A Photoelectrochemical Sensor for the Sensitive Detection of Cysteine Based on Cadmium Sulfide/Tungsten Disulfide Nanocomposites

In this work, a CdS-nanoparticle-decorated WS2 nanosheet heterojunction was successfully prepared and first used to modify ITO electrodes for the construction of a novel photoelectrochemical sensor (CdS/WS2/ITO). The thin-film electrode was fabricated by combining electrophoretic deposition with successive ion layer adsorption and reaction techniques. The results indicated that the synthesized heterojunction nanomaterials displayed excellent photoelectrochemical performance which was much better than that of pristine CdS nanoparticles and 2D WS2 nanosheets. Owing to the formation of the surface heterojunction and the effective interfacial electric field, the enhanced separation of photogenerated electron–hole pairs led to a remarkable improvement in the photoelectrochemical activity of CdS/WS2/ITO. This heterojunction architecture can protect CdS against photocorrosion, resulting in a stable photocurrent. Based on the specific recognition between cysteine and CdS/WS2/ITO, through the specificity of Cd-S bonds, a visible-light-driven photoelectrochemical sensor was fabricated for cysteine detection. The novel photoelectrochemical biosensor exhibited outstanding analytical capabilities in detecting cysteine, with an extremely low detection limit of 5.29 nM and excellent selectivity. Hence, CdS-WS2 heterostructure nanocomposites are promising candidates as novel advanced photosensitive materials in the field of photoelectrochemical biosensing

Surface Plasmon Resonance Enhanced Photoelectrochemical Sensing of Cysteine Based on Au Nanoparticle-Decorated ZnO@graphene Quantum Dots

In this work, Au nanoparticle-decorated ZnO@graphene core–shell quantum dots (Au-ZnO@graphene QDs) were successfully prepared and firstly used to modify an ITO electrode for the construction of a novel photoelectrochemical biosensor (Au-ZnO@graphene QDs/ITO). Characterization of the prepared nanomaterials was conducted using transmission electron microscopy, steady-state fluorescence spectroscopy and the X-ray diffraction method. The results indicated that the synthesized ternary nanomaterials displayed excellent photoelectrochemical performance, which was much better than that of ZnO@graphene QDs and pristine ZnO quantum dots. The graphene and ZnO quantum dots formed an effective interfacial electric field, enhancing photogenerated electron–hole pairs separation and leading to a remarkable improvement in the photoelectrochemical performance of ZnO@graphene QDs. The strong surface plasmon resonance effect achieved by directly attaching Au nanoparticles to ZnO@graphene QDs led to a notable increase in the photocurrent response through electrochemical field effect amplification. Based on the specifical recognition between cysteine and Au-ZnO@graphene QDs/ITO through the specificity of Au-S bonds, a light-driven photoelectrochemical sensor was fabricated for cysteine detection. The novel photoelectrochemical biosensor exhibited outstanding analytical capabilities in detecting cysteine with an extremely low detection limit of 8.9 nM and excellent selectivity. Hence, the Au-ZnO@graphene QDs is a promising candidate as a novel advanced photosensitive material in the field of photoelectrochemical biosensing

Economic Analysis on the Rational Allocation of Agricultural Production Factors in Henan Province

Based on the population floating theory under the Ranis-Fei dual economic structure, this paper designs an econometric model to study the isoquant curve and production factor substitution law. Finally, through the empirical analysis of labor-capital investment in Henan's agricultural production, combined with the principles of isoquant curve model, this paper determines the labor required for a certain scale of investment in agricultural production, and concludes that the fixed assets investment in Henan's agricultural production is not fully utilized, and too much labor is transferred. And this paper makes the corresponding policy recommendations for Henan's macroeconomic development

Advanced chemical strategies for lithium–sulfur batteries: A review

Lithium–sulfur (LiS) battery has been considered as one of the most promising rechargeable batteries among various energy storage devices owing to the attractive ultrahigh theoretical capacity and low cost. However, the performance of LiS batteries is still far from theoretical prediction because of the inherent insulation of sulfur, shuttling of soluble polysulfides, swelling of cathode volume and the formation of lithium dendrites. Significant efforts have been made to trap polysulfides via physical strategies using carbon based materials, but the interactions between polysulfides and carbon are so weak that the device performance is limited. Chemical strategies provide the relatively complemented routes for improving the batteries' electrochemical properties by introducing strong interactions between functional groups and lithium polysulfides. Therefore, this review mainly discusses the recent advances in chemical absorption for improving the performance of LiS batteries by introducing functional groups (oxygen, nitrogen, and boron, etc.) and chemical additives (metal, polymers, etc.) to the carbon structures, and how these foreign guests immobilize the dissolved polysulfides

A High-Response Electrochemical As(III) Sensor Using Fe3O4–rGO Nanocomposite Materials

Nowadays, heavy metal ion pollution in water is becoming more and more common, especially arsenic, which seriously threatens human health. In this work, we used Fe3O4–rGO nanocomposites to modify a glassy carbon electrode and selected square wave voltametric electrochemical detection methods to detect trace amounts of arsenic in water. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) showed that Fe3O4 nanoparticles were uniformly distributed on the rGO sheet, with a particle size of about 20 nm. Raman spectroscopy and electrochemical impedance spectroscopy (EIS) showed that rGO provides higher sensitivity and conductive substrates. Under optimized experimental conditions, Fe3O4–rGO-modified glassy carbon electrodes showed a higher sensitivity (2.15 µA/ppb) and lower limit of detection (1.19 ppb) for arsenic. They also showed good selectivity, stability, and repeatability

Treatment of tionite residue from titanium oxide industry for recovery of TiO2 and removal of silica

