Helical carbon nanotube membranes for efficient purification of ultrafine oily aerosols in moxa smoke and respiratory protection.

Scalable synthesis of electrically conductive polyethersulfone (PES)-carbon nanotube (CNT) membranes by sequential casting

Investigating the effect of membrane pore size on the permeability of carbon nanotubes in reverse electrodialysis using molecular dynamics simulation.

Bridging the gap between cutting-edge research and classroom practice, this work presents a laboratory module that introduces students to environmental functional materials through the fabrication and application of electroactive carbon nanotube (CNT) membranes. Designed for master’s and advanced undergraduate students, the module guides learners through a complete research-inspired workflow: synthesizing freestanding CNT membranes via vacuum filtration, characterizing their physicochemical properties using electron microscopy and spectroscopy, assessing electrochemical activity via cyclic voltammetry, and evaluating environmental performance through the degradation of methyl orange─a model organic pollutant. The integrated, hands-on experience enables students to explore core concepts in electrochemistry, materials science, and environmental catalysis within a cohesive, visually intuitive system. By systematically connecting synthesis, characterization, and application, students develop a deeper understanding of the structure–function–performance relationship that governs functional materials while cultivating essential skills in data interpretation and interdisciplinary problem-solving.

Desalination based on carbon nanomembranes offers high water permeance and salt rejection, making them promising for addressing global freshwater shortages and energy demands in reverse osmosis (RO) desalination. Enhancing ion rejection by modulating the energy barrier for ion transport through wide carbon nanotubes (CNTs) is a critical challenge for highly efficient desalination. We perform molecular dynamics simulations on water desalination using CNTs membranes, highlighting the key role of nanoconfinement coupled with an electric field. The results show that the electric field extends the threshold of CNT diameter required for complete ion rejection from 1.10 nm to 1.50 nm, achieving ∼100% ion rejection while maintaining water permeance of ∼97 L cm-2 day-1 MPa-1. The calculated energy barriers for ion transport demonstrate that the applied electric field significantly increases the inhibitory effect of wide CNTs on ion permeation. We elucidate that the molecular mechanism governing the free energy barrier of ion arises from the polarization of confined water induced by the coupling of the electric field and CNTs, leading to the stripping and reorganization of the ion hydration shell. This approach achieves water permeance that is up to three orders of magnitude higher than that of commercial RO membranes, enhancing the application potential of CNTs membranes coupled with external fields for water desalination. We expect this work to be valuable for understanding the thermodynamic and kinetic behaviors of solute transport and separation induced by molecular mechanisms.

Spectrally selective absorbers that maximize solar absorption and minimize thermal radiation loss are crucial for efficient solar thermal energy harvesting. However, limitations imposed by the intrinsic properties of conventional materials hinder the fabrication of interference-based absorbers with the desired optical properties. Herein, a high-performance solar absorber with a Dallenbach-type dielectric–metal tandem structure was fabricated using an ultrathin, subquarter-wavelength-thick single-walled carbon nanotube (SWCNT) membrane with tailored optical spectra as the absorbing layer. By mixing multiple SWCNT chiral structures, the optical response of the absorbing layer was tailored to approximate a theoretical complex refractive index spectrum of dielectrics, thereby enabling high solar absorptance, low infrared emittance, and a low angular dependence with a simple bilayer structure. The fabricated proof-of-concept 1 cm2 absorber exhibited excellent spectral selectivity (solar absorptance/infrared emittance of 0.84/0.03) and an equilibrium temperature of ≈190 °C (270 °C) under nonconcentrated (2× concentrated) sunlight, considerably outperforming a blackbody-like absorber. This study presents a high-performance solar absorber with a simple planar structure and proposes a concept of designing dielectrics with the desired optical properties by mixing various types of structure-sorted SWCNTs.

Abstract Adding luminescent defects to semiconducting single-walled carbon nanotubes (SWCNTs) significantly enhances photoluminescence (PL) at photon energies lower than intrinsic PL. Ultraviolet (UV) irradiation is a simple enhancement method. However, the optimal UV irradiation conditions for directly generating luminescent defects in structure-sorted SWCNT membranes remain unclear. In this study, the impacts of UV irradiation on the generation of luminescent defects in structure-sorted semiconducting (6, 5) SWCNT assemblies in air and distilled water were examined. Unlike irradiation in air, which severely damaged SWCNTs and reduced PL intensity, UV irradiation in water caused moderate luminescent defect generation, significantly enhancing defect-induced PL intensity.

