Copolymer Layer Research Articles

A ring resonators optical sensor for multiple biomarkers detection

In the recent years, the number of Point-Of-Care-Tests (POCTs) available for clinical diagnostic has steadily increased. POCTs provide a near-patient testing with the potential to generate a result quickly so that appropriate treatment can be implemented, leading to improved clinical outcomes compared to traditional laboratory testing. Technological advances, such as miniaturization of sensors and improved instrumentation, have revolutionized POCTs, enabling the development of smaller and more accurate devices. In this context, it has also gained increasing importance the screening of various analytes simultaneously to increase specificity and improve the characterization of the disease. This study is aimed at developing and characterizing a photonic integrated circuit for multiple markers detection, which represents the functional core towards a full developed POCT device for clinical pathology applications. The photonic sensor, based on microring resonators (MRRs), is functionalized by immobilizing specific antibodies on a copolymer layer deposited on the MRR’s surfaces. Surface chemical techniques were employed to analyse the surface chemical characteristics while fluorescence microscopy was involved to analyse the resulting bioreceptor surface density. The photonic sensor is characterized for the parallel detection of two biomarkers, the C-Reactive Protein (CRP) and the Creatine-Kinase-MB (CK-MB). The analyte-antibody binding curves were obtained both in buffer and in filtered un-diluted artificial saliva showing promising results both in terms of sensitivity, with limit of detection (LOD) of 103 pM for CRP and 140 pM for CK-MB, and in terms of specificity. These encouraging results let the assembly of a highly sensitive POC device for molecular diagnostics.

Innovating a EVOH composite coating towards outstanding H2 barrier and anti-corrosion properties

Concerning the mitigating leakage and hydrogen-induced embrittlement during the conveyance of hydrogen (H2), we have developed an innovative dual-layer composite coating that exhibits exceptional hydrogen gas barrier properties and good resistance to corrosion. Using a bottom-top approach combining hot pressing with spin-coating techniques, the bottom Ethylene-vinyl alcohol copolymer (EVOH) layer with glass flakes (GF) serves as an effective hydrogen gas barrier and the top fluorosilicone resin (FSR) layer with composite nanofiller possesses good corrosion resistance, ensuring the functional integrity of the EVOH layer. The composite coating shows an exemplary low hydrogen gas transmission rate (H2 GTR) value of 2.858 cm3/(m2·24 h·0.1 MPa), representing a substantial decrease of 99.98 % compared to the FSR coating and 15 times more effective than commercial gas barrier films. Moreover, even after a 90-day immersion in 3.5 wt% NaCl solution, the coating maintains an impressive impedance at 0.01 Hz (|Z|0.01 Hz) of 1.0 × 1011 Ω·cm2. The composite coating is exposed to 2 MPa hydrogen for 7 days, and we find that it still sustains outstanding hydrogen gas barrier and anti-corrosion properties.

Nanophase‐Separated Block Copolymer Layers Enabling Stable Zinc Metal Batteries

AbstractAqueous Zn‐ion batteries are promising and efficient energy storage systems owing to their low cost, high safety, and satisfactory capacity. However, the instability of Zn metal anodes, caused by dendritic growth and parasitic side reactions, hinders their practical application. In this study, a nanophase‐separated block copolymer layer that enhances the reversibility of Zn metal anodes is introduced. This layer consists of two components: a high‐performance engineering‐plastic‐based hydrophobic block exhibiting excellent mechanical properties and chemical stability, and a hydrophilic block that significantly improves the interfacial stability of the anode by selectively permeating Zn ions through the separated nanophase channels. Through an improved electrochemical system and scalable fabrication process, this block copolymer provides a feasible approach for the practical application of Zn metal anodes in aqueous energy storage systems.

Silica Nanoparticles Tailored with a Molecularly Imprinted Copolymer Layer as a Highly Selective Biorecognition Element.

