Ecole dIngenieurs du CESI EIA

La Couronne, France

Ecole dIngenieurs du CESI EIA

La Couronne, France
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Dervishi E.,University of Arkansas at Little Rock | Li Z.,University of Arkansas at Little Rock | Shyaka J.,University of Arkansas at Little Rock | Watanabe F.,University of Arkansas at Little Rock | And 6 more authors.
Chemical Physics Letters | Year: 2011

Large area and few to multi-layer graphene sheets were synthesized on a bimetallic catalyst system via radio-frequency chemical vapor deposition (RF-CVD). Synthesis conditions were varied and their effects on the morphological properties of the graphene structures were observed. As the flow rate of the hydrocarbon was varied, the diameter of the graphene structures increased from a few hundred nanometers to a few micrometers. The number of graphene layers was also found to be dependent on the hydrocarbon concentration. This method shows great potential for the synthesis of large area few-layer graphene sheets, which can be used in various electronic applications.


Dervishi E.,University of Arkansas at Little Rock | Li Z.,University of Arkansas at Little Rock | Shyaka J.,University of Arkansas at Little Rock | Watanabe F.,University of Arkansas at Little Rock | And 5 more authors.
Nanotechnology 2010: Advanced Materials, CNTs, Particles, Films and Composites - Technical Proceedings of the 2010 NSTI Nanotechnology Conference and Expo, NSTI-Nanotech 2010 | Year: 2010

Large area graphene sheets (several micro meters) were synthesized on a bimetallic catalyst system utilizing acetylene as the hydrocarbon source. After a simple purification, graphene sheets were thoroughly characterized by several microscopy techniques. It was observed that as the hydrocarbon rate increased from 4.5 to 8 ml/min, the diameter of the graphene sheets increased from a few hundred nanometers to a few micrometers. Therefore, by varying the hydrocarbon flow rate, we were able to control the size and the layer number of the CVD grown graphene sheets. This is a substrate free synthesis which makes it very attractive and flexible for a scaled up graphene production.


Bourdo S.E.,University of Arkansas at Little Rock | Saini V.,University of Arkansas at Little Rock | Piron J.,Ecole dIngenieurs du CESI EIA | Al-Brahim I.,Ecole dIngenieurs du CESI EIA | And 5 more authors.
ACS Applied Materials and Interfaces | Year: 2012

In this paper, we explore the use of two organic materials that have been touted for use as photovoltaic (PV) materials: inherently conducting polymers (ICPs) and carbon nanotubes (CNTs). Due to these materials' attractive features, such as environmental stability and tunable electrical properties, our focus here is to evaluate the use of polyaniline (PANI) and single wall carbon nanotube (SWNT) films in heterojunction diode devices. The devices are characterized by electron microscopy (film morphology), current-voltage characteristics (photovoltaic behavior), and UV/visible/NIR spectroscopy (light absorption). We have found that both PANI and SWNT can be utilized as photovoltaic materials in a simple bilayer configuration with n-type Silicon: n-Si/PANI and n-Si/SWNT. It was our aim to determine how photovoltaic performance was affected utilizing both PANI and SWNT layers in multilayer devices: n-Si/PANI/SWNT and n-Si/SWNT/PANI. The short-circuit current density increased from 4.91 mA/cm 2 (n-Si/PANI) to 12.41 mA/cm 2 (n-Si/PANI/SWNT), while an increase in power conversion efficiency by ∼91% was also observed. In the case of n-Si/SWNT/PANI and its corresponding device control (n-Si/SWNT), the short-circuit current density was decreased by an order of magnitude. The characteristics of the device were affected by the architecture and the findings have been attributed to the more effective transport of holes from the PANI to SWNT and less effective transport of holes from PANI to SWNT in the respective multilayer devices. © 2011 American Chemical Society.


Saini V.,University of Arkansas at Little Rock | Li Z.,University of Arkansas at Little Rock | Mustafa T.,University of Arkansas at Little Rock | Biris A.S.,University of Arkansas at Little Rock | And 5 more authors.
Conference Record - IAS Annual Meeting (IEEE Industry Applications Society) | Year: 2010

In this work we have reported low cost solar cells which can be processed to scalability by depositing direct and uniform films using airbrushing, inkjet printing, or spin-coating techniques. We have synthesized single wall carbon nanotubes (SWNTs) by catalytic Chemical Vapor Deposition (cCVD) method, which were subsequently doped with boron for photovoltaic applications. The carbon nanotubes were characterized by Raman spectroscopy, thermal gravimetric analysis (TGA), transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy (XPS). The solar cell devices were fabricated by depositing a uniform dispersion of b-SWNT films on n-Si creating numerous heterojunctions. These studies are the first in which b-SWNTs have been utilized directly for photo-generation. © 2010 IEEE.


Dervishi E.,University of Arkansas at Little Rock | Li Z.,University of Arkansas at Little Rock | Watanabe F.,University of Arkansas at Little Rock | Shyaka J.,University of Arkansas at Little Rock | And 5 more authors.
Materials Research Society Symposium Proceedings | Year: 2010

This work reports a low-cost method for large scale production of high quality graphene via radio-frequency chemical vapor deposition. High quantities of graphene were successfully synthesized on the Fe-Co/MgO (2.5:2.5:95 wt.%) catalytic system utilizing acetylene as a hydrocarbon source at 1000 °C. The as-produced graphene sheets were purified in a single step by washing with a diluted hydrochloric acid solution under sonication. Next, they were thoroughly characterized by microscopy, spectroscopy, and X-Ray diffraction. Advanced transmission electron microscopy and atomic force microscopy analyses have indicated the formation of 3-5 layered graphene nanosheets. Thorough analyses by Raman spectroscopy were also performed demonstrating the presence of high quality and few-layer graphene samples. This low cost and highly reproducible method may be applied in a straightforward way to produce large quantities of graphene for various advanced applications. © 2010 Materials Research Society.

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