Increasing AgNO3 Concentration Research Articles

Impact of electroplating salt (AgNO3) concentration on the morphological, optical, electrical and thermoelectric properties of silver assisted electrochemically etched silicon nanowires (SINWs)

Silicon nanowires (SINWs) are fabricated through silver assisted electrochemical etching route at room temperature. Very high yield vertically aligned SINWs are obtained through this electrochemical etching route. The effect of electroplating salt concentration on the properties of SINWs is investigated. Surface morphology shows grass like structures with increase of length and decrease of diameter with increasing salt concentration. Atomic force microscopy reveals increased surface roughness. UV–Visible spectra show reduced reflectivity enabling the material to be efficient for antireflection coatings. Photoluminescence spectra exhibit multiband transitions. Raman spectra show asymmetric peak broadening with peak downshift. Electrical properties display enhancement of SINWs current with higher AgNO3 concentration due to increased surface mediated effects. Current - voltage characteristics follow thermionic emission model. Samples exhibit space charge limited conduction at higher bias voltages due to presence of traps or crystal imperfections. Prepared samples are also investigated for thermoelectric properties and the results show enhanced Seebeck coefficient with increasing AgNO3 concentration.

Formation of silver particles in [PVA:CS:PEG]-AgNO3 based biopolymer electrolyte membranes: Structural and electric transport properties study

[Chitosan (CS)-poly(vinyl) alcohol (PVA)-polyethylene glycol (PEG-200)]+xwt% silver nitrate (AgNO3) (x = 0, 10, 20, 30, 40) based biopolymer blend electrolytes (BPBEs) were prepared using solution casting method. FTIR results show the interaction of Ag+/NO3− with the constituents of polymers CS/PVA. XRD results reveal that the amorphousness increases with increasing AgNO3 concentration. Optical morphological (OM) images show that the silver, Ag(o) particles are agglomerated on the surface of the membrane. Temperature dependent dc conductivity (σdc) and dielectric relaxation frequency (fr) for BPBEs follow the Arrhenius type behavior and the sample containing 30 wt% salt has optimum dc conductivity, σdc∼1.7×10−4 S/cm at 30oC with lowest activation energy∼ 0.16 eV. The ac conductivity spectra follow the Jonscher's power law (JPL) with power law exponent, s > 1. The scaling of AC conductivity and loss tangent (tanδ) spectra were performed with respect to temperatures/concentrations of salt. The dielectric permittivity study reveals that the electrode polarization effect predominates at low frequencies. The Ionic Transference Number (ITN) measurement was used to determine the nature species of charge carrier, either ionic or electronic. The linear sweep voltammetry (LSV), result shows that 30% AgNO3containing sample has the electrochemical stability window (ESW) ∼+1.5 to -1.5 V.

Arylated gold nanostars aided SERS study of breast cancer cells

Anisotropic gold nanomaterials are opening new approaches for the study of cancer cells using high-performance diagnostic devices. Aryldiazonium gold salt, AgNO3, and ascorbic acid were used as shape-directing agent to promote the growth of spikes over the seeds. We synthesized covalently aryl functionalized gold nanostars via diazonium route using three AgNO3 concentrations of 1 × 10−1, 5 × 10−1, and 1 × 10−4 M for spikes length optimization. The seed and growth solutions were mixed and left undisturbed for 24 h. Transmission electron microscopy results showed that the spike sharpness and length were decreased with increasing AgNO3 concentration. The biocompatible AuNS were incubated with human breast cancer cells MDA-MB-231 and the cellular uptake was estimated using confocal microscopy. Different cancer cell concentrations range of 10–500 cells/mL were used for SERS study. Our results highlight the significance of nano spike-morphology in SERS study on cellular components and efficient cellular uptake of AuNS by MDA-MB-231 compared to normal cells, jointly is important for developing nanomedicines for cancer therapy.

Wafer-Scale Fabrication of Silicon Nanocones via Controlling Catalyst Evolution in All-Wet Metal-Assisted Chemical Etching.

