A novel
coumarin derivative (
5
) was synthesized and
used as a colorimetric and fluorescent probe for selective detection
of Cu
2+
ions in the presence of other metal ions, with
the detection limits of 5.7 and 4.0 ppb, respectively. Cu
2+
ion reacts with probe
5
to form a 1:1 stoichiometry
complex, resulting in a remarkable redshift of absorption maximum
from 460 to 510 nm, as well as almost completely quenching fluorescence
intensity of probe
5
at the wavelength of 536 nm. These
changes can be distinctly observed by naked eyes. In addition, the
working pH range of probe
5
is wide and suitable for
physiological conditions, thus probe
5
may be used for
detection of Cu
2+
ions in living cells. The stable structures
of probe
5
and its 1:1 complex with Cu
2+
ion
were optimized at the PBE0/6-31+G(d) level of theory. The presence
and characteristics of bonds in compounds were studied through atoms
in a molecule and natural bond orbital analysis. The formation of
the complex led to a strong transfer of electron density from probe
5
as a ligand to Cu
2+
ion, resulting in breaking
the π-electron conjugated system, which is the cause of fluorescence
quenching and color change of
5-
Cu
2+
complex.
Zeolite imidazole framework-8 (ZIF-8) and the iron doped ZIF-8 (Fe-ZIF-8) were synthesized by the hydrothermal process. The obtained materials were characteristic of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), nitrogen adsorption/desorption isotherms, and atomic absorption spectroscopy (AAS). The results showed that the obtained Fe-ZIF-8 possessed the ZIF-8 structure with a large specific area. ZIF-8 and Fe-ZIF-8 were used for the removal of Remazol Deep Black (RDB) RGB dye from aqueous solutions. The various factors affecting adsorption such as pH, initial concentration, contact time, and temperature were investigated. The results showed that the introduction of iron into ZIF-8 provided a much larger adsorption capacity and faster adsorption kinetics than ZIF-8 without iron. The electrostatic interaction and π-π interaction between the aromatic rings of the RDB dye and the aromatic imidazolate rings of the adsorbent were responsible for the RDB adsorption. Moreover, the coordination of the nitrogen atoms and oxygen in carboxyl group in RDB molecules with the Fe2+ ions in the ZIF-8 framework played a vital role for the effective removal of RDB from aqueous solution.
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