Silver Ammonia Solution Research Articles

Antibacterial properties of silver nanoparticles grown in situ and anchored to titanium dioxide nanotubes on titanium implant against Staphylococcus aureus

Medical grade titanium alloy, Ti-6Al-4V, with TiO2 nanotubes (TiO2-NTs) grown on the surface and then decorated with silver nanoparticles (Ag NPs) is proposed to enhance the antimicrobial properties of the bone/dental implants. However, the decoration with Ag NPs is not consistent and there are concerns about the direct contact of Ag NPs with human tissue. The aim of this study was to achieve a more even coverage of Ag NPs on TiO2-NTs and determine their biocidal properties against Staphylococcus aureus, with and without a top coat of nano hydroxyapatite (nHA). The decoration with Ag NPs was optimised by adjusting the incubation time of the TiO2-NTs in a silver ammonia solution, and using biocompatible δ-gluconolactone as a reducing agent. The optimum incubation in silver ammonia was 7 min, and resulted in evenly distributed Ag NPs with an average diameter of 47.5 ± 1.7 nm attached to the surface of the nanotubes. The addition of nHA did not compromise the antimicrobial properties of the materials; high-resolution electron microscopy showed S. aureus did not grow on the composite with nHA and with >80% biocidal activity measured by the LIVE/DEAD assay, also limited lactate production. Dialysis experiment confirmed the stability of the coatings, and showed a slow release of dissolved silver (3.27 ± 0.15 μg/L over 24 h) through the top coat of nHA.

Dynamic reaction regulated surface-enhanced Raman scattering for detection of trace formaldehyde

A simple and reliable method was developed by combining redox reaction with surface-enhanced Raman scattering (SERS) for the indirect detection of formaldehyde (FA). Silver nanoparticles (AgNPs) can be generated from the reaction between the silver ammonia solution containing silver nanoclusters (AgNCs@Tollens) and FA, which can improve the SERS signal of rhodamine 6G (R6G). The detection principle was based on the enhancement of the SERS signal of R6G caused by the increase in the intensity of localized surface plasmon resonance (LSPR) upon the reduction of AgNCs@Tollens by FA. This method exhibits high sensitivity and selectivity for the detection of FA with a linear range from 5 μM to 160 μM and a limit of detection (LOD) of 2.5 μM. The proposed method was successfully used for the detection of FA released from furniture panels with a recovery rate of 95–100%.

Systematic post-synthetic modification of metal-organic framework (ZIF-67) with superior cyclability for lithium-ion batteries

In this work, carboxyl groups were introduced on the organic ligands of ZIF-67 through post-synthetic modification (-CH3→-CH2Br→-CHO→-COOH). A thin layer of Ag nanoparticles (3 nm in diameter) coating was deposited on external surface of ZIF-67 crystals through the reaction between the aldehyde groups in the ligands and silver ammonia solution. The carboxyl groups can participate in the lithium storage while the Ag nanoparticles coating help in increasing the conductivity. Electrochemical properties of the modified ZIF-67 electrodes are examined by cyclic voltammetry and galvanostatic charge/discharge tests. Benefiting from the outstanding conductivity of Ag nanoparticles and the synergistic effect between Ag nanoparticles and the modified ZIF-67, the composite exhibits enhanced electrochemical performance compared to its ZIF-67 counterpart. Nearly an invariable capacity of 800 mA h g−1 is maintained up to 100 cycles at 0.28 C (1C = 137 mA g−1) with a Coulombic efficiency of 99%. Furthermore, the ex situ X-ray diffraction and X-ray photoelectron spectroscopy studies on the electrode material under different states suggest that the Co ions remain in the Co2+ state during the charging/discharging process and the usual conversion reaction mechanism for lithium storage might not be suitable for the modified ZIF-67 electrode material.