Molecularly imprinted silica nanoparticles (SP-MIP) are synthesized for the real-time optical detection of low-molecular-weight compounds. Azo-initiator-modified silica beads are functionalized through reversible addition-fragmentation chain transfer (RAFT) polymerization, which leads to efficient control of the grafted layer. The copolymerization of methacrylic acid (MAA) and ethylene glycol dimethacrylate (EDMA) on azo initiator-coated silica particles (≈100nm) using chain transfer agent (2-phenylprop-2-yl-dithiobenzoate) is carried out in the presence of a target analyte molecule (l-Boc-phenylalanine anilide, l-BFA). The chemical and morphological properties of SP-MIP are characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller surface analysis, and thermogravimetric analysis. Finally, SP-MIP is located on the gold surface to be used as a biorecognition layer on the surface plasmon resonance spectrometer (SPR). The sensitivity, response time, and selectivity of SP-MIP are investigated by three similar analogous molecules (l-Boc-Tryptophan, l-Boc-Tyrosine, and l-Boc-Phenylalanine) and the imprinted particle surface showed excellent relative selectivity toward l-Boc-Phenylalanine (l-BFA) (k=61), while the sensitivity is recorded as limit of detection=1.72×10-4m.

Fabrication of a highly sensitive conductive copolymer layer modified immunosensing tool for cytokeratin-19 fragment detection

Design of a new and highly selective impedimetric biosensor based on the immobilization of a fragment of cytokeratin subunit 19 (CYFRA 21-1)-specific antibodies onto a conductive copolymer layer (poly(epoxy-substituted thiophene)-co-poly(3,4-ethylenedioxythiophene), CCL)-coated indium tin oxide (ITO) for the determination of CYFRA 21-1 in serum samples was reported. CCL was applied as a working electrode-modifying reagent to prepare the surface of the working ITO electrode, and CYFRA 21-1-specific antibodies bound to epoxy ends present in the copolymer layer matrix. The impedimetric response of the immunosensor to CYFRA 21-1 was recorded, and the signaling mechanism of the suggested immunosensor was based on an increase in the charge transfer resistance in the presence of target CYFRA 21-1. The developed biosensor exhibited excellent selectivity for CYFRA 21-1, and it could detect CYFRA 21-1 in a linear dynamic range from 0.0125 to 35 pg/mL with a limit of quantification (LOQ) of 12.25 fg/mL. The designed biosensor showed good storage stability, high sensitivity, suitable repeatability and reproducibility, and acceptable long-term stability. The clinical analysis of the manufactured immunosensor was explored for the analysis of serum samples, and high recoveries and good relative standard deviations (RSDs) were obtained in the range of 97.01 and 103.17 %, respectively. This copolymer-based biosensor could be a feasible tool for clinical diagnosis in complex serum samples.

Boosting the Cell Harvesting Performance of Poly(di(ethylene glycol)methyl ether methacrylate) Cell Release Layers via Copolymerization of Photo- and Thermoresponsive Monomers.

The performance of the cell-selective thermoresponsive poly(di(ethylene glycol)methyl ether methacrylate) (PDEGMA) cell harvest system is shown to be drastically enhanced by exploiting the combination of photoresponsive spiropyran derivates and PDEGMA in copolymerized brushes. The analysis of copolymerized 1'-(2-methacryloxyethyl)-3',3'-dimethyl-6-nitrospiro(2H-1-benzopyran-2,2'-indoline) (SPMA) (DEMGA) di(ethylene glycol)methyl ether methacrylate brushes revealed that a minor adjustment of the SPMA/DEGMA ratios results in a significant alternation of wettability as well as protein adsorption, when switching the temperature from 37 to 22°C and alternately irradiating using different light wavelengths (from 530 to 365nm). Thin P(SPMA-co-DEGMA) layers supported pancreatic tumor PaTu 8988t cells with high cell viability. Copolymer layers with 2.5% SPMA/DEGMA led to the highest efficiency of enzyme-free cell release with very good cell viability. The release is induced by cooling the cell culture medium to 22°C and irradiating the surface with 365nm light. Compared to neat PDEGMA, the P(SPMA-co-DEGMA) layers showed a threefold increase in the speed of the change of cell morphology of the attached cells and a >5 times increased fraction of detached cells, which underlines the potential of these dual responsive PDEGMA systems for optimized performance in the facile capture, culture, and release of different cell lines.

