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Rani, Janardhanan R.,Oh, Se-I,Woo, Jeong Min,Tarwal, Nilesh L.,Kim, Hyun-Woong,Mun, Bongjin Simon,Lee, Sungbae,Kim, Ki-Jeong,Jang, Jae-Hyung American Chemical Society 2015 ACS APPLIED MATERIALS & INTERFACES Vol.7 No.10
<P>Highly luminescent graphene oxide (GO)-phosphor hybrid thin films with a maximum quantum yield of 9.6% were synthesized Via a simple chemical method. An intense luminescence emission peak at 537 nm and a broad emission peak at 400 nm were observed from the GO-phosphor hybrid films. The maximum quantum yield of the emissions from the hybrid films was found to be 9.6%, which is 48 times higher than that of pristine GO films. The GO-phosphor hybrids were prepared via spin-coating and subsequent postannealing of the films, resulting in scrolling of the GO sheets. The resulting GO nanoscrolls exhibited a length of similar to 2 mu m with nanoscale interior cavities. Transmission electron microscopy and selected-area electron diffraction analyses revealed that the lattice structure of the tubular scrolls is similar to that of carbon nanotubes. While pristine GO films are p-type, in the GO-phosphor hybrids, the Fermi level shifted upward and fell between the HOMO-LUMO gap due to phosphor attachment via C-N bonding. The highly luminescent GO-phosphor hybrids will find important applications in graphene-based optoelectronic devices.</P>
High Volumetric Energy Density Hybrid Supercapacitors Based on Reduced Graphene Oxide Scrolls
Rani, Janardhanan R.,Thangavel, Ranjith,Oh, Se-I,Woo, Jeong Min,Chandra Das, Nayan,Kim, So-Yeon,Lee, Yun-Sung,Jang, Jae-Hyung American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.27
<P>The low volumetric energy density of reduced graphene oxide (rGO)-based electrodes limits its application in commercial electrochemical energy storage devices that require high-performance energy storage capacities. in small volumes. The volumetric energy density of rGO-based electrode materials is very low due to their low packing density. A supercapacitor with enhanced packing density and high volumetric energy density is fabricated using doped rGO scrolls (GFNSs) as the electrode material. The restacking of rGO sheets is successfully controlled through synthesizing the doped scroll structures while increasing the packing density. The fabricated cell exhibits an ultrahigh volumetric energy density of 49.66 Wh/L with excellent cycling stability (>10000 cycles). This unique design strategy for the electrode material has significant potential for the future super capacitors with high volumetric energy densities.</P>
Rani, J. R.,Oh, Se-I,Woo, Jeong Min,Jang, Jae-Hyung The Electrochemical Society 2016 Journal of the Electrochemical Society Vol.163 No.5
<P>Graphene oxide-oxynitride hybrid nanoscrolls (GOXNs) were synthesized by embedding oxynitride molecules onto the graphene oxide (GO) sheets through a simple solution-based reduction of GO. The synthesized GOXNs exhibit good structural stability and high specific capacitance when they are used as supercapacitor electrodes. All the films were prepared via spin coating, and the post deposition annealing of the films transformed GO sheets into nanoscrolls. X-ray photoelectron spectroscopy (XPS) analyses of the hybrid film reveal that GO sheets are transformed to nanoscrolls by C-N bonding and various nitrogen based functional groups are attached to the GO sheets. The electrochemical performance of GOXNs is much better than that of pristine GO. The high specific capacitance and energy density of 260 F/g and 36.2 Wh/kg, respectively, were exhibited by GOXNs, whereas the pristine GO exhibited specific capacitance and energy density of 215 F/g and 29.86 Wh/kg, respectively, at a current density of 2 A/g. The GOXNs show good cyclic stability for more than 2000 cycles at a current density of 5 A/g. The observed high specific capacitance of GOXNs is due to the pseudo-capacitive contribution of the nitrogen functional groups along with quinone oxygen (residual oxygen functional groups) that accelerates the faradaic reactions and facilitates faster wetting. The results suggest that GOXNs are a promising electrode material for supercapacitors and batteries. (C) 2016 The Electrochemical Society. All rights reserved.</P>
Rani, Adila,Chung, Kyungwha,Kwon, Jeong,Kim, Sung June,Jang, Yoon Hee,Jang, Yu Jin,Quan, Li Na,Yoon, Minji,Park, Jong Hyeok,Kim, Dong Ha American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.18
