A Correlative Analysis of Gold Nanoparticles Internalized by A549 Cells

Fluorescently labeled nanoparticles are widely used to investigate nanoparticle cell interactions by fluorescence microscopy. Owing to limited lateral and axial resolution, nanostructures (<100 nm) cannot be resolved by conventional light micro­scopy techniques. Especially after uptake into cells, a common fate of the fluorescence label and the particle core cannot be taken for granted. In this study, a correlative approach is presented to image fluorescently labeled gold nanoparticles inside whole cells by correlative light and electron microscopy (CLEM). This approach allows for detection of the fluorescently labeled particle shell as well as for the gold core in one sample. In this setup, A549 cells are exposed to 8 nm Atto 647N‐labeled gold nanoparticles (3.3 × 10⁹ particles mL^?1, 0.02 μg Au mL^?1) for 5 h and are subsequently imaged by confocal laser scanning microscopy (CLSM) and transmission electron microscopy (TEM). Eight fluorescence signals located at different intracellular positions are further analyzed by TEM. Five of the eight fluorescence spots are correlated with isolated or agglomerated gold nanoparticles. Three fluorescence signals could not be related to the presence of gold, indicating a loss of the particle shell.     

Preparation of magnetic FeCo nanoparticles by coprecipitation route

Magnetic FeCo nanoparticles with high saturation magnetization (M_s = 148 emu/g) at 15 kOe were prepared by a coprecipitation route. The value of M_s for FeCo nanoparticles depends on the ratio of Fe to Co components. The size of the nanoparticles was confirmed by transmission electron microscopy (TEM) images, and morphology of the nanoparticles was obtained by field emission scanning electron microscopy (FE-SEM) images. The crystal structure of the nanoparticles dependent on annealing was characterized by X-ray diffraction data. The magnetic properties were characterized by saturation magnetization from a hysteresis loop by VSM.     

Pick your carats: nanoparticles of gold–silver–copper alloy produced <Emphasis Type="Italic">in vivo</Emphasis>

Engineered gold nanoparticle catalysts containing a mixture of metals enable enhanced specificity and reactivity. We report the synthesis by plants of mixed metal nanoparticles suggesting the possibility of using plants to produce catalysts of specific composition, perhaps even those difficult to synthesise by traditional methods. The nanoparticles contain Au, Ag and Cu as an alloy. The structure and composition are confirmed by scanning transmission electron microscopy (STEM) and energy dispersive X-ray analysis (EDX).     

Imaging the Hydrated Microbe‐Metal Interface Using Nanoscale Spectrum Imaging

PdAu nanocrystals are synthesised by Geobacter sulfurreducens, a dissimilatory metal‐reducing bacterium, and the resulting bimetallic nanocrystal‐decorated microbes are imaged using a range of advanced electron microscopy techniques. Specifically, the first example of elemental mapping of fully hydrated biological nanostructures using scanning transmission electron microscope (STEM) energy dispersive X‐ray (EDX) spectrum imaging within an environmental liquid‐cell is reported. These results are combined with cryo‐TEM and ex situ STEM imaging and EDX analysis with the aim of better understanding microbial synthesis of bimetallic nanoparticles. It is demonstrated that although Au and Pd are colocalized across the cells, the population of nanoparticles produced is bimodal, containing ultrasmall alloyed nanocrystals with diameters <3 nm and significantly larger core‐shell structures (>200 nm in diameter) which show higher Pd contents and exhibit a Pd enriched shell only a few nanometers thick. The application of high‐resolution imaging techniques described here offers the potential to visualize the microbe‐metal interface during the bioproduction of a range of functional materials by microbial “green” synthesis routes, and also key interfaces underpinning globally relevant environmental processes (e.g., metal cycling).     

Magnetic properties of substituted strontium ferrite nanoparticles and thin films

SrFe_12−x(Zr_0.5Mg_0.5)_xO₁₉ nanoparticles and thin films with x=0-2.5 were synthesized by a sol-gel method on thermally oxidized silicon wafer (Si/SiO₂). Structural and magnetic characteristics of synthesized samples were studied employing x-rays diffraction (XRD), transmission electron microscopy (TEM), magnetic susceptometer, atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), and vibrating sample magnetometer (VSM). TEM micrographs display that the narrow size distribution of ferrite nanoparticles with average particle size of 50 nm were fabricated. Fitting obtained data of effective magnetic susceptibility by Vogel-Fulcher law confirms the existence of strong magnetic interaction among fine particles. XRD patterns and FE-SEM micrographs demonstrated that single phase c-axis hexagonal ferrite films with rather narrow grain size distribution were obtained. AFM micrographs exhibited that the surface roughness increases with an increase in Zr-Mg content. It was found from the VSM graphs that with an increase in substitution contents the coercivity decreases, while the saturation of magnetization increases. The Henkle plots confirms the existence of exchange coupling among nano-grain in ferrite thin films.     

