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RISS 인기검색어
- 검색키워드
- 저자 : Subramaniyan Ramasundaram (검색결과 11 건)
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Ramasundaram, Subramaniyan,Seid, Mingizem Gashaw,Kim, Hyung-Eun,Son, Aseom,Lee, Changha,Kim, Eun-Ju,Hong, Seok Won Elsevier 2018 Journal of hazardous materials Vol.360 No.-
<P><B>Abstract</B></P> <P>An immobilized photocatalyst was prepared by thermally treating TiO<SUB>2</SUB>-coated steel mesh (TiO<SUB>2</SUB>-IS) in a laboratory hot-press with no binder. TiO<SUB>2</SUB> coating was performed by electrospraying a 1 mg/mL methanol dispersion of Evonik P25 powder. The thermal treatment conditions at 350 °C, 100 Mpa, and 1 h were found to be the optimum conditions. Scanning electron microscopic images displayed a robust and adherent TiO<SUB>2</SUB> layer on steel mesh. X-ray photoelectron spectroscopy and elemental mapping studies confirmed that the Fe<SUB>3</SUB>O<SUB>4</SUB> interface formed during thermal treatment strongly bound the TiO<SUB>2</SUB> on steel mesh. The XRD patterns of TiO<SUB>2</SUB>-IS indicated the preservation of crystalline structure of Evonik P25 (anatase and rutile mixture) and the existence of iron oxide interface. Under UVA irradiation, 10 μM of methylene blue was completely decolorized within 40 min using an immobilized photocatalyst with 2.120 mg of TiO<SUB>2</SUB> per 2.5 × 5.0 cm<SUP>2</SUP> and showed stable efficacy in 25 consecutive photocatalytic runs. Furthermore, this sample degraded the organic micropollutants (e.g., pharmaceuticals) such as carbamazepine, ranitidine, acetaminophen, and trimethoprim at the rates of 0.041, 0.165, 0.089, and 0.079 min<SUP>−1</SUP>, respectively. Under UVA irradiation, it exhibited high photocatalytic disinfection activity for <I>Escherichia coli</I> and MS2 coliphage.</P> <P><B>Highlights</B></P> <P> <UL> <LI> TiO<SUB>2</SUB> nanoparticles were immobilized on steel mesh without polymer binder. </LI> <LI> Immobilization was performed by electrospraying and hot-pressing treatment. </LI> <LI> The immobilized photocatalyst was effective in the removal of pharmaceuticals. </LI> <LI> It also exhibited excellent disinfection activity against <I>E.coli</I> and MS2 phage. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Ramasundaram, Subramaniyan,Yoon, Sun,Kim, Kap Jin,Park, Cheolmin Wiley Subscription Services, Inc., A Wiley Company 2008 Journal of polymer science. Part B, Polymer physic Vol.46 No.20
<P>The role of organically modified silicate (OMS), Lucentite STN on the formation of β-crystalline phase of poly(vinylidene fluoride) (PVDF) is investigated in the present study. The OMS was solution blended with PVDF and cast on glass slide to form PVDF-OMS nanocomposites. Solution cast samples were subjected to various thermal treatments including annealing (AC-AN), melt-quenching followed by annealing (MQ-AN), and melt-slow cooling (MSC). Fourier-transform infrared spectroscopy (FT-IR), wide angle X-ray diffraction (WAXD), and differential scanning calorimetry (DSC) were used to investigate the crystalline structure of thermally treated samples. As a special effort, the combination of in situ thermal FT-IR, WAXD, and DSC studies was utilized to clearly assess the thermal properties. FT-IR and WAXD results of MQ-AN samples revealed the presence of β-phase of PVDF. Ion-dipole interaction between the exfoliated clay nanolayers and PVDF was considered as a main factor for the formation of β-phase. Melt-crystallization temperature and subsequent melting point were enhanced by the addition of OMS. Solid β- to γ-crystal phase transition was observed from in situ FT-IR and WAXD curves when the representative MQ-AN sample was subjected to thermal scanning. Upon heating, β-phase was found to disappear through transformation to the thermodynamically stable γ-phase rather than melting directly. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2173–2187, 2008</P>
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Ramasundaram, Subramaniyan,Seid, Mingizem Gashaw,Lee, Wonseop,Kim, Chan Ul,Kim, Eun-Ju,Hong, Seok Won,Choi, Kyoung Jin Elsevier 2017 Journal of hazardous materials Vol.340 No.-
