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A series of cyclomatrix polyphosphazene films have been prepared by nonaqueous interfacial polymerization (IP) of small aromatic hydroxyl compounds in a potassium hydroxide dimethylsulfoxide solution and hexachlorocyclotriphosphazene in cyclohexane on top of ceramic supports. Via the amount of dissolved potassium hydroxide, the extent of deprotonation of the aromatic hydroxyl compounds can be changed, in turn affecting the molecular structure and permselective properties of the thin polymer networks ranging from hydrogen/oxygen barriers to membranes with persisting hydrogen permselectivities at high temperatures. Barrier films are obtained with a high potassium hydroxide concentration, revealing permeabilities as low as 9.4 × 10-17 cm3 cm cm-2 s-1 Pa-1 for hydrogen and 1.1 × 10-16 cm3 cm cm-2 s-1 Pa-1 for oxygen. For films obtained with a lower concentration of potassium hydroxide, single gas permeation experiments reveal a molecular sieving behavior, with a hydrogen permeance of around 10-8 mol m-2 s-1 Pa-1 and permselectivities of H2/N2 (52.8), H2/CH4 (100), and H2/CO2 (10.1) at 200 °C.

In view of enhanced oil recovery, the adsorption behavior of surfactants is usually monitored on smooth model rock surfaces using quartz crystal microbalance with dissipation (QCM-D). However, this...

We investigated in detail the permeation selectivity in the electro-dialysis of Na+, K+, Mg2+ and Ca2+ in both binary and quaternary mixtures using a supported liquid membrane (SLM). The SLM consisted of the organic liquid 2-nitrophenyl octyl ether (NPOE) containing a lipophilic anion, i.e. tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, as the cation-exchanging site, which was used to fill the pores of the supporting membrane AccurelR. We first determined the electro-phoretic mobilities of the migrating cations in single salt solutions, yielding: Na+ > K+ > Mg2+ > Ca2+. This order reflects the different size of the migrating cations. The monovalent cations Na+ and K+ migrate in the dehydrated state and the divalent cations Ca2+ and Mg2+ migrate in a (partly) hydrated state, a conclusion was supported by Karl Fisher titrations. Both binary and quaternary salt experiments showed a permeation selectivity in the following order: K+ > Na+ > Ca2+ > Mg2+. Since this order does not correlate with the order of electro-phoretic mobilities, we have determined the ion-exchange selectivity constant (Kex) and found: K+ > Ca2+ > Mg2+ ≈ Na+. We conclude that the overall permeation selectivity is determined by the combination of ion-exchange selectivity and electro-phoretic mobility of the cations present in the membrane.

An interfacial polymerization process is introduced for the fabrication of thermally stable cyclomatrix poly(phenoxy)phosphazenes thin-film composite membranes that can sieve hydrogen from hot gas mixtures. By replacing the conventionally used aqueous phase with dimethyl sulfoxide/potassium hydroxide, a variety of biphenol molecules are deprotonated to aryloxide anions that react with hexachlorocyclotriphosphazene dissolved in cyclohexane to form a thin film of a highly cross-linked polymer film. The film membranes have persistent permselectivities for hydrogen over nitrogen (16–27) and methane (14–30) while maintaining hydrogen permeances in the order of (10−8–10−7 mol m−2s−1Pa−1) at temperatures as high as 260 °C and do not lose their performance after exposure to 450 °C. The unprecedented thermal stability of these polymer membranes opens the potential for industrial membrane gas separations at elevated temperatures.

Chemical loss such as surfactants and alkalis by adsorption to reservoir rock surface is an important issue in enhanced oil recovery (EOR). Here, we investigated the adsorption behaviors of anionic surfactants and alkalis on silica for the first time as a function of temperature using quartz crystal microbalance with dissipation (QCM-D). The results demonstrated that the temperature dependent critical micelle concentration of alcohol alkoxy sulfate (AAS) surfactant can be quantitatively described by the thermodynamics parameters of micellization, showing a mainly entropy-driven process. AAS adsorption was mediated under varying temperature conditions, by divalent cations for bridging effect, monovalent cations competitive for adsorption sites but not giving cation bridging, pH regulation of deprotonated sites of silica, presence of alkoxy groups in the surfactants, and synergistic effect of surfactant co-injection. The addition of organic alkalis can enhance the overall adsorption of the species with AAS, whereas inorganic alkali of Na2CO3 had capability of the sequestration of the divalent ions, whose addition would reduce AAS adsorption. The typical AAS adsorption indicated a non-rigid multilayer, estimated to have between 2 and 5 layers, with a likely compact bilayer followed by disorganized and unstable further layering. The new fundamental understanding about temperature effect on surfactants and alkalis adsorption contributes to optimizing the flooding conditions of chemicals and developing more efficient mitigation strategies.

Surfactants have the ability to mobilize residual oil trapped in pore spaces of matrix rocks by lowering the oil-water interfacial tension, resulting in a higher oil recovery. However, the loss of surfactants by adsorption onto the rock surface has become a major concern that reduces the efficiency of the surfactant flooding process. In this study, the adsorption behavior of an anionic surfactant to a clay mineral surface was investigated by quartz crystal microbalance with dissipation monitoring upon variations with different cation conditions. Through recording the change of frequency and dissipation of clay-modified sensors, it allows us to do a real-time quantitative analysis of the surfactant adsorption with nanogram sensitivity. The results revealed that the surfactant adsorption increased in a Ca2+-containing solution with increasing pH from 6 to 11, whereas from a Na+-containing solution, more adsorption occurred at acidic conditions. The adsorbed amount went through a maximum (∼200 mM) as a function of the Ca2+ concentration, and the Voigt model suggested that multilayer adsorption of surfactants could be as many as 4-6 monolayers. Using mixed cation (Ca2+ and Na+) solutions, the amount of adsorbed surfactant decreased linearly with decreasing fraction of CaCl2, but Na+ competed for about ∼30% adsorption sites. The importance of the presence of CaCl2 for the surfactant adsorption was stressed in high-salinity and low-salinity solutions in the presence and absence of Ca2+. Furthermore, increasing the temperature from 23 to 65 °C shows first a small increase of surfactant adsorption followed by a reduction of about 20%. The obtained results contribute to a better understanding of surfactant adsorption on clay surfaces and a guide to optimal flooding conditions with reduced surfactant loss.

