The application of different Stevia rebaudiana leaf extracts in the “green synthesis” of AgNPs

ABSTRACT

The present work reports a method for green synthesis of silver nanoparticles (AgNPs) by reducing Ag ions from silver nitrate solution using alcoholic, aqueous and alcoholic-aqueous Stevia rebaudiana extracts. Depending on a particular extract different sizes of AgNPs could be observed – 40?nm in aqueous and aqueous-alcoholic extracts and significantly bigger 170?nm in case of alcoholic extract. Synthesis of AgNPs was analyzed within spectra range of 300–700?nm. The performed research provided information that aqueous and aqueous-alcoholic extracts are excellent sources for synthesis of AgNPs; however AgNPs were unstable in the case of alcoholic extract. The aqueous-alcoholic extract showed the best properties during studies. Antioxidant potential, antimicrobial properties and cytotoxicity were determined. The 2,2-diphenyl-1-(2,4,6-triphenyl-hydrazyl) method showed that antioxidant activity of an extract containing AgNPs was higher compared to Stevia extract alone. Bacterial inhibition studies had shown substantial antibacterial properties of AgNPs, which was much higher than Stevia extract alone and silver nitrate.     

Biogenic Synthesis of Silver Nanoparticles with High Antimicrobial and Catalytic Activities using Sheng Di Huang (Rehmannia glutinosa)

Silver nanoparticles (AgNPs) are widely sought after for a variety of biomedical and environmental applications due to their antimicrobial and catalytic properties. We present here a green and simple synthesis of AgNPs utilizing traditional Chinese medicinal herbs. The screening of 20 aqueous herb extracts shows that Sheng Di Huang (Rehmannia glutinosa) had the most promising potential in producing AgNPs of 30±6 nm, with narrow size distribution and high crystallinity. The antimicrobial activities of these AgNPs conducted on E. coli cells were found to be superior in comparison to poly(vinylpyrrolidone)-capped AgNPs synthesized using common chemical method. Additionally, the AgNPs obtained possess excellent catalytic performance in the reduction of 4-nitrophenol to 4-aminophenol. We compared the phytochemical and FTIR spectral analyses of the herb extract before and after synthesis, in order to elucidate the phytochemicals responsible for the reduction of Ag⁺ ions and the capping of the AgNPs produced.     

Phyto-Extract-Mediated Synthesis of Silver Nanoparticles Using Aqueous Extract of Sanvitalia procumbens,and Characterization,Optimization and Photocatalytic Degradation of Azo Dyes Orange G and Direct Blue-15

Green synthesis of silver nanoparticles (AgNPs) employing an aqueous plant extract has emerged as a viable eco-friendly method. The aim of the study was to synthesize AgNPs by using plant extract of Sanvitalia procumbens (creeping zinnia) in which the phytochemicals present in plant extract act as a stabilizing and reducing agent. For the stability of the synthesized AgNPs, different parameters like AgNO₃ concentration, volume ratios of AgNO₃, temperature, pH, and contact time were studied. Further, AgNPs were characterized by UV–visible spectroscopy, FT-IR (Fourier Transform Infrared Spectroscopy), XRD (X-ray Diffraction), SEM (Scanning Electron Microscopy), and EDX (Energy Dispersive X-ray Spectrometer) analysis. FT-IR analysis showed that the plant extract contained essential functional groups like O–H stretching of carboxylic acid, N–H stretching of secondary amides, and C–N stretching of aromatic amines, and C–O indicates the vibration of alcohol, ester, and carboxylic acid that facilitated in the green synthesis of AgNPs. The crystalline nature of synthesized AgNPs was confirmed by XRD, while the elemental composition of AgNPs was detected by energy dispersive X-ray analysis (EDX). SEM studies showed the mean particle diameter of silver nanoparticles. The synthesized AgNPs were used for photocatalytic degradation of Orange G and Direct blue-15 (OG and DB-15), which were analyzed by UV-visible spectroscopy. Maximum degradation percentage of OG and DB-15 azo dyes was observed, without any significant silver leaching, thereby signifying notable photocatalytic properties of AgNPs.     

