Nanoscale Porosity Research Articles

Analytical Multimode Scanning and Transmission Electron Imaging and Tomography of Multiscale Structural Architectures of Sulfur Copolymer-Based Composite Cathodes for Next-Generation High-Energy Density Li-S Batteries.

Poly[sulfur-random-(1,3-diisopropenylbenzene)] copolymers synthesized via inverse vulcanization represent an emerging class of electrochemically active polymers recently used in cathodes for Li-S batteries, capable of realizing enhanced capacity retention (1,005 mAh/g at 100 cycles) and lifetimes of over 500 cycles. The composite cathodes are organized in complex hierarchical three-dimensional (3D) architectures, which contain several components and are challenging to understand and characterize using any single technique. Here, multimode analytical scanning and transmission electron microscopies and energy-dispersive X-ray/electron energy-loss spectroscopies coupled with multivariate statistical analysis and tomography were applied to explore origins of the cathode-enhanced capacity retention. The surface topography, morphology, bonding, and compositions of the cathodes created by combining sulfur copolymers with varying 1,3-diisopropenylbenzene content and conductive carbons have been investigated at multiple scales in relation to the electrochemical performance and physico-mechanical stability. We demonstrate that replacing the elemental sulfur with organosulfur copolymers improves the compositional homogeneity and compatibility between carbons and sulfur-containing domains down to sub-5 nm length scales resulting in (a) intimate wetting of nanocarbons by the copolymers at interfaces; (b) the creation of 3D percolation networks of conductive pathways involving graphitic-like outer shells of aggregated carbons;

Direct printing of anisotropic wetting patterns using aerodynamically focused nanoparticle (AFN) printing

Micro- and nanoscale structures are of interest in various engineering fields due to their unique properties, such as hydrophobicity. In particular, micro/nano hierarchical structures have been investigated to promote surface hydrophobicity. Here, aerodynamically focused nanoparticle (AFN) printing was used for direct printing of superhydrophobic patterns. As AFN printing is a room-temperature direct printing technique, printed features have a hierarchical structure of two levels; nanoscale porous surface and microscale-printed patterns in three-dimensional structures. Moreover, because it is an additive fabrication technique, the printed pattern is repairable and can be reconfigured as desired. In this study, silver nanoparticles were used to implement a superhydrophobic pattern with a minimum width of tens of microns. The contact angle of water droplets was measured for various patterns, and the effects of nanoscale porosity and pattern interval were investigated. In addition, patterns were designed and fabricated to have anisotropic superhydrophobicity. The experimental results were analyzed and explained with the classical Wenzel and Cassie–Baxter models.

A study on pressure-driven gas transport in porous media: from nanoscale to microscale

Gas flow in porous media can be seen in various engineering devices such as catalytic converters and fuel cells. It is important to understand transport phenomena in porous media for improvement of the performance of such devices. Porous media with pores as small as the mean free path of gas molecules are used in such devices as proton exchange membrane fuel cells. It is difficult to measure molecular transport through such small pores in the experimental approach. In addition, even when using theoretical or numerical approaches, gas flow through nanoscale pores must be treated by the Boltzmann equation rather than the Navier–Stokes equations because it cannot be considered as a continuum. Thus, conventional analyses based on the continuum hypothesis are inadequate and the transport phenomena in porous media with nanoscale pores are not yet clearly understood. In this study, we represented porous media by randomly arranged solid spherical particles and simulated pressure-driven gas flow through the porous media by using the direct simulation Monte Carlo (DSMC) method based on the Boltzmann equation. DSMC simulations were performed for different porosities and different sizes of solid particles of porous media. It was confirmed that Darcy’s law holds even in the case of porous media with micro-/nanoscale pores. Using the obtained results, we constructed expressions to estimate the pressure-driven gas transport in porous media with micro-/nanoscale pores and porosity ranging from 0.3 to 0.5. The flow velocities estimated by using the constructed expressions agreed well with those obtained in the DSMC simulations.

