Diameter-controlled Cu nanoparticles on saponite and preparation of film by using spontaneous phase separation

Abstract

Cu nanoparticles have attracted much attention due to their optical, catalytic, and electrical properties.Their syntheses, however, have required hazardous reducing agents. In addition, they are easily oxidized, which destroys their properties. It has also not been possible to control the diameter and the dispersibility for further applications in functional materials. To solve these problems, we have recently synthesized oxide-free Cu nanoparticles adsorbed on kaolinite, a non-dispersive layered clay, by environmentally friendly photoreduction. Focusing on the layer charge of the clay, we report diameterand dispersibility-controlled Cu nanoparticles on saponite, a dispersive clay, in the present study. The obtained oxide-free Cu nanoparticles were stable under N 2 atmosphere, while they exhibited a fast back reaction to Cu 2+ upon exposure to fresh air. The diameter of the Cu nanoparticles could be controlled simply with [Cu 2+ ], because Cu 2+ was adsorbed on saponite before the photoreduction. The dispersibility of the Cu nanoparticles was controlled without changing the diameter using the size of saponite aggregates: these were stably dispersed at low [Cu 2+ ], and flocculated at high [Cu 2+ ]. The flocculates could be collected by filtration and the obtained viscous paste was useful for preparing a film with the optical properties of the Cu nanoparticles without aggregation. Therefore, the present study revealed that combining the adsorption of Cu 2+ on saponite with photoreduction is a novel and environmentally friendly synthetic method for controlling the diameter and the dispersibility of Cu nanoparticles, and it has the potential to further their applications in functional materials.

Nanopartikel auf subnanometer dünnen oxidischen Filmen: Skalierung von Modellsystemen

“…[10] Durch die Kationenaustauschkapazitätd er Schichtsilikate kçnnen die Zwischenschichtkationen durch Präkursoren ausgetauscht werden, aus denen durch Reduktion (z. B. Pd, Cu, Ru) [11] oder Fällung (CdS) [12] Nanopartikel generiert werden kçnnen. Diese Kationenaustauschkapazitätv on natürlichen Schichtsilikaten liegt in der Grçßenordnung von < 100 mmol/100 g, [10] was die maximal mçg-liche Beladung limitiert.…”

Modification, hybridization and applications of saponite: An overview

“…In particular, Cu 2+ , Ni + and Fe 3+ can be converted into zero-valent metal nanoparticles by appropriate reduction reaction. In this context, two-dimensional Sap acts as a nanoreactor with limited space for generating metal nanoparticles and such metal nanoparticles are -free of organic protectants (Miyagawa et al, 2017).…”

“…Taking advantage of the swellability of Sap (Ferrage et al, 2010;Dazas et al, 2015;Ferrage, 2016), researchers can introduce functional guest molecules into the structure of Sap and thus tune porosity, acidity and other physical and chemical properties. Many types of Sap-based hybrids or composites have been successfully prepared by the intercalation of bulky organic (Kurokawa et al, 2014;Marcal et al, 2015;Sas et al, 2017) and inorganic (Franco et al, 2016b;Miyagawa et al, 2017) cationic species, neutral polar molecules (Marcal et al, 2015) and polymers (Mishchenko et al, 2016;Eguchi et al, 2017) into the interlayer space of Sap. Covalent grafting of a moiety of organic molecules onto the surface of Sap proves feasible.…”

Catalytic Activity of Nonaggregating Cu Nanoparticles Supported in Pores of Zeolite for Aerobic Oxidation of Benzyl Alcohol

“…In this study, we synthesized nonaggregating Cu NPs in pores of zeolite by the combination of ion-exchange and photoreduction methods. ,− Y-type zeolite, which has a relatively large pore size of ∼0.9 nm, was used because the size of acetate ions as the trigger of photoreduction by n-π* transition is smaller than the pore size of Y-type zeolite . We also investigated their catalytic activity for the aerobic oxidation of benzyl alcohol.…”