Analysis of electrochemical mechanism of coprecipitated nano-Ag4Bi2O5 as super high charge–discharge rate cathode materials for aqueous rechargeable battery

Nano Ag₄Bi₂O₅ as a novel cathode material of rechargeable alkaline batteries was successfully synthesized by precise control of precipitation reaction. KOH solution was used as precipitant and a mixture of AgNO₃ and Bi(NO₃)₃ as Ag–Bi source. The experimental results indicate that concentration of KOH, reaction temperature and PH value have the effects on the structure and electrochemical property of the product. The material was characterized by means of XRD, FSEM and TG–DSC. The results show that the sample is single crystals with 50–100 nm in width and 600–800 nm in length. The electrochemical performances of Ag₄Bi₂O₅ in the alkaline electrolyte were measured by galvanostatic method and cyclic voltammetry tests through film electrode. The sample shows three typical procedures during the charge–discharge, corresponding to Ag(II)–Ag(I), Ag(I)–Ag(0) and Bi(III)–Bi(0) transformation processes. This result is also verified by XRD tests. The Ag₄Bi₂O₅ electrode has excellent electrochemical properties. It undergoes a current density as high as 20 A g^?1, which greatly reduces charge time down to 55.9 s. The electrode offers a cycling capacity of 330 mAh g^?1 and a cycling life more than 400 cycles at 1–2 A g^?1.     

Influence of silver on the structure,dielectric and antibacterial effect of silver doped bioglass-ceramic nanoparticles

We present the structural, dielectric, biocompatibility and antibacterial properties of nano-sized calcium phosphosilicate bioglass ceramics doped with 0, 2, 4 and 6 mol% Ag₂O. Sol-gel processes were chosen to synthesize the silver embedded nanosized glass ceramic particles. All samples were characterized by powder X-ray diffraction (XRD), thermogravimetric analysis, Fourier transform infrared (FTIR) spectroscopy, UV–visible and high resolution transmission electron microscopy (HR-TEM). The glass-ceramic nature of the samples is confirmed by XRD analysis. The FTIR spectra reveal the probable stretching and bending vibration modes of silicate and phosphate groups. UV–visible absorption spectra reveal the silver embedment as Ag⁺/Ag° form in the glass matrix. Nano-size of the glass ceramics and silver nanoparticle embedment in glass matrix are confirmed by HR-TEM analysis. Dielectric spectra of samples reveal non-Debye relaxation processes. The dielectric constant of samples initially decreased and then increased with Ag₂O content. The antibacterial activities of these bioceramics were tested with different bacteria using an agar well diffusion method. Silver doped samples show good antibacterial effects without compromising the formation of hydroxyapatites. The dielectric constant of the bioglass ceramics is correlated to their antibacterial performance, with low dielectric constants giving higher antibacterial activity.     

Preparation and antibacterial activity of Ag/SiO2 thin film on glazed ceramic tiles by sol–gel method

In the present study, silver-doped silica thin films on glazed surface of ceramic tiles were well prepared by sol–gel method to achieve antibacterial activity. Thermal treatment was done in the air at 1100 °C for two hours. The Ag/SiO₂ thin films were investigated through Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD) and wavelength dispersive spectrometry (WDS). Atomic absorption spectroscopy (AAS) was used for the quantitative determination of the silver ion concentration being released from Ag/SiO₂ films over a 24 day period. The antibacterial effects of Ag/SiO₂ thin films against Escherichia coli and Staphylococcus aureus were also examined. From the analysis results, it was found that high temperature treated coating consists of two phases of SiO₂ and Ag based on the trapping of the Ag phase in the silica matrix. The presence of Ag elements on the surface of the coated tiles, were also observed. Thermal treatment at high temperatures caused sharp XRD peaks and high crystallinity in this system. Ag⁺ ions were released constantly and the mean release rate (±SD) was 0.104 ±0.01 μg/ml during 24 days. Coating films exhibited an excellent antibacterial performance against both bacterium.     