Head-Mounted coating on graphite host enabling highly reversible Li Plating/Stripping in Lithium-ion/Lithium metal hybrid anode

Commercial graphite hosting excessive Li is a promising hybrid Li-ion/Li metal anode for high energy battery. Nevertheless, the issue of Li plating on the top surface of the graphite anode (Gra) is not well tackled, resulting in the uncontrollable growth of Li dendrites and accumulation of “dead Li”, as well as the deactivation of graphite particles. In this work, an insulating ethylene vinyl alcohol copolymer (EVOH) layer is head-mounted covered on the graphite anode surface (Gra-OH) via a simple spray coating method. Due to the electron retarding ability of EVOH film, the top surface of the graphite host is passivated and the excessive Li can be well accommodated inside the porous structure of graphite host. Meanwhile, the lithiophilic –OH group of EVOH can regulate the Li+ flux and render the uniform Li plating behavior. Featuring these, the Gra-OH anodes with a Li storage capacity of 600 mAh/g show high Coulombic efficiencies (CEs) in both coin-cell and pouch cell even under carbonate electrolyte condition. When operating in Li-ion working mode, higher capacity retentions are readily achieved in the half-cell, full-cell and 5 Ah NCM811 pouch-cell, further demonstrating the application compatibility of this surface passivated Gra-OH anode.

Thermoresponsive block-copolymer brush-modified interfaces for effective fabrication of hepatocyte sheets

Hepatic tissue engineering has been investigated for the treatment of liver disease. One promising tissue is the hepatocyte sheet, cultured in temperature-responsive cell culture dishes. However, the preparation of hepatocyte sheets requires precoating of the dish with fetal bovine serum (FBS), which is not desirable for clinical applications. To overcome this issue, we developed a thermoresponsive polymer-modified glass with an affinity for hepatocytes. Poly(N-p-vinylbenzyl-O-β-d-galactopyranosyl-(1→4)-d-guliconamide)-b-poly(N-isopropylacrylamide) (PVLA-b-PNIPAAm) was prepared through two steps of atom transfer radical polymerization (ATRP). The prepared copolymer brushes were characterized using X-ray photoelectron spectroscopy, atomic force microscopy, gel permeation chromatography, contact angle measurements, and fluorescence labeled-fibronectin and -lectin adsorption assays. These characterizations showed that the smooth block copolymer layer was successfully modified by ATRP. The feasibility of using the prepared polymer brush-grafted glass as a hepatocyte sheet fabrication dish was investigated using primary rat hepatocytes. The PVLA-b-PNIPAAm brushes exhibited hepatocyte adhesion and proliferation without FBS precoating. By reducing the temperature from 37 °C to 20 °C, the hepatocyte sheet was recovered from the copolymer brush. These results indicated that the prepared PVLA-b-PNIPAAm brushes can be utilized for effective hepatocyte sheet fabrication without the need for FBS precoating.

Synthesis of magneto-thermal biresponsive temperature-sensitive copolymer/inorganic hybrid green nanoemulsifier with tunable LCST behavior and simulation and calculation of LCST transition behavior of its copolymer

