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PET pyrolysis and hydrolysis mechanism in the fixed pyrolyzer
No full textIn the conventional polyethylene terephthalate (PET) pyrolysis process, the formation of char by excessive pyrolysis is mainly due to the dehydration mechanism, so water is considered an auxiliary agent that can effectively inhibit excessive pyrolysis. The preparation of terephthalic acid (TPA) by steam-assisted pyrolysis of PET is an effective method to achieve closed-loop recycling of waste PET. To ensure that the reaction is mild enough to reduce excessive cracking products such as char and benzoic acid and thus increase the yield of TPA, it is critical to reduce the reaction rate while maintaining a sufficient excess steam coefficient. Under the optimal operating conditions, when the temperature rise rate was 0.5 degrees C min(-1) and the excess steam coeffi-cient was 150, the yield of TPA was 72.5 wt.%, and the purity was 85.5%. Noticeably, the steam-assisted pyrolysis system is a heterogeneous reaction sys-tem whose reaction mechanism is different from the conventional hydrolysis and pyrolysis reactions and has a unique reaction path. The mechanistic study indicates that, in addition to the thermal cracking of PET molecules occurring in conventional pyrolysis, hydroxyl attack and transfer, and supplementation of benzene ring hydrogen also occur between water and intermediate mole-cules. Meanwhile, it has also been proven that the intermolecular hydrogen transfer between intermediate molecules and water molecules is the key to reduce the intensity of the reaction and inhibit the formation of char. This dis-covery illustrates the mechanism of the reaction between water and PET in the steam-assisted pyrolysis process in the fixed pyrolyzer and justifies the distinc-tion between it and the pyrolysis and hydrolysis processes of PET. It provides a theoretical basis for optimizing the pyrolysis process of PET, which is essential for the industrialization of TPA preparation from PET steam-assisted pyrolysis
Aluminum Impurity from Current Collectors Reactivates Degraded NCM Cathode Materials toward Superior Electrochemical Performance
No full textThe huge amount of degraded NCM (LiNi0.5Co0.2Mn0.3O2) cathode materials from spent lithium-ion batteries is arising as a serious environmental issue as well as a severe waste of metal resources, and therefore, direct recycling of them toward usable electrode materials again is environmentally and economically more attractive in contrast to present metallurgical treatments. In this work, we design a robust two-step method for direct recycling of degraded NCM materials, which uses the aluminum impurity from the attached current collector to supplement the transition metal vacancies for simultaneous elemental compensation and structural restoration. This single-element compensation strategy leads to the