Hydrothermally synthesized Na₂Ti₃O₇ nanotube–V₂O₅ heterostructures with improved visible photocatalytic degradation and hydrogen evolution - Its photocorrosion suppression

Vattikuti, S.V. Prabhakar,Reddy, Police Anil Kumar,NagaJyothi, P.C.,Shim, Jaesool,Byon, Chan Elsevier 2018 JOURNAL OF ALLOYS AND COMPOUNDS Vol.740 No.-

<P><B>Abstract</B></P> <P>There is still a need to prepare heterostructure photocatalysts with high activity and recyclability but without using precious metals to reduce the cost of photocatalysts. Thus, a facile and simple method for the synthesis of a Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanotube–V<SUB>2</SUB>O<SUB>5</SUB> heterostructure photocatalyst via hydrothermal synthesis is reported herein. The chemical composition, morphology, and structural features of the photocatalyst were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), N<SUB>2</SUB> adsorption–desorption specific surface area analysis (BET), and diffuse reflectance absorption (DRS) methods. It was observed that the specific surface area of the Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanotube–V<SUB>2</SUB>O<SUB>5</SUB> heterostructure photocatalyst increased with the incorporation of V<SUB>2</SUB>O<SUB>5</SUB>. The Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanotube–V<SUB>2</SUB>O<SUB>5</SUB> heterostructure photocatalyst was then used for the removal of rhodamine B (RhB) under simulated solar light irradiation. The Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanotube–V<SUB>2</SUB>O<SUB>5</SUB> heterostructure photocatalyst revealed excellent photocatalytic activity and photodegradation kinetics as compared to pristine Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanotubes and V<SUB>2</SUB>O<SUB>5</SUB> photocatalysts. Furthermore, both the photoactivity and long-term stability of the Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanotube–V<SUB>2</SUB>O<SUB>5</SUB> heterostructure photocatalyst were superior to those of the pristine Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanotubes and V<SUB>2</SUB>O<SUB>5</SUB> photocatalysts. The excellent photocatalytic performance of the Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> nanotube–V<SUB>2</SUB>O<SUB>5</SUB> heterostructure photocatalyst can be ascribed to its high specific surface area (283.71 m<SUP>2</SUP>g<SUP>−1</SUP>), mesoporous structure, highly dispersed V<SUB>2</SUB>O<SUB>5</SUB> nanoparticles, and hindrance of electron–hole pair recombination of Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> due to the V<SUB>2</SUB>O<SUB>5</SUB> incorporation, which is proven by the photoelectrochemical results, including photocurrent and electron impendence spectroscopy results. In addition, during the study of photocatalytic hydrogen evolution, the hydrogen yield of the Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB>/V<SUB>2</SUB>O<SUB>5</SUB> nanocomposite was 1.83 times that of pristine Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB>, which also exhibited excellent photocatalytic activity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Heterojunction of Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> NTs/V<SUB>2</SUB>O<SUB>5</SUB> NPs was developed via hydrothermal method. </LI> <LI> Visible photocatalytic RhB degradation studies were performed over Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> NTs/V<SUB>2</SUB>O<SUB>5</SUB> NPs. </LI> <LI> Improved degradation efficiency was observed over Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> NTs/V<SUB>2</SUB>O<SUB>5</SUB> NPs when compared to pristine Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> NTs. </LI> <LI> V<SUB>2</SUB>O<SUB>5</SUB> NPs were successfully utilized as cocatalyst for pollutant degradation. </LI> <LI> Charge recombination was diminished in the Na<SUB>2</SUB>Ti<SUB>3</SUB>O<SUB>7</SUB> NTs by the addition of V<SUB>2</SUB>O<SUB>5</SUB> NPs. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Vertical GaN Reverse Trench-Gate Power MOSFET and DC-DC Converter

Nilesh Kumar Jaiswal,V. N. Ramakrishnan 한국전기전자재료학회 2021 Transactions on Electrical and Electronic Material Vol.22 No.3

A vertical GaN reverse trench-gate power MOSFET (RT-MOSFET) device is proposed. This Vertical RT-MOSFET features the negative incline of broaden-trench sidewalls at the bottom of the gate. Numerical device simulations using TCAD have been carried out for device and circuit performance study and analysis. The device performance like transfer characteristics, on-state, off -state characteristics, capacitance–voltage characteristics is observed. The simulation results are shown in comparison to the conventional such as perpendicular trench-gate (UT), and trapezoidal trench-gate (VT)-MOSFET devices. The RT-MOSFET has a ~ 9% and ~ 20% reduced on-state resistance (R on ), ~ 6% and ~ 10% enhanced electrical breakdown voltage (V br ), and ~ 21% and ~ 46% superior Baliga’s fi gure of merits ( V2 br∕Ron) compared to UT-MOSFET and VT-MOSFET, respectively. Next, we obtain lower energy loss using TCAD Mixed-mode simulation for DC-DC boost converter circuit performance with diff erent voltage. The RT-MOSFET saves ~ 30% and ~ 76% energy loss at 100 V, ~ 43%, and ~ 75% energy loss at 200 V and ~ 54% and ~ 87% energy loss at 400 V during DC-DC converter application compared to UT-MOSFET and VT-MOSFET, respectively.

