Fabrication and characterization of fibroin solution and nanoparticle from silk fibers of Bombyx mori

The present investigation aims to study the effect of degumming time on the structural property of silk fiber obtained by silk cocoons of Bombyx mori, followed by preparation of the regenerated silk fibroin (RSF) solution which can be subsequently molded into silk nanoparticles. Silk fibers degummed with different media at different time intervals were investigated for the degumming loss and were characterized using Ffourier transform infrared (FTIR), differential scanning calorimetry (DSC), x-ray diffraction (XRD), and scanning electron microscopy (SEM). Maximum degumming was observed when the fibers were treated with sodium carbonate for 60 min. SEM and atomic force microscopy (AFM) images of RSF solution showed aggregation of silk globules resulting in formation of solvated macrochains and giving it an appearance of island-like morphology. Blank silk nanoparticles prepared from the RSF solution showed a smooth and spherical surface devoid of any adhesion using SEM, AFM, and transmission electron microscopy (TEM). The prepared silk nanoparticles may further be explored for loading drug entities and targeting.     

Electrospun ultra-fine silk fibroin fibers from aqueous solutions

By using electrospinning technique, beaded, cylinder shaped and ribbon like ultra-fine silk fibroin (SF) fibers were obtained from its concentrated aqueous solution under different processing conditions. These fibers had an average diameter of 700 nm and were characterized by scanning electron microscopy (SEM), Wide-angle X-ray diffraction (WAXD) and Raman spectroscopy. It was found that the morphology and the secondary structure of the as-spun SF fibers were strongly influenced by the solution concentration, as well as the processing voltage. By adjusting these technological parameters, β-sheet conformation and silk II crystal structure of the SF fibers can be formed without any post-treatment.     

再生丝素蛋白水溶液静电纺丝性能的研究

运用静电纺丝方法,从再生蚕丝素蛋白水溶液中制得了念珠状的、圆形的或扁平状的超细再生丝,纤维的直径在100～900nm之间,平均为700nm.溶液浓度和电压强度对静电纺丝性能的影响很大,当纺丝液浓度为28%（质量分数）,电压为20kV,喷射距离为 11cm时,可制得具有光滑表面的圆形再生丝.大角X衍射（WAXD）测试结果认为,静电纺再生丝中含有α螺旋和β-折叠结构,但其结构既不同于无定型丝素膜,也不同于天然蚕丝纤维,介于二者之间.     

Adhesion characteristics of Cu/Ni–Cr/polyimide flexible copper clad laminates according to Ni:Cr ratio and Cu electroplating layer thickness

The adhesion strength of Cu/Ni–Cr/polyimide flexible copper clad laminate (FCCL) was evaluated according to the composition ratio of the Ni–Cr layer and the thickness of the Cu electroplating layer, by using a 90° peel test. The changes in the morphology, chemical bond and adhesion property were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The peel strength of the FCCL increased with increasing Cr content and increasing Cu electroplating layer thickness. This increasing FCCL peel strength was attributed to a lower C–N bond and higher C–O and carbonyl (C=O) bonds in the polyimide surface compared to the FCCL with a lower adhesion strength. The adhesion property of the FCCLs was significantly affected by the Ni:Cr ratio.     

AFM and SEM characterization of iron oxide coated ceramic membranes

Alumina–zirconia–titania (AZT) ceramic membranes coated with iron oxide nanoparticles have been shown to improve water quality by significantly reducing the concentration of disinfection by-product precursors, and in the case of membrane filtration combined with ozonation, to reduce ozonation by-products such as aldehydes, ketones and ketoacids. Commercially available ceramic membranes with a nominal molecular weight cut-off of 5 kilodaltons (kD) were coated 20, 30, 40 or 45 times with sol suspension processed Fe₂O₃ nanoparticles having an average diameter of 4–6 nm. These coated membranes were sintered in air at 900 °C for 30 min. The effects of sintering and coating layer thickness on the microstructure of the ceramic membranes were characterized using atomic force microscopy (AFM), scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). AFM images show a decreasing roughness after iron oxide coating with an average surface roughness of ∼161 nm for the uncoated and ∼130 nm for the coated membranes. SEM showed that as the coating thickness increased, the microstructure of the coating changed from a fine grained (average grain size of ∼27 nm) morphology at 20 coating layers to a coarse grained (average grain size of ∼66 nm) morphology at 40 coating layers with a corresponding increase in the average pore size from ∼57 nm to ∼120 nm. Optimum water quality was achieved at 40 layers, which corresponds to a surface coating morphology consisting of a uniform, coarse-grained structure with open, nano-sized interconnected pores.     

