In Situ Imaging and Spectroscopy of Particles in Liquid (original) (raw)
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Improving in situ liquid SEM imaging of particles
Surface and Interface Analysis, 2019
This work presents in situ imaging of synthesized boehmite (γ-AlOOH) particles ranging from 20 to 100 nm, suspended in liquid, in a vacuum compatible microfluidic sample holder using a scanning electron microscopy (SEM) under the high vacuum mode and highlights the advantage of in situ liquid imaging of colloids. Nanometersized boehmite particles in high-level radioactive wastes at the Hanford site are known to be difficult to dissolve and cause rheological problems for processing in the nuclear waste treatment plant. Therefore, it is important to characterize boehmite particles and understand how they form aggregates in the liquid state. Several technical advancements are made to optimize in situ liquid SEM chemical imaging resulting in the improved ability to obtain secondary electron (SE), backscattered electron (BSE) images, and energy dispersive X-ray spectroscopy (EDX) spectra. Moreover, our results show mixed particles could be studied and identified based on the particle shape and elemental composition using in situ SEM imaging and EDX. Thus, we provide a new and improved approach to observe the evolution of particle dispersion and stability in liquid under conditions similar to those in the waste tank.
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, 2008
In this paper we comprehensively characterized particles in drinking water originating from a lake water source. We focused on particles smaller than a few hundred nm. Several analytical techniques were applied to obtain information on number concentration, size distribution, morphology and chemical composition of the particles. Morphological information was obtained by atomic force microscopy (AFM) analysis. Two types of particles, spherical aggregates up to a few tens of nm and elongated fibers were identified. Similar structures were also observed in transmission electron microscope (TEM) images. A size distribution of the particles was obtained by applying image analysis (IA) tools on the TEM images. IA results showed an exponential increase of the particle number concentration down to 40 nm, which is the lower detection limit of our setup. The total number of particles down to 10 nm and the average particle diameter were determined with the laser-induced breakdown detection (LI...
Chemical modification and characterization of boehmite particles
To overcome the disadvantages of protein denaturation and nonspecific adsorption on poly(styrene-divinylbenzene) (PS) matrix as chromatographic supports, gigaporous PS microspheres, which we prepared in a previous study, were chemically modified with poly(vinyl alcohol) (PVA) through two-step reaction. The microspheres were chloroacetylated through Friedel-Crafts acetylation with chloroacetyl chloride and modified with hydrophilic PVA through Williamson reaction afterward. The modified microspheres were characterized by Fourier transform infrared (FTIR) spectra, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), mercury porosimetry measurements (MPM), BET nitrogen adsorption measurements, laser scanning confocal microscope (LSCM), and protein adsorption experiments. Results showed that PS microspheres were successfully coated with PVA, while the gigaporous structure could be maintained. Consequently, the hydrophilicity and biocompatibility of modified microspheres was greatly improved and nonspecific adsorption of proteins was significantly decreased. The coatings contained only stable chemical bonds (e.g., CÀ ÀC, CÀ ÀOÀ ÀC) and easily derived hydroxyl moieties. The large pores of gigaporous PS microspheres also facilitated the modification by PVA. After further derivation, the coated gigaporous base supports could apply in various modes of chromatography and have great potentials in high-speed protein chromatography.
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.
New sampling technique for collection of nanoparticles from liquids
Journal of Nanoparticle Research, 2013
Transmission electron microscopy (TEM) is the only technique which can give accurate information on the individual size, shape and composition of NPs. However, in dilute forms it is difficult to collect a sufficient number of NPs on an electron microscope grid for TEM analysis without some means of concentrating the dispersion of NPs. This study introduces a novel TEM sampling technique which overcomes this shortcoming and allows for both the natural and engineered NPs in dilute dispersions as found in waste and contaminated waters to be selectively sampled, based on their electrical charge. The technique is based on the use of carefully functionalized collector surfaces built by using the layer-by-layer assembly of polyelectrolytes on TEM grids. The layers are electrically charged and the top layer will attract and retain oppositely charged sampled NPs from aqueous solutions. The ability of the collector to attract both single particles and particle aggregates on the top polyelectrolyte layer collected from dilute aqueous dispersions after a short sampling time is demonstrated from the TEM images. The nature of the particles attracted to the collector can be identified from the TEM images, their diffraction pattern and the EDX spectrum.
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.
Scanning electron microscopy of individual nanoparticle bio-markers in liquid
Ultramicroscopy, 2014
We investigated SEM imaging of nanoparticle biomarkers suspended below a thin membrane, with the ultimate goal of integrating functional fluorescence and structural SEM measurements of samples kept at ambient or hydrated conditions. In particular, we investigated how resolving power in liquid SEM is affected by the interaction of the electron beam with the membrane. Simulations with the Geant4-based Monte Carlo scheme developed by [1] are compared to experimental results with suspended nanoparticles. For 20 nm and 50 nm thin membranes, we found a beam broadening of 1.5 nm and 3 nm, respectively, with an excellent agreement between simulations and experiments. 15 nm Au nanoparticles and bio-functionalized core-shell quantum dots can be individually resolved in denser clusters. We demonstrated the imaging of single EGF-conjugated quantum dots docked at filopodia during cellular uptake with both fluorescence microscopy and SEM simultaneously. These results open novel opportunities for correlating live fluorescence microscopy with structural electron microscopy.