Preparation and characterization of nanoboron for slurry fuel applications

Boron is a promising additive to hydrocarbon aviation fuels to enhance the volumetric energy density, which in turn leads to better specific impulse in hypersonic ramjet propelled missiles. This perspective article provides a summary of the different preparation methods of nanoboron, with an emphasis on its properties, quality and ease of scale-up. Self-propagating high temperature synthesis is projected as a promising method to produce amorphous nanoboron of high purity via metallothermic reduction of boron oxide. The effects of operating conditions such as time, temperature and concentration of diluent (NaCl) on particle size distribution, purity and yield are evaluated, and compared with the literature. In order to prepare slurries of boron in hydrocarbon fuels that are stable and long-standing, the addition of surfactants is necessary. The importance of Bancroft’s rule and hydrophilic-lipophilic balance are evaluated for the preparation of stable boron-fuel suspensions. Examples of stabilization of micron boron and nanoboron in jet fuels using different non-ionic surfactants like Spans and Tweens are discussed. Without any surfactant, complete settling of 10 wt% micon/nanoboron in Jet-A1 and JP-10 fuels occurred within 10 min. An optimized formulation of Span-80 and Tween-80 delayed the complete sedimentation of micron boron by a few days, and led to a much better stability of nanoboron in the fuels for over 7 days. Finally, the challenges and future prospects in scaling up of the nanoboron production process, and the preparation of slurry fuels with good stabilization of boron are discussed.     

Synthesis and characterization of nanoboron powders prepared with mechanochemical reaction between B<Subscript>2</Subscript>O<Subscript>3</Subscript> and Mg powders

Amorphous boron powders with small particle size, narrow size distribution and high purity are very important in the high-tech fields. Mechanochemical synthesis was used to prepare amorphous boron nanoparticles. Synthesis process stage was carried out using stoichiometric amounts of B₂O₃ and Mg powders (6.7 g). Milling was carried out under argon atmosphere in the high-energy planetary ball mill with a ball-to-powder weight ratio (32 : 1) for 10 h. The vial rotation speed was about 440 rpm. Milled products were leached by 28% hydrochloric acid (only one) to remove impurities. Boron powders were obtained after centrifuging, decanting, washing and drying operations. Sample was characterized by inductively coupled plasma (ICP), energy-dispersive spectroscopy, X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The ICP results showed that boron powders with purity about 91 wt% can be prepared in the planetary ball mill. Also, the leached powders had an amorphous structure. According to the SEM observation, average particle size of boron powders was smaller than 32 nm and the yield of synthesized nanoboron was more than 74%.     

Preparation and characterization of nanoboron by cryo-milling

Cryo-milling of coarse micron grade elemental boron powder was investigated for possible generation of nanosized boron powder. Process parameters were optimized for the least contamination and least particle size. The as-milled powders were characterized by scanning and transmission electron microscopy (SEM/TEM) and x-ray diffraction (XRD) for powder morphology, average particle size, and phase analysis. The particle size and surface area were also estimated using dynamic laser scattering (DLS) and BET techniques to correlate with the performance of the material. Thermo-gravimetric and differential thermal analysis (TG-DTA) studies were performed to ascertain mass change and energy release in unmilled and milled powder. The average particle size of boron powder after 9 h of cryo-milling was<100 nm. The cryo-milled powder was made air-stable and dispersible in JP10 fuel by coating it with ligand through the mechanical milling method. The TOPO (tri-n-octyl phosphine oxide) coated nano boron powder exhibited dispersion stability for a week.     

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.     

Environmentally friendly antibacterial cotton textiles finished with siloxane sulfopropylbetaine

This paper reports a novel environmentally friendly antibacterial cotton textile finished with reactive siloxane sulfopropylbetaine(SSPB). The results show that SSPB can be covalently bound onto the cotton textile surface, imparting perdurable antibacterial activity. The textiles finished with SSPB have been investigated systematically from the mechanical properties, thermal stability, hydrophilic properties and antibacterial properties. It is found that the hydrophilicity and breaking strength are improved greatly after the cotton textiles are finished with SSPB. Additionally, the cotton textiles finished with SSPB exhibit good antibacterial activities against gram-positive bacteria Staphylococcus aureus (S.aureus, ATCC 6538), gram-negative bacteria Escherichia coli (E.coli, 8099) and fungi Candida albicans (C.albicans, ATCC 10231). Moreover, SSPB is nonleachable from the textiles, and it does not induce skin stimulation and is nontoxic to animals. Thus, SSPB is ideal candidate for environmentally friendly antibacterial textile applications.     

