Two-dimensional metal-organic framework nanoleaf embedded with nitrogen-doped carbon dots for monitoring of picric acid

A novel preparation of 2D metal–organic framework (Zn-MOF, ZIF-8) nanoleaf (ZIF-L) embedded with nitrogen-doped carbon dots (NCDs) was applied successfully. The NCDs are synthesized through hydrothermal treatment of citric acid and ethylenediamine exhibiting excitation wavelength independence (λ_{ex-independence}) of 6 nm and higher quantum yield reaches 84 %. The ZIF-L embedded with NCDs generates a 2D continuous framework of NCDs@ ZIF-L nanocomposite. The nanocomposite was fully characterized by FTIR, XRD, TEM, and N₂ adsorption-desorption mechanism. The XRD data reveals no significant change in the crystallinity of ZIF-L upon the encapsulation of NCDs, but it enhances the fluorescence emission. The synergetic cooperation between ZIF-L and NCDs might free active sites that lead to higher adsorption capacity and thus enhance their application in chemical sensing. The NCDs@ZIF-L nanocomposite synergistically combines active-rich-electron nanospaces with a high surface area, both of which are particularly beneficial for the selective detection of hazardous picric acid (PA) because of reinforced hydrogen bonding interactions with the hydroxyl groups of PA aromatic rings. The NCDs@ZIF-L framework is utilized to monitor PA as a nitro explosive compound in aqueous media exhibiting a high sensing activity and selectivity to detect PA in diluted solutions with a low detection limit (LOD) reaching 0.139 µM. The nanocomposite was also utilized in real water samples spiked with different concentrations of PA in tap water, with R % reaching 91.3–102 % and RSD % less than 5 %, showing their applicability to detect PA under circumstances.