Antibacterial effects of biosynthesized silver nanoparticles using aqueous leaf extract of Rosmarinus officinalis L.

In this study, we demonstrate a green approach for the synthesis of silver nanoparticles (AgNPs) using aqueous leaf extract of Rosmarinus officinalis under ambient conditions. The uniqueness of this method lies in its rapid synthesis within 15 min. The synthesized AgNPs were characterized using UV–vis, FTIR, XRD, FE-SEM coupled with EDX, TEM and AFM. The synthesized particles were found to be 14.20–42.42 nm with face centered cubic geometry. The functional group of flavonoids and terpenoids was largely identified by FTIR which was found to be responsible for the synthesis and stabilization of the AgNPs. Further, antibacterial efficacy of the biologically synthesized AgNPs was investigated by the standard method against Pseudomonas aeruginosa and Staphylococcus aureus. The results showed that the aqueous leaf extract mediated synthesized AgNPs is an excellent antibacterial agent against clinical pathogens.     

Nigella arvensis leaf extract mediated green synthesis of silver nanoparticles: Their characteristic properties and biological efficacy

In the present study, the potential of aqueous leaf extract of Nigella arevensis for biosynthesis of silver nanoparticles (AgNPs) was evaluated. The formation of AgNPs was confirmed by color changes and UV–visible spectroscopy, which showed absorbance maxima peak at 416?nm. The transmission electron microscope (TEM) image showed the AgNPs to be anisotropic and mostly spherical with sizes in the range of 5–100?nm. Fourier transform infrared (FTIR) analysis indicated that the flavonoids, alkaloids and phenolic groups present in leaf extract were involved in the reduction and capping of phytogenic AgNPs. These nanoparticles showed the cytotoxic effects against H1229 and MCF-7 cancer cell lines with an IC₅₀ value of 10?μg/mL. AgNPs showed insignificant antioxidant properties compared to the crude extract, and it was effective against clinical isolated bacterial strains. Furthermore, the bioderived AgNPs displayed significant catalytic activity against methylene blue. These results confirmed the advantages and applications of these phytogenic AgNPs using the green method in various fields.     

壳聚糖修饰银纳米颗粒的制备及抗菌性能研究

采用液相化学还原法,以壳聚糖为修饰剂,硼氢化钠为还原剂,制备了壳聚糖修饰银纳米颗粒(chitosan-Ag NPs)。通过X射线粉末衍射仪、透射电子显微镜、傅立叶变换红外光谱仪等对所制备样品的结构和形貌进行了表征。结果表明,所制备纳米颗粒具有面心立方Ag的晶型结构,壳聚糖通过氨基和羟基中的N、O原子与Ag+的化学键合作用修饰在纳米颗粒表面,起到了限制颗粒粒径长大和防止其团聚的作用。采用肉汤连续稀释法检测了样品对大肠杆菌和金黄色葡萄球菌的抑菌杀菌性能,结果表明chitosan-Ag NPs具有优异的抗菌性,抗菌性能受到粒径大小的影响。     

Green synthesis of silver nanoparticles using aqueous solution of Ficus benghalensis leaf extract and characterization of their antibacterial activity

The present study reports an environmentally friendly and rapid method for synthesis of silver nanoparticles. Although several articles have been reported for the synthesis of silver nanoparticles from plant extract, here we have developed a green synthetic method for silver nanoparticles using Ficus benghalensis leaf extract which acts as a reducing and capping agent. It was observed that use of Ficus benghalensis leaf extract makes a fast and convenient method for the synthesis of silver nanoparticles and can reduce silver ions into silver nanoparticles within 5 min of reaction time without using any harsh conditions. Silver nanoparticles so prepared were characterized by using UV-visible spectroscopy, transmission electron microscope-energy dispersive spectra (TEM-EDS) and X-ray diffraction (XRD). Further, these nanoparticles show effective antibacterial activity toward E.coli MTCC1302 due to high surface to volume ratio.     

