Paper SS-TuP2
Reaction of ZnO Nanomaterial with a Mixture of Gas-phase Prop-2-ynoic acid and Acetic Acid to Control Surface Coverage of Reactive Functional Groups

Tuesday, October 22, 2019, 6:30 pm, Room Union Station B

Sensitization of oxide nanomaterials with a two-step process involving the reaction with gas-phase prop-2-ynoic acid followed by “click” attachment of functionalized azides to the resulting alkyne functionality has been recently reported by our group. One advantage of the first modification step being a gas phase reaction with a nanomaterial is in the ability to control surface concentration of alkyne functionality by dosing predetermined mixtures of prop-2-ynoic acid with another compound (in this case acetic acid) that reacts with the oxide surface in exactly the same way as prop-2-ynoic acid but does not lead to the formation of a reactive functionality to be utilized in the second step of sensitization. This approach is demonstrated for the mixture of these acids reacting with ZnO nanomaterial, and the concentration of surface alkyne functional groups is determined by the concentration of the prop-2-ynoic acid in the mixture with acetic acid. The resulting functionalized surface is interrogated by infrared spectroscopy to demonstrate that both acids co-adsorb on ZnO. Vibrational signatures of the CH₃ group at 1453 cm^-1 and that of the alkyne group at 2110 cm^-1 allow for quantification of the co-adsorbed species. This assessment is confirmed by the XPS investigation utilizing different ratios of the C 1s features corresponding to carboxylates compared to the methyl/alkyne carbon atoms in mixtures of pro-2ynoic and acetic acids. Solid state NMR spectroscopy is used to further confirm the formation and to quantify the concentration of two components in the mixed monolayer.