Presence Of Silver Nanoparticles Research Articles

Photocatalytic Properties of Materials Based on Titanium(IV) Oxide and Silver Nanoparticles

The effect of the phase composition, the presence of silver nanoparticles, and the pH of the medium on the catalytic activity of heterophasic materials based on titanium oxide(IV) was studied in the photodegradation reactions of methyl orange and methylene blue. It was found that the highest degree of photodegradation of dyes is achieved when the anatase/rutile phase ratio in the photocatalyst is in the range from 60/40 to 50/50 (wt %), the photocatalyst samples are modified with silver particles, and the pH of the dye solutions is less than 5. Justification for the detected patterns was based on the use of energy data of the phases of TiO2 and silver.

Liquid marble particle wetting separation

Liquid marbles to separate wetting (silver nanowires) from non-wetting (graphite and talcum) particles is described here. Two types of liquid marbles are formed by coating the dry mixture test material on pendant or sessile drops. The silver nanowire particles are separated from the graphite or talcum shell by entering into the liquid core of the marbles. The liquid core is extracted into capillary tubes where the presence of silver nanoparticles was confirmed by a blue to colourless change arising from silver-mediated catalytic reduction of methylene blue and sodium borohydride solution. The use of an inclined rotating surface to coat the pendant drop was found to create liquid marbles in a more controllable manner. A platform tilt angle of 15o followed by rotation was found to provide more uniform albeit only partially coating the bottom of the pendant drop.

Biosynthesis, characterization and photo-catalytic degradation of methylene blue using silver nanoparticles

Silver Nanoparticles have been successfully synthesized using Milletia pegunesis leaf extract at room temperature. X-ray diffraction studies (XRD) attributed to the formation of highly crystalline cubic silver nanoparticles. Transmission electron microscopic (TEM) studies showed the distribution of particles of silver in the range of 60–90 nm with an average particle size of 80 nm. Dynamic light scattering (DLS) measurement shows that the particle size ranges from 50–150 nm for Ag nanoparticles. Surface area measurements give the specific surface area of 26.7 m2g−1. UV–Visible absorption spectrum of silver nanoparticles shows surface plasmon resonance band at 430 nm. FT-IR shows the appearance of band at 1623 cm−1 which may be attributed to amide linkage and the stretching band at 3280 cm−1 is due to alcoholic and phenolic linkages present in biomolecules of Milletia pegunesis. The degradation rate of methylene blue dye in presence of silver nanoparticles under sun light was found to increase with the increase in reaction time.

Spectral-Luminescence and Lasing Properties of Merocyanine Dye Solutions in the Presence of Silver Nanoparticles

The effect of silver nanoparticles (NPs) on the spectral-luminescence and lasing properties of an ethanolic solution of positive solvatochromic merocyanine dye is studied. Increases in the absorption cross section, intensity, and duration of dye fluorescence are observed upon the addition of NPs to the solution. This leads to a decrease in the merocyanine lasing threshold. As a result, laser generation can be obtained in the presence of silver NPs (СAg = 10−12 mol/L) at a dye concentration (10–4 mol/L) at which it cannot be achieved in the absence of NPs. It is noteworthy that the power density of laser pumping in the former case is lower than in the latter case.

UV–vis spectroscopic method for the sensitive and selective detection of mercury by silver nanoparticles in presence of alanine

The present investigation reports highly specific and sensitive colorimetric method for the detection of mercuric ion from aqueous samples using silver nanoparticles (Ag NPs). Here, Ag NPs was synthesized by chemical reduction method, and polyvinyl alcohol (PVA) was used as stabilizing agent. The particles were characterized by UV–vis spectrophotometer, scanning electron microscope (SEM), energy-dispersive X-ray spectrometer (EDS), particle size analyser and zeta sizer. The particles were found to be spherical in shape and polydispersed. The effective diameter and zeta potential were determined to be 6 ± 0.8 nm and −39.96 ± 4 mV respectively. The formation of NPs-alanine facilitated the detection of Hg(II) in nano-molar level. The NPs-alanine conjugate solution changed from brownish yellow to colourless with increase in concentration of Hg(II). A good linear relationship was found between absorbance at 398 nm and the Hg(II) concentrations range from 200 to 1000 nM. The paper and hydrogel based probe were developed and found to be highly specific towards the detection of Hg(II). The detection of Hg(II) ions was not influenced by other metal ions. The present investigation may be applied for the assay to detect mercury qualitatively and quantitatively from aqueous samples.

