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.     

Biosynthesis,characterisation and antimicrobial activity of silver and gold nanoparticles by Dolichos biflorus Linn seed extract

The bioreduction method employed for the synthesis of colloidal AgNPs and AuNPs is reported here. Methanolic and aqueous extracts of Dolichos biflorus Linn seed was used as the bio-reducing agent. The structural and morphological aspects of the synthesised metal nanoparticles were investigated using X-ray diffraction (XRD), energy-dispersive spectroscopy (EDX), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). XRD, revealed crystalline nature of the synthesised particles, UV–vis spectrophotometric analysis showed characteristic absorption peak for both AgNPs and AuNPs. EDX analysis confirmed the presence of elemental silver and gold particles and the average size and morphology were determined by SEM and TEM. The synthesised AgNPs exhibited good antibacterial potential whereas AuNPs showed poor activity against human pathogenic, gram-positive bacteria such as Staphylococcus aureus, Bacillus subtilis and gram-negative bacteria, such as Escherichia coli, Pseudomonas aeruginosa.     

Synthesis,characterisation and catalytic activity of gold and silver nanoparticles in the bio-sensor application

Most of the hydrogen peroxide (H₂O₂) bio-sensors developed till date are based on enzymes and proteins causing them to have a limited lifetime. Moreover, complex procedures are followed for sensor fabrication. Therefore, an inorganic material-based sensor, with a simple design and longer shelf life is highly desirable. In this work, surfactant-metal (gold and silver) nanoparticles are prepared in aqueous solutions containing cetyltrimethylammonium bromide. The particle sizes of the metal nanoparticles obtained are characterised by UV–Vis, HRTEM, X-ray diffraction and FTIR; the average sizes of gold and silver nanoparticles are 8 and 10?±?0.2?nm, respectively. The nanoparticles are tested for H₂O₂ detection. The sensor is characterised and tested using samples from M to mM H₂O₂ range and a linear response is observed. Low-detection limits and high sensitivity are some of the advantages of this work. Same principle could be extended for the detection of other substrates as well.     

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     

Synthesis of gold nanoparticles using aqueous extract of Calotropis procera latex

This is an account of the use of aqueous extract of the latex of Calotropis procera for the synthesis of gold nanoparticles. UV-Vis spectroscopic studies of the products resulting from reaction between the aqueous latex extract and chlorauric acid indicated the successful synthesis of gold nanoparticles. Reaction parameters viz. concentration of latex extract and reaction time were optimized for maximum yield of gold nanoparticles. Effect of reaction temperature on the synthesis rate of the particles and their optical properties was also studied. Transmission electron microscopic (TEM) studies of the particles revealed the dominance of spherical particles. Mean particle size distribution was found to be 22 ± 10 nm. Crystalline nature of the particles was confirmed from X-ray diffractrograms. FT-IR analysis and protein coagulation test of the gold nanoparticles confirmed capping behaviour of the latex proteins that contributed to their long term stability (6 months) in aqueous medium. Toxicity of the particles was tested on three cell lines, HeLa, A549 and BHK21. The method exploits a cheap and easily available biomaterial not explored so far for the synthesis of metallic nanoparticles.     

Antibacterial,anticancer and antioxidant potential of silver nanoparticles engineered using Trigonella foenum‐graecum seed extract