Biosynthesised silver nanoparticles using aqueous leaf extract of Tagetes patula L. and evaluation of their antifungal activity against phytopathogenic fungi

In the recent decades, nanotechnology is gaining tremendous impetus due to its capability of modulating metals into their nanosize, which drastically changes the chemical, physical, biological and optical properties of metals. In this study, silver nanoparticles (AgNPs) synthesis using aqueous leaf extracts of Tagetes patula L. which act as reducing agent as well as capping agent is reported. Synthesis of AgNPs was observed at different parameters like temperature, concentration of silver nitrate, leaf extract concentration and time of reduction. The AgNPs were characterized using UV‐vis spectroscopy, scanning electron microscope with energy dispersive spectroscopy, transmission electron microscopy with selected area electron diffraction, X‐ray diffraction, Fourier transform infrared and dynamic light scattering analysis. These analyses revealed the size of nanoparticles ranging from 15 to 30 nm as well revealed their spherical shape and cubic and hexagonal lattice structure. The lower zeta potential (−14.2mV) and the FTIR spectra indicate that the synthesized AgNPs are remarkably stable for a long period due to the capped biomolecules on the surface of nanoparticles. Furthermore, these AgNPs were found to be highly toxic against phytopathogenic fungi Colletotrichum chlorophyti by both in vitro and in vivo and might be a safer alternative to chemical fungicides.Inspec keywords: silver, nanoparticles, nanofabrication, nanobiotechnology, ultraviolet spectra, visible spectra, scanning electron microscopy, X‐ray chemical analysis, electron diffraction, X‐ray diffraction, Fourier transform infrared spectra, crystal structure, electrokinetic effects, antibacterial activityOther keywords: biosynthesised silver nanoparticles, aqueous leaf extract, Tagetes patula L, antifungal activity, phytopathogenic fungi, nanotechnology, UV–vis spectroscopy, scanning electron microscope, energy dispersive spectroscopy, transmission electron microscopy, selected area electron diffraction, X‐ray diffraction, Fourier transform infrared spectra, dynamic light scattering analysis, hexagonal lattice structure, zeta potential, phytopathogenic fungi Colletotrichum chlorophyti, cubic lattice structure, size 15 nm to 30 nm, Ag     

Green synthesis,characterisation and biological evaluation of plant‐based silver nanoparticles using Quercus semecarpifolia Smith aqueous leaf extract

The development of reliable and green methods for the fabrication of metallic nanoparticles (NPs) has many advantages in the field of nanotechnology. In this direction, the present work describes an eco‐friendly and cost‐effective protocol for the production of silver NPs (AgNPs) using an aqueous extract of Quercus semecarpifolia leaves. Different techniques were carried out for the characterisation of the synthesised AgNPs. The ultraviolet–visible spectroscopic analysis showed the highest absorbance peak at 430 nm. The particle size and structure were confirmed by scanning electron microscopy as well as transmission electron microscopy (TEM) analysis. From TEM imaging, it was revealed that the formed particles were spherical with an average size of 20–50 nm. The crystalline nature of the NPs was determined by X‐ray powder diffraction patterns. Thermogravimetry and differential thermal analysis were also evaluated by a temperature increment from 100 to 1000°C. Bio‐inspired synthesis of AgNPs was performed for their pharmacological evaluation in relation to the activities of the crude methanolic, n ‐hexane, chloroform, ethyl acetate, and aqueous extracts. Good cytotoxic activity was exhibited by the green‐synthesised AgNPs (77%). Furthermore, the AgNPs were found to exhibit significant antioxidant activity at 300 μg/ml (82%). The AgNPs also exhibited good phytotoxic potential (75%).Inspec keywords: scanning electron microscopy, toxicology, visible spectra, particle size, nanofabrication, nanomedicine, transmission electron microscopy, silver, ultraviolet spectra, differential thermal analysis, nanoparticles, X‐ray diffraction, botany, biochemistry, cellular biophysicsOther keywords: green synthesis, biological evaluation, plant‐based silver nanoparticles, reliable methods, metallic nanoparticles, eco‐friendly cost‐effective protocol, silver NPs, ultraviolet–visible spectroscopic analysis, highest absorbance peak, particle size, structure, transmission electron microscopy analysis, TEM imaging, crystalline nature, X‐ray powder diffraction patterns, differential thermal analysis, pharmacological evaluation, aqueous extracts, good cytotoxic activity, significant antioxidant activity, AgNPs exhibited good phytotoxic potential, bio‐inspired synthesis, Quercus semecarpifolia Smith aqueous leaf extract, scanning electron microscopy, thermogravimetry, crude methanolic, n‐hexane, chloroform, ethyl acetate, phytotoxic potential, haemagglutination activity, size 20.0 nm to 50.0 nm, wavelength 430.0 nm, temperature 100 degC to 1000 degC, Ag     