Biological synthesis of silver nanoparticles in Tribulus terrestris L. extract and evaluation of their photocatalyst,antibacterial, and cytotoxicity effects

In recent years, progress of biological synthesis of nanoparticles is inevitable due to its important applications. In this research, a new and simple method for the synthesis of AgNPs from plant extracts is presented. The extract from shoots of the plant Tribulus terrestris L. was mixed with AgNO₃ with the aim of biologically synthesizing AgNPs. The biomolecules existing in the extract were accountable for the fast reduction of silver ions (Ag⁺) to AgNPs. Characterization of biosynthesized AgNPs was performed by UV–Vis, TEM, DLS, and XRD. The AgNPs exhibit a strong peak at 434 nm, and sphere-shaped AgNPs were found to be ~?25 nm. The biosynthesized silver nanoparticles have demonstrated high antibacterial effect against pathogenic bacteria (i.e., Staphylococcus aureus, Escherichia coli, Bacillus subtilis and Pseudomonas aeruginosa). In addition, the in vitro cytotoxicity effect of biosynthesized silver nanoparticles was also investigated and was detected to be up to 15.62 μg/mL in the treated Neuro2A cells. The plant-mediated biosynthesis of AgNPs has comparatively rapid, eco-friendly, inexpensive and wide-ranging application in modern medicine and the food industry.

     

Eco-friendly Synthesis of Silver Nanoparticles and its Application in Hydrogen Photogeneration and Nanoplasmonic Biosensing

Environmentally friendly methods for silver nanoparticles (AgNPs) synthesis without the use of hazardous chemicals have recently drawn attention. In this work, AgNPs have been synthesized by microwave irradiation using only honey solutions or aqueous fresh pink radish extracts. The concentrations of honey, radish extract, AgNO₃ and pH were varied. AgNPs presented mean sizes between 7.0 and 12.8 nm and were stable up to 120 days. The AgNPs were employed as co-catalyst (TiO₂@AgNPs) to increase the hydrogen photogeneration under UV-vis and only visible light irradiation, when compared to pristine TiO₂ NPs. The prepared photocatalyst also showed hydrogen generation under visible light. Additionally, AgNPs were used to assemble a nanoplasmonic biosensor for the biodetection of extremely low concentrations of streptavidin, owing to its specific binding to biotin. It is shown here that green AgNPs are versatile nanomaterials, thus being potential candidates for hydrogen photogeneration and biosensing applications.     

Daphne mucronata-mediated phytosynthesis of silver nanoparticles and their novel biological applications,compatibility and toxicity studies

This contribution reports the biosynthesis of silver nanoparticles (AgNPs) using aqueous leaf extracts of D. mucronata and their diverse applications. Synthesized AgNPs were characterized using diverse techniques, i.e. UV, XRD, EDS, SEM, TEM, FTIR and TGA/DTA. These techniques confirmed the authenticity of the synthesized nanoparticles. The bimodulated AgNPs revealed the highest radical scavenging potential, i.e. 86.4% relative to plant extract at 600?μg/ml. Escherichia coli was found to be the most susceptible strain to AgNPs. Growth of vancomycin-resistant Staphylococcus aureus was also inhibited. Hemolytic activity revealed negligible hemolysis, indicating the biocompatible nature of biomodulated AgNPs. Furthermore, no mutagenic properties were shown by the biogenic AgNPs. Synthesized nanoparticles possessed promising insecticidal potential and had no phytotoxic activity. No haemagglutination was observed for biogenic AgNPs.     