Porous Silicon Gradient Refractive Index Micro-Optics.

The emergence and growth of transformation optics over the past decade has revitalized interest in how a gradient refractive index (GRIN) can be used to control light propagation. Two-dimensional demonstrations with lithographically defined silicon (Si) have displayed the power of GRIN optics and also represent a promising opportunity for integrating compact optical elements within Si photonic integrated circuits. Here, we demonstrate the fabrication of three-dimensional Si-based GRIN micro-optics through the shape-defined formation of porous Si (PSi). Conventional microfabrication creates Si square microcolumns (SMCs) that can be electrochemically etched into PSi elements with nanoscale porosity along the shape-defined etching pathway, which imparts the geometry with structural birefringence. Free-space characterization of the transmitted intensity distribution through a homogeneously etched PSi SMC exhibits polarization splitting behavior resembling that of dielectric metasurfaces that require considerably more laborious fabrication. Coupled birefringence/GRIN effects are studied by way of PSi SMCs etched with a linear (increasing from edge to center) GRIN profile. The transmitted intensity distribution shows polarization-selective focusing behavior with one polarization focused to a diffraction-limited spot and the orthogonal polarization focused into two laterally displaced foci. Optical thickness-based analysis readily predicts the experimentally observed phenomena, which strongly match finite-element electromagnetic simulations.

Modeling the Formation of Alkali Aluminosilicate Gels at the Mesoscale Using Coarse-Grained Monte Carlo.

Alkali-activated materials (AAMs) are currently being pursued as viable alternatives to conventional ordinary Portland cement because of their lower carbon footprint and established mechanical performance. However, our understanding of the mesoscale morphology (∼1 to 100 nm) of AAMs and related amorphous aluminosilicate gels, including the development of the three-dimensional aluminosilicate network and nanoscale porosity, is severely limited. This study investigates the structural changes that occur during the formation of AAM gels at the mesoscale by utilizing a coarse-grained Monte Carlo (CGMC) modeling technique that exploits density functional theory calculations. The model is capable of simulating the reaction of an aluminosilicate particle in a highly alkaline solution (sodium hydroxide or sodium silicate). Two precursor morphologies have been investigated (layered alumina and silica sheets mimicking metakaolin and spherical aluminosilicate particles reminiscent of coal-derived fly ash) to determine if the precursor morphology has an impact on the structural evolution of the resulting alkali-activated aluminosilicate gel. The CGMC model can capture the three major stages of the alkali-activation process-dissolution, polycondensation, and reorganization-revealing that the dissolved silicate and aluminate species, ranging from monomers to nanoprecipitates (100s of monomers in size), exist in the pore solution of the hardened gel. The model also reveals that the silica concentration of the activating solution controls the extent of dissolution of the precursor particle. From the analysis of the aluminosilicate cluster size distributions, the mechanisms of AAM gel growth have been elucidated, revealing that Ostwald ripening occurs in systems containing free silica at the start of the reaction. On the other hand, growth of the hydroxide-activated systems (metakaolin and fly ash) occurs via the formation of intermediate-sized clusters in addition to continual growth of the largest particle. The simulation results indicate that the nature of the gel growth is not influenced by the precursor particle morphology.

Laser Carbonization of PAN-Nanofiber Mats with Enhanced Surface Area and Porosity.

Here we present a novel laser process to generate carbon nanofiber nonwovens from polyacrylonitrile. We produce carbon nanofabrics via electrospinning followed by infrared laser-induced carbonization, facilitating high surface area and well-controlled hierarchical porosity. The process allows precise control of the carbonization conditions and provides high nanoscale porosity. In comparison with classical thermal carbonization, the laser process produces much higher surface areas and smaller pores. Furthermore, we investigate the carbonization performance and the morphology of polyacrylonitrile nanofibers compounded with graphene nanoplatelet fillers.