In this paper, the electrochemical behavior of four fluoroquinolone antibiotics (FAs) [Ciprofloxacin (Cip), Enrofloxacin (Enr), Marbofloxacin (Mar) and Ofloxacin (Ofl)] at a polarized interface between two immiscible electrolyte solutions (ITIES) has been studied using ion–transfer voltammetry (ITV). The measurements were conducted in the traditional macroscopic (macro-ITIES) and a recently developed miniaturized (micro-ITIES) platform. The latter was obtained from fused silica micro-capillaries having an internal diameter of 25 μm. We used macroITIES to obtain a number of analytical parameters such as: standard Galvani potential of ion transfer (ΔΦ0), diffusion coefficients (D), free Gibbs energy of ion transfer (ΔG0) and partition coefficients (logPDCE). The latter were compared with the available literature values of logPoctanol. The effect of concentration of the studied antibiotics on the electrochemical response was investigated with the microITIES platform, setting statistical parameters such as: linear dynamic ranges (LDRs – studied from 1 μM up to 50 μM), lower limit of detections (LODs – around 1 μM) and sensitivity (found in the range from 2.6·10−2 to 6.8·10−2 nA·μM−). MicroITIES were further used to study the effect of pH on the analytical signal and the results are plotted in a form of ion partition diagrams. Working with microITIES supported with the fused silica capillaries significantly reduced the volumes of consumed chemicals and expedite all analytical experiments. The provided results can be successfully applied in pharmacology and electroanalysis for testing and determination of the chosen fluoroquinolone antibiotics.

In this review, we describe the importance and possible electrochemical screening methods for the illicit drug – cocaine. It covers the detection at bare and modified solid electrodes, soft electrified junctions and nanopore sensing. Emphasis is given on interfacial modification techniques and electroanalytical parameters for cocaine detection in different environments, covering the detection from both, model and real samples.

In this study, the preparation of a new, functional anion-exchange membrane (AEM), containing guanidinium groups as the anion-exchanging sites (Gu-100), is described as well as the membrane characterization by XPS, water uptake, permselectivities, and electrical resistances. The functional membrane was also employed in pH-dependent electrodialysis experiments using model dairy wastewater streams. The properties of the new membrane are compared to those of a commercially available anion-exchange membrane bearing conventional quaternary ammonium groups (Gu-0). Guanidinium was chosen for its specific binding properties toward oxyanions: e.g., phosphate. This functional moiety was covalently coupled to an acrylate monomer via a facile two-step synthesis to yield bulk-modified membranes upon polymerization. Significant differences were observed in the electrodialysis experiments for Gu-0 and Gu-100 at pH 7, showing an enhanced phosphate and citrate transport for Gu-100 in comparison to Gu-0. At pH 10 the difference is much more pronounced: for Gu-0 membranes almost no phosphate and citrate transport could be detected, while the Gu-100 membranes transported both ions significantly. We conclude that having guanidinium groups as anion-exchange sites improves the selectivity of AEMs. As the presented monomer synthesis strategy is modular, we consider the implementation of functional groups into a polymer-based membrane via the synthesis of tailor-made monomers as an important step toward selective ion transport, which is relevant for various fields, including water treatment processes and fuel cells.

Organic solvent nanofiltration (OSN) is gradually expanding from academic research to industrial implementation. The need for membranes with low and sharp molecular weight cutoffs that are able to operate under aggressive OSN conditions is increasing. However, the lack of comparable and uniform performance data frustrates the screening and membrane selection for processes. Here, a collaboration is presented between several academic and industrial partners analyzing the separation performance of 10 different membranes using three model process mixtures. Membrane materials range from classic polymeric and thin film composites (TFCs) to hybrid ceramic types. The model solutions were chosen to mimic cases relevant to today's industrial use: relatively low molar mass solutes (330–550 Da) in n-heptane, toluene, and anisole.

Surfactant losses by adsorption to rock surfaces make surfactant-based enhanced oil recovery economically less feasible. We investigated polyacrylate (PA) as a sacrificial agent in the reduction of anionic surfactant adsorption with focus on calcite surfaces by using quartz crystal microbalance with dissipation monitoring. It was found that the adsorption of the anionic surfactant alcohol alkoxy sulfate (AAS) followed a Langmuir adsorption isotherm, and the adsorbed amount reached saturation above its critical micellar concentration. Adsorption of PA was a much slower process compared to AAS adsorption. Increasing the calcium ion concentration also increased the amount of AAS adsorbed as well as the mass increase rate of PA adsorption. Experimental results combined with density functional theory calculations indicated that calcium cation bridging was important for anionic surfactant AAS and PA adsorption to calcite surfaces. To effectively reduce the amount of surfactant adsorption, it was needed to preflush with PA, rather than by a simultaneous injection. Preflushing with 30 ppm of PA gave a reduction of AAS adsorption of 30% under high salinity (HS, 31,800 ppm) conditions, compared to 8% reduction under low salinity (LS, 3180 ppm) conditions. In the absence of PA, the amount of adsorbed AAS was reduced by already 50% upon changing from HS to LS conditions. Lower calcium ion concentrations, as under LS conditions, contributed to this observation. On different mineral surfaces, PA reduced the AAS adsorption in the order of alumina > calcite > silica. These results offer important insights into mitigating surfactant adsorption using PA polyelectrolyte as sacrificial agent and contribute to improved flooding strategies with reduced surfactant loss.

