Mechanically Excellent, Notch-Insensitive, and Highly Conductive Double-Network Hydrogel for Flexible Strain Sensor.

A novel double-network conductive hydrogel based on lithium acetate/gelatin/polyacrylamide (PAAM) was synthesized by heating-cooling and subsequent γ-ray radiation-induced polymerization and cross-linking. Owing to the hydrogen bonding interaction between lithium acetate, physical cross-linked gelatin, and chemical cross-linked PAAM, the resultant hydrogel exhibited high tensile strength (1260 kPa), high ionic conductivity (35.2 mS cm-1), notch-insensitivity (tensile strength 415 kPa, elongation at break 872% with transverse notch), and extensive strain monitoring range (0.15-800%) under optimum conditions. The lithium acetate/gelatin/polyacrylamide hydrogel strain sensor attached to the skin can sensitively monitor the subtle movements of the human body. The strain sensor based on the resultant hydrogel with transverse notch can still work for 1200 cycles, due to that the covalent-cross-linked PAAm chain bridges the cracks and stabilizes the deformation, while the physical-cross-linked gelatin was unzipped to make the blunting of notch. The conductive hydrogel with high-sensitivity and high stability is expected to be used as materials for the preparation of flexible strain sensors in the future.

Mechanically Robust and Highly Conductive Poly(ionic liquid)/Polyacrylamide Double-Network Hydrogel Electrolytes for Flexible Symmetric Supercapacitors with a Wide Operating Voltage Range.

Flexible electronic devices, such as supercapacitors (SCs), place high demands on the mechanical properties, ionic conductivity, and electrochemical stability of electrolytes. Hydrogels, which combine flexibility and the advantages of both solid and liquid electrolytes, will meet the demand. Here, we report the synthesis of novel poly(ionic liquid)/polyacrylamide double-network (DN) (PIL/PAM DN) hydrogel electrolytes containing different metal salts via a two-step γ-radiation method. The resultant Li2SO4-1.0/PIL/PAM DN hydrogel electrolyte possesses excellent mechanical properties (tensile strength of 3.64 MPa, elongation at break of 446%) and high ionic conductivity (24.1 mS·cm-1). The corresponding flexible SC based on the Li2SO4-1.0/PIL/PAM DN hydrogel electrolyte (SC-Li2SO4) presents improved ion diffusion, ideal electrochemical double-layer capacitor behavior, good rate capability, and excellent cyclic stability. Moreover, symmetric SC-Li2SO4 achieves a wide operating voltage range of up to 1.5 V, with a maximum energy density of 26.0 W h·kg-1 and a capacitance retention of 94.1% after 10,000 galvanostatic charge-discharge cycles, owing to the deactivation of free water molecules by the synergistic effect of PIL, PAM, and SO42-. Above all, the capacitance of SC-Li2SO4 is well-maintained after overcharge, overdischarge, short circuit, extreme temperature, compression, and bending tests, indicating its high security and flexibility. This work reveals the enormous application potential of PIL-based conductive hydrogel electrolytes for flexible electronic devices.

Selective CO2 reduction to CH3OH over atomic dual-metal sites embedded in a metal-organic framework with high-energy radiation.

The efficient use of renewable X/γ-rays or accelerated electrons for chemical transformation of CO2 and water to fuels holds promise for a carbon-neutral economy; however, such processes are challenging to implement and require the assistance of catalysts capable of sensitizing secondary electron scattering and providing active metal sites to bind intermediates. Here we show atomic Cu-Ni dual-metal sites embedded in a metal-organic framework enable efficient and selective CH3OH production (~98%) over multiple irradiated cycles. The usage of practical electron-beam irradiation (200 keV; 40 kGy min-1) with a cost-effective hydroxyl radical scavenger promotes CH3OH production rate to 0.27 mmol g-1 min-1. Moreover, time-resolved experiments with calculations reveal the direct generation of CO2•‒ radical anions via aqueous electrons attachment occurred on nanosecond timescale, and cascade hydrogenation steps. Our study highlights a radiolytic route to produce CH3OH with CO2 feedstock and introduces a desirable atomic structure to improve performance.

Noble-Metal-Free Single- and Dual-Atom Catalysts for Artificial Photosynthesis.

