Diffusion behavior of copper atoms under Cu(II) reduction in Cucurbit[8]uril cavity at elevated temperatures

作者：Bakovets Vladimir V^*; Nadolinnii Vladimir A; Kovalenko Ekaterina A; Plyusnin Pavel E; Dolgovesova Irina P; Zaikovskii Vladimir I

来源：Journal of Solid State Chemistry, 2015, 221: 202-207.

DOI：10.1016/j.jssc.2014.10.005

• Copper clusters and nanoparticles
• Copper cyclen complex
• Copper reduction mechanism
• EPR spectroscopy
• Thermoanalysis

In this paper we describe copper clusters and nanoparticles formation by the reduction of copper (II) ions inside cavities of macrocycle molecules using supramolecular compound [Cu(Cyclen)(H2O)@CB[8]] (NO3)(2)center dot 12H(2)O followed by Cu atoms diffusion between macrocycle CB[8] molecules. To understand the copper cluster genesis and nanoparticles formation x-ray powder diffraction (XRD), electron paramagnetic resonance (EPR), FTIR-spectroscopies, HRTEM and thermal analysis were used. It was found that atomic Cu(0) was not fixed in the cavity under heating, and Cu clusters and nanoparticles were formed by heating of supramolecular compound powder at 200-340 degrees C in He, but more preferably in H-2. The process was partially reversible after heating the powder up to 300 degrees C for 15 min and air exposure for a few months. The process was irreversible after heating of the sample at temperatures higher than 340 degrees C due to CB[8] cavitand decomposition. In general, exposure of the samples to air leads to oxidation and hydration clusters of Cu. Nanoparticles up to 600 nm in size formed on the surface of agglomerated polycrystalline powder at temperatures lower than 200 degrees C. The clusters less than 7 nm and 40 nm in size were formed at 300 degrees C inside and outside agglomerating polycrystalline powder, respectively. The diffusion coefficient of copper atoms inside polycrystalline CB[8] agglomerates equal to 10(-10) cm(2)/s by heating the samples at 300 degrees C was found.

• 出版日期2015-1