Presence Of Silver Nanoparticles Research Articles

Optimal Ag concentration for H2 production via Ag:TiO2 nanocomposite thin film photoanode

TiO2 thin films containing different concentrations of Ag nanoparticles have been synthesized by sol-gel method. According to UV–visible spectra, presence of an intense surface plasmon resonance peak at 490 nm of wavelength indicated formation of silver nanoparticles in the TiO2 films. Based on atomic force microscopy (AFM) analysis, the surface roughness and the effective surface ratio increased by increasing the Ag mol%. Moreover, scanning electron microscopy (SEM) images showed formation of Ag nanoparticles on the surface for the samples containing high Ag concentration. X-ray diffraction (XRD) patterns revealed that the size of Ag nanocrystals increased by increasing the Ag content in the films while the nanocrystalline size of TiO2 reduced in the presence of silver nanoparticles. Based on x-ray photoelectron spectroscopy (XPS) data, a stoichiometric chemical composition was detected for TiO2 while, Ag presented in a combination a metal/oxide states on the surface. Studying photoresponse of the samples showed that the highest photocurrent was obtained for the sample containing 1 mol% Ag. By measuring the photovoltage versus time, it was found that addition of silver nanoparticles to the TiO2 layer resulted in reduction of the transient time of the photogenerated carriers in the samples. Impedance spectroscopy determined a slight decrease in charge transfer resistance by addition of Ag to the films. Moreover, measuring the amount of hydrogen produced during water splitting reactions verified that the highest quantum yield of 9.6% was obtained for the sample with 1 mol% Ag.

Regioselective O-alkylation: synthesis of 1-{2-[(2-chloroquinolin-3-yl)methoxy]-6-chloro-4-phenylquinolin-3-yl}ethanones

An efficient and regioselective O-alkylation of amides with a variety of electrophiles in the presence of silver nanoparticles is reported as part of our recent research on building blocks for synthesis of natural products. The nano-silver catalyst initiates O-alkylation of the amides by heteroalkyl halides. Reaction of equimolar 3-acetyl-6-chloro-4-phenylquinolin-2(1H)-one and 2-chloro-3-(chloromethyl)quinolines in the presence of silver nanoparticles in DMSO solution under reflux condition leads to the formation of 1-{1-[2-chloroquinolin-3-yl)methoxy]-6-chloro-4-phenylquinolin-3-yl}ethanones.

Improved Charge Separation Properties of Organic Hetero-Junction Solar Cells by Self-Assembled Monolayers Anchored Ag Nanoparticles

We investigate the effect of self-assembled monolayers and localized surface plasmons of silver nano-particles on an organic solar cell consisting of zinc phthalocyanine as an active layer. The device was fabricated by covalent attachment of silver nanoparticles on n-type silicon substrates using self-assembled monolayer of 4-mercaptophenol. Power conversion efficiency is increased up to 8 times as compared to a reference device with merely 0.13% photo-conversion efficiency containing no self-assembled monolayers and silver nano-particles. We believe that improved conductivity at the interface due to the aromatic self-assembled monolayer and the increased local electric field experienced by the active layer in presence of silver nano-particles act in synergy towards the higher population of excitons and dissipation of charge.

Nanotextured crystalline silicon solar cells

AbstractNano‐scale textures are formed on crystalline silicon surfaces by using a two‐step electroless wet‐chemical method consisting of a treatment in an activated Na2S2O8 (K2S2O8) solution for localized oxidation/surface reaction and silver nanoparticles deposition. The oxidation/reaction products are etched in an aqueous solution of HF and H2O2 assisted by the presence of silver nanoparticles. The reflectance of the nanotextured silicon wafer surfaces less than 5% in the spectral interval 300–900 nm is observed. It was found that the surface texture can withstand without significantly changing the high‐temperature solar cell processing. A weighted reflectance of 9.5% and 16.43% efficiency are obtained on nanotextured mc‐Si solar cells with an active area of 146 mm2 prepared using the standard screen‐printing technique.

