determined by energy-dispersive X-ray spectroscopy (EDS). Concentrated
colloidal solutions were drop-cast onto a Si substrate and measured
in a high-resolution scanning electron microscope (SEM) JEOL JSM-7500F
equipped with a cold field emission gun, and an Oxford X-Max 80 spectrometer
(based on an 80 mm2 Si drift detector). Standardless quantification
was achieved with the Aztec Energy EDS software. Elemental analyses
on single nanosheets were performed on a JEOL JEM-2200FS microscope
equipped with a Bruker Quantax solid state detector. The composition
of the nanosheets was also determined by inductively coupled plasma–optical
emission spectroscopy (ICP-OES) analysis performed on aiCAP 6000 spectrometer
(Thermo Scientific). The nanosheet solutions were digested in aqua
regia overnight and diluted to a known volume prior to the measurements.