Organic Boundary Research Articles

Green bifunctional unsaturated fatty acid modulated interfacial polymerization for augmented nanofiltration performance

Facile and precise regulation of the selective layer structure is challenging but highly crucial for the development of nanofiltration (NF) technology. In this work, we present an innovative strategy to modulate the polyamide physicochemical structure by introducing oleic acid (OA) into the organic boundary during interfacial polymerization (IP) process. As a naturally extracted product, OA is a kind of unsaturated fatty acid with a carboxylic head and a C17 alkyl chain tail. The presence of OA in organic phase allows to diminish the interfacial tension and accelerate the diffusion of piperazine (PIP) towards the organic boundary. Meanwhile, in situ reaction of OA with PIP during IP process yields organic particles that are embedded in the selective layer and alter its morphology. These two effects can result in opposite influence on membrane performance. Under the optimized OA dosage of 1 %, the MgSO4 rejection boosted from 70.8 % to 97.4 % while maintaining a high pure water permeability up to 16.4 ± 0.1 L m−2 h−1 bar−1. This improvement is closely attributed to the augmented crosslinking degree and lessened MWCO/average pore size. In comparison to the control sample, the membrane surface changed from a smooth to a clustered morphology while the film thickness increased. This is mainly caused by the embedding of organic particles into the selection layer. This advancement provides a convenient and effective method for the design of high-performance NF membranes.

Elevated water transport of polyamide nanofiltration membranes via aqueous organophosphorus mediated interfacial polymerization

As interfacial polymerization (IP) is a reaction-diffusion process, rational regulation of diamine diffusion rate is effective to heighten the nanofiltration (NF) performance of polyamide (PA) membranes. Herein, we propose an aqueous organophosphorus-regulated IP strategy that promotes the formation of thinner and moderately crosslinked films toward improved water transport. Two similar compounds tetrakis (hydroxymethyl) phosphonium chloride (THPC) and tetrakis (hydroxymethyl) phosphonium sulfate (THPS) were utilized as functional additives to physically interact with piperazine via hydrogen bonding and thus retard piperazine diffusion rate during an IP process. The resultant polyamide membranes have been analyzed in terms of surface morphologies, chemical structures, hydrophilicity, and separation performance in detail. Surface temperature monitoring results revealed that heat release from regulated IP was less than that from unmodified IP, which was ascribed to retard monomer diffusion toward organic boundary in the presence of THPC or THPS. Molecular dynamics simulation further confirmed that the addition of THPC and THPS could efficiently decline the monomer diffusion rate via hydrogen bonds and increased solution viscosity. The modified PA membranes exhibited a reduced film thickness, moderate crosslinking degree, as well as increased average pore size, as revealed by a series of characterizations. Furthermore, the incorporation of THPC or THPS resulted the PA membranes with higher surface hydrophilicity and stronger negative charges. These improved physicochemical features synergically conferred a two-fold water permeance while maintaining a high divalent salt rejection (THPC-0.01: 18.3 L m-2 h−1 bar−1, 99.0 %, THPS-0.015: 20.2 L m−2 h−1 bar−1, 98 %). This aqueous organophosphorus regulated IP offers a simple and feasible approach to the preparation of low-transport-resistance PA membranes for enhanced NF performance.

Variations of Organic and Inorganic Atmospheric Boundary Layer Gaseous Species by Observations in Moscow and Zvenigorod

Anthropogenic pollution of the atmosphere with organic and inorganic gaseous species has been studied using constant high-quality monitoring of the atmosphere composition both in megacity of Moscow and in its countryside. The article considers continuous measurements of the main climatically and chemically active atmospheric gaseous species concentrations, including volatile organic compounds. The main attention is paid to the comparative analysis, mainly between the megacity and its suburban area, by average species concentrations and some quality features of their seasonal and diurnal variations. The obtained results confirmed the previously studied features of the daily variations of inorganic gaseous species in Moscow and showed such features for organic compounds in the countryside.