Synthesis of Carbide Derived Carbon (CDC) By Electrolysis of Molten Chloride Salts

Synthesis of Carbide Derived Carbon (CDC) by Electrolysis of Molten Chloride Salts Mariusz Mika, Michael McNallan, Kai-yuan Cheng, Department of Civil and Materials Engineering, University of Illinois at Chicago, 842 w. Taylor St., Chicago, IL 60607 Carbide Derived Carbon (CDC) is a nanostructured porous carbon that is produced by extraction of the metal component from a ceramic carbide by a high temperature reaction. CDC materials are useful in a number of advanced devices, including supercapacators, lithium ion batteries, and tribological systems. [1-3] Carbide derived carbons have been produced by exposing carbide ceramics to vacuum at very high temperatures, by hydrothermal reactions, and by electrochemical processing in room temperature electrolytes,[4,5] but the largest quantities of these materials have been produced by exposing the ceramics to halogen gases, mainly chlorine, at temperatures between 800 and 1200oC, where the high vapor pressures of metal halide species, such as SiCl4, and TiCl4 leads to rapid removal of the metal component. Because this temperature is not sufficiently high to facilitate the crystallization of the carbon into the equilibrium graphite structure, the product is amorphous and nanocrystalline carbon containing nanoscale porosity. The use of chlorine gas to synthesize CDC presents many practical problems due to its corrosive and toxic nature. The system requires close monitoring for safety, and equipment tends to deteriorate rapidly because of exposure to the chlorine. If an application requires synthesis of CDC only on specific locations on the carbide, it is difficult to mask the surface of the carbide from the aggressive gas. As an alternative method to produce CDC, we have prepared CDC on several carbides by electrolysis of molten chloride salts. The apparatus used to produce CDC is shown schematically in Figure 1. The electrolyte was a KCl-NaCl eutectic at temperatures between 750oC and 900oC. Several carbides, including SiC and Ti2AlC have been processed, all resulting in carbide derived carbon synthesis as identified by Raman spectroscopy. The effects of process parameters including precursor carbide, temperature, cell voltage, and temperature will be discussed.

Electrochemical Pore Formation in InP: Understanding and Controlling Pore Morphology

Research on semiconductor nanostructures is motivated by two key considerations. The first is the continuing call for smaller and more efficient versions of existing semiconductor devices. The second is the characterisation and exploitation of the unique characteristics that are often exhibited by structures at the nano-scale. While a wide variety of semiconductor nanostructures can be produced without difficulty (e.g. by self-assembly or preferential etching), precise control over the morphology of these structures is often much harder to achieve. The electrochemical formation of nano-scale porosity in semiconductors has been studied extensively1-5 and has found some application due to its bulk characteristics e.g. the use of porous silicon as a passivation layer6. However, the exploitation of the nano-scale properties of these structures is unlikely until a comprehensive understanding of the factors affecting pore morphology has been obtained. We have previously demonstrated7-9 the formation of nano-scale porosity in n-type InP anodised in KOH. Pores emerge form pits in the electrode surface10 and grow and branch along the <111>A crystallographic directions9 forming tetrahedral porous domains8. Under certain conditions, current-line oriented pores can also be obtained.11 In order to understand the factors effecting pore morphology, porous InP was formed under a range of different temperatures, electrolyte concentrations, carrier concentrations and current densities. The morphology of the resulting porous layers was analysed in detail. In particular, the pore width, layer thickness and porosity of the layers were all measured. We show that at low current densities, the pore width is dominated by the magnitude of the current density. At higher current densities, we show that both the pore width and the porosity are inversely related to the kinetics of the electrochemical reaction: the pore width being lowest at high temperatures and intermediate KOH concentrations. The pore width decreases with increasing carrier concentration, which is likely due to the associated decrease in the space charge layer thickness. Porosity varies in a similar manner to pore width and the maximum porous layer thickness is correlated to the pore width in all cases. These results support a model9of pore formation based on competition in kinetics between hole supply at the pore tip and the electrochemical reaction at the semiconductor electrolyte interface. It will be shown that this model makes the correct qualitative predictions for the variation of pore morphology with temperature, electrolyte concentration, carrier concentration and current density. Such an understanding of the factors affecting the morphology of these porous layers is an essential step in achieving the process control necessary for them to be integrated into standard semiconductor fabrication techniques.