All-wet metal-assisted chemical etching (MACE) is a simple and low-cost method to fabricate one-dimensional Si nanostructures. However, it remains a challenge to fabricate Si nanocones (SiNCs) with this method. Here, we achieved wafer-scale fabrication of SiNC arrays through an all-wet MACE process. The key to fabricate SiNCs is to control the catalyst evolution from deposition to etching stages. Different from conventional MACE processes, large-size Ag particles by solution deposition are obtained through increasing AgNO3 concentration or extending the reaction time in the seed solution. Then, the large-size Ag particles are simultaneously etched during the Si etching process in an etching solution with a high H2O2 concentration due to the accelerated cathode process and inhibited anode process in Ag/Si microscopic galvanic cells. The successive decrease of Ag particle sizes causes the proportionate increase of diameters of the etched Si nanostructures, forming SiNC arrays. The SiNC arrays exhibit a stronger light-trapping ability and better photoelectrochemical performance compared with Si nanowire arrays. SiNCs were fabricated by using n-type 1–10 Ω cm Si(100) wafers in this work. Though the specific experimental conditions for preparing SiNCs may differ when using different Si wafers, the summarized diagram will still provide valuable guidance for morphology control of Si nanostructures in MACE processes.

Synthesis of silver nanoparticle-decorated hydroxyapatite nanocomposite with combined bioactivity and antibacterial properties

Combination of bioactive material such as hydroxyapatite (HAp) with antibacterial agents would have great potential to be used as bone implant materials to avert possible bacterial infection that can lead to implant-associated diseases. The present study aimed to develop an antibacterial silver nanoparticle-decorated hydroxyapatite (HAp/AgNPs) nanocomposite using chemical reduction and thermal calcination approaches. In this work, natural HAp that was extracted from chicken bone wastes is used as support matrix for the deposition of silver nanoparticles (AgNPs) to produce HAp/AgNPs nanocomposite. XRD, FESEM-EDX, HRTEM, and XPS analyses confirmed that spherical AgNPs were successfully synthesized and deposited on the surface of HAp particles, and the amount of AgNPs adhered on the HAp surface increased with increasing AgNO3 concentration used. The synthesized HAp/AgNPs nanocomposites demonstrated strong antibacterial activity against Staphylococcus aureus bacteria, where the antibacterial efficiency is relied on the amount and size of deposited AgNPs. In addition, the in vitro bioactivity examination in Hank’s balanced salt solution showed that more apatite were grown on the surface of HAp/AgNPs nanocomposite when AgNO3 concentration used >1 wt.%. Such nanocomposite with enhanced bioactivity and antibacterial properties emerged as a promising biomaterial to be applied for dentistry and orthopedic implantology.

Effects of synthesis conditions and storage on silver nanospheres chemically reduced by mulberry leaf extracts

Silver (Ag) nanospheres were chemically reduced from 1 mM silver nitrate (AgNO3) solutions using mulberry (Morus alba Linn.) leaf extracts. The increase of pH in the synthesis from 9 to 13 modified the surface plasmon resonance peak in UV-Vis spectra relating to the particle diameter around 20 nm. Smaller nanoparticles were obtained from the syntheses at pH 7.4-7.7 and their density was slightly increased with the increase in synthesis temperature from 25 °C to 90 °C. The particle size was increased with increasing AgNO3 concentration from 0.1 to 0.5 M but the mixed phases were obtained from the 0.5 M AgNO3 precursor. After storing for 10 months at room temperature, the nanosuspensions remained without Ag sediment but their colors had significantly changed due to particle agglomerations. The colors were characterized by the smartphone colorimetry according to the RGB, CIE space, as well as chroma and hue angle. Based on the chroma and CIE b* values, the effect of synthesis pH in the stored nanosuspensions was comparable to that before the storage. Although the temperature had only moderate effects, nanosuspensions synthesized at 25 °C, 80 °C, and 90 °C were clearly distinguished by the hue and CIE b* values.

