Zongling Ding

Nanohybrids of RGO nanosheets and 2-dimensional porous Co3O4 nanoflakes working as highly efficient counter electrodes for dye-sensitized solar cells

In this paper, nanohybrids (Co3O4@RGO) of 2-dimensional (2D) porous Co3O4 nanoflakes anchored on reduced graphene oxide nanosheets have been fabricated by a facile hydrothermal reduction process. The introduction of RGO nanosheets substantially improved the performance of 2D porous Co3O4 nanoflakes as counter electrodes (CEs) in dye-sensitized solar cells (DSSCs). The DSSCs with this Co3O4@RGO CE displayed a power conversion efficiency of 5.79%, which is greatly higher than that of pure Co3O4 CE (1.2%) or pure RGO CE (2.2%), and even comparable to that of the conventional Pt CE (6.16%). At the same time, with the addition of RGO, the electrochemical stability of Co3O4@RGO nanohybrids is also greatly improved. This work gives an idea on how to take the advantage and to avoid the disadvantage of 2D nanoflakes by introducing RGO nanosheets. Meanwhile, the experimental result demonstrates that Co3O4@RGO nanohybrids are advanced CEs in DSSCs and may open a window for potential applications in any other related fields.

Effect of edge passivation on electronic and transport properties of carbon nanotube-based molecular devices

The electronic and transport properties of the molecular devices of finite-sized carbon nanotubes (CNTs) have been studied by combining the density-functional theory and Greens function method. Different edge-passivated types are considered for the edge carbon atoms at the two open ends. It is shown that the electronic and transport properties of the finite-size CNTs are sensitive to the passivation types of edge atoms. An asymmetry passivation method which can tune the spin density of states of CNTs has been proposed. The electron transmission can be manipulated by modifying the CNTs, such as edge passivation types and concentrations.

The finite‐size effect on the transport properties in edge‐modified graphene nanoribbon‐based molecular devices

The size‐dependence on the electronic and transport properties of the molecular devices of the edge‐modified graphene nanoribbon (GNR) slices is investigated using density‐functional theory and Greens function theory. Two edge‐modifying functional group pairs are considered. Energy gap is found in all the GNR slices. The gap shows an exponential decrease with increasing the slice size of two vertical orientations in the two edge terminated cases, respectively. The tunneling probability and the number of conducting channel decreases with increasing the GNR‐slices size in the junctions. The results indicate that the acceptor‐donor pair edge modulation can improve the quantum conductance and decrease the finite‐size effect on the transmission capability of the GNR slice‐based molecular devices.

Effect of edge modification on transport properties of finite-sized, graphene nanoribbon-based molecular devices

The transport mechanisms of several finite-sized, graphene nanoribbon-based junctions have been computationally investigated using density functional theory and Greens functional method. Acceptor-type and donor-type functional groups were introduced, serving as electrode connection and edge modification, respectively. The introduction of acceptor and donor groups improve the electron transmission probabilities by several orders of magnitude. The electronic coupling mode, carrier concentration and distribution, and molecular orbital can be manipulated by the modification groups.

Transport properties of graphene nanoribbon-based molecular devices.

The electronic and transport properties of an edge‐modified prototype graphene nanoribbon (GNR) slice are investigated using density functional theory and Greens function theory. Two decorating functional group pairs are considered, such as hydrogen‐hydrogen and NH2‐NO2 with NO2 and NH2 serving as a donor and an acceptor, respectively. The molecular junctions consist of carbon‐based GNR slices sandwiched between Au electrodes. Nonlinear I‐V curves and quantum conductance have been found in all the junctions. With increasing the source‐drain bias, the enhancement of conductance is quantized. Several key factors determining the transport properties such as the electron transmission probabilities, the density of states, and the component of Frontier molecular orbitals have been discussed in detail. It has been shown that the transport properties are sensitive to the edge type of carbon atoms. We have also found that the accepter‐donor functional pairs can cause orders of magnitude changes of the conductance in the junctions.

The inelastic electron tunneling spectroscopy of edge-modified graphene nanoribbon-based molecular devices

The inelastic electron tunneling spectroscopy (IETS) of four edge-modified finite-size grapheme nanoribbon (GNR)-based molecular devices has been studied by using the density functional theory and Greens function method. The effects of atomic structures and connection types on inelastic transport properties of the junctions have been studied. The IETS is sensitive to the electrode connection types and modification types. Comparing with the pure hydrogen edge passivation systems, we conclude that the IETS for the lower energy region increases obviously when using donor–acceptor functional groups as the edge modification types of the central scattering area. When using donor–acceptor as the electrode connection groups, the intensity of IETS increases several orders of magnitude than that of the pure ones. The effects of temperature on the inelastic electron tunneling spectroscopy also have been discussed. The IETS curves show significant fine structures at lower temperatures. With the increasing of temperature, peak broadening covers many fine structures of the IETS curves. The changes of IETS in the low-frequency region are caused by the introduction of the donor–acceptor groups and the population distribution of thermal particles. The effect of Fermi distribution on the tunneling current is persistent.

The inelastic electron tunneling spectroscopy of curved finite-sized graphene nanoribbon based molecular devices

The inelastic electron scattering properties of the molecular devices of curved finite-sized graphene nanoribbon (GNR) slices have been studied by combining the density functional theory and Greens function method. Based on the extended molecular models, the inelastic electron tunneling spectroscopy, inelastic quantum conductance and inelastic current have been calculated systematically. The temperature dependences of the inelastic electron tunneling spectroscopy (IETS) and inelastic current have been discussed. Results show that the contributions of the inelastic conductance increase obviously and become comparable to the elastic conductance for curved GNR slices based junctions. The electron inelastic scattering of the curved GNR-based junctions are orders of magnitude stronger than that of the plane ones. The obvious dependences of the elastic and inelastic current of the finite-sized GNR slices make it have probable applications in molecular microprobes.

Effects of electrode contact on geometry structure and transport properties of the graphene-based nanomolecule Devices

A series of graphene-based nanomolecule devices are constructed by connecting the graphene nanodot to two Au electrodes through different bond length between the electrodes and molecules. The geometric structure and electronic properties are studied by using density functional theory calculations. Basing on the optimized structure, we calculate the quantum conductance of the system by using the Greens function method. We find that the geometry structures of the molecule and the transport properties are sensitive to the bond length dAu-H. The plane of carbon atoms increasingly bends with the decrease of the dAu-H. The ISD-VSD curves have the same threshold value under different dAu-H.