Rational design of forest-like nickel sulfide hierarchical architectures with ultrahigh areal capacity as a binder-free cathode material for hybrid supercapacitors

Rama Raju, G. Seeta,Pavitra, E.,Nagaraju, Goli,Sekhar, S. Chandra,Ghoreishian, Seyed Majid,Kwak, Cheol Hwan,Yu, Jae Su,Huh, Yun Suk,Han, Young-Kyu The Royal Society of Chemistry 2018 Journal of Materials Chemistry A Vol.6 No.27

<P>Evolution of a simple, efficient and reproducible strategy for the rational design of hierarchically structured metal chalcogenide-based supercapacitors has attracted considerable research interest in recent years. Herein, a facile wet-chemistry approach is employed to design three-dimensional forest-like porous nickel sulfide nanotrees on nickel foam (NiS NTs/Ni foam) for use as a cathode material in hybrid supercapacitors. The growth time plays a crucial role in controlling the surface morphology, and the optimal growth conditions (3 h at 85 °C) led to the growth of forest-like NiS NTs/Ni foam with reliable adherence. The forest-like NiS NTs/Ni foam shows maximum areal and specific capacities of 752.71 μA h cm<SUP>−2</SUP> and 342.1 mA h g<SUP>−1</SUP> at a current density of 4 mA cm<SUP>−2</SUP>, with an excellent cycling stability of 89.4%. This result is primarily due to the availability of more surface-active sites in the well-defined hierarchical architecture, which allow the rapid diffusion of electrolyte ions and minimize the electron transport limitation. Utilizing the hierarchical NiS NTs/Ni foam as a cathode and activated carbon-based anode, we further fabricated a hybrid supercapacitor, which demonstrates a wide potential window of 1.6 V with high areal energy and power densities of 0.472 mW h cm<SUP>−2</SUP> and 21.5 mW cm<SUP>−2</SUP>, respectively. The fabricated hybrid supercapacitor is successfully utilized to drive various electronic gadgets for real-life applications. The electrochemical performance of a hierarchically structured NiS-based binder-free electrode with our facile approach paves a new pathway for the development of novel metal chalcogenides for high-performance hybrid supercapacitors.</P>

Designed construction of yolk–shell structured trimanganese tetraoxide nanospheres via polar solvent-assisted etching and biomass-derived activated porous carbon materials for high-performance asymmetric supercapacitors

Nagaraju, Goli,Sekhar, S. Chandra,Rama Raju, G. Seeta,Bharat, L. Krishna,Yu, Jae Su The Royal Society of Chemistry 2017 Journal of Materials Chemistry A Vol.5 No.30

<▼1><P>Yolk–shell structured Mn3O4 nanospheres and biomass-derived activated carbon materials were prepared for use in high energy storage asymmetric supercapacitors.</P></▼1><▼2><P>Recently, yolk–shell structured electrode materials have attracted increasing interest in supercapacitors (SCs) due to their high surface area, good electrochemical activity and excellent mechanical stability towards superior energy storage performance. However, the synthesis strategies to prepare such yolk–shell structured materials without using chemical surfactants/solid templates are still inferior. Herein, a facile and cost-effective strategy to design yolk–shell structured trimanganese tetraoxide nanospheres (Mn3O4 NSs) with a distinctive core–void–shell configuration to use as an efficient positive electrode material in asymmetric SCs is demonstrated. Specifically, the yolk–shell structured Mn3O4 NSs were prepared by the inclusion of water droplets to the manganese precursor–isopropyl alcohol system, which facilitates the inside-out Ostwald ripening process to construct a yolk–shell-like configuration with porous properties. In aqueous electrolyte solution, the corresponding material exhibited a high specific capacitance (211.36 F g<SUP>−1</SUP> at a current density of 0.5 A g<SUP>−1</SUP>), a good rate capability (79.4% at 10 A g<SUP>−1</SUP>) and an excellent cycling stability (92% after 2000 cycles) compared to its solid counterparts. Meanwhile, a low-cost material based on biomass-derived activated carbon with a honeycomb-like structure is also prepared using waste corrugated boxes, which exhibits a reliable electrochemical performance for use as a negative electrode material. Moreover, the fabricated asymmetric SC using both electrode materials offers a maximum potential window of 2 V with higher energy density (19.47 W h kg<SUP>−1</SUP>) and power density (2263.89 W kg<SUP>−1</SUP>) values, which can effectively power up commercial light-emitting diodes for practical applications.</P></▼2>

