Zeolitic Imidazolate Framework-8-Encapsulated Nanoparticle of Ag/Cu Composites Supported on Graphene Oxide: Synthesis and Antibacterial Activity

Abstract

The rational approach motivated the design of novel antimicrobial silver and silver-copper bimetallic nanoparticles contained within zeolitic imidazolate framework-8 supported on graphene oxide (GO), Ag@ZIF-8@GO, and AgCu@ZIF8@GO. In the resultant composites, ZIF-8 was able to prevent the stacking of GO sheets and also acted as a carrier for the nanoparticles within its cavities. GO, on the other hand, acted as an anchoring support enabling uniform dispersion of the nanocomposites, thus eliminating their aggregation. The morphological and physicochemical properties of the composites were determined through a variety of characterization techniques, for example, transmission electron microscopy, scanning electron microscopy, Fourier-transform infrared spectroscopy, p-X-ray diffraction (XRD), nitrogen sorption, and X-ray photoelectron spectroscopy (XPS). The energy-dispersive system and XPS supplied evidence of the presence of all expected components in the composites. The XRD provided proof of a crystalline, distorted ZIF-8 structure. Ag@ZIF8@GO and Ag-Cu@ZIF-8@GO composites were effective against both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria as determined by the disc diffusion method. The role of silver nanoparticles (AgNPs) in the antibacterial activity of both Ag@ZIF8@GO and AgCu@ZIF8@GO was highlighted as crucial in the probable pathway in the antimicrobial activity of the composites.

Figure 1

TEM images of (A) GO, (B) ZIF-8, and (C) ZIF-8@GO; (D) size distribution curve of ZIF-8; (E) size distribution curve of ZIF-8@GO.

Figure 2

TEM images of (A) AgNPs, (B) CuNPs, (C) Ag–Cu, (D) Ag@GO, (E) Cu@GO, and (F) Ag–Cu@GO.

Figure 3

TEM images of (A) Ag@ZIF-8@GO, (B) Cu@ZIF-8@GO, and (C) Ag–Cu@ZIF-8@GO.

Figure 4

SEM micrographs of (A) GO, (B) ZIF-8, and (C) (ZIF-8)@GO; (D) EDX graph of (ZIF-8)@GO.

Figure 5

SEM micrographs of (A) AgNPs, (B) CuNPs, (C) Ag–Cu, (D) Ag@GO, (E) Cu@GO, and (F) Ag–Cu@GO; EDS graphs of (G) Ag–Cu, (H) Ag–Cu@GO; mapping images of (I) Ag–Cu, (J) Ag–Cu@GO.

Figure 6

SEM micrographs of (A) Ag@ZIF-8@GO, (B) Cu@ZIF-8@GO, and (C) Ag–Cu@ZIF-8@GO; EDX graphs of (D) Ag@ZIF-8@GO, (E) Cu@ZIF-8@GO, and (F) Ag–Cu@ZIF-8@GO; mapping images of (G) Ag@ZIF-8@GO, (H) Cu@ZIF-8@GO, and (I) Ag–Cu@ZIF-8@GO.

Figure 7

FTIR spectra of (A) GO, ZIF-8, ZIF-8@GO composites, (B) expansion of FTIR section (2000–650 cm^–1) and C 1s XPS spectra of (C) GO, (D) ZIF-8, and (E) ZIF-8@GO.

Figure 8

XRD patterns of GO, ZIF-8, and ZIF-8@GO composites.

Figure 9

XRD patterns of (A) nanoparticles, (B) nanoparticles@GO, and (C) nanoparticles@ZIF-8@GO.

Figure 10

N₂ sorption isotherms of GO, ZIF-8, and ZIF-8@GO composite.

Figure 11

XPS spectra of Ag@ZIF-8@GO: (A) XPS survey spectrum, (B) binding energy spectrum for Ag 3d, (C) binding energy for N 1s, (D) binding energy for O 1s, (E) binding energy for C 1s, and (F) binding energy for Zn 2p.

Figure 12

XPS spectra of Cu@ZIF-8@GO: (A) XPS survey spectrum, (B) binding energy spectrum for Cu 2p, (C) binding energy for N 1s, (D) binding energy for O 1s, (E) binding energy for C 1s, and (F) binding energy for Zn 2p.

Figure 13

XPS spectra of Ag–Cu@ZIF-8@GO: (A) XPS survey spectrum, (B) binding energy spectrum for Ag 3d, (C) binding energy for N 1s, (D) binding energy for O 1s, (E) binding energy for C 1s, (F) binding energy for Zn 2p, and (G) binging energy for Cu 2p.

Figure 14

Photographic images of inhibition zone produced by the synthesized materials with (A–E) E. coli and (A′–E′) S. aureus.

Figure 15

Zone of inhibition against (A) E. coli and (B) S. aureus.

Figure 16

(A) synthesis of ZIF-8, (B) in situ growth of ZIF-8@GO with the nanoparticles carried inside ZIF-8. Adapted with permission from ACS Sustainable Chem. Eng. 2017,5, 11204–11214. Copyright 2017 American Chemical Society.

Figure 17

Illustration of measuring the zone of inhibition.