Stability Of AgNPs Research Articles

Synthesis and Characterization of Silver Nanoparticles Using Alginate from the Brown Seaweed Laminaria ochroleuca: Structural Features and Antibacterial Activity

In this study, inexpensive and eco-friendly production of the silver nanoparticles (AgNPs) was explored using Laminaria ochroleuca sodium alginate as stabilizing and reducing agent. The synthesized nanoparticles were characterized by various analytical techniques such as UV–Vis spectroscopy, Energy dispersive X-ray spectrometer (EDX), X-ray diffraction (XRD), transmission electron microscopy (TEM), TEM selected area electron diffraction (SAED), Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA). The synthesis of AgNPs was elucidated by characteristic absorption peaks in the UV–Vis test. The FTIR analysis revealed the involvement of many functional groups in the bioreduction and the stabilization of AgNPs, while TEM images illustrated the spherical shape with maximum particles found in the size range of 10-20 nm. Prominent peaks and silver diffraction rings shown by the XRD spectrum and SAED pattern, respectively, confirmed the crystalline nature (fcc) of the synthesized AgNPs, which were found to be thermally stable based on TGA analysis. The AgNPs exhibited strong antibacterial activity against Gram+ and Gram– bacteria. The synthesized silver nanoparticles using Laminaria ochroleuca sodium alginate revealed interesting properties that could be potentially used for pharmaceutical applications.

Facile synthesis of chitosan/Ag-waterborne polyurethane composite films with a high stability and controllable water resistance for potential application in antibacterial materials

Waterborne polyurethane (WPU) and Ag NPs have been applied widely in packaging. However, WPU was susceptible to the contamination due to high moisture absorption, and the stability of Ag NPs in matrix polymers was still low. To resolve this problem, chitosan (CS) was used as the dispersant to synthesize CS/Ag NPs composites in this work, and then they were mixed with WPU to prepare CS/Ag-WPU films. CS macromolecules provided the carriers for Ag NPs with a diameter of about 2.5 nm, and Ag NPs were dispersed stably in WPU. Compared with pure WPU film, as-prepared CS/Ag-WPU films had a higher thermal stability at low temperature, and the crystal size for WPU increased after introducing CS/Ag NPs. Importantly, the water contact angle for CS/Ag-WPU-5 increased to 54.2° from 27.5° implying that the hydrophobicity was improved. In addition, CS/Ag-WPU composites exhibited an excellent inhibitory effect on Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Antibacterial performances of most samples were improved with the crease of the concentration of CS, and the inhibitory effect on S. aureus was preferred. Therefore, as-prepared CS/Ag-WPU films in this paper have a potential application in antibacterial packaging field.

Photochemical synthesis of metallic silver nanoparticles using Pistacia khinjuk leaves extract (PKL@AgNPs) and their applications as an alternative catalytic, antioxidant, antibacterial, and anticancer agents

AbstractIn recent decades, antimicrobial resistance of different bacteria against various antibiotics and contamination of water resources by various dyes has been one of the most important human problems. Therefore, in this research, biogenic silver nanoparticles were synthesized using nontoxic and rapid approach using Pistacia khinjuk leaves extract (P. khinjuk) as compatible and safe reducing agent (PKL@AgNPs). Nanoparticle optimization experiments were performed at different times, temperatures and concentrations in order to achieve the most optimal conditions. The biosynthesized AgNPs were characterized in terms crystalline, morphology and structural. The Fourier‐transform infrared spectroscopy (FT‐IR) spectra showed that the phenol compounds present in the P. khinjuk leaves extract were responsible for silver ion (Ag+) reduction and stabilization of AgNPs (Ag0). X‐ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) analysis results revealed that the product were face‐centered cubic structure, homogeneous, uniformly, oval‐like and spherical morphology with size of about 35–45 nm. The biosynthesized AgNPs exhibited a high photocatalytic activity for the degradation of the methylene blue (MB) and methyl orange (MO) as hazardous contaminants. The degradation efficiency of PKL@AgNPs for MB and MO pollutants were 93.2% and 85.37% under UV and 75.18% and 70.03% under sun‐light irradiations, respectively. Furthermore, the PKL@AgNPs showed strong antibacterial and antifungal activities against Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, Streptococcus mutans, Streptococcus mitis, Enterococcus faecalis, and Candida albicans with minimum inhibitory concentration (MIC) values of 0.58, 0.58, 0.58, 1.17, 2.34, 1.17, and 0.15 μg ml−1, respectively. The antioxidant activity of PKL@AgNPs was calculated and the results revealed that the percentage of DPPH inhibition increased (3.8% to 69.9%) with increasing the concentration of nanoparticles. Also, the PKL@AgNPs also revealed significant anticancer activity on k562 as a human leukemia cancer cell line (IC50 = 2.69 μg ml−1). All these investigations revealed that silver nanoparticles synthesized by natural extract have the potential to use as low‐cost and efficient nanoparticles for environmental and biomedical applications.

