Lattice engineering route for self-assembled nanohybrids of 2D layered double hydroxide with 0D isopolyoxovanadate: chemiresistive SO2 sensor

Tuning the interior chemical composition of layered double hydroxides (LDHs) via lattice engineering route is a unique approach to enable multifunctional applications of LDHs. In this regard, the exfoliated 2D LDH nanosheets coupled with various guest species lead to the lattice-engineered LDH-based multifunctional self-assembly with precisely tuned chemical composition. This article reports the synthesis and characterization of mesoporous zinc–chromium-LDH (ZC-LDH) hybridized with isopolyoxovanadate nanohybrids (ZCiV) via lattice-engineered self-assembly between delaminated ZC-LDH nanosheets and isopolyoxovanadate (iPOV) anions. Electrostatic self-assembly between 2D ZC-LDH monolayers and 0D iPOV significantly altered structural, morphological, and surface properties of ZC-LDH. The structural and morphological study demonstrated the formation of mesoporous interconnected sheet-like architectures composed of restacked ZCiV nanosheets with expanded surface area and interlayer spacing. In addition, the ZCiV nanohybrid resistive elements were used as a room-temperature gas sensor. The selectivity of ZCiV nanohybrid was tested for various oxidizing (SO₂, Cl₂, and NO₂) gases and reducing (LPG, CO, H₂, H₂S, and NH₃) gases. The optimized ZCiV nanohybrid demonstrated highly selective SO₂ detection with the maximum SO₂ response (72%), the fast response time (20 s), low detection limit (0.1 ppm), and long-term stability at room temperature (27 ± 2 °C). Of prime importance, ZCiV nanohybrids exhibited moderately affected SO₂ sensing responses with high relative humidity conditions (80%–95%). The outstanding SO₂ sensing performance of ZCiV is attributed to the active surface gas adsorptive sites via plenty of mesopores induced by a unique lattice-engineered interconnected sheet-like microstructure and expanded interlayer spacing.     

Hydrogen evolution reaction on Pt and Ru in alkali with volmer-step promotors and electronic structure modulators

Alkaline water electrolysis despite having a variety of choices for anodic oxygen evolution reaction (OER) catalysts out of non-precious metals suffers significantly due to the poor kinetics of cathodic hydrogen evolution reaction (HER) even with the state-of-the-art Pt and equally active Ru. The Volmer-step (water dissociation (WD) coupled proton adsorption) of alkaline HER is mostly the rate-determining step (RDS) and costs most of the work required. In this review, recent developments in improving the HER kinetics of Pt and Ru with Volmer-step promotors and electronic structure modulators have been comprehensively analyzed and critically presented with the challenges and prospects.     

服役温度对多壁碳纳米管/Li1.18Ni0.15Co0.15Mn0.52O2复合正极材料性能的影响

通过煅烧的方式制得多壁碳纳米管(MWCNT)质量分数为3%的MWCNT/Li1.18Ni0.15Co0.15Mn0.52O2锂离子电池复合正极材料,并测试了复合正极材料在不同服役温度环境下的电化学性能:-20和60℃下服役时,其放电容量分别高达169、303 mAh·g^-1,且展示出良好的倍率性能和循环稳定性。结合电化学阻抗测试结果可知,MWCNT均匀附着在层状粒子的表面,有效减少了电解液对电极材料的侵蚀,阻碍了表面膜的生成,同时提高了材料的电子电导率。     

An Efficient Novel Electrochemical Sensor for Simultaneous Determination of Vitamin C and Aspirin Based on a PMR/Zn-Al LDH/GCE

