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Inhibiting the recombination of photo-generated charge carriers remains one of the important challenges for photocatalytic materials nowadays. For this, we reported a series of novel bismuth layered structure ferroelectrics: M0.5Bi2.5Nb2O9 (M = Li, Na, K) nanosheets prepared by one-step hydrothermal method. The fabricated nanosheets with average thickness size of about 32 nm (Li0.5Bi2.5Nb2O9), 45 nm (Na0.5Bi2.5Nb2O9), 108 nm (K0.5Bi2.5Nb2O9) possess excellent photodegradation performance to various organic dye pollutants with high concentration of 20 mg/L [Rhodamine B (RhB), methyl orange (MO) etc.]. Interestingly, the degradation rate constants of RhB and MO can be further improved by polarization-induced charge separation under ultrasonic-assisted illumination condition, compared with those of light illumination alone, and increased by about 2.5 times for Na0.5Bi2.5Nb2O9 nanosheets. These findings make bismuth layered ferroelectric materials have a potential application in wastewater treatment as a kind of important photocatalysis.

Herein, we report a method of fabricating strong and thermosensitive double network (T-DN) poly(N-isopropyl acrylamide) (PNIPAM)-based hydrogels, i.e. rigid and brittle poly(2-acrylamido-2-methylpropanesulfonic acid sodium salt) (PNaAMPS) as the first and soft and ductile poly(N-isopropyl acrylamide-co-acrylamide) (P(NIPAM-co-AAm)) as the second interpenetrating each other. In particular, NIPAM was deliberately integrated into the double network as an adjustor of elastic modulus and hydrophilicity, besides thermosensitivity. Such double network construction strategy resulted in PNaAMPS/P(NIPAM-co-AAm) T-DN hydrogels of excellent mechanical properties (0.83-1.37 MPa) and desirable temperature-dependent swellabilities. Besides, T-DN hydrogels with various NIPAM contents exhibited good biocompatibility with high cell survival rates around normal body temperatures. Furthermore, crystal violet (CV) could be readily loaded to impart antibacterial functionality to the T-DN hydrogels against E. coli. The double network construction strategy could be adapted to fabricating high-strength antibacterial hydrogels for a broad range of biomedical applications.

Acrylic acid-modified polyhedral oligomeric silsesquioxane (AC-POSS) was synthesized by the reaction between the amine groups in polyhedral oligomeric silsesquioxane (POSS) and acrylic acid, which could dissolve in water and can be easily purified. Free-radical copolymerization was applied to synthesize azobenzene liquid crystalline polymer silsesquioxane (LCP-POSS) with different proportions of AC-POSS and liquid crystalline monomers. The trans-isomers of azobenzene moieties in LCP-POSS were gradually transformed to cis-isomers with increasing ultraviolet irradiation time. The photoisomerization reaction of liquid crystalline polymer (LCP) and LCP-POSS showed the first-order dynamic reaction. Compared with the LCP, the photoisomerization rate constant of LCP-POSS was decreased due to the space steric hindrance of the POSS as a rigid segment. The phase transition temperature of liquid crystalline in LCP-POSS increased with increasing POSS content, and the liquid crystalline texture in LCP-POSS became smaller under the polarized light. With further increasing the POSS content (>50 wt%) in LCP-POSS, the ordered structure of the liquid crystalline phase was gradually affected, resulting in one-way liquid crystal (LC) phase behavior. The synthesized LCP-POSS has LC properties, light-responsive properties, and thermal stability. When the POSS is introduced into the LC material, the phase state of the LC material will become more abundant and the LC phase will become more stable. The significance of this study is to develop and extend its applications as stimuli-responsive materials and devices.

This paper proposes a numerical three-dimensional (3D) mesoscopic approach based on the discrete element method combined with X-ray computed tomography (XCT) images to characterize the dynamic impact behavior of heterogeneous coal-rock (HCR). The dynamic impact loading in three directions was modelled to investigate the effects of the 3D meso-structure on the failure patterns and fracture mechanism, with different impact velocities. The XCT image-based discrete element model of HCR was calibrated through appropriate standard uniaxial compression tests. Numerical simulations were carried out to investigate how the breakage behaviors are affected by different loading directions with different impact velocities. The loading direction, input energy, and spatial distribution of the mineral phase had a remarkable influence on the failure patterns and load-carrying capacities. The shape of the gangue phase and the approximate location of the gangue interfaces are key parameters to consider when investigating the failure patterns and fracture mechanism of heterogeneous rock materials. The damage and fracture tended to propagate from the surfaces to the HCR interior. The gangue phase area contacting the loading wall, growth direction of the strong gangue interfaces, and loading directions greatly influenced the failure patterns of the heterogeneous rock materials.

Chitosan (CS) has become a favorable choice for synthesizing hydrogels due to its hydrophilic and biocompatible nature. However, achieving robust CS-based hydrogels remains challenging. Herein, we propose a multiple mechanisms-based network design for mechanical enhancement in CS-based double-network (DN) composite hydrogels. In the DN composite gels, graphene oxide-filled CS-based network serves as the first network and polyacrylamide network is the second network. The multi-structure of the first network enhances its energy dissipation capacity; when combining with the second network to form DN structure, the coupling effect between the multiple mechanisms-based networks allows for much more energy dissipation, enabling synergistic enhancement in mechanical properties of the DN composite gels. By regulating the mechanics, we further explore the role of the individual networks. The results indicate that both the individual networks are essential: The first network primarily contributes to the energy dissipation, while the second network plays a role to the synergistic enhancement in the DN composite gels. This work provides an effective reinforcing strategy for CS-based composite hydrogels.

