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>

Hydrogen Peroxide-induced Alterations in Na+-phosphate Cotransport in Renal Epithelial Cells

정순희 대한임상검사과학회 2009 대한임상검사과학회지(KJCLS) Vol.41 No.2

This study was undertaken to examine the effect of oxidants on membrane transport function in renal epithelial cells. Hydrogen peroxide (H2O2) was used as a model oxidant and the membrane transport function was evaluated by measuring Na+-dependent phosphate (Na+-Pi) uptake in opossum kidney (OK) cells. H2O2 inhibited Na+-Pi uptake in a dose-dependent manner. The oxidant also caused loss of cell viability in a dose-dependent fashion. However, the extent of inhibition of the uptake was larger than that in cell viability. H2O2 inhibited Na+-dependent uptake without any effect on Na+-independent uptake. H2O2-induced inhibition of Na+-Pi uptake was prevented completely by catalase, dimethylthiourea, and deferoxamine, suggesting involvement of hydroxyl radical generated by an iron-dependent mechanism. In contrast, antioxidants Trolox, N,N’-diphenyl-p-phenylenediamine, and butylated hydroxyanisole did not affect the H2O2 inhibition. Kinetic analysis indicated that H2O2 decreased Vmax of Na+-Pi uptake with no change in the Km value. Phosphonoformic acid binding assay did not show any difference between control and H2O2-treated cells. H2O2 also did not cause degradation of Na+-Pi transporter protein. Reduction in Na+-Pi uptake by H2O2 was associated with ATP depletion and direct inhibition of Na+-K+-ATPase activity. These results indicate that the effect of H2O2 on membrane transport function in OK cells is associated with reduction in functional Na+-pump activity. In addition, the inhibitory effect of H2O2 was not associated with lipid peroxidation. .

Hydrogen Peroxide-induced Alterations in Na⁺-phosphate Cotransport in Renal Epithelial Cells

Jung, Soon-Hee Korean Society for Clinical Laboratory Science 2009 대한임상검사과학회지(KJCLS) Vol.41 No.2

This study was undertaken to examine the effect of oxidants on membrane transport function in renal epithelial cells. Hydrogen peroxide ($H_2O_2$) was used as a model oxidant and the membrane transport function was evaluated by measuring $Na^+$-dependent phosphate ($Na^+$-Pi) uptake in opossum kidney (OK) cells. $H_2O_2$ inhibited $Na^+$-Pi uptake in a dose-dependent manner. The oxidant also caused loss of cell viability in a dose-dependent fashion. However, the extent of inhibition of the uptake was larger than that in cell viability. $H_2O_2$ inhibited $Na^+$-dependent uptake without any effect on $Na^+$-independent uptake. $H_2O_2$-induced inhibition of $Na^+$-Pi uptake was prevented completely by catalase, dimethylthiourea, and deferoxamine, suggesting involvement of hydroxyl radical generated by an iron-dependent mechanism. In contrast, antioxidants Trolox, N,N'-diphenyl-p-phenylenediamine, and butylated hydroxyanisole did not affect the $H_2O_2$ inhibition. Kinetic analysis indicated that $H_2O_2$ decreased Vmax of $Na^+$-Pi uptake with no change in the Km value. Phosphonoformic acid binding assay did not show any difference between control and $H_2O_2$-treated cells. $H_2O_2$ also did not cause degradation of $Na^+$-Pi transporter protein. Reduction in $Na^+$-Pi uptake by $H_2O_2$ was associated with ATP depletion and direct inhibition of $Na^+$-$K^+$-ATPase activity. These results indicate that the effect of $H_2O_2$ on membrane transport function in OK cells is associated with reduction in functional $Na^+$-pump activity. In addition, the inhibitory effect of $H_2O_2$ was not associated with lipid peroxidation.

Controlled phase stability of highly Na-active triclinic structure in nanoscale high-voltage Na_2-2xCo_1+xP₂O₇ cathode for Na-ion batteries

Song, Hee Jo,Kim, Jae-Chan,Dar, Mushtaq Ahmad,Kim, Dong-Wan Elsevier 2018 Journal of Power Sources Vol.377 No.-

