Dip-coating Process Research Articles

High-Strength and Conductive Electrospun Nanofiber Yarns

In electrospinning, nanofibers are frequently produced in nonwoven web form. Their poor mechanical properties (below 100 MPa) and difficulty in tailoring the fibrous structure have restricted their applications. However, advanced materials must be highly resistant to both deformation and fracture. By combining electrospinning technology with stretching, we have overcome this disadvantage and demonstrated a polyacrylonitrile nanofiber yarn with a tensile strength of 743 ± 20 MPa. The nearly perfect uniaxial orientation of the fibrils under the stretching process is crucial for the remarkable mechanical properties of the yarn. Additionally, the nanofiber yarn was functionalized by a dip-coating process with silver nanowires (AgNWs), imparting conductive properties. This conductive, high-strength nanofiber yarn demonstrates practical applications in flexible and wearable devices. The presented strategy is versatile and can be adapted to create other high-performance nanofiber yarns, with potential uses in fields such as biomedicine and smart textiles.

Dynamics of fluid–structure interaction in paintbrush

Fluid–structure interactions are fundamental in both natural phenomena and industrial applications, particularly in dip-coating processes where withdrawal velocity and drainage dynamics are crucial. Understanding these interactions is essential for optimizing various processes, from enhancing the efficiency of industrial coatings to developing advanced materials with tailored properties. Here, we examine the capillary-induced dynamics of fiber bundles using paintbrush-like structures. We submerge fiber bundles in water and withdraw them at various velocities, observing that water trapped within the bundles leads to capillary-driven fiber assembly. Our experiments show that the bundle diameter after emergence increases with higher withdrawal speed due to viscous effects. We develop a theoretical model that accurately predicts the dynamics of fiber assembly driven by capillary and viscous flows. The mathematical model agrees well with our experimental results, demonstrating the complex interplay between capillary forces and fiber packing. We anticipate that our findings improve the understanding of fluid-structure interactions in fibrous media, providing physical insights that can be applied to more complex systems such as nanopattern collapse and nano/micro-manufacturing.

Fabrication of Zinc Oxide Thin Films by Sol-Gel Dip Coating Process

Zinc oxide (ZnO) is a non-toxic material known for its distinctive physical and chemical properties, including a direct band gap energy of 3.37 eV and a large exciton binding energy of 60 meV, which contribute to its significant thermal and chemical stability at room temperature. Due to these characteristics, ZnO plays a critical role in various applications, such as UV light emitters, transparent conducting thin films in electronic devices, gas sensors, piezoelectric materials, transducers, and as a transparent conductive oxide (TCO) layer in thin-film photoelectrochemical cells. Numerous fabrication techniques have been employed to produce ZnO thin films. However, many of these methods require costly equipment, high vacuum environments, and elevated temperatures. In contrast, the sol-gel process stands out as a convenient, cost-effective, and versatile method for ZnO thin film fabrication. It offers advantages such as simplicity, low crystallization temperature, ease of reproducibility, molecular-level homogeneity, and precise compositional control. In this study, ZnO thin films were deposited onto Indium Tin Oxide (ITO) glass substrates using the sol-gel dip coating method, with varying preparative parameters: sol concentrations and annealing temperatures. The resulting samples were characterized using a UV-visible spectrophotometer, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and energy dispersive X-ray spectroscopy (EDX). The results demonstrated that the unique properties of ZnO thin films are highly dependent on the preparative parameters. Specifically, the band gap energy decreased from 3.25 eV to 3.18 eV with increasing sol concentration and also showed a similar decline with higher annealing temperatures. XRD patterns revealed a smaller full width at half maximum (FWHM) of the most intense peak (002) at higher sol concentrations and annealing temperatures, indicating an increase in crystallite size. FESEM images highlighted distinct morphological changes corresponding to the variations in sol precursor concentration and annealing temperature, while EDX analysis confirmed the formation of highly pure ZnO thin films on ITO glass substrates.

