Nanoparticle-Based Functional Nano-Materials—Modern Inorganic Aerogels

The focus of my talk will be laid on non-ordered superstructures made from nanocrystals. Here, gels and aerogels manufactured from a variety of different nanoparticles have recently proven to provide an opportunity to marry the nanoscale world with that of materials of macro dimensions which can be easily manipulated and processed, whilst maintaining some of the nanoscale properties. This is best demonstrated when using size-quantized semiconductor nanocrystals for the aerogel formation: 3.5 nm sized CdTe nanocrystals display an orange colour (while bulk CdTe is black) which is maintained in a 1 cm³ aerogel and so is also the emission.¹ In terms of applications, however, gels formed from metal nanocrystals provide a wider field, particularly in electrocatalysis.² For this we concentrated our work on the amelioration of the building blocks as a plausible approach to graft aerogels with distinguished properties while preserving the aerogel superiority.³ In a further study, we prepared and analyzed a new class of hierarchical aerogels composed of multimetallic Ni-Pd_xPt_y nanoparticle building blocks with continuously engineered shape and compositions. This approach results in aerogels with hierarchical structures organizing the nanoscale regulated architecture and macroscale three-dimensional network structure. For gaining highest performance of these catalysts the surface chemistry as well as the formation mechanisms have to be studied and tuned.^4,5 I will conclude my presentation with remarks on a set of more recent findings such as self-healing of metal gels and the formation of 2D-metal meshes.⁶ The latter display ligament sizes of 4 – 9 nm which is also the thickness of the meshes, surface coverages between 0.25 and 0.5, and fractal dimensions of 1.4 – 1.7. Those structures hold promise in various fields like sensors, electrodes, electrocatalysis, neural implants (stretchable electrodes), and fractal antennas.<br/>References<br/>[1] N. Gaponik, A. Wolf, R. Marx, V. Lesnyak, K. Schilling, A. Eychmüller, Adv. Mater. 20, 4257 (2008).<br/>[2] a) N.C. Bigall, A.K. Herrmann, M. Vogel, M. Rose, P. Simon, W. Carrillo- Cabrera, D. Dorfs, S. Kaskel, N. Gaponik, A. Eychmüller, Angew. Chem. Int. Ed. 48, 9731 (2009), b) W. Liu, A.-K. Herrmann, N.C. Bigall, P. Rodriguez, D. Wen, M. Oezaslan, T.J. Schmidt, N. Gaponik and A. Eychmüller, Acc. Chem. Res. 48, 154 (2015).<br/>[3] a) B. Cai, A. Dianat, R. Hübner, W. Liu, D. Wen, A. Benad, L. Sonntag, T. Gemming, G. Cuniberti, A. Eychmüller, Adv. Mater. 29, 1605254 (2017), b) B. Cai, R. Hübner, K. Sasaki, Y. Zhang, D. Su, C. Ziegler, M.B. Vukmirovic, B. Rellinghaus, R.R. Adzic, A. Eychmüller, Angew. Chem. Int. Ed. 57, 2963 (2018). c) B. Cai, V. Sayevich, N. Gaponik, A. Eychmüller, Adv. Mater. 30, 1707518 (2018).<br/>[4] R. Du, J. Wang, R. Hübner, X. Fan, I. Senkowska, Y. Hu, S. Kaskel, A. Eychmüller, Nat. Comm. 11, 1590 (2020).<br/>[5] a) H. Ishikawa, S. Henning, J. Herranz, A. Eychmüller, M. Uchida, T.J. Schmidt, J. Electrochem. Soc. 165, F2 (2018), b) S. Jungblut, J.-O. Joswig, A. Eychmüller, J. Phys. Chem. C 123, 950 (2019), c) S. Jungblut, J.-O. Joswig, A. Eychmüller, Phys. Chem. Chem. Phys 21, 5723 (2019), d) R. Du, Y. Hu, R. Hübner, J.-O. Joswig, X. Fan, K. Schneider, A. Eychmüller, Science Advances 5, 4590 (2019), e) P. Chauhan, K. Hiekel, J.S. Diercks, J. Herranz, V.A. Saveleva, P. Kavlyuk, A. Eychmüller, T.S. Schmidt, ACS Mater. Au 2, 278 (2022).<br/>[6] K. Hiekel, S. Jungblut, M. Georgi, A. Eychmüller, Angew. Chem. Int. Ed. 59, 12148 (2020).