Anodised TiO2 nanotubes as a scaffold for antibacterial silver nanoparticles on titanium implants

Medical grade titanium alloy is widely used for bone/dental implants, but the material alone has no innate antimicrobial properties that would reduce infection risk following surgery. However, silver nanoparticles (Ag NPs) are known to be antibacterial. This study investigated the growth of Ag NPs on titanium dioxide nanotubes (TiO2 NTs) on Ti-6Al-4V discs. The TiO2 NTs were grown on the Ti alloy using an electrochemical method, and then decorated with Ag NPs. The Ag NPs were synthesised by chemical reduction using δ-gluconolactone. A silver ammonia solution (silver nitrate + liquid ammonia) was used as the source of silver. Two separate approaches were used: (1) The δ-gluconolactone was mixed with the silver ammonia and then exposed to the TiO2 NTs (the ‘mixing method’), which produced micron-sized clusters of the Ag NPs. (2) The TiO2 NTs were exposed to the silver ammonia first and then to δ-gluconolactone (the ‘sequential addition method’), which resulted in the formation of nano-sized clusters of the nanoparticles. The Ag-TiO2 composites were confirmed by scanning electron microscopy and the elements analysed using energy dispersive X-ray spectroscopy (EDS). The composite coatings were exposed to a simulated body fluid for 24 h in order to determine the total Ag released. The release from the micron-sized clusters from the mixing method (14.6 ± 0.67 ppm) was higher than that from the nano-sized clusters (4.05 ± 0.36 ppm) when 0.015 M of silver ammonia was used. Additionally, Staphylococcus aureus, was cultured on the composite coatings for 24 h. Both the micron- and nano-sized clusters of the Ag NPs were found to be antibacterial using the Live/Dead assay. Overall, δ-gluconolactone was successfully used to reduce silver to Ag NPs on the surface of TiO2 NTs. The sequential addition method was the preferred method of synthesis because of its slower silver release, better coverage of the Ag-NPs on the TiO2 NTs and strong antibacterial properties.

Graphene Photocatalytic Catalyst Preparation and Properties of Composite Materials Research

Using a pan of the Ag/TiO2/rGO ternary composites, including ethanol as solvent, not only as a reductant in GO with the reduction of silver nitrate, the addition of ammonia water can not only catalytic hydrolysis TBOT to TiO2 can also form with silver nitrate silver ammonia solution is conducive to the reduction of silver nitrate. And the GO surface exist a large amount of oxygen-containing groups can provide nucleation points for the growth of the nanoparticles. Can control the dosing raio of TBOT and GO different morphology of TiO2/rGO composite material is prepared. Photocatalytic degradation of methylene blue test studied Ag modified enhanced the photocatalytic activity of TiO2 light influence.

Synthesis, characterization, and properties of porous silver spheres using rape pollen as novel bio-templates

Porous silver spheres were successfully prepared by reducing silver-ammonia solution and using rape pollen as novel bio-templates. The synthesized porous silver spheres with diameter of 50 μm have nanoparticles of ca. 25 nm. The samples were characterized by X-ray diffraction, scanning electron microscope (SEM), and transmission electron microscope (TEM) techniques. The thermal and electrical properties were also studied. We find that the reaction temperature and AgNO3 concentration have important influence on the morphology and electrical properties of the final products. TEM observations showed that the as-synthesized products are composed of nanoparticles with size around 25 nm. Volume resistivity results revealed that the volume resistivity was decreased with increasing the amount of AgNO3 concentration. The volume resistivity of porous silver was decreased two orders of magnitude while the AgNO3 increased twice.

Controllable Fabrication of Ag Nanoparticles-Coated Silica Core–Shell Microspheres and Its Optical Properties.

This paper described a one-step shell growth and extraordinarily facile method for the preparation of Ag nanoparticles-coated silica core–shell microspheres. The Ag nanoparticles could deposit on the silica microspheres to form continuous and compact shell layers at a balanced amount of polyvinyl pyrrolidone after the surface modification of the silica microspheres by (3-Mercaptopropyl) trimethoxysilane. The strong interactions between the thiol groups and Ag nanoparticles make it difficult to peel off the Ag shell from the core microspheres, obtaining extremely stable and homogeneous Ag nanoparticles-coated silica core–shell microspheres. Besides, the coating effect was controlled by varying the content of coupling agent, the type and amount of stabilizing agent, the quantity of silica microspheres as well as the mixing time between silica and silver ammonia solution. In addition, these Ag nanoparticles-coated silica core–shell microspheres were characterized using laser particle size analyzer (LPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The optical properties of the composite microspheres were observed by UV-vis spectroscopy.

