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The silver nanoparticles (Ag-Nps) synthesized by green reduction process using the leaf extract of Acacia leucophloea exhibited the surface plasmon resonance (SPR) at 435 nm. There were several techniques like UV–visible spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and selected area electron diffraction patterns (SAED) used to examine the growth kinetics, surface morphology, and crystallinity aspects of Ag-Nps in the absence and the presence of cationic surfactant, cetyltrimethylammonium bromide (CTAB). Fourier transform infrared spectrometry (FTIR) was used to confirm the reducing utility of leaf extract. The size of synthesized Ag-Nps varied from 10 to > 100 nm in the absence of CTAB and from 10 to 50 nm in its presence. While irregular or polytope-outlined Ag-NPs were detected in the absence of CTAB, spherical or oval shape prevailed in its prevalence. Williamson-Hall models were employed to deduce the crystallinity aspects of the procured Ag-Nps. Furthermore, the Ag-Nps effected in the presence of CTAB exhibited more antibacterial efficacy. [ABSTRACT FROM AUTHOR]

This paper presents two bottom-up methods for the green synthesis of spherical carbon dots (Cdots) and silver/Cdots (Ag@Cdots) nanoparticles at alkaline medium. Both syntheses are carried out without separation and purification steps with a microwave exposure time between 30 and 60 s. In both case a natural product as glucose was used as precursor and capping agent. The obtained Cdots and Ag@Cdots hybrid are spherical in shape and monodisperse, with average particle size of lower than 10 nm and 13 nm respectively. In comparison with the methods previously reported, which need high energy consumption and/or long reaction time. The proposed methodologies are simple, low cost, environment-friendly and in accordance with green chemistry research. The morphology, composition and structure of the obtained nanoparticles were characterized by Zeta Potential and hydrodynamic size measurements, transmission electron microscopy (TEM), X-ray diffraction (XRD), ATR-FTIR spectrophotometry and thermogavimetric analysis (TGA). The synthesized nanoparticles were applied to sense tetracycline residues taking into account their fluorescent properties. [ABSTRACT FROM AUTHOR]

Chitosan derived silver biocomposites (CsS) were produced by green synthesis using Carmona retusa (Vahl) Masam aqueous leaf extract. UV–Vis spectra of synthesized CsS biocomposites showed absorption maxima at 441 nm. FESEM average particle size was 51 nm and spherical in shape. TEM images of CsS biocomposite ranged between 30 nm to 60 nm, the DLS measurement showed the size of 234.1 nm for chitosan derived AgNPs. In FTIR spectra, the C–H winding and were observed for CsS biocomposites. In addition, the elemental composition showed uniform grain boundaries as recognized by EDaX spectra. In-vitro antioxidant activity CsS biocomposites showed the ability to scavenge free radicals. Cytotoxicity analysis of CsS biocomposites on MCF-7 breast cancer cell line revealed 90% inhibition at 500 μg/ml concentration. C. retusa mediated synthesis AgNPs coated chitosan biocomposite showed strong larvicidal activity with low LC50 and LC90 values against the malarial vector, An. stephensi, Ae. aegypti, and Cx. quinquefasciatus respectively. Eight bioactive components were present in aqueous leaf extracts of C. retusa. Based on this study we suggest that C. retusa plant mediated AgNPs chitosan derived silver biocomposites (CsS) has anti-cancerous and insecticidal activity which can further be explored for commercialization. [ABSTRACT FROM AUTHOR]

Bare Ag nanoparticles (∼10 nm) and Ag nanoparticles (1-20 nm) on the surfaces of larger TiO nanoparticles were prepared by laser ablation of microparticle aerosols (LAMA). The behaviors of the nanoparticles during high temperature annealing were then studied with ex situ and in situ transmission electron microscopy. For the ex situ heating experiments, Ag and Ag-on-TiO NPs were collected onto gold TEM grids and subjected to annealing treatments at 500 °C in argon, vacuum, and air. At this temperature, bare Ag NPs on carbon TEM supports coarsened rapidly in both air and argon atmospheres. In contrast, Ag-on-TiO NPs that were heated to 500 °C in flowing argon or in a vacuum did not coarsen significantly and were remarkably stable. Ag-on-TiO NPs that were heated to 500 °C in air, however, behaved quite differently. The TiO crystallized upon heating and a significant loss of Ag were observed from the surfaces of the TiO, likely due to sublimation. These results demonstrate that the surface defect structure and chemistry of the oxide support strongly influence the thermal stability of Ag NPs produced by LAMA. [ABSTRACT FROM AUTHOR]

