Synthesis and characterisation of selenium nanowires using template synthesis

Selenium (Se) nanowires were grown in the pores of anodic alumina membrane as template. Facile electrodeposition technique was used for the synthesis of Se nanowires. Scanning electron microscopy was used for the morphological study of the nanowires. X-ray diffraction and Energy dispersive X-ray fluorescence were utilised for the structural characterisation. The optical properties of Se nanowires were investigated using optical absorption spectroscopy.     

Elastic Liposomal Formulation for Sustained Delivery of Antimigraine Drug: In Vitro Characterization and Biological Evaluation

The aim of this study was to prepare and characterize a topical formulation for sustained delivery of rizatriptan. Elastic liposomal formulation of rizatriptan was prepared and characterized for different characteristics by evaluating in vitro and in vivo parameters. The in vivo performance of optimized formulation was evaluated for antimigraine activity in mice using morphine withdrawal-induced hyperalgesia. The in vitro skin permeation study across rat skin suggested carrier-mediated transdermal permeation for different elastic liposomal formulation to range between 18.1 ± 0.6 and 42.7 ± 2.3 μg/h/cm², which was approximately 8–19 times higher than that obtained using drug solution. The amount of drug deposited was 10-fold higher for elastic liposome (39.9 ± 3.2%) than using drug solution (3.8 ± 1%); similarly the biological activity of optimized elastic liposome formulation was found to be threefold higher than the drug solution. On the basis of the results, it can be concluded that the elastic liposomal formulation provided sustained action of rizatriptan due to depot formation in the deeper layer of skin.     

Nanohydroxyapatite shape and its potential role in bone formation: an analytical study

Bone cells (osteoblasts) produce a collagen-rich matrix called osteoid, which is mineralized extracellularly by nanosized calcium phosphate (CaP). Synthetically produced CaP nanoparticles (NPs) have great potential for clinical application. However few studies have compared the effect of CaP NPs with different properties, such as shape and aspect ratio, on the survival and behaviour of active bone-producing cells, such as primary human osteoblasts (HOBs). This study aimed to investigate the biocompatibility and ultrastructural effects of two differently shaped hydroxyapatite [Ca₁₀(PO₄)₆(OH)₂] nanoparticles (HA NPs), round- (aspect ratio 2.12, AR2) and rice-shaped (aspect ratio 3.79, AR4). The ultrastructural response and initial extracellular matrix (ECM) formation of HOBs to HA NPs were observed, as well as matrix vesicle release. A transmission electron microscopy (TEM)-based X-ray microanalytical technique was used to measure cytoplasmic ion levels, including calcium (Ca), phosphorus (P), sodium (Na) and potassium (K). K/Na ratios were used as a measure of cell viability. Following HA NP stimulation, all measured cytoplasmic ion levels increased. AR2 NPs had a greater osteogenic effect on osteoblasts compared with AR4 NPs, including alkaline phosphatase activity and matrix vesicle release. However, they produced only a moderate increase in intracellular Ca and P levels compared with AR4. This suggests that particular Ca and P concentrations may be required for, or indicative of, optimal osteoblast activity. Cell viability, as measured by Na and K microanalysis, was best maintained in AR2. Initial formation of osteoblast ECM was altered in the presence of either HA NP, and immuno-TEM identified fibronectin and matrilin-3 as two ECM proteins affected. Matrilin-3 is here described for the first time as being expressed by cultured osteoblasts. In summary, this novel and in-depth study has demonstrated that HA NP shape can influence a range of different parameters related to osteoblast viability and activity.     

