Multimode 8 system

Details on the growth and structural characterization of the Sn nanostructures can be found in ref. ^{32 (link)}. The Sn islands were grown using molecular beam epitaxy on Si(111) substrates. The Sn cluster-assembled film was grown on a SiO₂ substrate using a laser-vaporization cluster source⁵¹ . The AFM images were recorded using a Nanowizard 3 system (JPK, Germany) and a Multimode 8 system (Bruker, USA) and processed using WSxM^{52 (link)}. The superconducting behaviour of the different Sn samples was probed by SQUID magnetization measurements (LOT-Quantum Design, MPMS-XL). The phonon density of states of all Sn samples was measured using nuclear resonant inelastic X-ray scattering^{53 –55 (link)} at sector 3-ID of the Advanced Photon Source (Argonne National Laboratory, USA). Measurements were carried out at 35 ± 20 K in a grazing incidence geometry. The data were analyzed using the PHOENIX software^{56 (link)}. A more elaborate discussion of the nuclear resonant inelastic X-ray scattering measurements can be found elsewhere^{32 (link)}.

The assembled E-DNA nanopores were analyzed by 1% agarose gel electrophoresis while using 1 × TAE buffer. The agarose gel was pre-stained by 4S Red Plus Nucleic Acid Stain. For gel loading, a solution of 1 μL E-DNA nanopores, 1 μL 6 × loading buffer was mixed with 4 μL 1 × TAE buffer. The gel was run for 60 min at 70 V at room temperature. The bands were then visualized by UV illumination (Amersham imager 680). Transmission electron microscope (TEM) and atomic force microscope (AFM) were used to determine the morphology and detailed dimension of E-DNA nanopores. An appropriate amount of E-DNA nanopores were dropped on carbon-coated copper grids and incubated for 10 min before being drained with filter paper. 10 μL 2% sodium phosphotungstate was immediately added to the copper grids and incubated for 5 min for negative staining. After drying with filter paper, the samples were rinsed three times with ultra-pure water. The TEM images were captured by transmission electron microscope (HT7700, Hitachi). Initially, 5 μL E-DNA nanopores were mixed with 40 μL 1 × TAE buffer containing 10 mM MgCl₂ and 30 mM NiCl₂. An appropriate amount of the mixture was spread on the surface of freshly treated mica and incubated for about 2 min. The AFM images were obtained using a Multimode 8 system (Bruker Corp).

AFM was performed with a Bruker Multimode 8 system in tapping mode in air. An HOPG substrate was freshly cleaved before drop-casting the samples. A silicon cantilever (Bruker, MPP-11100–10) was used.