Properties of Bacterial Cellulose Composites with Silver Nanoparticles

Composites of bacterial cellulose, which were synthesized in a culture of the strain of acetic acid bacteria Komagataeibacter xylinus VKPM B-12068, with silver nanoparticles were produced hydrothermally by varying the concentrations of AgNO3 in the medium. The presence of silver in the composites was confirmed by elemental analysis. An increase in the number of silver nanoparticles in the composite from 1.08 to 9.1 wt % (from 0.044 to 0.370 mg/cm2) was shown under increasing AgNO3 concentration in the medium from 0.0001 to 0.01 M. The structure, properties of the surface, and the physicochemical properties of the composites depending on the silver content were investigated using scanning electron microscopy, differential scanning calorimetry, X-ray diffraction, and a water contact-angle measurement system. Using the disk-diffusion method, it was shown that the resulting composites have a pronounced antibacterial activity against pathogenic microflora E. coli, Ps. eruginosa, and St. aureus.

Synthesis and Optical Characterization of Ag/PVA Nanocomposites Films

ilver- Poly vinyl alcohol Ag/ PVA nanocomposite films were prepared by casting method at room temperature with different amount of AgNO3 solution (0.001, 0.0015, and 0.002ml). The prepared nanocomposites were characterized using UV–VIS spectrophotometer and the optical properties were investigated in the wavelength range 300-800 nm. The absorption peaks showed a shift towards higher wavelength with increasing AgNO3 concentration while the energy band gap and absorption edges shifted towards lower energies with the increase of AgNO3 concentration.

Biomimetic Nanowire Structured Hydrogels as Highly Active and Recyclable Catalyst Carriers

Nanowire hydrogels with high specific surface areas have great promise in many practical applications. However, the preparation of nanowire hydrogels using common materials and inexpensive means remains an outstanding challenge. This paper reports a novel method for creating aligned nanowire structured hydrogels by directional freezing and γ-radiation initiated polymerization of 2-hydroxyethyl methacrylate (HEMA) using t-butyl alcohol (TBA) as the solvent. The hydrogels prepared at a monomer concentration lower than 2.0 mol L–1 and a freezing rate higher than 10 mm min–1 are structured of nanowires, mimicking the microstructure of jellyfish mesogloea. Silver (Ag) nanoparticles (NPs) are introduced into the hydrogels with a chemical reduction method, and the Ag NPs are formed and deposited on the nanowires. Both size and content of Ag NPs in the hydrogels increase with increasing AgNO3 concentration. The PHEMA and PHEMA/Ag nanocomposite hydrogels all possess very good compressive properties, and the compos...

Rapid green synthesis of silver nanoparticles and nanorods using Piper nigrum extract

We report sun light driven rapid green synthesis of stable aqueous dispersions of silver nanoparticles and nanorods at room temperature using photoreduction of silver ions with Piper nigrum extract. Silver nanoparticles were formed within 3min of sun light irradiation following addition of Piper nigrum extract to the AgNO3 solution. The effects of AgNO3 concentration and irradiation time on the formation and plasmonic properties of biosynthesized silver nanoparticles were studied using UV–visible absorption spectroscopy. The morphology and structure of silver nanoparticles were well characterized by atomic force microscopy (AFM) and X-ray diffraction (XRD). The size of Ag nanoparticles increased with increase in irradiation time, leading to the formation of anisotropic nanostructures. Increasing the AgNO3 concentration resulted in the formation of Ag nanorods. UV–visible absorption studies revealed the presence of surface plasmon resonance (SPR) peaks which red shift and broaden with increasing AgNO3 concentration. We have demonstrated a facile, energy efficient and rapid green synthetic route to synthesize stable aqueous dispersions of silver nanoparticles and nanorods.

