Fabrication of antibacterial silver nanoparticle‐modified chitosan fibers using Eucalyptus extract as a reducing agent

Green chemical method could be a promising route to achieve large scale synthesis of nanostructures for biomedical applications. Here, we describe a green chemical synthesis of silver nanoparticles (Ag NPs) on chitosan‐based electrospun nanofibers using Eucalyptus leaf extract. A series of silver salt (AgNO₃) amounts were added to a certain composition of chitosan/polyethylene oxide aqueous acetic acid solution. The solutions were then electrospun to obtain nanofibrous mats and then, morphology and size of nanofibers were analyzed by scanning electron microscopy (SEM). Incubation of AgNO₃‐containing mats into Eucalyptus leaf extract led to the formation of Ag NP clusters with average diameter of 91 ± 24 nm, depicted by SEM and transmission electron microscopy. Surface enhanced Raman spectroscopy also confirmed formation of Ag NPs on the nanofibers. The mats also showed antimicrobial activity against Escherichia coli and Staphylococcus aureus bacteria with bigger inhibition zone for extract‐exposed mats against S. aureus. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42133.     

Antibacterial Ag containing core-shell polyvinyl alcohol-poly (lactic acid) nanofibers for biomedical applications

Core-shell-structured polyvinyl alcohol (PVA)-poly (lactic acid) (PLA) nanofibers combining the hydrophilic trait of PVA and the biocompatibility of PLA were produced using coaxial electrospinning. This allowed the incorporation of AgNO₃ in the PVA core of the distinct fibers as shown through transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). Scanning electron microscopy (SEM) showed relatively uniform and bead-free fibers with smooth surfaces. Ag-containing fibers show significantly decreased diameters compared with Ag-free samples as a result of the increased conductivity of the spinning solutions with increasing amounts of AgNO₃. In a postsynthetic treatment, the AgNO₃ was reduced forming silver nanoparticles (Ag NPs). Ag NPs of 45 to 90 nm size were located in the PVA core but also on the surface of the core-shell fibers and as individual, agglomerated, and polymer-coated particles of 100-200 nm. Powder X-ray diffraction (PXRD), energy dispersive X-ray spectroscopy (EDX), and UV-vis absorption spectroscopy confirmed the increasing amounts of Ag in the core-shell fibers when using increasing amounts of AgNO₃ in the spinning solutions. The antibacterial activity of the nanofiber mats against two prokaryotes Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) increased with increasing amounts of Ag, as expected and produces inhibition zones of 1 to 2 mm.     

In situ-prepared composite materials of PEDOT: PSS buffer layer-metal nanoparticles and their application to organic solar cells

We report an enhancement in the efficiency of organic solar cells via the incorporation of gold (Au) or silver (Ag) nanoparticles (NPs) in the hole-transporting buffer layer of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), which was formed on an indium tin oxide (ITO) surface by the spin-coating of PEDOT:PSS-Au or Ag NPs composite solution. The composite solution was synthesized by a simple in situ preparation method which involved the reduction of chloroauric acid (HAuCl₄) or silver nitrate (AgNO₃) with sodium borohydride (NaBH₄) solution in the presence of aqueous PEDOT:PSS media. The NPs were well dispersed in the PEDOT:PSS media and showed a characteristic absorption peak due to the surface plasmon resonance effect. Organic solar cells with the structure of ITO/PEDOT:PSS-Au, Ag NPs/poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM)/LiF/Al exhibited an 8% improvement in their power conversion efficiency mainly due to the enlarged surface roughness of the PEDOT:PSS, which lead to an improvement in the charge collection and ultimately improvements in the short-circuit current density and fill factor.     

