Engineering 3D Multi-Branched Nanostructures for Ultra- Sensing Applications

The fabrication of plasmonic nanostructures with sub-10 nm gaps supporting extremely large electric field enhancement (hot-spot) has attained great interest over the past years, especially in ultra-sensing applications. The “hot-spot” concept has been successfully implemented in surface-enhanced Raman spectroscopy (SERS) through the extensive exploitation of localized surface plasmon resonances. However, the detection of analyte molecules at ultra-low concentrations, i.e., down to the single/few molecule level, still remains an open challenge due to the poor localization of analyte molecules onto the hot-spot region. On the other hand, three-dimensional nanostructures with multiple branches have been recently introduced, demonstrating breakthrough performances in hot-spot-mediated ultra-sensitive detection. Multi-branched nanostructures support high hot-spot densities with large electromagnetic (EM) fields at the interparticle separations and sharp edges, and exhibit excellent uniformity and morphological homogeneity, thus allowing for unprecedented reproducibility in the SERS signals. 3D multi-branched nanostructures with various configurations are engineered for high hot-spot density SERS substrates, showing an enhancement factor of 1011 with a low detection limit of 1 fM. In this view, multi-branched nanostructures assume enormous importance in analyte detection at ultra-low concentrations, where the superior hot-spot density can promote the identification of probe molecules with increased contrast and spatial resolution

Photosensitizer Drug Delivery via an Optical Fiber

: An optical fiber has been developed with a maneuverable miniprobe tip that sparges O2 gas and photodetaches pheophorbide (sensitizer) molecules. Singlet oxygen is produced at the probe tip surface which reacts with an alkene spacer group releasing sensitizer upon fragmentation of a dioxetane intermediate. Optimal sensitizer photorelease occurred when the probe tip was loaded with 60 nmol sensitizer, where crowding of the pheophorbide molecules and self-quenching were kept to a minimum. The fiber optic tip delivered pheophorbide molecules and singlet oxygen to discrete locations. The 60 nmol sensitizer was delivered into petrolatum; however, sensitizer release was less efficient in toluene-d8 (3.6 nmol) where most had remained adsorbed on the probe tip, even after the covalent alkene spacer bond had been broken. The results open the door to a new area of fiber optic-guided sensitizer delivery for the potential photodynamic therapy of hypoxic structures requiring cytotoxic control

Neither Goodenough ionic model nor Zener polaron model for Bi0.5Ca0.5Mn1−xNixO3−δ system

The magnetic susceptibilities of three Bi0.5Ca0.5MnO3−δ compounds synthesised by three different methods were characterised and analysed. Large magnetic Mnx clusters (x ≥ 4) were considered to explain the high value of the Curie–Weiss constant. Unlike previous studies on similar systems, Goodenough ionic model or Zener polaron model is not suitable. In all cases, cluster behaviour is observed at low field and at low temperature. The influence of the oxygen stoichiometry and the homogeneity of the cation distribution depending on the method of the synthesis used is discussed. Finally, the effects of nickel doping on the magnetic properties were studied and the cluster behaviour was confirmed. The distribution in size of the clusters depends on the amount of nickel and it induces a glassy magnetic behaviour

Neither Goodenough ionic model nor Zener polaron model for Bi0.5Ca0.5Mn1−xNixO3−δ system

The magnetic susceptibilities of three Bi0.5Ca0.5MnO3−δ compounds synthesised by three different methods were characterised and analysed. Large magnetic Mnx clusters (x ≥ 4) were considered to explain the high value of the Curie–Weiss constant. Unlike previous studies on similar systems, Goodenough ionic model or Zener polaron model is not suitable. In all cases, cluster behaviour is observed at low field and at low temperature. The influence of the oxygen stoichiometry and the homogeneity of the cation distribution depending on the method of the synthesis used is discussed. Finally, the effects of nickel doping on the magnetic properties were studied and the cluster behaviour was confirmed. The distribution in size of the clusters depends on the amount of nickel and it induces a glassy magnetic behaviour

Multi-temperature synchrotron PXRD and physical properties study of half-Heusler TiCoSb

Phase pure samples of the half-Heusler material TiCoSb were synthesised and investigated. Multi-temperature synchrotron powder X-ray diffraction (PXRD) data measured between 90 and 1000 K in atmospheric air confirm the phase purity, but they also reveal a decomposition reaction starting at around 750 K. This affects the high temperature properties since TiCoSb is semiconducting, whereas CoSb is metallic. Between 90 K and 300 K the linear thermal expansion coefficient is estimated to be 10.5 x 10(-6) K(-1), while it is 8.49 10(-6) K(-1) between 550 K and 1000 K. A fit of a Debye model to the Atomic Displacement Parameters obtained from Rietveld refinement of the PXRD data gives a Debye temperature of 395(4) K. The heat capacity was measured between 2 K and 300 K and a Debye temperature of 375(5) K was obtained from modelling of the data. Coming from low temperatures the electrical resistivity shows a metallic to semiconducting transition at 113 K. A relatively high Seebeck coefficient of -250 mu VK(-1) was found at 400 K, but the substantial thermal conductivity (similar to 10 W mK(-1) at 400 K) leads to a moderate thermoelectric figure of merit of 0.025 at 400 K