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Facile preparation of self-assembled wool-based graphene hydrogels by electron beam irradiation
Park, Mira,Pant, Bishweshwar,Choi, Jawun,Park, Yong Wan,Lee, Chohye,Shin, Hye Kyoung,Park, Soo-Jin,Kim, Hak-Yong 한국탄소학회 2014 Carbon Letters Vol.15 No.2
Three dimensional self-assembled graphene hydrogels were easily fabricated by electron beam irradiation (EBI) using an aqueous solution of wool/poly(vinyl alcohol) and graphene oxide (GO). After exposure to various levels of EBI radiation, the highly porous, self-assembled, wool-based graphene hydrogels were characterized using scanning electron microscopy and Fourier-transform infrared spectroscopy; to determine the gel fraction, degree of swelling, gel strength, kinetics-of-swelling analyses and removal of hexavalent chromium (Cr(VI)) from the aqueous solution. X-ray diffraction results confirmed that EBI played a significantly important role in reducing GO to graphene. The adsorption equilibrium of Cr(VI) was reached within 80 min and the adsorption capacity was dramatically increased as the acidity of the initial solution was decreased from pH 5 to 2. Changes in ionic strength did not exert much effect on the adsorption behavior.
Park, Mira,Seo, Jong Hyeok,Kim, Ji Hyeon,Park, Gisang,Park, Joon Yong,Seo, Won Seok,Song, Hyunjoon,Nam, Ki Min American Chemical Society 2018 The Journal of Physical Chemistry Part C Vol.122 No.31
<P>A well-defined WO<SUB>3</SUB>/Bi<SUB>2</SUB>S<SUB>3</SUB> composite comprised of single-crystalline Bi<SUB>2</SUB>S<SUB>3</SUB> nanowire (Bi<SUB>2</SUB>S<SUB>3</SUB>NW) layers on top of the WO<SUB>3</SUB> nanoparticles (WO<SUB>3</SUB>NP) was synthesized via an in situ hydrothermal reaction. The single-crystalline Bi<SUB>2</SUB>S<SUB>3</SUB> nanowires were uniformly grown on the surface of the WO<SUB>3</SUB> nanoparticle layer. This in situ hydrothermal process is also a general route for the synthesis of well-aligned Bi<SUB>2</SUB>S<SUB>3</SUB> nanowires on various metal oxide substrates, such as TiO<SUB>2</SUB>, BiVO<SUB>4</SUB>, and ZnO. Compared to the sole Bi<SUB>2</SUB>S<SUB>3</SUB> electrode, the resulting WO<SUB>3</SUB>NP/Bi<SUB>2</SUB>S<SUB>3</SUB>NW composite showed enhanced photoelectrochemical activity. The origin of this enhanced activity is mainly attributed to the enhancement of charge separation on the Bi<SUB>2</SUB>S<SUB>3</SUB> layer, due to the effective photogenerated electron transfer from the Bi<SUB>2</SUB>S<SUB>3</SUB> conduction band to that of WO<SUB>3</SUB>. Furthermore, the single-crystalline longitudinal structure of the Bi<SUB>2</SUB>S<SUB>3</SUB> nanowires can provide a direct electrical pathway through a single domain of nanowires.</P> [FIG OMISSION]</BR>
Mira Park,Jae-Woong Yu,전명석,한성환,진병두 한국공업화학회 2008 Journal of Industrial and Engineering Chemistry Vol.14 No.3
We have investigated the role of gold nanoparticle incorporated in the bulk-heterojunction active layer of poly(3-hexylthiophene) (P3HT)/fullerene. Since the performance of this organic photovoltaic device is strongly related to the charge carrier transport mobility of bulk heterojunction that arises from the molecular ordering of P3HT semiconductor, we have set the range of nanoparticle concentration to the infinitesimal level, which does not affect the thermally-induced ordering and conductivity of P3HT/fullerene composite film. While the increase of power conversion efficiency is mainly attributed to the enhancement of photocurrent, both the fill factor and the open circuit voltage of photovoltaic device were not sensitive to the concentration of gold nanoparticles, which does not coincide with the previous report on the case of poly(3-octylthiophene)/fullerene/nanoparticle mixture. We suggest that an enhancement of the photoinduced short-circuit current and efficiency can be explained by the increased absorption of nanoparticlepolymer composite film with the condition of the consistent molecular ordering of donor-acceptor bulk-heterojunction. At the weight fraction of 6.25×108 for gold nanoparticle/P3HT, about 50% of enhancement (i.e. from 1.43 to 2.17%) was obtained in the power efficiency.