Challenges and solutions of environmental scanning electron microscopy characterisation of biomaterials: Application to hygro-expansion of paper

Most methodologies to measure the moisture-induced deformation (hygro-expansion) of paper microconstituents, including fibres and interfibre bonds, are low resolution or time-consuming. Hence, here, a novel method is proposed and validated to measure high-resolution full-field strain maps of paper microconstituents during hygro-expansion, based on environmental scanning electron microscopy (ESEM). To this end, a novel climate stage enables accurate control of the relative humidity (RH) near the specimen in the ESEM from 0%–100%. The fibre surface, which is decorated a priori with a microparticle pattern, is captured during RH change. Subsequently, correlating the fibre surface using a dedicated global digital image correlation algorithm enables high-resolution hygro-expansion strain maps. Method optimisation involved performing contrast enhancement, scan-correction to reduce ESEM artefacts and a background correction, resulting in a strain resolution of $6·10^{-4}$. Method validation revealed that the fibres' crystallinity is affected by the electron beam, even for minimal invasive electron beam settings. Interestingly, however, the fibres consistently exhibit conventional hygro-expansion behaviour during the drying slopes. Using the optimised procedure, hygro-expansion characterisation of two interfibre bonds and four interfibre bond cross-sections revealed the competition between the low longitudinal and large transverse fibre hygro-expansion in the bonded area.     

Characterisation and intrinsic magnetic resonance properties of nickel nanoparticles

Nickel nanoparticles have been extensively characterised by atomic force microscopy (AFM), scanning electron microscopy (SEM) and confocal micro-Raman spectroscopy. AFM underestimates the particle size compared to SEM measurements. It is shown that Raman spectroscopy can detect the nanometre-thick NiO layer on the particles having frequency shifts of the modes indicative of phonon confinement. The magnetic properties of the particles are studied by ferromagnetic resonance (FMR) of magnetic field aligned particles. The alignment is achieved by suspending the particles in the liquid crystal MBBA and freezing the liquid in a 0.4 T DC magnetic field. The in-field solidification locks the direction of maximum magnetisation of the particles parallel to the direction of the applied DC magnetic field. This removes the effects of dynamical particle fluctuations of the nanoparticles on the magnetic properties allowing a study of the intrinsic magnetic properties of the magnetic nanoparticles. The intensity of the FMR signal decreased with lowering temperature for the particles frozen in the liquid in a 0.4 T DC magnetic field. The effect is suggested to be due to a reduction of the microwave skin depth with lowering temperature.     

Sculpting the Plasmonic Responses of Nanoparticles by Directed Electron Beam Irradiation

Spatial confinement of matter in functional nanostructures has propelled these systems to the forefront of nanoscience, both as a playground for exotic physics and quantum phenomena and in multiple applications including plasmonics, optoelectronics, and sensing. In parallel, the emergence of monochromated electron energy loss spectroscopy (EELS) has enabled exploration of local nanoplasmonic functionalities within single nanoparticles and the collective response of nanoparticle assemblies, providing deep insight into associated mechanisms. However, modern synthesis processes for plasmonic nanostructures are often limited in the types of accessible geometry, and materials and are limited to spatial precisions on the order of tens of nm, precluding the direct exploration of critical aspects of the structure-property relationships. Here, the atomic-sized probe of the scanning transmission electron microscope is used to perform precise sculpting and design nanoparticle configurations. Using low-loss EELS, dynamic analyses of the evolution of the plasmonic response are provided. It is shown that within self-assembled systems of nanoparticles, individual nanoparticles can be selectively removed, reshaped, or patterned with nanometer-level resolution, effectively modifying the plasmonic response in both space and energy. This process significantly increases the scope for design possibilities and presents opportunities for unique structure development, which are ultimately the key for nanophotonic design.     

Writing Silica Structures in Liquid with Scanning Transmission Electron Microscopy

Silica nanoparticles are imaged in solution with scanning transmission electron microscopy (STEM) using a liquid cell with silicon nitride (SiN) membrane windows. The STEM images reveal that silica structures are deposited in well‐defined patches on the upper SiN membranes upon electron beam irradiation. The thickness of the deposits is linear with the applied electron dose. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) demonstrate that the deposited patches are a result of the merging of the original 20 nm‐diameter nanoparticles, and that the related surface roughness depends on the electron dose rate used. Using this approach, sub‐micrometer scale structures are written on the SiN in liquid by controlling the electron exposure as function of the lateral position.     

催化裂解聚苯乙烯制备碳纳米管的研究

通过在60℃氮气气氛中催化裂解聚苯乙烯,制备了大量管径为5～40nm的高质量的碳纳米管.利用扫描电子显微镜、透射电子显微镜和拉曼光谱对所制备的碳纳米管进行了表征.研究表明,所制备的碳纳米管石墨化程度高,在碳纳米管的管壁上仅有少量的无定形碳存在.催化裂解聚苯乙烯制备碳纳米管是一种有前途、低成本的绿色化学方法.     