Evaluation of antioxidant, antimicrobial and antiproliferative activity of silver nanoparticles derived from Galphimia glauca leaf extract

ObjectiveThe bio-synthesis of silver nanoparticles (AgNPs) is regarded as environment friendly and cost effective method compared to physical and chemical synthesis methods. Silver (Ag) is an important noble metal due to its tremendous use in research and medical fields throughout the world. This research work was aimed at green synthesis and characterizations of AgNPs from G. glauca leaf extract and evaluation of their bioactive potential. MethodsIn the current research work, synthesis of AgNPs from G. glauca aqueous leaf extracts was performed and was characterized by UV–Visible (UV–Vis.), Fourier transform infrared (FTIR), Atomic force microscopy (AFM), Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS), High-resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), Thermo gravimetric analysis (TGA) and Zeta potential exploration. Later, antioxidant, antimicrobial activity was examined against various pathogenic organisms and anticancer activities of AgNPs were carried out against SK-HEP1 cell line. ResultsThe first indication of synthesis of nanoparticles was the change in color from yellowish to brown. UV–Vis. band exhibited surface plasmon resonance (SPR) at 402 nm. FTIR analysis revealed the probable bio-molecules including alkanes, alkenes, aromatics, aromatic phosphates, imine or oxime, etc. subjected to reduction of silver ions to metallic silver. The AFM, SEM and TEM analysis reported the particles were spherical shaped, poly-dispersed, 17 to 40 nm in size. The zeta potential analysis expressed a peak at –32.0 ± 0.5 mV and suggested the particles with significant long term stability. The TGA analysis revealed the stability of AgNPs at high temperature (179 ℃). The antioxidant assay of AgNPs unveiled an effective dose dependent increase in scavenging activity. Antimicrobial activity showed efficient inhibitory activity against P. aeruginosa and C. glabrata. Lastly, the AgNPs revealed a strong anticancer activity against SK-HEP1 liver cancer cell line with an IC50 value of 19.12 μg/mL. ConclusionsTherefore, it could be concluded that a substantial in-vivo investigations are needed for antioxidant, antibacterial and anticancer activities, so that it will be useful in medical field in future.

Green Synthesis of Silver Nanoparticles using Medicinal Plants BerberisAsiatica and Cassia Fistula and Evaluation of Antioxidant and Anti-bacterial Activities

The application of silver nanoparticles in various sectors including health related field is remarkably profound. Nowadays, the research of synthesizing metal nanoparticles (MNPs) using plant extracts is fascinating field as it offers the eco-friendly and cost-effective method for nanoparticle synthesis. In this study, we synthesized silver nanoparticles (AgNPs) using methanolic extract of B.asiatica and C. fistula regarding their ethnomedical importance. The synthesized AgNPs were characterized by UV-Visible spectroscopy, Fourier transform infrared spectroscopy (FTIR) and X-ray diffractometer (XRD). UV-vis spectroscopy exhibited the characteristic Surface Plasmon Peak of silver nanoparticle~420 nm.FTIR data were measured to get a preliminary idea on the functional groups responsible for the stabilization of AgNPs. XRD data confirmed the natural crystal structure with a face centered cubic of AgNPs. The antibacterial activity of biosynthesized AgNPs was assessed by testing promptly available gram-positive Staphylococcus aureus and gram-negative Escherichia coli bacterial strain and antioxidant activity was calculated by DPPH assay. The overall outcomes of the studies concluded that the application of the biogenic synthesis of AgNPs of B. asiaticaas an antioxidant and antibacterial agent is more potent showing IC50 value 65.1±1.30 μg/mL and the highest zone of inhibition 15 mm in diameter against S. aureus.