Water Fast of Inkjet Print by Using Acrylic /Nano-Silver Ink

A colour ink jet printing with improved water fastness property was produced by using of special component in the ink’s formulation. In this study, the water fastness of ink jet prints which used acrylic/nano-silver resin nano-composite ink instead of conventional resin in ink’s formulation was examined. The nano composite resin was prepared via miniemulsion polymerization of acrylate monomers in the presence of silver nanoparticles. The water fastness properties of the prints were assessed by using the ASTM /F2292-03 water fastness test. The results indicated that acrylic/nano-silver resin increased impermeability of the printed paper and provided the water insoluble printed image on the paper. Also by adding acrylic/nano-silver resin, the hue of printed image was darker than conventional resin.

Enhanced chemiluminescence of the luminol–AgNO3 system by Ag nanoparticles

The oxidation reaction of luminol with AgNO(3) can produce chemiluminescence (CL) in the presence of silver nanoparticles (NPs) in alkaline solution. Based on the studies of UV-vis absorption spectra, photoluminescence (PL) spectra and CL spectra, a CL enhancement mechanism is proposed. The CL emission spectrum of the luminol-AgNO(3)-Ag NPs system indicated that the luminophore was still 3-aminophthalate. On injection of silver nanoparticles into the mixture of luminol and AgNO(3), they catalysed the reduction of AgNO(3) by luminol. The product luminol radicals reacted with the dissolved oxygen, to produce a strong CL emission. As a result, the CL intensity was substantially increased. Moreover, the influences of 18 amino acids, e.g. cystine, tyrosine and asparagine, and 25 organic compounds, including gallic acid, tannic acid and hydroquinone, on the luminol-AgNO(3)-Ag NPs CL system were studied by a flow-injection procedure, which led to an effective method for detecting these compounds.

Ultrasensitive Chemiluminescence Detection of Indoleacetic Acid Catalyzed by Silver Nanoparticles

A flow injection chemiluminescence (CL) method has been developed for the determination of indoleacetic acid (IAA). It is based on the fact that the weak CL of Ce(IV)-Ru(phen)32+ system is strongly enhanced in the presence of silver nanoparticles. Optimum conditions and possible mechanisms have been investigated. Under optimum experimental conditions, the linear range is from 1.0×10-8 – 6.0×10-7 g mL-1 with a detection limit 9.0×10-9 g mL-1

Nanoparticles in treatment of thermal injured rats: Is it safe?

The aim of this study was to assess whether thermal trauma induced oxidative stress altered the balance between oxidant and antioxidant systems in the blood of burn wound rats in the absence and presence of silver nanoparticles and S-nitrosoglutathione, GSNO. Free silver nanoparticles, free GSNO and silver nanoparticles + GSNO had no cytotoxic effects. Under anesthesia, the shaved dorsum of the rats was exposed to 90°C (burn group) water bath. Studied compounds were administered topically immediately and at 28 days after the burn injury, four times a day. Silver nanoparticles and silver nanoparticles + GSNO were no toxic in vitro and in vivo. There were no significant differences in the levels of urea, creatinine, aminotransferases and hematological parameters, in control-burn groups (free silver nanoparticles) and treated-burn groups (free GSNO or silver nanoparticles + GSNO). There were no differences in lipid peroxidation and in the levels of protein carbonyls and glutathione, used as oxidative stress markers. A little inflammatory cell response, papillary dermis vascularization, fibroblasts differentiated into contractile myofibroblasts and the presence of a large amount of extracellular matrix were evidenced in treated groups following skin injury. These results indicate that silver nanoparticles and GSNO may provide an effective action on wound healing.

Fabrication of silver nanocomposite films impregnated with curcumin for superior antibacterial applications

Silver nanocomposite films are found to be very effective material for anti-bacterial application. In the present work, sodium carboxylmethyl cellulose silver nanocomposite films (SCMC SNCF) were tried for antibacterial applications. To enhance their applicability novel film-silver nanoparticle-curcumin composites have been developed. SCMC SNCF are developed from sodium carboxylmethyl cellulose (SCMC), N,N(1)-methylenebisacrylamide (MBA) and silver nitrate solution. These films were characterized by FTIR, UV-visible, XRD, TGA, DSC and TEM techniques. The formed silver nanoparticles have an average particle size of ~15 nm as observed by transmission electron microscopy (TEM). Curcumin loading into SCMC SNCF is achieved by diffusion mechanism. The UV-Visible analysis indicated that higher encapsulation of curcumin in the films with higher SCMC content. Further, it was observed that the presence of silver nanoparticles in the films enhanced the encapsulation of curcumin indicating an interaction between them. Moreover, the antibacterial activity showed that the SCMC films generated with silver nanoparticles have a synergistic effect in the antimicrobial activity against Escherichia coli (E. coli). In order improve the healing efficacy as antibacterial agents, curcumin loaded with SCMC SNCFs were developed which showed significant inhibition of E. coli growth than the silver nanoparticles and curcumin alone film. Therefore, the present study clearly provides novel antimicrobial films which are potentially useful in preventing/treating infections.