High-Performance Composite Membranes: Embedding Yttria-Stabilized Zirconia in Polyphenylene Sulfide Fabric for Enhanced Alkaline Water Electrolysis Efficiency.

Due to their excellent alkali resistance and chemical stability, polyphenylene sulfide (PPS) fabric membranes are widely used in alkaline water electrolysis (AWE) for hydrogen production. However, traditional PPS membranes suffer from poor hydrophilicity, low airtightness, and high area resistance, resulting in high energy consumption and reduced safety in industrial applications. This study addresses the aforementioned issues by coupling 3-(2,3-epoxy propoxy) propyl trimethoxy silane (KH560) via self-condensation to the PPS membrane and blending it with self-synthesized yttrium-stabilized zirconia nanoparticles (YSZNPs). The YSZNPs are loaded onto the modified PPS fiber surface through dip-coating and hot-pressing processes, forming a micro-mechanical interlocking structure that enhances the overall performance of the membrane in practical hydrogen production applications. The findings indicate that the developed composite membrane demonstrate outstanding hydrophilicity, minimal area resistance (0.21 Ω cm2), and elevated bubble point pressure (2.93224bar). Significantly, tests on gas purity indicate that the produced hydrogen and oxygen attain purities of 99.90% and 99.75%, respectively, when evaluated at a current density of 1.5 A cm-2. Moreover, after 500h of electrolysis testing in a simulated industrial environment, minimal decline in membrane performance is observed, highlighting the competitive edge of this composite membrane in the current AWE market.

Development and evaluation of biocompatible coated microneedle array for controlled insulin delivery: Fabrication, characterization, in vitro, and in vivo investigations

Traditional insulin administration for people with diabetes often involves painful injections, leading to discomfort and challenges with patient compliance. A promising alternative to these conventional methods is transdermal insulin delivery using microneedle arrays, which offer a more comfortable way to deliver insulin through the skin. This study introduces an innovative approach using 3D-printed microneedle arrays coated with insulin via a dip-coating process. These microneedles present a compelling alternative to traditional injections, particularly due to their ability to gently pierce the stratum corneum, the outermost layer of skin, while minimizing discomfort. The microneedle arrays were fabricated using biocompatible resin polymers through 3D printing, creating solid conical needles with a length of 1200 µm, a base diameter of 200 µm, a tip diameter of 80 µm, and a needle spacing of 1.2 mm. The insulin coating was achieved by dip-coating the microneedles in a solution of insulin and polyvinyl alcohol (PVA), with careful optimization of the solution concentration, immersion time, and withdrawal speed to ensure a uniform and controlled coating thickness. Mechanical stability and skin penetration capabilities of the microneedles were assessed using skin models such as parafilm and porcine skin. The tests confirmed that the coated microneedles are robust enough to consistently penetrate the skin. In vivo studies with diabetic rats were conducted to evaluate skin irritation, penetration, and drug delivery efficiency. The insulin-coated microneedle arrays successfully penetrated the skin and delivered the drug with approximately 90 % efficiency. The study also showed that the microneedles provided consistent drug delivery, and the skin recovered without any signs of injury. Additionally, the hypoglycemic effect of the insulin-coated microneedles was comparable to that of traditional subcutaneous insulin injections. These findings underscore the potential of microneedle arrays as a painless and effective method for insulin delivery, maintaining stable glucose levels over an extended period. The demonstrated safety and efficacy of the coated microneedles open the door for clinical trials and potential use in diabetic patients, offering a promising advancement in diabetes management.