Artificial photosynthesis enables direct solar-to-chemical energy conversion aimed at mitigating environmental pollution and producing solar fuels and chemicals in a green and sustainable approach, and efficient, robust, and low-cost photocatalysts are the heart of artificial photosynthesis systems. As an emerging new class of cocatalytic materials, single-atom catalysts (SACs) and dual-atom catalysts (DACs) have received a great deal of current attention due to their maximal atom utilization and unique photocatalytic properties, whereas noble-metal-free ones impart abundance, availability, and cost-effectiveness allowing for scalable implementation. This review outlines the fundamental principles and synthetic methods of SACs and DACs and summarizes the most recent advances in SACs (Co, Fe, Cu, Ni, Bi, Al, Sn, Er, La, Ba, etc.) and DACs (CuNi, FeCo, InCu, KNa, CoCo, CuCu, etc.) based on non-noble metals, confined on an arsenal of organic or inorganic substrates (polymeric carbon nitride, metal oxides, metal sulfides, metal-organic frameworks, carbon, etc.) acting as versatile scaffolds in solar-light-driven photocatalytic reactions, including hydrogen evolution, carbon dioxide reduction, methane conversion, organic synthesis, nitrogen fixation, hydrogen peroxide production, and environmental remediation. The review concludes with the challenges, opportunities, and future prospects of noble-metal-free SACs and DACs for artificial photosynthesis.

Gamma Radiation Synthesis of Ag/P25 Nanocomposites for Efficient Photocatalytic Degradation of Organic Contaminant.

Titanium dioxide (TiO2) has garnered significant attention among various photocatalysts, whereas its photocatalytic activity is limited by its wide bandgap and inefficient charge separation, making the exploration of new strategies to improve its photocatalytic performance increasingly important. Here, we report the synthesis of Ag/P25 nanocomposites through a one-step gamma-ray radiation method using AgNO3 and commercial TiO2 (Degussa P25). The resulting products were characterized by powder X-ray diffraction, UV-Vis diffused reflectance spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The effect of free radical scavengers, feed ratios of Ag/P25, and dose rates on the photocatalytic activity of the Ag/P25 nanocomposites were systematically investigated using rhodamine B under Xenon light irradiation. The results showed that the Ag/P25 photocatalyst synthesized with a feed ratio of 2.5 wt% and isopropyl alcohol as the free radical scavenger at a dose rate of 130 Gy/min exhibited outstanding photocatalytic activity, with a reaction rate constant of 0.0674 min-1, much higher than that of P25. Additionally, we found that the particle size of Ag could be effectively controlled by changing the dose rate, and the Ag/P25 nanocomposites doped with smaller size of Ag nanoparticles performed higher photocatalytic activities. The synthesis strategy presented in this study offers new insight into the future development of highly efficient photocatalysts using radiation techniques.

Radiation synthesis of MXene/Ag nanoparticle hybrids for efficient photothermal conversion of polyurethane films.

Flexible conductive films based on light-to-heat conversion are promising for the next-generation electronic devices. A flexible waterborne polyurethane composite film (PU/MA) with excellent photothermal conversion performance was obtained by combination of PU and silver nanoparticle decorated MXene (MX/Ag). The silver nanoparticles (AgNPs) uniformly decorated on the MXene surface by γ-ray irradiation induced reduction. Because of the synergistic effect of MXene with outstanding light-to-heat conversion efficiency and the AgNPs with plasmonic effect, the surface temperature of the PU/MA-II (0.4%) composite with lower MXene content increased from room temperature to 60.7 °C at 5 min under 85 mW cm-2 light irradiation. Besides, the tensile strength of PU/MA-II (0.4%) increased from 20.9 MPa (pure PU) to 27.5 MPa. The flexible PU/MA composite film shows great potential in the field of thermal management of flexible wearable electronic devices.

Synthesis and property of superabsorbent polymer based on cellulose grafted 2-acrylamido-2-methyl-1-propanesulfonic acid.