Silver nanoparticle-initiated chemiluminescence reaction of luminol–AgNO3 and its analytical application

Ag(+) has been regarded as an inert chemiluminescent oxidant. In this work, it was found that in the presence of silver nanoparticles (AgNPs), AgNO(3) could react with luminol to produce strong chemiluminescence (CL). The AgNPs with smaller size could initiate stronger CL emission. To investigate the CL mechanism of the AgNPs-luminol-AgNO(3) system, the UV-visible spectra and the CL spectrum of the CL system were obtained. The CL reaction mechanism involving catalysis was proposed. Compared with the reported nanoparticles-luminol-H(2)O(2) CL system, the AgNPs-luminol-AgNO(3) CL system has the advantages of low background and good stability. Moreover, the new CL system was used in immunoassay for IgG.

Rheological and Flocculated Properties of Silver Nanoparticles Paste

Silver nanoparticles pastes were formatted by mixing different volumetric silver nanoparticles with the mixture of 12.7wt% bismuth subgallate and 87.3wt% organic vehicle. Rheological and flocculated properties of silver nanoparticles pastes were examined. All pastes demonstrated pseudoplastic flow behaviors and shear thinning characters over the solids-loading and shear-rate range studied. The viscosities of pastes reduce with increasing the shear rate in a logarithmic plot. G' (storage modulus) and G" (loss modulus) increase with increasing silver nanoparticles content and frequency. At high loading, G' and G" begin to level off and exhibit plateau in the low-frequency range. The appearance of the plateau at low frequency is due to the presence of silver nanoparticles in the system and forming the three-dimensional network structure. The shear stress increases with increasing silver nanoparticles content. Apparent yield value estimated by casson equation exhibits a power-law dependence on particle volume fraction.

Determination of dipyridamole using TCPO–H2O2 chemiluminescence in the presence of silver nanoparticles

The method is based on the fact that dipyridamole can enhance the chemiluminescence (CL) emission from the redox reaction of bis (2,4,6-tricholorophenyl) oxalate (TCPO) with H(2)O(2) in the presence of silver nanoparticles (AgNPs). The CL reaction mechanism was discussed. The effect of concentrations of TCPO, H(2)O(2), AgNPs and pH value on the CL reaction were investigated. Under the optimum conditions, the linear dynamic range was 1.0-1000 × 10(-9) g/mL and the detection limit (3σ) was 9 × 10(-10) g/mL. The relative standard deviation (RSD) was 4.8% for 1.0 × 10(-9) g/mL dipyridamole (n = 7). The proposed method has been successfully applied to the determination of dipyridamole tablets and the recovery was 99-103%.

Characterization of the effluent from a nanosilver producing washing machine

The increasing number of nanomaterial based consumer products raises concerns about their possible impact on the environment. This study provides an assessment of the effluent from a commercially available silver nanowashing machine. The washing machine released silver in its effluent at an average concentration of 11 μg L − 1 , as determined by inductive coupled mass spectrometry (ICP-MS). The presence of silver nanoparticles (AgNPs) was confirmed by single particle ICP-MS as well as ion selective electrode measurements and filtration techniques. Size measurements showed particles to be in the defined nanosize range, with an average size of 10 nm measured with transmission electron microscopy (TEM) and 60–100 nm determined with nanoparticle tracking analysis (NTA). The effluent was shown to have negative effects on a natural bacterial community as its abundance was clearly reduced when exposed to the nanowash water. If washing machines capable of producing AgNPs become a common feature of households in the future, wastewater will contain significant loadings of AgNPs which might be released into the environment.

