Magnetically-refreshable receptor platform structures for reusable nano-biosensor chips

Myungjae YANG,Haneul YOO,Dong Jun LEE,Dong-Guk CHO,Juhun PARK,Ki Wan NAM,Young Tak CHO,Jae Yeol PARK,Xing CHEN,Seunghun HONG 한국진공학회 2016 한국진공학회 학술발표회초록집 Vol.2016 No.8

Association Between Peroxisomal Biogenesis Factor 7 and Autism Spectrum Disorders in a Korean Population

Ro, MyungJa,Park, JungWon,Nam, Min,Bang, Hee Jung,Yang, JaeWon,Choi, Kyung-Sik,Kim, Su Kang,Chung, Joo-Ho,Kwack, KyuBum SAGE Publications 2012 Journal of child neurology Vol.27 No.10

<P>Autism spectrum disorder is a neurodevelopmental disorder characterized by deficits in social communication, impaired reciprocal social interaction, and repetitive patterns of behaviors or interests. Although the cause of autism spectrum disorder remains elusive, the present study identified peroxisomal biogenesis factor 7 (PEX7) as a gene associated with autism spectrum disorder, and this association was examined in a Korean population. PEX7 encodes a cytosolic receptor for peroxisome targeting signal 2 of peroxisomal matrix enzymes that are targeted to and translocated into the peroxisome. PEX7 defects are associated with rhizomelic chondrodysplasia punctata type 1 and Refsum disease. Mutations in PEX7 are related to a variety of mild to severe clinical symptoms, including mental retardation. The analysis of 9 intronic single nucleotide polymorphisms in 214 patients with autism spectrum disorder and 258 controls revealed the association of 2 single nucleotide polymorphisms and 1 haplotype with autism spectrum disorder (P < .05).</P>

Mapping reversible photoswitching of molecular resistance fluctuations during the conformational transformation of azobenzene-terminated molecular switches

Cho, Duckhyung,Yang, Myungjae,Shin, Narae,Hong, Seunghun IOP 2018 Nanotechnology Vol.29 No.36

<P>We report a direct mapping and analysis of electrical noise in azobenzene-terminated molecular monolayers, revealing reversible photoswitching of the molecular resistance fluctuations in the layers. In this work, a conducting atomic force microscope combined with a homemade spectrum analyzer was used to image electrical current and noise at patterned self-assembled monolayers (SAMs) of azobenzene-terminated molecular wires on a gold substrate. We analyzed the current and noise imaging data to obtain maps of molecular resistances and amount of mean-square fluctuations in the resistances of the regions of <I>trans-</I>azobenzene and a <I>cis</I>/<I>trans</I>-azobenzene mixture. We revealed that the fluctuations in the molecular resistances in the SAMs were enhanced after the <I>trans</I>–to–<I>cis</I> isomerization, while the resistances were reduced. This result could be attributed to enhanced disorders in the molecular arrangements in the <I>cis</I>-SAMs. Furthermore, we observed that the changes in the resistance fluctuations were reversible with respect to repeated <I>trans</I>–to–<I>cis</I> and <I>cis</I>–to–<I>trans</I> isomerizations, indicating that the effects originated from reversible photoswitching of the molecular structures rather than irreversible damages of the molecules. These findings provide valuable insights into the electrical fluctuations in photoswitchable molecules, which could be utilized in further studies on molecular switches and molecular electronics in general.</P>

Air–Liquid Interfacial Self-Assembly of Non-Amphiphilic Poly(3-hexylthiophene) Homopolymers

Oh, Saejin,Yang, Myungjae,Bouffard, Jean,Hong, Seunghun,Park, So-Jung American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.14

<P>Here, we demonstrate that the self-assembly of poly(3-hexylthiophene) (P3HT) at the air-water interface can lead to free-standing films of densely packed P3HT nanowires. Interfacial self-assembly on various liquid subphases, such as water, diethylene glycol, and glycerol, indicates that the-viscosity of the subpliase is an important factor for the formation of well-ordered nanostructures. The thin-film morphology is also sensitive to the concentration of P3HT, its molecular weight (MW), and the presence of oxidative defects. The densely packed nanowire films can be easily transferred to solid substrates for device applications. The ultrathin films of P3HT prepared by the interfacial assembly showed significantly higher hole mobility (similar to 3.6 X 10(-2) cm(2)/V s) in a field-effect transistor than comparably thin spin-cast films. This work demonstrates that the air liquid interfacial assembly is not limited to amphiphilic polymers and can, under optimized conditions, be applied to fabricate ultrathin films of widely used conjugated polymers with controlled morphologies.</P>

