Green-synthesis of Ag₂O nanoparticles for antimicrobial assays^**

Abstract

Silver oxide nanoparticles (Ag2O NPs) in the aqueous colloidal state were synthesized using the green method. Aqueous silver nitrate was prepared and mixed jointly with an aqueous extract of Lawsonia inermis (henna) leaf and heated with stirring at 75 °C for 1h. Then, an aqueous colloidal solution of Ag2O NPs with a dark brown colour is forming. The physicochemical characterization of Ag2O NPs was studied using different techniques. A polycrystalline structure of (Ag2O/Ag) in face-centred cubic and cubic phases was revealing via grazing incident X-ray diffraction (GIXRD) patterns. Energy-dispersive X-ray analysis (EDX) spectra confirmed GIXRD results through peaks corresponding to the silver and oxygen elements making up the accurate composition of the silver oxide. UV-Vis absorbance peak of the localized surface plasmon resonance (SPR) appeared at the visible region and exhibited a blueshift at ∼425 nm with an energy bandgap ∼2.8 eV. The surface morphology and the size of the silver nanoparticles were analyzed using high resolution (FE-SEM) microscopy. FTIR spectra of Ag2O NPs has showed a shift in the bands compared to those produced by aqueous extract of the henna leaf (only). (0.4 molars) Ag2O NPs has showed excellent antimicrobial activity assays against all the pathogens microbe's strains. Henna plant extract (only) has showed poor activity compared to Ag2O NPs. In comparison, the inhibition zone diameter of the gram-negative Bacteria is more considerable than the gram-positive bacteria. Moreover, Ag2O NPs activity against Bacteria is more prominent than fungi.

Ag2O Nanoparticles as a Candidate for Antimicrobial Compounds of the New Generation

“…The most common modification of Ag 2 O NP synthesis is the so-called "green synthesis". There are reports about the use of extracts of plants Abroma augusta, Lawsonia inermis, Ficus benghal, Lippia citriodora, Eupatorium odoratum, Cleome gynandra, Aloe vera, Vaccinium arctostaphylos, Coleus aromaticus, Rhamnus virgate, Cyathea nilgiriensis, Centella Asiatica, Tridax sp., Hylocereus undatus, Paeonia emodi, Pinus longifolia and Telfairia occidentalis Telfairia occidentalis [33][34][35][36][37]51,60,[64][65][66]69,73,76,[83][84][85]; fungi Fusarium oxysporum, Kitasatospora albolonga, Rhodotorula mucilaginosa and Aspergillus terreus VIT 2013 [27,78,79,135]; and culture media of bacteria Bacillus paramycoides, Bacillus thuringiensis SSV1, Nitrobacter sp. (strain NCIM 5067) and Pseudomonas aeruginosa M6 [63,77,113,114].…”

Polyethyleneimine-assisted formation of Ag–SiO2 hybrid microspheres for H2O2 sensing and SERS applications

“…An additional weak peak was observed at 32.2°, corresponding to (111) plane of the face-centered cubic (FCC) phase of Ag 2 O (JCPDS No. 01-076-1393), 50 indicating a very small presence of Ag 2 O, which could be attributed to slight surface oxidation of the metallic Ag nanoparticles. To estimate the crystallite size of the Ag nanoparticle from the XRD peaks, the Debye–Scherrer formula, 51 as shown below, was used.Here, d represents the crystalline size of Ag nanoparticles; K is the Debye–Scherrer constant, which depends on the shape of the crystallites.…”

Biosynthesis of Silver Nanoparticles Functionalized with Histidine and Phenylalanine Amino Acids for Potential Antioxidant and Antibacterial Activities

“…According to the pXRD diffractogram analysis, AgNPs were found to be crystalline and contain silver ions. Besides, the peak near 32.85° (110) implied the possible existence of Ag 2 O. , Ag ions (salt) were converted to silver­(I) oxide, whereas by significantly increasing the pH of the medium during the biosynthesis of silver nanoparticles, Ag + can be converted to silver­(I) oxide due to NaOH (aq) used for the pH adjustment. The use of NaOH to produce a solid Ag 2 O phase was previously reported , that silver ions in the presence of OH ions form AgOH (aq), which quickly decompose when heated and precipitate to form the desired Ag 2 O, as shown in the following chemical reaction eq .…”