Togashi Takanari, Nakayama Masato, Miyake Ryosuke, Uruma Keirei, Kanaizuka Katsuhiko, Kurihara Masato
Department of Science, Faculty of Science, Yamagata University, 1-4-12 Kojirakawa-machi, Yamagata, 990-8560, Japan.
Dalton Trans. 2017 Sep 26;46(37):12487-12493. doi: 10.1039/c7dt02510f.
Metal oxalates (CO, ox) have been explored as promising precursors for the direct transformation of their oxalate moieties into metallic or metal oxide crystals via thermal decomposition without the formation of any byproducts due to releasing CO gas. The copper(ii) oxalate (Cu(ox)) crystal is a coordination polymer composed of an infinite coordination network with a thermal decomposition temperature around 300 °C; however, their insoluble nature in any solvents and relatively high decomposition temperature do not allow the solution-based syntheses of surface-modified metallic Cu nanocrystals (NCs) in the presence of various surfactants such as long-chain alkylamines and alkylcarboxylates which have been used for increasing the dispersibility of NCs in organic solvents. In this study, the insoluble nature of Cu(ox) is overcome by mixing Cu(ox) crystals and N,N-diethyl-1,3-diaminopropane (dedap) to form a discrete complex, [Cu(ox)(dedap)], whose structure is determined by X-ray crystallographic analysis. The obtained complex is well soluble in polar solvents and miscible with surfactants. Furthermore, it is decomposed at a moderate temperature of <170 °C with the evolution of CO gas; as a result, Cu NCs dispersible in organic solvents have been synthesized in suitable surfactants, such as the mixture of oleic acid, dodecylamine, and octylamine utilized as a reaction solvent. In addition, their potential application of the surface-modified Cu NCs as a conductive-ink has been preliminarily tested. The Cu film sintered at 280 °C exhibits a resistivity of 40 μΩ cm.
金属草酸盐（CO，ox）已被探索作为有前景的前驱体，通过热分解将其草酸盐部分直接转化为金属或金属氧化物晶体，由于释放出CO气体而不会形成任何副产物。草酸铜（II）（Cu（ox））晶体是一种配位聚合物，由无限配位网络组成，热分解温度约为300°C；然而，它们在任何溶剂中都不溶且分解温度相对较高，这使得在存在各种表面活性剂（如长链烷基胺和烷基羧酸盐，用于提高纳米晶体在有机溶剂中的分散性）的情况下，无法通过溶液法合成表面改性的金属铜纳米晶体（NCs）。在本研究中，通过将Cu（ox）晶体与N，N-二乙基-1，3-二氨基丙烷（dedap）混合形成离散配合物[Cu（ox）（dedap）]，克服了Cu（ox）的不溶性，其结构通过X射线晶体学分析确定。所得到的配合物在极性溶剂中溶解性良好，且能与表面活性剂混溶。此外，它在<170°C的适中温度下分解并释放出CO气体；结果，在合适的表面活性剂（如用作反应溶剂的油酸、十二烷基胺和辛胺的混合物）中合成了可分散在有机溶剂中的Cu纳米晶体。此外，还初步测试了表面改性的Cu纳米晶体作为导电油墨的潜在应用。在280°C烧结的铜膜电阻率为40μΩ·cm。