Biosynthesis, Characterization and Antibacterial Application of Novel Silver Nanoparticles against Drug Resistant Pathogenic Klebsiella pneumoniae and Salmonella Enteritidis.

The present study highlights the biosynthesis of silver nanoparticles (AgNPs) using culture supernatant of Massilia sp. MAHUQ-52 as well as the antimicrobial application of synthesized AgNPs against multi-drug resistant pathogenic Klebsiella pneumoniae and Salmonella Enteritidis. Well-defined AgNPs formation occurred from the reaction mixture of cell-free supernatant and silver nitrate (AgNO3) solution within 48 h of incubation. UV-visible spectroscopy analysis showed a strong peak at 435 nm, which corresponds to the surface plasmon resonance of AgNPs. The synthesized AgNPs were characterized by FE-TEM, EDX, XRD, DLS and FT-IR. From FE-TEM analysis, it was found that most of the particles were spherical shape, and the size of synthesized nanoparticles (NPs) was 15–55 nm. EDX spectrum revealed a strong silver signal at 3 keV. XRD analysis determined the crystalline, pure, face-centered cubic AgNPs. FT-IR analysis identified various functional molecules that may be involved with the synthesis and stabilization of AgNPs. The antimicrobial activity of Massilia sp. MAHUQ-52 mediated synthesized AgNPs was determined using the disk diffusion method against K. pneumoniae and S. Enteritidis. Biosynthesized AgNPs showed strong antimicrobial activity against both K. pneumoniae and S. Enteritidis. The MICs of synthesized AgNPs against K. pneumoniae and S. Enteritidis were 12.5 and 25.0 μg/mL, respectively. The MBC of biosynthesized AgNPs against both pathogens was 50.0 μg/mL. From FE-SEM analysis, it was found that the AgNPs-treated cells showed morphological changes with irregular and damaged cell walls that culminated in cell death.

Green synthesis: characterization and biological activity of silver nanoparticles using aqueous extracts of plants from the Arecaceae family

This study proposes the preparation, characterization, and evaluation of the antimicrobial activity of silver nanoparticles (AgNPs). AgNPs were synthesized from the leaf extracts of plants from the Arecaceae family, which are abundant in the Amazon region. AgNPs were characterized using UV/Vis spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), dynamic light scattering (DLS), and their minimum inhibitory concentrations (MIC) against the bacteria Escherichia coli and Staphylococcus aureus. AgNPs presented maximum absorbance between 420 and 430 nm, the mean diameter obtained by DLS ranged from 130.43 to 352.93 nm and the polydispersity index (PdI) ranged from 0.523 to 0.689. The surface charge measured by the Zeta potential was negative and ranged from -17.2 to -26.97 mV. FTIR analysis suggests that the phenolic compounds and/or proteins in the chemical composition of the plants studied may have been responsible for the reduction of Ag+ ions and stabilization of AgNPs. The morphology of AgNPs observed was largely spherical and presented some agglomerates. Transmission electron microscopy analyses showed polydispersed AgNPs without the formation of large agglomerates. The synthesized AgNPs presented homogeneity and rapid bioreduction. The concentration of AgNPs required to eliminate microorganisms by up to 90% was lower for Gram-negative bacteria (2.75 μg mL-1) than for Gram-positive bacteria (21.75 μg mL-1). In addition, AgNPs synthesized from plant species that are native to the Amazon proved to be promising, since they showed excellent antimicrobial activity against microorganisms of clinical interest.