Three Ag(I)–cyanide coordination polymers with metal bonds tuned by N-heterocyclic ligands

Hydrothermal reactions of AgNO₃, K₃[Fe(CN)₆] with N-heterocyclic ligands afforded three novel Ag(I)–cyanide coordination polymers, [Ag₂(CN)₂(tpt)]_n (1), {[Ag(CN)(bpe)_0.5][Ag(CN)]}_n (2) and [Ag(CN)(btmb)_0.5]_n (3) (tpt = 2,4,6-tris(4-pyridyl)-1,3,5-triazine, bpe = 1,2-bis(4-pyridyl)ethane, btmb = 1,2-bis(1,2,4-triazol-1-ylmethyl)benzene). In complex 1, two Ag(CN) linear chains are bridged by bidentate tpt ligand to form a ladder-like structure, which are further connected by AgAg metal bond to generate a 2D polymeric network. Complex 2 is an interesting 3D supramolecular architecture assembled by 2D [Ag¹(CN)(bpe)_0.5]_n network and linear [Ag²(CN)]_n chain combined by strong AgAg metal bond. Complex 3 is a 1D ladder-like double-chain polymer constructed from Ag–cyanide linear chains and btmb spacer, which is further extended to a 2D supramolecular network by Ag–Ag weak interaction. The Ag–Ag metal interactions play important roles in the construction of three coordination polymers. Complexes 1 and 2 are respectively thermally stable at 300 and 180 °C. Complexes 1 and 3 emit strong blue luminescence.     

Antibacterial activity of organomontmorillonites and organovermiculites prepared using chlorhexidine diacetate

Organoclays with antibacterial activity were prepared from cation exchanged Ag⁺, Cu^2 + and Zn^2 + forms of montmorillonite and vermiculite using five concentrations of chlorhexidine diacetate. The samples were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The antibacterial activity against Enterococcus faecalis, Escherichia coli and Pseudomonas aeruginosa was evaluated by finding the minimum inhibitory concentration (MIC). All prepared organomontmorillonites and organovermiculites showed the best antibacterial activity against an E. coli bacterial strain.     

Adsorptive removal of tetrahydrothiophene (THT) and tert-butylmercaptan (TBM) using Na-Y and AgNa-Y zeolites for fuel cell applications

Adsorptive removal of tetrahydrothiophene (THT) and tert-butylmercaptan (TBM) that are widely used sulfur odorants in pipeline natural gas was studied using AgNa-Y zeolites at ambient temperature and atmospheric pressure. The AgNa-Y were obtained via Ag⁺-exchange with Na⁺ of Na-Y at various exchange levels, and the contributions of formed adsorption sites (Ag⁺, Na⁺, Ag⁰, H⁺, and Ag₂O) in the THT and TBM adsorption uptake and selectivity were characterized. THT adsorption strength on these sites followed an order of Ag⁺ > Na⁺ ∼ Ag⁰ > H⁺ > Ag₂O. The adsorption strength of THT on Na⁺ sites was sufficiently high, thus an increase in the Ag⁺-exchange level did not lead to a notable increase in the breakthrough THT uptake. Differently, adsorption of TBM on Na⁺ sites was weak, whereas that on Ag⁺ sites was strong. This resulted in a marked increase in the breakthrough TBM uptake with an increase in the Ag⁺-exchange level, showing an order of magnitude higher uptake on AgNa-Y compared with that on Na-Y. Noticeably, the adsorption strength of THT on these adsorption sites was higher than that of TBM. This resulted in an almost 100% adsorption selectivity for THT over TBM, when these two sulfur species coexisted in the feed stream.     

Jet pulse electrodeposition and characterization of Ni–AlN nanocoatings in presence of ultrasound

In current study, Ni–AlN nanocoatings were successfully prepared by adopting the jet pulse electrodeposition (JPE) technique with ultrasound. The scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Vickers microhardness test, electrochemical workstation and friction wear tests were utilized to investigate the microstructure, mechanical properties, corrosion degree and wear resistance of the coatings. The results indicated that the Ni–AlN nanocoatings deposited by using ultrasound demonstrated the minimum and most compact surface structure compared to the other coatings. The thicknesses of Ni coating and Ni–AlN nanocoatings were approximately 56 µm. The average atomic percent of Al and Ni elements in the Ni–AlN nano-coating prepared by using ultrasound, were approximately 21.4 at% and 47.5 at%, respectively. The maximum kinetic energy of the jet plating solution was 916 m²/s² during JPE-deposited Ni-AlN nanocoatings including ultrasound. The average micro-hardness value of the nano-coating prepared by using ultrasound equaled 767.9 HV. The Ni–AlN nanocoatings prepared using ultrasound had the minimum E_corr and I_corr values of ? 0.167 V and 6.363 × 10^?6 mA/cm², respectively. In this case, the demonstrated corrosion resistance was the most efficient. The Ni–AlN nanocoatings prepared using ultrasound sustained the minimum friction coefficients and the average friction coefficient was approximately 0.52. In contrast, the JPE-deposited Ni coating presented the maximum friction coefficient, while the average friction coefficient was approximately 1.43.     