A sensitive, low-cost, and simple electrochemical sensor based on Zn−Al layered double hydroxide (Zn−Al LDH) combined with a polymer film of methyl red (PMR) to modify a GCE has been created for the first time. Using cyclic voltammetry (CV), the electrochemical characteristics of the newly fabricated sensor were investigated. The characterised PMR/Zn−Al LDH/GCE shows high electro-catalytic activity towards the vitamin C (AA) and aspirin (ASA) oxidation. Schematic fabrication of PMR/Zn−Al LDH/GCE for the determination of AA or ASA was presented. The new sensor demonstrated superior analytical efficiency for the simultaneous identification of AA and ASA traces in well-spaced anodic peaks, even in the presence of certain intervening species. According to experimental results, the fabricated sensor represented two well-separated oxidation peaks for AA and ASA oxidation with potential difference of 799 mV (vs. Ag/AgCl). The linear dependences of the anodic peak currents of AA and ASA on their concentrations in the ranges of 0.10–53.17 μM are good. The detection limits of AA and ASA at the PMR/Zn−Al LDH/GCE were found to be 1.26 and 1.27 μM, respectively. Meanwhile, the quantification limits of AA and ASA were calculated as 4.21 and 4.25 μM, respectively. On other hand, the limit of detection (LODs) of AA and ASA oxidation were determined to be 0.47 and 0.21 μM, respectively, according to DPV method. The effect of scan rate (100 to 800 mV/s) on the anodic peak currents of AA and ASA was examined. A sensing model mechanism has been suggested and discussed in detail. Finally, the proposed sensor displayed a good reproducibility, stability and selectivity. The developed sensor was eventually used to successfully detect AA and ASA in urine samples.     

双活性磺酸基蔗渣木聚糖对羟基苯甲酸酯的合成及活性模拟

以蔗渣木聚糖(BX)为主要原料、氨基三磺酸钠为酯化剂,在一步酯化合成磺酸基蔗渣木聚糖酯的基础上,利用磺酸基蔗渣木聚糖酯和对羟基苯甲酸进行二步酯化反应,合成了磺酸基蔗渣木聚糖对羟基苯甲酸酯,并考察了反应条件对酯化反应的影响,通过单因素实验确定了第二步酯化反应较佳的合成工艺条件.蔗渣木聚糖酯化改性前后的样品分别用FT-IR,DG-DTG和XRD进行了表征,并对该双酯化衍生物的分子进行了优化与活性模拟.结果表明:FT-IR证明双酯化产物含有磺酸基团和对羟基苯甲酸酯基团,TG-DTG分析表明该双酯化衍生物的热稳定性提高,XRD说明发生双酯化改性后分子排列的规整性提高,结晶度增加;活性模拟实现了磺酸基蔗渣木聚糖对羟基苯甲酸酯与艾滋病毒的对接.     

An Effective Asphalt UV Blocking Material Based on Host‐Guest Schiff Base/Layered Double Hydroxides

The development of asphalt‐based UV blocking materials is important to extend the alphalt lifespan in road construction. In this work, we put forward that the fabrication of host‐guest system can be an effective way to obtain UV blocking materials. Firstly, a new anionic Schiff base, N ,N' ‐bis(salicylidine)‐4,4'‐diaminostilbene‐2,2'‐disulfonic acid (SDSD ), has been synthesized, which was intercalated into Zn‐Al‐LDH by anion‐exchange method. FT‐IR and XRD illustrate the layered organic–inorganic composite, Zn‐Al‐SDSD‐LDH , has been successfully synthesized with high crystallinity. Laser particle size analyzer, SEM and TEM show that particle size distributions of Zn‐Al‐SDSD‐LDH is in the range 100–500 nm. UV –vis absorption spectra show that Zn‐Al‐SDSD‐LDH has better UV absorption than the pristine Zn‐Al‐LDH and SDSD . Furthermore, the mixture of asphalt and 3 wt% Zn‐Al‐SDSD‐LDH presents enhanced UV blocking property relative to the pristine asphalt after irradiating by UV spray accelerated weathering test. Therefore, this work not only develops a new type of host‐guest Zn‐Al‐SDSD‐ LDH , but also confirms it can be an effective asphalt UV blocking material for practical application.     

The Origin of Hierarchical Structure Formation in Highly Grafted Symmetric Supramolecular Double‐Comb Diblock Copolymers

Involving supramolecular chemistry in self‐assembling block copolymer systems enables design of complex macromolecular architectures that, in turn, could lead to complex phase behavior. It is an elegant route, as complicated and sensitive synthesis techniques can be avoided. Highly grafted double‐comb diblock copolymers based on symmetric double hydrogen bond accepting poly(4‐vinylpyridine)‐block‐poly(N‐acryloylpiperidine) diblock copolymers and donating 3‐nonadecylphenol amphiphiles are realized and studied systematically by changing the molecular weight of the copolymer. Double perpendicular lamellae‐in‐lamellae are formed in all complexes, independent of the copolymer molecular weight. Temperature‐resolved measurements demonstrate that the supramolecular nature and ability to crystallize are responsible for the formation of such multiblock‐like structures. Because of these driving forces and severe plasticization of the complexes in the liquid crystalline state, this supramolecular approach can be useful for steering self‐assembly of both low‐ and high‐molecular‐weight block copolymer systems.     

