Biocidal activity of nanocrystalline silver powders and particles

While the activity of the SMAD powders is lower than that of pure silver nitrate, it has the ability to kill bacteria very effectively and over long periods of time.     

Cellulose fibers modified with silver nanoparticles

Cellulose fibers modified with silver nanoparticles were prepared using N-methylmorpholine-N-oxide as a direct solvent and analyzed in this study. Silver nanoparticles were generated as a product of AgNO₃ reduction by means of three methods under varying light conditions (daylight and darkroom). Influence of generating conditions on the size, the type and the number weighting of created nanoparticles was examined. Dynamic Light Scattering technique (DLS) was used for determination of those parameters. DLS analysis showed that the best method, i.e. the one that allowed the generation of the greatest number of silver nanoparticles with the smallest diameter and the smallest agglomerates, was incubation of cellulose pulp with AgNO₃ in a darkroom for 24 h. Mechanical and hydrophilic properties of all obtained fibers were also determined. Results showed that the method of silver nanoparticles generation did not influence significantly mechanical and hydrophilic properties of the modified fibers, because in all cases only small decreases of the studied parameters were observed.     

One-pot synthesis of luminol functionalized silver nanoparticles with chemiluminescence activity for ultrasensitive DNA sensing

A novel one-pot method for the synthesis of chemiluminescence functionalized AgNPs has been reported and an ECL sensor has been developed for the detection of M. tuberculosis DNA.     

Toward a comprehensive understanding of textiles functionalized with silver nanoparticles

This article provides a comprehensive understanding of development of textiles functionalized with silver nanoparticles (AgNPs). There are three established methods to fabricate textiles functionalized with AgNPs, namely, solution‐immersion, layer‐by‐layer deposition, and sonochemical. In addition, several textile types such as cotton, wool, polyester, silk, cotton/polyester blend, polyamide, and regenerated cellulose have been used for the fabrication. The AgNP deposition mechanism on textiles is mainly due to electrostatic interaction between AgNPs and textile constituents. It was exhibited that the deposition of AgNPs on textiles can transform their textiles colors. In addition, it was demonstrated that the deposition of AgNPs on textiles is not permanent, particularly against washing treatment. Textiles modified with AgNPs have several promising applications such as antibacterial, antifungal, catalyst, electronic devices, water treatment, sun protection, air treatment, and surface‐enhanced Raman scattering, which are comprehensively discussed in this article. Future challenges in fabricating textiles functionalized with AgNPs remain on how this can be carried out to improve long‐term stabilization of AgNPs on textiles to achieve their permanent deposition by employing greener approaches.     

Antibacterial thermoplastic polyurethane electrospun fiber mats prepared by 3-aminopropyltriethoxysilane-assisted adsorption of Ag nanoparticles

Antibacterial thermoplastic polyurethane(TPU) electrospun fiber mats were prepared by adsorption of Ag nanoparticles(Ag NPs) onto TPU/3-aminopropyltriethoxysilane(APS) co-electrospun fiber mats from silver sol. The use of APS can functionalize TPU fibers with amino groups, facilitating the adsorption of Ag NPs. The effects of p H of silver sol and APS content on Ag NP adsorption and antibacterial activity were investigated. Ag NP adsorption was evidenced by TEM, XPS and TGA. Significant Ag NP adsorption occurred at p H = 3-5. The main driving force for Ag NP adsorption is electrostatic interaction between ―NH3~+ of the fibers and ―COO-derived from the ―COOH group capped on the surfaces of Ag NPs. The antibacterial activity of the Ag NP-decorated TPU/APS fiber mats was investigated using both gram-negative Escherichia coli and gram-positive Bacillus subtilis. The antibacterial rate increases with increasing APS content up to 5% where the antibacterial rates against both types of bacteria are over 99.9%.     

Preparation and antibacterial activity of electrospun chitosan/poly(ethylene oxide) membranes containing silver nanoparticles

Fairly uniform chitosan (CS)/poly(ethylene oxide) (PEO) ultrafine fibers containing silver nanoparticles (AgNPs) were successfully prepared by electrospinning of CS/PEO solutions containing Ag/CS colloids by means of in situ chemical reduction of Ag ions. The presence of AgNPs in the electrospun ultrafine fibers was confirmed by X-ray diffraction patterns. The AgNPs were evenly distributed in CS/PEO ultrafine fibers with the size less than 5 nm observed under a transmission electron microscope. X-ray photoelectron spectroscopy suggested that the existence of Ag―O bond in the composite ultrafine fibers led to the tight combination between Ag and CS. Evaluation of antimicrobial activities of the electrospun Ag/CS/PEO fibrous membranes against Escherichia coli showed that the AgNPs in the ultrafine fibers significantly enhanced the inactivation of bacteria.     

