YUVRAJ S Negi - Profile on Academia.edu (original) (raw)

Papers by YUVRAJ S Negi

Functionalized 3D Bioactive Polymeric Materials in Tissue Engineering and Regenerative Medicine

Springer eBooks, 2022

Cellulose, Apr 18, 2020

The objective of the study was to explore the effect of the degree of deacetylation (DD) of the c... more The objective of the study was to explore the effect of the degree of deacetylation (DD) of the chitosan used on the degradation rate and rate constant during ultrasonic degradation. Chitin was extracted from red shrimp process waste. Four different DD chitosans were prepared from chitin by alkali deacetylation. Those chitosans were degraded by ultrasonic radiation to different molecular weights. Changes of the molecular weight were determined by light scattering, and data of molecular weight changes were used to calculate the degradation rate and rate constant. The results were as follows: The molecular weight of chitosans decreased with an increasing ultrasonication time. The curves of the molecular weight versus the ultrasonication time were broken at 1-h treatment. The degradation rate and rate constant of sonolysis decreased with an increasing ultrasonication time. This may be because the chances of being attacked by the cavitation energy increased with an increasing molecular weight species and may be because smaller molecular weight species have shorter relaxation times and, thus, can alleviate the sonication stress easier. However, the degradation rate and rate constant of sonolysis increased with an increasing DD of the chitosan used. This may be because the flexibilitier molecules of higher DD chitosans are more susceptible to the shear force of elongation flow generated by the cavitation field or due to the bond energy difference of acetamido and ␤-1,4-glucoside linkage or hydrogen bonds. Breakage of the ␤-1,4-glucoside linkage will result in lower molecular weight and an increasing reaction rate and rate constant.

Effect of dielectric thickness on performance of dual gate organic field effect transistors

In this research paper, performance characteristics of the various operating modes of dual gate o... more In this research paper, performance characteristics of the various operating modes of dual gate organic field effect transistors (DG-OFETs) are analyzed Comparative analysis between single-gate and dual-gate OFETs is carried out. Further, effect of gate dielectric thickness (tox) variations ranging from 100nm to 200nm is investigated. Observations reveal that the electrical characteristics are strongly affected by the dielectric thickness. It has been observed that the percentage improvement in the current on-off ratio is 95.4% and transconductance is reduced by 40.5% with variation in dielectric thickness.

Bioresources, Jun 2, 2011

Copper coating was deposited on Fraxinus mandshurica veneers for preparing EMI shielding composit... more Copper coating was deposited on Fraxinus mandshurica veneers for preparing EMI shielding composite by electroless plating using glyoxylic acid as reducing agent in the solution. XPS and SEM were used to analyze the activation process. It was found that a continuous chitosan membrane was loaded on the wood surface. XPS results showed that Pd(II) ions were chemically adsorbed on a chitosan membrane on the wood surface through an N-Pd σ coordination bond. After reduction, part of Pd(II) absorbed formed very little Pd(0) particles on the chitosantreated wood surface. The activated wood veneers were immersed into a plating bath in which copper film was successfully initiated. The coatings were characterized by SEM-EDS, XPS, and XRD. The metal deposition, surface resistivity, and electromagnetic shielding effectiveness were measured. The morphology of the coating was uniform, compact, and continuous. The wood grains were preserved on the plated wood veneer, which had a copper-like color and sheen. EDS, XPS, and XRD results indicated that the coating consisted of Cu 0 with crystalline structure. The surface resistivity and copper deposition reached 175.14 mΩ•cm -2 and 21.66 g/m 2 when the veneer was pretreated with 0.8 % chitosan for 8 min and plated for 30 min at 55 o C. The plated veneers exhibited good electromagnetic shielding effectiveness of over 60 dB in frequency ranging from10 MHz to 1.5 GHz.

Efficacy of Biodegradable Chitosan Polymer for Simultaneous Improvement in Ash and Strength Properties of Paper

Journal of Natural Fibers

Biochar: An Organic Amendment for Sustainable Soil Health

Encyclopedia of Green Materials

Proceedings of the 7th International Conference on Advances in Energy Research, 2020

Surface coating of chitosan of different degree of acetylation on non surface sized writing and printing grade paper

Carbohydrate Polymers, 2021

Chitosan is a renewable biopolymer which can be applied on the surface of writing and printing (W... more Chitosan is a renewable biopolymer which can be applied on the surface of writing and printing (W&P) grade paper to enhance its different properties. A variety of chitosan is available based on degree of acetylation (DA), molecular weight, viscosity, etc. DA has a profound effect on the performance of chitosan in many applications. Present study compared the performance of different DA chitosan for surface application of W&P grade paper. Chitosan samples of 23 %, 16 % and 6% DA were studied for their impact on various physical and surface properties of W&P grade paper. Surface coating of chitosan was done at 1.6 ± 0.2 g/m2 (lower dose) and 2.3 ± 0.3 g/m2 (higher dose) on W&P grade paper. Some properties including air permeance, TEA, showed considerable effect of DA in which high DA chitosan outperformed the low DA. Broadly, chitosan with different DA had varied impact on individual properties of paper.

