Crosslinking and fluorination reinforced PTFE nanofibrous membrane with excellent amphiphobic performance for low-scaling membrane distillations.

Membrane distillation (MD) has emerged as a promising technology for desalination and concentration of hypersaline brine. However, the efficient preparation of a structurally stable and salinity-resistant membrane remains a significant challenge. In this study, an amphiphobic polytetrafluoroethylene nanofibrous membrane (PTFE NFM) with exceptional resistance to scaling has been developed, using an energy-efficient method. This innovative approach avoids the high-temperature sintering treatment, only involving electrospinning with PTFE/PVA emulsion and subsequent low-temperature crosslinking and fluorination. The impact of the PVA and PTFE contents, as well as the crosslinking and subsequent fluorination on the morphology and MD performance of the NFM, were systematically investigated. The optimized PTFE NFM displayed robust amphiphobicity, boasting a water contact angle of 155.2º and an oil contact angle of 132.7º. Moreover, the PTFE NFM exhibited stable steam flux of 52.1 L·m-2·h-1 and 26.7 L·m-2·h-1 when fed with 3.5 wt % and 25.0 wt % NaCl solutions, respectively, and an excellent salt rejection performance (99.99 %, ΔT = 60 °C) in a continuous operation for 24 h, showing exceptional anti-scaling performance. It also exhibited stable anti-wetting and anti-fouling properties against surfactants (sodium dodecyl sulfate) and hydrophobic contaminants (diesel oil). These results underscore the significant potential of the PTFE nanofibrous membrane for practical applications in desalination, especially in hypersaline or polluted aqueous environments.

Silk Nanofibril-Palygorskite Composite Membranes for Efficient Removal of Anionic Dyes.

To develop membrane materials with good performance for water purification that are green and low cost, this work reports an organic-inorganic composite membrane composed of silk nanofibrils (SNFs) and palygorskite (PGS). To improve the stability of the the composite membrane, genipin was used as a crosslinking agent to induce the conformational transition of SNF chains from random coils to ß-sheets, reducing the swelling and hydrolysis of the membrane. The separation performance can be adjusted by tailoring the component ratio of the nanomaterial. The results showed that these membranes can effectively remove anionic dyes from water, and they exhibit excellent water permeability. The SNF-based membrane had strong mechanical and separation properties, and the PGS could tune the structure of composite membranes to enhance their permeability, so this green composite membrane has good prospects in water treatment and purification applications.

Electrospun Nanocomposite Fibrous Membranes for Sustainable Face Mask Based on Triboelectric Nanogenerator with High Air Filtration Efficiency.

Abstract: Air pollution caused by the rapid development of industry has always been a great issue to the environment and human being's health. However, the efficient and persistent filtration to PM0.3 remains a great challenge. Herein, a self-powered filter with micro-nano composite structure composed of polybutanediol succinate (PBS) nanofiber membrane and polyacrylonitrile (PAN) nanofiber/polystyrene (PS) microfiber hybrid mats was prepared by electrospinning. The balance between pressure drop and filtration efficiency was achieved through the combination of PAN and PS. In addition, an arched TENG structure was created using the PAN nanofiber/PS microfiber composite mat and PBS fiber membrane. Driven by respiration, the two fiber membranes with large difference in electronegativity achieved contact friction charging cycles. The open-circuit voltage of the triboelectric nanogenerator (TENG) can reach to about 8 V, and thus the high filtration efficiency for particles was achieved by the electrostatic capturing. After contact charging, the filtration efficiency of the fiber membrane for PM0.3 can reach more than 98% in harsh environments with a PM2.5 mass concentration of 23,000 µg/m3, and the pressure drop is about 50 Pa, which doesn't affect people's normal breathing. Meanwhile, the TENG can realize self-powered supply by continuously contacting and separating the fiber membrane driven by respiration, which can ensure the long-term stability of filtration efficiency. The filter mask can maintain a high filtration efficiency (99.4%) of PM0.3 for 48 consecutive hours in daily environments. Supplementary Information: The online version contains supplementary material available at 10.1007/s42765-023-00299-z.

Recent Progress on Graphene-Based Nanocomposites for Electrochemical Sodium-Ion Storage.