In vitro efficacy and toxicology evaluation of silver nanoparticle‐loaded gelatin hydrogel pads as antibacterial wound dressings

The silver nanoparticle (nAg)‐loaded gelatin hydrogel pads were prepared from 10 wt % gelatin aqueous solution containing silver nitrate (AgNO₃) at 0.75, 1.0, 1.5, 2.0, or 2.5 wt % by solvent‐casting technique. These AgNO₃‐containing gelatin solutions, that had been aged for 15, 12, 8, 8, and 8 h, respectively, showed noticeable amounts of the as‐formed nAgs, the size of which increased with an increase in the AgNO₃ concentration (i.e., from 7.7 to 10.8 nm, on average). The hydrogels were crosslinked with a glutaraldehyde aqueous solution (50 wt %, at 1 μL mL^?1). At 24 h of submersion in phosphate buffer saline (PBS) or simulated body fluid buffer (SBF) solution, about 40.5–56.4% or 44.4–79.6% of the as‐loaded amounts of silver was released. Based on the colony count method, these nAg‐loaded hydrogels were effective against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa, with at least about 99.7% of bacterial growth inhibition. Unless they had been treated with a sodium metabisulfite aqueous solution, these hydrogels were proven, based on the indirect cytotoxicity evaluation, to be toxic to human's normal skin fibroblasts. Lastly, only the hydrogels that contained AgNO₃ at 0.75 and 1.0 wt % were not detrimental to the skin cells that had been cultured directly on them. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Studies on the synthesis of electrospun PAN‐Ag composite nanofibers for antibacterial application

We have successfully synthesized polyacrylonitrile (PAN) nanofibers impregnated with Ag nanoparticles by electrospinning method at room temperature. Briefly, the PAN‐Ag composite nanofibers were prepared by electrospinning PAN (10% w/v) in dimethyl formamide (DMF) solvent containing silver nitrate (AgNO₃) in the amounts of 8% by weight of PAN. The silver ions were reduced into silver particles in three different methods i.e., by refluxing the solution before electrospinning, treating with sodium borohydride (NaBH₄), as reducing agent, and heating the prepared composite nanofibers at 160°C. The prepared PAN nanofibers functionalized with Ag nanoparticles were characterized by field emission scanning electron microscopy (FESEM), SEM elemental detection X‐ray analysis (SEM‐EDAX), transmission electron microscopy (TEM), and ultraviolet‐visible spectroscopy (UV‐VIS) analytical techniques. UV‐VIS spectra analysis showed distinct absorption band at 410 nm, suggesting the formation of Ag nanoparticles. TEM micrographs confirmed homogeneous dispersion of Ag nanoparticles on the surface of PAN nanofibers, and particle diameter was found to be 5–15 nm. It was found that all the three electrospun PAN‐Ag composite nanofibers showed strong antibacterial activity toward both gram positive and gram negative bacteria. However, the antibacterial activity of PAN‐Ag composite nanofibers membrane prepared by refluxed method was most prominent against S. aureus bacteria. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Antibacterial electrospun chitosan/poly(vinyl alcohol) nanofibers containing silver nitrate and titanium dioxide

Chitosan/poly(vinyl alcohol) (PVA) nanofibers with antibacterial activity were prepared by the electrospinning of a chitosan/PVA solution with a small amount of silver nitrate (AgNO₃) and titanium dioxide (TiO₂). Nanofibers with diameters of 270–360 nm were obtained. The yield of low‐viscosity chitosan (LCS)/PVA nanofibers was higher than that of high‐viscosity chitosan (HCS)/PVA, and the water content of the HCS/PVA nanofibers and the LCS/PVA nanofibers were 430 and 390%, respectively. The nanofibers developed in this study exhibited antibacterial activities of 99 and 98% against Staphylococcus aureus and Escherichia coli, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Wound-dressing materials with antibacterial activity from electrospun gelatin fiber mats containing silver nanoparticles

