllably varied from 10 to 100 nm), giving specific surface areas of 200 to 600 m2 g-1. These films are fully percolating, have very low tortuosity and a 90% porosity, good electronic conductivity of 2-10 S cm-1 and are robust [10]. While prior work has involved the preparation and testing of an MEA that contained Pt/NCS on the cathode side of the separator, in this work, the focus was on the first-time testing of a symmetrical cell with Pt/NCS on both sides of a Nafion membrane. Here, the Pt nanoparticles (NPs) were deposited throughout the NCS material by wet impregnation of the chloroplatinic acid precursor (Fig. 1) and then infiltrated with Nafion by drop-casting. The thickness of the Pt/NCS films used in the current study was 25 ± 2 μm, the NCS pore size was 85 nm, and the Pt loading at the cathode was < 1 mg Pt cm-2. The Nafion®117 membrane was sandwiched between two NCS catalyst layers by hot pressing and the performance of these new symmetrical MEAs was evaluated in a fuel cell test station using different temperatures. This presentation will focus on the performance of the symmetrical MEA design in comparison to conventional ink-deposited systems, as well as the durability of these novel materials. Because the NCS has such a uniform structure, discussion will also be focused on the changes observed to the carbon itself as well as to the Pt NP size and distribution after testing under PEMFC conditions.

Ultra-High-Rate Pseudocapacitive Energy Storage in Three-Dimensional Nanoporous Gold/Silver Oxide Composites through Oxidation/Reduction of Silver(I) Oxide to Silver (III) Oxide in Non-Aqueous Electrolytes

Charge storage in pseudocapacitive materials occurs through electron transfer (i.e. faradaic current) involving oxidation and reduction reactions. This process is usually extremely fast because the reactions take place near the surface of the material, meaning the species involved diffuse over short distances. Ionic species such as H+, OH-, Li+, and Na+ commonly used to store charge in pseudocapacitive materials are usually “foreign” elements in the materials. In this talk, I will demonstrate a pseudocapacitive charge storage approach where the ionic species is part of the material. Here we use Ag+ as the working ion in a non-aqueous electrode and silver (I) oxide grown on a three-dimensional nanoporous gold scaffold as the storage medium. Pseudocapacitive charge storage occurs through electrochemical oxidation/reduction of silver (I) oxide to silver (III) oxide at scan rates as high as 1000 mV/s. These high rates are justified by (i) the intrinsic nature of the working ion (Ag+), which is better accommodated by the host silver oxide material as opposed to foreign ions, and (ii) the excellent electronic conductivity provided by the 3D metallic scaffold current collector.

Poly(lactic-co-glycolic acid)-bioactive glass composites as nanoporous scaffolds for bone tissue engineering: In vitro and in vivo studies.

The aim of the present study was to investigate the feasibility of using composite scaffolds of poly(lactic-co-glycolic acid) (PLGA) and bioactive glass (BG) to repair bone defects. PLGA/BG composite scaffolds were prepared by thermally-induced phase separation. Scanning electron microscopy (SEM) was used to study the morphology, and liquid (absolute ethanol) replacement was used to calculate the porosity of the scaffold. The biocompatibility and degradation of the scaffold were determined using human osteosarcoma cell line MG-63 and animal experiments. SEM showed that the scaffold had a nanofibrous three-dimensional network structure with a fiber diameter of 160–320 nm, a pore size of 1–7 µm, and a porosity of 93.048±0.121%. The scaffold structure was conducive to cell adhesion and proliferation. It promoted cell osteogenesis and could be stably degraded in vivo.