Sol–gel synthesis of 8 nm magnetite (Fe3O4) nanoparticles and their magnetic properties

Magnetite (Fe₃O₄) nanoparticles were successfully synthesized by a sol–gel method. The obtained nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive analysis by X-ray (EDAX), transmission electron microscopy (TEM), superconducting quantum interference device (SQUID) and Mössbauer spectrometry. XRD and Mössbauer measurements indicate that the obtained nanoparticles are single phase. TEM analysis shows the presence of spherical nanoparticles with homogeneous size distribution of about 8 nm. Room temperature ferromagnetics behavior was confirmed by SQUID measurements. The mechanism of nanoparticles formation and the comparison with recent results are discussed. Finally, the synthesized nanoparticles present a potential candidate for hyperthermia application given their saturation magnetization.     

Synthesis and characterization of bovine femur bone hydroxyapatite containing silver nanoparticles for the biomedical applications

Bovine femur bone hydroxyapatite (HA) containing silver (Ag) nanoparticles was synthesized by thermal decomposition method and subsequent reduction of silver nitrate with N,N-dimethylformamide (DMF) in the presence of poly(vinylacetate) (PVAc). The structural, morphological, and chemical properties of the HA–Ag nanoparticles were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). TEM images showed that the Ag nanoparticles with size ranging from 8 to 20 nm and were arranged at the periphery of HA crystals. Bactericidal activity of HA–Ag with different concentration of Ag nanoparticles immobilized on the surface of HA was investigated against gram-positive Staphylococcus aureus (S. aureus, non-MRSA), Methicillin resistant S. aureus (MRSA) and gram-negative Escherichia coli (E. coli) by the disc diffusion susceptibility test. The HA–Ag nanoparticles showed that broad spectrum activity against non-MRSA, MRSA, and E. coli bacterial strains.     

Synthesis of Nanoscale Bimetallic Particles in Polyelectrolyte Membrane Matrix for Reductive Transformation of Halogenated Organic Compounds

Nanosized Fe/Ni and Fe/Pd particles were synthesized in the polyacrylic acid (PAA)/polyether sulfone (PES) composite membrane matrix for reductive transformation of halogenated organic compounds (HOCs). The advantages of using membrane to immobilize nanoparticles are the reduction of particles loss, prevention of particles agglomeration, and potential application of convective flow. Cross-linked PAA/PES composite membranes containing metal ions as particles precursor were prepared by heat treatment with ethylene glycol (EG) as a cross-linking agent. Nanoscale metal particles were formed and immobilized inside the membrane matrix after reduction with sodium borohydride. Membrane morphology and structure were observed by scanning electron microscopy (SEM). Particle size and distribution were characterized by SEM and transmission electron microscopy (TEM). Energy dispersive X-ray spectroscopy (EDS) was used to obtain the qualitative and quantitative element information of particles. A specimen-drift-free EDS line profile and EDS mapping system was performed in a scanning transmission electron microscopy (STEM) to determine the two-dimensional element distribution of iron and nickel in the nano domain. In the dechlorination study with trichloroethylene (TCE) as a representative HOCs, rapid and complete destruction of TCE was achieved by using nanosized bimetallic Fe/Ni or Fe/Pd in PAA/PES composite membranes. Typically more than 95% of 10 mg/l TCE was reduced within 1 h. Ethane was found in the headspace as the main product.     

Growth of β-Ga<Subscript>2</Subscript>O<Subscript>3</Subscript> nanoparticles by pulsed laser ablation technique

This work investigates pulsed laser ablation for Ga₂O₃ nanoparticles. Nanoparticles with diameters of 10 to 500 nm were deposited on silicon substrates in large quantities, by KrF excimer laser ablation of a GaN (99.99% purity) target in high purity nitrogen (99.9995%) background gas at room temperature, without a catalyst. The particle size and phase structure of the as-deposited nanoparticles are examined by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), and selected-area electron diffraction (SAD). FE-SEM images show that the nanoparticles aggregate to form micron-size nanoclusters at chamber pressures of 1 and 5 Torr. On the other hand, nanoparticles aggregate with chain-like nanostructures, are synthesized at high chamber pressures (10 Torr). TEM images further reveal that chain-like nanostructures are formed by the aggregation of individual spherical and ellipsoidal nanoparticles. Photoluminescence measurement shows stable and broad blue emission at 445 nm. PACS 81.20.-N; 81.15.Fg; 75.50.Vv     

