Optimal Pore Size Research Articles

Thermoreversible poly(ethylene glycol)-g-chitosan hydrogel as a therapeutic T lymphocyte depot for localized glioblastoma immunotherapy.

The outcome for glioblastoma patients remains dismal for its invariably recrudesces within 2 cm of the resection cavity. Local immunotherapy has the potential to eradicate the residual infiltrative component of these tumors. Here, we report the development of a biodegradable hydrogel containing therapeutic T lymphocytes for localized delivery to glioblastoma cells for brain tumor immunotherapy. Thermoreversible poly(ethylene glycol)-g-chitosan hydrogels (PCgels) were optimized for steady T lymphocyte release. Nuclear magnetic resonance spectroscopy confirmed the chemical structure of poly(ethylene glycol)-g-chitosan, and rheological studies revealed that the sol-to-gel transition of the PCgel occurred around ≥32 °C. T lymphocyte invasion through the PCgel and subsequent cytotoxicity to glioblastoma were assessed in vitro. The PCgel was shown to be cellular compatible with T lymphocytes, and the T lymphocytes retain their anti-glioblastoma activity after being encapsulated in the PCgel. T lymphocytes in the PCgel were shown to be more effective in killing glioblastoma than those in the Matrigel control. This may be attributed to the optimal pore size of the PCgel allowing better invasion of T lymphocytes. Our study suggests that this unique PCgel depot may offer a viable approach for localized immunotherapy for glioblastoma.

Preparation of N-doped activated carbons for electric double-layer capacitors from waste fiberboard by K2CO3 activation

N-doped activated carbons for electric double-layer capacitors were prepared from waste medium density fiberboard using K 2 CO 3 activation. The effects of carbonization temperature, activation temperature, activation time and K 2 CO 3 /coke mass ratios on surface chemical compositions, pore structure and electrochemical performance of the resulting activated carbons were investigated. Results indicated that the activated carbons had nitrogen contents from 0.93 to 2.86%, Brunauer–Emmett–Teller specific surface areas from 569 to 1027 m 2 /g and specific capacitances from 147 to 223 F/g, depending on carbonization and activation conditions. The maximum specific capacitance was attributed to a high surface area, optimum pore size, large pore volume and high N-5 (the pyrrolic nitrogen and pyridinic nitrogen in association with oxygen functionality) content. [New Carbon Materials 2014, 29(2): 89–95]

Electrochemical desalination of nacl solutions by electrosorption on nano-porous carbon aerogel electrodes

<div> <p>The objective of this study is to elucidate the efficiency of electrosorption on desalination of aqueous NaClsolution using nano-structured carbon aerogel electrodes. The experiments were performed in an electrosorption cell consisting of a pair of carbon aerogel sheets separated by a 0.5cm spacer. The electrosorption performance is investigated with different applied voltages and solution concentrations. It increases with increasing applied voltage, higher concentration gradient and less double-layer overlapping effect. Under the experimental conditions at the optimum applied voltage of 1.2 Volt and initial NaCl concentration 100 - 1000 mg l<sup>-1</sup>, the electrosorption capacity was found to be 5.20 - 14.22 mg NaCl/g carbon aerogel.Na<sup>+</sup> and Cl<sup>-</sup> ions are electro-absorbed at the electrical double layer without electron transfer redox reactions at anode and cathode. The good electrosorption performance of carbon aerogel electrodes might be attributed to their high specific area, high electrical conductivity, chemical inertness and optimal pore size distribution for the passage and easy movement of ions during electrosorption and electrodesorption. The process is reversible, as the electrode charge/discharge procedure can be repeated innumerable times without any significant loss of salt sorption capacity in all cycles. </p> </div> <p> </p>

Performance study of ZrO2 ceramic micro-filtration membranes used in pretreatment of DMF wastewater

