Measurement uncertainties of size, shape, and surface measurements using transmission electron microscopy of near-monodisperse, near-spherical nanoparticles

Carbon nanotubes are currently one of the most important materials due to their strong mechanical resistance, light weight, and transport properties. Since the publication of Ijima’s paper on tubular carbon structures (Iijima, Nature 354:56–58, 1991), approximately 80,000 research articles have been published according to the ISI web of science (WOS) database, using “carbon nanotube*” as the search criterion in the search by topic option. In this work, the development and impact of nanoscience and nanotechnology (N&N) and carbon nanotubes on several research areas, journals, specific papers, and emerging research areas are analyzed and discussed. Considering the production of papers in these areas from 1997 to 2012, quantitatively speaking, the People’s Republic of China is emerging as the leading country in N&N and carbon nanotube research, passing the United States of America. WOS data analysis of nanoscience, nanotechnology, and carbon nanotube research in developed and developing countries is discussed, and some ideas for accelerating the progress in these important research areas are proposed.     

Preparation of monolayers of nanoparticles for transmission electron microscopy

A novel procedure of sample preparation for transmission electron microscopy of nanoparticles is proposed yielding a monolayer of nanoparticles. The procedure offers the possibility of sorting nanoparticles by size and studying the influence of external fields on their arrangement. This technology can also be applied for the creation of ordered arrays of nanoparticles in ultrathin polymer films.     

Size effect on nanomechanical properties of ZnO cones using in situ transmission electron microscopy

Nanoscale fracture and strain-induced structure variation of ZnO nanocones are determined using in situ transmission electron microscopy compression experiments. For the single-crystalline nanocones with diameters of 100–300 nm, the Young's modulus is in the range of 7.7–48 GPa and the ultimate tensile strength is in the range of 2.4–4.3%. The Young's modulus and tensile strength increase with decreasing diameter. Here, we report the nanogenerator of ZnO nanocones can be used mechanical energy to output 90 nW/mm².     

Video-frequency scanning transmission electron microscopy of moving gold nanoparticles in liquid

Immobilized gold nanoparticles were imaged in a liquid containing water and 50% glycerol with scanning transmission electron microscopy (STEM). The specimen was enclosed in a liquid compartment formed by two silicon microchips with electron transparent windows. A series of images was recorded at video frequency with a spatial resolution of 1.5nm. The nanoparticles detached from their support after imaging them for several seconds at a magnification of 250,000. Their movement was found to be much different than the movement of nanoparticles moving freely in liquid as described by Brownian Motion. The direction of motion was not random-the nanoparticles moved either in a preferred direction, or radially outwards from the center of the image. The displacement of the gold nanoparticles over time was three orders of magnitude smaller than expected on the basis of Brownian Motion. This finding implies that nanoscale objects of flexible structure or freely floating, including nanoparticles and biological objects, can be imaged with nanoscale resolution, as long as they are in close proximity to a solid support structure.     

Tracing nanoparticles and photosensitizing molecules at transmission electron microscopy by diaminobenzidine photo-oxidation

During the last three decades, diaminobenzidine photo-oxidation has been applied in a variety of studies to correlate light and electron microscopy. Actually, when a fluorophore is excited by light, it can induce the oxidation of diaminobenzidine into an electron-dense osmiophilic product, which precipitates in close proximity to the fluorophore, thereby allowing its ultrastructural detection. This method has very recently been developed for two innovative applications: tracking the fate of fluorescently labeled nanoparticles in single cells, and detecting the subcellular location of photo-active molecules suitable for photodynamic therapy. These studies established that the cytochemical procedures exploiting diaminobenzidine photo-oxidation represent a reliable tool for detecting, inside the cells, with high sensitivity fluorescing molecules. These procedures are trustworthy even if the fluorescing molecules are present in very low amounts, either inside membrane-bounded organelles, or at the surface of the plasma membrane, or free in the cytosol. In particular, diaminobenzidine photo-oxidation allowed elucidating the mechanisms responsible for nanoparticles internalization in neuronal cells and for their escape from lysosomal degradation. As for the photo-active molecules, their subcellular distribution at the ultrastructural level provided direct evidence for the lethal multiorganelle photo-damage occurring after cell photo-sensitization. In addition, DAB photo-oxidized samples are suitable for the ultrastructural detection of organelle-specific molecules by post-embedding gold immunolabeling.     