Facile synthesis of hollow SnO2 nanospheres uniformly coated by Ag for electro-oxidation of hydrazine

Novel Ag/SnO2 has been synthesized by a facile two-step method using hollow SnO2 nanospheres as support. Firstly, monodispersed SnO2 hollow nanospheres have been obtained by solvothermal (ethanol/water) method. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show that hollow SnO2 nanospheres exhibit good crystalline and monodispersion with the diameter ranging from 200 to 400nm. Secondly, Ag/SnO2 nanospheres have been prepared by a facile reduction in silver-ammonia solution. XRD and selected area electron diffraction (SAED) confirm the formation of Ag in Ag/SnO2 nanospheres. SEM and TEM show the homogeneous coating of Ag nanoparticles on hollow SnO2 nanospheres. SEM mapping images confirm the uniform distribution of Ag element on SnO2 nanospheres. The electrocatalytic measurements for hydrazine electro-oxidation have been conducted. The results show that Ag/SnO2 nanospheres have excellent electrocatalytic activity with −0.12V (vs. SCE) at the scan rate of 20mVs−1. The hollow structure of SnO2 nanospheres can provide shorter distance of electron transport and better dispersion of Ag nanoparticles, which can be responsible for the enhanced conductivity and efficient utilization of active sites.

Ag-encapsulated Single-Crystalline Anatase TiO2 Nanoparticle photoanodes for enhanced dye-sensitized solar cell performance

In this article, Ag-encapsulated Single-Crystalline Anatase TiO2 Nanoparticles (SC-TiO2@Ag) are prepared and introduced into dye-sensitized solar cells (DSSCs). The Single-Crystalline Anatase TiO2 Nanoparticles (SCANPs) were prepared by the hydrothermal transformation of titanate nanotubes at pH of 2, and the SC-TiO2@Ag plasmonic nanocomposite materials were successfully prepared through a facile stepwise impregnation-chemical reduction method without using any stabilizer or surfactant. An optimized SC-TiO2@Ag modified DSSC is achieved with a power conversion efficiency (PCE) of 8.33%, which is significantly superior to that of the unmodified TiO2 DSSC with a PCE of 6.32%. This enhanced efficiency is mainly attributed to the plasmonic effect, improved interfacial charge transfer, and retarded charge recombination, reduction in the band gap energy, and enhanced the optical absorption of dye, as well as the increase of the amount of the dye absorption. The influence of silver ammonia solution [Ag(NH3)]2OH concentration on the overall efficiency was also investigated, and the optimum concentration was found to be 3 mM.

High sensitivity fibre surface plasmon resonance sensor based on silver mirror reaction

A novel fibre surface plasmon resonance (SPR) sensor fabricated by a silver mirror reaction is first proposed and demonstrated in this paper. The experimental results showed that the silver film characteristics of the fibre SPR sensing probe are affected by the concentration of silver ammonia solution, and the relations between the concentration of silver ammonia solution and properties of the sensors have been obtained, which is in accordance with the optimal parameters of fibre and silver film through a theoretical simulation. Firstly, a theoretical model of a silver film-based fibre SPR sensing mechanism has been built up. Then the numerical simulations towards the influence of sensing structure, thickness and sensing length of metal films on the sensing system sensitivity have been performed. Finally, the optimal structure parameters of the sensor are obtained. The results show that this fibre SPR sensing system provides a promising platform for sodium chloride solution concentration measurement with a concentration sensitivity of 710.4 nm/%.

A Facile Fabrication of Silver-Coated Copper Nanowires by Galvanic Replacement

We demonstrated a general strategy to fabricate silver-coated copper nanowires by a galvanic replacement, which is guided by the chemical principle that metal ions (silver ions) with a relatively high reduction potential can galvanically etch nanostructure made from a less metal (copper). Well-dispersed and high-yielded copper nanowires were initially synthesized and then introduced into silver-ammonia solution for the growth of silver nanocrystals on the nanowire surfaces under vigorous oscillation. The results of X-ray diffraction, scanning electron microscope, and transmission electron microscope revealed that the silver nanocrystals were uniformly distributed on the copper nanowire surfaces to form Cu-Ag heterostructures. The concentration of silver-ammonia solution and the time of replacement reaction determine the size and density of the silver nanocrystals. Our investigation might pave the way to the synthesis of other bimetallic nanostructures via a facile, fast, and economical route.