<P><B>Abstract</B></P> <P>With the increasing demand for high energy density in energy-storage systems, a high-voltage cathode is essential in rechargeable Li-ion and Na-ion batteries. The operating voltage of a triclinic-polymorph Na<SUB>2</SUB>CoP<SUB>2</SUB>O<SUB>7</SUB>, also known as the rose form, is above 4.0 V (vs. Na/Na<SUP>+</SUP>), which is relatively high compared to that of other cathode materials. Thus, it can be employed as a potential high-voltage cathode material in Na-ion batteries. However, it is difficult to synthesize a pure rose phase because of its low phase stability, thus limiting its use in high-voltage applications. Herein, compositional-engineered, rose-phase Na<SUB>2-2x</SUB>Co<SUB>1+x</SUB>P<SUB>2</SUB>O<SUB>7</SUB>/C (x = 0, 0.1 and 0.2) nanopowder are prepared using a wet-chemical method. The Na<SUB>2-2x</SUB>Co<SUB>1+x</SUB>P<SUB>2</SUB>O<SUB>7</SUB>/C cathode shows high electrochemical reactivity with Na ions at 4.0 V, delivering high capacity and high energy density.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The synthetic condition of metastable Na<SUB>2-2x</SUB>Co<SUB>1+x</SUB>P<SUB>2</SUB>O<SUB>7</SUB> rose phase is established. </LI> <LI> Rose is synthesized in Na<SUB>2-2x</SUB>Co<SUB>1+x</SUB>P<SUB>2</SUB>O<SUB>7</SUB>/C nanocomposite in the wide Na/Co ranges. </LI> <LI> Na<SUB>2-2x</SUB>Co<SUB>1+x</SUB>P<SUB>2</SUB>O<SUB>7</SUB>/C exhibits a long plateau in high-voltage range with a 90 mA h g<SUP>−1</SUP>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

1D-Na₂Ti₆O₁₃ 합성 변수에 따른 미세구조 및 밴드 갭 에너지 변화

윤강섭,구혜경,강우승,김선재,Yun, Kang-Seop,Ku, Hye-Kyung,Kang, Woo-Seung,Kim, Sun-Jae 한국전기전자재료학회 2012 전기전자재료학회논문지 Vol.25 No.8

Nano-structured one-dimensional $Na_2Ti_6O_{13}$ particles were synthesized by a molten salt process. Effects of processing parameters on the microstructure and band gap energy of the $Na_2Ti_6O_{13}$ powder were studied in this paper. For the synthesis of the $Na_2Ti_6O_{13}$ particles, two different raw materials of tubular shaped Na-titanate (Na-TiNT) and spherical shaped $TiO_2$ were utilized. Synthesizing with the raw material of Na-TiNT, around 70nm thick 1D-$Na_2Ti_6O_{13}$ with the bandgap energy of 3.5 eV was obtained at $810^{\circ}C$. Below $810^{\circ}C$ or without the presence of NaCl, 1D-$Na_2Ti_6O_{13}$ was in a relatively short in length and agglomerated state. With the processing temperature increased, the thickness of the 1D-$Na_2Ti_6O_{13}$ was also observed to be increased. On the other hand, when $TiO_2$ was employed as a raw material, the mixed amount of $Na_2CO_3$ played an important role in transforming the morphology and phase of the raw material, affecting the bandgap energy of the synthesized product. Specific surface area of the synthesized 1D-$Na_2Ti_6O_{13}$ was significantly affected by the raw and mixed materials as well as processing temperature. When Na-TiNT was processed at $810^{\circ}C$ with NaCl, the specific surface area of the 1D-$Na_2Ti_6O_{13}$ showed the best value of 30.63 $m^2/g$.

Na₂B₄O₇·10H₂O/Na₂B₄O₇·5H₂O 계의 열분해 탈수반응 및 내구성 고찰

최호상,박영태,Choi, Ho-Sang,Park, Young-Tae 한국공업화학회 1999 공업화학 Vol.10 No.6

본 연구에서는 $Na_2B_4O_7{\cdot}10H_2O/Na_2B_4O_7{\cdot}5H_2O$ 반응계의 열분해 탈수반응에 의한 반응속도상수를 결정하고 반응계의 재현성 및 화학축열재의 반복사용에 따른 내구성을 검토하였다. 반응계의 열분해 탈수반응의 차수는 1차이었고, 열분해 탈수 반응속도는 수증기의 분압차에 정비례하였다. 반응계의 반응속도상수는 약 0.27이었고, 반응속도상수와 반응차수에 대한 반응의 재현성이 우수하였다. 또한 화학축열재의 내구성은 연속적으로 반복 사용하여도 활성변화는 ${\pm}5%$ 범위 내에 있었다. This study was carried out to determine the reaction kinetic constant of the dehydration - thermal decomposition of $Na_2B_4O_7{\cdot}10H_2O/Na_2B_4O_7{\cdot}5H_2O$ and to investigate the durability during the repeated use of a chemical heat-storage material and the reproducibility of reaction system. The order of the dehydration reaction was 1st-order. The reaction rate was directly proportional to a partial pressure difference of water steam. The kinetic constant was 0.27 and the reproducibility of dehydration reaction for a kinetic constant and a reaction order was excellent. The activity variation in the durability test of a chemical heat-storage material was within range of ${\pm}5%$ during the repeatedly use in several times.