In this work, a series of oil soluble diblock copolymers poly(methyl methacrylate)-b-poly[2-(dimethylamino)ethyl methacrylate] (PMMAm-b-PDEAEMAn; where m is fixed at 49 and n is varied from 3 to 12) are synthesized using a reversible addition-fragmentation chain transfer RAFT method. The copolymers exhibit pH-dependant interfacial activities and behave as macromolecular surfactants under strong acidic conditions. The coassembly behavior and kinetics of cellulose nanocrystals (CNCs) and the copolymer at the water/toluene interface is probed by tracking the dynamic interfacial tension using pendant drop tensiometry. At low pH such as 2 and 3, the film that CNCs coassemble with the copolymer at the oil/water interface can stabilize the pendant drop from dripping down. At a higher pH value, CNCs enhance the interfacial activity of the copolymer through interfacial tension measured and emulsions test. When investigating the coassembly kinetics, it is found that the interfacial protonation reaction of the copolymer and absorbing at the oil/water interface is the rate-determining step and electrostatic binding with CNCs is a much faster process. Besides, the interfacial activity of PMMAm-b-PDEAEMAn is enhanced as n increases and the interfacial coassembly with CNCs is accelerated. A nanoparticle film can be formed because of the coassembly behavior of CNCs and diblock copolymers at the oil/water interface and can stabilize the liquid/liquid interface and endow the interface elastic property. Based on this property, liquid tubule can be generated through injecting CNC aqueous dispersion to copolymer toluene solution. This formation of liquid tubule opens a new platform for the additive manufacturing technique of three-dimensional printing of liquid constructs.

Hypothesis Novel Pickering emulsions stabilized by self-assembled nano-objects of amphiphilic copolymers are attractive in many applications. However, it is not clear to what extent those nano-objects could stay at the oil/water interface. Owing to the twisted intramolecular charge transfer state (TICT) property of Nile red, the distinguishable fluorescent characteristics of Nile red dissolved in n-dodecane and solubilized in copolymer micelles benefit the investigation of the oil/water interfacial nature of Pickering emulsions in situ. Experiments Two amphiphilic diblock copolymers PNMP53-b-PFMA5 and PNMP53-b-PFMA10 named poly(N-(2-methacryloylxyethyl) pyrrolidone)-block-poly(2-(perfluorooctyl) ethyl methacrylate) were synthesized, they can form spherical and wormlike micelles in water spontaneously, respectively. Oil in water (O/W) emulsions were generally produced at different conditions by employing these copolymer micelles as emulsifiers. The size and morphology of prepared emulsions were studied by light scattering and microscope techniques in detail. Moreover, the effect of emulsification conditions on the interfacial morphology evolution of prepared emulsions were characterized systematically in situ by the proposed method based on the confocal laser scanning microscopy (CLSM) measurements. Findings We clarified the progressive transition from Pickering emulsions to classic emulsions through the sustained changes of emulsification conditions by the developed CLSM method, in which block copolymer monomers and their assemblies were played as emulsifiers to stabilize emulsion droplets synergistically. Generally speaking, Pickering emulsions were produced in the presence of sufficient micelles at low emulsification shear rates. Otherwise, common emulsions stabilized by block copolymer monomers would be formed.

The design of efficient semiconductor oxide materials with heterojunction nanostructures for photocatalysis holds great promise in the fields of clean energy conversion and storage. Current synthesis methods for heterojunction composites readily result in phase separation and uncontrollable products, and require harsh preparation methods. In order to address these issues and optimize the microstructure of the heterojunction photocatalyst, controllable synthesis and differences in the porosity are introduced. For the first time, we synthesized a mesoporous Ga2O3/GaOOH heterojunction composite for photocatalytic hydrogen generation using an ingenious ultraviolet-induced Ostwald ripening strategy. Furthermore, the detailed formation mechanism and energy band structure of the as-synthesized material were elucidated. The intimate contact of the heterojunction, refined mesoporous structure and large specific surface area of the mesoporous Ga2O3/GaOOH heterojunction composite endow the material with efficient charge separation and transfer and significantly exposed junction active sites, which results in an enhanced photocatalytic hydrogen generation performance. This study opens up new horizons in the construction of mesoporous metal oxide heterojunction composites.

A family of amphiphilic diblock copolymers poly(lauryl methacrylate)-poly(N-(2-methacryloylxyethyl)pyrrolidone) (PLMA-PNMP) were developed by the reversible addition-fragmentation chain transfer (RAFT) solution polymerization method. The self-assembly behaviors of developed copolymers in the selective solvent, n-dodecane, were studied in detail by employing static light scattering, dynamic light scattering, transmission electron microscopy and rheology measurements, and the structure-property relationship of them was also established accordingly. It was noticed that the morphologies of formed aggregates were affected by temperature apparently because of the glass transition temperature (Tg) of PNMP segments. Generally speaking, spherical micelles, cylindrical micelles and vesicles were gradually formed upon increasing the degree of polymerization (DP) of PNMP segment at the constant DP of PLMA above Tg. However, nanoparticles with particular morphologies would be formed below Tg because of the Tg-induced solidification of PNMP core, resulting in apparent temperature-induced sol-gel transitions. For example, spherical micelles were formed spontaneously in 15 wt% PLMA19-PNMP39 solution at 85 °C, whereas nanoparticles with wormlike morphology were formed at 25 °C instead. The present work not only established the structure-property relationship of PLMA-PNMP copolymers, but also contributes to understand the nature of polymerization-induced self-assembly as well.

The use of glycidyl methacrylate (GMA) and acrylic acid (AAc) as grafting monomers to improve the mechanical properties, particularly tensile strength, of recycled polyethylene (R-PE) is re...

