Loading of green-synthesized cu nanoparticles on Ag complex containing 1,3,5-triazine Schiff base with enhanced antimicrobial activities

Abstract

The physicochemical properties of materials change significantly in nanometer dimensions. Therefore, several methods have been proposed for the synthesis of nanoparticles. Plant extracts and essential oils are applied as natural and economic resources to prepare nanomaterials especially metal nanoparticles. In this project, a green, simple and efficient method has been designed for the synthesis of Cu nanoparticles using Purple cabbage extract as a reducing and stabilizing agent. They were successfully loaded onto a new Ag complex containing 1,3,5-triazine Schiff base as ligand to form Cu@Ag-CPX nanocomposite. Phytochemical contents of extract were identified by standard qualitative analyses. The chemical structure of all synthesized compounds was characterized using spectral data. In FT-IR, coordination of C=N bond of Schiff base ligand to Ag⁺ ions shifted the absorption band from 1641 to 1632 cm^-1. The UV-Vis spectrum of Cu@Ag-CPX nanocomposite shown the peak related to Cu nanoparticles in the region of around 251 nm. 5:7 molar ratio of Cu to Ag in Cu@Ag-CPX was determined using ICP-OES. The FESEM, TEM, and DLS techniques provided valuable insights into the morphology and size distribution of the nanocomposite, revealing the presence of rods and monodispersed particles with specific diameter ranges. These analyses of the nanocomposite displayed rods with diameters from 40 to 62 nm as well as monodispersed and uniform particles with average diameter of 45 nm, respectively. The presence of elements including carbon, nitrogen, oxygen, Cu and Ag was proved by EDX-EDS analysis. The XRD pattern of Cu@Ag-CPX shown the diffraction peaks of Cu and Ag particles at 2θ values of 10°-80°, and confirmed its crystalline nature. The inhibitory properties of the synthesized compounds were evaluated in vitro against four Gram-negative and two Gram-positive bacteria, as well as two fungal strains. The MIC, MBC and MFC values obtained from microdilution and streak plate sensitivity tests were ranged from 128 to 4096 µg ml^-1. While Cu nanoparticles and Ag complexes were effective against some pathogens, they were not effective against all them. However, the growth of all tested microbial strains was inhibited by Cu@Ag-CPX nanocomposite, and makes it as a new promising antimicrobial agent. Modification of nanocomposite in terms of nanoparticle and complex can improve its blocking activities.

Figure 1

Various phytochemicals of Purple cabbage.

Scheme 1:

Schematic synthesis of Cu@Ag-CPX nanocomposite.

Scheme 2:

Possible mechanism of the formation of Cu NPs in the presence of purple cabbage extract.

Figure 2

FT-IR spectra of Schiff base (a), Cu@Ag-CPX nanocomposite (b) and Ag-CPX complex (c).

Figure 3

UV–Vis spectra of (A) Cu NP, Purple cabbage, Cu(OAc)₂ and (B) Cu@Ag-CPX Nanocomposite, Schiff Bass, Ag-CPX complex, AgNO₃.

Figure 4

FESEM and EDX-EDS images of Cu@Ag-CPX nanocomposite.

Figure 5

(a) TEM image and (b) DLS of Cu@Ag-CPX nanocomposite.

Figure 6

XRD of Cu@Ag-CPX nanocomposite.

Figure 7

MIC, MBC and MBC values of compounds and drugs; a zero value shows no inhibitory activity in the highest concentration (4096 μg ml⁻¹); 1399: E. coli, 1310: P. aeruginosa, 1290: K. pneumoniae, 1855: A. baumannii, 1447: S. pyogenes, 1435: S. epidermidis, 5027: C. albicans, 5009: A. fumigatus.