Photocatalysts convert light into potent reactivity. Here, we report a biohybrid catalyst in which a photosynthetic protein performs broad-spectrum light absorption and subsequent energy transfer to a conjugated photocatalyst, leading to improved yields in test reactions. This strategy has the potential to be generalized for applications in industrial and biological catalysis.

Whether a charged macromolecule remains solvated or adsorbs to the interface between two immiscible fluids depends on a variety of complex factors. Ions, in particular, have the capacity to affect the degree of polyelectrolyte hydrophobicity and conformation through electrostatic screening and site-specific interactions. Here, surface-specific vibrational spectroscopy is utilized to probe the roles of ions in the oil− water interfacial behavior of a model carboxylic acid-containing macromolecule. Specifically, the adsorption time dependence, conformation, and extent of carboxylate−cation interactions of poly(methacrylic acid) at the carbon tetrachloride−water interface are deduced as a function of CaCl 2 and KCl ionic strength. Additionally, the role of the polymer backbone configuration in interfacial behavior is explored through isomer-specific studies. Results show that ion binding and charge screening induce the adsorption of the isotactic isomer of poly(methacrylic acid) to the oil− water interface under solution conditions unfavorable to surface adsorptivity and that the degree of cation−carboxylate interactions strongly affects the adsorption dynamics and interfacial structure of the adsorbed polymer. The backbone structure of syndiotactic poly(methacrylic acid) does not allow for strong interactions with cations, and therefore, it remains water-solvated in the presence of salt. This work has significance for understanding the role of metal ions in the assembly of natural charged macromolecules at biological and environmental interfaces.

Fourier transform infrared and two-dimensional IR (2D-IR) spectroscopies were applied to two different silanes in three different solvents. The selected solutes exhibit different degrees of vibrational solvatochromism for the Si-H vibration. Density functional theory calculations confirm that this difference in sensitivity is the result of higher mode polarization with more electron withdrawing ligands. This mode sensitivity also affects the extent of spectral diffusion experienced by the silane vibration, offering a potential route to simultaneously optimize the sensitivity of vibrational probes in both steady-state and time-resolved measurements. Frequency-frequency correlation functions obtained by 2D-IR show that both solutes experience dynamics on similar time scales and are consistent with a picture in which weakly interacting solvents produce faster, more homogeneous fluctuations. Molecular dynamics simulations confirm that the frequency-frequency correlation function obtained by 2D-IR is sensitive to the presence of hydrogen bonding dynamics in the surrounding solvation shell.

A fully reflective two-dimensional IR (2D-IR) setup is described that enables efficient cancellation of scattered light from multiple pulses in the phase-matched direction. The local oscillator pulse and the pulse that stimulates the vibrational echo signal are synchronously modulated (or fibrillated) in time maintaining their phase relationships with the echo wavepacket. The modification is cost-effective and can be easily implemented on existing 2D-IR instruments, and it avoids the addition of dispersive elements into the beam paths. The fibrillation results in a decrease of waiting-time resolution of only tens of femtoseconds and has no impact on the spectral lineshape, making it a general improvement for 2D-IR spectrometers even for weakly or non-scattering samples.

An understanding of intramolecular charge transfer in 2-D linearly conjugated and cross-conjugated compounds is necessary for the rational design of molecular electronics, improved solar energy devices, semi-conducting polymers, and materials with nonlinear optical properties. In this work, the femtosecond transient absorption spectra and kinetics of several donor-bridgeacceptor compounds containing cross-conjugated or linearly conjugated bridging groups were obtained. The veratrole group was used as the donor, and the phthalimide group was used as an acceptor. 2-D conjugation was achieved by involving two bridging groups arranged cyclically between the donor and acceptor. The donor and acceptor were bridged by m-phenylene in the cross-conjugated compounds or 2,5-thiophene in the linearly conjugated compounds. We found slower charge separation times and slower charge recombination times in the compounds containing cyclic cross-conjugated bridging groups than in those containing the cyclic linearly conjugated groups in polar solvent. Charge separation rates that were found to be dependent on solvent were observed in the donor-bridge-acceptor compounds.