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.     

Perturbation-correlation moving-window two-dimensional correlation spectroscopic studies on the heat treatment of poly(vinyl alcohol)/silver nitrate film

In this paper, poly(vinyl alcohol)/silver nitrate (PVA/AgNO₃) films were annealed at 180 °C for 1 h to prepare highly electrically conductive poly(vinyl alcohol)/silver (PVA/Ag) nanohybrids. Ultraviolet (UV)-visible absorption spectra, X-ray diffraction (XRD) scans, and scanning electronic microscopy (SEM) were applied to investigate the structures and morphology of the PVA hybrids. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were employed to study the thermal property of PVA/AgNO₃ films. Furthermore, perturbation-correlation moving-window two-dimensional (PCMW2D) correlation spectroscopy combined with temperature-dependent Fourier transform infrared (FTIR) spectroscopy was used to investigate the conversion of AgNO₃ into Ag nanoparticles in PVA matrix. The results show that the chelates for AgNO₃ coordinated with hydroxyl groups are primarily decomposed in the temperature regions of 39.7–72.6 °C and 182.7–199.6 °C. AgNO₃ is reduced into Ag⁰ and the hydroxyl groups of PVA are oxidized into carbonyl groups. The PVA-AgNO₃ chelates are very rapidly decomposed in the temperature region of 182.7–199.6 °C. Large amounts of Ag⁰ produced by the reduction of AgNO₃ are aggregated into Ag nanoparticles which are homogeneously dispersed into the PVA matrix. When the temperature increases to 212.7 °C, the unhydrolyzed acetate groups in PVA chains are sharply decomposed.     

Synthesis and characterization of Ag nanoparticles embedded in PVA via UV-photoreduction technique for synthesis of Prussian blue pigment

Silver nanoparticles doped in polyvinyl alcohol (AgNps/PVA) were synthesized via polymer-promoted reductive reaction of AgNO₃ and PVA under time-dependent exposure to UV radiation. The AgNps/PVA composites were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction, UV–Vis spectroscopy, and transmission electron microscopy to describe the structure, nuclearity, and distribution of Ag Nps within the PVA matrix. The UV–Vis spectrum of AgNps/PVA exhibited a broad surface plasmon absorption around 425–443 nm which originated from the formation of Ag NPs. Surface analysis by XPS indicated that the Ag NPs were grown solely on the PVA surface at UV exposure time of 2 h (2.0AgNPs/PVA). Increasing the UV exposure time to 4 h will cause the transformation of metallic nanosilver to oxidized nanosilver. UV–Vis absorption spectra were in situ recorded to follow the synthesis of Prussian blue (PB) on 2.0AgNPs/PVA (PB@2.0AgNPs/PVA). The colloidal dispersion of 2.0AgNPs/PVA in an acidic medium containing free Fe(III) ions and potassium hexacyanoferrate(III) revealed an additional band centered at 720 nm due to the intermetal charge-transfer absorbance of the polymeric Fe(II)-C-N-Fe(III) of the PB@2.0AgNPs/PVA nanocomposite. Control experiments were shown to involve a spontaneous electron transfer reaction between 2.0AgNPs/PVA and Fe(III) ions, with a concomitant decomposition of hexacyanoferrate(III) and formation of PB was observed. Moreover, IR gave clear cut evidence for the synthesis of PB@2.0AgNPs/PVA from the appearance of a band for the cyano group at 2090 cm^?1.     

Preparation and Characterization of Gelatin Nanofibers Containing Silver Nanoparticles

Ag nanoparticles (NPs) were synthesized in formic acid aqueous solutions through chemical reduction. Formic acid was used for a reducing agent of Ag precursor and solvent of gelatin. Silver acetate, silver tetrafluoroborate, silver nitrate, and silver phosphate were used as Ag precursors. Ag⁺ ions were reduced into Ag NPs by formic acid. The formation of Ag NPs was characterized by a UV-Vis spectrophotometer. Ag NPs were quickly generated within a few minutes in silver nitrate (AgNO₃)/formic acid solution. As the water content of formic acid aqueous solution increased, more Ag NPs were generated, at a higher rate and with greater size. When gelatin was added to the AgNO₃/formic acid solution, the Ag NPs were stabilized, resulting in smaller particles. Moreover, gelatin limits further aggregation of Ag NPs, which were effectively dispersed in solution. The amount of Ag NPs formed increased with increasing concentration of AgNO₃ and aging time. Gelatin nanofibers containing Ag NPs were fabricated by electrospinning. The average diameters of gelatin nanofibers were 166.52 ± 32.72 nm, but these decreased with the addition of AgNO₃. The average diameters of the Ag NPs in gelatin nanofibers ranged between 13 and 25 nm, which was confirmed by transmission electron microscopy (TEM).     