The solar-driven interface water evaporation technology shows great potential for application in the field of seawater desalination. However, its practical application still faces persistent challenges: low evaporation rate, salt accumulation leading to performance degradation, and an inability to maintain long-term stable operation at high concentrations. To address these challenges, we designed and fabricated a photothermal membrane, a fluorinated carbon-enhanced porous membrane (F-CEP), which was composed of carbon nanotubes and epoxy and endowed with robust hydrophobicity through surface modification functionalization with perfluoroalkyl silane. This design demonstrated remarkable mechanical qualities (tensile strength: 3.28 MPa), a high capacity to absorb light (250–2500 nm, 97.5%), and the ability to reject salt. After 40 h of exposure to hypersaline brine (20 wt % NaCl), the evaporator maintained salt crystallization-free operation with a sustained vapor flux of 1.95 kg·m–2·h–1 under 1-sun irradiation. In contrast, nonfluorinated counterparts (CEP) exhibited substantial surface crystallization (∼2.0 mg/cm2) within 10 h. This study demonstrated a viable solution for sustained high-throughput evaporation during prolonged operation in high-salinity environments through the synergistic effects of surface hydrophobic modification and structural design, showcasing its significant potential for application in seawater desalination.

Functionalizing goethite on carbon nanotube membrane for heterogeneous electro-Fenton degradation of organic contaminant: Toward energy-efficient production of oxidizing species

Flow-through membranes have demonstrated promising potential in the oxidative removal of antibiotics in water. However, the delicate balance between electron and contaminant transfer during this process has not yet been disclosed. This study employed the continuous percolation theory to reveal the significance of the carbon nanotube (CNT) membrane topology to the anodic degradation of antibiotics. Based on the microscopic current distribution mapped by conductive atomic force microscopy, a conductive percolation threshold (pc) of 0.51 and a nonuniversal critical exponent (t) of 4.1 were determined for the membranes. The semiconductor-to-metal transition near pc shifted the conduction mechanism from electron tunneling at the subcritical-percolation region (SBPR) to the ohmic current at the supercritical region (SPPR). Furthermore, the conductive percolation state influenced sulfamethoxazole (SMX) degradation pathways at the membrane anodes: SPPR favored hydroxyl radical (·OH) addition due to rapid electron transfer, while SBPR and critical percolation promoted ring-opening reactions due to strong localized electric fields. Finally, the SPPR membrane having a CNT loading equal to 40 times that at pc achieved the highest SMX removal (97.3%) and mineralization (50.8%), with a low energy consumption of 0.04 kWh m-3. Overall, the multiscale percolation analysis provides a suitable paradigm for rational design of electrocatalytic membranes for effective antibiotic pollution control.

Abstract The sustainable provision of water is a major global challenge, exacerbated by increasing micropollutant contamination. Developing advanced treatment processes and understanding the fundamental mechanisms responsible for the water purification processes are therefore imperative. The removal of steroid hormone (SH) micropollutants at environmentally realistic concentrations is investigated using a flow‐through electrochemical membrane reactor (EMR) equipped with a carbon nanotube membrane. This EMR is a novel micro design, minimizes typical mass transfer limitations across varying system parameters, and enables an in‐depth study of the limiting factors at extremely low SH concentrations, typical for micropollutants. The integration of high‐performance liquid chromatography with a flow scintillator analyzer and liquid scintillation counting techniques allows elucidation of the complex interplay between adsorption, degradation, and byproduct transformation that takes place in the EMR. A permeate concentration below the detection limit (<2.5 ng L−1) is achieved in the reactor, with the heterogeneous electron transfer identified as the main pathway for steroid hormones degradation. The apparent rate of SH removal in the EMR is linear in the concentration range of 50 to 5 × 104 ng L−1. These findings indicate good potential of EMR for SH removal and provide new knowledge for designing and optimizing the EMR process.

