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DDC: 540 × Publisher: Cambridge [u.a.] : Royal Society of Chemistry ×

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    Imaging molecular structure through femtosecond photoelectron diffraction on aligned and oriented gas-phase molecules
    (Cambridge [u.a.] : Royal Society of Chemistry, 2014) Boll, R.; Rouzée, A.; Adolph, M.; Anielski, D.; Aquila, A.; Bari, S.; Bomme, C.; Bostedt, C.; Bozek, J.D.; Chapman, H.N.; Christensen, L.; Coffee, R.; Coppola, N.; De, S.; Decleva, P.; Epp, S.W.; Erk, B.; Filsinger, F.; Foucar, L.; Gorkhover, T.; Gumprecht, L.; Hömke, A.; Holmegaard, L.; Johnsson, P.; Kienitz, J.S.; Kierspel, T.; Krasniqi, F.; Kühnel, K.-U.; Maurer, J.; Messerschmidt, M.; Moshammer, R.; Müller, N.L.M.; Rudek, B.; Savelyev, E.; Schlichting, I.; Schmidt, C.; Scholz, F.; Schorb, S.; Schulz, J.; Seltmann, J.; Stener, M.; Stern, S.; Techert, S.; Thøgersen, J.; Trippel, S.; Viefhaus, J.; Vrakking, M.; Stapelfeldt, H.; Küpper, J.; Ullrich, J.; Rudenko, A.; Rolles, D.
    This paper gives an account of our progress towards performing femtosecond time-resolved photoelectron diffraction on gas-phase molecules in a pump-probe setup combining optical lasers and an X-ray free-electron laser. We present results of two experiments aimed at measuring photoelectron angular distributions of laser-aligned 1-ethynyl-4-fluorobenzene (C8H5F) and dissociating, laser-aligned 1,4-dibromobenzene (C6H4Br2) molecules and discuss them in the larger context of photoelectron diffraction on gas-phase molecules. We also show how the strong nanosecond laser pulse used for adiabatically laser-aligning the molecules influences the measured electron and ion spectra and angular distributions, and discuss how this may affect the outcome of future time-resolved photoelectron diffraction experiments.
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    Poisoning of bubble propelled catalytic micromotors: The chemical environment matters
    (Cambridge [u.a.] : Royal Society of Chemistry, 2013) Zhao, G.; Sanchez, S.; Schmidt, O.G.; Pumera, M.
    Self-propelled catalytic microjets have attracted considerable attention in recent years and these devices have exhibited the ability to move in complex media. The mechanism of propulsion is via the Pt catalysed decomposition of H2O2 and it is understood that the Pt surface is highly susceptible to poisoning by sulphur-containing molecules. Here, we show that important extracellular thiols as well as basic organic molecules can significantly hamper the motion of catalytic microjet engines. This is due to two different mechanisms: (i) molecules such as dimethyl sulfoxide can quench the hydroxyl radicals produced at Pt surfaces and reduce the amount of oxygen gas generated and (ii) molecules containing -SH, -SSR, and -SCH3 moieties can poison the catalytically active platinum surface, inhibiting the motion of the jet engines. It is essential that the presence of such molecules in the environment be taken into consideration for future design and operation of catalytic microjet engines. We show this effect on catalytic micromotors prepared by both rolled-up and electrodeposition approaches, demonstrating that such poisoning is universal for Pt catalyzed micromotors. We believe that our findings will contribute significantly to this field to develop alternative systems or catalysts for self-propulsion when practical applications in the real environment are considered.