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.     

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.     

Developing centrifugal spun thermally cross-linked gelatin based fibrous biomats for antibacterial wound dressing applications

Fibrous materials obtained from natural polymers, such as gelatin, have been used in medical applications due to their biocompatibility and biodegradability. Herein, free-standing durable fibrous gelatin biomats with antibacterial activity were developed via a simple, low cost and fast production route, centrifugal spinning, and subsequent thermal crosslinking. After a series of preliminary experiments, droplet−/bead-free porous biomats with fine fibers, 3.41 ± 1.8 μm in diameter, were fabricated. Subsequently, antimicrobial biomats were produced by adding AgNO₃ into the production solution. X-ray diffractometer and energy dispersive X-ray results showed Ag NPs existing as AgCl in the biomats, which could be attributed to chemical reaction between the Ag NPs and residual Cl in the impure gelatin. Later, both the neat-gelatin and Ag-gelatin biomats were thermally crosslinked at 170°C to gain stability against water. Although the Ag addition reduced ultimate tensile strength by half, from 881 to 495 kPa, the crosslinked biomats were robust enough to be used for wound dressing applications. They were also found to be highly breathable, with the air permeability of 256 and 81.2 mm/s, respectively. The biomats showed antibacterial activity against Escherichia coli and Staphylococcus aureus bacteria. The results show that the free-standing fibrous-gelatin-based biomats produced is applicable for wound dressing applications.     

Plasmonic-excitonic multi-hybrid glass-based nanocomposites incorporating Ag plus core-shell CdSe/CdS and alloyed CdSxSe1−x nanoparticles

Successful fabrication of glass-based hybrid nanocomposites (GHNCs) incorporating Ag, core-shell CdSe/CdS and CdS_xSe_1?x nanoparticles (NPs) is herein reported. Both metallic (Ag) and semiconductor (CdSe/CdS) NPs were pre-synthesized, suspended in colloids and added into the sol-gel reaction medium which was used to fabricate the GHNCs. During fabrication of the nanocomposites a fraction (20–60%) of core-shell CdSe/CdS NPs was alloyed into CdS_xSe_1?x (0.20 < x < 0.35) NPs without changing morphology. Modulation of in situ alloying is possible via the relative content of organics added into the sol-gel protocol. Within colloids Ag (core-shell CdSe/CdS) NPs presented average diameter and polydispersity index of 49.5 nm (4.2 nm) and 0.41 (0.21), respectively. On the other hand, the Ag (core-shell CdSe/CdS) NPs’ average diameter and polydispersity index assessed from the GHNCs were respectively 51.5 nm (4.1 nm) and 0.43 (0.25), revealing negligible aggregation of the nanophases within the glass template. The new GHNCs herein introduced presented two independent excitonic transitions associated to homogenously dispersed semiconductor NPs, peaking around 420 nm (core-shell CdSe/CdS) and 650 nm (CdS_xSe_1?x) and matching the plasmonic resonance (Ag NPs) in the 400–500 nm range. We envisage that the new GHNCs represent very promising candidates for superior light manipulation while illuminated with multiple laser beams in quantum interference-based devices.     

