Introduction Of Silver Nanoparticles Research Articles

Contact resistance improvement using interfacial silver nanoparticles in amorphous indium-zinc-oxide thin film transistors

We describe an approach to reduce the contact resistance at compositional conducting/semiconducting indium-zinc-oxide (IZO) homojunctions used for contacts in thin film transistors (TFTs). By introducing silver nanoparticles (Ag NPs) at the homojunction interface between the conducting IZO electrodes and the amorphous IZO channel, we reduce the specific contact resistance, obtained by transmission line model measurements, down to ∼10−2 Ω cm2, ∼3 orders of magnitude lower than either NP-free homojunction contacts or solid Ag metal contacts. The resulting back-gated TFTs with Ag NP contacts exhibit good field effect mobility of ∼27 cm2/V s and an on/off ratio >107. We attribute the improved contact resistance to electric field concentration by the Ag NPs.

Enhanced upconversion emissions in Ho3 +/Yb3 + codoped tellurite glasses containing silver NPs

Ho3+/Yb3+ codoped zinc-tellurite glasses containing silver nanoparticles (NPs) were prepared using the conventional melt-quenching technique. The detailed effect of silver NPs on the upconversion emission of Ho3+, thermal stability and structure behavior of glass hosts was investigated from the measured absorption spectra, upconversion emission spectra, differential scanning calorimeter (DSC) curves, X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM) images. Two frequency upconversion emission bands centered at 546nm (green) and 657nm (red) corresponding to Ho3+ transitions of 5F4(5S2)→5I8 and 5F5→5I8, respectively, are simultaneously observed under the 980nm excitation at room temperature. It is shown that the introduction of silver NPs can further improve the upconversion emissions of Ho3+and thermal stability of glass host, while the glass structure maintains the amorphous nature. The enhanced upconversion emission is mainly attributed to the increased local electric field around Ho3+induced by localized surface plasmon resonance (LSPR) effect of silver NPs. Furthermore, the energy transfer (ET) mechanism from Yb3+:2F5/2 level to Ho3+:5I6 level is quantitatively analyzed by calculating relevant micro- parameters and phonon contribution ratio.

Silver nanoparticles enhanced 1.53 µm band fluorescence of Er3+/Yb3+ codoped tellurite glasses

The silver nanoparticles (NPs) was introduced into the Er3+/Yb3+ codoped tellurite glasses with composition of TeO2–ZnO to improve the 1.53µm band fluorescence of Er3+ and the thermal stability of glass host. The UV–Vis–NIR absorption spectra, 1.53µm band fluorescence spectra and fluorescence decaying curves, the differential scanning calorimeter (DSC) curves, X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM) images of glass samples were characterized to investigate the effect of silver NPs on the fluorescence properties of Er3+, thermal stability and structure behavior of glass host. It is shown that the Er3+/Yb3+ codoped tellurite glass emits intense 1.53µm band fluorescence with peak wavelength located at about 1532nm under the 980nm excitation. The introduction of silver NPs further improves the fluorescence intensity of Er3+ which is attributed to the enhanced local electric field effect induced by localized surface Plasmon resonance (LSPR) of silver NPs and the possible energy transfer from silver NPs to Er3+. An improvement by about 62% of 1.53µm band fluorescence intensity was found in the studied Er3+/Yb3+ codoped tellurite glass containing 0.5mol% amount of AgNO3. In addition, the thermal stability of glass host increases with the introduction of silver NPs while the glass structure maintains the amorphous nature. The present results indicate that the prepared Er3+/Yb3+ codoped tellurite glass with an appropriate amount of silver NPs has good prospect as a gain medium applied for 1.53µm band broad and high-gain erbium-doped fiber amplifiers (EDFAs).

A comment on the article on EPR in silver-alanine nanocomposites for radiation detection by Guidelli et al. in Nanoscale, 4, 2012.

This comment refers to possibility of increasing the radiation sensitivity of alanine EPR dosimeters by introduction of silver nanoparticles.