Biofabrication of bacterial nanocellulose scaffolds with complex vascular structure

Bacterial nanocellulose (BNC) has proven to be an effective hydrogel-like material for different tissue engineering applications due to its biocompatibility and good mechanical properties. However, as for all biomaterials, in vitro biosynthesis of large tissue constructs remains challenging due to insufficient oxygen and nutrient transport in engineered scaffold-cell matrices. In this study we designed, biofabricated and evaluated bacterial nanocellulose scaffolds with a complex vascular mimetic lumen structure. As a first step a method for creating straight channeled structures within a bacterial nanocellulose scaffold was developed and evaluated by culturing of Human Umbilical Vein Endothelial Cells (HUVECs). In a second step, more complex structures within the scaffolds were produced utilizing a 3D printer. A print mimicking a vascular tree acted as a sacrificial template to produce a network within the nanoporous bacterial nanocellulose scaffolds that could be lined with endothelial cells. In a last step, a method to produce large constructs with interconnected macro porosity and vascular like lumen structure was developed. In this process patient data from x-ray computed tomography scans was used to create a mold for casting a full-sized kidney construct. By showing that the 3D printing technology can be combined with BNC biosynthesis we hope to widen the opportunities of 3D printing, while also enabling the production of BNC scaffolds constructs with tailored vascular architectures and properties.

Nanoconfining Optoelectronic Materials for Enhanced Performance and Stability

The solution processing of optoelectronic active layers promises to usher in a new era of technologies, from rollable displays to smart textiles, but critical challenges remain in the processing of these materials. While solution-based deposition of these compounds, including organic small-molecules and polymers and metal–halide perovskites, is key to driving down manufacturing costs, the rapid, uncontrolled nature of solution processing invariably results in the formation of kinetically trapped films, with heterogeneities and defects spanning multiple length scales that degrade device performance. Given such finite time, usually on the order of seconds, for molecules to organize as solvent evaporates from the active layers, the use of nanoporous scaffolds to select for desired crystallization outcomes is a promising approach to addressing this critical issue. As the size of crystals decreases, their surface free energy plays an increasingly important role in dictating their morphology and structure. By c...

Conductive nanostructured Si biomaterials enhance osteogeneration through electrical stimulation

It is well known that the differentiation of stem cells is affected by the cell culture medium, the scaffold surface and electrochemical signals. However, stimulation of patterned biomaterials seeded with stem cell cultures has not been explored. Herein the effect of electrical stimulation on osteogenic differentiation of rat bone marrow-derived mesenchymal stem cells (rBMSCs) cultured on solid and nanoporous micropyramid patterned Si surfaces was evaluated. It was found that both stimulation and scaffold patterning significantly enhanced osteo-differentiation. The stimulated nanoporous micropyramid scaffolds were more promising compared to the stimulated solid micropyramid surfaces, as they significantly promoted the osteogenic differentiation of rBMSCs via BMP/Smad signaling pathway. Particularly, as compared to the unstimulated patterned biomaterials, the stimulated patterned scaffolds allowed for a significant increase in core binding factor alpha l, alkaline phosphatase, the alpha l chain of type I Col, osteocalcin, and osteonectin, all of which are characteristic for osteo-differentiation. The proposed combination of electrical stimulation with scaffold patterning may provide novel promising strategies for bone tissue engineering and regenerative medicine.

Three-dimensional printed tissue engineered bone for canine mandibular defects

BackgroundThree-dimensional (3D) printed tissue engineered bone was used to repair the bone tissue defects in the oral and maxillofacial (OMF) region of experimental dogs. Material and methodsCanine bone marrow stromal cells (BMSCs) were obtained from 9 male Beagle dogs and in vitro cultured for osteogenic differentiation. The OMF region was scanned for 3D printed surgical guide plate and mold by ProJet1200 high-precision printer using implant materials followed sintering at 1250 °C. The tissue engineered bones was co-cultured with BASCs for 2 or 8 d. The cell scaffold composite was placed in the defects and fixed in 9 dogs in 3 groups. Postoperative CT and/or micro-CT scans were performed to observe the osteogenesis and material degradation. ResultsBMSCs were cultured with osteogenic differentiation in the second generation (P2). The nanoporous hydroxyapatite implant was made using the 3D printing mold with the white porous structure and the hard texture. BMSCs with osteogenic induction were densely covered with the surface of the material after co-culture and ECM was secreted to form calcium-like crystal nodules. The effect of the tissue engineered bone on the in vivo osteogenesis ability was no significant difference between 2 d and 8 d of the compositing time. ConclusionsThe tissue-engineered bone was constructed by 3D printing mold and high-temperature sintering to produce nanoporous hydroxyapatite scaffolds, which repair in situ bone defects in experimental dogs. The time of compositing for tissue engineered bone was reduced from 8 d to 2 d without the in vivo effect.

