Design of ternary hybrid ATO/g-C3N4/TiO2 nanocomposite for visible-light-driven photocatalysis

Devi Prashad Ojha,Hem Prakash Karki,kim han joo 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.61 No.-

Antimony-doped tin oxide (ATO) nanoparticles with an average size of ∼8 nm were prepared by co-precipitation and subsequent heat-treatment. A series of ATO/g-CN/TiO2 composites with various ATO contents were successfully prepared by sol–gel method. The composites were characterized using N2 adsorption/desorption (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). The results indicated that the highest photocatalytic performance is obtained with the incorporation of ATO and g-CN nanoparticles with TiO2. BET surface area, PL spectra, and CV measurements were presented to further study the mechanism of the photoactivity. The superior performance of the ATO/g-CN/TiO2 nanocomposite photocatalyst may be attributed to the high surface area charge-carrier transport medium, a higher carrier transfer rate and lower recombination rate.

WEYL'S THEOREMS FOR POSINORMAL OPERATORS

Bhagwati Prashad Duggal,Carlos Kubrusly 대한수학회 2005 대한수학회지 Vol.42 No.3

An operator T belonging to the algebra B(H) of bound-ed linear transformations on a Hilbert H into itself is said to be posinormal if there exists a positive operator P 2 B(H)such that TT¤ = T¤PT. A posinormal operator T is said to be condi-tionally totally posinormal (resp., totally posinormal), shortened to T 2 CTP (resp., T 2 TP), if to each complex number ¸ there corre-sponds a positive operator P¸ such that j(T¡¸I)¤j2 = jP 1/2¸ (T¡¸I)j2(resp., if there exists a positive operator P such that j(T ¡¸I)¤j2 =jP1/2 (T ¡ ¸I)j2 for all ¸). This paper proves Weyl's theorem type results for TP and CTP operators. If A 2 TP, if B¤ 2 CTP is isoloid and if dAB 2 B(B(H)) denotes either of the elementary op-erators ±AB(X) = AX ¡XB and 4AB(X) = AXB ¡X, then it is proved that dAB satis¯esWeyl's theorem and d¤AB satis¯es a-Weyl's theorem.

UPPER TRIANGULAR OPERATORS WITH SVEP

Bhagwati Prashad Duggal 대한수학회 2010 대한수학회지 Vol.47 No.2

A Banach space operator A ∈ B(X) is polaroid if the isolated points of the spectrum of A are poles of the resolvent of A; A is hereditarily polaroid, A ∈ (HP), if every part of A is polaroid. Let [수식]Xi, where Xi are Banach spaces, and let A denote the class of upper triangular operators A = (Aij )1≤i,j·n, Aij ∈ B(Xj ,Xi) and Aij = 0 for i > j. We prove that operators A ∈ A such that Aii for all 1≤ i · n, and A¤ have the single–valued extension property have spectral properties remarkably close to those of Jordan operators of order n and n-normal operators. Operators A 2 A such that Aii ∈ (HP) for all 1 ≤ i · n are polaroid and have SVEP; hence they satisfy Weyl’s theorem. Furthermore, A + R satisfies Browder’s theorem for all upper triangular operators R, such that [수식] is a Riesz operator, which commutes with A.

Photo-Fenton degradation of organic pollutants using a zinc oxide decorated iron oxide/reduced graphene oxide nanocomposite

Ojha, Devi Prashad,Joshi, Mahesh Kumar,Kim, Han Joo Elsevier 2017 CERAMICS INTERNATIONAL Vol.43 No.1

<P><B>Abstract</B></P> <P>Herein, we report a magnetically-separable tertiary composite, zinc oxide-decorated iron oxide deposited reduced graphene oxide (ZnO-Fe<SUB>3</SUB>O<SUB>4</SUB>/rGO), as a heterogeneous catalyst for photo-Fenton degradation of organic pollutants in aqueous media under ambient conditions. In this study, zinc oxide nanoparticles were hydrothermally deposited on the surface of Fe<SUB>3</SUB>O<SUB>4</SUB>/GO composite that was synthesized by a solvothermal process. The physicochemical properties of the as–synthesized composite were explored using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and photoluminescence (PL) studies. The as-prepared catalyst showed superior stability and, due to the presence of the magnetic Fe<SUB>3</SUB>O<SUB>4</SUB> nanospheres, could be conveniently separated from the reaction system with an external magnet for reuse. The as-synthesized, ZnO-Fe<SUB>3</SUB>O<SUB>4</SUB>/rGO composite exhibited superior catalytic activity for the degradation of azo-dye compared to pristine ZnO, ZnO/Fe<SUB>3</SUB>O<SUB>4</SUB>, Fe<SUB>3</SUB>O<SUB>4</SUB>, and Fe<SUB>3</SUB>O<SUB>4</SUB>/GO. These results revealed the synergistic effects between the different components of the catalyst and confirmed the rapid redox reaction between Fe<SUP>2+</SUP> and Fe<SUP>3+</SUP>. It was also observed that this catalytic behavior could be reproduced in consecutive experiments without a considerable decrease in efficiency. All of these merits indicate that the composite catalyst is a promising candidate for the degradation of organic compounds under visible light in environmental remediation applications.</P>