Luminescence Enhancement in Eu(III)-Doped Tellurite Glass Embedded Silver Nanoparticles

Introduction of the metallic nanoparticles (NPs) in the bulk glass received a large interest due to their versatile applications. The effect of silver NPs on optical properties of the Eu3+-doped zinc tellurite glasses is presented for the first time. Glass samples are prepared by melt-quenching technique. The surface plasmon absorption bands of silver NPs are recorded in the visible region. The enhancements in the order of 2.2-2.4 times are observed in the luminescence of the Eu3+ ions by introduction of silver NPs up to 1 mol% and are attributed to contribution of the NPs with average size of about 8 nm. In addition, energy transfer from surface of the metal to the rare earth ion is discussed as the second channel for the enhancement. This report highlights the excellent performance of tellurite glasses for applications such as LEDs, color displays and nanophotonics.

Plasmonic-enhanced Si Schottky barrier solar cells

By introducing silver nanoparticles (NPs) and SiO2 spacer layers on top of Si-based Schottky barrier solar cells, we demonstrated a positive and tunable light trapping effect introduced by metallic NPs. A redshift of the surface plasmon resonant wavelength of Ag NPs from 550nm to 650nm, corresponding to the optical absorption peak of the solar cell, was observed with an increased average particle diameter from 19.7nm to 85nm. Enhanced light trapping effects at distinct resonance wavelengths were observed in the optical spectra of the plasmonic-enhanced devices. Electrical measurements confirmed the expected photocurrent improvement at these corresponding wavelengths. It was also revealed that the Ag NPs enhance the carrier generation rate inside of the Si active layer without sacrificing carrier collection efficiency of the device. The short-circuit current density of the best cell we obtained in this work was improved from 13.7mA/cm2 to 19.7mA/cm2, with an enhancement factor of 43.7%.

The Effect of TiO2 Microstructure and Introduction of Silver Nanoparticles on Conversion Efficiency of Sb2S3 Sensitized Semiconductor Solar Cells

Sensitized semiconductor solar cells consisting of alternative heterojunction materials (TiO2/Sb2S3/CuSCN) are characterized by an extremely thin absorber that allows effective charge transportation due to reduction in recombination. In these cells, Sb2S3 exhibited both positive and negative effects; it generated photocarriers and protected the cell from leakage current, but also behaved as a recombination center and increased the ohmic resistance. CuSCN was the additional critical factor of a cell performance with porous TiO2. CuSCN deposited on top of the porous structure exhibited two effects: high ohmic resistance and control of effective Sb2S3 at pn junctions. To achieve maximization of photocarrier generation and minimization of recombination, silver nanoparticles, which express localized surface plasmons when illuminated, were then applied to Sb2S3 cells with compact TiO2. The results revealed improved photoabsorption without having to increase the amount of Sb2S3, and revealed an improved J SC from 0.66 mA/cm2 to 1.88 mA/cm2.

Probing the interaction of a globular protein with a small fluorescent probe in the presence of silver nanoparticles: spectroscopic characterization of its domain specific association and dissociation

Photoinduced intramolecular charge transfer produces a polar excited state in the small fluorescent probe 1-anilino-8-naphthalene-sulfonate (ANS) rendering the resulting emission sensitive to the medium polarity. The binding of ANS to proteins has been well characterized in the literature. The probe binds to the less polar hydrophobic, restricted proteinous environment of bovine serum albumin (BSA) resulting in a blue shift of the emission maximum with an increase in emission intensity. However, upon addition of silver nanoparticles to the probe–BSA system, there was found to be an interaction between the nanoparticle and protein resulting in a weakening of the probe–BSA binding and an associated conformational change of the protein in order to accommodate the silver nanoparticle. This has been hitherto undeciphered. Studies using site markers of flufenamic acid and phenylbutazone coupled with other spectroscopic techniques, REES, time resolved studies, FTIR, and SEM imaging studies have shed light on the interaction of silver nanoparticles with the probe bound protein. ANS was observed to move from its binding site in the protein to accommodate the silver nanoparticle surface which involved conformational changes of the protein near the probe binding site. The association of the probe to the protein and its dissociation from the sites on introduction of silver nanoparticles has thus been investigated using spectroscopic studies.

Hybrids of Graphenes and Silver Nanoparticles Prepared by <i>In Situ</i> Process Employing Microwaveirradiation

Fine dispersion of graphenes is crucial for the application of graphenein various fields. However, graphenes are frequently aggregated due to the large surface area and van der Waals interactions between themselves during the mixing process. Thus, various modifications of graphenes are necessary for the fine dispersion. Introduction of functional groups into graphenes accompanies loss of inherent advantages. In this study, introduction of silver nanoparticles into graphenes by in situ process was investigated. Especially, microwave irradiation was employed for the syntheses sincegraphenes absorb microwave efficiently and became heated quickly. Formation of silver nanoparticles on the grapheneafter microwave irradiation was confirmed and the average diameter of the silver nanoparticles in the hybrids was about 30 nm. Rheological and electrical properties of the epoxy resins filled with the hybrids are discussed in this report.

