Preparation of multicolor luminescence Schiff-base compound based on solvent control and its application in the detection of pentachloronitrobenzene

Fluorescent materials with tunable optical properties are critical to their potential application. So far, the tuning of double-color luminescence has been easily achieved for many organic materials, but there are very few reports on multicolor luminescence materials. In this work, a multicolor emissions Schiff-base fluorescent compound 1,1'-{4,4′-Biphenyldiylbis[nitrilo(E)methylylidene]}di(2-naphthol) (BPDN) with an aggregation induced emission (AIE) characteristic was synthesized, and its luminescent characteristic was investigated. The BPDN molecules with low concentration in solution can emit faint light, but a new AIE phenomenon will appear when the BPDN molecules are aggregated in the solvent with low solubility or high concentration. The color and efficiency of the AIE of BPDN can be tuned by changing its aggregation state: the luminescence of the aggregate gradually redshifts (blue, green, to orange) as the solvent with poor solubility in the mixture increases or increasing the concentration of the BPDN. Based on the multicolor luminescence BPDN, a molecularly imprinted ratiometric fluorescent probe test strip (MIRF test strip) had been prepared and successfully applied to visual detection of pentachloronitrobenzene (PCNB). The color of test strip could change gradually from orange to yellow to green with the increase of the concentration of PCNB. This work shows the characteristic and application of multicolor luminescence BPDN.