Influence Of Silver Nanoparticles Research Articles

Influence of silver nanoparticles on spectroscopic properties of biologically active iodinated 4-aryloxymethyl coumarin dyes

The interaction between silver nanoparticles and biologically active iodinated 4-aryloxymethyl coumarins4-(4-iodo-phenoxymethyl)-benzo[h]coumarin (4IPMBC) and 4-(4-iodo-phenoxymethyl)-6-methoxy coumarin (4IPMMC) has been studied using absorption and fluorescence spectroscopy. The absorption spectral changes of dyes with the addition of silver nanoparticles suggest their possible interaction with silver nanoparticles. Fluorescence quenching has been observed for both dyes with the addition of silver nanoparticles. The Stern–Volmer plots of fluorescence quenching are found to be nonlinear showing positive deviation. The magnitudes of quenching rate parameter and fluorescence lifetime measurements indicate the presence of static quenching mechanism. The binding constants and the number of binding sites have been estimated from fluorescence data. The role of diffusion, energy transfer and electron transfer processes in fluorescence quenching mechanism has been discussed.

Influence of silver nanoparticles on relaxation processes and efficiency of dipole – dipole energy transfer between dye molecules in polymethylmethacrylate films

The fluorescence and phosphorescence of dyes in thin polymethylmethacrylate (PMMA) films in the presence of ablated silver nanoparticles has been investigated in a wide temperature range by methods of femtosecond and picosecond laser photoexcitation. The fluorescence and phosphorescence times, as well as spectral and kinetic characteristics of rhodamine 6G (R6G) molecules in PMMA films are measured in a temperature range of . The temperature quenching activation energy of the fluorescence of R6G molecules in the presence of ablated silver nanoparticles is found. The vibrational relaxation rate of R6G in PMMA films is estimated, the efficiency of the dipole – dipole electron energy transfer between R6G and brilliant green molecules (enhanced by plasmonic interaction with ablated silver nanoparticles) is analysed, and the constants of this energy transfer are determined.

Influence of silver nanoparticles on the luminescence dynamics of Dy3+ doped amorphous matrix

In this work, we report on the deactivation of Dy3+ ions by increase in concentration of silver nanoparticles (NPs) in a silicate glassy system. The quench in luminescence of Dy3+ ions is consistent with increase in the long and short lifetime of 4F9/2 excited state which develops as the concentration of silver NPs increases by heat-treatment duration.

Influence of silver nanoparticles on metabolism and toxicity of moulds.

The unique antimicrobial features of silver nanoparticles (AgNPs) are commonly applied in innumerable products. The lack of published studies on the mechanisms of AgNPs action on fungi resulted in identification of the aim of this study, which was: the determination of the influence of AgNPs on the mould cytotoxicity for swine kidney cells (MTT test) and the production of selected mycotoxins, organic acids, extracellular enzymes by moulds. The conducted study had shown that silver nanoparticles can change the metabolism and toxicity of moulds. AgNPs decrease the mycotoxin production of Aspergillus sp. (81-96%) and reduce mould cytotoxicity (50-75%). AgNPs influence the organic acid production of A. niger and P. chrysogenum by decreasing their concentration (especially of the oxalic and citric acid). Also, a change in the extracellular enzyme profile of A. niger and P. chrysogenum was observed, however, the total enzymatic activity was increased.

Enhancement of Optical Absorption, Photoluminescence and Raman Transitions in Bi2O3-GeO2Glasses with Embedded Silver Nanoparticles

The influence of silver nanoparticles (Ag-NPs) on the optical properties of Bi2O3-GeO2 glasses was investigated aiming the characterization of their potential for applications in photonic devices. The samples were prepared by the melt-quenching technique starting from high purity oxides (GeO2, Bi2O3 and AgNO3). Heat-treatment during different times was performed to nucleate Ag-NPs. A transmission electron microscope was used to confirm the presence of Ag-NPs and to determine their sizes and composition. The glass network was studied by spontaneous Raman scattering. The optical absorption spectra showed an absorption band at ca. 500 nm associated to the bismuth ions, and a 7-fold enhancement of absorption was observed in the samples with Ag-NPs. Photoluminescence (PL) spectra were obtained by exciting the samples with a 808 nm laser. Maximum enhancements of ca. 100% of the PL band centered at 1300 nm and ca. 70% of the Raman spectrum were observed due to the nucleation of the Ag-NPs. The enhanced optical response of the samples with Ag-NPs is attributed to the growth of the local field on the isolated bismuth ions and clusters that are located in the vicinity of the nanoparticles. The results illustrate the large potential of Bi2O3-GeO2 with Ag-NPs to be used in photonic devices.