Biotechnology for Biofuels, 2020

Background To meet the present transportation demands and solve food versus fuel issue, microbial... more Background To meet the present transportation demands and solve food versus fuel issue, microbial lipid-derived biofuels are gaining attention worldwide. This study is focussed on high-throughput screening of oleaginous yeast by microwave-aided Nile red spectrofluorimetry and exploring pongamia shell hydrolysate (PSH) as a feedstock for lipid production using novel oleaginous yeast Rhodotorula pacifica INDKK. Results A new oleaginous yeast R. pacifica INDKK was identified and selected for microbial lipid production. R. pacifica INDKK produced maximum 12.8 ± 0.66 g/L of dry cell weight and 6.78 ± 0.4 g/L of lipid titre after 120 h of growth, showed high tolerance to pre-treatment-derived inhibitors such as 5-hydroxymethyl furfural (5-HMF), (2 g/L), furfural (0.5 g/L) and acetic acid (0.5 g/L), and ability to assimilate C3, C5 and C6 sugars. Interestingly, R. pacifica INDKK showed higher lipid accumulation when grown in alkali-treated saccharified PSH (AS-PSH) (0.058 ± 0.006 g/L/h) as...

Gels, 2020

Novel sodium carboxymethyl cellulose-g-poly (sodium acrylate)/Ferric chloride (CMC-g-PNaA/FeCl3) ... more Novel sodium carboxymethyl cellulose-g-poly (sodium acrylate)/Ferric chloride (CMC-g-PNaA/FeCl3) nanoporous hydrogel beads were prepared based on the ionic cross-linking between CMC-g-PNaA and FeCl3. The structure of CMC and CMC-g-PNaA were elucidated by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) spectroscopy, and the elemental composition was analyzed by energy dispersive X-ray analysis (EDX). The physicochemical properties of the CMC-g-PNaA/FeCl3 hydrogel beads were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and thermogravimetric analysis (TGA). The swelling percentage of hydrogel beads was studied at different time periods. The obtained CMC-g-PNaA/FeCl3 hydrogel beads exhibited a higher nanoporous morphology than those of CMC-g-PNaA and CMC beads. Furthermore, an AFM image of the CMC-g-PNaA/FeCl3 beads shows granule type topology. Compared to the CMC-g-PNaA (189 °C), CMC-g-PNaA/Fe...

Enhancement of processability, surface, and mechanical properties of paper based on rice straw pulp using biopolymers for packaging applications

July 2019, 2019

Two biopolymers, chitosan and oxidized starch, were used as wet-end additives to improve the stre... more Two biopolymers, chitosan and oxidized starch, were used as wet-end additives to improve the strength properties of the paper because of their biodegradable and non-hazardous qualities. The present study reports the improvement in surface and strength properties of packaging-grade paper made with rice straw pulp using biopolymers, chitosan, oxidized starch, and surface sizing added at the wet end of the paper machine. Use of chitosan at all doses from 0.5 to 10 kg/ton enhanced important surface and strength properties of paper. The breaking length, tear index, burst index, ring crush strength, stretch, tensile energy absorption index, and Taber stiffness of the paper with 10 kg/ton of chitosan as a wet-end additive showed 22%, 14%, 20%, 59%, 16%, 44%, and 48% improvement, respectively, in comparison to control, (i.e, without its addition). The Cobb60 was also reduced by 45%, showing better resistance to water in comparison to rice straw paper alone. The effects of chitosan added at ...