Recently, conductive M-Nb-O composites have gained much attention as a novel lithium ion storage anode material. However, the conductivity and rate performance of M-Nb-O composites still need to be further enhanced. Herein, we have designed a facile strategy to prepare ZnNb2O6/N-doped carbon (ZnNb2O6/NC) which is derived from Nb2O5@zeolitic imidazole frameworks precursor. The ZnNb2O6/NC exhibits advanced energy storage properties including high initial capacity (673 mA h g−1 at 100 mA g−1), superior reversible specific capacity (412.6 mA h g−1 until 100 cycles at 100 mA g−1), long-term cyclic stability and excellent rate capability (470.5 mA h g−1 after 800 cycles at a relatively high current density of 2 A g−1).

Recently, Cu3P has been targeted as an alternative anode material for alkali-metal-ion batteries because of their safety potential and high volumetric capacity. However, designing a high-rate Cu3P electrode with long durability is still faced with huge challenges. Here, we report a self-supporting three-dimensional (3D) composite of Cu3P and Co2P interconnected by N-doped C fibers (Cu3P–Co2P/N–C). The advanced 3D structure not only provides fast reaction kinetics but also improves the structural stability, leading to excellent rate capability and long-term cycling stability, and pseudocapacitance behavior is also beneficial to the high rate performance. Additionally, the synergistic effects between Cu3P, Co2P, and N-doped carbon can increase the electrical conductivity and active sites, ensuring more ion storage. The Cu3P–Co2P/N–C anode for lithium-ion batteries delivers high discharge capacity, superior rate performance, and ultralong lifespan over 2000 cycles accompanied by a stable capacity of around 3...

Borosilicate glasses containing Ag nanoclusters (Ag NCs), Eu3+ and Yb3+ were prepared with the melt-quenching method, in which an efficient energy transfer from Ag NCs to Yb3+ can be realized. Unlike the previous reports in which Eu3+ act as either sensitizer or luminescence center, the role of Eu3+ in this system is to promote the formation of Ag NCs and thus effectively increased the number of sensitizer at low AgNO3 doping. With optimized AgNO3 and YbF3 concentrations of 0.5 and 1.0 mol% respectively, 6.3 times further enhanced Yb3+ infrared emission can be obtained through the introduction of trace amount of EuF3. Additionally, the origin of Ag NCs visible emission, the mechanism that is responsible for the energy transfer from Ag NCs to Yb3+, and the effect of YbF3 and EuF3 doping on the formation of Ag NCs were discussed.

Various non-noble metal-based electrocatalysts have been studied to replace platinum for hydrogen production. The formation of a composite through adding a conductive polymer could be an efficient way to further enhance the performance of those catalysts further but applying conductive polymers in electrochemical catalysis has been hardly ever reported. In this research, we synthesized an extraordinary WO3@NPRGO composite using phosphotungstic acid-polypyrrole/reduced graphene oxide (PW12-PPy/RGO) as a precursor. The oxidation polymerization of pyrrole (Py) monomers prevents the PW12 and RGO from aggregating and WO3 nanoparticles were homogeneously imbedded in the N, P-codoped RGO nanosheets, which not only exposed massive active sites, but also resulted in faster charge transfer. Electrochemical characterizations reveal that the composite exhibits greatly enhanced electrocatalytic activity and has impressive long-term stability for the hydrogen evolution reaction. Our works opens a new path for the design and synthesis of novel nanostructure electrocatalysts.

For luminescent photochromic materials, the optical properties of lanthanide (Ln) ions, including emission color, excitation mode and lifetime, are extremely important in optical information storage and recording. Conventional dopants of single Ln ions generally display unicolor and unimodal emission, leading to low-level luminescence modulation and information readout. Therefore, it is urgent to develop multicolor and multimodal luminescence modulation in a single photochromic material, thus well modulating luminescent readout capability. In this study, superior multicolor emissions (red-green), multimodal properties (downshifting/upconversion) and tunable luminescent switching contrast were successfully obtained in Bi2.5Na0.5Nb2O9-based ferroelectric materials by dual-lanthanide ion doping (Pr/Er). Red/green emission ratios can be continuously tuned from red, orange and yellow to green range via controlling the excitation wavelengths and doped concentrations. Correspondingly, the luminescent switching contrast (ΔRt) gradually increases from 29% to 93% with increasing excitation wavelength upon visible irradiation (407 nm), while the ΔRt values decrease with emission wavelengths, which can be well explained by the Dexter energy transfer model. These findings offer a guide to designing tailored luminescence modulation behavior of luminescent photochromic materials for wide application in optical storage and switching devices.

In recent years, although there has been great progress in the exploration of high capacity alkali metal ion batteries, the design of high-durable anode materials with high power density remains challenging. In this study, a flexible three-dimensional network of WSe2/C is reported as a dual-role anode for lithium/sodium ion batteries, providing multichannels for the fast lithium/sodium ion diffusion and a buffer matrix to restrain the volume change as well as increase the electron conductivity. The in situ transmission electron microscopy characterizations reveal a minor volume expansion of the WSe2/C (∼8.2%) and a complete-amorphization event occurring after the first lithiation process. WSe2/C exhibited superior reversible capacity/rate capability/cycling stability in lithium/sodium ion batteries. Particularly, a large stable capacity and ultra-long cycling life at ultra-high rate (257.0 mA h g−1 at 25 A g−1 after 10 000 cycles) are achieved for the WSe2/C electrode in lithium ion batteries, accompanied by only 0.5% capacity loss per cycle over 1000 cycles, which reveals its excellent capacity stability at ultra-high rates. This study reveals the great potential of WSe2/C as a high-capacity dual-role anode for lithium/sodium ions batteries.

