Synthesis of silver nanoparticles in NMMO and their in situ doping into cellulose fibers

We present a method for synthesis of silver nanoparticles in N-methylmorpholine N-oxide (NMMO) and the associated mechanism, as well as their use for in situ volume modification of cellulose fibers. The synthesized particles had diameter of about 4 nm, and their colloid solution was stable for 1 year. The nanoparticles were stabilized using polyethylenimine, which apart from preventing nanoparticle agglomeration, also accelerated Ag⁺ ion reduction and prevented NMMO degradation. A mechanism for the nanoparticle synthesis is suggested based on the electrochemical potentials of all ions in solution, with perhydroxyl ions resulting from NMMO reducing the silver ions. We also created nanocomposites from fibers and silver nanoparticles, in which the latter showed very good dispersion in the fiber volume. Such spun fibers showed improved mechanical parameters in comparison with unmodified fibers.     

A novel and convenient preparation of antibacterial polyacrylonitrile nanofibers via post-modification using nitrile click chemistry and electrospinning

An efficient, novel and convenient method for the synthesis of modified polyacrylonitrile (PAN) with antibacterial property is reported. The modification of PAN was prepared by a nitrile click chemistry reaction with sodium azide (NaN₃) and silver nitrate (AgNO₃) as catalyst to yield antibacterial polymeric materials with 5-vinyltetrazole units. The results showed that 5-vinyltetrazole units had coordinated with silver ion (Ag⁺). Through the electrostatic spinning technology, the post-modification PAN nanofibers (PAN–Ag⁺ nanofibers) were prepared and the fibers were tested for their antimicrobial properties by the bacterial infection experiment. Afterwards, the antibacterial and stable performance of different proportions of silver ions in PAN nanofibers has been compared. The PAN–Ag⁺ nanofibers are characterized for mechanical and thermomechanical properties, structural analysis, appearance characteristics, as well as the antibacterial properties. And the nanofibers exhibit marvelous chemical stability according to the thermogravimetric analysis. When at 800 °C, the PAN decomposed about 60%, while the decomposition of the PAN–Ag⁺s was 40%. Based on the bacterial infection experiment, PAN–Ag⁺ nanofibers’ antibacterial properties were stronger with the increase of silver ions, such as the number of bacteria clone was smaller and the bacteriostatic ring was larger. Hence, with combination of silver ions, the final polymers show strong antimicrobial properties.     

Tuning the size,concaveness, and aspect ratio of concave cubic gold nanoparticles produced with high reproducibility

Reproducible fabrication of concave cubic gold nanoparticles with precise control over size, concaveness, and aspect ratio is important because the nanoscale structural characteristics can influence their plasmonic and catalytic properties. However, this is particularly challenging because the number of synthetic parameters involved in the fabrication strategy adds complexity to the reaction mechanism. Here, we introduce a simplified seed-mediated method and uncover the unknown conceptual insights on how the different halides and their concentration influence the surface structure and stability of underpotential silver monolayer deposited on the high energy facets of nanoparticles. The results reveal that adding Br^? and I^? ions to growth solution offers a predominant way to control the reaction kinetics and engineering nanoparticles with a predefined size, morphology, concaveness, aspect ratio, and plasmonic properties. Using spectroscopy and microscopy techniques, we shed new light on the reaction kinetics of concave cubic gold nanoparticles using the combined influence of silver underpotential deposition and halides. The strategy developed here can be expanded to fabricate gold nanoparticles of complex geometries. The results from our electromagnetic calculations suggest that the self-assembled superstructure of concave cubic gold nanoparticles can be more appealing for developing an ultra-sensitive sensing platform than to self-assembled superstructures of truncated cubic gold nanoparticles.     

Spinnability of Polyacrylonitrile Gel Dope in the Mixed Solvent of Dimethyl Sulfoxide/Dimethylacetamide and Characterization of the Nascent Fibers

In this work, acrylonitrile copolymers were prepared via precipitation polymerization. The copolymer solutions prepared at various ratio of dimethyl sulfoxide and dimethylacetamide were tested to prepare the nascent fibers by one-step wet-spun method. The effect of temperature, solvent ratio, molecular weight and the solid content on the rheological properties of polyacrylonitrile gel solution in different mixed solvent were studied. It was shown that the viscosity decreased with the increase of the temperature and fluctuated with the different solvent ratio reaching the minimal value at the ratio of dimethyl sulfoxide to dimethylacetamide equal to 1.25. The crystallinity of copolymers and the structure of the nascent fiber surface also depended from the solvent ratio in polymerization. The optimum conditions for spinnability of copolymers were determined. The high-quality polyacrylonitrile precursor was achieved with the controllable range of 0.5–0.8 dtex and the toughness of polyacrylonitrile precursor was greater than 6.0 cN/dtex after the wet spinning process, while the tensile strength of carbon fiber is up to 6.25 GPa after their pre-oxidation and carbonization process.     