Synthesis, structural and luminescent properties of Pr³⁺ activated GdAlO₃ phosphors by solvothermal reaction method

Seeta Rama Raju, G.,Park, J.Y.,Jung, H.C.,Balakrishnaiah, R.,Moon, B.K.,Jeong, J.H. Elsevier 2011 Current Applied Physics Vol.11 No.3

Different concentrations of trivalent praseodymium (Pr<SUP>3+</SUP>) ions activated GdAlO<SUB>3</SUB> nanophosphors were synthesized by solvothermal reaction method. Thermogravimetric/differential thermal analysis (TG/DTA) and X-ray diffraction (XRD) measurements were used to investigate the phase transformations that occur during the preparation of these phosphors. The morphology of the powder after heat treatment was observed by scanning electron microscopy (SEM). The luminescent studies on these compounds have been carried out from the measurements of their photoluminescence (PL) and photoluminescence excitation (PLE) spectra. The PL spectra show blue-green emission corresponding to the f-f transitions of Pr<SUP>3+</SUP> (<SUP>3</SUP>P<SUB>0</SUB> -> <SUP>3</SUP>H<SUB>4</SUB>) and red emission corresponding to the f-f transition of Pr<SUP>3+</SUP> (<SUP>3</SUP>P<SUB>0</SUB> -> <SUP>3</SUP>H<SUB>6</SUB>) by monitoring the excitation with f-f transition of Pr<SUP>3+</SUP> (<SUP>3</SUP>H<SUB>4</SUB> -> <SUP>3</SUP>P<SUB>2</SUB>) at 449 nm. Emission mechanism in these systems has also been elucidated by an energy level scheme.

Optical temperature sensing properties of Stokes fluorescence-based high color-purity green-emitting Sr₂Gd₈(SiO₄)₆O₂:Er³⁺ phosphors

Raju, G. Seeta Rama,Pavitra, E.,Rao, Gattupalli Manikya,Jeon, Tae-Joon,Jeon, Sie-Wook,Huh, Yun Suk,Han, Young-Kyu Elsevier 2018 JOURNAL OF ALLOYS AND COMPOUNDS Vol.756 No.-