An eco-friendly superabsorbent polymer (SAP) was prepared by grafting 2-acrylamido-2-methyl-1-propanesulfonic acid onto microcrystalline cellulose in lithium chloride/N, N-dimethylacetamide system. The synthesized SAP (cellulose-g-PAMPS) was characterized by FTIR, TGA, SEM, 1H NMR, 13C NMR and XRD. The water absorption equilibrium of cellulose-g-PAMPS could be achieved within 10 min in distilled water. Moreover, the maximum water absorption capacities of cellulose-g-PAMPS in distilled water, 0.9 wt% NaCl solution and 3.2 wt% Na2CO3 solution were 648.9, 298.4 and 207.3 g·g-1, respectively. The water absorption behavior of cellulose-g-PAMPS was interpreted by the pseudo-second-order model. Furthermore, cellulose-g-PAMPS could be used in some extreme conditions due to its high acid and alkali resistance. The water retention rate of cellulose-g-PAMPS could be maintained above 90 % at 25 °C for 6 h. As a consequence, the synthesized SAP can be applied to increase the plant growth and survival time under drought conditions, even under saline alkali conditions.

MXene/Gelatin/Polyacrylamide Nanocomposite Double Network Hydrogel with Improved Mechanical and Photothermal Properties.

The development of smart hydrogel with excellent mechanical properties and photothermal conversion capability is helpful in expending its application fields. Herein, a MXene/gelatin/polyacrylamide (M/G/PAM) nanocomposite double network (NDN) hydrogel was synthesized by γ-ray radiation technology for the first time. Compared with gelatin/polyacrylamide double network hydrogel, the optimized resultant M3/G/PAM NDN hydrogel shows better mechanical properties (tensile strength of 634 ± 10 kPa, compressive strength of 3.44 ± 0.12 MPa at a compression ratio of 90%). The M3/G/PAM NDN hydrogel exhibits a faster heating rate of 30 °C min-1, stable photothermal ability, and mechanical properties even after 20 cycles of on-off 808 nm near-infrared (NIR) laser irradiation (1.0 W cm-2). Furthermore, the temperature of M3/G/PAM NDN hydrogel can be increased rapidly from 25 °C to 90 °C in 10 s and could reach 145 °C in 120 s under irradiation by focused NIR laser irradiation (56.6 W cm-2). The high mechanical property and photothermal properties of M/G/PAM hydrogel are ascribed to the formation of double network and uniform hydrogen bonding between MXene and gelatin and PAM polymers. This work paves the way for construction of photothermal hydrogels with excellent mechanical properties.

Radiation synthesis of imidazolium-based polymeric ionic liquid gel for efficient adsorption of Re(VII) and U(VI) from aqueous solution.

In this research, an imidazolium-based polymeric ionic liquid (PIL) gel was effectively synthesized in one step via electron beam (EB) radiation technology. The synthesized gel with gel fraction of 78% under 80 kGy was used for the adsorption and separation of Re(VII) and U(VI). The structure of the gel was characterized by FTIR, SEM, BET, and XPS. Furthermore, batch adsorption was experimented to explore its performance of Re(VII) and U(VI) removal. The two adsorption processes all more fitted the Langmuir isotherm model with the maximum adsorption capacities of 892.9 mg/g for Re(VII) and 243.9 mg/g for U(VI). The adsorption reached equilibrium within 1 min for Re(VII), while within 4 min for U(VI), showing its greatly rapid adsorption rate because of its three-dimensional porous network structure. In addition, the separation experiments of Re/U replied that PIL gel could effectively separate Re(VII) from the simulated uranium leaching solution. Regeneration experiments present the good reusability of PIL gel. This work demonstrated the practical application of EB-radiation technology in the synthesis of PIL gel, which is a promising adsorbent for Re(VII) and U(VI) recovery .

Ultrastretchable and adhesive agarose/Ti3C2Tx-crosslinked-polyacrylamide double-network hydrogel for strain sensor.

A novel agarose/Ti3C2Tx-crosslinked-polyacrylamide (AG/T-PAM) double-network (DN) hydrogel is synthesized by combining heating-cooling and γ-ray radiation-induced polymerization. The AG/T-PAM DN hydrogel possesses excellent mechanical properties with 4250% stretchability, and good adhesion to different substrates, such as an adhesive strength of 1148 kPa to copper at 30 °C. The resultant hydrogel also exhibits excellent tensile and compression sensing properties due to the variation of conductive network within hydrogel. The flexible and wearable strain sensor composed of the AG/T-PAM DN hydrogel presents rapid response to strain withstand 1000 cycles, and can monitor various movements of human body with a high sensibility. The AG/T-PAM DN hydrogel-based strain sensor will have broad application in large-scale strain detection scenarios requiring high sensitivity and adhesion.

