Directed Immobilization of Janus-AuNP in Heterometallic Nanogaps: a Key Step Toward Integration of Functional Molecular Units in Nanoelectronics

Abstract

Forming reliable and reproducible molecule−nanoelectrode contacts is one of the key issues for the implementation of nanoparticles as functional units into nanoscale devices. Utilizing heterometallic electrodes and Janus-type nanoparticles equipped with molecules allowing selective binding to a distinct electrode material represents a promising approach to achieve this goal. Here, the directed immobilization of individual Janus-type gold nanoparticles (AuNP) between heterometallic electrodes leading to the formation of asymmetric contacts in a highly controllable way is presented. The Janus-AuNP are stabilized by two types of ligands with different terminal groups on opposite hemispheres. The heterometallic nanoelectrode gaps are formed by electron beam lithography in combination with a self-alignment procedure and are adjusted to the size of the Janus-AuNP. Thus, by choosing adequate molecular end group/metal combinations, the immobilization direction of the Janus-AuNP is highly controllable. These results demonstrate the striking potential of this approach for the building-up of novel nanoscale organic/inorganic hybrid architectures.

Integration of Individual Functionalized Gold Nanoparticles into Nanoelectrode Configurations: Recent Advances

“…[ 21e,23 ] In addition, properties like the pH‐dependent protonation/deprotonation enable specific binding properties of these anchoring groups to charged electrode surfaces. [ 4b,21a–21c,24 ] Therefore, ligands like 1,8‐mercaptooctanoic acid (MOA), 1,8‐aminooctanethiol (AOT) and 1‐mercapto‐11‐undecyl tetra‐(ethylene glycol) (MUTEG) are interesting candidates for functionalization experiments. For the synthesis of isotropic AuNPs with these ligands, citrate is exchanged by an excess of MOA or MUTEG as a straightforward approach (Figure 2, bottom).…”

“…For the synthesis of isotropic AuNPs with these ligands, citrate is exchanged by an excess of MOA or MUTEG as a straightforward approach (Figure 2, bottom). [ 21e,24b,25 ] The excess of the ligand and the exchanged citrate is removed afterwards by centrifugation. The synthesis of AOT‐functionalized AuNPs can be reached through a solid phase supported synthesis reported by Nath et al [ 24b,26 ] pH‐dependent UV/Vis measurements proved that MOA‐AuNP are stable in alkaline buffer solutions, while the AOT are stable in acidic buffer solutions.…”

“…[ 21e,24b,25 ] The excess of the ligand and the exchanged citrate is removed afterwards by centrifugation. The synthesis of AOT‐functionalized AuNPs can be reached through a solid phase supported synthesis reported by Nath et al [ 24b,26 ] pH‐dependent UV/Vis measurements proved that MOA‐AuNP are stable in alkaline buffer solutions, while the AOT are stable in acidic buffer solutions. This can be explained by the deprotonation and protonation of carboxylic acids and amines in the respective buffer solutions, enabling in both cases an electrostatic stabilization of the functionalized AuNPs.…”

Ion specific effects on the immobilisation of charged gold nanoparticles on metal surfaces

“…12,13 Our long term goal is to integrate ligand stabilised gold nanoparticles (AuNPs) by self-assembly on electrode surfaces, in a directed manner, thus building up hybrid nanoelectronic devices with advanced functionality. 14,15 In this context, we presented in our previous work the directionally controlled immobilisation of tailored ligand stabilised Janus-AuNPs on gold surfaces, prefunctionalised with self-assembled monolayers (SAMs) of thiol molecules. 16 Thereby, we took advantage of electrostatic and hydrophilic/hydrophobic interactions.…”

Optical properties of nanoalloys

“…30,[73][74][75][76][77][78][79][80][81][82][83][84][85][86][87][88][89] such as: catalysis and photocatalysis, nano-electronics, biomarkers, electro-chemistry, chemical sensors, polymer composites with fluorescence resonance energy transfer, biosensors, bioimaging, cancer treatment, anti-microbial applications, etc.From an analysis of the results of Secs. 3 and 4, in perfect agreement with previous work and analysis, it is possible to identify some trends which are typical of pure clusters but remain valid for nanoalloys as well.…”