Preparation and Antibacterial Effect of Bamboo Charcoal/Ag on Staphylococcus Aureus and Pseudomonas Aeruginosa

Bamboo charcoal supporting silver (BC/Ag) was prepared by activation and chemical reduction. The BC/Ag composites were characterized by silver particle size and distribution, silver ion (Ag⁺) release and antibacterial properties. Scanning and transmission electron microscopy (SEM and TEM) showed that the Ag particles were distributed uniformly on the BC matrix. The Ag particle size was found to be less than 150 nm based on TEM. The Ag⁺ release increased initially which was followed by a marginal increase between the 8th and 24th hour. Composites contained higher amounts of silver exhibited a further rise in Ag⁺ release from the 24‐hours of storage in water. The antibacterial effects of the BC/Ag composite powders against Pseudomonas aeruginosa and Staphylococcus aureus were assessed from the minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) method, and an excellent antibacterial performance was discovered.     

Effect of Manganese Dioxide Dispersion on the Absorbing Properties of Manganese Dioxide (MnO2)‐Epoxy Composites

Manganese dioxide (MnO₂) particle was synthesized and introduced into epoxy resin to be microwave absorber. The spectroscopic characterization of the formation processes of MnO₂ was studied by using X‐ray diffraction (XRD) and scanning electron microscopy (SEM). Microwave absorbing properties with different volume fractions of MnO₂ were investigated by measuring complex permittivity, complex permeability and reflection loss in the 2–18 and 18–40 GHz microwave frequency range using the free space method. The absorbing performance of MnO₂‐epoxy composites at same sample thickness and at various sample thickness were also studied. It was found that the best absorbing property and an absorption frequency range shifting could be obtained at the frequency range of 2–18 and 18–40 GHz.     

Effect of carbon black content on electrical and microwave absorbing properties of polyaniline/carbon black nanocomposites

Carbon black coated with polyaniline, forming a core-shell structure, was synthesized by in situ polymerization at different carbon black contents (5-30 wt.%) and introduced into epoxy resin to be a microwave absorber. The spectroscopic characterizations of the formation processes of polyaniline/carbon black composites were studied using Fourier transform infrared, ultraviolet-visible spectrophotometer, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and electron spin resonance. Microwave absorbing properties were investigated by measuring reflection loss in the 2-18 and 18-40 GHz microwave frequencies range using the free space method. The results showed that a wider absorption frequency range could be obtained by adding different carbon black contents in polyaniline.     

Preparation and characterization of Ag‐deposited aminosilane‐modified silicate by chemical reduction method

Nanocomposites based on silver (Ag) and organically modified silicate (Ormosil) were prepared by an in situ reduction method, in which silver nitrate, tetraethoxysilane and N‐[3‐(trimethoxysilyl)propyl]diethylenetriamine (ATS) acted as precursor, linker, and colloidal suspension stabilizer, respectively. The objective of the study was to produce silver nanoparticles through AgNO₃ chemical reduction in a continuous media, in which aminosilanes act as superficial modifiers of Ag nanoparticles, inhibiting their growth and preventing aggregation. The physical properties of the Ormosil/Ag composites were examined using NMR, electron spin resonance, scanning electron microscope, transmission electron microscope, and thermal gravimetric analysis spectroscopy, the results of which indicated that Ag was incorporated in the Ormosil matrix after impregnation. The Ag content and surface morphology of the Ormosil/Ag composites depended on the initial concentration of AgNO₃. The antibacterial effects of the Ormosil/Ag composites were assessed by the zone of inhibition and plate‐counting methods, and an excellent antibacterial performance was discovered. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Ku-band EMI shielding effectiveness and dielectric properties of Polyaniline-Y2O3 composites

Electromagnetic interference (EMI) shielding has become a phenomenon of great concern and there is growing demand towards the synthesis of materials with better EMI shielding effectiveness (EMI SE). This work highlights the preparation of Polyaniline-Yttrium Oxide (PANI-Y₂O₃) composites for EMI shielding applications in the frequency range from 12.4 to 18 GHz (Ku-band). The structure and morphology of the composites were investigated by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). EMI SE, microwave absorption and reflection, dielectric properties of the composites are discussed in detail. All the computations were based on microwave scattering parameters measured by transmission line waveguide technique. The observed results show absorption dominant EMI shielding in these composites with EMI SE of ?19 to ?20 dB, which mainly depends on the dielectric loss of the composites. Through the results of our observations, we propose these composites to be potential materials for microwave absorption and EMI shielding applications.     

