Fig. 1
Synthesis and structural characterization of Cu:ICO NCs. a Reaction scheme of the selective cation-exchange reaction. b–e TEM images of (b) ICO NCs (λinitial = 2196 nm) and c–e Cu:ICO NCs synthesized by reacting ICO NCs with varying concentrations of CuCl2. f STEM-HAADF image of a single NC for samples shown in (e). g–j STEM-EELS elemental maps of Cu:ICO NCs obtained after reacting ICO NCs with 75 mM CuCl2. Elemental maps for (g) Cu, (h) Cd, (i) In, and (j) overlay of three micrographs are shown. Scale bars: (b–e) 20 nm, (f) 2 nm, and (g–j) 10 nm. k Elemental composition of ICO and Cu:ICO NCs measured with SEM-EDS (assuming Cu + Cd + In = 100%). The total Cd content of pristine ICO NCs was determined by using ICP-MS. l Plot of the atomic ratio between Cd and In for Cu:ICO NCs vs. the input Cu/Cd ratio. m and n Statistical analysis of NC size for ICO and Cu:ICO NCs based on (m) TEM images and (n) SAXS data. o Powder XRD patterns of ICO and Cu:ICO NCs. The pattern of vertical lines shown at the bottom corresponds to the powder XRD pattern of bulk CdO phase (JCPDS Card no. 03-065-2908). The error bars in (k) and (m) represent the standard deviation between measurements on the same sample. A minimum of three SEX-EDX measurements were performed over different spots to determine the average atomic ratios presented in (k). The NC size values shown in (m) were determined by statistical analysis of more than 1000 NCs from TEM images
