Anionic Hofmeister Effect Regulated Conductivity in Polyelectrolyte Hydrogels for High-Performance Supercapacitor.

The Hofmeister effect not only affects the stability and solubility of protein colloids but also has specific effects on the polymer molecules. Here, the impact of the Hofmeister effect on the electrochemical properties of polyelectrolyte hydrogels at room temperature and subzero temperature studied for the first time. Polyelectrolyte hydrogels exhibit an anti-polyelectrolyte effect in low concentrations of ammonium salt, while they exhibit an obvious Hofmeister effect in high concentrations of ammonium salt. Kosmotropic ions demonstrate strong interaction with water molecules or polymer chains, resulting in the reduction of conductivity of polyelectrolyte hydrogels. However, chaotropic ions exhibit weak interactions with water molecules or molecular chains, leading to an increase in conductivity. The Hofmeister effect has a more significant effect on the polyzwitterion electrolyte. The conductivity of polyzwitterion hydrogel soaked in chaotropic ion is up to 6.2 mS cm-1 at -40 °C. The supercapacitor assembled by polyzwitterion electrolytes maintains a capacitance retention rate of 85% and ≈100% coulomb efficiency after 15 000 cycles at -40 °C. This study elucidates the influence of the Hofmeister effect on conductivity in polyelectrolytes and expands the regulatory approach for improving the performance of energy storage devices.

Sensitive and Selective Electrochemical Detection of Lead(II) Based on Waste-Biomass-Derived Carbon Quantum Dots@Zeolitic Imidazolate Framework-8.

An electrochemical sensor based on carbon quantum dots (CQDs) and zeolitic imidazolate framework-8 (ZIF-8) composite was fabricated to detect lead(II). The CQDs (2.47 ± 0.52 nm) were synthesized from platanus acerifoli leaves by carbonization and the hydrothermal method. Under the optimal conditions, the fabricated electrochemical sensor had excellent performance in detecting Pb2+. The linear range for Pb2+ was 1 nM-1 µM, and the limit of detection (LOD) was 0.04 nM and the limit of quantification (LOQ) was 0.14 nM. Moreover, when the solution contained Pb2+ and Cd2+, the linear range for Pb2+ was 50 nM to 1 µM and the LOD was 0.02 nM. When the solution contained Pb2+ and Cu2+, the linear range for Pb2+ was 50 nM-750 nM and LOD was 0.07 nM. Furthermore, even if the solution contained Pb2+, Cd2+ and Cu2+, the linear range for Pb2+ was 50 nM-1 µM and the LOD was 0.04 nM. The X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectrometer (FTIR) and Brunauer-Emmet-Teller (BET) results indicated that the composite electrode materials had abundant oxygen-containing functional groups, a large specific surface area and pore structure, which are conducive to the adsorption of heavy metal ions and improve the detection performance.

Removal behaviors and mechanism of polystyrene microplastics by coagulation/ultrafiltration process: Co-effects of humic acid.

Microplastics (MPs) have been detected in drinking water, which could absorb or accumulate humic acid (HA) and threaten the water quality. Coagulation-ultrafiltration (CUF) is a common drinking water treatment technology, but its behavior and mechanism of removing MPs and MPs-HA remain unclear. In this study, the removal mechanism of polystyrene (PS)-MPs coagulated by Al- and Fe-based salts with or without HA was investigated to optimize the CUF process. The results showed that Al-based salt (92.7 %) was better than Fe-based salt (91.2 %) in the removal efficiency of PS or HA, and the optimal coagulants dosage of PS-HA composite system (12 mg·L-1) was higher than that of the individual PS system (9 mg·L-1). Moreover, the coagulation mechanism was studied by Fourier transform infrared spectroscope (FTIR) and X-ray photoelectron spectroscopy (XPS). The oxygen group in PS and PS-HA was the main binding site of Al and Fe hydrolysate, and the effects of charge neutralization, adsorption bridging, and sweep flocculation became weaker in turn at the optimal dosage. In addition, the cake layer formed by coagulation and the presence of HA alleviated the irreversible membrane fouling by intercepting flow and re-adsorption. This study guides the improvement of the traditional drinking water treatment process to remove MPs.

Antifreezing Proton Zwitterionic Hydrogel Electrolyte via Ionic Hopping and Grotthuss Transport Mechanism toward Solid Supercapacitor Working at -50 °C.