Three kinds of 19-channel ZrO2 micro-filtration membranes with different pore size were used for pretreatment of dimethylformamide (DMF) wastewater from the polyurethane (PU) synthetic leather factories, which would enter the distillation column for further purification. The effects of membrane pore size, cross flow velocity (CFV) and transmembrane pressure (TMP) on ceramic membrane filtration performances were investigated. Experimental results indicated that the optimum membrane pore size, CFV and TMP were 0.2μm, 3m·s−1 and 0.2MPa, respectively, with the corresponding liquid turbidity removal rate of 99.62% and suspended solid content retention rate of 99.99%. The membrane fouling mechanism was analyzed by resistance in series model. The main resistance derived from the particle adsorption and sedimentation on the membrane surface. The ratio of particle adsorption and sedimentation resistance to total resistance was above 70% for the 0.2μm membrane. The backflushing technology was applied and the effect of backflushing on the permeate flux was studied. The permeate flux eventually increased by 50% with the optimum backflushing pressure of 0.6MPa, backflushing time of 5s and backflushing interval of 20min. A combination cleaning method was used to regenerate the ZrO2 micro-filtration membrane. The pure water flux recovered to 608.2L·m−2·h−1 and flux recovery rate was 96.8% which indicated that the combination cleaning method was effective.

Nitrogen-Doped Hierarchical Porous Carbon Nanowhisker Ensembles on Carbon Nanofiber for High-Performance Supercapacitors

Controlled synthesis of carbon nanomaterials with particular shape, composition, architecture, and doping is very important, yet still a great challenge, for enhancing supercapacitor performance with high energy and power densities and long lifetime. Herein, we demonstrate an interesting process combining surfactantless and templateless wet chemical and post-high-temperature carbonization strategies for obtaining a new class of nitrogen-doped hierarchical porous carbon nanowhisker ensembles supported on carbon nanofibers (NHCNs) with tunable micropores and a nitrogen-doping level for high-performance supercapacitors. Under the optimal pore size and nitrogen doping controlled by carbonization at different temperatures, the NHCNs (NHCNs-750) carbonized at 750 °C shows an optimal specific capacitance of 210.1 F g–1 at 5 mV s–1, which is much higher than other one-dimensional carbon nanostructures (e.g., pure carbon nanofibers (2.6 F g–1) and carbon nanotubes (10.6 F g–1) at 5 mVs–1). NHCNs-750 also showed go...

Influence of electrolyte ion–solvent interactions on the performances of supercapacitors porous carbon electrodes

The development of advanced and safe electrochemical supercapacitors or hybrid supercapacitors combining a battery electrode material such as graphite and a porous carbon electrode implies the use of new electrolytes containing a tetra-alkylammonium or lithium salt dissolved preferentially in a safe and environmentally friendly solvent such as alkylcarbonates. In those systems, the carbon porosity of the activated carbon electrode controls the electrochemical behavior of the whole device. In this work, it is demonstrated that electrolytes containing highly polarizing ions such as Li+ dissolved in polar solvents such as alkylcarbonates do not completely loss their solvation shell at the opposite of what is observed for poorly solvated cations like TEABF4. As a consequence, the optimal carbon pore size for obtaining the largest energy density, while keeping a high power density, is wider when strongly solvated cations, like Li+ are used than for conventional organic electrolytes using acetonitrile as solvent and TEA+ as salt cations. TEA+ cations are easily desolvated and hence are able to penetrate in small pores matching the dimensions of bare ions. The dissimilarity of behavior of alkylcarbonates and acetonitrile based electrolytes highlights the importance of ion–solvent interactions when searching the optimal porous texture for the electrode material.

Preparation of N-doped activated carbons for electric double-layer capacitors from waste fiberboard by K2CO3 activation

N-doped activated carbons for electric double-layer capacitors were prepared from waste medium density fiberboard using K2CO3 activation. The effects of carbonization temperature, activation temperature, activation time and K2CO3/coke mass ratios on surface chemical compositions, pore structure and electrochemical performance of the resulting activated carbons were investigated. Results indicated that the activated carbons had nitrogen contents from 0.93-2.86%, Brunauer-Emmett-Teller specific surface areas from 569 to 1 027 m2/g and specific capacitances from 147 to 223 F/g, depending on carbonization and activation conditions. The maximum specific capacitance was attributed to a high surface area, optimum pore size, large pore volume and high N-5 (the pyrrolic nitrogen and pyridinic nitrogen in association with oxygen functionality) content.

