Transport Of Gas Molecules Research Articles

Pebax-derived ultra-microporous carbon molecular sieve composite membrane assisted by organic interlayer for gas separation

In this study, novel Pebax-derived ultra-microporous carbon molecular sieve composite membrane assisted by polydopamine (PDA) interlayer was synthesized by dip-coating and pyrolysis method. Pebax was first explored as the precursor and PDA was selected as flexible coating layer on the polymeric substrate in preparation of CMS composite membranes. Pebax had long linear chain polyamine structure and contained large number of carbonyl groups and hydrogen bonds that were pyrolyzed under relatively low temperature. Compared with incorporating inorganic interlayer, the PDA organic interlayer constructed under mild condition had excellent adhesion towards the polymeric support. Since the intrusion of precursor Pebax into the pore of substrate was prevented, the channels of passage were shortened and the transport of gas molecules was greatly promoted. Through designable chemical bonding resistant to harsh conditions, the adhesion between organic interlayer and CMS layer were kept strong due to natural compatibility of materials, leading to the formation of defect-free CMS membranes with enhanced stability in operation. The fabricated CMS membrane displayed excellent H2/CO2 selectivity of 40.69 and very competitive permeability of 1.23 × 10−7 mol m−2 Pa−1 s−1.

Channels formation in cellulose materials by accelerated transport of gas molecules and glycerin

In this study, a microporous separator was produced using cellulose acetate (CA), which demonstrates heightened thermal stability in comparison to existing materials like polypropylene (PP) or polyethylene (PE). Furthermore, a pliable component was integrated into the CA membrane using glycerin as the plasticizing agent. Subsequently, gas pressure was exerted onto these areas to induce the formation of nano-sized pores. Examination through Scanning Electron Microscopy (SEM) unveiled the presence of abundant pores in the glycerin-plasticized areas. This substantiates that the pores generated under gas pressure were not only more uniform but also smaller than those created under water pressure. The interaction between CA and glycerin was validated using Fourier-Transform Infrared Spectroscopy (FT-IR), offering confirmation that a portion of the glycerin was extracted following the application of gas pressure. Additionally, the application of Thermogravimetric Analysis (TGA) allowed for an assessment of the thermal stability of the CA membrane, along with a verification of glycerin's removal post gas pressure treatment. The findings indicated that the incorporation of glycerin diminished the thermal stability of the CA membrane due to the plasticization effect. Furthermore, it was observed that a minor quantity of glycerin still persisted after the gas pressure treatment. Following the analysis of gas permeation, the porosity of the CA membrane was quantified at 78.8 %, exhibiting an average pore size measuring 224 nm.

Semiconducting MOFs on ultraviolet laser-induced graphene with a hierarchical pore architecture for NO2 monitoring

Due to rapid urbanization worldwide, monitoring the concentration of nitrogen dioxide (NO2), which causes cardiovascular and respiratory diseases, has attracted considerable attention. Developing real-time sensors to detect parts-per-billion (ppb)-level NO2 remains challenging due to limited sensitivity, response, and recovery characteristics. Herein, we report a hybrid structure of Cu3HHTP2, 2D semiconducting metal-organic frameworks (MOFs), and laser-induced graphene (LIG) for high-performance NO2 sensing. The unique hierarchical pore architecture of LIG@Cu3HHTP2 promotes mass transport of gas molecules and takes full advantage of the large surface area and porosity of MOFs, enabling highly rapid and sensitive responses to NO2. Consequently, LIG@Cu3HHTP2 shows one of the fastest responses and lowest limit of detection at room temperature compared with state-of-the-art NO2 sensors. Additionally, by employing LIG as a growth platform, flexibility and patterning strategies are achieved, which are the main challenges for MOF-based electronic devices. These results provide key insight into applying MOFtronics as high-performance healthcare devices.

Pyro-layered heterostructured nanosheet membrane for hydrogen separation

Engineering different two-dimensional materials into heterostructured membranes with unique physiochemical properties and molecular sieving channels offers an effective way to design membranes for fast and selective gas molecule transport. Here we develop a simple and versatile pyro-layering approach to fabricate heterostructured membranes from boron nitride nanosheets as the main scaffold and graphene nanosheets derived from a chitosan precursor as the filler. The rearrangement of the graphene nanosheets adjoining the boron nitride nanosheets during the pyro-layering treatment forms precise in-plane slit-like nanochannels and a plane-to-plane spacing of ~3.0 Å, thereby endowing specific gas transport pathways for selective hydrogen transport. The heterostructured membrane shows a high H2 permeability of 849 Barrer, with a H2/CO2 selectivity of 290. This facile and scalable technique holds great promise for the fabrication of heterostructures as next-generation membranes for enhancing the efficiency of gas separation and purification processes.