Ultrafine gelatin fiber mats with antibacterial activity against some common bacteria found on burn wounds were prepared from a gelatin solution (22%w/v in 70 vol% acetic acid) containing 2.5 wt% AgNO₃. Silver nanoparticles (nAg), a potent antibacterial agent, first appeared in the AgNO₃-containing gelatin solution after it had been aged for at least 12 h, with the amount of nAg increasing with increasing aging time. The average diameters of the as-formed nAg ranged between 11 and 20 nm. Electrospinning of both the base and the 12 h-aged AgNO₃-containing gelatin solutions resulted in the formation of smooth fibers, with average diameters of ∼230 and ∼280 nm, respectively. The average diameter of the as-formed nAg in the electrospun fibers from the 12 h-aged AgNO₃-containing gelatin solution was ∼13 nm. The nAg-containing gelatin fiber mats were further cross-linked with moist glutaraldehyde vapor to improve their stability in an aqueous medium. Both the weight loss and the water retention of the nAg-containing gelatin fiber mats in acetate buffer (pH 5.5), distilled water (pH 6.9) or simulated body fluid (SBF; pH 7.4) decreased with increasing cross-linking time. The release of Ag⁺ ions from both the 1- and 3 h-cross-linked nAg-containing gelatin fiber mats - by the total immersion method in acetate buffer and distilled water (both at a skin temperature of 32 °C) - occurred rapidly during the first 60 min, and increased gradually afterwards; while that in SBF (at the physiological temperature of 37 °C) occurred more gradually over the testing period. Lastly, the antibacterial activity of these materials, regardless of the sample types, was greatest against Pseudomonas aeroginosa, followed by Staphylococcus aureus, Escherichia coli, and methicillin-resistant S. aureus, respectively.     

Fabrication and characterization of chitosan/poly(vinyl alcohol) electrospun nanofibrous membranes containing silver nanoparticles for antibacterial water filtration

Electrospun nanofibrous membranes (ENMs) were fabricated based on chitosan/poly(vinyl alcohol) (CS/PVA) with a 70/30 mass ratio containing silver nanoparticles (AgNPs) via the electrospinning method. AgNPs were produced on the surface of CS/PVA nanofibers by adding AgNO₃ to a CS/PVA blend solution as a silver rendering component. The presence of AgNPs in the polymer blend solution was detected by UV spectrophotometry. The morphology of nanofibers before and after cross-linking with glutaraldehyde was investigated by the field emission scanning electron microscopy. The formation and size distribution of AgNPs onto the surface of nanofibers were observed by transmission electron microscopy and confirmed by energy dispersing X-ray spectroscopy. As-spun and cross-linked CS/PVA nanofibers revealed a smooth surface with diameters ranging from 58 to 73 nm and 95 to 109 nm, respectively. The effect of AgNP formation on the chemical structure of nanofibers was explored by Fourier transform infrared spectroscopy. Static and dynamic antibacterial filtration efficiencies of CS/PVA ENMs, containing differing amounts of AgNO₃, have been tested against Escherichia coli, a gram negative bacterium. The antibacterial assessment results exhibited a significant increase in both static and dynamic antibacterial filtration efficiencies of the prepared CS/PVA ENMs by addition of AgNO₃ as a bactericidal agent.     

Self synthesize of silver nanoparticles in/on polyurethane nanofibers: Nano‐biotechnological approach

In this study, we are introducing a new class of Polyurethane (PU) nanofibers containing silver nanoparticles (NPs) by electrospinning. A simple method not depending on the addition of foreign chemicals has been used to self‐synthesize of silver NPs in/on PU nanofibers. Typically, a sol?gel consisting of AgNO₃/PU/N,N‐dimethylformamide (DMF) has been electrospun and aged for a week, so silver NPs have been created in/on PU nanofibers. Syntheses of silver NPs were carried out by exploiting the reduction ability of the DMF solvent which is the main constituent to obtain PU electrospun nanofibers in decomposition of silver nitrate precursor into silver NPs. Physiochemical characterizations confirmed well oriented nanofibers and good dispersing of pure silver NPs. Various parameters affecting utilizing of the prepared nanofibers on various nano‐biotechnological fields have been studied. For instance, the obtained nanofiber mats were checked for mechanical properties which showed the improvement of the tensile strength upon increase in silver NPs content. Moreover, the nanofibers were subjected to 10 times successive washing experiments with using solid to liquid ratio of 3 : 5000 for 25 h, UV spectroscopy analysis reveals no losses of silver NPs from the PU nanofibers. 3T3‐L1 fibroblasts were cultured in presence of the designed nanofibers. The morphological features of the cells attached on nanofibers were examined by BIO‐SEM, which showed well attachment of cells to fibrous mats. The cytotoxicity results indicated absence of toxic effect on the 3T3‐L1 cells after cell culturing. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and properties of electrospun poly(vinyl alcohol)/silver fiber web as wound dressings

