Photofabrication of surface relief gratings from azobenzene containing perfluorocyclobutane aryl ether polymer

Chun, Chaemin,Ghim, Jieun,Kim, Mi-Jeong,Kim, Dong Yu Wiley Subscription Services, Inc., A Wiley Company 2005 Journal of polymer science Part A, Polymer chemist Vol.43 No.16

<P>An azobenzene based perfluorocyclobutane (PFCB) aryl ether polymer, poly[4-(phenylazo)triphenylamine-1,2-hexafluorocyclobutyl ether], was synthesized by using a palladium catalyzed amination reaction and the 2π + 2π cyclodimerization of 4-[(trifluorovinyl)oxy]bromobenzene. This polymer was designed and synthesized to permit azo chromophores to be incorporated, thus introducing photoinduced dynamic behavior into the PFCB containing polymer structure. The polymer exhibited a T<SUB>g</SUB> of about 122 °C, and the maximum absorption of the azo chromophores was 407 nm in the film state. A thin film was prepared through a spin coating process, and the rapid growth of diffraction efficiency was then achieved by irradiation with an interference beam. The efficient formation of holographic surface relief gratings was also verified from AFM images, which show regularly defined and aligned grating structures. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3525–3532, 2005</P> <B>Graphic Abstract</B> <P>An azobenzene based perfluorocyclobutane (PFCB) aryl ether polymer, poly[4-(phenylazo)triphenylamine-1,2-hexafluorocyclobutyl ether] (PPF), was synthesized using a palladium catalyzed amination reaction and the 2π + 2π cyclodimerization of 4-[(trifluorovinyl)oxy]bromobenzene. The PFCB polymer, PPF, contains both azobenzene groups, which show photoinduced dynamic behavior and PFCB rings with a high content of fluorine. This polymer permits the efficient, rapid growth of diffraction efficiency, and the holographic surface relief grating was successfully inscribed on PPF thin films with regularly defined grating structures when illuminated with interference beams. <img src='wiley_img/0887624X-2005-43-16-POLA20812-gra001.gif' alt='wiley_img/0887624X-2005-43-16-POLA20812-gra001'> </P>

<i>trans</i>-Stilbenoids: potent and selective inhibitors for human cytochrome P450 1B1

Chun, Young-Jin,Lim, Chaemin,Ohk, Seul Ong,Lee, Ji Min,Lee, Jin Hee,Choi, Sun,Kim, Sanghee Royal Society of Chemistry 2011 MedChemComm Vol.2 No.5

<P>On the basis of our previous insights into the structural requirements of stilbenoids for the inhibition of cytochrome P450 1B1 (CYP1B1), a series of 2,4-dimethoxy group-containing stilbenes was prepared and evaluated for their inhibitory effects on the activity of CYP1s with the ultimate goal of identifying a potent and selective CYP1B1 inhibitor. Among the thirteen derivatives prepared, five compounds exhibited similar or greater potency compared to the previous lead compound, 2,4,3′,5′-tetramethoxystilbene (2,4,3′,5′-TMS), in inhibiting CYP1B1. In particular, 2,2′,3′,4,6′-pentamethoxystilbene was found to be a more selective and more potent CYP1B1 inhibitor than 2,4,3′,5′-TMS. 2,4,2′,6′-TMS showed remarkably potent inhibitory activity against CYP1B1 (IC<SUB>50</SUB> = 1.77 ± 0.14 nM) and also had a very high selectivity toward CYP1 isoenzymes. Molecular modeling was performed to determine the key molecular interactions with the CYP1B1 and CYP1A2 structures. On the basis of these structural and biological studies, the design of more potent and more selective drug-like derivatives can be envisaged.</P> <P>Graphic Abstract</P><P>The inhibitory potency and selectivity against cytochrome P450 subfamily 1 (CYP1) depends strongly on the substitution pattern. 2,2′,3′,4,6′-Pentamethoxystilbene was found to be the most selective and potent CYP1B1 inhibitor to date. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0md00242a'> </P>

Well-ordered TiO₂ nanostructures fabricated using surface relief gratings on polymer films

Kim, Seok-Soon,Chun, Chaemin,Hong, Jae-Chul,Kim, Dong-Yu Royal Society of Chemistry 2006 Journal of materials chemistry Vol.16 No.4

<P>Well-ordered TiO<SUB>2</SUB> nanostructures such as 1-dimensional nanowire arrays, 2-dimensional square and hexagonal hole arrays, and 3-dimensional wire junction arrays were fabricated by a simple, controllable, economical, and reproducible method using surface relief gratings on azobenzene-functionalized polymer films as a template in the sol–gel reaction of a Ti precusor. In addition, as an application of TiO<SUB>2</SUB> nanostructure, transparent electrodes were patterned by selective dry etching with the TiO<SUB>2</SUB> nanowire array etch mask. Scanning electron microscope and atomic force microscope images confirmed the successful formation of a variety of well-ordered TiO<SUB>2</SUB> nanostructures and nanopatterning of transparent electrodes.</P> <P>Graphic Abstract</P><P>Well-ordered TiO<SUB>2</SUB> nanostructures such as 1D nanowire arrays, 2D square and hexagonal hole arrays, and 3D wire junction arrays were fabricated using surface relief gratings on azobenzene-functionalized polymer films as a template in the sol–gel reaction. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b512104c'> </P>

