Estimation of anthropogenic organo-chlorine, bromine and iodine compounds in apolar lipid fractions of bovine milk by solid-phase extraction and neutron activation analysis (SPE–NAA)

Articulo cientifico publicado en: Journal of Radioanalytical and Nuclear Chemistry (2018) 318:247–257 https://doi.org/10.1007/s10967-018-6086-8Milk lipids were separated using a hexane:isopropanol mixture; then they were fractionated into apolar, medium polar and polar portions by SPE using a LC-Si column. The apolar fraction was further separated into 4 more portions depending on their polarity by another SPE method using a Florosil column. Levels of Cl, Br and I were measured by NAA. Halogens were detected in all separated fractions; but their highest levels were found in the most apolar fraction containing hydrocarbons which strongly indicates the presence of anthropogenic organohalogen compounds in milk. In addition, iodide and iodate ions in whole milk samples were measured

Peptide-Directed Preparation and X‑ray Structural Study of Au Nanoparticles on Titanium Surfaces

We report the peptide-directed preparation and X-ray structural study of biofunctionalized Au nanoparticles (NPs) deposited on Ti surfaces. Au NPs were prepared by reduction of Au³⁺ compound onto HCl-refreshed Ti in the presence of thiol-functionalized small peptides. A modified extended X-ray absorption fine-structure (EXAFS) technique, equipped with a rotating-stage and glancing-angle setup, was able to more sensitively detect the structure and bonding of Au NPs on Ti with low surface coverage. It was found that the use of the tripeptide glutathione (GSH) results in smaller NP size when compared to <i>N</i>-(2-mercapto-propionyl) glycine (MPG), a pseudodipeptide, over a wide range of Au/peptide molar ratios (20:1, 10:1, 5:1, and 2:1). By varying the ligand concentration, the Au NP structure in both systems can be controlled, generating nanocrystals, nanoclusters, and Au–thiolate polymer, which is unique for substrate-supported NP synthesis. This work presents a facile preparation of Au–peptide nanoparticles on biocompatible surfaces, and illustrates the high sensitivity of this modified EXAFS technique for structural studies of substrate-supported nanoparticles with low coverage

Vocabulary of radioanalytical methods (IUPAC Recommendations 2020)

These recommendations are a vocabulary of basic radioanalytical terms which are relevant to radioanalysis, nuclear analysis and related techniques. Radioanalytical methods consider all nuclear-related techniques for the characterization of materials where 'characterization' refers to compositional (in terms of the identity and quantity of specified elements, nuclides, and their chemical species) and structural (in terms of location, dislocation, etc. of specified elements, nuclides, and their species) analyses, involving nuclear processes (nuclear reactions, nuclear radiations, etc.), nuclear techniques (reactors, accelerators, radiation detectors, etc.), and nuclear effects (hyperfine interactions, etc.). In the present compilation, basic radioanalytical terms are included which are relevant to radioanalysis, nuclear analysis and related techniques. </p

Unique Bonding Properties of the Au₃₆(SR)₂₄ Nanocluster with FCC-Like Core

The recent discovery on the total structure of Au₃₆(SR)₂₄, which was converted from biicosahedral Au₃₈(SR)₂₄, represents a surprising finding of a face-centered cubic (FCC)-like core structure in small gold–thiolate nanoclusters. Prior to this finding, the FCC feature was only expected for larger (nano)­crystalline gold. Herein, we report results on the unique bonding properties of Au₃₆(SR)₂₄ that are associated with its FCC-like core structure. Temperature-dependent X-ray absorption spectroscopy (XAS) measurements at the Au L₃-edge, in association with <i>ab initio</i> calculations, show that the local structure and electronic behavior of Au₃₆(SR)₂₄ are of more molecule-like nature, whereas its icosahedral counterparts such as Au₃₈(SR)₂₄ and Au₂₅(SR)₁₈ are more metal-like. Moreover, site-specific S K-edge XAS studies indicate that the bridging motif for Au₃₆(SR)₂₄ has different bonding behavior from the staple motif from Au₃₈(SR)₂₄. Our findings highlight the important role of “pseudo”-Au₄ units within the FCC-like Au₂₈ core in interpreting the bonding properties of Au₃₆(SR)₂₄ and suggest that FCC-like structure in gold thiolate nanoclusters should be treated differently from its bulk counterpart

