Diffusion behavior of copper atoms under Cu(II) reduction in Cucurbit[8]uril cavity at elevated temperatures
- Nikolaev Institute of Inorganic Chemistry SB RAS, 630090 Novosibirsk, Prospekt Akademika Lavrent’eva 3 (Russian Federation)
- Boreskov Institute of Catalysis SB RAS, 630090 Novosibirsk, Pospekt Akademika Lavrent’eva 5 (Russian Federation)
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)(H{sub 2}O)@CB[8]](NO{sub 3}){sub 2}·12H{sub 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 °C in He, but more preferably in H{sub 2}. The process was partially reversible after heating the powder up to 300 °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 °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 °C. The clusters less than 7 nm and 40 nm in size were formed at 300 °C inside and outside agglomerating polycrystalline powder, respectively. The diffusion coefficient of copper atoms inside polycrystalline CB[8] agglomerates equal to 10{sup −10} cm{sup 2}/s by heating the samples at 300 °C was found. - Graphical abstract: Copper nanoparticles and clusters are formed by the reduction of copper (II) ions inside cavities of macrocycle molecules at 200–340 °C in He, but more preferably in H{sub 2} using supramolecular compound [Cu(Cyclen)(H{sub 2}O)@CB[8]](NO{sub 3}){sub 2}·12H{sub 2}O followed by Cu atoms diffusion between macrocycle CB[8] molecules. Nanoparticles up to 600 nm in size formed on the surface of agglomerated polycrystalline powder at temperatures lower than 200 °C. The clusters less than 7 nm and 40 nm in size were formed at 300 °C inside and outside agglomerating polycrystalline powder, respectively. - Highlights: • We considered Cu NP's formation at CuCyclen thermolysis in H{sub 2} and He. • Initial complex CuCyclen was located inside cavitand CB[8]. • Cu(0) reduced in cavities diffuse between CB[8] molecules and Cu nuclei appear. • NPs less than 7 and 50 nm were formed inside and outside the CB[8] powder. • Coefficient of Cu(O) diffusion is 10{sup −10} cm{sup 2}/s for temperature at 300 °C.
- OSTI ID:
- 22443498
- Journal Information:
- Journal of Solid State Chemistry, Vol. 221; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
COPPER
DECOMPOSITION
DIFFUSION
ELECTRON SPIN RESONANCE
FOURIER TRANSFORMATION
HEATING
HYDROGEN
INFRARED SPECTRA
MOLECULES
NANOPARTICLES
NITRATES
NITROGEN OXIDES
OXIDATION
POLYCRYSTALS
POWDERS
SPECTROSCOPY
SURFACES
THERMAL ANALYSIS
TRANSMISSION ELECTRON MICROSCOPY
X-RAY DIFFRACTION