Green synthesis and characterization of silver nanoparticles using Juniperus communis leaf extract: Catalytic activity in real-outdoor conditions and electrochemical properties

The present study investigates the green synthesis of stable silver nanoparticles using Juniperus communis leaf aqueous extract at room temperature. Synthesized silver nanoparticles (AgNPs) were characterized with different techniques such as UV–vis spectroscopy, Fourier transforms infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), Scanning electron microscopy (SEM-EDAX) and electrochemical method. Photocatalytic and anti-bacterial activities of synthesized AgNPs are evaluated based on the obtained result showed an efficient inhibition growth for gram negative P. Aeruginosa, E. Coli, and gram positive bacteria S.aureus. The AgNPs exhibited an excellent photocatalytic activity toward the degradation of methylene blue both indoor and outdoor, under sunlight, an efficiency of 95% was achieved. As an easy and environmentally friendly process, AgNPs based on Juniperus communis leaf extract could be applied for the degradation of pollutants and wastewater treatment.     

Green synthesis of silver nanoparticles by seed of Phoenix sylvestris L. and their role in the management of cosmetics embarrassment

Recently, green synthesis of silver nanoparticles has attracted much curiosity in the field of life science research. In the present study, we have reported a green method for synthesis of silver nanoparticles (AgNPs) using aqueous seed extract of Phoenix sylvestris L. The green synthesized nanoparticles were characterized by aids of dynamic light scattering, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Fourier transform-infrared. Further, the study demonstrate the comparative phytochemical analysis as well as antioxidant and antibacterial activity of the extract and Phoenix sylvestris seed generated nanoparticles against acne-causing pathogens, that is, by using a DPPH-scavenging assay and broth microdilution method as well as Kirby–Bauer Disk diffusion method (recommended by CLSI), respectively. Moreover, a concentration-dependent time-kill kinetic studies were also carried out to determine their antimicrobial activity. The seed extract was found a better antioxidant and AgNPs exhibited highly biocidal agent against both the test pathogens, when compared to aqueous extracts. The results obtained indicate that seed extract of P. sylvestris is suitable for synthesizing stable silver nanoparticles, which act as excellent antimicrobial agents with promising treatments for cosmetics embarrassment.     

Effects of silver nanoparticles on seed germination and seedling growth: A review

The advancement in nanotechnology, nanoparticles are reported to have applications in various fields. Their positive role in the environment, especially in plant ecosystem, is extensively studied nowadays. Among the metal nanoparticles, the silver nanoparticles (AgNPs) are receiving special attention because of their ability to increase the growth and yield in many crops. Although many studies are found that shows the toxic effects of AgNPs, the perspective of the present review is to collect the information about their positive roles in growth and yield enhancement of crops. During this overview, there are many methods of synthesizing silver AgNPs nanoparticles discussed, including chemical, bacterial-induced, fungal-derived and plant-mediated synthesis. There are numerous approaches towards the synthesis of AgNPs, including biological and chemical methods. Because of the use of reducing agents such as sodium borohydride in the synthesis of AgNPs, conventional methods have opened a path that threatens environmental sustainability. The chemical synthesis of silver colloids is the consequence of increased aggregation as storage time increases. AgNPs possess unique properties which has many applications such as antimicrobial and anticancer activities. It was concluded that cautious and sensible use of nanotechnology can warrant food security through boosting agricultural production. This review is aimed at providing an insight into the syntheses of AgNPs, its significant applications in various fields, and characterization techniques involved.     

A Novel Green Synthesis of Silver Nanoparticles Using <Emphasis Type="Italic">Rubus crataegifolius</Emphasis> Bge Fruit Extract

We report a facile, cost effective, and environmentally friendly green chemistry method for preparing silver nanoparticles (AgNPs) using Rubus crataegifolius bge (RCB) fruit extract. The amount of the fruit extract used was found to be important parameters in the growth of AgNPs. In this study, the effect of RCB fruit extract on the synthesis of AgNPs was studied using UV–Vis spectroscopy, transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction (XRD), and dynamic light scattering analyses were performed to characterize the RCB fruit extract-stabilized AgNPs. The formation of the AgNPs was confirmed by the color change of the reaction medium and the absorbance peak observed at 420 nm. The XRD analysis confirmed the face centered cubic structure of the AgNPs. The catalytic property of the as-synthesized AgNPs was analyzed for the reduction of 4-nitrophenol to 4-aminophenol.     

