posted on 2015-07-06, 00:00authored byDebal Kanti Singha, Partha Mahata
A new
metal–organic framework [Co(OBA)(DATZ)0.5(H2O)] {OBA = 4,4′-oxybis(benzoic acid) and DATZ
= 3,5-diamino-1,2,4-triazole}, 1, was synthesized by
hydrothermal reaction. Single-crystal X-ray data of 1 confirmed two-dimensional rhombus grid network topology with a free
nitrogen site of triazole ring and two amine groups of each DATZ.
Photoluminescence study of 1 in aqueous medium shows
blue emission at 407 nm upon excitation at 283 nm. This emissive property
was used for the sensing of Al3+ ions in aqueous medium
through very high luminescence turn-on (6.3-fold) along with the blue
shifting (∼24 nm) of the emission peak. However, luminescence
studies in the presence of other common metal ions such as Mg2+, Zn2+, Ni2+, Co2+, Mn2+, K+, Na+, Ca2+, Cd2+, Hg2+, Cu2+, Fe2+, Fe3+, and Cr3+ in aqueous medium shows luminescence
quenching in varying extent. Interestingly, the luminescence turn-on-based
selectivity of Al3+ ions in aqueous medium was achieved
even in the presence of the highest quenchable metal ion, Fe3+. Furthermore, very high sensitivity was observed in the case of
Al3+ ions with a limit of detection of Al3+ of
57.5 ppb, which is significantly lower than the higher limit of U.S.
Environmental Protection Agency recommendation of Al3+ ion
for drinking water (200 ppb).