Materials behaviour and intermetallics characteristics in the reaction between SnAgCu and Sn–Pb solder alloys

The paper compares theoretical calculations with experimental data, to identify the metallurgical mechanisms with respect to the rework or repair that may be encountered in the transition period from Sn–Pb to Pb-free soldering. Thermodynamic calculations have been carried out to study material behaviour and possible formation of intermetallic precipitates during the reaction between Sn–Pb and Sn–Ag–Cu Pb-free alloys. Two Sn–Ag–Cu alloys that are relevant to current industrial interests, namely Sn–3.9Ag–0.6Cu* (known as ‘405 alloy’ in Europe and North America), and Sn–3.0Ag–0.5Cu (known as ‘305’ alloy in Asia), were reacted with different contamination levels of eutectic Sn–37Pb solder. The variables examined included those related to both the materials and processes, such as composition, temperature and cooling rate. Together these are the primary drivers with respect to the resultant solder microstructures, which were studied using scanning electron microscopy (SEM). Nanoindentation, which is suitable for the ultra-fine and complex microstructures, was also used to investigate the micromechanical properties, including hardness and elastic modulus, at both ambient and elevated temperatures. The results from this work provide guidance as to the consequence for microstructural evolution and hence mechanical integrity when small amounts of Pb exist in Pb-free alloys. The composition of alloys in this paper is in weight percentage (wt%)     

Preparation of Ag–Fe-decorated single-walled carbon nanotubes by arc discharge and their antibacterial effect

A simple one-step approach for the preparation of Ag–Fe-decorated single-walled carbon nanotubes (Ag–Fe/SWCNTs) by DC hydrogen arc discharge is presented in this article. The growth of SWCNTs and the attachment of Ag and Fe nanoparticles to the SWCNTs occur simultaneously during the arc discharge evaporation process. It has been confirmed that the Ag and Fe nanoparticles in the diameter range of 1–10 nm are well dispersed and tightly attached to the outer surfaces of SWCNTs. The as-grown Ag–Fe/SWCNTs have been purified by high-temperature hydrogen treatment to remove amorphous carbon and carbon shells. Antibacterial tests show that the antibacterial activity of the purified Ag–Fe/SWCNT hybrid nanoparticles is excellent against Escherichia coli. The percentage of the E. coli killed by 100 μg/ml Ag–Fe/SWCNTs can reach up to 85.1 % at a short residence time of 2 h, suggesting that the purified Ag–Fe/SWCNTs may have potential antibacterial applications.     

In situ synthesis of silver nanoparticles on silk fabric with PNP for antibacterial finishing

This research presents a generic strategy to fabricate antibacterial textile through in situ synthesis of silver nanoparticles on the fabric with smart polymeric molecules. Silk fabric and polyamide network polymer (PNP) were chosen for this study. PNP which has numerous amino groups and three-dimensional structure was applied to entrap silver ions into silk fabric. The pretreated silk fabrics were heated by steam method to make silver nanoparticles synthesized in situ on them without any other reductant and linker to provide silk fabric with antibacterial properties. The results indicated that the treated silk fabrics had excellent antibacterial activity and laundering durability. The quantitative bacterial tests showed the bacterial reduction rates of Staphylococcus aureus and Escherichia coli were able to reach above 99 % with not more than 0.05 mmol/L of AgNO₃. The whiteness of silk fabric only changed from 90.47 to 86.49. The antibacterial activity of the treated silk fabric was maintained at 98.86 % reduction even after being exposed to 30 consecutive home laundering conditions. In addition, the results of scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy confirmed that silver nanoparticles had generated and dispersed well in Ag⁰ form on the surface of silk fibers. The understanding acquired from this work will allow one to work with the preparation of other silver nanoparticles functional textiles with excellent antibacterial activities and laundering durability through this facile, eco-friendly in situ synthesis method.     