In this study, the authors report a simple and eco‐friendly method for the synthesis of silver nanoparticles (AgNPs) using Trigonella foenum‐graecum (TFG) seed extract. They explored several parameters dictating the biosynthesis of TFG‐AgNPs such as reaction time, temperature, concentration of AgNO₃, and TFG extract amount. Physicochemical characterisation of TFG‐AgNPs was done on dynamic light scattering (DLS), field emission electron microscopy, energy dispersive X‐ray spectroscopy, X‐ray diffraction and Fourier transform infrared spectroscopy. The size determination studies using DLS revealed of TFG‐AgNPs size between 95 and 110 nm. The antibacterial activity was studied against Escherichia coli, Proteus vulgaris, Pseudomonas aeruginosa and Staphylococcus aureus. The biosynthesised TFG‐AgNPs showed remarkable anticancer efficacy against skin cancer cell line, A431 and also exhibited significant antioxidant efficacy.Inspec keywords: antibacterial activity, cancer, biomedical materials, silver, nanofabrication, nanomedicine, nanoparticles, microorganisms, skin, cellular biophysics, biochemistry, light scattering, X‐ray chemical analysis, X‐ray diffraction, Fourier transform infrared spectra, particle sizeOther keywords: antibacterial potential, anticancer potential, antioxidant potential, silver nanoparticles, Trigonella foenum‐graecum seed extract, eco‐friendly method, biosynthesis, reaction time, AgNO₃ concentration, TFG extract amount, physicochemical characterisation, dynamic light scattering, field emission electron microscopy, energy dispersive X‐ray spectroscopy, X‐ray diffraction, Fourier transform infrared spectroscopy, size determination, TFG‐AgNPs size, Escherichia coli, Proteus vulgaris, Pseudomonas aeruginosa, Staphylococcus aureus, skin cancer cell line A431, Ag     

Green synthesis of silver nanoparticles using Glaucium corniculatum (L.) Curtis extract and evaluation of its antibacterial activity

The metal nanoparticles, due to interesting features such as electrical, optical, chemical and magnetic properties, have been investigated repeatedly. Also, the mentioned nanoparticles have specific uses in terms of their antibacterial activity. The biosynthesis method is more appropriate than the chemical method for producing the nanoparticles because it does not need any special facilities; it is also economically affordable. In the current study, the silver nanoparticles (AgNPs) were obtained by using a very simple and low‐cost method via Glaucium corniculatum (L.) Curtis plant extract. The characteristics of the AgNPs were investigated using techniques including: X‐ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy. The SEM and TEM images showed that the nanoparticles had a spherical shape, and the mean diameter of them was 53.7 and 45 nm, respectively. The results of the disc diffusion test used for measuring the anti‐bacterial activity of the synthesised nanoparticles indicated that the formed nanoparticles possessed a suitable anti‐bacterial activity.Inspec keywords: silver, nanoparticles, antibacterial activity, nanomedicine, nanofabrication, X‐ray diffraction, transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectraOther keywords: green synthesis, silver nanoparticles, Glaucium corniculatum Curtis extract, antibacterial activity, metal nanoparticles, biosynthesis method, X‐ray diffraction, transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, SEM, TEM, spherical shape, disc diffusion test, Ag     

Shaped gold and silver nanoparticles

Advance in the synthesis of shaped nanoparticles made of gold and silver is reviewed in this article. This review starts with a new angle by analyzing the relationship between the geometrical symmetry of a nanoparticle shape and its internal crystalline structures. According to the relationship, the nanoparticles with well-defined shapes are classified into three categories: nanoparticles with single crystallinity, nanoparticles with angular twins, and nanoparticles with parallel twins. Discussion and analysis on the classical methods for the synthesis of shaped nanoparticles in each category are also included and personal perspectives on the future research directions in the synthesis of shaped metal nanoparticles are briefly summarized. This review is expected to provide a guideline in designing the strategy for the synthesis of shaped nanoparticles and analyzing the corresponding growth mechanism.     

Synthesis of ZnO nanoparticles using Melia dubia leaf extract and its characterisation

The present work deals with the synthesis of zinc oxide (ZnO) nanoparticles (Nps) using the biocompounds extracted from Melia dubia leaves (MD L.) and zinc acetate as precursors. The choice of the precursors was based on the intention to use the synthesised ZnO Nps for the healthcare applications. In this line, the antimicrobial property of ethanolic extract of MD L., uncalcined ZnO Nps and calcined ZnO Nps has been assessed and compared. The prepared particles have been characterised by comparing their Fourier transform infrared spectrum, X‐ray diffraction (XRD) diffractogram and TEM images. The presence of ZnO has been confirmed using IR spectrum. The crystal structure and crystallite size have been found out using XRD diffractogram, and the obtained crystallite size was confirmed using TEM images. Finally, an attempt has been made to correlate the structure with the antimicrobial property of the material.Inspec keywords: zinc compounds, nanoparticles, nanofabrication, Fourier transform infrared spectra, X‐ray diffraction, transmission electron microscopy, crystal structure, antibacterial activity, nanobiotechnologyOther keywords: ZnO, antimicrobial property, crystallite size, crystal structure, TEM images, X‐ray diffraction, Fourier transform infrared spectrum, zinc acetate, biocompounds, Melia dubia leaf, zinc oxide nanoparticle synthesis     

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.     