Ag-functionalized nanocrystalline cellulose for paper preservation and strengthening

Waste paper is an environmentally friendly source of cellulosic material. Here we propose a new treatment based on nanocrystalline cellulose (CNC) for paper preservation and consolidation. Suspensions of CNC were prepared by sulfuric acid hydrolysis using waste paper as cellulose source (CNCWP) and compared with CNC from cotton linter (CNCCL). Both CNCs were obtained with good yield, showing high crystallinity index and comparable morphology, as demonstrated by DLS-ELS, XRD, FTIR, Raman and TEM analyses. CNCs were mixed with silver nanoparticles (CNC/Ag) and their biocidal activity was tested against Escherichia coli and Bacillus subtilis, measuring the minimum inhibitory concentration. CNCs were exploited as treatments for biocidal activity and consolidation on Whatman paper. The presence of silver nanoparticles doesn’t affect aesthetic appearance of the original paper and prevents the growth of Aspergillus niger fungus. Mechanical tests demonstrated that the coatings by CNC based products improve stretch and toughness of the paper support.

Detection of low dose of piroxicam polymorph in pharmaceutical tablets by surface-enhanced Raman chemical imaging (SER-CI) and multivariate analysis.

This study demonstrates, for the first time, the ability of surface-enhanced Raman chemical imaging (SER-CI) combined with multivariate analysis to detect low levels (0.1% (w/w)) of a polymorphic form in a pharmaceutical mixture. In the studied formulation, piroxicam was used as a model molecule to develop this approach. Piroxicam is a widely available non-steroidal anti-inflammatory drug, exhibiting an interesting case of polymorphism, with two most commonly observed forms (β and α2). In this work, the SERS spectra of piroxicam polymorphic forms β and α2 are presented. These forms showed clear spectral differences in terms of band position and intensity. From a crystallographic point of view, the difference of exaltation between both forms was correlated with a preferred orientation of crystallites of form α2 making its SERS detection difficult compared to form β. A preferred orientation of the (1k0) crystallographic planes of α2 was demonstrated in samples, not promoting an appropriate molecular orientation onto the metallic surface. Additionally, a semi-quantitative approach using SER-CI combined with chemometric tools was developed enabling to detect crystallites of form β below the detection limit of conventional Raman microscopy. The exaltation of the Raman signal in the presence of silver nanoparticles allowed a higher sensitivity and a reduction of the acquisition time by a factor of 6.

The influence of plasmons of Ag nanoparticles on photovoltaics of functionalized polymethine dye

The effect of localized plasmon resonance (LPR) of Ag nanoparticles on the photovoltaic and spectral-luminescent properties of a functionalized polymethine dye (PD) was studied. It was shown that in the presence of silver nanoparticles there is an increase in the efficiency of the solar cell sensitized by the dye by 20% was registered. Measurements of the spectral-luminescent characteristics showed that fluorescence intensity upon addition of Ag NPs was increased almost twofold. The increase in the efficiency of solar cell is a result of increasing of absorption properties of PD in the presence of Ag nanoparticles.

Preparation and Deep Characterization of Composite/Hybrid Multi-Scale and Multi-Domain Polymeric Microparticles.

Polymeric microparticles were produced following a three-step procedure involving (i) the production of an aqueous nanoemulsion of tri and monofunctional acrylate-based monomers droplets by an elongational-flow microemulsifier, (ii) the production of a nanosuspension upon the continuous-flow UV-initiated miniemulsion polymerization of the above nanoemulsion and (iii) the production of core-shell polymeric microparticles by means of a microfluidic capillaries-based double droplets generator; the core phase was composed of the above nanosuspension admixed with a water-soluble monomer and gold salt, the shell phase comprised a trifunctional monomer, diethylene glycol and a silver salt; both phases were photopolymerized on-the-fly upon droplet formation. Resulting microparticles were extensively analyzed by energy dispersive X-rays spectrometry and scanning electron microscopy to reveal the core-shell morphology, the presence of silver nanoparticles in the shell, organic nanoparticles in the core but failed to reveal the presence of the gold nanoparticles in the core presumably due to their too small size (c.a. 2.5 nm). Nevertheless, the reddish appearance of the as such prepared polymer microparticles emphasized that this three-step procedure allowed the easy elaboration of composite/hybrid multi-scale and multi-domain polymeric microparticles.

