Combination Of High Selectivity Research Articles

Selective Aqueous Ammonia Sensors Using Electrochemical Stripping and Capacitive-Based Detection

Harmful algal blooms (HABs) and eutrophication cause billions of dollars in damages and kill a large percentage of our aquatic ecosystem. According to Bernard et al. (2014), the costs of monitoring is on the order of 1 billion USD annually and Kim (2006) reported that due to HABs, Japan lost over 1 billion dollars in aquaculture.To monitor and predict such blooms, we need to cost-effectively and remotely monitor pollutants in our water bodies. One prominent pollutant that is a factor in causing harmful algal bloom is dissolved ammonia from agriculture and sewage treatment plants. To that end, we propose a novel and cost-effective sensing solution that can detect ammonia in water. Using selective membrane separation and electrochemical stripping, we are able to selectively isolate ammonium ions from dissolved river water and wastewater in our small-scale 3-chamber system. Through capacitive sensing, we can then measure with high sensitivity (28-bit resolution) and precision the concentration of ammonium ions present in our final chamber.Between the first and second chamber, there is a cation exchange membrane that allows only cations to pass through. Amongst the cations, only ammonium and hydrogen ions form gases and diffuse through the gas-permeable membrane between the second and third chamber. The ammonia gas is then dissolved into the sulfuric acid present in the third chamber. The dissolved ammonium ions change the permittivity of the overall solution and this change can be measured using highly sensitive capacitive-based sensors.Presently, we have higher than 99% selectivity in isolating ammonium ions from wastewater and river water. Our capacitive sensor has a noise floor of 0.3 femtofarad. The capacitive measurements show a linear response under 0.4 mg N/L. The combination of high selectivity and high sensitivity unlocks the ability to detect small traces of dissolved ammonia at low power draw and low costs (under $29) thus enabling the use of such methods for remote immersible ammonia sensors for environmental sensing applications along with IoT nodes.

Electro-Chemical Stripping and Capacitive Sensing Enabled Selective and Sensitive Ammonia Water Sensors

Harmful algal blooms (HABs) and eutrophication cause billions of dollars in damages and irreversibly damage our aquatic ecosystem. According to Bernard et al. (2014), the costs of monitoring is on the order of 1 billion USD annually and Kim (2006) reported that due to HABs, Japan lost over 1 billion dollars in aquaculture.To monitor and predict such blooms, we need to cost-effectively and remotely monitor pollutants in our water bodies. One prominent pollutant that is a factor in causing harmful algal bloom is dissolved ammonia from agriculture and sewage treatment plants. To that end, we propose a novel and cost-effective sensing solution that can detect ammonia in water. Using selective membrane separation and electrochemical stripping, we are able to selectively isolate ammonium ions from dissolved river water and wastewater in our small-scale 3-chamber system. Through capacitive sensing, we can then measure with high sensitivity (28-bit resolution) and precision the concentration of ammonium ions present in our final chamber.Between the first and second chamber, there is a cation exchange membrane that allows only cations to pass through. Amongst the cations, only ammonium and hydrogen ions form gases and diffuse through the gas-permeable membrane between the second and third chamber. The ammonia gas is then dissolved into the sulfuric acid present in the third chamber. The dissolved ammonium ions change the permittivity of the overall solution and this change can be measured using highly sensitive capacitive-based sensors.Presently, we have higher than 99% selectivity in isolating ammonium ions from wastewater and river water. Our capacitive sensor has a noise floor of 0.3 femtofarad. The combination of high selectivity and high sensitivity unlocks the ability to detect small traces of dissolved ammonia at low power draw, thus enabling the use of such methods for immersible ammonia sensors for environmental sensing applications.

Nanoscale trifunctional bovine hemoglobin for fabricating molecularly imprinted polydopamine via Pickering emulsions-hydrogels polymerization