Biomedical applications of electrospun polycaprolactone fiber mats

Polycaprolactone (PCL) is a biodegradable polyester emerging into biomedical applications because of its biodegradability, biocompatibility, chemical stability, thermal stability and good mechanical properties. Electrospinning is a versatile method using electrostatic forces for fabricating continuous ultrafine fibers that offer various advantages such as high surface area and high porosity. Thus, this method has gained interest for use in many fields, especially biomedical fields. This review focuses on researches and studies in electrospinning, PCL, electrospinning of PCL and also biomedical applications of the electrospun PCL fiber mats. Copyright © 2016 John Wiley & Sons, Ltd.     

Superhydrophobic behaviour of plasma modified electrospun cellulose nanofiber-coated microfibers

In this work, a method is presented for production of a textile cellulose fiber with non-wetting properties suitable for applications ranging from wound care and tissue engineering to clothing and other textile applications. Non-wettability is achieved by coating a textile cellulose microfiber with electrospun cellulose nanofibers, creating a large and rough surface area that is further plasma treated with fluorine plasma. High surface roughness and efficient deposition of covalently bound fluorine groups results in the fiber exhibiting non-wetting properties with contact angle measurements indicating superhydrophobicity (>150° water contact angle). It is an environmentally friendly method and the flexibility of the electrospinning process allows for careful design of material properties regarding everything from material choice and surface chemistry to fiber morphology and fiber assembly, pointing to the potential of the method and the developed fibers within a wide range of applications.     

Transport properties of electrospun nylon 6 nonwoven mats

In this work, we evaluate the physical properties of nylon 6 nonwoven mats produced from solutions with formic acid. Nonwoven electrospun mats from various solutions with different concentration are examined regarding their morphology, pore size, surface area, and gas transport properties. Each nonwoven mat with average fiber diameters from 90 to 500 nm was prepared under controlled electrospinning process parameters. From the results, it was observed that the fiber diameter was strongly affected by the polymer concentration (polymer viscosity). In additional the results showed that the pore size, Brunauer-Emmett-Teller (BET) surface area, and gas transport property of electrospun nylon 6 nonwoven mats were affected by the fiber diameter.     

Characterization of magnetic nanoparticles modified with thiol functionalized PAMAM dendron for DNA recovery

Magnetic nanoparticles (MNPs) modified with the thiol functionalized polyamidoamine (PAMAM) dendron were synthesized to estimate their DNA recovery capabilities. Aminosilane-modified MNPs and MNPs surrounded by a phospholipid (distearoylphosphatidylethanolamine (DSPE)) bilayer were used as core particles. Cystamine-core PAMAM dendrimers were reduced by dithiothreitol to dendron thiols and chemically conjugated to the core particles. Characterization of the synthesis revealed an increase of the surface amine charge from generation 1 (G1) to G6, starting with an aminosilane initiator. Particle size distribution analysis indicated that G6 PAMAM-modified MNPs exhibited monodispersity in an aqueous solution. G6 PAMAM-MNPs and G6 PAMAM-PE-MNPs synthesized by the proposed method have equivalent DNA recovery abilities to PAMAM-MNPs prepared by the conventional divergent synthesis method. In optimized conditions, 96% of λDNA was recovered using G6 PAMAM-PE-MNPs. Therefore, the method for preparing PAMAM-MNPs and PAMAM-PE-MNPs proposed in this study will be a novel approach for producing DNA carriers for efficient DNA purification by magnetic separation.     

Extracellular biosynthesis of functionalized silver nanoparticles by strains of Cladosporium cladosporioides fungus

In the present investigation, we report the extracellular biosynthesis of silver nanoparticles (AgNP) employing the fungus Cladosporium cladosporioides. The extracellular solution of C. cladosporioides was used for the reduction of AgNO(3) solution to AgNP. The present study includes time dependent formation of AgNP employing UV-vis spectrophotometer, size and morphology by employing TEM (transmission electron microscopy), structure from powder X-ray diffraction (XRD) technique and understanding of protein-AgNP interaction from Fourier transform infrared (FT-IR) spectroscopy. The AgNP were 10-100nm in dimensions as measured by TEM images.     

Simple colorimetric detection of dopamine using modified silver nanoparticles

Dopamine(DA) plays an important role in health and peripheral nervous systems. Colorimetric detection of DA has the advantage of color change and simplicity in operation and instrumentation. Herein, we report a highly sensitive and selective colorimetric detection of DA by using two specific ligands modified Ag nanoparticles, where the DA molecules can make dual recognition with high specificity. The colloidal suspension of modified Ag nanoparticles was agglomerated after interacting with DA, while the color of Ag nanoparticles suspension changed from yellow to brown, arising from the interparticle plasmon coupling during the aggregation of Ag nanoparticles. The modified Ag nanoparticles suspension and agglomeration were confirmed by transmission electron microscope images. The optical properties behind the color change were thoroughly investigated by using UV-Vis and Raman techniques. The changes in p H, zeta potential, particle size and surface charge density by adding DA were also determined by using dynamic light scattering measurements. The detection limits of modified Ag probes for DA was calculated to be 6.13′10~(-6) mol L~(-1)(S/N=2.04) and the correlation co-efficient was determined to be 0.9878. Because of the simplicity in operation and instrumentation of the colorimetric method, this work may afford a feasible, fast approach for detecting and monitoring the DA levels in physiological and pathological systems.     

