Improving in situ liquid SEM imaging of particles (original) (raw)
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In situ liquid SEM imaging analysis revealing particle dispersity in aqueous solutions
Journal of Microscopy, 2020
A quantitative description on dispersity of boehmite (γ-AlOOH) particles, a key component for waste slurry at Hanford sites, can provide useful knowledge for understanding various physicochemical nature of the waste. In situ liquid scanning electron microscopy (SEM) was used to evaluate the dispersity of particles in aqueous conditions using a microfluidic sample holder, System for Analysis at Liquid Vacuum Interface (SALVI). Secondary electron (SE) images and image analyses were performed to determine particle centroid locations and the distance to the nearest neighbor particle centroid, providing reliable rescaled interparticle distances as a function of ionic strength in acidic and basic conditions. Our finding of the particle dispersity is consistent with physical insights from corresponding particle interactions under physicochemical conditions, demonstrating delicate changes in dispersity of boehmite particles based on novel in situ liquid SEM imaging and analysis.
Water research, 2009
The increasing industrial production of engineered nanoparticles (ENPs) raises concern over their safety to humans and the environment. There is a lack of knowledge regarding the environmental fate and impact of ENPs and in situ methods are needed to investigate e.g. nanoparticle aggregation and adsorption in the media of concern such as water, sediment and soil. In this study, the application of wet scanning electron microscopy (WetSEM™) technology in combination with energy dispersive x-ray spectroscopy (EDS) to visualise and elementally identify metal and metal oxide nanoparticles (Au, TiO2, ZnO and Fe2O3) under fully liquid conditions in distilled and lake water as well as in a soil suspension has been investigated. WetSEM™ capsules comprise an electron transparent membrane enabling the imaging and EDS analysis of liquid samples. Results are compared with conventional SEM images and show that WetSEM™/EDS is a promising complementary tool for the in situ investigation of ENPs and their aggregates in natural matrices. In combination with other analytical tools (e.g. HDC- or FFF-ICP-MS, DLS), WetSEM™ could help to provide a better understanding of the fate and behaviour of ENPs in the environment.
Microscopy and Microanalysis, 2014
The use of analytical spectroscopies during scanning/transmission electron microscope (S/TEM) investigations of micro-and nano-scale structures has become a routine technique in the arsenal of tools available to today's materials researchers. Essential to implementation and successful application of spectroscopy to characterization is the integration of numerous technologies, which include electron optics, specimen holders, and associated detectors. While this combination has been achieved in many instrument configurations, the integration of X-ray energy-dispersive spectroscopy and in situ liquid environmental cells in the S/TEM has to date been elusive. In this work we present the successful incorporation/modifications to a system that achieves this functionality for analytical electron microscopy.
Boehmite Nanoparticles by the Two-Reverse Emulsion Technique
Journal of the American Ceramic Society, 2005
Boehmite (c-AlOOH) nanoparticles were successfully synthesized by the two-reverse emulsion technique at 901711C under constant agitation with varying Al 31 concentrations in the aqueous solution. A mixture of cyclohexane and the surfactant, sorbitan monooleate (Span 80), constituted the support solvent in the reverse emulsions. The synthesized particles were characterized by thermogravimetry, differential thermal analysis, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), particle size analysis, and transmission electron microscopy (TEM). XRD and FTIR results confirmed crystalline boehmite formation at 901711C. The average particle size of boehmite was found to be 10 nm. The spherical morphology of the boehmite nanoparticles was confirmed by TEM.
Environmental Science & Technology, 2003
A major challenge to the development of a fundamental understanding of transport and retardation mechanisms of trace metal contaminants (<10 ppm) is their identification and characterization at the nanoscale. Atomic-scale techniques, such as conventional transmission electron microscopy, although powerful, are limited by the extremely small amounts of material that are examined. However, recent advances in electron microscopy provide a number of new analytical techniques that expand its application in environmental studies, particularly those concerning heavy metals on airborne particulates or water-borne colloids. Highangle annular dark field scanning transmission electron microscopy (HAADF-STEM), STEM-energy-dispersive X-ray spectrometry (EDX), and energy-filtered TEM (EFTEM) can be effectively used to identify and characterize nanoparticles. The image contrast in HAADF-STEM is strongly correlated to the atomic mass: heavier elements contribute to brighter contrast. Gold nanocrystals in pyrite and uranium nanocrystals in atmospheric aerosols have been identified by HAADF-STEM and STEM-EDX mapping and subsequently characterized by high-resolution TEM (HRTEM). EFTEM was used to identify U and Fe nanocrystals embedded in an aluminosilicate. A rare, As-bearing nanophase, westerveldite (FeAs), was identified by STEM-EDX and HRTEM. The combined use of these techniques greatly expands the effective application of electron microscopy in environmental studies, especially when applied to metals of very low concentrations. This paper describes examples of how these electron microbeam techniques can be used in combination to characterize a low concentration of heavy metals (a few ppm) on nanoscale particles.
