Relative Chemical Shifts for Obtaining Accurate Chemical Shifts of Hydrogen Atoms in CH Groups

Accurate chemical shifts of hydrogen atoms in CH groups are difficult to obtain. To solve this problem, relative chemical shifts are introduced. Internal and external standard methods were used to measure the chemical shifts in a whole-concentration of N-methylacetamide- water system. Determination of the chemical shifts of hydrogen atoms, especially those of CH groups, according to the two methods yielded significant differences. Relative chemical shifts were proven to be independent of the reference and may be applied to other systems.

Chemical indexes of Paleoproterozoic sedimentary rocks from Liaohe Group,North China Craton:Implications for paleoclimate and provenance

Paleoproterozoic supracrustal materials have been widely identified in North China Craton,such as the Liaohe-,Hutuo-and Lyuliang groups.The Liaohe Group in the eastern part of the North China Craton is dominated by deformed and metamorphosed sedimentary and volcanic successions.Compared with that of the coeval volcanic rocks,geochemistry of the sedimentary rocks from the Liaohe Group has rarely been studied in detail,which can possibly provide information on the paleoclimate and provenance.The authors analyzed the whole-rock and detrital zircon geochemistry of sedimentary rocks from the Liaohe Group against a uniform process and proposed their different ways of paleoweathering of the lower and upper formations.That is to say,although the lower and upper formations within the Liaohe Group might be derived from the similar source composition in a tectonically active setting,the paleoclimate that they experienced was not exactly the same.The predominant derivations are the Paleoproterozoic granitoids and basalts within the Liaohe Group,with minor input of Archean continental crust.This study highlights the contributions of the Paleoproterozoic mafic sources,which has been generally overlooked in the previous researches.

A Giant of China's Cleaning Industry——The Blue Star Chemical Cleaning Group Corporation

First business: to clean a tea pot. Income: RMB 0.20 (less than 10 US cents at the time). Second business: to clean a boiler. Income: RMB 1, 200. Three months later, incomereached RMB 240, 000. Ten years later, the company had 350 subsidiaries across China and four joint ventures abroad, with an annual output value of more than RMB 300 million. The data are simple but intriguing, recording the history of the Blue

Bengbu Bayi Chemicals Group

Bangbu Bayi Chemicals Group is an enterprise assigned by theMinistry of Chemical Industry to produce nitrochlorobenzene seriesproducts. It has strong technical forces, advanced productiontechnology and quality control measures. Products include 20 varieties of chloro-anhydride series andnitrochlorobenzene series. They are widely used in pesticides,medicines, dyestuffs, rubber, daily chemicals, leather andpapermaking. Among these, the para-nitrochlorobenzene and otherthree products rank first in production scale in China, winning thetitles of excellent products from the Ministry of Chemical Industry.Many products sell well in southeast Asia, Europe and the Americas.

Beijing Chemical Group Import and Export Corp.

The Beijing Chemical Group Import and Export Corporation previously the Beijing Jinghuan Corporation, Ltd. was founded in September 1988 with the approval of the Beijing municipal government. A specialized foreign trade corporation under the Beijing Chemical Group, the corporation handles its own exports, mainly engaged in the import and export of the products produced individually or jointly by various enterprises in the group. Since it began operation in January 1989, the corporation has displayed the superiority of combined industry and trade and expanded

Advanced chemical strategies for lithium-sulfur batteries: A review

Lithium-sulfur(Li-S) 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 Li-S 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 Li-S 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.