Highly Efficient Blue Light‐Emitting Diodes Based on Perovskite Film with Vertically Graded Bandgap and Organic Grain Boundary Passivation Shells

AbstractMetal halide perovskite materials have emerged as a promising class of semiconductors for high‐performance optoelectronic applications, particularly for light‐emitting diodes (LEDs), due to their high quantum efficiency, facile color tunability, narrow emission line widths, as well as cost‐effectiveness. Despite the great successes on green and red perovskite LEDs (PeLEDs), the external quantum efficiency (EQE) of blue PeLEDs still lags far behind that of green and red counterparts. Here, wavelength tunable pure and deep blue PeLEDs with high EQE are presented, achieving 17.5% and 10.8% for emission wavelengths of 472 and 461 nm, respectively. The wavelength tenability and high EQE are attributed to the unique vertically graded bandgaps and grain boundary organic shells in the perovskite films. The results demonstrate a significant performance improvement in blue PeLEDs, provide a novel route to fabricate high‐performance pure and deep blue PeLEDs that can match the performance of the green and red PeLEDs for future lighting and display applications.

Microporous organic nanotube assisted design of high performance nanofiltration membranes

Microporous organic nanotubes (MONs) hold considerable promise for designing molecular-sieving membranes because of their high microporosity, customizable chemical functionalities, and favorable polymer affinity. Herein, we report the use of MONs derived from covalent organic frameworks to engineer 15-nm-thick microporous membranes via interfacial polymerization (IP). The incorporation of a highly porous and interpenetrated MON layer on the membrane before the IP reaction leads to the formation of polyamide membranes with Turing structure, enhanced microporosity, and reduced thickness. The MON-modified membranes achieve a remarkable water permeability of 41.7 L m−2 h−1 bar−1 and high retention of boron (78.0%) and phosphorus (96.8%) at alkaline conditions (pH 10), surpassing those of reported nanofiltration membranes. Molecular simulations reveal that introducing the MONs not only reduces the amine molecule diffusion toward the organic phase boundary but also increases membrane porosity and the density of water molecules around the membrane pores. This MON-regulated IP strategy provides guidelines for creating high-permeability membranes for precise nanofiltration.

Thin membrane-based potentiometric sensors for sensitive detection of polyions.

A novel protocol for development of sensitive and rapid polymeric membrane polyion sensitive electrodes has been explored in this work. In contrast to the traditional polyion electrodes which usually have a sensing membrane thickness of 100∼200 μm, a thin membrane electrode with a membrane thickness of 5 μm is proposed to detect polyions. By using such thin membrane configuration, the diffusion of polyions from the organic boundary layer into the bulk of the membrane can be effectively blocked. The induced accumulation of polyions in the membrane boundary layer largely enhances the obtained potential response. It has been found that the proposed electrode shows a remarkably improved sensitivity and measurement time over conventional potentiometric polyion sensors based on the thick membranes. By using protamine as a model of polyions, the new concept offers a detection limit nearly two orders of magnitude lower than those obtained by the traditional thick-membrane polyion electrodes for potentiometric measurements of polyions. The proposed polyion sensing platform offers great promise in the sensitive and rapid detection of polyions as well as other polyion-involved bioanalyses.

Ground Penetrating Radar Imaging of a Circular Patterned Ground near King Sejong Station, Antarctica