Porous photonic crystal external cavity laser biosensor.

We report the design, fabrication, and testing of a photonic crystal (PC) biosensor structure that incorporates a porous high refractive index TiO2 dielectric film that enables immobilization of capture proteins within an enhanced surface-area volume that spatially overlaps with the regions of resonant electromagnetic fields where biomolecular binding can produce the greatest shifts in photonic crystal resonant wavelength. Despite the nanoscale porosity of the sensor structure, the PC slab exhibits narrowband and high efficiency resonant reflection, enabling the structure to serve as a wavelength-tunable element of an external cavity laser. In the context of sensing small molecule interactions with much larger immobilized proteins, we demonstrate that the porous structure provides 3.7× larger biosensor signals than an equivalent nonporous structure, while the external cavity laser (ECL) detection method provides capability for sensing picometer-scale shifts in the PC resonant wavelength caused by small molecule binding. The porous ECL achieves a record high figure of merit for label-free optical biosensors.

Development of Porosity Measurement Method in Shale Gas Reservoir Rock

The pore scales have impacts on transport mechanisms in shale gas reservoirs. In this research, digital helium porosity meter is used for porosity measurement by considering real condition. Accordingly it is necessary to obtain a good approximation for gas filled porosity. Shale has the typical effective porosity that is changing as a function of time. Effective porosity values for three different shale rocks are analyzed by this proposed measurement. We develop the new measurement method for characterizing porosity phenomena in shale gas as a time function by measuring porosity in a range of minutes using digital helium porosity meter. The porosity of shale rock measured in this experiment are free gas and adsorbed gas porosoty. The pressure change in time shows that porosity of shale contains at least two type porosities: macro scale porosity (fracture porosity) and fine scale porosity (nano scale porosity). We present the estimation of effective porosity values by considering Boyle-Gay Lussaac approximation and Van der Waals approximation.

Density modulated nanoporous tungsten thin films and their nanomechanical properties

Abstract

A 1H NMR relaxometry investigation of gel-pore drying shrinkage in cement pastes

The first systematic study of the temporal evolution of the pore-size-distribution (PSD) in mature cement pastes following one and two cycles of drying and rewetting is presented. The PSD is measured using 1H nuclear magnetic resonance (NMR) relaxometry. For millimetre sized paste samples dried fairly strongly, the volume of water taken up shortly after rewetting slightly exceeds the pre-drying amount. The volume of water in pores >10nm far exceeds that in smaller pores. This reverses the situation observed prior to drying. Over subsequent days the water distribution reverts to its original form, so that the dominant fraction is again in the smaller pores. Since the total water content scarcely changes, this indicates a re-arrangement of the nano-scale porosity. Over two drying–rewetting cycles, both reversible and irreversible changes are seen. The effect is not observed in moderately dried pastes.

Atomistic Molecular Dynamics Simulations of Crude Oil/Brine Displacement in Calcite Mesopores

Unconventional reservoirs such as hydrocarbon-bearing shale formations and ultratight carbonates generate a large fraction of oil and gas production in North America. The characteristic feature of these reservoirs is their nanoscale porosity that provides significant surface areas between the pore walls and the occupying fluids. To better assess hydrocarbon recovery from these formations, it is crucial to develop an improved insight into the effects of wall-fluid interactions on the interfacial phenomena in these nanoscale confinements. One of the important properties that controls the displacement of fluids inside the pores is the threshold capillary pressure. In this study, we present the results of an integrated series of large-scale molecular dynamics (MD) simulations performed to investigate the effects of wall-fluid interactions on the threshold capillary pressures of oil-water/brine displacements in a calcite nanopore with a square cross section. Fully atomistic models are utilized to represent crude oil, brine, and calcite in order to accommodate electrostatic interactions and H-bonding between the polar molecules and the calcite surface. To this end, we create mixtures of various polar and nonpolar organic molecules to better represent the crude oil. The interfacial tension between oil and water/brine and their contact angle on calcite surface are simulated. We study the effects of oil composition, water salinity, and temperature and pressure conditions on these properties. The threshold capillary pressure values are also obtained from the MD simulations for the calcite nanopore. We then compare the MD results against those generated using the Mayer-Stowe-Princen (MSP) method and explain the differences.