In this study, an optical fiber temperature sensor based on up-conversion luminescence (UCL) is proposed. The core part is a new plan of the sensing unit, which is constructed with UCL materials of N a Y F 4 : Y b 3 + , E r 3 + nanocrystals by fiber fusion technology to achieve a wide range of temperature measurements. Experimental results show that the proposed optical fiber temperature sensor shows significant spectrum-temperature characteristics in 80–373 K temperature range. Its relative sensitivities at low temperature and normal temperature are 2.2 × 10 − 3 / K with a determination coefficient of 0.957 and 9.1 × 10 − 3 / K with a determination coefficient of 0.994, respectively. This type of sensor also has good mechanical strength and system stability and shows great potential for development, particularly in the aerospace field with large temperature differences.

Soft-oxometalates (SOMs) are colloid suspensions of superstructured assemblies of polyoxometalates (POMs) and are found to be very effective photo-catalysts in a number of chemical reactions. The stabilization of SOMs generally requires legends or stabilizers, e.g., polymers and surfactants. In this paper, a light responsive azobenzene surfactant, C10AZOC2N3, was developed and used to stable {Mo132} SOMs. Various techniques such as Dynamic light scattering, TEM, UV-Vis spectra and cyclic voltammetry were employed to characterize the experimental results. The outstanding structure-directing effect of surfactant self-assembly micelles in solution on inorganic counter-anions was demonstrated. Different amount of cyclohexane was solubilized into C10AZOC2N3 micelles to successfully control the size of {Mo132} SOMs cluster. Furthermore, the clusters exposed to UV light for a certain time can be served as a second trigger to control the size of SOMs due to the trans-cis conformation transition of surfactant molecules. The redox potentials of C10AZOC2N3-{Mo132} SOMs were investigated as the cluster size varied. Interestingly, the redox potential of {Mo132} was not affected by the cluster size, indicating that the presence of surfactant did not change the main function of {Mo132} as an electrochemical catalyst, but merely assisted in the size control of SOM aggregation.

Near infrared to ultraviolet (NIR-to-UV) up-conversion nanocomposites, composed of an upconversion nanoparticle (UCNP) core and a transformable polyspiropyran shell, were prepared by distillation precipitation polymerization and the template method. The polyspiropyran shell can undergo reversible hydrophoblic-hydrophilic transformations through the switching of UV and visible light and by variation of pH. About 10 wt% of the anticancer drug, doxorubicin (DOX), can be loaded into the drug carrying layer under pH 7.4 by electrostatic force. The NIR and pH responsive features of the polyspiropyran shell were shown by the dynamic light scattering (DLS) results, in which the size of nanocomposites (UCNPs@SP-MA/MAA) became larger under NIR irradiation and pH 4.5. The hydrophobic to hydrophilic surface transformation alters the permittivity of the polyspiropyran shell and the release behavior. The cumulative release rate of the DOX-loaded UCNPs@SP-MA/MAA reached 53.8% under pH 4.5 and NIR irradiation. The cytotoxicity of the bare UCNPs@SP-MA/MAA and the DOX-loaded UCNPs@SP-MA/MAA were evaluated against breast cancer cells and the results confirmed that the toxicity of UCNPs@SP-MA/MAA nanocomposites was minimal, even at high dosage (100 μg/mL), while the toxicity of DOX can be triggered by NIR light.

Hydrogels that possess adequate toughness in bulk and at soft interface are highly desirable. We report a fully physically crosslinked dual Amylopectin (Amy, the first network)/poly(N-hydroxyethyl acrylamide) (PHEAA, the second network) hydrogel, where both networks were hydrogen bonding (H-bonding) crosslinked, with super toughness in bulk and tunable adhesion at hydrogel-soft tissue interface. Through adjustment of hydrogen bond density, strong and tough hydrogels were prepared that exhibited different levels of adhesion strength and three adhesive failure mechanisms. We replaced Amy with oxidized starch (OSA) to synthesize dual and hybrid chemically/physically crosslinked OSA/PHEAA double network (DN) hydrogels that were capable of forming Schiff's bases at hydrogel-hydrogel or hydrogel-tissue interfaces, aside from interfacial H-bonding, incurring sustained, high interfacial toughness (1850 J m−2 hydrogel-hydrogel and 610 J m−2 hydrogel-tissue) in wet environments. Such tough and adhesive DN hydrogels have great potential in various applications such as engineering of artificial soft tissues or implantable devices that are intended to adhere to internal organs or tissues.

Based on genetic algorithm, on the basis of the performance evaluation of salt resistant polymer such as viscosity increasing, viscosity stability, anti cutting property and viscoelasticity, two salt resistant polymers with the best comprehensive performance were selected. The physical simulation experiment of secondary oil displacement results was carried out with ordinary polymer, and the h2500 salt resistant polymer with the best performance was selected for field test. As of November 2018, the EOR in the test area is 16.7%, and the EOR is 19.6% more than that of conventional polymer flooding under the same injection pore volume multiple. Therefore, the application of new salt resistant polymer is an effective way development effect.

Rewritable information record materials usually demand not only reversibly stimuli-responsive ability, but also strong mechanical properties. To achieve one photochromic hydrogel with super-strong mechanical strength, hydrophobic molecule spiropyran (SP) has been introduced into a copolymer based on ion-hybrid crosslink. The hydrogels exhibit both photoinduced reversible color changes and excellent mechanical properties, i.e., the tensile stress of 3.22 MPa, work of tension of 12.8 MJ m-3 , and modulus of elasticity of 8.6 MPa. Moreover, the SP-based Ca2+ crosslinked hydrogels can be enhanced further when exposed to UV-light via ionic interaction coordination between Ca2+ , merocyanine (MC) with polar copolymer chain. In particular, hydrogels have excellent reversible conversion behavior, which can be used to realize repeatable writing of optical information. Thus, the novel design is demonstrated to support future applications in writing repeatable optical information, optical displays, information storage, artificial intelligence systems, and flexible wearable devices.