Flow-Injection Chemiluminescence Determination of Lisinopril Using Luminol–KMnO<SUB>4</SUB> Reaction Catalyzed by Silver Nanoparticles

A simple, sensitive, and rapid chemiluminescence method combined with flow-injection analysis was developed for the determination of lisinopril. It was found that the chemiluminescence (CL) signal arising from the reaction of alkaline luminol with KMnO(4) could be significantly increased by addition of lisinopril in the presence of silver nanoparticles. The experimental parameters affecting the chemiluminescence reaction were carefully studied and the chemiluminescence reaction mechanism was briefly discussed. Under the selected conditions, the chemiluminescence intensity was proportional to the concentration of lisinopril ranging from 0.1 mg/L to 20.0 mg/L. The detection limit was 0.027 mg/L lisinopril and the relative standard deviation for 4.0 mg/L lisinopril solution was 1.9% over eleven repeated measurements. The proposed method was applied to the determination of lisinopril in tablets and spiked human urine samples.

Silver nanoparticles fluorescence enhancement effect for determination of nucleic acids with kaempferol–Al(III)

Nucleic acids can greatly enhance fluorescence intensity of the kaempferol (Km)–Al(III) system in the presence of silver nanoparticles (AgNPs). Based on this, a novel method for the determination of nucleic acids is proposed. Under studied conditions, there are linear relationships between the extent of fluorescence enhancement and the concentration of nucleic acids in the range of 5.0×10−9 to 2.0×10−6gmL−1 for fish sperm DNA (fsDNA), 7.0×10−9 to 2.0×10−6gmL−1 for salmon sperm DNA (smDNA) and 2.0×10−8 to 3.0×10−6gmL−1 for yeast RNA (yRNA), and their detection limits are 2.5×10−9gmL−1, 3.2×10−9gmL−1 and 7.3×10−9gmL−1, respectively. Samples were satisfactorily determined. And the system of Km–Al(III)–AgNPs was used as a fluorescence staining reagent for sensitive DNA detection by DNA pattern of agarose gel electrophoresis analysis. The results indicate that the fluorescence enhancement should be attributed to the formation of Km–Al(III)–AgNPs–nucleic acids aggregations through electrostatic attraction and adsorption bridging action of Al(III) and the surface-enhanced fluorescence effect of AgNPs.

Preparation of silver nanoparticle containing silica micro beads and investigation of their antibacterial activity

Silver nanoparticle containing silica micro beads (Ag-NPBs) were successfully prepared by using sodium silicate, a cheap precursor, involving chemical reductive method. First, silica gel was synthesized and crushed into micro beads which have sizes ranging from 0.5 to 1 mm. Silica micro beads were then modified with 3-aminopropyltriethoxysilane to graft amino functional groups onto their surface. Silver ions were loaded onto the surface of the modified silica and reduced to silver crystal by adding NaBH 4. The presence of silver nanoparticles as well as structure of materials was characterized with FT-IR, XRD, BET, FE-SEM, TEM, UV–vis spectrophotometer, and optical microscope. Silver nanoparticles with an average size about 5 nm were found in the pore and on the surface of amino functionalized silica beads. Ag-NPBs samples were tested for their antibacterial activity against Escherichia coli ( E. coli). The antibacterial activity was examined by both zone inhibition and test tube test method. Biological results indicated that the synthesized materials have an excellent antibacterial performance against E. coli which was completely inhibited after 5 min contact with Ag-NPBs.

Synthesis of latex based antibacterial acrylate polymer/nanosilver via in situ miniemulsion polymerization

Silver nanoparticles were incorporated into poly-{methyl methacrylate-butyl acrylate-acrylic acid} using two different approaches. The first approach was based on dispersing the nanosilver particles in acrylic latex (previously synthesized by the emulsion polymerization) and the second is the in situ polymerization of acrylate monomers in the presence of silver nanoparticles by miniemulsion polymerization. Miniemulsion polymerization can yield a better dispersion of nanosilver in the polymeric particles because organic particles can be dispersed directly in the monomer droplets becoming encapsulated upon polymerization. Morphological investigations were performed using SEM and TEM. FTIR and thermal analyses revealed the silver nanoparticles to be located in the polymeric structure of latex. The nanocomposite latex was compared with the neat latex of the same monomer structure. A comparison of these results showed an increase in the degradation temperature and glass transition temperature (Tg) compared to the blank latex. The antibacterial properties were determined using the disc diffusion method against both gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli). The nanocomposite synthesized via in situ miniemulsion polymerization showed highly potent antibacterial activity toward both gram-positive and gram-negative bacteria comparing the neat latex and the blended nanocomposite, which makes it useful for a wide range of biomedical and general applications. Open image in new window