Constraints on the structure and composition of the active layer are important for understanding permafrost evolution. Soil convection owing to repeated moisture-induced freeze-thaw cycles within the active layer promotes the formation of self-organized patterned ground. Here we present the results of ground penetrating radar (GPR) surveys across a selected sorted circle near King Sejong Station, Antarctica, to better delineate the active layer and its relation to the observed patterned ground structure. We acquire GPR data in both bistatic mode (common mid-points) for precise velocity constraints and monostatic mode (common-offset) for subsurface imaging. Reflections are derived from the active layer-permafrost boundary, organic layer-weathered soil boundary within the active layer, and frozen rock-fracture-filled ice boundary within the permafrost. The base of the imaged sorted circle possesses a convex-down shape in the central silty zone, which is typical for the pattern associated with convection-like soil motion within the active layer. The boundary between the central fine-silty domain and coarse-grained stone border is effectively identified in a radar amplitude contour at the assumed active layer depth, and is further examined in the frequency spectra of the near- and far-offset traces. The far-offset traces and the traces from the lower frequency components dominant on the far-offset traces would be associated with rapid absorption of higher frequency radiowave due to the voids in gravel-rich zone. The presented correlation strategies for analyzing very shallow, thin-layered GPR reflection data can potentially be applied to the various types of patterned ground, particularly for acquiring time-lapse imaging, when electric resistivity tomography is incorporated into the analysis.

Quantum Confined Tomonaga-Luttinger Liquid in Mo6Se6 Nanowires Converted from an Epitaxial MoSe2 Monolayer.

Confining interacting particles in one-dimension (1D) changes the electronic behavior of the system fundamentally, which has been studied extensively in the past. Examples of 1D metallic systems include carbon nanotubes, quasi-1D organic conductors, metal chains, and domain boundary defects in monolayer thick transition-metal dichalcogenides such as MoSe2. Here single and bundles of Mo6Se6 nanowires were fabricated through annealing a MoSe2 monolayer grown by molecular-beam epitaxy on graphene. Conversion from two-dimensional (2D) MoSe2 film to 1D Mo6Se6 nanowire is reversible. Mo6Se6 nanowires form preferentially at the Se-terminated zigzag edges of MoSe2 and stitch to it via two distinct atomic configurations. The Mo6Se6 wire is metallic and its length is tunable, which represents one of few 1D systems that exhibit properties pertinent to quantum confined Tomonaga-Luttinger liquid, as evidenced by scanning tunneling microscopic and spectroscopic studies.

High flux thin film nanocomposite membranes based on porous organic polymers for nanofiltration

Micro-porous organic polymers have garnered tremendous interest in membrane design because of their high nanoscale porosity, superior polymer affinity and chemical stability. In this study, o-hydroxy porous organic polymer (o-POP) utilized as nanofillers were introduced to thin film nanocomposite (TFN) membranes via an interfacial polymerization (IP) process. The o-POP with abundant phenolic –OH limited the diffusion rate of aqueous monomers toward the organic boundary via the robust interactions of electrostatic attraction and hydrogen bonding, as well as increased viscosity of aqueous phase, leading to formation of a regularly crumpled ring-shaped surface and causing a slightly increase in the average pore size of the membrane surface of 0.482 ± 0.03 nm. Such larger pore size surface with abundant bubble, tube or annular pipe structure thus distinctly elevates water transport through the membranes. More importantly, a TFN membrane containing 0.02 wt% o-POP was found to have a high water permeability (29.9 L m−2 h−1 bar−1) and an excellent bivalent salt rejection (97.5% for Na2SO4), which was three times higher than the water permeability of a commercial nanofiltration (NF) membrane.

Polarization Correction to the Interfacial Energy of Faces of Alkali Metal Crystals at the Borders with a Nonpolar Organic Liquid

Polarization is corrected using modified version of the electron-statistical theory of the interfacial energy at a metal–nonpolar organic liquid boundary. The dependence of the correction on the orientation and macroscopic dielectric permittivity of the liquid is established.

Gate-bias and temperature dependence of charge transport in dinaphtho[2,3-b:2′,3′-d]thiophene thin-film transistors with MoO3/Au electrodes

We investigated the gate-bias and temperature dependence of the voltage–current (V–I) characteristics of dinaphtho[2,3-b:2′,3′-d]thiophene with MoO3/Au electrodes. The insertion of the MoO3 layer significantly improved the device performance. The temperature dependent V–I characteristics were evaluated and could be well fitted by the Schottky thermionic emission model with barrier height under forward- and reverse-biased regimes in the ranges of 33–57 and 49–73 meV, respectively. However, at a gate voltage of 0 V, at which a small activation energy was obtained, we needed to consider another conduction mechanism at the grain boundary. From the obtained results, we concluded that two possible conduction mechanisms governed the charge injection at the metal electrode–organic semiconductor interface: the Schottky thermionic emission model and the conduction model in the organic thin-film layer and grain boundary.