Tailoring the Surface and Composition of Nanozymes for Enhanced Bacterial Binding and Antibacterial Activity

With the advantages of diverse structures, tunable enzymatic activity, and high stability, nanozymes are widely used in medicine, chemistry, food, environment, and other fields. As an alternative to traditional antibiotics, nanozymes attract more and more attention from the scientific researchers in recent years. Developing nanozymes-based antibacterial materials opens up a new avenue for the bacterial disinfection and sterilization. In this review, the classification of nanozymes and their antibacterial mechanisms are discussed. The surface and composition of nanozymes are critical for the antibacterial efficacy, which can be tailored to enhance both the bacterial binding and the antibacterial activity. On the one hand, the surface modification of nanozymes enables binding and targeting of bacteria that improves the antibacterial performance of nanozymes including the biochemical recognition, the surface charge, and the surface topography. On the other hand, the composition of nanozymes can be modulated to achieve enhanced antibacterial performance including the single nanozyme-mediated synergistic and multiple nanozymes-mediated cascade catalytic antibacterial applications. In addition, the current challenges and future prospects of tailoring nanozymes for antibacterial applications are discussed. This review can provide insights into the design of future nanozymes-based materials for the antibacterial treatments.     

Biosynthesis of silver nanoparticles in collagen gel improves their medical use in periodontitis treatment

Silver nanoparticles (AgNP) suspensions were biosynthesized by silver ions reduction in the presence of collagen, a nontoxic, organic polymer, intending to improve their medical use in periodontitis treatment. Spectrophotometric measurements showed a time- and concentration-dependent increase of AgNP formation in each suspension variant. Transmission electron microscopy revealed spherical morphology of AgNP in collagen and their mean diameter size was around 30?nm. The particle size distribution and zeta potential values of AgNP in collagen were determined by dynamic light scattering measurements. The surface charge of AgNP in collagen was positive, while commercial AgNP stabilized in citrate had negative surface charge. In vitro cytotoxicity testing of AgNP in collagen showed that they were biocompatible with human gingival fibroblasts in a wider range of concentrations than commercial nanoparticles. The antibacterial activity of AgNP in collagen against two pathogenic strains present in the periodontal pocket was dose-dependent and higher than that of AgNP in citrate. All these results demonstrated that AgNP prepared in collagen gel had improved properties, like small diameter, positive surface charge, high biocompatibility in human gingival fibroblasts, efficiency against bacterial growth and, thus, better therapeutic potential in periodontal disease treatment.     

Chitosan/poly (vinyl alcohol) films containing ZnO nanoparticles and plasticizers

In this study ZnO nanoparticles were prepared by the Pechini method from a polyester by reacting citric acid with ethylene glycol in which the metal ions are dissolved, and incorporated into blend films of chitosan (CS) and poly (vinyl alcohol) (PVA) with different concentrations of polyoxyethylene sorbitan monooleate, Tween 80 (T80). These films were characterized by infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), swelling degree, degradation of films in Hank's solution and the mechanical properties. Besides these characterizations, the antibacterial activity of the films was tested, and the films containing ZnO nanoparticles showed antibacterial activity toward the bacterial species Staphylococcus aureus. The observed antibacterial activity in the composite films prepared in this work suggests that they may be used as hydrophilic wound and burn dressings.     

