Proton transfer reaction plays an essential role in a myriad of chemical and biological processes, and to reveal the choreography of the proton motion intra- and intermolecularly, a spectroscopic technique capable of capturing molecular structural snapshots on the intrinsic time scale of proton transfer motions is needed. The photoacid pyranine (8-hydroxypyrene-1,3,6-trisulfonic acid, HPTS) serves as a paradigm case to dissect excited state proton transfer (ESPT) events in aqueous solution, triggered precisely by photoexcitation. We have used femtosecond stimulated Raman spectroscopy (FSRS) to yield novel insights into the ultrafast conformational dynamics of photoexcited HPTS in complex with water and acetate molecules. Marker bands attributed to the deprotonated form of HPTS (1139 cm(-1), ∼220 fs rise) appear earlier and faster than the monomer acetic acid peak (864 cm(-1), ∼530 fs rise), indicating that water molecules actively participate in the ESPT chain. Several key low-frequency modes at 106, 150, 195, and 321 cm(-1) have been identified to facilitate ESPT at different stages from 300 fs, 1 ps, to 6 ps and beyond, having distinctive dynamics contributing through hydrogen bonds with 0, 1, and more intervening water molecules. The time-resolved FSRS spectroscopy renders a direct approach to observe the reactive coupling between the vibrational degrees of freedom of photoexcited HPTS in action, therefore revealing the anharmonicity matrix both within HPTS and between HPTS and the neighboring acceptor molecules. The observed excited state conformational dynamics are along the ESPT multidimensional reaction coordinate and are responsible for the photoacidity of HPTS in aqueous solution.

Thiol−ene chemistry draws much attention nowadays in the construction of functional polymer materials due to its versatility and fast reaction kinetics, though only a few studies have been reported on its utilization in the fabrication of elastic polymer materials. Herein, a series of elastic, poly(dimethylsiloxane)−poly(ethylene glycol) methyl ether acrylate (PDMS−PEGMEA)-based co-polymer membranes are synthesized via a one-pot thiol−ene reaction. These membranes are highly stable and exhibit tunable thermal/ mechanical properties by tailoring the cross-linker and sidechain functionality. When used for gas separation application, all grafted elastomer membranes show excellent gas permeability and selectivity, and the membrane with an optimal composition (PDMS−PEGMEA 30 −EOPDMS 10 ) has reached the Robeson upper bound (CO 2 permeability ∼800 barrer and α[CO 2 /N 2 ] ∼39). The high permeability originates from the extremely fast chain mobility of PDMS molecules at the ambient temperature. Tailoring the PEGMEA content allows control of the α[CO 2 / N 2 ] ranging from 21 to 39 by enhancing gas solubility within the membrane matrix. This study provides a promising strategy to be utilized for the gutter layer, selective layer, or their combination in the industrial gas separation modules.

The optical anisotropy of Au protected Fe layers grown on a vicinal W(110) surface has been investigated using reflectance anisotropy spectroscopy (RAS). Iron nanostripes formed at submonolayer coverage, as well as Fe layers up to 3 ML coverage, were protected by 12 and 16 nm gold caps and measured ex situ under ambient conditions. The RAS is dominated by structures originating in the interfacial W(110) region, modified by the absorption in the Au cap and possibly by uniaxial strain in the Au cap itself. The Fe nanostructures themselves do not produce a significant RAS signature but, nevertheless, differences with Fe coverage were identified and explained in terms of a simple isotropic Fe absorbing layer, together with strain relief in the W/Fe/Au interfacial region.

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The main characteristics of the UK Fourth Generation Light Source (4GLS) are described. It is explained how the output of 4GLS could be used in studies of biological systems using Reflection Anisotropy Spectroscopy (RAS). (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)