The present study reports the biosafety assessment, the exact molecular effects, and apoptosis induction of newly developed chitosan-silver hybrid nanoparticles (Cs-Ag NPs) in HepG2 cells. The investigated hybrid NPs were green synthesized using Cs/grape leaves aqueous extract (Cs/GLE) or Cs/GLE NPs as reducing and stabilizing agents. The successful formation of Cs/GLE NPs and Cs-Ag hybrid NPs has been confirmed by UV-Vis spectrophotometry, FTIR spectroscopy, XRD, and HRTEM. From the TEM analysis, the prepared Cs/GLE NPs are uniform and spherical with an average size of 150 nm, and the AgNPs (5-10 nm) were formed mainly on their surface. The UV-Vis spectra of Cs-Ag NPs showed a surface plasmon resonance (SPR) peak at about 450 nm confirming their formation. The synthesized Cs-Ag NPs were found to be crystalline as shown by XRD patterns with fcc phase oriented along the (111), (200), (220), and (311) planes. The cytotoxicity patterns, the antiproliferative activities, and the possible mechanisms of anticancer activity at molecular level of the newly developed Cs-Ag hybrid NPs were investigated. Cytotoxicity patterns of all the preparations demonstrated that the nontoxic treatment concentrations are ranged from 0.39 to 50 %, and many of the newly prepared Cs-Ag hybrid NPs showed high anticancer activities against HpG2 cells, and induced cellular apoptosis by downregulating BCL2 gene and upregulating P53. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Using chemical reduction, silver nanoparticle hydrosols were obtained and studied in a wide range of ratios of the initial reagents-NaBH 4: AgNO 3 from 0.1 to 10 and AOT: AgNO 3 from 0 to 1—where AOT is dioctyl sulfosuccinate sodium salt. Silver hydrosols are studied using transmission electron microscopy, dynamic light scattering, UV spectroscopy, and ionometry. The optimal ratios of the initial reagents are determined, which make it possible to obtain samples with a narrow particle size distribution of 2 to 20 nm and average size of silver nanoparticles of 10 nm. The samples synthesized are stable over an extended period of time (up to six months) and contain an insignificant amount of ionic silver, which makes them useful for application in medicine. [ABSTRACT FROM AUTHOR]

The synthesis of stable colloidal solutions of silver nanoparticles is a major goal in the industry to control their fate in aqueous solutions. The present work studies 10-20-nm silver nanoparticle aggregation triggered by the presence of chloride ions. The aggregation process was followed by UV-Vis-NIR spectroscopy and transmission electron microscopy. We found that the mechanism involved differs from the classic explanation of nanoparticle aggregation triggered by an increase in the ionic strength. Moreover, our results give evidence that even when nanoparticles are resistant to an increment of the total amount of ions, the formation of insoluble salts in the vicinity of the nanoparticle is enough to induce the aggregation. The presence of silver chloride around the silver nanoparticles was documented by an X-ray diffraction pattern and electrochemical methods because chloride anions are ubiquitous in real media; this alternative process jeopardized the development of many applications with silver nanoparticles that depend on the use of stable colloids. [ABSTRACT FROM AUTHOR]

