The ATR-FTIR spectroscopy results of P. guajava extract and the synthesized P.g-CuNPs are depicted in Figures and. Characteristic peaks in the P. guajava extract were observed at 3693 cm -1 , 3280 cm -1 , 2918 cm -1 , 2851 cm -1 , 2109 cm -1 , 1884 cm -1 , 1617 cm -1 , 1449 cm -1 , 1364 cm -1 , 1326 cm -1 , 1222 cm -1 , 1028 cm -1 , 916 cm -1 , and 752 cm -1 . The peaks from 3693 cm -1 to 2600 cm -1 were attributed to single bonds of N-H stretching, O-H stretching, and C-H stretching, in line with previous studies . Bands between 3600 and 3200 cm -1 were associated with O-H stretching from phenol, N-H stretching from amide, and C-H stretching at 3000 -2840 cm -1 . Peaks from 2110 cm -1 to 1415 cm -1 were assigned to double bonds of C=C, C=N, C=C=C, C=O, and cyclic carbon (C=C), as well as triple bonds of C≡C and C≡N stretching vibration [38,13,31,37]. Similar peaks were reported within the range of 2110 to 1635 cm -1 , associated with C=C, C=N, C=C=C, C=O, aromatic (C=C), C≡C, and C≡N stretching vibration. Peaks from 1368 cm -1 to 752 cm -1 were attributed to C-O stretching, -CH2-bending vibrations, and alkyl halides , with reported peaks from 1330 cm -1 to 720 cm -1 associated with C-O stretch, -CH2-bending vibrations, and alkyl halides. and biomolecules in P.guajava leaf extracts, as well as the presence of secondary metabolites in leaves and fruit extracts. This observation aligns with Amer and Awwad , who reported a similar outcome in their study on green synthesis of copper nanoparticles using Citrus limon fruit extract. They observed spherical CuNPs with an average diameter of 28 nm. Nasrollahzadeh et al. also found spherical CuNPs (7 -35 nm) in their study on green synthesis using Plantago asiatica leaf extract, while Mostafa reported spherical particle sizes ranging from 22 -27 nm in his review on biogenic copper nanoparticles and their applications. Energy dispersive X-ray (EDX) analysis was conducted to ascertain the elemental composition of the synthesized P.g-CuNPs presented in Figure . The results revealed the presence of pure copper (Cu) at a significant proportion of 54.15%, detected at energy levels of 1, 8, and 9 keV. This robust signal in the metallic copper region serves as confirmation of the successful formation of copper nanoparticles using P. guajava. Additionally, peaks were observed for other elements, including aluminum (Al) at 21.47%, oxygen (O) at 10.58%, zinc (Zn) at 7.35%, and carbon (C) at 6.44%. Notably, a substantial percentage of aluminum atoms were noted on the surface of P.g-CuNPs nanoparticles, possibly originating as an impurity from the precursor or from agricultural chemicals used on the P. guajava plant, sourced from a farm.