Interlayer Anions of Layered Double Hydroxides as Mobile Active Sites To Improve the Adsorptive Performance toward Cd²⁺

Layered double hydroxides (LDHs) have been considered important sinks for ionic contaminants in nature and effectively engineered adsorbents for environmental remediation. The availability of interlayer active sites of LDHs is critical for their adsorptive ability. However, inorganic LDHs generally have a nano-confined interlayer space of ca. 0.3–0.5 nm, and it is unclear how LDHs can utilize their interlayer active sites during the adsorption process. Thus, LDHs intercalated with SO42–, PO43–, NO3–, Cl–, or CO32– were taken as examples to reveal this unsolved problem during Cd2+ adsorption. New adsorption behaviors and pronounced differences in adsorption performance were observed. Specifically, SO42–/PO43– intercalated LDHs showed a maximum Cd2+ adsorption capacity of 19.2/9.8 times higher than other LDHs. The ligand exchange of H+ (on the surface −OH) by Cd2+ and formation of Cd-SO42–/PO43– complexes led to the efficient removal of Cd2+. Interestingly, interlayer SO42– was demonstrated to be able to move to the edges/outer surfaces of LDHs, providing abundant movable adsorption sites for Cd2+. This novel phenomenon made the SO42– intercalated LDH a superior adsorbent for Cd2+ among the tested LDHs, which also suggests that LDHs with a nano-confined interlayer space can also highly utilize their interlayer active sites based on the mobility of interlayer anions, offering a new method for constructing superior LDH adsorbents

Transparent and Waterproof Ionic Liquid-Based Fibers for Highly Durable Multifunctional Sensors and Strain-Insensitive Stretchable Conductors

Ionic liquids (ILs) are regarded as ideal components in the next generation of strain sensors because their ultralow modulus can commendably circumvent or manage the mechanical mismatch in traditional strain sensors. In addition to strain sensors, stretchable conductors with a strain-insensitive conductance are also indispensable in artificial systems for connecting and transporting electrons, similar to the function of blood vessels in the human body. In this work, two types of ILs-based conductive fibers were fabricated by developing hollow fibers with specific microscale channels, which were then filled with ILs. Typically, the ILs-based fiber with straight microchannels exhibited a high strain sensitivity and simultaneously rapid responses to strain, pressure, and temperature. The other ILs-based fiber with helical microchannels exhibited a good strain-isolate conductance under strain. Due to the high transparency of ILs along with the sealing process, the as-prepared ILs-based fibers are both highly transparent and waterproof. More importantly, owing to the low modulus of ILs and the core–shell structure, both conductive fiber prototypes demonstrated a high durability (>10 000 times) and a long-term stability (>4 months). Ultimately, the ILs-based fibrous sensors were successfully woven into gloves, flaunting the ability to detect human breathing patterns, sign language, hand gestures, and arm motions. The ILs-based strain-insensitive fibers were successfully applied in stretchable wires as well

Transparent and Waterproof Ionic Liquid-Based Fibers for Highly Durable Multifunctional Sensors and Strain-Insensitive Stretchable Conductors

Ionic liquids (ILs) are regarded as ideal components in the next generation of strain sensors because their ultralow modulus can commendably circumvent or manage the mechanical mismatch in traditional strain sensors. In addition to strain sensors, stretchable conductors with a strain-insensitive conductance are also indispensable in artificial systems for connecting and transporting electrons, similar to the function of blood vessels in the human body. In this work, two types of ILs-based conductive fibers were fabricated by developing hollow fibers with specific microscale channels, which were then filled with ILs. Typically, the ILs-based fiber with straight microchannels exhibited a high strain sensitivity and simultaneously rapid responses to strain, pressure, and temperature. The other ILs-based fiber with helical microchannels exhibited a good strain-isolate conductance under strain. Due to the high transparency of ILs along with the sealing process, the as-prepared ILs-based fibers are both highly transparent and waterproof. More importantly, owing to the low modulus of ILs and the core–shell structure, both conductive fiber prototypes demonstrated a high durability (>10 000 times) and a long-term stability (>4 months). Ultimately, the ILs-based fibrous sensors were successfully woven into gloves, flaunting the ability to detect human breathing patterns, sign language, hand gestures, and arm motions. The ILs-based strain-insensitive fibers were successfully applied in stretchable wires as well

One-Pot Facile Synthesis of Graphene Quantum Dots from Rice Husks for Fe³⁺ Sensing

In this work, graphene quantum dots (GQDs) with an average size of 3.9 nm were synthesized using rice husk biomass as the raw material via a facile one-step one-pot hydrothermal method. The size and morphology of the rice husk-derived GQDs were characterized by transmission electron microscopy and atomic force microscopy. The GQDs exhibit bright blue photoluminescence under 365 nm ultraviolet irradiation and can be well dispersed in water. The GQDs reach the strongest photoluminescence excitation intensity at ca. 360 nm under an emission wavelength of 466 nm, suggesting that the GQDs were oxidized with oxygenous groups attached. The quenching tests showed that the synthesized GQDs were highly and selectively sensitive toward Fe³⁺ ions and thus can potentially be used for Fe³⁺ sensing