Preparation of the Silver-Superconductor Composite by Deposition of the Silver Nanoparticles in the Bismuth Cuprate Superconductor

BiSCCO (Bi–Sr–Ca–Cu–O) is high temperature superconductor with a lot of possible applications. Interfaces between superconductors and metal conductors are one of the technological problems. In this work, silver-superconductor composite was prepared by using flow of silver nanoparticles suspension in DMF (N,N-dimethylformamide) through superconductor’s pore system. Silver nanoparticles were prepared by reaction of silver nitrate with DMF. Properties of prepared composite were measured by SEM charting, XRD and critical current measurements. SEM chart showed uniform distribution of silver across sample. XRD and critical current measurements validated superconducting properties of prepared composite. In the future, materials based on this method could be used as an interface between superconductors and metals or as a base for superconducting composite with much better mechanical properties.     

Effects of different kinds of seed layers and heat treatment on adhesion characteristics of Cu/(Cr or Ni–Cr)/PI interfaces in flexible printed circuits

In this study, the effect of various seed layers (95Ni–5Cr, 80Ni–20Cr and Cr) on the adhesion strength of flexible copper clad laminate (FCCL), which was manufactured by the roll-to-roll process, was evaluated after heat treatment. The changes in the morphology, chemical bonding, and adhesion properties were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and a 90° peel test. The results showed that both the peel strength and thermal resistance of the FCCL increased as the Cr ratio of the seed layer increased. The roughness of the fracture surface decreased as the heat treatment temperature and holding time increased. The heat treatment of the FCCL increased the proportion of C–N bonds and reduced that of the C–O and carbonyl (C=O) bonds in the polyimide. The chemical function and roughness of the fracture surface were affected by the composition and ratio of the seed layer. Therefore, the adhesion strength between the metal and polyimide was mostly attributed to the chemical interaction between the metal layer and the functional groups of the polyimide.     

Fabricating of silver and copper nano/microtubes using nano-scale glass fibers as templates

In this paper, large-scale uniform silver and copper nano/microtubes with high length diameter ratios have been successfully synthesized by a facile approach, using low-cost nano-scale glass fibers as templates. The tubular structures can be obtained by reducing of Ag and Cu ions on the surface of the fibers, along with removing the templates. The samples are characterized by SEM and XRD. Results show the tubular structures are very uniform and the tubular walls are composed of densely coalesced crystalline nanoparticles of 30–50 nm.     

X-ray irradiation induced optical absorptions in silver and manganese doped soda-lime silicate glass

Silver nanoclusters formation was observed in Ag-doped or Ag–Mn-doped soda-lime silicate glasses after X-ray irradiation followed by thermal annealing. Silver nanoclusters were formed with mean-size of about 3 nm after heating at 420 °C for 1 h in Ag-doped glass, and were disappeared after heating at 600 °C for 1 h. Mn³⁺ was formed in Mn-doped glass after X-ray irradiation followed by heating at 400 °C for 1 h, and was reduced to Mn²⁺ upon subsequently heating at 600 °C for 1 h. The presence of Mn³⁺ led to a purple color, while the silver nanoclusters provided a yellow color in the glass. The Ag-doped or Mn-doped glass may be viable as recyclable coloration glasses. In Ag–Mn-doped glass silver nanoclusters were formed only after heating at a high temperature of 600 °C following the irradiation. In addition, manganese showed a similar X-ray-induced behavior in the Mn-doped glass and the Ag–Mn-doped glass. In contrast, silver behaved differently in the Ag-doped glass and the Ag–Mn-doped glass. Unlike those in Ag-doped glass, the silver nanoclusters would not be dissolved in Ag–Mn-doped once they were formed.     

TLP bonding of SiCp/2618Al composites using mixed Al–Ag–Cu system powders as interlayers

Mixed Al–Ag–Cu and Al–Ag–Cu–Ti powders were used as interlayers for transient liquid phase diffusion bonding (TLP bonding) of SiC particulate reinforced 2618 aluminum alloy matrix composite (SiCp/2618Al MMC). The results show that by using mixed Al–Ag–Cu powder with the eutectic composition as an interlayer, SiCp/2618Al MMC can be TLP bonded at 540 °C, however, the joining layer is porous. Adding a certain amount of titanium into the Al–Ag–Cu interlayer, the TLP bonding quality can be improved. The titanium added into the Al–Ag–Cu interlayer has an effect of shortening the solidification time of the joining layer, thus decreasing SiC particles from the parent materials entering into the joining layer. The joints bonded using Al–Ag–Cu–Ti interlayers have a maximum shear strength of 101 MPa when 2.1% titanium is added.     

