Spherical Silver Research Articles

Synthesis of Silver Nanoparticles with Reductant of Java Long Pepper Leaf Extract (Piper Retrofractum Vahl) and Its Application as a Mercury Detector

The synthesis of silver nanoparticles using the green chemistry concept utilizing Java long pepper leaf extract as a reducing agent has been successful. Silver nanoparticles were synthesized under optimum 1 mM silver nitrate concentration, 250 μL Java long pepper leaf extract, and 30 minutes under sunlight radiation. The silver nanoparticles formed can be confirmed by the change in the color of the solution from colorless to brownish red, indicating a reduction of Ag+ to Ag0. The Uv-vis spectrum showed a peak Surface Plasmon Resonance (SPR) at 441 nm. The FTIR spectrum showed that functional groups' vibrations in the Java Chili Leaf extract confirm that the phenol, alkaloid, and flavonoid compounds present in the extract act as reducing agents. TEM images show spherical silver nanoparticles with an average diameter of 17.65 nm. The potential of silver nanoparticles to detect Hg (II) metal is evidenced by a decrease in the color intensity of the silver nanoparticle solution along with the increasing concentration of Hg (II), which reacts back-oxidizing Ag0 to Ag+. The value of the correlation coefficient of the linear equation is 0.9807.

Latex/AgNPs: Synthesis, and Their Antibacterial Activity

Silver nanoparticles (Ag NPs) coated by an aqueous emulsion of copolymer were elaborated in a short time using polyol process and microwave (MW) heating. This approach is based on reducing AgNO3 powder in the presence of two main components; ethylene glycol as a dispersed medium and an industrial copolymer (latex) as protecting agent. The structural, morphological and optical properties of the prepared silver nanoparticles have been investigated by UV–Vis spectroscopy, Infrared Spectroscopy (IR), X Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). It was found that all these properties are strongly correlated to the latex copolymer concentration and the MW heating process. The absorption band was determined by UV Visible spectra, showing several bands (localized surface Plasmon band) in the visible region at wavelengths between 410 and 430 nm. The TEM analysis of the obtained products indicates the presence of straight nanowires and dispersed, spherical silver nanoparticles with well-controlled size ranging from 7 to 20 nm. The X Ray Diffraction showed that silver nanoparticles synthesized exhibit face centered cubic (fcc) structure. The infrared spectra show the strong coordination between the surface of silver particles and molecules of latex by O–H and C=O groups. Antimicrobial activity of latex/Ag NPs against E. coli, Staphylococcus aureus, and Pseudomonas aeruginosa has been also demonstrated. The results indicated that latex/AgNPs may damage the structure of bacterial cell membrane.

Tuning the dispersity and sphericity of silver particles by wrapping mechanism using Arabic gum

Monodisperse spherical silver micro-assemblies (AgMAs) were prepared through the chemical reaction of ascorbic acid (C6H8O6) and AgNO3. The Anhydrous citric acid (ACA) was used as the surface capping agent to generate silver nano plates (AgNPs) as primary particles. The long chain of Arabic gum (AG) was used as the carrier of primary silver to further synthesize spherical silver. The influence of ACA and AG (ACG) on the formation of silver particles via chemical adsorption is investigated systematically in the paper. AgMAs can be precisely tuned from 1.8 μm to 4.8 μm by adjusting reaction rate. It is a facile way to synthesize silver particles with high sphericity by the wrapping effect of AG, which is beneficial to the preparation of high-quality conductive paste.

