Nanoplating of functional plasmonic gold and silver films
Solid State and Surface Chemistry, Material Synthesis
Final Report Abstract
Electroless plating represents a facile, industrially established method for the conformal metallization of work pieces. Traditionally, it is focused on nickel and the deposition of compact, smooth films, which serve as wear and corrosion resistant or conductive coatings. To expand the utility of the approach to other application fields, new synthetic strategies are required to surpass its structural and compositional limits. For instance, depositing welldefined noble metal nanostructures with electroless plating would represent a versatile route for direct surface functionalization. This constitutes the core aim of the project. Using gold and silver as two metals of pronounced nanotechnological importance, new plating procedures for the fabrication of functional nanoparticle films were developed. The focus was laid on target morphologies suiting our envisioned application: the optical detection of biomolecules based on the phenomenon responsible for the distinct colour of gold and silver nanoparticles, localized surface plasmon resonance. Our first aim was producing films composed of isolated, roundish nanoparticles. We realized such materials by depositing spread-out, small nanoparticles on a glass surface. Consecutive electroless plating was employed to enlarge the particles and provided a convenient way for optimizing their plasmonic properties. Using these films, we designed a DNA sensor, which converts the selective binding of a single strand DNA sequence onto the nanoparticles into an optical signal. Pursuing a second strategy, we tuned the metal nucleation and growth characteristics in the deposition reactions, enabling the production of nanostructures of special shape unattainable with conventional electroless plating. In this regard, we developed protocols for gold nanowires and a family of interrelated silver nanomaterials, which is characterized by an intriguing interplay of one- and two-dimensional structural motifs. The latter includes nanobelts, porous nanoplates, multi-layered nanoplate superstructures and dendritic sheets. In this system, the directional growth is driven by planar crystal defects, which surface at the nanostructure edges and make them particularly reactive. While the diameter of individual plates remains in the nanoscale, their lateral dimension can reach tens of micrometres. At such levels, individual nanostructures can be identified with the naked eye. While the nanowire and nanoplate films did not exhibit the narrow plasmon band relevant for our biosensing scheme, they combine a wide range of desired properties: Their open-porous architecture results in a large and easily accessible surface area, which is characterized by a specific atomic structure and high activity. Furthermore, being composed of interconnected nano-objects and directly grown on a substrate, they are electrically conductive and show robust adhesion. Due to their valuable features, these nanofilms display promising platforms for surface engineering, electrochemistry, heterogeneous catalysis, flow chemistry, and microreactor design, which we demonstrated in various examples.
Publications
- Template-Free Electroless Plating of Gold Nanowires: Direct Surface Functionalization with Shape-Selective Nanostructures for Electrochemical Applications. ACS Appl. Mater. Interfaces 2017, 9, 31142–31152
F. Muench, S. Schaefer, L. Hagelüken, L. Molina-Luna, M. Duerrschnabel, H.-J. Kleebe, J. Brötz, A. Vaskevich, I. Rubinstein, W. Ensinger
(See online at https://doi.org/10.1021/acsami.7b09398) - Expanding the boundaries of metal deposition: High aspect ratio solver nanoplatelets created by merging nanobelts. Electrochim. Acta 2018, 264, 233–243
F. Muench, A. Vaskevich, R. Popovitz-Biro, T. Bendikov, Y. Feldman, I. Rubinstein
(See online at https://doi.org/10.1016/j.electacta.2018.01.103)
