Date of Award
Master of Science (MS)
Na’il Saleh Ibrahim
A host−guest complex of 6-mercaptonicotinic acid (MNA) and cucurbit  uril (CB7) was prepared and conjugated to γ-Fe2O3 nanoparticles (NPs) to detect toxic cadmium ions in water as a solid-state sensor. The formation of an inclusion host−guest complex with CB7 was confirmed by UV−vis absorption and proton NMR spectroscopy. CB7 preferentially binds the protonated MNA form compared to the neutral form, demonstrated by a binding constant for the protonated form that is four orders of magnitude higher than the neutral form. An increase in the pKa of MNA by 1.2 units was demonstrated after the addition of CB7, which further supports preferential binding between MNA and CB7. The NMR results confirm binding to cadmium via the carboxylic acid moiety. Stationary and time-resolved fluorescence results, in solution and in the solid-state, indicate that cadmium and CB7 cause a blue shift in the MNA emission bands and extend its excited-state lifetime due to dissociation of the MNA dimer. In the solid-state, switching the emission signals between Cd2+-MNA/CB7NPs (ON state) and MNAH+/CB7NPs (OFF state) was achieved by controlling the pH. An efficient, regenerable, and stable sensor device was fabricated for the sensitive and selective detection of Cd2+ in contaminated water samples.
H. H. Alzard, Reem, "pH-Controlled Preferential Binding Of CucurbitUril-Coated Iron Oxide Nanoparticles To 6-Mercaptonicotinic Acid For Fluoroscent Detection Of Cadmium Ions In The Solid State" (2020). Chemistry Theses. 8.