Materials Today: Proceedings, 2019

Bone tissue engineering has been area of substantial research since few decades but still a gap e... more Bone tissue engineering has been area of substantial research since few decades but still a gap exists when it comes to strength and healing tendency of biomaterials with respect to age group, accidental complications etc. Many researches are yet in progress to design a perfect material for bone regeneration. Our attempt in the present study is to develop a porous hybrid material based on Chitosan(CS)/Polyvinyl Alcohol(PVA)/ Beta Tricalcium Phosphate (β-TCP) composite matrix incorporated with various carbon based fillers i.e. Graphene Oxide(GO, Reduced Graphene Oxide (RGO), Carbon Nanotube(CNT) . Scanning electron microscopy (SEM) results of fabricated scaffolds revealed nearly threefold increase in pore diameter when the concentration of each carbon filler incorporated in CS/PVA/βTCP increased to 1%. Addition of fillers also demonstrated significant mineral depositions on samples when treated with SBF .The Ca/P ratio of deposited minerals on some scaffolds was found near 1.67, the stoichiometric ratio of natural bone apatite .Increase in carbon filler concentration in CS/PVA/βTCP matrix also increased the compressive modulus of scaffold.

Bulletin of Materials Science, 2019

Pathogenic infectious diseases, like bacterial infections, are one of the most prevalent types of... more Pathogenic infectious diseases, like bacterial infections, are one of the most prevalent types of diseases all over the world. Although antibiotics are commonly used and widely available drugs for the treatment of bacterial infections, bacteria show multiple drug resistance, have a tendency to get genetically mutated and become resistant to commonly employed antibiotic drugs. This makes the invention of novel drugs essential. One of the possible approaches is the use of nanomaterials for this purpose. The present study attempts to synthesize silver nanospheres and silver nanowires and compare their antibacterial activity. Silver nanospheres were synthesized by chemical reduction of silver nitrate in the presence of a suitable stabilizer. For the synthesis of silver nanowires, polyol method was employed. Silver nanowires neatly decorated with silver nanospheres were obtained. The antibacterial activity was estimated by separately determining the minimum inhibition concentration of the two nanostructures on Gram-positive bacteria Bacillus subtilis and Gram-negative bacteria Escherichia coli cultured on Luria Bertani agar media. The comparison shows that the antibacterial activity of silver nanospheres is better than that of silver nanowires which is attributed to its higher surface area and the difference in uptake mechanism by the bacterial cells.

Colloids and Surfaces B: Biointerfaces, 2019

The present study reports the fabrication of Xylan/Chitosan/Montmorillonite (MMT) composite scaff... more The present study reports the fabrication of Xylan/Chitosan/Montmorillonite (MMT) composite scaffold by freeze drying process with the aim of achieving improved properties for bone tissue engineering applications. The scaffolds were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Scanning electron microscopy (SEM) and mechanical testing. The fabricated scaffolds were found to be highly porous with variations in pore size (102 μm-290 μm) on varying the filler concentration. XRD study revealed complete exfoliation of MMT incorporated in polymer conjugates (Xylan/Chitosan) prepared by Maillard reaction. In-vitro bio-mineralization study revealed significant apatite deposition on polymer matrix. Scaffolds with 5% MMT concentration exhibited needle like morphology of deposited apatite which can further provide synergistic response in increasing the mechanical properties of scaffolds when placed in contact with body fluid. The average length and thickness of apatite needles were calculated to be 140 μm and 1.2 μm respectively. The deposited apatite crystals on scaffold with 2% MMT content demonstrated Ca/P ratio of 1.67, resembling that of natural bone apatite. Swelling and biodegradation behavior of scaffold were also studied with regard to hydrophilic and barrier effect of MMT on composites. MTT assay revealed non-cytotoxic nature of scaffold with good cell viability.

Journal of Cleaner Production, 2018

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

International Journal of Polymer Analysis and Characterization, 2016

Cellulose nanocrystal-reinforced poly(vinyl alcohol)/silica glass hybrid scaffolds were fabricate... more Cellulose nanocrystal-reinforced poly(vinyl alcohol)/silica glass hybrid scaffolds were fabricated using the freeze-drying method. In this study, we develop molecular-level-based hybrid scaffolds with possible bioactivity behavior by adding silica sol-gel. The results showed a highly porous structure and a significant improvement in mechanical performance (stiffness) of hybrid scaffolds with an increased content of cellulose nanocrystals followed by the addition of silica-based bioactive glass. In vitro cell study with MC3T3-E1 cells on hybrid scaffolds for 1 and 3 days revealed good cell adhesion and growth. Thus, the obtained hybrid scaffold may be a competitive candidate for bone tissue engineering applications.