Imaging Extracellular Matrix Remodeling In Vitro by Diffusion-Sensitive Optical Coherence Tomography

The mammary gland extracellular matrix (ECM) is comprised of biopolymers, primarily collagen I, that are created and maintained by stromal fibroblasts. ECM remodeling by fibroblasts results in changes in ECM fiber spacing (pores) that have been shown to play a critical role in the aggressiveness of breast cancer. However, minimally invasive methods to measure the spatial distribution of ECM pore areas within tissues and in vitro 3D culture models are currently lacking. We introduce diffusion-sensitive optical coherence tomography (DS-OCT) to image the nanoscale porosity of ECM by sensing weakly constrained diffusion of gold nanorods (GNRs). DS-OCT combines the principles of low-coherence interferometry and heterodyne dynamic light scattering. By collecting co- and cross-polarized light backscattered from GNRs within tissue culture, the ensemble-averaged translational self-diffusion rate, DT, of GNRs is resolved within ∼3 coherence volumes (10 × 5 μm, x × z). As GNRs are slowed by intermittent collisions with ECM fibers, DT is sensitive to ECM porosity on the size scale of their hydrodynamic diameter (∼46 nm). Here, we validate the utility of DS-OCT using pure collagen I gels and 3D mammary fibroblast cultures seeded in collagen/Matrigel, and associate differences in artificial ECM pore areas with gel concentration and cell seed density. Across all samples, DT was highly correlated with pore area obtained by scanning electron microscopy (R2 = 0.968). We also demonstrate that DS-OCT can accurately map the spatial heterogeneity of layered samples. Importantly, DS-OCT of 3D mammary fibroblast cultures revealed the impact of fibroblast remodeling, where the spatial heterogeneity of matrix porosity was found to increase with cell density. This provides an unprecedented view into nanoscale changes in artificial ECM porosity over effective pore diameters ranging from ∼43 to 360 nm using a micron-scale optical imaging technique. In combination with the topical deposition of GNRs, the minimally invasive nature of DS-OCT makes this a promising technology for studying tissue remodeling processes.

Coupling of Electrochemical Charging with Mechanical Expansion and Degradation in Nanostructured MnO2 Cathodes

The faster kinetics of nanostructured charge-storage materials are often accompanied by accelerated degradation and failure, compromising the potential advantages of nanostructure and nanoporosity. Understanding and controlling the exact mechanisms of this degradation is a complex materials characterization challenge. The recent availability of in situ and in operando techniques allows new fundamental studies of these issues, including the failure of nanoscale porosity to fully accommodate the mechanical strains of charge insertion. Here, we use atomic force microscopy in liquid electrolytes to experimentally measure the mechanical expansion of porous, nanostructured Li-ion cathodes during charge cycling. Using thin films of LixMnO2 on Pt collectors, we analyze expansion as a function of scan rate, voltage window, and porosity. Comparative measurements in aqueous and nonaqueous electrolytes confirm the role of Li-ion species in the results. The rate dependent measurements of expansion can be separated into diffusion-limited, bulk components driven by Mn3+/4+ charging and faster, surface processes, in the same way that these contributions to capacitance are normally separated. Consequently, we have extracted the electrochemical-mechanical coupling coefficients ∂V/∂Q for surface and bulk processes separately. While the bulk coupling coefficient provides an excellent match to values predicted from first-principles theory, the surface coupling is surprisingly large. In fact, surface capacitance is responsible for a majority of the mechanical expansion at high rates, even when most of this capacitance would normally be attributed to double-layer charging mechanisms. The result demonstrates the importance of Mn3+/4+ species at the electrolyte interface and the inability of these species to take advantage of the film’s nanoporosity for accommodating expansion. In other words, fast surface charging processes do not involve mechanical relaxation of the material into adjacent pores, but rather drive expansion of the solid matrix.

