Multi-component carbon-based composites containing high crystallinity NiBDC as high-performance electrodes for supercapacitors.

Herein, we propose a strategy combining in situ sol-gel hydrothermal growth and annealing treatment for preparing multi-component carbon-based composites with high crystallinity of NiBDC (C-Ni/NiO/NiBDC). The C-Ni/NiO/NiBDC can be used by both positive and negative materials to build a supercapacitor that shows superior capacitance over the wide potential range of 0-1.8 V, resulting from the high crystallinity of NiBDC and synergistic effect of NiBDC, Ni and NiO, as well as their mutual intimate interfacial contact.

Construction of Ni3+-rich nanograss arrays for boosting alkaline water oxidation.

The rational design of high-efficiency electrocatalysts for application in water oxidation in alkaline media remains a great challenge. In this paper, Ni3+-rich nanograss-like Mo-doped Ni3S2/NiS/VS arrays grown on nickel foam (denoted as Mo-NiVS@NF) have been successfully constructed through a hydro/solvothermal method. Interestingly, Mo-NiVS@NF exhibits superior catalytic OER performance, needing an overpotential of 217 mV to drive a current density of 10 mA cm-2, outperforming most previously reported NiS-based electrocatalysts. The result indicates that the Ni3+-rich active sites caused by the modulation of the electronic structure environment via the introduction of V and high-valency Mo play an important role in the high activity for the OER. Moreover, this catalyst shows high long-term electrochemical durability.

Radio Frequency Resonator-Based Flexible Wireless Pressure Sensor with MWCNT-PDMS Bilayer Microstructure.

Flexible pressure sensors have been widely applied in wearable devices, e-skin, and the new generation of robots. However, most of the current sensors use connecting wires for energy supply and signal transmission, which presents an obstacle for application scenarios requiring long endurance and large movement, especially. Flexible sensors combined with wireless technology is a promising research field for realizing efficient state sensing in an active state. Here, we designed and fabricated a soft wireless passive pressure sensor, with a fully flexible Ecoflex substrate and a multi-walled carbon nanotube/polydimethylsiloxane (MWCNT/PDMS) bilayer pyramid dielectric structure. Based on the principle of the radio-frequency resonator, the device achieved pressure sensing with a changeable capacitance. Subsequently, the effect of the pyramid density was simulated by the finite element method to improve the sensitivity. With one-step embossing and spin-coating methods, the fabricated sensor had an optimized sensitivity of 14.25 MHz/kPa in the low-pressure range. The sensor exhibited the potential for application in limb bending monitoring, thus demonstrating its value for long-term wireless clinical monitoring. Moreover, the radio frequency coupling field can be affected by approaching objects, which provides a possible route for realizing non-contact sensing in applications such as pre-collision warning.

Flexible Wireless Passive LC Pressure Sensor with Design Methodology and Cost-Effective Preparation.

Continuous monitoring of physical motion, which can be successfully achieved via a wireless flexible wearable electronic device, is essential for people to ensure the appropriate level of exercise. Currently, most of the flexible LC pressure sensors have low sensitivity because of the high Young's modulus of the dielectric properties (such as PDMS) and the inflexible polymer films (as the substrate of the sensors), which don't have excellent stretchability to conform to arbitrarily curved and moving surfaces such as joints. In the LC sensing system, the metal rings, as the traditional readout device, are difficult to meet the needs of the portable readout device for the integrated and planar readout antenna. In order to improve the pressure sensitivity of the sensor, the Ecoflex microcolumn used as the dielectric of the capacitive pressure sensor was prepared by using a metal mold copying method. The Ecoflex elastomer substrates enhanced the levels of conformability, which offered improved capabilities to establish intimate contact with the curved and moving surfaces of the skin. The pressure was applied to the sensor by weights, and the resonance frequency curves of the sensor under different pressures were obtained by the readout device connected to the vector network analyzer. The experimental results show that resonant frequency decreases linearly with the increase of applied pressure in a range of 0-23,760 Pa with a high sensitivity of -2.2 MHz/KPa. We designed a coplanar waveguide-fed monopole antenna used to read the information of the LC sensor, which has the potential to be integrated with RF signal processing circuits as a portable readout device and a higher vertical readout distance (up to 4 cm) than the copper ring. The flexible LC pressure sensor can be attached to the skin conformally and is sensitive to limb bending and facial muscle movements. Therefore, it has the potential to be integrated as a body sensor network that can be used to monitor physical motion.