Influence of sulfurization temperature on grain growth in Cu2ZnSnS4 thin films synthesized for solar cell applications

Copper-zinc-tin-sulfur (CZTS) thin films, prepared through a dip-coating solution method, present a highly attractive option as absorber materials for thin-film solar cells. This is due to their affordability, environmentally friendly composition, and abundant availability of raw materials. Although films processed with hydrazine-based solutions have achieved the highest efficiency of approximately 12.6%, the toxic and carcinogenic nature of hydrazine negates these advantages. In the ongoing global research on solution-based processing methods, the size of the grains has emerged as a critical factor in the fabrication of efficient solar cells. In our study, we have successfully prepared CZTS thin films with a pure kesterite phase, characterized by large micro-sized grains, using a dip-coating process with an ethanol-based precursor solution, followed by sulfurization. We investigated how the grain size evolves with varying sulfurization temperatures. Notably, we observed that increasing the temperature led to larger and more uniform grain growth. These results underscore the potential of our approach for the straightforward production of high-quality films with sizable grains, ultimately enhancing their photosensitivity and making them a promising candidate for efficient solar cell applications.

Graphene oxide/silicon dioxide (GO/SiO2) hybrid coating on zirconia ceramic for sustainable water desalination

Hybrid membranes combining graphene oxide (GO) and silicon dioxide (SiO2) were successfully developed for pervaporation desalination using porous zircon tube substrates. These GO/SiO2 membranes were carefully designed by adjusting the amount of GO and the pH levels during the dip-coating process on the zircon tube surface. The study aimed to investigate how varying amounts of GO and pH levels affect the membranes' properties and desalination performance. The results indicate that raising the pH level decreases the membranes' hydrophilicity and enhances their stability. Conversely, increasing the amount of GO increases the membranes’ hydrophilicity and reduces their pore size. Higher pH levels and GO amounts resulted in better salt rejection but lower water flux. Among the tested membranes, GS-6 (0.3 % GO/SiO2, pH 6) achieved the highest salt rejection rate of 99.96 % at 30 °C with a 1 % NaCl feed concentration. In contrast, GS-1 (0.1 % GO/SiO2, pH 4) showed the highest water flux of 8.54 kg m−2 h−1 at 60 °C with the same feed concentration. Increasing the temperature led to decreased salt rejection but increased water flux. Additionally, higher feed concentrations lowered both salt rejection and water flux.

Multifunctional pressure and humidity sensor modulated by electrostatic interactions and hydrogen bonds for wearable health monitoring

Breathing and urination, are vital physiological activities of the human body, continuous real-time monitoring of these physiological behaviors could offer timely feedback on an individual’s health status. However, current monitoring techniques predominantly rely on cumbersome and intricate medical apparatuses, posing challenges in adapting to the diverse requirements of multi-scenario detection. Consequently, there is a growing interest in developing wearable devices capable of monitoring breathing and urination. In this work, we developed a multifunctional sensor integrating humidity and pressure sensing modes using a simple dip-coating process. By introducing sodium carboxymethyl cellulose and conductive polyaniline hybrid intercalation between MXene layers, a stable conductive network is established through hydrogen bonds and electrostatic interactions among materials. The overall electromechanical properties of the composites will be well improved. And, the effects of different conductive filler ratios and the number of dipping times on the construction of conductive networks are investigated. The multifunctional sensor exhibited improved sensing characteristics, including detecting pressures up to 532 kPa and a sensitivity of 19.58 kPa−1. Furthermore, it also demonstrates good humidity-sensing capabilities. Tests on volunteers demonstrated the potential in the detection of breathing and urination. In addition, the sensors are capable of transmitting Morse code. This interesting application will offer the possibility of normal communication for people with speech impairments. Given its utility and sustainability, the sensor has potential for applications in wearable health monitoring, intelligent life and telemedicine.