<P><B>Abstract</B></P> <P>Fluorescence intensity ratio (FIR)-based optical thermometry has attracted a great deal of attention because it allows accurate and reliable temperature measurements with high spatial resolution and real-time monitoring. Herein, we report the novel Sr<SUB>2</SUB>Gd<SUB>8</SUB>(SiO<SUB>4</SUB>)<SUB>6</SUB>O<SUB>2</SUB>:Er<SUP>3+</SUP> (SGSO:Er<SUP>3+</SUP>) phosphor as an optical thermometry material. The sol-gel method is used to synthesize the oxyapatite structured SGSO:Er<SUP>3+</SUP> phosphors, which exhibits a rod-like morphology. The photoluminescence spectra of SGSO:Er<SUP>3+</SUP> phosphors displays two distinct green emission bands corresponding to the electronic transitions <SUP>2</SUP>H<SUB>11/2</SUB> → <SUP>4</SUP>I<SUB>15/2</SUB> and <SUP>4</SUP>S<SUB>3/2</SUB> → <SUP>4</SUP>I<SUB>15/2</SUB>. The temperature-induced variations in the FIR result in a maximum sensitivity of 3.4 × 10<SUP>−3</SUP> K<SUP>−1</SUP> at 463 K. Further, the CIE chromaticity coordinates do not shift from the green region when the temperature is increased from 303 to 483 K and the color purity only decreasing from 77.6 to 71.4%. The SGSO:2Er<SUP>3+</SUP> phosphor exhibits the color-purity of 93.5% when excited with low-energy electron beam. These results suggest that the SGSO:2Er<SUP>3+</SUP> phosphor is a promising material for optical temperature sensors and display devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Green-emitting Sr<SUB>2</SUB>Gd<SUB>8</SUB>(SiO<SUB>4</SUB>)<SUB>6</SUB>:Er<SUP>3+</SUP> is reported as a novel multifunctional material. </LI> <LI> Sr<SUB>2</SUB>Gd<SUB>8</SUB>(SiO<SUB>4</SUB>)<SUB>6</SUB>:Er<SUP>3+</SUP> phosphor exhibits a maximum sensitivity of 3.4 × 10<SUP>−3</SUP> K<SUP>−1</SUP> at 463 K. </LI> <LI> Green color-purity destruction under elevated thermal condition is only about 6%. </LI> <LI> Under low electron-beam excitation, phosphor unveil 93.5% green color-purity. </LI> </UL> </P>

Gd[sup 3+] Sensitization Effect on the Luminescence Properties of Tb[sup 3+] Activated Calcium Gadolinium Oxyapatite Nanophosphors

Raju, G. Seeta Rama,Park, Jin Young,Jung, Hong Chae,Moon, Byung Kee,Jeong, Jung Hyun,Kim, Jung Hwan The Electrochemical Society 2011 Journal of the Electrochemical Society Vol.158 No.2

Novel orange and reddish-orange color emitting BaGd₂O₄:Sm³⁺ nanophosphors by solvothermal reaction for LED and FED applications

Seeta Rama Raju, G.,Yu, J.S. Pergamon 2014 Spectrochimica acta. Part A, Molecular and biomole Vol.124 No.-

BaGd<SUB>2</SUB>O<SUB>4</SUB> (BG):Sm<SUP>3+</SUP> nanophosphors were synthesized by a solvothermal reaction method. The powder X-ray diffraction pattern confirmed their orthorhombic structure, and the morphological studies were carried out by taking the scanning and transmission electron microscopy images. The photoluminescence (PL) emission and PL excitation (PLE) spectra were investigated as a function of Sm<SUP>3+</SUP> ion concentration. The PLE spectra revealed both Gd<SUP>3+</SUP> and Sm<SUP>3+</SUP> excitation bands in the shorter and longer wavelength regions, indicating that the efficient energy transfer occurred from the Gd<SUP>3+</SUP> to Sm<SUP>3+</SUP> ions in the BG host lattice. The PL spectra exhibited an intense orange emission due to (<SUP>4</SUP>G<SUB>5/2</SUB>→<SUP>6</SUP>H<SUB>7/2</SUB>) transition along with two other moderate intense emission peaks due to the (<SUP>4</SUP>G<SUB>5/2</SUB>→<SUP>6</SUP>H<SUB>5/2</SUB>) and (<SUP>4</SUP>G<SUB>5/2</SUB>→<SUP>6</SUP>H<SUB>9/2</SUB>) transitions. Based on the emission performance related to (<SUP>4</SUP>G<SUB>5/2</SUB>→<SUP>6</SUP>H<SUB>7/2</SUB>) transition, the Sm<SUP>3+</SUP> ion concentration was optimized to be at 1mol%. The low-voltage cathodoluminescent (CL) measurements were also performed for BG:1mol% Sm<SUP>3+</SUP> nanophosphors as a function of accelerating voltage and filament current. From the CL spectra, the reddish-orange emission was observed. The Commission International De I-Eclairage chromaticity coordinates of BG:Sm<SUP>3+</SUP> nanophosphors were found to be very close to the chromaticity coordinates of Nichia Corporation developed amber light-emitting diodes.

