Figure 4.

Evolution of (a) Br 3d doublet and (b) O 1s core level spectra with temperature. The topmost spectrum (in green) was measured at −50 °C. The other spectra were recorded at room temperature (RT, blue), after annealing to 220 °C (purple), 320 °C (red), and finally 410 °C (orange). The low binding energy component reflects carbonyl, whereas the high binding energy component is attributed to hydroxyl at low temperature and to a covalent C−O−B link at higher temperatures.