Fluorescence detection of hazardous metals using polyaniline-supported layered double hydroxide nanocomposite

Abstract

Within the framework of this research paper, the hybrid composite composed of polyaniline/layered double hydroxide (PANI@Nd-Co/LDH) is regarded as a versatile substance under solvothermal conditions. A systematic structural and morphological analysis of PANI@Nd-Co/LDH was performed utilizing a diverse array of analytical methods, including Powder X-ray Diffraction (PXRD), Fourier Transform Infrared (FT-IR), Thermogravimetric Analysis (TGA) and Differential Thermal Analysis (DTA), and Scanning Electron Microscope (SEM). The synthesis approach involved polymerization to fabricate PANI@Nd-Co/LDH, which functions as a sensor enabling exceptionally sensitive and specific fluorescence detection of Pb(II) and Al(III) in comparison to other prevalent heavy metal ions. The sensor exhibits a fluorescence response characterized by “turn-off” behavior for Pb(II) ions, while it exhibits a fluorescence response marked by “turn-on” behavior when detecting Al(III) ions. With conditions optimized, the minimum detectable limit (MDL) was determined to be 9.6 nM for Pb(II) and 220 nM for Al(III), respectively. These results are consistent with the most minimal limits of detection (LOD) documented in the literature. Additionally, PANI@Nd-Co/LDH can be easily regenerated and employed for a minimum of three cycles by a straightforward process involving filtration and repetitive water washing. The detection mechanism is attributed to the inner filter effect (IFE), which occurs due to the concurrence of the emission and excitation spectra of PANI@Nd-Co/LDH with the absorption spectra of Pb(II). In contrast, the increased fluorescence observed for Al(III) can be linked to the chelation enhanced fluorescence (CHEF) effect, also known as the chelation-enhanced fluorescence phenomenon. These findings suggest that PANI@Nd-Co/LDH demonstrates excellent potential for detecting and/or recognizing Pb(II) and Al(III).