Excitation induced efficient luminescent properties of nanocrystalline Tb³⁺/Sm³⁺:Ca₂Gd₈Si₆O₂₆ phosphors

Raju, G. Seeta Rama,Park, Jin Young,Jung, Hong Chae,Pavitra, E.,Moon, Byung Kee,Jeong, Jung Hyun,Kim, Jung Hwan Royal Society of Chemistry 2011 Journal of materials chemistry Vol.21 No.17

<P>The cathodoluminescence and the excitation induced photoluminescence properties have been investigated for the nanocrystalline Tb<SUP>3+</SUP>/Sm<SUP>3+</SUP>:Ca<SUB>2</SUB>Gd<SUB>8</SUB>Si<SUB>6</SUB>O<SUB>26</SUB> phosphors prepared by a solvothermal reaction method. The XRD patterns confirm their hexagonal structure. The green, orange and white emissions have been obtained by exciting at 275, 378, and 405 nm wavelengths, respectively. The corresponding CIE chromaticity coordinates are found to be in close proximity to the standard points in their respective regions. The cathodoluminescence at low accelerating voltage has also covered the entire visible region, resulting in white emission. These luminescent powders are expected to find potential applications in the development of LEDs and FEDs.</P> <P>Graphic Abstract</P><P>Single-emitting component (Tb<SUP>3+</SUP>/Sm<SUP>3+</SUP>:Ca<SUB>2</SUB>Gd<SUB>8</SUB>Si<SUB>6</SUB>O<SUB>26</SUB> phosphor) produces the white light as well as individual colors at different excitation wavelengths. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0jm04337k'> </P>

Pechini synthesis of lanthanide (Eu³⁺/Tb³⁺or Dy³⁺) ions activated BaGd₂O₄ nanostructured phosphors: an approach for tunable emissions

Seeta Rama Raju, G.,Pavitra, E.,Yu, Jae Su The Royal Society of Chemistry 2014 Physical chemistry chemical physics Vol.16 No.34

<P>Trivalent lanthanide (Eu<SUP>3+</SUP>, Tb<SUP>3+</SUP> and Dy<SUP>3+</SUP>) ions activated tunable color emitting BaGd<SUB>2</SUB>O<SUB>4</SUB> (BG) phosphors were synthesized by a facile Pechini-type sol–gel process. The X-ray diffraction pattern confirmed the orthorhombic phase after annealing at 1300 °C for 5 h. Morphological studies were performed based on the analysis of transmission electron microscopy images, which showed needle type nanorods. The BG phosphor exhibited good photoluminescence (PL) properties in the respective regions when doped with Eu<SUP>3+</SUP>, Tb<SUP>3+</SUP> and Dy<SUP>3+</SUP> ions. The Eu<SUP>3+</SUP> co-activated BG:Tb<SUP>3+</SUP> phosphor yielded tunable emissions including tri-band established white light emission based on the co-activator concentration and excitation wavelength. The energy transfer from Tb<SUP>3+</SUP> to Eu<SUP>3+</SUP> ions was controlled by selecting a suitable excitation wavelength and the decay measurements were carried out for analyzing the energy transfer efficiency. The cathodoluminescence properties of these phosphors were almost similar to PL properties when doped with individual Eu<SUP>3+</SUP>, Tb<SUP>3+</SUP>, and Dy<SUP>3+</SUP> ions, but were different when co-doped with Eu<SUP>3+</SUP>/Tb<SUP>3+</SUP> or Eu<SUP>3+</SUP>/Dy<SUP>3+</SUP> ions. In the case of Eu<SUP>3+</SUP>/Tb<SUP>3+</SUP> doped samples, the energy transfer process occurred unlike the PL channel. The calculated Commission International de l'Eclairage chromaticity coordinates of individual ion doped BG phosphors confirmed red, green, and white emissions and for co-doped samples they showed tunable emission.</P> <P>Graphic Abstract</P><P>The Ln<SUP>3+</SUP> ions doped BaGd<SUB>2</SUB>O<SUB>4</SUB> host lattice based needle type nanorods provide similar or better luminescence properties than Ln<SUP>3+</SUP> ion doped BaGd<SUB>2</SUB>O<SUB>4</SUB> bulk materials. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c4cp02266a'> </P>

