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The influence of various grease compositions and silver nanoparticle additives on electrically induced rolling-element bearing damage

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Friction 2024年第4期12卷 796-811页

作者： Samuel BOND Robert L.JACKSON German MILLS department of chemistry and biochemistry Auburn UniversityAuburn 36849-5412USA department of Mechanical Engineering Auburn UniversityAuburn 36849-5412USA

Leakage currents accelerate surface degradation of metal contacts via small scale arcing across lubricating films,but recent observations suggest that metallic nanoparticle additives in lubricants may be useful to improve contact *** findings prompted a study that examined electrically induced surface pitting of steel contacts in the presence of several lubricating greases including some containing nanometer-sized colloidal silver(Ag)*** rolling sphere-on-disk experiments were conducted under electro-tribological loads employing polyurea greases derived from mineral and synthetic base oils with and without *** forces and electrical resistance were monitored continuously during the tests;surface changes were characterized by means of optical spectroscopy,stylus profilometry,and scanning electron microscopy(SEM)including compositional analysis using energy dispersive spectroscopy(EDS).The observations demonstrate that surface pitting induced by arcing occurs mainly at the points were the rolling motion changes direction and that eroded metal is deposited along the wear ***-sized pits are formed which contain carbon and oxygen indicating that arcing causes decomposition of the hydrocarbon *** findings indicate a significant inhibition of pitting is induced by the Ag nanoparticles;some greases containing other additives exhibit a similar,although less pronounced,effect.

关键词： electric motor bearings wheel bearings electric vehicles arcing electrically induced bearing damage pitting leakage current stray current

Design,Synthesis,and Applications of Mesoporous Covalent Organic Frameworks

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CCS chemistry 2024年第1期6卷 57-68页

作者： Niyati Arora Cassandra Flores Milinda C.Senarathna Christina M.Thompson Ronald A.Smaldone department of chemistry and biochemistry University of TexasDallasRichardsonTexas 75080

Covalent organic frameworks(COFs)are highly ordered and permanently porous organic polymers that can be classified as two-dimensional or *** tunable design and crystalline order endow a range of pore sizes,shapes,functions,and applications that differentiate them from other *** COF pore sizes and shapes rely on the geometry of the monomers and dynamic covalent chemistry,while the stacking of the sheets relies on noncovalent *** tunability allows for post-modification or the incorporation of additional functional groups for the reinforcement by various noncovalent *** limits of mesoporous COFs are still being investigated,with the design rules continuing to *** we report a comprehensive review of mesoporous COFs,explore strategies for large pore reinforcement,highlight structural design and features,elucidate their various functions and applications,discuss fundamental challenges faced that need to be addressed,and predict future directions.

关键词： covalent organic frameworks mesoporous supramolecular chemistry polymers pore size

Piling up multidecker pyrgos[n]cages as antibacterial materials

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Science China Materials 2024年

作者： Miguel A.Liuzzi-Vaamonde Jackson B.Lancaster Samantha A.Mason Yuanning Feng department of chemistry and biochemistry The University of Oklahoma

The development of antibiotics is regarded as one of the most significant scientific advances in modern *** the commercialization of antibiotics,infectious diseases were catastrophic throughout history[1].Penicillin was used to treat serious infections in the 1940s,but unfortunately,with the introduction of antibiotics came the emergence of antibiotic resistance[2,3].Evolved and adapted methicillin-resistant Staphylococcus aureus （MRSA） strains are presently impacting community and healthcare systems across the globe[4].

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Increasing polymer scission rate by tying an overhand knot

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Science China chemistry 2024年

作者： Yuheng Hu Jennifer T.Ou Jim Y.Huang Yuanning Feng department of chemistry and biochemistry The University of Oklahoma

Similar to the phenomenon of knotted ropes in life, knotted climbing ropes will reduce their strength due to knots. Although computer simulations [1], theoretical speculation[2,3], and intuition [3] suggest that similar processes may occur at the nanoscale, this hypothesis has not been experimentally proven before. With the increasing maturity of molecular recognition and self-assembly, a research communication by Leigh et al. [4]

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Stereospecific Assembly of Trisubstituted Alkenes via Photoinduced Nitrogen-Centered Radical-Triggered C—C Bond Cleavage/Functionalization of Oxime Esters

