Structural order enhances charge carrier transport in self-assembled Au-nanoclusters

Abstract

The collective properties of self-assembled nanoparticles with long-range order bear immense potential for customized electronic materials by design. However, to mitigate the shortcoming of the finite-size distribution of nanoparticles and thus, the inherent energetic disorder within assemblies, atomically precise nanoclusters are the most promising building blocks. We report an easy and broadly applicable method for the controlled self-assembly of atomically precise Au32(nBu3P)12Cl8 nanoclusters into micro-crystals. This enables the determination of emergent optoelectronic properties which resulted from long-range order in such assemblies. Compared to the same nanoclusters in glassy, polycrystalline ensembles, we find a 100-fold increase in the electric conductivity and charge carrier mobility as well as additional optical transitions. We show that these effects are due to a vanishing energetic disorder and a drastically reduced activation energy to charge transport in the highly ordered assemblies. This first correlation of structure and electronic properties by comparing glassy and crystalline self-assembled superstructures of atomically precise gold nanoclusters paves the way towards functional materials with novel collective optoelectronic properties.

Metal–Ligand Interface and Internal Structure of Ultrasmall Silver Nanoparticles (2 nm)

“…The calculated crystallite size (CS = 0.9 ± 0.1 nm) was smaller than the particle size (2 nm by TEM), indicating a polycrystalline (twinned) structure of the nanoparticles in accordance with earlier results on ultrasmall gold nanoparticles, general crystallographic considerations on small nanoparticles, and our TEM analysis given in Figure . The XRD results further demonstrate that the ultrasmall nanoparticles prepared here still have the fcc structure of the bulk silver metal (albeit twinned), unlike atom-sharp clusters. ,,,− However, the presence of single-crystalline particles cannot be ruled out, therefore it is possible that the sample contains both single-crystalline and twinned particles. Furthermore, the low number of atoms in each particle causes surface defects and contributes to X-ray diffraction peak broadening as well.…”

Metalloid gold clusters – past, current and future aspects

“…Thereby, it could be shown lately that the crystalline order leads to additional optical transitions and an enhancement of the charge carrier transport by two orders of magnitude with respect to a polycrystalline thin film. 140 Hence, the single crystalline state is not only of central importance for the structure solution but also influences the properties of the metalloid cluster compounds, an aspect that was also observed for the metalloid gallium cluster [Ga 84 [N(SiMe 3 ) 2 ] 20 ] 4− , 141,142 showing that the synthesis and characterization of metalloid clusters open the door for future novel applications.…”

Recent Notable Approaches to Study Self‐Assembly of Nanoparticles with X‐Ray Scattering and Electron Microscopy

“…[48][49][50] Such clusters crystallize readily and this has been and is frequently used for structure elucidation and to study properties. [1,51,52] These nanoclusters are considered as a class of materials on its own and their crystallization is not in the focus of this review.…”