Particle size determination of sunscreens formulated with various forms of titanium dioxide

Background: There has been some apprehension expressed in the scientific literature that nanometer-sized titanium dioxide (TiO₂) and other nanoparticles, if able to penetrate the skin, may cause cytotoxicity. In light of a lack of data regarding dermal penetration of titanium dioxide from sunscreen formulations, the Food and Drug Administration Center for Drug Evaluation and Research initiated a study in collaboration with the National Center for Toxicology Research using minipigs to determine whether nanoscale TiO₂ in sunscreen products can penetrate intact skin. Four sunscreen products were manufactured. Method: The particle size distribution of three TiO₂ raw materials, a sunscreen blank (no TiO₂) and three sunscreen formulations containing uncoated nanometer-sized TiO₂, coated nanometer-sized TiO₂ or sub-micron TiO₂ were analyzed using scanning electron microscopy (SEM), laser scanning confocal microscopy (LSCM), and X-ray diffraction (XRD) to determine whether the formulation process caused a change in the size distributions (e.g., agglomeration or deagglomeration) of the TiO₂. Results: SEM and XRD of the formulated sunscreens containing nanometer TiO₂ show the TiO₂ particles to have the same size as that observed for the raw materials. This suggests that the formulation process did not affect the size or shape of the TiO₂ particles. Conclusion: Because of the resolution limit of optical microscopy, nanoparticles could not be accurately sized using LSCM, which allows for detection but not sizing of the particles. LSCM allows observation of dispersion profiles throughout the sample; therefore, LSCM can be used to verify that results observed from SEM experiments are not solely surface effects.     

Ash deposit characterisation in a large-scale municipal waste-to-energy incineration plant

The deposition of ash - combustion residues - on superheaters and heat exchanger surfaces reduce their efficiency; this phenomenon was investigated for a large-scale waste-to-energy incineration facility. Over a period of six months, ash samples were collected from the plant, which included the bottom ash and deposits from the superheater, as well as flyash from the convective heat exchanger, the economiser and fabric filters. These were analysed for particle size, unburned carbon, elemental composition and surface morphology. Element partitioning was evident in the different combustion residues, as volatile metals, such as cadmium, antimony and arsenic, were found to be depleted in the bottom ash by the high combustion temperatures (1000+°C) and concentrated/enriched in the fabric filter ash (transferred by evaporation). Non-volatile elements by contrast were distributed equally in all locations (transported by particle entrainment). The heat exchanger deposits and fabric filter ash had elevated levels of alkali metals. 82% of flyash particles from the fabric filter were in the submicron range.     

二极溅射沉积Fe-N-O薄膜的形貌与结构分析

利用二极溅射的方法在不同衬底上沉积了Fe N O薄膜。通过扫描电子显微镜(SEM)、光电子能谱(XPS)和透射电子显微镜(TEM)等先进实验分析手段对二极溅射沉积Fe N O薄膜的形貌与结构进行了分析。XPS和TEM的结果表明,薄膜的主要成分为FeO和少量的Fe16N2多晶体组成,生长上存在择优取向;表面均匀、致密、平整,晶粒大小在50nm左右。     

电子显微分析技术在奥氏体合金应力腐蚀开裂研究领域中的应用

奥氏体合金广泛应用于核电领域。应力腐蚀开裂是核电材料主要的失效形式之一,奥氏体合金的应力腐蚀开裂关系到核电站的安全运行。综述了评估应力腐蚀开裂的试样方法以及运用现代电子显微分析技术表征应力腐蚀开裂的方法。对这些电子显微分析技术的优点进行了总结,并指出未来电子显微分析技术在应力腐蚀开裂研究中的发展方向。     

