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Sakthivel Gandhi,Swaminathan Sethuraman,Uma Maheswari Krishnan 한국고분자학회 2013 Macromolecular Research Vol.21 No.8
Biocompatible and biodegradable polyesters have immense potential in medical applications as drug delivery vehicles and tissue engineering scaffolds. In this study, we synthesized biodegradable aliphatic polyesters,namely poly(butylene pimelate) (PBPi), poly(butylene succinate) (PBSu), and poly(butylene sebacate) (PBSe), by the polycondensation of equimolar quantities of dicarboxylic acid and diol using mesoporous SBA-15 silica as heterogeneous catalyst. We then compared its performance with a conventional homogenous catalyst, SnCl2·2H2O, which did not form these polymers. The synthesized SBA-15 catalyst was characterized by electron microscopy, nitrogen adsorption-desorption isotherm and infrared spectroscopy. The synthesized polyesters were evaluated using infrared spectroscopy, X-ray diffraction, nuclear magnetic resonance spectroscopy, differential scanning calorimetry, gel permeation chromatography, scanning electron microscopy and goniometry. The combined results demonstrate that the SBA-15 mesoporous catalyst formed higher molecular weight degradable polyesters in addition to higher yield and purity, thus confirming the superiority of the mesoporous silica catalyst for polymer formation.
Gandhi, Sakthivel,Kumar, Prem,Thandavan, Kavitha,Jang, Kiwan,Shin, Dong-Soo,Vinu, Ajayan The Royal Society of Chemistry 2014 NEW JOURNAL OF CHEMISTRY Vol.38 No.7
<P>A successful method has been demonstrated for the synthesis of a mesoporous organic–inorganic nanohybrid using amine functionalized polyhedral oligomericsilsesquioxane (POSS) and pluronic polymer as a silica precursor and structure directing agent, respectively. The results confirmed the presence of porous structure, along with the high surface area and uniform pore size distribution which can be utilized for various applications namely catalysis, drug-delivery, <I>etc.</I></P> <P>Graphic Abstract</P><P>A novel mesoporous silica with high surface area and ordered porosity has been developed using <I>N</I>-methylamino POSS and dichloromethylsilane. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c4nj00292j'> </P>
권봉준,Sakthivel GANDHI,우현주,조경미,이호섭,장기완,신동수,정중현 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.67 No.3
We have studied the optical properties of CaSrSiO4:Eu2+ phosphors synthesized by using the conventional solid-state reaction method and the role of Eu3+ minority ions in those phosphors. The maximum photoluminescence integrated peak intensity was observed for the Ca1−xSr1−xSiO4:2xEu2+ (2x = 0.0050) phosphor. A red shift of 3 nm from 510 to 513 nm in the emission wavelength of the CaSrSiO4:Eu2+ phosphors was observed with increasing Eu concentration. Under an excitation of 244 nm, the Ca1−xSr1−xSiO4:2xEu2+ (2x = 0.0050) phosphor showed a broad emission band at about 515 nm due to the 4f65d1 ! 4f7 transition of the Eu2+ and small sharp peaks at about 594, 612, and 701 nm corresponding to the 5D0-7FJ transitions of Eu3+. The existence of Eu3+ minority ions in the phosphor resulted in a broader full width at half maximum in the emission of the phosphor at the excitation wavelength of 390 400 nm, even at low Eu concentration. The white light-emitting diodes (LEDs) were fabricated by using the CaSrSiO4:Eu2+ phosphors and 400-nm GaN-based LED chips and exhibited a high color rendering index of 95 and correlated color temperature of 5370 K. The broad emissions of the CaSrSiO4:Eu2+ phosphors combined with the GaN-based LED chips are suitable for the realization of white LEDs.
( M. Gandhi Pragash ),( K. Badri Narayanan ),( P. Ravindra Naik ),( N. Sakthivel ) 한국미생물 · 생명공학회 2009 Journal of microbiology and biotechnology Vol.19 No.1
Strain PUPC1 produces an antifungal protease as well as plant growth promoting enzymes such as 1-aminocyclopropane-1-carboxylate (ACC) deaminase and phosphatase. Morphological, cultural, and physiological characteristics as well as 16S rRNA gene-sequence-based phylogenetic analysis confirmed the taxonomic affiliation of PUPC1 as Chryseobacterium aquaticum. The optimum growth of PUPC1 was observed at pH 6.0 and 30℃, and maximum protease production was observed in medium B amended with 1% tryptone, 0.5% sucrose, and 0.005% MnCl2. The protease was purified by ammonium sulfate precipitation, Sephadex G-75 gel filtration chromatography, and electroelution from preparative SDS-PAGE. The protease had a molecular mass of 18.5 kDa. The optimum pH and temperature stability of the protease were pH 5.0-10.0 and temperature 40-70℃. Chryseobacterium aquaticum PUPC1 and its protease showed a broad-spectrum antifungal activity against phytopathogenic fungi. Strain PUPC1 also exhibited plant growth promoting traits. The objective of the present investigation was to isolate a strain for agricultural application for plant growth promotion and biocontrol of fungal diseases.