In this work, a novel strategy was developed for the selective recognition of protein based on oil-in-water Pickering emulsions-hydrogels polymerization and interfacial imprinting method. For the first time, nanoscale trifunctional bovine hemoglobin (BHb) played three roles simultaneously during the process, including emulsifier, template protein and sacrificial material for further exposing recognition sites. Prior to acting as stabilizers, bovine hemoglobin colloidal particles (BCPs) were firstly prepared by acidification and heat denaturation. Then the BCPs acted as “surfactant” to stabilize the Pickering emulsions composed of functional monomers in the water phase. After dopamine polymerized, the template proteins were removed, forming the BHb imprinted cavities on the surface of the polymeric materials. During this process, the interfacial BCPs also fell off, leaving more imprinted cavities exposed. FT-IR spectroscopy confirmed that BCPs were completely removed from the synthesized imprinted materials. The interconnected macropores structures of the materials encouraged nearly all of the rebinding sites located on its surface. Thus the prepared Hydro-MIPs exhibited rapid and selective recognition toward BHb. Owing to the hierarchical porous structure, the BHb imprinted polymers based on Pickering emulsions-hydrogels (Hydro-MIPs) possessed enhanced rebinding kinetics, and the maximum rebinding capacity is 449mgg−1, 3.97 times higher than that of the non-imprinted polymers (Hydro-NIPs). Besides these, the regeneration ability test suggested that the Hydro-MIPs could be used repeatedly without distinct loss in adsorption capacity. Overall, the combination of high selectivity, good mass transfer efficiency, easy preparation and trifunctional BHb provide a new insight into bioseparation and proteomics research in biological area.

Selective inhibition of human carbonic anhydrase IX in Xenopus oocytes and MDA-MB-231 breast cancer cells

Human carbonic anhydrase IX (CA IX) is overexpressed in the most aggressive and invasive tumors. Therefore, CA IX has become the promising antitumor drug target. Three inhibitors have been shown to selectively and with picomolar affinity inhibit human recombinant CA IX. Their inhibitory potencies were determined for the CA IX, CA II, CA IV and CA XII in Xenopus oocytes and MDA-MB-231 cancer cells. The inhibition IC50 value of microelectrode-monitored intracellular and extracellular acidification reached 15 nM for CA IX, but with no effect on CA II expressed in Xenopus oocytes. Results were confirmed by mass spectrometric gas analysis of lysed oocytes, when an inhibitory effect on CA IX catalytic activity was found after the injection of 1 nM VD11-4-2. Moreover, VD11-4-2 inhibited CA activity in MDA-MB-231 cancer cells at nanomolar concentrations. This combination of high selectivity and potency renders VD11-4-2, an auspicious therapeutic drug for target-specific tumor therapy.

Synthesis and fluorescent sensory properties of a 5-cyanostilbene derivative linked to monoaza-15-crown-5

To study the effect of electron-withdrawing group upon sensory characteristics of fluorescent chemosensors containing crown ether moiety (monoaza-15-crown-5), two stilbene derivatives CN-Crown and H-Crown were synthesized to compare their selectivity and sensitivity toward metal ions. CN-Crown contains two e-withdrawing groups (bromine and cyano) in stilbene unit, whereas H-Crown possesses bromine only. Fluorescence spectral variations in the presence of different metal ions or concentrations were used to elucidate the selectivity and sensitivity, respectively. CN-Crown displays dual fluorescence, where the short-wavelength emission (locally excited state) mainly results from the stilbene group and the long-wavelength emission is attributed to the intramolecular charge transfer (ICT) process between electron-donor (amino) and electron-acceptor (stilbene unit). CN-Crown shows high selectivity toward Li +, while H-Crown is quenched not only by Li + but also by Fe 3+. The sensitivity of CN-Crown toward Li + ( K sv = 6.39 × 10 4 M −1) is about one order higher than that of H-Crown ( K sv = 6.13 × 10 3 M −1). Clearly, e-withdrawing cyan group promotes ICT process in CN-Crown that leads to enhanced selectivity and sensitivity. Combination of high selectivity and sensitivity in CN-Crown promises its potential application as chemosensory materials.

Structure–property relationships for novel wholly aromatic polyamide–hydrazides containing various proportions of para-phenylene and meta-phenylene units III. Preparation and properties of semi-permeable membranes for water desalination by reverse osmosis separation performance