In recent years, intelligent nano-emulsifiers have received a lot of attention in oil fields. Here, a temperature-sensitive copolymer layer, P(NIPAM-co-DMAA), has been grafted in situ on the surface of Fe3O4@SiO2 nanoparticles using two monomers, N-isopropylacrylamide and N,N-dimethylacrylamide, by a single-electron-transfer living radical polymerization method. In this way, magneto-thermal dual-responsive temperature-sensitive copolymer/inorganic hybrid nanoparticles, Fe3O4@SiO2@P(NIPAM-co-DMAA), whave been successfully prepared. The lowest critical solution temperature (LCST) of P(NIPAM-co-DMAA) could be regulated between 39 and 58 °C by modulating the ratio of monomers, endowing Fe3O4@SiO2@P(NIPAM-co-DMAA) nanoparticles with a broader response temperature range for use in more applications. We have used density functional theory and molecular dynamics simulation to thoroughly study the LCST transition behavior of the temperature-sensitive copolymer P(NIPAM-co-DMAA) in water. The intelligent Pickering emulsion obtained by using Fe3O4@SiO2@P(NIPAM-co-DMAA) as a solid particle emulsifier can be regulated between “on” (emulsification) and “off” (breakage) states using temperature and magnetic field as trigger switches. A magnetic field allows the samples to be recycled and reused, which is in line with the energy saving concept. Therefore, the present research may find promising applications in enhanced oil recovery, and other industrial fields, and provides useful insight into the LCST transition behavior of temperature-sensitive polymers.

Polymer-Regulated Electrochemical Reduction of CO2 on Ag.

The influence of polymer overlayers on the catalytic activity of Ag for electrochemical CO2 reduction to CO is explored. Polystyrene and poly(4-vinylpyridine) films of varying thicknesses are applied as catalysis-directing overlayers atop Ag electrodes. For polystyrene, substantial suppression of CO2 reduction activity is observed while the hydrogen evolution reaction (HER) increases. The addition of a nitrogen heteroatom into the phenyl groups of polystyrene (e.g., a pyridine ring) results in an increase in the conversion of CO2 to CO and suppression of HER. Block copolymer variants containing both phenyl and pyridyl functionalities exhibit similar activity for CO evolution but appear to suppress HER further than the polymer layer containing only pyridine groups. The size of the blocks for the copolymer influences the catalytic output of the Ag electrode, suggesting that the hierarchical structure that forms in the block copolymer layer plays a role in catalytic activity at the electrode surface. Analysis of the polymer overlayers suggests that polystyrene significantly inhibits all ion transport to the metal electrode, while poly(4-vinylpyridine) enables CO2 transport while modifying the electronics of the Ag active site. Therefore, the engineered application of polymer overlayers, especially those containing heteroatoms, enables new avenues of electrochemical CO2 reduction to be explored.

Selective Gain in a Periodic Array of Nano-organic Light-Emitting Diodes.

We report nanoscale organic light-emitting diodes (OLEDs) arranged periodically into a large-area array, which produces an amplified emission with a selected spectrum in a narrow band. These nano-OLEDs share a common active layer of super yellow light-emitting PPV copolymer (SY-PPV), which acts both as a waveguide and as a gain channel for the light-emitting signals. The periodic structure supplies Bragg-like diffraction of the emission from SY-PPV under electrical excitation so that the electroluminescence signal is coupled into and confined in the SY-PPV waveguide. During propagation, the waveguide resonance mode interacts with the nano-OLED region and gains amplification. Both the waveguide resonance mode and the output coupling process have strong spectral selectivity, so that the amplification is observed within a spectrum as narrow as 32 nm at FWHM. Such a nano-OLED design not only defines a new scheme of nano-OLEDs, but also proposes potential approaches for electrically pumped organic lasers.

Scalable Synthesis of Carbon Nanomembranes from Amorphous Molecular Layers.

Nanoporous carbon nanomembranes (CNMs) created by self-assembled monolayers ideally combine a high water flux and precise ion selectivity for molecular separation and water desalination. However, their practical implementation is often challenged by the availability of large epitaxial substrates, limiting the membrane up-scaling. Here, we report a scalable synthesis of CNMs from poly(4-vinylbiphenyl) (PVBP) spin-coated on SiO2/Si wafers. Electron irradiation of the amorphous PVBP molecular layers induces the formation of a continuous membrane with a thickness of 15 nm and a high density of subnanometer pores, providing a water permeance as high as 530 L m-2 h-1 bar-1, while repelling ions and molecules larger than 1 nm in size. A further introduction of a reinforced porous block copolymer layer enables the fabrication of centimeter-scale CNM composites that efficiently separate organic dyes from water. These results suggest a feasible route for large-scale nanomembrane fabrication.