Interphase analysis of hierarchical composites via transmission electron microscopy

Observation and analysis of the interphase are essential for a detailed understanding of the global composite properties when nanofillers are incorporated as interfacial agents. Techniques such as atomic force microscopy and nano-indentation provide valuable information on interfacial properties associated with the viscoelastic behavior of each phase. However, when the morphology of this region is observed in detail, instrumental errors may regularly appear, decreasing the accuracy of measurements. In this work, the use of transmission electron microscopy (TEM) was explored to image the glass fiber-reinforced polymer GFRP interphase containing interfacial nanocellulose. TEM lamellas were prepared via a focused ion beam to observe the phases disposed within the composite arrangement. Energy dispersive X-ray spectroscopy was also performed to determine the elemental composition in each sample phase. Interphase sizes between 25 and 50 nm thick were found, highlighting the ability of this characterization route to give accurate interfacial measurements. This kind of measurement will open new routes for getting rich information on hierarchically structured composites containing a nanostructure as an interfacial agent.     

Structure and mass analysis by scanning transmission electron microscopy.

In the scanning transmission electron microscope (STEM) an electron beam of a few angstroms diameter is raster scanned over a thin sample and the scattered electrons are sequentially measured for each sample element irradiated. The mass, the elemental composition and the structure of a protein can be simultaneously assessed if all detector systems of the STEM are used. Aspects affecting the accuracy of the mass measurement technique and the demands placed on the instrument's dark-field detector system are outlined. In addition, the influences of some sample preparation techniques are noted and the mass-loss induced at ambient temperatures by the incidence of 80kV electrons on various biological samples is reported. Finally, the importance of the STEM for the structural analysis of proteins is documented by examples.     

Atomic surface diffusion on Pt nanoparticles quantified by high-resolution transmission electron microscopy

Aberration-corrected high-resolution transmission electron microscopy allows for the delocalization-free observation of atomic motions on metallic surfaces and thus enables measurements of the diffusion of single atoms on the surfaces of nanoscopic objects such as nanoparticles. Using this recently introduced method, the diffusion coefficient for surface self-diffusion of Pt nanoparticles is determined through the fluctuating occupation of the particle's atomic columns. This diffusion coefficient is determined to lie in the range D ∼ (10⁻¹⁷ … 10⁻¹⁶) cm²/s.     

Shell thickness determination of polymer-shelled microbubbles using transmission electron microscopy

Intravenously injected microbubbles (MBs) can be utilized as ultrasound contrast agent (CA) resulting in enhanced image quality. A novel CA, consisting of air filled MBs stabilized with a shell of polyvinyl alcohol (PVA) has been developed. These spherical MBs have been decorated with superparamagnetic iron oxide nanoparticles (SPIONs) in order to serve as both ultrasound and magnetic resonance imaging (MRI) CA. In this study, a mathematical model was introduced that determined the shell thickness of two types of SPIONs decorated MBs (Type A and Type B). The shell thickness of MBs is important to determine, as it affects the acoustical properties. In order to investigate the shell thickness, thin sections of plastic embedded MBs were prepared and imaged using transmission electron microscopy (TEM). However, the sections were cut at random distances from the MB center, which affected the observed shell thickness. Hence, the model determined the average shell thickness of the MBs from corrected mean values of the outer and inner radii observed in the TEM sections. The model was validated using simulated slices of MBs with known shell thickness and radius. The average shell thickness of Type A and Type B MBs were 651 nm and 637 nm, respectively.     

Thickness measurement of cobalt foils using ultramicrotome cuts and electron microscopy

A method of thickness measurement of cobalt foils using transverse ultramicrotome cuts of foils embedded in Araldite is described. A new two-stage gelatine-carbon replica technique was developed. For a foil with inhornogeneous thickness, the method enables an exact determination of the position on the foil of the spot where thickness is measured. Although glass knives only were available for cutting, the accuracy of thickness measurement was better than ±1000 Å.     