The effects of silver nitrate on the phase state of model multibilayer membranes

In order to study the effects caused by silver nitrate (AgNO3) on model lipid membranes, we studied multibilayer membranes based on L-α-dipalmitoylphosphatidylcholine (DPPC) and AgNO3 aqueous soluitions in a wide concentration range (up to 30 wt%) by means of differential scanning calorimetry. It has been shown that the presence of AgNO3 leads both to an increase in the main phase transition temperature (T(m)) and appearance of an additional phase transition peak (T(m)), suggesting increasing of both density and heterogeneity of the lipid membrane. The effect of nitrate ions (NO ) was shown to be of the opposite nature (bilayer fluidizing), so the integral densifying effect of AgNO3 can be referred solely to the action of silver ions (Ag(+)). With increasing AgNO3 concentration, the tendency was observed to opposite changes in T(m) and T'(m) peaks intensity, thereby at about 26. wt% of AgNO3 the initial peak (T(m)) disappeared. In the range of Ag+ therapeutic concentrations (up to 2 wt%) no significant changes in the DPPC membrane were revealed. This can be one of the reasons of the absence of a damaging effect of silver drugs on a host organism with simultaneous pronounced bactericidal effect.

Influence of Fabrication Parameter on the Nanostructure of SiNWs under HF/AgNO<sub>3</sub>/Fe(NO<sub>3</sub>)<sub>3</sub> Etching System

Large-area SiNWs has been successfully fabricated through one-step metal-assisted chemical etching process at room temperature. The effects of key fabrication parameters (AgNO3 concentration, Fe (NO3)3 concentration, and etching time) on the nanostructure SiNWs were carefully investigated by SEM, TEM, respectively. The results show that AgNO3 concentration and Fe (NO3)3 concentration play important roles to the lengths and arrangements of SiNWs arrays in one-step MACE. The morphological transition of Si surfaces from solid nanowires to porous nanowires can be found with increasing AgNO3 concentration and Fe (NO3)3 concentration, which indicates that the re-dissolved Ag+ would work as the main oxidative species for oxidizing the silicon substrate and forming SiNWs in the HF/ AgNO3/ Fe (NO3)3 etching system. The length of SiNWs is increased with increasing AgNO3 concentration from 0.005 mol/L to 0.02 mol/L and etching time, the chemical polish phoenomenon can be observed when the Fe (NO3)3 concentration increases to 0.5 mol/L. A novel mechanism is proposed to explain the formation of SiNWs in HF/ AgNO3/ Fe (NO3)3 solution.

Fabrication of Electrically Conductive Nickel–Silver Bimetallic Particles via Polydopamine Coating

Inspired by adhesive proteins excreted by marine mussels, dopamine can act as a versatile surface modification agent for various organic and inorganic materials. By using adhesive polydopamine (PDA) as an intermediate layer, a simple and novel method for fabricating nickel-PDA-silver (Ni-PDA-Ag) bimetallic composite particles was developed. Ni-PDA-Ag bimetallic particles were fabricated by dispersing Ni particles in an aqueous dopamine solution followed by electroless Ag plating on the prepared Ni-PDA particles. A PDA layer with nano-meter thickness was deposited spontaneously on the surface of the Ni particles by oxidative self-polymerization of dopamine under alkaline conditions. Electroless Ag plating on the prepared Ni-PDA particles was carried out in the presence of a glucose solution as a reducing agent. Ni-PDA particles and Ni-PDA-Ag composite particles with a PDA intermediate layer were characterized by X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared (FT-IR) spectroscopy, field-emission scanning electron microscopy (FE-SEM), field-emission transmission electron microscopy (FE-TEM), and X-ray diffraction (XRD). In addition, the electrical conductivity of as-prepared composite particles was evaluated by a 4-point probe. The PDA layer deposited on the surface of Ni was confirmed by XPS spectra, FT-IR spectroscopy, and FE-TEM. FE-SEM images demonstrated that Ag nanoparticles were successfully plated on the PDA layer-coated Ni particles after the electroless Ag plating process. XRD patterns also confirmed the presence of Ag in a metallic state. In addition, the sheet resistance of as-prepared composite particles showed a tendency to decrease with increasing AgNO3 concentration.

Ag-silica composite nanotube with controlled wall structures for biomedical applications

A range of Ag-silica composite nanotubes with tailored wall structures were successfully synthesized in situ by single-nozzle electrospinning. By increasing AgNO3 concentration, the wall structure of Ag-silica tubes changes from dense to porous, and eventually turns into a ‘lace-like’ structure. This is attributed to Ag ions doping into the SiOSi network of precursors, as illustrated in FTIR study. More importantly, Ag-silica composite nanotubes show robust antibacterial activity against both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli microorganisms. Therefore, it is a breakthrough of the nanostructure biomaterial research for future medical applications that require strong antibacterial properties.