Towards New Micro-Scale Supercapacitors: Pseudocapacitance of Hydrous Ruthenium Oxide Investigated By Multi-Scale Time-Resolved Electrochemical Methods

In recent years, the use of metal oxide thin films with nanoscale porosity for diverse electrochemical applications, e.g. energy storage, EC devices, etc. has become a subject of growing interest. 1 Among these materials, ruthenium oxide is a particular metal oxide which can offer a type of electrochemical capacitance termed pseudocapacitance which also involves faradaic charge-transfer reactions. RuOx. nH2O stands as an electroactive material with very high surface area which prosecute the fast reversible redox transitions in the potential window of charge and discharge. The amorphous and hydrous form exhibits noticable pseudocapacitance higher than its crystalline counterpart. 1, 2 For the improvement of the performance of metal oxide based electrodes, main attention has been attributed to their nanostructuration with various morphologies due to the unique properties and functionalities that can effectively be exploited in electrochemical devices. Among various synthesis methods such as sol-gel, spray pyrolysis and hydrothermal synthesis, electrochemical synthesis remains to be a fast, simple, low-cost and low-temperature technique which may also lead to the formation of homogenous nanoscale films with desirable qualities. Moreover, the incorporation of surfactant molecules in the electrogenerated film results in the production of thin nanostructured films by using potential-controlled self-assembly of surfactant-inorganic aggregates at solid-liquid interfaces 3 . The resulted nanostructures, with small sizes, and large surface area to volume ratios, are expected to facilitate the ion intercalation/extraction process. These improvements are attributed to a facilitated transfer and short diffusion length for ions transport, a high electrode/electrolyte contact area, and a better stress/strain management of the material during ion intercalation/adsorption. Despite the morphological information obtained by some in situ or ex situ characterization techniques such as X-ray photoelectron spectroscopy, small and wide-angle X-ray scattering, none of these methods alone provide the information on the exact identification of the transferred ionic species, their dynamics of transfer at the interfaces, as well as the role of electrolyte composition and the effect of ions solvation on the different electrochemical phenomena. Classical EQCM (Electrochemical Quartz Crystal Microbalance) was largely used to overcome these problems but its performances are not enough to extract pertinent results. Therefore, here, an alternative characterization tool was proposed to overcome the limitations of these classical EQCM. Specifically, the pseudocapacitive behavior related to the cation transfer in hydrous RuOx thin films was investigated by coupled time resolved characterization methods A c-electrogravimetry, consisting of in-situ coupling of electrochemical impedance spectroscopy (EIS) and fast quartz crystal microbalance (QCM), was used here: it measures simultaneously the electrochemical impedance, ΔE/ΔI (ω), and the mass/potential transfer functions (Δm/ΔE (ω)) It provides the access to the relevant information on the kinetics of species transferred at the solid/solution interfaces, and their transport in the bulk of the materials, the nature of these species as well as their relative concentration within the material. This coupling dominates over the limitations of QCM technique and has the ability to deconvolute the global mass variations provided by QCM measurements. Specifically, it detects the contribution of the charged or uncharged species and to identify anionic, cationic, and the free solvent contributions during various redox processes. 4,5 In the present work, this approach is exploited to study the ion transfer behaviour of amorphous hydrous RuOx in both mostly compact and rather porous structures. An electrochemical pathway was chosen, so-called surfactant-assisted electrodeposition is used for their preparation. In addition, we particularly focus on the amorphous materials rather than crystalline ones to emphasize its role in the electrochemical performance of such films. The electrochemical performance and ion intercalation/adsorption mechanisms were studied in aqueous H2SO4, Li2SO4 and Na2SO4 electrolytes by electrogravimetric methods (EQCM, and ac−electrogravimetry). Special attention is attributed to understand the nature of the ions involved in the charge compensation, solvation and the role of the electrolytes and the dynamic information of ions transfer at the electrode/electrolyte interfaces, ac−electrogravimetry as a gravimetric probe is used to study the complex H+ or Li+ intercalation/extraction mechanisms and to extract subtleties unreachable with classical tools.

