Dual-state
emitters (DSEs) are entities that exhibit fluorescence
in both the solution and solid state, which open up a wide range of
possibilities for their utilization in various fields. The development
of detection platforms using intrinsic luminescent metal–organic
frameworks (LMOFs) is highly desirable for a variety of applications.
DSE MOFs as a subclass of intrinsic LMOFs are highly attractive due
to no need for encapsulation/functionalization by fluorophores and/or
using luminescent linkers. Herein, a highly stable intrinsic dual-state
blue emission (λem = 425 nm) zinc-based MOF with
rodlike nanostructures (denoted as UoZ-2) was synthesized and characterized.
To the best of our knowledge, intrinsic DSE of Zn-MOFs with blue emission
in the dispersed form in solution and solid-state fluorescence have
not been reported yet. When tetracycline (TC) was added, a continuous
color evolution from blue to greenish-yellow with dramatic enhancement
was observed due to aggregation induced emission (AIE). Thus, a sensitive
ratiometry-based visual detection platform, in solution and on paper
independently, was designed for detection of TC exploiting the DSE
and AIE properties of UoZ-2 alone and UoZ-2:TC. The detection limit
was estimated to be 4.5 nM, which is considered to be one of the most
sensitive ratiometric fluorescent probes for TC sensing. The ratiometry
paper-based UoZ-2 sensor displays a reliable TC quantitative analysis
by recognizing RGB values in the on-site TC detection with satisfactory
recoveries.