Organic Boundary Location Based on Color-Texture of Visual Perception in Wireless Capsule Endoscopy Video.

This paper addresses the problem of automatically locating the boundary between the stomach and the small intestine (the pylorus) in wireless capsule endoscopy (WCE) video. For efficient image segmentation, the color-saliency region detection (CSD) method is developed for obtaining the potentially valid region of the frame (VROF). To improve the accuracy of locating the pylorus, we design the Monitor-Judge model. On the one hand, the color-texture fusion feature of visual perception (CTVP) is constructed by grey level cooccurrence matrix (GLCM) feature from the maximum moments of the phase congruency covariance and hue-saturation histogram feature in HSI color space. On the other hand, support vector machine (SVM) classifier with the CTVP feature is utilized to locate the pylorus. The experimental results on 30 real WCE videos demonstrate that the proposed location method outperforms the related valuable techniques.

From Uncles of Victoria Park to the Net Generation Square People: National Identity and Student Movements in Hong Kong

Recent protest movements in post-colonial Hong Kong have exposed a divided society that is grappling with an identity crisis. This study looks at the co-evolutionary trajectories of Chinese identity and Hong Kong student movements and analyses the mechanisms that have conditioned perceptions of Chinese identity since the 1960s. Using a structured process-based approach to identity, we argue that, same symbolic resources can be combined with organic boundary mechanism in one movement while with the voluntarist boundary mechanism in another, contingent on population structure, political system and the nature of social conflicts at a given time. Thus, through decades of student movements, ‘being Chinese’ has been articulated in relation to the oppressed in the British colony, Chinese nation, local society, and mainland Chinese. The outcome of each movement has redefined the connotation of ‘being Chinese’ and this updated connotation has in turn redirected the next wave of activism.

Modeling the Relative Importance of Nutrient and Carbon Loads, Boundary Fluxes, and Sediment Fluxes on Gulf of Mexico Hypoxia.

The Louisiana continental shelf in the northern Gulf of Mexico experiences bottom water hypoxia in the summer. In this study, we applied a biogeochemical model that simulates dissolved oxygen concentrations on the shelf in response to varying riverine nutrient and organic carbon loads, boundary fluxes, and sediment fluxes. Five-year model simulations demonstrated that midsummer hypoxic areas were most sensitive to riverine nutrient loads and sediment oxygen demand from settled organic carbon. Hypoxic area predictions were also sensitive to nutrient and organic carbon fluxes from lateral boundaries. The predicted hypoxic area decreased with decreases in nutrient loads, but the extent of change was influenced by the method used to estimate model boundary concentrations. We demonstrated that modeling efforts to predict changes in hypoxic area on the continental shelf in relationship to changes in nutrients should include representative boundary nutrient and organic carbon concentrations and functions for estimating sediment oxygen demand that are linked to settled organic carbon derived from water-column primary production. On the basis of our model analyses using the most representative boundary concentrations, nutrient loads would need to be reduced by 69% to achieve the Gulf of Mexico Nutrient Task Force Action Plan target hypoxic area of 5000 km(2).

