Particle Size Of Ag Nanoparticles Research Articles

The disruptive effect on the bacterial cell wall explored of the ultrasmall particle-sized Ag nanoparticles supported with Zn Cu-based hybrid nanoagents

The smaller the particle size of Ag nanoparticles, the higher their antibacterial activity against drug-resistant strains, and the greater their potential for application in living organisms. Therefore, preparing Ag nanoparticles with ultra-small particle sizes has become one of the greatest challenges at present. In this study, 1.75 nm Ag was uniformly anchored on the surface of a highly biocompatible carrier to synthesize Fe3O4/ZnO@Cu2S@Ag (FCA) nanocomposites. The antibacterial activity and mechanism of FCA were investigated, and the material was used to treat wound infections caused by bacteria. At a concentration of 175 μg/mL, the antibacterial rate of Escherichia coli, Staphylococcus aureus, and drug-resistant Salmonella was over 99.99 % within 45 min. The antibacterial activity is mainly composed of •OH and multiple cations. The antibacterial mechanism involves •OH and multiple cations synergistically targeting and damaging the bacterial cell wall, altering the secondary structure of the bacterial cell wall, leading to leakage of bacterial contents and bacterial death. Additionally, FCA exhibited high biocompatibility, curing bacterial infections within 7 days and completely eliminating bacterial burden. These findings elucidate the role of antibacterial activity in composite antibacterial materials and suggest that FCA has clinical application potential in treating bacterial infections.

Extracellular biosynthesis and characterization of silver and zinc oxide nanoparticles using Pseudomonas aeruginosa and Escherichia coli

Abstract Background: The development of dependable and environmentally friendly nanomaterial resources is an essential aspect of recent nanotechnology research and application. Microorganisms have recently been investigated as a potential biofactor for the synthesis of many nanoparticles (NPs). Objectives: The aim of this article is to evaluate the extracellular biosynthesis capabilities of metallic NPs such as silver (Ag) and zinc oxide (ZnO) by screening common bacteria. Materials and Methods: Silver nitrate and zinc nitrate were used as a source of Ag and ZnO NPs, by means of Escherichia coli and Pseudomonas aeruginosa as potential candidates for the rapid synthesis of NPs. Ag and ZnO NPs were synthesized using a reduction of aqueous solutions with cell-free filtrates of bacteria. Characterization of synthesized NPs was conducted by UV–Vis spectroscopy. Results: Transmission electron microscopy (TEM) was used to examine the particle size of (Ag, ZnO) NPs. The maximum absorbance was around (425, 450 nm) for Ag and (300, 380 nm) for ZnO by E. coli and P. aeruginosa, respectively. We found that particle size of Ag NP obtained from P. aeruginosa was smaller than that of NP obtained from E. coli. The range of particle size was 24–32 nm with an average of 29.5 nm for Ag P. aeruginosa and was 25–37 nm with an average of 32 nm for Ag E. coli. The particle size range of ZnO of P. aeruginosa was 23–28 nm with an average of 25 nm and was 25–34 nm with an average of 29.7 nm for E. coli. Conclusion: E. coli and P. aeruginosa are good candidates for biosynthesis of NPs. As a result, obliged characteristics and green synthesis and the potential issue for various environmental and health-related applications may exist.

Tuning Electrochemical Properties of Silver Nanomaterials by Doping with Boron: Application for Highly Non‐enzymatic Sensing of Hydrogen Peroxide

AbstractA new type of enzyme‐free electrochemical sensor with B−Ag nanomaterials as electrocatalyst was designed. The obtained nanomaterials were characterized by transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and powder X‐ray diffraction (XRD). The results show that B was successfully doped onto the surface of Ag, which reduces the particle size of Ag nanoparticles and expands the crystal plane spacing of Ag, therefore making Ag display larger specific surface area and faster electron transfer rate. The new enzyme‐free electrochemical sensor based on B−Ag shows high electrocatalytic activity for the H2O2 reduction and exhibits excellent sensing performance for the electrochemical detection of H2O2 with a wide range from 0.01 mM to 5.55 mM, a high sensitivity of 68.3 μA⋅mM−1cm−2 and a low detection limit of 0.04 μM. This study demonstrated B−Ag is a promising sensing material for electrochemical enzyme‐free sensors.

