Concentration Of Ag Precursor Research Articles

Interface-templated synthesis of single-crystalline silver chain-like nanobelts at the liquid-liquid interface between water and redox-active ionic liquid

Silver chain-like nanobelts (NBs) have been prepared by a redox-active ionic liquid (RAIL)|water (W) interfacial method with utilizing the soft interface as a template. A highly hydrophobic RAIL (ferrocenylmethyl)dodecyldimethylammonium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate ([FcMDDA+][TFPB−]) works as both the reducing agent and the liquid substrate in the RAIL|W interfacial system. The morphology of Ag chain-like NBs, which possesses flat surfaces, sharp corners on the edges, and large aspect ratio, combines the features of one-dimensional (1D) and 2D nanostructures. The formation of Ag chain-like NBs is realized by the linkage of small nanounits through an oriented growth along the RAIL|W interface. The size and shape of the Ag deposited at the RAIL|W interface can be controlled by regulating the concentration of Ag precursor in W, where higher (lower) concentration of AgNO3 induces the formation of Ag NBs with smaller (larger) size. The prepared Ag chain-like NBs show good surface enhanced-Raman scattering activity which can be used as the substrate for plasmonic applications.

Plasmonic Effects on the Growth of Ag Nanocrystals in Solution.

The light-stimulated transformation of ensembles of spherical nanoparticles into anisotropic metal nanostructures mediated by localized surface plasmon resonance (LSPR) excitation is an elegant way of synthesizing triangular silver nanoprisms with extraordinary control over size and shape. Generally, the transformation occurs in oxidizing environments along a pathway that involves the oxidative etching of small preexisting Ag seeds, followed by plasmon-mediated reduction of the resulting Ag ions and Ag0 incorporation into the anisotropic nanocrystals. Here, we investigate pathways toward Ag nanoprisms from initially homogeneous AgNO3 solutions held under reducing conditions. Observations using in situ electron microscopy show that reducing environments and high Ag precursor concentrations in the presence of sodium citrate favor two alternative transformation routes of initial spherical nuclei into anisotropic nanoprisms: (i) the aggregation of spherical nanoparticles and plasmon-mediated conversion of small clusters into triangular prisms; (ii) shape fluctuations of individual small nanoparticles. Simulated field distributions confirm that the coupling of the LSPR excitation between closely spaced nanoparticles causes significant field enhancements near the local plasmonic hot spots, which facilitates accelerated Ag incorporation and thus supports the transformation into nanoprisms.

MODIFICATION OF Ti–6Al–4V ALLOYS FOR DENTAL IMPLANT AND ITS CAPACITY TO GROW HUMAN OSTEOBLAST ATCC

Modification of Ti–6Al–4V alloys with silver-loaded TiO2 nanotubes was investigated. In this study, TiO2 nanotube (TiNT) was grown on the surface of Ti–6Al–4V plates by means of anodization in an electrolyte solution containing glycerol, water and 0.5[Formula: see text]wt.% of NH4F. Silver particles were deposited on TiNT using a Photo-Assisted Deposition (PAD) method. Formation of crystalline phase of TiO2 on the surface was confirmed by means of XRD while its superficial morphology was observed using FESEM/EDS. Hydrophilicity was assessed by means of contact angle measurement. As-synthesized silver-loaded TiNT on osteoblast ATCC growth in vitro was also investigated in terms of its capacity in supporting osseointegration. The cell viability was determined by MTT (3-[4,5-dimethylthiazol-2yl]-2,5diphenyl-2H-tetrazolium bromide) assay and its differentiation activity was measured by alkaline phosphatase (ALP) assay. The results showed that desposition of silver on TiNT increased cell viability after 14 days culture while improving the hydrophilicity feature. Silver-loaded TiNT on Ti–6Al–4V alloy with Ag precursor concentration of 0.10[Formula: see text]M showed the optimum viability of osteoblast growth, with 14% improvement in comparison to its unmodified counterpart. The MTT assay showed that no cytotoxicity in vitro was observed on this material. This study provides corroborating evidences that the modification of Ti–6Al–4V alloy may enhance the cell viability and its prominence as dental implant materials.