Experimental Study of Precision-Woven Fabrics for Oil-In-Water Emulsion Coalescence: Operating Conditions and Oil Saturation

Fabrics have the advantage of having high mechanical strength and low environmental sensitivity. The Kozeny–Carman equation and its modified form can be used to predict permeability, pressure drop, porosity, and oil saturation, as well as to help find optimum pore size. Experiments were conducted under a wide range of flow velocity, oil concentration, bed length, and pore size. Under optimal conditions, more than 90% of surfactant-stabilized emulsified oil could be removed. Relating the pressure drop and oil saturation with separation efficiency aids in a clearer understanding of emulsion transport in fibrous media and finding the optimum medium and operating conditions.

First-principles studies concerning optimization of hydrogen storage in nanoporous reduced graphite oxide

By means of Density Functional Theory (DFT) calculations we investigated the optimal pore size for reduced graphite oxide (GOH) to favor hydrogen storage and to prevent oxygen interference. The interlayer distance of GOH is found to increase with oxygen content, given by the number of hydroxyl groups. Four types of GOHs were considered, with O/C ratio within a 0.09–0.38 range. In the case of the highest O/C ratio considered, 0.38, a spontaneous redox-reaction between hydroxyl groups delivering a water molecule and an epoxy group was found. Thus, GOHs with high O/C ratio are not recommended for hydrogen storage. In these materials the absorption energy values of hydrogen is in the range of −0.2 and −0.5 eV/molecule, that is within the values expected to allow an efficient storage. The best GOH for hydrogen storage was found to be that with a 0.09 O/C ratio since it has the largest void space and adequate absorption energy, −0.52 eV/molecule. On the other hand, oxygen absorption energy is lower in absolute value than that of hydrogen, which favors absorption of the latter, thus creating adequate conditions for its storage without oxygen interference.

Energy storage of thermally reduced graphene oxide

The energy-storage capacity of reduced graphene oxide (rGO) is investigated in this study. The rGO used here was prepared by thermal annealing under a nitrogen atmosphere at various temperatures (300, 400, 500 and 600 °C). We measured high-pressure H2 isotherms at 77 K and the electrochemical performance of four rGO samples as anode materials in Li-ion batteries (LIBs). A maximum H2 storage capacity of ∼5.0 wt% and a reversible charge/discharge capacity of 1220 mAh/g at a current density of 30 mA/g were achieved with rGO annealed at 400 °C with a pore size of approximately 6.7 Å. Thus, an optimal pore size exists for hydrogen and lithium storage, which is similar to the optimum interlayer distance (6.5 Å) of graphene oxide for hydrogen storage applications.

Large Surface Area Ordered Porous Carbons via Nanocasting Zeolite 10X and High Performance for Hydrogen Storage Application

We report the preparation of ordered porous carbons for the first time via nanocasting zeolite 10X with an aim to evaluate their potential application for hydrogen storage. The synthesized carbons exhibit large Brunauer-Emmett-Teller surface areas in the 1300-3331 m(2)/g range and pore volumes up to 1.94 cm(3)/g with a pore size centered at 1.2 nm. The effects of different synthesis processes with pyrolysis temperature varied in the 600-800 °C range on the surface areas, and pore structures of carbons were explored. During the carbonization process, carbons derived from the liquid-gas two-step routes at around 700 °C are nongraphitic and retain the particle morphology of 10X zeolite, whereas the higher pyrolysis temperature results in some graphitic domains and hollow-shell morphologies. In contrast, carbons derived from the direct acetylene infiltration process have some incident nanoribbon or nanofiber morphologies. A considerable hydrogen storage capacity of 6.1 wt % at 77 K and 20 bar was attained for the carbon with the surface area up to 3331 m(2)/g, one of the top-ranked capacities ever observed for large surface area adsorbents, demonstrating their potential uses for compacting gaseous fuels of hydrogen. The hydrogen capacity is comparable to those of previously reported values on other kinds of carbon-based materials and highly dependent on the surface area and micropore volume of carbons related to the optimum pore size, therefore providing guidance for the further search of nanoporous materials for hydrogen storage.

