Jem 2010 microscope

The alloying reaction was conducted in an Eppendorf Comfort thermomixer. UV–vis absorption spectra of the samples were obtained from a Shimadzu UV-1800 spectrometer. Cluster concentrations were measured by ICP-OES on a Thermo Scientific iCAP 6000. Scanning transmission electron microscopy and energy dispersive X-ray spectroscopy elemental mappings were recorded on a JEOL JEM 2010 microscope operating at 200 kV. ESI-MS analysis was carried out on a Bruker microTOF-Q system in negative ion mode. Detailed operating conditions of ESI-MS analysis are given as followings: source temperature/120 °C, dry gas flow rate/4 L per min, nebulizer pressure/0.4 bar, and capillary voltage/3.5 kV. In a typical ESI-MS analysis, 0.2 mL of DMF solution of NCs (with a NC concentration of ~0.64 mM) was injected with a flow rate of 3 μL per min. PAGE was carried out on a Bio-Rad Mini-Protean Tetra Cell system, with a stacking and resolving gel prepared from 4 and 30 wt.% acrylamide monomers, respectively. In a typical analytical gel (1.0 × 83 × 73 mm, 10 wells), 10 μL of aqueous NC solution containing 5 vol.% glycerol was loaded into each well, followed by running the gels at a fixed voltage of 200 V at 4 °C for 4 h.