Chemical vapor deposition growth of crystal monolayer SnS2 with NaCl-assistant

As an important member of the two-dimensional layers of metal dichalcogenides family, the two-dimensional(2 D)group IV metal chalcogenides(GIVMCs) have been attracting intensive attention. However, the growth of monolayer tin disulfide(SnS2) remains a great challenge contrasted to transition metal dichalcogenides, which have been studied quite maturely. Till date, there have been scant reports on the growth of large-scale and large-size monolayer SnS2. Here, we successfully synthesized monolayer SnS2 crystal on SiO2/Si substrates via NaCl-assisted CVD and the edge can be as long as 80 μm. Optical microscope, Raman spectroscopy, x-ray diffraction, atomic force microscopy(AFM), and energydispersion x-ray(EDX) were performed respectively to investigate the morphology, crystallographic structure, and optical property of the 2 D SnS2 nanosheets. In addition, we discussed the growing mechanism of the NaCl-assisted CVD method.

Chemical Modification of Amino Acid Residues in Human Plasminogen

The chemical modification of human plasminogen(HPg) was studied with 1-ethyl-3-(3- dimethyl aminopropyl) carbodiimide(EDC), N -acetylimidazole(NAI), 1,2-cyclohexanedione(CHD), chloramine T(Ch-T) and N -bromosuccinimide(NBS) as modifying reagents at its carboxyl group, tyrosine, arginine, methionine and tryptophan residues, respectively. The results indicate that tyrosine and arginine residues are not essential for HPg activity, while carboxyl groups, methionine and tryptophan residues are important for the activity of HPg. The Keech and Farrant′s kinetic analysis reveals that one tryptophan residue, one methionine residue and two carboxyl groups are essential for HPg activity.

Stabilizing Buried Interface via Synergistic Effect of Fluorine and Sulfonyl Functional Groups Toward Efficient and Stable Perovskite Solar Cells

The interfacial defects and energy barrier are main reasons for interfacial nonradiative recombination.In addition,poor perovskite crystallization and incomplete conversion of PbI_(2) to perovskite restrict further enhancement of the photovoltaic performance of the devices using sequential deposition.Herein,a buried interface stabilization strategy that relies on the synergy of fluorine(F)and sulfonyl(S=O)functional groups is proposed.A series of potassium salts containing halide and non-halogen anions are employed to modify SnO_(2)/perovskite buried interface.Multiple chemical bonds including hydrogen bond,coordination bond and ionic bond are realized,which strengthens interfacial contact and defect passivation effect.The chemical interaction between modification molecules and perovskite along with SnO_(2) heightens incessantly as the number of S=O and F augments.The chemical interaction strength between modifiers and perovskite as well as SnO_(2) gradually increases with the increase in the number of S=O and F.The defect passivation effect is positively correlated with the chemical interaction strength.The crystallization kinetics is regulated through the compromise between chemical interaction strength and wettability of substrates.Compared with Cl−,all non-halogen anions perform better in crystallization optimization,energy band regulation and defect passivation.The device with potassium bis(fluorosulfonyl)imide achieves a tempting efficiency of 24.17%.

Characteristics of Chemical Modified Activated Carbons from Bamboo Scaffolding

In this study, bamboo scaffolding was used to produce activated carbon by carbonization at 600 ℃ and 900 ℃with the purge of nitrogen. The 600 ℃ char was then further modified chemically by acids and alkalis by reflux for 6 hours. The produced chars were then characterized by nitrogen adsorption isotherm, He pyncometry, pH, elemental analysis and Boehm titration. For most of the chemically modified carbons, the micropore surface areas and volumes have increased compared with the 600 ~C char, while the mesopore surface areas and volumes slightly decreased, which may have been due to the dissolving of some of the permeated inorganic matter and oxidizing deposited carbon that blocks the pore openings. For the acidic modified carbons, larger amounts of acidic groups were present in the carbons after being activated by phosphoric acid, phosphoric acid furth, er treated with 2 mol-L-1nitric-acid, and calcium hydroxide. Although carbon treated with 2 mol.L-1 and 5 mol·L-1 nitric acid also produced high acidity, the surface areas and pore volumes were relatively low, due to the destruction of pores by nitric acid oxidation. The reduction of porosity may impair the adsorption capacity.

