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Claus Feldmann1

1, Karlsruhe Institute of Technology, Karlsruhe, , Germany

Chemical synthesis of base metals is the more challenging the smaller the particles are and the lower the electrochemical potential of the respective metal is. The annual number of publications addressing metal nanoparticles, to this concern, is a useful indication. Thus, the synthesis of Au(0) nanoparticles (E0 = +1.5 V) was addressed by about 4000 publications in 2016, about 700 papers were related to Co(0) nanoparticles (E0 = –0.3 V), whereas only 8 publications addressed Ti(0) (E0 = –1.9 V), and none publication addressed the synthesis of Gd(0) nanoparticles (E0 = –2.4 V) [1]. Here, it must be noted that the electrochemical potential only reflects the reactivity of bulk metals. Due to the absence of any passivation layer, high surface areas, and the great number of surface atoms, nanosized base metals can be expected to be significantly more reactive.

Via sodium-naphthalenide-driven reduction in ethers (e.g. 1,2-dimethoxyethane, tetrahydrofuran), we could now obtain very uniform Mo(0), W(0), Fe(0), Zn(0), Ti(0), Gd(0), and U(0) nanoparticles with diameters £10 nm [2-5]. Simple metal chlorides were used as the starting materials. The reactive metal nanoparticles can be easily obtained with yields of 95-99%. It is to be noted that Gd(0) and U(0) nanoparticles were made via liquid-phase methods for the first time [5]. Whereas suspensions of the base metal nanoparticles are comparably inert, powder samples are highly reactive and show spontaneous ignition when in contact to air.

The synthesis strategy allows a reproducible synthesis of Mo(0), W(0), Fe(0), Zn(0), Ti(0), Gd(0), and U(0)0 nanoparticles with high purity and with large quantities. Such dependable and comparably uncomplex synthesis is even more relevant since Gd0 and U0 stand as representatives for further lanthanide and actinide metals. All in all, the synthesis has the potential to become a general and reliable strategy for base metal nanoparticles and metal compounds (e.g. alloys, intermetallics, bimetallic heterostructures, metal nitrides) with applications ranging from catalysis, magnetic and hard materials, to batteries and solar cells.

This presentation will summarize the current status regarding the synthesis, the reactivity and specific follow-up reactions of base metal nanoparticles.

References
[1] The American Chemical Society, Program Package Scifinder, Washington 2017.
[2] C. Schöttle, P. Bockstaller, D. Gerthsen, C. Feldmann, Chem. Commun. 2014, 50, 4547-4550
[3] C. Schöttle, P. Bockstaller, R. Popescu, D. Gerthsen, C. Feldmann, Angew. Chem. Int. Ed. 2015, 54, 9866-9870.
[4] C. Schöttle, D. Doronkin, R. Popescu, D. Gerthsen, J.-D. Grunwaldt, C. Feldmann, Chem. Commun. 2016, 52, 6316-6319.
[5] C. Schöttle, S. Rudel, R. Popescu, D. Gerthsen, F. Kraus, C. Feldmann, 2017, submitted.

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