Strategy of Constructing Light-Weight and Highly Compressible Graphene-Based Aerogels with an Ordered Unique Configuration for Wearable Piezoresistive Sensors.

Three-dimensional (3D) graphene aerogels (GAs) have attracted huge attention from researchers due to their great potential in vast applications. The hydrothermal reaction combined with freeze-drying using graphene oxide (GO) as a precursor has proven to be an effective method for obtaining relatively well-structured pure GAs. However, insufficient mechanical strength and low compressibility of the materials still limit their practical applications. Here, we report the microstructure-induced strong mechanical anisotropy of these monolithic GAs in transverse direction (TD) and longitudinal direction (LD), which has never been considered to be related to structural vulnerability. To overcome this anisotropy and enhance the structure, we hereby introduce our self-made poly(vinyl alcohol)- co-polyethylene (PVA- co-PE) nanofibers and low-molecular weight PVA as structural enhancers into the original 3D network to form a novel nanofiber-graphene composite aerogel. Intriguingly, a unique configuration is formed in the GA, in which the highly aligned stacked reduced GO sheets serve as the framework (cellular walls) and the nanofibers act as cross-linking columns anchored between the walls to support the structure along the TD, whereas the micro/nanosized PVA lamellae serve as binders. The resulting aerogel (referred to as graphene-PVA- co-PE nanofibers-PVA aerogel (GNPA)) has excellent compressive resilience along the TD and exhibits an ultrahigh gauge factor (14387%) at a very subtle strain (0.23%) in piezoresistive properties. The GNPA-TD has also been assembled into a variety of wearable sensors and demonstrates great potential for wireless human pressure sensing. In short, this study offers an extremely simple and effective method for developing graphene aerogels with a strong mechanical structure and paves the way for the application of 3D graphene in wearable sensors.

Photothermal and Moisture Actuator Made with Graphene Oxide and Sodium Alginate for Remotely Controllable and Programmable Intelligent Devices.

Functional materials with energy storage and conversion properties have been useful for actuating devices. Here, a new kind of torsional fiber-based actuator including graphene oxide (GO) and natural sodium alginate was prepared by traditional wet spinning and twisting methods, during which the fiber structure was reconstructed, and the mechanical energy was prestored. When the twisted GO/SA (graphene oxide/sodium alginate) fiber was stimulated by infrared light or moisture, the torsional structure of the fiber was activated instantaneously to generate rapid and reversible rotational motion, thus realizing the automatic release and re-storage process of rotational kinetic energy. In addition, the full revolutions of the twisted GO/SA fiber have no attenuation after 100 reversible rotations when stimulated by moisture, which proves the excellent rotational stability. Due to its excellent flexibility and wettability, the twisted GO/SA fiber can be woven into a network or prepared into a series of programmable intelligent devices, which is of great significance for future flexible intelligent electronic devices.

In Situ Generation of Fluorescent Copper Nanoclusters Embedded in Monolithic Eggshell Membrane: Properties and Applications.

Luminescent metal nanoclusters have attracted considerable research attention in recent years due to their unique properties and extensive usage in many fields. Three different synthetic routes were developed to in situ generate orange and red emitting copper nanoclusters embedded in monolithic eggshell membrane (Cu NCs@ESM) using different reducing reagents including N2H4·H2O, NH2OH·HCl and Vitamin C at room temperature for the first time. The routes are extremely facile, low-cost and versatile. The obtained Cu NCs@ESM nanocomposites exhibit excellent photostability and chemical stability, laying the foundation for various practical applications. Fluorescent surface patterning was demonstrated based on the proposed strategy easily. Significantly, the Cu NCs@ESM shows selective fluorescence quenching response to Hg2+ ions and good catalytic activity for methylene blue (MB) reduction degradation making it ideal as portable sensing strip and recyclable catalyst. The work provides a general strategy for the fabrication of other various monolithic nanomaterials with potential applications.

Simultaneous determination of uric Acid and xanthine using a poly(methylene blue) and electrochemically reduced graphene oxide composite film modified electrode.

