Photoinduced
generation of excitons and their nonradiative relaxation
dynamics are simulated at the interface of (10, 0) carbon nanotubes
(CNT) and a PbSe nanowire (NW). Possible pathways of photoinduced
excitations are explored by combining a reduced density matrix approach
in the basis of Kohn–Sham orbitals and on-the-fly nonadiabatic
couplings. A range of neutral photoexcitations localized on the CNT
is followed by formation of charge transfer (CT) states involving
PbSe NW. Depending on the wavelength of the incident light, the initial
photoexcitation can be followed by two directions of charge transfer:
either (PbSe)+(CNT)− or (PbSe)−(CNT)+. Excitation of a hot electron results in the CT
state with an electron located at the NW and the hole at the CNT with
shorter lifetime, while excitation of a hot hole leads to the CT state
with an electron at the CNT and the hole at the PbSe having much longer
lifetime. Observed ability to control the direction and the lifetime
of the CT state makes the CNT/PbSe NW composites promising for photovoltaic
applications.
Solar energy conversion into chemical form is possible using artificial means. One example of a highly-efficient fuel is solar energy used to split water into oxygen and hydrogen. Efficient photocatalytic water-splitting remains an open challenge for researchers across the globe. Despite significant progress, several aspects of the reaction, including the charge transfer mechanism, are not fully clear. Density functional theory combined with density matrix equations of motion were used to identify and characterize the charge transfer mechanism involved in the dissociation of water. A simulated porous silica substrate, using periodic boundary conditions, with Ti 4+ ions embedded on the inner pore wall was found to contain electron and hole trap states that could facilitate a chemical reaction. A trap state was located within the silica substrate that lengthened relaxation time, which may favor a chemical reaction. A chemical reaction would have to occur within the window of photoexcitation; therefore, the existence of a trapping state may encourage a chemical reaction. This provides evidence that the silica substrate plays an integral part in the electron/hole dynamics of the system, leading to the conclusion that both components (photoactive materials and support) of heterogeneous catalytic systems are important in optimization of catalytic efficiency.
Metal-organic supercontainer (MOSC) molecules are ideal candidates for gas storage applications due to their construction with customizable ligands and tunable cavity and window sizes, which are found to be elastic in nature. Force field molecular dynamics (MD) are used to evaluate the utilization of MOSCs as nanoporous structures for gas storage. A MOSC, with nitrogen gas molecules filling the cavity, progresses through MD and releases gas molecules by applying temperature to the MOSC. It is the MOSC's elasticity which is responsible for the desorption of guests at elevated temperatures. Data obtained from MD serves as a guide for the derivation of analytical equations that can be used to describe and explain the mechanism of gas desorption from within the cavity. Mathematical modeling of gas desorption from the center cavity can provide a method of predicting MOSC behavior for a broader range of pressures and temperatures, which is challenging for direct atomistic modeling. The utilization of MD can provide data for a wide variety of properties and processes in various materials under different conditions for a broad range of technology-related applications.View Article Online breaching the cavity barrier. At t ¼ 200 fs, the gas molecule has completely left the cavity. Based on these data, s ¼ 105 fs, so that desorption rate reads R ¼ 1/0.105 ps ¼ 9.52 ps À1 .This journal is
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.