Highly monodisperse and sub-nano silver particles synthesis via microemulsion technique

Suppression of Root Rot Fungal Diseases in Common Beans (Phaseolus vulgaris L.) through the Application of Biologically Synthesized Silver Nanoparticles

The biosynthesis of silver nanoparticles (AgNPs) using plant extracts has become a safe replacement for conventional chemical synthesis methods to fight plant pathogens. In this study, the antifungal activity of biosynthesized AgNPs was evaluated both in vitro and under greenhouse conditions against root rot fungi of common beans (Phaseolus vulgaris L.), including Macrophomina phaseolina, Pythium graminicola, Rhizoctonia solani, and Sclerotium rolfsii. Among the eleven biosynthesized AgNPs, those synthesized using Alhagi graecorum plant extract displayed the highest efficacy in suppressing those fungi. The findings showed that using AgNPs made with A. graecorum at a concentration of 100 μg/mL greatly slowed down the growth of mycelium for R. solani, P. graminicola, S. rolfsii, and M. phaseolina by 92.60%, 94.44%, 75.93%, and 79.63%, respectively. Additionally, the minimum inhibitory concentration (75 μg/mL) of AgNPs synthesized by A. graecorum was very effective against all of these fungi, lowering the pre-emergence damping-off, post-emergence damping-off, and disease percent and severity in vitro and greenhouse conditions. Additionally, the treatment with AgNPs led to increased root length, shoot length, fresh weight, dry weight, and vigor index of bean seedlings compared to the control group. The synthesis of nanoparticles using A. graecorum was confirmed using various physicochemical techniques, including UV spectroscopy, Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) analysis. Collectively, the findings of this study highlight the potential of AgNPs as an effective and environmentally sustainable approach for controlling root rot fungi in beans.

Myco-Fabrication of Copper Nanoparticles and Its Effect on Crop Pathogenic Fungi

Phytopathogens are responsible for huge losses in the agriculture sector. Amongst them, fungal phytopathogen is quite difficult to control. Many chemicals are available in the market, claiming the high activity against them. However, the development of resistance by the fungal pathogen is the main concern to overcome their menace. Nanotechnology-based products can be a potential alternative to conventional fungicides. Amongst various nanoparticles, Copper nanoparticles (CuNPs) are appearing to be a promising antifungal candidate. It can be synthesized by various methods, but the myco-fabrication appears to be an environmental-friendly approach. Hence, the present study is an attempt to synthesize CuNPs using Aspergillus flavus. The myco-fabricated CuNPs were characterized by UV spectrophotometer, Fourier transform infrared spectroscopy (FTIR), Nanoparticles tracking and analysis system (NTA), Transmission Electron Microscopy (TEM), X-ray diffraction (XRD) and Zeta potential measurement. Myco-fabricated CuNPs showed maximum absorbance at 602 nm and particle size ranging 5-12 nm with the least average size of 8 nm with spherical shape and moderate stability. Myco-fabricated CuNPs tested against selected fungal crop pathogens viz. Aspergillus niger, Fusariumoxysporum, and Alternaria alternata reveal a significant effect. Besides these we have given the hypothetical mechanism depicting the antifungal action of myco-fabricated CuNPs.

Biogenic Synthesis of Silver Nanoparticles Using Phyllanthus emblica Fruit Extract and Its Inhibitory Action Against the Pathogen Acidovorax oryzae Strain RS-2 of Rice Bacterial Brown Stripe

Biogenic synthesis of silver nanoparticles (AgNPs) using plants has become a promising substitute to the conventional chemical synthesis method. In this study, we report low-cost, green synthesis of AgNPs using fresh fruit extract of Phyllanthus emblica. The biosynthesized AgNPs was confirmed and characterized by analysis of spectroscopy profile of the UV-visible and Energy dispersive spectrophotometer, Fourier transform infrared, X-ray diffraction pattern, and electron microscopy images examination. UV-visible spectra showed a surface resonance peak of 430 nm corresponding to the formation of AgNPs, and FTIR spectra confirmed the involvement of biological molecules in AgNPs synthesis. In spherical AgNPs, the particle size ranged from 19.8 to 92.8 nm and the average diameter was 39 nm. Synthesized nanoparticles at 20 μg/ml showed remarkable antimicrobial activity in vitro against the pathogen Acidovorax oryzae strain RS-2 of rice bacterial brown stripe, while 62.41% reduction in OD600 value was observed compared to the control. Moreover, the inhibitory efficiency of AgNPs increased with the increase of incubation time. Furthermore, AgNPs not only disturbed biofilm formation and swarming ability but also increased the secretion of effector Hcp in strain RS-2, resulting from damage to the cell membrane, which was substantiated by TEM images and live/dead cell staining result. Overall, this study suggested that AgNPs can be an attractive and eco-friendly candidate to control rice bacterial disease.

Recent Progress in Rapid Sintering of Nanosilver for Electronics Applications

Recently, nanosilver pastes have emerged as one of the most promising high temperature bonding materials for high frequency and high power applications, which provide an effective lead-free electronic packaging solution instead of high-lead and gold-based solders. Although nanosilver pastes can be sintered at lower temperature compared to bulk silver, applications of nanosilver pastes are limited by long-term sintering time (20⁻30 min), relative high sintering temperature (>250 °C), and applied external pressure, which may damage chips and electronic components. Therefore, low temperature rapid sintering processes that can obtain excellent nanosilver joints are anticipated. In this regard, we present a review of recent progress in the rapid sintering of nanosilver pastes. Preparation of nanosilver particles and pastes, mechanisms of nanopastes sintering, and different rapid sintering processes are discussed. Emphasis is placed on the properties of sintered joints obtained by different sintering processes such as electric current assisted sintering, spark plasma sintering, and laser sintering, etc. Although the research on rapid sintering processes for nanosilver pastes has made a great breakthrough over the past few decades, investigations on mechanisms of rapid sintering, and the performance of joints fabricated by pastes with different compositions and morphologies are still far from enough.