Improved photoluminescence and spectroscopic features of Sm3+‒doped alkali borate glasses by embedding silver nanoparticles

Influence of Ag nanoparticles (NPs) on the improvement in photoluminescence and spectroscopic features of Sm3+‒doped alkali borate glass synthesized by the melt quenching process was systematically studied and analyzed. The increasing particle size of Ag NPs with the increase of AgCl concentration (0.1 – 0.5 mol%) causes the surface plasmon resonance peak to shift to a higher wavelength (red‒shift) side. Electron microscopic investigation confirmed the presence of silver NPs in the SmLAB‒1 glass sample with a median size of 4.57 nm. A significant enhancement in emission was noticed for 0.1 mol% AgCl concentration. Such improved emission was attributed to the enhanced local electric field by metallic NPs in the vicinity of Sm3+ ions and efficient energy transfer between Sm3+ ions and silver NPs. The Judd–Ofelt parameter, Ω2 decreased as the concentration of Ag NPs increases, indicating increased symmetry and ionicity between the trivalent samarium ions and their ligands. These prepared glass compositions could have applications in solid‒state devices such as LEDs and display applications.

Preparation of Silver Nanoparticles Dispersed in Almond Oil Using Laser Ablation Technique

Nanoparticle production by pulsed laser ablation (PLA) is a process that can generate pure nanoparticles (NPs) straight from a varied range of bulk substances and compounds. Silver nanoparticles (Ag NPs) are probably one of the most attractive noble metal nanostructures because of their unique and interesting physical and chemical properties. In this study, laser ablation of pure silver plate immersed in almond oil was carried out for Ag NPs production. Nd: Yag laser of wavelength 1064 nm, was used for the ablation of the Ag plate at different laser energies and ablation times. The almond oil permitted the formation of Ag NPs with a stable and homogeneity particle diameter in a reasonable time. The size distribution of the NPs was examined by High-Resolution Transmission Electron Microscopy (HRTEM). The particle sizes of the produced Ag NPs at laser energy 200 mJ in the solution at 10,15 and 20-min ablation times were 4.82, 3.11 and 1.82 nm respectively. The particle sizes of Ag NPs produced at different laser energies 150,200 and 250 mJ and at ablation time 10 min inside the solution were 5.39,4.82 and 1.92 nm respectively. The absorption peaks of the produced nanoparticles have been characterized using a UV-Vis spectrophotometer.

GREEN SYNTHESIS NANOPARTIKEL PERAK MENGGUNAKAN EKSTRAK DAUN PUCUK IDAT (Cratoxylum glaucum) SEBAGAI BIOREDUKTOR

An environment friendly technique for green synthesis of silver nanoparticles has been reported. Silver nanoparticle have been synthesized using water extract of leaves of pucuk idat (Cratoxylum glaucum), commonly known as local Bangka plant. The flavonoid and tannin present in the extract act as reducing agent. AgNO3 0,05 M solution was reducing using the extract at room temperature by stirring. Color changing of the solution was detected at 30 minutes reaction time. The color tends to be darker by the increasing of reaction time. Various techniques used to characterize synthesized nanoparticles are UV-Visible spectrophotometer, x-ray diffraction (XRD) and scanning electron microscopy (SEM). UV-Visible spectrophotometer showed absorbance peak in 405 nm, the XRD shows that silver nanoparticles formed are crystalline. The average particle size of Ag nanoparticles estimated from the Scherrer formula is 35,59 nm, while SEM image shows shape of silver nanoparticle is random and some spherical shape.