Simple synthesis of weather-resistant and self-cleaning anti-reflective coating for enhancing photovoltaic conversion efficiency

Transparent self-cleaning coatings have garnered significant attention for their promising prospects in outdoor applications, particularly in solar panels and high-end optical devices. However, existing technologies still grapple with the challenges of achieving high transmittance and superior weather resistance. Therefore, developing cost-effective coatings that possess both high transparency and excellent durability is paramount. A novel method for synthesizing an anti-reflective (AR) coating is presented in this paper, offering simplicity, cost-efficiency, and high performance. By merging acid-base catalyzed sol-gel chemistry with the dip-coating process, the coating's transparency, durability, and hydrophobicity are notably improved. Production time is significantly reduced through process optimization. The AR coating achieves an exceptional transmittance of 97.3 % at 620 nm, a 6.7 % increase over that of untreated glass. Furthermore, its 145° water contact angle demonstrates excellent hydrophobicity and self-cleaning properties. Mechanical stability tests indicate that the coating retains over 96 % transmittance even after 30 tape adhesion cycles. Long-term UV exposure tests reveal that the coating's transmittance and contact angle remain almost unchanged, underscoring its superior environmental stability and weather resistance. Additionally, the coating enhances the transmittance of multi-crystalline silicon (mc-Si) solar cells compared to commercial glass, boosting the photovoltaic conversion efficiency from 11.04 % to 11.81 %, an increase of 7 %. With these exceptional properties, this coating holds significant potential for applications in mc-Si solar cells and high-end optical devices, providing the industry with an efficient and economical solution.

Alkoxysilyl derivative of carbamoylphosphonate as a flame retardant modifier of cotton fabrics

This research describes the synthesis of a silane derivative containing phosphorus and nitrogen atoms, leveraging their synergistic flame retardant effect through the incorporation of a PH bond to the isocyanate moiety. The synthesized silane featured alkoxysilyl groups, facilitating permanent bonds with the cotton fabric surface via hydrolysis. Cotton fabrics were modified using silane solutions of varying concentrations (2.5 %, 5 %, and 10 %) through a dip-coating process to determine the effect of the modifier amount on fabric properties. The modified fabrics were subjected to FT-IR, TGA, SEM, and EDS analyses, as well as microcalorimetric and LOI tests, to assess changes in flammability. FT-IR, SEM/EDS, and add-on analyses confirmed effective coverage of the cotton fabric with the flame retardant. Thermogravimetric tests indicated a significant reduction in the mass loss rate during thermal degradation. LOI analyses demonstrated a decrease in flammability (increase in LOI value), while microcalorimetric tests showed a substantial decrease in the heat release rate, correlating with increased modifier concentration on the fabric surface. Post-washing analyses revealed that, although some of the modifier was washed out, the samples still retained reduced flammability.

Optical and Electrical Properties of Spin Coated Bilayer Graphene

Graphene is a 2D material with high transparency, high carrier mobility, and high electrical conductivity [1-4]. In this work, a thin graphene layer was coated on Si through spin coating, and dip coating technique.Graphene ink was prepared by expanding the graphite flakes through microwave irradiation followed by ultrasonic liquid phase exfoliation. 5 mg of the resulting graphene was dispersed in 1 ml of IPA through a probe sonication technique to obtain the graphene suspension/ink. To form the graphene/Si junction, pieces of 3 x 3 cm2 of n-type Si were used. In addition, same size of fused silica were used to measure the reflectance of deposited graphene. The graphene layer in the first sample was formed by spin coating 40 µl of graphene ink on the Si and the fused silica at a speed of 200 rpm for 40 s. The second sample was prepared by dip coating technique, where 13 ml of the graphene ink was added to 47 ml of IPA, followed by dipping Si and the fused silica pieces with a speed of 20 mm/min till they immersed completely and were kept for 1 min and were moved up at the same speed and dried at room temperature. This dip-coating process was repeated 10 times for each sample.The morphology of graphene-coated area was analyzed using the SEM technique. The SEM images of the spin-coated shows that the surface is fully covered with graphene flakes of different sizes stacked on each other with varied orientations, this shows the ability to obtain a continuous coating of graphene by spin coating. Also, Hall effect measurements were performed, and it showed that the conductivity of the Si substrate was 1.95x10-2 ohm-1cm-1, and it increased to 2.74 ohm-1cm-1 after adding the graphene. Finally, the reflectance of the graphene on fused silica was measured using a UV-VIS spectrophotometer, and it showed that the reflectance decreased from 8% to 4% in the range from 360 to 860 nm after adding the graphene.For dip-coated sample, the SEM image shows some voids, and empty areas linked with by graphene structure with a width of few microns, this shows that the dip-coating process needs to be optimized to get a full coverage of the surface. The electrical measurement of this sample showed that the conductivity increased to 2.66 ohm-1cm-1 after the dip coating of graphene. For the reflectance measurements, it was observed that the graphene has decreased the reflectance to 6-7% in the range from 360 to 860 nm.Finally, spin coating at higher speed, and less amount of graphene can be tested, to obtain a thinner graphene layer. For the dip coating process, higher graphene concentration in IPA, and longer immersion time will be investigated to get a better coverage.

