Special Issue "Silver Nanoparticles: Synthesis, Detection, Characterization and Assessment in Environment"

A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "Synthesis, Interfaces and Nanostructures".

Deadline for manuscript submissions: 29 July 2021.

Special Issue Editor

Dr. Mònica Iglesias
E-Mail Website
Guest Editor
Chemistry Department. Universitat de Girona, Girona, Spain
Interests: Analytical Chemistry, Atomic spectroscopy, development of analytical methodology, potentially toxic elements in the environment, Nanomaterials characterization and assessment

Special Issue Information

Dear Colleagues,

The production of silver nanoparticles (AgNPs) has grown in last years because of the special physicochemical properties that they present. As known, these nanomaterials are widely used in commercial products due to their antibacterial properties, which increase their intentional or unintentional release in the environment. Once there, AgNPs can suffer interactions with natural components, which can affect their final toxic effects. Therefore, characterization and quantification of these emerging pollutants in environmental and biological samples with adequate analytical methodologies is needed.

A wide range of methods and techniques to characterize and quantify nanosilver in simple matrices is available, but difficulties still exist to determine these emerging contaminants in complex samples. Moreover, the demanded analytical information can entail not only their detection and quantification, but also their particle characteristics determination. Furthermore, AgNPs can undergo transformations in different environmental compartments and living beings as a result of the interaction with some components, which makes their characterization and quantification even more difficult. Another challenge of analyzing AgNP in complex samples is the low concentration of these emerging pollutants and the co-existence of AgNPs with other silver containing chemical species (Ag(I)) or NPs of different origins (natural or manufactured) and with distinct characteristics (e.g. coating). For these reasons, the development and improvement of analytical techniques is needed.

The special Issue entitled “Silver Nanoparticles: Synthesis, Detection, Characterization and assessment in the environment” aims to cover current studies, in the field of the AgNPs synthesis and characterization. Advanced analytical methodologies and sample treatment procedures to determine and characterize AgNPS as well as to understand their behavior in the environment, are very welcome.

Dr. Mònica Iglesias
Guest Editor

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Keywords

  • Silver Nanoparticles
  • Sample preparation
  • Characterization
  • Analytical methodology
  • Speciation
  • Environmental Samples

Published Papers (8 papers)