Park, Mira,Moon, Dohyun,Yoon, Ji Woong,Chang, Jong-San,Lah, Myoung Soo Royal Society of Chemistry 2009 Chemical communications Vol.2009 No.15
<P>A 3D chiral microporous metal–organic framework containing a nonanuclear cluster as a secondary building unit was prepared using a bent and rigid dicarboxylic ligand, 2,7-naphthalene dicarboxylic acid, and the zinc ion, where a nonanuclear cluster with potential exposed metal sites is in the form of a corner-sharing cyclic trimer of a tetrahedral Zn<SUB>4</SUB>O motif.</P> <P>Graphic Abstract</P><P>A 3D chiral metal–organic framework containing a nonanuclear cluster as a secondary building unit was prepared using 2,7-naphthalene dicarboxylic acid and the zinc metal ion, where the nonanuclear cluster is in the form of a corner-sharing cyclic trimer of a tetrahedral Zn<SUB>4</SUB>O motif. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b818648k'> </P>
Park, Mira,Kim, Hyong-Ha,Kim, Dongho,Song, Nam Woong The Chemical Society of Japan 2005 Bulletin of the Chemical Society of Japan Vol.78 No.9
<P>By using the single molecule detection (SMD) technique based on laser scanning fluorescence microscopy, we have developed a method to count the number of labeled fluorophores in a single biomolecule. The number of labeled fluorophores in an individual molecule was measured by counting the number of discrete level jumps in the fluorescence-intensity transients, or Gaussian fitting of the fluorescence-intensity histogram. The instabilities of intensity transients due to humid environments of biomolecules were minimized by optimizing the matrix materials and sample-preparation condition and adding a strong triplet quencher, AET (2-aminoethanethiol). After validating the counting method and estimating the counting uncertainties through observations of a well-defined number of fluorophores, the distribution of the number of incorporated fluorophores in a DNA strand was observed. The advantages in biological analysis by using a single-molecule fluorescence technique have been considered.</P>
Park, Mira,Lee, Heung Soon,Kim, DongHo,Song, Nam Woong Korean Society of Photoscience 2004 Journal of Photosciences Vol.11 No.2
A laser scanning fluorescence microscope system has been fabricated for single molecule detection (SMD). Problems associated with the system set-up have been discussed along with proper suggestions. Based on the SMD results obtained by using the apparatus, a statistical method has been suggested to determine the minimum number of required molecules to form a group of uniform average in a selected error range.
Park, Mira,Kim, Hye-Ryun,Kim, Yeon Sun,Yang, Seung Chel,Yoon, Jung Ah,Lyu, Sang Woo,Lim, Hyunjung Jade,Hong, Seok-Ho,Song, Haengseok North-Holland 2018 Molecular and cellular endocrinology Vol.470 No.-
<P><B>Abstract</B></P> <P>Early growth response 1 (Egr1) is a key transcription factor that mediates the action of estrogen (E<SUB>2</SUB>) to establish uterine receptivity for embryo implantation. However, few direct target genes of EGR1 have been identified in the uterus. Here, we demonstrated that E<SUB>2</SUB> induced EGR1-regulated transcription of c-Kit, which plays a crucial role in cell fate decisions. Spatiotemporal expression of c-Kit followed that of EGR1 in uteri of ovariectomized mice at various time points after E<SUB>2</SUB> treatment. E<SUB>2</SUB> activated ERK1/2 and p38 to induce EGR1, which then activated c-Kit expression in the uterus. EGR1 transfection produced rapid and transient induction of c-KIT in a time- and dose-dependent manner. Furthermore, luciferase assays to measure c-Kit promoter activity confirmed that a functional EGR1 binding site(s) (EBS) was located within −1 kb of the c-Kit promoter. Site-directed mutagenesis and chromatin immunoprecipitation-PCR for three putative EBS within −1 kb demonstrated that the EBS at -818/-805 was critical for EGR1-dependent c-Kit transcription. c-Kit expression was significantly increased in the uterus on day 4 and administration of Masitinib, a c-Kit inhibitor, effectively interfered with embryo implantation. Collectively, our results showed that estrogen induces transcription factor EGR1 to regulate c-Kit transcription for uterine receptivity for embryo implantation in the mouse uterus.</P> <P><B>Highlights</B></P> <P> <UL> <LI> c-Kit expression was significantly reduced in uteri of Egr1 (−/−) mice. </LI> <LI> Spatiotemporal expression patterns of c-Kit coincided with those of Egr1 in the uterus after E<SUB>2</SUB> treatment. </LI> <LI> E<SUB>2</SUB>-ER-dependent activation of the ERK1/2 and p38 MAPK-EGR1 pathway regulated c-Kit induction in the uterus. </LI> <LI> The EBS at −818/-805 was critical for EGR1-dependent activation of c-Kit transcription. </LI> <LI> c-Kit expression was significantly increased in mouse uteri receptive for embryo implantation. </LI> </UL> </P>