Yolk-shell (Cu,Zn)Fe2O4 ferrite nano-microspheres with highly selective triethylamine gas-sensing properties.

Multicomponent spinel ferrites are essential to be used in high-performance gas-sensing materials. Herein, multinary (Cu,Zn)Fe2O4 spinel nano-microspheres with tunable internal structures, including solid, core-shell, and yolk-shell, were successfully synthesized by a simple self-templated solvothermal method combined with a subsequent annealing strategy. The internal structures of the (Cu,Zn)Fe2O4 nano-microspheres significantly rely on the heating rates of the precursors, which show promising selective response towards trimethylamine gas. Among them, the as-formed yolk-shell (Cu,Zn)Fe2O4 nano-microspheres exhibited high response to triethylamine with excellent selectivity of STEA/SX = 1.86 at 160 °C, fast response-recovery rate (58 s/136 s), and long-term repeatability and stability of more than one month. The corresponding triethylamine gas-sensing mechanism with the special microstructures is discussed. This work provides new insights into the rational design of interior structure and the modulation of high gas response and selectivity of multinary spinel ferrites in gas-sensing applications.

Synergetic Effect of Tetraethylammonium Bromide Addition on the Morphology Evolution and Enhanced Photoluminescence of Rare-Earth Metal-Organic Frameworks.

Controlled synthesis of rare-earth metal-organic frameworks (RE-MOFs) is of great significance to match their emerging multifunctional luminescence applications. Herein, we propose a green and general solvent-free synthetic strategy for the adjustment of morphology and dimension of various RE-MOFs (RE = Eu, Tb, Er, Dy, Y, Tm) by using a tetraethylammonium bromide-assisted thermal-heating method. These self-assembled RE-MOF materials possess controllable morphologies and hierarchical structures while retaining the structural topology of MIL-78, proving that the strategy is a feasible and effective way in opening up large-scale synthesis of RE-MOFs. It is further found that the tetraethylammonium could be carbonized into carbon dots and encapsulated in Eu/Tb-MIL-78 to enhance the fluorescence emission intensities significantly, making the hierarchical Eu/Tb-MIL-78 MOF materials good candidates for the latent fingerprints recognition application. This work provides a novel strategy for effectively controlling the morphology and dimension of RE-MOFs materials with enhanced photoluminescence and has great potential in their scaling-up syntheses and exploring the new luminescence applications.

Ionothermal synthesis of a photochromic inorganic-organic complex for colorimetric and portable UV index indication and UVB detection.

Extended exposure to sunlight or artificial UV sources (particularly UVA and UVB) is a major cause of serious skin cancers and ocular diseases. A photochromic inorganic-organic complex was ionothermally synthesized via a decomposition-reassembly strategy, generated from a low-cost deep-eutectic solvent and a 4,4'-bipyridine system. Benefiting from the intrinsic synergy of the hydrogen bonding and π-π stacking interactions, the complex exhibited insensitivity towards visible light, outstanding color contrast from colorless to purple, rapid response time up to seconds, excellent reversibility and high thermal stability. UV index and UVB detection procedures indicated that the coloration performances of the complex exhibited a linear response towards UV index and UVB dose. Besides, the complex can be made to a portable test tablet, a freestanding mixed film with a cellulose paper and a mixed-matrix membrane with PVDF, which make it highly promising for portable and efficient visual UV index and detecting UVB dose.

