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Organic Reaction Pathways in the Nonaqueous Synthesis of Metal Oxide Nanoparticles

机译:非水合成金属氧化物纳米粒子的有机反应途径

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Nonaqueous-solution routes to metal oxide nanoparticles are a valuable alternative to the known aqueous sol-gel processes,offering advantages such as high crystallinity at low temperatures,robust synthesis pa-rameters and ability to control the crystal growth without the use of surfactants.In the first part of the review we give a detailed overview of the various solution routes to metal oxides in organic solvents,with a strong focus on surfactant-free processes.In most of these synthesis ap-proaches,the organic solvent plays the role of the reactant that provides the oxygen for the metal oxide,controls the crystal growth,influences particle shape,and,in some cases,also determines the assembly behavior.We have a closer look at the following reaction systems in this order:1) metal halides in alcohols,2) metal alkoxides,acetates,and acetylacetonates in alcohols,3) metal alkoxides in ke-tones,and 4) metal acetylacetonates in benzylamine.All these systems offer some peculiarities with respect to each other,providing many possibilities to control and tailor the particle size and shape,as well as the surface and assembly properties.In the second part we present general mecha-nistic principles for aqueous and nonaqueous sol-gel pro-cesses,followed by the discussion of reaction pathways rel-evant for nanoparticle formation in organic solvents.De-pending on the system several mechanisms have been postulated:1) alkyl halide elimination,2) elimination of organic ethers,3) ester elimination,4) C-C bond forma-tion between benzylic alcohols and alkoxides,5) ketimine and aldol-like condensation reactions,6) oxidation of metal nanoparticles,and 7) thermal decomposition meth-ods.
机译:到金属氧化物纳米粒子的非水溶液途径是已知的水性溶胶-凝胶工艺的一种有价值的替代方法,具有诸如低温下的高结晶度,稳健的合成参数以及无需使用表面活性剂即可控制晶体生长的能力等优点。在本综述的第一部分中,我们详细介绍了有机溶剂中各种方法转化为金属氧化物的途径,重点是无表面活性剂的方法。在大多数这些合成方法中,有机溶剂起着为金属氧化物提供氧气,控制晶体生长,影响颗粒形状的反应物,并且在某些情况下还决定了组装行为。我们按以下顺序仔细研究以下反应系统:1)金属卤化物醇,2)醇中的金属醇盐,乙酸盐和乙酰丙酮化物,3)酮中的金属醇盐和4)苄胺中的金属乙酰丙酮化物。所有这些系统都有各自的特点相互之间,提供了控制和调整颗粒大小和形状以及表面和组装特性的许多可能性。在第二部分中,我们介绍了水性和非水性溶胶-凝胶工艺的一般机理,如下通过讨论与在有机溶剂中形成纳米颗粒有关的反应途径。在该系统上,有以下几种机理的推测:1)烷基卤的消除,2)有机醚的消除,3)酯的消除,4)CC键苯甲醇与醇盐之间的形成; 5)酮亚胺和醇醛类似的缩合反应; 6)金属纳米颗粒的氧化; 7)热分解方法。

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