International audience; Developing multifunctional polymeric binders is key to the design of energy storage technologies with value-added features. We report that a multigram-scale synthesis of perylene diimide polymer (PPDI), from a single batch via polymer analogous reaction route, yields high molecular weight polymers with suitable thermal stability and minimized solubility in electrolytes, potentially leading to improved binding affinity toward electrode particles. Further, it develops strategies for designing copolymers with virtually any desired composition via a subsequent grafting, leading to purpose-built binders. PPDI dye as both binder and electroactive additive in lithium half-cells using lithium iron phosphate exhibits good electrochemical performance.

A novel ion separation methodology using a cation-exchange membrane modified with iron oxide nanoparticles (Fe3O4 NPs) coated with polyhexamethylene guanidine (PHMG) is proposed. The separation is performed in an electrodialysis cell, where firstly phosphate is electro-adsorbed to the PHMG@Fe3O4 NP coating, followed by a desorption step by applying an electric current., A novel ion separation methodology using a cation-exchange membrane modified with iron oxide nanoparticles (Fe3O4 NPs) coated with polyhexamethylene guanidine (PHMG) is proposed.

We have investigated the conditions of colloidal stability of silica nanoparticles smaller than 100 nm for their applications in enhanced oil recovery (EOR), especially pertaining to chemical flooding processes. Using zeta sizer and dynamic light scattering techniques, the stability of silica nanoparticle (SNP) dispersions has been investigated by variation of the pH, composition of salt solutions, addition of surfactants and polyelectrolytes. Such conditions can be encountered in oil reservoirs. It was found that changing pH from 5 to 10 had a negligible effect on the size of SNPs, whereas its zeta potential increased with increasing pH. Aggregation of SNPs is a partially reversible process for low degrees of aggregation in 500 mM NaCl, whereas observed strong aggregation in 1000 mM NaCl was irreversible. A critical aggregation concentration (CAC) was defined for the different salts investigated, above which the SNP dispersion became unstable at a fixed pH of 9.5. The CAC for NaCl was approximately 200 times higher than for CaCl2 and MgCl2. Our observations could not be explained completely by the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Therefore, we have included non-DLVO interactions such as cation bridging, hydration forces, and steric effects. The additional presence of anionic alcohol alkoxy sulfate (AAS) surfactant slightly destabilized the SNP solution, but by the addition of polyacrylate (PA) was effectively stabilized. With increasing PA concentration, the CAC for both CaCl2 and MgCl2 increased. Upon addition of 100 ppm PA, the CAC increased by a factor of five compared to the situation in the absence of PA. Reducing the solution pH below 8.5, SNP can be stabilized in higher salinity in the presence of PA. The obtained results contribute to a better fundamental understanding of the SNP stability mechanism and a guide to optimize the SNP injection process with EOR chemicals.

Adsorption behavior of surfactants to rock surfaces is an important issue in oil recovery, especially in the process of surfactant flooding. The surfactant loss through adsorption to rock surfaces makes such process economically less feasible. Here, we investigated the adsorption behavior of anionic surfactants (alcohol alkoxy sulfate, AAS) onto silica with quartz crystal microbalance with dissipation monitoring. The results demonstrated that the surfactant adsorption followed the Langmuir adsorption isotherm. Up to solution pH 10, surfactant adsorption slightly increased with increasing pH. The higher pH leads to more anionic surface sites for binding with an anionic surfactant with the help of a calcium cation bridging. The amount of anionic surfactant binding also increases with increasing calcium ion concentration up to 50 mM. It was found that sodium ions were able to exchange calcium ions near the silica surface, which would reduce the affinity for surfactant adsorption. The effect of the polyanion polystyrene sulfonate (PSS) on the anionic AAS adsorption was investigated to learn the possible competitive adsorptions. Indeed, this was found. Upon addition of 50 ppm PSS to a 0.05 wt% AAS containing solution, the adsorption of AAS was reduced by about 85 %. The obtained results show the interplay of different interacting species affecting the overall degree of anionic surfactant adsorption to silica surfaces. Optimal tuning of the process conditions according to these results will contribute to a more efficient use of anionic surfactants in enhanced oil recovery.

In this work, the electrified liquid–liquid interface (LLI) was supported with the bare and polyelectrolyte modified fiberglass membranes. The permeability of these supports was then investigated with ion transfer voltammetry (ITV). This work descends from three mutually interconnected experimental tasks. (i) The study of an interfacial behavior of three polyelectrolytes, poly(ethyleneimine) (PEI), polystyrene sulfonate (PSS), and polyhexamethylene guanidine (PHMG) at the polarized LLI. (ii) Electrochemical characterization of the LLI supported by the unmodified fiberglass membrane. (iii) Polyelectrolyte multilayer placement, using layer-by-layer processing, at the surface of the fiberglass membrane and its further utilization as the support for the electrified LLI. Bare and modified membranes were characterized using ITV in the presence of a family of quaternary ammonium cations: tetramethylammonium (TMA+), tetraethylammonium (TEA+), tetrapropylammonium (TPrA+) and tetrabutylammonium (TBA+) initially dissolved in the aqueous phase as the chloride salts. The ionic currents related to their transmembrane transfer were affected already after the first polyelectrolyte layer placement. In addition to electrochemistry, the modification process was followed using several complementary techniques, including optical microscopy (OM), atomic force microscopy (AFM), infra-red (IR) spectroscopy, and scanning electron microscopy (SEM). The proposed methodology offers very simple, fast, and versatile (having in mind the available selection of functional polyelectrolytes) protocol for a membrane preparation having size sieving properties. In turn, the electrochemistry at the LLI can be used as an insightful tool to study the ionic transmembrane currents.

