Lanthanide and functionalization-free dual-state emitting zinc-based MOFs followed by dual-state detection: ratiometric and color-tonality visual detection of tetracycline in solution and on paper in food and environmental samples.

An efficient dual-state blue-emitting zinc-based metal-organic frameworks (MOFs), designated as UoZ-8 has been developed. Coordination-induced emission causes the UoZ-8 to give the blue emission in both solid and dispersed form in liquid. Upon the addition of tetracycline (TC), a noticeable shift from blue emission to greenish-yellow emission occurred, with a marked increase in intensity, which was attributed to the inner filter effect accompanied by aggregation-induced emission (IFE-AIE). Consequently, ratiometric-based fluorometry (in solution) and color tonality visual detection platform (on paper) were developed, exploiting the dual-state property of UoZ-8 alone and UoZ-8:TC. The detection limit using the ratiometric-based fluorescence method was 3.8 nM, while on paper it was 3.5 µM. Paper-based visual mode was used for the detection of TC in tap and river water samples showing satisfactory accuracy and precision.