As
a special heavy metal ion, copper ions (Cu2+) play
an indispensable role in the fields of environmental protection and
safety. Their excessive intake not only easily leads to diseases but
also affects human health. Therefore, it is particularly important
to construct a facile, effective, and highly selective Cu2+ probe. Herein, a novel Zr–tetraphenylporphyrin tetrasulfonic
acid hydrate (TPPS) metal–organic framework (ZTM) was fabricated
using TPPS as the ligand and exhibited strong red fluorescence with
a high quantum yield of 12.22%. In addition, we designed a ratiometric
fluorescent probe by introducing green fluorescein isothiocyanate
(FITC), which was not subject to environmental interference and had
high accuracy. When exposed to different amounts of Cu2+, the fluorescence emission at 667 nm from ZTMs is remarkably quenched,
while that at 515 nm from FITC is enhanced, accompanied by a change
in the solutions’ fluorescence color from red to green under
a UV lamp. Besides, the ZTMs solutions display an excellent ratiometric
colorimetric response for Cu2+ and produce an obvious color
change (from green to colorless) that is visible to the naked eye.
The fabricated ZTMs@FITC fluorescent probe exhibits distinguished
performance for Cu2+ detection with linear ranges of 0.1
to 5 μM and 5 to 50 μM, as well as a low detection limit
of 5.61 nM. Moreover, a colorimetric sensor based on ZTMs exhibits
a good linear range from 0.1 to 20 μM for Cu2+ with
the detection limit of 4.96 nM. Furthermore, the dual-signal ratiometric
sensor has significant specificity for Cu2+ and is successfully
applied for monitoring Cu2+ in water samples, which proves
its practical application value in the environment and biological
systems.
On account of the excessive residues and serious detriments, it is imminent to develop an efficient method to determine tetracyclines (TCs) for protecting human health. In this work, a novel ratiometric fluorescence sensor was constructed for TCs based on a powerful boron nitride quantum dot and europium ion (BNQD-Eu 3+ ) system. The blue-emitting BNQDs were synthesized via a facile hydrothermal route using boric acid and urea as precursors. When TCs were presented in the hybrid probe of BNQDs and Eu 3+ , blue fluorescence of BNQDs was quenched and red fluorescence of Eu 3+ was enhanced, which can be attributed to the inner filter effect, photo-induced electron transfer, as well as the antenna effect. Besides, it was confirmed that the proposed sensor possessed good detection limits of 0.019, 0.104, and 0.028 μM for tetracycline (TET), oxytetracycline, and doxycycline, respectively. Additionally, the results of BNQD-Eu 3+ -based sensing of TET in milk and beef samples showed an insignificant difference from those of liquid chromatography−mass spectrometry. Moreover, the BNQD-Eu 3+ -based test paper was successfully used in the easy and visual detection of TCs by the naked eyes, indicating the practical applicability of the sensor.
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