In this study we describe a novel and simple method to couple covalently poly (maleic anhydride-alt-1-alkenes) to γ-alumina nanofiltration membranes for the first time. The 1-alkenes varied from 1-hexene, 1-decene, 1-hexadecane to 1-octadecene. The grafting reaction was between the reactive anhydride moieties of the polymer and surface hydroxyl groups, resulting in highly stable bonds. The modified membranes were investigated for their permeation and rejection performance of Sudan Black (SB, Mw 457 Da) in either toluene or ethyl acetate (EA) solution, and very high rejections (> 90%) and high permeation flux were observed compared to unmodified membranes. Initially, the SB in toluene solution was found to bind strongly to the surface hydroxyl groups of the unmodified membranes, an effect not observed in EA solution.

We report a novel, simple and cheap generator–collector electrode system, employing platinum leaves, with micron-sized pores and typically 100–300 nm thickness, sandwiched with a porous track etch membrane spacer with typically 30 nm diameter pores. The electrode assembly is sealed into a polymer lamination pouch with one side 2 mm diameter exposed to electrolyte solution. The generator electrode with sweeping potential (top or bottom electrode) shows transient current with high capacitive current component. The collector electrode with fixed potential shows well-defined steady state current response at low potential sweep rates. The fabricated device shows good performance in monitoring both 1,1′-ferrocenedimethanol oxidation and proton reduction redox processes. Oxygen sensor signals are assigned to a lowering of the steady state proton reduction current.

With the increasing demand for efficient extraction of residual oil, enhanced oil recovery (EOR) offers prospects for producing more reservoirs’ original oil in place. As one of the most promising methods, chemical EOR (cEOR) is the process of injecting chemicals (polymers, alkalis, and surfactants) into reservoirs. However, the main issue that influences the recovery efficiency in surfactant flooding of cEOR is surfactant losses through adsorption to the reservoir rocks. This review focuses on the key issue of surfactant adsorption in cEOR and addresses major concerns regarding surfactant adsorption processes. We first describe the adsorption behavior of surfactants with particular emphasis on adsorption mechanisms, isotherms, kinetics, thermodynamics, and adsorption structures. Factors that affect surfactant adsorption such as surfactant characteristics, solution chemistry, rock mineralogy, and temperature were discussed systematically. To minimize surfactant adsorption, the chemical additives of alkalis, polymers, nanoparticles, co-solvents, and ionic liquids are highlighted as well as implementing with salinity gradient and low salinity water flooding strategies. Finally, current trends and future challenges related to the harsh conditions in surfactant based EOR are outlined. It is expected to provide solid knowledge to understand surfactant adsorption involved in cEOR and contribute to improved flooding strategies with reduced surfactant loss.

The electrochemical behavior of three differently charged drug molecules (zwitter-ionic acetylcarnitine, bi-cationic succinylcholine and tri-cationic gallamine) was studied at the interface between two immiscible electrolyte solutions. Tetramethylammonium was used as a model mono cationic molecule and internal reference. The charge and molecular structure were found to play an important role in the drug lipophilicity. The studied drugs gave a linear correlation between the water – octanol (logPoctanol) partition coefficients and the electrochemically measured water – 1,2-dichloroethane (logPDCE) partition coefficients. Comparison with tetraalkylammonium cations indicating that the correlation between logPoctanol and logPDCE is molecular structure dependent. The highest measured sensitivity and lowest limit of detection were found to be 0.543 mA·dm3·mol− 1 and 6.25 μM, respectively, for the tri-cationic gallamine. The sensitivity for all studied ions was found to be a linear function of molecular charge. The dissociation constant of the carboxylic group of zwiter-ionic acetylcarnitine was calculated based on voltammetric parameters and was found to be 4.3. This study demonstrates that electrochemistry at the liquid – liquid interface is powerful technique when it comes to electroanalytical or pharmacokinetic drug assessment.

Controlled localization of platinum nanoparticles (Pt NPs) at a solid support assisted by a polarized liquid-liquid interface is reported. Electrocatalytic water oxidation resulted in local pH modulation followed by the directed self-assembly of a dibenzoyl-l-cystine hydrogelator forming a structured hydrogel retaining the shape of the Pt NP deposit.

We report herein a versatile and user-friendly synthetic methodology based on sequential functionalization that enables the synthesis of previously unknown perylene bisimide (PBI) dyes with up to five different substituents attached to the perylene core (e.g., compound 15). The key to the success of our strategy is a highly efficient regiospecific 7-mono- and 7,12-di-phenoxy bay substitution at the "imide-activated" 7- and 12-bay positions of 1,6,7,12-tetrachloroperylene monoimide diester 1. The facile subsequent conversion of the diester groups into an imide group resulted in novel PBIs (e.g., compound 14) with two phenoxy substituents specifically at the 7- and 12-bay positions. This conversion led to the activation of C-1 and C-6 bay positions, and thereafter, the remaining two chlorine atoms were substituted to obtain tetraphenoxy-PBI (compound 15) that has two different imide and three different bay substituents. The methodology provides excellent control over the functionalization pattern, which enables the synthesis of various regioisomeric pairs bearing the same bay substituents. Another important feature of this strategy is the high sensitivity of HOMO-LUMO energies and photoinduced charge transfer toward sequential functionalization. As a result, systematic fluorescence on-off switching has been demonstrated upon subsequent substitution with the electron-donating 4-methoxyphenoxy substituent.

To the best of our knowledge, for the first time MIL-53(Al) and NH2-MIL-53(Al) modified α-alumina membranes are investigated for the adsorption of organic dyes from organic solvents. These new, modified membranes show excellent adsorption of high concentrations of Rose Bengal dye in methanol and isopropanol solutions.