In this study, a new processing design of an optical fiber cryogenic temperature sensor (OFCTS) is presented. The sensing unit is constituted by NaYF4:Yb3+, Er3+@NaYF4 core-shell upconversion nanocrystals-polymethyl methacrylate (UCNCs-PMMA) nanocomposites. The coupling is achieved by fiber fusion in the embodiment. The relative sensitivity of the OFCTS can reach the maximal value 13.241×10−3 K−1 at 80 K in a cryogenic environment, and stability is good with a standard deviation of 0.012. Research results show that the proposed OFCTS has good temperature responses at the cryogenic environment, and has a great potential of the superconducting application for generator, transmission line, maglev train and quantum interferometer.

A versatile ionic crosslink lithography (ICL) approach is reported to achieve geometry transitions of strong polyvinyl alcohol/sodium alginate (PVA/SA) hydrogels in a controllable and programmable manner. Specifically, localized PVA/SA and PVA/SA/Fe3+ hydrogel domains of significantly different swellabilities (i.e., in-plane gradient) are created by patterning and selective ionic crosslinking of one single type of PVA/SA hydrogel. A simple two-step sequential pre- and free-swelling, or each alone, directs the patterned, inhomogeneous hydrogel to transform in various programmable and quasi-quantitative ways through local bulging and/or global buckling. All types of shape changing are reversible and repeatable due to the reversible nature of ionic coordination in the hydrogel networks. The flexibility and versatility of 3D printing is also demonstrated in creating through-thickness gradient in PVA and PVA/SA hydrogel assemblies with similar morphing capability. The ICL approach developed in this work may help shed some light on developing strong and shape morphing hydrogels as soft sensors and actuators and for potentially biomimetic transformations. The ICL approach may also be transferable to fabrication of many other types of hydrogel materials for similar applications.

Developing multicomponent transition-metal phosphides has become an efficient way to improve the capacitive performance of single-component transition-metal phosphides. However, reports on quaternary phosphides for supercapacitor applications are still scarce. Here, we report high capacity and energy density of Zn-Ni-Co-P quaternary phosphide nanowire arrays on nickel foam (ZNCP-NF) composed of highly conductive metal-rich phosphides as an advanced binder-free electrode in aqueous asymmetric supercapacitors. In a three-electrode system using the new electrode, a high specific capacity of 1111 C g

The size of the steel section in concrete encased steel (CES) structure of bridge engineering is much larger than that of the building construction, accompanied by great shear demands at the steel–concrete interface. To enhance the interfacial shear performance, perforated web connection (PWC), which perforates the web of steel section with perforating rebars passing through the web openings, is proposed in this research for bridge application. Push-out tests and refined numerical analysis were performed on CES specimens with PWC, aiming to evaluate its effectiveness and to reveal the shear transfer mechanism. The effect of various parameters on the shear resistance was also investigated through a parametric study using the validated modeling method. Eventually, an Artificial Neural Network (ANN) was developed to predict the ultimate shear resistance of PWC. The results indicate that the interfacial shear-slip response especially the post-peak behavior is significantly improved by PWC with perforating rebars, which transforms the failure manner from brittle to ductile. The failure process of the PWC with perforating rebars experiences the loss of bonding, activation of perforating rebars, as well as shear failure of perforating rebars and concrete dowels. The parametric analysis shows that the PWC with large web openings exhibits great ultimate shear resistance and sensitivity to the variation in other parameters owing to good compatibility between the natural bond and reinforced concrete dowels. The well trained ANN model is a powerful tool for efficiently predicting the ultimate shear resistance of such connection.

As promising structural materials, various tough hydrogels have been developed recently by incorporating various kinds of bonds. An important challenge is to use dual physical cross-linking to develop both toughness and self-recovery in a single material. Here we report smart, strain-responsive hydrogels composed of a fully physically linked agarose/poly(acrylic acid)-ferric ion (agar/PAAc-Fe3+) double network (DN) with high toughness and pH-sensitivity. These hydrogels were fabricated in a one-pot reaction to generate dual physical cross-linking through, first, a hydrogen-bonded cross-linked agarose network, and, second, a physically linked PAAc-Fe3+ network via Fe3+ coordination interactions. The DN hydrogels possessed high toughness, with breaking strain of 1130%, fast self-recovery properties in ambient conditions (100% recovery in 30 min) and self-healing properties (the healed hydrogels can be manually stretched up to 700% of their original length after self-healing for 60 h from the cut-off state). In addition, the hydrogels exhibited pH-sensitivity due to the dissociation of ionic coordinate bonds between –COO− ions of the PAAc chains and Fe3+ ions. Double-layer hydrogel strips with two different concentrations of PAAc formed a “C”-shaped material when initially immersed in pH 7 solution and then soaked in a pH 3 solution. These characteristics make the hydrogels attractive candidates for tissue engineering, soft actuators and flexible electronics.

We report a dual ionic cross-linking approach for the preparation of double-network hydrogels with robustness, high strength, and toughness, sodium alginate/poly(acrylamide-co-acrylic acid)/Fe3+ (SA/P(AAm-co-AAc)/Fe3+), in a facile “one-step” dual ionic cross-linking method. We take advantage of the abundant carboxyl groups on alginate molecules and the copolymer chains and their high coordination capacity with multivalent metal ions to obtain hydrogels with high strength and toughness. The optimal SA/P(AAm-co-AAc)/Fe3+ (SA 2 wt % and AAc 5 mol %) hydrogels showed a remarkable mechanical performance with 3.24 MPa tensile strength and 1228% strain, both of which remained stable with 76% water content and were highly swelling resistant in an aqueous environment. The hydrogels possessed high fatigue resistance, self-recovery, pH-triggered healing capability, shape memory, and reversible gel–sol transition facilitated by pH regulation. Moreover, they show three-dimensional (3D) printing processability by prop...

