Chiral dual-emission composite material fluorescein/CCQDs @ZIF-8 for highly efficient recognition of phenylenediamine isomers and their oxidized product.

Abstract

As a new type of fluorescent nanomaterial, chiral carbon quantum dots (CCQDs) have the advantages of wide source, good water solubility and high chemical stability, and have been widely used in drug detection, bioimaging and chemical sensing. In this work, a chiral dual-emission hybrid material fluorescein/CCQDs@ZIF-8 (1) was synthesized by in-situ encapsulation strategy. Luminescence emission position of CCQDs and fluorescein are almost unchanged after the encapsulation into ZIF-8. The luminescent emissions of CCQDs and fluorescein can be observed to be located at 430nm and 513nm, respectively. When 1 is soaked in pure water, ethanol, dimethylsulfoxide, DMF, DMA and targeted substances solution for 24h, 1 can maintain its structural stability. Photo-luminescent (PL) studies show that 1 can discriminate p-phenylenediamine (PPD) from m-phenylenediamine (MPD) and o-phenylenediamine (OPD), which can detect the presence of PPD with high sensitivity and selectivity (ratiomeric fluorescent probe with KBH: 1.85×103 M-1 and detection limit: 8.51μM). Further, 1 also effectively distinguish the oxidized product of these phenylenediamine(PD) isomers. 1 can be used as a "turn-off" fluorescent probe to detect oxidized product of PPD (ratiomeric fluorescent probe with KSV: 6.82×102 M-1 and detection limit: 0.112mM) and a "turn-on" fluorescent probe to detect oxidized product of MPD (ratiomeric fluorescent probe: KBH: 1.65×103 M-1 and detection limit: 35.03μM) and oxidized product of OPD (ratiomeric fluorescent probe: KBH: 2.40×106 M-1 and detection limit: 0.105μM). Further, for the convenience of practical application, 1 can be developed as fluorescence ink and be prepared into a mixed matrix membrane. When the target substances are gradually added to the membrane, significant luminescence change with obvious color change can be observed.