Synthesis of Gossypium hirsutum‐derived silver nanoparticles and their antibacterial efficacy against plant pathogens

Malvaceae and Brassicaceae family crops are economically important; however, their production has been markedly decreased in recent years due to various plant pests. Hence, the search for novel classes of efficient biological approaches continues due to unavailability of precise pesticides. The present study was designed to synthesize, characterize and evaluate the efficacy of silver nanoparticles (AgNPs) obtained using stem extract of Gossypium hirsutum (cotton plant) against plant pathogens Xanthomonas axonopodis pv. malvacearum and Xanthomonas campestris pv. campestris. Biosynthesized AgNPs were characterized using UV–visible spectrophotometry, Dynamic Light Scattering, Scanning Electron Microscopy combined with energy‐dispersive X‐ray analysis and Fourier transform infrared spectroscopy. The synthesized AgNPs were spherical in shape with size ranging from 20 to 100 nm. The characterized AgNPs were investigated for their efficacy against bacterial plant pathogens using the paper disc method. In vitro studies with two concentrations of AgNPs (50 and 100 μg mL^?1) showed zone of inhibition 11.0 ± 1.0 and 12.3 ± 0.5 mm for X. axonopodis pv. malvacearum and 9.7 ± 0.6 and 15.33 ± 1.0 mm for X. campestris pv. campestris. Furthermore, the AgNPs exhibited strong antioxidant activity, and a phytotoxicity study on Vigna unguiculata (cowpea plant) showed no toxicity. Overall, the findings suggest that G. hirsutum stem extract could be efficiently used in the synthesis of AgNPs and showed antimicrobial activity against plant pathogens. Hence, the synthesized nanoparticles could be used to combat plant pathogens in the agriculture sector.     

Synthesis of Rumex hastatus-based silver nanoparticles induced the inhibition of human pathogenic bacterial strains

The development of antibiotic resistance in pathogenic bacterial strains has drawn attention to the quest for new natural antibacterial drugs. Therefore, in the present study, extracts of Rumex hastatus leaves were obtained in methanol and water, and R. hastatus-based silver nanoparticles (AgNPs) were synthesized. Structural and functional properties of synthesized silver nanoparticles were determined by UV–vis spectroscopy, XRD, FTIR and SEM. The synthesized AgNPs and crude extracts were tested to check their antibacterial potential against human pathogenic bacterial strains of Staphylococcus aureus, Staphylococcus haemoliticus, Bacillus cereus, Escherichia coli, Salmonella typhi and Pseudomonas aeruginosa in well diffusion and broth dilution methods. The present investigation has revealed for the first time that the broth dilution method was found more reproducible than that of the well diffusion method even at lower concentrations of AgNPs and crude extracts. UV– Vis spectroscopic analysis of AgNPs revealed a peak at 367 nm_. XRD pattern showed a face-centered cubical to the spherical structure of AgNP crystals. FTIR analysis revealed that flavonoids and terpenoids are responsible for the reduction of AgNO₃ to Ag⁺. SEM analysis determined the spherical structure and 51 nm average diameter of nanoparticles. The antibacterial activity of R. hastatus-based (AgNPs) was found to be significantly higher than aqueous plant extract and silver nitrate alone. Bacterial growth was inhibited by R. hastatus-based AgNPs in a dose-dependent manner. To our knowledge, silver nanoparticles (AgNPs) of R. hastatus were synthesized and characterized for the first time in this study and, based on the findings of current research work R. hastatus extract-based silver nanoparticles are suggested to be used as an antibacterial drug instead of synthetic drugs for the treatment of various human diseases/infections caused by the tested bacterial strains.     

Green synthesis of silver nanoparticles using Solanum indicum L. and their antibacterial,splenocyte cytotoxic potentials

Research on Chemical Intermediates - Green synthesis of silver nanoparticles was carried out using Solanum indicum L. plant extract as a reducing agent. The morphology of the AgNPs was determined...     

