Silver Nanoparticles Synthesized Using Lantana Camara Flower Extract by Reflux, Microwave and Ultrasound Methods

Refining shape and size of silver nanoparticles using ion irradiation for enhanced and homogeneous SERS activity

We present green synthesis of silver nanoparticles in water using unirradiated and Ag15 + ion irradiated phytoextracts of Bergenia Ciliata leaf, Eupatorium adenophorum leaf, Rhododendron arboreum leaf and flower. The use of different plant extracts and their subsequent ion irradiation allow for successful refinement of nanoparticle size and morphology. Due to changes in reducing and capping agents the nanoparticle surface functionalization also varies which not only controls the morphology but also allows for surface oxidation and aggregation processes. In this work, we have synthesized silver nanoparticles which exhibit sizes in the range from 13 to 24 nm and having shapes like spherical, quasispherical, trigonal, hexagonal, cylindrical, dendritic assemblies, and porous nanoparticles. Owing to changes in the size and shape of the nanoparticles, their direct bandgap (2.05 eV - 2.48 eV) and local surface plasmon resonance (420 nm - 490 nm) could also be tuned. These nanoparticles are examined as SERS substrates, where their enhancement factors, limit of detection for methylene blue, and SERS substrate homogeneity have been tested. It has been observed the nanoparticles synthesized using unirradiated plant extracts present an enhancement factor of 106 with a limit of detection 10- 8 M. Whereas nanoparticles with refined morphology and shapes upon irradiation present high enhancement factors of >107 and detection limit down to 10- 9 M. In addition, uniformity in Raman spectra over the SERS substrates has been obtained for selected Ag NPs substrates synthesized using irradiated extracts with minimum relative standard deviation in enhancement factor < 12%.

Biological Synthesis of Silver Nanoparticles and Prospects in Plant Disease Management

Exploration of nanoparticles (NPs) for various biological and environmental applications has become one of the most important attributes of nanotechnology. Due to remarkable physicochemical properties, silver nanoparticles (AgNPs) are the most explored and used NPs in wide-ranging applications. Also, they have proven to be of high commercial use since they possess great chemical stability, conductivity, catalytic activity, and antimicrobial potential. Though several methods including chemical and physical methods have been devised, biological approaches using organisms such as bacteria, fungi, and plants have emerged as economical, safe, and effective alternatives for the biosynthesis of AgNPs. Recent studies highlight the potential of AgNPs in modern agricultural practices to control the growth and spread of infectious pathogenic microorganisms since the introduction of AgNPs effectively reduces plant diseases caused by a spectrum of bacteria and fungi. In this review, we highlight the biosynthesis of AgNPs and discuss their applications in plant disease management with recent examples. It is proposed that AgNPs are prospective NPs for the successful inhibition of pathogen growth and plant disease management. This review gives a better understanding of new biological approaches for AgNP synthesis and modes of their optimized applications that could contribute to sustainable agriculture.