Simultaneous Surface-Enhanced Raman Scattering with a Kerr Gate for Fluorescence Suppression.

The combination of surface-enhanced and Kerr-gated Raman spectroscopy for the enhancement of the Raman signal and suppression of fluorescence is reported. Surface-enhanced Raman scattering (SERS)-active gold substrates were demonstrated for the expansion of the surface generality of optical Kerr-gated Raman spectroscopy, broadening its applicability to the study of analytes that show a weak Raman signal in highly fluorescent media under (pre)resonant conditions. This approach is highlighted by the well-defined spectra of rhodamine 6G, Nile red, and Nile blue. The Raman spectra of fluorescent dyes were obtained only when SERS-active substrates were used in combination with the Kerr gate. To achieve enhancement of the weaker Raman scattering, Au films with different roughnesses or Au-core-shell-isolated nanoparticles (SHINs) were used. The use of SHINs enabled measurement of fluorescent dyes on non-SERS-active, optically flat Au, Cu, and Al substrates.

Effect of alkali-metal cation on oxygen adsorption at Pt single-crystal electrodes in non-aqueous electrolytes.

The effect of Group 1 alkali-metal cations (Na+, K+, and Cs+) on the oxygen reduction and evolution reactions (ORR and OER) using dimethyl sulfoxide (DMSO)-based electrolytes was investigated. Cyclic voltammetry (CV) utilising different Pt-electrode surfaces (polycrystalline Pt, Pt(111) and Pt(100)) was undertaken to investigate the influence of surface structure upon the ORR and OER. For K+ and Cs+, negligible variation in the CV response (in contrast to Na+) was observed using Pt(111), Pt(100) and Pt(poly) electrodes, consistent with a weak surface-metal/superoxide complex interaction. Indeed, changes in the half-wave potentials (E1/2) and relative intensities of the redox peaks corresponding to superoxy (O2-) and peroxy (O22-) ion formation were consistent with a solution-mediated mechanism for larger cations, such as Cs+. Support for this finding was obtained via in situ shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS). During the ORR and in the presence of Cs+, O2- and weakly adsorbed caesium superoxide (CsO2) species were detected. Because DMSO was found to strongly interact with the surface at potentials associated with the ORR, CsO2 was readily displaced at more negative potentials via increased solvent adsorption at the surface. This finding highlights the important impact of the solvent during ORR/OER reactions.

Nanophase-photocatalysis: loading, storing, and release of H2O2 using graphitic carbon nitride.

A blue light mediated photochemical process using solid graphitic carbon nitride (g-C3N4) in ambient air/isopropanol vapour is suggested to be linked to "nanophase" water inclusions and is shown to produce approx. 50 µmol H2O2 per gram of g-C3N4, which can be stored in the solid g-C3N4 for later release for applications, for example, in disinfection or anti-bacterial surfaces.

Review of biosensing with whispering-gallery mode lasers.

Lasers are the pillars of modern optics and sensing. Microlasers based on whispering-gallery modes (WGMs) are miniature in size and have excellent lasing characteristics suitable for biosensing. WGM lasers have been used for label-free detection of single virus particles, detection of molecular electrostatic changes at biointerfaces, and barcode-type live-cell tagging and tracking. The most recent advances in biosensing with WGM microlasers are described in this review. We cover the basic concepts of WGM resonators, the integration of gain media into various active WGM sensors and devices, and the cutting-edge advances in photonic devices for micro- and nanoprobing of biological samples that can be integrated with WGM lasers.

Use of an imaging station for rapid colony counting in radiobiology studies.

Colony counting by eye is time consuming and subjective. Here comparison between the measurements of proliferative growth inhibition in plates of radiation-treated cells by an imaging station correlated highly significantly with counts determined by eye. This would suggest that an imaging station could be a viable alternative for colony counting for doses over 200KBq.

The Role of Small Nanoparticles on the Formation of Hot Spots under Microwave-Assisted Hydrothermal Heating.