Phytosanitary conditions of the organic field and boundary

Phytosanitary conditions of the organic field and boundary

One-Pot Synthesis of Oligo-Ladder Phenylsilsesquioxanes via Pyridine–Silicon Adduct Formation at Aqueous–Organic Liquid Boundary

Three kinds of oligo-ladder polyphenylsilsesquioxanes were synthesized by two unique methods through the aqueous–organic boundary reaction via octahedrally-coordinated pyridine–silicon adduct PhSiCl3(Py)2, which is formed from trichlorophenylsilane (TCP) monomer and pyridine in n-propyl acetate. When two equivalent pyridines to TCP were used, SQ polymer-1 was formed as a viscous solid, which was recrystallized in n-hexane to obtain SQ polymer-2B. When an excess pyridine was used (pyridine/Si = 10), SQ polymer-2A was directly obtained as a white solid. MALDI–TOF/TOF–MS, FT-IR and 29SiNMR clearly shows that the “Ladder” structure of SQ polymers is dominant in both methods. It was shown that in this one-pot synthesis, SQ polymer structure was controlled by pyridine amount. Furthermore, MO simulation of pyridine adduct formation (PhSiCl3(Py)2) supports the hydrolysis pathway for synthesis as well as the “Ladder” structure formation. Finally, it was also suggested that the hydrolysis reaction occurred in a stepwise manner.

Assessment of source contributions to air pollution in Beirut, Lebanon: a comparison of source-based and tracer-based modeling approaches

A chemical-transport model (CTM), Polyphemus/Polair3D, is used to investigate the contributions of various anthropogenic and biogenic sources to total organic carbon (OC) in PM2.5 in Beirut, Lebanon, during the summer of 2011. Those results are compared to a tracer-based source apportionment of OC at an ambient site in Beirut where a measurement campaign was conducted in July 2011. The results obtained from the CTM in the base simulation S1 suggest contributions to total simulated OC mass (3.24 μg/m3) of 66 % (2.14 ± 1.07 μg/m3) from fossil fuel burning (FFB) and 8 % (0.27 ± 0.135 μg/m3) from biogenic secondary organic carbon (BSOC). The tracer-based approach leads to contribution estimates to total measured OC mass (5.6 μg/m3) of 16 % (0.9 μg/m3 ± 0.22) from FFB, 53 % (2.9 ± 1.7 μg/m3) from BSOC, and 32 % (1.8 ± 0.88 μg/m3) from cooking activities. In a second CTM simulation S2, emissions related to cooking activities were added to the emission inventory, monoterpene and sesquiterpene secondary organic aerosol (SOA) surrogate species were added to the boundary conditions, and a lower ratio of semi-volatile organic compounds to primary organic aerosols (SVOC/POA) was used. The S2 results obtained showed contributions to total simulated OC mass (3.01 μg/m3) of 33 % (0.98 ± 0.49 μg/m3) from FFB, 18 % (0.53 ± 0.27 μg/m3) from BSOC, and 39 % (1.2 ± 0.6 μg/m3) from cooking activities. The differences between these two methods are discussed in terms of their uncertainties and biases. The comparison of both approaches showed that the model underestimates the secondary fraction of OC, which may be due to underestimations of some biogenic volatile organic compound (VOC) emissions and/or boundary concentrations as well as the use of SOA yields that may not be representative of the eastern Mediterranean region. Concerning the tracer-based approach, the use of tracer/OC ratios that are not specific to Lebanon because of a lack of data could represent a limitation of this methodology. Nevertheless, this comparative analysis suggests that on-road transportation and diesel generators used for electricity production are major sources of atmospheric PM and should be targeted for emission reduction. Finally, cooking activities, which were identified as a significant source of PM with the tracer-based approach, should be studied further.

Anionic microemulsion to solvent stacking for on‐line sample concentration of cationic analytes in capillary electrophoresis