Synthesis of Ag and Ag/SiO2 sols by solvothermal method and their bactericidal activity

Ag and Ag/SiO₂ sols containing nanocrystalline silver particles can be advantageously prepared by solvothermal methods using an autoclave with conventional thermal or microwave heating. In this process, the reduction of silver salts can be realized with alcohols like ethanol in the presence of polyvinylpyrrolidone at temperatures of more than 120 °C. Furthermore a combination of silver salt reduction with hydrolysis of alkoxysilanes during the solvothermal process can yield Ag/SiO₂ composite sols. Particle size and crystallinity of as-prepared particles are analyzed by means of X-ray diffraction and high-resolution transmission electron microscopy. Nanosized silver particles gained by this process exhibit antimicrobial properties that are investigated in detail after application on textile fabrics.     

Natural rubber–based composites filled with bioglasses from a CaO‐SiO2‐P2O5‐Ag2O system. Effect of Ag2O concentration in the filler on composite properties

Bioactive glass was first synthesized by L. Hench in 1971. There are many studies on the properties of several metals and metal ions dopants used in the SiO₂‐CaO‐P₂O₅ system of bioglasses, such as Ag, Cu, Zn, and Fe. A number of authors have carried out research related to the influence of silver oxide on the properties of bioglasses . However, publications on the properties of elastomer‐based composites containing bioactive glasses are relatively scarce. We have not found in the literature studies discussing how silver oxide concentration in bioglasses of the CaO‐SiO₂‐P₂O₅‐Ag₂O system affects the significant properties of a natural rubber biocomposite. In this regard, the purpose of the present work is to investigate the aforementioned influence on the properties of this type of composites, namely, vulcanization, physicomechanical, thermal, dynamic, dielectric, electric, and thermoconductive characteristics. We have established those parameters of the composites to be impacted considerably by both degree of filling with bioglass and the silver oxide content in the latter. The improvement in the composites thermostability and some of their physicomechanical performance is the most significant. The volume resistance decreases, and the thermal conductivity coefficients increase. Results from scanning electron microscopy and energy‐dispersive X‐ray (EDX) analyses have confirmed the influence of silver oxide initially on the phase composition of the bioglass, hence on the properties of the biocomposites through changes in the bioglass used as filler. The dielectric characteristics of some of the biocomposites suggest that they can be used as substrates and insulating layers in flexible antennas for short‐range wireless communications.     

UV‐curing synthesis of sulfonated polyaniline‐silver nanocomposites by an in situ reduction method

Sulfonated polyaniline‐silver (SPAni‐Ag) hybrid nanocomposites have been synthesized by the in situ reduction using a UV‐curing polymerization method without using any reducing or binding agent. An aqueous solution of aniline and orthoanilinic acid (OA) comonomers, a free‐radical oxidant and silver metal salts were irradiated by UV rays. Reduction of the silver salt in aqueous aniline and OA leads to the formation of silver particles which in turn catalyze the oxidation of comonomers to sulfonated polyaniline (SPAni). The resultant SPAni‐Ag nanocomposites were characterized by using different spectroscopy analyses like UV–visible (UV–Vis), X‐ray diffraction (XRD) and infrared spectroscopy. The absorption bands were revealed to be optically active and the peaks blue‐shifted due to the presence of metallic silver within the SPAni matrix. The XRD patterns displayed both the broad amorphous polymeric and sharp metallic peaks. Scanning electron microscopy and transmission electron microscopy of the nanocomposites showed a uniform size distribution with spherical and granular morphology. Thermogravimetric analysis revealed that the nanocomposites had a better thermal stability than the bulk SPAni. Copyright © 2008 John Wiley & Sons, Ltd.     

