Aqueous Solution Of AgNO3 Research Articles

Photocatalytic oxygen evolution using BaNbO2N modified with cobalt oxide under photoexcitation up to 740 nm

BaNbO2N was activated for photocatalytic sacrificial water oxidation and reduction by modifying the starting material for nitridation and loading appropriate cocatalysts. Addition of BaCO3 to the Ba5Nb4O15 precursor improved the crystallinity and uniformity of BaNbO2N as a nitridation product, leading to higher oxygen evolution activity. BaNbO2N generated oxygen from an aqueous AgNO3 solution under illumination up to 740 nm.

Ionic liquid induced sphere-to-ribbon transition in the block copolymer mediated synthesis of silver nanoparticles

Spherical silver nanoparticles (AgNPs) with size ∼20 nm have been synthesized from an aqueous AgNO3 solution using the amphiphilic block copolymer, Pluronic P123 (EO20–PO70–EO20), under ambient conditions without the use of any other reducing agents. The size of the AgNPs was highly dependent on the size and geometry of the micelles of the block copolymer. The AgNPs synthesized from the block copolymer mediated synthesis were characterized by UV-Vis spectroscopy, Transmission Electron Microscopy (TEM) and Dynamic Light Scattering (DLS). The addition of an ionic liquid (IL), N-alkyl pyridinium dodecyl sulphate, CnPyDs, where n = 4, 6, 8, prepared by modifying N-alkyl pyridinium chloride with an anionic surfactant, sodium dodecyl sulphate (SDS), induced a sphere-to-ribbon (cylindrical) transition of the AgNPs. We observed that the presence of ILs reduces the equilibrium time as well as acting as a shape directing agent. The micelles of P123 and ILs in aqueous solution were characterized by Small Angle Neutron Scattering (SANS) and DLS methods. The size and shape of the AgNPs correlate with the geometry of micelles of the amphiphilic block copolymer and ILs in aqueous solution.

Synthesis of Ag@SiO2 hybrid nanoparticles templated by a Triton X-100)/1-hexanol/cyclohexane/H2O water-in-oil microemulsion

A water-in-oil microemulsion was prepared by using nonionic surfactant Triton X-100, 1-hexanol, cyclohexane and AgNO3 aqueous solution with a concentration of 0.2 mol L−1. Successive addition of sodium borohydride (NaBH4), ammonium hydroxide (NH3·H2O) and tetraethyl orthosilicate (TEOS) to this microemulsion leads to the formation of hierarchically-organized Ag@SiO2 hybrid nanoparticles with Ag nanocrystals randomly distributed inside amorphous SiO2, as proved by transmission electron microscopy (TEM) and high-resolution electron microscopy (HRTEM) observations. In many cases, H2 gas bubbles, which were produced during the reduction of Ag+, were found to influence the structures of Ag nanocrystals. The morphologies of the hybrid nanoparticles and the H2-induced cavities can be easily tuned by the molar ratio of AgNO3 to NaBH4 and the volume ratio of AgNO3 aqueous solution to TEOS. Embedded in amorphous SiO2, the Ag nanoparticles are highly stable, while the unprotected Ag nanocrystals underwent fast aggregation. The inner Ag nanocrystals have dominant (111) planes and are optically active, as shown by X-ray powder diffraction (XRD) and UV-vis measurement, respectively. These properties make these Ag@SiO2 hybrid nanoparticles fascinating candidates for a variety of applications in catalysis and life science.

Preparation of Large-Aperture Macroporous Silicon with Controllable Pore Tip Angle on Low-Resistivity p-Type c-Si Substrate by Metal-Catalyzed Electrochemical Etching

Macroporous silicon has been widely utilized in many electronic and optoelectronic applications. However, it is quite difficult to prepare macroporous silicon with large aperture on p-type low-resistivity c-Si substrate by the conventional fabrication methods, such as reactive ion etching (RIE), electrochemical etching (ECE), and metal-catalyzed electroless etching (MCEE). Such work was realized here by metal–catalyzed electrochemical etching (MCECE). Firstly, Ag nanoparticle catalyst was fabricated on the c-Si substrate by immersing the substrate into a mixed aqueous solution of HF and AgNO3. Electrochemical etching was then performed in a HF-H2O2 solution. The synergetic effect of Ag catalyst and the external applied electric field successfully facilitated the formation of large-aperture macroporous silicon. By adjusting the specific MCECE conditions, macroporous silicon with the pore aperture large up to several micrometers was successfully obtained on p-type c-Si substrate with the low resistivity of about 0.1–3 ohm·cm. Especially, the pore tip angle could be controlled flexibly from 3.5° to 41°. The pore tip angle enlarged with the increase of the etching current density and was independent on the etching time. Thus, MCECE can provide a potential way to controllably fabricate complex microstructures on low-resistivity p-type c-Si substrate.

