Search Results (17)

The current research developed an optical carbon dioxide (CO₂) sensor using anodized aluminum oxide (AAO) as the substrate. We developed an optical carbon dioxide (CO₂) sensor utilizing CdSe/ZnS quantum dots (QDs) as the fluorescent dye and Phenol Red as the pH indicator. The QDs acted as the CO₂-responsive fluorophore and were embedded in a polyimide butyl methacrylate (polyIBM) matrix. This sensing solution was applied to an anodized aluminum oxide (AAO) substrate, which provided a porous and stable platform for sensor fabrication. Photoluminescence measurements were conducted using the coated AAO substrate, with excitation from a 405 nm LED light source. The sensor exhibited red fluorescence emission at 570 nm and could detect CO₂ concentrations in the linear range of 0–100%. Experimental results showed that fluorescence intensity increased with CO₂ concentration, achieving a sensitivity of 211. A wavelength shift of 0.1657 nm/% was observed, indicating strong interactions among CO₂ molecules, Phenol Red, and the QDs within the AAO matrix. The sensor demonstrated a response time of 55 s and a recovery time of 120 s. These results confirm the effectiveness of this optical sensing approach in minimizing fluctuations from the excitation light source and highlight the potential of the AAO-supported QDs and Phenol Red composite as a reliable CO₂ sensing material. This advancement holds promise for applications in both medical and industrial fields. Full article

The need for renewable alternatives to petroleum-based polymers is growing in response to environmental concerns and resource depletion. Polyimides (PIs), which are traditionally synthesized from petroleum-derived monomers, raise sustainability issues. In this work, renewable 2,5-furandicarboxylic acid (FDCA) was employed as a sustainable feedstock to synthesize a bio-based diamine monomer, N,N′-bis(4-aminophenyl)furan-2,5-dicarboxamide (FPA). Subsequently, FPA was polymerized with various aromatic dianhydrides through thermal imidization, yielding four distinct bio-based polyimide (FPA-PI) films. The resulting films exhibited exceptional thermal stability, with 5% weight loss temperatures exceeding 425 °C and char yields ranging from 54% to 60%. Mechanical characterization revealed high elastic moduli (2.14–3.20 GPa), moderate tensile strengths (50–99 MPa), and favorable aging resistance. Gas permeation tests demonstrated promising CO₂/N₂ separation performance, with FPA-DODDA achieving superior CO₂/N₂ selectivity (27.721) compared to commercial films such as Matrimid^®, polysulfone, and polycarbonate, while FPA-BPFLDA exhibited enhanced CO₂ permeability (P(CO₂) = 2.526 Barrer), surpassing that of Torlon^®. The CO₂/N₂ separation performance of these FPA-PI films is governed synergistically by size-sieving effects and solution-diffusion mechanisms. This work not only introduces a novel synthetic route for bio-based polymers but also highlights the potential of replacing conventional petroleum-based materials with renewable alternatives in high-temperature and gas separation applications, thereby advancing environmental sustainability. Full article

In the growing field of personalized medicine, non-invasive wearable devices and sensors are valuable diagnostic tools for the real-time monitoring of physiological and biokinetic signals. Among all the possible multiple (bio)-entities, pH is important in defining health-related biological information, since its variations or alterations can be considered the cause or the effect of disease and disfunction within a biological system. In this work, an innovative (bio)-electrochemical flexible pH sensor was proposed by realizing three electrodes (working, reference, and counter) directly on a polyimide (Kapton) sheet through the implementation of CO₂ laser writing, which locally converts the polymeric sheet into a laser-induced graphene material (LIG electrodes), preserving inherent mechanical flexibility of Kapton. A uniform distribution of nanostructured PEDOT:PSS was deposited via ultrasonic spray coating onto an LIG working electrode as the active material for pH sensing. With a pH-sensitive PEDOT coating, this flexible sensor showed good sensitivity defined through a linear Nernstian slope of (75.6 ± 9.1) mV/pH, across a pH range from 1 to 7. We demonstrated the capability to use this flexible pH sensor during dynamic experiments, and thus concluded that this device was suitable to guarantee an immediate response and good repeatability by measuring the same OCP values in correspondence with the same pH applied. Full article

