Ramanspectroscopywasperformed with a PerkinElmerRaman-Flex 400F analyzer equipped with a 785nm laser covering the spectral range of 230–3500cm−1 and providing 4 cm−1 peak resolution.The laser power was adjustable to up to 10mW. A 5-meter steel-encased fiber optic probe was used for data collection with a stainless-steel housing (0.5 in diameter, 8 in length) mounted at the end. All Raman data were collected with automatic background subtraction and baseline correction. Other experimental parameters(exposure time, number of scans for each acquisition, laser power, etc.) were adjusted case-by-case based on material properties and experimental purpose. The Raman analyzer was enabled for constant data acquisition at fixed frequency. The overall exposure
time of each acquisition, however, could not exceed the time interval corresponding to the frequency selected