<P><B>Abstract</B></P> <P>Photocatalytically active TiO<SUB>2</SUB>-patterned polyimide (PI) films (PI-TiO<SUB>2</SUB>) were fabricated using thermal transfer patterning (TTP). When subjected to hot pressing, the TiO<SUB>2</SUB> nanoparticles electrosprayed on steel mesh templates were successfully transferred and formed checker plate patterns on PI film. FE-SEM studies confirmed that pressing at 350°C and 100MPa was optimum for obtaining patterns with uniform TiO<SUB>2</SUB> coverage. When the quantity of TiO<SUB>2</SUB> on the template increased, the amount of it immobilized on PI film also increased from 0.3245 to 1.2378mg per 25cm<SUP>2</SUP>. XPS studies confirmed the presence TiO<SUB>2</SUB> on the patterns, and indicated the formation of carboxylic acid and amide groups on the PI surface during TTP. When tested under UVA irradiation, PI-TiO<SUB>2</SUB> with 1.2378mg/25cm<SUP>2</SUP> TiO<SUB>2</SUB> loading exhibited the highest photocatalytic performance for methylene blue (10μM) degradation, with a rate constant of 0.0225min<SUP>−1</SUP> and stable photocatalytic efficacy for 25 cycles of reuse. The PI-TiO<SUB>2</SUB> was also successfully used to degrade amoxicillin, atrazine, and 4-chlorophenol. During photocatalysis, the toxicity of 4-chlorophenol against <I>Vibrio fischeri</I> and the antibiotic activity of amoxicillin against <I>Escherichia coli</I> were decreased. Overall, TTP was found to be a potentially scalable method for fabricating robust immobilized TiO<SUB>2</SUB> photocatalyst.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Polyimide-TiO<SUB>2</SUB> photocatalyst prepared by thermal transfer patterning (TTP). </LI> <LI> TiO<SUB>2</SUB>-coated steel mesh and laboratory hot press were effective for TTP. </LI> <LI> Highly stable performance for degrading methylene blue for 25 consecutive runs. </LI> <LI> Simultaneous reduction of pollutant concentration and residual toxicity was observed. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Ramasundaram, Subramaniyan,Rahaman, Ashiqur,Kim, Byungki Elsevier 2019 Polymer Vol.183 No.-
<P><B>Abstract</B></P> <P>A 96% β-crystalline poly(vinylidene fluoride) nanofibers (PVDF NFs) were prepared by collecting electrospun NFs on a roller operated at 5000 rpm, followed by annealing at 150 °C. Dodecylamine functionalized non-polar silver nanoparticles (Ag NPs) were synthesized. The Ag NPs were brush coated on a PVDF NFs support and used as an electrode to demonstrate a piezoelectric sensor (PS). PVDF NFs was characterized with Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and field emission-scanning electron microscopy (FE-SEM). Changes in the absorbance of FTIR peak, 1275 cm<SUP>−1</SUP>, revealed that the rise in roller speed from 0 to 5000 rpm, increased the β-phase composition from 64 to 92% (rest was γ-phase), decreased the lowest observed NFs diameter from 399 to 260 nm, and increased the orientation of NFs along the direction of rotation. The peaks relevant to β-phase found in XRD patterns (20.8°) and DSC thermograms (166 °C) were confirmed these findings. Annealing of NFs prepared at 5000 rpm (R5000) at 150 °C, increased the degree of crystallinity from 54.7 to 58.3% and the % of β-phase from 92 to 96%, highest among all samples. The electrode was characterized using FE-SEM and energy dispersive X-ray spectroscopy (EDXS), which confirmed the Ag NPs coating (35–184 nm diameter). The static and dynamic load analyses were suggested that PS made using R5000 annealed at 150 °C was capable of sensing 0.3–500 N force. The voltage generated (400 mV) upon applying load on PS with a fingertip (~3 N) can charge a 1 μF capacitor in 0.8 s and also upon 10 × amplification a 4 V light emitting diode turned on to glow. Overall, the PS made with β-crystalline R5000/150 and non-polar Ag NPs coated electrodes was found to be useful for force sensing and energy harvesting.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A 96% β-crystalline PVDF nanofibers were prepared without incorporating fillers. </LI> <LI> Non-polar Ag NPs coated flexible PVDF nanofibers electrodes were also prepared. </LI> <LI> The fabricated piezosensor was capable of sensing 0.3–500 N force. </LI> <LI> Voltage generated from piezosensor upon applying ~3 N force charged a 1 μF capacitor in 0.8 s. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Ramasundaram, Subramaniyan,Yoon, Sun,Kim, Kap Jin,Lee, Jong Soon,Park, Cheolmin WILEY-VCH Verlag 2009 Macromolecular chemistry and physics Vol.210 No.11
<P>Ultra-thin films of poly(vinylidene fluoride) (PVDF) and its organically modified silicate (OMS) nanocomposites were prepared by heat-controlled spin coating and characterized using FTIR-GIRAS, AFM, DC-EFM, and P–E measurements. Incorporation of OMS, Lucentite STN into the PVDF matrix favored the preferential formation of β-phase in nanoscale thin films, irrespective of preparation temperature. The PVDF–OMS nanocomposite films have a little higher degree of orientation of molecular chains along the ITO substrate surface than that of the neat PVDF film. This gave the PVDF–OMS nanocomposite higher remanent polarization and better contrast in a DC-EFM phase image. Unlike the thick PVDF–OMS nanocomposites films showing only α-crystalline phase after quenching and slow cooling from the melt, the nanoscale thin PVDF–OMS films showed a mixture of β- and γ-crystalline phases without any trace of α-crystalline phase.