To the best of our knowledge, for the first time MIL-53(Al) and NH 2 -MIL-53(Al) modified α-alumina membranes are investigated for the adsorption of organic dyes from organic solvents. These new, modified membranes show excellent adsorption of high concentrations of Rose Bengal dye in methanol and isopropanol solutions.

Here, we report the covalent coupling of poly (styrene-co-maleic anhydride) onto γ-alumina to develop high-performance organic solvent nanofiltration (OSN) membranes. A high molecular weight (M w ) alternating copolymer of maleic anhydride (MA) and styrene (St) was synthesized and directly grafted to the γ-alumina membrane, while commercially available low M w random copolymers of St and MA were also investigated. We show that solute rejection and membrane permeability strongly depend on the nature of the applied copolymer. In particular, the M w of the copolymer applied is potentially the key for improving the membrane performance. When a high M w copolymer was applied, the grafted layer covered the surface of the membrane. This results in membranes with significantly improved rejection, while maintaining a high permeability. In contrast, we observed pore grafting by applying low M w copolymers, which resulted in membranes with slightly higher rejection and dramatically lower permeability compared to unmodified membrane. The best results were obtained by grafting γ-alumina with a high M w alternating copolymer. These membranes showed a solute rejection of 98% for Sudan Black B (457 g mol −1 ) in toluene, while the permeability remained high at 2.9 L m −2 h −1 bar −1 .

The ability to study the adsorption behavior of surfactant species is of interest in the field of enhanced oil recovery (EOR), especially pertaining to alkaline surfactant flooding. In this work, a calcite model mineral surface was obtained by electrochemically assisted deposition. This was achieved via the nitrate and/or oxygen electroreduction reactions in the presence of bicarbonate and calcium ions, by which controlled deposition of calcium carbonate was effected on a quartz crystal microbalance sensor covered with an electroactive gold layer. In addition, the effect of pH and Ca 2+ concentration on the effective surface charge of the deposited calcite particles was mapped. Calcite-modified sensors were used in conjunction with a quartz crystal microbalance with dissipation monitoring to study the effect of Na + and Ca 2+ concentration on the adsorption behavior of an anionic alcohol alkoxy sulfate (AAS) surfactant. Adsorption of the surfactant remained indifferent to ionic concentrations around the isoelectric point of calcite. Still, electrostatics play an important role in this regard, and it is essential to decrease the Ca 2+ concentration sufficiently to minimize AAS adsorption. The results from this study show that a relatively simple method allows for the controlled deposition of a model rock surface, and there is ample opportunity to extend the work to other metal oxide surface types, including complex mixtures as can be obtained by co-deposition. Furthermore, the findings from these adsorption studies aid in the determination of optimal flooding parameters, with the aim to increase the efficiency and efficacy of EOR.

We report an advanced treatment method for phosphoric acid recovery from leached sewage sludge ash. Layer-by-layer (LbL) polyelectrolyte deposition has been used as a tool to modify and convert a hollow ultrafiltration membrane into a nanofiltration (NF) LbL membrane for H3PO4 recovery. To build the LbL membrane, poly(styrenesulfonate) PSS was chosen as polyanion, while three different polycations were used: a permanently charged polyelectrolyte, poly(diallyldimethylammonium chloride), PDADMAC; a pH-dependent charged polyelectrolyte poly(allylamine hydrochloride), PAH; and a PAH modified with guanidinium groups (PAH-Gu). Based on detailed surface characterizations (AFM, XPS and Zeta-potential) it was concluded that both charge density and pH-responsiveness of the polycations are key parameters to control the final membrane surface structure and transport properties. The surface properties of LbL-coated membranes were correlated with the membrane filtration performance, when exposed to the real leached sewage sludge ash solution. The highest permeability was recorded for (PDADMAC/PSS)6, a result that was rationalized on its loose, and possibly less interpenetrated, structure, followed by (PAH-Gu/PSS)6 characterized by a more dense, compact layer. H3PO4 recovery was the highest in the case of (PDADMAC/PSS)6, but the retention of multivalent metals (Fe3+ and Mg2+) was low, leading to a more contaminated permeate. The opposite trend was observed for (PAH-Gu/PSS)6, resulting in a less metal-contaminated, but also a less H3PO4-concentrated permeate. Our LbL-modified membranes were found to improve the permeability and H3PO4 recovery compared to a commercially available acid-resistant NF membrane.

The development of controlled polymerization techniques in the last decade has enabled polymer brushes to be grown from inorganic substrates with precision. Less studied are brushes grown from concave geometries of high curvature, such as mesopores, despite their application potential in the separation sciences. The method used here, surface-initiated, activators-regenerated-by-electron-transfer, atom-transfer radical polymerization (SI-ARGET-ATRP), is used to grow a polystyrene brush grown from aluminum oxide pores of 5 nm diameter, to-date the most confined geometry in which ATRP has been conducted. The brush is characterized by TGA, AFM, and FTIR, the latter two methods applied specifically to the external brush. Additionally, permporometry as well as permeability and retention measurements are used to characterize the graft within the mesopores. We show that the brush length is tunable, that the brush length is solvent-dependent, and we also demonstrate the application potential of this hybrid material as an organic solvent nanofiltration membrane. This new class of membranes shows excellent performance: a toluene permeability of 2.0 L m−2 h−1 bar−1 accompanied by a 90% rejection of diphenylanthracene (MW 330 g mol−1).