Green synthesis of silver nanoparticles using Mentha pulegium and investigation of their antibacterial,antifungal and anticancer activity

A simple and eco‐friendly method for efficient synthesis of stable colloidal silver nanoparticles (AgNPs) using Mentha pulegium extracts is described. A series of reactions was conducted using different types and concentrations of plant extract as well as metal ions to optimize the reaction conditions. AgNPs were characterized by using UV–vis spectroscopy, transmission electron microscopy, atomic force microscopy, dynamic light scattering, zetasizer, energy‐dispersive X‐ray spectroscopy (EDAX) and Fourier transform infrared spectroscopy (FTIR). At the optimized conditions, plate shaped AgNPs with zeta potential value of ‐15.7 and plasmon absorption maximum at 450 nm were obtained using high concentration of aqueous extract. Efficient adsorption of organic compounds on the nanoparticles was confirmed by FTIR and EDAX. The biogenic AgNPs displayed promising antibacterial activity on Escherichia coli, Staphylococcus aureus, and Streptococcus pyogenes. The highest antibacterial activity of 25 µg mL‐1 was obtained for all the strains using aqueous extract synthesized AgNPs. The aqueous extract synthesised AgNPs also showed considerable antifungal activity against fluconazole resistant Candida albicans. The cytotoxicity assay revealed considerable anticancer activity of AgNPs on HeLa and MCF‐7 cancer cells. Overall results indicated high potential of M. pulegium extract to synthesis high quality AgNPs for biomedical applications.Inspec keywords: silver, nanoparticles, nanofabrication, botany, antibacterial activity, biomedical materials, nanomedicine, ultraviolet spectra, visible spectra, transmission electron microscopy, atomic force microscopy, X‐ray chemical analysis, Fourier transform infrared spectra, electrokinetic effects, microorganisms, cellular biophysics, cancerOther keywords: antibacterial activity, antifungal activity, anticancer activity, stable colloidal silver nanoparticle, Mentha pulegium, plant extract, UV‐visible spectroscopy, transmission electron microscopy, atomic force microscopy, DLS, zetasizer, energy‐dispersive X‐ray spectroscopy, Fourier transform infrared spectroscopy, methanolic extract, aqueous extract, plate‐shaped silver nanoparticle, zeta potential, plasmon absorption maximum, organic compounds adsorption, biogenic silver nanoparticle, Escherichia coli, Staphylococcus aureus, Streptococcus pyogenes, fluconazole‐resistant Candida albicans, MTT assay, HeLa cancer cell, MCF‐7 cancer cell, Ag     

银纳米粒子的制备及其在光催化中的应用

在乙醇/水溶剂中,以AgNO3为银源、聚乙烯吡咯烷酮为稳定剂,采用溶剂热还原法合成纳米银.通过调变乙醇-水的相对比例、AgNO3浓度和反应时间等,获得了尺寸均匀的准球形、立方体、线状等不同形貌的银纳米颗粒,利用XRD、SEM、TEM和紫外-可见吸收光谱进行了表征.初步考察了球形纳米银(粒径分布30～70nm)和立方纳米银(粒径80～140nm)修饰介孔二氧化钛对甲基橙的光催化降解性能,结果表明两种纳米银粒子对TiO2的光催化均具有增效作用,且银粒径越小,对光催化活性的提高越显著.     