Preparation and characterization of sub-20 nm CuX@Ag1 core-shell nanoparticles by changing concentration of silver precursor

Ultrafine Ag-coated Cu (Cu@Ag) nanoparticles (NPs) less than 20 nm in diameter were prepared. After synthesizing ultrafine Cu NPs using a solvothermal method to serve as the core particles, Cu@Ag NPs were fabricated with different initial Ag precursor concentrations, resulting in different thicknesses, densities, and uniformities of Ag shells. The average thickness and density of the Ag shell increased with increasing initial Ag precursor concentration in a Cu:Ag atomic ratio from 6:1 to 1:1. However, excessive Ag precursor concentrations induced homogeneous nucleation and growth of surplus fine pure NPs. Ag dewetting behavior and Cu oxidation in the Cu4@Ag1 NPs were observed, they occurred during heating at 200 and 250 °C, respectively. The electrical resistivities of sintered Cu4@Ag1 films decreased with increasing temperature from 200 to 240 °C. The resistivity after washing the OA and sintering for 60 min at 240 °C in air was measured to be 4.96 × 10−3 Ω cm. The film was sintered in nitrogen using the ink containing non-washed Cu4@Ag1 NPs indicated the lower resistivity of 2.70 × 10−3 Ω cm owing to the non-oxidation atmosphere, although the chemically capped oleylamine in the core-shell NPs hindered the sintering behavior.

Size‐controlled synthesis of silver nanoparticles from silver mirror reaction in toluene

Size-controlled silver nanoparticles (Ag NPs) with a size of 2–15 nm have been synthesised from silver (Ag) mirror reaction in toluene, which refers to reduction of Ag precursor (Ag–dodecylamine complexes solution) by acetaldehyde (CH3CHO) in the presence of oleic acid (OLA). In this synthesis, the size of Ag NPs was finely tuned by just varying the Ag precursor concentrations (cAg). The addition of OLA can play an important role in stabilising the emerging Ag nuclei. With the OLA/Ag molar ratio at 3:1, the adsorption layer of enough OLA on the surface of the emerging Ag nuclei prevented the direct contact between Ag+ ions and Ag nuclei, and Ag nuclei grew up to their final size by the aggregation mechanism.

Optical and Vibrational Properties of Ag Nanometal-Enhanced Blue Light-Emitting Graphene Oxide-Polyvinylpyrrolidone Polymer Composite Films

We report ex situ synthesis, optical, phonon, and photoluminescence (PL) properties of silver nanoparticles (AgNPs) decorated on graphene oxide (GO) and polyvinylpyrrolidone (PVP) composite polymer matrix. Optical absorption studies show a band at 435 nm which is due to the surface plasmon resonance (SPR) of silver (Ag) and the full width half maximum (FWHM) of SPR band is found to be decreased with Ag concentration suggesting an increase in particle size. Raman spectra exhibit a D (disorder band) and a G (graphitic) band of GO with a red shift in G band with increasing Ag precursor concentration. The mechanism for the red shift is explained by the charge transfer between GO and AgNPs. PL spectra shows a shift towards longer wavelength as AgNPs size increases which is due to the overlap of interband of PVP and the SPR of AgNPs.

Assessment of the migration potential of nanosilver from nanoparticle-coated low-density polyethylene food packaging into food simulants

ABSTRACTAn experimental nanosilver-coated low-density polyethylene (LDPE) food packaging was incubated with food simulants using a conventional oven and tested for migration according to European Commission Regulation No. 10/2011. The commercial LDPE films were coated using a layer-by-layer (LbL) technique and three levels of silver (Ag) precursor concentration (0.5%, 2% and 5% silver nitrate (AgNO3), respectively) were used to attach antimicrobial Ag. The experimental migration study conditions (time, temperature and food simulant) under conventional oven heating (10 days at 60°C, 2 h at 70°C, 2 h at 60°C or 10 days at 70°C) were chosen to simulate the worst-case storage period of over 6 months. In addition, migration was quantified under microwave heating. The total Ag migrant levels in the food simulants were quantified by inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Mean migration levels obtained by ICP-AES for oven heating were in the range 0.01–1.75 mg l−1. Migration observed for microwave heating was found to be significantly higher when compared with oven heating for similar temperatures (100°C) and identical exposure times (2 min). In each of the packaging materials and food simulants tested, the presence of nanoparticles (NPs) was confirmed by scanning electron microscopy (SEM). On inspection of the migration observed under conventional oven heating, an important finding was the significant reduction in migration resulting from the increased Ag precursor concentration used to attach Ag on the LDPE LbL-coated films. This observation merits further investigation into the LbL coating process used, as it suggests potential for process modifications to reduce migration. In turn, any reduction in NP migration below regulatory limits could greatly support the antimicrobial silver nanoparticle (AgNP)-LDPE LbL-coated films being used as a food packaging material.

