The ATR-FTIR analysis presented in Table and figure 1 reveals significant shifts and peak changes in the functional groups of Polyaltha longifolia (P. longifolia) extracts during the synthesis of aluminium-potassium nanoparticles (Al/KNPs). The observed alterations in the wave number regions of O-H/N-H stretching (3200-3600 cm⁻¹), C-H stretching (2850-3000 cm⁻¹), and C=O stretching (1630-1820 cm⁻¹) highlight the involvement of these functional groups in the nanoparticle synthesis process. Peaks corresponding to O-H and N-H stretches (3928.6, 3574.5, and 3507.4 cm⁻¹) in P. longifolia extracts decrease in intensity or disappear entirely after nanoparticle formation, as observed at 3291.2 cm⁻¹ for Al/KNPs. This disappearance aligns with findings by and , which demonstrate that hydroxyl groups from alcohols and phenols often donate electrons, facilitating the reduction of metal ions and stabilizing the nanoparticles. Similarly, carbonyl (C=O) stretching vibrations, initially detected at 1628.8 cm⁻¹ in the plant extract, remain unchanged in the Al/KNP spectrum. This suggests that while these carbonyl groups participate in the reduction phase, they persist in the final nanoparticle structure, likely serving as stabilizing ligands. These findings are consistent with green synthesis pathways described by , where carbonyl compounds facilitate metal ion stabilization through coordination bonding. Additionally, the bending vibrations of N-H and C-H groups (1520.8 and 1438.8 cm⁻¹, respectively) show peak shifts or alterations in intensity, indicative of their involvement in nanoparticle capping. As noted by , amine groups contribute to stabilizing nanoparticles by forming hydrogen bonds and electrostatic interactions with the nanoparticle surface. In the Pl-Al/KNPs, the presence of aromatic and aliphatic functional groups ensures structural integrity and long-term stability. Overall, the FTIR analysis, supported by literature, highlights the synergistic roles of alcohols, phenols, amines, and carbonyl groups in both the reduction and stabilization processes during Pl-Al/KNP synthesis.