Interactions between Ultrastable Na4Ag44(SR)30 Nanoclusters and Coordinating Solvents: Uncovering the Atomic-scale Mechanism

We report the mechanism on the ultrahigh stability of Na4Ag44(SR)30 by uncovering how coordinating solvents interact with the Na4Ag44(SR)30 nanocluster at the atomic scale. Through synchrotron X-ray experiments and theoretical calculations, it was found that strongly coordinating aprotic solvents interact with surface Ag atoms, particularly between ligand bundles, which compresses the Ag core and relaxes surface metal-ligand interactions. Furthermore, water was used as a cosolvent to demonstrate that semi-aqueous conditions play an important role in protecting exposed surface regions and can further influence the local structure of the silver nanocluster itself. Notably, under semi-aqueous conditions, aprotic coordinating solvent molecules preferentially remain on the metal surface while water molecules interact with ligands, and ligand bundling persisted across the varied solvation conditions

Vocabulary of radioanalytical methods (IUPAC Recommendations 2020)

These recommendations are a vocabulary of basic radioanalytical terms which are relevant to radioanalysis, nuclear analysis and related techniques. Radioanalytical methods consider all nuclear-related techniques for the characterization of materials where 'characterization' refers to compositional (in terms of the identity and quantity of specified elements, nuclides, and their chemical species) and structural (in terms of location, dislocation, etc. of specified elements, nuclides, and their species) analyses, involving nuclear processes (nuclear reactions, nuclear radiations, etc.), nuclear techniques (reactors, accelerators, radiation detectors, etc.), and nuclear effects (hyperfine interactions, etc.). In the present compilation, basic radioanalytical terms are included which are relevant to radioanalysis, nuclear analysis and related techniques. Accepted Author ManuscriptRST/Applied Radiation & Isotope

Impact of the Selenolate Ligand on the Bonding Behavior of Au₂₅ Nanoclusters

We report the intriguing bonding behavior of selenolate-protected Au₂₅ nanoclusters (Au₂₅(SeR)₁₈), revealed by temperature-dependent X-ray absorption spectroscopy (XAS) from both the metal (Au L₃-edge) and ligand (Se K-edge) perspectives. The structure of Au₂₅(SeR)₁₈ was first analyzed in great detail using a site-specific, multishell (i.e., Au–Au core/surface/staple, Au–Se/Se-Au and Se–C shells) approach. It was found that the Au₁₃ core of Au₂₅(SeR)₁₈ remains relatively unchanged at low temperature while aurophilic interactions on the surface are significantly longer in distance compared with their thiolate-protected counterpart, Au₂₅(SR)₁₈. Remarkably, temperature-dependent studies showed a significant thermal contraction of the Au–Au framework in Au₂₅(SeR)₁₈, which is absent in the Au₂₅(SR)₁₈ system. This unusual bonding behavior of Au₂₅(SeR)₁₈ is proposed to be induced by the dimeric staple-like motif (−Au–Se–Au–Se–Au−) surface structures, where aurophilic bond distances and Au–Se–Au bond angles are sensitive toward temperature change. Density functional theory and molecular dynamics (DFT-MD) simulations were conducted to confirm this mechanism and provide further insight into the bonding behavior of the Au₂₅(SeR)₁₈ nanocluster. Finally, we use near-edge XAS results to demonstrate that the thermal contraction effect induces a change to the electronic properties of both the Au and Se and consistently accounted for using ab initio simulations of the near-edge and valence band structure