Ylang-ylang (Cananga odorata) essential oils with flora odorants enhanced active function of biodegradable polyester films produced by extrusion

Ylang-ylang (Cananga odorata) essential oils (EO) has several active components with flora odorants which are compatible with several foods and desserts. Incorporation of Ylang-ylang EO into biodegradable polymers potentially produce functional packaging, releasing desirable aroma which is attractive to consumers. This research aimed to enhance active function of biodegradable polyester blend films namely polybutylene adipate-co-terephthalate (PBAT) and polybutylene succinate (PBS) using cast extrusion with Ylang-ylang EO. Characterizations of the film include morphology, relaxation, infrared absorption and packaging properties. Adding EO gave a smoother microstructure and surface topography and modified the crystal lattice of the PBS phase. Infrared absorption indicated EO-polymer interaction involving C–H stretching vibration. Polymer relaxation influenced transport of gas molecules through PBAT/PBS/EO matrices. Decreased α-relaxation temperature suggested plasticization effects of the amorphous PBAT phase by EO, increasing oxygen and water vapor permeability by 2.52 and 1.16 times, respectively. Polymer relaxation and crystallinity influenced transport of non-polar oxygen through PBAT/PBS/EO matrices. Moreover, films containing EO effectively delayed fungal growth in pandan pudding and layered pudding by more than 3 days due to the release of volatiles that exhibited antifungal activities. Findings suggested potential of Ylang-ylang EO incorporated biodegradable films to produce active packaging for aroma release, extending product shelf-life.

Improved triethylamine sensing properties of fish-scale-like porous SnO2 nanosheets by decorating with Ag nanoparticles

Three dimensional (3D) porous nanostructures assembled by low-dimensional nanomaterials are widely applied in gas sensor according to porous structure which can facilitate the transport of gas molecules. In this work, fish-scale-like porous SnO2 nanomaterials assembled from ultrathin nanosheets with thickness of 16.8 nm were synthesized by a facile hydrothermal route. Then Ag nanoparticles were decorated on the surface of SnO2 nanosheets via one-step method to improve their gas-sensing performances. The sensing properties of pristine SnO2 and Ag/SnO2 nanosheets were investigated intensively. After decorating with Ag nanoparticles, the characteristics of SnO2 based sensor for triethylamine detection were significantly improved. Especially, the Ag/SnO2 based sensor with Ag content of 2 at% exhibited the highest triethylamine sensing sensitivity at optimum work temperature of 170 °C. The improved sensing properties of Ag/SnO2 sensors were attributed to the sensitizing actions of Ag nanoparticles as well as the unique hierarchical porous architecture.

ZIF-L membrane with a membrane-interlocked-support composite architecture for H2/CO2 separation

Metal–organic framework (MOF) membranes hold great promise in energy-efficient chemical separations. The outstanding challenges of the microstructural design stem from (1) thinning of membranes to immensely reduce the mass-transfer resistance (for high permeances); (2) tuning of orientation to optimize the selective transport of gas molecules, and (3) reinforcement of intercrystalline structure to subside leakage through defective gaps (for high selectivity). Here, we propose the ZIF-L membrane that is completely confined into the voids of the alumina support through an interfacial assembly process, producing an appealing membrane-interlocked-support (MIS) composite architecture that meets the requirements of the microstructural design of MOF membranes. Consequently, the membranes show average H2 permeances of above 4000 GPU and H2/CO2 separation factor (SF) of above 200, representing record-high separation performances of ZIF-L membranes and falling into the industrial target zone (H2 permeance > 1000 GPU and H2/CO2 SF > 60). Furthermore, the ZIF-L membrane possessing the MIS composite architecture that is established with alumina particles as scaffolds shows mechanical stability, scraped repeatedly by a piece of silicon rubber causing no selectivity loss.