On Self-commutator Approximants

Duggal, Bhagwati Prashad Department of Mathematics 2009 Kyungpook mathematical journal Vol.49 No.1

Let B(X) denote the algebra of operators on a complex Banach space X, H(X) = {h ${\in}$ B(X) : h is hermitian}, and J(X) = {x ${\in}$ B(X) : x = $x_1$ + $ix_2$, $x_1$ and $x_2$ ${\in}$ H(X)}. Let ${\delta}_a$ ${\in}$ B(B(X)) denote the derivation ${\delta}_a$ = ax - xa. If J(X) is an algebra and ${\delta}_a^{-1}(0){\subseteq}{\delta}_{a^*}^{-1}(0)$ for some $a{\in}J(X)$, then ${\parallel}a{\parallel}{\leq}{\parallel}a-(x^*x-xx^*){\parallel}$ for all $x{\in}J(X){\cap}{\delta}_a^{-1}(0)$. The cases J(X) = B(H), the algebra of operators on a complex Hilbert space, and J(X) = $C_p$, the von Neumann-Schatten p-class, are considered.

UPPER TRIANGULAR OPERATORS WITH SVEP

Duggal, Bhagwati Prashad Korean Mathematical Society 2010 대한수학회지 Vol.47 No.2

A Banach space operator A $\in$ B(X) is polaroid if the isolated points of the spectrum of A are poles of the resolvent of A; A is hereditarily polaroid, A $\in$ ($\mathcal{H}\mathcal{P}$), if every part of A is polaroid. Let $X^n\;=\;\oplus^n_{t=i}X_i$, where $X_i$ are Banach spaces, and let A denote the class of upper triangular operators A = $(A_{ij})_{1{\leq}i,j{\leq}n$, $A_{ij}\;{\in}\;B(X_j,X_i)$ and $A_{ij}$ = 0 for i > j. We prove that operators A $\in$ A such that $A_{ii}$ for all $1{\leq}i{\leq}n$, and $A^*$ have the single-valued extension property have spectral properties remarkably close to those of Jordan operators of order n and n-normal operators. Operators A $\in$ A such that $A_{ii}$ $\in$ ($\mathcal{H}\mathcal{P}$) for all $1{\leq}i{\leq}n$ are polaroid and have SVEP; hence they satisfy Weyl's theorem. Furthermore, A+R satisfies Browder's theorem for all upper triangular operators R, such that $\oplus^n_{i=1}R_{ii}$ is a Riesz operator, which commutes with A.

Design of ternary hybrid ATO/g-C₃N₄/TiO₂ nanocomposite for visible-light-driven photocatalysis

Ojha, Devi Prashad,Karki, Hem Prakash,Kim, Han Joo THE KOREAN SOCIETY OF INDUSTRIAL AND ENGINEERING 2018 Journal of Industrial and Engineering Chemistry Vol.61 No.-

<P><B>Abstract</B></P> <P>Antimony-doped tin oxide (ATO) nanoparticles with an average size of ∼8nm were prepared by co-precipitation and subsequent heat-treatment. A series of ATO/g-CN/TiO<SUB>2</SUB> composites with various ATO contents were successfully prepared by sol–gel method. The composites were characterized using N<SUB>2</SUB> adsorption/desorption (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). The results indicated that the highest photocatalytic performance is obtained with the incorporation of ATO and g-CN nanoparticles with TiO<SUB>2</SUB>. BET surface area, PL spectra, and CV measurements were presented to further study the mechanism of the photoactivity. The superior performance of the ATO/g-CN/TiO<SUB>2</SUB> nanocomposite photocatalyst may be attributed to the high surface area charge-carrier transport medium, a higher carrier transfer rate and lower recombination rate.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Amine-assisted synthesis of FeWO₄ nanorodg-C₃N₄ for enhanced visible light-driven Z-scheme photocatalysis

Ojha, Devi Prashad,Karki, Hem Prakash,Song, Jun Hee,Kim, Han Joo Elsevier 2019 Composites Part B, Engineering Vol.160 No.-