In this study, metallocene linear low density polyethylene (abbreviated as mPE) was grafted with glycidyl methacrylate (GMA) and acrylic acid (AAc) forming long-chain branched polymers, which act as an interfacial modifier of recycled high-density polyethylene (abbreviated as rPE)/low-density polyethylene (LDPE) blends. AAc was shown to increase GMA grafting efficiency onto mPE producing mPE-g-GMA/AAc. The mechanical properties, crystalline structure, rheological properties, and phase structure of rPE/LDPE/mPE-g-(GMA-co-AAc) (abbreviated as rPE/LDPE/mPE-g-G/A) blends were investigated using uniaxial tensile, differential scanning calorimeter, rheometer, and X-ray diffraction experiments. The tensile strength of rPE/LDPE/mPE-g-G/A was 34.51 MPa and the multiphase polymer displayed co-crystallization characteristics indicating good compatibility between the two components. The changes in the interface layer thickness and dispersed phase size further indicate the existence of partial compatibility among the multiphase polymer.

The realization of asymmetric hollow carbonaceous nanostructures remains a great challenge, especially when biomass is chosen as the carbon resource through hydrothermal carbonization (HTC). Herein, a simple and straightforward solvent-induced buckling strategy is demonstrated for the synthesis of asymmetric spherical and bowl-like carbonaceous nanomaterials. The formation of the bowl-like morphology was attributed to the buckling of the spherical shells induced by the dissolution of the oligomers. The bowl-like particles prepared through this solvent-driven approach demonstrated a well-controlled morphology and a uniform particle size of approximately 360 nm. The obtained nanospheres and nanobowls were loaded with CoS2 nanoparticles to act as heterogeneous catalysts for the selective hydrogenation of aromatic nitro compounds. As expected, the CoS2 /nanobowls catalyst showed good tolerance to a wide scope of reducible groups and afforded both high activity and selectivity in almost all the tested substrates.

To take advantage of the polymer’s special properties, we synthesized PVDAT coated polystyrene (PVDAT@PS) microspheres through semi-continuous precipitation polymerization, and demonstrated the possibility of controlling the size of microspheres by using different sized PS cores. Mechanism of the microsphere synthesis was investigated. Preliminary application studies indicated that the synthesized microspheres adsorbed double-stranded DNAs (dsDNAs) comprising A-T base pairs in pH7.4 phosphate buffered saline, and the adsorption capacity was in a range of 3.28mg to 5.58mg per gram PVDAT@ PS microspheres depending on A-T base pair percentage and chain length of the dsDNAs.

Efficient aerobic oxidation has been developed for the selective preparation of a sequence of valuable p-hydroxybenzaldehydes from corresponding p-cresols, using a new magnetically separable catalyst of nano-structured cobalt–cobalt oxide/nitrogen-doped carbon (CoOx@CN) material. CoOx@CN showed high activity for the 2-methoxy-4-cresol oxidation to vanillin, giving great yield (90%) and with good turnover number (210), as well as other p-cresols in good to great yields. The catalytic performance was investigated and related to the structural, chemical and magnetic properties which determined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR) and vibrating sample magnetometer (VSM). The effects of base to substrate molar ratio, catalyst concentration, temperature, and solvent on the conversion and selectivity patterns also have been studied. The investigation revealed that remarkable catalytic properties of CoOx@CN could be ascribed to the active species cobalt oxide, doped nitrogen and porous carbon with large surface area. The size of the catalyst is a key factor for catalyst performance. The ferromagnetic property of catalyst enables to recycle easily by an external magnetic field and reuse six successive times without significant activity loss.

In this work, a carbon nanotube (CNT)-based membrane [(4-((4-((11-ferroceneundecyl)oxy)phenyl)diazenyl)phenoxy)-diethylene triamine (FADETA)/polyethyleneimine (PEI)-decorated CNT membrane] with stimuli-switchable separation fluxes was developed. The multiwalled CNTs were modified by a pH-, light-, and redox stimuli-responsive surfactant FADETA initially, and then the FADETA-decorated CNTs were further cross-linked by PEI and finally coated on the polypropylene membrane. Interestingly, the particular membrane was successfully applied in emulsion systems to separate oil and water with high efficiency. First, the FADETA-/PEI-decorated CNT membrane showed highly porous microstructural characteristics owing to the overlapped and cross-linked CNTs as confirmed by the scanning electron microscopy observation. Then, it showed strong hydrophilicity to water in the air and high oleophobicity to oil underwater, thereby endowing the membrane with the potential to separate oil and water. Owing to the modified multiple stimuli-responsive FADETA on CNTs, the separation fluxes were stimuli-switchable, which could be adjusted reversibly by environmental factors including pH, light, and redox.

In this work, we developed a new type of photo-catalysts composed of the urchin-like cupric oxide (CuO) microparticle and polyvinylidene fluoride (PVDF) hybrid composites by the convenient organic-inorganic hybrid strategy, which show high-efficiency and conveniently recyclable for dye degradation including methylene blue (MB), Congo red (CR), and malachite green (MG) by visible light irradiation. The micro-structural characteristics of urchin-like CuO microparticles are crucial and dominant over the photo-degrading efficiency of hybrid catalyst because of their highly exposed {0 0 2} facet and larger specific surface area. Simultaneously, the intrinsic porous framework of PVDF membrane not only remains the excellent photo-catalytic activity of urchin-like CuO microparticles but also facilitates the enrichment of dyes on the membrane, and thereby synergistically contributing to the photo-catalytic efficiency. The microstructures of both urchin-like CuO microparticles and hybrid catalysts are systematically characterized by various techniques including scanning electron microscopy (SEM), transmission electron microscope (TEM), high-resolution transmission electron microscope (HRTEM), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and nitrogen adsorption/desorption isotherms, which evidently support the mentioned mechanism.

