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Articles 1 - 15 of 15

Full-Text Articles in Semiconductor and Optical Materials

Bulk Heterojunction Photodiode: To Detect The Whole Visible Spectrum, Shahino Mah Abdullah Feb 2013

Bulk Heterojunction Photodiode: To Detect The Whole Visible Spectrum, Shahino Mah Abdullah

Shahino Mah Abdullah

In this paper, we report an organic bulk heterojunction photo-sensor that has been fabricated by using a composite of a polymer material poly(3-hexylthiophene-2,5-diyl) (P3HT) and a dye material vanadyl-phthalocyanine (VOPcPhO). The UV–Vis spectrum shows that this composite exhibits a broad absorption over the whole visible range. The photoluminescence (PL) spectra of P3HT and VOPcPhO blend have been studied to optimize the ratio of P3HT and VOPcPhO. The photo-sensitivity has been investigated under different applied voltages in reverse direction. The photoconductivity sensitivity value has been calculated as 5.65 × 102 Sm/W. The photo-responsivity of the sensor has been investigated under 100 …


Organic Semiconductors: Applications In Solar Photovoltaic And Sensor Devices, Shahino Mah Abdullah Jan 2013

Organic Semiconductors: Applications In Solar Photovoltaic And Sensor Devices, Shahino Mah Abdullah

Shahino Mah Abdullah

Organic semiconductor-based solar photovoltaic cells and sensors are scalable, printable, solution processable, bendable and light-weight. Furthermore, organic semiconductors require low energy fabrication process, hence can be fabricated at low cost as light-weight solar cells and sensors, coupled with the ease of processing, as well as compatibility, with flexible substrates. Organic semiconductors have been identified as a fascinating class of novel semiconductors that have the electrical and optical properties of metals and semiconductors. The continuous demand to improve the properties of organic semiconductors raises the quest for a deep understanding of fundamental issues and relevant electronic processes. Organic semiconductor thin film …


Microfabricated Nanotopological Surfaces For Study Of Adhesion-Dependent Cell Mechanosensitivity, Weiqiang Chen, Yubing Sun, Jianping Fu Jan 2013

Microfabricated Nanotopological Surfaces For Study Of Adhesion-Dependent Cell Mechanosensitivity, Weiqiang Chen, Yubing Sun, Jianping Fu

Weiqiang Chen

Cells exhibit high sensitivity and diverse responses to the intrinsic nanotopography of the extracellular matrix through their nanoscale cellular sensing machinery. A simple microfabrication method for precise control and spatial patterning of the local nanoroughness on glass surfaces by using photolithography and reactive ion etching is reported. It is demonstrated that local nanoroughness as a biophysical cue could regulate a diverse array of NIH/3T3 fi broblast behaviors, including cell morphology, adhesion, proliferation, migration, and cytoskeleton contractility. The capability to control and further predict cellular responses to nanoroughness might suggest novel methods for developing biomaterials mimicking nanotopographic structures in vivo for …


The Impact Of Controlled Solvent Exposure On The Morphology, Structure And Function Of Bulk Heterojunction Solar Cells, Raghavendra R. Hegde Dr Dec 2012

The Impact Of Controlled Solvent Exposure On The Morphology, Structure And Function Of Bulk Heterojunction Solar Cells, Raghavendra R. Hegde Dr

Raghavendra R Hegde Dr

Films of poly(3-hexyl thiophene) (P3HT):[6,6]-phenyl C61-butyric acid methyl ester (PCBM) were controllably exposed to CS2 vapor in a column with a linear solvent vapor pressure gradient. Changes in the morphology of the P3HT:PCBM thin film were monitored and correlated to the ability of this thin film to act as the active layer in an organic solar cell. The results show that the crystallinity and crystal size of the P3HT increase initially with solvent vapor pressure and annealing time, but longer exposure to solvent decreases P3HT crystallinity and photovoltaic efficiency. Neutron reflectivity indicates that the PCBM segregates to the Si substrate …


The Miscibility And Depth Profile Of Pcbm In P3ht: Thermodynamic Information To Improve Organic Photovoltaics, Raghavendra R. Hegde Dr Apr 2012

The Miscibility And Depth Profile Of Pcbm In P3ht: Thermodynamic Information To Improve Organic Photovoltaics, Raghavendra R. Hegde Dr

