Scanning Transmission X-ray Microscopy Research Articles

Microscale and molecular analyses of river biofilm communities treated with microgram levels of cerium oxide nanoparticles indicate limited but significant effects

Cerium oxide (CeO2) nanoparticles are used as in-fuel catalysts and in manufacturing processes, creating a potential for release to aquatic environments. Exposures at 1 and 10 μg/L CeO2-nanoparticles were made to assess effects during the development of river biofilm communities. Scanning transmission x-ray microscopy (STXM) indicated extensive sorption of nanoparticles to the community and co-localization with lipid moieties. Following 8 weeks of development, polycarbonate coupons were removed from the reactors and used for molecular analyses, denaturing gradient gel electrophoresis analysis (DGGE-16S rRNA) and 16S rRNA amplicon sequencing. Microscopic imaging of the biofilm communities (bacterial, photosynthetic biomass, exopolymer composition, thickness, protozoan numbers), as well as carbon substrate utilization fingerprinting was performed. There was a trend toward reduced photosynthetic biomass, but no significant effects of CeO2 exposure were found on photosynthetic and bacterial biomass or biofilm thickness. Sole carbon source utilization analyses indicated increased utilization of 10 carbon sources in the carbohydrate, carboxylic acid and amino acids categories related to CeO2 exposures; however, predominantly, no significant effects (p < 0.05) were detected. Measures of microbial diversity, lectin binding affinities of exopolymeric substances and results of DGGE analyses, indicated significant changes to community composition (p < 0.05) with CeO2 exposure. Increased binding of the lectin Canavalia ensiformis was observed, consistent with changes in bacterial-associated polymers. Whereas, no significant changes were observed in binding to residues associated with algal and cyanobacterial exopolymers. 16S rRNA amplicon sequencing of community DNA indicated changes in diversity and shifts in community composition; however, these did not trend with increasing CeO2 exposure. Counting of protozoans in the biofilm communities indicated no significant effects on this trophic level. Thus, based on biomass and functional measures, CeO2 nanoparticles did not appear to have significant effects; however, there was evidence of selection pressure resulting in significant changes in microbial community composition.

Introduction to Scanning photoelectron microscope (SPEM) and Scanning transmission x-ray microscope (STXM) based on soft x-rays at the Pohang Light Source (PLS-II)

Introduction to Scanning photoelectron microscope (SPEM) and Scanning transmission x-ray microscope (STXM) based on soft x-rays at the Pohang Light Source (PLS-II)

Magnetite magnetosome biomineralization in Magnetospirillum magneticum strain AMB-1: A time course study

Magnetotactic bacteria are a highly studied group of diverse prokaryotes that biomineralize chains of magnetosomes, single domain, single crystal magnetic nanoparticles of magnetite or greigite, enclosed by a lipid bilayer membrane whose synthesis is under strict genetic control. In addition to characterizing the genetics and physicochemical properties of both cultured and uncultured environmental species, there have been a number of investigations using a time course approach to determine the chemical pathway of magnetite biomineralization in these organisms. In time course studies, cells of MTB are typically grown in the absence of iron so they cannot make magnetite, and then provided with iron in culture medium which initiates the biomineralization of magnetosome chains over a subsequent time period. Results from previous time course studies are not consistent with one another, differing with regard to the nature of chemical intermediates and the rate of establishment of magnetosome chains. In this work we report a time course study of Magnetospirillum magneticum strain AMB-1 over a 48h (hour) period, using transmission electron microscopy (TEM) and soft X-ray scanning transmission X-ray microscopy (STXM) at the Fe L-edge. STXM provides capability to measure X-ray absorption spectra (XAS) and map chemical species with ∼25nm spatial resolution and thus gives detailed results on the chemistry of individual particles in single cells. An evolution of the iron oxide speciation, from a more Fe(III)-rich species, possibly α-hematite (Fe2O3), to magnetite (Fe3O4), was observed in the early stages, with evidence for the presence of the Fe(III)-rich character persisting up to 24 h. The spectromicroscopy (X-ray absorption, XAS and X-ray magnetic circular dichroism, XMCD) and TEM results show that biomineralization occurs in a stepwise fashion. First, very small particles, with no measurable magnetization, are produced at different sites in the cell without significant chain formation. The Fe L3 spectra of these early stage particles typically differ from magnetite with an additional signal at 708.4 eV that is consistent with α-hematite. By 6–8h the particles are more numerous, partial chain formation is evident, and the L3 spectrum is very similar to that of magnetite. By 24 h particles-in-chains are the dominant motif and magnetism with the moment along the chain is established. By 48 h the cells are essentially the same as cells grown in Fe-rich medium.

Observation of Metal Micro-Nanoparticles in an Epoxy Matrix during Thermal Annealing Using Synchrotron X-ray Imaging Techniques

We investigated the thermal annealing behavior of Ag-coated Cu nanoparticles in an epoxy matrix by using synchrotron X-ray transmission microscopy, coherent X-ray diffraction imaging, and scanning transmission X-ray microscopy (STXM). We observed thermal-annealing-induced void formation around the metal particles as well as shape changes in the metal particles because of the volume changes in the epoxy matrix. In addition, the density distribution of the metal particles was changed by thermal annealing. Based on the optical density measurements from the X-ray transmittance analysis, we could distinguish between the Cu-dominant region and the Ag-dominant region from the STXM images.

Emerging X-ray imaging technologies for energy materials

With the growing need for sustainable energy technologies, advanced characterization methods become more and more critical for optimizing energy materials and understanding their operation mechanisms. In this review, we focus on the synchrotron-based X-ray imaging technologies and the associated applications in gaining fundamental insights into the physical/chemical properties and reaction mechanisms of energy materials. We will discuss a few major X-ray imaging technologies, including X-ray projection imaging, transmission X-ray microscopy, scanning transmission X-ray microscopy, tender and soft X-ray imaging, and coherent diffraction imaging. Researchers can choose from various X-ray imaging techniques with different working principles based on research goals and sample specifications. With the X-ray imaging techniques, we can obtain the morphology, phase, lattice and strain information of energy materials in both 2D and 3D in an intuitive way. In addition, with the high-penetration X-rays and the high-brilliance synchrotron sources, operando/in-situ experiments can be designed to track the qualitative and quantitative changes of the samples during operation. We expect this review can broaden readers’ view on X-ray imaging techniques and inspire new ideas and possibilities in energy materials research.

(Invited) Latest Advances in 2D and 3D Microstructural Characterization of Fuel Cell Components