Calibration of High-Resolution X-Ray Tomography With Atomic Force Microscopy

For two-dimensional x-ray imaging of thin films, the technique of scanning transmission x-ray microscopy (STXM) has achieved images with feature sizes as small as 40 nm in recent years. However, calibration of three-dimensional tomographic images that are produced with STXM data at this scale has not yet been described in the scientific literature, and the calibration procedure has novel problems that have not been encountered by x-ray tomography carried out at a larger scale. In x-ray microtomography, for example, one always has the option of using optical imaging on a section of the object to verify the x-ray projection measurements; with STXM, on the other hand, the sample features are too small to be resolved by light at optical wavelengths. This fact implies that one must rely on procedures with higher resolution, such as atomic force microscopy (AFM), for the calibration. Such procedures, however, generally depend on a highly destructive sectioning of the sample, and are difficult to interpret because they give surface information rather than depth information. In this article, a procedure for calibration is described that overcomes these limitations and achieves a calibration of an STXM tomography image with an AFM image and a scanning electron microscopy image of the same object.A Ge star-shaped pattern was imaged at a synchrotron with a scanning transmission x-ray microscope. Nineteen high-resolution projection images of 200 × 200 pixels were tomographically reconstructed into a three-dimensional image. Features in two-dimensional images as small as 40 nm and features as small as 80 nm in the three-dimensional reconstruction were resolved. Transverse length scales based on atomic force microscopy, scanning electron microscopy, x-ray transmission and tomographic reconstruction agreed to within 10 nm. Toward the center of the sample, the pattern thickness calculated from projection images was (51 ± 15) nm vs (80 ± 52) nm for tomographic reconstruction, where the uncertainties are evaluated at the level of two standard deviations.     

Crystalline and amorphous carvedilol-loaded nanoemulsions: formulation optimisation using response surface methodology

This study aimed to evaluate the crystalline and amorphous carvedilol along with their lipidic mixtures using various instrumental techniques and to use response surface methodology in conjunction with factorial design to establish the functional relationships between operating variables (capmul GMS 50?K and cremophor RH 40).

The response variables selected are spectroscopic absorbance (Y ₁), mean particle size in distilled water (Y ₂) and in phosphate buffer pH 6.8 (Y ₃), polydispersibility index (PDI) (Y ₄) and zeta potential (Y ₅).

The optimal formulations of crystalline and amorphous carvedilol-loaded nanoemulsions were composed of fixed levels, ?0.41 and ?0.42, of capmul GMS 50?K and cremophor RH 40, respectively. The predicted and observed values of Y ₁–Y ₅ for blank nanoemulsions showed the percentage bias error of ?12.12%, ?10.25%, ?18.47%, +14.81 and ?2.89, respectively. The bias percent ranged between ?2.70% and ?29.41% for the responses Y ₁–Y ₄ for both crystalline and amorphous carvedilol-loaded nanoemulsions, indicating high degree of prognosis. However, the bias percent values for the response variable Y ₅ were 294.2% and 262.6%, for the crystalline and amorphous carvedilol-loaded nanoemulsions, respectively, possibly due to cationisation of emulsion droplets. The transmission electron microscopy of selected optimal nanoemulsions showed the spherical shape of globules with no signs of coalescence and precipitation of drug.

This study demonstrates the use of factorial design for the preparation of nanoemulsions of crystalline and amorphous carvedilol. The desirable goals can be obtained by systematic formulation approach in the shortest possible time.     

Investigations on Factors Affecting Chitosan for Dissolution Enhancement of Oxcarbazepine by Spray Dried Microcrystal Formulation With an Experimental Design Approach

In the present work effect of chitosan on microcrystal formulation for dissolution enhancement of oxcarbazepine using controlled crystallization technique coupled with spray drying was explored. The work was extended for exploration of simplified approach for stable particle size reduction. The study was performed with an experimental design approach i. e. a fractional factorial design of resolution 5 (with all 2 factor interaction) for the screening of predefined independent variables drug concentration, chitosan concentration, feed rate, inlet temperature and percent aspiration for spray drying. Whereas percent drug dissolved, wettability time, flowability in terms of angle of repose and particle size were designated as response variables. Resultant models were analyzed using multiple linear regression analysis, which generated equation to plot response surface curves along with desirability function. Results showed that chitosan concentration had significant effect on dissolution enhancement of oxcarbazepine at a level of 2% w/v. Increase in drug concentration showed decreased dissolution rate however on particle size it did not show statistically significant effect. Topographical characterization was carried out by SEM which showed that feed rate, percent aspiration and inlet temperature had significant effect on particle morphology. For deriving optimized formulation results were analyzed using desirability function for the maximum percent drug dissolved and least drug polymer matrix particle size. DSC studies showed that drug was molecularly associated with chitosan matrix or particles.     