Antibacterial activity of SPIONs versus ferrous and ferric ions under aerobic and anaerobic conditions: a preliminary mechanism study

In modern medicine, major attention has been paid to superparamagnetic iron oxide nanoparticles (SPIONs). Recent studies have shown the antibacterial properties of SPIONs against some Gram‐positive and Gram‐negative bacterial strains. These nanoparticles (NPs) can bind to bacterial membranes via hydrophobic or electrostatic interactions and pass through cell barriers. In this study, the authors evaluated the antibacterial activity of magnetic NPs in comparison with ferrous and ferric ions. The level of reactive oxygen species (ROS) in the treated Staphylococcus aureus and Escherichia coli bacteria were directly measured by fluorometric detection. The results showed that iron ions and SPIONs had significant dependent antimicrobial activities. SPIONs showed greater inhibitory effects than ferrous and ferric ions against the growth of treated bacterial strains under anaerobic conditions, while in aerobic conditions, ferrous showed the strongest antibacterial activity. In anaerobic conditions, they observed the greatest ROS formation and lowest minimum inhibitory concentration in the SPION‐treated group in comparison with the other groups. It seems that the release of iron ions from SPIONs and subsequent activation of ROS pathway are the main antibacterial mechanisms of action. Nevertheless, the greater antibacterial effect of SPIONs in anaerobic conditions represents other mechanisms involved in the antibacterial activity of these NPsInspec keywords: nanomagnetics, antibacterial activity, hydrophobicity, nanoparticles, superparamagnetism, biomedical materials, iron compounds, membranes, nanobiotechnologyOther keywords: ferrous ions, anaerobic conditions, superparamagnetic iron oxide nanoparticles, antibacterial properties, bacterial membranes, electrostatic interactions, bacterial strains, aerobic conditions, SPION‐treated group, antibacterial effect, cell barriers, 2′,7′‐dichlorodihydrofluorescein diacetate, reactive oxygen species, fluorometric detection, Staphylococcus aureus, Escherichia coli     

油酸修饰纳米BN/TiN润滑添加剂的摩擦学性能研究EI北大核心CSCD

使用油酸对BN,TiN,BN/TiN纳米添加剂进行表面改性修饰,通过傅里叶红外光谱仪进行表征,利用四球摩擦磨损试验机考察润滑油纳米添加剂的摩擦学性能。结果表明:油酸成功枝接在纳米颗粒表面,提高其分散性能。与纯基础油相比,纳米添加剂工况摩擦因数降低11.7%,磨斑直径降低29.5%,磨斑表面未出现起皮脱落现象,沟槽深度、宽度明显降低,混合BN/TiN纳米添加剂表现出协同润滑作用。纳米BN,TiN颗粒能够进入摩擦副中,起到微轴承作用,降低摩擦磨损,进入摩擦副中的纳米BN与摩擦副基体材料发生化学反应,生成氮化硼、氧化硼、氧化铁等物质修复磨损表面。     

The effect of filler particle size on the antibacterial properties of compounded polymer/silver fibers

Antibacterial activity has become a significant property of textiles used in applications such as medicine, clothing, and household products. In this study, we compounded polypropylene with either micro- or nano-sized silver powders. These polypropylene/silver compounds were prepared by direct melt-compounding using a conventional twin-screw mixer. We analyzed the characteristics of the compounds using wide-angle X-ray diffractometry (WAXS), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). The DSC and WAXS results indicated that the crystallinity of the polypropylene component decreased slightly when compared with that of the pure polymer. The SEM micrographs indicated that the silver particles had good dispersibility in the matrix. We measured the mechanical properties of these materials using a universal tensile tester and evaluated the antibacterial activities of these compounds by performing quantitative antibacterial tests using the AATCC-100 test method. From these evaluations of antibacterial activity, we conclude that the compounds incorporating the silver nanoparticles exhibited superior antibacterial activity relative to the samples containing micron-sized particles.     

Highly stable,protein capped gold nanoparticles as effective drug delivery vehicles for amino-glycosidic antibiotics

A method for the production of highly stable gold nanoparticles (Au NP) was optimized using sodium borohydride as reducing agent and bovine serum albumin as capping agent. The synthesized nanoparticles were characterized using UV–visible spectroscopy, transmission electron microscopy, X‐ray diffraction (XRD) and dynamic light scattering techniques. The formation of gold nanoparticles was confirmed from the appearance of pink colour and an absorption maximum at 532 nm. These protein capped nanoparticles exhibited excellent stability towards pH modification and electrolyte addition. The produced nanoparticles were found to be spherical in shape, nearly monodispersed and with an average particle size of 7.8 ± 1.7 nm. Crystalline nature of the nanoparticles in face centered cubic structure is confirmed from the selected‐area electron diffraction and XRD patterns. The nanoparticles were functionalized with various amino-glycosidic antibiotics for utilizing them as drug delivery vehicles. Using Fourier transform infrared spectroscopy, the possible functional groups of antibiotics bound to the nanoparticle surface have been examined. These drug loaded nanoparticle solutions were tested for their antibacterial activity against Gram-negative and Gram-positive bacterial strains, by well diffusion assay. The antibiotic conjugated Au NP exhibited enhanced antibacterial activity, compared to pure antibiotic at the same concentration. Being protein capped and highly stable, these gold nanoparticles can act as effective carriers for drugs and might have considerable applications in the field of infection prevention and therapeutics.     