Mechanism of gas molecule transport through erythrocytes’ membranes by kinks-solitons

Mechanism of gas molecule transport through erythrocytes’ membranes by kinks-solitons

Structural characterization and gas sensing applications of ultrafine ZrO2 nanospheres using low temperature solution route

Monophasic ZrO2 nanoparticles were successfully prepared by using low temperature solution route. As-prepared nanoparticles were characterized by different techniques like XRD, SEM, TEM, BET and UV–Visible studies. X-ray diffraction analysis revealed the crystalline tetragonal phase of ZrO2. Transmission electron microscopic studies show the formation of 15 nm sized spherical particles of zirconia. The surface morphological studies were established by Scanning Electron Microscopy. UV–Visible diffused reflectance spectroscopy studies give the optical band gap of 4.9 eV for the synthesized nanoparticles. BET surface area studies revealed the high surface area of 128 m2/g. Enhanced gas sensing property was revealed by the ZrO2 nanoparticles over carbon monoxide at 50 ppm concentration and at a minimal operating temperature of 240 °C. The good sensing properties can indeed be ascribed to the large oxygen surface vacancies available and the high surface area possessed by the ZrO2 nanoparticles which are favorable for both the transport of gas molecules and sensing reactions to occur as was deduced from the sensing mechanism.

Tunable sieving of small gas molecules using horizontal graphene oxide membrane

Graphene oxide membrane (GOM) has attracted extensive attraction as a molecular sieve for the separation of water, ions, and gases. However, Å-level control of the GOM interlayer spacing for separating the specific size of gas molecule is difficult and the vertical transport mechanism of molecules through the GOM is highly complex because of the existence of several possible pathways. Here we fabricated GOMs with different Å-scale interlayer spacing through heat treatment and made them allow horizontal entrance and transport of gas molecules. The GOMs with angstrom channels exhibited superior performance in permeance in horizontal mode and moderate selectivity for H2/CO2 and He/CO2 by tuning the sieving size of the channels. Molecular dynamics (MD) simulations reveal that the precisely controlled interlayer spacing plays a primary role as a molecular sieve indeed, but increased graphitic area, a result of heat treatment, also affects observed selectivity. Our results provide insight into the transport mechanism of gas molecules through GO nanochannel, which has not been accurately identified due to its complex behavior and suggest the possibility of studying nanochannels as effective vehicle for separating molecules precisely.

Improving Artificial Photosynthesis over Carbon Nitride by Gas-Liquid-Solid Interface Management for Full Light-Induced CO2 Reduction to C1 and C2 Fuels and O2.

The activity and selectivity of simple photocatalysts for CO2 reduction remain limited by the insufficient photophysics of the catalysts, as well as the low solubility and slow mass transport of gas molecules in/through aqueous solution. In this study, these limitations are overcome by constructing a triphasic photocatalytic system, in which polymeric carbon nitride (CN) is immobilized onto a hydrophobic substrate, and the photocatalytic reduction reaction occurs at a gas–liquid–solid (CO2–water–catalyst) triple interface. CN anchored onto the surface of a hydrophobic substrate exhibits an approximately 7.2‐fold enhancement in total CO2 conversion, with a rate of 415.50 μmol m−2 h−1 under simulated solar light irradiation. This value corresponds to an overall photosynthetic efficiency for full water–CO2 conversion of 0.33 %, which is very close to biological systems. A remarkable enhancement of direct C2 hydrocarbon production and a high CO2 conversion selectivity of 97.7 % are observed. Going from water oxidation to phosphate oxidation, the quantum yield is increased to 1.28 %.

Mass Transfer Through Graphene-Based Membranes

The problems related to the transport of gases through nanoporous graphene (NG) and graphene oxide (GO) membranes are considered. The influence of surface processes on the transport of gas molecules through the aforementioned membranes is studied theoretically. The obtained regularities allow finding the dependence of the flux of the gas molecules passing through the membrane on the kinetic parameters which describe the interaction of the gas molecules with the graphene sheets. This allows to take into account the influence of external fields (e.g., resonance radiation), affecting the aforementioned kinetic parameters, on the transport of gas molecules through the membranes. The proposed approach makes it possible to explain some experimental results related to mass transfer in the GO membranes. The possibility of the management of mass transfer through the NG and GO membranes using resonance radiation is discussed.

A Nanomotor-Based Active Delivery System for Intracellular Oxygen Transport.

Active transport of gas molecules is critical to preserve the physiological functions of organisms. Oxygen, as the most essential gas molecule, plays significant roles in maintaining the metabolism and viability of cells. Herein, we report a nanomotor-based delivery system that combines the fast propulsion of acoustically propelled gold nanowire nanomotors (AuNW) with the high oxygen carrying capacity of red blood cell membrane-cloaked perfluorocarbon nanoemulsions (RBC-PFC) for active intracellular delivery of oxygen. The oxygen delivery capacity and kinetics of the AuNW nanomotors carrying RBC-PFC (denoted as "Motor-PFC") are examined under ultrasound field. Specifically, the fast movement of the Motor-PFC under an acoustic field accelerates intracellular delivery of oxygen to J774 macrophage cells. Upon entering the cells, the oxygen loaded in the Motor-PFC is sustainably released, which maintains the cell viability when cultured under hypoxic conditions. The acoustically propelled Motor-PFC leads to significantly higher cell viability (84.4%) over a 72 h period, compared to control samples with free RBC-PFC (44.4%) or to passive Motor-PFC (32.7%). These results indicate that the Motor-PFC can act as an effective delivery vehicle for active intracellular oxygen transport. While oxygen is used here as a model gas molecule, the Motor-PFC platform can be readily expanded to the active delivery of other gas molecules to various target cells.

