Rowlandcarlsen2864

Semiconductor-metal heterojunction nanostructures possess an ability to store electrons upon photoexcitation through Fermi level equilibration. The unique role of capping ligands in modulating the equilibration of Fermi level in CdSe-Au heteronanostructures is explored by taking alkyl thiols and alkyl amines as examples. Alkyl thiol having its highest occupied molecular orbital (HOMO) above the valence band of the heterojunction nanostructure inhibits the exciton recombination by scavenging the photogenerated hole. This leads to the elevation in the Fermi level of Au and equilibration with the conduction band of CdSe. The Fermi level equilibrated electrons are further transferred to an acceptor molecule such as methyl viologen, demonstrating the potential of heterojunction nanostructures capped with hole accepting ligands for charge transport application in photovoltaics. In contrast, alkyl amine being a non-hole acceptor ligand with its HOMO placed below its valence band promotes rapid Au mediated exciton recombination, limiting its usefulness in charge transport application. Thus, the energetics of ligands on heterojunction nanostructures plays a decisive role in Fermi level equilibration.In this work, the reaction properties of mixed silver-nickel oxide AgNiO2 were investigated in the reaction of CO oxidation ranging from room temperature up to 350 °C. X-ray photoelectron spectroscopy revealed the presence of a single oxidized silver state and the combination of Ni2+ and Ni3+ species on the surface of the as-prepared mixed oxide. It was established that AgNiO2 was able to interact with CO at room temperature. learn more It was accompanied by the simultaneous titration of the lattice (O2--like) and weakly charged (O--like) oxygen species. The interaction with CO below 100 °C resulted in the accumulation of carbonate-like species on the AgNiO2 surface. Above 150 °C, the surface structure of mixed oxide was found to be disrupted, resulting in the formation of individual particles of metallic silver and oxidized nickel.In describing the charge carriers' separation mechanism in the organic solar cell, providing a method, which considers the impact of all parameters of interest on the same footing within an inexpensive numerical effort, could play an essential role. We use here a simple tight-binding model to describe the dissociation of the charge carriers and investigate their dependence on the physical parameters of the system. We demonstrate that the quantum yield of the cell is subtly controlled by the collective action of the Coulomb interaction of the electron-hole pair, electron-phonon coupling, and the geminate recombination of the charge carriers. This approach should help us understand the performance of organic solar cells and optimize their efficiency.Low energy vibrations in the excited state have been hypothesized to play an important role in quickly and efficiently generating free charges in bulk heterojunctions of some conjugated polymer systems. While time-resolved vibrational spectroscopies seemingly are well poised to address the relationship between kinetics and vibrational motions after initial photoexcitation, uncertainty in the measurement arises due to overlapping signals and difficulties in assigning observed oscillatory signals to the molecular response. Here, we demonstrate a high sensitivity strategy to distinguish between signal oscillations originating from lab noise and those molecular in origin in order to isolate the low energy excited-state vibrations in the model conjugated copolymer PCDTBT. Furthermore, to distinguish modes that may be implicated in different kinetic pathways, coherent signal oscillations extracted from 2-dimensional electronic spectroscopy (2DES) are compared for the polymer in two solvents with different polarities resulting in different kinetics. We observe that the change in solvent affects dynamics on the >2 ps scale but not on the time scale required for free charge generation in heterojunctions (∼200 fs time scale). By the same token, the excited state vibrational modes that appear and disappear based on solvent polarity may also be associated with the slower kinetic process. The observation of low energy vibrational motions coupled to the excited state manifold that persists through the solvent change and thus can be associated with the fast kinetic process supports the hypothesis that direct polaron formation, rather than exciton formation and diffusion followed by interfacial charge separation, is a more likely route toward free charges in organic heterostructures.This paper presents data for the physical aging of the density of squalane upon both non-linear and nearly linear temperature jumps from states of thermal equilibrium. Invoking the single-parameter-aging scenario [Hecksher et al., J. Chem. Phys. 142, 241103 (2015); Proc. Natl. Acad. Sci. U. S. A. 116, 16736-16741 (2019)], the linear-response aging relaxation function is extracted from the data. Based on this, it is shown that the relaxation toward equilibrium follows a simple exponential function at long times; a stretched-exponential function provides a poor fit. This demonstrates the existence of a terminal relaxation rate for the physical aging of squalane, corresponding to an effective long-time cutoff in the spectrum of structural relaxation times.We theoretically propose a spectroscopic method for measuring optically forbidden states using entangled two-photon absorption (TPA). As a model system, we consider a diatomic molecular system consisting of three adiabatic potentials, namely, ground, intermediate, and excited states, where the intermediate state cannot be directly excited from the ground state. In our method, we pump the excited state using entangled TPA and indirectly measure the optically forbidden intermediate state through the photon emission from the excited state to the intermediate state. The condition required for this method is only that the transition rate between the excited and intermediate states is sufficiently high. Using our proposed method, we show that the optically forbidden state can be detected with a high degree of accuracy when highly efficient and selective TPA is realized.