Controllable synthesis of Ag nanoparticles encapsulated in non-ionic surfactant-based vesicle for photodegradation of methylene blue

This work reported a novel processing route for producing Ag nanoparticles in non-ionic surfactant structures through microwave assisted reverse micelle method and investigation its application for degradation of methylene blue. In addition, Taguchi statistical design method was applied in order to optimize parameters affecting nanoparticle synthesis. The influences of microwave power and irradiation time on the morphology and particle size of Ag nanoparticles in non-ionic surfactant-based vesicle were also investigated. The results have important implications for controlled synthesis of Ag nanoparticles encapsulated in non-ionic surfactant structures constructed using Span/cholesterol. The particle size of products by the Debye–Scherrer equation calculated about 65 nm. Porosimetric measurements showed the highest pore diameter was 10.6 A also surface area and pore volumes were 2010 m2/g and 0.3687 cm3/g respectively. The maximum amount for photocatalytic decomposition of methylene blue with Ag nanoparticles dopted in niosomes and niosomes lack of nanoparticles evaluated about 94% and 76% after 90 min respectively. The Ag nanoparticles encapsulated in niosomes were characterized by FT-IR, and UV–Vis spectroscopy, as well as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis and nitrogen adsorption [i.e. Brunauer–Emmett–Teller (BET)] surface area analysis methods.

Continuous Synthesis of Highly Uniform Noble Metal Nanoparticles over Reduced Graphene Oxide Using Microreactor Technology

Batch reactors always suffer from inefficient transport properties, discontinuity, and scale-up effects, challenging the particle size control, reproducibility, and large-scale production of noble metal-reduced graphene oxide composites. To address these issues, a microfluidic-based strategy for the continuous synthesis of highly uniform Ag nanoparticles (NPs) over reduced graphene oxide (Ag-rGO composites) was developed in this study. Ag-rGO composites were formed by the coreduction of AgNO3 and GO with NaBH4, which was confined inside the dispersed aqueous plugs segmented by octane. By virtue of enhanced mixing and precise control of reaction parameters in the plugs, ultrafine Ag NPs with controlled particle size (1.5–5.6 nm) and narrow particle size distribution (PSD) were evenly deposited on rGO. The average particle size of Ag NPs and relative standard deviation of particle size in Ag-rGO composites synthesized via microfluidic-based strategy were smaller than those via batch method. Moreover, the versatility of this microfluidic-based strategy was further demonstrated in the continuous synthesis of Pt-rGO and Pd-rGO composites.

Green synthesis of novel silver nanocomposite hydrogel based on sodium alginate as an efficient biosorbent for the dye wastewater treatment: prediction of isotherm and kinetic parameters

This paper is focused on simple, cost-effective and one-step green synthesis of silver nanocomposite hydrogel (SNC) based on sodium alginate toward the removal of methylene blue (MB) dye from aqueous solutions. Mukia maderaspatna plant extract was used as a reducing agent and the reaction occurred at room temperature. The novel SNC was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electronic microscope (SEM), transmission electron microscope (TEM), thermogravimetric analysis (TGA), and X-ray diffraction (XRD) analyses. The FTIR results observed indicated the presence of silver ions in the inside of the hydrogel composite. The XRD results revealed that the SNC are crystalline in nature. It was observed from the TEM results that the particle size of Ag nanoparticles was around 19 nm. Furthermore, the prepared SNC was found to exhibit excellent adsorbent properties for the removal of MB dye from the aqueous solution. This has been experimentally studied through Langmuir, Freundlich, Redlich–Peterson, and Sips adsorption isotherms. The maximum Langmuir monolayer adsorption capacity was calculated as 213.7 mg of MB dye/g of SNC. The pseudo-first-order, pseudo-second-order, and Elovich kinetic models were used to fit the adsorption kinetics data. The prepared SNC can be effectively utilized for the removal of dyes from the industrial wastewater.