Aminomethylpyridine isomers functionalized cellulose microspheres for TcO4-/ReO4- uptake: Structure-properties relationship and their application in different aquatic systems.

Technetium-99 (99Tc) is a long-lived radioactive nuclide that poses great threat to environment, hence selective removal of 99Tc from aquatic system is always an issue. Aminomethylpyridine (AMP) equipped with pyridine and amino, is a promising receptor for TcO4- and its surrogate ReO4-, thus it is of interest to explore and understand the structure-properties relationship of ReO4- adsorption related to n-AMP structure that differ in amino methyl position. In this work, three n-AMP functionalized cellulose microspheres (n-AMPR, n = 2, 3, 4) were synthesized and employed for TcO4-/ReO4- uptake. The effect of aminomethyl position on adsorption properties of n-AMPR for ReO4- were investigated and compared. Adsorption kinetics and adsorption isotherm showed that adsorption speed and adsorption capacity were in order of 3-AMPR > 2-AMPR > 4-AMPR. DFT calculation verified that the adsorption of ReO4- by n-AMPR was attributed to electrostatic interaction and hydrogen bonding interaction, the order of adsorption abilities of n-AMPR was due to that steric effect and hydrogen bond collaborated in stabilizing n-AMPR-ReO4- complexes. The column experiments demonstrated that 3-AMPR can be selectively remove ReO4- from simulated groundwater. More importantly, 99Tc column experiments showed that 3-AMPR had a better ability for actual radioactive TcO4-.

Polyacrylamide/Copper-Alginate Double Network Hydrogel Electrolyte with Excellent Mechanical Properties and Strain-Sensitivity.

The double network (DN) hydrogel has attracted great attention due to its wide applications in daily life. However, synthesis DN hydrogel with excellent mechanical properties is still a big challenge. Here, polyacrylamide/copper-alginate double network (PAM/Cu-alg DN) hydrogel electrolyte is successfully synthesized by radiation-induced polymerization and cross-linking process of acrylamide with N, N'-methylene-bis-acrylamide and subsequent cupric ion (Cu2+ ) crosslinking of alginate. The content of sodium alginate, absorbed dose, and the concentration of Cu2+ are investigated in detail for improving the overall properties of PAM/Cu-alg DN hydrogel electrolyte. The PAM/Cu-alg DN hydrogel electrolyte synthesizes by radiation technique and Cu2+ crosslinking shows superior mechanical properties with a tensile strength of 2.25 ± 0.02 MPa, excellent energy dissipation mechanism, and the high ionic conductivity of 4.08 ± 0.17 mS cm-1 . PAM/Cu-alg DN hydrogel is characterized with attenuated total reflection Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, and X-ray photoelectron spectroscopy analyses and the reason for the improvement of mechanical properties is illustrated. Furthermore, PAM/Cu-alg DN hydrogel electrolyte exhibits excellent strain-sensitivity, cyclic stability, and durability. This work paves for the new way for the preparation of DN hydrogel electrolytes with excellent properties.

Recent progress in environmental applications of functional adsorbent prepared by radiation techniques: A review.

Environmental pollution has been accelerated due to fast urbanization and industrialization, and thus hazardous contaminants removal and valuable metal recovery have become urgent. Adsorption has become a promising technology for water treatment because of its advantages of low-cost, good reusability, low energy consumption, high capacity and high selectivity. Particularly, radiation techniques including radiation induced graft copolymerization and radiation crosslinking have been found to be widely utilized to exploit adsorbents for water treatment. In this review, the current status and progress of adsorbents in environmental pollution in the past decade are summarized, including adsorbents (in form of particles, fiber and fabric, membrane, novel nanomaterials) synthesized by radiation induced graft copolymerization and hydrogel-based adsorbents fabricated by radiation crosslinking. Finally, further perspective on the development and challenge of adsorbents by radiation techniques is also suggested.

Aminotriazole isomers modified cellulose microspheres for selective adsorption of U(VI): Performance and mechanism investigation.