Ultrastructural examination of dentin using focused ion-beam cross-sectioning and transmission electron microscopy

Focused ion-beam (FIB) milling is a commonly used technique for transmission electron microscopy (TEM) sample preparation of inorganic materials. In this study, we seek to evaluate the FIB as a TEM preparation tool for human dentin. Two particular problems involving dentin, a structural analog of bone that makes up the bulk of the human tooth, are examined. Firstly, the process of aging is studied through an investigation of the mineralization in ‘transparent’ dentin, which is formed naturally due to the filling up of dentinal tubules with large mineral crystals. Next, the process of fracture is examined to evaluate incipient events that occur at the collagen fiber level. For both these cases, FIB-milling was able to generate high-quality specimens that could be used for subsequent TEM examination. The changes in the mineralization suggested a simple mechanism of mineral ‘dissolution and reprecipitation’, while examination of the collagen revealed incipient damage in the form of voids within the collagen fibers. These studies help shed light on the process of aging and fracture of mineralized tissues and are useful steps in developing a framework for understanding such processes.     

Atomic force microscopy and transmission electron microscopy of biocompatible magnetic fluids: A comparative analysis

The present study provides a comparative analysis of the size dispersity of magnetic nanoparticles (MNPs) within magnetic fluids as obtained from atomic force microscopy (AFM) and transmission electron microscopy (TEM). Whereas the mean particle diameter obtained from the AFM data presented a reduction of about 34% as compared to the value obtained from the TEM data, the standard deviation obtained from the AFM data is twice the value found from the TEM data. Similarities and differences in the size dispersity parameters are discussed in terms of sample preparation and tip characteristics. A two-dimensional mode for the deposition of the MNPs on top of the mica substrate is discussed as well.     

Observation of structural vacancies in titanium monoxide using transmission electron microscopy

Structural vacancies were directly observed in nonstoichiometric ordered titanium monoxide using high-resolution transmission electron microscopy under a magnification of 4×10⁶. The observation of structural vacancies became possible due to their ordering and the formation of continuous vacancy channels in certain crystallographic directions. Microdiffraction was employed to orient the sample in the direction permitting the observation of vacancy channels. Transmission electron microscopy providing a magnification of tens of thousands of times revealed that titanium monoxide grains do not contain cracks and macropores and confirmed that the free volume detected picnometrically in the titanium monoxide is concentrated in structural vacancies on the titanium and oxygen sublattices.     

The characterization of nanostructured CVD Ni powders using transmission electron microscopy

Studies of Ni powders using a state-of-the-art transmission electron microscope with a field-emission electron source show that this instrument can be an invaluable tool for studying the morphology and character of nanostructured Ni powder manufactured by a commercial nickel carbonyl vapor deposition process. This study has revealed the presence of surface coatings, including NiO and turbostratic graphite on some powders, which can degrade the electrical conductivity of the powder. Due to the high curvature of hexagonal carbon (graphene) planes, and subsequent high density of defects, the turbostratic graphitic nanocarbon may exhibit new properties.     

The investigation of multiply twinned L10-type FePt nanoparticles by transmission electron microscopy

Thin films of FePt nanoparticles were prepared by co-deposition of Fe and Pt on to amorphous C films kept at 350°C. As-prepared films were composed of disordered Fe–Pt nanoparticles with a fcc structure, where twinned and multiply twinned Fe–Pt nanoparticles could be identified by transmission electron microscopy (TEM) and electron diffraction. Atomic ordering from fcc to L1₀ structure was followed by in-situ TEM observation during heating up to 750°C. Multiply twinned (fivefold) nanoparticles of the L1₀ FePt were observed for the first time by high-resolution TEM observation. In these nanoparticles the crystallographic c axes of L1₀ structure is oriented parallel to the film plane in each segment. The stability of the fivefold FePt nanoparticles is briefly discussed.     