The water – resistant zeolite imidazolate framework 67 is a viable solid phase sorbent for fluoroquinolones while efficiently excluding macromolecules

The determination of antibiotics in biological samples is compromised by their interaction with proteins. It is showed here that the water resistant zeolite imidazolate framework 67 (ZIF-67) represents a useful sorbent for solid-phase extraction (SPE) of fluoroquinolones (FQs) from biological samples. ZIF-67 is unique in possessing permanent nanoscale porosity and a high surface area. As a result, it efficiently excludes proteins from the inner network but can well adsorb small organic molecules. Its extraction capacity for FQs exceeds that of isostructural ZIF-8, probably due to high affinity for Co(II) ions in ZIF-67. The findings were exploited to design a method for the analysis of FQs, which were extracted from bio-samples by ZIF-67 via SPE. Following elution of the absorbed FQs with NaOH/methanol, they were quantified by HPLC with diode array detection. The assay has a wide linear range that extends from 3.9 to 4000 μg⋅kg‾1, with detection limits between 1.2 and 2.9 μg⋅kg‾1. The method was successfully applied to the determination of FQs in manure.

Preparation of zeolitic imidazolate framework-8 /graphene oxide composites with enhanced VOCs adsorption capacity

Hybrid nanocomposites of zeolitic imidazolate framework-8 (ZIF-8) and graphene oxide (GO) were prepared in a methanol system at room temperature. The ZIF-8/GO composites exhibited tunable nanoscale morphology and porosity, both determined by the GO content. A series of characterization techniques confirmed the formation of strong interactions between ZIF-8 and GO in the synthesized composites. The as-synthesized ZIF-8/GO composites were composed of aggregated nano-sized particles, and exhibited a higher volatile organic compounds (VOCs) uptake capacity than normal ZIF-8 crystal owing to the synergistic effect between ZIF-8 and graphene oxide(GO). Also an increase in the content of GO resulted in enhancing in the VOCs adsorption capacity, and the maximum adsorption capacity for VOCs was up to 240 mg/g on ZIF-8/GO with the GO content of 15 wt%. The synergistic interactions of ZIF-8 and GO may provide a new path to fabricate novel ZIFs/GO composites for a wide range of applications such as adsorption.

Separation of small organic molecules using covalent organic frameworks-LZU1 as stationary phase by open-tubular capillary electrochromatography

Covalent organic frameworks (COFs) have attracted much attention because of their permanent nanoscale porosity and higher surface area compared to zeolites as well as robustness. COFs have great potential in several fields such as hydrogen storage, gas separation, and catalysis. However, COFs have not yet been applied in capillary electrochromatography. Herein, covalent organic frameworks-LZU1 (COF-LZU1) was used as the stationary phase in open-tubular capillary electrochromatography for the first time. Compared to the monoliths used in electrochromatography, the preparation technique of a COF-LZU1-coated capillary was simple and practical. The baseline separation of model analytes including alkylbenzenes, polyaromatic hydrocarbons, and anilines by the COF-LZU1-coated capillary was achieved based on the size selectivity of COF-LZU1 porous structure and hydrophobic interactions between the model analytes and organic ligands of COF-LZU1. The load capacity of the COF-LZU1-coated capillary for naphthalene was 0.6mg/mL. For three consecutive runs, the intraday relative standard deviations (RSDs) were 1.4–2.6% for the migration time and 2.7–8.7% for the peak area. The interday RSDs were 1.3–3.9% for the migration time and 3.7–9.7% for the peak area. The column-to-column reproducibility of migration time was in the range 1.0–3.9%. Moreover, the coated capillary was used for >300 runs with no changes in the separation efficiency. Thus, COFs have great potential in capillary electrochromatography and may provide a new method for chromatographic separation.

