Search

The authors report Myxobacteria virescens (M. virescens) mediated synthesis of silver nanoparticles (AgNPs) and its efficacy against Staphylococcus aureus (ATCC‐33591), Salmonella typhi (ATCC‐51812), Escherichia coli (E. coli) (ATCC‐14948), Klebsiella pneumoniae (MTCC‐4030) and Pseudomonas aeruginosa (MTCC‐4673). The organism exhibiting resistance to various antibiotics showed remarkable sensitivity, when used in combination of antibiotics and AgNPs. Antimicrobial property of AgNPs is playing a significant role in medicine and food storage. In this study, they have used M. virescens for the synthesis of AgNPs, which were characterised by using UV‐Vis spectrophotometer, nano‐particles tracking and analysis, zeta potential, Fourier transform infrared spectroscopy, X‐ray diffraction and transmission electron microscopy. Synthesised AgNPs were impregnated into paper by three different methods, i.e. glass rod method (without binder), glass rod method (with binder) and direct synthesis of AgNPs on paper. Nanoparticles synthesis on paper showed the significant antimicrobial activity against Staphylococcus aureus (ATCC‐33591), Salmonella typhi (ATCC‐51812), E. coli (ATCC‐14948), Klebsiella pneumoniae (MTCC‐4030) and Pseudomonas aeruginosa (MTCC‐4673). Paper impregnated with AgNPs was used for wrapping of fruits (apples) which increases their shelf life up to 15 days. This study demonstrates a new method for wrapping of fruits, which increases the shelf life of apples. [ABSTRACT FROM AUTHOR]

The capacity of Ag nanoparticles to destroy various micro‐organisms makes it one of the most powerful antimicrobial agents, an attractive feature against antibiotic resistant bacteria. Here, a simple method to develop coating of colloidal silver on paper using a biological method is presented. The coated paper was studied by scanning electron microscopy, X‐ray diffraction technique and atomic absorption spectroscopy. The antibacterial activity of the coated paper against Escherichia coli and Staphylococcus aureus was measured by agar diffusion method. This study shows the potential use of the coated paper as a food antimicrobial packing material for longer shelf life. [ABSTRACT FROM AUTHOR]

A facile photoreduction strategy to attach silver nanoparticles on filter paper (AgNPs@FP) to form surface-enhanced Raman scattering (SERS) substrate array was proposed and examined. As prepared, SERS substrate array was applied to detect low concentration of adenine and other nucleobases in aqueous solutions. In addition, the formed SERS substrate array allows mass analysis of aqueous samples with a requirement of only 10 μL in sample volume. To optimize and understand the parameters in preparations, factors such as the concentrations of citrate and silver nitrate, photoreduction time, and concentration of sodium hydroxide were varied and examined. Para-nitrothiophenol was used as a Raman probe molecule and scanning electron microscope (SEM) images of the substrates were used to explore the influences of experimental factors in the preparation of SERS array. Results indicated that silver ions could be effectively reduced and deposited in/on filter paper with the presence of citrate. The formed AgNPs@FP exhibits a three-dimensional structure as the particles formed on and beneath the surface of the cellulosic fibers could be observed. Deposition of analyte on restricted substrate array rendered reproducible results and the spot-to-spot SERS intensity varied within 8%. At optimal conditions, the substrate enhancement factor approached 107. We demonstrated that the filter paper-based SERS substrates can be used as a suitable tool for biological analysis, and a limit of detection better than 160 nM was obtained in detection of adenine molecules in aqueous solutions with a linear range up to 20 μM. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Silver nanoparticles have shown inhibitory capabilities and its use in battling viral infections are strengthened by its potent antibacterial activity. Notably, since it directly affects antiviral efficacy, the proper choice of synthesis process for making silver nanoparticles is a vital element to be taken into consideration. The synthesis of silver nanoparticles for the treatment of viral and bacterial infections involves creating silver particles at the nanoscale with unique antimicrobial properties. Various methods exist for synthesizing silver nanoparticles, including chemical reduction, green synthesis, and physical methods. Chemical reduction involves using reducing agents to convert silver ions into silver nanoparticles. Green synthesis employs reducing agents in an environmentally friendly manner. Physical methods rely on techniques such as laser ablation or thermal evaporation to produce silver nanoparticles. In order to provide technological guidance for choosing antiviral silver nanoparticle manufacturing methods, this paper introduces and explores alternative synthesis methods for creating silver nanoparticles. [ABSTRACT FROM AUTHOR]