Hydrogel electrolyte is widely used in solid energy storage devices because of its high ionic conductivity, environmental friendliness, and non-leakage property. However, hydrogel electrolyte is not resistant to freezing. Here, a high proton conductive zwitterionic hydrogel electrolyte with super conductivity of 1.51 mS cm-1 at -50 °C is fabricated by random copolymerization of acrylamide and zwitterionic monomer in the presence of 1 m H2 SO4 and ethylene glycol (EG). The antifreezing performance and low temperature conductivity are ascribed to hydrogen bonds and ionic bonds between the components and water molecules in the system and can be tuned by changing the monomer ratio and EG contents. The proton hopping migration on the ionic group of the polymer chains and Grotthuss proton transport mechanism are responsible for the high proton conductivity while Grotthuss transport is dominated at the glassy state of the polymer chains. The electrolyte-assembled supercapacitor (SC) offers high specific capacitance of 93.5 F g-1 at 25 °C and 62.0 F g-1 at -50 °C with a capacitance retention of 91.1% and 81.5% after 10 000 cycles, respectively. The SC can even work at -70 °C. The electrolyte outperforms most reported antifreezing hydrogel electrolytes and has high potential in low-temperature devices.

Electrolytes with Micelle-Assisted Formation of Directional Ion Transport Channels for Aqueous Rechargeable Batteries with Impressive Performance.

Low-cost and ecofriendly electrolytes with suppressed water reactivity and raised ionic conductivity are desirable for aqueous rechargeable batteries because it is a dilemma to decrease the water reactivity and increase the ionic conductivity at the same time. In this paper, Li2SO4-Na2SO4-sodium dodecyl sulfate (LN-SDS)-based aqueous electrolytes are designed, where: (i) Na+ ions dissociated from SDS increase the charge carrier concentration, (ii) DS-/SO42- anions and Li+/Na+ cations are capable of trapping water molecules through hydrogen bonding and/or hydration, resulting in a lowered melting point, (iii) Li+ ions reduce the Krafft temperature of LN-SDS, (iv) Na+ and SO42- ions increase the low-temperature electrolyte ionic conductivity, and (v) SDS micelle clusters are orderly aggregated to form directional ion transport channels, enabling the formation of quasi-continuous ion flows without (r.t.) and with (≤0 °C) applying voltage. The screened LN-SDS is featured with suppressed water reactivity and high ionic conductivity at temperatures ranging from room temperature to -15 °C. Additionally, NaTi2(PO4)3‖LiMn2O4 batteries operating with LN-SDS manifest impressive electrochemical performance at both room temperature and -15 °C, especially the cycling stability and low-temperature performance.

A Skin-Inspired Design Integrating Mechano-Chemical-Thermal Robustness into Superhydrophobic Coatings.

Designing scalable coatings with a wide spectrum of functions such as liquid repellency, anticorrosion, and antiflaming and a high level of mechano-chemical-thermal robustness is crucial in real-life applications. However, these individual functionalities and robustness are coupled together or even have conflicting requirements on the interfacial or bulky properties of materials, and thus, simultaneously integrating all these individual features into one coating has proved challenging. Herein, an integral skin-inspired triple-layered coating (STC) that resolves conflicting demands imposed by individual features on the structural, chemical, mechanical, and thermal properties of materials is proposed. Specifically, the rational design of multiple gradients in roughness, wetting, strength, and flame retardancy and the formation of continuous interfaces along its triple layers endow a sustained liquid repellency, anticorrosion, and flame retardancy even under harsh environments, as well as strong antiabrasion on surfaces and adhesion with the substrate. Such an all-in-one design enhances the durability and lifetime of coatings and reduces the maintenance and repair, thereby contributing to cost and energy saving. Together with a facile spraying fabrication process, this STC provides a feasible and sustainable strategy for constructing energy and resource-saving materials.

Efficient Removal of Cr(VI) by TiO2 Based Micro-Nano Reactor via the Synergy of Adsorption and Photocatalysis.

