Green Synthesis of ZnO and SnO₂: Structural and Morphological Studies Based on Citrus Extracts

ZnO and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{SnO}_{2}$</tex> nanoparticles were synthesized using orange (Citrus sinensis) and lemon (Citrus latifolia) peel extracts via homogeneous precipitation. Fourier-transform infrared (FTIR) confirmed the presence of metallic bonds, while Raman spectroscopy highlighted structural disorder due to organic residue interference. X-ray diffraction (XRD) indicated that ZnO nanoparticles formed a hexagonal wurtzite structure, while <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{SnO}_{2}$</tex> displayed a tetragonal rutile phase. SEM and DLS results showed that <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$Z$</tex> nO and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{SnO}_{2}$</tex> nanoparticles varied significantly in size and morphology depending on the extract used. Nanoparticles synthesized with lemon extract were larger and more agglomerated, due to the high acidity of the extract, which affected its stability. In contrast, orange extract produced smaller and more uniform nanoparticles, particularly in the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{SnO}_{2}$</tex> samples, making them more suitable for photocatalytic applications. This study highlights the impact of pH and metabolites on green synthesis and suggests that process optimization can improve the quality of nanomaterials.