热解预处理对昭通褐煤润湿性的影响机制

褐煤的强亲水性为其加工和利用造成了许多不利影响,热解预处理是调控褐煤润湿性的有效方法之一。采用工业分析、傅立叶变换红外光谱(FTIR)、X射线衍射(XRD)和接触角测量探究了热解预处理对褐煤润湿性的影响机制。热解预处理的温度分别为200℃,300℃,400℃和500℃,时间分别为30 min,60 min,90 min和120 min。结果表明:热解预处理改变了褐煤的化学结构和组成,显著影响了褐煤的润湿性。褐煤的羧基在200℃时开始裂解逸出,并在300℃时基本消失;褐煤的酯基在300℃时开始裂解逸出,并在400℃时基本消失;而褐煤的C—O(醚键、酚和醇)的热稳定性较好,热解预处理后其相对含量略微增加;褐煤的芳碳率随着热解温度和时间的增加而增大,且芳香核尺寸在300℃时开始增大。如果使用热解预处理来减弱褐煤的亲水性,则应确保在较低温度下有足够的热解时间来去除褐煤的含氧官能团,而在较高温度下应使用较短的时间来防止褐煤的有机质过度损失。在300℃(120 min)或400℃(30 min)热解条件下,褐煤的亲水性含氧官能团(羧基或酯基)裂解逸出,且疏水性芳香核尺寸增大,从而使其亲水性显著减弱,接触角由原煤的44.00°分别增大为87.50°和85.75°。然而,在400℃(热解时间大于30 min)和500℃条件下,褐煤的有机质过度损失,导致矿物质或无机质的相对含量增加,使其亲水性仍然较强。

强化工程案例教学,促进研究能力培养——以“MATLAB与化工数值计算”课程为例

为了更好地培养学生基于科学思维和工程实践的研究能力,以大量真实化工案例剖析为驱动,将工程案例教学法有机融入“MATLAB与化工数值计算”各个教学环节,通过工程案例教学架构设计、工程案例教学群组开发、工程案例教学方案实施以及工程案例教学考核评价等多种教学方式来不断强化学生利用先进技术方法和工具解决化学化工过程复杂工程问题的专业综合能力,有效助力我国能源化工行业“工业4.0”的升级与改造。

基于醇解-酯交换法再生PET的固相缩聚

为研究再生聚对苯二甲酸乙二醇酯(CRPET)固相缩聚反应规律及影响因素,在真空条件下,对比分析原生对苯二甲酸乙二醇酯(vPET)和CRPET的固相缩聚反应特征,探究不同端甲基含量和不同尺寸CRPET的固相缩聚反应规律;通过改变反应氛围,在真空和氮气两种反应氛围下分别考察了真空度、氮气流速以及预结晶温度对CRPET特性黏度的影响,对比分析了固相缩聚前后CRPET性能的变化。结果表明:在相同反应条件下,vPET的固相缩聚反应速率大于CRPET;端甲基的存在会阻碍CRPET固相缩聚反应正向进行,但随着温度的升高,这种阻碍逐渐减弱;减小CRPET尺寸或升高反应温度均会提高特性黏度增长速率;CRPET特性黏度在真空条件下比氮气条件下的增量更大;固相缩聚反应在较高氮气流速和真空度下更容易进行;预结晶温度上升会促使固相缩聚反应正向进行,但过高结晶温度会阻碍CRPET内部小分子的扩散逸出,导致特性黏度增长减缓;固相缩聚反应能够提升CRPET的结晶性能,对其热性能影响微弱。

Impact of strain relaxation on the growth rate of heteroepitaxial germanium tin binary alloy