纳米羟基磷灰石/丝素蛋白/聚己内酯复合超细纤维的制备及表征

通过静电纺丝法制备出纳米羟基磷灰石/丝素蛋白/聚己内酯复合超细纤维,利用扫描电镜、红外光谱仪、X射线衍射仪对纳米羟基磷灰石/丝素蛋白/聚己内酯复合超细纤维形貌和结构进行表征,并进行了拉伸测试。结果表明,随着超细纤维中羟基磷灰石含量的增加,纤维的直径逐渐降低,纤维中聚己内酯的结晶逐渐变差。相比于丝素蛋白/聚己内酯超细纤维,含有质量比为30%羟基磷灰石的复合超细纤维仍具有较好的力学性能。体外小鼠成纤维细胞(L929)培养表明,纳米羟基磷灰石/丝素蛋白/聚己内酯复合超细纤维对细胞没有毒性。     

Wetting behavior and interfacial microstructure of palladium- and silver-based braze alloys with C–C and SiC–SiC composites

High-temperature sessile-drop wettability tests were conducted on unpolished C–C and SiC–SiC composite substrates using commercial braze alloys Palco (Pd-35Co), Palni (Pd-40Ni), Cusil-ABA (63Ag–35.3Cu–1.75Ti), and Ticusil (68.8Ag–26.7Cu–4.5Ti). Observations revealed non-uniform, anisotropic spreading, copious braze infiltration of the composite substrates, particularly C–C composite, and Ti enrichment at the composite/braze interface together with dissolution of Si (from SiC–SiC composite) in braze and diffusion of Co (from Palco) in the composite. The droplet/composite contact region near the droplet center revealed intimate and microstructurally sound bonding. However, inter-laminar shear cracking within the SiC–SiC composite in contact with Ticusil, Palco, and Palni, and partial substrate/droplet de-cohesion near the edge of the droplet were also observed. In Palco and Palni droplets, fiber tows in the contact region de-laminated from the main body of the composite via inter-laminar shear cracking resulting in fiber flotation, segregation, and surface degradation. The study is one of the first empirical enquiries into the complex wetting and spreading behavior of brazes on commercial C–C and SiC–SiC composites.     

Biogenic synthesis of biopolymer‐based Ag–Au bimetallic nanoparticle constructs and their anti‐proliferative assessment

This study reports an eco‐friendly‐based method for the preparation of biopolymer Ag–Au nanoparticles (NPs) by using gum kondagogu (GK; Cochlospermum gossypium), as both reducing and protecting agent. The formation of GK‐(Ag–Au) NPs was confirmed by UV‐absorption, fourier transformed infrared (FTIR), atomic force microscopy (AFM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The GK‐(Ag–Au) NPs were of 1–12 nm in size. The anti‐proliferative activity of nanoparticle constructs was assessed by MTT assay, confocal microscopy, flow cytometry and quantitative real‐time polymerase chain reaction (PCR) techniques. Expression studies revealed up‐regulation of p53, caspase‐3, caspase‐9, peroxisome proliferator‐activated receptors (PPAR) PPARa and PPARb, genes and down‐regulation of Bcl‐2 and Bcl‐x(K) genes, in B16F10 cells treated with GK‐(Ag–Au) NPs confirming the anti‐proliferative properties of the nanoparticles.Inspec keywords: nanomedicine, transmission electron microscopy, genetics, cellular biophysics, molecular biophysics, enzymes, nanofabrication, gold, silver, scanning electron microscopy, nanoparticles, Fourier transform infrared spectra, atomic force microscopy, biomedical materialsOther keywords: size 1.0 nm to 12.0 nm, Ag‐Au, anti‐proliferative assessment, eco‐friendly‐based method, anti‐proliferative activity, anti‐proliferative properties, biopolymer‐based Ag–Au bimetallic nanoparticle, Cochlospermum gossypium, gum kondagogu, biopolymer preparation, biogenic synthesis, UV‐absorption, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, MTT assay, confocal microscopy, flow cytometry, caspase‐3, caspase‐9, peroxisome proliferator‐activated receptors, Bcl‐2 gene, Bcl‐x(K) gene, B16F10 cells     

Antibacterial properties of padded PP/PE nonwovens incorporating nano-sized silver colloids