A novel wound dressing material was prepared by electrospinning poly(vinyl alcohol) (PVA)/AgNO₃ aqueous solution into nonwoven webs and then treating the webs by heat or UV radiation. Through SEM, TEM, and XPS analyses, it was observed that the silver (Ag) nanoparticles were generated and existed in the near surface of the electrospun nanofibers. It was found that heat treatment as well as UV radiation reduced the Ag⁺⁺⁺ ions in the electrospun PVA/AgNO₃ fiber web into the Ag nanoparticles. Also the heat treatment improved the crystallinity of the electrospun PVA fiber web and so it made the web unsolved in moisture environment. Therefore, it was concluded that the only heat treated electrospun PVA/AgNO₃ fiber web was a good material as wound dressings because it had structural stability in moisture environment as well as excellent antimicrobial ability and, quick and continuous release of the effectiveness. POLYM. ENG. SCI., 47:43–49, 2007. © 2006 Society of Plastics Engineers     

Electrospun antibacterial nylon nanofibers through in situ synthesis of nanosilver: preparation and characteristics

A new method for production of nylon nanofibers with antibacterial properties containing silver nanoparticles (nylon nanofibers/Ag NPs) is introduced via in situ synthesis of nano-silver by reduction of silver nitrate in the polymer solution prior to electrospinning. The properties of the electrospinning solutions and the structures of the electrospun fibers were studied using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDAX), UV?Cvis spectrophotometer and reflection spectrophotometer. Further, the antibacterial properties of the nanofibers were investigated against Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) bacteria. Interestingly, an antibacterial properties has been found on nylon 6 nanofibers while the nylon nanofibers/Ag NPs showed excellent antibacterial activities against both tested bacteria. The produced nylon nanofibers/Ag NPs can be a good candidate for biomedical applications, water and air filtration.     

Photocatalytic degradation of dairy effluent using AgTiO2 nanostructures/polyurethane nanofiber membrane

Dairy effluent (DE) is environmentally toxic and needs special attention. Photocatalytic degradation of DE was studied using novel polyurethane (PU)-based membranes. Typically, silver–titanium dioxide nanofibers (AgTiO₂ NFs) and silver–titanium dioxide nanoparticles (AgTiO₂ NPs) were individually incorporated in PU electrospun nanofibers to overcome the mandatory sophisticated separation of the nanocatalysts, which can create a secondary pollution, after the treatment process. These nanomembranes were characterized in SEM, TEM, XRD and UV studies. The polymeric electrospun nanofibers were smooth and continuous, with an average diameter of about 550 nm, and held their nanofibrous morphology even after more than 2 h of photocatalytic degradation of DE, due to the good stability of PU in the aqueous solutions, which indicates good imprisoning of the functional photocatalysts. The PU–AgTiO₂ NPs and PU–AgTiO₂ NFs were effective materials for degradation of DE, even after two successive cycles. PU–AgTiO₂ NPs and PU–AgTiO₂ NFs showed a maximum degradation of 75% and 95%, respectively after 2 h. The significant enhancement of degradation in the PU–Ag–TiO₂ NPs and PU–Ag–TiO₂ NFs is attributed to the photoactivity of Ag–TiO₂ material under visible light irradiation.     

