Ultrafast dynamics of isolated fluorenone

The ultrafast dynamics of isolated 9-fluorenone was studied by femtosecond time-resolved photoionization and photoelectron spectroscopy. The molecule was excited around 264-266 nm into the S(6) state. The experimental results indicate that the excitation is followed by a multistep deactivation. A time constant of 50 fs or less corresponds to a fast redistribution of energy within the initially excited manifold of states, i.e., a motion away from the Franck-Condon region. Internal conversion to the S(1) state then proceeds within 0.4 ps. The S(1) state is long-lived, and only a lower bound of 20 ps can be derived. In addition, we computed excited state energies and oscillator strengths by TD-DFT theory, supporting the interpretation of the experimental data.     

Copper-Photocatalyzed Hydrosilylation of Alkynes and Alkenes under Continuous Flow

Herein, the photocatalytic hydrosilylation of alkynes and alkenes under continuous flow conditions is described. By using 0.2 mol % of the developed [Cu(dmp)(XantphosTEPD)]PF₆ under blue LEDs irradiation, a large panel of alkenes and alkynes was hydrosilylated in good to excellent yields with a large functional group tolerance. The mechanism of the reaction was studied, and a plausible scenario was suggested.     

Elicitor-Induced VOC Emission by Grapevine Leaves: Characterisation in the Vineyard

The present study is aimed at determining whether leaf volatile organic compounds (VOCs) are good markers of the grapevine response to defence elicitors in the field. It was carried out in two distinct French vineyards (Burgundy and Bordeaux) over 3 years. The commercial elicitor Bastid^® (Syngenta, Saint-Sauveur, France) (COS-OGA) was first used to optimise the VOCs’ capture in the field; by bagging stems together with a stir bar sorptive extraction (SBSE) sensor. Three elicitors (Bastid^®, copper sulphate and methyl jasmonate) were assessed at three phenological stages of the grapevines by monitoring stilbene phytoalexins and VOCs. Stilbene production was low and variable between treatments and phenological stages. VOCs—particularly terpenes—were induced by all elicitors. However, the response profiles depended on the type of elicitor, the phenological stage and the vineyard, and no sole common VOC was found. The levels of VOC emissions discriminated between weak (Bastid^® and copper sulphate) and strong (methyl jasmonate) inducers. Ocimene isomers were constitutively present in the overall blends of the vineyards and increased by the elicitors’ treatments, whilst other VOCs were newly released throughout the growing seasons. Nonetheless, the plant development and climate factors undoubtedly influenced the release and profiles of the leaf VOCs.     

Hyperchromats with linear dependence of longitudinal chromatic aberration on wavelength

Optical lens systems that are characterized by a chromatic aberration of a predefined form are called hyperchromats. Our work describes a theory of hyperchromats with a linear dependence of longitudinal chromatic aberration on wavelength. The equations are derived for calculation of basic design parameters of these optical systems and some examples of hyperchromatic optical systems are shown. Mentioned optical systems can be used especially in 3D imaging systems and confocal microscopy.     

Excited State Dynamics of Isolated 6- and 8-Hydroxyquinoline Molecules

The photoinduced dynamics of isolated n-hydroxyquinoline (nHQ) molecules (n=6,8) was investigated in femtosecond pump-probe experiments. A qualitative difference was found between 8HQ and 6HQ. After an initial rapid decay corresponding to the departure of the initial wavepacket out of the Franck-Condon region of the excitation, the 8HQ probe signal decays to zero in 0.37 ps whereas a much longer time constant of 10.4 ps is observed in 6HQ. This interrogates on the role played by the intramolecular H-bond N HO which is at play the 8HQ molecule. Ab-initio were performed at the MCSCF/aug-cc-pVDZ level on the 8HQ molecule to help the discussion. A complex energy landscape was found, which includes a conical intersection.     

Covalent Grafting of BPin functions on Carbon Nanotubes and Chan–Lam–Evans Post-Functionalization

The chemical functionalization of carbon nanotubes is often a prerequisite prior to their use in various applications. The covalent grafting of 4,4,5,5-tetramethyl-1,3,2-dioxaborolane (BPin) functional groups directly on the surface of multi- and single-walled carbon nanotubes, activated by nucleophilic addition of nBuLi, was carried out. Thermogravimetric analysis (TGA) coupled with mass spectrometry, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ions mass spectrometry (ToF-SIMS) confirmed the efficiency of this methodology and proved the integrity and covalent grafting of the BPin functional groups. These groups were further reacted with various nucleophiles in the presence of a copper(II) source in the conditions of the aerobic Chan–Lam–Evans coupling. The resulting materials were characterized by TGA, XPS and ToF-SIMS. This route is efficient, reliable and among the scarce reactions that enable the direct grafting of heteroatoms at carbonaceous material surfaces.     

Künstlich hergestellte OberflÄchenschichten auf Glas

Zusammenfassung Der Verfasser führt in erster Reihe die Me\ergebnisse des Brechungsindex mittels der polarimetrischen Methode und mittels der Methode der kleinsten Ablenkung auf Prismen aus den verschiedenen Glassorten (Tabelle II) und auf den 20 Jahre alten Prismen vor und nach dem frischen Polieren (Tabelle III und IV) an. Der Schwerpunkt dieser polarimetrischen Messungen liegt in den Studien der künstlich hergestellten OberflÄchenschichten auf den Glasprismen. Die Tabellen V und VI geben die Me\ergebnisse von Studien der OberflÄchenschichten, welche künstlich mit einer chemischen Einwirkung 1,0-norm. NaOH- und H₂SO₄-Lösungen erzielt wurden. Die H₂SO₄ bildet auf der GlasoberflÄche eine dünne OberflÄchenschicht, welche das Glas vor der Einwirkung der SÄure schützt. Diese OberflÄchenschicht macht das Glas widerstandsfÄhig gegen die SÄuren. Demgegenüber bildet die NaOH-Lösung keine solche Schicht, welche das Glas schützen würde; daher korrodieren die Alkalilösungen (NaOH) das Glas. Weitere Untersuchungen haben bewiesen, da\ die NaOH-Lösung die OberflÄchenschicht auflöst, und zwar auf dem Crownglasprisma schneller als auf dem Flintglas. Auf dem Quarz, der einer vierstündigen Einwirkung NaOHund H₂SO₄-Lösungen ausgesetzt wurde, konnte keine Änderung auf der OberflÄche festgestellt werden. Ein Beweis der Anwesenheit der OberflÄchenschichten auf dem Glas sind die Interferenzerscheinungen des Lichtes. Aus der Interferenzfarbe wurde die Dicke der OberflÄchenschicht auf dem Flintglas ca. 2,10^–4 mm berechnet. Aus dem Vorliegenden ist ersichtlich, da\ die polarimetrischen Messungen sich als wertvolle Hilfsmittel für die Untersuchung der OberflÄchenschichten auf dem Glas und den verschiedenen Stoffen bewÄhren.