Novel methyl-orange assisted core-shell polyaniline-silver nanosheets for highly sensitive ammonia chemiresistors

A cost-effective, eco-friendly, one-pot synthesis of a new class of homogenous core-shell polyaniline-silver nanocomposite was fabricated with the assistance of supramolecular aggregates of amphiphilic methyl-orange (MO) and oxidant ions of silver nitrate (AgNO₃). The morphology of nanocomposite transforms from spherical (core-shell type: PA-1) to plate-like polygonal particles (PA-2) with surge in concentration of AgNO_3. The strong contrast of the TEM images depicts the presence of silver (Ag) at core and polyaniline (PAN) at the shell. The core-shell structure of the synthesized nanocomposite was confirmed using KCN washing technique. The SAED pattern reveals the hexagonal nature of PAN-Ag hybrid nanosheets with [111] orientation with interplanar spacing around 2.4 Å corresponding to face-centered-cubic structure of Ag. The X-ray diffraction spectra reveal the crystalline nature of the hybrid. Furthermore, the chemiresistors fabricated using the PA nanocomposite was analyzed for ammonia (NH₃) monitoring behavior. The fabricated room temperature chemiresistor was found to be highly sensitive (~47.1% sensitivity) towards low concentration (as low as 1 ppm) of NH₃ with high selectivity and stability, which opens a new window for fabricating cost-effective commercial sensors.     

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.     

Radiation synthesis and characterization of polyvinyl alcohol/chitosan/silver nanocomposite membranes: antimicrobial and blood compatibility studies

Polyvinyl alcohol/chitosan/silver (PVA/CS/Ag) nanocomposite membranes were synthesized by γ-radiation with promising antimicrobial and biomedical applications. The nanocomposite membranes were prepared by mixing PVA and CS solutions with different copolymer compositions in the presence of silver nitrate (AgNO₃) and glutaraldehyde as cross-linker, followed by in situ reduction with γ-radiation at different doses. The nanocomposite membranes were characterized by ultraviolet spectroscopy (UV), Fourier transform infrared, X-ray diffraction (XRD) and transmission electron microscopy (TEM). UV studies showed a strong peak around λ _max at 430 nm due to surface plasmon resonance of silver nanoparticles formed during irradiation. As the irradiation dose increased from 25 to 75 kGy, the plasmon band is shifted from 430 to 418 nm with high intensity, indicating the formation of smaller particles. TEM investigation showed uniform distribution of silver nanoparticles (AgNPs) in the membranes with mean diameter of 32–19 nm. XRD results confirmed that the mean diameter of AgNPs estimated from the Debye–Scherrer formula was in the range of 27.5–12.8 nm which confirms the TEM results. The PVA/CS/Ag nanocomposite membranes exhibited good antibacterial activity and were found to cause significant reduction in microbial growth. The nanocomposite membranes showed non-thrombogenicity effect and slightly haemolytic potential, suggesting their promising use in biomedical applications.     

Impact of nano-perovskite La2CuO4 on dc-conduction,opto-electrical sensing and thermal behavior of PVA nanocomposite films

ABSTRACT

Nanocomposite (NC) films of poly vinyl alcohol (PVA) incorporated with varying amounts of perovskite lanthanum cuprate (La₂CuO₄) nanoparticles (NPs) have been fabricated by solution intercalation technique. TEM result showed the size of NPs between 91-134nm. The effects of NPs content on structural and morphological behaviors of PVA have been established by XRD, FTIR and SEM methods. Electrical properties of NC films were performed using LCR-meter. Current (I)–voltage (V) data displayed dc-conductivity increased with increasing NPs content and trends of I–V indicate the dominant Ohmic behavior at voltage <5V and above that Poole–Frenkel emission is the dominant conduction mechanism. Ac-conductivity increases with increase in frequency and dosage of NPs. The maximum ac-conductivity obtained in this investigation is 2.43X10^?5S/cm for PVA/2wt% La₂CuO₄ with lowest activation energy of 0.147 eV at 25^°C. Cyclic voltammetry (CV) revealed the specific capacitance of PVA-NC improved compared to pristine PVA. The reduction in T_g with increment NPs contents was observed. The optical behaviors of NCs were deduced by UV-visible spectroscopy where the result showed band gap energy was reduced from 5.23eV to 3.25eV whereas refractive index increased from 1.71 to 2.44 for pure PVA and PVA/2wt%La₂CuO₄, respectively.     