Antimicrobial regenerated cellulose/nano-silver fiber without leaching

The formation of antimicrobial regenerated cellulose fibers using an ionic liquid solvent, 1-butyl-3-methylimidazolium chloride, and silver nanoparticles was studied. The cellulose preparation and dispersion efficiency of the silver nanoparticles in the solvent were evaluated via scanning electron microscope and transmission electron microscopy in terms of different processing conditions. The influence of silver nanoparticles on regenerated cellulose fiber crystallization and strength was examined using a wide angle X-ray diffractometry and tensiometry, respectively. The bioactive efficacy of the cellulose/nano-silver fiber was tested in accordance with the standard method of ASTM E 2149-10. The cellulose/nano-silver fibers were bioactive and killed Escherichia coli almost completely without any leaching problems. The addition of nano-silver significantly increased the cellulose fiber tensile strength and modulus with an insignificant reduction in fiber elongation, and a slower thermal decomposition rate, evidenced by increased fiber crystallinity. Higher processing temperatures improved the nano-silver dispersion efficiency. The final nano-silver suspension in the regenerated cellulose matrix was composed of scattered clusters with an average size of 700 nm and a distribution density of 14,098 mm−2.

The influence of silver nanoparticles on the stimulated luminescence of rhodamine 6G solutions

The influence of silver nanoparticles on the spontaneous and stimulated luminescence of rhodamine 6G molecules in aqueous solutions is studied. It is found that the laser photoexcitation of the dye solution gives rise to spontaneous fluorescence, which, with increasing pump power, transforms into stimulated laser radiation and superluminescence. Addition of silver nanoparticles to rhodamine 6G solutions enhances all types of luminescence and lowers the generation threshold for both types of the stimulated emission. The dependences of the laser radiation and superluminescence intensities on the concentration of silver nanoparticles correlate with the data on the spontaneous fluorescence.

Spectral investigations on the influence of silver nanoparticles on the fluorescence quenching of 1,4-dimethoxy-2,3-dibromomethylanthracene-9,10-dione

Silver nanoparticles (Ag NPs) of different sizes from 9 to 17 nm were synthesized by Creighton method and characterized using UV-vis spectroscopy and high resolution transmission electron microscopy (HRTEM). Fluorescence quenching of 1,4-dimethoxy-2,3-dibromomethylanthracene-9,10-dione (DMDBMAD) in methanol has been studied by fluorescence spectroscopy combined with UV-vis absorption spectroscopic techniques. It has been observed that the fluorescence intensity of DMDBMAD decrease with increase in the size of the Ag NPs. The quenching rate constant and association constant were determined using Stern-Volmer and Benesi-Hildebrand plots. The Stern-Volmer plot suggested that the quenching of DMDBMAD fluorescence by silver NPs was a dynamic process. The obtained value of the association constant infers that there is an association between DMDBMAD and the Ag NPs. Using Forster resonance energy transfer (FRET) theory, the distance between the donor (DMDBMAD) to acceptor (Ag NPs) and the critical energy transfer distance were obtained. Long range dipole-dipole interaction between the excited donor and ground state acceptor molecules is the dominant mechanism responsible for the energy transfer.