Poly(methylene blue) and electrochemically reduced graphene oxide composite film modified electrode (PMB-ERGO/GCE) was successfully fabricated by electropolymerization and was used for simultaneous determination of uric acid (UA) and xanthine (Xa). Based on the excellent electrocatalytic activity of PMB-ERGO/GCE, the electrochemical behaviors of UA and Xa were studied by cyclic voltammetry (CV) and square wave voltammetry (SWV). Two anodic sensitive peaks at 0.630 V (versus Ag/AgCl) for UA and 1.006 V (versus Ag/AgCl) for Xa were given by CV in pH 3.0 phosphate buffer. The calibration curves for UA and Xa were obtained in the range of 8.00 × 10(-8)~4.00 × 10(-4) M and 1.00 × 10(-7)~4.00 × 10(-4) M, respectively, by SWV. The detection limits for UA and Xa were 3.00 × 10(-8) M and 5.00 × 10(-8) M, respectively. Finally, the proposed method was applied to simultaneously determine UA and Xa in human urine with good selectivity and high sensitivity.

Design of Lewis acid-base complex: enhancing the stability and first hyperpolarizability of large excess electron compound.

In the present paper, a new type of Lewis acid-base complex BX3...Li@Calix[4]pyrrole (X = H and F) was designed and assembled based on electride molecule Li@calix[4]pyrrole (as a Lewis base) and the electron deficient molecule BX3 (as a Lewis acid) by employing quantum mechanical calculation. The new Lewis acid-base complex offers an interesting push-excess electron-pull (P-e-P) framework to enhance the stability and nonlinear optical (NLO) response. To measure the nonlinear optical response, static first hyperpolarizabilities (ß 0) are exhibited. Significantly, point-face assembled Lewis acid-base complex BF3...Li@Calix[4]pyrrole (II) has considerable first hyperpolarizabilities (ß 0) value (1.4 × 106 a.u.), which is about 117 times larger than reported 11,721 a.u. of electride Li@Calix[4]pyrrole. Further investigations show that, in BX3...Li@Calix[4]pyrrole with P-e-P framework, a strong charge-transfer transition from the ground state to the excited state contributes to the enhancement of first hyperpolarizability. Theory calculation of enthalpies of reaction (ΔrH0) at 298 K demonstrates that it is feasible to synthetize the complexes BX3...Li@Calix[4]pyrrole. In addition, compared with Li@Calix[4]pyrrole, the vertical ionization potential (VIP) and HOMO-LUMO gap of BX3...Li@Calix[4]pyrrole have obviously increased, due to the introduction of the Lewis acid molecule BX3. The novel Lewis acid-base NLO complex possesses not only a large nonlinear optical response but also higher stability.

catena-Poly[[[bis-(4-bromo-benzoato-κO)zinc]-µ-1,2-bis-(4-pyrid-yl)ethene-κN:N'] acetonitrile monosolvate].

In the title coordination compound, {[Zn(C(7)H(4)BrO(2))(2)(C(12)H(10)N(2))]·CH(3)CN}(n), the Zn(II) atom is four-coordinated in a distorted tetra-hedral environment by two carboxyl-ate O atoms from two different 4-bromo-benzoate (bpe) ligands and two N atoms from two symmetry-related 1,2-bis-(4-pyrid-yl)ethene ligands. The Zn(II) atoms are bridged by the bpe ligands, which lie across centres of inversion, forming a zigzag chain along [001]. The void space of each unit cell is occupied by an acetonitrile solvent mol-ecule, which is connected to the complex mol-ecule by a weak C-H⋯N hydrogen bond.

[Determination of trace manganese by non-organic solvents extraction catalytic spectrophotometry in Mn(II)-H2O2-EBT-PEG-2000 system].

A new non-organic solvents extraction catalytic spectrophotometric method for the determination of trace amounts of manganese was studied. The method is based onthe manganese (II) catalyzing hydrogen peroxide to oxidate o f eriochrome black T in hydroxide-ammonium chloride buffer medium. The reaction time and the degree of indicating reaction are controlled by non-organic solvents extraction equilibrium using polyethylene glycol-2000. The absorbance of polyethylene glycol-2000 phase is measured at 539 nm in weak acidic medium. The calibration graph is linear for 0.0080-0.55 microg x mL(-1) Mn (II), and the detection limit is 3.0 x 10(-9) g x L(-1). The method can be applied to the determination of trace manganese in tea and aluminum alloy with satisfactory results.