Targeting autophagy in gastrointestinal malignancy by using nanomaterials as drug delivery systems

Raju, G. Seeta Rama,Pavitra, E.,Merchant, Neha,Lee, Hoomin,Prasad, Ganji Lakshmi Vara,Nagaraju, Ganji Purnachandra,Huh, Yun Suk,Han, Young-Kyu Elsevier 2018 Cancer letters Vol.419 No.-

<P><B>Abstract</B></P> <P>Autophagy is a conserved catabolic process involving large protein degradation by a ubiquitous autophagosomic signaling pathway, which is essential for cellular homeostasis. It is triggered by environmental factors such as stress, lack of nutrients, inflammation, and eliminating intracellular pathogens. Although the mechanisms underlying autophagy are still unclear, increasing evidence illuminates the magnitude of autophagy in a wide range of physiological processes and human diseases. Simultaneously, research community has focused on the triggering of autophagy by the internalization of engineered nanomaterials, which indicates a new line of revolution in cancer cure. However, most studies on nanoparticle-induced autophagy focus on brain, breast, and cervical cancers; limited reports are available on gastrointestinal (GI) cancers. Therefore, the aim of this mini review is to discuss in detail the role of autophagy in GI malignancy and the status of research on nanoparticle-induced autophagy.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Role of autophagy in GI growth and metastasis. </LI> <LI> Autophagy as a new therapeutic target in GI malignancy. </LI> <LI> Use of nanoparticles as diagnostic and therapeutic agents in GI malignancy. </LI> <LI> Modulation of autophagy by nanoparticles as drug delivery carriers. </LI> </UL> </P>

A facile and efficient strategy for the preparation of stable CaMoO₄ spherulites using ammonium molybdate as a molybdenum source and their excitation induced tunable luminescent properties for optical applications

Raju, G. Seeta Rama,Pavitra, E.,Ko, Yeong Hwan,Yu, Jae Su The Royal Society of Chemistry 2012 Journal of materials chemistry Vol.22 No.31

<P>Stable CaMoO<SUB>4</SUB> spherulites were synthesized by a facile hydrothermal method using (NH<SUB>4</SUB>)<SUB>6</SUB>Mo<SUB>7</SUB>O<SUB>24</SUB>·4H<SUB>2</SUB>O as a Mo source and these spherulites were formed according to the theoretical predictions of the crystal splitting theory. Rietveld refinement and photoluminescence studies confirmed that the CaMoO<SUB>4</SUB> spherulites are defect-free. The CaMoO<SUB>4</SUB> spherulites showed greenish-blue emission and the single emitting component of CaMoO<SUB>4</SUB>:Eu<SUP>3+</SUP> spherulites led to a novel excitation induced efficient emission property like organic light emitting diodes. Cathodoluminescent properties of the CaMoO<SUB>4</SUB>:Eu<SUP>3+</SUP> exhibited individual emissions from MoO<SUB>4</SUB><SUP>2−</SUP> clusters and Eu<SUP>3+</SUP> ions. The white color emissions were clearly explained using Gaussian fitting curves. The corresponding CIE chromaticity coordinates provided their emission potentiality in the green, red and white regions for optical and biological applications.</P> <P>Graphic Abstract</P><P>Stable CaMoO<SUB>4</SUB> spherulites with tunable luminescent properties have been synthesized and the growth mechanism is in well agreement with the theoretical predictions of the crystal splitting theory. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2jm32049e'> </P>