The Impact of Silver Nanoparticles Produced by Bacillus pumilus As Antimicrobial and Nematicide

This study evaluates the potential application of silver nanoparticles (AgNPs) as antimicrobial or nematicidal agents produced by the extremophile Bacillus pumilus, which was isolated from the alkaline Wadi El-Natrun Lake in Egypt. The AgNPs were characterized by ultraviolet-visible absorption spectroscopy, transmission electron microscopy, and energy dispersive x-ray spectroscopy. The size of AgNPs formed ranged from 20.12 to 29.48 nm. Panagrellus redivivus was exposed to different concentrations (0, 50, 100, 150, and 200 μg/mL) of AgNPs in a 5 mL nematode suspension (1 × 103 mL-1). The best result occurred at AgNP concentrations of 150 and 200 μg/mL, with death rates of 80 and 91%, respectively, following 48 h of exposure. AgNPs also exhibited potent antimicrobial properties when using Gram-negative and Gram-positive human pathogens, with MIC and MBC values of 5 and 10 μg/mL, respectively. These laboratory assays prove that biologically synthesized AgNPs are an ecofriendly material that can be used in lieu of solvents or toxic chemicals.

Noble metal-based bimetallic nanoparticles: the effect of the structure on the optical, catalytic and photocatalytic properties

Nanoparticles composed of two different metal elements show novel electronic, optical, catalytic or photocatalytic properties from monometallic nanoparticles. Bimetallic nanoparticles could show not only the combination of the properties related to the presence of two individual metals, but also new properties due to a synergy between two metals. The structure of bimetallic nanoparticles can be oriented in random alloy, alloy with an intermetallic compound, cluster-in-cluster or core-shell structures and is strictly dependent on the relative strengths of metal-metal bond, surface energies of bulk elements, relative atomic sizes, preparation method and conditions, etc. In this review, selected properties, such as structure, optical, catalytic and photocatalytic of noble metals-based bimetallic nanoparticles, are discussed together with preparation routes. The effects of preparation method conditions as well as metal properties on the final structure of bimetallic nanoparticles (from alloy to core-shell structure) are followed. The role of bimetallic nanoparticles in heterogeneous catalysis and photocatalysis are discussed. Furthermore, structure and optical characteristics of bimetallic nanoparticles are described in relation to the some features of monometallic NPs. Such a complex approach allows to systematize knowledge and to identify the future direction of research.

Optimization of biosurfactant production by Bacillus brevis using response surface methodology

The present study aims to evaluate and validate a statistical model for maximizing biosurfactant productivity by Bacillus brevis using response surface methodology. In this respect, twenty bacterial isolates were screened for biosurfactant production using hemolytic activity, oil spreading technique, and emulsification index (E24). The most potent biosurfactant-producing bacterium (B. brevis) was used for construction of the statistical response surface model. The optimum conditions for biosurfactant production by B. brevis were: 33 °C incubation temperature at pH 8 for 10 days incubation period and 8.5 g/L glucose concentration as a sole carbon source. The produced biosurfactant (BS) (73%) exhibited foaming activity, thermal stability in the range 30–80 °C for 30 min., pH stability, from 4 to 9 and antimicrobial activity against (Escherichia coli). The BS gave a good potential application as an emulsifier.

UV-irradiation-induced templated/in-situ formation of ultrafine silver/polymer hybrid nanoparticles as antibacterial

Two types of facile approaches toward ultrafine Ag/polymer hybrid nanoparticles (NPs) within 10 nm are introduced. Template and in-situ formation method are developed by photoreduction based on inverse microemulsion (IME) polymerization of N,N-dimethylacrylamide (DMAA). The template method refers to the usage of size-varied polymeric PDMAA NPs as templates for the preparation of Ag/PDMAA hybrids with desired morphology and optical property. To avoid the self-seeding nucleation of free Ag(+) in the solution, in-situ formation method is developed by introducing AgNO3 during IME polymerization, in which product hybrids could be obtained via autoprecipitation in large scale. Additionally, the produced Ag/PDMAA hybrids show high antibacterial performance.

Extracellular biosynthesis and characterization of silver nanoparticles using Aspergillus flavus NJP08: a mechanism perspective

The present study demonstrates an eco-friendly and low cost protocol for synthesis of silver nanoparticles using the cell-free filtrate of Aspergillus flavus NJP08 when supplied with aqueous silver (Ag+) ions. Identification of the fungal isolate was based on nuclear ribosomal DNA internal transcribed spacer (ITS) identities. Transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) revealed the formation of spherical metallic silver nanoparticles. The average particle size calculated using Dynamic Light Scattering measurements (DLS) was found to be 17±5.9 nm. UV-Visible and Fourier transform infrared (FTIR) spectroscopy confirmed the presence of extracellular proteins. SDS-PAGE profiles of the extracellular proteins showed the presence of two intense bands of 32 and 35 kDa, responsible for the synthesis and stability of silver nanoparticles, respectively. A probable mechanism behind the biosynthesis is discussed, which leads to the possibility of using the present protocol in future "nano-factories".