Peanut skin extract mediated synthesis of gold nanoparticles,silver nanoparticles and gold–silver bionanocomposites for electrochemical Sudan IV sensing

Sustainable methods are needed for rapid and efficient detection of environmental and food pollutants. The Sudan group of dyes has been used extensively as adulterants in food and also are found to be polluting the soil and water bodies. There have been several methods for detection of Sudan dyes, but most of them are not practical enough for common use. In this study, the electrochemical detection efficiency and stability of gold nanoparticle (AuNPs), silver NPs and Au–Ag bionanocomposites, synthesised by peanut skin extract, modified glassy carbon electrode has been investigated. The synthesised nanomaterial samples were characterised, for their quality and quantity, using ultra–visible spectroscopy, inductive coupled plasma mass spectrophotometer, Fourier transform infrared spectroscopy, energy‐dispersive X‐ray spectroscopy, high‐resolution transmission electron microscope and field emission scanning electron microscope. The nanomaterial hybrid electrodes showed great efficiency and stability in the detection of Sudan IV compared with the other previous electrodes. The peak current of the Sudan IV oxidation and reduction was found to be proportional to its concentration, in the range of 10–80 µM, with a detection limit of 4 µM. The hybrid electrodes showed 90% stability in detection for 20 cycles.Inspec keywords: gold, silver, nanoparticles, nanocomposites, biomedical materials, electrochemical sensors, dyes, nanofabrication, ultraviolet spectra, visible spectra, spectrophotometry, Fourier transform infrared spectra, X‐ray chemical analysis, transmission electron microscopy, scanning electron microscopy, field emission electron microscopyOther keywords: peanut skin extract mediated synthesis, gold nanoparticles, silver nanoparticles, gold–silver bionanocomposites, electrochemical Sudan IV sensing, electrochemical detection efficiency, modified glassy carbon electrode, ultra–visible spectroscopy, inductive coupled plasma mass spectrophotometer, Fourier transform infrared spectroscopy, energy‐dispersive X‐ray spectroscopy, high‐resolution transmission electron microscope, field emission scanning electron microscope, oxidation, reduction, detection limit, Au, Ag, Au‐Ag     

Green synthesis and characterization of hexagonal shaped MgO nanoparticles using insulin plant (Costus pictus D. Don) leave extract and its antimicrobial as well as anticancer activity

Green synthesis is an ecofriendly novel technology and attractive research area for the production of metal oxide nanoparticles in bio-medical and chemical applications. The green perspective includes solvents, reductants or stabilizing agents obtained from a natural resource as they are non-toxic and ecofriendly. In this study, a sustainable green synthetic strategy to synthesize magnesium oxide nanoparticles by employing Costus pictus D. Don plant leaf extract as a reducing agent. The successful formation of magnesium oxide nanoparticles was confirmed by comprehensive characterization techniques. The presence of biomolecules and metal oxides were confirmed by Fourier transform Infrared (FT-IR) spectral data analysis. The X-ray diffraction (XRD) revealed the formation of pure cubic MgO crystalline nanoparticles. The surface morphology of MgO particles observed by Scanning electron microscope (SEM) showed the hexagonal-shaped MgO crystallites. The average size of biosynthesized MgO nanoparticles was measured to be around 50?nm by Transmission Electron Microscopy (TEM). The mechanism for the formation of MgO nanoparticles was suggested in this study. The biosynthesized magnesium oxide particles showed good antimicrobial and exhibited maximum inhibition rate for MgO nanoparticles at 200?µg showing efficient anticancer activity.     