Raghavendra R Hegde Dr

Recent work has shown that poly(3-hexylthiophene) (P3HT) and the surface-functionalized fullerene 1-(3-methyloxycarbonyl)propyl(1-phenyl[6,6])C(61) (PCBM) are much more miscible than originally thought, and the evidence of this miscibility requires a return to understanding the optimal morphology and structure of organic photovoltaic active layers. This manuscript describes the results of experiments that were designed to provide quantitative thermodynamic information on the miscibility, interdiffusion, and depth profile of P3HT : PCBM thin films that are formed by thermally annealing initial bilayers. It is found that the resultant thin films consist of a 'bulk' layer that is not influenced by the air or substrate surface. …


Nanotopography Influences Adhesion, Spreading, And Self-Renewal Of Human Embryonic Stem Cells, Weiqiang Chen, Luis G. Villa-Diaz, Yubing Sun, Shinuo Weng, Jin Koo Kim, Raymond H. W. Lam, Lin Han, Rong Fan, Paul H. Krebsbach, Jianping Fu Apr 2012

Nanotopography Influences Adhesion, Spreading, And Self-Renewal Of Human Embryonic Stem Cells, Weiqiang Chen, Luis G. Villa-Diaz, Yubing Sun, Shinuo Weng, Jin Koo Kim, Raymond H. W. Lam, Lin Han, Rong Fan, Paul H. Krebsbach, Jianping Fu

Weiqiang Chen

Human embryonic stem cells (hESCs) have great potentials for future cell-based therapeutics. However, their mechanosensitivity to biophysical signals from the cellular microenvironment is not well characterized. Here we introduced an effective microfabrication strategy for accurate control and patterning of nanoroughness on glass surfaces. Our results demonstrated that nanotopography could provide a potent regulatory signal over different hESC behaviors, including cell morphology, adhesion, proliferation, clonal expansion, and self-renewal. Our results indicated that topological sensing of hESCs might include feedback regulation involving mechanosensory integrin-mediated cell matrix adhesion, myosin II, and E-cadherin. Our results also demonstrated that cellular responses to nanotopography were cell-type …


Pigments For Improving Plant Health In Organic Systems, Gregory Keith Bartley Jr. Apr 2011

Pigments For Improving Plant Health In Organic Systems, Gregory Keith Bartley Jr.

Gregory Keith Bartley Jr.

Photosynthesis, arguably the most important biological process on earth, solely relies on the ability of pigments to capture, utilize, and convert the sun‟s energy to form life. The adequate conversion of light into harvestable food, fuel, and fiber regulates rates of population and economic growth. In order to meet the expanding needs of humanity with the earth‟s potential for agricultural production, new sustainable techniques for increased photosynthetic efficiency in plants must be implemented. The earth's pattern of light exposure is extremely dynamic, exhibiting constant changes in quantity and quality throughout time and space. For photosynthetic organisms, this meant evolving various …


Fabrication And Characterization Of Graphene Hydrogel Via Hydrothermal Approach As A Scaffold For Preliminary Study Of Cell Growth, Huang Nay Ming Jan 2011

Fabrication And Characterization Of Graphene Hydrogel Via Hydrothermal Approach As A Scaffold For Preliminary Study Of Cell Growth, Huang Nay Ming

Huang Nay Ming

Three-dimensional assembly of graphene hydrogel is rapidly attracting the interest of researchers because of its wide range of applications in energy storage, electronics, electrochemistry, and waste water treatment. Information on the use of graphene hydrogel for biological purposes is lacking, so we conducted a preliminary study to determine the suitability of graphene hydrogel as a substrate for cell growth, which could potentially be used as building blocks for biomolecules and tissue engineering applications. A three-dimensional structure of graphene hydrogel was prepared via a simple hydrothermal method using two-dimensional large-area graphene oxide nanosheets as a precursor. The concentration and lateral size …


Regulating Factors In Anthocyanin Biosynthesis, Gregory Keith Bartley Jr. Oct 2010

Regulating Factors In Anthocyanin Biosynthesis, Gregory Keith Bartley Jr.

Gregory Keith Bartley Jr.

No abstract provided.


Ultrathin, Ultrasmooth And Low-Loss Silver Films Via Wetting And Annealing, Weiqiang Chen, Kuo-Ping Chen, Mark Daniel Thoreson, Alexander Kildishev, Vladimir M. Shalaev Jan 2010

Ultrathin, Ultrasmooth And Low-Loss Silver Films Via Wetting And Annealing, Weiqiang Chen, Kuo-Ping Chen, Mark Daniel Thoreson, Alexander Kildishev, Vladimir M. Shalaev

Weiqiang Chen

We have demonstrated that a thermal annealing treatment can reduce the optical losses in ultrathin, ultrasmooth, silver films deposited on a Ge wetting layer to values as low as the bulk material value and at the same time maintain an ultrasmooth surface. The annealing effect is sensitive to the annealing temperature and time, both of which should be carefully controlled. This annealing treatment is also effective for Ag–SiO2 multilayer composite films.