Herein, we report a detailed study of microwave-matter interaction focused on the role of small nanoparticles and the effects on microwave thermal heating. We have used a model reaction (degradation of methylene blue) to study the influence of temperature, size, and catalytic properties of the nanoparticles in the potential formation of hot spots. Total mineralization was achieved after 3 h microwave heating at 200 °C in the presence of 2 nm TiO2 nanoparticles (92% calculated TOC decay), but the reaction resulted in a mixture of intermediates (52% TOC decay) in the absence of TiO2. The effect of temperature was evaluated by carrying out the reaction at 120 °C, and the results were similar to those obtained in the absence of TiO2, but with lower TOC removal efficiencies (12-14%). For comparison, the degradation of MB was also followed using (noncatalytic) SiO2 and MnO2 nanoparticles of comparable size. Differences in the degradation efficiency may be ascribed to the formation of hot spots at the particles surface, as a result of large heat accumulation liable to provide enough energy to the system to accomplish C-C bond break and to achieve total mineralization.

Physicochemical Tools: Toward a Detailed Understanding of the Architecture of Targeted Radiotherapy Nanoparticles.

Targeted radiotherapy is proving to be an effective alternative to external beam radiotherapy for cancer treatment. Gold nanoparticles are biocompatible, commercially available, and readily functionalized, which makes them perfect candidates for the delivery of cytotoxic radionuclides labeled with antibodies to proteins abnormally expressed on cancer tissue. However, there is a lack of information regarding the efficacy of the successive modification steps involved in the functionalization process, as well as of the actual final state of the nanoparticles prior to preclinical tests, which results in a very inefficient screening and that will further impact on biological barriers, such as half-life interactions with serum proteins. Here, gold nanoparticles (15 nm diameter) were functionalized with linkers for antibody and radionuclide conjugation, following a well-stablished method. Successful coating of the gold nanoparticles was demonstrated using state-of-the-art physicochemical techniques, which include AF4-UV-ICPMS-MALS, Raman spectroscopy, and force-distance spectroscopy, which have led to an accurate description of the hydrodynamic diameter of the functionalized NPs and also about the adhesion energy and elastic properties of the modified NPs. Successive steps involved in the coating led to an organic shell of 12 nm diameter and no nanoparticle aggregation was observed. This may be a consequence of a decrease (or even the total absence) in water adsorption on the metal surface and/or of the organic labeling, that decreases the surface tension of the particles as estimated from the atomic force microscopy force-distance curves. Radiolabeling of gold nanoparticles prescreened using these physicochemical tools with 177Lu resulted in >75% efficiency.

Non-covalent interactions at electrochemical interfaces: one model fits all?

The shift with increasing concentration of alkali-metal cations of the potentials of both the spike and the hump observed in the cyclic voltammograms of Pt(111) electrodes in sulfuric acid solutions is shown to obey the simple model recently developed by us to explain the effect of non-covalent interactions at the electrical double layer. The results suggest that the model, originally developed to describe the effect of alkali-metal cations on the cyclic voltammogram of cyanide-modified Pt(111) electrodes, is of general applicability and can explain quantitatively the effect of cations on the properties of the electrical double layer.

Adsorbed formate: the key intermediate in the oxidation of formic acid on platinum electrodes.

The electrooxidation of formic acid on Pt and other noble metal electrodes proceeds through a dual-path mechanism, composed of a direct path and an indirect path through adsorbed carbon monoxide, a poisoning intermediate. Adsorbed formate had been identified as the reactive intermediate in the direct path. Here we show that actually it is also the intermediate in the indirect path and is, hence, the key reaction intermediate, common to both the direct and indirect paths. Furthermore, it is confirmed that the dehydration of formic acid on Pt electrodes requires adjacent empty sites, and it is demonstrated that the reaction follows an apparently paradoxical electrochemical mechanism, in which an oxidation is immediately followed by a reduction.

The structural intolerance of the PrP alpha-fold for polar substitution of the helix-3 methionines.

The conversion of the cellular prion protein (PrP(C)) into its disease-associated form (PrP(Sc)) involves a major conformational change and the accumulation of sulfoxidized methionines. Computational and synthetic approaches have shown that this change in the polarity of M206 and M213 impacts the C-terminal domain native alpha-fold allowing the flexibility required for the structural conversion. To test the effect in the full-length molecule with site-specificity, we have generated M-to-S mutations. Molecular dynamics simulations show that the replacement indeed perturbs the native state. When this mutation is placed at the conserved methionines of HaPrP(23-231), only substitutions at the Helix-3 impair the alpha-fold, stabilizing a non-native state with perturbed secondary structure, loss of native tertiary contacts, increased surface hydrophobicity, reduced thermal stability and an enhanced tendency to aggregate into protofibrillar polymers. Our work supports that M206 and M213 function as alpha-fold gatekeepers and suggests that their redox state regulate misfolding routes.