Biosynthesis,characterization, and antimicrobial effect of silver nanoparticles obtained using <Emphasis Type="Italic">Lavandula</Emphasis> × <Emphasis Type="Italic">intermedia</Emphasis>

The use..... of aqueous leaf extract of Lavandula × intermedia for biosynthesis of silver nanoparticles (AgNPs) is presented. The plant extract was obtained by boiling dried leaves and using the obtained filtrate for the synthesis of AgNPs. The study was conducted to investigate an ecofriendly approach to metal nanoparticle synthesis and to evaluate the antimicrobial potential of both the aqueous plant extract and resulting silver nanoparticles against different microbes using the disc diffusion method. The synthesis of silver nanoparticles was monitored using ultraviolet–visible (UV–v is) spectroscopy, which showed a localized surface plasmon resonance band at 411 nm and a shift of the band to higher wavenumber of 422 nm after 90 min of reaction. Powder X-ray diffraction analysis and transmission electron microscopy of the obtained AgNPs revealed their crystalline nature, with average size of 12.6 nm. Presence of elemental silver was further confirmed by energy-dispersive X-ray spectroscopy. Fourier-transform infrared spectroscopy confirmed presence of phytochemicals from Lavandula × intermedia leaf extract on the AgNPs. The AgNPs showed good antimicrobial activity with inhibition zone ranging from 10 to 23 mm; the largest inhibition zone (23 mm) occurred against Escherichia coli. Generally, the AgNPs displayed more antimicrobial activity against all investigated pathogens compared with Lavandula × intermedia leaf extract, and were also more active than streptomycin against Klebsiella oxytoca and E. coli at the same concentration. The silver nanoparticles showed prominent antimicrobial activity with a lowest minimum inhibitory concentration (MIC) value of 15 μg/mL against E. coli, K. oxytoca, and Candida albicans.     

Synthesis of Silver Nanoparticles Using Ionic‐Liquid‐Based Microwave‐Assisted Extraction from Polygonum minus and Photodegradation of Methylene Blue

A green biogenic, nontoxic, high‐yielding synthetic method is introduced for the synthesis of silver nanoparticles (AgNPs) using ionic‐liquid‐based, microwave‐assisted extraction (ILMAE) from Polygonum minus . The aqueous ionic liquid (1‐butyl‐3‐methylimidazolium chloride [BMIM]Cl)‐based plant extract was used as reducing agent to reduce silver ions to AgNPs. The synthesis of AgNPs was confirmed by UV–visible spectrophotometry. Fourier transforms infrared (FTIR) spectra showed that the plant bioactive compounds capped the AgNPs. The particle size and morphology of Ag NPs were characterized by dynamic light scattering (DLS) and field emission scanning electron microscopy (FESEM), respectively. Elemental analysis was carried out by energy‐dispersive X‐ray (EDX) spectroscopy. Photodegradation studies showed that the AgNPs degraded 98% of methylene blue in 12 min.     

Antibacterial and Antifungal Studies of Biosynthesized Silver Nanoparticles against Plant Parasitic Nematode Meloidogyne incognita,Plant Pathogens Ralstonia solanacearum and Fusarium oxysporum

The possibility of using silver nanoparticles (AgNPs) to enhance the plants growth, crop production, and control of plant diseases is currently being researched. One of the most effective approaches for the production of AgNPs is green synthesis. Herein, we report a green and phytogenic synthesis of AgNPs by using aqueous extract of strawberry waste (solid waste after fruit juice extraction) as a novel bioresource, which is a non-hazardous and inexpensive that can act as a reducing, capping, and stabilizing agent. Successful biosynthesis of AgNPs was monitored by UV-visible spectroscopy showing a surface plasmon resonance (SPR) peak at ~415 nm. The X-ray diffraction studies confirm the face-centered cubic crystalline AgNPs. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques confirm the rectangular shape with an average size of ~55 nm. The antibacterial and antifungal efficacy and inhibitory impact of the biosynthesized AgNPs were tested against nematode, Meloidogyne incognita, plant pathogenic bacterium, Ralstonia solanacearum and fungus, Fusarium oxysporum. These results confirm that biosynthesized AgNPs can significantly control these plant pathogens.     