Composite of Rh y Cr2−y O3/(Ga1−x Zn x )(N1−x O x ) Photocatalysts with Hydrophobic Polytetrafluoroethylene (PTFE) Membranes for the Fabrication of Novel Reaction Sites for Water Vapor Splitting Under Visible Light

Rh y Cr2−y O3/(Ga1−x Zn x )(N1−x O x ) photocatalysts immobilized in polytetrafluoroethylene (PTFE) membranes has been investigated for the design of novel reaction sites. In the case of hydrophobic PTFE membranes, the Rh y Cr2−y O3/(Ga1−x Zn x )(N1−x O x ) photocatalyst simultaneously evolved both H2 and O2, even from an aqueous AgNO3 solution as sacrificial reagent. This indicates that water vapor was split into H2 and O2 by the Rh y Cr2−y O3/(Ga1−x Zn x )(N1−x O x ) photocatalyst particles in the hydrophobic pores of PTFE.

Photo-induced exciton generation in polyvinylpyrrolidone encapsulated Ag2S core-shells: Electrochemical deposition, regular shape and high order of particle size distribution

Visible light induced frequency switching behavior, exhibited by the electrochemically deposited thin films of polyvinylpyrrolidone (PVP) encapsulated Ag2S nanosphere (core-shell) is shown here. A low frequency (∼40 Hz) pulse was found to be generated upon illumination with 1 Sun due to excitonic transition, which also showed good switching behavior with the “on” and “off” state of the light. Capping of the semiconductor surface by a polymer like PVP reduces the surface states and thus lowers the built in barrier height and the width of depletion region. So, the number of photo generated but non recombining electron-hole pairs (excitons) increases, which put their signature in some unique physical properties like increase in photoluminescence (PL) intensity, light induced frequency switching behavior due to free exciton generation, etc. Here, the depositions were carried out on indium tin oxide coated glass substrates from an aqueous solution of AgNO3, thioacetamide, and PVP. The films were structurally characterized using high resolution X-ray diffraction, field emission scanning electron microscopy, and high resolution transmission electron microscopic techniques. The deposited particles were regular in shape with significantly high order of size distribution. Furrier transform infrared spectroscopy confirmed the presence of PVP as the encapsulating agent. Optical characterization, viz., UV – vis – NIR and NIR-PL revealed noteworthy amount of NIR emission from the deposited material.

The influence of Ni nanoparticles and Ni (II) on the growth of Ag dendrites immobilized on the chelating copolymer membrane

Preparation of Ag dendrites on the surface of chelating copolymer membranes (PBAGI), which was synthesized by using the soap-free emulsion copolymerization of n-butylacrylate (BA) and acrylonitrile (AN), as well as 2-methacrylic acid 3-(bis-carboxymethylamino)-2-hydroxy-propyl ester (GMA-IDA) that was used as a chelating group, is presented in this study. The characteristics of polymer membranes were investigated by Fourier transform infrared (FTIR) spectroscopy and elementary analysis (EA). The weight fraction of GMA-IDA in the polymer was 4.2wt% as revealed by elemental analysis. The chelating group, –N(CH2COO−Na+)2 on the polymer was used to coordinate different amounts of Ni(II), controlled by different chelating times and subsequently reduced to Ni nanoparticles, as templates for growing Ag nanocrystals from 1.67wt% AgNO3 aqueous solution with 55.7 ppm poly(vinyl pyrrolidone) (PVP) added. In addition, the effect of Ni2+ concentration on the growth of the Ag dendrites was studied. Crystallinity and morphology of Ag dendrites were examined with X-ray diffraction (XRD) and scanning electronic microscopy (SEM), respectively. Amount of Ag dendrites increased with the increasing of Ni nanoparticles on the PBAGI membrane or the dose of Ni2+ present in the aqueous solution. Notable, under higher amount of Ni nanoparticles (over 200mmol Ni2+/g PBAGI membrane), Ag dendrites could be successful grown on the membrane. However, higher dose of Ni2+ (over 41.3ppm) might inhibit the growth of Ag dendrites.