regeneration of high-quality NCM material with depressed cation disordering and stabilized layered structure. Moreover, the regenerated NCM material with controllable Al doping delivered an outstanding electrochemical performance; specifically, the capacity (158.6 mAh g-1), rate capability (91.6 mAh g-1 at 5 C), and cycling stability (89.6% capacity retention after 200 cycles) of the regenerated NCM material are even comparable with those of fresh materials. The as-established regeneration protocol has its chance in simplifying the industrial recycling process of degraded NCM materials
Ultrafine SnPd Nanoalloys Promise High-Efficiency Electrocatalysis for Ethanol Oxidation and Oxygen Reduction
No full textThe catalytic activity and stability of palladium (Pd)-based electrocatalysts for ethanol oxidation reaction (EOR) and oxygen reduction reaction (ORR) can be improved by optimizing their composition and structure. Alloying tin (Sn) into Pd can induce electronic and synergistic effects, which weaken the adsorption of intermediate species (e.g., O and OH in ORR and CO in EOR) on Pd sites and even promote their further transformation. However, the SnPd alloys often suffer from complicated synthesis, large particle size, and inhomogeneity. In this context, we report the synthesis of SnPd nanoalloys with an ultrafine size of ca. 3.8 nm using a simple one-pot approach and their superior catalytic performance for EOR and ORR. Specifically, the SnPd alloy nanoparticles with an optimized Sn/Pd ratio of 18/82 show the mass and specific activity of 3.8 A mg-1 and 5.72 mA cm-2, respectively, for EOR, while excellent performance for ORR with a half-wave potential of 0.92 V and specific activity of 3.46 mA cm-2 at 0.9 V, both of which are much higher than those of their commercial Pd/C and Pt/C counterparts
Fc effector of anti-Aβ antibody induces synapse loss and cognitive deficits in Alzheimer's disease-like mouse model
No full textPassive immunotherapy is one of the most promising interventions for Alzheimer's disease (AD).However,almost all immune-modulating strategies fail in clinical trials with unclear causes although they attenuate neuropathology and cognitive deficits in AD animal models.Here,we showed that Aβ-targeting antibodies including their IgG1 and IgG4 subtypes induced microglial engulfment of neuronal synapses by activating CR3 or FcγRllb via the complex of Aβ,antibody,and complement.Notably,anti-Aβ antibodies without Fc fragment,or with blockage of CR3 or FcγRllb,did not exert these adverse effects.Consistently,Aβ-targeting antibodies,but not their Fab fragments,significantly induced acute microglial synapse removal and rapidly exacerbated cognitive deficits and neuroinflammation in APP/PS1 mice post-treatment,whereas the memory impairments in mice were gradually rescued thereafter.Since the recovery rate of synapses in humans is much lower than that in mice,our findings may clarify the variances in the preclinical and clinical studies assessing AD immunotherapies.Therefore,Aβ-targeting antibodies lack of Fc fragment,or with reduced Fc effector function,may not induce microglial synaptic pruning,providing a safer and more efficient therapeutic alternative for passive immunotherapy for AD
胶原的百年研究历程回顾与展望
No full text胶原作为细胞外基质的主要成分,是脊椎动物体内含量最丰富的蛋白。胶原研究历程与人们对生命本质的认识过程密不可分,从纤维学说到细胞学说确立经历了数百年的历程。近百年来,胶原的应用从制革和黏合剂等,逐渐拓展至食品、药品、化妆品、生物材料,近年来拓展至组织工程、再生医学及干细胞定向转化等。结合已有的文献报道及相关研究经验,针对胶原的研究历程、应用范围以及相关技术在胶原研究中的应用、取得的阶段性进步或成果等进行梳理。以期为胶原领域的研究人员提供胶原研究的最新动向,使其充分理解技术进步与科学研究之间的关系,同时有助于促进不同学科领域的交叉与融合
基于阴离子与手性调控的短肽自组装与酶催化研究
No full text肽与蛋白分子的自组装广泛存在于自然界各种生命过程中，无序的分子自组装形成有序的纳米结构，不仅为生命体的功能实现提供物质保障，还可能成为引发许多疾病的致病因素。尤其是近年来，在越来越多的研究中认识到淀粉样蛋白组装在神经退行性疾病发展中所起的关键作用，这使得对于自组装过程的研究与调控变得尤为重要。相比于多肽与蛋白分子，短肽（通常氨基酸组成＜10）具有分子设计简单、组装灵活可控等特点，因此借助短肽自组装的研究来反映蛋白质的复杂结构和组装策略，为组装行为的调控以及先进功能材料的构建提供思路。本论文基于短肽超分子体系自组装行为、结构与性能的调控规律，研究阴离子与手性对超分子组装与酶催化体系的影响机制，为自然界手性选择、生物催化、疾病形成机理的研究奠定理论基础。具体研究内容分为以下三个部分：
（1）阴离子调控作用下短肽超分子自组装结构的可逆转化。基于两亲性二肽 9-芴甲氧羰基-L-酪氨酸-L-赖氨酸（Fmoc-YLKL）的自组装体系，研究不同类型的阴离子对组装过程中各种驱动力的调控与平衡作用，从而触发Fmoc-YLKL不同的组装路径，形成不同的组装体形貌。通过调控 C 末端羧基的质子化和去质子化状态，实现Fmoc-YLKL/SO42-体系超分子结构与手性的可逆转换，并揭示 pH 开关触发的超分子组装机理。另外该自组装体系发射的圆偏振发光能够触发 2,4-二炔基二十一烷酸的对映选择性聚合反应。本章节研究内容将在超分子自组装体系的精准调控以及手性功能材料的制备方面具有广泛的参考与应用价值。
（2）Hofmeister 效应介导的短肽超分子水凝胶体系，应用于肿瘤模型的细胞三维（3D）培养。基于 Hofmeister 效应下Fmoc-YLKL超分子水凝胶对阴离子（SO42-）的响应规律，通过 3D 生物打印制备水凝胶支架。该材料体系具有固化成型迅速（＜20 s）、浸泡细胞培养基增韧、细胞相容性高等优势，在 3D 培养过程中能够维持细胞的生长增殖，从而制备毫米级别的肿瘤组织微球。本章节通过研究短肽超分子水凝胶的性能调控策略以及肿瘤模型的体外构建，为组织工程与生物医药领域提供理论依据。
（3）分子手性对短肽自组装行为和酶催化动力学的影响机制。手性结构及其调控与生命现象密切相关，本章节通过改变短肽序列与手性，阐明氨基酸手性对超分子组装以及酶与底物亲和作用的影响规律。结果表明底物中任意位置 D-氨基酸的存在均会对嗜热蛋白酶的催化作用（包括催化水解与缩合反应）产生抵抗，使酶的催化效率由 63.8%～100%降至 9.6%以下。本章节由分子水平的手性出发，研究短肽的自组装以及酶与底物的结合机制，有助于理解自然界生命过程中的手性选择，对生物催化中的手性依赖以及人体内 D-氨基酸积累有关的疾病形成具有启示作用。 </div
醇类表面活性剂光照下产生VOCs二次污染的机理研究
No full text醇类表面活性剂作为洗涤剂、个人护理品等的关键成分，广泛使用于工业及日常生活中。由于独特的双亲结构，污废水中残余的醇类表面活性剂随着废水排放并自发富集在水环境表面。近期研究发现，表面活性剂通过光化学反应产生挥发性有机化合物（VOCs），从而引发跨介质污染转移，该现象在大气领域引起了广泛关注。然而从水环境角度开展醇类表面活性剂通过光反应产生VOCs的机理研究较少，尤其缺乏对活性氧物种（ROS）在其中的作用的探究。为此，本文针对典型醇类表面活性剂，重点针对其光化学转化途径与VOCs产生机理，考察了ROS在醇类表面活性剂光反应产生VOCs过程中的作用，提出了脂肪醇和芳香醇等醇类在光照下产生VOCs的共性规律，为表面活性剂光化学跨介质二次污染防控提供新的视角。以下是本文的主要研究内容和结果：
首先，本研究基于原位光化学-VOCs产物在线检测装置（GC-MS/FID）探究了典型脂肪醇，壬醇，通过光反应产生VOCs的机理，发现不同反应气氛对VOCs的生成量有显著影响；进一步采用电子顺磁共振波谱仪、电喷雾质谱等分析方法，证实了单线态氧（1O2）在脂肪醇光化学过程中发挥关键作用；结合密度泛函理论（DFT）计算，从分子水平阐明了“1O2夺氢反应”的机制，即1O2通过壬醇的α-CH2和-OH位置夺氢、使其氧化为壬醛，继而在光照下通过Norrish II型反应产生气态庚烯等VOCs。
其次，针对实际水环境中油污形成水面上有机层的情况，发现柴油等不同有机层对脂肪醇光反应产生VOCs的影响存在显著差异：针对正己烷、甲基叔丁基醚等易挥发的有机层，探讨了VOCs在不同有机层中溶解自由能的差异和其改变VOCs释放过程的机理；而乙酸乙酯等惰性有机层明显促进了脂肪醇光反应，揭示了有机层对稳定1O2活性的机理。
进一步根据亲疏水性指标Kow探究了芳香醇、脂环醇和脂肪醇的不同结构对其光反应产生VOCs的影响，VOCs分布和生成量存在较大差异；重点探讨了以苯甲醇为代表的芳香醇光反应产生VOCs的机理，揭示了芳香醇在光照下被1O2和羟基自由基夺氢氧化和直接光解产生嗅味VOCs的反应途径与机理规律。
最后，总结了醇类表面活性剂光反应产生VOCs的共性机理，提出醇类表面活性剂光照下经过“1O2夺氢-Norrish裂解”产生VOCs的反应规律；考察了共存无机盐、有机物、太阳光等实际环境条件对醇类表面活性剂光反应产生VOCs的影响，发现环境条件对ROS的影响将显著改变醇类表面活性剂的光反应过程和VOCs产物分布。</p