Ice accumulation poses considerable challenges in transportation, notably in the domain of general aviation. The present study combines the strengths and limitations of conventional aircraft deicing techniques with the emerging trend toward all-electric aircraft. This study aims to utilize laser-induced graphene (LIG) technology to create a multifunctional surface, seamlessly integrating hydrophobic properties with efficient electrical heating to mitigate surface icing effectively. We investigated the utilization of a 10.6 μm CO₂ laser for direct writing on polyimide (PI), a widely used insulating encapsulation material. From the thermomechanical perspective, our initial analysis using COMSOL Multiphysics software (V5.6) revealed that when the laser power P exceeds 5 W, the PI substrate experiences ablative damage. The experimental results show that when P ≤ 5 W, an increase in power has a positive impact on the quality, surface porosity, roughness reduction, line-spacing reduction, and water contact-angle enhancement of the graphene. Conversely, when P > 5 W, higher power negatively affects both the substrate and the graphene structure by inducing excessive ablation. However, it influences the graphene line height positively and is consistent with overall experimental–simulation congruence. Furthermore, the incorporation of high-quality graphene resulted in a surface that exhibited higher contact angles (CA > 120°), lower energy consumption, and higher heating efficiency compared to the use of traditional electrically heated materials for anti-icing applications. The potential applications of this one-step fabrication method extend across various industries, particularly aviation, marine engineering, and other ice-prone domains. Moreover, the method has extensive prospects for addressing pivotal challenges associated with ice formation and serves as an innovative and efficient anti-icing technology. Full article

The urgent removal of Cd, Co, and Ni from nitrate and sulfate is essential to mitigate the potential risk of chemical pollution from large volumes of industrial wastewater. In this study, these metal ions were rapidly recovered through applying voltage on nitrate and sulfate, utilizing laser-induced graphene/polyimide (LIG/PI) film as the electrode. Following the application of external voltage, both the pH value and conductivity of the solution undergo changes. Compared to Co²⁺ and Ni²⁺, Cd²⁺ exhibits a lower standard electrode potential and stronger reducibility. Consequently, in both nitrate and sulfate solutions, the reaction sequence follows the order of Cd²⁺ > Co²⁺ > Ni²⁺, with the corresponding electrode adsorption quantities in the order of Cd²⁺ > Co²⁺ ~ Ni²⁺. Additionally, using the recovered Co(OH)₂ as the raw material, a LiCoO₂ composite was prepared. The assembled battery with this composite exhibited a specific capacity of 122.8 mAh g⁻¹, meeting practical application requirements. This research has significance for fostering green development. Full article

3-nitro-1,2,4-triazol-5-one (NTO) has been widely used as a kind of insensitive single-compound explosive owing to its excellent balance between safety and explosive energy. To reduce its possible acid corrosion and extend its application to insensitive ammunition, acid protection research on NTO-based explosives is significant. Traditionally, the acid protection effect was evaluated by metal corrosion, which is time-consuming and qualitative. An efficient and quantitative method is desirable for evaluating the acid protection effect and exploring novel protection materials. Herein, a polyimide of 4,4’-(hexafluoroisopropene)diphthalic anhydride (6FDA)/2,2-bis(trifluoromethyl)-4,4-diaminobiphenyl (TFMB) was synthesized by replacing the 4,4’-diaminodiphenyl ether (ODA) monomer with a TFMB monomer to act as an acid-protective coating material for NTO-based explosives. Compared with three other coating materials, polyvinylidene fluoride (PVDF), polyetherimide (PEI), and copolyimide (P84), the fluorinated polyimide exhibits the best acid protection effect. Moreover, a new method was constructed to obtain the pH time-dependent curve in order to evaluate efficiently the acid protection effect of the polymer materials. By the virtue of molecular dynamic simulation (Materials Studio 2023), the interfacial effects of the coating materials with NTO-based explosives were obtained. The study provides an interpretation of the acid protection effect on the molecular level, suggesting that the higher content of fluorine atoms is beneficial for stabilizing the active hydrogen atom of the NTO by forming intermolecular hydrogen bonds. Full article

