Influence of rare earth elements on porosity controlled synthesis of MnO₂ nanostructures for supercapacitor applications

Rajagopal, Rajesh,Ryu, Kwang-Sun Pergamon Press 2018 Electrochimica Acta Vol. No.

<P><B>Abstract</B></P> <P>Nanostructured MnO<SUB>2</SUB> was synthesized using a facile hydrothermal technique with potassium permanganate as a precursor. Rare earth elements, lanthanum and cerium, were used to control the porosity of the MnO<SUB>2</SUB> nanostructures. Nanorod-, nanoflower-, nanoneedle-, and nanoneedles/nanopetal-shaped MnO<SUB>2</SUB> nanostructures were synthesized by changing the concentration of the rare earth elements. The as-synthesized MnO<SUB>2</SUB> nanorods, La – MnO<SUB>2</SUB> nanoneedles, Ce – MnO<SUB>2</SUB> nanoflowers, and La/Ce – MnO<SUB>2</SUB> nanoneedles/nanopetals were examined using a range of physico chemical characterization techniques. Scanning electron microscopy and transmission electron microscopy – energy dispersive X-ray spectroscopy confirmed the morphology of the MnO<SUB>2</SUB> nanostructures and the elemental distribution. The porous natures of the synthesized MnO<SUB>2</SUB> nanostructures were analyzed by nitrogen adsorption technique. The electrochemical behavior of the MnO<SUB>2</SUB> nanostructures was examined by cyclic voltammetry, charge – discharge and electrochemical impedance spectroscopy tests. The La/Ce – MnO<SUB>2</SUB> nanoneedles/nanopetals electrode exhibited a high specific capacitance of 825 F g<SUP>−1</SUP> at an applied current density of 10 A g<SUP>−1</SUP>. The La/Ce – MnO<SUB>2</SUB> nanoneedles/nanopetals were also mixed with 5, 10, 15 and 20 wt% of rGO nanosheets to enhance the electrochemical behavior. The 20 rGO@La/Ce – MnO<SUB>2</SUB> sample showed extraordinary electrochemical behavior; the calculated specific capacitance was 1165 F g<SUP>−1</SUP> at an applied current density of 10 A g<SUP>−1</SUP>. A 20 rGO@La/Ce – MnO<SUB>2</SUB> and activated carbon asymmetric supercapacitor coin cell device exhibited ∼93% capacitance retention after 1000 cycles. These results highlight the potential of 20 rGO@La/Ce – MnO<SUB>2</SUB> as an electrode material for supercapacitor applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Manganese oxide nanostructures were synthesized by hydrothermal process. </LI> <LI> Lanthanum and cerium used to control the porosity of manganese oxide. </LI> <LI> La/Ce mixed MnO<SUB>2</SUB> nanoneedles/nanopetals showing good electrochemical behavior. </LI> <LI> rGO mixed La/Ce – MnO<SUB>2</SUB> was prepared to improve the storage capacity. </LI> <LI> 20rGO@ La/Ce – MnO<SUB>2</SUB> electrode exhibited high specific capacitance of 1165 F g<SUP>−1</SUP>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Growth of ZnO nanoneedles on silicon substrate by cyclic feeding chemical vapor deposition: Structural and optical properties

Yoon-Bong Hahn,Suk Lee,우마르아메드,Sang Hoon Kim,N. Koteeswara Reddy 한국화학공학회 2007 Korean Journal of Chemical Engineering Vol.24 No.6

vapor deposition (CFCVD) process using diethyl zinc and oxygen as precursors for zinc and oxygen, respectively. Mor-phological investigations revealed that the as-grown nanoneedles exhibited sharpened tips and wider bases, having thetypical diameters at their bases and tips, 6010 nm and 2010 nm, respectively. Detailed structural characterizationsconfirmed that the as-grown products were single crystalline with a wurtzite hexagonal phase and were grown pre-ferentially along the [0001] direction. The room-temperature photoluminescence (PL) spectrum showed a strong andsharp UV emission at 378 nm with a very weak, suppressed and broad green emission at 520 nm, substantiating goodoptical properties for the as-grown ZnO nanoneedles.