Dielectric characteristics of donor-acceptor modified BaTiO3 ceramics

Sm/Mn codoped BaTiO₃ ceramics were investigated for their microstructure and dielectric characteristics. The powders were prepared by the conventional solid state procedure. The concentration of Sm₂O₃ as a donor dopant has been kept from 0.1 up to 5.0 at%. The content of MnO₂ as acceptor was kept constant at 0.05 at% Mn in all samples. The specimens were sintered at 1290 °C, 1320 °C and 1350 °C in an air atmosphere for two hours.A mainly uniform and homogeneous microstructure with average grain size ranging from 0.3 µm to 2.0 µm was observed in low doped samples. In highly doped samples, apart from the fine grained matrix, the appearance of local area with secondary abnormal grains was observed.The dielectric properties were investigated as a function of frequency and temperature. The low doped samples exhibit the high value of dielectric permittivity at room temperature and the greatest change at the Curie temperature. The highest value of dielectric constant (ε_r=6800) was measured for 0.1Sm/BaTiO₃ samples sintered at 1350 °C. A nearly flat permittivity-temperature response and lower values of ε_r were obtained in specimens with 2.0 and 5.0 at% additive content. The dielectric constant increases with the increase of sintering temperature. The dissipation factor ranged from 0.01 to 0.22 and decreases with the increase of sintering temperature. The Curie constant (C), Curie-Weiss temperature (T₀) and critical exponent of nonlinearity (γ ) were calculated using a Curie-Weiss and modified Curie-Weiss law. The highest value of Curie constant (C=9.06·10⁵ K) was measured in 0.1 at% doped samples. The Curie constant decreased with increasing dopant content. The γ values, ranging from 1.001 to 1.58, point out the sharp phase transition in low doped samples, and the diffuse phase transition in heavily doped BaTiO₃ samples.     

Enhanced thermoelectric properties and electronic structures of p-type BiCu1−xAgxSeO ceramics

The thermoelectric properties and electronic structures were investigated on p-type BiCu_1-xAg_xSeO (x=0, 0.02, 0.05, 0.08) ceramics prepared using a two-step solid state reaction followed by inductively hot pressing. All the samples consist of single BiCuSeO phase with lamella structure and no preferential orientation exists in the crystallites. Upon replacing Cu⁺ by Ag⁺, maximum values of electrical conductivity of 36.6 S cm⁻¹ and Seebeck coefficient of 350 μV K⁻¹ are obtained in BiCu_0.98Ag_0.02SeO and BiCu_0.92Ag_0.08SeO, respectively. Nevertheless, a maximum power factor of 3.67 μW cm⁻¹K⁻² is achieved for BiCu_0.95Ag_0.05SeO at 750 K owing to the moderate electrical conductivity and Seebeck coefficient. Simultaneously, this oxyselenide exhibits a thermal conductivity as low as 0.38 W m⁻¹ K⁻¹ and a high ZT value of 0.72 at 750 K, which is nearly 1.85 times as large as that of the pristine BiCuSeO. The enhancement of thermoelectric performance is mainly attributed to the increased density of states near the Fermi level as indicated by the calculated results.     

A fluorescein derivative FLTC as a chemosensor for Hg2 + and Ag+ and its application in living-cell imaging

FLTC was synthesized and used as a fluorescent chemosensor to detect Hg^2 +. It showed high selectivity toward Hg^2 + over many heavy metal ions in an ethanol–H₂O (3:2, v/v, HEPES buffer, 0.5 mM, pH 7.15) solution with a detection limit of 0.21 μM. After complexation with Hg^2 +, FLTC showed extremely high selectivity toward Ag⁺ with a detection limit of 0.009 μM. Therefore, detection of Hg^2 + and Ag⁺ could be realized using FLTC and the FLTC–Hg^2 + complex, respectively. Cytotoxicity assays and fluorescence microscopy analysis showed that FLTC could be used as a fluorescent probe to detect Hg^2 + and Ag⁺ in L-02 human liver cells.     

Photoluminescent metal–organic coordination polymer incorporating one-dimensional silver chains

Solution phase reaction of AgNO₃ with a mixture of benzene-1,3,5-tricarboxylic acid (H₃BTC) and heterocyclic 2-aminopyrimidine (APYM) under the ammoniacal conditions gives rise to a novel metal–organic coordination polymer Ag₃(BTC)(APYM)₂ (1). The structure of 1 possesses a unique three-dimensional (3D) framework with one-dimensional channels surrounded by carboxylato-supported Ag–Ag dimers, Ag–Ag chains, fully deprotonated [BTC]^3? and APYM ligands. Moreover, 1 exhibits strong blue photoluminescence maximized at 464 nm at room temperature (λ_ex = 383 nm) and upon cooling to 77 K, the emission spectrum seems narrowly red-shifted.     

