Graphite Oxide Thin Films Research Articles

Effect of thickness on nonlinear absorption properties of graphite oxide thin films

We report the thickness dependent structural, linear and nonlinear optical properties of graphite oxide (GO) thin films synthesized by spin coating method. We observed that the structural, linear and nonlinear optical properties can be tuned by the film thickness in GO. The nonlinear absorption studies by open aperture z scan technique exhibited a saturable absorption. The nonlinear absorption coefficient and saturation intensity varies with film thickness which is attributed to increased localized defect states in the energy band gap. Our results emphasize relatively large thickness dependent optical nonlinearity of GO thin films and its potential for optical pulse generation, exploring the way to GO based nonlinear applications in Q switched mode locking laser systems. All the coated GO films were characterized by X-Ray diffraction method (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, UV-Vis absorption spectroscopy (UV-Vis), Photoluminescence (PL) and Scanning electron microscope (SEM) measurements.

Preparation of pillared carbon thin films from the reduction of silylated graphite oxide by UV light irradiation and their size selective electrical response to various molecules

Silylated graphite oxide thin films were reduced by UV light irradiation using a super high pressure Hg lamp at 95°C. The reduction of silylated graphite oxide was completed within 24h and a new pillared carbon with an interlayer spacing of 0.81nm was obtained. Pillared carbons with larger interlayer spacings of about 1.13nm were also obtained from graphite oxide silylated with octyltrichlorosilane and then with 3-aminopropyltriethoxysilane for 1.5–6h, when they were reduced by UV light irradiation and heating at 200°C under vacuum. Selective electrical response during exposure to gaseous vinylene carbonate, acetonitrile, ozone and hydrogen molecules has been achieved by changing the pillar density in the resulting pillared carbon films.

Highly responsive hydrogen gas sensing by partially reduced graphite oxide thin films at room temperature

Novel chemo-resistive gas sensors based on reduced graphite oxide (rGO) thin films have been fabricated and evaluated for hydrogen detection. The rGO materials were thermally treated at various conditions and analyzed using X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy techniques to investigate the change of functional groups. The semiconductor type of the rGOs treated at different conditions were checked by flowing hydrogen gas at 20cm3/min (sccm) under 10Torr partial pressure. The rGOs treated at 70°C in atmosphere (rGO070a), 200°C in a vacuum (rGO200v), and 500°C in a vacuum (rGO500v) exhibited n-type, ambipolar, and p-type behavior, respectively. The rGO500v was adopted as active sensing element without any rare metal decoration, and its sensing response to hydrogen was studied by using air as carrier gas. The rGO500v exhibited good sensitivity (∼4.5%), response time (∼20s), and recovery time (∼10s) to 160ppm hydrogen gas at room temperature.

Aligned carbon nanotube, graphene and graphite oxide thin films via substrate-directed rapid interfacial deposition

A procedure for depositing thin films of carbon nanostructures is described that overcomes the limitations typically associated with solution based methods. Transparent and conductively continuous carbon coatings can be grown on virtually any type of substrate within seconds. Interfacial surface tension gradients result in directional fluid flow and film spreading at the water/oil interface. Transparent films of carbon nanostructures are produced including aligned ropes of single-walled carbon nanotubes and assemblies of single sheets of chemically converted graphene and graphite oxide. Process scale-up, layer-by-layer deposition, and a simple method for coating non-activated hydrophobic surfaces are demonstrated.

Preparation and Evaluation of Graphite Oxide Reduced at 220 °C

The reduction of graphite oxide (GO) thin films was evaluated at 220 °C using a combination of infrared (FTIR) and X-ray photoemission spectroscopies (XPS). The results were correlated with electrical resistance measurements. The chemical composition of GO was C8(OH)3O0.8 and reduced to C8(OH)0.5O0.3 after nearly 24 h of low-temperature processing, defined as 220 °C. The sheet resistance of dropcast GO thin films processed at 220 °C in air was 8 kΩ sq−1, similar to GO reduced at >800 °C in an inert atmosphere.

Capacitance-voltage and current-voltage characteristics of graphite oxide thin films patterned by ultraviolet photolithography

Electrical characteristics of graphite oxide (GO) thin films deposited on a p-type silicon substrate were investigated to explore its potential application as a dielectric material in organic field effect transistors. Channel current in the GO films exhibited linear response with the applied bias in the positive voltage regime and increased exponentially for negative source-drain bias. This rectifying behavior arises due to the Coulombic interaction between the electrons emitted from the metal contact and the space charge region in the GO film. A clockwise hysteresis loop was observed in the capacitance-voltage characteristics due to the presence of traps at the interface.

Transparent and flexible polymerized graphite oxide thin film with frequency-dependent dielectric constant

Here we report on the preparation of transparent and flexible polymerized graphite oxide, which is composed of carbons with sp3-hybridized orbitals and a nonplanar ring structure, and which demonstrates dispersion in its dielectric constant at room temperature. This frequency dependence renders the material suitable for creating miniaturized, flexible, and transparent variable capacitors, allowing for smaller and simpler integrated electronic devices. We discuss this polarizability in terms of space charge effects.

Preparation and Fluorescent Properties of Rhodamine B–hexadecylamine-intercalated Graphite Oxide Thin Film

Abstract Thin film samples of Rhodamine B–hexadecylamine-intercalated graphite oxides were prepared by cast method from chlorofolm solution of Rhodamine B and hexadecylamine-intercalated graphite oxide. The emission maxima red-shifted with increasing Rhodamine B content in the sample. The tilted alkylamine may prevent the formation of nonfluorescent Rhodamine B H-dimer.