Carbon nanotube fibers as efficient p- and n-type thermoelements within geopolymers: A route for large-scale thermal energy harvesting from building structures

This study reports for the first time, the thermoelectric (TE) performance of continuous p- and n-type carbon nanotube fiber (CNTF) filaments integrated within a sustainable, fine-grained geopolymer (GP) based concrete matrix for the complete replacement of cement with supplementary cementitious materials towards CO2 emissions reduction policy. Moreover, CNTF as CO2 negative, conductive, durable and lightweight material could multidimensionally contribute on the achievement of sustainability goals. Herein, pristine CNTF filaments were molecularly modified with p- and n-type aqueous-based dopants in order to stably tune their intrinsic semi-conducting properties via a facile and scalable dip-coating process. The achieved Seebeck coefficient values of the optimized p- and n-type CNTF were +45.2 μV/K and −38.4 μV/K, respectively. Thereafter, the p- and n-type CNTF filaments were employed as pillar-like thermoelectric elements incorporated within a GP mixture for the assembly of a structural thermoelectric generator (TEG) device. The obtained TEG-enabled GP-based concrete demonstrator comprising of 8 p-n serially interconnected junctions is capable of generating a power output of 0.3 μW at an applied through-thickness temperature gradient (ΔT) of 50 Κ. Subsequently, the experimental work was validated using coupled field of TE simulations. Self-powered infrastructures are forecasted to efficiently benefit from available ΔT on large-scale upon their operational lifetime, further promoting future net-zero energy consumption concepts.

Design and fabrication of metal spherical conformal thin film multisensor for high-temperature environment

Conformal thin-film sensors enable precise monitoring of the operating conditions of components in extreme environments. However, the development of these sensors encounters major challenges, especially in uniformly applying multiple film layers on complex metallic surfaces and accurately capturing diverse operational parameters. This work reports a multi-sensor design and multi-layer additive manufacturing process targeting spherical metallic substrates. The proposed high-temperature dip-coating and self-leveling fabrication process achieves high-temperature thin-film coatings with excellent uniformity, high-temperature electrical insulation, and adhesion properties. The fabricated Ag/Pt thin film thermocouple arrays and a heat flux sensor exhibit a maximum temperature resistance of up to 960 °C, with thermoelectric potential outputs and high-temperature resistance closely mirroring those of wire-based Ag/Pt thermocouples. Harsh environmental testing was conducted using high-power lasers and a flame gun. The results show that the array of thin-film conformal thermocouples more accurately reflected temperature changes at different points on a spherical surface. The heat flux sensors achieve responses within 95 ms and withstand environments with heat fluxes over 1.2 MW/m2. The proposed multi-sensor design and fabrication method offers promising monitoring applications in harsh environments, including aerospace and nuclear power.

