## 3 Results and Discussion  
The UV-Vis spectrum of _P. ostreatus_-synthesized ZnO NPs displayed absorption peaks in the range between 300 and 600 nm, as displayed in Figure 1A. The observed absorption peaks of 340 and 400 nm confirmed the formation of ZnO NPs. Previous studies also obtained absorption peaks similar to those of our study, obtaining absorption peaks between 300 and 400 nm, which were reported to be typical of ZnO NP peaks [37]. Thus, this confirms the presence of ZnO NPs in our mushroom-synthesized nanoparticles. The results of the study were also in line with the findings of [PERSON] et al. [38], who obtained an absorption peak of 350 nm for _P. dijmor_ mushroom-synthesized ZnO NPs. Figure 1B shows the Fourier-transform infrared spectroscopy (FTIR) spectra of the _Pleurotus ostreatus_ mushroom extract and synthesized ZnO NPs. Hence FTIR was used to identify functional groups present within _Pleurotus ostreatus_ mushroom extract and within synthesized ZnO NPs. FTIR spectra showed a broad band at 3291.06 cm\({}^{-1}\) for a mushroom extract, which shifted to 3359.06 cm\({}^{-1}\) on synthesized ZnO NPs. These broad bands correspond to the O-H stretching vibrations, which were attributed to the alcohol or phenols found in mushrooms that might be transferred to ZnO NPs during synthesis. Furthermore, the mushroom extract had absorption bands of 2117.60 cm\({}^{-1}\), which also shifted to 2172.97 and 2009.37 cm\({}^{-1}\) within ZnO NPs due to C=C interactions. The presence of C=O (amide1) was observed for the absorption band of 1633.04 cm\({}^{-1}\) in the mushroom extract. This absorption band was slightly shifted to 1646.94 cm\({}^{-1}\) in ZnO NPs. This shift was an indication that mushroom extract contained functional groups that could act as a capping and reducing agent in the synthesis of ZnO NPs. The peaks of 1410.79 and 1028.01 cm\({}^{-1}\) were noted in the mushroom extract, which shifted to 138.58 and 1024.51 cm\({}^{-1}\) within the spectra of mushroom-synthesized ZnO NPs, indicating the bending alkane vibrations of C-H (138.58 cm\({}^{-1}\)) and amine C-N (1024.51 cm\({}^{-1}\)) stretching vibrations. The peaks (1024.51 and 574.91 cm\({}^{-1}\)) observed on the fingerprint region of ZnO  
NPs probably corresponded to the ZnO stretching vibrations; metal oxides are known to have absorption peaks between 600 and 400 cm\({}^{-1}\)[39]. Such findings corroborate with other findings reported by [PERSON] et al. [40], who also established a deep absorption band from 610 cm\({}^{-1}\) to a lower wavelength corresponding to ZnO. The observed peak at 574.91 cm\({}^{-1}\) was attributed to the ZnO stretching band, meaning the _P. ostreatus_ extracts successfully acted as capping and stabilizing agents in the synthesis of ZnO NPs. The mushroom-synthesized ZnO NPs were further analyzed with XRD to determine the crystallinity and purity of the nanoparticles, as indicated in Figure 1C. The diffraction pattern of ZnO NPs at three theta angles of 34.93, 60.14, and 69.43, which are indexed to (002), (103) and (201) planes, were observed, as shown in Figure 1C. Thus, the XRD pattern of the study was in line with the research conducted by [PERSON] et al. [38], where _P. dijmor_ mushrooms were used for the synthesis of ZnO NPs. The average particle size of the sample was found to be 7.50 nm, derived from the full width at half-maximum (FWHM) of the more intense peak; hence, this corresponded to the 002 plane located at 34.93\({}^{\circ}\). The elemental composition of the green-synthesized ZnO NPs was determined using EDX spectrum analysis. The EDX spectrum shown in Figure 2C revealed the presence of Zn and O within the samples, as expected, with no traces of impurities. Hence, a strong signal in Zn and O regions was observed, confirming that mushroom extracts were able to reduce and stabilize Zn\({}^{+}\) ions, and that ZnO NPs were synthesized. Previous research conducted by [PERSON] et al. [41] also proved that mushrooms can act as a reducing agent in synthesizing ZnO NPs.