Jin, Dongri,Sakthivel, Kavitha,Gandhi, Sakthivel,Huy, Bui The,Lee, Yong-Ill Elsevier 2016 Sensors and actuators. B, Chemical Vol.237 No.-
<P><B>Abstract</B></P> <P>We have studied the electrochemical and optical properties of europium; a rare-earth ion functionalized ordered hybrid mesoporous silica material and evaluated its potential application for a non-enzymatic hydrogen peroxide sensor. Europium ion was introduced into the organic-inorganic hybrid mesoporous channels through complexation method. The modifications were confirmed by FT-IR whereas; the structural and textural properties of mesoporous silica are evaluated using FE-SEM, FE-TEM, and nitrogen physisorption isothermal analysis. The optical properties such as the excitation and emission behavior of rare-earth ion introduced ordered mesoporous silica was investigated using photoluminescence spectroscopy. The material is also evaluated for its electrochemical properties by the way of sensing H<SUB>2</SUB>O<SUB>2</SUB> in aqueous samples by using cyclic voltammetry and chronoamperometry. It showed a linear range between 1.0 and 1400μM. The response time of 4s is also observed with a detection limit of 0.5μM. It showed a good reproducibility, high stability and anti-interference ability which are considered vital for any electrochemical applications. The results obtained were quite challenging and thus, it has been applied for the detection of hydrogen peroxide in the presence of commercial disinfectant sample with satisfying results.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Design of novel europium incorporated mesoporous material for H<SUB>2</SUB>O<SUB>2</SUB> detection. </LI> <LI> Good analytical performance with non-interferent ability. </LI> <LI> A quick response time of <4s and low detection limit of 0.5μM. </LI> <LI> Successful detection of H<SUB>2</SUB>O<SUB>2</SUB> in the presence of disinfectant samples. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
CaSrSiO$_{4}$에 전하보상제로 첨가된 Li$^{+}$ 또는 La$^{3+}$이 Eu$^{(3+/2+)}$의 발광효율에 미치는 영향
조경미,장기완,우현주,Sakthivel GANDHI,신동수 한국물리학회 2016 새물리 Vol.66 No.3
The divalent or trivalent europium-ion-activated calcium-strontium-silicate phosphor was synthesized through a conventional solid-state reaction method and co-doped with Li$^+$ or La$^{3+}$ ions. The co-dopants (Li$^+$ or La$^{3+}$) were used in the Eu$^{(3+/2+)}$:CaSrSiO$_4$ system as a charge compensator to increase the luminescence intensity, and the system was investigated thoroughly. The obtained results showed an increased luminescence intensity for Eu$^{3+}$:CaSrSiO$_4$ phosphor co-doped with Li$^+$ ions whereas a decreased luminescence intensity was noted for the Eu$^{2+}$:CaSrSiO$_4$ phosphor. However, another co-dopant, namely, La$^{3+}$ ions, had no effect on the luminescence intensity of Eu$^{3+}$:CaSrSiO$_4$ but increased the intensity as the Eu$^{2+}$ was replaced with Eu$^{3+}$. These results represent unusual phenomena found in the CaSrSiO$_4$ phosphor. CaSrSiO$_{4}$모체에 광 활성제로 첨가된 0.5 mol\%의 Eu$^{3+}$ 및 Eu$^{2+}$의 발광효율을 증대시키기 위하여 전하보상차원으로 첨가된 Li$^{+}$ 또는 La$^{3+}$가 Eu$^{(3+/2+)}$의 발광효율에 미치는 효과를 연구하였다. 고상법을 사용하여 Li$^{+}$ 또는 La$^{3+}$가 첨가된 CaSrSiO$_{4}$: Eu$^{(3+/2+)}$ (0.5 mol\%) 시료를 제조하여 연구를 수행한 결과, Li$^{+}$이온은 Eu$^{3+}$의 발광효율은 증대시키지만 Eu$^{2+}$의 발광효율은 감소시켰다. 하지만, La$^{3+}$는 Eu$^{3+}$에 기인한 발광효과에는 별 영향을 미치지 못하나, Eu$^{2+}$들에 기인한 발광효율을 증대시키는 효과를 가져왔다. 다른 모체들에 첨가된 기존의 연구결과들과는 달리 전하보상이온들의 농도가 특정농도까지는 발광세기를 증가시켰다가 감소된 후, 다시 증가시킨 후 감소시키는 특이한 현상을 보였다. 이러한 현상은 CaSrSiO$_{4}$모체에 첨가된 경우에 발견되는 특이현상이다.
Kwon, Bong-Joon,Gandhi, Sakthivel,Woo, Hyun-Joo,Jang, Kiwan,Shin, Dong-Soo,Kim, Kyungnam,Jeong, Sohee Korean Physical Society 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.11
The optical properties and the carrier dynamics of CaSrSiO4:Eu3+ phosphors synthesized by using a solid-state reaction method have been studied by means of scanning electron microscopy, X-ray diffraction, photoluminescence (PL), PL excitation, time-resolved PL, and PL quantum-yield measurements. The phosphor synthesized with a Eu concentration of 5% and sintered at 1380 A degrees C for 2 h in air showed a high quantum yield of 88.53% and good CIE chromaticity coordinate values. The strong excitation bands observed at 395 nm (F-7(0)-L-5(6)) and 466 nm (F-7(0)-D-5(2)) lead to an intense D-5(0)-F-7(2) transition (614 nm). The forbidden transitions (D-5(0)-F-7(0) and D-5(0)-F-7(2)) were observed and showed lifetimes shorter than that of the magnetic dipole transition (D-5(0)-F-7(1)).