Transport of gas molecules through dense membranes and intensification of mass transfer by radiation

It is known that fouling of membranes decreases their performance. New modern types of membranes which are used for separation of gas mixtures (e.g. supported ionic liquid and graphene-based membranes) require the methods for cleaning which differ from the methods used in classical membrane technology (e.g. backflushing). Mass transfer in these membranes can be blocked by the adsorbed foreign gas molecules or/and aerosol nanoparticles which are present in a gas phase near the feed side surface of the membranes. The new method of the intensification of mass transfer through the membranes by resonance radiation is considered. It is shown that resonance radiation, leading to selective excitation of the foreign gas molecules and a change in their sticking coefficient and the rate coefficient of desorption as well as to heating of the membrane, can reduce the affinity constant of the foreign gas that in turn decreases the surface coverage and the blocking effect of the adsorbed foreign gas molecules. A model is given for the transport of gas molecules through a dense flat membrane with the deposition of aerosol particles on the feed side surface of the membrane.

Modelling for Gas Transport in Enhanced Polymeric Blend Membrane

The main aim of this research work is to develop a model of carbon dioxide (CO2) separation from natural gas by using membrane separation technology. This study includes the transport mechanism of the porous membrane. The fundamental theories of diffusion, poiseuille (viscous) flow, Knudsen diffusion and surface diffusion are used. The developed model of incorporating three diffusion mechanisms to be modified for modeling of polymeric blends towards membrane selectivity and permeability. For the purpose of assessing the gas permeance using the theoretical models, the experimental data taken from CO2 permeance in the PSU/PVAc (85/15) wt. % /DEA enhanced polymeric blend membrane was considered. The results obtained from modified Cho Empirical model of total gas permeance showed the least error as compared to other models. The modified Cho Empirical mathematical models were extended by blending factor to predict CO2 gas molecule transport in Enhanced Polymeric Blend Membrane (EPBM) to obtain precise theoretical values that are close to the experimental values. The Extended modified Cho Empirical model validation demonstrated the ability to predict CO2 permeance with reasonable accuracy.

Thermodynamic Scaling of Interfering Hemoglobin Strain Field Waves.

Hemoglobin (Hgb) forms tetramers (dimerized α-β dimers), which enhance its globular stability and may also facilitate small gas molecule transport, as shown by recent all-atom Newtonian solvated simulations. Hydropathic bioinformatic thermodynamic scaling enables close comparisons of hemoglobin dimers with myoglobin and neuroglobin, and reveals many nonlocal wave-like features of strained Hgb structures at the coarse-grained amino acid level. The thermodynamic analysis employs two hydropathic scales, one describing abrupt first-order unfolding transitions, the other continuous second-order transitions. Small molecule exchange at hemes is a first-order process. Wave-like collective tetrameric features appropriate to ligand absorption and release, seen in optical experiments (short times), are identified thermodynamically at long times. Strain fields localized near hemes interfere with extended strain fields associated with dimer interfacial misfit, resulting in novel wavelength dependent dimer correlation function Fano antiresonances.

3D inverse opal nanostructured multilayer films of two-component heterostructure composites: A new-generation synthetic route and potential application as high-performance acetone detector

The preparation of highly ordered porous semiconducting metal oxides (SMOs) films is a hot issue in the field of chemical sensor. Herein, we successfully fabricated 3D inverse opal (IO) ZnO-In2O3 composites multilayer films (MFs) via a novel strategy that combing ultrasonic nebulization deposition technique with polystyrene (PS) spheres template. Such one-step synthetic method is advantageous to achieve the construction of large-scale interconnected macro-porous (pore size: ∼170 nm) structure in composites materials, which is beneficial for facilitating gas molecule transport into the sensing layers and accelerating the surface reactions process. More significantly, by using this method, the large-scale 3D IO MFs made in this work can be easily transferred onto any target substrates without being destroyed. Due to the IO multilayer films structure and abundant heterointerfaces, the 3D IO ZnO-In2O3 MFs-based gas sensor exhibited higher response toward acetone at lower operating temperature, better selectivity and long-term stability, faster recovery speed and lower detection limit. Consequently, the approach described herein is more suitable for the synthesis of porous composites materials films, in order to fabricate high performance chemical sensor.