Absorption Wavelength Dependent Photodynamic Motions in Donor-Acceptor Type of Azobenzene Polymer Films

Kim, Mi Jeong,Chun, Chaemin,Nakayama, Tomonobu,Kim, Dong Yu IOP Publishing 2006 Japanese journal of applied physics Vol.45 No.4

Fabrication of Nano Dot and Line Arrays Using NSOM Lithography

Kwon Sangjin,Kim Pilgyu,Jeong Sungho,Chang Wonseok,Chun Chaemin,Kim Dong-Yu Optical Society of Korea 2005 Current Optics and Photonics Vol.9 No.1

Using a cantilever type nanoprobe having a 100㎚m aperture at the apex of the pyramidal tip of a near-field scanning optical microscope (NSOM), nanopatterning of polymer films are conducted. Two different types of polymer, namely a positive photoresist (DPR-i5500) and an azopolymer (Poly disperse orange-3), spincoated on a silicon wafer are used as the substrate. A He-Cd laser with a wavelength of 442㎚ is employed as the illumination source. The optical near-field produced at the tip of the nanoprobe induces a photochemical reaction on the irradiated region, leading to the fabrication of nanostructures below the diffraction limit of the laser light. By controlling the process parameters properly, nanopatterns as small as 100㎚ are produced on both the photoresist and azopolymer samples. The shape and size variations of the nanopatterns are examined with respect to the key process parameters such as laser beam power, irradiation time or scanning speed of the probe, operation modes of the NSOM (DC and AC modes), etc. The characteristic features during the fabrication of ordered structures such as dot or line arrays using NSOM lithography are investigated. Not only the direct writing of nano array structures on the polymer films but also the fabrication of NSOM-written patterns on the silicon substrate were investigated by introducing a passivation layer over the silicon surface. Possible application of thereby developed NSOM lithography technology to the fabrication of data storage is discussed.

Latent Tuberculosis Infection Screening and Treatment in Congregate Settings (TB FREE COREA): Demographic Profiles of Interferon-Gamma Release Assay Cohort

Kim Hyung Woo,Min Jinsoo,Choi Joon Young,Shin Ah Young,Myong Jun-Pyo,Lee Yunhee,Yim Hyeon Woo,Jeong Hyunsuk,Bae Sanghyuk,Shim Eunhye,In Hyekyung,Chun Chaemin,Kim Gahee,Kang Ji Young,Lee Sung-Soon,Park 대한의학회 2021 Journal of Korean medical science Vol.36 No.36

In 2017, the Korean government launched an unprecedentedly large-scaled latent tuberculosis infection (LTBI) screening project which covered more than a million individuals in congregate settings. A total of 1,047,689 participants of source population (n = 2,336,157) underwent LTBI testing from 2017 to 2018. The overall LTBI test uptake rate during this project was 44.8%. Workers in daycare centers (83.5%) and kindergartens (78.9%) showed high participation rate. A total of 1,012,206 individuals with valid results of interferongamma release assay (IGRA) were selected to constitute the IGRA cohort. Most of the enrolled participants in the IGRA cohort were in their working age. Approximately, threequarters of total enrolled population were female. Investigating the LTBI prevalence, stages of LTBI care cascade, natural history of LTBI, efficacy of LTBI treatment and cost-effectiveness of LTBI screening are feasible within this IGRA cohort.

Epidemiological Characteristics of COVID-19 Outbreak at Fitness Centers in Cheonan, Korea

Bae Sanghyuk,Kim Hwami,Jung Tae-Young,Lim Ji-Ae,Jo Da-Hye,Kang Gi-Seok,Jeong Seung-Hee,Choi Dong-Kwon,Kim Hye-Jin,Cheon Young Hee,Chun Min-kyo,Kim Miyoung,Choi Siwon,Chun Chaemin,Shin Seung Hwan,Kim H 대한의학회 2020 Journal of Korean medical science Vol.35 No.31

Background: In February 2020, a coronavirus disease 2019 (COVID-19) outbreak was reported in fitness centers in Cheonan, Korea. Methods: From February 24 to March 13, an epidemiological investigation was conducted on the fitness center outbreak. All those who were screened were tested for severe acute respiratory syndrome coronavirus-2 (SARS CoV-2) using real-time reverse transcriptase polymerase chain reaction. Contacts were traced and self-isolated for 14 days. We determined the epidemiological characteristics of confirmed cases of SARS-CoV-2 infection, and estimated the time-dependent reproduction number to assess the transmission dynamics of the infection. Results: A total of 116 cases were confirmed, and 1,687 contacts were traced. The source cases were 8 Zumba instructors who led aerobics classes in 10 fitness centers, and had the largest average number of contacts. A total of 57 Zumba class participants, 37 of their family members, and 14 other contacts were confirmed as cases. The attack rate was 7.3%. The contacts at Zumba classes and homes had a higher attack rate than other contacts. The mean serial interval (± standard deviation) were estimated to be 5.2 (± 3.8) days. The time- dependent reproduction number was estimated to be 6.1 at the beginning of the outbreak, but it dropped to less than 1, 2 days after the epidemiological investigation was launched. Conclusion: The results suggest that the COVID-19 outbreak was effectively contained with rigorous contact tracing, isolating, and testing in combination with social distancing without a lock-down.