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Bera, Sandipan,Rawal, Sher Bahadur,Kim, Hark Jin,Lee, Wan In American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.12
<P>A quadrilateral disk-shaped FeWO<SUB>4</SUB> nanocrystal (NC) with an average size of ∼35 nm was prepared via hydrothermal reaction. The obtained dark brown FeWO<SUB>4</SUB> NC with a bandgap (<I>E</I><SUB>g</SUB>) of 1.98 eV was then coupled with TiO<SUB>2</SUB> to form FeWO<SUB>4</SUB>/TiO<SUB>2</SUB> composites. The valence band (VB) of FeWO<SUB>4</SUB> (+2.8 eV vs NHE) was more positive than that of TiO<SUB>2</SUB> (+2.7 eV); thus this system could be classified as a Type-B heterojunction. Under visible-light irradiation, 5/95 FeWO<SUB>4</SUB>/TiO<SUB>2</SUB> (by wt %) exhibited remarkable photocatalytic activity: the amount of CO<SUB>2</SUB> evolved from gaseous 2-propanol (IP) and the decomposition rate of aqueous salicylic acid (SA) were, respectively, 1.7 and 2.5 times greater than those of typical nitrogen-doped TiO<SUB>2</SUB> (N-TiO<SUB>2</SUB>). This unique catalytic property was deduced to arise from the intersemiconductor hole transfer between the VBs of FeWO<SUB>4</SUB> and TiO<SUB>2</SUB>. Herein, several experimental evidence were also provided to confirm the hole-transfer mechanism. To further enhance the catalytic efficiency, double-heterojunctioned FeWO<SUB>4</SUB>/TiO<SUB>2</SUB>/CdS composites were prepared by loading CdS quantum dots (QDs) onto the FeWO<SUB>4</SUB>/TiO<SUB>2</SUB> surface. Surprisingly, the catalytic activity for evolving CO<SUB>2</SUB> from IP was 2.6 times greater than that of bare FeWO<SUB>4/</SUB>TiO<SUB>2</SUB> and 4.4 times greater than that of N-TiO<SUB>2</SUB>, suggesting that both holes and electrons were essential species in decomposing organic compounds.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-12/am502079x/production/images/medium/am-2014-02079x_0015.gif'></P>
Bera, P.,Kim, C.H.,Seok, S.I. Elsevier Sequoia [etc.] 2009 Inorganica chimica acta Vol.362 No.8
Lead(II) complexes of S-methyldithiocarbazate (SMDTC), [Pb(SMDTC)(NO<SUB>3</SUB>)<SUB>2</SUB>] (1) and S-benzyldithiocarbazate (SBDTC), [Pb(SBDTC)(NO<SUB>3</SUB>)<SUB>2</SUB>] (2) have been synthesized for the first time and characterized by elemental analysis, IR and TGA techniques. The complexes were obtained by addition of the appropriate ligand to an aqueous ethanolic solution of lead(II) nitrate in 1:1 molar ratio. The X-ray crystal structure of complex 1 has been determined by single crystal X-ray diffractometry. In complex 1, lead(II) is in a nine coordinated sphere with seven oxygen atoms of the nitrate groups and thione sulfur, β-nitrogen of neutral bidentate NS chelating ligand. Three nitrate groups act as bidentate chelating whereas the fourth nitrate group is coordinating to the central lead(II) and at the same time it bridges with neighboring lead(II) atom. Coordination geometry of the central lead(II) atom has a tricapped trigonal prismatic arrangement with streochemically inactive lone pair. The lead atoms are linked into polymeric chains and these chains form twin polymeric ribbons linked through bridging oxygen atoms. The N-H...O hydrogen bond network between N<SUB>SMDTC</SUB> and O<SUB>nitrate</SUB> atom leads to self-assembled molecular conformation and stabilizes the crystal structure. The complex 2 with similar spectral and thermal behavior is expected to have a tricapped trigonal prismatic structure. The thermal behavior studies shows that the complexes start to decompose at relatively low temperature (ca. 110<SUP>o</SUP>C) to give PbS residue.
