In Situ Synthesis of Nanostructured Composites of NiFe Layered Double Hydroxide and Polyaniline for Photocatalytic Degradation of Organic Pollutants and Remediation of Biological Contaminants

Abstract

The present work discusses on the development of a solid-state mediator Ag0-based-Z-scheme LDH/PANI/MAA/Ag heterojunction nanocomposite with an intimate morphological contact interface through an electrostatic self-assembly strategy. Here, an Ag0-decorated layered double hydroxide (LDH) nanosheet-based polymeric nanocomposite has been synthesized by ultrasonic treatment of NiFe LDH with aniline followed by in situ polymerization-stabilization and adsorption-reduction of Ag+ ions at low temperatures. In this synthesis, a mercaptoacetic acid (MAA)-functionalized polyaniline (PANI) promotes the exfoliation of NiFe LDH and stabilizes the nanosheets (LDH) followed by successful adsorption-reduction of Ag+ ions by its chelating groups to Ag0. The synthesized ternary photocatalyst displayed an enhanced photocatalytic degradation of emerging pollutants (Ciprofloxacin: 97.4%, Reactive Blue 4: 97.7%, and Safranin: 93.1% of degradation) under sunlight irradiation within 80 min. The enhanced photocatalytic performance of the LDH/PANI/MAA/Ag nanocomposite indicates a synergistic effect on electron transfer over components, which is systematically identified by the delayed electron–hole recombination as supported by photoluminescence and electrochemical impedance spectroscopy measurements as well as photostability of the material supported by the chronoamperometry analysis. The synthesized LDH/PANI/MAA/Ag nanocomposite possesses a large specific surface area and an excellent interface between LDH nanosheets, PANI/MAA, and Ag0, which has been confirmed from the N2 sorption isotherm, transmission electron microscopy, and high-resolution transmission electron microscopy studies. In addition, the antibacterial potential against Bacillus pumilus (Gram-positive) and Escherichia coli (Gram-negative) bacteria authenticates further advancement of the LDH/PANI/MAA/Ag nanocomposite as a potent material composition.

In Situ Synthesis of Exfoliated Ni(OH)2 Nanosheets and AgNPs-Embedded Functionalized Polyindole-Based Trinary Hybrid Microspheres: A Z-Scheme Photocatalyst for the Sunlight-Driven Degradation of Organic Pollutants with Enhanced Antibacterial Efficacy

“…In addition, two more satellite peaks are observed at 861.1 and 879.3 eV . In contrast, both the deconvoluted Ni 2p high-resolution spectra of binary NH/PIn/MAA and ternary NH/PIn/MAA/Ag heterostructures show a positive shifting in the binding energy of about 0.6–0.8 eV (Figure a), suggesting prominent interactions between NH moieties with the other constituents via reduction of outer electron cloud density. − In the deconvoluted O 1s XPS spectrum of Ni(OH) 2 microflowers, three well-defined peaks at 529.0, 529.9, and 531.2 eV are, respectively, attributed to lattice oxygen (M–O–M, where M = Ni), surface hydroxyl group, and adsorbed water (Figure b). ,, For both NH/PIn/MAA and NH/PIn/MAA/Ag, the O 1s spectrum can be deconvoluted to four distinct XPS peaks, where one peak is associated with the lattice oxygen (M–O–M, where M = Ni), one is for the surface hydroxyl group, and the remaining two are designated for the carboxyl oxygens of the MAA moieties (Figure b) . The peaks for NH/PIn/MAA at 284.3, 285.6, and 286.8 eV and for NH/PIn/MAA/Ag at 284.5, 285.9, and 286.8 eV in the deconvoluted XPS spectra of C 1s (Figure S6a) correspond to CC, C–N/C–S, and O–CO bonds, respectively, suggesting the existence of polymer moieties in both the microspheres.…”

“…(iii) The electron-rich functionalities (−SH, −COO – , and −NH−) of the polymeric framework (PIn/MAA) readily attracted the Ag + ions during the adsorption of the silver salt precursor (AgNO 3 ) onto the active sites of the composite due to the high chelating capacity of Ag + ions . In addition, during the sorption process at room temperature or low temperature, the functional groups of the polymer framework, such as −SH and −NH–, reduced the adsorbed Ag + ions with a high standard reduction potential to plasmonic silver (Ag 0 ) or metallic nanosilver (AgNP) . For a more in-depth understanding of the formation pathways of the NH/PIn/MAA/Ag microspheres, XRD, FESEM, TEM, and XPS analyses were performed.…”