Hydrogen Peroxide-induced Alterations in Na+-phosphate Cotransport in Renal Epithelial Cells

( Soon-hee Jung ) 대한임상검사과학회 2009 대한임상검사과학회지(KJCLS) Vol.41 No.2

This study was undertaken to examine the effect of oxidants on membrane transport function in renal epithelial cells. Hydrogen peroxide (H2O2) was used as a model oxidant and the membrane transport function was evaluated by measuring Na+-dependent phosphate (Na+-Pi) uptake in opossum kidney (OK) cells. H2O2 inhibited Na+-Pi uptake in a dose-dependent manner. The oxidant also caused loss of cell viability in a dose-dependent fashion. However, the extent of inhibition of the uptake was larger than that in cell viability. H2O2 inhibited Na+-dependent uptake without any effect on Na+-independent uptake. H2O2-induced inhibition of Na+-Pi uptake was prevented completely by catalase, dimethylthiourea, and deferoxamine, suggesting involvement of hydroxyl radical generated by an iron-dependent mechanism. In contrast, antioxidants Trolox, N,N’-diphenyl-p-phenylenediamine, and butylated hydroxyanisole did not affect the H2O2 inhibition. Kinetic analysis indicated that H2O2 decreased Vmax of Na+-Pi uptake with no change in the Km value. Phosphonoformic acid binding assay did not show any difference between control and H2O2-treated cells. H2O2 also did not cause degradation of Na+-Pi transporter protein. Reduction in Na+-Pi uptake by H2O2 was associated with ATP depletion and direct inhibition of Na+-K+-ATPase activity. These results indicate that the effect of H2O2 on membrane transport function in OK cells is associated with reduction in functional Na+-pump activity. In addition, the inhibitory effect of H2O2 was not associated with lipid peroxidation.

Efficient degradation of methylene blue dye by catalytic oxidation using the Na_8Nb_6O_19.13H_2O/H_2O-2 system

Chengtang Liu,Huaming Li,Hui Xu,Ling Liu,Li Xu,Zhixiang Ye 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.4

Na_8Nb_6O_19.13H_2O particles were synthesized by a simple hydrothermal method. The catalysts were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and thermogravimetric and differential scanning (TG-DSC). The XRD and TG-DSC analyses indicated that Na_8Nb_6O_19.13H-2O was an intermediate hexaniobate during the preparation of NaNbO_3 powders. Methylene blue (MB) dye degradation using Na_8Nb_6O_19.13H_2O/H_2O_2,Nb_2O_5/H_2O_2 and NaNbO_3/H_2O_2 systems were investigated, respectively. Among the catalytic oxidation systems, Na_8Nb_6O_19·13H_2O showed the highest activity for degradation of MB in the presence of H_2O_2. The results indicated that the dye degradation efficiency could be 93.5% at 30 ℃ after 60 min in the presence of the Na_8Nb_6O_19·13H_2O/H_2O-2 system. It was also found that the degradation of MB over the catalytic systems followed pseudo-first-order kinetics, and the degradation rate was 0.02376 min−1 in the Na_8Nb_6O_19.13H_2O/H_2O_2 system, which was higher than that in the Nb_2O_5/H_2O_2and NaNbO_3/H_2O_2 systems. A possible mechanism for MB catalytic oxidation degradation using the Na_8Nb_6O_19.13H-2O/H_2O_2 system was proposed.

Layered Na_2/3Ni_1/3Mn_2/3O₂ as electrode material with two redox active transition metals for high performance supercapacitor

Nti, Frederick,Han, Jeong In Elsevier 2017 JOURNAL OF ALLOYS AND COMPOUNDS Vol.728 No.-