(Invited) Self-Supported Nanoporous Carbon Scaffold As a Novel Material for Use in Fuel Cells and Electrolysis Cells

Several years ago, our group pioneered the use of mesoporous colloid imprinted carbon (CIC) powders (1-3) for a wide variety of electrochemical applications, including as catalyst supports in PEM fuel cells, as electrodes in supercapacitors and redox-flow batteries, sensors, and for water deionization. The CICs have an ordered, close-packed internal porous (spherical) structure and are typically prepared by imprinting a mesophase carbon pitch powder with a colloidal silica template, followed by carbonizing the imprinted pitch and then removal of the silica template. One of the biggest advantages associated with the CICs is the tunability of their pores, controlled by the size of the silica colloid (from ca. 10 to 100’s of nanometers) used in the templating step, with our CICs having pore sizes ranging from ca. 8 – 100 nm. This pore size is ideal for the deposition of catalytic nanoparticles inside the pores, as well as the infiltration of an ionomer phase, such as Nafion, for use in PEM fuel cell catalyst layers. However, one disadvantage of the CIC powders, especially in PEMFC applications, is that there are variable pore sizes between the CIC particles and thus varying access to Nafion and water. Also, the use of powders makes it challenging to image the same particle or region before and after catalyst testing to determine any changes that have occurred, including carbon corrosion.Partly for these reasons, as well as the desire for improved reproducibility of the catalyst layer microstructure, our team recently developed a novel, self-supported, nanoporous carbon scaffold (NCS) material (4,5) for use in PEMFCs, but also in electrolysis systems. The preparation method used to produce the NCS membranes is similar to what was used by our group to make the CIC powders, employing mesophase pitch as the carbon precursor and imprinting with silica colloids of controlled diameter. The pore size can be similarly tailored (from 5 nm to > 100 nm) and the thickness can be controlled to 1-100 microns, with the NCS being formed using a tape casting method. We have also successfully modified the internal wettability of the NCS through surface functionalization, examples being a hydrophilic group (e.g., -PhSO3H) or a hydrophobic group (e.g., PhF5), and have also successfully loaded the NCS with Pt nanoparticles using a variety of approaches. The electrochemistry of the NCS materials, carried out in aqueous solutions using 3-electrode circuitry, shows that the internal surface of the NCS is fully percolating, with all of the pores being 3-D interconnected. Similar to the CICs, the ink bottle-shaped pores within the NCS material are connected bypore necks, which are typically 25-50% of the diameter of the corresponding spherical pores. The necks may hinder mass transport within the NCS during device operation and thus efforts have been made to tailor the pore neck size. The performance of the NCS material within a full PEMFC MEA has also been determined as a function of NCS pore and pore neck size. As well, the behavior of the NCS material in a flow through mode, including for CO2reduction in an electrolysis cell, has been demonstrated, while also having been characterized using nitrogen gas sorption, field emission microscopy (FE-SEM), transmission electron microscopy (TEM), 3-D TEM, TEM tomography, and elemental analysis.

Amorphous nanoporous WOx modification for stability enhancement and hysteresis reduction in TiO2-based perovskite solar cells

This work focuses on reducing the hysteresis and improving the stability of TiO2-based perovskite solar cells. A simple slow hydrolysis and rapid evaporation (SHRE) method was developed to deposit amorphous nanoporous WOx up on the TiO2 base at low temperature to form a TiO2-WOx bilayer as composite electron transport materials (ETMs) for efficient CH3NH3PbI3 solar cells. In the composite bilayers, the nanoporous WOx sublayer functions as an effective scaffold to modify the electrical contact between the perovskite and TiO2, and also as an anti-reflective film to enhance light transmittance. The WOx modifying layer much reduces the serious hysteresis and the dependence of power conversion efficiencies (PCEs) on the J–V scan rates. Moreover, it has also significantly enhanced the long-term stability of solar cells. The functioning mechanism for the WOx modifying layer in the TiO2-WOx composite ETMs is explored and interpreted in terms of nanoporous inorganic scaffolds and also the salutary effect of capacitive currents from the high-capacitance WOx.

