Development of novel reduced graphene oxide/metalloporphyrin nanocomposite with photocatalytic and antimicrobial activity for potential wastewater treatment and medical applications

Abstract

This research investigates a novel nanocomposite material composed of reduced graphene oxide (rGO) and nickel-5,15-bisdodecylporphyrin (Ni-BDP) nanoparticles for the effective removal of methyl orange (MO), a harmful synthetic dye, from water. The structure and composition of the synthesized rGO/Ni-BDP nanocomposite were characterized using high-resolution transmission electron microscopy (HR-TEM), Raman spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry, and ultraviolet-visible (UV-Vis) spectroscopy. The study demonstrates the material's efficacy as both a catalyst and adsorbent for MO removal. Optimal performance was observed at pH 3.0, where the positively charged nanocomposite surface facilitated strong interactions with negatively charged MO molecules, leading to enhanced photocatalytic activity. Under these conditions, 0.01 g of the nanocomposite achieved an impressive 86.2% MO removal efficiency. Furthermore, the study explored the reusability of the rGO/Ni-BDP nanocomposite in repeated cycles of photocatalytic MO degradation under visible light irradiation. While exhibiting some decrease in efficiency over five cycles, the nanocomposite maintained a respectable degradation rate even after multiple uses. Finally, the antimicrobial properties of the nanocomposite were evaluated against both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria exhibiting a zone of inhibition measuring 23 mm and 26, respectively. The minimum inhibitory concentration (MIC) values of 2.50 µg/ml and 1.25 µg/ml for Escherichia coli and Staphylococcus aureus, respectively. The results revealed significant antibacterial activity, demonstrating the broad-spectrum efficacy of the rGO/Ni-BDP nanocomposite. This research underscores the potential of the rGO/Ni-BDP nanocomposite as a versatile material for environmental remediation and antibacterial applications.

Keywords: Antimicrobial activity; Metalloporphyrins; Methyl orange; Nanocomposite; Nickel; Photocatalysis; Reduced graphene oxide; Water treatment.

Fig. 1

Chemical structure of Nickel-5,15-bisdodecylporphyrin (Ni-BDP). In the context of Ni-BDP modeling, the constituent elements comprising carbon-hydrogen-nitrogen (C-H-N) and Nickel (Ni) atoms are depicted using distinct colors, specifically grey-white-blue for the former and green for the latter.

Fig. 2

The photocatalytic setups for (a) UV, and (b) visible light, irradiation.

Fig. 3

(a) TEM image, (b) Raman spectrum, (c) UV-Visible absorption spectrum of the produced rGO.

Fig. 4

UV-Visible spectra (in CHCl₃) of rGO, Ni-BDP, and rGO/Ni-BDP nanocomposite.

Fig. 5

HR-TEM images of (a) rGO nanosheets and (b) rGO-NiBDP NPs.

Fig. 6

(a) UV-Visible spectrum of MO (10 mg/L), (b) Removal % of MO via: photolysis without catalyst, adsorption in dark on rGO/Ni-BDP nanocomposite surface, photocatalysis under UV irradiation, and photocatalysis under visible light irradiation. (c) UV-Visible spectrum illustrating the complete degradation of MO.

Fig. 7

(a) MO removal rates changed over time at four different solution pHs (3.0, 5.0, 7.0, and 9.0) (10 mg of rGO/Ni-BDP nanocomposite in 50 ml of 10 mg/L MO at 25 °C), (b) Point of zero charge of rGO/Ni-BDP nanocomposite at different pH values.

Fig. 8

(a) The variation of removal % as a function of contact time at different initial MO concentration (5–15 mg/L) with 10.0 mg rGO/Ni-BDP nanocomposite at pH 3.0, (b) Effect of the nanocatalyst amount (5–15 mg) on removal efficacy (10 mg/L MO solution, Temperature = 25 °C and pH 3.0).

Fig. 9

(a) Pseudo-first-order reaction model for MO degradation under visible-light irradiation (MO initial concentrations (5–15 mg/L), (b) The relation of apparent pseudo-first-order rate constants vs. initial concentration of MO.

Fig. 10

A proposed photocatalytic reaction mechanism for MO photodegradation by rGO/Ni-BDP nanocomposite.

Fig. 11

Effect of scavengers on MO degradation over rGO/Ni-BDP nanocomposite.

Fig. 12

The bar graph shows zone of inhibition produced by rGO/Ni-BDP NPs (10 and 20.0 µg/ml) against standard gentamycin antibiotic (10.0 µg/disc).

Fig. 13

Schematic representation of the main pathways underlying the antibacterial potential of the rGO/Ni-BDP NPs: (I) Adheres of rGO/Ni-BDP NPs to and wrap the bacterial cell surface, resulting in damage of bacterial cell. (II) rGO/Ni-BDP NPs penetrate the microbial cells and affect the respective cellular machinery. (III) rGO/Ni-BDP NPs creates and increases ROS, leading to cell damage. (IV) rGO/Ni-BDP NPs modulates the cellular signal system and causing cell death. (V) Finally, rGO/Ni-BDP NPs block the ion transport from and to the microbial cells.