Browsing by Author "Anand Sharma"

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A Lithography-Free Fabrication of Low-Operating Voltage-Driven, Very Large Channel Length Graphene Field-Effect Transistor with NH3Sensing Application
(Institute of Electrical and Electronics Engineers Inc., 2020) Nitesh K. Chourasia; Abhishek Kumar Singh; Suyash Rai; Anand Sharma; P. Chakrabarti; Anchal Srivastava; Bhola N. Pal
Large-area-based field-effect transistor (FET) gas sensor has the potential to provide a larger sensing area for a chemical analyte. So far, graphene FETs (GFETs) are mostly fabricated by expensive lithographic techniques with a minimum channel length. We have demonstrated a simple way to fabricate a very large channel length of 0.45 mm GFET using ion-conducting dielectric with thermally evaporate source/drain electrodes and has been demonstrated for an application of ambient atmosphere ammonia gas sensing. Ion-conducting Li5AlO4 gate dielectric has reduced operating voltage up to 2.0 V with good current saturation. The chemical vapor deposition (CVD) grown uniform monolayer of graphene has been used as an active channel layer of FET. The fabricated device has been tested for different concentrations of ammonia in ambient environment conditions at 25 °C temperature, which indicates that the Dirac point voltage of the device varies up to 0.8 V when the concentration of ammonia has been changed from 0 to 3 ppm. Moreover, this study also reveals that this GFET is capable of detecting ammonia up to the concentration level of 0.1 ppm. © 1963-2012 IEEE.
Lithography-free fabrication of low operating voltage and large channel length graphene transistor with current saturation by utilizing Li+of ion-conducting-oxide gate dielectric
(American Institute of Physics Inc., 2020) Nitesh K. Chourasia; Vijay K. Singh; Anand Sharma; Anchal Srivastava; Bhola N. Pal
The large channel length graphene field-effect transistor (GFET) can outperform its competitors due to its larger active area and lower noise. Such long channel length devices have numerous applications, e.g., in photodetectors, biosensors, etc. However, long channel length graphene devices are not common due to their semi-metallic nature. Here, we fabricate large channel length (up to 5.7 mm) GFETs through a simple, cost-effective method that requires thermally evaporated source-drain electrode deposition, which is less cumbersome than the conventional wet-chemistry based photolithography. The semiconducting nature of graphene has been achieved by utilizing the Li+ ion of the Li5AlO4 gate dielectric, which shows current saturation at a low operating voltage (∼2 V). The length scaling of these GFETs has been studied with respect to channel length variation within a range from 0.2 mm to 5.7 mm. It is observed that a GFET of 1.65 mm channel length shows optimum device performance with good current saturation. This particular GFET shows a "hole"mobility of 312 cm2 V-1 s-1 with an on/off ratio of 3. For comparison, another GFET has been fabricated in the same geometry by using a conventional SiO2 dielectric that does not show any gate-dependent transport property, which indicates the superior effect of Li+ of the ionic gate dielectric on current saturation. © 2020 Author(s).
Properties and types of chitosan-based nanomaterials
(Elsevier, 2022) Priyanka Tiwari; Anand Sharma; Vanya Nayak; Ranjana Verma; Jay Singh
This chapter briefly discusses immense research on chitosan-based nanomaterials as well as also highlights the current developments and their utility in different applications majorly focusing on the biomedical field. Chitosan is a well-known nontoxic, biocompatible, and biodegradable polymer possessing enormous possibilities for structural modification either by chemical or mechanical pathways, thereby generating novel polymeric designs with enhanced properties and functions, particularly in biology. Chitosan has been used as a fascinating biomaterial in developing different types of drug delivery techniques, as regenerative medicine in the area of health science or pharmacy. Tremendous use of agrochemicals for increasing crop production and their protection causes significant health and environmental concerns; therefore, chitosan-based nanomaterials such as nanoparticles, hydrogels, and nanocomposites have been applied in agriculture due to their unique antimicrobial and plant growth-promoting properties. These special properties endorse chitosan with promising potentialities for development in biomedicine fields like drug delivery, gene delivery, cell and molecular imaging, development of different sensors, and the treatment and diagnosis of some diseases like cancer, neurodegenerative diseases, etc. In contrast to the native chitosan, the chitosan-based nanomaterials are known to exhibit improved chemical, mechanical, and physical properties like higher surface area, tensile strength, porosity, conductivity, photo-luminescence, etc. This chapter focuses on the current research aspects of chitosan-based nanomaterials by highlighting their properties and potentialities in different domains. © 2022 Elsevier Inc. All rights reserved.
Simple and Direct Synthetic Route to a Rod-Coil Conjugated Block Copolymer from Either a Rod or Coil Block Using a Single Bifunctional Initiator: A Solvent Dependent Self-Assembly and Field Effect Mobility Study
(American Chemical Society, 2020) Soumili Daripa; Koomkoom Khawas; Anand Sharma; Amit Kumar; Bholanath Pal; Santanu Das; Satyabrata Jit; Biplab Kumar Kuila
Here, we have described a simple and straightforward methodology for synthesis of rod-coil conjugated block copolymer poly(3-hexylthiophene)-block-polystyrene (P3HT-b-PS) of varying molecular weight and low polydispersity by chain extension of either a rod or coil block starting from a single bifunctional initiator through combination of Kumada catalyst transfer polymerization (KCTP) and atom transfer radical polymerization (ATRP). Advantages of the present method include the facile synthesis of the Ni(II) catalytic initiators from readily available laboratory reagents, avoiding high reactive intermediates for preparing Ni(ii) catalytic initiator, and the in situ nature of all the steps making large scale preparation of the block copolymer viable. Studies on solvent-induced structure formation and their impact on optical and electronic properties of the block copolymer were systematically performed. The block copolymer device fabricated from toluene shows the best field effect mobility of (2.1 ± 0.75) × 10-3 cm2 V-1 s-1 compared to results for other solvents. Overall, this work describes a facile synthetic strategy for a rod-coil conjugated block copolymer and its solvent-induced structure formation as guidance for fabricating high-performance organic electronic and optoelectronic devices. Copyright © 2020 American Chemical Society.
Synthesis, characterization, and application of chitosan nanomaterials loaded with other metals/elements in plant
(Elsevier, 2022) Aparna Shukla; Anand Sharma; Vanya Nayak; Ranjana Verma; Jay Singh
In the last few decades, chitosan nanomaterials have been broadly explored in the field of biology, pharmaceutical, and agriculture because of their unique properties such as diverse biological functions, biodegradability, nontoxic nature, and facile availability. Metal-embedded chitosan-based nanomaterials have gained significant attention as they possess dual properties i.e., growth promotion as well as protection in plants. Furthermore, metals or elements encapsulated in chitosan are less toxic due to the slow-release phenomenon and showed a long-lasting effect in plants. The blending of various metals Zn, Cu, Ag, and other elements with chitosan is known to supplement properties like providing nutrition to plants and help plant growth by protecting them from biotic and abiotic stress. Furthermore, metal-chitosan nanoparticles have predominantly shown antimicrobial functions against many plant pathogenic bacteria and fungi. However, the role of chitosan-based nanomaterials their bioactivity, and pathogenic mode of action is still not much explored which limits their application in agriculture. In order to expedite the predicted role of chitosan metal nanomaterials, it is crucial to assemble all the bioactivity processes responsible for the sustainable growth of plants. In this chapter, we discuss different chitosan/metal-based nanomaterials that have been explored in plant growth and their protection from microbes usually fungi, bacteria and viruses along with their mode of action. © 2022 Elsevier Inc. All rights reserved.