Fuel cells are complex systems whose performance and degradation depend on a number of factors spreading over multiple scales. At the lowest spatial scale are nano-sized Pt-group or Pt-group-metal-free (PGM-free) catalysts, various types of catalyst supports, proton-conducting nanometer-thin ionomer film, and gas-transporting nano-pores, all contained within the electrodes of a membrane electrode assembly (MEA). Their properties, composition and spatial distribution largely determine fuel cell performance and affect degradation trends. At the next scale are electrodes, membrane and gas diffusion layer, dictating mass, electrical and thermal transport at the micron-scale. Finally, millimeters-thick flow field plates and larger system components affect the gas transport, water and overall system management. Understanding how all of these factors affect fuel cell performance and degradation is of crucial importance, and it is only possible by applying highly correlated efforts in testing, structural characterization and mathematical modeling. The focus of this talk is to present the latest advancements in the structural characterization approaches for fuel cells at multiple scales. In the recent years, a whole suite of novel 2D and 3D characterization approaches have been developed to provide information ranging from nano-sized catalysts used in the electrodes to macro-level flow field plates. This talk will give an overview of a number of advanced characterization techniques used for fuel cell analysis, starting from some more typically used, such as scanning electron microscopy (SEM), to highly sophisticated techniques such as 3D electron tomography. Techniques such as 2D and 3D high-resolution transmission electron microscopy (HR-TEM), 2D and 3D scanning transmission electron microscopy with energy dispersive spectroscopy (STEM-EDS), 3D focused-ion beam SEM (FIB-SEM), electron energy loss spectroscopy (EELS), scanning transmission X-ray microscopy (STXM), atomic force microscopy (AFM), and micro- and nano-computed tomography (CT), as well as developed in-situ techniques will be discussed. Challenges in characterization, ranging from sample preparation, ionomer and water imaging, image processing and quantification will be addressed. Finally, the author’s work on advanced characterization of fuel cells will be reported. Multi-scale approach in 3D imaging and property modeling, utilizing electron tomography, FIB-SEM and micro-CT, will be presented with encountered challenges [1]. Advanced 2D STEM characterization with quantification and its application for analysis of fuel cell degradation will be discussed [2]. Lastly, a collaborative work on in-situ water imaging using X-ray synchrotron imaging and revealed effect on membrane changes during operation at high current densities will be shown [3]. The talk will close by discussing the challenges and plan forward for continuing development of fuel cell characterization approaches. Jankovic, S. Zhang, A. Putz, M. S. Saha, D. Susac, Multi-scale imaging and transport modeling for fuel cell electrodes, (invited) Journal of Materials Research, 34 (4) (2019).Kneer, J. Jankovic, D. Susac, A. Putz, N. Wagner, M. Sabharwal, M. Secanell, Correlation of changes in electrochemical and structural parameters due to voltage cycling induced degradation in PEM fuel cells, Journal of The Electrochemical Society, 165 (6) F3241-F3250 (2018).N. Ge, R. Banerjee, D. Muirhead, J. Lee, H. Liu, P. Shrestha, A.K.C. Wong, J. Jankovic, M. Tam, D. Susac, J. Stumper, A. Bazylak, Membrane dehydration with increasing current density at high inlet gas relative humidity in polymer electrolyte membrane fuel cells, Journal of Power Sources, 422 (2019) 163-174.

Stress-Controlled Three-Dimensional Phase Evolution in Lithium Iron Phosphate

Many battery compounds undergo first-order phase transformations induced by ion (de)intercalation during battery operation, and their rate capability is often controlled by the kinetics of two-phase boundary movement. LiFePO4, a commercial cathode materials for Li-ion batteries, is a model system for studying the unique aspects of phase transitions in battery intercalation compounds. In a recent in-situ scanning transmission X-ray microscopy (STXM) study [Ohmer et al. Nature Communication 6, 6045 (2015)], Li deintercalation and phase evolution in microsized LiFePO4 single crystal upon delithiation are found to be highly non-uniform. FePO4 phase was observed to form [010]-aligned filaments growing into the LiFePO4 crystal, which is postulated to be dominated by elastic effects. In this work, we performed three-dimensional phase-field simulation to examine in the details phase evolution in LiFePO4 and the effect of misfit strain energy arising from the lattice match between FePO4 and LiFePO4. Our simulation reproduces the filamentary growth morphology of FePO4 phase (Figure 1) as observed in experiment, and confirms the dominating role of misfit stress in causing such behavior. We show that phase evolution in LiFePO4 goes through two steps during delithiation. In the first step, phase separation occurs in LiFePO4 via surface-mode coherent spinodal decomposition and results in the formation of individual FePO4 domains on particle surface. Next, FePO4 grows into the LiFePO4 matrix as wedge shaped domains that coarsen at the same time. The filamentary morphology of FP phase within (001) plane is mainly a result of the anisotropic misfit strain between LiFePO4 and FePO4, which favors the elongation of FP domains along the [010] axis to reduce elastic strain energy. Simulation reveals that Li diffusion anisotropy also significantly influences the phase growth morphology. The existence of three-dimensional Li diffusion in LiFePO4, which results from the presence of antisite defects, is found to be essential for the development of filamentary FePO4. The excellent agreement between the phase-field simulation and in-situ STXM experiment suggests that misfit stress plays an important role in triggering non-uniform Li (de)intercalation especially in large electrode particles, which is detrimental to battery performance and life and deserves close attention. Figure 1