HVPE 방법으로 성장시킨 수직하게 나열된 GaN 나노 바늘의 원자배열과 성장 방위

이하영,전인준,노지연,임경원,안형수,이삼녕,신기삼,전헌수,신민정,유영문 한국물리학회 2017 New Physics: Sae Mulli Vol.67 No.1

Low-dimensional GaN nanoneedles were grown on GaN/Si(111) by using HVPE (hydride vapor phase epitaxy), and the initial growth morphologies were analyzed. The nanoneedles were grown with a HCl:NH$_3$ gas flow ratio of 1:38 at 600 $^\circ$C for 5, 10, and 60 min. The atomic arrangements and the orientational relationships between the substrate and the GaN nanoneedles were investigated by using FE-SEM (field-emission scanning electron microscopy), HR-TEM (high-resolution transmission electron microscopy), and X-ray pole figure measurements. For the sample grown for 10 min, most of the nanoneedles were grown in the [0001] direction along the growth axis with single-crystalline structures, but a few GaN nanoneedles were partially tilted. Vertically-aligned Growth is known to depend on the roughness of the substrate, the uniformity of the gas flow, and the temperature. Among them, we observed that the tilting was caused by the roughness of the substrate. 본 연구에서는 GaN/Si(111) 기판 위에 HVPE(hydride vapor phase epitaxy) 장비를 이용하여 GaN 나노 바늘을 성장시키고, 초기성장시의 원자배열과 기판에 대한 나노 바늘의 수직성장 정도를 살펴 보았다. 기판은 600 $^\circ$C 영역에 위치시켰으며 HCl:NH$_3$ 유량비는 1:38인 조건에서 GaN 나노 바늘을 5분, 10분 및 60분간 성장시켰다. 성장된 GaN 나노 바늘의 표면과 단면 형상은 FE-SEM (field emission scanning electron microscopy)으로, 단결정 구조는 HR-TEM (high resolution transmission electron microscopy)으로, 그리고 기판에 대한 나노 바늘의 방위는 X-ray 극점도 측정으로부터 분석하였다. 그 결과 (0002) 면 사이의 거리가 0.25 nm 를 가진 단결정 형태의 GaN 나노 바늘이 성장 되었음을 볼 수 있었고 10분간 성장 된 샘플에서는 나노 바늘의 일부가 수직방향으로부터 약간 기울어진 형태로 성장이 됨을 관찰 할 수 있었다. 이는 표면 거칠기, 반응가스와 캐리어 가스의 균일하지 않은 흐름, 온도 등의 원인에 의해 발생 되는데 본 실험에서는 표면 거칠기에 의한 기울기를 관찰할 수 있었다.

Hierarchical copper selenide nanoneedles grown on copper foil as a binder free electrode for supercapacitors

Pazhamalai, P.,Krishnamoorthy, K.,Kim, S.J. Pergamon Press ; Elsevier Science Ltd 2016 International journal of hydrogen energy Vol.41 No.33

<P>In this communication, we demonstrated the use of CuSe2 nanoneedles grown on copper foil as a binder-free electrode for supercapacitors. Studies using X-ray diffraction, laser Raman spectroscopy and field emission scanning electron microscopy confirmed the formation of crystalline CuSe2 nanoneedles on the surface of copper foil. Cyclic voltammetry and electrochemical impedance spectroscopy revealed the pseudocapacitive nature of the CuSe2/Cu electrode. The galvanostatic charge discharge analysis showed that the CuSe2/Cu binder-free electrode delivered a high specific capacitance of about 1037.5 F/g at a constant current density of 0.25 mA/cm(2). (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.</P>