Carbon nanospheres and their derived superstructures have attracted increasing attention due to their widespread applications ranging from electrochemistry to catalysis. However, it remains a great challenge to achieve mass production of biomass-derived monodisperse carbon nanospheres with a diameter

In the process of conversion of solar energy into electricity and fuel, efficient electrocatalysts are indispensable. Rieske iron–sulfur protein and FeS catalysts play an important role in natural photosynthesis (NPS), and in artificial photoelectrochemical cells, respectively. Nano–micro composite catalysts (NMCCs) possess not only high catalytic activity but also fast electron transport. Herein, we prepared a nano–micro composite (NMC) of Fe1−xS nanoparticles decorated on sulfur-doped graphene oxide (S-GO) sheets (namely, Fe1−xS@S-GO–NMC) to be used as a cathode in dye-sensitized solar cells (DSCs). The GO effectively inhibit the aggregation of Fe1−xS nanoparticles. Notably, DSCs based on an Fe1−xS@S-GO–NMC cathode achieved a high solar-to-electrical conversion efficiency up to 7.23%. The conversion efficiency is, to our knowledge, one of the highest efficiencies for DSCs based on an FeS or FeS2 cathode. Although the Fe1−xS@S-GO–NMC exhibited a low thermodynamic possibility for redox reactions, it showed a higher kinetic rate than that of Pt for the charge transfer between the reaction medium and the cathode. This indicates that a fast electron exchange process occurs at the interface between the reaction and the cathode. The value of the time constant (τ) corresponding to the charge exchange resistance based on Fe1−xS@S-GO–NMC (0.0215 ms) was smaller than that obtained with Pt (0.261 ms). Therefore, we ascribed the superior performance of the photoelectrochemical device based on Fe1−xS@S-GO–NMC to its good electrocatalytic performance. The results are of great interest for fundamental research and for practical applications of FeS and FeS2 and their composites in the solar splitting of water, artificial photoelectrochemical cells, and electrocatalysts.

Strong and tough poly(vinyl alcohol) (PVA)/alginate hydrogen-bonded-ionic dual-physical double-network (DN) hydrogels have been successfully prepared by a facile route of a freeze–thaw (25–25–25 °C) cycle followed by concentrated (1.0 mol L−1 of) aqueous-Ca2+ immersion of PVA/Na alginate (SA) mixed aqueous solutions. It was found that, at mole ratios of the PVA- to SA repeat units of 20/1 to 80/1, the DN gels likely evolved a semi-interpenetrating polymer network (IPN) morphology of rigid alginate networks dispersed in while interlocking with ductile PVA network to accomplish DN synergy that gave their high strength and toughness, where the high alginate rigidity originated probably from its dense cross-link induced syneresis and dispersion along crosslink-defective voids to result in little internal stress concentration. Tentatively mechanistically, as the 20/1–80/1 DN gels were stretched steadily, their mechanical response was gradually differentiated into distinct synergistic states: the sparsely hydrogen-bonded PVA served as a ductile matrix to bear small fractions of the established stresses at its large elongations; whereas the densely ionically (i.e. Ca2+) cross-linked alginate functioned as a rigid skeleton to sustain the remaining larger stresses upon its smaller local strains. Promisingly, this ductile-rigid matrix-skeleton synergistic mechanism of semi-IPN morphology may be universally extended to all A/B DN hydrogels of large A–B rigidity (or cross-link density) contrast, whether the cross-link nature of network(s) A or B is covalent, ionic, hydrogen bonded or van der Waals interacted. The strong and tough DN gels also displayed satisfactory self-recovery of viscoelastic behaviour, in that their Young's modulus and dissipated energy in the uniaxial tensile mode and dynamic storage and loss moduli in the oscillatory shear mode all recovered significantly from non-linear viscoelastic regimes despite different degrees of failure to revert to (quasi)linear viscoelasticity.

A novel process for preparing carbon nanotubes (CNTs) reinforced magnesium nanocomposites were developed, which combined friction stir processing (FSP) and ultrasonic assisted extrusion. A very good dispersion of CNTs in AZ91D alloy could be observed. It was demonstrated that the strength of Mg nanocomposites was remarkably enhanced. This was contributed to dislocation strengthening mechanism and stress transfer mechanism, not concerned with the grain refinement. Moreover, the composites maintained good ductility. The interfaces between CNTs and Mg matrix were well bonded, and the interfacial reaction product formation of Al 2 MgC 2 was confirmed. A few edge dislocations were observed at CNTs-matrix boundaries by adding carbon nanotubes.

The surrounding rocks of underground engineering are usually subjected to the coupling of compressive and shear stresses. The variable angle shear tests (VASTs) and direct shear tests (DSTs) are two types of lab tests that can easily achieve different compression-shear stress states. The VASTs and DSTs on cubic rock specimens were conducted to analyze the shear strength parameters and acoustic emission (AE) characteristics during rock failure process. The test results show that it is more reasonable to use the test data in VASTs with shear angles greater than 45° for calculating the shear strength parameters of rocks. The essence of changing the shear angles in VASTs or the normal loads in DSTs is to change the micro-crack component produced in the compression-shear failure mode, in which the shear cracking mainly trigger the AE signals with low peak frequency around 100 kHz, and the tensile cracking mainly induce the AE signals with relatively high peak frequency around 300 kHz. Although the main type of micro-crack produced by shear failure and compression failure are both shear micro-crack, the micro-cracks generated by shear failure have higher efficiency in generating AE energy compared with compression failure, which means that the large-scale micro-crack expansion activities are more intense in shear failure than that in compression failure.