Solid waste tionite generated in the sulfate process for TiO2 production is a secondary titanium resource with high silicon content. To recover titanium and remove silicon from the tionite, a process involving hydrothermal conversion, water washing, and acid leaching was proposed. To avoid Na2O loss, the formation of Na2TiSiO5 by-product was prevented by adding CaO. XRD, ICP-OES and FT-IR were used to examine the transformation of the titanium and silicon. The optimum hydrothermal conditions are NaOH/tionite mass ratio of 4:1 and Ca/Si molar ratio of 1:1 in 45% NaOH solution at 240 degrees C for 1 h. Under these conditions, the titanium conversion was 97.3% with Na2TiO3 as the main titanium phase, while most silicon was converted to Ca(2)Sia(4), and katoite, and NaCaHSiO4, instead of Na2TiSiO5. About 97.5% of the Na2O was recovered after washing the hydrothermal products with water, and 93.1% of the silicon retained in the washed solution was removed by adding CaO. After leaching the washed products with 40% H2SO4 solution at 60 degrees C, about 97% of the titanium was easily recovered, forming the titanyl sulfate solution that was employed for TiO2 production. The Ca and Si components formed CaSO4 and silica gel, which were then separated from the acid leaching solution. (C) 2015 Elsevier B.V. All rights reserved

A Novel Bioflocculant from Raoultella planticola Enhances Removal of Copper Ions from Water

Copper is one of the most toxic heavy metals. In this work, a sampling survey of copper ions in the water of Songhua River flowing through the chemical and living areas of Jilin City was studied. A new bioflocculant from Raoultella planticola was obtained. The investigation of Songhua River flowing through Jilin City shows that the copper concentration is between 0.07 ppb and 0.16 ppb. The bioflocculant supporting graphite oxide (GO) as a bioflocculant inducer used in this study has been utilized in treatment of copper ions in water. GO and bioflocculant infrared radiation (IR) spectrum and zeta potential were studied. Flocculational conditions of copper ion (0.2 ppm) were modeled and optimized using RSM (response surface methodology). Our data showed that flocculation efficiency was over 80%. Significant influencing factors and variables were pH, flocculation time, bioflocculant dosage, and GO inducer which had major impact effects on flocculation efficiency. The highest flocculation efficiency which is 86.01% was achieved at pH=5, at 1.62 h and 13.11 mg bioflocculant with 13.11 mg GO as an inducer. However, temperature (A) and GO inducer were significant impact factors on the flocculation efficiency

Recovery of titanium from undissolved residue (tionite) in titanium oxide industry via NaOH hydrothermal conversion and H_2SO_4 leaching

To recover titanium from tionite, a new process consisting of NaOH hydrothermal conversion, water washing, and H_2SO_4 leaching for TiO_2 preparation was developed. The experimental results show that under the optimum hydrothermal conversion conditions, i.e., 50% NaOH (mass fraction) solution, NaOH/tionite mass ratio of 4:1, reaction temperature of 240 °C, reaction time of 1 h and oxygen partial pressure of 0.25 MPa, the titanium was mainly converted into Na_2TiO_3, and the conversion was 97.2%. The unwanted product Na_2TiSiO_5 remained stable in water washing, and its formation was prevented by improving NaOH concentration. In water washing process, about 97.6% of Na~+ could be recycled by washing the hydrothermal product. The NaOH solutions could be reused after concentration. 96.7% of titanium in the washed product was easily leached in H_2SO_4 solution at low temperatures, forming titanyl sulfate solution to further prepare TiO_2

STRUCTURAL CONTROL OF NA(2)TIO(3) IN PRE-TREATING NATURAL RUTILE ORE BY ALKALI ROASTING FOR TIO2 PRODUCTION

To improve the use of natural rutile ore with fine particle size and high contents of MgO and CaO in China, a novel pre-treatment method of natural rutile ore by NaOH roasting to prepare -Na2TiO3 for TiO2 production was proposed. -Na2TiO3 is a stable by-product that can lead to serious caking in the reactor and low titanium yield. Thus, structural control in alkali roasting is necessary. The influence of particle size of natural rutile ore, NaOH-to-ore mass ratio, roasting temperature and roasting time on the crystal forms of Na2TiO3 was systematically investigated. The optimized reaction parameters were as follows: average particle size of natural rutile ore, -9.2 mu m; NaOH-to-rutile mass ratio, 1.2; roasting temperature, 550 degrees C; and roasting time, 70min. In these conditions, the titanium conversion and the fraction of -Na2TiO3 exceeded 99.5% and 98%, respectively. Moreover, the addition of H2O or as-prepared partial -Na2TiO3 as crystal seeds into the reaction system could prepare the roasting product with -Na2TiO3 as its main phase using -45 mu m (-325mesh) natural rutile ore.</p

In situ interfacial architecture of lithium vanadate-based cathode for printable lithium batteries

Summary: Most Li3VO4 anodes are obtained by pre-architecture methods in which Li3VO4 anode materials are prepared with more than six key processes including high-temperature annealing and long preparation time. Herein, we propose an in situ post-architecture strategy including Li3VO4-precursor solution (ink) preparation and then annealing at 250°C. The integrated Li3VO4 based electrode not only possesses good electrical conductivity and porous microstructure but also has superior stability because of Cu anchoring and inclusion by in situ catalysis. The integrated electrode demonstrates a high reversible capacity (865 mA h g−1 at 0.2 A g−1) and good cyclability (100% capacity retention after 200 cycles at 1 A g−1). More importantly, the post-architecture electrode has a high energy density of 773.8 Wh kg−1, much higher than reported Li3VO4-based materials, as well as most cathodes. Therefore, the electrode could be used to the printable cathode of low-voltage high-energy-density lithium batteries