The optical properties of Ag-NPs were monitored by UV–VIS absorption spectroscopy (PG Instruments Ltd. T80 UV–VIS spectrophotometer, Loughborough, UK) in the central lab of the Biochemistry Department, Faculty of Agriculture, Cairo University. UV–VIS spectra were recorded in the wavelength range of 300–700 nm.
The UV–VIS spectrum of Ag-NPs in Figure 1 was adjusted from the reaction medium as an incubation time function. Ag-NPs from Moringa gave absorption peaks between 300 and 700 nm. With time, the absorption intensity increased, indicating an increase in the quantity of formed Ag-NPs. The characteristic feature of the peak at 400–500 nm, which was checked in the UV–VIS spectrum, validated the synthesis of Ag-NPs. This single peak of the plasmon surface resonance indicated that the Ag-NPs were spheres with a wide distribution of size. The UV–VIS spectrum of synthesized Ag-NPs gave absorbance at 472 nm after 24 h of incubation in the dark.
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