Extended π-backbone for highly efficient near-infrared thermally activated delayed fluorescence with enhanced horizontal molecular orientation

The near-infrared thermally activated delayed fluorescence (NIR-TADF) materials with emission over 700 nm were insufficiently investigated mainly due to the limited choice of strong donor/acceptor units for the molecular construction...

Near-Infrared Vapochromism in Lipid-Packaged Mixed-Valence Coordination Polymers

Reversible vapochromism in the NIR region is achieved for a mixed-valence platinum complex with lipid counterions, from which exclusion of crystallization water by organic vapor alters lipid molecular orientation that...

De Novo Determination of Molecular Orientation at Interfaces through Multimode Polarization-Dependent Sum-Frequency Generation Spectroscopy

Many essential processes occur at soft interfaces, from chemical reactions on aqueous aerosols in the atmosphere to biochemical recognition and binding at the surface of cell membranes. The spatial arrangement of molecules specifically at these interfaces is crucial for many of such processes. The accurate determination of the interfacial molecular orientation has been challenging due to the low number of molecules at interfaces and the ambiguity of their orientational distribution. Here, we combine phase- and polarization-resolved sum-frequency generation spectroscopy to obtain the molecular orientation at the interface. We extend an exponentially decaying orientational distribution to multiple dimensions, which, in conjunction with multiple SFG data sets obtained from the different vibrational modes, allows us to determine molecular orientation. We apply this new approach to formic acid molecules at the air-water interface. The inferred orientation of formic acid agrees very well with ab initio molecular dynamics data. The phase-resolved SFG multimode analysis scheme using the multi-dimensional orientational distribution thus provides a universal approach for obtaining the interfacial molecular orientation.

Impact of graphene-molecular interaction on collective orientation barrier for organic film growth

The temperature-dependent molecular orientation variation of pentacene (PEN) on a graphene-covered substrate (PEN/Gr) was investigated via p-polarized multiple-angle incidence resolution spectrometry (pMAIRS). The temperature regime of the orientation transition of PEN/Gr was different from that of PEN/SiO2. The collective orientation barrier (COB), an energy barrier that molecules need to overcome to form a standing orientation, was estimated via pMAIRS. Consequently, the COB of PEN/Gr was found to be 10 times larger than that of PEN/SiO2. This indicated that the COB is valuable for understanding the effect of substrate interaction on the molecular orientation.

Angle-dependent interferences in electron emission accompanying stimulated Compton scattering from molecules

The high brilliance of ultrashort X-ray pulses recently generated in free electron lasers will soon open the way to the investigation of non-linear processes that still remain inaccessible due to the smallness of the corresponding cross sections. One of them is stimulated Compton scattering from molecules. In this work, we investigate stimulated Compton scattering from fixed-in-space H2 molecules in the few-hundred eV photon energy range, where both dipole and non-dipole transitions are important. We show that the interference between dipole and non-dipole transitions leads to pronounced asymmetries in the electron angular distributions. These asymmetries strongly depend on molecular orientation, to the point that they can lead to electron emission in either the forward or the backward directions with respect to the propagation axis, or in both directions, or even in the orthogonal direction. This is in contrast with Compton scattering from free electrons or atomic targets.

Relationship between Molecular Orientation Relaxation during Physical Aging and Heat Resistance of Polystyrene Injection Moldings

This work examined the relationship between changes in molecular orientation and the heat resistance (heat distortion temperature) of polystyrene injection moldings following heat treatment below the glass transition temperature. Molecular orientation around the core layer of the injection moldings was found to be relaxed by the heat treatment. Also, in the untreated specimen, the molecular orientation around the core layer was relaxed from 60°C during the heating process. Since loss tangent (tanδ) also increased from 60°C during the heating process in the untreated specimen, it was considered that the increase in tanδ occurred with the molecular motion due to the relaxation of molecular orientation from 60°C. After the heat treatment, because of the relaxation of molecular orientation around the core layer by the heat treatment, the relaxation of molecular orientation from 60 °C did not occur during the subsequent heating process, and the tanδ of the polymer between 60 and 90 °C was decreased. Because this decrease in the tanδ over this temperature range improved the heat resistance of the material, the enhanced heat resistance by the heat treatment was attributed to the suppression of the relaxation of molecular orientation from 60°C during the heating process. Furthermore, relaxation of molecular orientation and enthalpy relaxation were related to improvement in the heat resistance.