Parameters optimization of Fe3O4 NPs synthesis by Tamarindus indica leaf extract possessing both peroxidase as well as excellent dye removal activity

Abstract

This study reports optimized conditions for the green synthesis of iron (II,III) oxide nanoparticles (Fe₃O₄ NPs) from Tamarindus indica (T. indica) leaf extract. The synthetic parameters like concentration of leaf extract, solvent system, buffer, electrolyte, pH, and time were optimized for Fe₃O₄ NPs synthesis. Fe₃O₄ NPs were obtained from the synthesis protocol by measuring size (80 $\pm$ 3 nm approx.), characteristics color changes, and an absorption peak between 270 nm and 280 nm using a UV-visible spectrophotometer, scanning electron microscope (SEM), and an energy dispersive X-ray spectrometer (EDS) study. Peroxidase activity was tested with 3,3,5,5-Tetramethylbenzidine (TMB) oxidation in the presence of hydrogen peroxide and dye removal activity was tested with malachite green (MG). The results indicated that the successful synthesis of Fe₃O₄ nanoparticles using aqueous leaf extract of T. indica is a practical alternative for biomedical applications due to its potent peroxidase activity and high dye removal capacity (about 93% with UV light and 55% with room light).

Keywords: Dye removal activity; Fe3O4 nanoparticle; Green synthesis; Peroxidase activity; Tamarindus indica leaf Extract.

Graphical abstract

Scheme 1

Schematic representation for the (A) preparation of T. indica leaf extract and (B) synthesis of Fe₃O₄ NPs from T. indica leaf extract.

Fig. 1

UV–Visible spectra (A) of the synthesized Fe₃O₄ NPs (green curve), precursor 0.0017 M FeCl₃ (red curve) and 0.0536 g/mL leaves extract (blue curve) and (B) of the synthesized Fe₃O₄ NPs on 0.0536 g/mL (blue curve), 0.0268 g/mL (red curve) and 0.0134 g/mL (green curve) concentration of leaves extract in PBS buffer (46 mM) pH 7.4. (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)

Fig. 2

UV–Visible spectra of the synthesized Fe₃O₄ NPs in (A) distilled water (red curve), PBS buffer (46 mM) pH 7.4 (green curve), (B) PBS buffer (green curve), Borate buffer (blue curve) and Carbonate buffer (red curve) (46 mM) pH 7.4, (C) PBS buffer (46 mM) pH 7.4 (green curve), pH 12.0 (blue curve) and pH 2.0 (red curve) and (D) PBS buffer pH 7.4 with 137 mM NaCl and 2.7 mM KCl as electrolyte (red curve), without electrolyte (blue curve) respectively. (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)

Fig. 3

SEM images of the synthesized Fe₃O₄ NPs as (A) 1 μm scal bar with ×20,000 magnification and (B) 100 nm scal bar with ×30,000 magnification in PBS buffer pH 7.4 with electrolyte.

Fig. 4

(A) EDS, (B) ATR and (C) XRD spectra of the synthesized Fe₃O₄ NPs in PBS buffer pH 7.4 with electrolyte.

Fig. 5

(A) Schematic representation of TMB oxidation by H₂O₂ and Fe₃O₄ NPs as peroxidase enzyme and (B) UV–Visible spectra of the synthesized Fe₃O₄ NPs in PBS buffer (50 mM) pH 7.4 with 0.00208 M TMB (in acetate buffer pH 4.5), and 0.1 M H₂O₂.

Fig. 6

UV–Visible spectra of the 10 mg/L MG in water after adding 1 mg/mL synthesized Fe₃O₄ NPs as adsorbent for a period of time in (A) UV light irradiation condition and (B) room light condition respectively.