Characterisation and antifungal activity of silver nanoparticles biologically synthesised by Amaranthus retroflexus leaf extract

ABSTRACT

Following the emergence of resistant fungal pathogens, silver nanoparticles (AgNPs) biosynthesized by plants have been recognized as promising tools to combat parasitic fungi. This study evaluated the potency of Amaranthus retroflexus in producing AgNPs, followed by testing their antifungal effects. The AgNPs exhibited a maximum absorption at 430 nm through ultraviolet-visible spectroscopy, while the X-ray diffraction indicated that they were crystal in nature. Fourier transform infrared spectroscopy confirmed the conversion of Ag⁺ ions to AgNPs due to the reduction by capping material of plant extract. The transmission electron microscope analysis further revealed that the AgNPs were spherical ranging from 10 nm to 32 nm in size. The AgNPs at the concentrations of 50, 100, 200, and 400 μg/mL were applied to the growth of plant, mushroom, and human pathogenic fungi. The 50% minimum inhibitory concentrations (MIC₅₀) against Macrophomina phaseolina, Alternaria alternata and Fusarium oxysporum were observed to be 159.80 ± 14.49, 337.09 ± 19.72, and 328.05 ± 13.29 μg/mL, respectively. However, no considerable inhibition was observed regarding Trichoderma harzianum or Geotrichum candidum. These findings may suggest A. retroflexus as a green solution for biosynthesizing AgNPs with potent antifungal activities against plant pathogenic fungi.     

Evaluation of antimicrobial activity of synthesised silver nanoparticles using Thymus kotschyanus aqueous extract

Development of a green chemistry process for the synthesis of silver nanoparticles (AgNPs) has become a focus of interest. Characteristics of AgNPs were determined using techniques, such as ultraviolet–visible spectroscopy (UV–vis), Fourier transform infrared (FTIR) analysis, scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy and X‐ray diffraction (XRD). The synthesised AgNPs using Thymus kotschyanus had the most growth inhibition against gram‐positive bacteria such as Staphylococcus aureus and Bacillus subtilise, while the growth inhibition of AgNPs at 1000–500 µg/ml occurred against Klebsiella pneumonia and at 1000–250 µg/ml of AgNPs was observed against E. coli. The UV–vis absorption spectra confirmed the formation of the AgNPs with the characteristic peak at 415 nm and SEM micrograph acknowledged spherical particles in a nanosize range. FTIR measured the possible biomolecules that are responsible for stabilisation of AgNPs. XRD analysis exhibited the crystalline nature of AgNPs and showed face‐centred cubic structure. The synthesised AgNPs revealed significant antibacterial activity against gram‐positive bacteria.Inspec keywords: visible spectra, microorganisms, ultraviolet spectra, biomedical materials, nanofabrication, nanoparticles, X‐ray diffraction, scanning electron microscopy, molecular biophysics, X‐ray chemical analysis, nanomedicine, silver, antibacterial activity, Fourier transform infrared spectraOther keywords: green chemistry process, ultraviolet–visible spectroscopy, gram‐positive bacteria, silver nanoparticles, Thymus kotschyanus aqueous extract, UV–vis spectroscopy, Fourier transform infrared spectroscopy, FTIR analysis, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, SEM micrograph, X‐ray diffraction, XRD, Staphylococcus aureus, Bacillus subtilise, Klebsiella pneumonia, E. coli, UV–vis absorption spectra, face‐centred cubic structure, antibacterial activity, antimicrobial activity, wavelength 415.0 nm, Ag     