With the acceleration of industrialization, the removal of refractory organic dyes from water and how to promote its practical application remains a challenge. Herein, we synthesized an FeCo-LDH/LI-NDG composite electrode material by a simple laser-induced technique on polyimide films, which could electrocatalytically activate peroxymonosulfate (PMS) to completely degrade MB in about 6 min. The reaction rate constant (k_obs) was 0.461 min⁻¹. It was faster than most of the currently reported electrocatalysts. The reaction system demonstrated good interference resistance and catalytic effectiveness in the pH range of 3 to 9. According to the chemical quenching and electron paramagnetic resonance (EPR) experiments, the non-radical pathway of ¹O₂ and the radical pathways of SO₄^·−, ·OH and O₂^·− were involved in the reaction synergistically, with ¹O₂ playing the dominant role. ¹O₂ was produced through the dual pathway of PMS electron loss at the anode and O₂^·− intermediate transformation at the cathode. The two activation methods of electro-activation and catalytic activation of PMS had synergistic effects to achieve high efficiency in the whole process of production, reaction and recovery, providing new ideas to advance practical applications. Full article

In this study, multilayer graphene oxide (GO) was used to prepare the functional layer of polyimide/GO composite membrane with polyimide (P84) used as the supporting layer. Chitosan added in the functional layer was utilized to adjust the selectivity of the composite membrane. The effects of GO and chitosan contents on membrane morphology and separation performance were investigated in detail. The composite membrane showed high rejection to Congo red and Methyl orange with high flux but low rejection to Na₂SO₄ and MgCl₂ at 0.2 MPa and ambient temperature. The membrane exhibited excellent solvent resistance in N,N-dimethylacetamide (DMAc) after being crosslinked with 0.5 wt.% triethylene tetramine. The result means that a highly selective and solvent-resistant P84/GO composite membrane was prepared with the facile filtration preparation method. Full article

This research introduces zeolite carbon composite (ZCC) as a new filler on polymeric membranes based on the BTDA-TDI/MDI (P84) co-polyimide for the air separation process. The separation performance was further improved by a polydimethylsiloxane (PDMS) coating to cover up the surface defect. The incorporation of 1 wt% ZCC into P84 co-polyimide matrix enhanced the O₂ permeability from 7.12 to 18.90 Barrer (2.65 times) and the O₂/N₂ selectivity from 4.11 to 4.92 Barrer (19.71% improvement). The PDMS coating on the membrane further improved the O₂/N₂ selectivity by up to 60%. The results showed that the incorporation of ZCC and PDMS coating onto the P84 co-polyimide membrane was able to increase the overall air separation performance. Full article

Three new isomeric 6FDA-based polyimide-ionenes, with imidazolium moieties and varying regiochemistry (para-, meta-, and ortho- connectivity), and composites with three different ionic liquids (ILs) have been developed as gas separation membranes. The structural-property relationships and gas separation behaviors of the newly developed 6FDA polyimide-ionene + IL composites have been extensively studied. All the 6FDA-based polyimide-ionenes exhibited good compatibility with the ILs and produced homogeneous hybrid membranes with the high thermal stability of ~380 °C. Particularly, [6FDA I4A pXy][Tf₂N] ionene + IL hybrids having [C₄mim][Tf₂N] and [Bnmim][Tf₂N] ILs offered mechanically stable matrixes with high CO₂ affinity. The permeability of CO₂ was increased by factors of 2 and 3 for C₄mim and Bnmim hybrids (2.15 to 6.32 barrers), respectively, compared to the neat [6FDA I4A pXy][Tf₂N] without sacrificing their permselectivity for CO₂/CH₄ and CO₂/N₂ gas pairs. Full article

A series of linear aromatic copolyimides (Co-PIs) were synthesized by reacting 4,4′-biphthalic anhydride (BPA) with various molar contents of 2,2′-bis(trifluoromethyl)benzidine (TFB) and p-xylylenediamine (p-XDA) in N,N′-dimethylacetamide (DMAc). Co-PI films were fabricated by solution casting and thermal imidization with poly(amic acid) (PAA) on glass plates. The thermo-optical properties and gas permeabilities of Co-PI films composed of various molar ratios of p-XDA (0.2–1.0 relative to BPA) were investigated. Thermal properties were observed to deteriorate with increasing p-XDA concentration. However, oxygen-transmission rates (O₂TRs) and optical transparencies improved with increasing p-XDA concentration. Co-PI hybrids with a 1:0.2:0.8 molar ratio of BPA:TFB:p-XDA and organically modified hectorite (STN) were prepared by the in situ intercalation method. The morphologies and the thermo-optical and gas permeation properties of the hybrids were examined as functions of STN loading (5–50 wt %). XRD and TEM revealed substantial increases in clay particle agglomeration in the Co-PI hybrid films as the clay loading was increased from 5 to 50 wt %. The coefficient of thermal expansion (CTE) and the O₂TR of a Co-PI hybrid film were observed to improve with increasing STN concentration; however, its optical transparency decreased gradually with increasing STN concentration. Full article

