Influence of the Nature of Self-Assembled Monolayers on Their Reactivity under Ionizing Radiation: A Solid-State NMR Study

Abstract

The behavior of different nanoporous grafted silicas (−Si(CH 3 ) 2 R) under ionizing radiation is investigated as a function of the chemical nature of the grafting. The structure and reactivity of the grafting after irradiation is characterized by solid-state NMR spectroscopy. The chemical reactivity is also investigated by mass spectrometry gas analysis . The major gases detected after irradiation are H 2 and/or CH 4 . Different types of behaviors under ionizing radiation are depicted as a function of R. When R contains an aromatic ring or is the cyclopentadienyl moiety, then the overall measured radiolytic yields are low and CH 4 is the major gas detected. The aromatic ring acts as an efficient energy trap. When R contains an alkyl chain with a −CN ending, the major gas detected is dihydrogen due to the lysis of the −CH(H) bond, but it is also shown that the −CN group acts as an energy trap, even if it is of course less efficient than an aromatic ring. When R consists of a long alkyl chain, an efficient energy transfer occurs at the interface and leads to a significant H 2 production due to the lysis of the −CH(H)− bond. Lastly, when R is small (a methyl or an ethyl group), the situation is different and the Si−C bond is preferentially cleaved over the C−H bond.

Hydrogen production on nano Al2O3 surface by water splitting using gamma radiation

“…The samples were exposed to gamma rays at an isotope 60 Co with a dose rate of P = 1.04 kGy/h. The dose rate was defined by Ferrosulfate dosimetry 25‐31 . A system made of d = 5–50 nm sized and double distilled water was utilized.…”

“…The dose rate was defined by Ferrosulfate dosimetry. [25][26][27][28][29][30][31] A system made of d = 5-50 nm sized and double distilled water was utilized. 5 mL solution was taken and packed in glass ampoules (15 mL).…”

“…The yields and mechanism of the transitory species and molecular products generated by water radiolysis have been studied in detail in previous articles. [26][27][28][29][30][31][32][33] Based on the literature and experimental results, the following mechanism is proposed.…”

Grafted mesoporous silicas for radionuclide uptake: Radiolytic stability under electron irradiation

“…Iqbal et al [23,27] evidenced no or little reduction of the sorption ability of ethylenediaminetetraacetic acid, aminopropyl and N-propylsalicyl-aldimino grafted SBA-15 irradiated up to 1 kGy. In the case of grafted controlled pore glasses, electron irradiation was performed up to a dose of 500 kGy [29][30] and significant modifications of the materials could be evidenced, depending on the nature of the grafted molecules. In these studies, ionizing radiation creates electron-hole pairs within the material that can recombine to form excitons if the walls of the materials are thick enough [31].…”