Investigations on pure and Ag doped lithium lanthanum titanate (LLTO) nanocrystalline ceramic electrolytes for rechargeable lithium-ion batteries

The nano-crystalline Li_0.5La_0.5TiO₃ (LLTO) was prepared as an electrolyte material for lithium-ion batteries. The effect of Ag⁺ ion doping in three different concentrations were investigated: Ag_0.1Li_0.4La_0.5TiO₃, Ag_0.3Li_0.2La_0.5TiO₃, and Ag_0.5La_0.5TiO₃ along with Li_0.5La_0.5TiO₃. The prepared pure and Ag⁺ doped LLTO were subjected for structural, morphological, electrical and optical characterizations. The cubic superlattice structure of LLTO nano-powder was altered due to the Ag⁺ substitution tending towards a tetragonal phase. Increasing Ag⁺ substitution a complete tetragonal phase occurs in Ag_0.5La_0.5TiO₃. The average particle size of the prepared ceramic electrolyte ranged between 80 nm and 120 nm. The photoluminescence study reveals that the LLTO and Ag doped LLTO gives a blue emission peak. The size effect on grain and grain boundary resistance was observed and reported. With Ag⁺ substitution, the conductivity got decreased due to the impedance caused by Ag⁺ ions in the conducting path of Li⁺ ion. Among all the samples, Ag_0.5La_0.5TiO₃ shows maximum conductivity of the order of 10^?3 S cm^?1.     

Resistance to sulfidation of the catalytic reduction of NOx over Ag/Al2O3 by controlling the loadings of Ag and Ag+

SO₂ strongly decreased the catalytic activities of low loading Ag/Al₂O₃ below 500 °C in selective catalytic reduction (SCR) of NO_x by propene with or without the assistance of non-thermal plasma (NTP), which was mainly attributed to the competition between SO₂ and NO. By controlling the loadings of Ag and Ag⁺ over alumina, the resistance of SO₂ was remarkably enhanced between 400 °C and 500 °C in thermal SCR. In the NTP-assisted SCR, most of the NO_x conversions were also apparently recovered from 250 °C to 500 °C.     

Influence of Ag doping on electrical and magnetic properties of La0.625(Ca0.315Sr0.06)MnO3 ceramics

Polycrystalline Ag-doped [La_0.625(Ca_0.315Sr_0.06)MnO₃]_1-x:Ag_x (LCSMO) ceramics with (x = 0, 0.03, 0.05, 0.10, 0.15, and 0.20) were prepared by sol-gel method, and their structures and properties were characterized. X-ray diffraction results indicated that all bulk samples had single phase with orthorhombic phase (space group of Pbnm) without impurities. With the increase of Ag doping content, the resistivity of the samples decreased, while the remanent magnetization and coercive field increased. The metal to insulator transition temperature (T_p), temperature coefficient of resistance (TCR) and Curie temperature (T_c) for x = 0.20 were determined as 300 K, 9.38% (292.6 K) and 291.86 K respectively. The highest MR value of 28.36% (295.03 K) was obtained at x = 0.15. XPS data revealed that substitution between A-site ions and Ag⁺ could increase the ratio of Mn⁴⁺ ion. Double exchange effect (DE) enhanced by changing Mn–O bond distance, Mn–O–Mn bond angle, and increasing Mn⁴⁺ ion concentration. These features promoted the transfer of itinerant electron between Mn³⁺ and Mn⁴⁺ ions. However, the magnetization obtained at x = 0.20 was less than that at x = 0, as diamagnetic Ag released magnetism of the samples. The results suggested that the LCSMO polycrystalline ceramics could be used as a candidate to prepare room temperature infrared detectors, magnetic sensors or magneto-electric devices, and so on.     

Ethanol to hydrocarbons using silver substituted polyoxometalates: Physicochemical and catalytic study

Thermally stable and insoluble silver salts of 12-molybdophosphoric acid with varying amount of Ag cations were prepared. XRD results indicated the presence of single phase of Ag_xH_3−xPMo₁₂O₄₀ (0 < x < 3). FTIR and Raman results indicated that Ag was incorporated in the secondary structure of Keggin ion. The catalytic conversion of ethanol increased in the order of H₃PMo > Ag₂PMo > Ag₁PMo > Ag₃PMo. Pure H₃PMo is highly selective to dimethyl ether formation; in contrast Ag_xH_3−xPMo₁₂O₄₀ catalysts offered better ethylene selectivity. The pyridine adsorption studies revealed that increase of Ag incorporating led to increase the Lewis acid sites.     

