Lower limit of determination values for trace elements in iron certified reference materials by neutron activation analysis with multiple gamma-ray detection

Recycling steel products demands a new technique for determining tramp elements in steel. Tramp elements, As and Sb, in some iron certified reference materials were determined by neutron activation analysis with multiple gamma-ray detection method and reported in MTAA11. In MTAA12, the authors reported the lower limit of determination values (LDL) and the dispersion of this method. The values of the LDLs for As and Sb in high purity iron were 0.002 and 0.0009 μg·g⁻¹. The dispersion is small enough to satisfy the demand from materials science.     

Purity of rubrene single crystals

Liquid chromatography connected with mass spectroscopy reveals that the oxidized form of rubrene is the major impurity in commercial powder of rubrene as well as in rubrene single crystals. One form of rubrene impurity can be transformed into the other. In solution, rubrene undergoes photo-oxidation completely until the red color of the rubrene solution disappears. Single crystals, due to compact packing of molecules and the required molecular shape change during oxidation, oxidize only on the surface.     

Multi-quasiparticle excitations in ~(145)Tb

Nuclei with N and Z near magic number can be well described by the nuclear shell model. The 145Tb nucleus has a valence proton and a pair of neutron holes with respect to the doubly closed 146Gd nucleus. Therefore, it is expected that the excitations in 145Tb be dominated by single-particle configurations. A detailed measurement of the excitation scheme in 145Tb would give us an opportunity to examine the behavior of multi-particle excitations involving high angular momentum orbits and provi…     

Analysis of toxic elements by MPGA

In order to improve the sensitivity for the quantification of trace elements, we propose the combination of prompt gamma-ray analysis (PGA) and a multiple gamma-ray detection method. A new Ge detector system for multiple prompt gamma-ray analysis (MPGA) was constructed at the neutron guide-hall of the JRR-3M reactor of the Japan Atomic Energy Agency (JAEA). The first demonstration of this system was given with a plastic sample containing traces of cadmium. The quantification limit of cadmium in a plastic sample was found to be about 0.1 ppm.     

Mechanism of mercury detection based on interaction of single-strand DNA and hybridized DNA with gold nanoparticles

Mechanisms of interaction of single-strand DNA and hybridized DNA on gold nanoparticles in the presence of Hg²⁺ was studied in this work. Recently the detection of Hg²⁺ using unmodified gold nanoparticles (AuNPs) combined with DNA is becoming a promising technique with the advantages of simplicity, cost-effectiveness and high sensitivity. However, few studies focused on the interaction of ssDNA and hybridized DNA on AuNPs to date. In the present work, we compared the interactions of different DNA probes on AuNPs using both absorption and fluorescence detection. It was found that there were only small partial dsDNA dissociated from the surface of AuNPs after hybridization in the presence of Hg²⁺. Moreover, we found that the aggregated AuNPs/DNA system tended to be dispersed again with increasing Hg²⁺ concentration up to 250 μM. Based on these results, the mechanisms of mercury detection based on interaction between DNA-conjugated gold nanoparticles were investigated. Positively charged dsDNA could bind to the surface of AuNPs and dominate the electrostatic interactions and consequently aggregation of the AuNPs/DNA system.     

Heterogeneous and Homogeneous Aptamer‐Based Electrochemical Sensors for Thrombin

Nanomolar concentrations of thrombin were electrochemically monitored using heterogeneous switch‐on and homogeneous switch‐off approaches that incorporated ferrocenyl aptamers. For the first time, the heterogeneous approach was coupled to a glucose/glucose oxidase (GOx) amplification‐regeneration system which increased its sensitivity by 2 folds with detection limits of 4.3 nM and 2.5 nM in the absence and presence of glucose/GOx, respectively. We also present a new homogeneous system involving the ferrocenyl aptamer binding thrombin in solution causing a significant decrease in its diffusion coefficient. Thus the ferrocene anodic current decreased at an unmodified gold electrode with detection limit of 3.9 nM and 12 times larger linear range than the heterogeneous method.     

Anodic Stripping Voltammetry of Silver Nanoparticles: Aggregation Leads to Incomplete Stripping

The influence of nanoparticle aggregation on anodic stripping voltammetry is reported. Dopamine-capped silver nanoparticles were chosen as a model system, and melamine was used to induce aggregation in the nanoparticles. Through the anodic stripping of the silver nanoparticles that were aggregated to different extents, it was found that the peak area of the oxidative signal corresponding to the stripping of silver to silver(I) ions decreases with increasing aggregation. Aggregation causes incomplete stripping of the silver nanoparticles. Two possible mechanisms of ‘partial oxidation’ and ‘inactivation’ of the nanoparticles are proposed to account for this finding. Aggregation effects must be considered when anodic stripping voltammetry is used for nanoparticle detection and quantification. Hence, drop casting, which is known to lead to aggregation, is not encouraged for preparing electrodes for analytical purposes.     

Chemical structure of composites derived from poly(silicic acid) and 2‐hydroxyethylmethacrylate

Organic–inorganic hybrids from 2‐hydroxyethylmethacrylate (HEMA) and poly(silicic acid)s were prepared and characterized. The molecular architecture of the inorganic phase was studied with ²⁹Si NMR spectroscopy, and the effect of acid concentration and reaction time on the properties of poly(silicic acid) were elucidated. Interactions between phases were studied with NMR spectroscopy and gel permeation chromatography, and the coexistence and connectivity of the two phases were investigated. Contrary to previous assumptions, evidence was found that indicated that the organic and inorganic phases of this class of sol–gel materials were not covalently linked. The curing process was studied by infrared spectroscopy, by which the disappearance of terminal double bonds of HEMA monomer were monitored. Thermogravimetric analysis profiles showed that the inorganic phase content was about 10 wt %, and it was varied slightly by changes in the molar ratio of the components. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1342–1352, 2001     

Systemically Injectable Enzyme‐Loaded Polyion Complex Vesicles as In Vivo Nanoreactors Functioning in Tumors

The design and construction of nanoreactors are important for biomedical applications of enzymes, but lipid‐ and polymeric‐vesicle‐based nanoreactors have some practical limitations. We have succeeded in preparing enzyme‐loaded polyion complex vesicles (PICsomes) through a facile protein‐loading method. The preservation of enzyme activity was confirmed even after cross‐linking of the PICsomes. The cross‐linked β‐galactosidase‐loaded PICsomes (β‐gal@PICsomes) selectively accumulated in the tumor tissue of mice. Moreover, a model prodrug, HMDER‐βGal, was successfully converted into a highly fluorescent product, HMDER, at the tumor site, even 4 days after administration of the β‐gal@PICsomes. Intravital confocal microscopy showed continuous production of HMDER and its distribution throughout the tumor tissues. Thus, enzyme‐loaded PICsomes are useful for prodrug activation at the tumor site and could be a versatile platform for enzyme delivery in enzyme prodrug therapy.