In situ formed silver nanoparticles on glass fibers grafted with polyacrylamide and their antibacterial activity

In this paper, grafted polyacrylamide from the surface of glass fibers was prepared by surface initiated atom transfer radical polymerization in order to control the matrix surface structure and properties. The uniform and stable grafted polymer layer was utilized to prepare silver ions complexes, and then the silver ions were reduced by AlLiH₄ to form in situ silver nanoparticles. The structure, composition, properties and surface morphology of the modified glass fibers were characterized by X-ray photoelectron spectroscopy, fourier transform infrared spectroscopy, thermo gravimetric analysis and scanning electron microscopy. The antibacterial activities of modified glass fibers against E. coli, B. subtilis and S. cerevisiae had been studied respectively by Shake Flask Method. The results show that the antibacterial ratio of Ag nanoparticles loaded glass fibers is significantly improved than that of Ag⁺ loaded, and the highest antibacterial ratio is 72.2% against E. coli.     

XPS study of silver and copper nanoparticles demonstrated selective anticancer,proapoptotic, and antibacterial properties

Silver and copper nanoparticles were produced by an ecologically safe metal vapor synthesis (MVS) method using acetone as an organic dispersion medium. Transmission electron microscopy (TEM) showed that the specimens are spherical and polydisperse, and their average size is 2.5 nm for silver nanoparticles (Ag NPs) and 2.6 nm for copper nanoparticles (Cu NPs). X-ray photoelectron spectroscopy analyses showed that the state of silver in the nanoparticles is close to that of silver in the Ag⁰ state, whereas copper black contains two oxidized states of the metal—Cu⁺ and Cu²⁺. Biological in vitro studies demonstrated that the nanoparticles have antibacterial activity against Gram-positive and Gram-negative bacterial species. Cu NPs exhibited more prominent antibacterial effects and induced significant growth inhibition of Bacillus cereus and Escherichia coli. Both types of nanoparticles showed anticancer properties in vitro. Cu NPs induced intense cytotoxicity in cancer and normal fibroblasts in vitro cultures, but their inhibitory effect against noncancerous cells was milder compared with cancer cell lines. Ag NPs demonstrated selective cytotoxicity against human lung and cervical adenocarcinoma cell lines. Further in vitro studies indicated that the mechanism of Ag NPs and Cu NPs anticancer effects involves induction of apoptosis. The present study describes a green synthesis approach for production of biologically active silver and copper nanoparticles and highlights their potential for medical application.     

Synthesis and characterization of silver—poly(methylmethacrylate) nanocomposites

The optical properties of silver nanoparticles embedded in poly(methylmethacrylate) (PMMA) was investigated as well as the influence of silver nanoparticles on the thermal properties of polymer matrix. The average size and particle size distribution of silver nanoparticles was determined using transmission electron microscopy. The obtained transparent nanocomposite films were optically characterized using UV-Vis and FTIR spectroscopy. Thermal stability of polymer matrix was improved upon incorporation of small amount of silver nanoparticles. Also, silver nanoparticles have pronounced effect on thermo-oxidative stability of PMMA matrix. The glass transition temperatures of nanocomposites are lower compared to the pure polymer.     

In-situ synthesis,characterization and antimicrobial activity of viscose fiber loaded with silver nanoparticles

In order to broaden applications of viscose fiber, graft copolymerization of acrylic acid was conducted on its surface followed by in situ loading of Ag nanoparticles (Ag-NPs). The loading amount of Ag-NPs was affected by the concentrations of Ag⁺ and trisodium citrate, and their optimum concentrations were found to be 0.014 and 0.030 g/ml. The Ag-NP-loaded fibers presented a prolonged Ag release behavior in aqueous solution, of which the cumulative release was less than 5 % within 48 h. In addition, the viscose fibers showed good antimicrobial activity against S. aureus, and their consecutive antimicrobial activity was kept at more than 90 % after several washing cycles. Modified viscose fibers, therefore, offer a great opportunity for use as antimicrobial fabrics.     

Durable antibacterial Ag/polyacrylonitrile (Ag/PAN) hybrid nanofibers prepared by atmospheric plasma treatment and electrospinning

Durable antibacterial Ag/polyacrylonitrile (Ag/PAN) hybrid nanofibers were prepared by atmospheric plasma treatment and electrospinning. Atmospheric helium plasma treatment was first used to reduce the AgNO₃ precursor in pre-electrospinning solutions into metallic silver nanoparticles, followed by electrospinning into continuous and smooth nanofibers with Ag nanoparticles embedded in the matrix. SEM, TEM, and EDX spectra were used to study the structure and surface elemental composition of the nanofibers. Silver nanoparticles, with diameters ranging between 3 and 6 nm, were found to be uniformly dispersed in the nanofiber matrix. The Ag/PAN nanofibers exhibited slow and long-lasting silver ion release, which provided robust antibacterial activity against both Gram-positive Bacillus cereus and Gram-negative Escherichia coli microorganisms.     