Anisotropic nanoparticles are a potential foundation for emerging materials engineering having anomalous properties often to an extraordinary degree‐enabling widespread new applications. In the bottom‐up approach, isotropic nanoparticles are formed by self‐assembly following the basic packing rule but lack directional interaction. On the other hand, anisotropic nanoparticles involve complex programmability having directional interaction and thus become of utmost interest in science and technology. In this paper, the anisotropic plasmonic effects in silver (Ag) nanoparticles under microwave‐induced plasma‐in‐liquid‐assisted decomposition of saccharides and di‐saccharides following the green chemistry process are investigated. The effect of microwave power, irradiation time, and relative chemical composition has been investigated in detail using extinction spectroscopy and Mie theory. The relationship between extinction curve shape parameter (S) and Mie theory has been established. The extinction spectroscopy and transmission electron microscopy (TEM) study confirm the existence of anisotropic plasmonic effects in Ag nanoparticles following two‐generation growth mechanisms having an average particle size of 2 and 32 nm. This technique offers rapid (20–40 sec) bulk production and is cost/energy effective than the conventional synthesis route. [ABSTRACT FROM AUTHOR]

Synthetic dyes are one of the major classes of pollutant released in the environment by industries such as textile, paper, leather, rubber, cosmetics, pharmaceutical etc. They are known carcinogen and extremely hazardous to human, plant and aquatic life. Conventional chemical, physical and biological methods used for treatment of industrial effluent are costly, time‐consuming and produces secondary waste. Silver nanoparticle and nanocomposite‐based catalyst are very effective in decomposition of dyes due to their high surface area‐to‐volume ratio, stability and biocompatibility. The degradation reaction takes place in presence of light (photocatalytic) or in presence of a reagent such as NaBH4 or H2O2.Of various methods of silver nanoparticle/nanocomposite synthesis, green synthesis has been quite popular in recent times due to ease in synthesis and sustainability factor. In this review, current state of knowledge about application of green synthesized silver nanoparticles /nanocomposites in degradation of synthetic dyes and other organic pollutant have been summarized. Moreover, the article also emphasizes on the mechanism of degradation, the kinetic parameters and optimum treatment conditions. [ABSTRACT FROM AUTHOR]

This paper describes the utilization of waste from the argentometric determination of chloride in a chemistry teaching laboratory as a source of silver for the synthesis of p‐hydroxybenzoic acid capped silver nanoparticles (AgNPs). All white and red‐brick precipitates in the waste were first separated from the liquid and converted to silver chloride precipitate by washing the precipitates using hydrochloride acid 0.1 M. The silver chloride precipitate was then converted to diammineargentate complex ion by dissolving it into an ammonia solution. The conversion was successfully conducted by using 50 moles of ammonia for every mole of silver chloride. The formation of AgNPs was optimum by applying diammineargentate complex ion and p‐hydroxybenzoic acid solutions at a molar ratio of 1 : 10. The formed AgNPs showed a yellow color and absorption peak at around 420 nm with an average particle size of 26.4 nm. The as‐synthesized AgNPs were stable at least 16 weeks of storage, indicating that p‐hydroxybenzoic acid did not only act as a reducing agent but also play a role as a capping agent. [ABSTRACT FROM AUTHOR]

This paper details the selective optical, fluorescent and electrochemical detection of Zn2+ among various divalent metal ions in aqueous solution by the green synthesized silver nanoparticles (AgNP) using the fresh extract of Myristica fragrans (MF) with the aid of microwave energy. The synthesized silver nanoparticles stabilized with MF were analysed using UV-vis., Fourier-transform infrared (FT-IR), X-ray diffraction (XRD), and transmission electron microscopy (TEM) techniques. Due to the effective complexation between silver nanoparticles and metal ions, absorbance of AgNP-MF diminished with increasing concentration of Zn2+. This is visually identified through the color changes. Fluorescent sensing studies involved the changes in fluorescent intensity of AgNP-MF in the presence of Zn2+. Electrochemical sensing of Zn2+ was carried through cyclic and differential pulse voltammetric techniques using AgNP-MF modified platinum electrode (AgNP-MF􀀀 Pt). The developed electrochemical sensor showed a limit of detection (LOD) of 0.6148 μM and its good sensing ability was checked for the detection of Zn2+ in environmental water samples. Recoveries of Zn2+ in the various real water samples were obtained in the range from 100.2% to 100.6%. The multifunctional utility of the AgNP-MF as a catalyst towards the reduction of two environmentally toxic contaminants such as o/p-nitroanilines through NaBH4 was also evaluated. The complete degradations were achieved within few minutes and the reactions followed pseudo first order kinetics. The effect of catalytic dosage on the rate of reduction reactions was also studied. [ABSTRACT FROM AUTHOR]

