Cysteine combined with carbon black as support for electrodeposition of poly (1,8-Diaminonaphthalene): Application as sensing material for efficient determination of nitrite ions

Poly 1,8-Diaminonaphtahlene/cysteine (poly 1,8-DAN/Cys) combined with carbon black (CB) nanoparticles are proposed as an excellent sensor for the detection of nitrite ions. To design the electrocatalyst, a simple approach consisting on drop-casting method was applied to disperse carbon black on the surface of glassy carbon electrode, followed by the immobilization of cysteine on the surface of CB nanoparticles. The electrochemical polymerization of 1,8-Diaminonaphthalene was conducted in acidic medium by using cyclic voltammetry. The prepared hybrid material was denoted poly 1,8-DAN /Cys/CB. Several methods were used to characterize the structural and electrochemical behavior of the reported hybrid material including Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), amperometry and differential pulse voltammetry (DPV). The prepared electrode displayed an outstanding electroactivity towards nitrite ions reflected by an enhancement in the intensity of the current and a decrease of the charge transfer resistance. Poly 1,8-DAN/Cys/CB displayed an excellent sensing performance towards the detection of nitrite with a very low detection limit of 0.25 µM. Two linear ranges of 1–40 µM and 20–210 µM when using amperometry and differential pulse voltammetry (DPV) were obtained respectively. This work highlights the simple preparation of a polymeric film rich in amine and thiol groups for nitrite detection.     

MXene: A two-dimensional material in selective water separation via pervaporation

MXene, well-identified as Ti₃C₂T_X, belongs to the family of two-dimensional (2D) materials, which have been currently explored in various applications. Very recently, such materials have been pointed out as potential nanomaterials for advanced solute separations when introduced in membranes, such as ion separation, gas separation, nanofiltration, chiral molecular separation, and solvent separation. This latter separation, generally named Pervaporation (PV), is identified as a highly selective technology for water separations. To date, few pieces of research have been released but providing interesting insights into several solvent (including water) separations. Hence, this brief review aims to analyze and discuss the latest advances for utilizing MXenes for PV membranes. Particular emphasis has been devoted to the relevant outcomes in the field, along with the strategies followed by researchers to tailor membranes. Based on the current findings, the perspectives in the field are also stated.     

Covalent Organic Frameworks for Chemical and Biological Sensing

Covalent organic frameworks (COFs) are a class of crystalline porous organic polymers with polygonal porosity and highly ordered structures. The most prominent feature of the COFs is their excellent crystallinity and highly ordered modifiable one-dimensional pores. Since the first report of them in 2005, COFs with various structures were successfully synthesized and their applications in a wide range of fields including gas storage, pollution removal, catalysis, and optoelectronics explored. In the meantime, COFs also exhibited good performance in chemical and biological sensing, because their highly ordered modifiable pores allowed the selective adsorption of the analytes, and the interaction between the analytes and the COFs’ skeletons may lead to a detectable change in the optical or electrical properties of the COFs. In this review, we firstly demonstrate the basic principles of COFs-based chemical and biological sensing, then briefly summarize the applications of COFs in sensing some substances of practical value, including some gases, ions, organic compounds, and biomolecules. Finally, we discuss the trends and the challenges of COFs-based chemical and biological sensing.     

Synthesis,Crystal Structure and Ferromagnetic Properties of a New Dicyanamide Bridged Dicopper（Ⅱ） Complex with IM-1＇-MeBzIm-k2 N,O Mode

A new dinuclear copper（Ⅱ） complex with imino nitroxide radicals [Cu2（NO3）2（IM- 1 ′-MeBzIm）2（dca）2] （IM-1 ′-MeBzIm = 2-{2′-[（1′-methyl）benzimidazolyl]}-4,4,5,5-tetramethylimidazoline-1-oxyl, dca = dicyanamide anion） has been prepared and structurally characterized by single-crystal X-ray diffraction. The complex crystallizes in triclinic, space group P 1^-, with α = 9.440（5）, b = 10.124（6）, c = 11.603（7） A, α = 102.904（7）, β = 94.033（6）,γ = 104.299（7）°, C34H40Cu2N16O8, Mr = 927.90, V= 1038.2（10） A^3, Z = 1, Dc = 1.484 g/cm^3, μ（MoKα） = 1.093 mm^-1, F（000） = 478, R = 0.0609 and wR = 0.1512 for 2889 observed reflections with Ⅰ 〉 2σ（I）. X-ray analysis reveals that two Cu（Ⅱ） atoms are bridged by two dicyanamides to form a centrosymmetric Cu（Ⅱ）-Cu（Ⅱ） dinuclear entity. Every Cu（Ⅱ） ion is five-coordinated with a distorted square pyramidal coordination geometry and IM-1′-MeBzlm ligand coordinates to the metal ion with the k^2 N（1 ′-MeBzlm）, O（IM） mode to avoid steric hindrance with the methyl group in the complex. Meanwhile, the molecules are linked by intermolecular hydrogen bonds, leading to a 1-D chain structure. Moreover, such chains are further linked by π-π stacking interactions to form a 2-D network structure. Magnetic measurement demonstrates that the intramolecular exchange couplings between Cu（Ⅱ） ion and the IM-1 ′-MeBzIm are ferromagnetic with J = 12.46 cm^-1, where the spin Hamitonian is defined as H^ = -2JS^1S^2 within the complex.     