Synthesis of Layered Double Hydroxide Single-Layer Nanosheets in Formamide

Layered double hydroxide (LDH) single-layer nanosheets were synthesized through a single-step process in the presence of formamide. This one-step process is simple, fast, and efficient and thus is potentially viable for large-scale production. Two key factors for the growth of LDH single-layer nanosheets, formamide concentration and LDH layer charge, were investigated thoroughly. A higher formamide concentration and a higher LDH layer charge are favorable for the growth of LDH single-layer nanosheets. The LDH single-layer nanosheets obtained at the premium formamide concentration and LDH layer charge were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and atomic force micrscopy (AFM). Poly­(vinyl alcohol) (PVA)/LDH nanocomposite coatings were also prepared. The coated polyethylene terephthalate (PET) and poly­(lactic acid) (PLA) films exhibited significantly improved oxygen gas barrier properties thanks to the well-dispersed and -aligned LDH single-layer nanosheets in the coating

Room-Temperature Synthesis of Mn-Doped Cesium Lead Halide Quantum Dots with High Mn Substitution Ratio

Here we report the room-temperature, atmospheric synthesis of Mn-doped cesium lead halide (CsPbX₃) perovskite quantum dots (QDs). The synthesis is performed without any sort of protection, and the dual-color emission mechanism is revealed by density functional theory. The Mn concentration reaches a maximum atomic percentage of 37.73 at%, which is significantly higher in comparison to those achieved in earlier reports via high temperature hot injection method. The optical properties of as-prepared nanocrystals (NCs) remain consistent even after several months. Therefore, red-orange LEDs were fabricated by coating the composite of PS and as-prepared QDs onto ultraviolet LED chips. Additionally, the present approach may open up new methods for doping other ions in CsPbX₃ QDs under room temperature, the capability of which is essential for applications such as memristors and other devices

A Critical Review on the Heterogeneous Catalytic Oxidation of Elemental Mercury in Flue Gases

Nowadays, an increasing attention has been paid to the technologies for removing mercury from flue gases. Up to date, no optimal technology that can be broadly applied exists, but the heterogeneous catalytic oxidation of mercury is considered as a promising approach. Based on a brief introduction of the pros and cons of traditional existing technologies, a critical review on the recent advances in heterogeneous catalytic oxidation of elemental mercury is provided. In this contribution, four types of Hg oxidation catalysts including noble metals, selective catalytic reduction (SCR) catalysts, transition metals, and fly ash have been summarized. Both the advantages and disadvantages of these catalysts are described in detail. The influence of various acidic gases including SO₂, SO₃, NH₃, NO_<i>x</i>, HCl, Cl₂, etc. have been discussed as well. We expect this work will shed light on the development of heterogeneous catalytic oxidation of elemental mercury technology in flue gases, particularly the synthesis of novel and highly efficient Hg⁰ oxidation catalysts

In Situ Laminated Separator Using Nitrogen–Sulfur Codoped Two-Dimensional Carbon Material to Anchor Polysulfides for High-Performance Li–S Batteries

The high theoretical specific capacity of lithium–sulfur battery is regarded as a promising candidate for next-generation battery systems. However, “polysulfide shuttle” is known as a major issue of accelerating capacity fading and corroding the metal lithium anode, which impedes its commercial application. Here, a nitrogen–sulfur codoped two-dimensional carbon material is synthesized using a novel template method by pyrolyzing chemical adsorption of montmorillonite and methylene blue. The microstructure and morphologies of the synthesized two-dimensional carbon materials are fully characterized using SEM, TEM, XRD, and Raman techniques. The experiment results indicate that the carbon material shows a typical graphene structure. The micro/mesoporous and heteroatoms codoped structure of the synthesized carbon material exhibits excellent performance in electronic conductivity and polysulfides confinement. The functional separator laminated with the binder-free carbon material endows the battery outstanding electrochemical and rate performances. The excellent rate performance is discovered a capacity of 828 mAh g^–1 at 4 <i>C</i> with good reversibility. The battery presents a high initial discharge specific capacity of 1049 mAh g^–1 with good capacity retention of 690 mAh g^–1 after 500 cycles at 1 <i>C</i>. Consequently, the separator laminated with the nitrogen–sulfur codoped graphene is promising for the construction of high performance Li–S batteries

Facile Synthesis of Three-Dimensional Heteroatom-Doped and Hierarchical Egg-Box-Like Carbons Derived from Moringa oleifera Branches for High-Performance Supercapacitors

In this paper, we demonstrate that Moringa oleifera branches, a renewable biomass waste with abundant protein content, can be employed as novel precursor to synthesize three-dimensional heteroatom-doped and hierarchical egg-box-like carbons (HEBLCs) by a facile room-temperature pretreatment and direct pyrolysis process. The as-prepared HEBLCs possess unique egg-box-like frameworks, high surface area, and interconnected porosity as well as the doping of heteroatoms (oxygen and nitrogen), endowing its excellent electrochemical performances (superior capacity, high rate capability, and outstanding cycling stability). Therefore, the resultant HEBLC manifests a maximum specific capacitance of 355 F g^–1 at current density of 0.5 A g^–1 and remarkable rate performance. Moreover, 95% of capacitance retention of HEBLCs can be also achieved after 20 000 charge–discharge cycles at an extremely high current density (20 A g^–1), indicating a prominent cycling stability. Furthermore, the as-assembled HEBLC//HEBLC symmetric supercapacitor displays a superior energy density of 20 Wh kg^–1 in aqueous electrolyte and remarkable capacitance retention (95.6%) after 10 000 charge–discharge cycles. This work provides an environmentally friendly and reliable method to produce higher-valued carbon nanomaterials from renewable biomass wastes for energy storage applications