Photo-induced synthesis of polypyrrole-silver nanocomposite films on N-(3-trimethoxysilylpropyl)pyrrole-modified biaxially oriented polyethylene terephthalate flexible substrates

Polypyrrole-silver (PPy–Ag) nanocomposite films were prepared on a N-(3-trimethoxysilylpropyl)pyrrole modified biaxially oriented polyethylene terephthalate (BOPET) substrate by photopolymerisation of pyrrole using AgNO3 as a photo-initiator. The films were prepared for a fixed molar concentration of pyrrole (0.5 M), varying molar concentrations of AgNO3 (0.05–0.7 M) and different UV exposure times (15 min–180 min). With increasing AgNO3 concentration or with increasing polymerisation time, the film morphology shows a transition from two dimensional lamellar to granular structures. The films are adherent, flexible and exhibit a maximum room temperature electrical conductivity of ∼15 S cm−1 (for AgNO3 ∼ 0.5 M, 120 min of UV exposure). However, the films directly prepared on pristine BOPET show granular morphology and their conductivity value is ∼0.5 S cm−1. The high conductivity of PPy–Ag films is attributed to the high conjugation length, the incorporation of Ag nano-particles between the polypyrrole chains and the ordered structure due to the templating effect of the silanised pyrrole layer, as confirmed by GIXRD, FTIR, Raman and temperature dependent conductivity measurements. The metallic state of the embedded Ag nano-particles in the polypyrrole matrix is confirmed by XRD and XPS. The films with the least amount of Ag (AgNO3 ∼ 0.1 M) only show a reversible conductivity change in the opposite manner on exposure to ppm levels of H2S and NH3 gases. The mechanism has been proposed to explain these antagonistic responses for reducing gases.

Mechanism of polypyrrole and silver nanorod formation in lauric acid–cetyl trimethyl ammonium bromide coacervate gel template: Physical and conductivity properties

Polypyrrole (PPy) and silver (Ag) nanorods are synthesized in cetyl trimethylammonium bromide–lauric acid (CTAB–LA) complex coacervate gel template. When PPy–CTAB–LA system is polymerized with AgNO3, Ag nanorods are produced while use of ammonium persulphate (APS) as initiator yields PPy nanorods. Ag-nanorods are produced from the initial stage while PPy nanorods take a longer time. The average diameter of Ag nanorods varies from 60 to 145nm by increasing AgNO3 concentration from 0.27M to 1.08M and that of PPy varies from 145nm to 345nm by changing pyrrole concentration from 1×10−4 to 2×10−4 M, respectively. Fourier transformed infrared (FTIR) spectra indicate stabilization of Ag nanorods through complexation of PPy with adsorbed Ag+ ions. PPy nanoparticles are stabilized by adsorbed sulphate ions and lauric acid, both are acting as dopant to it. FFT pattern and EDX spectra clearly indicate the presence of Ag nanocrystals and PPy on the surface of Ag nanorods, respectively. The mechanism of nanorod formation is attributed from UV–Vis spectra showing a red shift of surface plasmon band of Ag and π–π* transition band of PPy with time. The highest dc conductivity of PPy–Ag composite is found to be 414.2S/cm, 7 orders higher than that of PPy nanorods (9.3×10−4S/cm). PPy–Ag systems show Ohmic behavior while PPy nanorods exhibit semi-conducting behavior. The preferential formation of Ag nanorod in AgNO3 initiated polymerization is attributed to the higher cohesive force of Ag than that of PPy. With two times higher LA and CTAB concentration in the gel the Ag nanorod diameter decreases only 12% while that of PPy nanorod decreases by 50%. Possible reasons are discussed from the hard and soft nature of the two nanorods and from the elasticity of the gel template.