Preparation, characterization and antibacterial activity of core–shell Cu2O@Ag composites

Monodisperse Cu2O colloidal spheres were produced by a sol–gel reaction. The Cu2O@Ag composite spheres with core–shell structure were prepared by photodeposition route. The size and shape as well as the optical properties of the composites were characterized with transmission electron microscopy (TEM) and UV–vis spectroscopy. The results showed that the average particle size of Cu2O among the composites was about 150nm, and the average particle size of Ag nanoparticles (NPs) was around 8nm. Ag NPs were relatively monodisperse and presented spherical shape, and their deposition on the Cu2O surface was uniform. Formation of metallic Ag NPs on the surface of Cu2O spheres was also confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The antibacterial activity of the as-synthesized Cu2O spheres and Cu2O@Ag composites was also investigated. Owing to the synergistic action between Cu2O and Ag NPs, the Cu2O@Ag composites exhibit more excellent antibacterial activity compared to the pristine Cu2O.

A simple approach for the synthesis of silver nanoparticles and their application as a catalyst for the photodegradation of methyl violet 6B dye under solar irradiation

In the present study, we established for the first time a simple method for the preparation of silver nanoparticles (Ag NPs) using saturated fatty acid and tryptophan as capping and reducing agent, respectively. The -NH2 group of tryptophan and the carboxylate group of saturated long chain carboxylate endow them as reducing and stabilising property respectively. The -NH2 group of the tryptophan reduced the Ag+ ions while the carboxylate group bounded strongly to the surface of the nanoparticles (NPs). This approach is a very special, size controlled synthetic approach for the large-scale synthesis of Ag NPs. The sizes of the synthesised Ag NPs were controlled by varying the processing parameters, such as reaction time and the chain length of the silver carboxylate (C12–C16). Studies showed that the particle size of Ag NPs increases with increase in reaction time and carbon chain length. The synthesised Ag NPs were characterized by ultra-violet spectroscopy (UV–vis), transmission electron spectroscopy (TEM), selected area electron diffraction (SAED), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The synthesised Ag NPs was used to evaluate the photo catalytic degradation of the methyl violet 6B dye under solar irradiation. The efficiency and rate of photo degradation of methyl violet 6B dye were also studied.

Atmospheric-pressure cold plasma for synthesizing Ag modified Degussa P25 with visible light activity using dielectric barrier discharge

Atmospheric-pressure cold plasma was employed to fabricate Ag/TiO2 visible light photocatalyst. UV–vis, XPS and XRD spectra were used to investigate Ag valence in the Ag/TiO2 samples. UV–vis spectra indicated that metal Ag nanoparticles were present after plasma treatment, and the surface plasmon peak became narrower and shifted to shorter wavelengths when the discharge voltage was increased. XPS and XRD spectra proved that Ag ions were completely reduced to metallic Ag nanoparticles. The morphologies of the Ag/TiO2 samples were observed by transmission electron microscopy (TEM). TEM micrographs of the Ag/TiO2 sample fabricated at 36kV showed that the average particle size of Ag nanoparticles was ca. 7.4nm. Photocatalytic activity of the Ag/TiO2 samples was evaluated by photodegradation of methylene blue (MB) under visible light (λ>420nm). Compared with Degussa P25, the Ag/TiO2 catalyst fabricated by DBD cold plasma exhibited a high activity for MB degradation. Atmospheric-pressure DBD cold plasma was highly efficient for preparation of supported metallic Ag catalyst.

Synthesis of PS/Ag Nanocomposite Spheres with Catalytic and Antibacterial Activities

This paper describes a simple, mild, and environmentally friendly approach to synthesize polystyrene/Ag (PS/Ag) nanocomposite spheres, which makes use of both reducing and stabilizing functions of polyvinylpyrrolidone (PVP) in aqueous media. In this approach, monodisperse polystyrene (PS) spheres, which are used as templates for the synthesis of core-shell nanocomposite spheres, are sulfonated first. Then, [Ag(NH(3))(2)](+) ions are adsorbed onto the surface of the PS template spheres via electrostatic attraction between -SO(3)H groups (grafted on the surface of the PS template spheres) and [Ag(NH(3))(2)](+) ions. [Ag(NH(3))(2)](+) ions are then reduced by and simultaneously protected by PVP. In this way, the PS/Ag nanocomposite spheres in aqueous media are obtained through a so-called one-pot method. Neither additional reducing agents nor toxic organic solvents are utilized during the synthesis process. Furthermore, the coverage degree and the particle size of Ag nanoparticles on PS/Ag nanocomposite spheres is easily tuned by changing the concentration of [Ag(NH(3))(2)](+) ions in aqueous media. Moreover, these PS/Ag nanocomposite spheres can be used as catalyst for the reduction of organic dyes and as antibacterial agents against Salmonella and Escherichia coli. In the present study, these PS/Ag nanocomposite spheres exhibit excellent catalytic properties (both in efficiency and recyclability) for the reduction of organic dyes, and the preliminary antibacterial assays indicate that these PS/Ag nanocomposite spheres also possess extraordinary antibacterial abilities against Salmonella and Escherichia coli.

Ag‐nanoparticle‐modified single Ag nanowire for detection of melamine by surface‐enhanced Raman spectroscopy

Silver nanowires synthesized by a solvothermal method were used as templates for fabricating silver‐nanoparticle‐decorated silver (AgNP/Ag) nanowires. The number density and particle size of Ag nanoparticles can be controlled by varying the concentration of Ag precursor. Single AgNP/Ag nanowire exhibited strong surface‐enhanced Raman scattering effect. Detection of melamine molecules at concentrations as low as 1.0 × 10−8 M was used as an example to show the possible applications of such AgNP/Ag nanowires. Their application in rapid detection of melamine in milk solution was further demonstrated. It was shown that melamine in milk solution at a low concentration of 5.0 × 10−8 M can be easily detected with little sample pretreatment. The results demonstrate the potential of single AgNP/Ag nanowire as a surface‐enhanced Raman scattering substrate for convenient and sensitive detection of trace amounts of melamine in a complex mixture. Copyright © 2012 John Wiley & Sons, Ltd.

Fabrication of visible-light-driven one-dimensional anatase TiO2/Ag heterojunction plasmonic photocatalyst

Abstract Visible-light-driven one-dimensional (1D) anatase TiO2/Ag plasmonic photocatalyst was successfully prepared through a facile wet impregnation method. Experimental results indicate that Ag nanoparticles cover on the surface of TiO2 uniformly and the heterogeneous structure is formed efficiently. The obtained 1D anatase TiO2/Ag heterogeneous composites exhibit excellent photocatalytic activity (nearly 100% within 2 h) for degradation of 2,4-dichlorophenol in wastewaters, which is ascribed to the suitable particle size of Ag nanoparticles in favor of enhancing the surface plasmon resonance and the heterogeneous structure advantageous of the separation of photogenerated electron–hole pairs. After reusage for ten times, the composites still present high photocatalytic activity, indicating the excellent stability.

Surface-Enhanced Raman Detection of Melamine on Silver-Nanoparticle-Decorated Silver/Carbon Nanospheres: Effect of Metal Ions

Silver/carbon (Ag/C) core-shell nanospheres synthesized by a hydrothermal method were used as templates for fabricating silver nanoparticle-decorated Ag/C (Ag/C/AgNps) nanospheres. The particle size of Ag nanoparticles can be tuned by varying the concentration of Ag precursor. Detection of melamine molecules at concentrations as low as 5.0×10(-8) M shows that the Ag/C/AgNps nanosphere is a good SERS-active substrate. The effect of heavy metal ions on the detection of melamine is also investigated. It was found that the SERS spectrum profile of melamine is very sensitive to the presence of heavy metal ions: the peak positions of the SERS bands exhibit some apparent change with the kind of metal ion, showing a blue or red shift compared with those in the SERS spectrum of melamine; the SERS signal intensity decrease with increasing the concentration of metal ion.