Calcium carbonate (CaCO3) deposition plays a significant role in processes such as scale formation in power plants and in oil or gas production wells. The development of appropriate methods based on well suitable in situ sensors is important to evaluate and predict the deposition process. In this study, a combination of electrochemical techniques and quartz crystal microbalance with dissipation monitoring (QCM-D) in one analysis setup (EQCM-D) was used for the first time to monitor the CaCO3 deposition in real time and provide kinetic details of the CaCO3 deposition process. Through recording the frequency change of quartz crystal sensors, it allows us to perform a quantitative analysis of the morphology, coverage, deposition rate, and mass changes with nanogram sensitivity. By varying the applied voltage, it was found that a lower applied voltage resulted in more deposition of CaCO3 mass and increase of the thickness of the deposited layer. Under the absence of flow, the CaCO3 growth rate switched from accelerating to decelerating and this point is characterized by an inflection point (IP). A lower applied voltage resulted in a lower IP. Increasing Ca2+ and HCO3− concentrations, both the deposited amount of CaCO3 mass and coating thickness increased correspondingly. With the addition of 50 mM Mg2+, a reduction in the deposition rate of CaCO3 as high as 73% was achieved. The higher the Mg2+ concentration, the larger the deposition rate reduction, which was attributed to the incorporation of Mg2+ into the growing CaCO3 mineral, resulting in the reduction of growth sites (inhibiting effect). The obtained results contribute to a better understanding of electrochemically induced CaCO3 deposition and provide valuable insights into the determination of optimal precipitation parameters, with the aim to optimize industry scaling and anti-scaling processes.

Organic solvent nanofiltration (OSN) is an emerging technology in which membranes are used for organic solvent separation and purifications. Its fields of applications range from pharmacy, catalyst regeneration, to oil and solvent treatments. A major challenge is to maintain a high stability of these (modified) membranes under different feed conditions. Tailoring the selective layer of OSN membranes is the main approach to develop functionalized membranes which show stable high selectivities and permeabilities. During the past decade, methods such as grafting, light-induced modification, plasma treatment, and polyelectrolyte modification have been intensively studied. This paper reviews the recent progress in this field of surface modification of different types of polymeric and also of ceramic OSN membranes. First, the most crucial surface layer properties that affect the OSN membranes properties are described in detail. Next, different surface modification methods and their effects on membrane selectivity and permeability are reviewed and compared. Finally, a perspective is given on expected future trends in this highly challenging and important field of current research.

Porous carbon nanohybrids are promising materials as high-performance electrodes for both sensing and energy conversion applications. This is mainly due to their high specific surface area and specific physicochemical properties. Here, new porous nanohybrid materials are developed based on exfoliated MoS2 nanopetals and either negatively charged phenylsulfonated carbon nanoparticles or positively charged sulfonamide functionalized carbon nanoparticles. MoS2 nanopetals not only act as a scaffold for carbon nanoparticles to form 3D porous hierarchical architectures but also result in well-separated electrochemical signals for different compounds. The characteristics of the new carbon nanohybrid materials are studied by dynamic light scattering, zeta potential analysis, high resolution X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy, infrared spectroscopy and electrochemistry. The new hybrid materials show superior charge transport capability and electrocatalytic activity toward selected biologically relevant compounds compared to earlier reports on porous carbon electrodes.

A family of novel unsymmetrical "peri"-substituted perylene-3,4,9,10-tetracarboxylic acid derivatives (5-10), with 1,6,7,12-tetrachloro-substituents at the bay-positions, has been synthesized. Subsequently, their redox and optical properties have been explored with the intent of unveiling opto-electronic characteristics of these newly synthesized compounds. To synthesize these new compounds, pure 1,6,7,12-tetrachloroperylene-3,4,9,10-tetracarboxylic tetra-n-butylester (4) has been employed as the precursor and the structural modifications have been carried out exclusively at the "peri" positions in an efficient manner. The two synthons prepared in this work, 1,6,7,12-tetrachloroperylene-3,4,9,10-tetracarboxylic di-n-butylester monoanhydride (5) and 1,6,7,12-tetrachloroperylene-3,4,9,10-tetracarboxylic monoimide monoanhydride (8), are extremely valuable and versatile starting materials as they possess free anhydride functionality at the "peri" position in addition to the 1,6,7,12-tetrachloro-bay-substituents. Finally, the conventional methodology for the synthesis of 1,6,7,12-tetraphenoxy-bay-functionalized perylene bisimides and perylene bisbenzimidazoles has been modified to make it faster and more convenient.

In this work, we have simultaneously examined, electrochemically driven deposition of three proteins (haemoglobin, acid phosphatase, and α-amylase) and silica films at a polarized liquid–liquid interface. The interfacial adsorption of the proteins occurs efficiently within the acidic pH range (pH = 2–4). The interfacial charge transfer reactions recorded in the presence of fully positivity charged macromolecules were followed with cyclic voltammetry on the positive side of the potential window. Faradaic currents attributed to the presence of proteins in the aqueous phase appeared for concentrations equal to ca. 0.1 µM for haemoglobin and acid phosphatase and ca. 1 µM for the α-amylase. Concomitant deposition of silica films was achieved via the addition of tetraethoxysilane molecules to the organic phase (1,2-dichloroethane). The hydrolysis and condensation reactions of tetraethoxysilane were controlled via the interfacial transfer of H+ coinciding with the potential for protein adsorption. The effect of tetraethoxysilane concentration – up to 50% by volume – revealed significant shrinkage of the potential window (the region where capacitive currents are recorded). The optimized platform was then used to prepare silica-proteins co-deposits. These could be easily collected from the interface and further analyzed with infrared spectroscopy and transmission electron microscopy.