Vertex and Edge Truncated Octahedron Gold Crystals. N-alkylimidazole and Silver(I) Ion Controlled Morphology Transformation

Two interesting morphology transformations of Au crystals are observed through reacting a mixture of N-alkylimidazole (denoted as C(n)-im, where C(n) = C(n)H(2n+1), and n = 18 and 1), AgNO(3), and HAuCl(4) at 200 degrees C. The long chain C(18)-im with increasing AgNO(3) concentration leads to a progressive truncation of octahedrons at {100} vertices to produce cubes. On the other hand, increasing the concentrations of C(1)-im and AgNO(3), results in a progressive truncation of octahedrons at {110} edges to give rhombic dodecahedrons, which further transform to the unprecedented tetrahexahedrons. The phenomenon could be understood by considering that while both C(18)-im and C(1)-im function as a capping agent with preferential adsorption on Au {111} facets, Ag(+) adsorbs and is subsequently reduced to Ag on Au {110} facets for the sterically demanding C(18)-im, but on the Au {100} facets for C(1)-im. The competition between the growth of the facets protected by imidazole and Ag controls the morphology transformation via truncation of octahedrons at vertices or edges.

Dielectric properties of crystalline binary KNO3—AgNO3 mixtures embedded in nanoporous silicate matrices

The results of dielectric studies of MCM-41 sili cate matrices with cellular pores (37.0 and 26.1 A in diameter) filled by binary mixtures of K1−xAgxNO3 (x=0, 0.05, 0.10) are reported in comparison with those obtained for bulk salts of the same composition in the temperature range of structural phase transitions. It has been revealed that, upon heating, the nanocomposites undergo transitions from crystal modification II to phase I, as in bulk KNO3, whereas the bulk mixtures with x=0.05 and 0.10 have a complex structure in accordance with the phase diagram. It has been shown that embedding binary salts and pure potassium nitrate in pores with a diameter of 26.1A results in the formation of an intermediate ferroelectric phase upon cooling. The permittivity and electrical conductivity are found to increase with increasing AgNO3 concentration in bulk samples, as well as with decreasing pore size in the nanocomposites for all values of x.

Nanocomposites of silver nanoparticle and dinonylnaphthalene disulfonic acid‐doped thermoreversible polyaniline gel

AbstractSilver/polyaniline‐dinonylnaphthalene disulfonic acid (PANI‐DNNDSA) gel nanocomposites are prepared from the reduction of silver salt by polyaniline in formic acid medium. Scanning electron micrographs (SEM) indicate the presence of three‐dimensional fibrillar network structure and the silver nanoparticles remain dispersed within the PANI‐DNNDSA fibrillar network. Differential scanning calorimetric (DSC) study shows reversible first‐order phase transition characterizing the composite to behave as a thermoreversible gel. Transmission electron micrographs (TEM) show a decrease of nanoparticle size with increasing AgNO3 concentration. Wide angle X‐ray scattering (WAXS) patterns show lamellar structure in the gel as well as in the gel metal nanocomposites (GMNCs) and the two melting peaks in the DSC patterns correspond to the melting of monolayer and bilayer crystals produced from the interdigitation of DNNDSA tails anchored from PANI chains within the PANI lamella. The above melting points are greater in the GMNCs than that of pure gel indicating the formation of complex melting thermogram with crystallites produced from the anchored surfactants tails at the surface of Ag nanoparticles. The GMNCs show a higher thermal stability than that of pure PANI‐DNNDSA gel. PANI‐DNNDSA gel has an emission peak at 354 nm but fluorescence quenching occurs in the GMNCs and the emission peak becomes red shifted. Also in the UV–vis spectra the π band‐polaron band transition peak shows a red shift and the DC conductivity increases with increasing Ag nanoparticle concentration in the GMNCs. The current (I)–voltage (V) characteristic curves indicate Ohmic nature of conductivity of the gel and the current at the same voltage increases appreciably with increasing Ag nanoparticle concentration. These GMNCs are easily processible due to its thermoreversible nature. So, an easily processible, thermally stable and highly conducting DNNDSA‐doped PANI‐Ag gel nanocomposite with interesting photoluminescent property has been successfully developed suitable for optoelectronic applications. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers