Fig. 3: Deciphering the phenoxy radical (PhO·) intermediate of PhOH oxidation and elucidating the crucial decontamination contribution of in situ formed CuIII.
From: Proton-coupled electron transfer controls peroxide activation initiated by a solid-water interface
A The MALDI-TOF-MS spectrum of the oxidation products of 2,6-M-PhOH washed with toluene. The inset in (A) is a partially magnified view of the MALDI-TOF-MS spectrum. It can be seen that the mean mass interval of 120.1 corresponds to the polymeric unit of poly-(2,6-dimethyl-1,4-phenylene oxide) (PPO), as well as a schematic of the polymerization reaction pathway. B The high-resolution mass spectrum of the oxidation products of 2,6-M-PhOH washed with ethanol. The exact theoretical mass of 3,3′,5,5′-tetramethyldiphenoquinone (positive ion acquisition mode, +H) is 241.1228, which agrees with the experimental value in (B) (i.e., 241.1308). The inset in (B) shows a schematic of the surface coupling reaction pathway. The results from (A and B) indicate that the predominant formation is of the PhO· intermediate during PhOH oxidation. C EPR spectra of the CuO/PMS system at pH 6.8, 7.4, and 9.0 with 0.1-M DMPO as a spin-trapping agent. The positive correlation between the EPR peak height and the kinetic activity indicates that the pH-dependent production of CuIII occurs. Experimental conditions: [PMS] = 0.3 mM, [CuO] = 0.2 g L–1, T = 25 ± 2 °C, 0.2 M borate buffer. D The ultraviolet-visible spectrum of the CuIII-periodate complex showed a distinct light absorption at 420 nm, indicating the formation of CuIII. Experimental conditions: [NaIO4] = 0.5 mM, [PhOH] = 0.15 mM, [PMS] = 0.3 mM, [CuO] = 0.2 g L–1, T = 25 ± 2 °C, pH = 7.4, 0.2 M borate buffer.
