Studies on properties of rice straw/polymer nanocomposites based on polycaprolactone and Fe₃O₄ nanoparticles and evaluation of antibacterial activity

Abstract

Modified rice straw/Fe3O4/polycaprolactone nanocomposites (ORS/Fe3O4/ PCL-NCs) have been prepared for the first time using a solution casting method. The RS/Fe3O4-NCs were modified with octadecylamine (ODA) as an organic modifier. The prepared NCs were characterized by using X-ray powder diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FT-IR). The XRD results showed that as the intensity of the peaks decreased with the increase of ORS/Fe3O4-NCs content in comparison with PCL peaks, the Fe3O4-NPs peaks increased from 1.0 to 60.0 wt. %. The TEM and SEM results showed a good dispersion of ORS/Fe3O4-NCs in the PCL matrix and the spherical shape of the NPs. The TGA analysis indicated thermal stability of ORS/Fe3O4-NCs increased after incorporation with PCL but the thermal stability of ORS/Fe3O4/PCL-NCs decreased with the increase of ORS/Fe3O4-NCs content. Tensile strength was improved with the addition of 5.0 wt. % of ORS/Fe3O4-NCs. The antibacterial activities of the ORS/Fe3O4/PCL-NC films were examined against Gram-negative bacteria (Escherichia coli) and Gram-positive bacteria (Staphylococcus aureus) by diffusion method using nutrient agar. The results indicated that ORS/Fe3O4/PCL-NC films possessed a strong antibacterial activity with the increase in the percentage of ORS/Fe3O4-NCs in the PCL.

Figure 1

XRD pattern of RS, and RS/Fe₃O₄-NCs, and ORS/Fe₃O₄-NCs (a) PCL; and ORS/Fe₃O₄/PCL-NCs in 1.0, 5.0, 15.0, 30.0 and 60.0 wt. % (b).

Figure 2

Transmission electron microscopy micrograph of ORS/Fe₃O₄/PCL-NCs in 1.0, 5.0, 15.0, 30.0 and 60.0 wt. % (a–e).

Figure 3

Scanning electron microscopy images of RS (a), ORS (b), RS/Fe₃O₄-NCs (c) and energy dispersive X-ray spectroscopy of RS peaks (d) and RS/Fe₃O₄-NCs peaks (e).

Figure 4

Scanning electron microscopy micrograph of ORS/Fe₃O₄/PCL-NCs in 1.0, 5.0, 15.0, 30.0 and 60.0 wt. % (a–e).

Figure 5

Magnetization curve of Fe₃O₄-NPs (a), RS/Fe₃O₄-NCs (b), and ORS/Fe₃O₄/PCL-NCs with 5.0, 15.0, 30.0 and 60.0 wt. % ORS/Fe₃O₄-NCs (c–f).

Figure 6

FT-IR spectra of RS, RS/Fe₃O₄-NCs, ODA and ORS/Fe₃O₄-NCs (a), PCL, and NCs with 5.0, 15.0, 30.0 and 60.0 wt. % ORS/Fe₃O₄-NCs (b).

Figure 7

Schematic illustration of preparation of ORS/Fe₃O₄/PCL-NCs.

Figure 8

TGA (a,b) and DTG (c) thermograms of PCL, Fe₃O₄-NPs, ORS/Fe₃O₄-NCs and ORS/Fe₃O₄/PCL-NCs, with 1.0, 5.0, 15.0, 30.0 and 60.0 wt. % ORS/Fe₃O₄.

Figure 9

Fe⁺³and Fe⁺² release curves of ORS/Fe₃O₄/PCL-NCs in PBS (pH = 7.00) with 1.0, 5.0, 15.0, 30.0 and 60.0 wt. %, respectively.

Figure 10

Tensile strength (a), tensile modulus (b), and Elongation at break (c) ORS/Fe₃O₄/PCL-NCs in different wt. % of ORS/Fe₃O₄-NCs.

Figure 11

Inhibition zone of ORS/Fe₃O₄/PCL-NCs against Gram-negative (E. coli) and Gram-positive (S. aureus) bacteria at 1.0, 5.0, 15.0, 30.0 and 60.0 wt. % ORS/Fe₃O₄-NCs (a–e), respectively.