Electrospun polylactic acid non-woven mats incorporating silver nanoparticles

This research is focused on the influence of silver nanoparticles (AgNPs) on the spinnability, morphology and wetting properties of electrospun polylactic acid (PLA) non-woven mats. PLA was electrospun from a chloroform solution (4.7 % g/g) and a filament and beads morphology was obtained, the filaments having an average diameter of 1.25 μm. Interestingly, water contact angle measurements showed a contact angle of θ = 81°, an improvement relative to as-cast film which exhibited a contact angle of θ = 54°. When AgNP, of ca. 12 nm size, were incorporated at 1 % g/g relative to PLA weight, to the 4.7 % PLA-chloroform solution, and electrospun, the filaments diameter was greatly reduced to an average of 0.65 μm, and the density of polymer beads was also reduced. It is believed that the electric conductivity of silver enhanced the spinnability of the polymer solution. Strikingly, water contact angle measurements showed that the PLA/AgNP mats exhibited an angle as high θ = 134°. Increasing the solution concentration to 6.7 % g/g still produced a beads-and-filament morphology, but with larger filament diameters, probably due to an increase in solution viscosity. When AgNP were added (again at 1 % g/g relative to PLA weight), the occurrence of beads diminished and the average filament diameter decreased confirming the enhancement in spinnability by the AgNPs. Moreover, contact angles remained above 110° suggesting that the overall morphology is key to PLA’s mats hydrophobic behavior and not only filament diameter. Finally, the non-woven mats were rather amorphous, as revealed by differential scanning calorimetry and X-ray scattering, due presumably to the quenching process associated with the electrospinning process.

Influence of silver nanoparticles on absorption and fluorescence properties of laser dyes

The interaction of silver nanoparticles with four laser dyes, namely, LD-425, LD-489, LD-473, and LD-423, dispersed in methanol has been studied at room temperature by absorption and fluorescence spectroscopy. The silver nanoparticles were synthesized by chemical reduction and estimated size is 11 nm according to Mie theory. The changes in absorption spectrum of these dyes with the addition of silver nanoparticles suggest possible interaction with the silver nanoparticles. The magnitudes of the association constants are estimated using the Benesi–Hildebrand model. Fluorescence quenching has been observed for all the dyes with the addition of silver nanoparticles of different concentrations. The Stern–Volmer plots of fluorescence quenching in the case of LD-425 and LD-489 are found to be linear, suggesting the fluorescence quenching is because of the dynamic quenching process. But in the case of LD-473 and LD-423, the Stern–Volmer plots are nonlinear showing positive deviation and the fluorescence quenching in these dyes is because of static quenching processes. Also, it is found that the fluorescence quenching is not solely due to diffusion.

Influence of silver nanoparticles on the activity of rat liver mitochondrial ATPase

Mitochondria are one of the most sensitive targets for the toxicity of silver nanoparticles (AgNPs). Limited studies have demonstrated nanoparticle-induced impairment of mitochondrial oxidative phosphorylation. Reduced adenosine triphosphate (ATP) production can be due to inhibition of the respiratory chain and/or to direct effects of AgNPs on the activity of mitochondrial ATP synthase/ATPase. In this regard, we synthesized and evaluated the in vitro effects of two types of AgNPs with various environmental friendly coatings—polysaccharide starch (AgNPs/Starch, D av = 15.4 ± 3.9 nm) and trisaccharide raffinose (AgNPs/Raff, D av = 24.8 ± 6.8 nm), with an emphasis on their potential action on rat liver mitochondrial ATPase. Both types of AgNPs showed decoupling effect on intact mitochondria. Unlike AgNPs/Raff, AgNPs/Starch reduced 2,4-dinitrophenol-stimulated ATPase activity of intact mitochondria, which suggests that they are able to penetrate the inner mitochondrial membrane. Both types of AgNPs inhibited ATPase activity of freeze/thawed mitochondria and submitochondrial particles as the effects of AgNPs/Starch were more pronounced. UV–Visible absorption measurements showed changes in the absorption spectrum of AgNPs/Raff added to the reaction medium. This suggests nanoparticle aggregation and thus a possible reduction in their reactivity. The distinction in the effects of the two types AgNPs studied may be due to their different sizes and/or to the stabilizing agents used for their synthesis, which determine AgNPs colloidal stability in the assay media. This study suggests the need for further research into the importance of surface modifications of AgNPs for their interaction with cellular components. Our findings could contribute to the elucidation of the mechanisms underlying AgNPs toxicity.