A Novel Two-Step Method for Fabricating Silver Plating Cotton Fabrics

A novel two-step method was presented for fabricating silver plating cotton fabrics (SPCFs) with high electrical conductivity and excellent washing fastness. First, polydopamine (PDA) film was coated on the surface of cotton fabrics byin situpolymerization of dopamine, the silver ions in silver nitrate solution were reduced by the catechol groups of polydopamine, and silver nanoparticles were combined with polydopamine by covalent bond on the surface of cotton fabrics. Second, silver ions were reduced by glucose, and silver plating was coated on the surface. Subsequently, the properties of SPCFs were characterized by field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA), and so forth. With the increasing of silver-ammonia solution concentration or dopamine concentration, the surface resistivity of SPCFs decreases and gradually stabilized. The surface resistivity of the SPCFs can reach0.12±0.02 Ω, and electromagnetic shielding effectiveness (ESE) of the SPCFs can reach58.5±4.5 dB. Conductive fabrics have wide application prospect in many of fields, such as antibacterial, intelligent textiles, smart garments, electromagnetic shielding, and flexible sensors.

Mesoporous Ag nanocubes synthesized via selectively oxidative etching at room temperature for surface-enhanced Raman spectroscopy

Silver nanocubes enriched with 100 facets have been extensively used for surface-enhanced Raman scattering. Herein, we report a new water-phase synthesis method for well-defined Ag nanocubes with tunable sizes via a two-step procedure at room temperature. First, irregularly shaped Ag nanoparticles (INPs) were prepared by reducing silver ammonia solution using ethylal. Second, the agglomerated INPs were selectively etched with HNO3 and Cl− to yield 100 facet-rich mesoporous Ag nanocubes. The mechanism of Ag-nanocube formation and growth was investigated in detail by elucidating the involved chemical reactions and physical changes at each step during the synthesis. The addition of Cl− anions was responsible for facilitating Ag nanoparticle growth by removing surface-adsorbed AgCl+ species, thereby eliminating inter-particle repulsive forces. This agglomeration was found crucial for the subsequent selective oxidation of Ag nanoparticles because the protective agent used, polyvinylpyrrolidone (PVP), was the most effective one for adsorption on the surfaces of Ag nanoparticles of size greater than approximately 50 nm. Importantly, mesopores were found inside the Ag nanocubes; this can be attributed to the unavoidable imperfect packing during the agglomeration of INPs. The newly prepared Ag nanocubes were further used to enhance the Raman signal of rhodamine 6G, which is capable of reducing the detection limitation to 10−16 mol·L−1.

One-step preparation of silver–polyaniline nanotube composite for non-enzymatic hydrogen peroxide detection

A modified glassy carbon electrode with silver nanoparticles–polyaniline nanotubes (AgNPs–PANINTs) composite is used as a non-enzymatic nanobiosensor for detecting hydrogen peroxide (H2O2). The electrocatalytic activity for the reduction was strongly affected by the concentration of silver ammonia solution in the nanocomposites, with the best electrocatalytic activity observed for the composite of 6:1 volume ratios of PANI to Ag(NH3)2OH (0.04M). Field emission scanning electron microscope images and their size distribution diagrams indicated that using the silver ammonia complex instead of silver nitrate caused uniform distribution of nanometer-sized silver nanoparticles with a narrow size distribution in the composite. The corresponding calibration curve for the current response showed a linear detection range of 0.1–90mM (R2=0.9986), while the limit of detection was estimated to be 0.2μM at the signal to noise ratio of 3.

One-step hydrothermal green synthesis of silver nanoparticle-carbon nanotube reduced-graphene oxide composite and its application as hydrogen peroxide sensor

A novel sensing composite of silver nanoparticles (AgNPs)-reduced graphene oxide (rGO)-carbon nanotube (MWCNT) was successfully synthesized by a simple one-step hydrothermal method without reducing agent. Mild reduction of GO was carried out under hydrothermal condition. While most conventional approaches make use of multistep chemical methods wherein strong reducing agents, such as hydrazine, hydroquinone, and sodium borohydride are employed, our method provides the notable advantage of a single-step reaction without employing any toxic solvent or reducing agent by providing a novel green synthetic route to produce the nanocomposites of rGO, carbon nanotube and silver. The results of X-ray diffraction (XRD) and Fourier-transform infrared transmission spectroscopy (FT-IR) confirmed the simultaneous formation of silver nanoparticles in the GO and MWCNT matrix. Field emission scanning electron microscope (FESEM) images and transmission electron microscopy (TEM) showed uniform distribution of nanometer-sized silver nanoparticles and narrow-sized MWCNT on GO sheets, which was achieved using silver ammonia complex as the precursor, instead of the commonly used silver nitrate. The composite exhibited excellent electrocatalytic activity for the reduction of H2O2 with a fast amperometric response time less than 3s. The electrocatalytic activity for the reduction was strongly affected by the concentration of silver ammonia solution in the nanocomposites, with the best electrocatalytic activity observed for the composite of 6:1 volume ratios of MWCNT–GO (3:1, v/v) to Ag(NH3)2OH (0.04M). The corresponding calibration curve for the current response showed a linear detection range of 0.1–100mM (R2=0. 9985), while the limit of detection was estimated to be 0.9μM.

