Vibrational spectroscopy of nitroaromatic self-assembled monolayers under extreme conditions

Vibrational spectra up to 8 GPa and 600 °C were obtained for self-assembled monolayers (SAMs) on noble metal surfaces of the energetic material simulant 4-nitrobenzenethiol (NBT). The high-pressure measurements used a surface-enhanced Raman sensor. The high-temperature measurements used femtosecond laser flash-heating and nonlinear coherent vibrational spectroscopy. The SAM nitro stretching transition ν NO 2 s is insensitive to flash-heating where there is no time for chemical reactivity or thermal expansion. A large pressure broadening in ν NO 2 s of the SAM but not in solid NBT was associated with surface adlayer rearrangement. The implications for time-resolved measurements of shock-compressed energetic materials are discussed.