Target recognition and preferential degradation of toxic chemical groups by innovative group-imprinted photocatalyst with footprint cavity

Target recognition and preferential degradation of toxic chemical groups remain critical challenges in photocatalytic degradation of organic contaminant. In this study, the concept of group-imprinting was first proposed, and group-imprinted copolymers of aniline and pyrrole were grafted from the surface of magnetic CuFeO2@MnO2 nanocomposites (MIP-CuFeO2@MnO2) using acrylamide as dummy templates for imprinting the amide group of tetracycline for the first attempt, and the molar ratios of dummy template molecule to functional monomer was optimized. The magnetic MIP-CuFeO2@MnO2 showed high adsorption capacity and good recognition for tetracycline. In mixture solution of tetracycline and ibuprofen, the distribution coefficient (kd) value of MIP-CuFeO2@MnO2 for tetracycline was 0.308 L/g, which is 6.86 times more than for ibuprofen (only 0.045 L/g). The selection factor (α) of MIP-CuFeO2@MnO2 is about 3.2 times that of non-imprinted counterpart, indicating that the imprinting cavities in copolymer layer which match with the amide groups of tetracycline can selectively recognize and adsorb tetracycline. More importantly, MIP-CuFeO2@MnO2 exhibited preferential degradation performance for amide groups, which was confirmed by the intermediates and degradation pathway. The E. coli growth suggests effective toxicity reduction of tetracycline due to the preferential degradation of amide groups by photocatalysis of MIP-CuFeO2@MnO2.

Mechano-Electrochemically Promoting Lithium Atom Diffusion and Relieving Accumulative Stress for Deep-Cycling Lithium Metal Anodes.

Lithium metal batteries (LMBs) can double the energy density of lithium-ion batteries. However, the notorious lithium dendrite growth and large volume change are not well addressed, especially under deep cycling. Here, an in-situ mechanical-electrochemical coupling system is built, and it is found that tensile stress can induce smooth lithium deposition. Density functional theory (DFT) calculation and finite element method (FEM) simulation confirm that the lithium atom diffusion energy barrier can be reduced when the lithium foils are under tensile strain. Then tensile stress is incorporated into lithium metal anodes by designing an adhesive copolymer layer attached to lithium in which the copolymer thinning can yield tensile stress to the lithium foil. Elastic lithium metal anode (ELMA) is further prepared via introducing a 3D elastic conductive polyurethane (CPU) host for the copolymer-lithium bilayer to release accumulated internal stresses and resist volume variation. The ELMA can withstand hundreds of compression-release cycles under 10% strain. LMBs paired with ELMA and LiNi0.8 Co0.1 Mn0.1 O2 (NCM811) cathode can operate beyond 250 cycles with 80% capacity retention under practical condition of 4 mAh cm-2 cathode capacity, 2.86g Ah-1 electrolyte-to-capacity ratio (E/C) and 1.8 negative-to-cathode capacity ratio (N/P), five times of the lifetime using lithium foils.

Prediction of water vapor permeation and desiccant saturation in vacuum insulation panels with a glass fiber core

