Charge behavior in a plasmonic photocatalyst composed of Au and TiO2

Redox reaction sites on a Au nanoparticle-deposited TiO2 (Au/TiO2) plasmonic photocatalyst are visualized using a chemical microanalytical technique for investigating charge behaviors in Au/TiO2.

Simultaneous X-ray fluorescence and scanning X-ray diffraction microscopy at the Australian Synchrotron XFM beamline

Owing to its extreme sensitivity, quantitative mapping of elemental distributionsviaX-ray fluorescence microscopy (XFM) has become a key microanalytical technique. The recent realisation of scanning X-ray diffraction microscopy (SXDM) meanwhile provides an avenue for quantitative super-resolved ultra-structural visualization. The similarity of their experimental geometries indicates excellent prospects for simultaneous acquisition. Here, in both step- and fly-scanning modes, robust, simultaneous XFM-SXDM is demonstrated.

Bioavailability of heavy metals in the soil from different locations of medicinal herbs

SUMMARY Medicinal herbs and their mixtures, which are widely used for prevention and treatment of some disease, can also present health risks due to the presence of toxic metals such as Pb and Cd. The application of different agrotechnical practices during plant growing season, as well as the process of circulation of substances in nature, may be the cause of plant contamination. The aim of this study was to determine the content of lead, cadmium and copper from soil which are bioavailable for absorption by plant, as well as the total content of these metals in some medicinal herbs that were cultivated in two different locations. The presence of these metals in the samples was detected using highly sensitive microanalytical technique potentiometric stripping analysis (PSA). The mean value of lead total content in the analyzed samples of medicinal herbs Chamimillae flos, Urticae folium, Menthae folium, Altheae radix and Basilici herba, which were grown at the sites near the industrial zone, was about 1.55 μg/g, 1.82 μg/g, 1.90 μg/g, 1.99 μg/g and 2.74 μg/g, respectively. Contrary to this, the total content of this toxic metal in the analyzed plant samples grown on rural areas was detected only on some sites. Based on the results of this study, it can be concluded that medicinal herbs contained a certain amount of lead and that its content varied depending on the location at which the plant species were grown as well as on plant affinity to certain metal. Cadmium and copper were not detected in the tested plant material.

The content of lead in herbal drugs and tea samples

Heavy metals are highly toxic to living organisms even in low concentrations owing to their cumulative effect. In this study the overall content of lead in herbal drugs was determined, as well as the content of lead which was released from tested drugs during the preparation of tea drinks. To determine the content of toxic lead, the highly sensitive microanalytical technique of the potentiometric stripping analysis (PSA) with oxygen as the oxidant was used. The lowest overall content of lead was detected for chamomile and ranged from 0.73 to 0.77 µg/g, while the greatest content of lead was determined in the samples of the frangula bark, and yielded approximately 3 µg/g. The lead content in the prepared tea drinks ranged from 0.26 to 1.23 µg/g and depended on the manner in which tea drink was prepared. All of the herbal drugs in this study contain a certain amount of the toxic metal lead, but at the same time, the contents were below the levels prescribed for this metal. The content of lead released from the herbal drug into the tea drink was three to five times lower than those of the overall content of this metal.

Introduction: Special Issue on Cathodoluminescence

Cathodoluminescence (CL) microanalysis provides high-sensitivity spectra and high-resolution images associated with impurity and structural defects at the nanoscale and from luminescent materials including minerals, semiconductor, and dielectric/insulating materials. Cathodoluminescence is the non-incandescent emission of light (photons) emitted from materials excited by an electron beam. CL photons (UV-VIS-NIR) are produced as a result of electronic transitions between the conduction and valence band and may also involve electronic transitions associated with defect levels within the band gap. Microscopic defects such as imperfections and impurities influence the optical, electrical, and mechanical properties of scientifically and technologically important materials. CL microanalysis is therefore a useful microanalytical technique for characterizing these properties with high sensitivity and spatial resolution. CL image resolution can range from sub-10 nm to microns, dependent on experimental arrangement (STEM-CL, SEM-CL, optical CL microscopy), electron beam parameters, specimen configuration, carrier diffusion, etc. The sensitivity of CL microanalysis is dependent on the specimen and, in the absence of self-absorption and competitive recombination centers, can be several magnitudes more sensitive than X-ray microanalysis. In particular, quantitative CL microanalysis of trace impurity concentrations while challenging has recently been shown to be possible for a range of minerals.