Luminescence properties of ZrO2 mesoporous thin films doped with Eu3+ and Agn

Rare earth doped zirconium oxides are of interest as active materials in high-performance luminescent devices. Transparent ZrO2:Eu3+ mesoporous thin films with different doping ion concentrations were prepared by Evaporation Induced Self Assembly (EISA). The films exhibited high specific area and periodicity through connected networks of nanometer scaled pores. Thermal treatments at 600°C allowed the conversion of amorphous films into semi-crystalline ones. A detailed analysis of the structural and optical characterizations revealed that the Eu3+ ions sit inside the ZrO2 tetragonal crystallites as well as in the enriched zirconia amorphous phase of the walls nanoarchitecture. The introduction of silver nanoparticles in the porous network allowed to a strong modulation of the photoluminescence emission intensity.

Magnetically recoverable core–shell nanocomposites γ-Fe2O3@SiO2@TiO2–Ag with enhanced photocatalytic activity and antibacterial activity

In this study, we synthesized γ-Fe2O3@SiO2@TiO2–Ag nanocomposites with a core–shell structure using a hydrothermal method and a sol–gel method. Transmission electron microscope images showed that the γ-Fe2O3@SiO2@TiO2–Ag nanocomposites had a core–shell structure. Photocatalytic examination of the γ-Fe2O3@SiO2@TiO2–Ag was carried out using methyl orange solution under UV irradiation. The γ-Fe2O3@SiO2@TiO2–Ag nanocomposites showed stronger photocatalytic activity than pure TiO2. With γ-Fe2O3@SiO2@TiO2–Ag, about 84% of the methyl orange was decomposed after 1h of UV irradiation, versus 49% for pure TiO2. The antibacterial activity of γ-Fe2O3@SiO2@TiO2–Ag nanocomposites was remarkably greater than that of bare TiO2 nanoparticles. The introduction of silver nanoparticles into the TiO2 matrix facilitates charge separation by trapping photo-generated electrons, thereby enhancing biological activity and photoactivity.

The Effect of TiO2 Microstructure and Introduction of Silver Nanoparticles on Conversion Efficiency of Sb2S3 Sensitized Semiconductor Solar Cells

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Electrochemical behavior of mixed conducting oxide cathode on oxygen excess-type solid electrolyte

Electrochemical oxygen reduction behavior for a half cell composed of a mixed ionic and electronic conducting (MIEC) oxide and an oxygen excess-type solid electrolyte was investigated. A perovskite-type MIEC oxide, (La0.6Sr0.4)(Co1−yFey)O3−δ (LSCF), was employed as a base material for an electrode catalyst of oxygen reduction reaction. As an electrolyte, Al-doped lanthanum silicate [La10(Si5.8Al0.2)O26.9 (ALSO)] was used, which is a new class of oxide ion conductors with apatite-type structure. The evaluated polarization resistance, Rpol, for the reaction largely depended on y, and the minimum resistance was obtained for y = 0.2. The Rpol value was 0.3 Ω cm2 at 1073 K in ambient air [P(O2) = 2.1 × 104 Pa] for y = 0.2. To improve the performance, introduction of silver nano-particles onto the LSCF particles was studied. With the Ag-modification, Rpol at 1073 K could be minimized toward 0.08 Ω cm2. The cathodic overpotential of the electrode evaluated from DC polarization at 1073 K was 18 mV at 0.1 A cm−2.