Abstract Flat sheet asymmetric reverse osmosis membranes were successfully prepared from N , N -dimethylacetamide (DMAc) solutions of a series of novel wholly aromatic polyamide–hydrazides that contained different amounts of para - and meta -phenylene rings. These polyamide–hydrazides were synthesized by a low temperature solution polycondensation reactions of either 4-amino-3-hydroxybenzhydrazide or 3-amino-4-hydroxybenzhydrazide with an equimolar amount of either terephthaloyl dichloride [TCl], isophthaloyl dichloride [ICl] or mixtures of various molar ratios of TCl and ICl in anhydrous DMAc as a solvent. All the polymers have the same structural formula except of the way of linking phenylene units inside the polymer chains. The content of para - to meta -phenylene moieties was varied within these polymers so that the changes in the latter were 10 mol% from polymer to polymer, starting from an overall content of 0–100 mol%. All the membranes were characterized for their salt rejection (%) and water permeability (cm 3 cm −2 day −1 ) of 0.5 N aqueous sodium chloride feed solution at 3924 kPa operating pressure. The effects of polymers structural variations together with several processing parameters to achieve the best combination of high selectivity and permeability were studied. Effects of various processing parameters of the membranes on their transport properties were investigated by varying the temperature and period of the solvent evaporation of the cast membranes, coagulation temperature of the thermally treated membranes, annealing of the coagulated membranes, casting solution composition, membrane thickness and the operating pressure. During the thermal treatment step, the asymmetric structure of the membranes with a thin dense skin surface layer supported on a more porous layer was established. The former layer seems to be responsible for the separation performance. The results obtained showed that membrane performance was very much influenced by all of the examined processing variables and that membranes with considerably different properties could be obtained from the same polymer sample by using different processing parameters. Thus, the use of higher temperatures and longer exposure times in the protomembrane forming thermal treatment step would result in a membrane of lower solvent content and with a thicker skin layer and consequently led to higher salt rejection at lower water permeability. Most significantly, the membrane properties clearly depended on the polymer structure. Under identical processing condition, substitution para -phenylene rings for meta -phenylene ones within the polymer series resulted in an increase in salt rejection capability of the membranes. This may be attributed to an increase in their chain symmetry associated with increased molecular packing and rigidity through enhanced intermolecular hydrogen bonding. This produces a barrier with much smaller pores that would efficiently prevent the solute particles from penetration. Coagulation temperature controls the structure (porosity) of the membrane particularly its supported layer and consequently its water permeability. Moreover, annealing of the prepared membranes in deionized water at 100 °C was found essential for useful properties in the single-stage separation applications, which required optimum membrane selectivity. Upon annealing, the membrane shrinks resulting in reducing its pore size particularly in the skin layer and consequently improving the salt rejection. Addition of lithium chloride to the casting solution produced a membrane with increased porosity and improved water permeability. Salt rejection capability of the membranes is clearly affected by the applied pressure, reaching its maximum at nearly 4000 kPa. Furthermore, the water permeability is inversely proportional to the membrane thickness, while the salt rejection is not substantially influenced.

Novel wholly aromatic polyamide-hydrazides: 6. Dependence of membrane reverse osmosis performance on processing parameters and polymer structural variations

Integrally skinned phase inversion membranes were successfully cast from dimethylacetamide solutions of a series of novel wholly aromatic polyamide-hydrazides for reverse osmosis performance. All the membranes were characterized for their salt rejection (percentage) and water permeability (cm3 cm−2 day−1) of 0.5 N aqueous sodium chloride feed solution at 3924 kPa operating pressure. The effect of polymer structural variations together with several processing parameters to achieve the best combination of high selectivity and permeability were discussed. The polymers structural variations were obtained by varying their para- and meta-oriented phenylene rings content. The latter was changed from 0 to 50 mol%. The processing variables included temperature and period of the solvent evaporation of the cast membranes, coagulation temperature of the thermally treated membranes and annealing of the coagulated membranes, casting solution composition, membrane thickness and the operating pressure. During the thermal treatment step the asymmetric structure of the membranes with a thin dense skin surface layer supported on a more porous layer was established. The former layer seems to be responsible for the separation performance. The results revealed that the membrane performance depended strongly on the conditions of its processing as well as the structure of the polymer from which it is cast. Under identical preparation condition, substitution of p-phenylene rings for m-phenylene ones within the polymer series resulted in an increase in salt rejection capability of the membranes. This may be attributed to an increase in their chain symmetry associated with increased molecular packing and rigidity through enhanced intermolecular hydrogen bonding. This produces a barrier with much smaller pores that would efficiently prevent the solute particles from penetration. For a given membrane, the higher the temperature and the longer the period of the solvent evaporation would result in a membrane of lower solvent content and with a thicker skin layer and consequently led to higher salt rejection at lower water permeability. Further, annealing in deionized water at 100°C produced membranes with optimum salt rejection. Upon annealing, the membrane shrinks resulting in decreasing its pore size particularly in the skin layer. This membrane morphology change improved the salt rejection. Addition of lithium chloride to the casting solution produced a membrane with increased porosity and improved its water permeability. The effects of coagulation temperature and thickness of the membrane on the separation efficiency were also discussed. The optimum salt separation of the membranes was attained at nearly 4000 kPa operating pressure. Membranes showed rejection up to 99.5% at water permeability 13 cm3 cm−2 day−1. © 1997 Elsevier Science Ltd.