This paper deals with the electrical properties of polydimethylsiloxane nanocomposites filled with Ag nanoparticles (AgNPs) of different sizes. The measurements were carried out over a very broad range of frequencies (20 Hz‐40 GHz), and the results showed that the percolation threshold in the composites is close to 20 vol% and that it is almost independent of particle size. The observed critical exponents reasonably agree with the theoretical values. Above the percolation threshold, the values of dielectric permittivity and electrical conductivity are quite high, ε′ ≈ 107 and σ ≈ 1 S/cm at room temperature and frequency of 129 Hz (which is close to our low frequency limit). The dielectric permittivity of composites decreases strongly with frequency, especially in the microwave range, while the frequency behavior of conductivity strongly depends on the concentration of nanoparticles. Nevertheless, the electrical conductivity and the dielectric permittivity remain high at microwaves (0.1 S/m and 10, respectively), for composites with AgNPs of size 80 to 100 nm at a concentration of 30 vol%. [ABSTRACT FROM AUTHOR]

This paper presents the first worldwide inter-laboratory comparison of small-angle X-ray scattering (SAXS) for nanoparticle sizing. The measurands in this comparison are the mean particle radius, the width of the size distribution and the particle concentration. The investigated sample consists of dispersed silver nanoparticles, surrounded by a stabilizing polymeric shell of poly(acrylic acid). The silver cores dominate the X-ray scattering pattern, leading to the determination of their radius size distribution using (i) the generalized indirect Fourier transformation method, (ii) classical model fitting using SASfit and (iii) a Monte Carlo fitting approach using McSAS. The application of these three methods to the collected data sets from the various laboratories produces consistent mean number- and volume-weighted core radii of Rn = 2.76 (6) nm and Rv = 3.20 (4) nm, respectively. The corresponding widths of the lognormal radius distribution of the particles were σn = 0.65 (1) nm and σv = 0.71 (1) nm. The particle concentration determined using this method was 3.0 (4) g l−1 or 4.2 (7) × 10−6 mol l−1. These results are affected slightly by the choice of data evaluation procedure, but not by the instruments: the participating laboratories at synchrotron SAXS beamlines, commercial and in-house-designed instruments were all able to provide highly consistent data. This demonstrates that SAXS is a suitable method for revealing particle size distributions in the sub-20 nm region (at minimum), out of reach for most other analytical methods. [ABSTRACT FROM AUTHOR]

This paper presents a new approach in modeling the particle dispersion structure of micro-nano silver particles of conductive adhesive considering the van der Waals interaction energy. As there are many possible combinations of hybrid micro-nano system, this work only focuses on two types of micro-nanoparticles interconnecting; the first is single microparticles with nanoparticles, and the second is two microparticles with nanoparticles. The particle coordinates were imported into cad software to produce 3D geometry, and finally, the finite element method was used to determine the electrical conductivity. The experimental data were taken at the volume ratios of the hybrid system using micro-sized and nano-sized particles at 50 : 50 for validation purpose. As a result, the predicted electrical conductivity shows a good agreement with experiment data with error less than 4%. Simulation result gives a value 1.46 × 101, 9.18, 6.86 and 4.54 S/cm for single-micro/50 nanoparticles, single-micro/75 nanoparticles, single-micro/100 nanoparticles and single-micro/125 nanoparticles, respectively. The electrical conductivity is optimum in a particular nano-size number as it could settle interconnection path in shorter particle chain. The electrical conductivity show decreasing by increasing particle network chain due to nano-particles added. © 2015 Curtin University of Technology and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Sphingomonas is a novel and abundant microbial resource for biodegradation of aromatic compounds. It has great potential in environment protection and industrial production. The use of microorganisms for the synthesis of nanoparticles is in the limelight of modern nanotechnology, since it is cost effective, non‐toxic and friendly to the ever‐overwhelmed environment. In this paper, the biosynthesis of silver nanoparticles (AgNPs) using Sphingomonas paucimobilis sp. BDS1 under ambient conditions was investigated for the first time. Biosynthesised AgNPs were characterised with powder ultraviolet–visible spectroscopy, X‐ray diffraction, Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy and energy dispersive X‐ray spectroscopy. The overall results revealed that well‐dispersed face centred cubic spherical AgNPs in the range of 50–80 nm were produced on the surface of Sphingomonas paucimobilis sp. BDS1, after challenging pure wet biomass with silver nitrate solution. This suggests that the capture of silver ions may be a complex process of physical and chemical adsorption and the proteins on the surface of the bacteria may play the role of reduction and stabilising agent with regard to the result of FTIR. [ABSTRACT FROM AUTHOR]

