Search

Titanium dioxide, also known as titania is an important semiconducting oxide that has gained prominence in recent years for applications in photoelectrochemical/dye-sensitized solar cells. TiO 2 is at present preferred over oxides such as ZnO or SnO 2 for applications in dye-sensitized solar cell, because of its mesoporous structure, which offers high surface area for efficient dye loading. It is also important that the band gap of the metal oxide can be adjusted for efficient electron injection from most available commercial dyes since the generation of voltage in the device depends mainly on the band edge matching. Herein, TiO 2 thin films were deposited in a polyvinyl pyrolidon medium by the chemical bath deposition technique at 65 °C. The inclusion of lead ions during the film formation process led to structural modification of the thin films of titania – anatase (TiO 2 ) and subsequent formation of structurally disordered Pb-doped TiO 2 thin films. The resulting films retain the high band gap energy of crystalline anatase and substantially tuned in the range, 2.85–3.26 ± 0.05 eV by the Pb 2+ inclusion.

A simplified sol-gel method that can be scaled up for large-scale production was adopted for the preparation of manganese oxide nanocrystals. Prepared Mn2O3 exhibited micron-sized particles with a nanoporous structure. In the present study, a simple and low-cost strategy has been employed to fabricate nanoporous Mn2O3 with an increased surface area for an electrode/electrolyte interface that improved the conduction of Mn2O3 material. The crystal phase and morphology of the prepared material was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The prepared electrode materials were deposited on a nickel foam substrate to investigate the electrochemical properties. The galvanostatic charge/discharge (GCD), cyclic voltammetry (CV), and complex impedance studies confirmed excellent specific capacitance and capacitive behavior of the prepared material. The synthesized Mn2O3/graphene composites exhibited an excellent specific capacitance of 391 F/g at a scan rate of 5 mV/S. Moreover, a specific capacitance of 369 F/g was recorded at a current density of 0.5 A/g using the galvanostatic charge/discharge test. The high porosity of the materials provided a better electrolyte-electrode interface with a larger specific area, thus suggesting its suitability for energy storage applications.

We measured and modeled the electrical, optical and thermal properties of transparent and conducting thin films based on graphene and graphitic platelets. Thermal conductivity of our films decreases with increasing electrical conductivity. Our experiments indicate that, for sufficiently large platelets, the influence factor in controlling the thermal conductivity is represented by the junctions between neighboring graphene platelets. The thickness of such junctions is determined by the average number of graphene layers (N) forming each platelet. The fact that both the thermal and electrical properties depend on N allows us to establish a model that leads to a theoretical relationship between the thermal and electrical conductivity in our samples, which is general enough to be applied to a large class of graphene-based thin films.

Addition of few-layer graphene and graphite to poly(3,4-ethylenedioxy-thiophene):poly (styrenesulfonate) (PEDOT:PSS) is of great technological relevance for a host of applications, including electrodes for organic solar cells and the development of solution-processable conducting inks with improved thermal properties. In this paper we investigate the optical, electrical, morphological and thermal properties of nanocomposites formed by the incorporation of PEDOT:PSS into carbon-based thin films in which the thermal properties approach those of graphene. The properties of these nanocomposite thin films can be understood in the framework of a two-layer model, with a bottom layer formed by an effective medium of PEDOT:PSS and graphene-like flakes and a top layer of pure PEDOT:PSS. Strong dependence on the film thickness and morphology was found for all of the thermophysical properties we studied. We show a strong improvement in thermal conductivity due to the addition of graphene-like material to PEDOT:PSS.

In this paper we review some of the relationships existing between the optical properties, electrical conductivity, and thermal conductivity in graphene based transparent and conducting thin films. We provide a set of tools that are useful to identify the optimal trade-off between transmittance and electrical conductivity in these films. In addition we present a set of thermal conductivity measurements of graphene thin films and relate them to the electrical properties in order to build a comprehensive picture of the electrical, thermal, and optical properties of graphene based thin films (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Ribonucleic acid (RNA) is proposed as a nonionic surfactant for the efficient exfoliation of graphite in thin flakes of few-layer graphene and the subsequent preparation of transparent and conducting thin films. Parameters such as the type of RNA used and the size of starting graphite flakes are demonstrated to be essential for obtaining RNA-graphene thin films of good quality. A model explaining the exfoliation of graphene by RNA in water is suggested. A number of post- and predeposition treatments (including thermal annealing, functionalization of the films, and the preoxidation of graphite) are critical to improve the performance of graphene-RNA nanocomposites as transparent conductors. The study establishes an ideal link between RNA and graphene, the fundamental building blocks for nanobiology and carbon-based nanotechnology.

We demonstrate a facile and cost effective method to obtain gold nanoparticles on graphene by dispersing Au144 molecular nanoclusters by spin coating them in thin layers on graphene-based films and subsequent annealing in a controlled atmosphere. The graphene-based thin films used for these experiments are prepared by solvent-assisted exfoliation of graphite in water in the presence of ribonucleic acid as a surfactant and by subsequent vacuum filtration of the resulting graphene-containing suspensions. Not only is this method easily reproducible, but it leads to gold nanoparticles that are not dependent in size on the number of graphene layers beneath them. This is a distinct advantage over other methods. Plasmonic effects have been detected in our gold nanoparticle-decorated graphene layers, indicating that these thin films may be useful in applications such as plasmonic solar cells and optical memory devices.