## 4 Discussion
The surfaces of aluminum phosphate nanoplates may interact with light in ways distinct from bulk materials, leading to specific absorption characteristics [42]. The Full Width at Half Maximum (FWHM) provides a precise measure of the nanoparticle size distribution. A narrow FWHM indicates a more uniform size distribution, whereas a broader FWHM suggests greater variability in particle size. The narrow FWHM value of 53 nm suggests minimal variation in nanoparticle dimensions [39], which is advantageous for applications requiring precise control over optical characteristics, such as in sensors and photonic devices. The nanoplates synthesized from cork oak have been identified as aluminum phosphate (AlPO4) through XRD analysis. Previous studies characterizing aluminum phosphate nanoparticles [43; 44; 45] do not report the formation of nanoplates or utilize green synthesis methods for their formation, contrasting with our findings. Furthermore, the crystal systems identified in our nanoplates are triclinic (anorthic), a unique structure in the context of AlPO4, and monoclinic. The triclinic irregular crystal structure can significantly influence the material's optical properties, potentially leading to direction-dependent behaviors such as birefringence, where the refractive index varies with the direction of light propagation [46]. AlPO4 exhibits crystal structures analogous to tridymite and cristobalite found in SiO2. However, triclinicity is not typically observed in cristobalite or tridymite phases of AlPO4, which typically crystallize in tetragonal or monoclinic forms. Tridymite in AlPO4 undergoes a complex transformation sequence, culminating in monoclinic and triclinic modifications at room temperature; both phases of tridymite coexist and are often intergrow in the same crystal showing unique transformation behaviors, including multiple twinning under specific conditions [47]. Thus, our discovery of monoclinic-triclinic aluminum phosphate nanoplates synthesized via green methods represents a novel route to obtain these structures, potentially offering new opportunities for applications in optoelectronics and other fields requiring directional optical properties. Aluminum nanoparticles (AINPs) synthesized via green synthesis from cork oak somatic embryos were also characterized using electron microscopy, TEM, and SEM. The microscopic analysis revealed aluminum nanoplates with varying sizes yet consistent structures. While not all nanoplates exhibit nanoscale dimensions uniformly across their entire area, their significant transparency suggests that nanoscale dimensions are achieved in at least one dimension in agreement with the XRD analysis. Importantly, the presence of nanoplates instead of the more commonly observed spherical shapes of aluminum nanoparticles [48; 49], as evidenced in the microscopic images, underscores a unique aspect of our study. The SEM image shows an irregular and complex surface with laminar and possibly crystalline structures. The observation of large laminar formations along with smaller structures in the SEM image suggests that the sample has a hierarchical organization. The hierarchy in the structure may result from self-assembly processes, where particles spontaneously organize into ordered structures [50]. To date, the scientific literature has extensively documented the synthesis of alumina (aluminum oxide) nanoplates using various templates such as graphene oxide [51]. However, nanoplates of aluminum phosphate like ours have not been described. Our approach represents a significant advancement by demonstrating the direct synthesis of phosphate nanoplates, specifically aluminum phosphate (AlPO4), without the need for a templating mold. This innovative method provides a novel pathway for obtaining nanoplate structures in aluminum materials. The EDX analysis confirmed the presence of aluminum in the nanoplates derived from _Quercus suber_ somatic embryos. In the TEM-EDX spectrum, around 2.01 keV, there is a distinct peak that corresponds to phosphorus.