Facile Synthesis of Ag/Ag3PO4 Composites with Highly Efficient and Stable Photocatalytic Performance under Visible Light

The Ag/Ag₃PO₄ composites with various shapes (spheres, polyhedral, and microcubes) were synthesized by a facile precipitation method and a subsequent light‐reduction route at room temperature. The as‐prepared Ag/Ag₃PO₄ composites were characterized in detail by X‐ray diffraction, Fourier transform infrared spectra, X‐ray photoelectron spectroscopy, scanning electron microscopy, UV–vis diffuse reflection, and photoluminescence spectroscopy. The growth processes of different morphologies Ag/Ag₃PO₄ composites are also discussed. The decomposition test of rhodamine B (RhB) indicated that the Ag/Ag₃PO₄ composites enhanced the photocatalytic performance compared with pure Ag₃PO₄, which was attributed to the surface plasmon resonance (SPR) of Ag nanoparticles and the stability of the photocatalysts. Moreover, uniform cubes of Ag/Ag₃PO₄ showed the highest photocatalytic activity and could completely degrade RhB in 7 min, which could be primarily ascribed to the cubic structure of Ag/Ag₃PO₄ with strong visible‐light absorption and efficient separation of the photo‐generated electrons and holes. Furthermore, the possible photocatalytic mechanism is also discussed.     

Synthesis of core‐shell silver–polyaniline nanocomposites by gamma radiolysis method

Core‐shell silver (Ag)–polyaniline (PAni) nanocomposites have been synthesized by the in‐situ gamma radiation‐induced chemical polymerization method. Aqueous solution of aniline, a free‐radical oxidant, and/or silver metal salt were irradiated by γ‐rays. Reduction of the silver salt in aqueous aniline leads to the formation of silver nanoparticles which in turn catalyze oxidation of aniline to polyaniline. The resultant Ag‐PAni nanocomposites were characterized by using different spectroscopy analyses like X‐ray photoelectron, UV–visible, and infrared spectroscopy. The optical absorption bands revealed that the bands at about 400 nm are due to the presence of nanosilver and the blue‐shifted peak at ～ 555 nm is due to the presence of metallic silver within the PAni matrix. X‐ray diffraction pattern clearly indicates the broad amorphous polymer and the sharp metal peaks. Scanning electron microscopy and transmission electron microscopy of the nanocomposite showed a uniform size distribution with spherical and granular morphology. Thermogravimetric analysis revealed that the composites have a higher degradation temperature than polyaniline alone. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5741–5747, 2007     

Ag Nanoparticle/Nanofibrillated Cellulose Composite as an Effective and Green Catalyst for Reduction of 4-Nitrophenol

In this work, silver nanoparticles (Ag NPs) prepared through in situ green and facile synthesis by using nanofibrillated cellulose (NFC) hydrogel as support, stabilizer and reducing agent by two different methods. Their catalytic abilities were examined for conversion of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). The structure of as-synthesized composites with different AgNO₃ concentrations were characterized by ultraviolet–visible spectroscopy, field emission scanning electron microscopy, transmission electron microscopy; energy dispersive spectroscopy, Fourier transform infrared spectroscopy and X-ray diffraction. Results show that all nanocomposites demonstrated excellent catalytic activity. Among them, Ag@NFC-2 sample, with spherical and well-dispersed Ag NPs along the nanofiber, produced by the second method having 0.25 M AgNO₃ concentration presented outstanding catalytic efficiency.     

Rational Design of Ag/TiO2 Nanosystems by a Combined RF‐Sputtering/Sol‐Gel Approach

The present work is devoted to the preparation of Ag/TiO₂ nanosystems by an original synthetic strategy, based on the radio‐frequency (RF) sputtering of silver particles on titania‐based xerogels prepared by the sol–gel (SG) route. This approach takes advantage of the synergy between the microporous xerogel structure and the infiltration power characterizing RF‐sputtering, whose combination enables the obtainment of a tailored dispersion of Ag‐containing particles into the titania matrix. In addition, the system′s chemico‐physical features can be tuned further through proper ex situ thermal treatments in air at 400 and 600 °C. The synthesized composites are extensively characterized by the joint use of complementary techniques, that is, X‐ray photoelectron and X‐ray excited Auger electron spectroscopies (XPS, XE‐AES), secondary ion mass spectrometry (SIMS), glancing incidence X‐ray diffraction (GIXRD), field emission scanning electron microscopy (FE–SEM), transmission electron microscopy (TEM), electron diffraction (ED), high‐angle annular dark field scanning TEM (HAADF–STEM), energy‐filtered TEM (EF–TEM) and optical absorption spectroscopy. Finally, the photocatalytic performances of selected samples in the decomposition of the azo‐dye Plasmocorinth B are preliminarily investigated. The obtained results highlight the possibility of tailoring the system characteristics over a broad range, directly influencing their eventual functional properties.     