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.     

Bio-protected flax nanocomposites as basis for manufacturing of high-tech eco-products

Data on biodegradation of flax fibers of different chemical composition, structure of cellulose, and included natural impurities (pectic compounds, lignin, and hemicelluloses) are presented. The influence of silver nanoparticles immobilized in the fiber on biodegradation of the objects under study is evaluated. It is demonstrated that this effect depends on the concentration and size of nanoparticles in the polymer matrix.     

Preparation of antibacterial polyimide films containing silver nanoparticles

Polyimide/silver composite films were successfully prepared by in situ polymerization. A precursor, AgNO₃ was used as the source of the silver nanoparticles. The structure and morphology of resulting films were characterized by FTIR spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Consequently, the silver nanoparticles were well dispersed in polyimide matrix. Meanwhile, thermal properties from thermal gravimetric analyses (TGA) and mechanical properties from tensile test which confirmed composites were kept good performance as compared to pure polyimide. In addition, the antimicrobial activity of polyimide/silver composite films against three different bacteria, B. subtilis, S. aureus, and E. coil, illustrated excellent activity. This composite is potential useful as antimicrobial material with good thermal performance in a wide variety of biomedical and general use applications.     

Process optimization and empirical modeling for electrospun polyacrylonitrile (PAN) nanofiber precursor of carbon nanofibers

Ultrafine fibers were spun from polyacrylonitrile (PAN)/N,N-dimethyl formamide (DMF) solution as a precursor of carbon nanofibers using a homemade electrospinning set-up. Fibers with diameter ranging from 200 nm to 1200 nm were obtained. Morphology of fibers and distribution of fiber diameter were investigated varying concentration and applied voltage by scanning electric microscopy (SEM). Average fiber diameter and distribution were determined from 100 measurements of the random fibers with an image analyzer (SemAfore 5.0, JEOL). A more systematic understanding of process parameters was obtained and a quantitative relationship between electrospinning parameters and average fiber diameter was established by response surface methodology (RSM). It was concluded that concentration of solution played an important role to the diameter of fibers and standard deviation of fiber diameter. Applied voltage had no significant impact on fiber diameter and standard deviation of fiber diameter.     

Dependence of Property of Silver Nanoparticles within Dendrimer-template on Molar Ratios of Ag+ to PAMAM Dendrimers

G5.0‐OH PAMAM dendrimers were used to prepare fluorescent silver clusters with weaker ultraviolet irradiation reduction method, in which the molar ratio of Ag⁺ to PAMAM dendrimers was the key factor to determine the geometry and properties of silver nanoparticles. The results showed that because of G5.0‐OH PAMAM dendrimers as strong encapsulatores, when the molar ratios of Ag⁺ to PAMAM dendrimers was smaller than 5, the obtained Ag_n clusters (n<5) had line structures and "molecular‐like" properties, which were highly fluorescent and quite stable in aqueous solution. Whereas when the molar ratios were between 5 and 8, the obtained Ag_n clusters were 2D structures and their fluorescence was weaker. When the molar ratio was larger than 8, the structure of silver nanoparticles was 3D and no fluorescence was observed from the obtained silver nanoparticles.     

载银磷酸活化剑麻基活性炭纤维的抗菌性能研究

本文利用磷酸化方法，制备各种剑麻基活性炭纤维，并利用活性炭纤维的氧化还原特性及吸附性能，在其上负载金属银，研究并比较了这些载银活性炭纤维对大肠杆菌和金黄色葡萄球菌的杀灭作用，结果表明，磷酸浓度，活化方法，活化时间，纤维的比表面积等因素的均对材料的抗菌性能有一定的影响，磷酸活化的活性炭纤维表现出强的抗菌杀菌能力，高浓度磷酸活化后的纤维抗菌能力有所提高，并且抗菌能力随活化时间的延长而增加，抗菌前后纤维上负载的银未曾大量脱落，经5次抗菌试验后材料仍显示出很强的抗菌能力。     

N‐Heterocyclic Carbene‐Protected Ag Nanoparticles Immobilized on Polyacrylonitrile Fiber as Efficient Catalysts for a Three‐Component Coupling Reaction