[Extraction catalytic spectrophotometric determination of trace chromium by synergetic catalytic effect].

In this paper, a new synergetic extraction catalytic spectrophotometric method for the determination of trace chromium was studied. The method is based on the iron(III) and chromium(VI) synergetic catalyzed oxidation of o-aminophenol by hydrogen peroxide in weak acidic medium at pH 5.5. The reaction time, concentration of o-aminophenol in aqueous phase, and degree of reaction were controlled by extraction equilibrium. The absorbance of organic phase was measured at 424 nm. The linear range of the method is 0.0010-0.90 mg x L(-1). The detection limit for chromium(VI) is 5.0 x 10(-6) g x L(-1). The relative standard deviation (n = 11) for 0.20 microg x mL(-1) level of Cr(VI) is 2.0%. The method has been applied to the determination of chromium in tap water and waste water with satisfactory results.

[Determination of activator aluminum by catalytic kinetic spectrophotometry].

In this paper, a new catalytic kinetic spectrophotometric method for the determination of activator aluminum was studied. The method was based on the activation effect of aluminum (III) on the copper (II) which catalyzes the oxidation of pyrocatechol by hydrogen peroxide in acetic acid-sodium acetate buffer solution at pH 5.0. The increase in absorbance of pyrocatechol oxidation product was monitored at 360 nm. The optimization of the operating conditions regarding measuring wavelength, concentrations of the reagents, reaction temperature, reaction time and interfering ions were also investigated and chosen. Under the optimum experimental conditions, the linear range of the determination was 0.0040-0.20 mg.L-1, the detection limit of the method was 8.2 x 10(-7) g.L-1. Combined with separation of extraction of dithizone-carbon tetrachloride solution, the method was applied to the determination of aluminum in water and tea samples with satisfactory results.

[Study on the reaction mechanism of the system of Tl(III)-Cu(II)-EDTA-H2O2-DPC].

In this paper, the reaction mechanism of the system of thallium (III)-copper(II)-ethylenediaminete-traacetate-hydrogen peroxide-diphenylcarbazide has been studied by spectrophotometric method. The experimental results show that the reaction mechanism of the system is based on the replacement of copper(II) by thallium (III) in copper-ethylenediamine-tetraacetate complex and the copper(II) catalyzed oxidation of diphenylcarbazide by hydrogen peroxide to form diphenylcarbazone and the color reaction of copper(II) with diphenylcarbazone in weak acidic medium at pH 5.5. The complex of copper(II)-diphenylcarbazone has an absorption maximum in organic phase at 550 nm. The optimal condition of the experimental system has been discussed.

[Simultaneous determination of iron and molybdenum by extraction catalytic spectrophotometry].

In this paper, a new extraction catalytic spectrophotometric method for the simultaneous determination of iron and molybdenum has been studied. The method is based on the difference of the reaction rate of iron(III) and molybdenum(VI) catalyzed oxidation of o-aminophenol by hydrogen peroxide in weak acidic medium at pH 5.5. The reaction time, concentration of o-aminophenol in aqueous phase and degree of reaction are controlled by extraction equilibrium. The absorbance of organic phase is measured at 424 nm. The linear ranges of the method are 0.010-0.30 microgram.mL-1 (for iron) and 0.50-2.0 micrograms.mL-1 (for molybdenum). The method has been applied to the simultaneous determination of iron and molybdenum in soybean with satisfactory results.

[Determination of trace molybdenum by extraction catalytic kinetic spectrophotometry].

A new extraction catalytic kinetic spectrophotometric method for the determination of trace molybdenum is studied. The method is based on the molybdenum (VI) catalytic oxidation of o-aminophenol by hydrogen peroxide in week acidic medium at pH 5.5. The reaction is carried out at room temperature. The reaction time, concentration of o-aminophenol in aqueous phase and degree of reaction are controlled by extraction equilibrium. The absorbance of organic phase is measured at 424 nm. Under the optimum experiment conditions, the linear range of the determination is 0.0050-2.0 mg.L-1, the detection limit is 2.0 x 10(-6) g.L-1. Combining with separation of ionic exchange, the method has been applied to the determination of trace molybdenum in bean samples with satisfactory results. The kinetic equation of extraction catalytic reaction is discussed.