Photodynamic cytotoxic and antibacterial evaluation of Tecoma stans and Narcissus tazetta mediated silver nanoparticles

Nanobiotechnology is the intersection of nanotechnology and biology, where nano systems are applied to help study biological systems. There is a growing interest of researchers in the application of nanotechnology in improving the efficacy of photodynamic therapy. In this study, the antioxidant, photodynamic, anticancer, and antibacterial potential of plant extracts and silver nanoparticles (AgNPs) were investigated. In order to synthesize AgNPs, 10 g of dried powder of Tecoma stans and Narcissus tazetta was boiled in deionized water (100 ml) and mixed with aqueous solution of silver metals, resulting in the formation of AgNPs. The synthesized AgNPs were spherical having size in a range of 15–100 nm. The application of extract (50 µl) and AgNPs to rhabdomyosarcoma cell line showed a decreased cell viability (%). Photodynamic study revealed an improvement in photosensitizer efficacy on introducing AgNPs. Both plant extracts and AgNPs had significant effect against methicillin resistant Staphylococcus aureus (MRSA) as well as sensitive Staphylococcus aureus with minimum inhibitory concentration (MIC) values of AgNPs lower (32–256 µg/ml) than the plant extracts. According to the current findings, these AgNPs have an enhancing effect on the photodynamic cytotoxic potential of plant extracts. Because of biological efficacy, these AgNPs may play a crucial role in determining therapeutic potential of Tecoma stans and Narcissus tazetta.     

Eco-friendly decoration of graphene oxide with green synthesized silver nanoparticles: cytotoxic activity

Research on Chemical Intermediates - The aim of the present study was to focus on the green synthesis of silver nanoparticles (AgNPs) using the aqueous extract of dried jujube fruit and the...     

A Review of Silver Nanoparticles: Research Trends,Global Consumption,Synthesis, Properties,and Future Challenges

Silver nanoparticles (AgNPs) are intensively investigated for their superior physical, chemical, and biological properties. A proper knowledge of these properties is essential to maximizing the potential applications of AgNPs in several areas while minimizing their risks to humans and the environment. This paper aims to critically review AgNPs from the perspectives of research trends, global consumption, synthesis, properties, and future challenges. Generally, AgNPs can be synthesized using three methods, namely physical, chemical, and biological, and the related works as well as their numerous advantages and disadvantages are presented in this review. In addition, AgNPs can be potentially explored for various applications. Future challenges on (AgNP) synthesis, their release into the environment, and scaling up production, as presented in the review, suggest that several potential topics for future works are available to promote a safer and more efficient use of these nanoparticles. Studies on AgNPs in Malaysia have increased since the Malaysian government officially established a directorate for nanotechnology development. This calls for a proper set of policies on AgNPs starting from their production to utilization as well as their effects on various related industries and the environment.     

Biogenic synthesis of silver nanoparticles; study of the effect of physicochemical parameters and application as nanosensor in the colorimetric detection of Hg2+ in water

This research demonstrates the ability of biogenic synthesised silver nanoparticles (AgNPs) to sensitively and selectively detect the presence of mercury (Hg²⁺) in water. To achieve this, the following study investigated the synthesis of AgNPs using plant extract from basil and characterised the synthesised AgNPs using scanning electron microscopy, energy dispersive X-ray spectroscopy, UV-visible spectrophotometry, X-ray diffractometry and Fourier transform infrared spectroscopy. We studied the effect of various factors, such as broth concentration, precursor concentration, temperature, contact time and pH, on the synthesis of the nanoparticles. The synthesised AgNPs were then used in the colorimetric detection of Hg²⁺ in water. The as-prepared AgNPs showed high selectivity to detect Hg²⁺ alone compared to other cations and high sensitivity at different concentration of Hg²⁺. The limit of detection for Hg²⁺ was 6.25 × 10^–8 mol/L (12 µg/L) indicating that these biogenic synthesised AgNPs represent a highly sensitive Hg²⁺ detection tool.