Self-assembly morphology and packing structures depend on the ‘head’ of organic cations anchored on polyoxometalate anions in hybrids

Two organic-polyoxometalates (organic-POMs) hybrids were constructed by fan-shaped 1-methyl-3-[3, 4, 5-tris(octadecyloxy) benzyl]imidazolium salts (labelled as I–Cl) and triethyl-[3, 4, 5-tris (octadecyloxy) benzyl] ammonium salts (labelled as Q–Cl) and Keggin anions [SiW₁₂O₄₀]^4? by electrostatic interaction. Self-assembled behaviours of two aggregates in organic solvent and solid state were investigated in detail by scanning electron microscopy, transmission electron microscopy and X-ray analysis. The mixed solution of chloroform–methanol or chloroform–acetone provided the stable environment for aggregates and aggregates showed a uniform micron size. X-ray analysis results showed that flower-like aggregates morphology of I₄[SiW₁₂O₄₀] based on imidazole ring as ‘head’ in organic cations was formed by the stacking of multilamellar discs and kept the lamellar structure in solid state. Bulk thorn spheres appeared in Q₄[SiW₁₂O₄₀] aggregates, which were formed by closely interspersed of lots flatted blocks with hexagonal structure characteristics in solid state. The comprehension for the self-assembly morphology and solid structure of organic-polyoxometalate hybrids would help us to use easily modified organic moiety and functional inorganic polyoxoanions as blocks to build novel and giant supramolecular architecture.     

12-磷钨酸插层MgAl水滑石的合成、表征及催化酯化原油脱酸性能

采用离子交换法合成了不同Mg/Al物质的量比的12-磷钨酸(H_3PW_(12)O_(40),HPW)插层水滑石(LDHs),采用XRD、FT-IR、Raman、ICP-AES、TG-DSC等分析手段表征其物化性质,Hammett指示剂-正丁胺滴定法测定其酸强度和酸量分布。进一步将其用于原油催化酯化脱酸反应,并与NO_3型LDHs对比,探讨酯化活性与催化剂性质之间的关系。结果表明,催化剂的活性主要受酸性和比表面积的影响。HPW插层LDHs的酯化活性明显优于NO3型LDHs,归因于增强的酸性和增大的比表面积。对于弱酸性的NO_3型LDHs,酯化活性与比表面积呈正向关系,Mg/Al物质的量比为4时,具有最大的比表面积和脱酸活性。而对于较强酸性的HPW插层LDHs,酯化活性主要受到酸量的影响,Mg/Al物质的量比为2的催化剂具有最高的酸量和脱酸活性。     

Double-stranded ladderphanes with C2-symmetric planar chiral ferrocene linkers

Eight ladderphanes with C₂-symmetric planar chiral ferrocene linkers are synthesized by ring opening metathesis polymerization of bisnorbornene monomers using Grubbs-I catalyst. The aminobenzoate in both monomers and polymers shows absorption maximum around 320 nm. Both monomers and polymers are Circular dichroism (CD) active. Little enhancements of CD profiles around 320 nm are observed for ladderphanes having chiral chloro- or phenyl-substituted ferrocene linkers. However, ladderphanes with a phenyl substituent on the cyclopendienyl ring exhibits enhancement of CD curves aound 240–300 nm. The congested phenyl moieties in adjacent linkers in this polymer might be well oriented such that interactions between these aromatic substituents on different monomeric units might provoke the enhancement of the CD curves in this region. When the methyl-substituted cyclopendienyl ligand is used for chiral ferrocene linkers, the ladderphanes exhibit two-fold enhancement of CD spectrum around 320 nm. This enhancement is further increased when the cyclopentadienyl ligand contains an additional phenyl substituent, owing to exciton coupling between aminobenzoate moieties in adjacent monomeric units. Moreover, the intensity of the CD curves in the region of 240–300 nm is significantly increased. These results suggest that the later polymer may adopt a posible helical structure. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2999–3010