Bulk hierarchical anatase-titania/cellulose composite sheets were fabricated by subjecting an ultrathin titania gel film pre-deposited filter paper to a solvo-co-hydrothermal treatment by using titanium butoxide as the precursor to grow anatase-titania nanocrystallites on the cellulose nanofiber surfaces. The titanium butoxide specie is firstly absorbed onto the nanofibers of the cellulose substance through a solvothermal process, which was thereafter hydrolyzed and crystallized upon the subsequent hydrothermal treatment, leading to the formation of fine anatase-titania nanoparticles with sizes of 2-5 nm uniformly anchored on the cellulose nanofibers. The resulting anatase-titania/cellulose composite sheet shows a significant photocatalytic performance towards degradation of a methylene blue dye, and introduction of silver nanoparticles into the composite sheet yields an Ag-NP/anatase-titania/cellulose composite material possessing excellent antibacterial activity against both Gram-positive and Gram-negative bacteria. [ABSTRACT FROM AUTHOR]

Purpose: Noble metal nanoparticles have found several medical applications in the areas of radiation detection; x-ray contrast agents and cancer radiation therapy. Based on computational methods, many papers have reported the nanoparticle effect on the dose deposition in the surrounding medium. Here the authors report experimental results on how silver and gold nanoparticles affect the dose deposition in alanine dosimeters containing several concentrations of silver and gold nanoparticles, for five different beam energies, using electron spin resonance spectroscopy (ESR). Methods: The authors produced alanine dosimeters containing several mass percentage of silver and gold nanoparticles. Nanoparticle sizes were measured by dynamic light scattering and by transmission electron microscopy. The authors determined the dose enhancement factor (DEF) theoretically, using a widely accepted method, and experimentally, using ESR spectroscopy. Results: The DEF is governed by nanoparticle concentration, size, and position in the alanine matrix. Samples containing gold nanoparticles afford a DEF higher than 1.0, because gold nanoparticle size is homogeneous for all gold concentrations utilized. For samples containing silver particles, the silver mass percentage governs the nanoparticles size, which, in turns, modifies nanoparticle position in the alanine dosimeters. In this sense, DEF decreases for dosimeters containing large and segregated particles. The influence of nanoparticle size-position is more noticeable for dosimeters irradiated with higher beam energies, and dosimeters containing large and segregated particles become less sensitive than pure alanine (DEF < 1). Conclusions: ESR dosimetry gives the DEF in a medium containing metal nanoparticles, although particle concentration, size, and position are closely related in the system. Because this is also the case as in many real systems of materials containing inorganic nanoparticles, ESR is a valuable tool for investigating DEF. Moreover, these results alert to the importance of controlling the sizeposition of nanoparticles to enhance DEF. [ABSTRACT FROM AUTHOR]

It is been widely reported that plasmonic effects in metallic nanomaterials can enhance light trapping in organix solar cells (OSCs). However, typical nanoparticles (NP) of high quality (i.e., mono-dispersive) only possess a single resonant absorption peak, which inevitably limits the power conversion efficiency (PCE) enhancement to a narrow spectral range. Broadband plasmonic absorption is obviously highly desirable. In this paper, a combination of Ag nanomaterials of different shapes, including nanoparticles and nanoprisms, is proposed for this purpose. The nanomaterials are synthesized using a simple wet chemical method. Theoretical and experimental studies show that the origin of the observed PCE enhancement is the simultaneous excitation of many plasmonic low- and high-order resonances modes, which are material-, shape-, size-, and polarization-dependent. Particularly for the Ag nanoprisms studied here, the high-order resonances result in higher contribution than low-order resonances to the absorption enhancement of OSCs through an improved overlap with the active material absorption spectrum. With the incorporation of the mixed nanomaterials into the active layer, a wide-band absorption improvement is demonstrated and the short-circuit photocurrent density ( Jsc) improves by 17.91%. Finally, PCE is enhanced by 19.44% as compared to pre-optimized control OSCs. These results suggest a new approach to achieve higher overall enhancement through improving broadband absorption. [ABSTRACT FROM AUTHOR]

