3.4.3. X-ray Diffraction (XRD) Analysis

The crystalline nature of myco-synthesized MgO-NPs was investigated using XRD analysis. Data showed five intense peaks at 2θ ◦ of 36.9◦ , 42.6◦ , 62.2◦ , 75.4◦ , and 78.6◦ that correspond to planes of (111), (200), (220), (311), and (222), respectively (Figure 5A). These data confirmed that the as-formed MgO-NPs by *R. oryaze* strain E3 were crystallographic structures according to the JCPDS standard (JCPDS file No. 89-7746) [64]. The observed XRD peaks indicate the presence of oxide in the sample as Mg(OH)<sup>2</sup> and MgO, confirmed by XPS analysis. Lekota et al. [65] reported that the peaks observed at 2θ ◦ of 36.9◦ (111) and 75.4 (311) correspond to Mg(OH)2, whereas the diffraction peaks at 2θ ◦ of 42.6◦ (200), 62.2◦ (220), and 78.6◦ (222) signified cubic MgO-NPs. The crystal size of myco-synthesized MgO-NPs was measured as 50 nm from the XRD pattern by the Debye–Scherrer equation.

**Figure 5.** (**A**) XRD analysis showed the crystalline nature; (**B**) DLS analysis of myco-synthesized MgO-NPs.