Optical properties of silver nanoparticles in R-phycoerythrin nanochannels in aqueous solutions and films

The optical properties of Ag⁰ nanoparticles in R-phycoerythrin nanochannels have been studied in liquid and solid phases by confocal fluorescence microscopy, absorption spectroscopy, and fluorescence spectroscopy. The optical properties of the Ag⁰ nanoparticles are shown to depend on their phase state at the levels of an individual nanoparticle and many nanoparticles. UV irradiation has different effects on Ag⁰ nanoparticles in deionized water and in thin films on glass.     

Preparation and antibacterial properties of hybrid-zirconia films with silver nanoparticles

The antimicrobial effect of incorporating silver nanoparticles (AgNps) into zirconia matrix–polyether glycol was studied. AgNps of 4–6 nm in size were synthesized using the inverse micelles method, and different doses of metallic nanoparticles were incorporated into zirconia–polyether glycol mixtures during the ageing procedure. Atomic force microscopy (AFM) of the modified hybrid film showed a homogenous distribution of 20–80 nm diameter AgNps, indicating agglomeration of these structures during film modification; such agglomerations were greater when increasing the dosage of the colloidal system. The AgNps-hybrid films showed higher antimicrobial activity against Gram-positive bacteria than for Gram-negative bacteria. Hybrid films prepared with dioctyl sodium sulfosuccinate (AOT) stabilized AgNps presented enhanced antibacterial activity compared to that obtained through the addition of a high AgNO₃ concentration (0.3 wt%).     

Biosynthesis of silver nanoparticles using Moringa oleifera leaf extract and its application to optical limiting

The Development of biologically inspired experimental processes for the synthesis of nanoparticles is evolving into an important branch of nanotechnology. The work presented here with the biosynthesis of silver nanoparticles using Moringa oleifera leaf extract as reducing and stabilizing agent and its application in nonlinear optics. The aqueous silver ions when exposed to Moringa oleifera leaf extract are reduced resulting in silver nanoparticles demonstrating the biosynthesis. The silver nanoparticles were characterized by UV-Visible, X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FT-IR) and transmission electron microscopy (TEM) techniques. TEM analysis shows a dispersion of the nanoparticles in a range of 5-80 nm with the average around 46 nm and are crystallized in face centred cubic symmetry. To show that these biosynthesized silver nanoparticles possess very good nonlinear properties similar to those nanoparticles synthesized by chemical route, we carried out the Z-scan studies with a 6 ns, 532 nm pulsed laser. We estimated the nonlinear absorption coefficient and compare it with the literature values of the nanoparticles synthesized through chemical route. The silver nanoparticles suspended in solution exhibited reverse saturable absorption with optical limiting threshold of 100 mJ/cm2.     

A novel approach for the biosynthesis of silver oxide nanoparticles using aqueous leaf extract of Callistemon lanceolatus (Myrtaceae) and their therapeutic potential

This study describes a novel biological route for the biosynthesis of silver oxide nanoparticles utilising the aqueous extract of Callistemon lanceolatus D.C. leaves. Formation of silver oxide nanoparticles was confirmed by UV–visible spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscope–energy dispersive X-ray spectroscopy and X-ray diffraction spectroscopy analysis. The biologically synthesised silver oxide nanoparticles were found to be 3–30 nm in size with spherical and hexagonal shape by high-resolution transmission electron microscope analysis. Furthermore, the biogenic silver oxide nanoparticles demonstrated significant (p?in vitro antioxidant methods. These particles also exhibited significant (p?相似文献   

Black tea leaf extract derived Ag nanoparticle-PVA composite film: Structural and dielectric properties

