Amine Hole Scavengers Facilitate Both Electron and Hole Transfer in a Nanocrystal/Molecular Hybrid Photocatalyst.

A well-known catalyst, -Re(4,4'-R-bpy)(CO)Cl (bpy = bipyridine; R = COOH) (ReC0A), has been widely studied for CO reduction; however, its photocatalytic performance is limited due to its narrow absorption range. Quantum dots (QDs) are efficient light harvesters that offer several advantages, including size tunability and broad absorption in the solar spectrum. Therefore, photoinduced CO reduction over a broad range of the solar spectrum could be enabled by ReC0A catalysts heterogenized on QDs.

Faking self-reports of health behavior: a comparison between a within- and a between-subjects design.

Background: This study examines people's ability to fake their reported health behavior and explores the magnitude of such response distortion concerning faking of preventive health behavior and health risk behavior. As health behavior is a sensitive topic, people usually prefer privacy about it or they wish to create a better image of themselves (Fekken et al., 2012; Levy et al.

Ultrafast vibrational dynamics of a solute correlates with dynamics of the solvent.

Two-dimensional infrared (2D-IR) spectroscopy is used to measure the spectral dynamics of the metal carbonyl complex cyclopentadienyl manganese tricarbonyl (CMT) in a series of linear alkyl nitriles. 2D-IR spectroscopy provides direct readout of solvation dynamics through spectral diffusion, probing the decay of frequency correlation induced by fluctuations of the solvent environment. 2D-IR simultaneously monitors intramolecular vibrational energy redistribution (IVR) among excited vibrations, which can also be influenced by the solvent through the spectral density rather than the dynamical friction underlying solvation.

Transmission Mode 2D-IR Spectroelectrochemistry of Electrocatalytic Intermediates.

Unraveling electrocatalytic mechanisms, as well as fundamental structural dynamics of intermediates, requires spectroscopy with high time and frequency resolution that can account for nonequilibrium concentration changes inherent to electrochemistry. Two-dimensional infrared (2D-IR) spectroscopy is an ideal candidate, but several technical challenges have hindered development of this powerful tool for spectroelectrochemistry (SEC). We demonstrate a transmission-mode, optically transparent thin-layer electrochemical (OTTLE) cell adapted to 2D-IR-SEC to monitor the important Re(bpy)(CO)Cl CO-reduction electrocatalyst.

Robust Binding of Disulfide-Substituted Rhenium Bipyridyl Complexes for CO Reduction on Gold Electrodes.

Heterogenization of homogenous catalysts on electrode surfaces provides a valuable approach for characterization of catalytic processes conditions using surface selective spectroelectrochemistry methods. Ligand design plays a central role in the attachment mode and the resulting functionality of the heterogenized catalyst as determined by the orientation of the catalyst relative to the surface and the nature of specific interactions that modulate the redox properties under the heterogeneous electrode conditions. Here, we introduce new [Re(L)(CO)Cl] catalysts for CO reduction with sulfur-based anchoring groups on a bipyridyl ligand, where L = 3,3'-disulfide-2,2'-bipyridine (SSbpy) and 3,3'-thio-2,2'-bipyridine (Sbpy).

Ultrafast X-ray Absorption Near Edge Structure Reveals Ballistic Excited State Structural Dynamics.

Polarized ultrafast time-resolved X-ray absorption near edge structure (XANES) allows characterization of excited state dynamics following excitation. Excitation of vitamin B, cyanocobalamin (CNCbl), in the αβ-band at 550 nm and the γ-band at 365 nm was used to uniquely resolve axial and equatorial contributions to the excited state dynamics. The structural evolution of the excited molecule is best described by a coherent ballistic trajectory on the excited state potential energy surface.

Solvent exchange in preformed photocatalyst-donor precursor complexes determines efficiency.

In homogeneous photocatalytic reduction of CO, it is widely assumed that the primary electron transfer from the sacrificial donor to the catalyst is diffusion controlled, thus little attention has been paid to optimizing this step. We present spectroscopic evidence that the precursor complex is preformed, driven by preferential solvation, and two-dimensional infrared spectroscopy reveals triethanolamine (donor)/tetrahydrofuran (solvent) exchange in the photocatalyst's solvation shell, reaching greatest magnitude at the known optimal concentration (∼20% v/v TEOA in THF) for catalytically reducing CO to CO. Transient infrared absorption shows the appearance of the singly reduced catalyst on an ultrafast (<70 ps) time scale, consistent with non-diffusion controlled electron transfer within the preformed precursor complex.