한국인 자폐스펙트럼장애와 UROC1 유전자의 연관성 분석

박정원(JungWon Park),노명자(MyungJa Ro),남민(Min Nam),방희정(Hee Jung Bang),양재원(Jae Won Yang),최경식(Kyung-Sik Choi),김수강(Su Kang Kim),정주호(Joo-Ho Chung),곽규범(KyuBum Kwack) 대한소아청소년정신의학회 2012 소아청소년정신의학 Vol.23 No.1

Objectives:Urocanase domain containing 1 (UROC1) has never been studied in prior studies on autism spectrum disorders (ASDs). UROC1 causes urocanic aciduria, one of the symptoms of which is mental retardation. The aim of this study was to investigate the association between the UROC1 gene and ASDs in a Korean population. Methods:A total of 258 control and 214 patients with ASD were used as subjects of this study. SNPs selected from UROC1 were genotyped using Illumina Golden-Gate Genotyping assay with VeraCode® technology. Statistical analysis was performed using SAS and Plink software. Results:We found no association of the 12 SNPs in the UROC1 gene with ASDs in a Korean population. Conclusion:Our study suggests that the 12 SNPs (11 SNPs and 1 SNP in the intron and 3’UTR region, respectively) in the UROC1 were not associated with ASDs in a Korean population. Further study on the exon region of UROC1 is needed.

Nanoscale anomalous noise source switching with a trap-free current transition in a PEDOT:PSS film

Cho, Dong-guk,Yang, Myungjae,Lee, Minju,Hong, Seunghun IOP 2018 Nanotechnology Vol.29 No.42

<P>We imaged localized charge traps in a PEDOT:PSS film by using a scanning noise microscopy (SNM) system and observed anomalous noise source switching behaviors affecting the electrical characteristics of the film. The SNM system enabled us to measure the localized electrical current and noise maps of a PEDOT:PSS film with nanoscale resolution. The measured maps of the currents and noises were utilized to calculate effective charge trap densities in the film. As a result, we found non-homogeneous distributions of currents and effective charge trap densities on the localized area of the film due to the non-uniform distribution of PEDOT-rich and PSS-rich grains. At a low bias voltage, we observed high current levels and high charge trap densities in PEDOT-rich grains, while PSS-rich grains showed low-current levels and charge trap densities. Interestingly, the charge trap densities in both grains showed a noise source switching behavior with respect to the applied bias voltages, and the behavior strongly affected their electrical characteristic such as the trap-free transition of currents. These results indicate that the charge traps in a PEDOT:PSS film play an important role in the electrical characteristics of the films. Our observations provide a valuable insight on the understanding of the electrical characteristics of PEDOT:PSS films and an important guideline for its practical applications.</P>

Nanoscale mapping of noise-source-controlled hopping and tunneling conduction in domains of reduced graphene oxide

Shekhar, Shashank,Lee, Hyungwoo,Cho, Duckhyung,Yang, Myungjae,Lee, Minju,Hong, Seunghun Elsevier 2019 Carbon Vol.148 No.-

<P><B>Abstract</B></P> <P>We report a nanoscale mapping of noise-source-controlled transport characteristics in the domains of reduced graphene oxide by utilizing noise-source imaging strategies. In this method, current and noise images were measured simultaneously using a scanning noise microscopy and analyzed to map sheet−resistances (<I>R</I> <SUB>□</SUB>) and noise−source densities (<I>n</I> <SUB>eff</SUB>). The maps showed the formation of conducting and insulating domains, where the insulating domains exhibited up to three-four orders of higher <I>R</I> <SUB>□</SUB> and <I>n</I> <SUB>eff</SUB> than those of conducting domains. Interestingly, the sheet−conductance (<I>Σ</I> <SUB>□</SUB>) and <I>n</I> <SUB>eff</SUB> followed rather opposite power−law behaviors like <I>Σ</I> <SUB>□</SUB>∝ <I>n</I> <SUB>eff</SUB> <SUP>−0.5</SUP> and <I>Σ</I> <SUB>□</SUB> ∝ <I>n</I> <SUB>eff</SUB> <SUP>0.5</SUP> in <I>conducting</I> and <I>insulating</I> domains, respectively, which could be attributed to the difference in mesoscopic charge transport mechanisms controlled by <I>n</I> <SUB>eff</SUB> in domains. Notably, high biases resulted in the increased conductance (Δ<I>Σ</I> <SUB>□</SUB>) and decreased noise−source density (Δ<I>n</I> <SUB>eff</SUB>) following a relationship like Δ<I>Σ</I> <SUB>□</SUB> ∝−Δ<I>n</I> <SUB>eff</SUB> <SUP>0.5</SUP> for both conducting and insulting domains, which could be explained by the passivation of noise−sources at high biases. Furthermore, Δ<I>Σ</I> <SUB>□</SUB> <I>versus</I> Δ<I>n</I> <SUB>eff</SUB> plot on the annealing also followed a power−law dependence (Δ<I>Σ</I> <SUB>□</SUB> ∝−Δ<I>n</I> <SUB>eff</SUB> <SUP>0.5</SUP>) in conducting domains, which could be attributed to carrier generation on the annealing. Our results about mesoscopic charge transports could be significant advancements in fundamental researches and applications.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Mapping nanoscale effects of localized noise-source activities on photoconductive charge transports in polymer-blend films