Influence of silver nanoparticles on post-surgical wound healing following topical application

AbstractPrevention of surgical site infection and wound dehiscence are imperative and also challenging in clinical practice. This study examines the healing response of laparotomy wounds following application of silver nanoparticles.Dermal fibroblasts were exposed to incremential doses of silver nanoparticles and its effect on collagen synthesis and cytotoxicity was assessed. Laparotomy surgery was performed on rabbits and the operation site was treated topically either with silver nanoparticle once, or once daily for 14 days or with vehicle. Healing response and local tissue reaction was evaluated clinically by histopathology and scanning electron microscopy (SEM); microbial load on the operation site was assessed. Clinical tests and histopathology were performed to assess systemic toxicity.Silver nanoparticles increased collagen expression from dermal fibroblasts and longer time exposure increased caspase 3 expression and produced cyotoxic effect with an IC50 of 0.16 mg/mL. Daily treatment of operation sites resulted in increased collagen deposition and improved wound healing, microbial load was reduced. Although a sub dermal edema was evident in histopathology, SEM showed normal architecture of cells with infiltration of lymphocytes. There was no systemic toxicity.Silver nanoparticles exhibit a positive influence on wound healing but its effect on local tissue remains a concern.

The Influence of Silver Nanoparticles on the Blood-Brain and the Blood-Cerebrospinal Fluid Barrier in vitro

The use of silver nanoparticles in medical and consumer products such as wound dressings, clothing and cosmetic has increased significantly in recent years. Still, the influence of these particles on our health and especially on our brain, has not been examined adequately up to now. We studied the influence of AgEO- (Ethylene Oxide) and AgCitrate-Nanoparticles (NPs) on the protective barriers of the brain, namely the blood-brain barrier (BBB) and the blood-cerebrospinal fluid (blood-CSF) barrier in vitro. The NPs toxicity was evaluated by examining changes in membrane integrity, cell morphology, barrier properties, oxidative stress and inflammatory reactions. AgNPs decreased cell viability, disturbed barrier integrity and tight junctions and triggered oxidative stress and DNA strand breaks. However, all mentioned effects were, at least partly, suppressed by a Citrate-coating and were most pronounced in the cells of the BBB as compared to the epithelial cells representing the blood-CSF barrier. AgEO- but not AgCitrate-NPs also triggered an inflammatory reaction in porcine brain capillary endothelial cells (PBCEC), which represent the BBB. Our data indicate that AgNPs may cause adverse effects within the barriers of the brain, but their toxicity can be reduced by choosing an appropriate coating material.

Influence of silver nanoparticles on Er3+ up-conversion in CaF2 precipitated oxyfluoride glass-ceramics

The influence of silver nanoparticles on Er3+ up-conversion in CaF2 precipitated oxyfluoride glass-ceramics is investigated. After heat-treatments, transmission electron microscopy images show that CaF2 nanocrystals precipitate in the glass matrix uniformity, and sliver nanoparticles are spread around the CaF2 nano-crystals simultaneously. Comparing with the samples without Ag doped, high efficiency up-conversion luminescences of Er3+ at 540 and 658 nm are distinctly observed in the silver nanoparticles containing glass-ceramics by the 980-nm excitation. Moreover, since the intensity ratio of green and red emissions changes after silver nanoparticles precipitation, the up-conversion mechanism of Er3+ is discussed.

Influence of silver nanoparticles on food components in wheat

Abstract During storage, grain might be affected by bacterial and fungal infections. Pathogens diminish the grain quality through contamination with excrements and second metabolites. It is very important to prevent grain from infections. Due to their antimicrobial properties, silver nanoparticles can play the role of an effective protector. The influence of nanoparticles on wheat quality was studied. The gluten parameters and falling number did not change after covering the grain with silver nanoparticles stabilized by sodium citrate. Changes in the structure of starch and gluten were investigated using Fourier-transform infrared spectroscopy. Infrared spectra of the whole meal and starch have shown a slight shift (from 1 000 to 995cm-1) of the band connected with the C-O-H bending. This displacement is probably related to the changes in sample moisture. Significant differences, corresponding to changes in the protein secondary structure, have appeared in the gluten spectra after covering.A decrease of absorbance in the amide and CH and OH regions has been observed regardless of the covering time.