Application of silver nanodots for potential use in antimicrobial packaging applications

Abstract A simple method to fabricate well-defined silver nanodots of different sizes using self-assembled polystyrene-b-poly(ethylene oxide) (PS-b-PEO) block copolymer was developed. The most well-defined nanodot patterns were observed using optimal concentrations of silver precursor (0.4, 0.6, and 1.2%) with average sizes of 10, 18, and 28 nm by different molecular weights of PS-b-PEO. Silver nanodot patterns were not observed at higher Ag precursor concentrations. In addition, after repeated depositions, the antimicrobial activity (AA) towards bacteria increased compared to well-defined nanodot arrangements. The AA of the silver nanodots was significantly affected by the concentration used independent of the particle size of the silver nanodots. Potentially, silver nanodots can be used as antimicrobial packaging application to preserve the quality of food products due to the data generated here demonstrated that these materials significantly delayed the growth of Pseudomonas fluorescens and Staphylococcus aureus. Industrial relevance Food wastage is a significant cost to industry and society as a whole and impacts all stages of the food distribution cycle from transport and storage to shelf life and end-consumer use. Antimicrobial packaging could significantly decrease product decomposition and add value for producers by preserving product shelf life. Metal-based nanoparticles (NPs) (especially Ag) have previously been identified as potential antimicrobials but their performance is dependent on factors such as size and shape, concentration, morphology, composition and crystallinity. Their use in packaging has been limited partly by issues such as size control, powder handling, surface attachment and application to polymer films which can be challenging. We developed a novel method for generating antimicrobial surfaces based around the self-assembly of a polystyrene-b-polyethylene (PS-b-PEO) block copolymer that is a simple, effective and efficient method for generating highly uniform size and shape defined NPs (as nanodots) on a surface in a well-defined arrangement without the need of expensive lithographic techniques. The developed silver nanodot surfaces exhibited good antimicrobial activity against Gram-positive and Gram-negative bacteria and potentially can be used in antimicrobial packaging applications.

Facile synthesis of core–shell CuO/Ag nanowires with enhanced photocatalytic and enhancement in photocurrent

CuO nanowires were grown on Cu foil via a simple cost-effective wet-chemical route in large scales and used as templates for making silver-coated CuO (CuO/Ag) core–shell nanowires. The coverage of Ag shells on CuO nanowires was controlled by varying the concentration of Ag precursor. The structure, composition, morphology and optical properties of the synthesized core–shell CuO/Ag nanowires (CACs) were considered. The discussion on the growth process of CACs revealed the important role of Sn2+. And, the novel structure enlarged the range of absorbed light and enhanced the absorption intensity of light. The CACs were evaluated for their ability to degrade methyl orange (MeO) solution under visible-light irradiation. The rate of degradation of the as-prepared CACs was more than 7 times faster than that of using pure CuO nanowires under solar light irradiation. Moreover, the incorporation of Ag shells at the surface causes a quenching of PL emissions and enhanced photocurrent of CuO nanowires. The mechanisms of enhanced photocatalytic activity, luminescence emission quenching, and photocurrent multiplication of the core–shell nanowires have been discussed.

Plasmonic and Nonlinear Optical Absorption Properties of Ag:ZrO2 Nanocomposite Thin Films

Ag nanoparticles (NPs) embedded in a zirconium oxide matrix in the form of Ag:ZrO2 nanocomposite (NC) thin films were synthesized by using the sol–gel technique followed by thermal annealing. With the varying of the concentration of Ag precursor and annealing conditions, average sizes (diameters) of Ag nanoparticles (NPs) in the nanocomposite film have been varied from 7 to 20 nm. UV–VIS absorption studies reveal the surface plasmon resonance (SPR)-induced absorption in the visible region, and the SPR peak intensity increases with the increasing of the Ag precursor as well as with the annealing duration. A red shift in SPR peak position with the increase in the Ag precursor concentration confirms the growth of Ag NPs. Surface topographies of these NC films showed that deposited films are dense, uniform, and intact during the variation in annealing conditions. The magnitude and sign of absorptive nonlinearities were measured near the SPR of the Ag NPs with an open-aperture z-scan technique using a nanosecond-pulsed laser. Saturable optical absorption in NC films was identified having saturation intensities in the order of 1012 W/m2. Such values of saturation intensities with the possibility of size-dependent tuning could enable these NC films to be used in nanophotonic applications.