Visualized and pH-responsive hydrogel antibacterial coating for ventilator-associated pneumonia

Ventilator-associated pneumonia (VAP) is a common healthcare-acquired infection often arising during artificial ventilation using endotracheal intubation (ETT), which offers a platform for bacterial colonization and biofilm development. In particular, the effects of prolonged COVID-19 on the respiratory system. Herein, we developed an antimicrobial coating (FK-MEM@CMCO-CS) capable of visualizing pH changes based on bacterial infection and releasing meropenem (MEM) and FK13-a1 in a controlled manner. Using a simple dip-coating process with controlled loading, chitosan was cross-linked with sodium carboxymethyl cellulose oxidation (CMCO) and coated onto PVC-based ETT to form a hydrogel coating. Subsequently, the coated segments were immersed in an indicator solution containing bromothymol blue (BTB), MEM, and FK13-a1 to fabricate the FK-MEM@CMCO-CS coating. In vitro studies have shown that MEM and FK13-a1 can be released from coatings in a pH-responsive manner. Moreover, anti-biofilm and antibacterial adhesion results showed that FK-MEM@CMCO-CS coating significantly inhibited biofilm formation and prevented their colonization of the coating surface. In the VAP rat model, the coating inhibited bacterial growth, reduced lung inflammation, and had good biocompatibility. The coating can be applied to the entire ETT and has the potential for industrial production.

Intelligent process monitoring of smart polymer composites using large area graphene coated fabric sensor.

Herein, we report the development of an online process monitoring system for vacuum-assisted resin transfer molding (VARTM) process using large area graphene coated in-situ fabric sensor. Besides imparting excellent mechanical properties to the final composites, these sensors provide critical information during the composite processing including detecting defects and evaluating processing parameters. The obtained information can be used to create a digital passport of the manufacturing phase to develop a cost-effective production technique and fabricate high-quality composites. The fabric sensor was produced using a scalable dip-coating process by coating 1-, 3- or 5-layers of thermally reduced graphene oxide (rGO) onto glass fabric surface according to the number of dips of the fabrics into GO solution. The electrical resistances from all electrode pairs were simultaneously and continuously recorded during distinct stages of the VARTM process to determine the relative conductance. During the vacuum cycle, the range of relative conductance increased with the number of coated rGO layers, with the 5-layer rGO-coated sensor showing the highest conductance range of 16.9 %. Additionally, it was observed that the 5-layer coated sensor showed a consistent decrease in conductance during the infusion phase due to the fluid flow pressure dominating the resin electrical conductivity.

MXene coating on waste textiles for wearable electronics and thermal regulation

AbstractTransforming discarded textiles into more valuable products through upcycling offers a multi-pronged approach to alleviating textile industry-related pollution. In this study, we employed a facile approach to upcycling waste textile fabrics via MXene functionalization using a passive dip-coating process. The method is straightforward and versatile, producing a continuous coating on a variety of natural and synthetic textile substrates such as cotton, hemp, and nylon. Even with a minimal amount of MXene, the coated fabrics displayed sufficient conductivity, unlocking their potential for a multitude of applications including Joule heating, strain sensing, and infrared (IR) camouflage. The simplicity of this method provides an alternative utilization for fabric off-cuts and end-of-life garments in the production of multifunctional textiles for smart wearable clothing, potentially mitigating the expected scarcity of textile resources in the forthcoming decades. Graphical abstract This study employed a simple and versatile approach of upcycling waste textile fabrics via MXene functionalization through a passive dip coating process, meeting the demands for materials that are both sustainable and multi-functional.

Development of multifunctional chitosan-based composite film loaded with tea polyphenol nanoparticles for strawberry preservation

Incorporating polysaccharide-based composite films with nanobiotechnology offers a new strategy for food preservation. This study initially focuses on the preparation of tea polyphenol nanoparticles (TPNP), novel and derived from natural antibacterial agents, which serve to improve stability. Afterwards chitosan-based composite films loaded with TPNP (CTN film) were developed using solution casting method. The incorporation of TPNP significantly improved the UV/water/oxygen barrier properties, mechanical properties and thermal stability, alongside notable physical properties including water contact angle (93.65 ± 0.04°), low water vapor permeability (33.72 ± 3.32 g/m2h) and oxygen permeability (0.11 ± 0.02 g/m2h), tensile strength (61.83 ± 0.70 %), and elongation at break (31.60 ± 6.12 %). The CTN film not only exhibited exceptional biodegradability and nontoxicity, but also demonstrated remarkable antimicrobial efficacy against Escherichia coli and Bacillus subtilis. Additionally, it showcased potent antioxidant activity, boasting DPPH and ABTS radical scavenging rates up to 89.25 ± 0.18 % and 93.84 ± 0.42 %. The CTN film was successfully formed on the surface of strawberries through dip-coating process and their shelf life was extended from 4 to 6 days at 20 °C without side-effect on the weight loss, harness, pH and total soluble solids, illustrating its potential for enhancing food preservation.