This paper describes the synthesis, characterization, and applications of a mesoporous silica/ multiwalled carbon nanotube (SiO2/MWCNT) hybrid material, which was obtained by a sol-gel process and decorated with silver nanoparticles (AgNPs) ranging in size from 5 to 8 nm. The AgNPs were prepared directly on the surface of the SiO2/MWCNTs material by using N, N-dimethylformamide (DMF) as the reducing agent, and the resulting material was designated Ag/SiO2/MWCNT. The Ag/SiO2/MWCNT material was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HR-TEM), and X-ray photoelectron spectroscopy (XPS). A glassy carbon electrode, modified with the Ag/SiO2/MWCNT material, was used in the development of a sensitive electrochemical sensor for the determination of hydroquinone and catechol in the presence of resorcinol by squarewave voltammetry. Well-defined and separate oxidation peaks were observed in phosphate buffer solution (PBS) at pH 7. The Ag/SiO2/MWCNT-modified electrode exhibited high sensitivity for the simultaneous determination of hydroquinone and catechol in the presence of resorcinol, and the limits of detection for hydroquinone and catechol are 0.0117 and 0.0121 μ M, respectively. No significant interference was seen for 2,6-dichloroindophenol, phenol, 4-nitrophenol, and nitrite ions in the detection of dihydroxybenzenes. Our study demonstrates that the resultant Ag/SiO2/MWCNT-modified electrode can be used for hydroquinone and catechol detection in the presence of resorcinol and other potentially interfering materials in river water samples. [ABSTRACT FROM AUTHOR]

In this paper, it is demonstrated that aggregation of Ag nanoparticles dispersed in pure water is mediated by strong dipole-dipole interactions produced by light irradiation. Expecting the effect of attractive forces caused by the dipole moments arising from localized surface plasmon resonance, an irradiation source based on the spectrum of the scattering cross section calculated from the geometric characteristics and dielectric constants of Ag and pure water is employed. In this process, it is possible to modulate the optical color of the dispersion by controlling the degree of aggregation of particles using the irradiation time without a chemical reaction. [ABSTRACT FROM AUTHOR]

Heterogeneous Catalysis Metal – support interactions (MSIs) and particle size are important for catalytic reactions. In their Full Paper on page 15746 ff., H. Yamashita and co ‐ workers report silver nanoparticles supported on CeO2 ‐ SBA ‐ 15 with tunable particle size and MSIs, owing to the preparation by microwave irradiation, which gives a strong charge polarization of the CeO2 clusters. Silver nanoparticle size and MSIs were predominantly responsible for the high turnover frequency in ammonia borane dehydrogenation and 4 ‐ nitrophenol reduction. [ABSTRACT FROM AUTHOR]

Green chemistry‐based biowaste has been taken attention toward new components for many applications especially in dermatophytes of animals and humans. The main goal of this study is to assist the synthetic pathways; clean and large‐scale synthesis of silver nanoparticles is achieved as a promising alternative green technique with high efficiency, simplicity and less hazardous waste based on agro‐waste of banana peels extract powder. The preparation of silver nanoparticles is directly via solid‐state reaction and the liquid one based on the natural agro‐waste of banana peels under specific conditions for treating ringworm in pets. Ultraviolet (UV)‐visible spectroscopy, Fourier transform infrared spectroscopy (FT‐IR), and transmission electron microscope (TEM) were used to prove the prepared nanoparticles. A total of 30 samples from pets (dogs and cats) were subjected to mycological examination. Ten (33.3%) were culture positive, and 100% of the positive samples were Microsporum canis. In vitro antifungal activity against M. canisisolates using both the disc diffusion and the broth microdilution methods was evaluated. The significant results for solid silver nanoparticles (Ags1 and Ags2) than liquid Ag NPs (AgL) with p < 0.05 compared with itraconazole were observed. This biomaterial from waste could be used as a fast, simple, eco‐friendly, and efficient method to prepare Ag NPs on solid that can be applied in the veterinary sector against ringworm. [ABSTRACT FROM AUTHOR]