<P><B>Abstract</B></P> <P>In this work, simple solid state method was employed to synthesize Na<SUB>2/3</SUB>Ni<SUB>1/3</SUB>Mn<SUB>2/3</SUB>O<SUB>2</SUB> which has two redox active transition metals. The electrochemical performance of the material was studied in a three electrode system with 1 M KOH aqueous solution as electrolyte, Hg/HgO as reference electrode and platinum wire as the counter electrode. Na<SUB>2/3</SUB>Ni<SUB>1/5</SUB>Mn<SUB>4/5</SUB>O<SUB>2</SUB> and Na<SUB>2/3</SUB>MnO<SUB>2</SUB> were also synthesized and used as control experiments to study the contribution of Ni in the complex. Our results confirmed that doping the base material (Na<SUB>2/3</SUB>MnO<SUB>2</SUB>) with an active mass of Ni increases the supercapacitive properties of the resulting material as a result of the multiple redox active sites offered by the two transition elements (Ni and Mn). Thus, the Na<SUB>2/3</SUB>Ni<SUB>1/3</SUB>Mn<SUB>2/3</SUB>O<SUB>2</SUB> sample showed a specific capacitance of 532.121 F/g at a current density of 0.5 A/g while Na<SUB>2/3</SUB>Ni<SUB>1/5</SUB>Mn<SUB>4/5</SUB>O<SUB>2</SUB> and Na<SUB>2/3</SUB>MnO<SUB>2</SUB> samples showed specific capacitance of 283.50 F/g and 210.29 F/g respectively at a current density 0.5 A/g. Na<SUB>2/3</SUB>Ni<SUB>1/3</SUB>Mn<SUB>2/3</SUB>O<SUB>2</SUB> also retained about 79% of its initial capacitance after 3000 cycles at 1.3 A/g.</P> <P><B>Highlights</B></P> <P> <UL> <LI> First application of sodium based material with two redox active transition metals in supercapacitors. </LI> <LI> Simple and scalable solid state synthesis method used. </LI> <LI> Performance of Na<SUB>2/3</SUB>MnO<SUB>2</SUB> is improved by doping Ni to form Na<SUB>1</SUB>/<SUB>5</SUB>Ni<SUB>1/3</SUB>Mn<SUB>4/5</SUB>O<SUB>2</SUB> and Na<SUB>2</SUB>/<SUB>3</SUB>Ni<SUB>1/3</SUB>Mn<SUB>2/3</SUB>O<SUB>2</SUB>. </LI> <LI> The influence of Ni doping in Na<SUB>2/3</SUB>MnO<SUB>2</SUB> is explored. </LI> <LI> Na<SUB>2</SUB>/<SUB>3</SUB>Ni<SUB>1/3</SUB>Mn<SUB>2/3</SUB>O<SUB>2</SUB> is a promising electrode material for supercapacitor application. </LI> </UL> </P>

생분해성 Calcium Metaphosphate골이식재의 골조직재생효과에 관한 연구

채한승,이용무,양승민,천성수,김석영,구영,정종평,한수부,최상묵,류인철,Chae, Han-seung,Lee, Yong-Moo,Yang, Seung-Min,Chun, Sung-Soo,Kim, Suk-Young,Ku, Young,Choung, Chong-Pyoung,Han, Soo-Boo,Choi, Sang-Mook,Rhyu, In-Chul 대한치주과학회 2003 Journal of Periodontal & Implant Science Vol.33 No.1

Periodontal regeneration therapy with bone-substituting materials has gained favorable clinical efficacy by enhancing osseous regeneration in periodontal bony defect. As bone-substituting materials, bone powder, calcium phosphate ceramic, modified forms of hydroxyapatite, and hard tissue replacement polymer have demonstrated their periodontal bony regenerative potency. Bone-substituting materials should fulfill several requirements such as biocompatibility, osteogenecity, malleability, biodegradability. The purpose of this study was to investigate biocompatibility, osteo-conduction capacity and biodegradability of $Na_2O$, $K_2O$ added calcium metaphosphate(CMP). Beta CMP was obtained by thermal treatment of anhydrous $Ca_2(H_2PO_4)_2$. $Na_2O$ and $K_2O$ were added to CMP. The change of weight of pure CMP, $Na_2O$-CMP, and $K_2O$-CMP in Tris-buffer solution and simulated body fluid for 30 days was measured. Twenty four Newzealand white rabbits were used in negative control, positive control(Bio-Oss), pure CMP group, 5% $Na_2$-CMP group, 10% $Na_2O$-CMP goup, and 5% $K_2O$-CMP group. In each group, graft materials were placed in right and left parietal bone defects(diameter 10mm) of rabbit. The animals were sacrificed at 3 months and 6 months after implantation of the graft materials. Degree of biodegradability of $K_2O$ or $Na_2O$ added CMP was greater than that of pure CMP in experimental condition. All experimental sites were healed with no clinical evidence of inflammatory response to all CMP implants. Histologic observations revealed that all CMP grafts were very biocompatible and osseous conductive, and that in $K_2O$-CMP or $Na_2O$-CMP implanted sites, there was biodegradable pattern, and that in site of new bone formation, there was no significant difference between all CMP group and DPBB(Bio-Oss) group. From this result, it was suggested that all experimental CMP group graft materials were able to use as an available bone substitution.