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Research

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Open AccessArticle
Study of the Stability of Citrate Capped AgNPs in Several Environmental Water Matrices by Asymmetrical Flow Field Flow Fractionation
Nanomaterials 2021, 11(4), 926; https://doi.org/10.3390/nano11040926 - 05 Apr 2021
Viewed by 512
Abstract
Asymmetrical flow field-flow fractionation (AF4) coupled to UV-Vis and dynamic light scattering (DLS) detectors in series, was tested for stability studies of dispersions of citrate-capped silver nanoparticles (AgNPs) in several water matrices. The main goal is to provide knowledge to understand their possible [...] Read more.
Asymmetrical flow field-flow fractionation (AF4) coupled to UV-Vis and dynamic light scattering (DLS) detectors in series, was tested for stability studies of dispersions of citrate-capped silver nanoparticles (AgNPs) in several water matrices. The main goal is to provide knowledge to understand their possible behavior in the environment for short times since mixturing (up to 180 min). Ultrapure (UPW), bottled (BW1, BW2), tap (TW), transitional (TrW) and sea water (SW) matrices were assayed. Observations were compatible with the aggregation of AgNPs, a change in the plasmon band and a size growth with time were done. Fractograms showed different evolution fingerprints in the function of the waters and batches. The aggregation rate order was BW2, SW, TrW, BW1 and TW, being BW2 the lowest and TW the highest. NP aggregation can be induced by increasing the salt concentration of the medium, however transitional and sea waters did not follow the rule. Both matrices presented a lower aggregation rate in comparison with other aqueous matrices with much lower ionic strength (BW1 and TW), which can be explained by the potential presence of dissolved organic matter and/or the high concentration of halides providing their stabilization and passivation, respectively. AF4 provides relevant information with respect to static DLS and UV-Vis Spectroscopy showing that at least two populations of aggregates with different sizes between them, depending on both, the mixture time for a given matrix and type of water matrix for the same time. Full article
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Open AccessArticle
Phytotoxicity of Silver Nanoparticles on Tobacco Plants: Evaluation of Coating Effects on Photosynthetic Performance and Chloroplast Ultrastructure
Nanomaterials 2021, 11(3), 744; https://doi.org/10.3390/nano11030744 - 16 Mar 2021
Viewed by 374
Abstract
Silver nanoparticles (AgNPs) are the most exploited nanomaterial in agriculture and food production, and their release into the environment raises concern about their impact on plants. Since AgNPs are prone to biotransformation, various surface coatings are used to enhance their stability, which may [...] Read more.
Silver nanoparticles (AgNPs) are the most exploited nanomaterial in agriculture and food production, and their release into the environment raises concern about their impact on plants. Since AgNPs are prone to biotransformation, various surface coatings are used to enhance their stability, which may modulate AgNP-imposed toxic effects. In this study, the impact of AgNPs stabilized with different coatings (citrate, polyvinylpyrrolidone (PVP), and cetyltrimethylammonium bromide (CTAB)) and AgNO3 on photosynthesis of tobacco plants as well as AgNP stability in exposure medium have been investigated. Obtained results revealed that AgNP-citrate induced the least effects on chlorophyll a fluorescence parameters and pigment content, which could be ascribed to their fast agglomeration in the exposure medium and consequently weak uptake. The impact of AgNP-PVP and AgNP-CTAB was more severe, inducing a deterioration of photosynthetic activity along with reduced pigment content and alterations in chloroplast ultrastructure, which could be correlated to their higher stability, elevated Ag accumulation, and surface charge. In conclusion, intrinsic properties of AgNP coatings affect their stability and bioavailability in the biological medium, thereby indirectly contributing changes in the photosynthetic apparatus. Moreover, AgNP treatments exhibited more severe inhibitory effects compared to AgNO3, which indicates that the impact on photosynthesis is dependent on the form of Ag. Full article
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Open AccessArticle
Supported Silver Nanoparticles as Catalysts for Liquid-Phase Betulin Oxidation
Nanomaterials 2021, 11(2), 469; https://doi.org/10.3390/nano11020469 - 12 Feb 2021
Viewed by 440
Abstract
Herein, it has been shown that betulin can be transformed into its biologically active oxo-derivatives (betulone, betulinic and betulonic aldehydes) by liquid-phase oxidation over supported silver catalysts under mild conditions. In order to identify the main factors determining the catalytic behavior of nanosilver [...] Read more.
Herein, it has been shown that betulin can be transformed into its biologically active oxo-derivatives (betulone, betulinic and betulonic aldehydes) by liquid-phase oxidation over supported silver catalysts under mild conditions. In order to identify the main factors determining the catalytic behavior of nanosilver catalysts in betulin oxidation, silver was deposited on various alumina supports (γ-alumina and boehmite) using deposition–precipitation with NaOH and incipient wetness impregnation methods, followed by treatment in H2 or O2. Silver catalysts and the corresponding supports were characterized by X-ray diffraction, nitrogen physisorption, inductively coupled plasma optical emission spectroscopy, photoelectron spectroscopy and transmission electron microscopy. It was found that the support nature, preparation and treatment methods predetermine not only the average Ag nanoparticles size and their distribution, but also the selectivity of betulin oxidation, and thereby, the catalytic behavior of Ag catalysts. In fact, the support nature had the most considerable effect. Betulin conversion, depending on the support, increased in the following order: Ag/boehmite < Ag/boehmite (calcined) < Ag/γ-alumina. However, in the same order, the share of side reactions catalyzed by strong Lewis acid centers of the support also increased. Poisoning of the latter by NaOH during catalysts preparation can reduce side reactions. Additionally, it was revealed that the betulin oxidation catalyzed by nanosilver catalysts is a structure-sensitive reaction. Full article
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Open AccessArticle
Starch-Capped AgNPs’ as Potential Cytotoxic Agents against Prostate Cancer Cells
Nanomaterials 2021, 11(2), 256; https://doi.org/10.3390/nano11020256 - 20 Jan 2021
Viewed by 702
Abstract
One of the major therapeutic approaches of prostate cancer (PC) is androgen deprivation therapy (ADT), but patients develop resistance within 2–3 years, making the development of new therapeutic approaches of great importance. Silver nanoparticles (AgNPs) synthesized through green approaches have been studied as [...] Read more.