This work describes a facile approach allowing Dibenzoyl- l -Cystine (DBC) based hydrogel controlled deposition and controlled detachments over a conducting support. The method itself is an electrochemically assisted approach, where the water oxidation at the electrode surface results in a local pH drop inducing DBC gelation and hydrogel formation. We have comprehensively described the possibility of the hydrogel shaping by alternating the anodic deposition potential, DBC concentration and finally the working electrode geometry. The latter includes macro-electrodes in a form of platinum discs having diameter equal to 200 and 500 μm; hexagonal arrays of circular platinum microelectrodes with a diameter of a single electrode equal to 5 or 10 μm and custom made platinum microelectrodes, having the shape of circles, triangles and squares, that are used to shape the microgels. Over the course of our work we were able to define the conditions to form a number of different hydrogel shapes such as: (i) flat and planar deposits; (ii) hemispherical deposits with an oxygen bubble pocket; (iii) spongy hydrogel structures or (iv) hemispherical micro-cups build from radially oriented DBC fibres directionally growing from the support. Furthermore, we were also able to remotely form and then detach the hydrogel deposit in the initial formulation solution using only an electrochemical trigger. Our work represents a solid proof of concept and opens a number of new avenues for the electrochemically assisted soft matter fabrication down to micrometre scale.

The behaviour of acid phosphatase at an electrified liquid–liquid interface was studied in this work. It was found that only the protonated form of the protein can undergo interfacial adsorption which is affected by the pH of the aqueous phase. With ion transfer voltammetry we could detect acid phosphatase in concentrations as low as 0.1 μM. We were able to co-deposit the protein and silica at the electrified liquid–liquid interface via controlled proton transfer to the organic phase where it catalyzed tetraethoxysilane hydrolysis, followed by polycondensation to silica. Keywords: ITIES, Sol-gel process of silica, Interfacial deposition, Proteins, Acid phosphatase

The molecular geometry and supramolecular packing of two bichromophoric prototypic light harvesting compounds D1A2 and D2A2, consisting of two naphthylimide energy donors that were attached to the 1,7 bay positions of a perylene monoimide diester energy acceptor, have been determined by a hybrid approach using magic angle spinning NMR and electron nano crystallography (ENC), followed by modelling. NMR shift constraints, combined with the P-1 space group obtained from ENC, were used to generate a centrosymmetric dimer of truncated perylene fragments. This racemic packing motif is used in a biased molecular replacement approach to generate a partial 3D electrostatic scattering potential map. Resolving the structure of the bay substituents is guided by the inversion symmetry and the distance constraints obtained from heteronuclear correlation spectra. The antenna molecules form a pseudocrystalline lattice of antiparallel centrosymmetric dimers with pockets of partially disordered bay substituents. The two molecules in a unit cell form a butterfly-type arrangement. The hybrid methodology that we have developed is robust and widely applicable for critical structural underpinning of self-assembling structures of large organic molecules.

© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. During the last decade, the synthesis and application of metal-organic framework (MOF) nanosheets has received growing interest, showing unique performances for different technological applications. Despite the potential of this type of nanolamellar materials, the synthetic routes developed so far are restricted to MOFs possessing layered structures, limiting further development in this field. Here, a bottom-up surfactant-assisted synthetic approach is presented for the fabrication of nanosheets of various nonlayered MOFs, broadening the scope of MOF nanosheets application. Surfactant-assisted preorganization of the metallic precursor prior to MOF synthesis enables the manufacture of nonlayered Al-containing MOF lamellae. These MOF nanosheets are shown to exhibit a superior performance over other crystal morphologies for both chemical sensing and gas separation. As revealed by electron microscopy and diffraction, this superior performance arises from the shorter diffusion pathway in the MOF nanosheets, whose 1D channels are oriented along the shortest particle dimension.

A straightforward, direct, and selective method is presented for electrochemical cocaine identification in street samples. The sensing mechanism is based on a simple ion transfer reaction across the polarized liquid-liquid interface. The interfacial behavior of a number of cutting agents is also reported. Interfacial miniaturization has led to improved electroanalytical properties of the liquid-liquid interface based sensor as compared with the macroscopic analogue. The reported method holds great potential to replace colorimetric tests with poor selectivity for on-site street sample analysis.

Silicon semiconductors with a thin surface layer of silica were first modified with polyelectrolytes (polyethyleneimine, polystyrene sulfonate and poly(allylamine)) via a facile layer-by-layer deposition approach. Subsequently, lipid vesicles were added to the preformed polymeric cushion, resulting in the adsorption of intact vesicles or fusion and lipid bilayer formation. To study involved interactions we employed optical reflectometry, electrochemical impedance spectroscopy and fluorescent recovery after photobleaching. Three phospholipids with different charge of polar head groups, i.e. 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), 1,2-dioleoyl-sn-glycero-3-phospho-L-serine (DOPS) and 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) were used to prepare vesicles with varying surface charge. We observed that only lipid vesicles composed from 1:1 (mole:mole) mixture of DOPC/DOPS have the ability to fuse onto an oppositely charged terminal layer of polyelectrolyte giving a lipid bilayer with a resistance of >100 kΩ. With optical reflectometry we found that the vesicle surface charge is directly related to the amount of mass adsorbed onto the surface. An interesting observation was that zwitterionic polar head groups of DOPC allow the adsorption on both positively and negatively charged surfaces. As found with fluorescent recovery after photobleaching, positively charged surface governed by the presence of poly(allylamine) as the terminal layer resulted in intact DOPC lipid vesicles adsorption whereas in the case of a negatively charged silica surface formation of lipid bilayers was observed, as expected from literature.

Short pieces of fused silica capillary tubing were used to support an electrified liquid–liquid interface. A methyl deactivated silica capillary having a diameter of 25 μm was filled with 1,2-dichloroethane solution and served as the organic part of the liquid–liquid interface. A nondeactivated fused silica capillary having a diameter of 5, 10, or 25 μm was filled with an aqueous HCl solution and served as the aqueous part of the electrochemical cell. For the latter, silanization of the capillary interior with chlorotrimethylsilane allowed for a successful phase reversal. All capillaries were characterized by ion transfer voltammetry using tetramethylammonium cation as a model ion. This simple, fast, and low-cost miniaturization technique was successfully applied for detection of the antibiotic ofloxacin. K.R. is grateful for the funding obtained from the Erasmus+ program.

