A highly stretchable nanocomposite (NC) hydrogel was fabricated
via in situ
free radical polymerization of acrylamide. In particular, an exfoliated two-dimensional MXene (Ti
3
C
2
) nanosheet was ...utilized as a crosslinker instead of traditional organic crosslinkers. The exfoliated Ti
3
C
2
nanosheets were confirmed by atomic force microscopy (AFM) and dynamic light scattering (DLS) measurements. Compared with traditional organic crosslinked
N
,
N
-methylene bisacrylamide (BIS)/polyacrylamide (PAM) hydrogels (fracture strength of 32.0 kPa and elongation of 109.6%), the synthesized Ti
3
C
2
/PAM NC hydrogels exhibited greatly improved mechanical properties with fracture strengths of 66.5 to 102.7 kPa, compressive strengths of 400.6 to 819.4 kPa and elongations at break of 2158.6% to 3047.5% as the Ti
3
C
2
content increases from 0.0145% to 0.0436%. The enhanced mechanical performances can be attributed to the honeycomb-like fine structure with uniform pores as well as more flexible polymer chains in NC hydrogel networks. When loaded with drugs, Ti
3
C
2
/PAM NC hydrogels exhibited good sustained-release performance, higher drug loading amounts (97.5-127.7 mg g
−1
) and higher percentage releases (62.1-81.4%), greatly superior to those of the BIS/PAM hydrogel (46.4 mg g
−1
, 45.0%). Our work reveals the application of MXene materials in the fabrication of NC hydrogels with enhanced mechanical and drug release behaviors.
Novel Ti
3
C
2
/polyacrylamide nanocomposite hydrogels with excellent mechanical and drug release performances were fabricated
via in situ
polymerization, employing ultralow content Ti
3
C
2
nanosheets as crosslinkers instead of organic crosslinkers.
Various kinds of structure designs have been proposed to achieve the multiple-band metamaterial absorbers. However, the discrete distance of adjacent frequencies of multiple absorbers is considerably ...large, which will inevitably overlook a large amount of information hidden in the off-resonance absorption areas. Herein, a narrow discrete distance of dual-band terahertz absorber based on two pairs of an Au strip/dielectric layer backed by Au film is designed. Two nearly 100% absorptivities of resonance peaks having the discrete distance of only 0.30 THz are realized. The relative discrete distance of the device is 13.33%, and this value can be adjusted via the length change of an Au strip. Furthermore, we present two narrow discrete distances of a triple-band absorber through stacking one more pair of an Au strip and dielectric layer. Results prove that two discrete distances of only 0.14 THz and 0.17 THz in adjacent absorption modes of the first two and the last two are achieved, respectively; the relative discrete distances of them are respectively 6.57% and 7.22%, which are far from previous reports. Narrow discrete distances (or low values of relative discrete distance) of the multiple-band absorbers have a large number of applications in the investigation of some hidden information in very near frequencies.
Summary
A wide compositional range of Pd‐Ni/Cd on polypyrrole (PPy)‐modified Ti plates (Pd‐Ni/Cd/PPy/Ti) was fabricated via electrochemical deposition. The hydrogen absorption properties of the ...prepared Pd‐Ni/Cd/PPy/Ti electrodes were evaluated using cyclic voltammetry and chronoamperometry in acidic media. The optimal Pd36‐Ni7/Cd57/PPy/Ti electrode achieved a hydrogen storage capacity of 331.3 mC cm−2 mg−1 and an H/Pd ratio of 0.77. The enhancement of the hydrogen storage was attributed to a synergistic effect between the Pd‐Ni/Cd catalysts. The surface morphology, crystallinity, and chemical composition of the Pd‐Ni/Cd/PPy/Ti electrode were characterized using scanning electron microscope (SEM), X‐ray diffraction (XRD), and X‐ray photoelectron spectroscopy (XPS), respectively. Hydrogen spillover occurred on the trimetallic catalysts, and secondary hydrogen spillover occurred on the PPy/Ti support. The enhanced hydrogen sorption capacity was due to both the synergistic effect of the trimetallic catalysts and the assistance of PPy, making Pd‐Ni/Cd/PPy/Ti a promising hydrogen storage material.
A novel Pd‐Ni/Cd loaded PPy/Ti composite electrode was prepared for hydrogen storage.
The optimal Pd36‐Ni7/Cd57/PPy/Ti electrode has a H/Pd ratio of 0.77 and a hydrogen storage capacity of 331.3 mC cm−2 mg−1.
Good hydrogen adsorption properties were due to the synergetic effect of Pd, Ni, and Cd and assistance of PPy.
Layered double hydroxide (LDH)/polyacrylamide (PAM) nanocomposite (NC) hydrogels were successfully prepared utilizing Co/Al-LDH nanosheet as inorganic crosslinker, acrylamide as monomer via in-situ ...free radical polymerization at room temperature in water. The Co/Al-LDH used here is freshly prepared Co/Al-LDH solution with a Tyndall phenomenon, which avoids the exfoliation and dispersion process of LDH using toxic organic solvent or modifiers. The hydrogel formation mechanism can be ascribed to the coordination and hydrogen bonding interactions between hydroxyl groups on LDH nanosheet and amide groups on acrylamide. The effect of LDH content on viscoelastic properties were studied by rheology measurement. The removal of methyl orange as a probe dye by Co/Al-LDH/PAM NC hydrogel accords with Langmuir adsorption isotherm and pseudo-second-order equation.
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•LDH/PAM hydrogels reinforced with LDH were prepared.•Exfoliation and dispersion of LDHs is simply achieved without using toxic organic solvent or modifiers.•The effect of LDH content in LDH/PAM NC hydrogel is investigated by rheology measurement.•The potential of LDH/PAM NC hydrogel for removal of methyl orange (MO) was studied.