Drug Entrapment Efficiency of Silver Nanocomposite Hydrogel

Silver nanocomposite hydrogel (SNH) with biodegradable polymers, sodium alginate and sodium lignosulphonate was synthesized employing principles of green chemistry for possible application in the field of controlled drug release. One of the factor that determines the release of drug from blend is the quantity of drug present/trapped inside the polymer network. The entrapment of drug in the polymer matrix depends upon the stability of matrix and interaction between the drug and the matrix. In the present study effect of presence silver nanoparticles in the polymeric matrix on the Drug Entrapment Efficiency (DEE) for the drug ciprofloxacin (CPX) was investigated. The drug entrapment efficiency for CPX loaded beads of SA/LS was calculated for similar conditions, to evaluate the effect of silver nanoparticles. Experimental results confirmed role of crosslinking and presence of silver nanoparticles on the stability of SNH and its entrapment efficiency. Observations indicate that the drug entrapment is more for the SNH as compared to the blend. Presence of silver nanoparticles help stabilize the polymer matrix, improves binding inside the matrix, which leads to the better drug entrapment.

Ag-AgCl Nanoparticles Fixation on Electrospun PVA Fibres: Technological Concept and Progress

Polymer-metal based material with unique 3D structure is an attractive substrate for the development of biomedical applications. A novel preparation of the composite from polymer fibres and silver nanoparticles has been designed through: (1) preparation of silver nanoparticles by phytosynthesis and (2) incorporation of these nanoparticles in a fibrous membrane prepared by electrospinning. The nanoparticle biosynthesis was performed in a pure environmental-friendly, easy, static, bottom-up in vitro regime using Tilia sp. leachate. TEM and XRD depict the formation, stabilisation and encapsulation of crystalline silver (14 ± 9 nm) nanoparticles (NPs) in one simple step with low tendency to aggregate. We achieved successful incorporation in the uniform electrospun 221 ± 24 nm poly(vinylalcohol) fibres, and this confirms the possibility of its use in the biomedical field. Both SEM with EDX and TEM analysis determined fibre uniformity with the presence of silver NPs, and ICP-AES confirmed the relatively similar metal concentration throughout the triplicate measurement of fibre structures on the 2 × 2 cm area in the following manner: 0.303 ± 0.018 wt. %, 0.282 ± 0.017 wt. %, and 0.281 ± 0.017 wt. %. Our hypothesis is based on previously verified preparation of active silver NPs and the easily prepared PVA electrospun fibres which act as a water soluble matrix. The simple methodology of incorporating biosynthetically prepared NPs in the PVA fibers highlights the effectiveness of this material, with simple release from water-soluble PVA and final activation of the prepared NPs.

Catalytic Reduction of Organic Dyes with Green Synthesized Silver Nanoparticles using Aloe vera Leaf Extract

In this present study, we report a facile, cost-effective and non-toxic method of synthesis of silver nanoparticles using 4mM silver nitrate and aqueous leaf extract of Aloe vera as reducing and capping agent in presence of 25% ammonia solution. Then these green synthesized nanoparticles are used as catalysts for the degradation of organic dyes. The synthesized silver nanoparticles (AVSNPs) were characterized using different techniques like UV-Visible spectroscopy, Fourier infrared spectroscopy (FTIR), Dynamic light scattering (DLS), X-ray diffraction (XRD), Field emission-scanning electron microscopy (FESEM) and Energy Dispersive X-Ray Spectroscopy (EDAX). Further, the nanoparticles were seen to degrade organic dyes which were visibly seen and also recorded in UV-Visible Spectrometer. The initial synthesis of silver nanoparticles is confirmed by a peak at 417nm. The nanoparticles were found to be spherical in shape with an average size ranging between 11-23 nm. XRD analysis confirmed the formation of silver nanoparticles of crystalline nature and a face-centered cubic (fcc) lattice and FTIR analysis showed the involvement of the biomolecules in the reduction of silver to form silver nanoparticles and the EDAX confirmed the presence of silver nanoparticles. The green synthesized nanoparticles catalyze the degradation of different organic dyes in a very short period of time. The green synthesized silver nanoparticles were seen to show excellent activity in catalyzing the degradation of organic dyes in an aqueous medium in the presence of the electron donor sodium borohydride (NaBH 4 ). Keywords: Aloe vera, catalysis, dye reduction, green synthesis, NaBH4, organic dyes, silver nanoparticles

GREEN SYNTHESIS OF SILVER NANOPARTICLES AND THEIR CATALYTIC APPLICATION FOR THE DEGRADATION OF ORGANIC POLLUTANTS

A simple and rapid method of green synthesis of silver nanoparticles (AgNPs) was developed using aqueous extract of grape pomas (GP) obtained from by plasma-chemical extraction technique, and their catalitic potential was investigated. With this aim, the plasma-chemical obteained aqueous solutions of grape pomace and AgNO3 (0.25-6.0 mM) were mixed (1:1 v/v), and heated for 10 mim. The synthesized GP-AgNPs were characterized by UV-visible spectroscopy, AFM, DSL analyses. The synthesized AgNPs showed an intense surface plasmon resonance band at 405-420 nm. The AgNPs were in highly uniform shape (everage size 20 nm). The role of pH in the green synthesis of silver nanoparticles (AgNPs) is investigated. The presence of silver nanoparticles with sun light was proven very effective for degradation of organic dyes. The reaction kinetics was found to be pseudo first order with respect to the dye concentration. The outcomes of the current study confirmed that the synthesized AgNPs had an awesome guarantee for application in catalysis and wastewater treatmen.

