## 3 Results and Discussion  
In order to confirm the presence of silver and gold nanoparticles, to determine their size and to show the arrangement of graphene inside the bionanocomposite, analysis was performed using a scanning electron microscope. Graphene oxide-sodium alginate nanocomposites containing Ag and Au nanoparticles are shown in Figure 2.  
The surfaces of the obtained nanocomposites have a vesicular structure, which may be due to the fact that during nanoparticle generation, the alginate formed as nanocapsules with a size of about 20-50 nm (Figure 2B,F). During the measurement, due to the electron beam passing through the sample, numerous cracks were formed on the surface of the film (Figure 2C,G), allowing for the observation of the internal structure of the film. Figure 3 clearly shows that the internal structure of the film is porous; the resulting nanopores are most likely due to the presence of graphene oxide [43]. Figure 2: **(A–D)** SEM micrographs of ALG/Ag/GOX foils taken at different magnifications, 25,000\(\times\), 200,000\(\times\), 200,000\(\times\), 100,000\(\times\), respectively. **(E–H)** SEM micrographs of ALG/Au/GOX foils taken at different magnifications, 20,000\(\times\), 200,000\(\times\), 200,000\(\times\), 100,000\(\times\), respectively. Using higher magnification in this method, we observe an alternating arrangement of graphene oxide sheets. By using secondary electron detection (in the COMPO system), the presence of nanogold and nanosilver in the whole structure of the obtained composites was proved (Figure 2D,H). The resulting silver nanostructures are characterized by different sizes; their sizes vary between 5-10 nm and 20-25 nm, while the average size of the obtained gold nanoparticles is about 10-20 nm. The obtained metal nanoparticles are in regular and spherical shapes. Figure 4 shows the UV-vis absorption spectra of the control ALG sample and the ALG/Au/GOX and ALG/Ag/GOX nanocomposites, which show an absorption band at 540 nm for ALG/Au/GOX and between 380-550 nm for ALG/Ag/GOX. The results indicate the formation of Au and Ag nanoparticles [44]. The width of the peak band indicates that the formed nanoparticles are characterized by different sizes, which has already been confirmed by the scanning electron microscope (SEM) images. Figure 4: UV–vis spectra of ALG (black line), ALG/Au/GOX (red line) and ALG/Ag/GOX (blue line). Figure 3: SEM micrograph taken at 150,000 magnification: ALG/Ag/GOX foil. The FTIR absorption spectra of pure GOX and the obtained bionanocomposites are shown in Figure 5. GOX displayed characteristic FTIR peaks corresponding to its oxygen functionalities, including the C=O stretching vibration peak at 1731 cm\({}^{-1}\), the C-O (epoxy) stretching vibration peak at 1227 cm\({}^{-1}\), the C-O (alkoxy) stretching vibration peak at 1065 cm\({}^{-1}\), and the vibration and deformation peaks of O-H groups at 3412 cm\({}^{-1}\) and 1627 cm\({}^{-1}\), respectively. The characteristic spectrum of the sodium alginate biopolymer is composed of a broad band centered at approximately 3219 cm\({}^{-1}\) that arises from the stretching of hydroxyl groups, low intensity bands at about 2934 cm\({}^{-1}\) attributed to -CH\({}_{2}\) groups, two peaks at 1597 cm\({}^{-1}\) and 1404 cm\({}^{-1}\) that come from the asymmetric and symmetric stretching modes, respectively, of carboxylate salt groups (-COONa), and a number of vibrations in the range 1100-1000 cm\({}^{-1}\) assigned to the glycoside bonds in the polysaccharide (C-O-C stretching) [45]. The absence of significant changes in the shape of the obtained spectra indicates that the synthesis of nanometals did not cause structural changes in the alginate molecule. The decrease in the absorbance at 3219 cm\({}^{-1}\), 2934 cm\({}^{-1}\), 1597 cm\({}^{-1}\) and 1401 cm\({}^{-1}\) could be explained by different water content and various intermolecular interactions (e.g., hydrogen bonds) between polysaccharide molecules and GOX and indicate that there should be good miscibility between ALG and GOX [46].