<P>Low cost, charged, and large scale graphene multilayers fabricated from nitrogen-doped reduced graphene oxide N-rGO(+), nitrogen and sulfur codoped reduced graphene oxide NS-rGO(+), and undoped reduced graphene oxide rGO(-) were applied as alternative counter electrodes in dye-sensitized solar cells (DSSCs). The neat rGO-based counter electrodes were developed via two types of layer-by layer (LBL) self-assembly (SA) methods: spin coating and spray coating methods. In the spin coating method, two sets of multilayer films were fabricated on poly(diallyldimethylammonium chloride) (PDDA)-coated fluorine-doped tin oxide (FTO) substrates using GO(-) combined with N-GO(+) followed by annealing and denoted as [rGO(-)/N-rGO(+)](n) or with NS-GO(+) and denoted as [rGO(-)/NS-rGO(+)](n) for counter electrodes in DSSCs. The DSSCs employing new types of counter electrodes exhibited similar to 7.0% and similar to 6.2% power conversion efficiency (PCE) based on ten bilayers of [rGO(-)/N-rGO(+)](10) and [rGO(-)/NS-rGO(+)](10), respectively. The DSSCs equipped with a blend of one bilayer of [rGO(-):N-rGO(+)] and [rGO(-):NS-rGO(+)] on PDDA-coated FTO substrates were prepared from a spray coating and showed similar to 6.4% and similar to 5.6% PCE, respectively. Thus, it was demonstrated that a combination of undoped, nitrogen-doped, and nitrogen and sulfur codoped reduced graphene oxides can be considered as potentially powerful Pt-free electrocatalysts and alternative electrodes in conventional photovoltaic devices.</P>
Structural and magnetic properties of electrodeposited cobalt nanowires in polycarbonate membrane
Rani, V. Sudha,Anandakumar, S.,Lee, Hojun,Bang, Wonbae,Hong, Kimin,Yoon, S. S.,Jeong, J.-R.,Kim, CheolGi WILEY-VCH Verlag 2009 Physica status solidi. PSS. A, Applications and ma Vol.206 No.4
<P>We analyzed the structural and magnetic properties of an array of electrodeposited cobalt nanowires grown in polycarbonate membrane with pore size 50 nm diameter and thickness ≤6 μm. The current-time profiles were recorded during the deposition, in order to estimate and understand the growth rate and mechanism of the cobalt nanowires respectively. The formation of single and multi-domains in the nanowires was explained by using simple domain model assumptions. The X-ray diffraction patterns show that the cobalt nanowires were grown in a mixture of fcc and hcp phases. The magnetic properties of the deposited nanowires show that the preferential magnetization orientation close to the perpendicular direction of the nanowire axis. The structural properties of the nanowires were observed by Scanning Electron Microscope (SEM). The magnetic properties were analyzed by Vibrating Sample Magnetometer (VSM) at room temperature. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>
Exploring the Current Status of Chatbot Services for Fashion Jewelry Brands
( Myeongseon Jeong ),( Uiseong Oh ),( Rani Eom ) 한국감성과학회 2023 한국감성과학회 국제학술대회(ICES) Vol.2023 No.-
There is a recent trend of introducing chatbot service platforms to their online stores in fashion jewelry brands. This study explores the current status of chatbot services that jewelry brands have brought to online shopping malls and suggests progressive future directions. We analyzed the features of the chatbot service and discovered that there were more chatbots that could have single-turn conversation than multi-turn conversation, after selecting 30 jewelry brands shopping malls, creating a list of questions, and applying it to the chatbot service. We found out the advantages and disadvantages of single-turn and multi-turn depending on the purpose of using the chatbot. By analyzing the style of consumers who use jewelry brands at shopping malls, we learned that there is a need to improve chatbot performance through superior natural language processing technology.
Panda, Kalpataru,Rani, Revati,Kumar, Niranjan,Sankaran, Kamatchi Jothiramalingam,Park, Jeong Young,Ganesan, K.,Lin, I-Nan Elsevier 2019 Ceramics international Vol.45 No.17
<P><B>Abstract</B></P> <P>Investigation of dynamic changes in friction behavior of ultrananocrystalline diamond (UNCD) films is a complex mainly because of the rapid change in chemical composition at the sliding interfaces. To address this issue, for the first time, we report chemical phase analysis of transferfilm using the depth-resolved X-ray photoelectron spectroscopy (XPS) technique. The friction coefficient of the UNCD films was high during the initial run-in regime, but it gradually decreased to an ultralow value after longer sliding cycles at the ambient atmospheric tribo-condition. Depth-resolved XPS analysis showed a higher sp<SUP>3</SUP>/sp<SUP>2</SUP> carbon ratio during the initial run-in regime. This ratio decreased with increasing sliding cycles and consequently the friction coefficient decreased. However, a higher value of the friction coefficient throughout the run-in regime persisted at the high-vacuum tribo-condition. In this case, the sp<SUP>3</SUP>/sp<SUP>2</SUP> carbon ratio inside the transferfilm was quite high and no considerable changes were observed in the depth-resolved XPS analysis. This investigation confirmed that the dynamic friction behavior in UNCD films was manipulated by the sp<SUP>3</SUP>/sp<SUP>2</SUP> carbon ratio inside the transferfilm which showed tribo-atmospheric dependence.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>