Ag–Ni bimetallic SiBEA zeolite as an efficient catalyst of hydrodechlorination of 1,2-dichloroethane towards ethylene

Dealuminated form of BEA zeolite with Si/Al ratio of 1500 was used for the synthesis of Ag_2.0SiBEA, Ni_2.0SiBEA and Ag_2.0Ni_2.0SiBEA by two-step postsynthesis method. The calcination of zeolite samples led to the formation of well dispersed isolated mononuclear Ag(I) and Ag_n^δ + clusters and a pseudo-tetrahedral Ni(II), incorporated in BEA framework as evidenced by DR UV–vis investigations. The treatment of samples in flowing 10% H₂/Ar stream gave small (average 3.1 nm) and well dispersed metal nanoparticles. Reduced catalysts were investigated in 1,2-dichloroethane hydrodechlorination at atmospheric pressure, at low reaction temperature (523 K) with ~ 100% of selectivity to ethylene, desired product of the reaction.     

Bioactivity and antibacterial activity against E-coli of calcium-phosphate-based glasses: Effect of silver content and crystallinity

In this work we developed improved bioactive glasses and glass-ceramics for biomedical applications, investigating their in vitro bioactivity, biocompatibility and antibacterial properties against E-Coli. A melt-quenched bioactive glass of the SiO₂-CaO-P₂O₅-MgO system was modified with the addition of 1 and 2 mol% Ag₂O and the 1 mol% Ag₂O-containing glasses were then heat treated to produce glass-ceramics. Surface modifications after soaking in SBF and ionic concentration changes showed that addition of silver and crystallization did not affect bioactivity although crystalline phases promoted a decrease in the degradation rate.Biocompatibility of all Ag-containing glasses and glass-ceramics was confirmed for certain samples concentrations. The antibacterial activity of the glasses against E-Coli was generally improved with decreasing particle size or increasing Ag₂O. The Ag-containing glass-ceramics with higher content of crystalline phase appears as a promising biocompatible biocidal material with potential applications in bone-related diseases.     

Divalent silver oxide-diatomite hybrids: Synthesis,characterization and antibacterial activity

To produce better antibacterial and low water-soluble submicron powders of divalent silver oxide (AgO), divalent silver oxide-diatomite (AgO-d) hybrids were studied. AgO-d hybrids were prepared by chemical oxidation, using silver nitrate and diatomite as raw materials and potassium persulfate as oxidant. The results show that AgO-d hybrids with AgO weight percentage up to 20.8% are obtained by oxidation of Ag⁺ adsorbing on diatomite in alkaline solution (n(KOH)/n(AgNO₃)=7.5) for 1.5 h at 333.15 K. Products were characterized by laser particle sizer, SEM, XRD, XPS, FT-IR and atomic absorption spectrophotometer (AAS). AgO-d hybrids are composed of tetragonal cristobalite, amorphous silica, monoclinic divalent silver oxide and a few of cubic silver oxide. Element Ag can be released from AgO-d hybrids but the dissolution speed is slow, which is about 3.20×10^?2 mg (L h)^?1. Antibacterial effectiveness of AgO-d hybrids was tested against Staphylococcus aureus (S. aureus ATCC6538) and Escherichia coli (E. coli ATCC8099) by the shake-flask method. Results show that AgO-d hybrids possess excellent antibacterial properties. When the concentration of AgO-d hybrids is 10 mg L^?1 and the contact time with S. aureus and E. coli is 30 min, the bactericidal rates reach up to 99.974% and 99.944%, respectively.     

The first substituted macrocyclic ligand Py2N4S2 containing four naphthylmethylene pendant-armed groups: Synthesis and photophysical properties

The synthesis of a pendant donor emissive macrocyclic ligand Py₂N₄S₂ with up to four naphthylmethylene arms (L) has been achieved. Their derivative solid metal complexes (Co^2 +, Ni^2 +, Cu^2 +, Zn^2 +, Cd^2 +, Hg^2 + and Ag⁺) have been isolated and characterized. The photophysical properties of the free ligand L and their complexation behaviour have been investigated in solution. In dichloromethane, the free ligand presents two emission bands which are related to the monomer naphthalene emission and a red-shifted band attributable to ground state dimers (interaction between two naphthalene chromophores), which was further validated from time-resolved data, with bi-exponential decay with absence of dynamic components. UV–Vis spectroscopy has revealed a 2:1 binding stoichiometry for Co^2 +, Cu^2 +, Zn^2 +, Hg^2 + and Ag⁺.