Assessment of anti bacterial, anti inflammation and wound healing activity in Wistar albino rats using green silver nanoparticles synthesized from Tagetes erecta leaves

Silver nanoparticles synthesized from plant material have superior bioactivities. The purpose of this current study was to synthesis, characterize and to explore the bioactive efficacy of silver nanoparticles (Ag-NPs) using aqueous leaf extract of Tageteserecta. The biosynthesized Ag-NPs were characterized using ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction and Scanning electron microscopy. Ag-NPs were studied for in-vivo anti-inflammatory and wound healing activities performed in female Wistar albino rats. UV –Vis absorption spectrum of the T.erecta leaves extract was obtained at 428nm due to excitation of surface plasmon vibration in nanoparticles and confirms the synthesis of silver nanoparticles. The FTIR analysis showed the presence of sulfate, alkene and alcohol in the AgNP of T.erectaleaves. The average crystallite size of AgNP synthesized was found to be 27.2 nm. The spherical silver grain of 15.5 nm average size has been depicted with high-resolution scanning electron microscopy. Maximum activity (15mm) of T.erecta leaves silver nanoparticles was observed against Salmonella typhi (15mm) followed by Escherichia coli (12mm). Ag-NPs exhibited significant wound healing activity and anti-inflammatory activity in carrageenan-induced paw volume tests performed in female Wistar albino rats. Colloidal Ag-NPs can be synthesized by simple, nonhazardous methods, and biosynthesized Ag-NPs using T.erectaleaves extract have significant therapeutic properties.This work evidently confirmed that silver nanoparticles mediated T.erecta could be considered as a potential source for anti-inflammatory and wound healing drug.

High-sensitivity Hg2+ sensor based on the optical properties of silver nanoparticles synthesized with aqueous leaf extract of Mimusops coriacea

In the presented manuscript, spherical silver nanoparticles (AgNPs) which were prepared via green chemical method in a single step take only a few minutes to be ready as a Hg2+ ions detector based on the plasmon band changes. The AgNPs were obtained with the aqueous extract of Mimusops coriacea leaves. The components of the extract as tannins and polyphenolic compounds were responsible for the reduction in metal ions and the particles encapsulation. The AgNPs were characterized by UV–Vis spectroscopy, fluorescence, Fourier transform infrared, dynamic light scattering analysis and transmission electron microscopy. The AgNps presented an average diameter of 15 nm and a zeta potential value of ~ − 28 mV. They were monodispersed and stable for up to 180 days. AgNPs are used as a Hg2+ sensor with high sensitivity and selectivity. The fast, simple and low-cost method is based on changes in the AgNP surface plasmon resonance band (λ ≈ 410 nm) with LOD 6.5 ng/mL (32.5 nM), without functionalization of the AgNPs. The low LOD demonstrates its potential for Hg2+ quantification in environmental samples such as fish, soil, and effluent discharge.

Facile Electro-Assisted Green Synthesis of Size-Tunable Silver Nanoparticles and Its Photodegradation Activity

An eco-benign procedure was developed to synthesize ultrafine and discrete spherical shape silver nanoparticles (5–20 nm) in the presence of ionic liquid. Different types of leaves extract, including Cymbopogon nardus, Polygonum minus, Allium Cepa, and Petroselinum crispum, were used as a green reducing and capping agents for the synthesis process. The Ag nanoparticles were denoted as AgCN, AgPM, AgAC, and AgPC, respectively. Notably, it was demonstrated that the Ag nanoparticles' size could simply be altered by varying the amount of total phenolic content (TPC) using different leaves. It was indicated from the characterization results that the AgPC nanoparticles’ size was nine-fold smaller compared to the conventional Ag nanoparticles due to the high amount of total phenolic compounds (TPC) in the Petroselinum crispum. The results also revealed that ionic liquid and phenolic compounds had a synergistic effect on reducing silver ions (Ag+) into silver nanoparticles (Ag) and the stabilization of the nanoparticles. The order obtained for the degradation of methylene blue (MB) was AgPC > AgPM > AgCN > AgAC > Ag was influenced by a large amount of TPC and led to a decrease in particle size and enhanced photocatalytic activity. The AgPC remained effective and stable even after five subsequent cycles.

Influence of optical radiation on the silver nanoparticles formation

In this work, the synthesis of spherical silver nanoparticles in aqueous solution was performed by photostimulated reduction. A research of the laser exposure time effect of silver colloids on the optical response and nanoparticles concentration in the studied solution was carried out. The influence of long time exposure (up to 6 days) of silver colloid by LEDs with radiation wavelengths of 525 and 633 nm on their geometric, spatial and optical parameters was studied. It has been shown that prolonged irradiation of silver colloid leads to changes in the nanoparticles morphology, which is confirmed by a change in the colloidal color and appearance of additional plasmon absorption peaks on the spectral scale. The formation of silver nanoparticles and nanoprisms in aqueous solution was confirmed by spectrophotometry and transmission electron microscopy. Modelling of absorption spectra of triangular silver nanoparticles by the discrete dipole approximation approach, implemented in DDSCAT software, was carried out.. The electromagnetic radiation of the optical range is a promising tool that can be effectively used for both synthesis and modification of optical and spatial parameters of silver nanoparticles.

Exploiting Combinatorics to Investigate Plasmonic Properties in Heterogeneous AgAu Nanosphere Chain Assemblies

AbstractChains of coupled metallic nanoparticles are of special interest for plasmonic applications because they can sustain highly dispersive plasmon bands, allowing strong ballistic plasmon wave transport. Whereas early studies focused on homogeneous particle chains exhibiting only one dominant band, heterogeneous assemblies consisting of different nanoparticle species came into the spotlight recently. Their increased configuration space principally allows engineering multiple bands, bandgaps, or topological states. Simultaneously, the challenge of the precise arrangement of nanoparticles, including their distances and geometric patterns, as well as the precise characterization of the plasmonics in these systems, persists. Here, the surface plasmon resonances in heterogeneous AgAu nanoparticle chains are reported. Wrinkled templates are used for directed self‐assembly of monodisperse gold and silver nanospheres as chains, which allows assembling statistical combinations of more than 109 particles. To reveal the spatial and spectral distribution of the plasmonic response, state‐of‐the‐art scanning transmission electron microscopy coupled with electron energy loss spectroscopy accompanied by boundary element simulations is used. A variety of modes in the heterogeneous chains are found, ranging from localized surface plasmon modes occurring in single gold or silver spheres, respectively, to modes that result from the hybridization of the single particles. This approach opens a novel avenue toward combinatorial studies of plasmonic properties in heterosystems.

Light scattering and absorption by two-dimensional arrays of nano and micrometer monodisperse spherical silver particles

The problem of light scattering and absorption is considered for a free-standing two-dimensional array (monolayer) of nano- and micrometer spherical silver particles. To solve this problem for short- and imperfect long-range ordered arrays the statistical theory of multiple scattering of waves is used. The key points of the developed semi-analytical method are described. The method is based on the quasicrystalline approximation and the multipole expansion of electromagnetic fields and the dyadic Green's function in terms of vector spherical wave functions. Results for the angular distribution of scattered light, the coefficients of coherent transmission and reflection, incoherent scattering, and absorption of a monolayer are obtained for a spectral range corresponding to the nanoparticle plasmonic resonance. Some features of light propagation through two-dimensional arrays of particles with different spatial order are investigated and discussed. The results are in close agreement with the existing experimental data for a partially ordered array and the calculations for a regular array obtained under the extended low-energy electron diffraction theory.

Facile synthesis of self-assembling silver spheres and evaluation of their catalytic properties in organic dyes degradation

Hierarchical self-assembly nanostructures have an important interest in nanoscience and nanotechnology. This research reports a facile method for self-assembly of silver spheres using the Hamelia patens plant extract as a reducing agent. Furthermore, the degradation of organic dyes assesses the catalytic properties of Ag nanostructures. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), UV–Vis, and Fourier transform infrared techniques characterized the Ag spheres’ morphology and structure. SEM and TEM images revealed porous Ag assemblies with spherical morphologies of an average size of ~2 µm integrated by 20 nm thick petals. Also, more compact Ag spheres with an average size of around 3 µm, containing nanorods of around 100 nm on their surface, were obtained. Energy dispersive spectrometer and XRD techniques determined the chemical composition and crystal structure of the spheres. UV–Vis spectra show bands ranging from 400 to 500 nm, confirming quantum confinement in the material. Silver spheres with petals showed the best degradation performance of organic dyes such as methylene blue, methyl orange, and rhodamine B.

Silver Nanocubes as Electrochemical Labels for Bioassays.

Here, we report on the use of 40 ± 4 nm silver nanocubes (AgNCs) as electrochemical labels in bioassays. The model metalloimmunoassay combines galvanic exchange (GE) and anodic stripping voltammetry (ASV). The results show that a lower limit of detection is achieved by simply changing the shape of the Ag label yielding improved GE with AgNCs when compared to GE with spherical silver nanoparticles (sAgNPs). Specifically, during GE between electrogenerated Au3+ and the Ag labels, a thin shell of Au forms on the surface of the NP. This shell is more porous when GE proceeds on AgNCs compared to sAgNPs, and therefore, more exchange occurs when using AgNCs. ASV results show that the Ag collection efficiency (AgCE%) is increased by up to ∼57% when using AgNCs. When the electrochemical system is fully optimized, the limit of detection is 0.1 pM AgNCs, which is an order of magnitude lower than that of sAgNP labels.

Development of a green synthesized silver nanoparticle-based antioxidant capacity method using carob extract

The measurement of total antioxidant capacity (TAC) indicating the cooperative action of all antioxidants in a complex sample is an important analytical challenge. A novel green silver nanoparticle-based antioxidant capacity (GSNP-AC) method using carob extract was designed for TAC measurement. Green synthesis of nanoparticles has various advantages such as environmentally friendliness, reliability, sustainability and fast production. In the presence of silver seeds formed with carob extract, Ag+ is reduced to spherical silver nanoparticles (SNPs) with antioxidants, resulting in enlarged particles with a symmetric surface plasmon resonance (SPR) absorption band at 434 nm. The SPR of SNPs allowed quantification of antioxidants (i.e., increase in SPR absorbance being correlated to antioxidant concentration), and the GSNP-AC method gave a linear response over a wide concentration range of antioxidants. The molar absorptivity and LOD for trolox were 11700 L mol−1 cm−1 and 0.31 µM, respectively. The proposed method was validated in terms of concentration-dependent linear response, additivity of absorbances, precision and accuracy. The results obtained with the proposed method for standard antioxidants, synthetic mixtures and real sample extracts were correlated with those of the traditional CUPRAC method. This green synthesized silver nanoparticle-based TAC method showed simple, rapid, cost-effective, and eco-friendly superiorities over similar other nanoparticle-based assays.

Electromagnetic response of nanoparticles with a metallic core and a semiconductor shell

We study the interplay between localized surface plasmon resonances from metallic cores and electromagnetic resonances from semiconducting shells in core@shell nanoparticles in the optical and near-infrared regions. To this end, we consider silver (Ag) spheres as plasmonically active nanoparticles with radii 20 nm, covered with shells of silicon (Si) up to 160 nm in thickness. We use the classical Lorenz-Mie theory to calculate the response of the core@shell nanoparticles to an external electromagnetic field that reveals a high degree of tunability of the Ag surface plasmons with a varying Si shell thickness, and a consequent merging of their Mie resonances. In contrast with pure metallic systems, the use of a low-bandgap semiconducting shell allows for a unique interrelation between its strong characteristic magnetic dipole mode and the localized surface plasmon resonance of the metallic core. This allows control over the forward and backward scattering efficiencies in the near-infrared in accordance with the predictions based on the Kerker conditions. Employing several other core@shell materials (Al@Si, Au@Si and Ag@Ge), we show that this approach to tailoring the absorption and scattering efficiencies, based on Kerker’s conditions, can be further generalized to other similar core@shell systems.

Green synthesis and characterization of silver nanoparticles using ethanolic extract of Mimosa Pudica linn leaves

Green synthesis of metal nanoparticles using plant extract is an eco-friendly and cost-effective method for synthesizing metal nanoparticles. In this present work silver nanoparticles have been synthesized using ethanolic extract of Mimosa Pudica Linn plant (MPL) leaves. Green synthesized silver nanoparticles (AgNps) have been characterized by UV-Vis spectrometer, Fourier Transform Infra-Red ((FTIR) spectra, dynamic light scattering (DLS), Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) methods. UV-Vis spectrum of synthesized silver nanoparticles from Mimosa pudica Linn leaves extract shows a characteristic absorption peak at 421 nm. FTIR analysis reveals that presence of silver nanoparticles the presence of some biomolecules in extracts that act as reducing and capping agent for green synthesis of silver nanoparticles. DLS analysis showed AgNPs are drifted widely from 58.6 to 157.7 nm, with an average particle size of 104.7 nm. The particles are found to be polydisperse and slightly agglomerated due to the presence of phytochemicals present in the plant extract. Scanning electron microscope showed silver nanoparticles are spherical shaped. The XRD pattern revealed the presence of crystalline, dominantly spherical silver nanoparticles in the sample having size ranging from 42 to 50 nm. The XRD peaks 38.08, 44.22, 64.42, and 77.32 for leaves extract and 38.1, 44.3, 64.5, 77.5, and 81.33 for callus extract can be assigned the plane of silver crystals (111), (200), (220), and (311), respectively, and shows face-centered, cubic and crystalline nature of the silver nanoparticles. The green synthesized silver nanoparticles show significant antibacterial activity.

Electrodes Based on a Titanium Dioxide Nanotube-Spherical Silver Nanoparticle Composite for Sensing of Proteins.

The aim of the research was to provide electrochemical, chemical, phase, and microscopic characteristics of electrodes based on titanium dioxide nanotubes (TNTs) containing uniformly deposited, nonagglomerated spherical silver nanoparticles (AgNPs). The nanoparticles were produced with the use of electrodeposition and sputter deposition methods. This paper presents the results of research of these platforms with the use of the following techniques: electrochemical impedance spectroscopy, X-ray diffraction analysis, X-ray photoelectron spectroscopy, and scanning electron microscopy. Evaluation of the adsorption of proteins-bovine serum albumin (BSA)-was carried out to establish the possibility of the use of the electrodes in a low-cost, simple detection system without surface functionalization. The research proved that the AgNP deposition facilitated the electron transfer increasing their conductivity properties as well as promoting the protein adsorption. The AgNPs/TNT electrodes showed a high selectivity to the BSA-anti-BSA complex. Half an hour of immobilization was enough to completely saturate the TNT electrodes, whereas for AgNPs/TNTs, 1 h of immobilization seemed to be not enough. The impedance parameter changes for electrodes with the AgNPs reached even about 300%. The biggest changes were noted for the platform obtained using cyclic voltammetry, so it is the best detection platform for biosensing.

A novel composite of triangular silver nanoplates on BiVO4 for gaseous formaldehyde degradation

In this work, a series of Ag/BiVO4 photocatalysts with various Ag nanostructures, namely spherical silver nanoparticles (SAgNPs) and triangular silver nanoplates (TAgNPts), were synthesized for degrading formaldehyde. The as-prepared photocatalysts were characterized through a variety of analytical techniques, such as X-ray diffraction, ultraviolet–visible spectroscopy, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and photoluminescence spectroscopy. From the experiment results, among the various types of photocatalysts, 0.003 wt% TAgNPts on BiVO4 induced the highest photocatalytic degradation rate (83.9%) for gaseous formaldehyde under visible light illumination for 5 h. The HCHO degradation rate on TAgNPt/BiVO4 was higher than those on BiVO4 (74.5%) and SAgNP/BiVO4 (81.0%). In addition, Ag/BiVO4 retained over 95% of its initial photocatalytic activity after five test cycles. Therefore, this work provides a promising approach for designing efficient photocatalysts for gaseous formaldehyde removal.