Design of visible-light photocatalysts by coupling of inorganic semiconductors
Bera, Sandipan,Won, Dong-Il,Rawal, Sher Bahadur,Kang, Hye Jin,Lee, Wan In Elsevier 2019 CATALYSIS TODAY - Vol.335 No.-
<P><B>Abstract</B></P> <P>The design of advanced photocatalytic systems, effectively working under visible-light, is essential for practical application of photocatalysts in removing environmental pollutants. To achieve high efficiency, the required properties for the photocatalysts are profound solar light absorption in the visible-range, efficient charge-separation, suitable energy band locations for redox reactions, and extended photostability. As a single semiconductor-based photocatalyst cannot satisfy all of these requirements, a potential strategy will be construction of coupled structures between two or more semiconductors. In the present study, we explore various types of photocatalytic systems constructed by coupling semiconductors and their working mechanisms. When two narrow bandgap semiconductors (NBSs) absorbing visible-light are coupled to form heterojunction structures, they can be classified as <I>p-n</I> junction or Z-scheme systems, according to the charge-flow pathway between the two semiconductors. When a NBS that absorbs visible-light is coupled with a wide bandgap semiconductor (WBS) functioning as the main photocatalyst, the fabricated catalytic systems can be classified as Type-A or Type-B heterojunction systems dependent on their relative energy band locations. Herein various semiconductor composites reported to be visible-light photocatalysts in the literature are classified using these categories, and their photocatalytic mechanisms, including charge-flow pathways, are discussed in depth. In addition, recent progress and future perspectives for heterojunction systems are reviewed and discussed.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Various visible-light photocatalysts can be designed by coupling of semiconductors. </LI> <LI> Photocatalytic systems were classified as p-n junction, Z-scheme, Type-A and Type-B. </LI> <LI> Design concept and working mechanism for each catalytic system were handled in depth. </LI> <LI> Individual example and perspective for each heterostructure were described intimately. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Bera, Bireshwar,Manna, Buddhadeb Korean Society of Sericultural Science 2009 International Journal of Industrial Entomology Vol.18 No.2
The presence of considerable amount of enzymes of TCA cycle isocitrate dehydrogenase (ICDH-NADP+, EC1.1.1.42), $\alpha$-ketogluterate dehydrogenase ($\alpha$-KGD, EC1.2.4.2) and malate dehydrogenase (MDH, EC1.1.1.37) in fresh control and in vitro starved adult Isoparorchis hypselobagri establish the functional TCA cycle in this fluke. The major metabolic end products are pyruvate, lactate, oxaloacetate and malate. The ratio of oxaloacetate/malate assess that oxaloacetate is reduced to malate and in this fluke the reverse TCA cycle is active. The pyruvate/lactate ratio shows pyruvate is reduced to lactate and the fluke is homolactate farmenters.
Compaction and unconfined compressive strength of sand modified by class F fly ash
Bera, Ashis K.,Chakraborty, Sourav Techno-Press 2015 Geomechanics & engineering Vol.9 No.2
In the present investigation, a series of laboratory compaction and unconfined compressive strength laboratory tests has been performed. To determine the effect of compaction energy, type of sand, and fly ash content, compaction tests have been performed with varying compaction energy ($2700kJ/m^3-300kJ/m^3$), types of sand, and fly ash content (0% to 40%) respectively. From the experimental results, it has been found that the optimum value of unconfined compressive strength obtained for a sand-fly ash mixture comprised of 65% sand and 35% fly ash. Based on the data obtained in the present investigation, a linear mathematical model has been developed to predict the OMC of sand-fly ash mixture.
A Novel Iron(III) Selective Membrane Electrode Containing a Tripodal Polycatacholamine as Sensor
Bera, Rati Kanta,Sahoo, Suban K,Baral, Minati,Kanungo, B.K. Korean Chemical Society 2011 Bulletin of the Korean Chemical Society Vol.32 No.10
A novel poly(vinylchloride)-based membrane sensor using $N^1$,$N^3$,$N^5$-tris(2-(2,3-dihydroxybenzylamino)-ethyl)cyclohexane-1,3,5-tricarboxamide (CYCOENCAT, L) as ionophore has been prepared and explored as $Fe^{3+}$ selective electrode. The membrane electrode composed of ionophore, poly(vinylchloride) and o-nitropheyloctyl ether in the optimum ratio 4:33:63 gave excellent potentiometric response characteristics, and displayed a linear log[$Fe^{3+}$] versus EMF response over a wide concentration range of $1.0{\times}10^{-5}-1.0{\times}10^{-1}$ M with super nernstian slope of 28.0 mV/decade and the detection limit of $8.0{\times}10^{-6}$ M. The proposed ion selective electrode showed fast response time (< 15 s), wide pH range (3.0-7.0), high non-aqueous tolerance (up to 20%) and adequate long life time (120 days). It also exhibited very good selectivity for $Fe^{3+}$ relative to a wide variety of alkali, alkaline earth, transition and heavy metal ions. Further, the analytical applicability of the sensor was tested as an indicator electrode in the potentiometric titration of $Fe^{3+}$ with EDTA.
AN OPTIMAL PRAM ALGORITHM FOR A SPANNING TREE ON TRAPEZOID GRAPHS
Bera, Debashis,Pal, Madhumangal,Pal, Tapan K. 한국전산응용수학회 2003 Journal of applied mathematics & informatics Vol.12 No.1
Let G be a graph with n vertices and n edges. The problem of constructing a spanning tree is to find a connected subgraph of G with n vertices and n -1 edges. In this paper, we propose an O(log n) time parallel algorithm with O(n/ log n) processors on an EREW PRAM for constructing a spanning tree on trapezoid graphs.
A DELAY DYNAMIC MODEL FOR HIV INFECTED IMMUNE RESPONSE
BERA, S.P.,MAITI, A.,SAMANTA, G.P. The Korean Society for Computational and Applied M 2015 Journal of applied mathematics & informatics Vol.33 No.5
Human Immune Deficiency Virus (or simply HIV) induces a persistent infection that leads to AIDS causing death in almost every infected individual. As HIV affects the immune system directly by attacking the CD4+ T cells, to exterminate the infection, the natural immune system produces virus-specific cytotoxic T lymphocytes(CTLs) that kills the infected CD4+ T cells. The reduced CD4+ T cell count produce reduced amount of cytokines to stimulate the production of CTLs to fight the invaders that weakens the body immunity succeeding to AIDS. In this paper, we introduce a mathematical model with discrete time-delay to represent this cell dynamics between CD4+ T cells and the CTLs under HIV infection. A modified functional form has been considered to describe the infection mechanism. Characteristics of the system are studied through mathematical analysis. Numerical simulations are carried out to illustrate the analytical findings.