Plasmon-induced photocatalytic degradation of methylene blue dye using biosynthesized silver nanoparticles as photocatalyst

Bio-fabrication of silver nanoparticles, using stem extracts of Nepeta leucophylla and their photocatalytic degradation activity, has been undertaken. The synthesized silver nanoparticles are characterized using ultraviolet-visible spectroscopy, Fourier transformed infrared spectroscopy, X-ray diffractometry, Transmission Electron Microscopy, Field Emission Scanning Electron Microscopy, Energy-dispersive X-ray spectroscopy and thermal gravimetric and differential scanning calorimetry analysis. The Surface Plasmon Resonance band detected at 430 nm in the ultraviolet-visible spectrum confirms the formation of silver nanoparticles in the aqueous solution. Transmission Electron and Field Emission Scanning Electron micrographs reveal that the synthesized silver nanoparticles are spherical with an average size in the range of 15-25 nm. But, the X-ray diffraction confirms the face-centred cubic structure of silver nanoparticles with an average crystal size of the nanoparticles is about 10 nm. Furthermore, the infrared spectrogram confirms that the stem extract of Nepeta leucophylla contains phenol which causes reduction of silver salt to silver nanoparticles and protein might act as an overlaying agent which prevents the agglomeration of these nanoparticles. Moreover, the photocatalytic degradation of methylene blue dye, by using biosynthesized silver nanoparticles of optimized dose (1.8 ml) for 180 min in the presence and absence of light are 82.8% and 61.25%, respectively, specifies that the resultant photocatalyst is proved to have good photocatalytic activity for the degradation of methylene blue dye from the liquid phase.