Three polyimides and six inorganic fillers in a form of nanometer-sized particles were studied as thick film solution cast mixed matrix membranes (MMMs) for the transport of CO₂, CH₄, and H₂O. Gas transport properties and electron microscopy images indicate good polymer-filler compatibility for all membranes. The only filler type thatdemonstrated good distribution throughout the membrane thickness at 10 wt.% loading was BaCe_0.2Zr_0.7Y_0.1O₃ (BCZY). The influence of this filler on MMM gas transport properties was studied in detail for 6FDA-6FpDA in a filler content range from one to 20 wt.% and for Matrimid^® and P84^® at 10 wt.% loading. The most promising result was obtained for Matrimid^®—10 wt.% BCZY MMM, which showed improvement in CO₂ and H₂O permeabilities accompanied by increased CO₂/CH₄ selectivity and high water selective membrane at elevated temperatures without H₂O/permanent gas selectivity loss. Full article

Novel polymer composite materials, including unique nanoparticles, contribute to the progress of modern technologies. In this work, the endohedral fullerene C₆₀ with incapsulated iron atom (endometallofullerene Fe@C₆₀) is used for modification of P84 copolyimide. The impact of 0.1, 0.5, and 1 wt % endometallofullerene on the structure and physicochemical properties of polymer films is studied through scanning electron microscopy, thermogravimetric analysis, and thermomechanical tests. Transport properties are estimated through sorption and pervaporation techniques toward methanol and methyl acetate mixture. The inclusion of endometallofullerene into the copolyimide matrix improves membrane permeability and selectivity in the separation of methanol—methyl acetate mixtures. The maximal effect is achieved with a composite containing 0.5 wt % Fe@C₆₀. The developed composites are effective for energy and resource saving purification of methyl acetate by pervaporation. Full article

Membrane gas separation is a prospective technology for hydrogen separation from various refinery and petrochemical process streams. To improve efficiency of gas separation, a novel hybrid membrane consisting of nanodiamonds and P84 copolyimide is developed. The particularities of the hybrid membrane structure, physicochemical, and gas transport properties were studied by comparison with that of pure P84 membrane. The gas permeability of H₂, CO₂, and CH₄ through the hybrid membrane is lower than through the unmodified membrane, whereas ideal selectivity in separation of H₂/CO₂, H₂/CH₄, and CO₂/CH₄ gas pairs is higher for the hybrid membrane. Correlation analysis of diffusion and solubility coefficients confirms the reliability of the gas permeability results. The position of P84/ND membrane is among the most selective membranes on the Robeson diagram for H₂/CH₄ gas pair. Full article

Fluctuating energy sources require enhanced energy storage demand, in order to ensure safe energy supply. Power to gas offers a promising pathway for energy storage in existing natural gas infrastructure, if valid regulations are met. To improve interaction between energy supply and storage, a flexible power to gas process is necessary. An innovative multibed methanation concept, based on ceramic honeycomb catalysts combined with polyimide membrane gas upgrading, is presented in this study. Cordierite monoliths are coated with $\gamma$-Al₂O₃ and catalytically active nickel, and used in a two-stage methanation process at different operation conditions (p = 6–14 bar, GHSV = 3000–6000 h⁻¹). To fulfill the requirements of the Austrian natural gas network, the product gas must achieve a CH₄ content of ≥96 vol %. Hence, CH₄ rich gas from methanation is fed to the subsequent gas upgrading unit, to separate remaining H₂ and CO₂. In the present study, two different membrane modules were investigated. The results of methanation and gas separation clearly indicate the high potential of the presented process. At preferred operation conditions, target concentration of 96 vol % CH₄ can be achieved. Full article