Clay and charcoal composites: characterisation and application of factorial design analysis for dye adsorption

The characterisation of smectite clay, charcoal and prepared clay-charcoal composites was carried out through the X-ray diffractometry, energy dispersive X-ray spectroscopy (EDS), simultaneous thermal analysis (TGA/DTA), infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The analysis revealed the composites to have different characteristics from the precursor clay and charcoal, and a peak displacement (d ₀₀₁) was observed through the X-ray diffraction; this suggests the incorporation of charcoal into the clay lamellas and the formation of a new phase. Tests of adsorption with methylene blue dye were also carried out to evaluate the percentage of dye removal by the adsorbent, in which the composites presented better results than charcoal, indicating great potential for industrial use. A 2³ factorial design was employed to evaluate the influence of temperature, ionic strength and pH on the adsorption of methylene blue using the AV₅₀ composite that presented the best adsorption efficiency.     

Preparation and characterization of multi‐walled carbon nanotubes decorated with silver nanoparticles through ultraviolet irradiation reduction

A facile, green and efficient approach was applied to synthesize multi‐walled carbon nanotubes (MWNTs) decorated with silver nanoparticles (MWNT‐Ag) for further potential application. Oxidized MWNTs were decorated with silver nanoparticles (Ag NPs) via a method combining ultraviolet irradiation‐induced reduction and conventional silver mirror reaction without any reducing agent. The obtained product was characterized using various methods. X‐ray diffraction proved that the Ag NPs were synthesized successfully. Moreover, Ag NPs with a diameter of 80 nm, attached onto MWNTs, could be clearly observed in field emission scanning electron microscopy images, which also confirmed Ag NPs. Energy‐dispersive spectroscopy and transmission electron microscopy also indicated the presence of Ag NPs. Furthermore, thermogravimetric analysis was used to measure the content of Ag NPs in MWNT‐Ag, the result indicating that the weight content of Ag NPs was up to 31.88%. UV–visible absorption spectroscopy was adopted to evaluate the dispersion property of MWNT‐Ag. The result illustrated that MWNT‐Ag had a good dispersibility and stability in water. Characterization was also carried out through Fourier transform infrared spectroscopy, Raman spectroscopy and dynamic light scattering analysis.     

The Preparation of Slag Fiber and Its Application in Microwave Absorption

In this research, the slag fibers coming from water‐quenched slags by using thermal plasma technology were successfully prepared and introduced into epoxy resin to be microwave absorber. The fiber‐blowing equipment for manufacturing slag fibers through controlling the nozzle angle and vertical distance from the nozzle to the melt outlet was also studied. The spectroscopic characterization of the formation processes of slag fiber was studied by using X‐ray diffraction (XRD), inductively‐coupled plasma (ICP), differential thermal analysis (DTA) and scanning electron microscopy (SEM). Microwave absorbing properties of the slag fibers and thermal plastic resin were investigated by measuring reflection loss in the 2–18 and 18–40 GHz microwave frequency range using the free space method. It was found that the composite specimens of slag fiber and thermal plastic resin had the best microwave absorption due to the reflection losses between from −4 to −8 dB and from −11 to −17 dB at frequencies between 2–18 and 18–40 GHz.     

Fe3O4 – Glutathione stabilized Ag nanoparticles: A new magnetically separable robust and facile catalyst for aqueous phase reduction of nitroarenes

The heterostructured Ag nanoparticles decorated Fe₃O₄ Glutathione (Fe₃O₄‐Glu‐Ag) nanoparticles (NPs) were synthesized by sonicating glutathione (Glu) with magnetite and further surface immobilization of silver NPs on it. The ensuing magnetic nano catalyst is well characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), powder X‐ray diffraction (PXRD), thermogravimetric analysis (TGA). The prepared Fe₃O₄‐Glu‐Ag nanoparticles have proved to be an efficient and recyclable nanocatalyst with low catalyst loading for the reduction of nitroarenes and heteronitroarenes to respective amines in the presence of NaBH₄ using water as a green solvent which could be easily separated at the end of a reaction using an external magnet and can be recycled up to 5 runs without any significant loss in catalytic activity. Gram scale study for the reduction of 4‐NP has also being carried out successfully and it has been observed that this method can serve as an efficient protocol for reduction of nitroarenes on industrial level.     