Effect of Laser Parameters on the Characteristics and Stability of Ag NPs Produced by Laser Ablation in Stationary Conditions

The effect of laser ablation parameters on the size and stability of synthesized silver nanoparticles (Ag NPs) by laser ablation in deionised water was investigated. The results showed that the selected laser parameters (laser pulse wavelength and laser fluence) and ablation of the target in a fixed beam position had a direct effect on the size and size distribution of Ag NPs. The stability of all Ag nanoparticle samples prepared in different laser parameters has been studied. All the samples of Ag NPs presented remarkable long-term stability up to two months.

Trace level detection of explosives and pesticides using robust, low-cost, free-standing silver nanoparticles decorated porous silicon.

We report results from our extensive studies on the fabrication of ultra-thin, flexible, and cost-effective Ag nanoparticle (NP) coated free-standing porous silicon (FS-pSi) for superior molecular sensing. The FS-pSi has been prepared by adopting a simple wet-etching method. The deposition time of AgNO3 has been increased to improve the number of hot-spot regions, thereby the sensing abilities are improved efficiently. FESEM images illustrated the morphology of uniformly distributed AgNPs on the pSi surface. Initially, a dye molecule [methylene blue (MB)] was used as a probe to evaluate the sensing capabilities of the substrate using the surface-enhanced Raman scattering (SERS) technique. The detection was later extended towards the sensing of two important explosive molecules [ammonium nitrate (AN), picric acid (PA)], and a pesticide molecule (thiram) clearly demonstrating the versatility of the investigated substrates. The sensitivity was confirmed by estimating the analytical enhancement factor (AEF), which was ∼107 for MB and ∼104 for explosives and pesticides. We have also evaluated the limit of detection (LOD) values in each case, which were found to be 50 nM, 1 µM, 2 µM, and 1 µM, respectively, for MB, PA, AN, and thiram. Undeniably, our detailed SERS results established excellent reproducibility with a low RSD (relative standard deviation). Furthermore, we also demonstrate the reasonable stability of AgNPs decorated pSi by inspecting and studying their SERS performance over a period of 90 days. The overall cost of these substrates is attractive for practical applications on account of the above-mentioned superior qualities.

Green synthesis of antimicrobial silver nanoparticles using fruit extract of Glycosmis pentaphylla and its theoretical explanations

The present study reports a novel, one-pot, cost-effective, green synthesis route of silver nanoparticles (AgNPs) from the fruit epicarp extract of Glycosmis pentaphylla (FGP). The UV–Vis spectroscopy (UV-Vis), dynamic light scattering (DLS), and transmission electron microscopy (TEM) studies confirmed that the synthesis produces stable, monodispersed AgNPs with an average size of 17 nm. Fourier transform infrared spectroscopy (FTIR) studies suggested that the carbonyl group of the different compounds of FGP made significant interaction with AgNPs. With this indication, a theoretical simulation using density functional theory (DFT) was performed, which established that among the different compounds of FGP, arborine was mainly responsible for the stabilization of AgNPs with a binding energy of 58.45 kJ/mol. Synthesized AgNPs showed strong antifungal (against Alternaria alternata, Colletotrichum lindemuthianum, Fusarium moniliforme, and Candida glabrata) and antibacterial (against Bacillus subtilis, Streptococcus mutans, Escherichia coli, and Salmonella enterica serovar Typhimurium) activity. Synthesized AgNPs showed the highest antifungal activity against Fusarium moniliforme and the highest antibacterial activity against Salmonella enterica serovar Typhimurium. A remarkable synergistic activity of AgNPs was observed with fungicide Bavistin (∼25% increased activity against Alternaria alternata) and antibiotic Streptomycin (∼33.3% increased activity against Bacillus subtilis), which indicated that AgNPs could be applied to control crop and human pathogens with a lower dose of synthetic antimicrobial compounds (e.g., Bavistin, Streptomycin, etc.). Hence, green synthesized AgNPs by this method can be a blessing for crop productivity and hospital management as an effective alternative to conventional fungicides and antibiotics, respectively.

