Hydrogen-and methyl-capped polyynes have been synthesized by irradiating pure liquid toluene with 35 femtosecond, 300 μJ laser pulses having a central wavelength of 800 nm, generated by a regeneratively amplified Ti:sapphire tabletop laser at a repetition rate of 1 kHz. Raman spectroscopy was used to confirm the presence of polyynes in the irradiated samples while highperformance liquid chromatography was used to separate hydrogen-capped polyynes up to C18H2 and methyl-capped polyynes up to HC14CH3. These represent the first such methyl-capped polyynes and the longest hydrogen capped chains synthesized to date by the ultrafast laser based method. Furthermore our results show that choice of the starting solvent molecule directly influences the end caps of the polyynes which can be produced.
Graphene and its functionalized derivatives are unique and multifaceted novel materials with a wide range of applications in chemistry, healthcare, and optoelectronic engineering. 3D graphene materials exhibit several advantages over 2D (monolayer) graphene for a variety of devices applications. Here a novel and effective room temperature technique is introduced to convert an aqueous graphene oxide solution into a reduced graphene oxide gel with tunable physical and chemical properties comparable to a monolayer graphene sheet, without the need for any additives or chemical agents. The femtogel is synthesized by exposing an ultrahigh concentration graphene oxide solution with single‐layer flakes to high intensity femtosecond laser pulses. The femtosecond laser beam is focused on the air/aqueous solution interface to enhance the vaporization of functional groups and water, enabling femtogel formation. By controlling the pulsed laser intensity, beam focal parameters, and pulse duration, it is possible to produce several milliliters of femtogel in as little as 8 min. Through initial optimization of the irradiation parameters, a thin film is produced from a femtogel that demonstrates a surface roughness less than 6 nm, and more than 95% reduction in OH absorbance, as compared to a thin film produced from the unexposed graphene oxide solution.
Soft X-rays (90-173 eV) from the 3 rd generation Canadian Light Source have been used in conjunction with a multi coincidence time and position sensitive detection apparatus to observe the dissociative ionization of OCS. By varying the X-ray energy we can compare dynamics from direct and Auger ionization processes, and access ionization channels which result in two or three body breakup, from 2+ to 4+ ionization states. We make several new observations for the 3+ state such as kinetic energy release limited by photon energy, and using Dalitz plots we can see evidence of timescale effects between the direct and Auger ionization process for the first time. Finally, using Dalitz plots for OCS 4+ we observe for the first time that breakup involving an O 2+ ion can only proceed from out of equilibrium nuclear arrangement for S(2p) Auger ionization.
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