Polarized XANES Monitors Femtosecond Structural Evolution of Photoexcited Vitamin B.

Ultrafast, polarization-selective time-resolved X-ray absorption near-edge structure (XANES) was used to characterize the photochemistry of vitamin B, cyanocobalamin (CNCbl), in solution. Cobalamins are important biological cofactors involved in methyl transfer, radical rearrangement, and light-activated gene regulation, while also holding promise as light-activated agents for spatiotemporal controlled delivery of therapeutics. We introduce polarized femtosecond XANES, combined with UV-visible spectroscopy, to reveal sequential structural evolution of CNCbl in the excited electronic state.

NOESY-Like 2D-IR Spectroscopy Reveals Non-Gaussian Dynamics.

We have identified an unexpected signature of non-Gaussian dynamics in a conventional 2D IR measurement on a system with rapid intermolecular vibrational energy transfer. In a ternary mixture of the CO reduction photocatalyst, ReCl(bpy)(CO), NaSCN, and THF solvent, preferential association between the metal carbonyl catalyst and the NaSCN ion pairs facilitates intermolecular energy transfer on a few picoseconds time scale. Monitoring the cross peak between the highest frequency metal carbonyl band and the CN bands of NaSCN contact ion pairs, we find a striking time evolution of the cross-peak position on the detection axis.

Dynamics of rhenium photocatalysts revealed through ultrafast multidimensional spectroscopy.

Rhenium catalysts have shown promise to promote carbon neutrality by reducing a prominent greenhouse gas, CO2, to CO and other starting materials. Much research has focused on identifying intermediates in the photocatalysis mechanism as well as time scales of relevant ultrafast processes. Recent studies have implemented multidimensional spectroscopies to characterize the catalyst's ultrafast dynamics as it undergoes the many steps of its photocycle.

Solvent-dependent dynamics of a series of rhenium photoactivated catalysts measured with ultrafast 2DIR.

The spectral dynamics of a series of rhenium photocatalysts, fac-Re(4,4'-R2-bpy)(CO)3Cl, where R = H, methyl, t-butyl, and carboxylic acid, as well as Re(1,10-phenanthroline)(CO)3Cl were observed in multiple aprotic solvents using two-dimensional infrared spectroscopy (2DIR). The carbonyl vibrational stretching frequencies showed slight variations due to the electron-donating or -withdrawing nature of the substituents on the bipyridine. The different substituents had minimal to no influence on the spectral diffusion time scales of the compounds within a particular solvent, but among the three different solvents investigated (DMSO, THF, and CH3CN), we find the spectral diffusion times to correlate with the solvent's donor number (DN).

Equilibrium excited state dynamics of a photoactivated catalyst measured with ultrafast transient 2DIR.

A detailed understanding of photocatalyzed reaction dynamics requires a sensitive means of investigating the transient catalytically active species. Ideally, the method should be able to compare the electronically excited photocatalyst directly to the ground state species. We use equilibrium and transient two-dimensional infrared (2DIR and t-2DIR) spectroscopy to study the ground and excited state spectral dynamics of [Re(CO)3(bpy)Cl] in tetrahydrofuran (THF).

Liver-specific expression of the agouti gene in transgenic mice promotes liver carcinogenesis in the absence of obesity and diabetes.

Background: The agouti protein is a paracrine factor that is normally present in the skin of many species of mammals. Agouti regulates the switch between black and yellow hair pigmentation by signalling through the melanocortin 1 receptor (Mc1r) on melanocytes. Lethal yellow (Ay) and viable yellow (Avy) are dominant regulatory mutations in the mouse agouti gene that cause the wild-type protein to be produced at abnormally high levels throughout the body.

Use of a multiple-enzyme/multiple-reagent assay system to quantify activity levels in samples containing mixtures of matrix metalloproteinases.

Matrix metalloproteinases (MMPs) are a family of enzymes that are up-regulated in many diseases, including osteoarthritis (OA) and rheumatoid arthritis (RA). Here we report on a novel technique that can be used to simultaneously measure activity levels for a panel of enzymes, such as the MMPs. The technique, termed the multiple-enzyme/multiple-reagent assay system (MEMRAS), relies on the use of reagents such as substrates with varying selectivity profiles against a group of enzymes.