Efficiency improvement of a silicon-based thin-film solar cell using plasmonic silver nanoparticles and an antireflective layer

This paper presents a silicon thin-film solar cell (TFSC) integrated with the silver nanoparticles. It consists of anti-reflection, absorption and reflective layers in which the anti-reflective layer is made of pyramids of TiO2. The purpose of this structure is to allow sunlight to enter the cell at any angle with the minimum reflection and absorption in the wavelength range of 300–1100 nm. The absorbing layer is composed of silicon and when sunlight enters this layer, the molecular bonds break down and release many electrons due to its high absorption coefficient. In this layer, silver spherical nanoparticles are placed to increase the absorption of solar energy by the localized surface plasmon resonances, which will increase the efficiency of the TFSC. The last layer of the structure is a reflective surface of aluminum, which aims to reflect the light into the upper layer to enhance its absorption. We will calculate the key performance metrics for a solar cell such as short-circuit current, open-circuit voltage, fill-factor, and photovoltaic efficiency considering the effects of recombination between silicon substrate and other materials. The numerical results based on the finite-difference time-domain method reveal that the proposed structure has much more absorption due to the anti-reflection layer and the presence of silver nanoparticles that leads to light scattering, light localization, and guided mode excitation compared to conventional TFSC. Our simulations based on the finite-element method show the presented TFSC integrated with silver nanoparticles has a fill-factor of 0.82 and an efficiency of 16.18%.

Effects of silver nanoparticles coated with anti-HER2 on irradiation efficiency of SKBR3 breast cancer cells.

Breast cancer is the second cause of death in the world. Ionising radiation is a potent mutagen that can cause DNA damage, chromosomes breakage, and cell death. In the present study, radiotherapy and nanoparticle-antibodies (ABs) have been combined to enhance the efficacy of cancer cell treatment. Silver nanoparticles (SNP) were synthesised, coated with anti-HER2, and then characterised with different techniques such as X-ray diffraction, dynamic light scattering, transmission electron microscopy, Fourier transform infrared, and UV-Vis spectroscopy. SKBR3 cells were irradiated with cobalt-60 in the presence of nanoparticle-AB as the drug. Cell viability was measured using the diphenyltetrazolium bromide assay, and the cellular status was assessed by Raman spectroscopy. Irradiation considerably decreased cell viability proportionate to the dose increase and post-irradiation time. The surface-enhanced Raman spectroscopy increased the signal in the presence of SNP. Increasing the dose to 2 Gy increased the irradiation resistance, and higher dose increases (4 and 6 Gy) enhanced the irradiation sensitivity. Moreover, the cellular changes induced by irradiation in the presence of the drug were stable after 48 h. The authors results introduced the combination of the drug with radiation as an effective treatment for cancer and Raman spectroscopy as a suitable tool to diagnose effective irradiation doses.

UV random laser emission from flexible ZnO-Ag-enriched electrospun cellulose acetate fiber matrix

We report an alternative random laser (RL) architecture based on a flexible and ZnO-enriched cellulose acetate (CA) fiber matrix prepared by electrospinning. The electrospun fibers, mechanically reinforced by polyethylene oxide and impregnated with zinc oxide powder, were applied as an adsorbent surface to incorporate plasmonic centers (silver nanoprisms). The resulting structures – prepared in the absence (CA-ZnO) and in the presence of silver nanoparticles (CA-ZnO-Ag) - were developed to support light excitation, guiding and scattering prototypes of a RL. Both materials were excited by a pulsed (5 Hz, 5 ns) source at 355 nm and their fluorescence emission monitored at 387 nm. The results suggest that the addition of silver nanoprisms to the ZnO- enriched fiber matrix allows large improvement of the RL performance due to the plasmon resonance of the silver nanoprisms, with ~80% reduction in threshold energy. Besides the intensity and spectral analysis, the RL characterization included its spectral and intensity angular dependences. Bending the flexible RL did not affect the spectral characteristics of the device. No degradation was observed in the random laser emission for more than 10,000 shots of the pump laser.