Sonochemical synthesis of (3-aminopropyl)triethoxysilane-modified monodispersed silica nanoparticles for protein immobilization

3-Aminopropyltriethoxysilane modified monodispersed silica nanoparticles were synthesized by a rapid sonochemical co-condensation synthesis procedure. The chemical nature of surface organic modifier on the obtained modified silica nanoparticle was characterized by ¹³C and ²⁹Si MAS Nuclear Magnetic Resonance (NMR) spectroscopies, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA)- differential scanning calorimetry (DSC). Due to the strengthened positive surface charge of the silica nanoparticles by the modification with aminopropyl groups, the capability for bovine serum albumin (BSA) adsorption was significantly increased as compared with bare silica nanoparticles. 80 mg/g BSA was adsorbed on modified silica nanoparticles, whereas only 20 mg/g BSA could be loaded on pure silica nanoparticles. The enhanced positive surface charge repelled proteins with net positive charge and the modified silica nanoparticles exhibited negligible adsorption of lysozyme, thus a selective adsorption of proteins could be achieved.     

表面沉积铜纳米颗粒的细菌纤维素/壳聚糖交联复合膜的制备及其抗菌性能研究

通过戊二醛交联制备了细菌纤维素/壳聚糖复合材料,并采用磁控溅射技术在交联复合膜表面沉积铜(Cu)纳米颗粒。利用扫描电子显微镜观察纳米纤维膜表面形貌,采用傅里叶红外光谱仪、热重分析仪和X射线衍射仪比较交联复合前后以及镀铜前后复合膜基本化学结构、热稳定性和晶面结构的变化。通过能量色散X射线光谱对壳聚糖和铜在复合膜表面的分布情况进行表征。同时借助抗菌实验探究复合膜对金黄色葡萄球菌和大肠杆菌的抗菌能力。结果表明:壳聚糖与细菌纤维素发生了有效交联,改变了细菌纤维素的基本形貌、化学结构、晶体形态以及热学性能,并且镀铜后交联复合膜的抗菌性能得到了明显的提升(膜与细菌接触20min,对金黄色葡萄球菌和大肠杆菌的抗菌效果均达到了99.999%)。     

Creating water-repellent and super-hydrophobic cellulose substrates by deposition of organic nanoparticles

A series of organic nanoparticles is synthesized by imidization of poly(styrene-maleic anhydride) copolymers under pure conditions or in presence of palm oil. The nanoparticles are applied as a coating onto paper substrates, offering enhanced water-repellence and hydrophobicity. The latter properties can be further tuned by thermal curing of the coatings. After depositing the nanoparticles onto tissue papers, super-hydrophobic surfaces with self-cleaning properties can be prepared. The presented materials offer an attractive alternative for surface treatments of textiles, avoiding the use of environmental unfriendly fluorderivates.     

Morphological and permeable properties of antibacterial double-layered composite nonwovens consisting of microfibers and nanofibers

Melt-blown nonwovens consisting of only micron-sized fibers were not sufficient to completely prevent bacterial invasion using a structure property of filter media composed of micro pore size alone. To improve the percent filtration efficiency (E) and antibacterial activity of nonwovens, a novel type of polyurethane (PU) composite nonwovens composed of double layers was fabricated using a combination of melt-blowing and electrospinning. In this study, melt-blown thermoplastic polyurethane (TPU) nonwovens were used to support the mechanical property to act as a substrate layer. In addition, the electrospun PU nanofibrous layer containing the AgCl nanoparticles (NPs) as an antibacterial agent provided antibacterial activity and filtration efficiency. Double-layered composite nonwovens were characterized in terms of pore structure and antibacterial activity. The filtration efficiency of PU composite nonwovens containing an AgCl NPs was improved in comparison with PU composite nonwovens, and their antibacterial activity against three micro-organisms was 99.9%.     