One of the major therapeutic approaches of prostate cancer (PC) is androgen deprivation therapy (ADT), but patients develop resistance within 2–3 years, making the development of new therapeutic approaches of great importance. Silver nanoparticles (AgNPs) synthesized through green approaches have been studied as anticancer agents because of their physical-chemical properties. This study explored the cytotoxic capacity of starch-capped AgNPs, synthesized through green methods, in LNCaP and in PC-3 cells, a hormonal-sensitive and hormone-resistant PC cell line, respectively. These AgNPs were synthesized in a microwave pressurized synthesizer and characterized by ultraviolet-visible (UV-Vis) spectroscopy, transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDX). Their cytotoxicity was assessed regarding their ability to alter morphological aspect (optical microscopy), induce damage in cytoplasmic membrane (Trypan Blue Assay), mitochondria (WST-1 assay), cellular proliferation (BrdU assay), and cell cycle (Propidium iodide and flow-cytometry). AgNPs showed surface plasmon resonance (SPR) of approximately 408 nm and average size of 3 nm. The starch-capped AgNPs successfully induced damage in cytoplasmic membrane and mitochondria, at concentrations equal and above 20 ppm. These damages lead to cell cycle arrest in G0/G1 and G2/M, blockage of proliferation and death in LNCaP and PC-3 cells, respectively. This data shows these AgNPs’ potential as anticancer agents for the different stages of PC. Full article
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Open AccessArticle
Silicon-Based Ag Dendritic Nanoforests for Light-Assisted Bacterial Inhibition
Nanomaterials 2020, 10(11), 2244; https://doi.org/10.3390/nano10112244 - 12 Nov 2020
Viewed by 383
Abstract
Silver dendritic nanoforests (Ag-DNFs) on silicon (Ag-DNFs/Si) were synthesized through the fluoride-assisted Galvanic replacement reaction (FAGRR) method. The synthesized Ag-DNFs/Si were characterized by scanning electron microscopy, energy-dispersive X-ray spectrometry, inductively coupled plasma mass spectrometry (ICP-MS), reflection absorbance spectrometry, surface-enhanced Raman scattering spectrometry, and [...] Read more.
Silver dendritic nanoforests (Ag-DNFs) on silicon (Ag-DNFs/Si) were synthesized through the fluoride-assisted Galvanic replacement reaction (FAGRR) method. The synthesized Ag-DNFs/Si were characterized by scanning electron microscopy, energy-dispersive X-ray spectrometry, inductively coupled plasma mass spectrometry (ICP-MS), reflection absorbance spectrometry, surface-enhanced Raman scattering spectrometry, and X-ray diffractometry. The Ag+ concentration in ICP-MS measurements indicated 1.033 mg/cm2 of deposited Ag synthesized for 200 min on Si substrate. The optical absorbance spectra indicated the induced surface plasmon resonance of Ag DNFs increased with the thickness of the Ag DNFs layer. Surface-enhanced Raman scattering measurement and a light-to-heat energy conversion test presented the superior plasmonic response of Ag-DNFs/Si for advanced applications. The Ag-DNFs/Si substrate exhibited high antibacterial activity against Escherichia coli and Staphylococcus aureus. The large surface area of the dense crystal Ag DNFs layer resulted in high antibacterial efficiency. The plasmonic response in the metal–crystal Ag DNFs under external light illumination can supply energy to enhance bacterial inhibition. High-efficiency plasmonic heating by the dense Ag DNFs can lead to localized bacterial inhibition. Thus, the Ag-DNFs/Si substrate has excellent potential for antibacterial applications. Full article
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Open AccessArticle
Silver Nanoparticles Alter Cell Viability Ex Vivo and in Vitro and Induce Proinflammatory Effects in Human Lung Fibroblasts
Nanomaterials 2020, 10(9), 1868; https://doi.org/10.3390/nano10091868 - 18 Sep 2020
Viewed by 647
Abstract
Silver nanoparticles (AgNPs) are commonly used in commercial and medical applications. However, AgNPs may induce toxicity, extracellular matrix (ECM) changes and inflammatory responses. Fibroblasts are key players in remodeling processes and major producers of the ECM. The aims of this study were to [...] Read more.
Silver nanoparticles (AgNPs) are commonly used in commercial and medical applications. However, AgNPs may induce toxicity, extracellular matrix (ECM) changes and inflammatory responses. Fibroblasts are key players in remodeling processes and major producers of the ECM. The aims of this study were to explore the effect of AgNPs on cell viability, both ex vivo in murine precision cut lung slices (PCLS) and in vitro in human lung fibroblasts (HFL-1), and immunomodulatory responses in fibroblasts. PCLS and HFL-1 were exposed to AgNPs with different sizes, 10 nm and 75 nm, at concentrations 2 µg/mL and 10 μg/mL. Changes in synthesis of ECM proteins, growth factors and cytokines were analyzed in HFL-1. Ag10 and Ag75 affected cell viability, with significantly reduced metabolic activities at 10 μg/mL in both PCLS and HFL-1 after 48 h. AgNPs significantly increased procollagen I synthesis and release of IL-8, prostaglandin E2, RANTES and eotaxin, whereas reduced IL-6 release was observed in HFL-1 after 72 h. Our data indicate toxic effects of AgNP exposure on cell viability ex vivo and in vitro with altered procollagen and proinflammatory cytokine secretion in fibroblasts over time. Hence, careful characterizations of AgNPs are of importance, and future studies should include timepoints beyond 24 h. Full article
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Open AccessArticle
High Variability in Silver Particle Characteristics, Silver Concentrations, and Production Batches of Commercially Available Products Indicates the Need for a More Rigorous Approach
Nanomaterials 2020, 10(7), 1394; https://doi.org/10.3390/nano10071394 - 17 Jul 2020
Cited by 2 | Viewed by 716
Abstract
Due to the beneficial properties of silver, it is anticipated that the number of commercially available applications will keep growing during the next decade. In this study, 14 different commercial products that claim to contain solid silver were characterized by visual analysis, UV-VIS [...] Read more.
Due to the beneficial properties of silver, it is anticipated that the number of commercially available applications will keep growing during the next decade. In this study, 14 different commercial products that claim to contain solid silver were characterized by visual analysis, UV-VIS spectroscopy, inductive coupled plasma optical emission spectrometry (ICP-OES), scanning transmission electron microscopy with energy dispersive x-ray spectroscopy (STEM-EDX), and dynamic light scattering (DLS). Moreover the variation between production batches—which has never been researched before—was investigated. All four techniques corroborated that some products were highly concentrated and contained spherically-shaped silver nanoparticles (AgNPs), while in others, no (solid) silver was detected or only irregularly-shaped silver particles with a high size polydispersity were present. For almost all products, a significant difference between the claimed and measured silver concentration was detected and a high variability between different production batches of the same product was observed. Our results show the need for a more rigorous approach regarding the manufacturing, labeling, and use of silver-containing products. Full article
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Review