Electrospinning of hyaluronan/polyvinyl alcohol in presence of in-situ silver nanoparticles: Preparation and characterization

Novel nanofibers mats were fabricated by electrospinning of polyvinyl alcohol/hyaluronan (PVA/HA) solutions in the presence of silver nanoparticles (AgNPs). The AgNPs were synthesized by in-situ chemical reduction of silver ions (Ag+) using HA as a reducing and stabilizing agent. Narrow size distribution and spherical shape of AgNPs were achieved by optimizing the initial silver nitrate concentration (0.01 to 1 M) and reaction time (10–60 min). HA-AgNPs nanocomposite and PVA/HA-AgNPs nanofibrous mats were fabricated by electrospinning technique from aqueous solution containing a different mass ratio of PVA and HA-AgNPs and characterized by UV/Vis spectroscopy, SEM, TEM, DLS, XRD, TGA, and ATR-FTIR. Mechanical and rheological properties were also investigated and discussed. The novel nanofibrous mats show great potential in skin regeneration and drug carrier applications.

Effective optical properties of the one-dimensional periodic structure of $$\hbox {TiO}_{{2}}$$ and $$\hbox {SiO}_{2 }$$ layers with a defect layer of nanocomposite consisting of silver nanoparticle and E7 liquid crystal

In this work, the dielectric property of a nanocomposite (NC) consisting of silver nanoparticle and E7 liquid crystal (LC) has been investigated theoretically at different temperatures. The study shows that the surface plasmon resonance (SPR) and filling fraction of the silver nanoparticle significantly change the dielectric property of the NC. To study the optical property of the defective periodic structure, the NC was considered as a defect layer in a semifinite one-dimensional periodic structure (1DPS) of $$\hbox {TiO}_{{2}}$$ and $$\hbox {SiO}_{{2}}$$ layers, i.e. ( $$\hbox {TiO}_{{2}}{\vert }\hbox {SiO}_{2})^{5}{\vert }\hbox {NC}{\vert }(\hbox {TiO}_{{2}}{\vert }\hbox {SiO}_{2})^{5}$$ . The optical properties of the 1DPS with the NC as the defect layer have been studied by the simple transfer matrix method (TMM). Moreover, the transmission and absorption characteristics of the 1DPS in the presence of silver nanoparticle in the NC have been studied with different orientations of the LC molecule.

Preparation of Nano-Ag-TiO2 Composites by Co-60 Gamma Irradiation to Enhance the Photocurrent of Dye-Sensitized Solar Cells

Nano-silver-titanium dioxide (Ag-TiO2) composites were prepared from commercial TiO2 (P25, Degussa) and silver nitrate (AgNO3) by gamma Co-60 irradiation method with various initial concentrations of AgNO3. The nano-AgTiO2 composites are utilized as the photoanode for dye-sensitized solar cells (DSCs). Under full sunlight illumination (1000 W/m2, AM 1.5), the efficiency of DSCs has improved significantly despite the Ag content of below 1%. The DSC—assembled with 0.75 Ag-TiO2 (0.75% Ag) photoanode—showed that the photocurrent was significantly enhanced from 8.1 mA.cm−2 to 9.5 mA.cm−2 compared to the DSCs using bared TiO2 photoanode. The unchanged open-circuit voltage resulted in the overall energy conversion efficiency to be increased by 25% from 3.75% to 4.86%. Electrochemical impedance spectroscopy (EIS) analysis showed that the charge transfer resistance is reduced when increasing Ag content, demonstrating that the charge transfer at TiO2/dye interface was enhanced in the presence of silver nanoparticles.

Plasma-enhanced magnetron sputtering of silver nanoparticles on reverse osmosis membranes for improved antifouling properties

The reverse osmosis process is an efficient water purification technology with comparatively low energy consumption. However, unwanted biofilm formation remains a major challenge for membrane plant operators, and effective fouling control strategies are highly sought for. A material-based antifouling approach is the deposition of silver nanoparticles onto the polyamide layer of thin film composite membranes by plasma-enhanced magnetron sputtering, as described in this study. The particle size and distributions were analyzed from Scanning Electron Microscopy (SEM) images and discussed with the elemental composition of the membrane surfaces derived by X-ray Photoelectron Spectroscopy (XPS). The desalination efficiency of the silver coated membranes was determined by use of a coupon tester, and the antimicrobial effect was verified by inducing a reproducible microbial stress on the membranes with a chemostat. In the presence of silver nanoparticles, which had an average diameter of 30 nm, the biofilm formation of pseudomonas sp. was significantly reduced by 64.6% on average after 14 days of continuous cultivation. A sputtering time of 5 s proved to be successful both in significantly improving the antifouling properties as well as fully maintaining the filtration performance of the membranes.