Long-life and self-cleaning membrane by dissolved oxygen activation in natural conditions

In this study, a dissolved oxygen-activated self-cleaning membrane was obtained by efficiently loading the catalyst (CuZn-C) onto the membrane surface through a simple dip-coating and vacuum filtration process. The results showed that the catalytic membrane presented a high flux recovery rate and achieved 100% retention for anionic dyes. It was confirmed by quenching experiments and electron paramagnetic resonance (EPR) that the prepared membrane exhibited excellent dissolved oxygen activation to generate reactive oxygen species (ROS) for pollutant degradation under natural conditions, without extra oxidants input. This study presented a high-performance membrane, which achieved long lifespan and self-cleaning capability by activating natural dissolved oxygen in water.

Fabrication of hollow electrospun Polypyrrole@Cellulose fibrous membrane for ultrahigh-flux dye removal

Membrane technology is a promising method for wastewater treatment, and the balancing between high water flux and high rejection is crucial but extremely challengeable. Herein, an advanced polypyrrole@cellulose fibrous membrane with a hollow structure was prepared through electrospinning followed by a dip-coating process. The sustainable and low-cost cellulose was applied as the raw material while the nontoxic and environmentally stable polypyrrole was chosen as the active layer. Benefiting from the unique hollow structure and the abundant adsorption sites from the polypyrrole, the resulting membrane achieved 99.4 % rejection of anionic Congo red, along with a water flux of 3025.5 L m−2 h−1, which was 4–140 times higher than that of the previously reported membranes. Moreover, it could also efficiently separate cationic methylene blue (a rejection ratio of >96.0 %). This work confirmed the feasibility of hollow electrospun membrane with high dye rejection at ultrahigh water flux, and offered new possibilities to overcome the conflicts between permeation and selectivity in dyeing wastewater treatment.

Development of a Sensitive Colorimetric Indicator for Detecting Beef Spoilage in Smart Packaging.

This study aimed to fabricate and characterize a novel colorimetric indicator designed to detect ammonia (NH3) and monitor meat freshness. The sensing platform was constructed using electrospun nanofibers made from polylactic acid (PLA), which were then impregnated with anthocyanins as a natural pH-sensitive dye, extracted from red cabbage. This research involved investigating the relationship between the various concentrations of anthocyanins and the colorimetric platform's efficiency when exposed to ammonia vapor. Scanning electron microscope (SEM) results were used to examine the morphology and structure of the nanofiber mats before and after the dip-coating process. The study also delved into the selectivity of the indicator when exposed to various volatile organic compounds (VOCs) and their stability under extreme humidity levels. Furthermore, the platform's sensitivity was evaluated as it encountered ammonia (NH3) in concentrations ranging from 1 to 100 ppm, with varying dye concentrations. The developed indicator demonstrated an exceptional detection limit of 1 ppm of MH3 within just 30 min, making it highly sensitive to subtle changes in gas concentration. The indicator proved effective in assessing meat freshness by detecting spoilage levels in beef over time. It reliably identified spoilage after 10 h and 7 days, corresponding to bacterial growth thresholds (107 CFU/mL), both at room temperature and in refrigerated environments, respectively. With its simple visual detection mechanism, the platform offered a straightforward and user-friendly solution for consumers and industry professionals alike to monitor packaged beef freshness, enhancing food safety and quality assurance.