Micromachined biosensors are increasingly indispensable tools for the sensitive, rapid, and cost-effective detection of biological analytes. Their diverse applications, spanning clinical diagnostics to environmental monitoring, make them critical to modern science and technology. Among the different classes of biosensors, electrochemical biosensors stand out for their simplicity, high sensitivity, and versatility [1]. These biosensors utilize electrical signals to detect analyte interactions, offering advantages in real-time monitoring and miniaturization. However, one of the major limitations lies in their ability to detect trace analytes present in concentrations below a specific threshold. At such low levels, the analyte's interaction with the detection site may be insufficient to generate a measurable signal. Addressing this issue requires novel strategies to amplify the detection capability of the sensor.A promising solution involves using localized analyte accumulation to increase the concentration of the target molecule at the detection interface over time. This accumulation enhances the electrical signal, effectively improving the sensor’s sensitivity [2]. Carbon nanotube (CNT) membranes are particularly well-suited for this task due to their unique structural and chemical properties. CNT membranes feature nanoscale porosity, high surface area, and remarkable chemical selectivity, enabling them to act as efficient filters. They trap and concentrate analytes while allowing the passage of smaller or non-target components such as solvents or impurities. The strong interaction between the analyte and CNT surfaces, driven by mechanisms such as van der Waals forces, π-π stacking, and electrostatic attraction, facilitates this accumulation. The result is a significant increase in the local analyte concentration at the detection site, leading to a stronger and more detectable electrochemical response [3].This study presents a novel electrochemical biosensor incorporating a single-walled carbon nanotube (SWCNT) membrane that serves as both a working electrode and a filtering layer. The device is integrated into a microfluidic chip designed to enable real-time analyte accumulation and amplification. The biosensor employs three electrodes fabricated on a polyethylene terephthalate (PET) substrate: the SWCNT membrane functions as the working electrode, a graphite layer acts as the counter electrode, and an Ag/AgCl electrode serves as the reference. The SWCNT membrane is synthesized through vacuum filtration and deposited onto the PET substrate, while the counter and reference electrodes are patterned using screen-printing techniques. The PET substrate is bonded to a polydimethylsiloxane (PDMS) microfluidic channel, which facilitates fluid flow and ensures direct interaction between the analyte and the working electrode.The experimental configuration involves injecting a sodium citrate buffer solution containing gold nanoparticles (AuNPs, 60 nm in diameter, 1 mol/L) into the microfluidic channel using a syringe pump. Cyclic voltammetry (CV) [4] is conducted at regular intervals, with the potential swept between -0.35 V and 0.8 V at a scan rate of 10.0 mV/s. Over the course of the experiment, the SWCNT membrane demonstrates a substantial analyte amplification effect. Initially, the oxidation peak current is observed at 8 µA. Over 14 minutes of operation, the current increases progressively, reaching a saturation value of 56 µA. This corresponds to a remarkable 700% sensitivity enhancement. In comparison, a control experiment (no filter membrane) conducted on an identical device that blocks fluid flow through the SWCNT membrane shows no significant increase in current, saturating at 8 µA regardless of analyte contact. This result underscores the importance of the filtration and accumulation mechanism enabled by the SWCNT membrane.Further experiments explore the device’s detection limits under different analyte concentrations. The minimum detectable concentration using the SWCNT membrane is found to be 10⁻⁴ mol/L, significantly lower than the 75 × 10⁻³ mol/L achieved in the absence of filtration. These results confirm that the CNT-based approach enables not only higher sensitivity but also improved precision in detecting low analyte concentrations. The filtering mechanism effectively concentrates the analyte at the detection interface, increasing the likelihood of detection even under challenging conditions.

Nitrogen-doped carbon nanotube membrane with hierarchical porous structure for catalytic degradation of phenol

Optimization of carbon membrane performance in reverse osmosis systems for reducing salinity, nitrates, phosphates, and ammonia in aquaculture wastewater.

The unique attributes of carbon nanotubes (CNTs) establish them as the preferred material for fabricating sophisticated membrane architectures. However, CNT membranes are also susceptible to degradation under harsh environmental conditions, necessitating protective measures to maintain their functionalities. This study presents deposition of boron carbide (B4C) thin films as protective coatings on CNT membranes using chemical vapor deposition. Electron microscopy shows that B4C films were uniformly deposited on the CNTs. Raman spectroscopy shows the preservation of the G and D bands, with a notable stability in the RBM bands, while XPS measurements show sp2 hybridized C-C bonds and an additional shoulder characteristic of the deposited B4C film. This suggests that the CVD process does not degrade the CNTs, but merely adds a layer of B4C to their outer surface. This deposition process also allows for precise control over the membrane's pore size, offering the potential to fine-tune the properties of CNT membranes.

