Emx a300 spectrometer

The concentration of commercially available H₂O₂ was about 10 M, and considering that H₂O₂ is easily decomposed, it needed to be prepared for use before each experiment. Accurate concentrations of H₂O₂ could be reflected by UV absorbance. The concentration of H₂O₂ that remained after the reaction was quantified by measuring the absorption at 240 nm. In short, the decomposition experiment was performed by adding DPP-Ir nanoparticles (50 μg mL⁻¹) to a buffer solution (pH = 7.4) containing H₂O₂ (20 mM). After a certain period of incubation at 37 °C, the UV–vis spectrum of the residual H₂O₂ was recorded.
ESR measurements were carried out using a Bruker EMX A300 spectrometer. The water-soluble spin-label CTPO was used for the quantitative measurement of oxygen content via ESR spin-label oximetry. When these measurements were performed, 0.1 mM CTPO solution was added to 20 mM H₂O₂ solution in a phosphate buffer and bubbled with nitrogen for 15 min, followed by the addition of 50 μg mL⁻¹ DPP-Ir solution or 2 U mL⁻¹ catalase. The ESR spectrum was recorded immediately.

Transmission electron microscopy (TEM) images were used from a JEM 2100 Plus Microscope (JEOL Ltd., Tokyo, Japan) operating at 200 kV. The aberration‐corrected scanning transmission electron microscopy (AC‐STEM) images were collected by a JEM‐ARM200F transmission electron microscope, equipped with a probe spherical aberration corrector. The X‐ray diffraction (XRD) patterns were collected on a SmartLab X‐ray diffractometer with a scan rate of 2° min⁻¹ over the 2θ range of 10–60°. X‐ray photoelectron spectroscopy (XPS) (ESCALAB, 250Xi, Thermo Fisher Scientific, USA) was used to examine the chemical states of the catalysts. A series of X‐ray absorption fine structure (XAFS) spectra was collected at Shanghai Synchrotron Radiation Facility's BL14W1 station. Fe foil and Fe₂O₃ were used as references and measured simultaneously. The ROS levels were measured by electron spin resonance (ESR) investigations using a Bruker EMX A300 spectrometer.