Oxygen vacancy and dopant concentration dependent magnetic properties of Mn doped TiO2 nanoparticle

Biswajit Choudhury,Amarjyoti Choudhury 한국물리학회 2013 Current Applied Physics Vol.13 No.6

Mn doped TiO2 nanoparticles are synthesized by solegel method. Incorporation of Mn shifts the diffraction peak of TiO2 to lower angle. The position and width of the Raman peak and photoluminescence intensity of the doped nanoparticles varies with oxygen vacancy and Mn doping level. The electron spin resonance spectra of the Mn doped TiO2 show peaks at g ¼ 1.99 and 4.39, characteristic of Mn2þ state. Reduction in the emission intensity, on Mn doping, is owing to the increase of nonradiative oxygen vacancy centers. Mn doped TiO2, with 2% Mn, shows ferromagnetic ordering at low applied field. Paramagnetic contribution increases as Mn loading increases to 4% and 6%. Temperature dependent magnetic measurement shows a small kink in the ZFC curve at about 40 K, characteristic of Mn3O4. The ferromagnetic ordering is possibly due to the interaction of the neighboring Mn2þ ions via oxygen vacancy (Fþ center). Increase in Mn concentration increases the fraction of Mn3O4 phase and thereby increases the paramagnetic ordering.

Lattice distortion and corresponding changes in optical properties of CeO2 nanoparticles on Nd doping

Biswajit Choudhury,Amarjyoti Choudhury 한국물리학회 2013 Current Applied Physics Vol.13 No.1

Doping of Nd distorts the lattice structure of CeO2, increases the lattice strain and expands the lattice. Oxygen vacancies and other ceria related defects contribute to the lattice strain. Shifting and broadening of the F2g Raman peak of doped sample, compared to pure CeO2, is indicative of local structure distortion on doping. Dopant induced enhancement of oxygen vacancies, in the CeO2 lattice, is further confirmed by the generation of a new Raman peak at 543 cm1 that is otherwise absent in the pure one. UVevis spectroscopy gives an understanding of the different types of fef electronic transition of Nd in the crystalline environment of CeO2. Effective band gap of CeO2 reduces upto Nd concentration of 2.5%. The band gap, however, increases at 4% of Nd due to BursteineMoss shift. Photoluminescence intensity of pure CeO2 decreases with Nd concentration owing to the increase in the number of non radiative oxygen vacancies. These vacancies act as luminescence quencher and reduce the emission intensity. Photoluminescence excitation spectra confirm the presence of these oxygen vacancies in the CeO2 nanocrystallites.

In-situ synthesis of vanadium pentoxide nanofibre/exfoliated graphene nanohybrid and its supercapacitor applications

Choudhury, Arup,Bonso, Jeliza S.,Wunch, Melissa,Yang, Kap Seung,Ferraris, John P.,Yang, Duck J. Elsevier 2015 Journal of Power Sources Vol.287 No.-

<P><B>Abstract</B></P> <P>A novel nanohybrid material composed of vanadium pentoxide nanofibres (VNFs) and exfoliated graphene were prepared by <I>in-situ</I> growth of VNFs onto graphene nanosheets, and explicated as electrode material for supercapacitor applications. The existence of non-covalent interactions between VNFs and graphene surfaces was confirmed by Raman and Fourier transform infrared (FTIR) spectroscopes. Morphological analysis of the nanohybrid revealed that the VNF layer uniformly grown on the graphene surfaces, producing high specific surface area and good electronic or ionic conducing path. High crystalline structure with small d-spacing of the VNFs on graphene was observed in X-ray diffraction (XRD) analysis. Compared to pristine VNF, the VNF/graphene nanohybrid exhibited higher specific capacitance of 218 F g<SUP>−1</SUP> at current density of 1 A g<SUP>−1</SUP>, higher energy density of 22 Wh kg<SUP>−1</SUP> and power density of 3594 W kg<SUP>−1</SUP>. Asymmetric supercapacitor devices were prepared using the Spectracarb 2225 activated carbon cloth and VNF/graphene nanohybrid as positive and negative electrode, respectively. The asymmetric device exhibited capacitance of 279 F g<SUP>−1</SUP> at 1 A g<SUP>−1</SUP>, energy density of 37.2 Wh kg<SUP>−1</SUP> and power density of 3743 W kg<SUP>−1</SUP>, which are comparable and or superior to reported asymmetric devices consisting of carbon material and metal oxide as electrode components.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Preparation of novel nanohybrid by <I>in-situ</I> growth of V<SUB>2</SUB>O<SUB>5</SUB> nanofibres on graphene. </LI> <LI> Electrochemical characterizations of the nanohybrid for supercapacitor application. </LI> <LI> Maximum capacitance observed for asymmetric devices. </LI> <LI> Energy density of asymmetric devices was 69% higher than that of symmetric device. </LI> </UL> </P>