Formation of hydroxyapatite nanoneedles on the surface of a novel calcium phosphate/blood plasma proteins biocement in simulated body fluid (SBF)

Mahdi Rezvannia,Fathollah Moztarzadeh,Mohammadreza Tahriri 한양대학교 세라믹연구소 2009 Journal of Ceramic Processing Research Vol.10 No.5

In this study, we report on needle-like hydroxyapatite grown on the surface of calcium phosphate/blood plasma proteins biocement in simulated body fluid (SBF). Scanning electron microscope revealed the formation of nano-sized needle-like hydroxyapatite crystals on the surface of the biocement after 7 days immersion in the simulated body fluid. X-ray diffraction analysis of the biocement structures indicated that the nanoneedle crystals were hydroxyapatite. Finally Fourier transform infra-red investigations were employed to detect the functional groups of the biocement which this technique demonstrated to be hydroxyapatite. In this study, we report on needle-like hydroxyapatite grown on the surface of calcium phosphate/blood plasma proteins biocement in simulated body fluid (SBF). Scanning electron microscope revealed the formation of nano-sized needle-like hydroxyapatite crystals on the surface of the biocement after 7 days immersion in the simulated body fluid. X-ray diffraction analysis of the biocement structures indicated that the nanoneedle crystals were hydroxyapatite. Finally Fourier transform infra-red investigations were employed to detect the functional groups of the biocement which this technique demonstrated to be hydroxyapatite.

Room temperature synthesis of high purity 2D ZnO nanoneedles

E. J. A. Campo,A. C. Caballero,M. Villegas,J. E. Rodríguez-Páez,M. Peiteado 한양대학교 세라믹연구소 2009 Journal of Ceramic Processing Research Vol.10 No.4

Current technological requirements demand ZnO particles of controlled morphology, distribution and size. The achievement of such specific conditions cannot be guaranteed with conventional synthesis routes and new techniques should be applied to attain this goal. In the present contribution we prove that the controlled precipitation method (CPM) could be successfully applied to obtain high purity 2D zinc oxide nanoparticles with needle-type morphology. By using the appropriate precursors and washing medium, the synthesis could be achieved at room temperature without any additional thermal treatment required. Current technological requirements demand ZnO particles of controlled morphology, distribution and size. The achievement of such specific conditions cannot be guaranteed with conventional synthesis routes and new techniques should be applied to attain this goal. In the present contribution we prove that the controlled precipitation method (CPM) could be successfully applied to obtain high purity 2D zinc oxide nanoparticles with needle-type morphology. By using the appropriate precursors and washing medium, the synthesis could be achieved at room temperature without any additional thermal treatment required.

Facile Atmospheric Generation of Water Radical Cations via TiO2-Nanoneedle Arrays for Aromatic Hydrocarbon Detection Based on Corona Discharge

Dongbo Mi,Jinhaojie Cui,Siliang Kuang,Xiaofeng Dong,Haiyan Lu 대한화학회 2021 Bulletin of the Korean Chemical Society Vol.42 No.3

Water radical cations, (H2O)n+?, have attracted considerable attention owing to their potential practical applications in analytical chemistry, structural chemistry, radiotherapy, and radiochemistry. Recently, atmospheric pressure chemical ionization has emerged as a versatile method for direct mass spectrometric analysis. Usually, H3O+ is the major proton donor during ionization and only the pseudo molecular ion peaks, instead of molecular ions are detected. In this work, (H2O)2+? ions with high oxidizability and reactivity were generated using hydrothermally grown TiO2 nanoneedle arrays in combination with a linear ion trap mass spectrometer under low operating voltage and applied to the direct mass spectrometric analysis of a mixture of volatile aromatic hydrocarbons. (H2O)2+? ions were generated with a high absolute ion current of up to 1.07???105?counts/s at atmospheric pressure. Using the generated (H2O)2+? as the primary ion permitted the tandem mass spectrometric analysis of a mixed vapor sample of aromatic hydrocarbons.