Aminotriazole isomers with high nitrogen content show potential affinity for U(VI). Combining the advantages of both aminotriazole and cellulose, two n-aminotriazole isomers modified cellulose microspheres (n-ATARs, n = 3, 4) were newly prepared as adsorbents via radiation technology. Batch adsorption experiments showed that n-ATARs possessed good adsorption capacity of U(VI) in the order of 3-ATAR > 4-ATAR, and the adsorption process followed the Langmuir-Freundlich isotherm model and the pseudo-second-order kinetic model. Both n-ATARs exhibited good selectivity and reusability. Besides, 3-ATAR and 4-ATAR were more suitable for the extraction of trace amount of U(VI) from the contaminated groundwater and the simulated seawater, respectively. The effect of amino position on triazole ring on adsorption behavior of n-ATAR was studied and explained by DFT calculation. Finally, the adsorption mechanism of U(VI) onto n-ATARs was revealed to be inner-sphere complexation via different 1:1 or 1:2 coordination models by FTIR, MS, XPS analysis and DFT calculation.

Quaternary phosphonium modified cellulose microsphere adsorbent for 99Tc decontamination with ultra-high selectivity.

Decontamination of radioactive TcO4- from nuclear wastes is increasingly crucial for spent nuclear fuel reprocessing and environmental remediation. In the presence of a large excess of competitive anions, the selective separation of TcO4- is a major challenge for adsorbents. Herein, by using pre-radiation induced grafting polymerization, we have modified economical and environmentally friendly cellulose microspheres to obtain quaternary phosphonium decorated TcO4- adsorbents with an ultra-high selectivity, designated CMS-g-VBPPh3NO3. The prepared materials show adsorption capacities of 251 mg g-1 (for the surrogate Re). The selective factor against NO3- in 0.5 mol kg-1 HNO3 is as high as 168, showing excellent anion-exchange selectivity towards TcO4-. Moreover, CMS-g-VBPPh3NO3 was packed in column for treating simulated acidic waste solutions containing Cs, Sr, Eu, Zr, Ru, U and Re, and it showed excellent Re separation performance. Tracer amount of 99mTc experiments showed that comparing to ReO4-, CMS-g-VBPPh3NO3 has a better adsorption selectivity for TcO4-.

Facile preparation of L-cysteine-modified cellulose microspheres as a low-cost adsorbent for selective and efficient adsorption of Au(III) from the aqueous solution.

A facile method to synthesize adsorbent based on cellulose modified by amino acid was developed. The novel L-cysteine-functionalized adsorbent for Au(III) recovery was synthesized via radiation grafting technique. Glycidyl methacrylate (GMA) was grafted on the surface of microcrystalline cellulose microsphere (MCC); next, ring-opening reaction was performed to immobilize L-cysteine. The adsorption abilities of the adsorbent (CysR) were tested. Batch experiments suggested that the maximum adsorption capacity of Au(III) is 714.28 mg/g calculated by Langmuir model. The adsorption kinetic data was followed by pseudo-second-order model. CysR showed excellent selectivity for Au(III) even the concentration of competing ions was all ten times than that of Au(III). The column experiments revealed that Au(III) could be efficiently adsorbed by CysR competition with equal amounts of Ni(II) and Zn(II). Moreover, XPS analysis demonstrated that the adsorbed Au(III) was reduced to Au(I) and Au(0). The adsorption performance certified that CysR was a promising adsorbent for Au(III) recovery.

One-Pot Hydrothermal Preparation of Fe3O4 Decorated Graphene for Microwave Absorption.

Fe3O4 decorated graphene was synthesized for electromagnetic wave absorption via a facile one-pot hydrothermal approach. The structure and morphology of the as-prepared nanomaterials were systematically investigated. The graphene oxide (GO) was reduced and Fe3O4 nanoparticles were evenly decorated on the surface of reduced graphene oxide (rGO) nanosheets. The average particle size of Fe3O4 nanoparticles is about 15.3 nm. The as-prepared rGO-Fe3O4 nanocomposites exhibited a good microwave absorption performance because of the combination of graphene and magnetic Fe3O4. When the thicknesses are 1.6 mm and 6.5 mm, the reflection loss (RL) values are up to -34.4 dB and -37.5 dB, respectively. The effective bandwidths are 3.8 and 1.9 GHz.