A rapid two-step electroless deposition process to fabricate superhydrophobic coatings on steel substrates

The present study reports a simple, highly effective, and safe two-step electroless deposition process for rapidly fabricating superhydrophobic Ag coatings on steel substrates. The steel plates were first immersed in the 1 mol/L aqueous CuSO4 solution for 20 s, and then immersed in the 0.03 mol/L aqueous AgNO3 solution containing 1 wt% fluoroalkylsilane (FAS) for 2 min. The sample surfaces were characterized by energy-dispersive x-ray spectroscopy, Fourier transform infrared spectrophotometry (FTIR), x-ray diffraction, scanning electron microscopy, step profiler, and optical contact angle measurements. The results show that, after the two-step electroless deposition process, the Ag coatings composed of the binary micro/nanometer-scale rough structures containing the FAS molecules with a low surface energy are formed on the steel surfaces. The as-prepared Ag coatings exhibit a good superhydrophobicity with a 163.4 ± 1.8° water contact angle and 1.5 ± 0.5° rolling angle.

Pore Size Dependent Behavior of Hydrated Ag+ Ions Confined in Mesoporous MCM-41 Materials under Synchrotron X-ray Irradiation

The behavior of hydrated Ag+ ions in a 1.5 mol dm(-3) AgNO3 aqueous solution confined in mesoporous silica MCM-41 with different pore sizes was characterized by synchrotron X-ray absorption spectroscopy. The hydrated Ag+ ions are stabilized in 4-fold coordination down to 195 K in the pores (21 Å in diameter), whereas in the larger pores (28 Å) the hydrated Ag+ ions are reduced to Ag0 to form nano clusters with the Ag-Ag interactions of 2.80 Å.

Metal nanoparticles decorated PET/PET-TiO2 bi-component filaments by photocatalytic deposition

Gold, silver, and platinum nanoparticles were immobilized on the surface of TiO2 in the sheath part of bi-component filaments. The processes involved include the spinning process used to prepare polyethylene terephthalate (PET)/PET-TiO2 bi-component filaments and the photocatalytic deposition process of gold, silver and platinum nanoparticles. The core part and the sheath part consist of virgin PET and 4 wt.% of TiO2 compounded PET, respectively. The sheath: core ratio of the filament was 50:50. For the photo-deposition of metal nanoparticles, adsorption of the metal ions on the surface of the fabrics was performed by immersing them in AgNO3, HAuCl4, and H2PtCl6 aqueous solutions, with simultaneous addition of methanol as a sacrificial agent. Photo-deposition was then carried out under UV light with an irradiation time of 60 seconds. The structural and antibacterial properties of the bi-component filaments were characterized. The nano-sized noble metal particles in a polka dot form were observed around the surface of the TiO2 particles in sheath region of bi-component filaments after photocatalytic deposition. Ag, Au, and Pt metal photo-deposited fabrics showed excellent antimicrobial effect against the two types of bacteria Staphylococcus aureus and Klebsiella pneumoniae under dark conditions.

Green synthesis process of a polyurethane-silver nanocomposite having biocide surfaces

Monodispersed spherical silver nanoparticles with 35±5 nm diameter were prepared by microwave irradiation of an AgNO3 aqueous solution in poly(ethylene glycol) (PEG). Thanks to the hydroxyl groups at the chain-ends of the PEG, the matrix of the Ag nanoparticles suspension was well incorporated into a polyurethane backbone, allowing a good distribution of the metal particles inside the final nanocomposite without aggregation. An optimal antibacterial activity was observed for a 35 p.p.m. Ag concentration against P. aeruginosa and E. faecalis without significant variation of the intrinsic physicochemical properties of polyurethane material.