3D-Printed Nanoporous Scaffolds Impregnated with Zoledronate for the Treatment of Spinal Bone Metastases

ABSTRACT:Zoledronate (Zol) is a bone-preserving/ anti-tumoral drug that is widely used for the treatment of many cancers including spinal bone metastases. High systemic Zol doses required to elicit an adequate effect in the spine often lead to significant side effects, limiting its prolonged use and effectiveness. Here, we aim to provide an alternative strategy to locally deliver Zol at the tumor site. We show that nanoporous 3D-printed scaffolds can be loaded with Zol and possess the ability to release Zol (10-28%) over a sustained period. Additionally, we demonstrate that Zol-impregnated scaffolds, mostly Gel Lay, impair the proliferation of the prostate cancer cell line LAPC4 and the prostate-induced bone metastasis cells in vitro. 3D-printed nanoporous polymers offer a novel and versatile opportunity for potential local delivery of drugs in future clinical settings. These polymers can decrease systemic exposure and related side effects of Zol while at the same time concentrating the drug effect at the tumor site thereby inhibiting tumor proliferation. Also, these scaffolds could be co-printed or coupled with other materials to produce custom implants that offer better structural support for bone growth at the tumor site following resection.

Highly Efficient and Environmentally Stable Flexible Color Converters Based on Confined CH3NH3PbBr3 Nanocrystals.

In this work, we demonstrate a synthetic route to attain methylammonium lead bromide (CH3NH3PbBr3) perovskite nanocrystals (nc-MAPbBr3, 1.5 nm < size < 3 nm) and provide them with functionality as highly efficient flexible, transparent, environmentally stable, and adaptable color-converting films. We use nanoparticle metal oxide (MOx) thin films as porous scaffolds of controlled nanopores size distribution to synthesize nc-MAPbBr3 through the infiltration of perovskite liquid precursors. We find that the control over the reaction volume imposed by the nanoporous scaffold gives rise to a strict control of the nanocrystal size, which allows us to observe well-defined quantum confinement effects on the photo-emission, being the luminescence maximum tunable with precision between λ = 530 nm (green) and λ = 490 nm (blue). This hybrid nc-MAPbBr3/MOx structure presents high mechanical stability and permits subsequent infiltration with an elastomer to achieve a self-standing flexible film, which not only maintains the photo-emission efficiency of the nc-MAPbBr3 unaltered but also prevents their environmental degradation. Applications as adaptable color-converting layers for light-emitting devices are envisaged and demonstrated.

Three-dimensional nanoporous polyacrylonitrile-based carbon scaffold for effective separation of oil from oil/water emulsion

The hydrophobic nature of the substances has served as important tools for governing the spatial behaviors of various fibrous substances depending on their affinities to oils or organic liquids. Herein, electrospun two-dimensional (2D) polyacrylonitrile (PAN) fiber mat was converted into three-dimensional (3D) mesh by hydrogen gas foaming technique using aqueous sodium borohydride (NaBH4) solution, which on heating at high temperature under a nitrogen atmosphere produced ultra-light, low density, hydrophobic 3D carbon scaffold with distinct affinities to oil phases. The fibrous materials were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FT-IR) spectra. Specific surface area and porosity of the fiber were analyzed by the Brunauer-Emmett-Teller (BET) technique. The carbon scaffold exhibit dominance as absorbents for selectively separating oils such as diesel, canola oil, xylene, and n-hexane with absorption capacity from 68.71 g g−1 to 131.33 g g−1. More interestingly, the absorbed oils were readily collected by simple mechanical squeezing and the recovered 3D carbon scaffold could be reused for the successive absorptions. This carbon scaffold could be a versatile platform to offer a kind of efficient and selective absorbent material for absorption of oils or organic liquids from the water.