Eu3+/Tb3+ functionalized Bi-based metal-organic frameworks toward tunable white-light emission and fluorescence sensing applications.

The rational design strategy to construct lanthanide ion functionalized metal organic frameworks (MOFs) has attracted tremendous attention as they are promising candidates for developing novel luminescence materials and optical sensors owing to their intense, long-lived and tunable luminescence performances. In this work, a series of Eu3+/Tb3+ singly doped or codoped bismuth-based MOFs were prepared under in situ facile solvothermal conditions using BiOBr nanoplates as bismuth resources. A red-green-blue-based trichromatic white-light emission can be finely achieved by modulating the doping ratio of Eu3+/Tb3+ in the blue-emitting Bi-MOF host material and such photoluminescence tuning can also be realized by controlling the excitation wavelength. In addition, the Eu3+/Tb3+ singly incorporated Bi-MOF can serve as a multifunctional fluorescent probe for sensing Fe3+ and Cr2O72- ions in aqueous solution, as well as small organic pollutants of acetone molecules, and their sensing mechanisms have also been analyzed. These lanthanide ion functionalized Bi-MOF materials exhibit great potential in exploring white-light emitting devices and construction of supersensitive multifunctional sensors.

Production of p-xylene from biomass by catalytic fast pyrolysis using ZSM-5 catalysts with reduced pore openings.

Pores for thought: Chemical liquid deposition of silica onto ZSM-5 catalysts led to smaller pore openings that resulted in >90% selectivity for p-xylene over the other xylenes in the catalytic fast pyrolysis of furan and 2-methylfuran (see scheme). The p-xylene selectivity increased from 51% with gallium spray-dried ZSM-5 to 72% with a pore-mouth-modified catalyst in the pyrolysis of pine wood.

Needs and trends in rational synthesis of zeolitic materials.

Zeolites are an important class of materials which are widely used in industry as catalysts, adsorbents and ion-exchangers. Their superior properties are closely related to their unique porous framework structure, as well as composition and morphology. The ever-growing needs for zeolitic materials in applications inspire us to think of the rational synthesis of zeolites with desired structures and properties. However, rationalization of zeolitic materials remains one of the most challenging issues in the zeolite research field due to their unclear formation mechanism. Despite this, many efforts have been devoted to synthesize zeolites in a more rational way. In this tutorial review, first, we demonstrate how the geometrical characteristics of zeolite frameworks affect the catalytic performances of the resulting materials; then, we present recent advances in synthetic innovations to target materials, and we further highlight the developments in computer simulations toward ab initio design and synthesis; finally, the future perspective on the rational synthesis of zeolitic materials with desired functions and structures will be described.

Hydrothermal synthesis of zeolites with three-dimensionally ordered mesoporous-imprinted structure.

Zeolites are microporous materials with pores and channels of molecular dimensions that find numerous applications in catalysis, separations, ion exchange, etc. However, whereas uniformity of micropore size is a most desirable and enabling characteristic for many of their uses, in certain cases, for example in reactions involving bulky molecules, it is a limitation. For this reason, synthesis of hierarchical zeolites with micro- and mesoporosity is of considerable interest as a way to control molecular traffic for improved catalytic and separation performance. Herein, we report a general synthesis route for the confined synthesis of zeolites within three-dimensionally ordered mesoporous carbon templates by conventional hydrothermal synthesis. Various zeolites, including BEA, LTA, FAU, and LTL, with three-dimensionally ordered mesoporous-imprinted structure have been synthesized by this approach. It is expected that these hierarchical zeolite materials will provide building blocks for thin-film and other syntheses and may provide a basis for quantitatively studying the mass-transfer limitation on the catalytic performance of zeolite catalysts.

A structural resolution cryo-TEM study of the early stages of MFI growth.

Room-temperature aging of zeolite precursor silica sol was followed by SAXS and cryo-TEM. Cryo-TEM imaging of zeolite materials with structural resolution is demonstrated. The results suggest the formation of predominantly amorphous aggregates before MFI crystallization.