Metal nanoparticles (NPs) are routinely stabilized by the introduction of capping agents or their distribution on supports. In this context, we report the preparation and characterization of N‐heterocyclic carbene (NHC)‐stabilized silver NPs supported on polyacrylonitrile fiber (PANF). As a result, Ag loadings of up to 8 % and particle sizes of 11.0±3.2 nm were achieved. This novel nanocomposite catalyst demonstrated high activity in addition to excellent stability and reusability in the three‐component reaction between alkynes, haloalkanes, and amines. In this system, the AgNPs were stabilized by both a support effect and a ligand effect. The unique NHC‐protected AgNP structure and the PANF support provide a synergistic effect in the deprotonation of C_sp?H bonds, with turnover numbers of up to 3500. This catalyst was successfully recycled over eight runs without any significant loss in activity, and with no significant aggregation of the AgNPs. Moreover, implementation of a flow system with PANF‐NHC@Ag as catalyst leads to an efficient productivity of 57 mmol h^?1.     

High Density Polyethylene Containing Antibacterial Silver Nanoparticles for Medical Applications

High density polyethylene (HDPE) and composites with silver nanoparticles were processed via extrusion and injection moulding. The materials thus produced were tested against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli. The release of silver ions Ag⁺ from composites was measured by means of ICP-MS method. Surface parameters such as wettability and roughness were determined because of their effect on the most important processes at biomaterial interface. Scanning electron microscopy was used to investigate the microstructure. Durability tests of polymer and composite materials were carried out in a simulated biological solution by monitoring the pH and electrical conductivity, mass changes as well as the longitudinal ultrasonic wave measurements. Antibacterial tests prove that nanosilver modified materials have bactericidal activity against tested bacteria. Biological durability studies reveal stable behavior of incubated materials. Spectrometric analysis shows that the amount of silver release depends on the immersion time and the amount of nanopowder introduced into the polymer matrix.     

Elemental Selenium Enriched Nanofiber Production

This study aimed to produce electrospun nanofibers from a polyvinyl butyral polymer (PVB) solution enriched with red and grey selenium nanoparticles. Scanning electron microscopic analysis was used to observe the samples, evaluate the fiber diameters, and reveal eventual artifacts in the nanofibrous structure. Average fiber diameter is determined by manually measuring the diameters of randomly selected fibers on scanning electron microscopic (SEM) images. The obtained nanofibers are amorphous with a diameter of approximately 500 nm, a specific surface area of approx. 8 m² g⁻¹, and 5093 km cm⁻³ length. If the red and grey selenium nanoparticles were produced in powder form and suspended to the ethanolic solution of PVB then they were located inside and outside the fiber. When selenium nanoparticles were synthesized in the PVB solution, then they were located only inside the fiber. These nanofiber sheets enriched with selenium nanoparticles could be a good candidate for high-efficiency filter materials and medical applications.     

A novel approach for electromembrane extraction based on the use of silver nanometallic-decorated hollow fibers

A novel approach based on the use of nanometallic-decorated hollow fibers to assist electromembrane extraction is proposed. Microporous polypropylene hollow fibers, on which nanometallic silver was deposited, have been used for the first time as liquid membrane support in electromembrane extraction (EME). Different methods for the generation/deposition of silver nanoparticles (AgNPs) were studied. The best results were obtained with chemical reduction of silver nitrate using NaBH₄ in aqueous solution followed by direct deposition on the hollow fibers. The extraction performance of the new supports was compared with a previously developed EME procedure used for the extraction of selected non-steroidal anti-inflammatory drugs (NSAIDs), resulting in an increase in the extraction ratio by a factor of 1.2–2 with a 30% reduction in the extraction time. The new nanometallic-decorated supports open new possibilities for EME due to the singular properties of nanometallic particles, including chemical fiber functionalization.     

硫代酰胺基螯合纤维的合成及其吸附性能研究

以腈纶纤维(PAN)为起始原料,分别经水合肼、乙二胺、二乙烯三胺预交联后,以N,N-二甲基甲酰胺(DMF)作溶剂与硫化钠反应,合成了3种携硫代酰胺功能基可达6.8mmol/g·干纤维的螯合功能纤维。利用红外光谱、元素分析、热稳定分析、重量分析等对该螯合纤维的结构、性能等进行了表征;研究了该螯合纤维对Au3 ,Ag ,Pd2 等贵金属离子的吸附性能;考察了温度、pH、硫含量等对纤维吸附Ag 离子的影响。结果表明,纤维对Au3 ,Ag 等贵金属离子具有良好的吸附性能,对Au3 的吸附容量为800mg/g·干纤维;对Ag 离子的吸附容量可达1510mg/g·干纤维,并具有良好的吸附动力学特性,该螯合纤维可用于混合溶液中Ag(I)离子的吸附分离。