Gold and silver nanoparticles functionalized with known numbers of oligonucleotides per particle for DNA detection

The biospecificity of gold and silver nanoparticles, functionalized with known numbers of oligonucleotides, is demonstrated in colorimetric microbead assays for complementary and mismatch sequences.     

A direct synthetic approach to vanadium pentoxide nanofibres modified with silver nanoparticles

Small amounts of silver ions have been found to significantly enhance the growth rate of vanadium pentoxide (V(2)O(5)) nanofibres in aqueous solution at room temperature, yielding fibres with lengths of several micrometers within a few days; the V(2)O(5) fibres are decorated with silver nanoparticles with sizes in the range of 5-15 nm, which opens perspectives for applications in chemical sensors.     

Degradation patterns and surface wettability of electrospun fibrous mats

Degradation profiles and surface wettability are critical for optimal application of electrospun fibrous mats as drug carriers, tissue growth scaffolds and wound dressing materials. The effect of surface morphologies and chemical groups on surface wettability, and the resulting matrix degradation profiles were firstly assessed for electrospun poly(d,l-lactide) (PDLLA) and poly(d,l-lactide)-poly(ethylene glycol) (PELA) fibers. The air entrapment between the fiber interfaces clarified the effects of various surface morphologies on the surface wettability. Chemical groups with lower binding energy were enriched on the fiber surface due to the high voltage of the electrospinning process, and a surface erosion pattern was detected in the degradation of electrospun PDLLA fibers, which was quite different from the bulk degradation pattern for other forms of PDLLA. Contributed by the hydrophilic poly(ethylene glycol) segments, the degradation of electrospun PELA fibers with hydrophobic surface followed a pattern different from surface erosion and typical bulk degradation.     

纳米银修饰电极差分脉冲伏安法测定盐酸金霉素

建立了快速测定盐酸金霉素(CTC)的方法。通过NaBH4还原法制备纳米银(AgNPs)溶胶,并利用X射线衍射和紫外-可见光谱进行表征。将制备好的AgNPs滴涂到玻碳电极表面制备修饰电极(AgNPs/GCE),研究了CTC在AgNPs/GCE上的电化学行为及伏安法测定,优化了缓冲溶液和pH等检测条件。结果表明,CTC在pH 3.3的柠檬酸-NaOH-HCl缓冲溶液中检测效果最佳。CTC在AgNPs/GCE上发生2个电子和2个质子的不可逆电化学氧化反应,且反应受吸附控制。最佳条件下,CTC的氧化峰电流与其浓度呈现良好的线性关系,线性范围为0.5~100μmol/L,检出限为0.14μmol/L。该修饰电极可用于河水样品检测。     

Gas chromatographic properties of methacrylate polymers modified by silver nanoparticles

Russian Chemical Bulletin - The gas chromatographic properties of the porous methacrylate polymers, copolymers of 2,3-epoxypropyl methacrylate (2,3-EPMA) and ethylenedimethacrylate (EDMA), modified...     

Silica coating of silver nanoparticles using a modified Stober method

Silver nanoparticles prepared through a borohydride-reduction method were directly coated with silica by means of a seeded polymerization technique based on the Stober method. Various amine catalysts were used for initialization of a sol-gel reaction of TEOS with no need for a prior surface modification. Use of dimethylamine (DMA) as a catalyst was found to be necessary to obtain a proper coating. The silica shell thickness was varied from 28 to 76 nm for TEOS concentrations of 1-15 mM at 11.1 M water and 0.8 M DMA. The optical spectra of the core-shell silver-silica composite particles show a qualitative agreement with predictions by Mie theory.     

Concentration of polycyclic aromatic hydrocarbons by chemically modified silver nanoparticles

The ability of silver nanoparticles stabilized by cetyltrimethylammonium bromide (CTAB) to concentrate polycyclic aromatic hydrocarbons (PAHs) from aqueous solutions was shown. It was found that fixed PAH molecules are capable of acting as electronic energy donors and of generating sensibilized fluorescence of silver nanoparticles. It was shown by spectral-luminescent investigations of dilute PAH solutions (5 × 10⁻¹⁰−1 × 10⁻⁶ g/ml) in the presence of silver nanoparticles (∼0.7 vol %) that the concentration of PAH molecules from solutions occurs due to its sorption on hydrocarbon CTAB radicals in close contact to the surface of metallic silver. On the basis of the spectral data, the sorption isotherms were obtained and the values of extraction degree and partition coefficients for naphthalene, phenanthrene, anthracene, chrysene, pyrene, and 3,4-benzopyrene were calculated. It was found that the degree of extraction values of the investigated PAHs fall within the range of 73–98%, the partition coefficients (logD) ∼ 6, and the concentration coefficients ∼10⁵.