(Invited) In Situ x-Ray Spectroscopies Gear up for Energy Science

To reduce global greenhouse gas emissions in response to globalization and increasingly strict carbon emission policies, green energy technologies must be developed. Improving the energy conversion/generation/storage efficiency of energy materials has always been a great challenge. Monitoring the atomic/electronic structures close the interface in many important energy materials, such as nanostructured catalysts, artificially photosynthesizing materials, smart materials, and energy storage devices, is of great importance. Understanding and controlling the interfacial electronic structures of energy conversion/storage materials require in-situ/operando characterization tools, of which synchrotron x-ray spectroscopy is one with many unique features. The last decade has witnessed a golden age of operando and in situ synchrotron x-ray spectroscopy for energy materials. X-ray absorption spectroscopy can be used to determine local unoccupied electronic structures while X-ray emission spectroscopy can be utilized to examine the occupied electronic structure. The additional use of resonant inelastic X-ray scattering reveals inter- or intra-electric transitions (d-d or f-f excitation or charge transfer excitation). An emerging scanning transmission x-ray microscopy is a spatial-resolved x-ray absorption spectroscopy which allows us to study the regional electronic structures. The in situ/operando approach enables modifications of atomic/electronic structures of an energy material in an operational environment to be tracked. This presentation will report recent studies and perspectives of the application of in situ/operando synchrotron x-ray spectroscopy to energy materials. It will also introduce Tamkang University (TKU) end-station constructed at the Taiwan Photon Source (TPS) 45A and 27A beamlines for the in situ/operando x-ray spectroscopic investigation of energy materials.

Combining Nanofocused X-Rays with Electrical Measurements at the NanoMAX Beamline

The advent of nanofocused X-ray beams has allowed the study of single nanocrystals and complete nanoscale devices in a nondestructive manner, using techniques such as scanning transmission X-ray microscopy (STXM), X-ray fluorescence (XRF) and X-ray diffraction (XRD). Further insight into semiconductor devices can be achieved by combining these techniques with simultaneous electrical measurements. Here, we present a system for electrical biasing and current measurement of single nanostructure devices, which has been developed for the NanoMAX beamline at the fourth-generation synchrotron, MAX IV, Sweden. The system was tested on single InP nanowire devices. The mechanical stability was sufficient to collect scanning XRD and XRF maps with a 50 nm diameter focus. The dark noise of the current measurement system was about 3 fA, which allowed fly scan measurements of X-ray beam induced current (XBIC) in single nanowire devices.

Soft X-ray study on electronic structure of passive oxide layer of carbon steel and low alloy steel in flow-accelerated corrosion environments of pressurized water reactors

Due to susceptibility of carbon steels under flow-accelerated corrosion environments, 2.25Cr-1Mo has been adopted as replacement. However, the mechanism of enhancement in the passivity has not been completely elucidated. We employed synchrotron scanning transmission X-ray microscopy to test the microstructure and chemistry of the alloys after flow-accelerated corrosion tests at 150 °C. Carbon steel exhibited a mixture of Fe2+ and Fe3+ states as a passive layer while 2.25Cr-1Mo presented two oxide layers composed of Fe2O3, Fe3O4, and FeO. A small quantity of Cr2O3 was observed which was not enriched. Furthermore, Mo was not observed in the oxide layer of 2.25Cr-1Mo.

Relationship between mechanical strain and chemical composition in LiFePO4 via 4D-scanning transmission electron microscopy and scanning transmission X-ray microscopy