Preparation and antibacterial activity of polyvinyl alcohol/regenerated silk fibroin composite fibers containing Ag nanoparticles

Polyvinyl alcohol (PVA)/regenerated silk fibroin (SF)/AgNO₃ composite nanofibers were prepared by electrospinning. A large number of nanoparticles containing silver were generated in situ and well‐dispersed nanoparticles were confirmed by transmission electron microscopy (TEM) intuitionally. Ultraviolet (UV)‐visible spectroscopy and X‐ray diffraction (XRD) patterns indicated that nanoparticles containing Ag were present both in blend solution and in composite nanofibers after heat treatment and after subsequent UV irradiation. By annealing the nanofibers, Ag⁺ therein was reduced so as to produce nanoparticles containing silver. By combining heat treatment with UV irradiation, Ag⁺ was transformed into Ag clusters and further oxidized into Ag₃O₄ and Ag₂O₂. Especially size of the nanoparticles increased with heat treatment and subsequent UV irradiation. This indicated that the nanoparticles containing silver could be regulated by heat treatment and UV irradiation. The antimicrobial activity of heat‐treated composite nanofibers was evaluated by Halo test method and the resultant nanofibers showed very strong antimicrobial activity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Improvements on electrical conductivity of the electrospun microfibers using the silver nanoparticles

Conductive electrospun polymer fibers have attracted a great deal of interest in recent years. This study describes the preparation of electrically conductive microfibers composed of polyethersulfone/polydopamine/silver nanoparticles (PES/PDA/Ag NPs). Ag NPs acted as conductive centers, while hydroxyl- and amino-rich functional groups and excellent adhesion properties of PDA served to connect the Ag NPs and PES microfibers. Fourier transform infrared spectroscopy and scanning electron microscopy (SEM) showed that PDA was firmly adhered to PES microfibers. PES/PDA microfibers absorbed considerable amounts of silver ion from AgNO₃ solution, resulting in Ag NPs. X-ray diffraction, X-ray photoelectron spectroscopy, and SEM data represented the successful formation of PES/PDA/Ag NPs microfibers. Microfibers with optimal conductivity were obtained using a solution of 2% AgNO₃ at pH 9 at 50 °C for 45 min. The electrical resistivity of our PES/PDA/Ag NPs microfibers was only 202 Ω/cm, much lower than that of regular PES microfibers (2.1 × 10⁹ Ω/cm). These results show that the PES/PDA/Ag NPs microfibers are suitable for use as conductive polymer fibers in electromagnetic shielding, and conductivity-sensing applications, and in flexible electronic devices and biosensors. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48788.     

Preparation and Characterization of Polypyrrole Silver Nanocomposites via Interfacial Polymerization

Conducting polypyrrole silver (Ppy-AgNC) nanocomposite was synthesized by an interfacial polymerization method. Ag⁺ ions from the AgNO₃ solution were taken in the formation of Ppy-AgNC. The incorporated silver was confirmed by X-ray diffraction (XRD). During the polymerization in a nitrate ion-containing solution, the impregnation leads to the formation of metallic silver. The size distribution of Ag into the polymer is confirmed by transmission electron microscopy (TEM), and proves the formation of a uniform species with spherical particles of Ag (mean diameter of 8-12 nm) branching at the border of Ppy. The thermal behavior of the material was studied by thermogravimetric measurements.     

在NiCl2、MnCl2或FeCl3存在下用多元醇法高浓度合成银纳米线

报道了一种用于高浓度制备银纳米线的改性多元醇法。在NiCl₂、MnCl₂或FeCl₃存在下高浓度地制得了具有均一尺寸和形貌的银纳米线。所得银纳米线的直径约为60～100 nm、长度约30～60 μm。研究了AgNO₃溶液浓度、PVP和AgNO₃比例和控制剂浓度等对所得银纳米线形貌的影响。研究发现可以通过反应条件的改变来调节所得银纳米线的形貌。本方法的可能机理是由于引入的金属阳离子可以除掉吸附在晶种表面的氧,从而促进银纳米线的生长。     

Acidic hydrolysis of a poly(vinyl acetate) matrix by the catalytic effect of Ag nanoparticles and the micellization of Ag‐metal‐containing polymer