SO2 retention by highly cycled modified CaO-based sorbent in calcium looping process

The limestone modified by pyroligneous acid has been proved to have good CO2 capture behavior in the calcium looping process. In this work, SO2 retention of the highly cycled modified limestone in the carbonation/calcination cycles was investigated in a thermogravimetric analyzer (TG). The cyclic carbonation/calcination of the modified limestone was performed in a dual fixed-bed reactor and then the cycled modified limestone was sent for sulfation in TG. The effects of sulfation temperature, cycle number, and prolonged carbonation on SO2 retention of the cycled modified limestone were discussed. The optimum temperature for sulfation of the cycled modified limestone should be in the range of 900–950 °C. The effect of sulfation temperature on SO2 retention of the modified limestone drops with increasing cycle number. With increasing cycle number from 20 to 100, the sulfation conversion of the cycled modified limestone is stable and can reach ~0.4. The cycled modified limestone exhibits obviously higher SO2 retention than the cycled raw one for the same number of cycles. The prolonged carbonation increases SO2 retention of the modified limestone and the raw one after the subsequent cycles. The sulfation conversions of the modified limestone and the raw one at 118 min after 9-h carbonation in the 20th cycle increase 43 and 56 %, respectively. The cycled modified limestone shows a greater SO2 retention than the cycled raw one after the same prolonged carbonation treatment. The prolonged carbonation increases the pores in 5–20 nm range which is considered the optimum pore size for sulfation of CaO-based sorbent, so it results in an improvement in SO2 retention of the cycled sorbents.

Relationship between Porous and Mechanical Properties of Hydrothermally Synthesized Porous Materials from Diatomaceous Earth

Hydrothermal solidification/synthesis of diatomaceous earth based material has been carried out so as to investigate the relationship between porous and mechanical properties. Compaction pressure could make contact of particles closer, which accelerated the hydrothermal reaction and thus improved the strength of the solidified specimen; however, it could shrink the pore volume yet seemed to exert a small influence on the surface area. Curing time and temperature affected the porous and mechanical properties of synthesized specimens significantly, and the toughest specimen seemed to possess the largest surface area and optimum pore size distribution. As such, a porous and tough humidity regulating material seemed to be manufactured easily by the hydrothermal solidification/synthesis technology.

The first systematic analysis of 3D rapid prototyped poly(ε-caprolactone) scaffolds manufactured through BioCell printing: the effect of pore size and geometry on compressive mechanical behaviour and in vitro hMSC viability

Novel additive manufacturing processes are increasingly recognized as ideal techniques to produce 3D biodegradable structures with optimal pore size and spatial distribution, providing an adequate mechanical support for tissue regeneration while shaping in-growing tissues. With regard to the mechanical and biological performances of 3D scaffolds, pore size and geometry play a crucial role. In this study, a novel integrated automated system for the production and in vitro culture of 3D constructs, known as BioCell Printing, was used only to manufacture poly(ε-caprolactone) scaffolds for tissue engineering; the influence of pore size and shape on their mechanical and biological performances was investigated. Imposing a single lay-down pattern of 0°/90° and varying the filament distance, it was possible to produce scaffolds with square interconnected pores with channel sizes falling in the range of 245–433 µm, porosity 49–57% and a constant road width. Three different lay-down patterns were also adopted (0°/90°, 0°/60/120° and 0°/45°/90°/135°), thus resulting in scaffolds with quadrangular, triangular and complex internal geometries, respectively. Mechanical compression tests revealed a decrease of scaffold stiffness with the increasing porosity and number of deposition angles (from 0°/90° to 0°/45°/90°/135°). Results from biological analysis, carried out using human mesenchymal stem cells, suggest a strong influence of pore size and geometry on cell viability. On the other hand, after 21 days of in vitro static culture, it was not possible to detect any significant variation in terms of cell morphology promoted by scaffold topology. As a first systematic analysis, the obtained results clearly demonstrate the potential of the BioCell Printing process to produce 3D scaffolds with reproducible well organized architectures and tailored mechanical properties.