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Chinese Journal of chemistry 2024年第12期42卷 1399-1406页

作者： Yu Bao Zhi-Jie Song Jin-Long Dai Shenghu Yan Yue Zhang Jia-Yin Wang Guigen Li School of Pharmacy Changzhou UniversityChangzhouJiangsu 213164China department of chemistry and biochemistry Texas Tech University79409USA

Comprehensive Summary A general and convenient photoredox-catalyzed acylation and alkylcyanation of MBH acetates has been established,enabling the assembly of the C(sp2)–C(sp3)bond by a nitrogen-centered radical strategy for the synthesis of trisubstituted alkenes in moderate to excellent chemical yields(48 examples in total).The reaction of MBH acetates with acyl(indanone)oxime esters afforded trisubstituted alkenes containing 1,4-dicarbonyl ***,the use of Eosin Y as a photocatalyst in the catalytic system resulted in the formation of distal cyano group-anchored trisubstituted alkenes via deconstructive functionalization of cycloketone oxime ***,these resulting 1,4-dicarbonyl compounds could be applied to late-stage transformations,providing important methods for the synthesis of dihydropyridazin-3(2H)-one.

关键词： Photocatalysis Radical reactions MBH acetates Oxime esters Stereoselectivity Acylation Alkylation Green chemistry

以芳基重氮盐为芳基前体电化学合成芳基取代的苯并噻吩和菲

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电化学（中英文） 2024年第4期30卷 6-48页

作者：蓝丽媛蒋洋叶 R.Daniel Little 曾程初北京工业大学环境与生命学院北京100124 department of chemistry&biochemistry University of CaliforniaSanta BarbaraCalifornia 93106USA

芳基取代的苯并噻吩和菲是药物化学和材料科学中的重要结构单元。尽管已经投入了很多来制备这类化合物,并且已经开发了多种方法来构建2-取代的苯并噻吩核心结构,但仍然需要环境友好且有效的合成方法。基于我们以前的以芳基重氮盐为芳基... 详细信息

芳基取代的苯并噻吩和菲是药物化学和材料科学中的重要结构单元。尽管已经投入了很多来制备这类化合物,并且已经开发了多种方法来构建2-取代的苯并噻吩核心结构,但仍然需要环境友好且有效的合成方法。基于我们以前的以芳基重氮盐为芳基前体的电化学Minisci型芳基化反应,以及来自Konig小组的工作,本文使用成对电解以苯重氮盐为芳基前体来获得2-芳基苯并噻吩和9-芳基菲。首先,选择2-甲硫基苯重氮盐1a和4-甲基苯乙炔2a作为模型底物,通过考察溶剂、支持电解质、电极材料和电流密度来优化反应条件。经过大量的努力,发现在装备有石墨毡阳极、镍片阴极的单室电解池中,使用n-Bu_(4)NBF_(4)作为支持电解质,DMSO作为溶剂,控制在4mA·cm^(-2)条件下恒流电解,获得89%产率的所需产物3a。在最佳条件下,考察该电化学方案和底物范围的普适性。结果表明,烷基乙炔和芳基乙炔都适用于该方法,并成功地得到了一系列芳基取代的苯并噻吩衍生物。考虑到菲类化合物在药物化学和材料科学中的广泛应用,将此方案应用到菲衍生物的合成中,获得了相应的9-芳基菲衍生物。最后,通过循环伏安法分析了可能的机理。2-甲硫基苯重氮盐1a在CH_(3)CN中相对于Ag/Ag^(+)在-0.4 V处产生一个显著的不可逆还原峰,而在扫描电位窗口中没有检测到苯乙炔2a的信号。此外,尽管峰电流略有增加,2a的存在没有改变1a的还原峰电位。这些结果表明1a的还原比2a的还原容易。基于循环伏安分析和光催化结果,我们提出了成对电解机制,即芳基重氮盐1a在阴极的电化学还原产生芳基5a,然后芳基5a加成到苯乙炔上,在分子内环化后产生乙烯基6a和磺酰基7a。最后,7a的阳极氧化,接着用DMSO脱甲基化,生成目标产物3a。总之,我们发展了一种成对电解法来合成2-芳基苯并噻吩衍生物和9-芳基菲衍生物。该方案具有广泛的底物范围和官能团耐受性,进一步证明了芳基重氮盐作为多用途芳基自由基来源通过电化学还原产生芳基自由基的实用性。