Amphoteric Ion Exchange Membranes Prepared by Preirradiation-Induced Emulsion Graft Copolymerization for Vanadium Redox Flow Battery.

A series of poly(vinylidene difluoride)-based amphoteric ion exchange membranes (AIEMs) were prepared by preirradiation-induced graft copolymerization of styrene and dimethylaminoethyl methacrylate in an aqueous emulsion media followed by solution casting, sulfonation, and protonation. The effects of absorbed dose and comonomer concentration on grafting yield (GY) were investigated. The highest GY of 44.5% at a low comonomer concentration of 0.9 M could be achieved. FTIR, TGA, and X-ray photoelectron spectroscopy (XPS) confirmed the successful grafting and sulfonation of the as-prepared AIEMs. Properties of the AIEMs such as water uptake, ion exchange capacity (IEC), ionic conductivity, and crossover behavior of VO2+ ions prepared by this novel technique were systematically investigated and compared with those of the commercial Nafion 115 membrane. It was found that at a GY of 28.4%, the AIEMs showed higher IEC and conductivity, lower permeability of VO2+ ions, and a longer time to maintain open circuit voltage than Nafion 115, which was attributed to their high GY and elaborate amphoteric structure. Consequently, this work has paved the way for the development of green and low-cost AIEMs with good performance for vanadium redox flow battery applications.

Novel Functionalized Cellulose Microspheres for Efficient Separation of Lithium Ion and Its Isotopes: Synthesis and Adsorption Performance.

The adsorption of lithium ions(Li+) and the separation of lithium isotopes have attracted interests due to their important role in energy storage and nuclear energy, respectively. However, it is still challenging to separate the Li+ and its isotopes with high efficiency and selectivity. A novel cellulose-based microsphere containing crown ethers groups (named as MCM-g-AB15C5) was successfully synthesized by pre-irradiation-induced emulsion grafting of glycidyl methacrylate (GMA) and followed by the chemical reaction between the epoxy group of grafted polymer and 4'-aminobenzo-15-crown-5 (AB15C5). By using MCM-g-AB15C5 as adsorbent, the effects of solvent, metal ions, and adsorption temperature on the adsorption uptake of Li+ and separation factor of 6Li/7Li were investigated in detail. Solvent with low polarity, high adsorption temperature in acetonitrile could improve the uptake of Li+ and separation factor of lithium isotopes. The MCM-g-AB15C5 exhibited the strongest adsorption affinity to Li+ with a separation factor of 1.022 ± 0.002 for 6Li/7Li in acetonitrile. The adsorption isotherms in acetonitrile is fitted well with the Langmuir model with an ultrahigh adsorption capacity up to 12.9 mg·g-1, indicating the unexpected complexation ratio of 1:2 between MCM-g-AB15C5 and Li+. The thermodynamics study confirmed the adsorption process is the endothermic, spontaneous, and chemisorption adsorption. As-prepared novel cellulose-based adsorbents are promising materials for the efficient and selective separation of Li+ and its isotopes.

Facile Preparation of EVOH-Based Amphoteric Ion Exchange Membrane Using Radiation Grafting Technique: A Preliminary Investigation on Its Application for Vanadium Redox Flow Battery.

A novel amphoteric ion exchange membrane (AIEM) was successfully prepared by one-step radiation grafting of sodium styrene sulfonate (SSS) and dimethylaminoethyl methacrylate (DMAEMA) onto ethylene-vinylalcohol copolymer (EVOH) powder and sequent transferring into film by casting method. Fourier transform infrared spectrometry (FT-IR), thermal gravimetric analyzer (TGA) and elemental analysis testified SSS and DMAEMA were successfully grafted onto EVOH. The ion exchange capacity, water uptake and proton conductivity of the resulting AIEM increased with grafting yield (GY). At the GY of 40.9%, the permeability of vanadium ions of AIEM was 3.98 × 10-7 cm2 min-1, which was better than Nafion117 membrane. Furthermore, the cost of this AIEM is much lower than that of Nafion117 membrane. This work provided a low cost and simple method for fabrication of the ion exchange membrane for vanadium redox flow battery (VRFB). Meanwhile, it also provided a new direction for the application of EVOH.