Journal Article Relationship between mechanical strain and chemical composition in LiFePO4 via 4D-scanning transmission electron microscopy and scanning transmission X-ray microscopy Get access LA Hughes, LA Hughes National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA 94708, USA Corresponding author, laurenhughes@lbl.gov Search for other works by this author on: Oxford Academic Google Scholar Benjamin H Savitzky, Benjamin H Savitzky National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA 94708, USA Search for other works by this author on: Oxford Academic Google Scholar Haitao D Deng, Haitao D Deng Depart. of Mat. Sci. & Eng., Stanford University, Stanford, CA 94305, USA Search for other works by this author on: Oxford Academic Google Scholar Norman L Jin, Norman L Jin Depart. of Mat. Sci. & Eng., Stanford University, Stanford, CA 94305, USA Search for other works by this author on: Oxford Academic Google Scholar Eder G Lomeli, Eder G Lomeli Depart. of Mat. Sci. & Eng., Stanford University, Stanford, CA 94305, USA Search for other works by this author on: Oxford Academic Google Scholar William C Chueh, William C Chueh Depart. of Mat. Sci. & Eng., Stanford University, Stanford, CA 94305, USA Search for other works by this author on: Oxford Academic Google Scholar Patrick Herring, Patrick Herring Toyota Research Institute, Los Altos, CA 94022, USA Search for other works by this author on: Oxford Academic Google Scholar Colin Ophus, Colin Ophus National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA 94708, USA Search for other works by this author on: Oxford Academic Google Scholar Andrew M Minor Andrew M Minor National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA 94708, USADepart. of Mat. Sci. & Eng., University of California, Berkeley, CA 94720, USA Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 25, Issue S2, 1 August 2019, Pages 2068–2069, https://doi.org/10.1017/S1431927619011073 Published: 01 August 2019

Study of local structure at crystalline rubrene grain boundaries via scanning transmission X-ray microscopy

Abstract Rubrene is a promising and archetypal organic semiconductor owing to its high reported hole mobility. However, this high mobility only exists in its crystalline state, with orders of magnitude reduction in disordered films. Thus, as it pertains to thin film polycrystalline rubrene, it is important to understand structure and the presence of disordered regions at grain boundaries. Here, we use scanning transmission X-ray microscopy (STXM) to investigate polycrystalline rubrene thin films with either platelet or spherulite morphology. The STXM images allow us to distinguish and quantify the arrangement of the local structure in the crystal. The analysis suggests that the platelet film has more oriented molecules in the crystal than in the spherulite phase. Also, at spherulite grain boundaries, we reveal a high number of misaligned molecules compared to the smooth boundary in the platelet case, with grain boundary sinuosity of 0.045 ± 0.002 and 0.139 ± 0.002 μm for the platelet and spherulite cases, respectively, which help to explain the higher mobility in the former case.

Extracting the Dynamic Magnetic Contrast in Time-Resolved X-ray Transmission Microscopy.

Using a time-resolved detection scheme in scanning transmission X-ray microscopy (STXM), we measured element resolved ferromagnetic resonance (FMR) at microwave frequencies up to 10 GHz and a spatial resolution down to 20 nm at two different synchrotrons. We present different methods to separate the contribution of the background from the dynamic magnetic contrast based on the X-ray magnetic circular dichroism (XMCD) effect. The relative phase between the GHz microwave excitation and the X-ray pulses generated by the synchrotron, as well as the opening angle of the precession at FMR can be quantified. A detailed analysis for homogeneous and inhomogeneous magnetic excitations demonstrates that the dynamic contrast indeed behaves as the usual XMCD effect. The dynamic magnetic contrast in time-resolved STXM has the potential be a powerful tool to study the linear and nonlinear, magnetic excitations in magnetic micro- and nano-structures with unique spatial-temporal resolution in combination with element selectivity.

Uranium Uptake in Paracentrotus lividus Sea Urchin, Accumulation and Speciation.

Uranium speciation and bioaccumulation were investigated in the sea urchin Paracentrotus lividus. Through accumulation experiments in a well-controlled aquarium followed by ICP-OES analysis, the quantification of uranium in the different compartments of the sea urchin was performed. Uranium is mainly distributed in the test (skeletal components), as it is the major constituent of the sea urchin, but in terms of quantity of uranium per gram of compartment, the following rating: intestinal tract > gonads ≫ test, was obtained. Combining both extended X-ray Absorption Spectroscopy and time-resolved laser-induced fluorescence spectroscopic analysis, it was possible to identify two different forms of uranium in the sea urchin, one in the test, as a carbonato-calcium complex, and the second one in the gonads and intestinal tract, as a protein complex. Toposome is a major calcium-binding transferrin-like protein contained within the sea urchin. EXAFS data fitting of both contaminated organs in vivo and the uranium-toposome complex from protein purified out of the gonads revealed that it is suspected to complex uranium in gonads and intestinal tract. This hypothesis is also supported by the results from two imaging techniques, i.e., Transmission Electron Microscopy and Scanning Transmission X-ray Microscopy. This thorough investigation of uranium uptake in sea urchin is one of the few attempts to assess the speciation in a living marine organism in vivo.