Polypropylene fiber, as a micro-scale reinforcement, can effectively inhabit the continuous micro-crack propagation of concrete during service. This paper aimed at examination of the fatigue life of polypropylene fiber reinforced concrete (PFRC) as subjected to repetitive compressive stress at multiple levels. A total of 18 groups of prismatic specimens were tested for different stress levels and polypropylene fiber parameters (volume fractions and aspect ratios). A two-parameter Weibull distribution was employed to describe the fatigue life probability distribution of PFRC. The shape parameter and characteristic life parameter were derived by averaging the values estimated by graphical method, moment method and maximum likelihood estimation method. The results indicated that the addition of polypropylene fiber into the concrete matrix can remarkably prolong the fatigue strength of concrete. Compared with plain concrete, the fatigue strength of PFRC could be increased by up to 28.1% under the failure probability of 5%. The fatigue life of PFRC was increased with an increase in the polypropylene fiber volume fraction up to 0.15%. However, the fatigue life of PFRC was decreasing with an increase in the fiber aspect ratio. The PFRC specimen with a volume fraction of 0.15% and an aspect ratio of 167 possessed the highest fatigue compressive strength among all the designed specimens. The fatigue life probability distribution of PFRC also obeyed the two-parameter Weibull distribution. Finally, a single-logarithm fatigue equation for PFRC was developed with both fiber parameters and failure probabilities taken into account, which can realistically predict the fatigue life of PFRC. This research outcome provides new knowledge and database that underpin the future development of design specifications for PFRC structures.

Novel porous and mulberry-like hydroxyapatite (HAp) nanoparticles with three-dimensionally hierarchical microstructures were developed by using the dual-hydrophilic block copolymer poly(methacrylate acid)-b-poly[N-(2-methacryloylxyethyl) pyrrolidone] (PMAA-b-PNMP) as the template. It was found that the morphology and Ca/P ratio of synthesized HAp was highly related to the concentration of block copolymer and solution pH, respectively. The morphological evolution of HAp nanoparticles in different conditions was investigated systematically by scanning electron microscopy (SEM), transmission electron microscope (TEM), high-resolution transmission electron microscope (HRTEM), powder X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The possible mechanism of PMAA-b-PNMP assisted mulberry-like HAp formation was also proposed based on the time-dependent TEM results. Attributing to the high specific surface area (SSA) of 119 m2 g−1, these mulberry-like HAp nanoparticles exhibited excellent adsorption ability for Congo Red (CR). The maximum adsorption capacity was 467 mg g−1 according to the Langmuir monolayer adsorption model.

Broader applications of polymer hydrogels are largely constrained by their poor mechanical performance. Here, we report our strategy of achieving ultrahigh mechanical strength, toughness, and self-healing properties simultaneously in a hybrid dual crosslinked polyacrylic acid (PAAc) hydrogel. The hybrid PAAc hydrogel was fabricated in a one-pot reaction with two types of crosslinking points, i.e. the primary chemical cross-linkers that create covalent cross-linking among PAA chains and the secondary physical cross-linkers Fe 3+ that introduce ionic coordinates between Fe 3+ and −COO − groups. The resulting hybrid PAA hydrogel was subsequently subject to a simple saline solution soaking to become highly mechanically robust as a result of chain entanglement within the network. Favorable mechanical properties possessed by such hybrid hydrogels included high tensile strength (ca. 1.794 MPa), large elongation at break (ca. 13.209 times), and excellent work of extension (ca. 11.475 MJ m −3 ). In addition, the hydrogels exhibited self-healing properties because of their inter-chain interactions at ambient conditions (tensile strength can recover approximately 30% of the initial after self-healing for 48 h from a cut-off state). This work demonstrates a simple and promising strategy of preparation of novel ductile and doughty hydrogels through dual crosslinking and saline solution soaking.

Fluorescent carbon dots (CDs) originated from natural biomass have been of great interest in recent years because of their superior optical and chemical properties. However, previously reported CDs used only one natural biomass as precursor, and the fluorescence quantum yield (QY) and long-wavelength emissions are usually weak, which restrict their further applications in biology-relevant fields. Here a green method was demonstrated for the preparation of S and N codoped fluorescent CDs (S,N/CDs) by adopting two natural biomasses (water chestnut and onion) as precursors. The fabrication process is simple and environmentally friendly. By hydrothermal heating of water chestnut and onion, monodispersed, highly fluorescent S,N/CDs (diameter 3.5 nm) were obtained. The carboxyl on the surface of S,N/CDs can bind to Cu(II) ion, resulting in the luminescence quenching of S,N/CDs. And coenzyme A (CoA) can restore the luminescence of S,N/CDs. Based on the above features of S,N/CDs, an innovative off–on fluorescence...

A new series of amphiphilic pyrrolidone diblock copolymers poly[N-(2-methacrylaoyxyethyl)pyrrolidone]-block-poly(methyl methacrylate) (PNMPm-b-PMMAn; where m is fixed at 37 and n is varied from 45 to 378) is developed. Spontaneously situ-gelling behaviors are observed in isopropanol when n varies from 117 to 230, whereas only dissolution or precipitation appears when n is beyond this region. Further analysis reveals that uniform thermoinduced reversible gel–sol transitions are observed in those organogels, which is attributed to the disassembly from micellar networks to micelles as confirmed by electron microscopy and other techniques. The gel–sol transition temperature is highly dependent on n and increases as n increases. Conformational interactions analyzed using 1H NMR and 2D Noesy NMR suggest that the thermoinduced stretch of solvophilic PNMP segments within micelles and the sequencing variation in the isopropanol molecules are the major cause of the gel–sol transitions.