Green synthesis of silver nanoparticles using flower extract of Malva sylvestris and investigation of their antibacterial activity

High‐quality colloidal silver nanoparticles (AgNP) were synthesised via a green approach by using hydroalcoholic extracts of Malva sylvestris. Silver nitrate was used as a substrate ion while the plant extract successfully played the role of reducing and stabilising agents. The synthesised nanoparticles were carefully characterised by using transmission electron microscopy, atomic‐force microscopy, energy dispersive X‐ray spectroscopy, Fourier transform infrared spectroscopy and UV–vis spectroscopy. The maximum absorption wavelengths of the colloidal solutions synthesised using 70 and 96% ethanol and 100% methanol, as extraction solvents, were 430, 485 and 504 nm, respectively. Interestingly, the size distribution of nanoparticles depended on the used solvent. The best particle size distribution belonged to the nanoparticles synthesised by 70% ethanol extract, which was 20–40 nm. The antibacterial activity of the synthesised nanoparticles was studied on Escherichia coli, Staphylococcus aureus and Streptococcus pyogenes using disk diffusion, minimum inhibitory concentrations and minimum bactericidal concentrations assays. The best antibacterial activity obtained for the AgNPs produced by using 96% ethanolic extract.Inspec keywords: silver, nanoparticles, nanofabrication, antibacterial activity, colloids, particle size, transmission electron microscopy, atomic force microscopy, X‐ray chemical analysis, Fourier transform spectra, infrared spectra, ultraviolet spectra, visible spectra, microorganisms, nanomedicine, biomedical materialsOther keywords: Green synthesis, flower extract, Malva sylvestris, antibacterial activity, high‐quality colloidal silver nanoparticles, hydroalcoholic extracts, plant extract, reducing agents, stabilising agents, transmission electron microscopy, atomic‐force microscopy, energy dispersive X‐ray spectroscopy, Fourier transform infrared spectroscopy, UV– vis spectroscopy, colloidal solutions, particle size distribution, Escherichia coli, Staphylococcus aureus, Streptococcus pyogenes, disk diffusion, minimum inhibitory concentrations, minimum bactericidal concentrations assays, ethanolic extract, size 430 nm, size 485 nm, size 504 nm, size 20 nm to 40 nm, Ag     

Synthesis of silver nanoparticles from a Desmodium adscendens extract and its antibacterial evaluation on wound dressing material

The one‐pot synthesis of silver nanoparticles (AgNPs) using the medium‐polar extract of Desmodium adscendens (Sw.) DC. is presented here as an alternative synthesis of metal NPs. Characterisation of the formed NPs showed polydispersed AgNPs ranging from 15 to 100 nm where the concentration of metal ions was found to play a role in the size and shape of the prepared NPs. It could be established that the flavonoids, saponins, and alkaloids present in the extract acted as both reducing and stabilising agents during the formation of the capped metal NPs. This means of NP synthesis was also employed during the in situ immobilisation of AgNPs on gauze and plaster. An evaluation of the antibacterial activity of the medium‐polar D. adscendens extract, AgNPs suspended in solution, and the immobilised AgNPs against Staphylococcus aureus (ATCC 25923), Bacillus cereus (ATCC 11778), and Escherichia coli (ATCC 25922) showed high efficacy against the latter in particular. This suggests that gauze, dilute silver nitrate solutions, and D. adscendens extract could be used successfully in the simple in situ preparation of effective antibacterial wound dressings.Inspec keywords: wounds, silver, nanoparticles, nanomedicine, biomedical materials, antibacterial activityOther keywords: size 15 nm to 100 nm, antibacterial wound dressings, in situ preparation, dilute silver nitrate solutions, alkaloids, saponins, flavonoids, metal ions, wound dressing material, antibacterial evaluation, Desmodium adscendens extract, silver nanoparticle synthesis     

Antibacterial potential of silver nanoparticles biosynthesised using Canarium ovatum leaves extract