Wide characterisation to compare conventional and highly effective microwave purification and functionalization of multi-wall carbon nanotubes

Both microwave-assisted and conventional acidic treatments for the purification and functionalization of multi-wall carbon nanotubes were investigated. Impurities such as zeolite, catalyst particles and amorphous carbon were eliminated. In comparison to the harshness of the acidic treatment of a conventional technique, the microwave-assisted procedure makes it possible to obtain a material with a higher degree of purity (> 98%) and -COOH functionalization in a shorter time, at a lower temperature, with a smaller amount and lower concentration of acid, as well as without agitation. An extensive step-by-step characterization of the treated samples has shown that the microwave-assisted treatment has limited effects on the significant characteristics of the nanotubes.     

Ultrasmall Liquid Droplets on Solid Surfaces: Production,Imaging, and Relevance for Current Wetting Research

The investigation of micro‐ and nanoscale droplets on solid surfaces offers a wide range of research opportunities both at a fundamental and an applied level. On the fundamental side, advances in the techniques for production and imaging of such ultrasmall droplets will allow wetting theories to be tested down to the nanometer scale, where they predict the significant influence of phenomena such as the contact line tension or evaporation, which can be neglected in the case of macroscopic droplets. On the applied side, these advances will pave the way for characterizing a diverse set of industrially important materials such as textile or biomedical micro‐ and nanofibers, powdered solids, and topographically or chemically nanopatterned surfaces, as well as micro‐and nanoscale devices, with relevance in diverse industries from biomedical to petroleum engineering. Here, the basic principles of wetting at the micro‐ and nanoscales are presented, and the essential characteristics of the main experimental techniques available for producing and imaging these droplets are described. In addition, the main fundamental and applied results are reviewed. The most problematic aspects of studying such ultrasmall droplets, and the developments that are in progress that are thought to circumvent them in the coming years, are highlighted.

     

Optical Emission Study of RF Thermal Plasma During Fullerene Synthesis

Results on studies of molecular spectra emitted in the initial stages of fullerene synthesis during processing of graphite powder in RF thermal plasma conditions are presented in this work. CN—usually present in carbon plasmas—and C₂ were found as dominant molecular species. The role of CN radicals on the fullerene formation was discussed in detail. Intensities of CN and C₂ lines were studied against the composition of gas phase and the feed rate of graphite powder. The rotational-vibrational temperatures of CN species were calculated by fitting the experimental spectra to the simulated ones. It was concluded that in the plasma region CN radicals could be formed by the reaction of C₂ with atomic nitrogen at smaller loads. This reaction lowered the yield of fullerenes. At larger loads, C₂ formation was decreased due to lower temperature of the particles compared to smaller load. The CN radicals were produced by the surface reaction of the hot carbon particles with nitrogen atoms. Results confirmed that for effective fullerene synthesis, the nitrogen content of the precursors and the plasma gases should be minimized.     

Effect of acetylene flow rate on morphology and structure of carbon nanotube thick films grown by thermal chemical vapor deposition

Carbon nanotube (CNT) films were grown on nickel foil substrates by thermal chemical vapor deposition (CVD) with acetylene and hydrogen as the precursors. The morphology and structure of CNTs depending on the acetylene flow rate were characterized by a scanning electron microscope (SEM), a transmission electron microscope (TEM) and a Raman spectrometer, respectively. The effect of acetylene flow rate on the morphology and structure of CNT films was investigated. By increasing the acetylene flow rate from 10 to 90 sccm (standard cubic centimeter per minute), the yield and the diameter of CNTs increase. Also, the defects and amorphous phase in CNT films increase with increasing acetylene flow rate. Translated from Journal of Inorganic Materials, 2006, 21(1): 75–80 [译自: 无机材料学报]