The growth of high-quality germanium tin(Ge_(1–y)Sn_(y))binary alloys on a Si substrate using chemical vapor deposition(CVD)techniques holds immense potential for advancing electronics and optoelectronics applications,including the development of efficient and low-cost mid-infrared detectors and light sources.However,achieving precise control over the Sn concentration and strain relaxation of the Ge_(1–y)Sn_(y)epilayer,which directly influence its optical and electrical properties,remain a significant challenge.In this research,the effect of strain relaxation on the growth rate of Ge_(1–y)Sn_(y)epilayers,with Sn concentration>11at.%,is investigated.It is successfully demonstrated that the growth rate slows down by~55%due to strain relaxation after passing its critical thickness,which suggests a reduction in the incorporation of Ge into Ge_(1–y)Sn_(y)growing layers.Despite the increase in Sn concentration as a result of the decrease in the growth rate,it has been found that the Sn incorporation rate into Ge_(1–y)Sn_(y)growing layers has also decreased due to strain relaxation.Such valuable insights could offer a foundation for the development of innovative growth techniques aimed at achieving high-quality Ge_(1–y)Sn_(y)epilayers with tuned Sn concentration and strain relaxation.

An improved installation of 2-hydroxy-4-methoxybenzyl(iHmb)method for chemical protein synthesis

The 2-hydroxy-4-methoxybenzyl(Hmb)backbone modification can prevent amide bond-mediated sidereactions(e.g.,aspartimide formation,peptide aggregation)by installing the removable Hmb group into a peptide bond,thus improving the synthesis of long and challenging peptides and proteins.However,its use is largely precluded by the limited Hmb’s installation sites.In this report,an improved installation of Hmb(iHmb)method was developed to achieve the flexible installation and the convenient removal of Hmb.The iHmb method involves two critical steps:(1)oxidative diazotization of the readily installed 2-hydroxy-4-methoxy-5-amino-benzyl(Hmab)to give 2-hydroxy-4-methoxy-5-diazonium-benzyl(Hmdab)by combining soamyl nitrite(IAN)/HBF_(4),and(2)reductive elimination of Hmdab to give the desired Hmb by 1,2-ethanedithiol(EDT).The iHmb method enables the installation of Hmb at any primary amino acid including the highly sterically hindered amino acids(e.g.,valine and isoleucine).The practicality and utility of the iHmb method was demonstrated by one-shot solid-phase synthesis of a challenging aspartimide-prone peptide,the mirror-image version of a hydrophobic peptide and a long-chain peptide up to 76-residue.Furthermore,the iHmb method can be utilized to facilitate chemical protein ligation,as exemplified by the synthesis of the single-spanning membrane protein sarcolipin.The iHmb method expands the toolkit for peptide synthesis and ligation and facilitates the preparation of peptides/proteins.

Variations in surface functional groups, carbon chemical state and graphitization degree during thermal deactivation of diesel soot particles

The thermal deactivation of diesel soot particles exerts a significant influence on the control strategy for the regeneration of diesel particulate filters(DPFs).This work focused on the changes in the surface functional groups,carbon chemical state,and graphitization degree during thermal treatment in an inert gas environment at intermediate temperatures of 600℃,800℃,and 1000℃ and explore the chemical species that were desorbed from the diesel soot surface during thermal treatment using a thermogravimetric analyser coupled with a gas-chromatograph mass spectrometer(TGA-GC/MS).The surface functional groups and carbon chemical statewere characterized using Fourier transform infrared spectroscopy(FT-IR)and X-ray photoelectron spectroscopy(XPS).The graphitization degree was evaluated by means of Raman spectroscopy(RS).The concentrations of aliphatic C–H,C–OH,C=O,and O–C=O groups are reduced for diesel soot and carbon black when increasing the thermal treatment temperature,while the sp^(2)/sp^(3) hybridized ratio and graphitization degree enhance.These results provide comprehensive evidence of the decreased reactivity of soot samples.Among oxygenated functional groups,the percentage reduction during thermal treatment is the largest for the O–C=O groups owing to its worst thermodynamic stability.TGA-GC/MS results show that the aliphatic and aromatic chains and oxygenated species would be desorbed from the soot surface during 1000℃ thermal treatment of diesel soot.

