Hard X-ray photoelectron spectroscopy (HAXPES) measurements were conducted with two keV excitation energy to analyze the chemical structure of SnO2 and ATO NPs. The survey spectra of the sample series, along with photoemission line identification, the spectra of the ATO series in the Sn 3d and the overlapping Sb 3d/O1s peaks regions. The Sn doublets are centered at binding energies (BEs) of ~ 487.6±0.1 eV for 3d5/2 and ~ 495.9±0.1 eV for 3d3/2, in agreement with literature values for SnO2, while the BE of the Sb doublets are centered at ~ 531.2±0.1 eV for 3d5/2 and ~ 540.50±0.1 eV for 3d3/2. With increasing the nominal Sb doping concentration, an increase in the Sb-related signal and a decrease in the Sn-related signal are observed, trends expected for a scenario in which Sb cations substitute the Sn4+ions in the SnO2 lattice matrices. The Sn 3d peaks are slightly broadened towards higher BE with increasing Sb content; this effect could have different plausible origins, such as different screening effects in the HAXPES measurements, changes in energy loss features related to changes in electronic structure, or due to the presence of an increasing amount of amorphous oxide (discussed above). As mentioned above intense bluish coloration of the solution indicates the possibility of the coexistence of two different antimony oxidation states, Sb3+ and Sb5+, which is inevitable in this doping case. Hence, Sb 3d core levels (specifically the Sb 3d3/2 line, as there is a superposition of the Sb 3d5/2 and the O 1s line) were closely analyzed. If you are looking for high quality, high purity, and cost-effective ATO, or if you require the latest price of ATO, please feel free to email contact mis-asia.