Synthesis and Growth Observation of Flower- and Spike-like Gold–Silver Nanoparticles

Abstract In this paper, we report a simple and reproducible synthesis of flower- and spike-like gold–silver (Au–Ag) nanoparticles. Reduction of aqueous solution of AgNO3 and HAuCl4 mixtures by l-ascorbic acid (AA) in the presence of poly(vinylpyrrolidone) (PVP) afforded the nanoparticles in a few minutes at room temperature. Stepwise trapping of the intermediate nanoparticles revealed the growth process of the petals of the flower-like nanoparticles from an initially formed nanoplate.

Heat Treatment-Based One-Step Preparation of Highly Concentrated, Well-Stable Silver Colloids that Can Form Stable Films on Bare Electrodes for H2O2 Detection

A simple thermal process for the one-step preparation of highly concentrated (up to 0.21 M) but well-stable silver colloids with a bimodal size distribution is developed for the first time, carried out by directly heating an aqueous solution of concentrated AgNO3 and poly[(2-ethyldimethylammonioethyl methacrylate ethyl sulfate)-co- (1-vinylpyrrolidone)] (PQ11), a kind of cationic polyelectrolyte, at 100 °C without the extra introduction of other reducing agents and protective agents. Time-dependent UV-vis spectra were collected to gain further insight into the Ag nanoparticles (AgNPs) formation process. Most importantly, it is found that the colloidal solution can form stable films on bare electrode surfaces and the AgNPs contained therein exhibit notable catalytic activity toward the reduction of H2O2, leading to a H2O2 sensor with a fast amperometric response time of less than 2 s. The linear detection range is estimated to be from 100 μM to 150 mM (r = 0.9995), and the detection limit is estimated to be 1.8 μM at a signal-to-noise ratio of 3.

Biological Synthesis of Silver Nanoparticles by Aspergillus flavus , Isolated from Soil of Ahar Copper Mine

In this study, silver nanoparticles were synthesized using the fungus, Aspergillus flavus at high yield with an aqueous solution of AgNo 3 . The formation of silver nanoparticles was confirmed using UV-visible spectrophotometer and their presence was displayed by XRD studies. The size and place formation of silver nanoparticles were investigated using Scanning Electron Microscopy (SEM).

Biological synthesis of silver nanoparticles by Aspergillus flavus, isolated from soil of Ahar copper mine

In this study, silver nanoparticles were synthesized using the fungus, Aspergillus flavus at high yield with an aqueous solution of AgNo 3 . The formation of silver nanoparticles was confirmed using UV-visible spectrophotometer and their presence was displayed by XRD studies. The size and place formation of silver nanoparticles were investigated using Scanning Electron Microscopy (SEM).

Facile, template-free synthesis of silver nanodendrites with high catalytic activity for the reduction of p-nitrophenol

Here we report a facile, surfactant-free and template-free synthesis process of highly uniform dendritic silver nanostructures with high catalytic activity for the reduction of p-nitrophenol. By controlling the concentration of AgNO3 aqueous solution and the reaction time, various shapes of silver nanodendrites (SNDs) could be obtained easily. The effects of different parameters such as concentrations of the reagents and reaction time on the morphology and structure of as-prepared tree-like nanostructures have also been investigated by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Also, the X-ray photoelectron spectroscopy (XPS) has been used to identify the oxidation state of SNDs. In addition, the catalytic activity of the as-prepared SNDs samples at 200mM AgNO3 aqueous solution was evaluated by a redox reaction of p-nitrophenol in the presence of an excess amount of NaBH4. It was found that the highly symmetrical SNDs with roughly 60–120nm in stem and branch diameter and 3–12μm in length obtained after 120s reaction time do have higher catalytic activity than other SNDs prepared at different reaction time, several times stronger catalytic activity in the sodium borohydride reduction of p-nitrophenol to p-aminophenol, compared to some other silver nanoparticles reported in literature. The crystallinity provided by X-ray diffraction (XRD) analysis indicates that the improvement of the crystallinity is also very crucial for SNDs’ catalytic activities. The SNDs are very promising catalytic candidates for the reduction of p-nitrophenol because of easily simple preparation route and high catalytic activity.

