The Decoration of ZnO Nanoparticles by Gamma Aminobutyric Acid, Curcumin Derivative and Silver Nanoparticles: Synthesis, Characterization and Antibacterial Evaluation

Abstract

Zinc oxide nanoparticles (ZnO NPs) are applied in various applications in catalysis, biosensing, imaging, and as antibacterial agents. Here we to prepare ZnO nanomaterials decorated by γ-amino butyric acid (GABA), curcumin derivatives (CurBF₂) and silver nanoparticles (CurBF₂-AgNPs). The structures of all ZnO nanostructures were characterized using Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), UV-VIS spectrophotometry, fluorescence spectrophotometry, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HR-TEM). Further, their antibacterial activities against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria were investigated through analysis of minimum inhibitory concentration (MIC) method. Among the prepared nanostructures, the ZnO NPs-GABA/CurBF₂-AgNPs showed excellent antibacterial activity against both Gram-positive and -negative bacteria. ZnO NPs fabricated here may have potential use in future anti-bacterial compositions and coatings technologies.

Keywords: ZnO nanoparticles; antibacterial activity; curcumin derivative; gamma-aminobutyric acid; surface functionalization.

Scheme 1

Synthetic scheme of the fluoroboronated curcumin derivative CurBF₂.

Scheme 2

Schematic representation of synthesis of ZnO NPs-GABA, ZnO NPs-GABA-CurBF₂ and CurBF₂-AgNPs decorated on ZnO NPs-GABA. GABA binds to the ZnO NP surface via an amine group during synthesis, driving NP growth towards rod-like shapes and leaving carboxylic groups available at the particle surface. Following activation of those carboxylic groups, a fluoroboronated curcumin could be coupled via an ester linkage.

Figure 1

(a) UV–VIS spectrum of CurBF₂-AgNPs, (b) TEM image of CurBF₂-AgNPs, inset the average diameter of 7.75 ± 2.26 nm (n = 70).

Figure 2

(a) SEM image of ZnO NPs, (b) FIB-SEM images of ZnO NPs-GABA, (c) ZnO NPs-GABA-CurBF₂, and (d) ZnO NPs-GABA/CurBF₂-AgNPs.

Figure 3

(a) TEM image of ZnO NPs, (b) TEM and (c) HRTEM images of ZnO NPs-GABA, (d) TEM and (e) HRTEM images of ZnO NPs-GABA-CurBF₂, and (f) TEM image of ZnO NPs-GABA/CurBF₂-AgNPs.

Figure 4

XRD patterns of ZnO NPs, ZnO NPs-GABA, ZnO NPs-GABA-CurBF₂ and ZnO NPs-GABA/CurBF₂-AgNPs powder (the * on top of each peak in the ZnO NPs-GABA, ZnO NPs-GABA-CurBF₂, and ZnO NPs-GABA/CurBF₂-AgNPs diffractograms are peaks that also appear for ZnO NPs).

Figure 5

FTIR spectra of CurBF₂, ZnO NPs-GABA/CurBF₂-AgNPs, ZnO NPs-GABA-CurBF₂, ZnO NPs-GABA, and ZnO NPs.

Figure 6

(a) UV–VIS diffuse reflectance spectra of free GABA and CurBF₂, and powders of ZnO NPs, ZnO NPs-GABA, ZnO NPs-GABA-CurBF₂, and ZnO NPs-GABA/CurBF₂-AgNPs at room temperature. (b) Fluorescence spectra of ZnO NPs, ZnO NPs-GABA, ZnO NPs-GABA-CurBF₂, and ZnO NPs-GABA/CurBF₂-AgNPs with slit widths at 5 nm/5 nm excited at 260 nm.

Figure 7

Antimicrobial activity of (i) CurBF₂-AgNPs (ii) ZnO-GABA/CurBF₂-AgNPs, (iii) gentamicin, (iv) DI water against (a) E. coli and (b) S. aureus.