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Open AccessReview
Silver Nanoparticle-Based Nanocomposites for Combating Infectious Pathogens: Recent Advances and Future Prospects
Nanomaterials 2021, 11(3), 581; https://doi.org/10.3390/nano11030581 - 26 Feb 2021
Viewed by 453
Abstract
Silver nanoparticles (Ag NPs) and their nanocomposites with polymers are potent agents for antibacterial and disinfectant applications. The structural parameters of Ag-NPs, such as size, shape, and surface area, are very critical for developing appropriate formulations for the targeted applications. The impact of [...] Read more.
Silver nanoparticles (Ag NPs) and their nanocomposites with polymers are potent agents for antibacterial and disinfectant applications. The structural parameters of Ag-NPs, such as size, shape, and surface area, are very critical for developing appropriate formulations for the targeted applications. The impact of these factors on the performance of Ag NPs is analyzed. Ag NPs with a broad spectrum of antibacterial activities have already found applications in wound and burn dressing, food preservation, agricultural ponds, treatment for infected areas, coatings, water treatment, and other biomedical applications. Ag NPs are quite useful against antibiotic-resistant bacteria, but their level of toxicity needs careful investigation as their toxicity could be very harmful to human health and the environment. This review discusses the challenges and prospects of various Ag NPs and their composites. The review will enrich the knowledge about the efficiency and mechanism of various Ag nanoparticle-based antibacterial agents. Full article
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