Physical Study by Surface Characterizations of Sarin Sensor on the Basis of Chemically Functionalized Silicon Nanoribbon Field Effect Transistor

Surface characterizations of an organophosphorus (OP) gas detector based on chemically functionalized silicon nanoribbon field-effect transistor (SiNR-FET) were performed by Kelvin Probe Force Microscopy (KPFM) and ToF-SIMS, and correlated with changes in the current-voltage characteristics of the devices. KPFM measurements on FETs allow (i) to investigate the contact potential difference (CPD) distribution of the polarized device as function of the gate voltage and the exposure to OP traces and, (ii) to analyze the CPD hysteresis associated to the presence of mobile ions on the surface. The CPD measured by KPFM on the silicon nanoribbon was corrected due to side capacitance effects in order to determine the real quantitative surface potential. Comparison with macroscopic Kelvin probe (KP) experiments on larger surfaces was carried out. These two approaches were quantitatively consistent. An important increase of the CPD values (between + 399 mV and + 302 mV) was observed after the OP sensor grafting, corresponding to a decrease of the work function, and a weaker variation after exposure to OP (between - 14 mV and - 61 mV) was measured. Molecular imaging by ToF-SIMS revealed OP presence after SiNR-FET exposure. The OP molecules were essentially localized on the Si-NR confirming effectiveness and selectivity of the OP sensor. A prototype was exposed to Sarin vapors and succeeded in the detection of low vapor concentrations (40 ppm).Comment: Paper and supporting information, J. Phys. Chem. C, 201

Synthesis of Perylene-3,4-mono(dicarboximide)−Fullerene C60 Dyads as New Light-Harvesting Systems

Fullerene C60−perylene-3,4-mono(dicarboximide) (C60−PMI) dyads 1−3 were synthesized in the search for new light-harvesting systems. The synthetic strategy to the PMI intermediate used a cross-coupling Suzuki reaction for the introduction of a formyl group in the ortho, meta, or para position. Subsequent 1,3-dipolar cycloaddition with C60 led to the target C60−PMI dyad. Cyclic voltammetry showed that the first one-electron reduction process unambiguously occurs onto the C60 moiety and the following two-electron process corresponds to the concomitant second reduction of C60 and the first reduction of PMI. A quasi-quantitative quenching of fluorescence was shown in dyads 1−3, and an intramolecular energy transfer was suggested to occur from the PMI to the fullerene moiety. These C60−PMI dyads constitute good candidates for future photovoltaic applications with expected well-defined roles for both partners, i.e., PMI acting as a light-harvesting antenna and C60 playing the role of the acceptor in the photoactive layer

Fluorescent Discrimination between Traces of Chemical Warfare Agents and Their Mimics

An array of fluorogenic probes is able to discriminate between nerve agents, sarin, soman, tabun, VX and their mimics, in water or organic solvent, by qualitative fluorescence patterns and quantitative multivariate analysis, thus making the system suitable for the inthe- field detection of traces of chemical warfare agents as well as to differentiate between the real nerve agents and other related compounds.Ministerio de Economía y Competitividad, Spain (Project CTQ2012- 31611), Junta de Castilla y León, Consejería de Educación y Cultura y Fondo Social Europeo (Project BU246A12-1), the European Commission, Seventh Framework Programme (Project SNIFFER FP7-SEC-2012-312411) and the Swedish Ministry of Defence (no. A403913

Second-order nonlinear optical properties of cyclometallated Ir(III) and Pt(II) complexes

The second-order NLO properties of various cyclometallated cationic Ir(III) and neutral Pt(II) complexes were determined by both Electric Field Induced Second Harmonic generation (EFISH) and Harmonic Light Scattering (HLS) techniques. Cationic 1,10-phenanthroline and bipyridine iridium(III) complexes (1, 2) are characterized by high negative EFISH \uf06d\u3b2 values which decrease when the ion-pair strength between the cation and the counterion (PF6\u2013, C12H25SO3\u2013) increases. Neutral Pt(II) complexes (3, 4) are also characterized by a good to high negative NLO response. For all these cyclometallated complexes, the EFISH response is mainly controlled by MLCT/L'LCT processes. Interestingly, a combination of HLS and EFISH techniques, used to evaluate both the dipolar and octupolar contributions to the total quadratic hyperpolarizability, shows that the major contribution is controlled by the octupolar part. [...] 1. V. Aubert, L. Ordronneau, M. Escadeillas, J. A. G. Williams, A. Boucekkine, E. Coulaud, C. Dragonetti, S. Righetto, D. Roberto, R. Ugo, A. Valore, A. Singh, J. Zyss, I. Ledoux-Rak, H. Le Bozec, V. Guerchais, Inorg. Chem. 2011. ASA