The Effect of Surfactant Extraction Method on Pore Characteristics of Mesoporous Carbonated Hydroxyapatite

Incorporated with pore sizes of 2-50 nm, CHA was found to be a promising drug delivery agent for disease treatment and could be a carrier for different types of proteins. A desired drug delivery system should consist of an ordered pore network, optimum pore size, and volume, as well as a high surface area, to allow a high drug adsorption rate, controllable drug loading, and release. However, until now, most results are still not up to expectation; since the BET surface area and pore volume obtained has been rather low, compared to the existing mesoporous silica. The objective of this work was to investigate the effect of surfactant washing on the pore characteristics and the importance of this step in the synthesis process of mesoporous carbonated hydroxyapatite (CHA). In this study, mesostructured CHA particles were prepared, via a self-assembly mechanism, between CHA and non-ionic surfactant (P123), using the co-precipitation synthesis method. The synthesized mesoporous CHA samples were washed five times using different types of solvents for surfactant removal. A sphere-like particle shape of CHA was observed under SEM for all samples; regardless of the type of solvent used. The formation of CHA was confirmed by FTIR analysis, where the carbonate ion peaks were observed in the spectrums. It was found that the mesoporous CHA with a high surface area was synthesized when high polarity solvents were used during surfactant washing. These results imply that high surface area mesoporous CHA can be obtained through surfactant washing, without applying calcination for surfactant removal, which may change the structure of the CHA during heat treatment.

Effect of pore size and cross-linking of a novel collagen-elastin dermal substitute on wound healing

Collagen-elastin (CE) scaffolds are frequently used for dermal replacement in the treatment of full-thickness skin defects such as burn wounds. But little is known about the optimal pore size and level of cross-linking. Different formulations of dermal substitutes with unidirectional pores were tested in porcine full-thickness wounds in combination with autologous split skin mesh grafts (SSG). Effect on wound healing was evaluated both macro- and microscopically. CE scaffolds with a pore size of 80 or 100μm resulted in good wound healing after one-stage grafting. Application of scaffolds with a larger average pore size (120μm) resulted in more myofibroblasts and more foreign body giant cells (FBGC). Moderate crosslinking impaired wound healing as it resulted in more wound contraction, more FBGC and increased epidermal thickness compared to no cross-linking. In addition, take rate and redness were negatively affected compared to SSG only. Vascularization and the number of myofibroblasts were not affected by cross-linking. Surprisingly, stability of cross-linked scaffolds was not increased in the wound environment, in contrast to in vitro results. Cross-linking reduced the proliferation of fibroblasts in vitro, which might explain the reduced clinical outcome. The non-cross-linked CE substitute with unidirectional pores allowed one-stage grafting of SSG, resulting in good wound healing. In addition, only a very mild foreign body reaction was observed. Cross-linking of CE scaffolds negatively affected wound healing on several important parameters. The optimal non-cross-linked CE substitute is a promising candidate for future clinical evaluation.

Performance of Electric Double Layers Capacitor Using Activated Carbon Materials from Rice Husk as Electrodes

Abstract Activated carbon (AC) was synthesized from rice husks using the chemical activation method with KOH, NaOH,a combination of (NaOH + Na 2 CO 3 ), and a combination of (KOH + K 2 CO 3 ) as the chemical activating reagents. The activatedcarbon with the highest surface area (around 2000 m 2 /g) and high porosity, which allows the absorption of a large number ofions, was applied as electrode material in electric double layer capacitors (EDLCs). The AC for EDLC electrodes is requiredto have a high surface area and an optimal pore size distribution; these are important to attain high specific capacitance of theEDLC electrodes. The electrodes were fabricated by compounding the rice husk activated carbons with super-P and mixed withpolyvinylidene difluoride (PVDF) at a weight ratio of 83:10:7. AC electrodes and nickel foams were assembled with potassiumhydroxide (KOH) solution as the electrolyte. Electrochemical measurements were carried out with a three electrode cell using6 M KOH as electrolyte and Hg/HgO as the reference electrode. The specific capacitance strongly depends on the porestructure; the highest specific capacitance was 179 F/g, obtained for the AC with the highest specific surface area. Additionally,different activation times, levels of heating, and chemical reagents were used to compare and determine the optimal parametersfor obtaining high surface area of the activated carbon.Key wordssupercapacitor, EDLC, activated carbons, specific capacitance, rice husk.