Silver nanoparticles (AgNPs) have been extensively used as antibacterial agents, owing to their ease of preparation. In the present study, leaves extract of Canarium ovatum have been employed for the biosynthesis of silver nanoparticles (CO‐AgNPs). CO‐AgNPs were synthesised under very mild, eco‐friendly manner where the plant extract acted both as reducing and capping agent. These AgNPs were synthesised by taking into account several parameters, that included, time of reaction, concentration of AgNO₃, amount of extract and temperature of reaction. The optimisation studies suggested efficient synthesis of CO‐AgNPs at 25°C when 1.5 mM AgNO₃ was reduced with 1:20 ratio of plant extract for 40 min. Size determination studies done on dynamic light scattering and scanning electron microscope suggested of spherical shape nanoparticles of size 119.7 ± 7 nm and 50–80 nm, respectively. Further, characterisations were done by Fourier transform infrared and energy‐dispersive X‐ray spectroscopy to evaluate the functional groups and the purity of CO‐AgNPs. The antibacterial efficacy of CO‐AgNPs was determined against the bacterial strain Pseudomonas aeruginosa. As evident from disc diffusion method studies, CO‐AgNPs remarkably inhibited the growth of the tested microorganism. This study suggested that C. ovatum extract efficiently synthesises CO‐AgNPs with significant antibacterial properties and can be good candidates for therapeutics.Inspec keywords: antibacterial activity, nanoparticles, silver, nanofabrication, particle size, light scattering, scanning electron microscopy, Fourier transform infrared spectra, X‐ray chemical analysis, microorganisms, biomedical materials, nanomedicineOther keywords: antibacterial potential, silver nanoparticles, biosynthesis, Canarium ovatum leave extract, plant extract, reducing agent, capping agent, antibacterial agents, reaction time, reaction temperature, dynamic light scattering, scanning electron microscopy, spherical shape nanoparticles, Fourier transform infrared spectroscopy, functional groups, bacterial strain Pseudomonas aeruginosa, disc diffusion method, microorganism, energy‐dispersive X‐ray spectroscopy, temperature 25 degC, time 40 min, Ag     

Synthesis, characterization and electrocatalytic activity of fused gold nanoparticles

This paper describes the synthesis of fused spherical gold nanoparticles (AuNPs) and their electrocatalytic activity towards the oxidation of hydroxylamine (HA). Fused AuNPs were prepared by one-pot synthesis using 2-mercapto-4-methyl-5-thiazoleacetic acid (TAA) as a stabilizing agent and sodium borohydride (NaBH4) as a reducing agent. The HR-TEM images showed that two individual AuNP were joined via on its surface with a size range of approximately 7 nm and a length of approximately 15 nm diameter. The pH studies showed that the synthesized fused AuNPs was stable at pH > 8. This indicated that the carboxylate ion present on the TAA molecule stabilized the AuNPs from aggregation. Further, the fused AuNPs were utilized for the electrocatalytic oxidation of hydroxylamine (HA) after immobilized them on (3-mercaptopropyl)-trimethoxysilane (MPTS) sol-gel film modified Au electrode. The AuNPs modified electrode showed an excellent electrocatalytic activity towards the oxidation of HA in 0.2 M phosphate buffer solution (pH 7.2) by shifting its oxidation potential to 100 mV less positive and enhancing its oxidation current for more than three times when compared to bare Au electrode. Further, it was found that the fused AuNPs modified electrode showed greater electrocatalytic activity towards HA than the spherical AuNPs modified electrodes.     

Biosynthesis of gold and silver nanoparticles using Emblica Officinalis fruit extract, their phase transfer and transmetallation in an organic solution

The design, synthesis and characterization of biologically synthesized nanomaterials have become an area of significant interest. In this paper, we report the extracellular synthesis of gold and silver nanoparticles using Emblica Officinalis (amla, Indian Gooseberry) fruit extract as the reducing agent to synthesize Ag and Au nanoparticles, their subsequent phase transfer to an organic solution and the transmetallation reaction of hydrophobized silver nanoparticles with hydrophobized chloroaurate ions. On treating aqueous silver sulfate and chloroauric acid solutions with Emblica Officinalis fruit extract, rapid reduction of the silver and chloroaurate ions is observed leading to the formation of highly stable silver and gold nanoparticles in solution. Transmission Electron Microscopy analysis of the silver and gold nanoparticles indicated that they ranged in size from 10 to 20 nm and 15 to 25 nm respectively. Ag and Au nanoparticles thus synthesized were then phase transferred into an organic solution using a cationic surfactant octadecylamine. Transmetallation reaction between hydrophobized silver nanoparticles and hydrophobized chloroaurate ions in chloroform resulted in the formation of gold nanoparticles.