XRF mapping and TEM analysis of coated and uncoated silica nanoparticles in A549 cells and human monocytes

The evaluation of nanomaterials intracellular distribution still remains a challenge in nanomedicine applications and toxicological studies. Synchrotron radiation X-ray microscopy combined with X-ray fluorescence (XRF) microspectroscopy provides unique information that has pushed the frontiers of biological research, particularly when investigating intracellular mechanisms. In this work, the presence of silica nanoparticles in in vitro cultured human lung epithelial cell line and freshly extract human monocytes has been investigated. For the uptake and intracellular distribution of NPs, cells were cultured on polymeric substrates (Mylar). The SiO₂–NPs have been synthesized at JRC and characterized by dynamic light scattering, centrifugal liquid sedimentation, and transmission electron microscopy (TEM), whereas their interaction with cells was investigated with TEM and XRF. For the latter, we used TwinMic in scanning transmission mode coupled with low-energy XRF spectroscopy, paying particular attention to the distribution of different elements, namely, Fe, O, C, Si, and Mg. Si XRF signals recorded on cells exposed to uncoated silica and epoxy-coated silica nanoparticles are comparable, indicating low difference in cellular uptake and suggesting a similar interaction between nanoparticles and cells. However, the TEM analysis indicates a better affinity of the coated nanoparticles for the cell membrane. Moreover, the TEM analysis shows also the presence of nanoparticles in endosomes.     

Optimization of the preparation of GaN-based specimens with low-energy ion milling for (S)TEM

We report on optimization of electron transparent GaN based specimens for transmission electron microscopy (TEM) and scanning TEM (STEM) studies by combining focused ion beam thinning and low-energy (≤500 eV) Ar-ion milling. Energy dependent ion milling effects on GaN based structures are investigated and the quality of ion milled samples is compared with that of specimens prepared by wet chemical etching. Defects formed during ion milling lead to amorphization of the specimen. The experimental results are compared with Monte-Carlo simulations using the SRIM (stopping and range of ions in matter) software. Specimen thickness was deduced from high-angle annular dark field STEM images by normalization of measured intensities with respect to the intensity of the scanning electron probe and comparison with multislice simulations in the frozen lattice approach. The results show that the thickness of the amorphous surface layer can be successfully reduced below 1 nm by low energy ion milling, leading to a homogeneous image contrast in TEM and STEM, so that good conditions for quantitative analysis can be achieved. For an ion energy of 400 eV the thickness measurements resulted in an etching rate of about 6-8 nm/min.     

Synthesis and characterization of the SnS nanowires via chemical vapor deposition

Single-crystal SnS nanowires have been successfully synthesized by catalysis-assistant chemical vapor deposition. Applying Au nanoparticles which were applied on the ITO surface as the catalysator, using SnS powder and S powder as precursors and the Ar+H₂ mixed atmosphere as the shielding and carrier gas, the SnS nanowires were obtained. X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS) and Raman spectroscopy were employed to characterize the as-synthesized SnS nanostructures. The room-temperature photoluminescence properties of these as-prepared SnS nanowires were presented.     

High-resolution electron microscopy for heterogeneous catalysis research

Heterogeneous catalysts are the most important catalysts in industrial reactions. Nanocatalysts, with size ranging from hundreds of nanometers to the atomic scale, possess activities that are closely connected to their structural characteristics such as particle size, surface morphology, and three-dimensional topography. Recently, the development of advanced analytical transmission electron microscopy(TEM) techniques, especially quantitative high-angle annular darkfield(HAADF) imaging and high-energy resolution spectroscopy analysis in scanning transmission electron microscopy(STEM) at the atomic scale, strengthens the power of(S)TEM in analyzing the structural/chemical information of heterogeneous catalysts. Three-dimensional reconstruction from two-dimensional projected images and the real-time recording of structural evolution during catalytic reactions using in-situ(S)TEM methods further broaden the scope of(S)TEM observation. The atomic-scale structural information obtained from high-resolution(S)TEM has proven to be of significance for better understanding and designing of new catalysts with enhanced performance.     

Three-dimensional characterization of drug-encapsulating particles using STEM detector in FEG-SEM

New drug-encapsulating particles were investigated using bright field (BF) scanning transmission electron microscopy (STEM) in a field emission gun (FEG) scanning electron microscope (SEM). Thickness characterization was done based on measuring the effective cross-section for interaction in our sample-detector configuration using calibration particles. A simplified analytical model, taking account of BF-STEM contrast and effective cross-section for interaction, was utilized for transforming projected two-dimensional BF-STEM images into three-dimensional thickness images. The three-dimensional characterization is demonstrated on a new family of biological materials composed of submicron to micron drug-free and drug-encapsulating particles. The importance of using BF-STEM in SEM, relative to other electron microscopy methods, is discussed as well as the lateral and depth resolution.     