</P><P> <img src='wiley_img/10221352-2009-210-11-MACP200800600-gra001.gif' alt='wiley_img/10221352-2009-210-11-MACP200800600-gra001'> </P> <B>Graphic Abstract</B> <P>Thin films of PVDF–organically modified silicate (OMS) nanocomposites spin- coated on the ITO substrate were preferentially crystallized into β-phase, regardless of preparation conditions. The ultra-thin β-phase film without defects could be obtained from spin coating at the temperature higher than 40 °C. The incorporation of OMS favored the formation of β-phase even after melt-quenching and melt-slow cooling. The PVDF–OMS nanocomposites showed much better ferroelectric response image and much greater remanent polarization than the neat PVDF sample. <img src='wiley_img/10221352-2009-210-11-MACP200800600-content.gif' alt='wiley_img/10221352-2009-210-11-MACP200800600-content'> </P>
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Subbiah, Ramesh,Ramasundaram, Subramaniyan,Du, Ping,Hyojin, Kim,Sung, Dongkyung,Park, Kwideok,Lee, Nae-Eung,Yun, Kyusik,Choi, Kyoung Jin Royal Society 2013 Journal of the Royal Society, Interface Vol.10 No.88
<P>Hybrids consisting of carboxylated, single-walled carbon nanotube (c-SWNT)–silver nanoparticles (AgNPs)-DNA–poly vinyl alcohol (PVA) are synthesized via sequential functionalization to mimic the theragnostic (therapy and diagnosis) system. Carboxylation of SWNT has minimized the metal impurities with plenty of –COOH groups to produce hybrid (c-SWNT-AgNPs). The hybrid is further wrapped with DNA (hybrid-DNA) and encapsulated with PVA as hybrid composite (HC). Materials were tested against human alveolar epithelial cells (A549), mouse fibroblasts cells (NIH3T3) and human bone marrow stromal cells (HS-5). The composition-sensitive physico-chemical interactions, biophysics and biomechanics of materials-treated cells are evaluated. The cell viability was improved for HC, hybrid-PVA and c-SWNT when compared with SWNT and hybrid. SWNT and hybrid showed cell viability less than 60% at high dose (40 µg ml<SUP>−1</SUP>) and hybrid-PVA and HC retained 80% or more cell viability. The treatment of hybrid nanomaterials considerably changed cell morphology and intercellular interaction with respect to the composition of materials. Peculiarly, PVA-coated hybrid was found to minimize the growth of invadopodia of A549 cells, which is responsible for the proliferation of cancer cells. Surface roughness of cells increased after treatment with hybrid, where cytoplasmic regions specifically showed higher roughness. Nanoindentation results suggest that changes in biomechanics occurred owing to possible internalization of the hybrid. The changes in force spectra of treated cells indicated a possible greater interaction between the cells and hybrid with distinct stiffness and demonstrated the surface adherence and internalization of hybrid on or inside the cells.</P>
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Trung, Tran Quang,Dang, Thi My Linh,Ramasundaram, Subramaniyan,Toi, Phan Tan,Park, Sang Yoon,Lee, Nae-Eung American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.2
<P>To realize the potential applications of stretchable sensors in the field of wearable health monitoring, it is essential to develop a stable sensing device with robust electrical and mechanical properties in the present of varying external conditions. Herein, we demonstrate a stretchable temperature sensor with the elimination of strain-induced interference via geometric engineering of the free-standing stretchable fibers (FSSFs) of reduced graphene oxide/polyurethane composite. The FSSFs were formed in serpentine structures and enabled the implementation of a strain-insensitive stretchable temperature sensor. On the basis of the controlled reduction time of graphene oxide, we can modulate the response and thermal index of the device. These results are attributed to the variation in the density of oxygen-containing functional groups in the FSSFs, which affect the hopping charge transport and thermal generation of excess carriers. The FSSF temperature sensor yields increased responsivity (0.8%/°C), stretchability (90%), sensing resolution (0.1 °C), and stability in response to applied stretching (±0.37 °C for strains ranging from 0 to 50%). When the sensor is sewn onto a stretchable bandage and attached to the human body, it can detect the temperature changes of the human skin during different body motions in a continuous and stable manner.</P> [FIG OMISSION]</BR>
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