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. 2021 May 25;11(1):10924.
doi: 10.1038/s41598-021-90408-y.

Statistical optimization of experimental parameters for extracellular synthesis of zinc oxide nanoparticles by a novel haloalaliphilic Alkalibacillus sp.W7

Hend M H Al-Kordy  1 , Soraya A Sabry  2 , Mona E M Mabrouk  3
Affiliations

Statistical optimization of experimental parameters for extracellular synthesis of zinc oxide nanoparticles by a novel haloalaliphilic Alkalibacillus sp.W7

Hend M H Al-Kordy et al. Sci Rep. .

Abstract

Green synthesis of zinc oxide nanoparticles (ZnO NPs) through simple, rapid, eco-friendly and an economical method with a new haloalkaliphilic bacterial strain (Alkalibacillus sp. W7) was investigated. Response surface methodology (RSM) based on Box-Behnken design (BP) was used to optimize the process parameters (ZnSO4.7H2O concentration, temperature, and pH) affecting the size of Alkalibacillus-ZnO NPs (Alk-ZnO NPs). The synthesized nanoparticles were characterized using UV-visible spectrum, X-ray diffraction (XRD), Scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX), Transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and Zeta potential. The UV-Vis spectrum of ZnO NPs revealed a characteristic surface plasmon resonance (SPR) peak at 310 nm. XRD pattern confirmed the hexagonal wurtzite structure of highly pure with a crystallite size 19.5 nm. TEM proved the quasi-spherical shape nanoparticles of size ranging from 1 to 30 nm. SEM-EDX showed spherical shaped and displayed a maximum elemental distribution of zinc and oxygen. FTIR provided an evidence that the biofunctional groups of metabolites in Alkalibacillus sp.W7 supernatant acted as viable reducing, capping and stabilizing agents.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
UV–vis absorption spectra of biosynthesised Alk-ZnO NPs, with maximum absorption at 334 nm. Inset shows visual observation of color change (I) Pure precursor (ZnSO4.7H2O), (II) reducing agent (culture supernatant), (III) white clusters of Alk-ZnO NPs formed after mixing reducing agent and precursor.
Figure 2
Figure 2
A Pareto chart illustrating the main effects of Box-Behnken result, with the order of significance of the variables affecting Alk-ZnO NPs size. Bars that exceed the vertical line indicate the significance of the terms (P < 0.05).
Figure 3
Figure 3
Three-dimensional response surface graphs and contour plots showing the effect of independent variables on the average size of Alk-ZnO NPs; (A) Effect of metal concentation and temperature, (B) Effect of metal concentation and pH and (C) Effect of temperature and pH.
Figure 4
Figure 4
Scanning electron micrograph of Alk-ZnO NPs synthesized under optimum conditions at 35,000 × magnification.
Figure 5
Figure 5
Energy dispersive x-ray spectroscopic analysis of Alk-ZnO NPs. Other elemental signal as carbon was also recorded possibly from enzymes or proteins present in the culture supernatant. Inset image of scanned area and elemental composition.
Figure 6
Figure 6
Transmission electron microscopic image of Alk-ZnO NPs (A) low magnification (X80k), (B) high magnification (X120k), and (C) particle size distribution histogram.
Figure 7
Figure 7
X-ray diffraction pattern of ZnO nanoparticles synthesized by Al. sp. W7 supernatant. All peaks indicate purity and crystalline nature. No traces of other impurity phases were detected.
Figure 8
Figure 8
Zeta potential of Alk-ZnO NPs dispersed in water.
Figure 9
Figure 9
Fourier transforms infrared spectroscopy (FTIR) of Alk-ZnO NPs.
See this image and copyright information in PMC

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