Metal-tolerant microorganisms have been exploited in recent years to synthesize nanoparticles due to their potential to offer better size control through peptide binding and compartmentalization. In this paper, we report the intracellular synthesis of silver nanoparticles (SNPs) by the highly silver-tolerant marine bacterium, Idiomarina sp. PR58-8 on exposure to 5 mM silver nitrate. SNPs were characterized by UV-visible spectrophotometry, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). UV-visible absorption scan of a 48 h culture exposed to 5 mM silver nitrate revealed a broad peak at 450 nm indicative of the surface plasmon resonance of SNPs. XRD analysis confirmed the presence of elemental silver and the crystallite size was calculated to be 25 nm using Scherrer formula. The average particle size as per TEM analysis was found to be 26 nm. Metal stress is known to induce the production of non-protein thiols (NP-SHs) which sequester metal ions. In this study, the production of NP-SHs was followed from 6-48 h, wherein it was observed that the NP-SH levels in the silver-exposed culture were consistently higher (261% on an average) than in the unexposed culture. [ABSTRACT FROM AUTHOR]

A simple and green chemical method has been developed to synthesize stable bare and capped silver nanoparticles based on the reduction of silver ions by glucose and capping by poly(α,γ, l-glutamic acid) (PGA). The use of ammonia during synthesis was avoided. PGA has had a dual role in the synthesis and was used as a capping agent to make the silver nanoparticle more biocompatible and to protect the nanoparticles from agglomerating in the liquid medium. The synthesized PGA-capped silver nanoparticles in the size range 5-45 nm were stable over long periods of time, without signs of precipitation. Morphological examination has shown that the silver nanoparticles had a nearly spherical, multiply twinned structure. The effects of the reaction temperature and the reaction time during the synthesis were investigated too. The biocompatibility of the PGA-capped silver nanoparticles is discussed in terms of in vitro toxicity with human intestinal Caco-2 cells. The samples were characterized by UV-Visible spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, and zeta potential measurements. [ABSTRACT FROM AUTHOR]

The increasing use of manufactured nanoparticles ensures these materials will make their way into the environment. Silver nanoparticles in particular, due to use in a wide range of applications, have the potential to get into water systems, e.g., drinking water systems, ground water systems, estuaries, and/or lakes. One important question is what is the chemical and physical state of these nanoparticles in water? Are they present as isolated particles, agglomerates or dissolved ions, as this will dictate their fate and transport. Furthermore, does the chemical and physical state of the nanoparticles change as a function of size or differ from micron-sized particles of similar composition? In this study, an electrospray atomizer coupled to a scanning mobility particle sizer (ES-SMPS) is used to investigate the state of silver nanoparticles in water and aqueous nitric acid environments. Over the range of pH values investigated, 0.5–6.5, silver nanoparticles with a bimodal primary particle size distribution with the most intense peak at 5.0 ± 7.4 nm, as determined from transmission electron microscopy (TEM), show distinct size distributions indicating agglomeration between pH 6.5 and 3 and isolated nanoparticles at pH values from 2.5 to 1. At the lowest pH investigated, pH 0.5, there are no peaks detected by the SMPS, indicating complete nanoparticle dissolution. Further analysis of the solution shows dissolved Ag ions at a pH of 0.5. Interestingly, silver nanoparticle dissolution shows size dependent behavior as larger, micron-sized silver particles show no dissolution at this pH. Environmental implications of these results are discussed. [ABSTRACT FROM AUTHOR]

In this article, we describe a simple one-pot rapid synthesis route to produce uniform silver nanoparticles by thermal reduction of AgNO3 using oleylamine as reducing and capping agent. To enhance the dispersal ability of as-synthesized hydrophobic silver nanoparticles in water, while maintaining their unique properties, a facile phase transfer mechanism has been developed using biocompatible block co-polymer pluronic F-127. Formation of silver nanoparticles is confirmed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV–vis spectroscopy. Hydrodynamic size and its distribution are obtained from dynamic light scattering (DLS). Hydrodynamic size and size distribution of as-synthesized and phase transferred silver nanoparticles are 8.2 ± 1.5 nm (σ = 18.3%) and 31.1 ± 4.5 nm (σ = 14.5%), respectively. Antimicrobial activities of hydrophilic silver nanoparticles is tested against two Gram positive ( Bacillus megaterium and Staphylococcus aureus), and three Gram negative ( Escherichia coli, Proteus vulgaris and Shigella sonnei) bacteria. Minimum inhibitory concentration (MIC) values obtained in the present study for the tested microorganisms are found much better than those reported for commercially available antibacterial agents. [ABSTRACT FROM AUTHOR]