A study on the relationship between electronic structure and corrosion characteristics of zirconium alloy in high-temperature hydrogenated water

The corrosion behavior of zirconium alloy was investigated using synchrotron scanning transmission X-ray microscopy and X-ray absorption spectroscopy. Scanning transmission X-ray micrographs showed different electronic structures at the oxide/metal interface of Zr–Nb–Sn alloy after exposure to high-temperature hydrogenated water. The orbital hybridization structure at the oxide/metal interface exhibited weaker t2g and eg peaks in X-ray absorption spectra, suggesting that zirconium suboxide can form just above the oxide/metal interface. The suboxide layer that formed at a high dissolved hydrogen concentration is thicker than the suboxide layer that formed at a normal dissolved hydrogen concentration after 100 d of oxidation.

Qualifying X-ray and Stimulated Raman Spectromicroscopy for Mapping Cutaneous Drug Penetration.

Research on topical drug delivery relies on reconstructed human skin (RHS) in addition to ex vivo human and animal skin, each with specific physiological features. Here, we compared the penetration of dexamethasone from an ethanolic hydroxyethyl cellulose gel into ex vivo human skin, murine skin, and RHS. For comprehensive insights into skin morphology and penetration enhancing mechanisms, scanning transmission X-ray microscopy (STXM), liquid chromatography tandem-mass spectrometry (LC-MS/MS), and stimulated Raman spectromicroscopy (SRS) were combined. STXM offers high spatial resolution with label-free drug detection and is therefore sensitive to tissue damage. Despite differences in sample preparation and data analysis, the amounts of dexamethasone in RHS, detected and quantified by STXM and LC-MS/MS, were very similar and increased during the first 100 min of exposure. SRS revealed interactions between the gel and the stratum corneum or, more specifically, its protein and lipid structures. Similar to both types of ex vivo skin, higher protein-to-lipid ratios within the stratum corneum of RHS indicated reduced lipid amounts after 30 min of ethanol exposure. Extended ethanol exposure led to a continued reduction of lipids in the ex vivo matrixes, while protein integrity appeared to be compromised in RHS, which led to declining protein signals. In conclusion, LC-MS/MS proved the predictive capability of STXM for label-free drug detection. Combining STXM with SRS precisely dissected the penetration enhancing effects of ethanol. Further studies on topical drug delivery should consider the potential of these complementary techniques.

Assessing the effect of pyrolysis temperature on the molecular properties and copper sorption capacity of a halophyte biochar

The capacity of biochar to take up heavy metals from contaminated soil and water is influenced by the pyrolysis temperature. We have prepared three biochar samples from Jerusalem artichoke stalks (JAS) by pyrolysis at 300, 500 and 700 °C, denoted as JAS300, JAS500, and JAS700, respectively. A variety of synchrotron-based techniques were used to assess the effect of pyrolysis temperature on the molecular properties and copper (Cu) sorption capacity of the samples. The content of oxygen-containing functional groups in the biochar samples decreased, while that of aromatic structures and alkaline mineral components increased, with a rise in pyrolysis temperature. Scanning transmission X-ray microscopy indicated that sorbed Cu(II) was partially reduced to Cu(I), but this process was more evident with JAS300 and JAS700 than with JAS500. Carbon K-edge X-ray absorption near edge structure spectroscopy indicated that Cu(II) cations were sorbed to biochar via complexation and Cu-π bonding. With rising pyrolysis temperature, Cu(II)-complexation weakened while Cu-π bonding was enhanced. In addition, the relatively high ash content and pH of JAS500 and JAS700 facilitated Cu precipitation and the formation of langite on the surface of biochar. The results of this investigation will aid the conversion of halophyte waste to useable biochar for the effective remediation of Cu-contaminated soil and water.