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

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

Rapid synthesis of Ag nanoparticles-embedded mesoporous silica via solution plasma and its catalysis for 4-nitrophenol reduction

The rapid synthesis of Ag nanoparticles-embedded mesoporous silica (AgNP@SiO2) was completed within a one-pot process in which a discharge occurred in solution of the substances utilized for synthesizing mesoporous silica (tetraethyl orthosilicate (TEOS), P123 block copolymer) and various Ag precursor concentrations (AgNO3: 1, 5, and 10mM). The solidification of the polysilicate network via hydrolysis and condensation during sol–gel reaction could be rapidly achieved after discharge at 3min. The morphology of rope-like particles with hexagonal mesopore arrangements was observed using electron microscopy. The catalytic activity of AgNP@SiO2 particles with high surface areas for 4-nitrophenol reduction was investigated under sodium borohydride (NaBH4) solution with reaction time dependence. The results showed that reduction of concentrated 4-nitrophenol (0.25mM) was completed at 12min using AgNP@SiO2 from 10mM Ag precursor.

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

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

Tailoring surface plasmon resonance in Ag:ZrO 2 nanocomposite thin films

Ag:ZrO 2 nanocomposite thin films have been synthesized by a modified sol–gel technique. The effect of post-deposition treatments i.e. thermal annealing and UV irradiation on micro-structural, chemical and optical properties of nanocomposite thin films have been studied by a transmission electron microscope, X-ray photoelectron spectrophotometer and UV–vis spectrophotometer. Films deposited with a polymeric ZrO 2 sol containing Ag + ions when treated with either thermal annealing or with UV irradiation exhibit formation of Ag:ZrO 2 nanocomposite thin films via decomposition of Ag 2O 3 into metallic Ag. The formed Ag nanoparticles are found predominantly in spherical shape and density of Ag nanoparticles increases with increase in annealing duration for a particular concentration of Ag precursor. A protocol is provided to tailor the surface plasmon resonance-induced absorption peak at wavelength from 454 to 586 nm. These nanocomposite thin films show saturable absorption and exhibit high value of non-linear absorption coefficient.

Antibacterial properties of Ag (or Pt)‐containing calcium phosphate coatings formed by micro‐arc oxidation

Silver (or platinum)-containing calcium phosphate (hydroxyapatite (HA) and tricalcium phosphate (alpha-TCP)) coatings on titanium substrates were formed by micro-arc oxidation (MAO) and their in vitro antibacterial activity and in vitro cytotoxicity were evaluated. MAO was performed in an electrolytic solution containing beta-glycerophosphate disodium salt pentahydrate (beta-GP) and calcium acetate monohydrate (CA), and Ag and Pt were introduced in the form of AgNO(3) (or CH(3)COOAg) and H(2)PtCl(6), respectively. The MG63 and human osteosarcoma (HOS) cell lines were used to investigate the proliferation and differentiation behavior of the cells, respectively, whereas two strains of bacteria, Staphylococcus aureus and Escherichia coli, were used to evaluate the antibacterial activity of the coatings. The phase, morphology, and Ag content of the coatings were strongly dependent on the applied voltage and Ag precursor concentration. HA and alpha-TCP phases were detected in the coatings oxidized above 400 V and the presence of Ag was confirmed by EDS. While the coatings with a high content of Ag were cytotoxic and those obtained in the Pt-containing electrolyte had no apparent antibacterial activity, the calcium phosphate coatings obtained in the low Ag concentration electrolyte exhibited in vitro antibacterial activity but no cytotoxicity. Thus, biocompatible calcium phosphate coatings on Ti implants with antibacterial activity can be achieved by one-step MAO.