报告题目Title：Photochemistry, spectroscopy and mass spectrometry of protonated aromatics: gas-phase and liquid microdroplets 质子化芳香族气相和液相的光化学、光谱、质谱
报 告 人Speaker：A/Prof Adam J. Trevitt, Laser Chemistry Laboratory, School of Chemistry, University of Wollongong, NSW, 2522 卧龙岗大学
报告时间Time：2016年11月10日(周四) 10:00
报告地点Venue：校本部E106 Meeting Room 会议室，上海大学量子与分子结构国际中心SHU ICQMS

摘要：Photons initiate chemical action by exciting molecules to more active bound states or by breaking bonds to create reactive products. Fundamental insights into these processes has led to a useful understanding of atmospheric photochemistry (like haze formation), pin-pointed inefficiencies in organic-sensitized solar cells and enabled targeted photodynamic therapies in biological systems. To make further inroads and master the photochemistry underpinning these applications, our research group is engaged with the study of photoactivation – in gas-phase isolation and in solution. This presentation will outline our recent results concerning protonated N-substituted aromatics using ion trap mass spectrometry and a new microdroplet mass spectrometry technique.
Two projects will be described:
(i) tunable UV-vis laser radiation coupled to a linear ion-trap for gas-phase action spectroscopy of ions.
Several protonated aromatic systems that are fundamental chromophores in many settings are probed using UV photodissociation spectroscopy. These species include pyridineH+ and (iso)quinolineH+ chromophores. New insights into the stability and fate of their low-lying excited states will be described.
(ii) a unification of single microdroplet generation, laser photolysis and mass spectrometry for rapidacquisition of liquid-phase action spectroscopy. Our single-droplet desorption strategy, shown in the figure (ii) below, involves single droplets falling on a thin needle held at 2 kV. The subsequent electrospray is sampled by a mass spectrometer. This is performed at 10-20 Hz, one droplet at a time:
one droplet (40 pL); one laser pulse; one spectrum. Solution-born photoproducts are detected mass spectroscopically within milliseconds. Since there is no cross-contamination between droplets, laser on/off statistics are rapidly obtained. Results probing the photochemistry of s- and p-type aromatic radical systems and a novel liquid-phase action spectroscopy method will be discussed.
(i)
(ii)
References
(i) C. S. Hansen, S. J. Blanksby, N. Chalyavi, E. J. Bieske, J. R. Reimers and A. J. Trevitt, Ultraviolet photodissociation action spectroscopy of the N-pyridinium cation, J. Chem. Phys. 142, 014301 (2015), C. S. Hansen, S. J. Blanksby, A. J. Trevitt,
Ultraviolet photodissociation action spectroscopy of gas-phase protonated quinoline and isoquinoline cations, Phys. Chem. Chem. Phys., 17, 25882-25890 (2015)
(ii) P. J. Tracey, B. S. Vaughn, B. J. Roberts, B. L. J. Poad, A. J. Trevitt*, Rapid profiling of laser-induced photochemistry in single microdroplets using mass spectrometry, Anal. Chem. 2014, 86, 2895 (2014), B. Vaughn, Phillip J. Tracey and A. J. Trevitt, Drop-on-demand microdroplet generation: a very stable platform for single-droplet experimentation, RSC Advances, 6, 60215-60222 (2016).