Green Synthesis of Silver Nanoparticles Using Natural Extracts with Proven Antioxidant Activity.

Natural extracts are a rich source of biomolecules that are useful not only as antioxidant drugs or diet supplements but also as complex reagents for the biogenic synthesis of metallic nanoparticles. The natural product components can act as strong reducing and capping substrates guaranteeing the stability of formed NPs. The current work demonstrates the suitability of extracts of Camellia sinensis, Ilex paraguariensis, Salvia officinalis, Tilia cordata, Levisticum officinale, Aegopodium podagraria, Urtica dioica, Capsicum baccatum, Viscum album, and marine algae Porphyra Yezoensis for green synthesis of AgNPs. The antioxidant power of methanolic extracts was estimated at the beginning according to their free radical scavenging activity by the DPPH method and reducing power activity by CUPRAC and SNPAC (silver nanoparticle antioxidant capacity) assays. The results obtained by the CUPRAC and SNAPC methods exhibited excellent agreement (R2~0.9). The synthesized AgNPs were characterized by UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), dynamic light scattering (DLS) particle size, and zeta potential. The UV-vis absorption spectra showed a peak at 423 nm confirming the presence of AgNPs. The shapes of extract-mediated AgNPs were mainly spherical, spheroid, rod-shaped, agglomerated crystalline structures. The NPs exhibited a high negative zeta potential value in the range from −49.8 mV to −56.1 mV, proving the existence of electrostatic stabilization. FTIR measurements indicated peaks corresponding to different functional groups such as carboxylic acids, alcohol, phenol, esters, ethers, aldehydes, alkanes, and proteins, which were involved in the synthesis and stabilization of AgNPs. Among the examined extracts, green tea showed the highest activity in all antioxidant tests and enabled the synthesis of the smallest nanoparticles, namely 62.51, 61.19, and 53.55 nm, depending on storage times of 30 min, 24 h, and 72 h, respectively. In turn, the Capsicum baccatum extract was distinguished by the lowest zeta potential, decreasing with storage time from −66.0 up to −88.6 mM.

Polyvinyl-Pyrrolidone-Coated Silver Nanoparticles-The Colloidal, Chemical, and Biological Consequences of Steric Stabilization under Biorelevant Conditions.

(1) Background: Several properties of silver nanoparticles (AgNPs), such as cytotoxic, anticancer, and antimicrobial activities, have been subjects of intense research; however, important aspects such as nanoparticle aggregation are generally neglected, although a decline in colloidal stability leads to a loss of the desired biological activities. Colloidal stability is affected by pH, ionic strength, or a plethora of biomolecules that interact with AgNPs under biorelevant conditions. (2) Methods: As only a few studies have focused on the relationship between aggregation behavior and the biological properties of AgNPs, here, we have systematically evaluated this issue by completing a thorough analysis of sterically (via polyvinyl-pyrrolidone (PVP)) stabilized AgNPs that were subjected to different circumstances. We assessed ultraviolet–visible light absorption, dynamic light scattering, zeta potential measurements, in vitro cell viability, and microdilution assays to screen both colloidal stability as well as bioactivity. (3) Results: The results revealed that although PVP provided outstanding biorelevant colloidal stability, the chemical stability of AgNPs could not be maintained completely with this capping material. (4) Conclusion: These unexpected findings led to the realization that stabilizing materials have more profound importance in association with biorelevant applications of nanomaterials than just being simple colloidal stabilizers.