Shekhar, Shashank,Cho, Duckhyung,Cho, Dong-Guk,Yang, Myungjae,Hong, Seunghun IOP 2018 Nanotechnology Vol.29 No.20

<P>We develolped a method to directly image the nanoscale effects of localized noise-source activities on photoconducting charge transports in domain structures of phase-separated polymer-blend films of Poly(9,9-di-n-octylfluorenyl-2,7-diyl) and Poly(9,9-di<I>-n</I>-octylfluorene-<I>alt</I>-benzothiadiazole). For the imaging, current and noise maps of the polymer-blend were recorded using a conducting nanoprobe in contact with the surface, enabling the conductivity (<I>σ</I>) and noise-source density (<I>N</I> <SUB>T</SUB>) mappings under an external stimulus. The blend-films exhibited the phase-separation between the constituent polymers at domains level. Within a domain, high <I>σ</I> (low <I>N</I> <SUB>T</SUB>) and low <I>σ</I> (high <I>N</I> <SUB>T</SUB>) regions were observed, which could be associated with the ordered and disordered regions of a domain. In the <I>N</I> <SUB>T</SUB> maps, we observed that noise-sources strongly affected the conduction mechanism, resulting in a scaling behavior of <I>σ</I>?∝?<img ALIGN='MIDDLE' ALT='${{N}_{{\rm{T}}}}^{-0.5}$' SRC='http://ej.iop.org/images/0957-4484/29/20/205204/nanoaab2ddieqn1.gif'/> in both ordered and disordered regions. When a blend film was under an influence of an external stimulus such as a high bias or an illumination, an increase in the <I>σ</I> was observed, but that also resulted in increases in the <I>N</I> <SUB>T</SUB> as a trade-off. Interestingly, the Δ<I>σ </I>versus Δ<I>N</I> <SUB>T</SUB> plot exhibited an unusual scaling behavior of Δ<I>σ</I>?∝?<img ALIGN='MIDDLE' ALT='${\rm{\Delta }}{{N}_{{\rm{T}}}}^{0.5},$' SRC='http://ej.iop.org/images/0957-4484/29/20/205204/nanoaab2ddieqn2.gif'/> which is attributed to the de-trapping of carriers from deep traps by the external stimuli. In addition, we found that an external stimulus increased the conductivity at the interfaces without significantly increasing their <I>N</I> <SUB>T</SUB>, which can be the origin of the superior performances of polymer-blend based devices. These results provide valuable insight about the effects of noise-sources on nanoscale optoelectronic properties in polymer-blend films, which can be an important guideline for improving devices based on polymer-blend.</P>

Nanoscale reduction of resistivity and charge trap activities induced by carbon nanotubes embedded in metal thin films

Shin, Narae,Kim, Jeongsu,Shekhar, Shashank,Yang, Myungjae,Hong, Seunghun Elsevier 2019 Carbon Vol.141 No.-

<P><B>Abstract</B></P> <P>We mapped the nanoscale reduction of resistivity and noise source activities induced by metallic single walled carbon nanotubes (m-SWCNTs) embedded in gold thin films. In this method, current and noise maps of m-SWCNTs/gold hybrid thin films were recorded using a conducting probe in contact with the surface, and the maps were utilized to estimate the nanoscale variation of resistivity (<I>ρ</I>) and the density distribution of noise sources (<I>N</I> <SUB>eff</SUB>) generating electrical noises in the hybrid thin film. The m-SWCNTs/gold hybrid thin films with a 5 nm thick gold layer exhibited 300% improved conductivity compared to that of pristine gold thin films. Additionally, the regions with embedded m-SWCNTs showed significantly reduced noise source densities compared with pristine gold film regions. These results clearly show that embedded m-SWCNTs improve the conductivity and reduce electrical noises of metallic electrodes. Interestingly, we observed that the <I>ρ</I> and the <I>N</I> <SUB>eff</SUB> on both m-SWCNTs/gold hybrid and pristine gold regions exhibited a scaling behavior of <I>ρ</I> ∝ <I>N</I> <SUB>eff</SUB> <SUP>0.5</SUP>, implying the hopping charge conduction and noise characteristics of m-SWCNTs/gold hybrid films. Our works can be a useful guideline for the development of high performance electrodes based on CNTs.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>