In situ environmental transmission electron microscopy to determine transformation pathways in supported Ni nanoparticles

We have applied in situ environmental transmission electron microscopy (ETEM) to follow the dynamic phase transformations that take place in SiO(2) supported Ni nanoparticles during oxidation and reduction processes. The gas environments used for in situ ETEM studies were relevant to partial oxidation of methane (POM) reaction. In the presence of the CH(4)+O(2) gas mixture (in 2:1 ratio) at 400°C, Ni transforms to NiO due to the high O-chemisorption energy. NiO void structures were formed during the oxidation because of the Kirkendall type process where diffusion of Ni cations along NiO grain boundaries is eight orders of magnitude greater than the diffusion of O anions. Reduction was performed under a CO+H(2) mixture at 400°C (in 1:2 ratio) and also in the presence of CH(4) at 500°C. Particle reduction processes also takes place via the diffusion of Ni cations along the NiO grain boundaries leaving NiO on the surface of the nanoparticle. NiO is the phase that is present on the surface of the nanoparticle during the intermediate stage of reduction.     

Secondary electron microscopy and transmission electron microscopy studies of carbon nanotubes in C-Ni films

Carbon nanotubes films have been studied with SEM and TEM. The studied films were obtained using a two step method: PVD process and CVD process. Strongly defected and curled carbon nanotubes containing Ni nanoparticles formed the film with thickness of about 300–400 nm. Observed carbon nanotubes were of lengths from 100 nm to 300 nm and did not stick to each other.     

Size measurement of nanoparticles using the emission intensity distribution of laser-induced plasma

A two-dimensional optical imaging method is presented for monitoring the laser-induced breakdown events of aqueous nanoparticles. The method is based on measuring the light intensity distribution of plasma from spatially resolved breakdown events. The number of laser breakdown events as a function of the emission intensity follows the Gaussian distribution and its full-width at a half-maximum appears in direct correlation with the particle size. Hence the particle size can be determined by measuring the plasma emission intensity distribution. Calibration of the method is carried out with reference polystyrene particles dispersed in water. Application is demonstrated for measuring bentonite colloidal particles of different sizes in groundwater. PACS 42.62.Eh; 52.25.Rv; 52.70.Nc     

Energy-resolved analysis of ferroelectric electron emission from TGS using emission electron microscopy

Ferroelectric electron emission arises when the spontaneous polarization of a ferroelectric is switched due to the application of an electric field. In order to study the origin of emission and the related emission mechanism, space-resolved emission electron microscopy has been employed. The integral energy distribution of the emitted electrons from triglycine-sulfate surfaces has been investigated using a cylindrical sector analyzer and an imaging retarding field analyzer. Space-resolved emission photography and energy distribution measurements were obtained, revealing the effect of ferroelectric switching on the electric field distribution and hence on the emission process. Evidence of secondary electron emission from the metal electrodes has been found.     

扫描电子显微镜法测定金属衬底上石墨烯薄膜的覆盖度

利用化学气相沉积法生长在金属衬底上的石墨烯薄膜,由于其尺寸的可控性和转移的便利性,被广泛用作各种透明电极.石墨烯薄膜的方块电阻是衡量其品质的重要指标之一,而石墨烯覆盖完全是保证薄膜拥有优良导电性能的基本前提.本文通过研究评估不确定度的分量,提出利用扫描电子显微镜像素计算微区和宏观覆盖度的方法.考虑到石墨烯薄膜覆盖区域与未覆盖区域边界的确定,以及晶畴数目的选取这两个因素对覆盖度测定造成的误差.通过微区有效扫描电子显微镜图像的确定、宏观石墨烯薄膜有效扫描电子显微镜图像的测量数目以及宏观石墨烯薄膜覆盖均匀性的表达,系统研究了化学气相沉积法生长在金属衬底上的石墨烯薄膜的微区覆盖度、宏观覆盖度和覆盖均匀性.该方法通过获得有限次微区扫描电子显微镜图像,不仅可以计算宏观石墨烯薄膜的覆盖度,还可以给出覆盖均匀性,既节省了测量时间,同时也能保证测量有效性.