Real-time imaging of nanoscale electrochemical Ni etching under thermal conditions

The ability to vary the temperature of an electrochemical cell provides opportunities to control reaction rates and pathways and to drive processes that are inaccessible at ambient temperature. Here, we explore the effect of temperature on electrochemical etching of Ni–Pt bimetallic nanoparticles. To observe the process at nanoscale resolution we use liquid cell transmission electron microscopy with a modified liquid cell that enables simultaneous heating and biasing. By controlling the cell temperature, we demonstrate that the reaction rate and dissolution potential of the electrochemical Ni etching process can be changed. The in situ measurements suggest that the destabilization of the native nickel oxide layer is the slow step prior to subsequent fast Ni removal in the electrochemical Ni dissolution process. These experiments highlight the importance of in situ structural characterization under electrochemical and thermal conditions as a strategy to provide deeper insights into nanomaterial transformations as a function of temperature and potential.

The combination of electrochemical analysis, temperature control and in situ TEM imaging directly probes the etching of Ni from bimetallic Ni–Pt nanoparticles.     

mTHPC-mediated photodynamic therapy is effective in the metastatic human 143B osteosarcoma cells

Photodynamic therapy (PDT) is a minimally invasive therapeutic modality approved for palliative and curative treatment of some forms of local cancers, precancerous lesions and nononcological disorders. As a prerequisite for future studies in animal models aiming at an intraoperative application of PDT in osteosarcoma (OS), in the present study, we investigated the uptake and the dark- and photo-toxicity of the photosensitizer mTHPC in the metastatic human OS cell line 143B, which, intratibially injected into SCID mice, reproduces spontaneous, aggressive lung metastasis, the main cause of death in OS patients. The uptake of mTHPC by 143B cells was time- and dose-dependent. mTHPC accumulated to higher levels in the 143B than in the parental low-metastatic HOS cell line. A significant decrease in viability of 143B cells, reflecting mTHPC dark-toxicity, occurred upon incubation in the dark at mTHPC concentrations ≥2.5 μg mL(-1). In phototoxicity experiments with illumination by 652 nm laser light (2.5-10 J cm(-2)), the half-maximal lethal doses of mTHPC ranged from 0.012 to 0.047 μg mL(-1). This treatment activated caspase-3, -7 and -9 and Z-VAD-FMK-inhibitable PARP cleavage, indicating caspase-dependent apoptosis. In conclusion, PDT with mTHPC is effective in the metastatic 143B human osteosarcoma cell line in vitro.     

Fission fragment distribution following antiproton absorption at rest on238U

The distribution of nuclei resulting from the annihilation of stopped antiprotons on²³⁸U has been studied by an off-line measurement of the residual radioactivity. It was found that the probability of fission exceeds 84% (68% c.l.). The charge and mass distributions of the fission products can be separated into two parts, a more frequent symmetric component originating from high energy fission (excitation energy between 100 MeV and 1 GeV) and an asymmetric component from low energy fission (excitation energy less than 40 MeV).     

Muon channeling in Ge: Evidence for pionium formation

In a recent experiment observing muon channeling from the decay of positive pions implanted in high-purity Ge single crystals, the pion decay site is found to be sensitive to the concentration of excess charge carriers produced by photon absorption. Distinctly different channeling profiles are observed in Ge at 100 K for illuminated samples (high carrier concentration) as compared to unilluminated samples (low carrier concentration). From these data we conclude that different electronic states of the pion in a semiconductor host lattice must account for the observed changes in the pion location. Furthermore we suggest that the pion exists in the solid both as the bare entity π⁺ and as pionium (π⁺ e⁻), i.e., a hydrogen-like atom with a mesonic nucleus.     

Elemental fingerprinting of gypsum drywall using sector field ICP-MS and multivariate statistics

Outgassing of volatile sulphur compounds from gypsum drywall from some sources has resulted in odours, corrosion of wiring and metals and health problems for homeowners. Infrared spectroscopy has been the primary analytical tool to identify ‘problematic’ drywall. In this paper, we demonstrate that elemental fingerprinting using inductively coupled plasma mass spectrometry and multivariate statistics is an effective alternative. The approach also showed potential in determining the geographic source of gypsum. Nineteen elements (Al, Ba, Ca, Cd, Co, Cr, Cs, Cu, Fe, Mg, Mn, Ni, Pb, Rb, Sr, Tl, U, V and Zn) were measured in 20 samples of drywall, half of which were classified as positive for contamination by Fourier Transform Infrared Spectroscopy. Gypsum from three different mines and a flue gas desulphurisation plant were also analysed. Principal component analysis and multivariate analysis of variance of the elemental data showed significant differences between the problematic and non-problematic drywall and between sources of gypsum. Strontium averaged 1800 ± 500 µg/g in problematic drywall compared to 400 ± 100 µg/g in non-problematic drywall (p < 0.0001).     

Structural studies on alkylisocyanate polymers by thermal degradation tandem mass spectrometry

Homopolymers and copolymers of alkylisocyanates having n-hexyl, 2,6-dimethylheptyl, 3,7-dimethyloctyl, and (2,2-dimethyl-1,3-dioxolan-4-yl)methyl substituents underwent thermal degradation in the course of desorption electron ionization to yield trimers and monomers that were characterized in situ by tandem mass spectrometry. The trimers were trisubstituted cyanuric acids, the protonated molecules displaying a characteristic series of alkene eliminations on collision-induced dissociation to yield protonated cyanuric acid, m/ z 130. Confirmation of the identity of the pyrolysates was obtained by using two types of MS3 experiments: the reaction intermediate scan and the two-dimensional familial scan. The ion chemistry of the trimers and of the protonated monomer, the alkylisocyanate, was elucidated. Among the many interesting fragmentation processes undergone by the ionized trimers were a and 3 C-C bond cleavages and charge-remote fragmentations, which provided information on branching in the alkyl substituent. The dioxolane-containing substituent showed unique ion chemistry. The monomer distribution in the copolymers was deduced from the abundances of the various protonated trimers. The distribution was found to be random in all copolymers except that containing the dioxolane substituent.     

13C-Isotope ratio mass spectrometry as a potential tool for the forensic analysis of white architectural paint: a preliminary study

Paints have a dual role in society, to protect materials from environmental agents such as ultraviolet light, moisture and oxygen, and to make painted materials look more attractive. Variability in paint samples is often due to binder and pigment type within the sample. The most common resin used in decorative paints is drying oil alkyd resin, which incorporates soybean oil and vinyl acrylic based latexes. Traditional analytical methods used by forensic scientists may be able to say whether two paint samples are indistinguishable but cannot conclusively say that they both originate from the same source. To find out if isotopic composition can provide an added dimension of information, 28 different white architectural paints were analysed for (13)C abundance using isotope ratio mass spectrometry. In addition, variations in application, drying time and thickness were also investigated to assess the discriminatory power of (13)C data from white paints with an unknown history. Preliminary results indicate that this method could aid screening of paint samples.     

Residual nuclei after antiproton annihilation in Mo and Ho

The distributions of residual nuclei after annihilation of stopped antiprotons in⁹²Mo,⁹⁵Mo,⁹⁸Mo and¹⁶⁵Ho targets have been measured by means of the induced radioactivity. In the case of the¹⁶⁵Ho target the residual nucleus¹¹⁶Te was observed thus indicating that about 50 nucleons may be emitted after annihilation. The distributions have also been calculated with two versions of an intranuclear cascade model. The agreement between theory and experiment is satisfactory. The effects of heavy mesons in the annihilation process, of local reduction of the nuclear density during the intranuclear cascade and of multifragmentation are discussed.