Enhancement and Quenching of Fluorescence by Silver Nanoparticles in Organic Light‐Emitting Diodes

The influence of silver nanoparticles (SNPs) on the performance of organic light‐emitting diodes (OLEDs) is investigated in this study. The SNPs are introduced between the electron‐transport layers by means of thermal evaporation. SNPs are found to have the surface plasmon resonance at wavelength 525 nm when the mean particle size of SNPs is 34 nm. The optimized OLED, in terms of the spacing between the emitting layer and SNPs, is found to have the maximum luminance 2.4 times higher than that in the OLED without SNPs. The energy transfer between exciton and surface plasmons with the different spacing distances has been studied.

Bio-protected flax nanocomposites as basis for manufacturing of high-tech eco-products

Data on biodegradation of flax fibers of different chemical composition, structure of cellulose, and included natural impurities (pectic compounds, lignin, and hemicelluloses) are presented. The influence of silver nanoparticles immobilized in the fiber on biodegradation of the objects under study is evaluated. It is demonstrated that this effect depends on the concentration and size of nanoparticles in the polymer matrix.

Genotoxicity and effects of nanosilver contamination in drinking water disinfection

This study was conducted to examine the genotoxicity and the influence of silver nanoparticles (AgNPs) contamination when drinking water is exposed to five different disinfection treatments: chlorine, chlorine dioxide, ozone, ozone/chlorine and ozone/chlorine dioxide. Experiments were conducted with water samples of different chemical composition, from three water supply systems in Croatia. AgNPs are of interest because of their use as an antimicrobial in numerous commercial products, and as a drinking water disinfection agent. To examine possible effects of AgNP contamination, the disinfection treatments were repeated with AgNPs in the water samples. AgNP contamination generally caused a decrease in the level of trihalomethanes by up to 59%. Influence of AgNPs on bromide ion incorporation into disinfection by-products (DBPs) was also examined. The most obvious example was the Osi water where ozonation step prior to chlorination increased the bromine incorporation factor from 0.156 to 0.339, while addition of AgNPs limited the increase to 0.249. Also, AgNP presence in almost all disinfection treatments increased dicarbonyl disinfection by-products. All treated waters were tested for genotoxicity using the comet assay and showed similar genotoxic potential. The results are preliminary, but could provide a basis for further studies evaluating the environmental impact of AgNPs in natural aquatic systems.

Infrared-to-visible upconversion emission in Er3+ doped TeO2-WO3-Bi2O3 glasses with silver nanoparticles

The influence of silver nanoparticles (NPs) on the frequency upconversion luminescence in Er3+ doped TeO2-WO3-Bi2O3 glasses is reported. The effect of the NPs on the Er3+ luminescence was controlled by appropriate heat-treatment of the samples. Enhancement up to 700% was obtained for the upconverted emissions at 527, 550, and 660 nm, when a laser at 980 nm is used for excitation. Since the laser frequency is far from the NPs surface plasmon resonance frequency, the luminescence enhancement is attributed to the local field increase in the proximity of the NPs and not to energy transfer from the NPs to the emitters as is usually reported. This is the first time that the effect is investigated for tellurite-tungstate-bismutate glasses and the enhancement observed is the largest reported for a tellurium oxide based glass.

Luminescence amplification of dye molecules in the presence of silver nanoparticles

The influence of silver nanoparticles on the luminescence intensity of dye molecules (methylene blue and acridine yellow) is investigated. It is shown that the fact that the attenuation spectrum of the silver particles coincides with the absorption spectrum of the dye molecules results in a small change of their absorption coefficient. At the same time, the luminescence intensity of the molecules increases in the presence of the silver particles by a sizable factor. The dependence of the luminescence gain on the size of the nanoparticles and the mean spacing between them and the dye molecules is determined.