Concentration of polycyclic aromatic hydrocarbons by chemically modified silver nanoparticles

The ability of silver nanoparticles stabilized by cetyltrimethylammonium bromide (CTAB) to concentrate polycyclic aromatic hydrocarbons (PAHs) from aqueous solutions was shown. It was found that fixed PAH molecules are capable of acting as electronic energy donors and of generating sensibilized fluorescence of silver nanoparticles. It was shown by spectral-luminescent investigations of dilute PAH solutions (5 × 10−10−1 × 10−6 g/ml) in the presence of silver nanoparticles (∼0.7 vol %) that the concentration of PAH molecules from solutions occurs due to its sorption on hydrocarbon CTAB radicals in close contact to the surface of metallic silver. On the basis of the spectral data, the sorption isotherms were obtained and the values of extraction degree and partition coefficients for naphthalene, phenanthrene, anthracene, chrysene, pyrene, and 3,4-benzopyrene were calculated. It was found that the degree of extraction values of the investigated PAHs fall within the range of 73–98%, the partition coefficients (logD) ∼ 6, and the concentration coefficients ∼105.

Fabrication of Curcumin Encapsulated Chitosan-PVA Silver Nanocomposite Films for Improved Antimicrobial Activity

The present study explores the in situ fabrication of chitosan-poly(vinyl alcohol)-silver nanocomposite films in view of their increasing applications as antimicrobial packaging, wound dressing and antibacterial materials. The reduction of silver ions into silver nanoparticles (AgNPs) is achieved in acidic solution of chitosan (C) and poly (vinyl alcohol) (PVA) using their functional groups (-OH, -COOH, -NH2 groups). The presence of silver nanoparticles in the chito-san-PVA film is confirmed by UV-Vis spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy and X-ray Dif-fraction (XRD) analysis. The Scanning Electron Microscopic (SEM) images illustrate the presence of embedded silver nanoparticles throughout the films. In addition, the formed silver nanoparticles have an average particle size of ~ 16.5 nm as observed by Transmission Electron Microscopy (TEM). The anti-microbial and anti-fungal activity of the chitosan-PVA silver nanoparticle films have demonstrated significant effects against Escherichia coli (E. coli), Pseudomonas, Staphylococcus, Micrococcus, Candida albicans, and Pseudomonas aeruginosa (P. aeruginosa). To improve further their therapeutic efficacy as anti-microbial agents, curcumin encapsulated chitosan-PVA silver nanocomposite films are developed which showed enormous growth inhibition of E. coli compared to curcumin and chitosan-PVA silver nanoparticles film alone. Therefore, the present study clearly provides novel antimicrobial films which are potentially useful in preventing/treating infections.

Antibacterial activity of pH-sensitive genipin cross-linked chitosan/poly(ethylene glycol)/silver nanocomposites

Novel nanocomposites consisting of genipin cross-linked chitosan (GC), poly(ethylene glycol) (PEG), and silver nanoparticles were prepared for such biomedical applications as the wound-healing materials. Various amounts of silver nanoparticles were dispersed in the GC/PEG hydrogel matrix without severe aggregation. The effects of composition and silver nanoparticles on the physico-chemical properties of samples were evaluated by infrared analysis, contact angle measurements, and swelling tests. The GC/PEG/Ag nanocomposite showed a pH-sensitive swelling behavior. The surface hydrophilicity of GC/PEG/Ag nanocomposites was improved with the increase of silver nanoparticle content. L929 cell attachment was improved in the presence of silver nanoparticles. The antimicrobial function was assessed for the GC/PEG/Ag nanocomposites containing the silver content over 100 ppm. The silver nanoparticles had the dual functions of reinforcing structural stability and enhancing antimicrobial activity of GC/PEG/Ag nanocomposites. Copyright © 2010 John Wiley & Sons, Ltd.