Three-Dimensional Carbon-Honeycomb as Nanoporous Lithium and Sodium Deposition Scaffold

Using the density functional theory method, we demonstrate that the recently synthesized three-dimensional carbon-honeycomb (C-honeycomb) can serve as a promising nanoporous scaffold for both lithi...

Nanoporous 3D-Printed Scaffolds for Local Doxorubicin Delivery in Bone Metastases Secondary to Prostate Cancer.

The spine is the most common site of bone metastasis, often originating from prostate, lung, and breast cancers. High systemic doses of chemotherapeutics such as doxorubicin (DOX), cisplatin, or paclitaxel often have severe side effects. Surgical removal of spine metastases also leaves large defects which cannot spontaneously heal and require bone grafting. To circumvent these issues, we designed an approach for local chemotherapeutic delivery within 3D-printed scaffolds which could also potentially serve as a bone substitute. Direct treatment of prostate cancer cell line LAPC4 and patient derived spine metastases cells with 0.01 µM DOX significantly reduced metabolic activity, proliferation, migration, and spheroid growth. We then assessed uptake and release of DOX in a series of porous 3D-printed scaffolds on LAPC4 cells as well as patient-derived spine metastases cells. Over seven days, 60–75% of DOX loaded onto scaffolds could be released, which significantly reduced metabolic activity and proliferation of both LAPC4 and patient derived cells, while unloaded scaffolds had no effect. Porous 3D-printed scaffolds may provide a novel and inexpensive approach to locally deliver chemotherapeutics in a patient-specific manner at tumor resection sites. With a composite design to enhance strength and promote sustained drug release, the scaffolds could reduce systemic negative effects, enhance bone repair, and improve patient outcomes.

Tissue Engineering Scaffolds Fabricated in Dissolvable 3D-Printed Molds for Patient-Specific Craniofacial Bone Regeneration.

The current gold standard treatment for oral clefts is autologous bone grafting. This treatment, however, presents another wound site for the patient, greater discomfort, and pediatric patients have less bone mass for bone grafting. A potential alternative treatment is the use of tissue engineered scaffolds. Hydrogels are well characterized nanoporous scaffolds and cryogels are mechanically durable, macroporous, sponge-like scaffolds. However, there has been limited research on these scaffolds for cleft craniofacial defects. 3D-printed molds can be combined with cryogel/hydrogel fabrication to create patient-specific tissue engineered scaffolds. By combining 3D-printing technology and scaffold fabrication, we were able to create scaffolds with the geometry of three cleft craniofacial defects. The scaffolds were then characterized to assess the effect of the mold on their physical properties. While the scaffolds were able to completely fill the mold, creating the desired geometry, the overall volumes were smaller than expected. The cryogels possessed porosities ranging from 79.7% to 87.2% and high interconnectivity. Additionally, the cryogels swelled from 400% to almost 1500% of their original dry weight while the hydrogel swelling did not reach 500%, demonstrating the ability to fill a defect site. Overall, despite the complex geometry, the cryogel scaffolds displayed ideal properties for bone reconstruction.

Nanoporous diopside modulates biocompatibility, degradability and osteogenesis of bioactive scaffolds of gliadin-based composites for new bone formation.