The common SDS microemulsion (i.e. 3.3% SDS, 0.8% octane, and 6.6% butanol) and organic solvents were investigated for the stacking of cationic drugs in capillary zone electrophoresis using a low pH separation electrolyte. The sample was prepared in the acidic microemulsion and a high percentage of organic solvent was included in the electrolyte at anodic end of capillary. The stacking mechanism was similar to micelle to solvent stacking where the micelles were replaced by the microemulsion for the transport of analytes to the organic solvent rich boundary. This boundary is found between the microemulsion and anodic electrolyte. The effective electrophoretic mobility of the cations reversed from the direction of the anode in the microemulsion to the cathode in the boundary. Microemulsion to solvent stacking was successfully achieved with 40% ACN in the anodic electrolyte and hydrodynamic sample injection of 21 s at 1000 mbar (equivalent to 30% of the effective length). The sensitivity enhancement factors in terms of peak height and corrected peak area were 15 to 35 and 21 to 47, respectively. The linearity R(2) in terms of corrected peak area were >0.999. Interday precisions (%RSD, n = 6) were 3.3-4.0% for corrected peak area and 2.0-3.0% for migration time. Application to spiked real sample is also presented.

Investigation of friction and surface degradation of innovative boundary lubricant functionalized hydrogel material for use as artificial articular cartilage

Hydrogels have been proposed as a synthetic bearing material to replace locally damaged articular cartilage in order to delay a joint replacement. A crucial limitation is that hydrogel tribological properties do not compare to natural cartilage. In this study, the well-known hydrogel polymer, polyvinyl alcohol, was functionalized with organic fatty acid derivative boundary lubricants to create boundary lubricant functionalized hydrogels prepared by freeze–thaw methods. The tribological behavior of the boundary lubricant functionalized hydrogels was investigated and compared against polyvinyl alcohol hydrogels by friction and polymer loss measurements from a pin-on-flat reciprocating sliding apparatus. The wear behavior of the hydrogels was compared while articulated against steel pins in deionized water and bovine cartilage pins in phosphate buffer saline solution. Also the effect of increasing the hydrocarbon chain length of boundary lubricant was investigated. Polymer loss results revealed that at high wear cycles neat polyvinyl alcohol hydrogels displayed the highest polymer loss, while the boundary lubricant functionalized hydrogels exhibited greater wear resistance. Optical microscopy qualitatively showed the polyvinyl alcohol hydrogels exhibited a predominant abrasive wear mechanism, while the boundary lubricant functionalized hydrogel exhibited an adhesive wear mechanism with reduced wear, with the hydrogels having the lowest hydrocarbon chain length boundary lubricant displaying the most improved wear performance with barely noticeable wear track formation. Sliding against cartilage, all hydrogels displayed low polymer loss, and qualitative microscopy showed virtually no wear track development on the boundary lubricant functionalized hydrogel surface for all wear cycles and minimal damage of the cartilage pins. This is the first study reporting the tribological properties of boundary lubricant functionalized hydrogels and established that the boundary lubricant functionalized hydrogels exhibited improved tribological performance as compared to neat polyvinyl alcohol hydrogel.

Trace-Level Potentiometric Detection in the Presence of a High Electrolyte Background

Polymeric membrane ion-selective electrodes (ISEs) have become attractive tools for trace-level environmental and biological measurements. However, applications of such ISEs are often limited to measurements with low levels of electrolyte background. This paper describes an asymmetric membrane rotating ISE configuration for trace-level potentiometric detection with a high-interfering background. The membrane electrode is conditioned in a solution of interfering ions (e.g., Na(+)) so that no primary ions exist in the ISE membrane, thus avoiding the ion-exchange effect induced by high levels of interfering ones in the sample. When the electrode is in contact with the primary ions, the interfering ions in the membrane surface can be partially displaced by the primary ions due to the favorable ion-ligand interaction with the ionophore in the membrane, thus causing a steady-state potential response. By using the asymmetric membrane with an ion exchanger loaded on the membrane surface, the diffusion of the primary ions from the organic boundary layer into the bulk of the membrane can be effectively blocked; on the other hand, rotation of the membrane electrode dramatically reduces the diffusion layer thickness of the aqueous phase and significantly promotes the mass transfer of the primary ions to the sample-membrane interface. The induced accumulation of the primary ions in the membrane boundary layer largely enhances the nonequilibrium potential response. By using copper as a model, the new concept offers a subnanomolar detection limit for potentiometric measurements of heavy metals with a high electrolyte background of 0.5 M NaCl.