Influence of the anode material on the characteristics of an analytical glow discharge cell

The energy transfer to the discharge gas due to various collision processes in the plasma and the heating of the sample are widely known effects in glow discharge (GD) spectroscopy. Despite of the considerable thermal effects and their serious influence on the performance of GD devices, measurements of the discharge gas and sample temperatures are not common at all. The gas temperature depends on the power absorption of the discharge as well as on the temperature of boundaries (sample and anode). In this work the influence of different anode materials in a Grimm-type source on the voltage–current characteristics, crater shapes and GD spectra is investigated. Anodes made of titanium and copper alloys, graphite, and steel with thermal conductivities covering a wide range of values are used. For a fixed voltage and pressure a decrease of the measured current is observed for bad thermal conductive anodes. Cooling of the sample results in an increase of the measured current. Both observations can be explained by changes of the discharge gas temperature. The temperature of the sample is measured from the back side and compared for different anodes. Further, it is found that the choice of the anode material (i) has no significant influence on the crater shape, (ii) results in slightly different sputtering rates and (iii) strong differences of the GD spectra.     

The fractal dimension as estimator of the fractional content of metal matrix composite materials

Electrochemical techniques are applied to estimate the fractal dimension value of electroactive surface structures. However, the fractal dimension value is an abstract concept, which sometimes is hard to understand. Herein, this abstract concept is used to calculate the fractional content of the nickel/graphite–polypropylene hybrid composite material, putting into practice this concept in the study of composite materials.     

Graded PZT ceramics for piezoelectric transformers

In the present study two types of the synthesized Pb(Zr_1−xTi_x)O₃ (PZT) powders differing in Zr/Ti ratio were used to prepare the spatially inhomogeneous (i.e., graded) structure. A position-dependent chemical composition was expected to cause the property gradient. Disk-shaped compacts were prepared in a way such that two different orientations of the radial gradients were formed. The solid state sintering under pressure was utilized to prepare ceramics. Simultaneous thermal analysis was used to study thermal behavior of the ceramic powders. Graded PZT ceramics were characterized using X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. It was also characterized in terms of its dielectric properties by both bridge technique and the impedance spectroscopy. On the basis of graded PZT ceramics the disk-shaped radial mode piezoelectric transformer was developed and fabricated.     

Carbon-coated Li3VO4 with optimized structure as high capacity anode material for lithium-ion capacitors

Due to the high capacity,moderate voltage platform,and stable structure,Li₃VO₄(LVO) has attracted close attention as feasible anode material for lithium-ion capacitor.However,the intrinsic low electronic conductivity and sluggish kinetics of the Li⁺ insertion process severely impede its practical application in lithium-ion capacitors(LICs).Herein,a carbon-coated Li₃VO₄(LVO/C) hierarchical structure was prepared by a facial one-step solid-sta...     

以醚胺为模板剂合成含二价金属杂原子的开放骨架磷酸铝化合物M(Ⅱ)-CJ50

在水热体系中, 以2,2'-(乙烯二氧)双(乙胺)为模板剂, 合成了3种含二价金属杂原子的开放骨架磷酸铝化合物M(Ⅱ)-CJ50(|C₆H₁₇N₂O₂| [MAl₃P₄O₁₆], 其中M=Mg, Mn和Fe). 单晶及粉末X射线衍射分析表明, 这3种化合物与以咪唑为模板剂合成的含三价金属杂原子的M(Ⅲ)-CJ50具有相似的骨架拓扑结构. 二者的区别在于: 由于使用了还原性较强的醚胺作模板剂, M(Ⅱ)-CJ50结构中的金属杂原子具有比M(Ⅲ)-CJ50更低的氧化态; M(Ⅱ)-CJ50中的金属杂原子与1个醚胺模板剂分子中的2个醚氧原子形成双齿配位, 而M(Ⅲ)-CJ50中的金属杂原子则与2个咪唑模板剂分别形成单齿配位. 此外, 磁性测试结果表明, 由于金属杂原子的氧化态以及配体模板剂分子的差异, 导致M(Ⅱ)-CJ50中的过渡金属杂原子处于电子高自旋态, 而M(Ⅲ)-CJ50中的杂原子则处于低自旋态.     

四元体系LiNO3-Mg(NO3)2-NH4NO3-H2O相图预测及相关相变储能材料的研究

应用修正的BET热力学模型对Mg(NO3)2-NH4NO3-H2O三元体系和LiNO3-Mg(NO3)2-NH4NO3-H2O四元体系在273～320 K的相图进行预测,并找到一个相变温度较低的四元共晶点Mg(NO3)2.6H2O-LiNO3.3H2O-NH4NO3,其质量百分数组成为:25.5%的硝酸铵,28.4%的硝酸锂,13.8%的硝酸镁和32.3%的水,通过实验对共晶点组成材料的吸放热行为进行测定,发现其熔化温度为286.3 K,且DSC测试其相变热焓为192.7 J.g-1,表明该材料可用作潜在的低温相变储能材料。