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>

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>

Versatile properties of CaGd₂ZnO₅:Eu³⁺ nanophosphor: its compatibility for lighting and optical display applications

Seeta Rama Raju, G.,Pavitra, E.,Nagaraju, Goli,Yu, Jae Su The Royal Society of Chemistry 2015 Dalton Transactions Vol.44 No.4

<P>Red color-emitting CaGd<SUB>2</SUB>ZnO<SUB>5</SUB>:Eu<SUP>3+</SUP> (CGZO:Eu<SUP>3+</SUP>) nanophosphors were synthesized by a facile sol–gel process. The structural and luminescent properties of these phosphors were investigated as a function of annealing temperature and Eu<SUP>3+</SUP> ion concentration. The orthorhombic phase was confirmed at different annealing temperatures, showing an irregular morphology within the nanoscale range. Photoluminescence (PL) excitation spectra of CGZO:Eu<SUP>3+</SUP> showed host absorption band (HAB), charge transfer band (CTB), and intense f–f transitions of Eu<SUP>3+</SUP> in the violet and blue wavelength regions. The CTB intensity increased and the HAB intensity decreased with increasing annealing temperature or Eu<SUP>3+</SUP> ion concentration. The CGZO:Eu<SUP>3+</SUP> exhibited a strong absorption in the blue region as compared to the CTB and had a superior property compared to available commercial phosphors. This feature facilitates the fabrication of high color rendering index white light-emitting diodes for display systems. In PL spectra, an intense red emission was observed due to the hypersensitive <SUP>5</SUP>D<SUB>0</SUB>→<SUP>7</SUP>F<SUB>2</SUB> transition with good asymmetry ratio and chromaticity coordinates. Optimized annealing temperature and concentration of Eu<SUP>3+</SUP> ions were observed for CGZO host lattice based on the 466 nm excitation wavelength. The cathodoluminescent properties were also similar to the PL results.</P> <P>Graphic Abstract</P><P>A CGZO:Eu<SUP>3+</SUP> nanophosphor is advantageous for obtaining natural white light with higher color rendering index when mixing with YAG:Ce<SUP>3+</SUP> yellow phosphor. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c4dt03181d'> </P>

Cross-relaxation induced tunable emissions from the Tm³⁺/Er³⁺/Eu³⁺ ions activated BaGd₂O₄ nanoneedles

Seeta Rama Raju, G.,Pavitra, E.,Yu, Jae Su The Royal Society of Chemistry 2014 Dalton Transactions Vol.43 No.25

<P>Tm<SUP>3+</SUP>, Er<SUP>3+</SUP>, Tm<SUP>3+</SUP>/Er<SUP>3+</SUP>, Tm<SUP>3+</SUP>/Er<SUP>3+</SUP>/Eu<SUP>3+</SUP> single, double and triple activator ion/ions doped nanocrystalline BaGd<SUB>2</SUB>O<SUB>4</SUB> (BG) phosphors were prepared by a Pechini type sol–gel process. After annealing at 1300 °C, X-ray diffraction patterns confirmed their orthorhombic structure. Field-emission transmission electron microscope images of the BG sample indicated a nanoneedle-type morphology. Photoluminescence (PL) and cathodoluminescence (CL) measurements were utilized to establish the emission properties of rare-earth ions doped nanocrystalline BG host lattice. Under near-ultraviolet (NUV) excitations, BG:Tm<SUP>3+</SUP> and BG:Er<SUP>3+</SUP> exhibited their characteristic emissions in the blue and green regions, respectively, while BG:Tm<SUP>3+</SUP>/Er<SUP>3+</SUP> and BG:Tm<SUP>3+</SUP>/Er<SUP>3+</SUP>/Eu<SUP>3+</SUP> showed cyan and white light emissions, respectively, when doped with appropriate amounts of activator ions. In the PL, the cross-relaxation process is dominant rather than the energy transfer process. Due to the different mechanism from PL, the CL spectra showed different emission features of BG:Tm<SUP>3+</SUP>/Er<SUP>3+</SUP>/Eu<SUP>3+</SUP> phosphor. The CL spectra of BG:Tm<SUP>3+</SUP> and BG:Er<SUP>3+</SUP> established the high purity blue and green emissions, respectively. From the PL and CL investigations, the white-light emission was realized from the single-phase BG:Tm<SUP>3+</SUP>/Er<SUP>3+</SUP>/Eu<SUP>3+</SUP> phosphor under NUV and low voltage electron beam excitations.</P> <P>Graphic Abstract</P><P>A novel combination of rare-earth ions activated BaGd<SUB>2</SUB>O<SUB>4</SUB> unveiled tunable emissions owing to its dominant cross-relaxation rather than the energy transfer process. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c4dt00656a'> </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

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>

Imaging and curcumin delivery in pancreatic cancer cell lines using PEGylated α-Gd₂(MoO₄)₃ mesoporous particles

Seeta Rama Raju, G.,Pavitra, E.,Purnachandra Nagaraju, Ganji,Ramesh, Kandimalla,El-Rayes, Bassel F.,Yu, Jae Su The Royal Society of Chemistry 2014 Dalton Transactions Vol.43 No.8

<P>Mesoporous particles are emerging as multifunctional biomaterials for imaging and drug delivery in several disease models, including cancer. We developed PEGylated α-Gd<SUB>2</SUB>(MoO<SUB>4</SUB>)<SUB>3</SUB> marigold flower-like mesoporous particles for the purpose of drug delivery and, more specifically, evaluated their ability to deliver curcumin. The obtained mesoporous particles significantly conjugated the curcumin particles on their surfaces by inducing the formation of curcumin nanoparticles. <I>In vitro</I> studies of the PEGylated mesoporous particles filled with curcumin demonstrated that these particles could considerably facilitate the continuous and sustained release of curcumin into the cytoplasm and nucleus. As a result, the intracellular release of curcumin can inhibit proliferation in two human pancreatic cancer cell lines: MIA PaCa-2 and PANC-1. Additionally, the particles showed the increased inhibition of pIKKα, pIKKα/β and NF-κB–DNA binding activity as compared to pure curcumin. The curcumin conjugated mesoporous particles are concentrated in the cytoplasm and nucleus of the treated cancer cell lines. Consequently, these mesoporous particles are an effective method for drug delivery that can cross the biological barriers of the body targeting the cellular nucleoplasm.</P> <P>Graphic Abstract</P><P>The advantage of PEGylated α-Gd<SUB>2</SUB>(MoO<SUB>4</SUB>)<SUB>3</SUB> marigold-like mesoporous flowers with curcumin is to facilitate nuclear localization and release of the conjugated drug, triggering the signal within the nucleoplasm. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c3dt52692e'> </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>

Luminescence properties of Dy3+ ions activated novel warm white-light emitting CaGd2ZnO5 nanophosphors

Seeta Rama Raju, G.,Pavitra, E.,Su Yu, Jae Elsevier Science B.V., Amsterdam. 2015 CERAMICS INTERNATIONAL Vol.41 No.-

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>