Silver/polystyrene nanocomposites: Optical and thermal properties

AbstractNanocomposites consisted of different quantities of silver (Ag) nanoparticles incorporated in a polystyrene (PS) matrix have been prepared by solution mixing method. Transmission electron microscopy was applied to determine the size distribution of the Ag nanoparticles, while the morphology of fractured surfaces of pure PS and Ag/PS nanocomposites was examined by scanning electron microscopy. Absorption spectra of nanocomposites were compared with theoretically calculated spectra based on the Maxwell‐Garnett effective medium theory. The influence of Ag content on thermal properties of Ag/PS nanocomposites was investigated by thermogravimetric analysis and differential scanning calorimetry. Thermal and thermo‐oxidative stability of the host polymer were improved by introduction of silver nanoparticles. The glass transition temperature of the prepared Ag/PS nanocomposites was lower in comparison with the neat PS and decreased with the increase of the Ag content due to the very weak interfacial interaction between Ag nanoparticles and polymer matrix. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers

Fiber-optic chemical sensor of amine-type compounds

A scheme of a fiber chemical sensor of amine-type compounds has been implemented. The sensor includes a film nanostructure deposited on the end face of an optical fiber 600 μm in diameter. The film consists of luminescent silica nanoparticles modified by functional pyrylocyanine dye, silver nanoparticles, and a photonic crystal opal film. An additional coating of the sensor film from above by a porous selective mirror, such as a photonic crystal, and introduction of silver nanoparticles 5–7 nm in diameter into it make it possible to increase the sensor sensitivity by an order of magnitude.

The effect of silver ions and nanoparticles on the properties of ion-exchange materials

The effect of silver ions and nanoparticles on the electrochemical properties of KU-2-8 sulfocationite, MF-4SK homogeneous sulfocationite membrane, and MA-40 heterogeneous anion-exchange membrane is studied. Using scanning electron microscopy, the particle distribution throughout the cationexchanger thickness is studied. The method of IR spectroscopy is used for studying the interaction of silver nanoparticles and ions and also of Cu2+ and Ni2+ ions with secondary and tertiary amino groups. It is shown that the mobilities of sodium and silver ions are close in sulfocationites, which suggests that silver ions are quickly washed out of such materials. In the anion-exchange membrane, silver ions are bound into complexes with ionogenic groups and induce an increase in the water dissociate rate in the membrane. The reduction of silver ions contained in cation-exchangers in a molar fraction of 80% with sodium borohydride affords a conducting metal silver film on their surfaces. The introduction of silver nanoparticles into the MA-40 anionexchange membrane is accompanied by the increase in both the limiting electrodiffusion current and the water dissociation rate in the membrane, which is apparently due to the partial oxidation of metal silver particles to afford silver oxide in the near-surface membrane layer. The latter oxide exhibits weak catalytic activity with respect to water dissociation reaction in the membrane, which results in an insignificant increase in the effective transport numbers of hydroxide ions through the membrane.

Facile method of preparing silver-embedded polymer beads and their antibacterial effect

Research designed to prevent human beings from being infected by microorganisms such as bacteria, molds, yeasts, and viruses from the living environment has attracted tremendous interest. Therefore, many researchers have tried to develop novel and effective antimicrobial materials with free of resistance and low cost [1, 2]. One of the most widely used antibacterial materials is based on silver (silver ions or silver nanoparticles) which exhibits strong biocidal effects towards a broad range of microorganisms, along with advantages such as a lack of odor, taste, and color [3– 6]. Until now, various routes for preparing antimicrobial silver compounds or silver nanoparticles (NPs) have been reported [7, 8]. Especially, silver NPs have more severe effects on bacterial cells than silver ions [9]. However, silver NPs are easily aggregated which causes the deterioration of their chemical properties and decreases their antimicrobial properties. Moreover, the fate of silver NPs for biological applications is still debatable [10, 11]. In addition, some synthetic methods of silver NPs as antimicrobial materials are time-consuming and require expensive instruments. In addition, silver NPs can easily become aggregated, which causes the deterioration of their chemical properties and decreases their antimicrobial properties. To solve these problems, silver has been introduced onto stable supporting materials, in which the antimicrobial mechanism is closely related to the release of silver ions. These methods have several advantages, such as sustained antibacterial effects based on the release of silver ions, good mechanical properties and inexpensive and easy manufacturing processes for industrial applications [12–17]. Recently, many different methods have been proposed to introduce silver NPs into polymers. Among the various polymers, polystyrene (PS)–divinylbenzene (DVB) porous resin is particularly useful, due to its large surface area, chemical stability, and low cost. Moreover, silver NPs can be easily embedded on it after sulfonation, and their size and the loading amount can be adjusted by changing of reaction condition [18]. The deposition of silver on polymer materials has been enhanced by the activation of the surface-functional groups. Among the various functional groups, sulfonated groups are good candidates to introduce silver NPs for the purpose of producing antibacterial materials. Recently, we introduced silver NPs into sulfonated PS–DVB resins (4–8 lm) with mild reduction using the polyol method for use as surface-enhanced Raman scattering (SERS) active materials for multiplex protein analysis [18, 19]. In this study, silver NPs embedded into ion-exchange resin (Ag-IER) (ca. 0.9 mm) were readily prepared by the polyol method and characterized by several instrumental analyses, such as field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy-dispersive X-ray emission (EDX), and inductively coupled plasma atomic emission spectroscopy (ICP-AES). Then, their anti-bacterial activity was tested using Escherichia coli, which is well known as indicator bacteria. Moreover, we investigated their antibacterial effect at a low silver loading level and silver ion release conditions. B.-H. Jun J. Y. Kim H.-J. Park J. Yoon Y.-S. Lee (&) School of Chemical and Biological Engineering, Seoul National University, Seoul 151-747, Korea e-mail: yslee@snu.ac.kr