关键词：苯并噻吩菲成对电合成芳基重氮盐芳基自由基

Facile synthesis of intra-nanogap enhanced Raman tags with different shapes

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Nano Research 2024年第9期17卷 8415-8423页

作者： Sanjun Fan Brian T.Scarpitti Zhewen Luo Abigail E.Smith Jian Ye Zachary D.Schultz department of chemistry and biochemistry The Ohio State UniversityColumbusOhio 43210USA School of Biomedical Engineering Shanghai Jiao Tong UniversityShanghai 200030China

Hot spot engineering in plasmonic nanostructures plays a significant role in surface-enhanced Raman scattering(SERS)for bioanalysis and cell ***,creating stable,reproducible,and strong SERS signals remains challenging due to the potential interference from surrounding chemicals and locating SERS-active analytes into hot-spot ***,we developed a straightforward approach to synthesize intra-gap nanoparticles encapsulating 4-nitrobenzenethiol(4-NBT)as a reporter molecule within these gaps to avoid outside *** made three kinds of intra-gap nanoparticles using nanorods,bipyramids,and nanospheres as cores,in which the nanorods based intra-gap nanoparticles exhibit the highest SERS *** advantage of our method is the ease of preparation of high-yield and stable intra-gap nanoparticles characterized by a short incubation time(10 min)with 4-NBT and quick synthesis without requiring an additional step to centrifuge for the purification of core *** intense localized field in the synthesized hot spots of these plasmonic gap nanostructures holds great promise as a SERS substrate for a broad range of quantitative optical applications.

关键词： hot spot engineering surface enhanced Raman scattering intra-gap nanoparticles 4-nitrobenzenethiol

Conformational dynamics as an intrinsic determinant of prion protein misfolding and neurotoxicity

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Neural Regeneration Research 2024年第10期19卷 2095-2096页

作者： Alessandro Cembran Pedro Fernandez-Funez department of chemistry and biochemistry University of Minnesota DuluthDuluthMNUSA department of Biomedical Sciences University of Minnesota Medical SchoolDuluth CampusDuluthMNUSA

The prion protein(PrP) is the key molecular and pathological mediator of prion diseases,a heterogeneous group of brain disorders with fatal *** diseases are rare but deserve special attention because of their unique f... 详细信息

关键词： folding intrinsic dynamics

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Potassium ions and cyano group modified g-CNfor effective generation of HOthrough two-electron oxygen reduction

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Science China chemistry 2024年

作者： Dongying Wang Shulan Pu Yongmin Chen Ke Lei Yujie Duan Linjiao Mao Xuhui Zeng Xi Luo Yuntao Zhang Yuqin Dong Jinzhong Zhang Yan Sun School of Mechanical Engineering Chengdu University department of chemistry and biochemistry University of California

Potassium ions （K+） doped graphitic carbon nitride （g-C3N4） was prepared by a thermal etching method using potassium hydroxide （KOH） as an ion source. Fourier transform infrared spectroscopy （FTIR） and X-ray photoelectron spectroscopy （XPS）results showed that the generation of the cyano group was detected while introducing K+. Under simulated sunlight irradiation,the sample with a K+doping amount of 10%showed the highest hydrogen peroxide （H2O2） generation rate of 2,140.2μmol h-1g-1. The apparent quantum yield （AQY） at 400 nm and the solar-to-chemical conversion （SCC） are 4.35%and1.23%, respectively. K+acted as a bridge between g-C3N4layers, which enhanced charge transfer efficiency. Meanwhile, the cyano group enhanced the adsorption capacity of protons （H+） and promoted the yield of H2O2. The catalyst exhibited excellent photocatalytic stability based on four-cycle experiments. In addition, a mechanism study showed that superoxide radicals （·O2-）were the most important active species in the reaction system. Photocatalytic production of H2O2was achieved through consecutive single-electron steps. This study deepens the understanding of the oxygen reduction reaction process and opens up a new venue for improving H2O2generation.

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