In this study, we conveniently obtained Ag(0)–polymer nanocomposites by reacting AgNO₃ with commercial poly(vinyl acetate) (PVAc) in the absence of a special reducing agent. The formation of Ag(0) metal was detected after formic acid (HCOOH) was added to a PVAc–AgNO₃ complex system, and some of the acetate groups of the PVAc backbone were hydrolyzed to form hydroxyl groups (OH) under the catalytic effect of the reduced Ag(O) metal. Here, the structure of the partially hydrolyzed PVAc backbone was represented as PVOH‐PVAc. X‐ray diffraction spectra showed that the Ag(0) metal generated in this method was in the form of Ag crystals. The structure of the Ag(0)–polymer was analyzed by ¹H‐NMR and ¹³C‐NMR spectroscopy. The micellization of the Ag(0)–polymer was also investigated by the addition of an inducing solvent to the formic acid solution of Ag(0)–polymer. The image showed that the morphology of the Ag micelles in the H₂O‐induced solvent was a Ag corona with a Ag shell, and that in the p‐xylene induced solvent showed a Ag cluster core structure. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1457–1464, 2006     

Laser-Induced Silver Nanoparticles on Titanium Oxide for Photocatalytic Degradation of Methylene Blue

Silver nanoparticles doped on titanium oxide (TiO₂) were produced by laser-liquid interaction of silver nitrate (AgNO₃) in isopropanol. Characteristics of Ag/TiO₂ (Ag doped TiO₂) nanoparticles produced by the methods presented in this article were investigated by XRD, TEM, SEM, EDX, and UV-Vis. From the UV-Vis measurements, the absorption of visible light of the Ag/TiO₂ photocatalysts was improved (additional absorption at longer wavelength in visible light region) obviously. The photocatalytic efficiency of Ag/TiO₂ was tested by the degradation of methylene blue (MB) in aqueous solution. A maximum of 82.3% MB degradation is achieved by 2.0 wt% Ag/TiO₂ photocatalyst under 2 h illumination with a halogen lamp.     

Synthesis and intercalation of silver nanoparticles in kaolinite/DMSO complexes

Ag nanoparticles were synthesized in the interlamellar space of a layered kaolinite. Disaggregation of the lamellae of the nonswelling kaolinite was achieved by the intercalation of dimethyl sulfoxide (DMSO). The kaolinite was suspended in aqueous AgNO₃ solution and the adsorbed Ag⁺ ions were reduced on the surface of kaolinite lamellae with NaBH₄ or UV light irradiation. The silver nanoparticles formed were characterized by X-ray diffraction (XRD), small angle X-ray scattering (SAXS), and transmission electron microscopy (TEM). We studied the effects of the two reduction methods on the size and the size distribution of Ag nanoparticles and how clay mineral structure is altered as a consequence of particle formation. It was established that the size of Ag nanoparticles depends on both silver content and the reduction method. Photoreduction of silver led to the formation of relatively large Ag nanoparticles (diameter 8–14 nm).     

Photocrosslinkable acid urethane dimethacrylates from renewable natural oil and their use in the design of silver/gold polymeric nanocomposites

Castor oil-based acid urethane macromers were prepared and employed for obtaining Ag/Au/polymer nanocomposites. Structure and UV induced photopolymerization of the macromers were investigated by spectral methods. The polymerization rate and the degree of conversion decreased with about 10% in the presence of 2.5 wt.% silver nanoparticles (Ag NPs). For the diacid macromer, the surface plasmon intensity increased with irradiation time (the optical density of the absorption maximum (430 nm) attained 2.3 after 600 s), whereas a diminished efficiency was found for Ag NPs in situ generated. Transmission electron microscopy and X-ray photoelectron spectroscopy confirmed uniform distribution of the spherical nanoparticles (0.6 nm (Ag NPs); 5 nm (Au NPs)) and the appearance of Ag 3d_3/2, Ag 3d_5/2, Au 4f_7/2 and Au 4f_5/2 peaks corresponding to Ag (0) or Au (0). Environmental scanning electron microscope with energy-dispersive X-ray detector, contact angle and mechanical parameters measurements complemented the above observations.