Abstract

• In this research work, silver nanoparticles were synthesized by using green synthesis. In green synthesis, neem leaf extract was used as reducing agent. Silver nanoparticles (SNP) were prepared by mixing neem leaf extract and 0.01 M AgNO3 solution in the different ratios of 1:4, 2:4 and 3:4 v/v and the resulting silver nanoparticles were designated as SNP-NL1, SNP-NL2 and SNP-NL3 respectively. The existence of SNP in colloidal solutions was confirmed by Tyndall effect and UV-visible spectroscopy. The UV-visible spectrum revealed the formation of silver nanoparticles by exhibiting the typical surface plasmon absorption maxima at 415-420 nm. The silver nanoparticles after centrifugation of colloidal solution were characterized by modern techniques XRD, FT IR, SEM and EDXRF analyses. In XRD analysis, it was found that average crystallite size of SNP powders are in the range of 4.80 nm to 8.46 nm. From XRD analyses, all of the prepared SNP powders had the crystalline nature. The high intensity peaks of the prepared samples confirmed the diffraction faces of silver. According to the XRD spectra of all of the prepared SNP-NL, there was impurity peaks in the SNP-NL1 and SNP-NL3 but no impurity peaks found in the SNP-NL2. The crystallite size of SNP-NL2 was 6.93 nm. From the FT IR spectra of all of the prepared SNP-NL, it was observed that the stretching and bending vibration of residual organic functional groups from the leaf extract are present. SEM micrographs of all of the prepared SNP-NL showed agglomeration and larger particle size distribution. From EDXRF analyses, the main constituent element in the SNP-NL2 is Ag (92.384 %). The different types of polyvinyl alcohol (PVA) film were prepared by using different concentrations (1 - 5 % w/v) of PVA in distilled water. The obtained PVA films were designated as PVA-1, PVA-2, PVA-3, PVA-4 and PVA-5. According to the physicomechanical properties, the optimum conditions of PVA-3 film has tensile strength (31.7 MPa), elongation at break (241 %) and tear strength (155.8 kNm-1). The selected PVA-3 film was characterized by XRD, SEM, FT IR and TG-DTA analyses. The PVA-SNP composite films were prepared by varying the volume ratios of 3 % w/v PVA solution and colloidal SNP-NL2 solution. The antimicrobial activity of the prepared PVA-SNP composite films was investigated by using agar well diffusion method.