IntroductionIt is predicted that with increased life expectancy in the whole world, there will be a greater demand for synthetic biomedical materials to repair or regenerate lost, injured or diseased tissues. Natural polymers, as biomedical materials, have been widely applied in the field of regenerative medicine.Materials and methodsBy incorporation of nanoporous diopside bioglass (nDPB) into glia-din (GL) matrix, macro–nanoporous scaffolds of nDPB/GL composites (DGC) were fabricated by method of solution compressing and particles leaching.ResultsThe results revealed that the DGC scaffolds possessed well-interconnected macropores of 200–500 μm and nanopores of 4 nm, and the porosity and degradability of DGC scaffolds remarkably increased with the increase in nDPB content. In addition, in vitro cell experiments revealed that the adhesion and growth of MC3T3-E1 cells on DGC scaffolds were significantly promoted, which depended on nDPB content. Moreover, the results of histological evaluations confirmed that the osteogenic properties and degradability of DGC scaffolds in vivo significantly improved, which were nDPB content dependent. Furthermore, the results of immunohistochemical analysis demonstrated that, with the increase in nDPB content, the type I collagen expression in DGC scaffolds in vivo obviously enhanced, indicating excellent osteogenesis.Discussion and conclusionThe results demonstrated that the DGC scaffolds containing 30 wt% nDPB (30nDGC) exhibited good biocompatibility and new bone formation ability, which might have a great potential for applications in bone regeneration.

Investigation of Nanoporous Carbon Scaffold with Ordered Pore Structure As Microporous Layer for PEM Fuel Cells

The microporous layer (MPL) is a key component of the membrane electrode assembly (MEA) of a polymer electrolyte membrane fuel cell (PEMFC). Historically, the MPL has been prepared by applying a slurry of carbon particles and Teflon onto the carbon paper. Together, the carbon paper with the MPL on it is known as the gas diffusion layer. The MPL fabricated by the aforementioned method results in a random pore structure varying both in pore size (ranging 20-200 nm) and wettability (hydrophobic and hydrophilic). Although the primary role of the MPL is thought to improve water management, delineation of the effect of pore size from wettability becomes difficult in a physically and chemically heterogenous porous structure of a conventional MPL. Recently, the Birss group has developed nanoporous carbon scaffolds (NCS) with an inverse opal structure that has well-defined and tunable pore sizes. The wettability of the internal surface of the NCS films can also be altered by functionalization, from highly hydrophilic to hydrophobic. We have successfully integrated the NCS as an MPL in PEMFCs and evaluated its performance under low and high RH operations. The effect of pore size and wettability of NCS-based MPLs on the performance of PEMFCs will be presented in this talk.

(Invited) Ordered, Nanoporous Carbon Scaffolds (NCS) for Use in Energy Conversion and Related Applications

Nanoporous carbon materials are of significant interest for use in various electrochemical applications, including as catalyst supports in fuel cells, sensors, and as electrodes in supercapacitors, redox flow batteries, and lithium batteries. The nanoporous carbons under study in our group include both soft- and hard-templated ordered mesoporous carbons as well as colloid-imprinted carbons (CICs). While all of these carbons have well-controlled and narrow pore size distributions and high surface areas, they are all produced in the form of powders, which can cause problems when used in electrochemical devices. This is due to challenges in relation to reproducible powder packing and binders must normally be used to hold particles together. The binder may then block ions and electrons from passing through the pores and between particles, thus preventing full utilization of their surfaces. Furthermore, fine particulates may also cause health concerns (e.g., PM2.5). In order to overcome these challenges, our research group has focussed on the development of a series of novel nanoporous carbon scaffolds (NCS membranes), possessing a fully ordered and monodisperse porous structure. The NCS materials have pore diameters in the range of 5 to 100’s of nm and contain a fully inter-connected nano/macro-porous network (porosity ~80%). These NCS membranes, which can be made to be 0.5 - 100’s of microns in thickness, also have a very good conductivity of 2-10 S/cm and are fully electrochemically accessible in aqueous solutions, exhibiting a capacitance of 40-100 F/g. The fabrication method used to form these novel NCS membranes is also environmentally friendly and has been demonstrated to be applicable for manufacturing at large scale. Due to these exceptional properties, the NCS materials are of great interest for use in a wide range of clean energy and water remediation products. In this presentation, the preparation and properties of these materials will be discussed, including the successful loading of the NCS membranes with catalytic metal nanoparticles and internal surface functionalization. An overview of the application of the NCS material in PEM fuel cells, redox flow batteries, capacitors, and in nanofiltration applications will also be presented.