Hybrid films of cellulose nanofibrils, chitosan and nanosilica—Structural, thermal, optical, and mechanical properties

Organic-inorganic hybrid films were fabricated from cellulose nanofibrils (CNF) and nanosilica (5–30% wt) embedded in a chitosan (Chi) biopolymer matrix using a slow evaporation method. The self-standing films exhibited high strength and modulus up to 120 ± 5 MPa and 7.5 ± 0.4 GPa, respectively, which are remarkably high values for biopolymer/chitosan hybrids. Scanning electron microscopy showed that the nanosilica is formed of larger aggregates within the lamellar CNF network structure. This observation was further confirmed using synchrotron-based scanning transmission x-ray microscopy (STXM) with the capability to determine the spatial and chemical distribution analysis of the constituents of films. It is interesting that the thermal stability of the hybrid films improved as the nanosilica content increased. Furthermore, the nanosilica effectively filled the pores in the CNF network, thus decreasing the UV transmission and the visible light transmittance of the films.

Concentration and distribution of silica nanoparticles in colon cancer cells assessed by synchrotron based X-ray techniques

The quantitative uptake of Silica nanoparticles (SiNPs), although representing an essential prerequisite for their theranostic use, is difficult to address and it is still not utterly investigated. In this study, we tested the uptake and toxicity of two different types of luminescent core–shell silica–PEG (polyethylene glycol) nanoparticles SiNP and their carboxylate analogues on human adenocarcinoma cell line LoVo. We assessed the intracellular spatial distribution and concentration of Si element in the cell by a state-of-the-art approach merging synchrotron-based X-ray techniques (XRFM) with scanning transmission X-Ray microscopy (STXM). The concentration maps of Si obtained reflect the distribution of the SiNPs. In addition, we calculated the number of SiNPs per volume unit in each single cell, quantitating the exact amount of conveyed particles. The absence of effects on proliferation and cell death was confirmed by viability assays, morphological analysis and cytofluorimetric evaluation of ROS content. The three-dimensional analysis of intracellular uptake of both types of nanoparticles (with different surface charge) was performed by confocal fluorescence microscopy, which showed a main localization in the cytosolic region with no sign of nuclear uptake.

Quantitative capabilities of STXM to measure spatially resolved organic volume fractions of mixed organic ∕ inorganic particles

Abstract. Scanning transmission X-ray microscopy coupled with near-edge X-ray absorption and fine structure (STXM-NEXAFS) spectroscopy can be used to characterize the morphology and composition of aerosol particles. Here, two inorganic ∕ organic systems are used to validate the calculation of organic volume fraction (OVF) and determine the level of associated error by using carbon K-edge STXM data at 278, 285.4, 288.6, and 320 eV. Using the mixture of sodium chloride and sucrose as one system and ammonium sulfate and sucrose as another, three solutions were made with 10:1, 1:1, and 1:10 mass ratios (inorganic to organic). The OVFs of the organic-rich aerosols of both systems deviated from the bulk OVF by less than 1%, while the inorganic-rich aerosols deviated by approximately 1 %. Aerosols from the equal mass mixture deviated more (about 4 %) due to thick inorganic regions exceeding the linear range of Beer's law. These calculations were performed after checking the data for poor image alignment, defocusing issues, and particles too thick to be analyzed. The potential for systematic error in the OVF calculation was also tested by assuming the incorrect composition. There is a small (about 0.5 %) OVF difference if the organic is erroneously assumed to be adipic acid rather than the known organic, sucrose. A much larger difference (up to 25 %) is seen if sodium chloride is assumed instead of ammonium sulfate. These results show that the OVF calculations are fairly insensitive to the organic while being much more sensitive to the choice of inorganic.