In situ fabrication of the Bi₂O₃–V₂O₅ hybrid embedded with graphitic carbon nitride nanosheets: Oxygen vacancies mediated enhanced visible-light–driven photocatalytic degradation of organic pollut

Vattikuti, S.V. Prabhakar,Police, Anil Kumar Reddy,Shim, Jaesool,Byon, Chan Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.447 No.-

<P><B>Abstract</B></P> <P>Novel mesoporous ternary hybrids comprising Bi<SUB>2</SUB>O<SUB>3</SUB>/V<SUB>2</SUB>O<SUB>5</SUB> photocatalysts anchored on graphitic carbon nitride (g-C<SUB>3</SUB>N<SUB>4</SUB>) nanosheets were synthesized via an in situ co-pyrolysis approach and characterized by a series of techniques, including X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller analysis, thermogravimetric-differential thermal analysis, Fourier transform infrared spectroscopy, ultraviolet–visible spectrometry, photoluminescence and electron paramagnetic resonance (EPR). The hybrids were subsequently tested as photocatalysts for the degradation of the phenol red (PR) pollutant under visible light irradiation. The well-designed ternary hybrids showed pure and randomly distributed Bi<SUB>2</SUB>O<SUB>3</SUB>/V<SUB>2</SUB>O<SUB>5</SUB> (denoted as BiV) nanoparticles on monodispersed g-C<SUB>3</SUB>N<SUB>4</SUB> nanosheets. The as-prepared ternary Bi<SUB>2</SUB>O<SUB>3</SUB>/V<SUB>2</SUB>O<SUB>5</SUB>@g-C<SUB>3</SUB>N<SUB>4</SUB> (i.e., BiV@g-C<SUB>3</SUB>N<SUB>4</SUB>) hybrids demonstrated high specific surface areas with remarkable mesoporous characteristics. The photodegradation efficiencies of the ternary hybrids for PR were 1.2 and 1.8 times higher than those of binary BiV and pristine Bi<SUB>2</SUB>O<SUB>3</SUB>, respectively, at 50 min irradiation time under simulated solar light irradiation. At the end of the phototreatment, the amount of PR pollutant was reduced to 98.1% in 50 min by using the BiV@g-C<SUB>3</SUB>N<SUB>4</SUB> nanocomposites under simulated solar light irradiation and more efficient for photocatalytic H<SUB>2</SUB> production. Based on an electrochemical analysis, we propose a photocatalytic degradation pathway for PR under visible light irradiation. In addition, the BiV@g-C<SUB>3</SUB>N<SUB>4</SUB> nanocomposite photocatalysts exhibited both long-term stability and photocatalytic efficiency for the degradation of the PR dye. The excellent photoelectrochemical performance of the BiV@g-C<SUB>3</SUB>N<SUB>4</SUB> photocatalysts can be ascribed to their highly dispersed V<SUB>2</SUB>O<SUB>5</SUB> and Bi<SUB>2</SUB>O<SUB>3</SUB> nanoparticles, mesoporous structure, and high specific surface area (83.75 m<SUP>2</SUP> g<SUP>−1</SUP>).</P> <P><B>Highlights</B></P> <P> <UL> <LI> BiV@g-C<SUB>3</SUB>N<SUB>4</SUB> photocatalyst was successfully synthesized via co-pyrolysis. </LI> <LI> Synthetic procedure may open up an opportunity to tailor the morphologies of nanocomposites. </LI> <LI> Studied the oxygen vacancies enhanced photocatalytic activity of BiV@g-C<SUB>3</SUB>N<SUB>4.</SUB> </LI> <LI> Photodegradation and H<SUB>2</SUB> evolution mechanism of the BiV@g-C<SUB>3</SUB>N<SUB>4</SUB> photocatalyst is elucidated and discussed. </LI> <LI> BiV@g-C<SUB>3</SUB>N<SUB>4</SUB> photocatalyst demonstrated 21.08 folds higher H<SUB>2</SUB> production rate than pure ones. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Estimating Total Factor Productivity and Its components - Evidence from Manufacturing Sector of Tamilnadu, India

Kumar,T. Sampath,Pradeep V. 한국유통과학회 2019 KODISA ICBE (International Conference on Business Vol.2019 No.-