Pervaporation (PV) has many potential advantages in fluid catalytic cracking (FCC) gasoline desulfurization. The PV membrane performance was improved by incorporating SiO2 nanoparticles in polyvinyl ...butyral (PVB). The coupling agent was used to enhance the compatibility between the inorganic phase and the organic phase to avoid the occurrence of film defects. Polyurethane membranes were characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, and atomic force microscopy. To evaluate the PV performance, the real FCC gasoline was tested. The effects of the SiO2 content, the operating temperature, and the active layer thickness on the PV performance of the PVB/SiO2 membranes were investigated.
PVB/SiO2 membranes were prepared using a coupling agent to covalently link inorganic SiO2 particles and organic PVB polymers. Crosslinking improves the compatibility between the inorganic and organic phases and avoids the generation of membrane defects. The composite membranes displayed superior performance for the removal of organosulfur compounds from fluid catalytic cracking gasoline.
Forward osmosis (FO), which is an emerging osmotic driving membrane separation process, can be directly used in high-salinity oil-bearing (HSOB) wastewater treatment. In this study, the thin film ...composite (TFC) polyamide FO membranes were fabricated for HSOB wastewater treatment. The impacts of the draw solution (DS) concentration, cross-flow rate, stirring rate, and membrane orientation on membrane performances were researched. The results indicated that the FO operation mode was better to achieve a stable water flux of TFC membranes as 29 L/(m2 h) under a cross-flow rate of 15 cm/s and 3 M NaCl as the DS, which was 61% higher than the water flux in the unoptimized operating conditions (18 L/(m2 h)). The rejection rate of salt and oil was 99% and 96%. In addition, the effect of different oil concentrations of HSOB wastewater was studied, and the results showed that FO performed well to treat HSOB wastewater when the oil concentration was <700 mg/L.
Mumps remains one of the worldwide major health problems over the past decade. Seasonal variations of mumps indicate that meteorological factors play an important role in the development of mumps, ...but few studies have investigated the relationship between extreme meteorological factors and the incidence of mumps. Daily mumps cases and meteorological factors in Hefei, China, from 2011 to 2016 were obtained. A generalized additive model combined with the distributed lag nonlinear model (DLNM) was used to quantify the risk of extreme meteorological factors on mumps incidence. Nonlinear relationships were observed among all meteorological factors and mumps incidence. We found that extremely low and high temperatures increased the risk of mumps. The relative risks (RRs) of the cumulative effects along 30 lag days were 2.02 (95%CI: 1.14–3.56) and 2.42 (95%CI: 1.37–4.24), respectively. Both short and long sunshine duration had negative correlation on mumps, with cumulative RRs of 0.64 (95%CI: 0.46–0.92) and 0.57 (95%CI: 0.44–0.74), respectively. In the subgroup analysis, males were found to be more sensitive to extreme weather, especially extreme temperatures and sunshine duration. This study suggests that extreme meteorological factors, especially extreme temperatures and sunshine duration, exert a significant impact on the incidence of mumps. When formulating and implementing effective strategies to the prevention and control of mumps, authorities should take the effect caused by extreme meteorological factors into consideration and pay more attention to susceptible populations, such as male children and teenagers.
We propose a dual-band transparent window terahertz metamaterial consisting of a closed-ring resonator and a square patch. This structure can achieve two transparent windows with transmission ...intensity of more than 90%. The formation of the two windows can be attributed to the coupling of the localized resonance modes between the closed-ring and square patch. The influence of the geometrical dimensions of the closed-ring resonator and the square patch on the transmitted spectrum is also discussed; it is found that the change of sizes can strongly affect the frequencies of the two transparent windows. This novel terahertz metamaterial may open up new avenues toward the control of terahertz waves in many technology-related areas.
An approach to realize a multiple-band perfect light absorber is demonstrated using a simple metamaterial design featuring a composite metallic structure consisting of a closed ring and a rectangular ...patch atop a metallic substrate separated by an insulator. Three narrow-band and discrete resonance peaks with nearly 100% absorption rates are obtained. The first absorption peak is due to the dipole resonance of the closed ring, while the last two absorption peaks are caused by the coupling effect of the closed ring and rectangular patch. The field distribution of the three absorption peaks is given to provide additional evidence. Unlike traditional multiple-band light absorbers that eliminate (or avoid) the interaction between the metallic array structures, our design is based on the mode coupling of the composite structure. This method can obviously reduce the number of metallic resonators, simplify the structure design and reduce fabrication costs.
Multiple-band metamaterial absorbers as an important branch of metamaterial-based resonant devices have shown considerable application prospects in real life. However, current designs have many ...shortcomings in the realization of multiple-band absorption, including complex pattern structure, time-consuming fabrication steps, and strong interaction between sub-elements. Herein, a simple design of multiple-band metamaterial absorber based on single metallic resonator is presented. Basic cell of the multiple-band absorption is formed by a square metallic patch (cut by a concentric air gap) placed on a metallic mirror separated by an insulating medium material. The metamaterial structure can interact strongly with the incident beam to produce the fundamental mode resonance, third-order resonance, and two other resonances resulted from the concentric air gap introduction. The combining effect of the four discrete resonance modes provides the ability to achieve quad-band absorption. The quad-band absorption shows great dependence on the structure dimensions. Based on this, we further design a kind of multiple-band absorption having the adjustable number of absorption peaks by introducing photosensitive silicon material in the initial area of the air gap. The number of resonance peaks can be tuned flexibly from quad-band absorption to dual-band absorption by changing the conductivity (i.e., material property) of photosensitive silicon material.
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