Highly sensitive,stretchable and durable strain sensors based on conductive double-network polymer hydrogels

Hydrogel-based strain sensors have been attracting immense attention for wearable electronic devices owing to their intrinsic soft characteristics and flexibility. However, developing hydrogel sensors with hightensile strength, stretchability, and strain sensitivity remains a great challenge. Herein, we report a technique to synthesize highly sensitive hydrogel-based strain sensors by integrating carbon nanofibers (CNFs) with a double-network (DN) polymer hydrogel matrix comprising of a physically cross-linked agar network and a covalently cross-linked polyacrylamide (PAAm) network. The resultant nanocomposite sensors display superior piezoresistive sensitivity with a hightrue gauge factor (GF_T = 1.78) at an ultrahigh strain of 1,000%, a fast response time and linear correlation of ln(R/R₀) and ln(L/L₀) up to 1,000% strain. Most significantly, these sensors possess highmechanical strength (~0.6 MPa) and superb durability (>1,000 cycles at strain of 100%), stemming from the effective energy dissipation mechanism of the first agar network acting as sacrificial bonds and the CNFs serving as dynamic nanofillers. The combination of highstrain sensitivity and ultrahigh stretchability of hydrogel sensors makes it possible to sense both small mechanical deformations induced by human motions and large strain up to 1,000%.     

Suppressing Dehydroisomerization Boosts n-Butane Dehydrogenation with High Butadiene Selectivity

Butadiene (BD) is a critical raw material in chemical industry, which is conventionally produced from naphtha cracking. The fast-growing demand of BD and the limited oil reserve motivate chemists to develop alternative methods for BD production. Shale gas, which mainly consists of light alkanes, has been considered as cheap raw materials to replace oil for BD production via n-butane direct dehydrogenation (n-BDH). However, the quest for highly-efficient catalysts for n-BDH is driven by the current drawback of low BD selectivity. Here, we demonstrate a strategy for boosting the selectivity of BD by suppressing dehydroisomerization, an inevitable step in the conventional n-BDH process which largely reduces the selectivity of BD. Detailed investigations show that the addition of alkali-earth metals (e. g., Mg and Ca) into Pt-Ga₂O₃/S10 catalysts increases Pt dispersity, suppresses coke deposition and dehydroisomerization, and thus leads to the significant increase of BD selectivity. The optimized catalyst displays an initial BD selectivity of 34.7 % at a n-butane conversion of 82.1 % at 625 °C, which outperforms the reported catalysts in literatures. This work not only provides efficient catalysts for BD production via n-BDH, but also promotes the researches on catalyst design in heterogeneous catalysis.     

Facile Fabrication of Cu-doped Carbon Aerogels as Catalysts for the Thermal Decomposition of Ammonium Perchlorate

We report a simple and effective method to produce copper-doped carbon aerogel (Cu-CA) using sodium alginate as a carbon precursor through ion crosslinking and high-temperature carbonization. Results indicate that Cu-alginate has a 3D scaffold structure with pores. The effect of using different metal salt mass ratios of Cu-CA on the catalytic thermal decomposition of AP is also investigated. The thermal decomposition temperature of AP decreases by 94.24 °C, and the activation energy of the decomposition reaction is reduced by 45.7 kJ/mol. These results demonstrate that the composite exhibits superior catalytic performance compared with a single-component transition metal salt.     

Preparation of a zeolite imidazole skeleton–silica hybrid monolithic column for amino acid analysis via capillary electrochromatography

We developed a novel, convenient and low-cost one-pot strategy for preparing a zeolitic imidazolate framework-8 (ZIF-8)–silica hybrid monolithic column by adding ZIF-8 directly to a polymer solution of the silica matrix. The simulated stationary phase and monolithic column prepared under optimal conditions were characterized using X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy, thermogravimetric analysis nitrogen physisorption and zeta potential. The results obtained confirmed the successful introduction of ZIF-8 into the silica monolithic column, and the prepared monolithic column exhibited good permeability and physicochemical stability. A capillary electrochromatography method was developed based on a ZIF-8–silica hybrid monolithic column through which 15 mixed amino acids, 4 neutral compounds, 4 nipagin esters and 2 chlorinated fungicides were separated in 14, 5, 7 and 6 min, respectively, under optimal conditions. The relative standard deviations retention times and column efficiencies in run-to-run, day-to-day and column-to-column varied in the ranges of 1.90%–2.21%, 2.13%–2.51% and 3.08%–6.65%, respectively, which demonstrated that ZIF-8–silica hybrid monolithic column exhibited satisfactory reproducibility and stability. The incorporation of ZIF-8 into a silica monolithic column is a promising method for preparing novel monolithic columns composed of a metal–organic framework.     

Dual ambient plasma source ionization mass spectrometry for the rapid detection of trace sterols in urban water

A direct analytical method based on dual ambient plasma ion source tandem mass spectrometry was used for the simultaneous determination of four sterols in the environment. This technology has very high sensitivity and the method detects the four sterols in methanol–water (1:3) solutions with limits of detection (LOD) and limits of quantification (LOQ) ranging from 1.2 ng/L to 6.9 ng/L and 7.6 ng/L to 10.0 ng/L, respectively. The method was also used to test water quality at three locations within the city and successfully detected all four sterols at very low concentrations. The dual plasma source tandem mass spectrometry technique is extremely simple, rapid, sensitive and highly efficient compared to other traditional methods, providing a useful screening tool for sterols in water.     

Analytical Solution of the Bending Problem for Rectangular Orthotropic Plates with a Variable in-Plane Stiffness

Mechanics of Composite Materials - The analytical solution of the bending problem for a clamped rectangular plate with a variable in-plane stiffness is found by using the method of superposition....     

Catalyst-Free Intermolecular Sulfonyl/Fluoromethyl Heteroarylation of Vinyl Ethers via Visible-Light-Induced Charge Transfer

We report a visible-light-induced three-component sulfonyl-heteroarylation of vinyl ethers with sulfinates and five-membered heteroaryl chlorides. This protocol proceeds via electron-donor-acceptor (EDA) complexes between sulfinates and heteroaryl chlorides, giving β-sulfonyl alkyl five-membered heteroarenes with high efficiency and excellent regioselectivity under mild and catalyst-free conditions. Utilization of CF₃SO₂Na or CF₂HSO₂Na as coupling partners further achieves three-component fluoromethyl-arylation of vinyl ethers, furnishing a series of valuable CF₃/CF₂H-incorporated alkyl heterocycles under mild conditions.     

Relaxor-like dielectric behavior and its effect on energy storage performance in P(TFE-HFP-VDF) terpolymers

Capacitors are critical components in many advanced electronic and electrical systems,such as pulse power systems,due to their fast charging-discharging speed and high power density[1-4].The ever-increasing demand for compact energy storage devices requires the dielectrics,which are the energy storage materials in capacitors,to have a higher energy density and low dielectric loss[2,3].Furthermore,a stable high-temperature performance is another important parameter to be considered for some applications in which high-temperature conditions are present,such as hybrid vehicles[4-7].     

Optimization and effect of wall conduction on natural convection in a cavity with constant temperature heat source: Using lattice Boltzmann method and neural network algorithm

Journal of Thermal Analysis and Calorimetry - In this paper, the natural convection (NC) of the Al2O3–H2O nanofluids (NFs) in a cavity with a heat source in its center is numerically...