The permeation of dry air in vacuum insulation panels (VIPs) with a glass fiber core has been often prevented using laminated films with metallized ethylene vinyl alcohol copolymer (EVOH) layers; meanwhile, desiccants are incorporated to control the increasing pressure due to the permeation of water vapor. Previously proposed models can predict the changes in long-term performance caused by dry-air permeation, but a method that accounts for water-vapor permeation and desiccant saturation has not been reported before. Predicting the long-term performance of VIPs when exposed to outdoor temperature and humidity is essential for using it as a building insulation material. In this study, we investigated the dependence of the water-vapor transmission rate (WVTR) of metallized EVOH film on temperature and relative humidity, and the effect of ambient water-vapor pressure on the WVTR of metallized EVOH film. To reduce the measurement time of WVTR, we developed a new measurement method using a small sensor device and confirmed that its accuracy is equivalent to that of the conventional method. We measured the water-vapor transmission coefficient of glass fiber core VIPs under various temperature and humidity conditions using this measurement method. For the same water-vapor pressure, the amount of transmission significantly depended on the temperature and humidity conditions. Therefore, the WVTR of metallized EVOH films should be more concerned with the effect of relative humidity than that of the water vapor pressure of the ambient air. Based on these results, a new model that accounts for desiccant saturation was proposed and validated based on the conventional model to predict the long-term performance under permeation of mixed gases. The new model accurately evaluated the long-term performance of VIPs with confirmed desiccant saturation, supporting the long-term performance of glass fiber core VIPs.

Effects of the Donor Unit on the Formation of Hybrid Layers of Donor-Acceptor Copolymers with Silver Nanoparticles.

Donor-acceptor (D-A) copolymers containing perylene-3,4,9,10-tetracarboxydiimide (PDI) electron-acceptor (A) units belonging to n-type semiconductors are of interest due to their many potential applications in photonics, particularly for electron-transporting layers in all-polymeric or perovskite solar cells. Combining D-A copolymers and silver nanoparticles (Ag-NPs) can further improve material properties and device performances. Hybrid layers of D-A copolymers containing PDI units and different electron-donor (D) units (9-(2-ethylhexyl)carbazole or 9,9-dioctylfluorene) with Ag-NPs were prepared electrochemically during the reduction of pristine copolymer layers. The formation of hybrid layers with Ag-NP coverage was monitored by in-situ measurement of absorption spectra. The Ag-NP coverage of up to 41% was higher in hybrid layers made of copolymer with 9-(2-ethylhexyl)carbazole D units than in those made of copolymer with 9,9-dioctylfluorene D units. The pristine and hybrid copolymer layers were characterized by scanning electron microscopy and X-ray photoelectron spectroscopy, which proved the formation of hybrid layers with stable Ag-NPs in the metallic state with average diameters <70 nm. The influence of D units on Ag-NP diameters and coverage was revealed.

In Situ Solution-Processed Submicron Thick SiOx Cy /a-SiNx (O):H Composite Barrier Film for Polymer:Non-Fullerene Photovoltaics.

Aiming to improve the environmental stability of organic photovoltaics, a multilayered SiOx Cy /a-SiNx (O):H composite barrier film coated with a hydrophobic perfluoro copolymer stop layer for polymer:non-fullerene solar cells is developed. The composite film is prepared by spin-coating of polysilicone and perhydropolysilazane (PHPS) following a densification process by vacuum ultraviolet irradiation in an inert atmosphere. The transformation of polysilicone and PHPS to SiOx Cy and a-SiNx (O):H is confirmed by Fourier transform infrared and energy-dispersive X-ray spectroscopy measurement. However, the as-prepared PHPS-derived silicon nitride (PDSN) can react with moisture in the ambient atmosphere, yielding microscale defects and a consequent poor barrier performance. Treating the incomplete PDSN with methanol vapor significantly densifies the film yielding low water vapor transmission rates (WVTRs)of 5.0 × 10-1 and 2.0 × 10-1 gm-2 d-1 for the one- and three-couple of SiOx Cy /a-SiNx (O):H (CON) composite films, respectively. By incorporating a thin hydrophobic perfluoro copolymer layer, the three-coupled methanol-treated CON film with a total thickness of 600nm shows an extremely low WVTR of 8.7 × 10-4 gm-2 d-1 . No performance decay is measured for the PM6:Y6 and PM6:L8-BO cells after such an encapsulation process. These encapsulated polymer cells show good stability storaged at 25°C/50% relative humidity, or under simulated extreme rainstorm tests.