Effect of particle size variation of Ag nanoparticles in Polyaniline composite on humidity sensing

The results of synthesis of Ag-Polyaniline nanocomposite along with an investigation of optical fiber based humidity sensor using evanescent wave absorption spectroscopy are discussed. The sensor was fabricated using Ag-Polyaniline nanocomposite deposited on an optical fiber clad and tested in the range of 5-95% relative humidity (RH). Optimization of clad length (2-8mm) was done and then particle size (15-30 nm) variation of silver nanoparticles in Polyaniline composite was studied for better performance of sensor. The effect of particle size on sensing humidity was investigated. The reduction of particle size, leads to a dramatic improvement in sensitivity and speed of response. The optimized clad length of 6mm exhibits the better results for 15 nm particle size of Ag nanoparticles dispersed in Polyaniline. The sensor response is fully reversible having almost 1% of standard deviation. Response time of the sensor is 30s with a slow recovery of 90 s.

Polymer Driven Covalently Bonded Decahedral-Twinning of Ag Nanoparticles Prepared by ICP Enhanced Magnetron Sputtering Method

In this paper, an inductively coupled plasma (ICP) enhanced magnetron sputtering (MS) method was utilized to deposit silver (Ag) nanoparticles embedded inside of simultaneously polymerized poly(ethylene oxide) (PEO) thin film. Ex situ transmission electron microscopy (TEM), selected area electron diffraction (SAED), and X-ray photoelectron spectroscopy (XPS) have been employed to elucidate the Ag nanoparticle structure, shape, and growth process during ICP enhanced MS deposition. The results showed that, when capped by polymer PEO film, the Ag nanocrystals were shaped in multiple-twinned particles (MTP) and further transformed into decahedrons held five-twinning structure with distinct twinning boundaries. The formation of particle size of Ag nanocrystalline on Si (100) surfaces was found unambiguously dependent on the ICP power, and the estimated particle size of Ag nanoparticles was in the range of 5―10 nm. From the results, it was assumed that PEO coating was the reason for inducing the formation of Ag MTP and nanodecahedron structures.

Growth of Ag nanoparticles using plasma-modified multi-walled carbon nanotubes

This study presents a novel method for preparing multi-walled carbon nanotubes(MWNTs) grafted with a poly(2-hydroxyethyl methacrylate) (HEMA)–silver complex(CNTs–HEMA–Ag complex) through plasma-induced grafting polymerization. Thecharacteristics of the MWNTs after being grafted with HEMA polymer are monitored byFourier transform infrared (FT-IR) spectroscopy. The chelating groups in the HEMApolymer grafted on the surface of the CNTs–HEMA are the coordination sites forchelating silver ions, and are further used as nanotemplates for the growing of Agnanoparticles (quantum dots). Transmission electron microscopy (TEM) revealsthat the particle size of Ag nanoparticles on the CNT surfaces increases with theAg+ chelating concentration, reaction time, and reaction temperature. Moreover, thecrystalline phase of Ag nanoparticles is identified by using x-ray diffraction(XRD). In addition, high-resolution x-ray photoelectron spectroscopy (XPS) isused to characterize the functional groups on the surface of the MWNTs afterchemical modification through plasma treatment; it demonstrates that thegrowing amount of the Ag nanoparticles on the nanotubes increases with theAg+ chelating concentration due to the blocking effect of the Ag particles forming on theMWNTs.

The optical properties between an incident wave and the active layer of a bubble-pit AgOx-type super-resolution near-field structure

The deformation and plasmon effects of collective localized surface plasmons between incident light and bubble-pit AgOx-type super-RENS structure have been studied using finite-difference time-domain (FDTD) method. We find that the polarization, wavelength of incident light, and particle sizes of Ag nanoparticles are sensitive to the plasma resonance. The Ag nanoparticles inside the bubble-pit AgOx-type super-RENS structure give the additional outer boundaries to the motion of the Ag nanoparticles, and excite more evanescent field which located in the far edge of the bubble from the optical axis of the incident beam. The optical properties between active layer and incident light with polarization direction, different wavelengths, and varied particle sizes of Ag nanoparticles exhibits nonlinear optical behavior in the near field. The far-field signals of different wavelength of incident light confirm the relation between highly localized near-field distributions and enhanced resolution of far-field signals. The subwavelength recording marks smaller than the diffraction limit were distinguishable since the Ag nanoparticles with high localized fields transferred evanescent waves to detectable signals in the far field.