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Chung, Kyungwha,Rani, Adila,Lee, Ji-Eun,Kim, Ji Eun,Kim, Yonghwi,Yang, Heejin,Kim, Sang Ouk,Kim, Donghyun,Kim, Dong Ha American Chemical Society 2015 ACS APPLIED MATERIALS & INTERFACES Vol.7 No.1
<P>The use of graphene in conventional plasmonic devices was suggested by several theoretic research studies. However, the existing theoretic studies are not consistent with one another and the experimental studies are still at the initial stage. To reveal the role of graphenes on the plasmonic sensors, we deposited graphene oxide (GO) and reduced graphene oxide (rGO) thin films on Au films and their refractive index (RI) sensitivity was compared for the first time in SPR-based sensors. The deposition of GO bilayers with number of deposition L from 1 to 5 was carried out by alternative dipping of Au substrate in positively- and negatively charged GO solutions. The fabrication of layer-by-layer self-assembly of the graphene films was monitored in terms of the SPR angle shift. GO-deposited Au film was treated with hydrazine to reduce the GO. For the rGO-Au sample, 1 bilayer sample showed a higher RI sensitivity than bare Au film, whereas increasing the rGO film from 2 to 5 layers reduced the RI sensitivity. In the case of GO-deposited Au film, the 3 bilayer sample showed the highest sensitivity. The biomolecular sensing was also performed for the graphene multilayer systems using BSA and anti-BSA antibody.</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>
( Adila Rani ),( Kyungwha Chung ),김동하 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.0
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 spin coating method, two sets of multilayer counter electrodes were fabricated on poly(diallyldimethylammonium chloride) (PDDA) coated fluorine-doped tin oxide (FTO) substrates using [GO(-)] combined with [N-GO(+)] ([rGO(-)/N-rGO(+)]n) or with [NS-GO(+)] ([rGO(-)/NS-rGO(+)]n). The DSSCs employing new types of counter electrodes exhibited ~7.0 and ~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 blend of one bilayer of PDDA[rGO(-):N-rGO(+)] and [rGO(-):NS-rGO(+)]prepared from spray coating showed ~ 6.4 and ~ 5.6% PCE, respectively,with ~ 56% fill factor value. This work indicates that combination of un-doped, nitrogen-doped and/or nitrogen sulfur dual-doped reduced graphene oxides can be used as a new class of electro catalysts as alternative electrodes in conventional photovoltaic devices.
Kim, Kiheung,Lee, Wonju,Chung, Kyungwha,Lee, Hongki,Son, Taehwang,Oh, Youngjin,Xiao, Yun-Feng,Ha Kim, Dong,Kim, Donghyun Elsevier Applied Science 2017 Biosensors & bioelectronics Vol. No.
<P><B>Abstract</B></P> <P>In this work, we investigate the detection sensitivity of surface plasmon resonance (SPR) biosensors by engineering spatial distribution of electromagnetic near-fields for colocalization with molecular distribution. The light-matter colocalization was based on plasmonic nanolithography, the concept of which was confirmed by detecting streptavidin biotin interactions on triangular nanoaperture arrays after the structure of the aperture arrays was optimized for colocalization efficiency. The colocalization was shown to amplify optical signature significantly and thereby to achieve detection on the order of 100 streptavidin molecules with a binding capacity below 1fg/mm<SUP>2</SUP>, an enhancement by more than three orders of magnitude over conventional SPR detection.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We describe plasmonic nanolithography for colocalization of fields and molecules. </LI> <LI> Experimental evaluation was performed by measuring streptavidin-biotin interactions. </LI> <LI> The results show enhanced sensitivity by 1000 times over traditional detection. </LI> </UL> </P>
Viable stretchable plasmonics based on unidirectional nanoprisms
Lee, Ji-Eun,Park, Choojin,Chung, Kyungwha,Lim, Ju Won,Marques Mota, Filipe,Jeong, Unyong,Kim, Dong Ha The Royal Society of Chemistry 2018 Nanoscale Vol.10 No.8
<P>Well-defined ordered arrays of plasmonic nanostructures were fabricated on stretchable substrates and tunable plasmon-coupling-based sensing properties were comprehensively demonstrated upon extension and contraction. Regular nanoprism patterns consisting of Ag, Au and Ag/Au bilayers were constructed on the stretchable polydimethylsiloxane substrate. The nanoprisms had the same orientation over the entire substrate (3 × 3 cm<SUP>2</SUP>) <I>via</I> metal deposition on a single-crystal microparticle monolayer assembly. The plasmonic sensor based on the Ag/Au bilayer showed a 6-fold enhanced surface enhanced Raman scattering signal under 20% uniaxial extension, whereas a 3-fold increase was observed upon 6% contraction, compared with the Au nanoprism arrays. The sensory behaviors were corroborated by finite-difference time-domain simulation, demonstrating the tunable electromagnetic field enhancement effect <I>via</I> the localized surface plasmon resonance coupling. The advanced flexible plasmonic-coupling-based devices with tunable and quantifiable performance herein suggested are expected to unlock promising potential in practical bio-sensing, biotechnological applications and optical devices.</P>
Plasmonic Solar Cells: From Rational Design to Mechanism Overview
Jang, Yoon Hee,Jang, Yu Jin,Kim, Seokhyoung,Quan, Li Na,Chung, Kyungwha,Kim, Dong Ha American Chemical Society 2016 Chemical reviews Vol.116 No.24
<P>Plasmonic effects have been proposed as a solution to overcome the limited light absorption in thin-film photovoltaic devices, and various types of plasmonic solar cells have been developed. This review provides a comprehensive overview of the state-of-the-art progress on the design and fabrication of plasmonic solar cells and their enhancement mechanism. The working principle is first addressed in terms of the combined effects of plasmon decay, scattering, near-field enhancement, and plasmonic energy transfer, including direct hot electron transfer and resonant energy transfer. Then, we summarize recent developments for various types of plasmonic solar cells based on silicon, dye-sensitized, organic photovoltaic, and other types of solar cells, including quantum dot and perovskite variants. We also address several issues regarding the limitations of plasmonic nanostructures, including their electrical, chemical, and physical stability, charge recombination, narrowband absorption, and high cost. Next, we propose a few potentially useful approaches that can improve the performance of plasmonic cells, such as the inclusion of graphene plasmonics, plasmon-upconversion coupling, and coupling between fluorescence resonance energy transfer and plasmon resonance energy transfer. This review is concluded with remarks on future prospects for plasmonic solar cell use.</P>