Highly selective CO2 capture by S-doped microporous carbon materials

S-doped microporous carbon materials were synthesized by the chemical activation of a reduced-graphene-oxide/poly-thiophene material. The material displayed a large CO2 adsorption capacity of 4.5mmolg−1 at 298K and 1atm, as well as an impressive CO2 adsorption selectivity over N2, CH4 and H2. The material was shown to exhibit a stable recycling adsorption capacity of 4.0mmolg−1. The synthesized material showed a maximum specific surface area of 1567m2g−1 and an optimal CO2 adsorption pore size of 0.6nm. The microporosity, surface area and oxidized S content of the material were found to be the determining factors for CO2 adsorption. These properties show that the as synthesized S-doped microporous carbon material can be more effective than similarly prepared N-doped microporous carbons in CO2 capture.

Microfluidic immunodetection of cancer cells via site-specific microcontact printing of antibodies on nanoporous surface

We demonstrate an efficient method for cancer cell capture via cell line-specific protein deposition on nanoporous surface in microfluidic channels. Specifically, anti-epithelial cell adhesion molecules (EpCAM) were microcontact printed onto nanoporous silica substrate with optimal pore size of 4nm, porosity of 52.4±0.2%, and thin film thickness of 130±0.5nm. SkBr3, Colo205, and MDA-MB-435 cancer cells suspended in buffer solution were captured on the stamped nanoporous silica substrate. The method demonstrated significantly higher numbers of captured EpCAM-positive cancer cells within anti-EpCAM stamped areas. For site-selective cell capture, grooved microfluidic channels were designed to investigate effects of local confinement due to the laminar flows. Both theoretical modeling and experiments show that the integration of the microfluidic channels greatly enhances cell capture. Patterning of anti-EpCAM in areas of downward flow (optimal regions for cell capture), generated by grooves of the microchannel, enables higher capture numbers than that of stamped areas of upward flow (non-optimal). Fluorescence microscopy images were acquired for captured SkBr3 and Colo205 cells using anti-EpCAM on the nanoporous silica substrate. It was shown that higher numbers of cells were captured across all EpCAM-positive cell lines in optimal areas versus non-optimal areas. Spatial control and large scale patterning of proteins enable novel designs and productions of cost effective, high throughput, and integrated detection and analysis systems. Site-selective detection provides the capability of defining optimal locations for cell capture based on various channel geometries and flow profile. The demonstrated method shows great potential for point-of-care cancer diagnostic tools to quantify the progression and status of the disease.

Soft-chemical synthesis, characterization and humidity sensing behavior of WO3/TiO2 nanopowders

Tungsten oxide/titania (WO3/TiO2) nanopowders were synthesized by the polymeric precursor method which varied the WO3 content between 0 and 10mol%. The powders were thermally treated in a conventional furnace and their structural, microstructural and electric properties were evaluated by X-ray diffraction (XRD), Raman spectrometry, N2 physisorption, NH3 chemisorption, temperature-programmed reduction (TPR), X-ray absorption near-edge spectroscopy (XANES) in situ XANES and extended X-ray absorption fine structure spectroscopy (EXAFS) and transmission electron microscopy (TEM). XRD and Raman spectrometry confirmed the homogeneous distribution of an amorphous WO3 phase in the TiO2 matrix which stabilized the anatase phase through the generation of [TiO5·V0] or [TiO5·V0] complex sites. Conventional TPR-H2 (temperature programmed reduction) along with XANES TPR-H2 and XANES TPR-EtOH showed that WO3/TiO2 sample reduction occurs through the formation of these complex clusters. Moreover, the addition of WO3 promoted an increase in the surface acidity of doped samples as revealed by NH3 chemisorption. The WO3/TiO2 bulk-ceramic samples were further used to estimate their potential application in a humidity sensor in the range of 15–85% relative humidity. Probable reasons that lead to the different humidity sensor responses of samples were given based on the structural and surface characterizations. Correlation between the sensing performance of the sensor and its structural features are also discussed. Although all samples responded as a humidity sensor, the W2T sample (2mol% added WO3) excelled for sensitivity due to the increase in acid sites, optimum mean pore size and pore size distribution.