Bioprinting heterogeneous 3D tumor models

Event Abstract Back to Event Bioprinting heterogeneous 3D tumor models Tao Jiang1, Jose G. Munguia-Lopez2, Joel Grant3, Sanahan Vijayakumar3 and Joseph M. Kinsella3, 4, 5 1 McGill university, Mechanical Engineering, Canada 2 Instituto Potosino de Investigación Científica y Tecnológica (IPICyT), Department of Molecular Biology, Mexico 3 McGill University, Department of Materials Engineering, Canada 4 McGill University, Department of Bioenginnering, Canada 5 McGill University, Department of Biomedical Engineering, Canada Using 3D bioprinting technologies we have developed a method to embed tumor cells within a cross-linked alginate matrix and form 3D cell-laden matrices with control over the physical, chemical, and biological conditions thus mimicking the in vivo tumor microenvironment. These 3D hydrogel models allow cells to grow, proliferate and achieve higher viability than standard 2D systems while more accurately simulating physiological conditions[1],[2]. A solution of 2.66% (w/v) sodium alginate was stirred for 3 h at RT before 0.23% (w/v) CaCl2 solution was added. MDA-MB-231 and IRM-90 labeled with GFP and RFP, respectively were cultured at 37°C and 5% of CO2. Each cell type was independently mixed into alginate solutions at 1.5x106 cells/mL. The resulting cell-alginate suspensions were used to generate 3D lattice arrays using a BioScaffolder 3.1 extrusion bioprinter with a G27 dispenser tip (Fig. 1). Rheology was performed using an MCR 301 rheometer with parallel plate geometry (PP25). Mechanical Indentation experiments were performed to verify material stiffness. Scanning electron microscopy (SEM) and confocal microscopy were used to analyze the morphology of the scaffold and the presence and localization of the cells embedded within the alginate matrix. The mechanical properties of the hydrogel were measured in an effort to tune them to match those of the tumor microenvironment. The moduli of the material was measured by rheometry using a frequency sweep at 2% strain (Fig. 2 A). Storage modulus increased from 250 Pa to 460 Pa during the sweep and loss modulus increased from 25 Pa to 150 Pa. Shear rate sweep indicated that the viscosity of the alginate decreases under increasing shear rate (Fig. 2 B), indicating the shear thinning properties of the material. Indentation shows an average stiffness of 342 N/mm, which provides enough strength to avoid collapse of the 3D structure. The morphology of the matrix was observed at multiple scales using optical and electron microscopy to determine porosity and print fidelity. SEM imaging shows a high degree of micro and nanoscale porosity (Fig. 3 A), which could lead to enhanced cell growth due to increased surface area and greater exchange rates of essential nutrients and gases. Confocal imaging confirms that the cells are embedded within the alginate in a multilayer 3D matrix with control over their initial placement relative to each cell type. The two cell types were each extruded by independent cartridges creating interlaced strands (delimited by the dotted line, Fig. 3 B). This 3D model could achieve high viability and well-spread cells creating a toll to study intracellular signaling pathways within tumors. 3D bioprinting can be used to create 3D heterogeneous disease models with high-throughput, low cost, and high reproducibility as a more realistic alternative to traditional cell culture and small animal tumor models. Volodymyr Kriuchkov; Allen Ehrlicher; Hossein khadivi heris; Adele Khavari; China Scholarship Council (CSC); McGill Engineering Doctoral Award (MEDA); Townshend-Lamarre Family Foundation; Innovative Research Award