The study applied Data Envelopment Analysis (DEA) to estimate total factor productivity growth and to identify the sources of productivity growth in the manufacturing sector of Tamil Nadu. The study considered 12 major sectors and estimated productivity growth and the major sources of productivity growth during the period 1981-82 to 2007-08. The study found that the productivity growth in the industrial sector of Tamil Nadu at the aggregate level during the test period was almost nil. While it is the case at the aggregate level, there are mixed results at the sectoral level. During the pre-reform period, there was significantly higher productivity growth in almost all the sectors contributed mainly by the improvements in efficiency. On other hand, there was productivity deterioration in the post-reform period since almost all the sectors witnessed negative productivity growth despite a technical change in the post-reform period. The study based on the empirical findings suggests that there will be productivity growth only if any improvement in the technology is accompanied by the corresponding improvement in the efficiency with which the technology can be turned into productivity gains. A well developed and skilled labour force along with the improvements in the technological developments will lead to higher productivity growth in the manufacturing sector both at the aggregate and sectoral level.

Photo-induced rapid biosynthesis of silver nanoparticle using aqueous extract of Xanthium strumarium and its antibacterial and antileishmanial activity

Vijay Kumar,Ravi Kumar Gundampati,Devendra Kumar Singh,Medicherla V. Jagannadham,Shyam Sundar,Syed Hadi Hasan 한국공업화학회 2016 Journal of Industrial and Engineering Chemistry Vol.37 No.-

The current work describes the biosynthesis of stable AgNPs using aqueous extract of Xanthiumstrumarium (AEX) which act as both reducing as well as a stabilizing agent. The biosynthesis wasconfirmed by UV–visible spectroscopy where the presence of SPR band at lmax 436 nm corresponded tothe existence of AgNPs in reaction mixture. The optimum conditions for biosynthesis of AgNPs were30 min of sunlight exposure time, 3.0% (v/v) of AEX inoculum dose and 3.5 mM AgNO3 concentration. The synthesized AgNPs was characterized by HRTEM, SAED, FESEM, EDX, XRD, AFM, and FTIR whichshowed potent antibacterial and antileishmanial activity.

SEM Studies on the Leaf Surface of Promising Mulberry(Morus spp.) Genotypes

Singhal, B. K.,Kumar, V.,Rajan, M. V. 한국식물학회 1999 Journal of Plant Biology Vol.42 No.1

Mulberry (Morus spp.) leaf quality has a great role in silkworm rearing which in turn affects the overall silk yield. In the recent past, many varieties of mulberry have been evolved considering the morphological characters, growth, yield, and quality parameters based on bioassay. The present investigation was carried out on ten promising mulberry genotypes viz. Tr-10, K-2, S-36, S-54, S-1, V-1, Mysore local, S-13, S-34, and RFS-135 to characterize stomatal size and frequency, trichomes and idioblasts using SEM. These new parameters will provide useful information for cultivars identification as well as for selecting mulberry genotypes adapted to different eco-climatic conditions and assessing the feeding quality of leaf for silkworm rearing.

Electro-enhanced removal of perchlorate ions from aqueous solution using capacitive deionization process

Govindaraj Divyapriya,Keshav V. kumar,Lohita Rajesh,Indumathi M. Nambi 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.89 No.-

The study was performed to understand the feasibility of graphite felt for electro-enhanced removal ofperchlorate ions through capacitive deionization process (CDI) in aqueous solution. The cyclicvoltammetry studies indicated that the perchlorate ions neither get oxidized nor reduced under theoperating conditions for the applied potential range of 1.5 V. The effect of voltage,flow rate, perchlorateconcentration, pH of the solution and temperature on the electrosorption was studied. Theelectrosorption capacity increased with increasing applied potential,flow rate and perchlorateconcentration. The change in pH significantly affected the removal efficiency due to competitive ioniceffect. The increase in temperature had a negative impact on the electrosorption capacity. Langmuirmodel was found to be a betterfit than the Freundlich model and the maximum electrosorption capacitywas found to be 21.1 mg g 1. It was observed that electro-enhanced adsorption followed pseudofirstorder kinetic model with a rate constant of 0.45 min 1 for an initial concentration of 1000 mg L 1operated at 1.5 V. Moreover the graphite felt exhibited good repeatability of the electrosorption processand affinity toward perchlorate ions. Thus it can be concluded that the graphite felt electrode can bepotentially used for electrosorptive removal of perchlorate ions from the aqueous solution.