Biosynthesized metal (Ag) nanoparticles have been used to prepare high dielectric polymer composite film of technological importance. Different amounts of the tea leaf extract (E) (mother leaker prepared by soaking 2 g tea leaf in 100 ml boiled water for 3 min) were used to synthesize silver nanoparticles from 10⁻³ M AgNO₃ solution. Such a resultant solution containing Ag nanoparticles was mixed with 20 ml PVA solution (5 g PVA in 100 ml water) was used to make anhydrous Ag/PVA composite film where spherical silver nanoparticles (AgNPs) of average diameter 10 nm are well dispersed in the composite. The Ag particle size in the composite was found to enhance with the increase of E content in PVA. XRD, SEM, TEM, FT-IR, UV–vis, TGA and DSC studies are made to characterize the nanoparticles. Detailed frequency and E concentration dependent electrical and dielectric properties of the nanocomposites have been made showing low loss (∼0.14) and high dielectric property of these films. Maximum value of dielectric permittivity (∼900 which is almost 170 times higher than that of pure PVA ∼ 5.2) have been observed for 15 ml E-AgNPs/PVA nanocomposite film at 1 kHz and room temperature. Present study establishes the importance of the biosynthesized metal nanoparticles for industrial applications as in capacitors.     

Synthesis of silver nanoparticles in an eco-friendly way using Phyllanthus amarus leaf extract: Antimicrobial and catalytic activity

In the present study, silver nanoparticles (AgNPs) with a flower-like structure were synthesized through an easy, rapid and eco-friendly pathway using Phyllanthus amarus leaf extract. The obtained AgNPs were characterized using ultraviolet–visible (UV–Vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM). In addition, the antimicrobial and catalytic activities of the bio-synthesized AgNPs were carried out. Our results indicated that the concentration of the Ag precursor and the volume of the leaf extract played key roles in the formation of the flower-shaped AgNPs. Morphology study confirms the shape of the obtained bio-AgNPs as flower like structure. This study also showed the presence of clear capping layers surrounding and apparently interacting with the nanoparticles. Moreover, our studies indicated this interaction to involve bio-organic capping agents in the leaf extract. UV–Vis absorption spectra confirmed the formation of AgNPs with an optimized size. The zeta (ζ) potential of the AgNPs attests the stability of the nanoparticles. FTIR spectra provided evidence for the presence of biomolecules responsible for the reduction as well as capping of the AgNPs. Finally, the bio-synthesized AgNPs were shown to be an excellent microbial activity against the selected pathogens and enhanced catalyst of the reduction of rhodamine B.     

Preparation and optical properties of silver nanoparticles in R-phycoerythrin,a protein matrix

Ag⁺ chemisorption by R-phycoerythrin in an aqueous solution is shown to lead to the formation of silver nanoparticles, without the need for a reductant of Ag⁺. According to electron-microscopic results, most of the nanoparticles are elongated, (3 ± 0.5) × (6 ± 2) nm in dimensions. Also present are cubic Ag crystallites 22.5 nm in size (standard deviation of ±5.9 nm) and aggregates 53 × 48 nm in dimensions (standard deviation of ±8.8 × 8 nm). The absorption spectrum of the Ag nanoparticles in R-phycoerythrin is typical of small nanoparticles. Their fluorescence spectrum shows peaks of individual nanoparticles (450 nm) and fractal aggregates (630 and 670 nm). The fluorescence intensity of the Ag nanoparticles and their aggregates is an order of magnitude higher in comparison with other matrices.     

Extracellular synthesis of silver nanoparticles using the leaf extract of Coleus amboinicus Lour.