The low-toxicity treatment of chromium-containing wastewater represents an important way of addressing key environmental problems. In this study, a core-shell structural ZIF-8@TiO2 photocatalyst was synthesized by a simple one-step hydrothermal method. The obtained composite photocatalyst possessed improved photocatalytic activity compared with TiO2. The results indicated that the optimized ZIF-8@TiO2 composite exhibited the highest removal efficiency with 93.1% of Cr(VI) after 120 min under UV-vis irradiation. The removal curves and XPS results indicated that the adsorbed Cr(VI) on the ZIF-8 during the dark process was preferentially reduced. The superior removal efficiency of ZIF-8@TiO2 is attributed to the combination of both high adsorption of ZIF-8, which attracted Cr(VI) on the composite surface, and the high separation efficiency of photo-induced electron-hole pairs. For the mixture of wastewater that contained methyl orange and Cr(VI), 97.1% of MO and 99.7% of Cr(VI) were removed after 5 min and 60 min light irradiation, respectively. The high removal efficiency of multiple pollutants provides promising applications in the field of Cr(VI) contaminated industrial wastewater treatment.

Biomass-based superhydrophobic coating with tunable colors and excellent robustness.

Multicolored superhydrophobic coating with high durability has been receiving tremendous attention in decorative applications. Herein, a facile method to fabricate multicolored superhydrophobic coating with excellent robustness has been developed by using cellulose and chitosan. The multicolored coatings can be obtained through single dyeing or mixed dyeing based on three primary dyes. The coating can be applied on hard substrates (e.g. glass, aluminum sheet) and soft substrates (e.g. cotton fabric) by diverse methods including spraying, dip-coating and painting. The colorful coating firmly adheres to the substrates due to the multiple interactions (siloxane covalent bonds and hydrogen bonds). The colorful coating exhibits water-repellant behaviors and can withstand sandpaper abrasion, tape-peeling cycles, water impact, salt spray test and UV environments. Furthermore, the multicolored coating can be used as a new type of pigment for painting on different substrates and is expected to have a huge potential application in technological design or decoration.

Flame-Retardant, Highly Conductive, and Low-Temperature-Resistant Organic Gel Electrolyte for High-Performance All-Solid Supercapacitors.

Traditional liquid electrolytes are volatile, flammable, and easy to leak, which makes the energy storage device easy to burn and explode in the case of overcharge and short circuit. Here, by utilizing the active P-H bond of a flame retardant (DOPO) to graft onto the polymer chain, flame-retardant organic gel electrolytes were fabricated to address these issues. The gel electrolyte had good ionic conductivity of 4 mS cm-1 at 20 °C and good flame retardant ability. By changing the molar ratio of the monomers and the salt concentrations, the mechanical strength of the gel electrolyte could be adjusted (maximum stress≈28 KPa, maximum strain≈305 %). The transport mechanism of lithium ions in the gel polymer electrolyte was proposed. The gel electrolyte-assembled supercapacitor (SC) possessed better electrochemical properties than that of SC assembled by liquid electrolyte. Importantly, the gel-based SC remained basically unchanged under multiple bending cycles. Additionally, the gel electrolyte had good low-temperature tolerance (0.1 mS cm-1 at -40 °C). The gel electrolyte-assembled SC could work normally in the temperature range of -20 to 60 °C. The multiple advantages of gel electrolyte expand the applications in ionic conductor and energy storage devices.

Surfactant-free synthesis of Fe3O4@PANI and Fe3O4@PPy microspheres as adsorbents for isolation of PCR-ready DNA.

Magnetic separation with composite microspheres presents an alternative strategy for applications in biomedical and bioengineering fields. However, the synthesis of core-shell structured magnetic composites universally assumes the surfactant-directing and/or silica-assisting polymerization approach to modify and stabilize the magnetic cores. In this paper, we report on the surfactant-free synthesis of well-defined core-shell structured Fe(3)O(4)@PANI and Fe(3)O(4)@PPy microspheres with high magnetization. The temperature dependence of magnetization of the samples was examined as a function of temperature between 3 and 300 K in an applied field of 500 Oe. It was found that the blocking temperature (T(B)) values of the composite spheres are well above the room temperature. The small variation in magnetization as the temperature changes renders the composite spheres a suitable candidate when used at elevated temperatures. Also, the genomic DNA can be effectively isolated from Aspergillus niger (A. niger) cells with the composite microspheres, using a PEG-NaCl binding buffer and a phosphate eluting buffer. The magnetic isolation of genomic DNA with the composite microspheres was shown to be superior to the conventional phenol-chloroform extraction, which was confirmed by agarose gel eletrophoresis and polymerase chain reaction (PCR) diagnosis. The Fe(3)O(4)@PANI and Fe(3)O(4)@PPy microspheres presented here have great potential in enzyme immobilization, drug delivery, catalysis, and sensors.