The Potential of Polymer Membranes for Recovery of Xenon from Medical Waste Gas Mixtures

This work is devoted to the evaluation of xenon permeability coefficients for a wide range of polymeric membrane materials, as well as the primary experimental verification of the calculation results for materials used in the production of gas separation membranes. Emphasis is placed on solving the problem of O2/Xe mixture separation as a base for xenon-containing waste medical gas mixtures where it is possible to recover xenon for its reuse. The xenon permeability coefficients were evaluated using a correlation approach, that relates the molecular properties of a gas to gas permeability, and available literature data on the permeability of other gases. The results obtained make it possible to distinguish two main groups of membrane polymers in the Robson diagram for O2/Xe gas pair: xenon-selective (polysiloxane-based rubbers and highly permeable functional polyacetylenes) and oxygen-selective (polyimides, PIMs, perfluorinated polymers). Industrial composite membrane MDK with a selective layer of silicone copolymer and laboratory composite membranes based on PSf and PVTMS were experimentally investigated. The obtained data demonstrate satisfactory convergence of the experimental values with the estimated ones. Based on the results obtained, MDK membrane can be recommended as xenon-selective for xenon recovery.

New homogeneous and bilayer anion-exchange membranes based on N,N-diallyl-N,N-dimethylammonium chloride and ethyl methacrylate copolymer

The paper presents the electrochemical characteristics of a bilayer membrane and a homogeneous anion-exchange membrane based on the new N,N-diallyl-N,N-dimethylammonium chloride and ethyl methacrylate copolymer. The electrochemical behavior and stability under high-intensity electrodialysis conditions were studied using the rotating membrane disk. It has been shown that the casting of a thin layer of an anion-exchange copolymer on the surface of a heterogeneous anion-exchange membrane MA-41 leads to a significant increase in the limiting current (from 4.0 to 8.2 mA/cm2 in 0.01 M NaCl at 100 rpm) and a decrease in the rate of water-splitting reaction at the membrane/solution interface. A decrease in water-splitting rate leads to an increase in the contribution of the electroconvective component to the overlimiting mass transfer, significantly increasing the useful transfer of ions. For membranes formed using the new copolymer, resource tests were carried out for 50 and 400 h at i = 2ilim. Heterocyclic quaternary ammonium bases formed because of N,N-diallyl-N,N-dimethylammonium chloride copolymerization are stable under conditions, while ester fragment of the copolymer undergo hydrolysis. Despite the decrease in the contribution of nonequilibrium electroconvection to the total mass transfer after resource tests, the limiting current on the bilayer and homogeneous membranes does not undergo significant changes.

Flexible electroactive membranes for the electrochemical detection of dopamine

In addition of a key catecholamine neurotransmitter, dopamine is is the metabolite predominantly produced by specific types of tumors (e.g. paragangliomas and neuroblastomas), which cannot be diagnosed using conventional sensitive tests. Within this context, development of flexible electrochemical sensors to monitor dopamine levels in physiological fluids for the early diagnosis and control of diseases related to abnormal levels of such compound, is necessary. In this work, a flexible self-supported membrane, which acts directly as electrode, has been developed to detect dopamine. The membrane consists of three nanoperforated polylactic acid (PLA) layers, which provide flexibility and mechanical integrity, separated by two layers of an electroactive copolymer, which are obtained by electrochemical copolymerization of 3,4-ethylenedioxythiophene and aniline. The sensitivity and detection limit provided by the electroactive copolymer, which is accessible to dopamine molecules through the nanoperforations of the PLA outer layers, is 1.846 µA/(cm2·µM) and 1.7 µM, respectively, in a urea-rich environments that mimics urine. These values allow us to propose the self-standing flexible electrodes developed in this study for the detection of dopamine in patients affected by paragangliomas and neuroblastomas tumors, which typically present dopamine concentrations between 2 and 7 μM.