Facile Route For The decoration of Nickel Hydroxide Sheets as Antibacterial Nanocomposite for Cellulose Acetate Butyrate Films

The research for the development of antibiotic efficiency against bacteria responsible for common infections is considered of growing worldwide concern. Here, a facile and straight forward method for decorating nickel hydroxide sheets with polypyrrole-silver nanocomposite (Ppy-Ag) was developed by the interfacial polymerization of pyrrole monomer without using any reducing agent. The polypyrrole was used to facilitate the decoration and stabilization of AgNPs on the surface of nickel hydroxide sheets (NH). NH was synthesized using emulsion coprecipitation method. The thermal and morphological properties of the decorated NH have been investigated to confirm the existence of the polypyrrole wrapped layer. Cellulose acetate butyrate (CAB) films were also plasticized with polyvinyl pyrrolidone (PVP) in different mass ratios between PVP and CAB. The results showed that CAB film with 20 wt.% PVP gave the optimal values in terms of mechanical properties. The decorated NH were then added to CAB20 in various mass ratios (3, 6, 9 and 12%) achieving a very good compatibility and forming well dispersed nanocomposites films. The antibacterial activity, water permeability, contact angle and mechanical properties of the developed nanocomposite films were studied. The clear inhibition zone for the new nanocomposite films against S. aureus and E. coli bacteria was recorded as 25.33 ± 1 and 29 ± 1 mm, respectively. Furthermore, the water vapour permeability for the novel CAB nanocomposite films was found 68.83 g/m2/day achieving 29% reduction compared to the blank CAB20 (97.28g/m2/day). Additionally, the mechanical properties were also significantly improved. The different materials were characterized using TGA, FTIR and SEM.

Phyto-Mediated silver nanoparticles via melissa officinalis aqueous and methanolic extracts: Synthesis, characterization and biological properties against infectious bacterial strains

Background: The present study was aimed to examine the influence of extraction method on the morphology, physico-chemical characteristics and antimicrobial properties of silver nanoparticles (AgNPs) synthesized from Melissa officinalis.Methods: AgNPs were prepared by two extraction methods. The properties of obtained nanoparticles were characterized by SEM, UV-Vis, XRD and FTIR techniques. SEM images showed different shape, size and morphology of AgNPs using two different extracts types.Results: The UV-Vis spectroscopy confirmed the formation of AgNPs by observing a distinct surface Plasmon resonance band around 450 nm. SEM images showed different shape, size and morphology of AgNPs using two different extracts types. AgNPs derived from the aqueous extract were rod-shaped with a diameter of 19 to 40 nm whereas spherical particles were synthesized by the methanolic extract found smaller with size distribution ranging from 13 to 35 nm. The XRD pattern indicated that AgNPs formed by the reduction of Ag+ ions using the methanolic extract were crystal-like in nature. The functional groups of the methanolic extract involved in synthesis and stabilization of AgNPs were investigated by FTIR. In addition, AgNPs containing methanolic extract showed higher antioxidant activity.Conclusion: The disc diffusion and agar well diffusion methods revealed the antimicrobial potential of these particles exhibited remarkable antimicrobial activity against Gram positive and Gram negative bacteria and a fungus. The production of silver nanoparticles using plant extract is rapid, low cost and eco-friendly. Silver nanoparticles can be used as an antiseptic to sterilize the surrounding area and the hospital wastes.

Mycosynthesis of silver nanoparticles using Aspergillus caespitosus: Characterization, antimicrobial activities, cytotoxicity, and their performance as an antimicrobial agent for textile materials

AbstractMycosynthesis of stable silver nanoparticles (AgNPs) using Aspergillus caespitosus exo‐ and endo‐filtrates were obtained. Both exo‐ and endo‐AgNPs showed an absorbance peak at 410 nm, spherical, hexagonal, and anisotropic crystalline nanoparticles with 22–57 nm in size. FTIR analysis of mycosynthesized AgNPs showed presence of amide and carbonyl functional groups, which depicts the presence of peptides that involved in the synthesis and stability of AgNPs. Nitrate reductase activity was found to be 0.71 and 0.36 μM/min/ml for exo‐ and endo‐filtrates, respectively. The optimum conditions for the synthesis of exo‐ and endo‐AgNPs were at 6:4 and 8:2 filtrate:double distilled water dilution, respectively. Also, both AgNPs syntheses were the maximum at using one mM AgNO3 in aqueous solution, 24‐h incubation at 30°C under static and illuminating conditions. Aspergillus caespitosus‐synthesized AgNPs showed antimicrobial activities against Gram‐positive and Gram‐negative bacteria and Candida albicans. They showed non‐cytotoxic effect with exception of endo‐AgNPs on MCF‐7 breast carcinoma cells. Different textile samples treated with these nanoparticles exhibited antimicrobial activities against the tested pathogenic microorganisms. Finally, Aspergillus caespitosus is a promising nano‐factory for simple, green, and cost‐effective biosynthesis of AgNPs using extracellular and intracellular filtrates.