TEM Characterization on the Nanocomposite Al 7075 and Silver Nanoparticles Synthesized by Powder Metallurgy

Aluminum-based nanocomposites have been produced by mechanical milling, introducing silver nanoparticles within the matrix of a 7075 aluminum alloy using a high energy ball mill. The milled products were compacted by uniaxial load and pressure-less sintered under argon atmosphere, and finally hot extruded. Silver nanoparticles are well dispersed into the matrix of the powder particles as well as in the matrix of the extruded material. Transmission electron microscopy (TEM) analyses are used to corroborate and understand the hypothesis that second-phase particles finely and homogeneously dispersed in the matrix give greater strength to the material. In addition to the strengthening effect, the nanoparticles act like a process control agent (PCA) since the crystallite size of the nanocomposite is smaller at higher contents of nanoparticles.

Nonlinear optical properties of nanometer-size silver composite azobenzene containing polydiacetylene film

Diacetylene monomer containing p-nitrophenyl azobenzene moiety (NADA) was synthesized. Silver nanoparticles with different concentrations were adulterated in the above polymerized NADA (PNADA) films and the third-order nonlinear optical properties were investigated in detail. UV–vis spectra and transmission electron microscopy were used to confirm the formation of PNADA/Ag nanocomposite films. The silver nanoparticles (average size of 10 nm) were well dispersed in the polymer films. The value of the nonlinear refractive index n2 for PNADA films (8.48×10−15 cm2/W) was much higher than that of pure polydiacetylene films. Further, the introduction of silver nanoparticles into the PNADA polymer films led to the further enhancement of nonlinear optical properties. The maximum value of n2 for PNADA/Ag nanocomposite films could be 11.6×10−15 cm2/W. This enhancement should be ascribed to the surface plasmon resonance of silver nanoparticles.

The relationship between the antimicrobial effect of catheter coatings containing silver nanoparticles and the coagulation of contacting blood

It is well known that surface coatings for medical devices can be made antimicrobial through introduction of silver nanoparticles. By virtue of their extremely large surface-to-volume ratio, the silver particles serve as a depot for sustained release of silver ions, despite the fact that silver is not readily oxidized. Antimicrobial coatings are especially important in connection with indwelling catheters with a high risk of bacterial line infections, such as central venous catheters (CVCs). This study specifically addressed the question what the impact of silver nanoparticles (exposed at the coating's surface) and/or the release of silver ions would be on coagulation of contacting blood. Studies, performed in vitro with fresh platelet-rich blood plasma (PRP) from 5 different healthy volunteer donors, clearly pointed out that: (i) the presence of silver nanoparticles correlates with accelerated thrombin formation upon contact of the coating with PRP; (ii) platelet activation is stronger as a result from the contact with silver nanoparticle-containing coatings as compared to other coatings which are devoid of silver. A series of titration experiments, in which the potential effect of silver ions is mimicked, revealed that the observed activation of blood platelets can be best explained through a collision mechanism. The results suggest that platelets that collide with silver, exposed at the surface, become activated without adhering to the surface. These new results point, rather unexpectedly, at a double effect of the silver nanoparticles in the coating: a strong antimicrobial effect occurs simultaneously with acceleration of the coagulation of contacting blood. This new information is, evidently, most relevant for the development of improved surface coatings for indwelling catheters (such as CVCs) which should combine antimicrobial features and close-to-zero thrombogenicity.