Study of the effective surface plasmon in a nano-composite of silver nanoparticles with a host ZrO2 in one-dimensional ternary periodic structure for solar cell application

Effective surface plasmons for dielectric properties of nanocomposite (NC) with spherical silver nanoparticles (Ag-NPs) in a host ZrO2 has investigated at different radii and filling fractions of nanoparticles (NPs) using the Maxwell-Garnett model. The optical properties of one-dimensional ternary periodic structure (1-DTPS) containing SiO2, TiO2, and NC with different parameters has investigated using the transfer matrix method (TMM). Moreover, the absorption properties of the considered structure for transverse electric (TE) and transverse magnetic (TM) have been studied at different incident angles and thicknesses of the NC layer. The dielectric and optical properties of the considered structure has affected by surface waves of dielectric layers as well as surface plasmons of Ag-NPs. The optical properties of the 1-DTPS for TE and TM modes has been studied with varying thicknesses of NC and angles of incidence wave. With the optimum values of the optical parameters of NC and Ag-NPs, the proposed ternary periodic structure may be used as a broadband absorber for solar cells.

The study of radiation attenuation in disordered silver nanoparticles arrays formed by dry aerosol printing

The interaction processes of continuous laser radiation with wavelengths 527 and 980 nm with disordered arrays of spherical silver nanoparticles formed by dry aerosol printing are studied. The arrays were deposited on a glass substrates in the form of lines of various thickness and differed in the mean sizes of nanoparticles. It is shown that the radiation attenuation by arrays with disordered nanoparticle structure depends on the optical effects both on isolated spherical nanoparticles and on nanoparticle agglomerates.

Natural circular dichroism in the surface plasmon resonance and interband transition of noble metal nanocrystals induced by surface magnetism

Circular dichroism is typically used in the visible and ultraviolet wavelength range to study the structure of chiral substances which lacks inversion symmetry. When a magnetic dipole moment interferes the electric dipole transition, circular dichroism arises from achiral substances even in the absence of an applied magnetic field. Here, the experimental observation of natural circular dichroism in the surface plasmon resonances and interband transitions of spherical gold, silver, and copper nanocrystals in solution is presented. The anomalous circular dichroism is qualitatively explained by spin-orbit coupling and exchange interaction that occur through local magnetic moments from surface defects. The s-d and d-d exchange interactions occur between spins of adatoms and the conduction and d-band electrons. Dipolar and quadrupolar plasmon modes showed opposite sign of ellipticity (dipoles: −, quadrupoles: +), manifesting the conservation of orbital angular momentum and indicating the nature of an orbital excitation in the magnetoplasmon. The plasmon-mode dependent ellipticity was consistently observed at anisotropic nanocrystals including triangles, octahedra, decahedra, nanorods, and core-shell nanoparticles regardless of chirality and polarity of adsorbate molecules. Interband transitions in gold nanocrystals of small size showed a sign reversal to negative ellipticity, and thus the surface has magnetic moments of d-electrons opposite to the core.

Lilium casa blanca petals mediated silver nanoparticles with antioxidant and surface enhanced Raman scattering activities

A facile, eco-friendly and green synthesis method was used to prepare spherical silver nanoparticles (AgNP) with ~5.6 ± 1.5 nm diameters using Lilium casa blanca (LCB) petals. Synthesized AgNP showed good antioxidant and surface enhanced Raman scattering (SERS) activities. After reacting at 37 °C for 12 h, 10 mg LCB petal's biomass with 5 mL 5 mM silver nitrate solutions at pH 12, became a golden color with a characteristic absorption peak at 410 nm. The conversion rate of Ag+ to Ag0 reached 98.3%. The formation of AgNP was due to the combined action of several reducing substances in the LCB petals. Antioxidant and SERS activities of the AgNP were also obtained. ABTS, FRAP and RP assays all showed that AgNP had good antioxidant activity in comparison with the antioxidant activity of LCB petals. AgNP also showed good SERS activity.