Synthesis of Ultrastable and Bioconjugable Ag, Au, and Bimetallic Ag_Au Nanoparticles Coated with Calix[4]arenes.

Compared to gold nanoparticles, silver nanoparticles are largely underexploited for the development of plasmonic nanosensors. This is mainly due to their easy chemical degradation through oxidation, poor colloidal stability, and usually broad size distribution after synthesis, which leads to broad localized surface plasmon resonance bands. Coatings based on polymers such as poly(ethylene glycol) (PEG) or poly(vinylpyrrolidone) (PVP) and plant extracts have been used for the stabilization of AgNPs; however, these thick coatings are not suitable for sensing applications as they isolate the metallic core. The examples of stable AgNPs coated with a thin organic layer remain scarce in comparison to their gold counterparts. In this work, we present a convenient one-step synthesis strategy that allows to obtain unique gold, silver, and bimetallic NPs that combine all of the properties required for biosensing applications. The NPs are stabilized by a tunable calix[4]arene-based monolayer obtained through the reduction of calix[4]arene-tetradiazonium salts. These multidentate ligands are of particular interest as (i) they provide excellent colloidal and chemical stabilities to the particles thanks to their anchoring to the surface via multiple chemical bonds, (ii) they allow the subsequent (bio)conjugation of (bio)molecules under mild conditions, and (iii) they allow a control over the composition of mixed coating layers. Ag and Ag_Au nanoparticles of a high stability are obtained, opening perspectives for development of numerous biosensing applications.

Biosynthesis and characterization of silver nanoparticles using Cinnamomum zeylanicum extract anda study of antibacterial effect against multi-drug resistance Gram-negativebacteria

Introduction and Aim:Nanoparticles for some metals can be used in the treatment of diseases caused by different pathogenic bacteria that are resistant to antibiotics due to the antibacterial properties of thesenanoparticles.In the current study, thesynthesis of silver nanoparticles (Ag) from Cinnamon zeylanicum bark extractwas investigated.
 
 Materials and Methods:One mL of cinnamon bark extract was added to 50mL of 1mM of the silver nitrate (AgNO3). After incubation time of bark extract with AgNO3at room temperature for 1-18hours, the silver nanoparticles synthesis through changed colour of the mixture to dark brown.The UV, TEM and FT-IR analysis were carried out to characterize the biosynthesized Ag-NPs, UV-Vis scan showed absorption around 435 nm while TEM showedAg-NPs spherical shape and the sizes of the and FT-IR spectrum detected the presence of different functional groups responsible for reduction and stability of Ag-NPs in an aqueous solution.
 
 Results:Biosynthesized Ag-NPs showed inhibitory effect against someGram-negative bacterial species that have complete resistance to the antibiotics P, NA, VA, E, TE. The inhibition zone of Ag-NPs wasdetermined as follows (Citrobacter freundii19mm, Klebsiella pneumonae23mm, E.coli 23mm, Enterobacter spp 20 mm, Acinetobacter baumannii20mm.Therefore, Ag-NPs can be used as alternative treatment for some antibiotics.
 
 Conclusion: The Ag-NPs can be successfully prepared form Cinnamomum bark plant. Besides their low cost, these NPs had an antibacterial effect especially against Gram negative bacteria which had a complete resistance to the most common antibiotics

Biodistribution of essential oil-conjugated silver nanoparticles.