Antibacterial Characterization of Silver Nanoparticles against E. Coli ATCC-15224

Silver nanoparticles of mean size 16 nm were synthesized by inert gas condensation （IGC） method. Crystalline structure, morphology and nanoparticles size estimation were conducted by X-ray diffraction （XRD） and transmission electron microscopy （TEM）. Antibacterial activity of these silver nanoparticles as a function of particles concentration against gram-negative bacterium Escherichia coli （E. coli） was carried out in liquid as well as solid growth media. Scanning electron microscopy （SEM） and TEM studies showed that silver nanoparticles after interaction with E.coli have adhered to and penetrated into the bacterial cells. Antibacterial properties of silver nanoparticles are attributed to their total surface area, as a larger surface to volume ratio of nanoparticles provides more efficient means for enhanced antibacterial activity.     

金属-有机骨架抗菌复合材料与纤维的研究进展及应用

金属-有机骨架(MOFs)抗菌材料因其具有比表面积大、孔隙率高且孔径可调及良好的生物相容性等优点而备受关注,是开发高效可循环使用抗菌医护口罩的热点材料。本文首先分析了MOFs抗菌复合材料的特点及其抗菌机制,然后综述了Ag、Cu、Zn基几类常用MOFs抗菌复合材料及其纤维的研究进展,最后探讨了MOFs抗菌功能纺织品在医疗卫生方面的应用,展望了MOFs抗菌复合纤维在医护口罩方面的潜在应用价值。      

Tribological behaviour of mechanically synthesized titanium-boron carbide nanostructured coating

In this paper, titanium-boron carbide (Ti/B4C) nanocomposite coatings with different B4C nanoparticles contents were fabricated by surface mechanical attrition treatment (SMAT) method by using B4C nanoparticles with average nanoparticle size of 40 nm. The characteristics of the nanopowder and coatings were evaluated by microhardness test, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Friction and wear performances of nanocomposite coatings and pure titanium substrate were comparatively investigated, with the effect of the boron carbide content on the friction and wear behaviours to be emphasized. The results show the microhardness, friction and wear behaviours of nanocomposite coatings are closely related with boron carbide nanoparticle content. Nanocomposite coating with low B4C content shows somewhat (slight) increased microhardness and wear resistance than pure titanium substrate, while nanocomposite coating with high B4C content has much better (sharp increase) wear resistance than pure titanium substrate. The effect of B4C nanoparticles on microhardness and wear resistance was discussed.     

Functionalization of textile materials by alkoxysilane-grafted titanium dioxide

Modern materials, including textiles for specific applications, have to satisfy growing requirements. Regulations concerning man and natural environment protection against harmful substances emission, UV radiation, and electromagnetic field radiation become more and more stringent. Intensive development of nanotechnology offers great possibilities to create novel—conforming to the requirements—multifunctional materials based on textile substrates. Nanoparticles of metal oxides, e.g., titania (TiO₂), belong to a group of compounds having photocatalytic properties, which are able to absorb UV radiation and provide antibacterial barrier. The aim of research works was the modification of selected textiles using nanoparticles of metal oxides. Nano-TiO₂ and modified nano-TiO₂ with aminosilane were applied. In the first stage, the works concerned the methodology development of such nanoparticles incorporation onto selected textile substrates. Commonly used techniques, such as padding and spraying were used as well as sol–gel coating. The evaluation of microstructure of textile fabrics covered with nanostructural titanium dioxide was performed using high-resolution SEM and TEM electron microscopes. Assessment of modified textiles pertained to the determination of protective properties against UV radiation and photocatalytic and antibacterial properties. Absorption spectra of textiles were determined using double beam type of UV–Vis Jasco V-550 with integrating sphere attachment. The same apparatus was used to determine ultraviolet protection factor (UPF) of textiles according to the standard EN 13758-1:2002. Textiles modified with nano-TiO₂ demonstrated high absorption of UV radiation in a full wavelength and their good photocatalytic properties were also confirmed.