The thermal‐electrical properties of polyvinyl alcohol/AgNO3 films

In this article, one cast technique to fabricate 20–40 wt %AgNO₃‐doped polyvinyl alcohol (PVA) composite films of which electrical resistance sharply dropped (4–5 order) in a certain temperature range was reported. The phase, structure thermal, and electrical resistivity properties of films at different heat treatment temperatures were studied by X‐ray diffraction (XRD), scanning electrical microscopy (SEM) and differential scanning calorimetry (DSC). The results showed that all the AgNO₃ (20–40 wt %) doped PVA films presented an exothermic peak at 182°C. And the temperature of exothermic peak kept constant for various contents of AgNO₃. Meanwhile, the phase composition of the films was greatly affected by the heat treatment temperature. Ag particles were generated during the heat treatment process, and the content of Ag particles increased with increasing the temperature. The resistivity of PVA/AgNO₃ films decreased with increasing the temperature. And a sharp decrease appeared at 155–165°C due to the generation and contact of a mass of Ag particles at this temperature. The thermal‐electrical results suggested the applicability of these materials in temperature sensor, for example, critical temperature resistor thermistor. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A promising technique of Aegle marmelos leaf extract mediated self‐assembly for silver nanoprism formation

The Aegle marmelos leaf extract (LE) mediated synthesis of prismatic and spherical Ag nanoparticles (NPs) has been studied. The formation of prismatic structures from spherical NPs was observed microscopically using scanning electron microscope, transmission electron microscope, and atomic force microscope. The shape transformation from spherical NPs to prismatic nanostructures was studied by simply changing LE concentration, keeping constant AgNO₃ concentration (1 mM). The role of pH toward prism formation and the effect of sonication on the formed structures were also investigated. The antimicrobial activity of the synthesized Ag spherical/prismatic NPs was evaluated against gram negative bacteria (Escherichia coli, Pseudomonas aeruginosa) and on a phytopathogen Fusarium solani. This green synthesis approach for the synthesis of prismatic Ag nanostructures may be useful for surface‐enhanced Raman spectroscopy application for the detection of low concentration organic molecules, apart from the studied antimicrobial activity. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3670–3680, 2017     

Well-defined core-shell nanoparticles containing cyclodextrin in the shell: A comprehensive study

The purpose of this study was to conceive novel nanoparticles (NPs) designed for drug delivery applications. The NPs were based on a hydrophobic poly (lactic acid) (PLA) core and a hydrophilic β-cyclodextrin polymer (Poly-β-CD) shell. The PLA NPs were prepared by the nanoprecipitation method. The Poly-β-CD shell was obtained by adsorption from Poly-β-CD solution. Different complementary techniques have been used to fully characterize the system including dynamic light scattering, Zeta potential measurements, solution proton nuclear magnetic resonance spectroscopy, transmission electron microscopy, and small angle neutron scattering. They provide good evidence of a core-shell structure. The NPs parameters are dependent on the elaboration process, Poly-β-CD characteristics and adsorption conditions. In the conditions of adsorption’ saturation, the shells were constituted of Poly-β-CD monolayers covering the PLA surfaces with adsorption amounts from 2 to 4 mg/m², allowing reaching Poly-β-CD weight fractions of 10-20% in the NPs.     

Synthesis of ultrathin carbon dots-coated iron oxide nanocubes decorated with silver nanoparticles and their excellent catalytic properties

A facile ultrasonic method has been successfully developed for the fabrication of multifunctional Fe₃O₄@carbon dot/Ag (Fe₃O₄@C-dot/Ag) nanocubes (NCs), and the resulting materials are well characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), Vibrating sample magnetometer (VSM) and fluorescence measurements. The Ag nanoparticles (NPs) are uniform and well dispersed on the surface of Fe₃O₄@C-dot, while maintaining the shape and the size of the core-shell Fe₃O₄@C-dot NCs. In addition, its catalytic activities are evaluated by measuring the reduction of p-nitroaniline (p-NA) and crystal violet (CV), and the composite materials exhibit excellent catalytic activity towards reduction of p-NA and CV dye, which is superior to most reported catalysts. The good catalytic performance of Fe₃O₄@C-dot/Ag NCs may be attributed to the specific characteristics of its nanostructure and the synergistic effect on the delivery of electrons between Ag NPs and Fe₃O₄@C-dot NCs. Furthermore, the as-prepared catalysts also show good activity for the reduction of other nitrobenzene analogs. The effect of solvent and reducing agent was also studied on the catalytic activity of Fe₃O₄@C-dot/Ag NCs. Most importantly, the Fe₃O₄@C-dot/Ag catalyst shows excellent recycling stabilities, which can be potentially applied in the fields of catalysis and green chemistry.     