A bio-inspired method to inkjet-printing copper pattern on polyimide substrate

In this work, we propose a mussel-inspired method to fabricate copper pattern on polyimide substrate by an inkjet printing method. A new type of catalytic ink containing polydopamine (PDA) and silver ammonia solution was developed, which can induce the formation of electroless copper coating. As a result, we successfully prepared copper pattern which has good adhesion by inkjet-printing. Due to the unique property of PDA that is able to adhere to almost every kind of material, this method may be applied to diverse substrates in the future.

Monodisperse silver microspheres: A facile BSA template method

The spherical silver mirco/nano-particles with narrow size distributions were obtained by chemical reduction of silver ammonia solution with ascorbic acid as reducing agent and bovine serum albumin (BSA) as bio-template. The effects of the concentration of Ag+ ions, BSA and ammonia, reactive temperature on the silver morphology and particle sizes were investigated. SEM, TEM and XRD were employed to characterize the morphology and structures of the prepared silver mirco/nano-particles. The results show that the spherical silver particle with smooth surface and narrow size distributions can be obtained by controlling the concentration of Ag+ ions, BSA, reaction temperature, etc. By controlling the above parameters, the silver spherical mirco/nano-particles with particle sizes ranging from 0.2 to 2.3 μm can be well prepared, which is expected to be used in manufacturing high performance electronic pastes.

Synthesis of graphene decorated with silver nanoparticles by simultaneous reduction of graphene oxide and silver ions with glucose

A green and efficient approach for the synthesis of graphene decorated with silver nanoparticles is demonstrated by simultaneously reducing both graphene oxide (GO) sheets and silver ions with glucose as the reducing agent and poly(N-vinyl-2-pyrrolidone) (PVP) as the surface modifier. Different silver-containing materials are obtained by changing the synthesis temperature. The oxygen-containing groups of the substrate influence its decoration with the in situ formed silver nanoparticles. The combination of glucose and a silver–ammonia solution, as well as maintaining a good dispersion of GO by using PVP are crucial for the decoration of graphene with silver nanoparticles. The materials exhibit a distinct surface-enhanced Raman scattering effect.

Silver Conductive Features on Flexible Substrates from a Thermally Accelerated Chain Reaction at Low Sintering Temperatures

In this study, a simple and effective silver ink formulation was developed to generate silver tracks with high electrical conductivity on flexible substrates at low sintering temperatures. Diethanolamine (DEA), a self-oxidizing compound at moderate temperatures, was mixed with a silver ammonia solution to form a clear and stable solution. After inkjet-printed or pen-written on plastic sheets, DEA in the silver ink decomposes at temperatures higher than 50 °C and generates formaldehyde, which reacts spontaneously with silver ammonia ions to form silver thin films. The electrical conductivity of the inkjet-printed silver films can be 26% of the bulk silver after heating at 75 °C for 20 min and show great adhesion on plastic sheets.

A Facile One‐Pot Synthesis of Layered Protonated Titanate Nanosheets Loaded with Silver Nanoparticles with Enhanced Visible‐Light Photocatalytic Performance

Layered protonated titanate nanosheets (LPTNs) loaded with silver nanoparticles are prepared by a simple one-pot hydrothermal route in silver-ammonia solution. The as-synthesized Ag-loaded LPTNs possess large specific surface area. The Ag nanoparticles are highly dispersed on the surface of the LPTNs. They have negligible effects on the crystal structure, crystallinity, and surface area of the LPTNs but result in considerable enhancement of visible-light absorption and in a red-shift of the band gap for the LPTNs. The Ag-loaded LPTNs show enhanced photocatalytic activity for both liquid- and gas-phase reactions under visible-light irradiation. Moreover, the photocatalytic activity first increases gradually with increasing Ag loading content, and then decreases after maximizing at an optimal Ag content. At the Ag loading content of 2.87 mol% and 1.57 mol%, the Ag-loaded LPTNs exhibit the highest visible-light photocatalytic activity for degradation of rhodamine B in water and mineralization of benzene in air, respectively. An alternative possible mechanism for the enhancement of the visible-light photocatalytic activity is also proposed.