<P><B>Abstract</B></P> <P>Highly crystalline FeWO<SUB>4</SUB> nanorods (FWO NRs) were prepared using an amine in a hydrothermal reaction. A photocatalyst active to visible light was designed by preparing 5FWO/g-CN heterostructures via in-situ hydrothermal methods. Fabricated heterostructures were analyzed using X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), BET measurements, transmission electron microscopy (TEM), X-ray photoelectron microscopy (XPS), and Fourier transform spectroscopy (FTIR). The photocatalytic activity toward the degradation of salicylic acid (SA) was investigated under visible light irradiation. The active species trapping experiments showed that the holes, as well as the electrons, exhibited an obvious influence on the photocatalytic degradation process. Examinations of the mechanism showed that the enhanced photocatalytic activity was mainly ascribed to reduced recombination rate and band gap broadening in a Z-scheme mechanism, which enhance the efficient transfer and the oxidation potential of the holes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Wolframite-type FeWO<SUB>4</SUB> nanorod was synthesized hydrothermally using triethanolamine. </LI> <LI> Photodegradation of salicylic acid was enhanced by FeWO<SUB>4</SUB>/g-C<SUB>3</SUB>N<SUB>4</SUB> heterostructure. </LI> <LI> Predominant active species were identified by using scavengers. </LI> <LI> Z-scheme photodegradation mechanism was suggested. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

WEYL@S THEOREMS FOR POSINORMAL OPERATORS

DUGGAL BHAGWATI PRASHAD,KUBRUSLY CARLOS Korean Mathematical Society 2005 대한수학회지 Vol.42 No.3

An operator T belonging to the algebra B(H) of bounded linear transformations on a Hilbert H into itself is said to be posinormal if there exists a positive operator $P{\in}B(H)$ such that $TT^*\;=\;T^*PT$. A posinormal operator T is said to be conditionally totally posinormal (resp., totally posinormal), shortened to $T{\in}CTP(resp.,\;T{\in}TP)$, if to each complex number, $\lambda$ there corresponds a positive operator $P_\lambda$ such that $|(T-{\lambda}I)^{\ast}|^{2}\;=\;|P_{\lambda}^{\frac{1}{2}}(T-{\lambda}I)|^{2}$ (resp., if there exists a positive operator P such that $|(T-{\lambda}I)^{\ast}|^{2}\;=\;|P^{\frac{1}{2}}(T-{\lambda}I)|^{2}\;for\;all\;\lambda)$. This paper proves Weyl's theorem type results for TP and CTP operators. If $A\;{\in}\;TP$, if $B^*\;{\in}\;CTP$ is isoloid and if $d_{AB}\;{\in}\;B(B(H))$ denotes either of the elementary operators $\delta_{AB}(X)\;=\;AX\;-\;XB\;and\;\Delta_{AB}(X)\;=\;AXB\;-\;X$, then it is proved that $d_{AB}$ satisfies Weyl's theorem and $d^{\ast}_{AB}\;satisfies\;\alpha-Weyl's$ theorem.

Decoration of g-C₃N₄ with hydrothermally synthesized FeWO₄ nanorods as the high-performance supercapacitors

Ojha, Devi Prashad,Karki, Hem Prakash,Song, Jun hee,Kim, Han Joo Elsevier 2018 Chemical physics letters Vol.712 No.-

<P><B>Abstract</B></P> <P>Highly crystalline FeWO<SUB>4</SUB> nanorods (FWO NRs) prepared by a hydrothermal reaction is combined with g-C<SUB>3</SUB>N<SUB>4</SUB> (gCN) nanosheet as an electrode material for the supercapacitor. Fabricated nanocomposites were analysed using X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM), X-ray photoelectron microscopy (XPS), and Raman Spectroscopy. Pseudocapacitive performance of the FWO/gCN nanocomposite was evaluated by cyclic voltammetry (CV), electrochemical impedance and galvanometric experiments in an alkaline medium. Thus FWO/gCN nanocomposite exhibited a high specific capacitance of 357 F g<SUP>−1</SUP> at 5 mV s<SUP>−1</SUP> and demonstrated a superior long-term cyclic stability, with the specific capacitance retention of about 80% after 1000 cycles.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The g-C<SUB>3</SUB>N<SUB>4</SUB> decorated FeWO<SUB>4</SUB> nanorod was synthesized by in-situ hydrothermal method. </LI> <LI> High surface area and low aggregation enabled fast diffusion of ion and electrons. </LI> <LI> The electrical conductivity of low cost, abundant FeWO<SUB>4</SUB> is improved with g-C<SUB>3</SUB>N<SUB>4</SUB>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>