An in vivo microanalytical technique for measuring the local biochemical milieu of human skeletal muscle

Myofascial pain associated with myofascial trigger points (MTrPs) is a common cause of nonarticular musculoskeletal pain. Although the presence of MTrPs can be determined by soft tissue palpation, little is known about the mechanisms and biochemical milieu associated with persistent muscle pain. A microanalytical system was developed to measure the in vivo biochemical milieu of muscle in near real time at the subnanogram level of concentration. The system includes a microdialysis needle capable of continuously collecting extremely small samples (∼0.5 μl) of physiological saline after exposure to the internal tissue milieu across a 105-μm-thick semi-permeable membrane. This membrane is positioned 200 μm from the tip of the needle and permits solutes of <75 kDa to diffuse across it. Three subjects were selected from each of three groups (total 9 subjects): normal (no neck pain, no MTrP); latent (no neck pain, MTrP present); active (neck pain, MTrP present). The microdialysis needle was inserted in a standardized location in the upper trapezius muscle. Due to the extremely small sample size collected by the microdialysis system, an established microanalytical laboratory, employing immunoaffinity capillary electrophoresis and capillary electrochromatography, performed analysis of selected analytes. Concentrations of protons, bradykinin, calcitonin gene-related peptide, substance P, tumor necrosis factor-α, interleukin-1β, serotonin, and norepinephrine were found to be significantly higher in the active group than either of the other two groups ( P < 0.01). pH was significantly lower in the active group than the other two groups ( P < 0.03). In conclusion, the described microanalytical technique enables continuous sampling of extremely small quantities of substances directly from soft tissue, with minimal system perturbation and without harmful effects on subjects. The measured levels of analytes can be used to distinguish clinically distinct groups.

Quantitative Analysis of Si1-xGex using Convergent Beam Electron Diffraction for Extinction Distance Measurements.

IntroductionSiGe epitaxy on Si has been extensively studied, for semiconductor gap modeling and band structure engineering. Quantitative measurement of the Ge concentration is not a trivial exercise at the microscopic level, where classical tools such as X-Ray diffraction, ellipsometry and SIMS cannot be used. A new quantitative microanalytical technique is proposed based on extinction distance measurements using Convergent Beam Electron Diffraction (CBED) combined with dynamical diffraction simulations. A Ge concentration accuracy of less than 2% is demonstrated on strain relaxed SiGe epitaxial layers.ExperimentUnstrained SiGe epitaxial layers are analyzed for different Ge concentrations, with two-beam CBED, using the transmitted and the 004 diffracted disc. Energy filtered CBED patterns are acquired at 197 keV with a Philips CM 200 FEG transmission electron microscope, using the Ik x Ik CCD camera of the Gatan GIF energy filter. A liquid nitrogen cryo-holder is used, to sharpen up the CBED patterns and to avoid contamination and degradation of the samples.

Atom Probe Tomography: A Tutorial

Atom probe tomography (APT) is an ultrahigh resolution microanalytical technique that enables the spatial coordinates and elemental identities of the atoms in a small volume of material to be determined. The specimen volume that may be analyzed is typically ∼ 10 to 20 nm square by ∼ 100 to 250 nm deep, and contains up to ∼ 1 million atoms. The distribution of the solute atoms within this volume may then be reconstructed from these data. The compositions of small volumes are determined by simply counting the number of atoms of each type within that volume, and thus the technique provides a fundamental measure of local concentrations. Atom probe tomography requires that the specimen has some electrical conductivity and may be applied to almost all metals and alloys, many semiconductors, and some electrically conducting ceramics. The sharp needle-shaped specimens may be fabricated from bulk and thin film materials with the use of electropolishing, chemical or ion milling methods.