Axis nova x ray photoelectron spectrometer

For quantifying the loading amount of Au, Au NPs loaded on TiO₂ were dissolved by using aqua regia, and the concentration was determined by inductively coupled plasma spectroscopy. The samples for TEM and HR-TEM observation were prepared by dropping a suspension of the samples in ethanol onto a copper grid with a carbon support film (grid-pitch 150 μm, Okenshoji Co., Ltd, #10-1006). The measurements were performed by using a JEOL JEM-2100F at an applied voltage of 200 kV. The Au particle size (d_Au) was determined from the image analysis of ∼200 Au particles observed in TEM images. Diffuse reflectance UV-vis-NIR absorption spectra were measured by using a UV-2600 spectrometer (Shimadzu) with an integrating sphere unit (Shimadzu, ISR-2600Plus). BaSO₄ was used as a reference for the reflectance (R_∞). The Kubelka–Munk function [F(R_∞) = (1 − R_∞)²/2R_∞] was used for expressing the relative absorption coefficient. The measurement was carried out by using sample powder without dilution. X-ray photoelectron spectra (XPS) were collected by using a Kratos Axis Nova X-ray photoelectron spectrometer at 15 kV and 10 mA using Al Kα as the X-ray source. For the energy reference, the peak of C 1s (284.6 eV) was used.