Toward Superlensing With Metal-Dielectric Composites And Multilayers, Rasmus Bundgaard Nielsen, Mark Thoreson, Weiqiang Chen, Anders Kristensen, Jørn Hvam, Vladimir M. Shalaev, Alexandra Boltasseva Jan 2010

Toward Superlensing With Metal-Dielectric Composites And Multilayers, Rasmus Bundgaard Nielsen, Mark Thoreson, Weiqiang Chen, Anders Kristensen, Jørn Hvam, Vladimir M. Shalaev, Alexandra Boltasseva

Weiqiang Chen

We report on the fabrication of two types of adjustable, near-field superlens designs: metal–dielectric composites and metal–dielectric multilayer films. We fabricated a variety of films with different materials, thicknesses and compositions. These samples were characterized physically and optically to determine their film composition, quality, and optical responses. Our results on metal–dielectric composites indicate that although the real part of the effective permittivity generally follows effective medium theory predictions, the imaginary part does not and substantially higher losses are observed. Going forward, it appears that multilayer metal–dielectric designs are more suitable for sub-diffraction imaging applications because they could provide both tunability …


Fabrication And Optical Characterizations Of Smooth Silver-Silica Nanocomposite Films, Weiqiang Chen, Mark Daniel Thoreson, Alexander V. Kildishev, Vladimir Shalaev Jan 2010

Fabrication And Optical Characterizations Of Smooth Silver-Silica Nanocomposite Films, Weiqiang Chen, Mark Daniel Thoreson, Alexander V. Kildishev, Vladimir Shalaev

Weiqiang Chen

We have studied the surface-smoothing effect of an ultrathin germanium (Ge) layer on silver (Ag)-silica (SiO2) nanocomposite films for superlensing applications. Our experimental results indicate that inserting a thin Ge layer below the silver-silica composite films can reduce the final surface root-mean-squared (RMS) roughness to under 1 nm. Additionally, the metal nanostructure plays a role in both the smoothing effect and the optical properties of the nanocomposite films. Our experimental results show that the Bruggeman effective medium theory (EMT) is not sufficiently accurate to describe some properties of our nanocomposite films. In addition to the constituent materials and their filling …


Simple Room-Temperature Preparation Of High-Yield Large-Area Graphene Oxide, Huang Nay Ming Jan 2010

Simple Room-Temperature Preparation Of High-Yield Large-Area Graphene Oxide, Huang Nay Ming

Huang Nay Ming

Graphene has attracted much attention from researchers due to its interesting mechanical, electrochemical, and electronic properties. It has many potential applications such as polymer filler, sensor, energy conversion, and energy storage devices. Graphene-based nanocomposites are under an intense spotlight amongst researchers. A large amount of graphene is required for preparation of such samples. Lately, graphene-based materials have been the target for fundamental life science investigations. Despite graphene being a much sought-after raw material, the drawbacks in the preparation of graphene are that it is a challenge amongst researchers to produce this material in a scalable quantity and that there is …


Preparation Of Wo3 Nanoparticles Using Cetyl Trimethyl Ammonium Bromide Supermolecular Template, Nilofar Asim, S. Radiman, M.A. Bin Yarmo Jan 2009

Preparation Of Wo3 Nanoparticles Using Cetyl Trimethyl Ammonium Bromide Supermolecular Template, Nilofar Asim, S. Radiman, M.A. Bin Yarmo

Nilofar Asim

WO3 is one of the most interested metal oxides because of its application as catalysts, sensors, electrochromic devices, ceramic, solar cell, pigments and so on. More investigation is needed to find the good and low cost method for preparation of WO3 nanoparticles with uniform morphology and narrow distribution using a surfactant mediated method. Approach: In this study, the synthesis of WO3 nanoparticles was accomplished using a cationic surfactant (cetyl trimethyl ammonium bromide) as the organic supermolecular template and WCl6 and NH4 OH as the inorganic precursor and counter ion source, respectively. The effects of reaction temperature and surfactant concentration in …


Dielectric Relaxation Behaviour Of Glycine In Acqueous Solution Medium In The Microwave Frequency Region, Ajaya Kumar Kavala Apr 2008

Dielectric Relaxation Behaviour Of Glycine In Acqueous Solution Medium In The Microwave Frequency Region, Ajaya Kumar Kavala

Mr Ajaya Kumar Kavala

No abstract provided.