Medium constituents mediated engineering for size and shape tuning of gold nanocrystallites

Anil K. Suresh,Veena Vijay,Bahrudeen S. Hameed,Sureshkumar Ramasamy,Natarajan Sakthivel 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.51 No.-

The current investigation introduces the utilization of cell culture mediums as a novel source for the oneplotsynthesis as well as stabilization of metal nanoparticles. By varying the medium constituents wecould control the size and shape distributions of the gold nanoparticles. Nanospheres of diameter24 6 nm and 19 5 nm were produced using DMEM and M199 mediums respectively, nanoneedles of150 50 nm using RPMI medium and nanoflowers of 60 25 nm using IMDM medium, with an overallyield of 91 2%. A remarkable decrease in the reaction duration (<3 min) was noted, irrespective of thegrowth mediums used. Fourier transform infrared spectroscopy and zeta potential measurementsrevealed them to have a common protenacious encapping agent with different overall surface charges of23 3,211,24 2, and20 1 mV for Au@DMEM, Au@RPMI, Au@IMDM andAu@M199 respectively. X-ray diffraction confirmed the purity and crystallinity of the particles withBragg peaks at (111), (200), (220) and (311) for gold nanocrystals. This approach could lead to the creativeutilization of novel eco-friendly sources for the production and size/shape control of nanoparticles. Moreover, the adopted methodology is absolutely green, robust and facile, offering new insights forsustainable synthesis for various biomedical and engineering applications.

Nanoneedle-structured Anode Catalyst for Low-Temperature Proton Exchange Membrane Fuel Cells

Padmini Basumatary,Dimpul Konwar,윤영수 대한화학회 2019 Bulletin of the Korean Chemical Society Vol.40 No.6

A new state-of-the-art NiMnCo anode co-catalyst has been prepared and investigated with the aim of reducing dependence on expensive Pt catalysts in hydrogen-based fuel cells. The as-prepared co-catalyst exhibited a three dimensional (3D) nanoneedle structure, which was observed using transmission electron microscopy. Pt nanoparticles (approximately 10 wt %) were deposited on the surface of the 3D NiMnCo nanoneedles to further increase their electrocatalytic activity, and the performance of membrane-electrode-assemblies based on the Pt@NiMnCo and NiMnCo anode catalysts was evaluated. The peak power densities of the Pt@NiMnCo- and NiMnCo- based fuel cells were found to be 352.64 and 299.78?mW/cm2, respectively, at 80 °C. Furthermore, the Pt@NiMnCo nanoneedle catalyst exhibited a power density slightly lower than that of a commercial Pt/C (40?wt% Pt) catalyst at 60 °C. Thus, the NiMnCo nanoneedle co-catalyst could reduce the dependence of proton exchange membrane fuel cells on Pt catalysts.

Functionalized inclined-GaN based nanoneedles

Kim, Kwon-Ho,Lee, Kyuseung,Hong, Hyeonaug,Yang, Dasom,Ryu, WonHyoung,Nam, Okhyun,Kim, Yeu-Chun THE KOREAN SOCIETY OF INDUSTRIAL AND ENGINEERING 2018 JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY -S Vol.59 No.-

<P><B>Abstract</B></P> <P>Techniques for the delivery foreign materials into living cells as well as for sensing have undeniable worth in cell biology research. A major barrier for intracellular delivery is to cross the cell membrane with little or no damage. Among the various intracellular delivery methods, one-dimensional nanoneedles are one of the promising methods for insertion with minimal invasiveness to a cell. Most of the previous studies have been conducted using vertical nanoneedle. Here, we synthesized new inclined nanoneedles and demonstrated a novel platform using inclined-gallium nitride nanoneedles (iGaN NNs) to facilitate efficient intracellular delivery. In our system, foreign molecules were successfully delivered into cytoplasm of a cell through the penetration of the cell membrane by the iGaN NNs.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>