Hierarchical morphology and hydrogen sensing properties of N2-based nanodiamond materials produced through CH4/H2/Ar plasma treatment

Due to the development of emerging technologies we are now able to produce nano-diamonds in a cost-effective way for the commercially viable production of nano-diamond sensors. In this study, we develop an appropriate hybridized plasma treatment technique for the fabrication of nitrogen incorporated diamond films and study their H2 sensing properties. The morphology and crystallinity of as-prepared nitrogen-ultrananocrystalline diamond (N-UNCD) films can be improved by using a suitable hybridized plasma process with Ar/CH4/H2 for the formation of nitrogen-hybrid diamond (N-HiD) materials. The as-prepared N-UNCD and N-HiD films were then subjected to lithography with a lateral electrode to fabricate H2 sensing devices. The sensitivity of the as-prepared N-UNCD films and the N-HiD films for H2 gas was studied at room temperature. The results of this systematic study demonstrate that the N-HiD films possess an improved H2 gas response of 6.2%, which is better than that of the as-prepared N-UNCD films (0.7%). The N-HiD films also exhibit excellent selectivity, repeatability, and long-term stability after 60 days of exposure to H2 in the on/off state. The significant improvement in the H2 sensing performance of the N-HiD based sensor can be attributed to the modification of the surface morphology and the resistance. The hybridized plasma alters the resistivity of the surface by etching of the nanographite to form ultranano-sized diamond grains, which support the efficient electron transport of gas molecules. This study is a noteworthy step to fulfilling the demand for diamond based sensor applications.

One-step synthesis of in-situ N-doped ordered mesoporous titania for enhanced gas sensing performance

In-situ N-doped ordered mesoporous titania was synthesized by a simple solvent evaporation induced aggregating assembly (EIAA) method using lab-made amphiphilic diblock copolymer polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) as a structure directing agent and titanium tetrabutoxide (TBOT) as a titanium source. The obtained N-doped mesoporous titanium dioxide materials had a pore size of ∼6.2 nm, a large accessible surface area of 119 m2 g-1 and a large pore volume of 0.160 cm3 g-1, respectively, which facilitated the diffusion and transport of gas molecules. The as-prepared samples were characterized by the FT-IR spectra, Raman spectra, X-ray photoelectron spectroscopy and UV–vis absorption spectroscopy. The results showed that the nitrogen atoms were in situ incorporated into the lattice of TiO2, thus resulting in smaller crystallite size and more defects, which facilitated promoting gas sensing performance. Its response reached 17.6 for 250 ppm acetone, which was 11.4 times higher than that of their undoped TiO2-based sensors (1.54 for 250 ppm), and the fast response and recovery time were 4s and 4s, respectively.

Exploration of gas molecules transport in composite poly (4-methyl-2-pentyne) and carbon nanotubes employing molecular dynamics simulation

In order to design optimal membrane composites it is important to have an in-depth understanding of penetrants transport in such membranes. In that spirit, molecular dynamics was employed to study the transport of gas molecules in a composite membrane consisting of poly (4-methyl-2-pentyne) (PMP) and close-ended carbon nanotubes (PMPCNTC) or open-ended carbon nanotubes (PMPCNTO). The logarithm plot of mean-squared displacement (MSD) versus time for the transport of methane in PMPCNTC and PMPCNTO was drawn. It is observed that there are three regimes: the ballistic regime, the subdiffusive regime and the Fickian diffusive regime. The ballistic regime in PMPCNTC is shorter than it is in PMPCNTO, because the average cavity size of PMPCNTC is smaller than that of PMPCNTO and the penetrants have more space to move freely in PMPCNTO than they do in PMPCNTC before they hit any matrix units. Then the diffusivities of penetrants were achieved according to the plot of MSD versus time for the transport of penetrants in the Fickian diffusive regime. The solubility coefficients and the permeability of gas molecules in the composites were also calculated. In PMPCNTC, the 25 locations that contribute most to solubilities are outside the nanotubes while in PMPCNTO, they are inside the nanotubes. In PMPCNTO it is the nanotube that solvates the majority of the gas molecules. The huge channels inside the nanotube cause the high solubility of these penetrants. Finally, the selectivity of n-C4H10 over CH4 in PMPCNTC is observed to be higher than it is in both PMPCNTO and pure PMP. The research results may be employed in membrane design.