In the present investigation, Coleus amboinicus Lour. leaf extract-mediated green chemistry approach for the synthesis of silver nanoparticles was described. The nanoparticles were characterized by ultraviolet-visible (UV-Vis) spectroscopy, X-ray diffraction (XRD), energy dispersive X-ray analysis (EDAX), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The influence of leaf extract on the control of size and shape of silver nanoparticles is reported. Upon an increase in the concentration of leaf extract, there was a shift in the shape of nanoparticles from anisotrophic nanostructures like triangle, decahedral and hexagonal to isotrophic spherical nanoparticles. Crystalline nature of fcc structured nanoparticles was confirmed by XRD spectrum with peaks corresponding to (1 1 1), (2 0 0), (2 2 0) and (3 1 1) planes and bright circular spots in the selected-area electron diffraction (SAED). Such environment friendly and sustainable methods are non-toxic, cheap and alternative to hazardous chemical procedures.     

三角形纳米银导电胶的制备及其性能研究

简单液相还原法获得大量三角形纳米银材料,利用透射电子显微镜、电子衍射能谱和紫外-可见吸收光谱等手段研究表明,该法制备的纳米银粒子杂质含量低,粒度分布集中,颗粒均匀一致,形貌呈等边三角形,以其含量为60%制备的导电胶,其体积电阻率为1.79×10-4Ω·cm,同时连接强度可达25.1MPa,具有良好的工业化应用前景.     

Biosynthesis of silver nanoparticles using sun-dried mulberry leaf

The biosynthesis of silver nanoparticles (AgNPs) has been successfully conducted by reduction of silver nitrate with sun-dried mulberry leaf. Such AgNPs have been characterized by UV-visible spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, high-resolution transmission electron microscopy (HRTEM) and atomic force microscopy (AFM). The results showed that such dispersed, uniform and spherical AgNPs would not aggregate under high-concentration NaCl solution and have good antibacterial activity. It was suggested that the polyol components (such as polyhydroxylated alkaloids) and protein residues of mulberry leaf should be mainly responsible for the stabilization of AgNPs. Such AgNPs produced by the environmentally friendly method have the potential for use in antibacterial and medical applications.     

Synthesis and characterisation of silver nanoparticles using leaf extract of Artemisia afra and their in vitro antimicrobial and antioxidant activities

In this study, the conversion of silver ions into ∼30.74 nm sized silver nanoparticles (AgNPs) was achieved in 30 min at a reaction temperature of 80–90°C in aqueous leaf extract of Artemisia afra. The synthesised AgNPs showed surface plasmon resonance in the range of 423–438 nm. Spherical and face‐centred cubic nanoparticles were confirmed by transmission electron microscope (TEM) and X‐ray diffraction (XRD) analysis, respectively. Fourier transform infra‐red (FTIR) results indicated that the obtained nanoparticles were stabilised and capped through the carbonyl and carboxylate ion groups possibly from flavonoids, terpenoids, phenolics and esters content of the extracts. In addition, the AgNPs were assessed for their biological potentials against some microbes and, also, their free radical scavenging ability was established. The AgNPs exhibited interesting antimicrobial and antioxidant properties better than the aqueous extract of A. afra. Inspec keywords: silver, transmission electron microscopy, ultraviolet spectra, visible spectra, surface plasmon resonance, antibacterial activity, X‐ray diffraction, microorganisms, nanoparticles, nanofabrication, Fourier transform infrared spectraOther keywords: silver nanoparticles, reaction temperature, surface plasmon resonance, face‐centred cubic nanoparticles, antioxidant properties, silver ion conversion, aqueous leaf extract, carboxylate ion group, antimicrobial properties, Artemisia afra, spherical nanoparticles, TEM, XRD, FTIR spectra, Ag, temperature 80 degC to 90 degC, time 30.0 min, free radical scavenging, esters, phenolics, terpenoids, flavonoids, carbonyl ion group     

Preparation and characterization of dendritic silver nanoparticles

Dendritic silver nanoparticles have been prepared by a soft solution technique from the aqueous solution of silver nitrate and poly (vinyl pyrrolidone) (PVP) in the presence of ethanol used as a reducing agent. The resultant silver nanoparticles were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive analyses of X-ray (EDX), and UV-Visible absorption spectroscopy. It was found that the well-defined dendritic silver nanoparticles which had the length 0.5–1 m and the width of 100–200 nm.