In advancing battery technologies, primary attention is paid to developing and optimizing low-cost electrode materials capable of fast reversible ion insertion and extraction with good cycling ability. Sodium-ion batteries stand out due to their inexpensive price and comparable operating principle to lithium-ion batteries. To achieve this target, various graphene-based nanocomposites fabricate strategies have been proposed to help realize the nanostructured electrode for high electrochemical performance sodium-ion batteries. In this review, the graphene-based nanocomposites were introduced according to the following main categories: graphene surface modification and doping, three-dimensional structured graphene, graphene coated on the surface of active materials, and the intercalation layer stacked graphene. Through one or more of the above strategies, graphene is compounded with active substances to prepare the nanocomposite electrode, which is applied as the anode or cathode to sodium-ion batteries. The recent research progress of graphene-based nanocomposites for SIBs is also summarized in this study based on the above categories, especially for nanocomposite fabricate methods, the structural characteristics of electrodes as well as the influence of graphene on the performance of the SIBs. In addition, the relevant mechanism is also within the scope of this discussion, such as synergistic effect of graphene with active substances, the insertion/deintercalation process of sodium ions in different kinds of nanocomposites, and electrochemical reaction mechanism in the energy storage. At the end of this study, a series of strategies are summarized to address the challenges of graphene-based nanocomposites and several critical research prospects of SIBs that provide insights for future investigations.

Construction of α-MnO2 on Carbon Fibers Modified with Carbon Nanotubes for Ultrafast Flexible Supercapacitors in Ionic Liquid Electrolytes with Wide Voltage Windows.

In this study, α-MnO2 and Fe2O3 nanomaterials are prepared on a carbon fiber modified with carbon nanotubes to produce the nonbinder core-shell positive (α-MnO2@CNTs/CC) and negative (Fe2O3@CNTs/CC) electrodes that can be operated in a wide voltage window in ultrafast asymmetrical flexible supercapacitors. MnO2 and Fe2O3 have attracted wide research interests as electrode materials in energy storage applications because of the abundant natural resources, high theoretical specific capacities, environmental friendliness, and low cost. The electrochemical performance of each electrode is assessed in 1 M Na2SO4 and the energy storage properties of the supercapacitors consisting of the two composite electrodes are determined in Na2SO4 and EMImBF4 electrolytes in the 2 V and 4 V windows. The 2 V supercapacitor can withstand a large scanning rate of 5000 mV S-1 without obvious changes in the cyclic voltammetry (CV) curves, besides showing a maximum energy density of 57.29 Wh kg-1 at a power density of 833.35 W kg-1. Furthermore, the supercapacitor retains 87.06% of the capacity after 20,000 galvanostatic charging and discharging (GCD) cycles. The 4 V flexible supercapacitor shows a discharging time of 1260 s and specific capacitance of 124.8 F g-1 at a current of 0.5 mA and retains 87.77% of the initial specific capacitance after 5000 GCD cycles. The mechanical robustness and practicality are demonstrated by physical bending and the powering of LED arrays. In addition, the contributions of the active materials to the capacitive properties and the underlying mechanisms are explored and discussed.

Visual Detection of COVID-19 from Materials Aspect.

Abstract: In the recent COVID-19 pandemic, World Health Organization emphasized that early detection is an effective strategy to reduce the spread of SARS-CoV-2 viruses. Several diagnostic methods, such as reverse transcription-polymerase chain reaction (RT-PCR) and lateral flow immunoassay (LFIA), have been applied based on the mechanism of specific recognition and binding of the probes to viruses or viral antigens. Although the remarkable progress, these methods still suffer from inadequate cellular materials or errors in the detection and sampling procedure of nasopharyngeal/oropharyngeal swab collection. Therefore, developing accurate, ultrafast, and visualized detection calls for more advanced materials and technology urgently to fight against the epidemic. In this review, we first summarize the current methodologies for SARS-CoV-2 diagnosis. Then, recent representative examples are introduced based on various output signals (e.g., colorimetric, fluorometric, electronic, acoustic). Finally, we discuss the limitations of the methods and provide our perspectives on priorities for future test development.

Efficient coupling of MnO2/TiN on carbon cloth positive electrode and Fe2O3/TiN on carbon cloth negative electrode for flexible ultra-fast hybrid supercapacitors.