We have investigated in detail properties of hybrid polyelectrolyte-anion exchange membranes (AEMs) having different amounts of a guanidinium-modified poly(allylamine hydrochloride) (PAH-Gu) derivative (2, 5, and 8 wt%). The presence of guanidinium groups at the membrane surface was confirmed by XPS. For 2 and 5 wt% the blended membranes are homogeneous, while at 8 wt% segregation is observed by AFM. The membrane permselectivity and ionic electrical resistance for phosphate reduce upon incorporation of the PAH-Gu in the membrane, reflecting an increased co-ion (H+ and Na+) permeation. We conclude that PAH-Gu loaded in the AEM favors an interaction with phosphate. In electrodialysis, using sodium sulfate and sodium dihydrogen phosphate at equal concentrations in the source phase a slight preference for phosphate was observed. Our work shows that this facile membrane fabrication procedure shows great potential in terms of tuning the membrane properties. One way to boost selective ion transport could be by increasing the number of functional groups in the membrane.

Capacitive detection of organic pollutants present in water at low ppm and ppb levels by means of polymer-coated interdigitated electrode (IDE) structures is a challenging research and engineering task. The detection limit of a measuring system is dependent on its noise level and systematic physical nonidealties. To achieve a high detection sensitivity all parasitic impedance effects must be reduced as much as possible in order not to interfere with the information carrying signal. In comparison to ‘closed’, three-dimensional structures, the electrical sensing field of the ‘open’, planar IDE structure is geometrically difficult to guard. Direct exposure to aqueous solutions may cause unpredictable parasitic coupling to the surrounding, which results in changes in the sensitivity of response of the device to changes in environmental conditions such as salt concentration and pH. Thicker polymer layers increase the distance between the electrode plane and the water phase, thereby reducing the parasitic coupling effects but at significant cost of the sensing response time. In this work we demonstrate how water-enhanced electrical coupling to guarding electrodes is a key mechanism in achieving response immunity to parasitic electric-field bending without impairing the detection performance of the polymer-coated IDE platform. Our work contributes to the knowledge of capacitive response interpretation and mechanisms and points out important design considerations for improved sensing systems, in particular for applications in aqueous environments such as droplet and flow detectors for biomedical and environmental fields.

DNA methylation plays an essential role in regulating cell growth and proliferation, and disease. Changes in aberrant DNA methylation are disease-specific, and, accordingly, the stage of disease progression can be anticipated. Aberrant forms of DNA methylation are recognized as biomarkers in various cancers. Thus, many research efforts recently focused on the detection of these epigenetics for both early cancer diagnoses and prognoses. Here, we provide the most important and relevant current developments while we discuss and assess the pros and cons of common detection strategies.

Metal–organic frameworks (MOFs) are porous crystalline materials consisting of metal ions bound through coordination bonds to organic linkers. Much research over the last few decades have been devoted to the synthesis of these materials in view of their promising applications in, for example, catalysis, separation, gas storage, drug delivery and sensing. Among the variety of methods developed for the synthesis of MOFs are electrochemical techniques. These methods have several advantages such as mild synthesis conditions, shorter synthesis times and the possibility to control the reaction conditions directly during the synthesis process. However, the progress of electrosynthesis methods has lagged behind that of other methods such as solvothermal and microwave-assisted synthesis. In this Review, we summarise and critically assess research on the electrosynthesis of MOFs and provide a full picture of the developments within this field. The various ways in which electrochemistry has contributed to the synthesis of MOFs are explained, their strengths and shortcomings are discussed, and an outlook for future research is provided.

A robust and scalable procedure to obtain pure 1,6,7,12-tetrachloroperylene-3,4,9,10-tetracarboxy bisanhydride, a highly valuable synthon, has been developed via synthesis of a novel intermediate compound 1,6,7,12-perylene-3,4,9,10-tetracarboxy tetrabutylester.

In this work commercially available Fe3O4 NPs were coated with polyallylamine hydrochloride (PAH) and PAH functionalized with guanidinium groups (PAH–Gu) for investigating the phosphate adsorption properties under alkaline conditions. The coating can be prepared easily and rapidly and results in Fe3O4 NPs with improved properties related to phosphate binding and colloidal stability. At a low initial phosphate concentration (2 mg L−1), the novel Fe3O4@PAH–Gu material was able to remove phosphate rather independently of the pH condition (4.0, 3.6 and 3.7 mg g−1 at pH = 5, 8 and 10, respectively), whereas for the uncoated Fe3O4 NPs the amount of adsorbed phosphate drops by >75% upon changing from acidic to alkaline conditions (0.84 mg g−1 at pH = 10). Under alkaline conditions, the fastest adsorption was observed for Fe3O4@PAH–Gu followed by Fe3O4@PAH and Fe3O4. This can be related to the additional interaction forces due to the presence of primary amine groups (in PAH and PAH–Gu) and Gu groups (in PAH–Gu only) in coatings. Over 80% of the phosphate adsorbed on the novel Fe3O4@PAH–Gu material was successfully desorbed and the coated NPs were re-used over three adsorption/desorption cycles. This work will stimulate the design and preparation of functionalized polyelectrolytes for an extended area of applications, especially for the selective removal of target compounds from wastewater.

We report a strategy for the fabrication of a new type of electrochemical nanogap transducer. These nanogap devices are based on signal amplification by redox cycling. Using two steps of electron-beam lithography, vertical gold electrodes are fabricated side by side at a 70 nm distance encompassing a 20 attoliter open nanogap volume. We demonstrate a current amplification factor of 2.5 as well as the possibility to detect the signal of only 60 analyte molecules occupying the detection volume. Experimental voltammetry results are compared to calculations from finite element analysis.