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Barddhamān, India

Jash S.K.,Saldiha College | Gangopadhyay A.,Kalna College | Sarkar A.,Kapastikuri K.M. Vidyapeeth | Gorai D.,Kulti College
Der Pharma Chemica

The chemical investigation of the stem bark of Peltophorum pterocarpum (DC.) belonging to the family Leguminosae/Fabaceae led to the isolation of four phytoconstituents namely Stigmasterol, ß-Sitosterol, Lupeol and Lupenone. The isolated compounds were characterized using various spectroscopic data as well as chemical studies. Out of the four compounds isolated, lupenone has been isolated for the first time from the plant. Source

The observation of large photoresponsivity in a π-conjugated small organic molecule, viz., N,N′-dioctyl-3,4,9,10-perylene tetracarboxylic diimide (PTCDI-C8) and consequently, fabrication of organic photodetector with single layer of PTCDI-C8 is reported. The same device, without any actual gate terminal, can also be used to obtain field-effect transistor (FET) characteristics by exploiting the photoresponse properties of the material. Photo-illumination on the active material which ensured an induced channel by the photo generated charge carriers, resembled as the pseudo gate electrode. The simple lateral structure with gold (Au) as source and drain electrodes and vacuum deposited thin film of PTCDI-C8 as the active layer produced high-performance photodetector and transistor behavior, showing pseudo-output and transfer curves with an on/off ratio of 4 × 102. The two terminal organic devices exhibited photoresponsivity value ca. 50 mA/W, external quantum efficiency ∼40%, reproducible and reversible photo-switching behavior with photo to dark current ratio ca. 200 and a switching time <10 ms. Modulation and tuning of the device's performance were done by controlling the number of photo generated carriers. The multifunctional ability, such as, photosensing, photoswitching, and signal amplification realized in a single unit opens up immense possibilities for integrated device applications in large-scale and low-cost plastic optoelectronic devices. © 2015 Elsevier GmbH. Source

Mukherjee B.,Kalna College | Mukherjee M.,Saroj Mohan Institute of Technology

Fabrication of high-performance organic thin film transistors (OTFTs) with solution processed organic charge transfer complex (TTF-TCNQ) film as bottom contact source-drain electrodes is reported. A novel capillary based method was used to deposit the source-drain electrodes from solution and to create the channel between the electrodes. Both p- and n-type OTFTs have been fabricated with solution deposited organic charge transfer film as contact electrodes. Comparison of the device performances between OTFTs with TTF-TCNQ as source-drain electrodes and those with Au electrodes (both top and bottom contact) indicate that better results have been obtained in organic complex film contacted OTFT. The high mobility, low threshold voltage, and efficient carrier injection in both types of OTFTs implies the potential use of the TTF-TCNQ based complex material as low-cost contact electrodes. The lower work function of the TTF-TCNQ electrode and better contact of the complex film with the organic thin film owing to the organic-organic interface results in efficient charge transfer into the semiconductor yielding high device performance. The present method having organic metal as contact materials promises great potential for the fabrication of all-organics and plastic electronics devices with high throughput and low-cost processing. © 2011 American Chemical Society. Source

Sen S.,Kalna College | Chakravarty S.,Visva Bharati
Korea Australia Rheology Journal

The present study is dealt with the constricted flow characteristics of blood in arteries by making use of an appropriate mathematical model. The constricted artery experiences the generated wall shear stress due to flow disturbances in the presence of constriction. The disturbed flow in the stenosed arterial segment causes malfunction of the cardiovascular system leading to serious health problems in the form of heart attack and stroke. The flowing blood contained in the stenosed artery is considered to be non-Newtonian while the flow is treated to be two-dimensional. The present pursuit also accounts for the motion of the arterial wall and its effect on local fluid mechanics. The flow analysis applies the time-dependent, two-dimensional incompressible nonlinear Navier-Stokes equations for non-Newtonian fluid representing blood. An extensive quantitative analysis presented at the end of the paper based on large scale numerical computations of the quantities of major physiological significance enables one to estimate the constricted flow characteristics in the arterial system under consideration which deviates significantly from that of normal physiological flow conditions. © 2012 The Korean Society of Rheology and Springer. Source

Mukherjee B.,Konkuk University | Mukherjee B.,Kalna College | Sim K.,Konkuk University | Shin T.J.,Pohang Accelerator Laboratory | And 4 more authors.
Journal of Materials Chemistry

High quality, single crystalline, ordered arrays of a π-conjugated organic molecule, N,N′-dioctyl-3,4,9,10-perylene tetracarboxylic diimide (PTCDI-C 8), were grown by solution processing and used to fabricate a low-cost, high-performance organic phototransistor (OPT). The single crystalline nature of the microstructure was investigated using 2D-GIXD measurement. The organic field-effect transistor fabricated using periodic arrays of elongated crystals exhibited a photoresponsivity (P) of ca. 1 A W -1 and a photo to dark current ratio (I on/I off) of 2.5 × 10 3 at V G = 12 V and a maximum P of ca. 7 A W -1 at the high gate bias regime (V G = 50 V) with an optical power of ca. 7.5 mW cm -2. With polymeric gate dielectric, the OPT exhibited very stable n-type characteristics both in the dark and under light illumination and showed reproducible photo-switching behavior. The dependence of the photocurrent on the gate/drain voltage and on illumination intensity provided an effective way to control the number of photo-carriers generated in the active material, enabling the precise tuning of the device's performance. Performance comparison between OPTs with ordered crystal arrays and thin films of PTCDI-C 8 confirmed that the material's intrinsic properties were better realized in the crystalline device, presumably because of higher charge carrier mobility and better charge transport capability. This one-step, solution-based, self-assembly fabrication of multifunctional (photodetection, photoswitching, signal amplification) optoelectronic devices has potential to aid the development of organic semiconductors with high-quality micro/nanostructures for large-scale application and low-cost optoelectronic devices. © 2012 The Royal Society of Chemistry. Source

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