Recent research and development of energy storage devices has focused on new electrode materials because of the critical effects on the electrochemical properties of supercapacitors. In particular, MnO2 and Fe2O3 have drawn extensive attention because of their low cost, high theoretical specific capacity, environmental friendliness, and natural abundance. In this study, MnO2 ultrathin nanosheet arrays and Fe2O3 nanoparticles are fabricated on TiN nanowires to produce binder-free core-shell positive and negative electrodes for a flexible and ultra-fast hybrid supercapacitor. The MnO2/TiN/CC electrode shows larger pseudocapacitance contributions than MnO2/CC. For example, at a scanning rate of 2 mV s-1, the pseudocapacitance contribution of MnO2/TiN/CC is 87.81% which is nearly 25% bigger than that of MnO2/CC (71.26%). The supercapacitor can withstand a high scanning rate of 5000 mV s-1 in the 2 V window and exhibits a maximum energy density of 71.19 W h kg-1 at a power density of 499.79 W kg-1. Even at 5999.99 W kg-1, it still shows an energy density of 31.3 W h kg-1 and after 10 000 cycles, the device retains 81.16% of the initial specific capacitance. The activation mechanism is explored and explained.

A Quantitative Bacteria Monitoring and Killing Platform Based on Electron Transfer from Bacteria to a Semiconductor.

A platform with both bacteria killing and sensing capabilities is crucial for monitoring the entire bacteria-related process on biomaterials and biomedical devices. Electron transfer (ET) between the bacteria and a Au-loaded semiconductor (ZnO) is observed to be the primary factor for effective bacteria sensing and fast bacteria killing. The electrons produce a saturation current that varies linearly with the bacteria number, semi-logarithmically, with R2 of 0.98825, thus providing an excellent tool to count bacteria quantitatively in real-time. Furthermore, ET leads to continuous electron loss killing of about 80% of Escherichia coli in only 1 h without light. The modularity and extendability of this ET-based platform are also demonstrated by the excellent results obtained from other semiconductor/substrate systems and the stability is confirmed by recycling tests. The underlying mechanism for the dual functions is not due to conventional attributed Zn2+ leaching or photocatalysis but instead electrical interactions upon direct contact. The results reveal the capability of real-time detection of bacteria based on ET while providing information about the antibacterial behavior of ZnO-based materials especially in the early stage. The concept can be readily incorporated into the design of smart and miniaturized devices that can sense and kill bacteria simultaneously.

An ion-gating multinanochannel system based on a copper-responsive self-cleaving DNAzyme.

We developed an ion-gating nanochannel composite system by immobilizing a Cu(2+)-responsive self-cleaving DNAzyme into PET conical multinanochannels, which could control the ion transport by regulating the surface charge density of the channels.

Cooperative effect of pH-dependent ion transport within two symmetric-structured nanochannels.

A novel and simple design is introduced to construct bichannel nanofluid diodes by combining two poly(ethylene terephthalate) (PET) films with columnar nanochannel arrays varying in size or in surface charge. This type of bichannel device performs obvious ion current rectification, and the pH-dependent tunability and degree of rectification can be improved by histidine modification. The origin of the ion current rectification and its pH-dependent tunability are attributed to the cooperative effect of the two columnar half-channels and the applied bias on the mobile ions. As a result of surface groups on the bichannel being charged with different polarities or degrees at different pH values, the function of the bichannel device can be converted from a nanofluid diode to a normal nanochannel or to a reverse diode.

Calcein-modified multinanochannels on PET films for calcium-responsive nanogating.

Calcein-modified multiporous films with conical channels are introduced in a nanofluid device to enhance the calcium-responsive intensity and stability of ionic currents. Calcein with more carboxyls enhances the response of channels to calcium ions, and the capability of immobilized calcein for Ca(2+)-binding could be regulated by the deprotonation of these carboxyls.

Ion current behaviors of mesoporous zeolite-polymer composite nanochannels prepared by water-assisted self-assembly.

Inspired by the asymmetry of biological ion channels in structure and composition, we designed a novel type of artificial asymmetric nanochannels based on mesoporous zeolite (MCM-41) and polyimide (PI) by water-assisted self-assembly. Meanwhile, we studied ionic current behaviors and rectifying characteristics of the mesoporous zeolite-polymer composite nanochannels.

Artificial ion channels regulating light-induced ionic currents in photoelectrical conversion systems.

Artificial ion channels are introduced into a photosystem II photoelectrical conversion system to mimic the photocurrent regulating of the natural PSII energy system on the thylakoid membrane. In the composite system, PSII complexes act as pumps to convert light into currents and artificial ion channels act as valves to regulate light-induced ionic currents.

Photo-induced current amplification in L-histidine modified nanochannels based on a highly charged photoacid in solution.

By UV light irradiation, we can adjust the charge of bistable photoacid molecules reversibly, so that photo-induced current amplification can be obtained, which offers a way to control nanochannels by turning the UV light on and off, alternately.