A depth analysis for different structures of organic thin film transistors: Modeling of performance limiting issues

Microelectronic Engineering, 2016

This research paper is focused on finding reasons for performance diversity between top contact (... more This research paper is focused on finding reasons for performance diversity between top contact (TC) and bottom contact (BC) structures of organic thin film transistors (OTFTs). The electrical characteristics, device physics, performance parameters and conduction mechanism are deeply analyzed using Atlas-Silvaco numerical device simulator. The simulation methodology consists of different approaches based on mapping of crucial issues for OTFTs. Few calibration are common for both TC and BC structures like material parameters along with Poole-Frenkel mobility model, defects in bulk OSC, dipoles at OSC-dielectric interface, correction for drain offset current and elimination of contacts voltage drop. After mapping of these issues, the results for TC structure are found close to the reported experimental results. However, performance of BC structure is reasonably matched only after incorporating some additional fabrication based issues such as unfilled corners and low mobility region around the S/D contacts. The drive current and the mobility are obtained higher by four and three times, respectively for TC than that of BC structure. Also, the sub-threshold slope is improved by 50%. On the contrary, the threshold voltage is lower by 8% for BC structure due to closer proximity of contacts to the dielectric interface. Characteristic plots for (a) drain current & threshold voltage and (b) mobility & sub-threshold slope with respect to different simulation strategies; 1. Material and model parameters, 2. Defects in bulk OSC, 3. Dipoles at OSC-dielectric interface, 4. Correction for drain offset current, 5. Correction for non-ohmic contacts, 6. Unfilled corners near the contacts and 7. Low mobility region around the S/D contacts) proposed to model various issues of TC and BC transistors.Display Omitted Paper is focused on finding reasons for performance diversity between top contact (TC) and bottom contact (BC) structures of OTFTs.Electrical behavior, device physics, performance parameters and conduction mechanism are deeply analyzed for both TC and BC structures.Simulation methodology consists of different approaches based on mapping of crucial issues for OTFTs.Comparison is performed for top and bottom contact OTFT devices.Drive current and the mobility are obtained higher by four and three times, respectively for TC than that of BC structure.

Journal of Applied Chemistry, 2013

Polyelectrolyte membrane (PEM) is an important part of PEM fuel cell. Nafion is a commercially kn... more Polyelectrolyte membrane (PEM) is an important part of PEM fuel cell. Nafion is a commercially known membrane which gives the satisfactory result in PEM fuel cell operating at low temperature. Present research paper includes functionalization of Poly(ether ether ketone) (PEEK) polymer with phosphonic acid group. The functionalization was done with the help of nickel-based catalyst. Further, the polymer was characterized by the FTIR, EDAX, DSC, TGA, and 1H NMR, and it was found that PEEK polymer was functionalized with phosphonic acid group with good thermal stability in comparison to virgin PEEK. Finally, the thin films of functionalized polymer were prepared by solution casting method, and proton conductivity of film samples was measured by impedance spectra whose value was found satisfactory with good thermal stability in comparison to commercially available Nafion membrane.

Synthesis and Modification of Poly(ether ether ketone) and their Properties: A Review

Polymer Reviews, 2012

Synthetic aromatic polyarylether ketones are known for their high performance applications. Poly(... more Synthetic aromatic polyarylether ketones are known for their high performance applications. Poly(ether ether ketone) is an important material which is most widely used in such aggressive environments as nuclear plants, oil and geothermal wells, chemical plants, and high-pressure steam valves. Considering the wide range of properties of PEEK polymers, a variety of structurally modified PEEK polymers are also reported. This

Microelectronics Journal, 2012

This research paper analyzes, finite element based two dimensional device simulations for top and... more This research paper analyzes, finite element based two dimensional device simulations for top and bottom contact organic field effect transistors (OFETs) by considering uniform and non-consistent mobility regions. To model the morphological disorder in bottom contact structure, some calibrated standards for simulation is developed viz. by considering variable low mobility regions near the contacts. An analytical model is developed, by considering contact resistance and field dependent mobility. The effect of channel length variation (5-40 mm) on performance parameters is highlighted for both the structures. Subsequently, results shows only 1% change in current for bottom contact with 0.5 mm and 1 mm low mobility region near the contacts, due to dominant contact resistance, whereas, linear dependency is observed for other simulated structures. The top contact device shows 0.43 cm 2 / V s saturation mobility at 5 mm and 13% decrease up to 20 mm and afterwards constant behavior is noticed, whereas low mobility is extracted in bottom contact devices and shows 10-20% increase in both the mobilities for increasing channel length from 5 to 40 mm. For top and bottom devices, total 65% and 62% decrease in contact resistance is observed for increasing gate voltage from À 1.8 V to À 3 V and this percentage reduces for increasing the length of low mobility region. Further, we have evaluated 13%, 40% and 78% increase in the trap density, while proceeding for 0.25 mm, 0.5 mm and 1 mm low mobility region in the bottom contact structure.