Reply to ''Comment on ''Facile chemical bath deposition of CuS nano peas like structure as a high efficient counter electrode for quantum-dot-sensitized solar cells'' by H.-J. Kim, J.-H. Kim, CH. S. S. Pavan Kumar, D. Punnoose, S.-K. Kim, C. V. V. M. Gop

Kim, H.J.,Kim, J.H.,Pavan Kumar, C.H.S.S.,Punnoose, D.,Kim, S.K.,Gopi, C.V.V.M.,Rao, S.S. Elsevier Sequoia 2015 Journal of Electroanalytical Chemistry Vol.756 No.-

Influence of rapid thermal annealing on electrical and structural properties of double metal structure Au/Ni/n-InP (1 1 1) diodes

M. Bhaskar Reddy,V. Janardhanam,A. Ashok Kumar,V. Rajagopal Reddy,P. Narasimha Reddy 한국물리학회 2010 Current Applied Physics Vol.10 No.2

The effect of rapid thermal annealing on the electrical and structural properties of Ni/Au Schottky contacts on n-InP have been investigated by current–voltage (I–V), capacitance–voltage (C–V), auger electron spectroscopy (AES) and X-ray diffraction (XRD) techniques. The Au/Ni/n-InP Schottky contacts are rapid thermally annealed in the temperature range of 200–500 ℃ for a duration of 1 min. The Schottky barrier height of as-deposited Ni/Au Schottky contact has been found to be 0.50 eV (I–V) and 0.86 eV (C–V),respectively. It has been found that the Schottky barrier height decreased with increasing annealing temperature as compared to as-deposited sample. The barrier height values obtained are 0.43 eV (I–V),0.72 eV (C–V) for the samples annealed at 200 ℃, 0.45 eV (I–V) and 0.73 eV (C–V) for those at 400 ℃. Further increase in annealing temperature to 500 ℃ the barrier height slightly increased to 0.46 eV (I–V) and 0.78 eV (C–V) compared to the values obtained for the samples annealed at 200 ℃ and 400 ℃. AES and XRD studies showed the formation of indium phases at the Ni/Au and InP interface and may be the reason for the increase in barrier height. The AFM results showed that there is no significant degradation in the surface morphology (rms roughness of 1.56 nm) of the contact even after annealing at 500 ℃.

Current–voltage–temperature (I–V–T) characteristics of Pd/Au Schottky contacts on n-InP (111)

M. Bhaskar Reddy,A. Ashok Kumar,V. Janardhanam,V. Rajagopal Reddy,P. Narasimha Reddy 한국물리학회 2009 Current Applied Physics Vol.9 No.5

We have investigated the current–voltage–temperature (I–V–T) characteristics of Pd/Au/InP Schottky barrier diodes in the temperature range of 220–400 K. The I–V analysis based on thermionic emission (TE) theory shows an abnormal decrease of apparent barrier height and increase of ideality factor at low temperatures. The conventional Richardson plot exhibits nonlinearity with activation energy of 0.17 eV and the Richardson constant value of 5.63 × 10-6 A cm-2 K-2. The nonlinearity in the Richardson plot and strong dependence of Schottky barrier parameters on temperature may be attributed to the spatial inhomogeneity in the interface. Further, the homogeneous barrier height has been obtained from the linear relationship between experimentally obtained effective barrier heights and ideality factors. Φb versus (2kT)-1 plot has been drawn to obtain the mean barrier height [Φbo(T = 0 K)] and the standard deviation (σs) at zero-bias which are found to be 0.84 eV, 138 meV, respectively. The series resistance is also estimated from the forward current–voltage characteristics of Pd/Au/InP Schottky contacts using Cheung’s method and found that it is strongly dependent on temperature and also decreases with increase in temperature. We have investigated the current–voltage–temperature (I–V–T) characteristics of Pd/Au/InP Schottky barrier diodes in the temperature range of 220–400 K. The I–V analysis based on thermionic emission (TE) theory shows an abnormal decrease of apparent barrier height and increase of ideality factor at low temperatures. The conventional Richardson plot exhibits nonlinearity with activation energy of 0.17 eV and the Richardson constant value of 5.63 × 10-6 A cm-2 K-2. The nonlinearity in the Richardson plot and strong dependence of Schottky barrier parameters on temperature may be attributed to the spatial inhomogeneity in the interface. Further, the homogeneous barrier height has been obtained from the linear relationship between experimentally obtained effective barrier heights and ideality factors. Φb versus (2kT)-1 plot has been drawn to obtain the mean barrier height [Φbo(T = 0 K)] and the standard deviation (σs) at zero-bias which are found to be 0.84 eV, 138 meV, respectively. The series resistance is also estimated from the forward current–voltage characteristics of Pd/Au/InP Schottky contacts using Cheung’s method and found that it is strongly dependent on temperature and also decreases with increase in temperature.