Study on the Growth Parameters and the Electrical and Optical Behaviors of 2D Tungsten Disulfide.

Transition-metal dichalcogenides (TMDCs) with atomic thickness are promising materials for next-generation electronic and optoelectronic devices. Herein, we report uniform growth of triangular-shaped (∼40 µm) monolayer WS2 using the atmospheric-pressure chemical vapor deposition (APCVD) technique in a hydrogen-free environment. We have studied the optical and electrical behaviors of as-grown WS2 samples. The absorption spectrum of monolayer WS2 shows two intense excitonic absorption peaks, namely, A (∼630 nm) and B (∼530 nm), due to the direct gap transitions at the K point. Photoluminescence (PL) and fluorescence studies reveal that under the exposure of green light, monolayer WS2 gives very strong red emission at ∼663 nm. This corresponds to the direct band gap and strong excitonic effect in monolayer WS2. Furthermore, the efficacy of the synthesized WS2 crystals for electronic devices is also checked by fabricating field-effect transistors (FETs). FET devices exhibit an electron mobility of µ ∼ 6 cm2 V-1 s-1, current ON/OFF ratio of ∼106, and subthreshold swing (SS) of ∼641 mV decade-1, which are comparable to those of the exfoliated monolayer WS2 FETs. These findings suggest that our APCVD-grown WS2 has the potential to be used for next-generation nanoelectronic and optoelectronic applications.

A critical appraisal of dementia with special reference to Smritibuddhihrass.

Dementia (Smritibuddhihrass) is a chronic organic mental disorder, characterized by progressive usually irreversible, global cognitive deficit. Presently no reliable treatment is available to check the progression of the disease in the conventional medicine. Although this condition is not described as a disease moiety in a separate chapter among Ayurvedic classics but the signs and symptoms along with pathogenesis of dementia can be understood in terms of Ayurvedic concepts. As a large part of pathogenesis of dementia involves neurodegeneration, Rasayana and Panchkarma therapy play an a very important role in the management of dementia. These therapeutic techniques have the potential to check the progression of disease as well as can improve the deficit in cognitive functions of these patients. In the present paper the possible pathogenesis of Dementia in the terms of Ayurvedic concepts has been discussed and suggested the management profiles from Ayurvedic perspectives which can be beneficially utilized for this important class of geriatric disorders.

Scalable synthesis of aligned carbon nanotubes bundles using green natural precursor: neem oil.

Practical application of aligned carbon nanotubes (ACNTs) would have to be determined by a matter of its economical and large-scale preparation. In this study, neem oil (also named Margoaa oil, extracted from the seeds of the neem--Azadirachta indica) was used as carbon source to fabricate the bundles of ACNTs. ACNTs have been synthesized by spray pyrolysis of neem oil and ferrocene mixture at 825°C. The major components of neem oil are hydrocarbon with less amount of oxygen, which provided the precursor species in spray pyrolysis growth of CNTs. The bundles of ACNTs have been grown directly inside the quartz tube. The as-grown ACNTs have been characterized through Raman spectroscopy, scanning and transmission electron microscopic (SEM/TEM) techniques. SEM images reveal that the bundles of ACNTs are densely packed and are of several microns in length. High-resolution TEM analysis reveals these nanotubes to be multi-walled CNTs. These multi-walled CNTs were found to have inner diameter between 15 and 30 nm. It was found that present technique gives high yield with high density of bundles of ACNTs.