Synthesis of Silver Nanoparticles Using Ionic‐Liquid‐Based Microwave‐Assisted Extraction from Polygonum minus and Photodegradation of Methylene Blue

A green biogenic, nontoxic, high‐yielding synthetic method is introduced for the synthesis of silver nanoparticles (AgNPs) using ionic‐liquid‐based, microwave‐assisted extraction (ILMAE) from Polygonum minus . The aqueous ionic liquid (1‐butyl‐3‐methylimidazolium chloride [BMIM]Cl)‐based plant extract was used as reducing agent to reduce silver ions to AgNPs. The synthesis of AgNPs was confirmed by UV–visible spectrophotometry. Fourier transforms infrared (FTIR) spectra showed that the plant bioactive compounds capped the AgNPs. The particle size and morphology of Ag NPs were characterized by dynamic light scattering (DLS) and field emission scanning electron microscopy (FESEM), respectively. Elemental analysis was carried out by energy‐dispersive X‐ray (EDX) spectroscopy. Photodegradation studies showed that the AgNPs degraded 98% of methylene blue in 12 min.     

Microwave‐Hydrothermal Preparation and Visible‐Light Photoactivity of Plasmonic Photocatalyst Ag‐TiO2 Nanocomposite Hollow Spheres

Visible‐light‐driven plasmonic photocatalyst Ag‐TiO₂ nanocomposite hollow spheres are prepared by a template‐free chemically‐induced self‐transformation strategy under microwave‐hydrothermal conditions, followed by a photochemical reduction process under xenon lamp irradiation. The prepared samples are characterized by using scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, N₂ adsorption‐desorption isotherms, X‐ray photoelectron spectroscopy, UV/Vis and Raman spectroscopy. Production of ?OH radicals on the surface of visible‐light illuminated TiO₂ was detected by using a photoluminescence method with terephthalic acid as the probe molecule. The photocatalytic activity of as‐prepared samples was evaluated by photocatalytic decolorization of Rhodamine B (RhB) aqueous solution at ambient temperature under visible‐light irradiation. The results show that the surface plasmon absorption band of the silver nanoparticles supported on the TiO₂ hollow spheres was red shifted, and a strong surface enhanced Raman scattering effect for the Ag‐TiO₂ nanocomposite sample was observed. The prepared nanocomposite hollow spheres exhibits a highly visible‐light photocatalytic activity for photocatalytic degradation of RhB in water, and their photocatalytic activity is higher than that of pure TiO₂ and commercial Degussa P25 (P25) powders. Especially, the as‐prepared Ag‐TiO₂ nanocomposite hollow spheres at the nominal atomic ratio of silver to titanium ( R ) of 2 showed the highest photocatalytic activity, which exceeds that of P25 by a factor of more than 2.     

Significant enhancement of electrical and thermal conductivities of polyethylene carbon nanotube composites by the addition of a low amount of silver nanoparticles

Electrically and thermally conductive high‐density polyethylene composites filled with hybrid fillers, multiwall carbon nanotubes (MWCNTs) and silver nanoparticles (Ag‐NPs), have been prepared in the melt state. The investigation of their electrical and thermal conductivities while comparing with high‐density polyethylene/MWCNT binary composites shows that the addition of only 3 vol% of Ag‐NPs does not reduce the electrical percolation threshold (P_c) that remains as low as 0.40 vol% of MWCNTs but leads to an increase in the maximum dc electrical conductivity of PE/MWCNT composites by two orders of magnitudes. Moreover, the association of both Ag‐NPs and carbon nanotube particles improved our composite's thermal conductivity. Copyright © 2014 John Wiley & Sons, Ltd.     

Green conversion of a three‐dimensional organometallic coordination polymer to a three‐dimensional organometallic supramolecular polymer upon mechanochemical 2‐aminopyridine addition

Green conversion of three‐dimensional organometallic [Ag₂(μ₆‐tp)]_n ( 1 ) coordination polymer (CP) nanosheets, prepared by sonochemical procedure, to three‐dimensional organometallic [Ag₂(μ₄‐tp)(apy)₂]_n ( 2 ) (where H₂tp = terephthalic acid and apy = 2‐aminopyridine) CP nanoparticles has been observed upon solid‐state mechanochemical reaction of compound 1 with 2‐aminopyridine. The AgO₃ Ag ···C₆ coordination sphere of silver ion in 1 changed to NO₂ Ag ···C coordination sphere in 2 during this mechanochemical addition. These samples were characterized by infrared spectroscopy, thermogravimetric and differential thermal analyses, X‐ray powder diffraction and scanning electron microscopy.