Mitochondria to nucleus translocation of AIF in mice lacking Hsp70 during ischemia/reperfusion

Choudhury, Sangita,Bae, Soochan,Ke, Qingen,Lee, Ji Yoo,Kim, Jacob,Kang, Peter M. Springer-Verlag 2011 Supplement to Basic Research in Cardiology . v.87( Vol.106 No.3

Evolution of a honeycomb network of precipitates in a hot-rolled commercial Mg-Y-Nd-Zr alloy

Choudhuri, D.,Meher, S.,Nag, S.,Dendge, N.,Hwang, J.Y.,Banerjee, R. Taylor Francis 2013 Philosophical magazine letters Vol.93 No.7

Polysaccharides Obtained from Vegetables: an effective source of alternative excipient

Choudhury Ananta,Sarma Satyabrat,Sarkar Snehashis,Kumari Madhusmita,Dey Biplab Kumar 대한약침학회 2022 Journal of pharmacopuncture Vol.25 No.4

Polymers are the major constructive material of pharmaceutical formulations that play a prime role in designing effective drug-delivery systems and releasing drugs at their sites of application. Polymers are composed of multiple repeating units of high molecular mass components with attendant properties. Most synthetic polymers are non-biocompatible, expensive, and extremely inclined to deliver adverse impacts. Meanwhile, edible polymers obtained from natural sources have gained remarkable recognition for their promising use in modern medicine. Moreover, polymers derived from natural sources are generally preferred due to certain of their unique features such as abundant availability, biocompatibility, nontoxicity, economical, safe, and effective functions that fit the purpose. Polysaccharides including starch, cellulose, hemicellulose, pectin, and mucilage are identified as a major class of naturally obtained molecules that have a substantial role as functional polymers. This review summarizes the potential role of polysaccharides derived from vegetable sources such as adhesives, anticaking agents, binders, disintegrants, emulsifiers, film-framing agents, and thickeners. This is simply an opportunity to abandon synthetic excipients that hurt our bodies and think back to nature from where we originate.

Photometric metallicity map of the Small Magellanic Cloud

Choudhury, S,Subramaniam, A,Cole, A A,Sohn, Y-J Oxford University Press 2018 Monthly notices of the Royal Astronomical Society Vol.475 No.4

CHINA'S POLICY TOWARD SOUTH ASIA

Choudhury, G W 경남대학교 극동문제연구소 1990 ASIAN PERSPECTIVE Vol.14 No.2

Causal State Communication

Choudhuri, C.,Young-Han Kim,Mitra, U. IEEE 2013 IEEE transactions on information theory Vol.59 No.6

<P>The problem of state communication over a discrete memoryless channel with discrete memoryless state is studied when the state information is available strictly causally at the encoder. It is shown that block Markov encoding, in which the encoder communicates a description of the state sequence in the previous block by incorporating side information about the state sequence at the decoder, yields the minimum state estimation error. When the same channel is used to send additional independent information at the expense of a higher channel state estimation error, the optimal tradeoff between the rate of the independent information and the state estimation error is characterized via the capacity-distortion function. It is shown that any optimal tradeoff pair can be achieved via rate-splitting. These coding theorems are then extended optimally to the case of causal channel state information at the encoder using the Shannon strategy.</P>

Potential Role of Bioactive Phytochemicals in Combination Therapies against Antimicrobial Activity

Choudhury, Ananta KOREAN PHARMACOPUNCTURE INSTITUTE 2022 Journal of pharmacopuncture Vol.25 No.2

Since ancient times, plants have been a major source of novel drug molecules and have been used in the treatment of different infectious diseases. Secondary plant metabolites have miraculous healing properties and show potent therapeutic responses when used in combination drug therapy. The prime objective of this review is to summarize the concept of drug combination with special emphasis on the synergistic interactions between plant-derived bioactive phytochemicals with commercially available antimicrobial agents. The study also assesses the roles, importance, and applicability of phytochemicals in the management of different diseases. The review focuses on different aspects of combined antimicrobial activities, the possible mechanisms involved, and the current status of research in the field. The study was conducted based on an extensive literature survey that resulted in the following hypothesis: secondary metabolites derived from plants possess remarkable therapeutic activities. The study was designed as a systematic review that ensures unbiased and accurate representations of the relevant data and information. Jadad scale selection criteria were used for qualitative analysis of the articles to assess them based on the relevant secure score (minimum and maximum scores range between 1 and 5, respectively). Articles with secure scores > 3 were considered for the study. A comprehensive literature survey was conducted using resource databases including PubMed, Google Scholar, Bielefeld Academic Search Engine, Research Gate, Scopus, Medline, and Science Direct up to June 2019. This article contains concise information about the most commonly used bioactive phytochemicals with potent antifungal and antibacterial effects.