The beneficial synergy between antimicrobial silver nanoparticles (AgNPs) and essential oils (EOs), with therapeutic effects that have been acknowledged and explored for a long time, opens the way towards developing new and promising alternatives for anti-infective therapies. With the aim to improve the cytocompatibility and stability of AgNPs and to overcome the volatilization of EOs, AgNPs conjugated with sage (Salvia officinalis) and cinnamon (Cinnamomum aromaticum) EOs were obtained in our study. The synthesis process was realized either by classical or ultrasound-assisted chemical reduction. Compositional and microstructural characterization of the as-obtained Ag@EO NPs was performed by X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The biodistribution of Ag@EO NPs was evaluated on a mouse animal model.

Microplasma assisted synthesis of silver nanoparticles capped with PVA, PVP and Sucrose

Silver nanoparticles (Ag NPs) have been synthesized by exposing Ar gas microplasma to liquid solution containing Ag+ ions. Sucrose, Polyvinyl Alcohol (PVA) and Polyvinylpyrrolidone (PVP) were added separately as capping agents in aqueous solution to avoid agglomeration of Ag NPs. There are two main mechanism involved in this experiment (1). interaction of electrons from microplasma with Ag+ ions present in aqueous solution and (2). Control of Ag NPs size by capping agents by surrounding Ag NPs. We have performed a comparison of capping performance of Sucrose and PVA in terms of stability of Ag NPs with the help of Ultraviolet-Visible spectroscopy (UV-vis). X-ray diffraction (XRD) analysis of Ag NPs capped with PVA and Sucrose shows average crystal size of 25 nm and 60 nm respectively. Dynamic Light Scattering (DLS) analysis was employed to measure the size distribution of Ag NPs capped with Sucrose, PVA and PVP capping agents. DLS showed that PVA-capped Ag NPs formed are more uniform in size as compared to Sucrose-capped. Average size of Ag NPs measured from DLS is 65 nm when capped with PVA and 120 nm when capped with Sucrose. Fourier Transform Infrared Spectroscopy (FTIR) spectrum obtained have bands of wavenumbers corresponding to functional groups of Sucrose and PVA which are present around Ag NPs.

Green Synthesis of Silver Nanoparticles Using Catharanthus roseus Flower Extracts and the Determination of Their Antioxidant, Antimicrobial, and Photocatalytic Activity

The present study describes the antioxidant, antimicrobial, and photocatalytic activity of silver nanoparticles (AGNPs) synthesized using six varieties of Catharanthus roseus flower extracts for the first time. Initially, the synthesized AgNPs were visually confirmed by color change. Further, the formation, size, and shape of the synthesized AgNPs were characterized by UV-Vis spectroscopy and scanning electron microscopy (SEM). The SEM image of purple flower AgNPs and the calculated bandgap energies of the synthesized AgNPs showed that the synthesized AgNPs were in the range of 0–30 nm. Qualitative phytochemical analysis revealed the presence of the phytocompounds that were responsible for the capping, formation, bioreduction, and stabilization of AgNPs. The antioxidant ability of the AgNPs and their respective flower extracts were analyzed using TFC, TPC, TAC, DPPH, FRAP, and IC50 assays. The results of the antioxidant assays indicated that the AgNPs showed higher antioxidant activity compared to their respective flower extracts. The synthesized AgNPs showed significant antimicrobial activity against Gram-negative Escherichia coli compared to Gram-positive Staphylococcus aureus assayed using the agar well diffusion method. Furthermore, the photocatalytic activity of the synthesized purple flower AgNPs at two different concentrations 5000 ppm and 333 ppm was analyzed by the removal of methyl orange dye from an aqueous solution under sunlight irradiation in the presence of NaBH4 catalyst. Results indicated that 333 ppm purple flower AgNPs exhibited an efficient photocatalytic activity in the degradation of methyl orange compared to 5000 ppm purple flower AgNPs in 20 minutes. Thus, the results obtained indicated that Catharanthus roseus is an ecofriendly source for the green synthesis of AgNPs which can be used as a novel antioxidant, antimicrobial, and photocatalytic agent; thereby, it can be used in a variety of applications to improve the quality of human life.