Search

Replacement of protecting ligands of gold nanoclusters by ligand exchange has become an established post-synthetic tool for selectively modifying the nanoclusters' properties. Several Au nanoclusters are known to additionally undergo size transformations upon ligand exchange, enabling access to cluster structures that are difficult to obtain by direct synthesis. This work reports on the selective size transformation of Au15(SG)13 (SG: glutathione) nanoclusters to Au16(2-PET)14 (2-PET: 2-phenylethanethiol) nanoclusters through a two-phase ligand exchange process at room temperature. Among several parameters evaluated, the addition of a large excess of exchange thiol (2-PET) to the organic phase was identified as the key factor for the structure conversion. After exchange, the nature of the clusters was determined by UV–vis, electrospray ionization-time of flight mass spectrometry, attenuated total reflection-Fourier transform infrared, and extended x-ray absorption fine-structure spectroscopy. The obtained Au16(2-PET)14 clusters proved to be exceptionally stable in solution, showing only slightly diminished UV–vis absorption features after 3 days, even when exposed to an excess of thiol ligands. [ABSTRACT FROM AUTHOR]

Suspended membranes of two-dimensional (2D) materials are of interest for many applications. Much of their characterization relies on scanning probe microscopy (SPM) techniques such as atomic force microscopy (AFM) or scanning tunneling microscopy (STM). Unlike rigid samples, the suspended atomically thin 2D membranes are, however, flexible and do not remain mechanically undisturbed during SPM measurements. Local deformations can occur at the location of the scanning tip and thus result in measurements that misrepresent actual membrane topography and nanomechanical properties. Exact levels of such SPM tip-induced deformations in 2D membranes remain largely unknown, as they are to date only indirectly accessible via dual probe microscope concepts that either are not mechanically independent (e.g., SPM-SPM setups resulting in complicated imaging crosstalk) or suffer from intrinsically limited lateral resolution (e.g., optical far-field techniques as the second probe). Circumventing these shortcomings, we here demonstrate that by coupling an AFM with a scanning electron microscope (SEM) as the second, mechanically independent probe, we can directly and in situ visualize by SEM at high resolution 2D membrane deformations that result from controllable AFM tip manipulations in the nN range. Employing few-layer graphene as model membranes, we discuss the experimental realization of our coupled in situ AFM-SEM approach. [ABSTRACT FROM AUTHOR]

Replacement of protecting ligands of gold nanoclusters by ligand exchange has become an established post-synthetic tool for selectively modifying the nanoclusters' properties. Several Au nanoclusters are known to additionally undergo size transformations upon ligand exchange, enabling access to cluster structures that are difficult to obtain by direct synthesis. This work reports on the selective size transformation of Au15(SG)13 (SG: glutathione) nanoclusters to Au16(2-PET)14 (2-PET: 2-phenylethanethiol) nanoclusters through a two-phase ligand exchange process at room temperature. Among several parameters evaluated, the addition of a large excess of exchange thiol (2-PET) to the organic phase was identified as the key factor for the structure conversion. After exchange, the nature of the clusters was determined by UV–vis, electrospray ionization-time of flight mass spectrometry, attenuated total reflection-Fourier transform infrared, and extended x-ray absorption fine-structure spectroscopy. The obtained Au16(2-PET)14 clusters proved to be exceptionally stable in solution, showing only slightly diminished UV–vis absorption features after 3 days, even when exposed to an excess of thiol ligands. [ABSTRACT FROM AUTHOR]

Replacement of protecting ligands of gold nanoclusters by ligand exchange has become an established post-synthetic tool for selectively modifying the nanoclusters' properties. Several Au nanoclusters are known to additionally undergo size transformations upon ligand exchange, enabling access to cluster structures that are difficult to obtain by direct synthesis. This work reports on the selective size transformation of Au 15 (SG) 13 (SG: glutathione) nanoclusters to Au 16 (2-PET) 14 (2-PET: 2-phenylethanethiol) nanoclusters through a two-phase ligand exchange process at room temperature. Among several parameters evaluated, the addition of a large excess of exchange thiol (2-PET) to the organic phase was identified as the key factor for the structure conversion. After exchange, the nature of the clusters was determined by UV-vis, electrospray ionization-time of flight mass spectrometry, attenuated total reflection-Fourier transform infrared, and extended x-ray absorption fine-structure spectroscopy. The obtained Au 16 (2-PET) 14 clusters proved to be exceptionally stable in solution, showing only slightly diminished UV-vis absorption features after 3 days, even when exposed to an excess of thiol ligands.