This work reports on the ability of Clitoria ternatea aqueous flower extract to prepare biogenic silver nanoparticles (AgNPs). The obtained AgNPs were used as efficient nanocatalysts for the elimination of methyl orange, a carcinogenic azo dye, from an aqueous solution. Several parameters that affected the AgNPs formation were examined. The prepared AgNPs were characterised by UV-Vis spectroscopy, FTIR, SEM-EDX, XRD, TEM, and zeta potential. The formation of AgNPs was confirmed by the development of yellowish-brown colour which was further proved by a surface plasmon peak at 430 nm in UV-Vis spectroscopy. FTIR analysis revealed that anthocyanin present in the extract might be responsible for the reduction of Ag⁺ to AgNPs and capping the particles. Production of stable, well-dispersed face centred cubic spherical crystalline particles with diameters in the range of 10–30 nm was obtained from XRD and TEM studies. SEM-EDX result affirmed the silver content of 73.7%, and zeta potential measurement showed excellent stability of AgNPs with high negative values of −27.77 ± 1.51 mV. Further, the AgNPs catalyst exhibited the excellent catalytic performance in the degradation of methyl orange dyes by NaBH₄. The degradation process was completed within 10 min, together with a constant rate value of 0.3285 min⁻¹. The results show strong potential of the biosynthesised AgNPs as a candidate for use in environmental remediation.

A green, simple, and rapid synthesis of gold nanoparticles using plant extract, Cryptolepis buchanani Roem. and Schult, and their applications are first described in this paper. The formation of gold nanoparticles was visually observed by the appearance of a ruby red color, which was further indicated by an absorption peak at 530 nm in UV-Vis spectroscopy. Optimization of reaction parameters for the gold nanoparticles was also investigated. Various analytical techniques were employed as part of the process of characterizing the resulting gold nanoparticles. Fourier transform infrared (FTIR) analysis revealed that the phenol compounds present in the extract were responsible for gold(III) reduction and stabilization of gold nanoparticles. Transmission electron microscopy (TEM) analysis showed that the gold nanoparticles were spherical in shape with an average diameter of 11 nm. Powder X-ray diffraction (XRD) pattern indicated that the green synthesis approach produced highly crystalline, face-centered cubic gold nanoparticles. Energy-dispersive X-ray spectroscopy (EDS) measurements confirmed the presence of elemental gold in the prepared nanoparticles. The negative zeta potential value of gold nanoparticles was found to be -30.28 mV. The green synthesized gold nanoparticles expressed effective antibacterial activity against Staphylococcus aureus, methicillin-resistant Staphylococcus aureus, and Acinetobacter baumannii and exhibited an excellent catalytic property in terms of its reduction ability of methylene blue.