Laboratory X-ray microscopy for high-resolution imaging of environmental colloid structure
Chemical Geology, 2012
Transmission X-ray microscopy is a uniquely suited technique for studies of environmental colloids since it allows imaging in aqueous media with high spatial resolution, presently down to the 20 nm range. Such nanoscale morphological description of these high-specific-surface-area compounds show promise for improved understanding of soils, sediments or groundwater aquifers. However, present high-quality X-ray microscopes are located at synchrotron radiation facilities resulting in limited applicability and accessibility for colloid scientists. Here we investigate the applicability of a laboratory-scale transmission X-ray microscope for studies of colloids of the environment. The microscope is based on a laser-plasma source in combination with multilayer and zone plate optics. Samples are held at atmospheric pressure in their natural wet state. We show images revealing the nano-scale morphology of the clay nontronite, soils such as chernozem and luvisol, and the mineral hematite, an iron oxide. Comparative studies of dried substances clearly show the need for imaging in the wet state. The image quality approaches that of synchrotron-based microscopes, albeit at longer exposure times. Stereo imaging is investigated as a means for giving 3D information with shorter exposure times than tomography requires. Finally the future development of the laboratory X-ray microscope is discussed, especially with regard to the reduction of exposure times.
High energy X-ray microscopy for characterisation of fuel particles
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2001
For the first time different high energy microanalysis techniques were combined to characterise individual micrometer sized radioactive particles. It was shown that particle characteristics including weathering rates and mobilisation of associated radionuclides are source specific and release-scenario dependent. Fuel particles released during the explosion are characterised by UO 2 -cores with surrounding layer of reduced U with low weathering rates. In contrast, fuel particles released during the subsequent fire show UO 2 -core with surrounding layers of oxidised U 2 O 5 /U 3 O 8 with high weathering rates r
2003
In this paper, we demonstrate the utility of single-particle analysis to investigate the chemistry of isolated, individual particles of atmospheric relevance such as NaCl, sea salt, CaCO 3 , and SiO 2. A variety of state-of-the-art scanning electron microscopy techniques, including environmental scanning electron microscopy and computer-controlled scanning electron microscopy/energy-dispersive X-ray analysis, were utilized for monitoring and quantifying phase transitions of individual particles, morphology, and compositional changes of individual particles as they react with nitric acid. Clear differences in reaction mechanisms were observed between SiO 2 , CaCO 3 , NaCl, and sea salt particles. SiO 2 particles exposed to HNO 3 showed no change, indicating that the reaction of SiO 2 particles is limited to the particle surface and would not involve bulk atoms in its reactivity. Calcium carbonate was seen to convert to aqueous calcium nitrate droplets while sodium chloride formed microcrystallites of sodium nitrate on top of the particle. Sea salt particles showed morphology changes that could be described as a combination of these as both spherical droplets and microcrystallites were observed. This is consistent with the multicomponent composition of sea salt. Further differences were found in the reaction rates for sea salt and sodium chloride with nitric acid. Sea salt yielded a significant increase in reactivity when compared to the NaCl particles under similar conditions. The reaction of nitric acid with calcium carbonate was found to be strongly enhanced at higher relative humidity.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2000
Environmental scanning electron microscopy (ESEM) is a rather new form of electron microscopy, which permits the observation of hydrated samples in their native state, and also does not require that insulators are coated with a conducting layer. These two factors make it ideal for studying colloidal dispersions as they aggregate and/or film form. This paper describes the application of ESEM to three situations involving aggregating latices. Firstly the nature of fractal structures grown from aggregating acrylic latices is discussed, with a comparison given of the behaviour with and without added salt as the screening between particles is altered. Secondly the behaviour of vinyl latices is considered. The impact of the addition of starch, both modified and unmodified, upon the particle size distribution and ability to film form is examined. Finally, the structures which form when the hard inorganic component silica is added to acrylic latices are explored. Together these three examples illustrate some of the many strengths of the ESEM in the field of colloidal dispersions and aggregates.
Chemical modification and characterization of boehmite particles
Chemistry and Chemical Technology, 2008
Polymerizable organic silane molecules 3-(trimethoxysilyl)propylmethacrylate (3MPS) and vinyltri(2-methoxyethoxy)silane (VTMES) have been introduced onto surfaces of high purity Boehmite (a commercial alumina) via hydroxyl groups on the oxides in order to obtain organic-inorganic hybrid macromonomers. Changes of surface characteristics have been determined using thermogravimetric analysis (TGA) and Fouriertransform infrared spectroscopy (FTIR). The influence of the type of silane used and modification conditions have been determined. Preheating was applied to some Boehmite samples; it leads to lower concentrations of OH groups on the powder surface and the adsorption yields lower than in samples without preheating. Modification leads to surface hydrophobicity and thus reduces significantly water adsorption; in TGA we see desorption of water below 423 K only in unmodified Boehmite.