This paper deals with the effects that nano-sized silver colloids have on the antibacterial properties of PE/PP nonwovens against three kinds of bacteria: Staphylococcus aureus, Klebsiella pneumoniae, and Escherichia coli. These silver colloids comprise silver nanoparticles that are a non-toxic and non-tolerant disinfectant. PE/PP nonwovens are used as back sheets or coverstocks of baby diapers, adult diapers, sanitary napkins, and wipes. These materials are readily contaminated by bacteria present in moisture and dirt and can cause disease. We finished the nonwovens using a normal dipping–pad–dry method. From SEM images, we determined that the silver nanoparticles were generally dispersed well on the surface of the nonwoven fibers. We used the AATCC-100 test method to study the antibacterial properties of the treated fabrics. Bacteria were disinfected completely to below a count of 10 cells after 10 min when using the samples treated with 10 ppm of silver colloids. The ethanol-based silver/sulfur composite colloid (SNSE) has the best antibacterial efficacy when compared with the other nano-sized silver colloids. The silver particles having the smallest sizes gave the higher dispersibilities and the strongest antibacterial efficacies.     

Preparation of pH-responsive silver nanoparticles by RAFT polymerization

Silver nanoparticles were prepared by chemical reduction of AgNO₃ in the presence of the PDMAEMA-b-PPA, which was synthesized by the reversible addition-fragmentation transfer technique. The formation of the silver nanoparticles was determined by the transmission electron microscopy (TEM) images and UV–Vis absorption spectra. The average size of the silver nanoparticles was shown to 11.4 nm. Particularly, the pH-responsive property of the silver nanoparticle was further observed. It was characterized by the zate potential, the UV–Vis spectra, and TEM images. The results show that the pH-responsive property is attributed to the aggregate of the silver nanoparticles as a function of pH. The characteristic is expected to apply in the nanoscale optical biosensor and biomaterials.     

Oral insulin delivery by self-assembled chitosan nanoparticles: In vitro and in vivo studies in diabetic animal model

We have developed self-assembled chitosan/insulin nanoparticles for successful oral insulin delivery. The main purpose of our study is to prepare chitosan/insulin nanoparticles by self-assembly method, to characterize them and to evaluate their efficiency in vivo diabetic model. The size and morphology of the nanoparticles were analyzed by dynamic light scattering (DLS), atomic force microscopy (AFM) and scanning electron microscopy (SEM). The average particle size ranged from 200 to 550 nm, with almost spherical or sub spherical shape. An average insulin encapsulation within the nanoparticles was ~ 85%. In vitro release study showed that the nanoparticles were also efficient in retaining good amount of insulin in simulated gastric condition, while significant amount of insulin release was noticed in simulated intestinal condition. The oral administrations of chitosan/insulin nanoparticles were effective in lowering the blood glucose level of alloxan-induced diabetic mice. Thus, self-assembled chitosan/insulin nanoparticles show promising effects as potential insulin carrier system in animal models.     

Ammonia sensing by hydrochloric acid doped poly(<Emphasis Type="Italic">m</Emphasis>-aminophenol)–silver nanocomposite

Processable poly(m-aminophenol) (PmAP) was synthesized using ammonium persulfate oxidant in 0.6 M sodium hydroxide solution at room temperature. Then, in situ PmAP–silver nanocomposite film was obtained by casting PmAP film from dimethyl sulfoxide with silver hydroxide ammonia mixture at 140 °C. The nanocomposite film was doped with hydrochloric acid (HCl) by general solution doping technique. The undoped and HCl-doped films were characterized by ultraviolet visible spectroscopy, Fourier transformed Infrared spectroscopy, transmittance electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffraction analysis. Spectroscopic characterizations confirmed that the PmAP was doped by silver nanoparticles and it was further doped by HCl used. So, the synthesized PmAP–silver nanocomposite showed a conductivity of 1.01 × 10⁻⁶ S/cm, which was increased to 3.27 × 10⁻⁴ S/cm after HCl doping. The well dispersed silver nanoparticles with average size 130–150 nm was observed by SEM and TEM analysis. Unlike conventional ammonia sensor here, the resistivity of the nanocomposite film was decreased on exposure to ammonia gas and the sensing properties of the HCl-doped nanocomposite films were also reproducible. It can be seen that the % response of doped nanocomposite was unchanged while, the response time was decreased with increasing ammonia vapor concentrations in air. The ammonia-sensing characteristics of the HCl-doped nanocomposite film was explained on the basis of a proposed mechanism.