化肥减量配施有机肥对橡胶园土壤细菌群落及其功能的影响

为明确化肥减量配施有机肥对土壤细菌群落结构和功能类群的影响,通过大田试验,设置100%配方肥为对照组(CK),80%配方肥+10 kg有机肥(Y10),60%配方肥+15 kg有机肥(Y15)和40%配方肥+20 kg有机肥(Y20)为试验组,研究土壤细菌群落结构,并对细菌进行FAPROTAX功能预测。测序结果表明,与CK相比,化肥减量配施有机肥提高了土壤细菌群落多样性和丰富度,增加了变形菌门和拟杆菌门相对丰度,减少放线菌门和绿弯菌门相对丰度,且Y15和Y20处理提高了厚壁菌门相对丰度。此外,与CK相比,Y10、Y15和Y20处理上调慢生根瘤菌属相对丰度;Y15和Y20处理上调酸杆菌属相对丰度;Y20处理上调芽孢杆菌属相对丰度。FAPROTAX功能预测结果表明,化肥减量配施有机肥改变了细菌群落中部分氮循环的潜在功能。与CK相比,化肥减量配施有机肥提高了固氮作用和硝酸盐还原作用等氮循环功能菌群相对丰度。综上,化肥减量配施有机肥能增加土壤细菌多样性和丰富度,改善土壤微生物群落结构及功能,从而提高土壤微生态系统的多样性和抗冲击能力。

生物炭的化学改性及其对重金属离子的吸附性能

生物炭的化学改性中,表面修饰和负载可增加化学吸附位点来实现对重金属离子的吸附,被认为是有效提高生物炭吸附性能的可行之法。本文面向化学改性,将上述两类改性方法细分为六种,阐述和讨论了各种改性方法的原理及优缺点。最后,对化学改性生物炭未来发展趋势进行了展望。

基于催化加氢与端基封端的老化沥青化学修复机制研究与效果评价

从沥青老化的本质出发,首先采用三乙氧基硅烷在催化条件下与老化沥青发生氢化还原反应,将老化沥青中强极性的羰基和亚砜基还原成低极性物质;考虑到老化沥青的活泼端基会诱导新沥青加速老化,采用自由基抑制剂异氰酸酯对老化沥青活泼端基进行封端。通过测试老化沥青催化加氢与端基封端前后化学结构与极性变化,探究其修复机理;进而以基质沥青为参比,分析测试催化加氢与端基封端前后老化沥青宏观性能的变化,评价催化加氢与端基封端对老化沥青的化学修复效果;最后通过红外光谱与低温弯曲试验结果联动分析,建立了老化沥青化学结构与低温性能之间的内在联系。结果表明,催化加氢与端基封端使老化沥青的化学结构发生了本质的变化,三乙氧基硅烷可将老化沥青中羰基和亚砜基转化成酯或者醚,异氰酸酯通过酯化反应将老化沥青羟基转化为酯,降低了端基活泼性和极性。经催化加氢与端基封端之后,老化沥青的介电常数下降到3.2,下降了27.3%,粘度下降了近20%,而对石灰石的粘附功提高了15.8%,低温劲度模量和蠕变速率对的变化幅度达到14.0%以上;表明催化加氢与端基封端引起了老化沥青极性的显著减弱,分子间作用力和粘度明显降低,粘附性和低温性能得以显著改善;劲度模量和蠕变速率与老化沥青的含氧官能团指数之间具有良好的对应关系。

浅谈农药杂质分析及特征官能团杂质的识别方法

农药中的杂质,特别是相关杂质,常常对农药产品的品质造成不良影响,并增加农药产品的使用风险。本文概述了农药原药中杂质的一般分析流程,并解析了杂质的主要来源。并详细分类介绍了主要相关杂质的类型及主要特征官能团,阐述了胺类化合物的主要化学衍生化反应类型,进一步引出了稳定同位素同时标记的化学衍生化方法在杂质识别过程中独特作用。论文相关内容有利于增强对农药杂质分子特性的了解,并为提升农药相关杂质的识别和解析提供有价值的参考。