Studies on the effect of long-chain and head groups of nonionic surfactants synthesized from palm and coconut oil on the formation of silver nanoparticles

Four fatty amides were synthesized using coconut and palm oil sources. The chemical structure of the as-prepared fatty acids was confirmed using Fourier Transform Infrared (FT-IR) and ¹H, ¹³C NMR spectroscopy. The effect of different chain lengths and head groups of these compounds on Ag nanoparticles (NPs) synthesis was investigated. Ultraviolet–visible spectroscopic studies showed characteristic absorbance peaks (λ_max ≈ 410 nm). FT-IR results indicated that the surfactant functionalities are responsible for the Ag NPs stability. The effect of fatty amides on the morphology and size distribution of the Ag NPs was investigated using transmission electron microscope (TEM). The TEM micrographs showed the formation of fine spherical morphology due to surfactant-mediated self-assembly with an average particle size of 1–3 nm. Dynamic light scattering (DLS) analysis showed the micellar self-assembly of Ag NPs-fatty amides. The effect of surfactant on the solution behavior was analyzed using surface tension measurements. Cocamide and palm DEA showed relatively low free energy (∆G_mic) values, resulting in smaller particles with good distribution. Finally, the Ag NPs showed outstanding antimicrobial activity against Pseudomonas putida bacteria.     

Enhanced antibacterial activity of bimetallic gold-silver core-shell nanoparticles at low silver concentration

Herein we report the development of bimetallic Au@Ag core-shell nanoparticles (NPs) where gold nanoparticles (Au NPs) served as the seeds for continuous deposition of silver atoms on its surface. The core-shell structure and morphology were examined by UV-Vis spectroscopy, transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis and X-ray diffraction (XRD). The core-shell NPs showed antibacterial activity against both gram negative (Escherichia coli and Pseudomonas aeruginosa) and gram positive (Enterococcus faecalis and Pediococcus acidilactici) bacteria at low concentration of silver present in the shell, with more efficacy against gram negative bacteria. TEM and flow cytometric studies showed that the core-shell NPs attached to the bacterial surface and caused membrane damage leading to cell death. The enhanced antibacterial properties of Au@Ag core-shell NPs was possibly due to the more active silver atoms in the shell surrounding gold core due to high surface free energy of the surface Ag atoms owing to shell thinness in the bimetallic NP structure.     

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     

Preparation and characterization of poly(vinyl alcohol) cryogel‐silver nanocomposites and evaluation of blood compatibility,cytotoxicity, and antimicrobial behaviors

In this investigation, cryogels composed of poly(vinyl alcohol) (PVA) were prepared by repeated freeze‐thaw method. The prepared cryogels served as templates for producing highly stable and uniformly distributed silver nanoparticles via in situ reduction of silver nitrate (AgNO₃) using alkaline formaldehyde solution as reducing agent. The structure of the PVA/Ag cryogel nanocomposites was characterized by a Fourier transform infrared and Raman spectroscopy. The morphologies of pure PVA cryogels and PVA/Ag nanocomposites were observed by a scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The SEM analysis suggested that cryogels show a well defined porous morphology whereas TEM micrographs revealed the presence of nearly spherical and well separated Ag nanoparticles with diameter about 100 nm. XRD results showed all relevant Bragg's reflections for crystal structure of silver nanoparticles. The amount of silver in cryogel nanocomposites and thermal stability were determined by inductively coupled plasma atomic emission spectrometry (ICP‐AES) and thermogravimetric analysis measurements. Mechanical properties of nanocomposites were observed in terms of tensile strength. The antibacterial studies of the synthesized nanosilver containing cryogels showed good antibacterial activity against both gram‐negative and gram‐positive bacteria. The prepared PVA/Ag nanocomposites were also investigated for swelling and deswelling behaviors. The results reveal that both the swelling and deswelling process depends on the chemical composition of the cryogel silver nanocomposites, number of freeze‐Thaw cycles and pH and temperature of the swelling medium. The biocompatibility of the prepared nanocomposites was judged by in vitro methods of percent hemolysis and protein (BSA) adsorption. POLYM. COMPOS., 36:1983–1997, 2015. © 2014 Society of Plastics Engineer