Objectives The reversible electrical modulation of chemical delivery is crucial for various biomedical engineering applications, enabling a tailored drug delivery profile. Electroosmosis flow (EOF) represents a significant electrokinetic phenomenon where a bulk flow is induced through narrow channels including capillaries or microfluidic devices or porous medium, under the influence of an applied electric field (Fig. 1a). Since the velocity of EOF is directly proportional to the applied current density ( I ) and the EOF strength ( K eo ), a standardized indicator related to the zeta potential of the channel walls, it provides the possibility of controlling the direction and velocity of EOF by simply adjusting the surface zeta potential.[1] Herein, a novel concept of electrically modulated delivery utilizing EOF generated within the porous network of the carbon nanotube (CNT) membrane is reported. The charge sign and magnitude of the micropores inside the CNT membrane are altered by applying varying voltages, leading to corresponding changes in the direction and velocity of the EOF. Results and Discussion The multi-walled carbon nanotubes powered are first treated with ozone and dispersed in ethanol. Then, the suspension is formed into the random alignment and cohesive CNT membrane by vacuum-assisted filtration (Fig. 1b-c). The experimental setup consists of symmetrically positioned reservoirs at both ends and a CNT membrane placed between the two reservoirs filled with 0.1 M KCl solution. The electrically modulated system is comprised of two circuits: the main circuit that generates an axial electric field to drive the EOF and the sub-circuit that varies the sign and magnitude of charges on the CNT membrane. The controllability of the EOF direction and velocity is evaluated by observing the movement of the liquid column in the reservoirs (Fig. 1d -e). Based on the established experimental setup, the voltage at which EOF is unobserved is referred to as the neutral voltage (or bias voltage) and is used as the reference for electrical modulation. Significant differences in the direction and velocity of EOF can be observed and measured on the CNT membrane when a positive (or negative) voltage relative to the bias voltage is applied. The EOF under the main circuit of + 0.25 mA and the sub-circuit voltage of + 0.5 V and - 0.5 V relative to the bias voltage, indicating a mobility rate of - 0.781 μL/mm2·min and + 0.972 μL/mm2·min, respectively (Fig. 1f). The plus and minus means that opposite directions of EOF are generated with applied voltages. Next, to demonstrate the effect of applied voltages on the EOF rate, the sub-circuit voltage of + 0.5 V and + 0.25 V relative to the neutral voltage was applied (with the same main circuit of + 0.25 mA), generating a mobility rate of - 0.781 μL/mm2·min and - 0.431 μL/mm2·min. The difference in velocity is due to the differential surface zeta potential within the microchannels of the CNT membrane. Conclusion Here, this study introduces a novel concept of a chemical delivery system by focusing on the electrically modulated EOFs generated in the microchannels of the CNT membrane. According to the results of the experiments, it can be demonstrated that altering the direction and velocity of EOF through electrical modulation is achievable. Additionally, the electrical modulation on EOF is feasible under varying axial electric field strengths and concentration solution environments. Reference [1] Kusama, S., Sato, K., Matsui, Y., Kimura, N., Abe, H., Yoshida, S., & Nishizawa, M. (2021). Transdermal electroosmotic flow generated by a porous microneedle array patch. Nature communications , 12 (1), 658. Fig. 1 Experimental setup and electrical modulation performance. (a) The mechanism of EOF. (b) Optical and SEM images of CNT membrane. (c) Schematic illustration of EOF generated in the micropores of CNT membrane. (d) An experimental setup consisting of Franz Cells with insertion of CNT membrane and the EOF direction and velocity were analyzed by observing the liquid movement. (e) Electrical modulation. (f) The relationship between the applied voltages (relative to the neutral voltage) and flow rates. Figure 1

Broadband efficient light-absorbing SS-PPy@CNT membranes prepared by electrochemical deposition for photothermal conversion

Electro-assisted carbon nanotube dual catalytic membrane system for high-efficiency and energy-efficient water treatment

The growing concern over micropollutants in aquatic ecosystems motivates the development of electrochemical membrane reactors (EMRs) as a sustainable water treatment solution. Nevertheless, the intricate interplay among adsorption/desorption, electrochemical reactions, and byproduct formation within EMR complicates the understanding of their mechanisms. Herein, the degradation of micropollutants using an EMR equipped with carbon nanotube membrane are investigated, employing isotope-labeled steroid hormone micropollutant. The integration of high-performance liquid chromatography with a flow scintillator analyzer and liquid scintillation counting techniques allows to differentiate hormone removal by concurrent adsorption and degradation. Pre-adsorption of hormone is found not to limit its subsequent degradation, attributed to the rapid adsorption kinetics and effective mass transfer of EMR. This analytical approach facilitates determining the limiting factors affecting the hormone degradation under variable conditions. Increasing the voltage from 0.6 to 1.2 V causes the degradation dynamics to transition from being controlled by electron transfer rates to an adsorption-rate-limited regime. These findings unravels some underlying mechanisms of EMR, providing valuable insights for designing electrochemical strategies for micropollutant control.

Polydopamine-coated carbon nanotube catalytic membrane with enhanced water decontamination and antifouling capability under photothermal assistance