In
this study, the rhodamine 6G hydrazide (R6GH) complex was synthesized
to develop an “off–on” output platform for fluorescence
and visual dual-mode analysis of lead(II) (Pb2+). The prepared
R6GH complex using the heat to reflux reaction of rhodamine 6G (R6G)
and hydrazine hydrate was characterized through FT-IR, MS, 1H NMR, and 13C NMR and demonstrated to have good fluorescence
stability and reversibility. The microenvironment for Pb2+ detection has been optimized in detail. Under the optimal conditions,
the “off–on” R6GH-based fluorescence output platform
showed a good response to Pb2+ in the concentration range
of 0.05–6.0 μM (R
2 = 0.9851)
with a limit of detection (LOD) of 0.02 μM. Furthermore, at
three spiked Pb2+ levels in the selected agricultural (tap
water, soil) and food (fish, shrimp) samples, the developed R6GH-based
fluorescence assays obtained a significant recovery range of 84.0–102.0%
(RSD < 5.0%, n = 3), which had a good correlation
with the results from ICP-MS (R
2 = 0.9915).
The developed R6GH immobilized paper-based array sensor can reach
the lower LOD (2.5 μM) for Pb2+ through the naked
eye. By combining with LAB analysis, a good
linear response was obtained in the Pb2+ concentration
range of 1.0–50.0 μM. These results indicated that the
developed R6GH probe had great application potential in accurate detection
of fluorescence and rapid visual and semiquantitative screening for
Pb2+.