Radiation synthesis and characterization of nanosilver/gelatin/carboxymethyl chitosan hydrogel

A series of antibacterial hydrogels were fabricated from an aqueous solution of AgNO3, gelatin and carboxymethyl chitosan (CM-chitosan) by radiation-induced reduction and crosslinking at ambient temperature. The nanosilver particles were in situ synthesized accompanying with the formation of gelatin/CM-chitosan hydrogel. Transmission Electron Microscope and UV–vis analysis have verified the formation and homogeneous distribution of nanosilver particles in the hydrogel matrix. The nanosilver/gelatin/CM-chitosan hydrogels possessed interconnected porous structure, had a compressive modulus of 44 to 56kPa, and could absorb 62 to 108 times of deionized water to its dry weight. Furthermore, the hydrogels were found to have sound antibacterial effect on Escherichia coli (E. coli), and their antibacterial ability could be significantly enhanced by the increasing of AgNO3 content. The comprehensive results of this study suggest that nanosilver/gelatin/CM-chitosan hydrogels have potential as an antibacterial wound dressing.

Characterization of Electron-Beam-Induced Silver Deposition from Liquid Phase

ABSTRACTElectron-beam-induced deposition (EBID) using gas-phase precursor molecules is an extensively studied fabrication technique. Liquid-phase metal deposition has recently been shown to achieve higher purity levels than traditional gas-phase deposition [1]. The goal of this investigation was to characterize liquid-phase silver deposition for further studies in photonics. A Scanning Electron Microscope (SEM) (FEI Nova 600 NanoLab Dual Beam) was used to deposit silver on polyimide membranes from aqueous AgNO3 solution by accelerating electrons into the solution for silver ion reduction. Atomic Force Microscopy (AFM) and SEM were subsequently used to characterize the size dependence to electron dosage. We observed granular silver deposits with sub-75 nm particle size and 200-250 nm total aggregate diameters. The CASINO (monte CArlo SImulation of electroN trajectory in sOlids) program was used to model electron trajectory in the solution to relate the size to the electron spread.

Silver Nanoparticles Shoot Up from the Root ofDaucus carrota(L.)

Extensive work has been done to explore the potential promises of plant systems in the synthesis of metal nanoparticles. Herein, a convenient and rapid process for the formation of silver nanoparticles with natural reducing and capping agents of Daucus carrota (L.) is reported. The synchronization of secondary metabolites and enzymes as reducing/capping agents plays a vital role in the synthesis and stability of silver nanoparticles for approximately two months. Stable silver nanoparticles were formed by reacting tap root extract of D. carrota with an aqueous solution of AgNO3, which reduced Ag++ to Ag0. The synthesized silver nanoparticles were further characterized using UV spectrophotometry, Energy Dispersive X-ray Spectroscopy (EDAX), Scanning Electron Microscopy (SEM), and X-ray Diffraction (XRD) methods. The synthesized silver nanoparticles were spherical and stable in aqueous medium ranges from 31–52 nm.

Surfactantless photochemical growth of Ag nanostructures on GaN epitaxial films with controlled morphologies and their application for SERS

Ag nanostructures with controlled morphologies have been synthesized on GaN epitaxial films through a convenient, fast, and surfactantless photochemical method. On n-type GaN, uniform spheroidic Ag nanoparticles (NPs) of high density were obtained after photochemical reaction for a short time (30 s to 5 min) in AgNO3 aqueous solution. Reducing AgNO3 concentration yielded branched Ag nanostructures. The Ag NPs on the GaN substrates exhibit a Fabry–Perot-type surface plasmon resonance (SPR). On p-type GaN, Ag nanocrystals (NCs) with well-defined shapes ranging from cubes, truncated cubes, cuboctahedra, truncated octahedra, and octahedra were obtained through varying the concentration of AgNO3 solution. We propose that the formation of polyhedral Ag NCs is induced by the separation of the nucleation and growth processes by the GaN surface. Both surface states and carrier concentration are considered to play substantial roles during the growth process. This surfactantless photochemical method is general and enables the facile synthesis of Ag nanostructures at room temperature, which may be extended for the synthesis of other noble metal nanostructures, e.g.Au, Pt, and Pd, on GaN or other wide bandgap semiconductors, e.g.SiC. The obtained Ag/GaN hybrid systems show potential application as solid substrates for surface enhanced Raman scattering (SERS) analysis.