An MOCVD route to In2O3 one-dimensional materials with novel morphologies

We have successfully synthesized one-dimensional (1-D ) indium oxide (In₂O₃) arrays by the metalorganic chemical vapor deposition (MOCVD) method. We have characterized the products by means of X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). The SEM images showed that the 1-D materials with serrated surfaces had cross-sections in the shape of an acute triangle. The XRD and TEM studies revealed that the 1-D materials possessed a single-crystalline cubic structure and that the growth occurred preferentially along the [111] direction. PACS 81.15.Gh     

The morphology of mass selected ruthenium nanoparticles from a magnetron-sputter gas-aggregation source

We have investigated the morphology of mass selected ruthenium nanoparticles produced with a magnetron-sputter gas-aggregation source. The nanoparticles are mass selected using a quadrupole mass filter, resulting in narrow size distributions and average diameters between 2 and 15 nm. The particles are imaged in situ by scanning electron microscopy and scanning tunneling microscopy (STM) as well as ex-situ using transmission electron microscopy (TEM). For each distribution of mass selected nanoparticles, the height determined by STM and the width determined by TEM are seen to be similar throughout the mass range investigated. The particles are found to have a well-defined morphology for diameters below approximately 6 nm. Larger nanoparticles are less well-defined having rough surfaces, unlike the equilibrium morphology determined from the Wulff construction. The morphology of the particles is, in general, believed to be determined by the conditions inside the gas-aggregation source and the morphology is retained as the particles are soft-landed on the substrate.     

Low voltage high-resolution SEM (LVHRSEM) for biological structural and molecular analysis

High-resolution scanning electron microscopy (HRSEM) is being used increasingly to gain new insights into three-dimensional organization of biological structure, macromolecular complexes and interactions of cellular components as well as isolated cell organelles. Modern scanning electron microscopes (SEMs) combined with adequate sample preparation can now provide resolution comparable with that achieved using transmission electron microscopes (TEMs) down to 2-5 nm for biological material. The versatility of the instrument and new sample preparation techniques have allowed detailed analysis of chromosomes, cytoskeletal components, virus and other biological material that has not been possible with TEM. The present review addresses resolution and specific specimen preparations for HRSEM, and highlights the importance of specimen preparation and choice of methods to achieve optimal results for proteins, macromolecular complexes and subcellular structures using low voltage HRSEM (LVHRSEM).     

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.     

Preparation, characterization and surface morphology of novel optically active poly(ester-amide)/functionalized ZnO bionanocomposites via ultrasonication assisted process

Novel bionanocompoites (BNCs) were prepared using zinc oxide (ZnO) nanoparticles which functionalized by γ-methacryloxypropyltrimethoxysilane (KH570) as a coupling agent. Poly(ester-amide) (PEA) based on tyrosine natural amino acid was synthesized and used as a polymer matrix. PEA/ZnO BNCs were characterized by fourier transform infrared spectra (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM) and transmission electron microscopy (TEM). All the results confirmed that the surface of ZnO particle has sufficient compatibility with PEA through the link of the coupling agent between ZnO and polymer and also proved that the presence of ZnO nanoparticles appeared to be dispersed in nanosize in polymer composite matrix. In addition, thermogravimetric analysis (TGA) data indicated an enhancement of thermal stability of new BNC materials compared with the pure polymer.     

Growth Mechanism and Characterization of Single-crystalline Ga-doped SnO2 Nanowires and Self-organized SnO2/Ga2O3 Heterogeneous Microcomb Structures

Ga掺SnO2单晶纳米线和SnO2/Ga2O3自组织异质微米梳是通过简单的热蒸发沉淀法一步制得的,并通过X射线粉末衍射(XRD)、场激发扫描电子显微镜(FE-SEM)、透射电子显微镜(TEM)、X射线能量散射谱仪(EDS)、选区电子衍射谱(SAED)进行表征．从FE-SEM的图片上可以看出生成的产物具有纳米线和一种新的微米梳状形貌．XRD、SAED和EDS显示他们是单晶四角形的SnO2．产物的主干呈带状,纳米带阵列均匀的分布在主干的一侧或两侧．大量的Ga2O3纳米颗粒沉积在微米梳的表面．主干纳米带主要沿着[100]方向生长, 自组织的纳米带分支则在主干的(100)面上沿着[110]或者[110]方向生长．由于Ga的大量掺杂,光致发光谱的衍射峰发生红移并严重变宽．针对SnO2:Ga2O3异质微米梳的生长过程进行了解释,并讨论了实验条件对形貌的影响．