Low-energy electron-induced reactions in thin films of glucose and N-acetyl-glucosamine

Reactions induced in thin films of α-d-glucose and N-acetylglucosamine by low-energy electron exposure at incident electron energies (E₀) between 5 eV and 15 eV have been investigated by high-resolution electron energy loss spectroscopy (HREELS). The reactions of α-d-glucose upon electron exposure were also studied in the presence of molecular oxygen. Electron exposure leads to characteristic changes of the vibrational spectra indicating that OH groups are lost with the formation of CC double bonds taking place preferentially above the ionisation threshold of the investigated molecules. At lower E₀, OH groups are equally decomposed suggesting that dissociative electron attachment contributes to the reactions but formation of double bonds is not observed. The results show that different reaction channels are effective depending on E₀ and that the outcome of electron-driven chemistry in saccharides may be controlled by changing from the subionisation regime to E₀ above the ionisation threshold. Generally, low-energy electron exposure in the absence of O₂ produces a material with lower oxygen content, i.e. leads to a reduction of the saccharide. In the case of N-acetylglucosamine, removal of the amide group from the sugar is also important at subionisation energies. In contrast, as shown for α-d-glucose, low-energy electron exposure in the presence of O₂ leads to oxidation of the sugar even at cryogenic temperature.