Crystallization Modes of Poly(3-dodecylthiophene)-Based Block Copolymers Depend on Regioregularity and Morphology

Coote, Jonathan P.,Kim, Jin-Seong,Lee, Byeongdu,Han, Junghun,Kim, Bumjoon J.,Stein, Gila E. American Chemical Society 2018 Macromolecules Vol.51 No.22

<P>Conjugated block copolymers (BCPs) can self-assemble into highly ordered nanostructures in a melt state. However, when cooled below the melting temperature, crystal growth can disrupt the self-assembled structure and produce a poorly ordered fibrillar texture. We demonstrate that crystallization modes of conjugated BCPs based on poly(3-dodecylthiophene) (P3DDT) and poly(2-vinylpyridine) (P2VP) can be tuned through P3DDT regioregularity (RR), as this attribute controls the melting temperature and crystallization rates of P3DDT. When RR is low (70-80%), crystallization is observed at temperatures near or below the glass transition of P2VP, so crystal growth is largely confined by the glassy cylindrical or lamellar BCP structure. When RR is high (94%), crystallization occurs at 40 K above the glass transition of P2VP, so there is no longer a restriction of glassy domains. Importantly, crystal growth remains confined by the rubbery P2VP lamellae, but breaks through the rubbery P2VP cylinders. This morphology-dependent behavior is attributed to geometric compatibility of P3DDT crystal growth and the self-assembled symmetry. In a lamellar phase, the P3DDT chain orientations at the P3DDT-<I>block</I>-P2VP interface are compatible with crystal growth, and both the alkyl-stacking and π-π growth directions are unrestricted within a lamellar sheet. In a cylindrical phase, the radial orientation of P3DDT chains at the P3DDT-<I>block</I>-P2VP interface is not compatible with crystal growth, and the hexagonal close-packed symmetry only allows for one direction of unrestricted crystal growth. Significantly, these studies demonstrate that tuning RR of polyalkylthiophenes can open up multiple crystallization modes with the same monomer chemistries and block lengths, thereby decoupling the parameters that govern classical BCP self-assembly and crystal growth.</P> [FIG OMISSION]</BR>

High performance photodiodes based on chemically processed Cu doped SnS₂ nanoflakes

Mohan Kumar, G.,Xiao, Fu,Ilanchezhiyan, P.,Yuldashev, Sh.,Madhan Kumar, A.,Cho, H.D.,Lee, D.J.,Kang, T.W. Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.455 No.-

<P><B>Abstract</B></P> <P>In this work, Cu doped SnS<SUB>2</SUB> nanoflakes were synthesized through a simple hydrothermal method. The influence of Cu doping on the structural, optical and electrical properties of SnS<SUB>2</SUB> were investigated in detail. Optical properties explores the Cu doping in SnS<SUB>2</SUB> crystal lattice to result with a red-shift in absorption spectrum, which benefits visible-light absorption. Photodiodes were further fabricated by spin coating Cu doped SnS<SUB>2</SUB> nanoflakes on p-type silicon (Si). Electrical and photoelectrical parameters of Cu doped SnS<SUB>2</SUB> nanoflakes were determined by studying their impedance and current–voltage (I–V) characteristics, respectively. The diodes were found to exhibit excellent rectifying behavior and good sensitivity on par to pristine photodiodes. Impedance results identified the resistance of device to reduce considerably on Cu doping. The enhanced photoelectrical properties of the heterojunctions has been ascribed to Cu ions, which act as effective dopant and contribute to the varied carrier concentration in SnS<SUB>2</SUB>. Finally the obtained results suggest the potential of Cu-doped SnS<SUB>2</SUB> for application in photodetection and sensors applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Cu doped SnS<SUB>2</SUB> nanoflakes were synthesized in hexagonal phase. </LI> <LI> Nature of charge carriers/carrier density was determined using Mott-Schottky plots. </LI> <LI> Photodiode based on Cu doped SnS<SUB>2</SUB> nanoflakes were fabricated on p-Si substrate. </LI> <LI> Photodiode revealed improved photocurrent and responsitivity values under illumination. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Differential regulation of p53 and p21 by MKRN1 E3 ligase controls cell cycle arrest and apoptosis.

Lee, Eun-Woo,Lee, Min-Sik,Camus, Suzanne,Ghim, Jaewang,Yang, Mi-Ran,Oh, Wonkyung,Ha, Nam-Chul,Lane, David P,Song, Jaewhan Published for the European Molecular Biology Organ 2009 The EMBO journal Vol.28 No.14

<P>Makorin Ring Finger Protein 1 (MKRN1) is a transcriptional co-regulator and an E3 ligase. Here, we show that MKRN1 simultaneously functions as a differentially negative regulator of p53 and p21. In normal conditions, MKRN1 could destabilize both p53 and p21 through ubiquitination and proteasome-dependent degradation. As a result, depletion of MKRN1 induced growth arrest through activation of p53 and p21. Interestingly, MKRN1 used earlier unknown sites, K291 and K292, for p53 ubiquitination and subsequent degradation. Under severe stress conditions, however, MKRN1 primarily induced the efficient degradation of p21. This regulatory process contributed to the acceleration of DNA damage-induced apoptosis by eliminating p21. MKRN1 depletion diminished adriamycin or ultraviolet-induced cell death, whereas ectopic expression of MKRN1 facilitated apoptosis. Furthermore, MKRN1 stable cell lines that constantly produced low levels of p53 and p21 exhibited stabilization of p53, but not p21, with increased cell death on DNA damage. Our results indicate that MKRN1 exhibits dual functions of keeping cells alive by suppressing p53 under normal conditions and stimulating cell death by repressing p21 under stress conditions.</P>

Synthesis and photophysical property of well-defined donor–acceptor diblock copolymer based on regioregular poly(3-hexylthiophene) and fullerene

Lee, Jea Uk,Cirpan, Ali,Emrick, Todd,Russell, Thomas P.,Jo, Won Ho Royal Society of Chemistry 2009 Journal of materials chemistry Vol.19 No.10

<P>A new, well-defined diblock copolymer (P3HT-<I>b</I>-C<SUB>60</SUB>) based on regioregular poly(3-hexylthiophene) (P3HT) and fullerene was synthesized. First, regioregular P3HT was synthesized through Grignard metathesis polymerization, and then methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA) were copolymerized by using an end-functionalized P3HT as a macroinitiator for the atom transfer radical polymerization to yield a diblock copolymer (P3HT-<I>b</I>-P(MMA-<I>r</I>-HEMA)). A fullerene derivative functionalized with carboxylic acid, [6,6]-phenyl-C<SUB>61</SUB>-butyric acid (PCBA), was then chemically linked to the HEMA unit in the second block (P(MMA-<I>r</I>-HEMA)) to produce a diblock copolymer with the second block containing fullerenes. Annealing thin films of the copolymer revealed nanometer-scale phase separation, a more suitable morphology for enabling excitons generated in the P3HT domain to more efficiently reach the donor–acceptor interface, relative to simple blends of P3HT and C<SUB>60</SUB>. As a result, photoluminescence of the P3HT-<I>b</I>-C<SUB>60</SUB> diblock copolymer in the films showed a complete quenching of photoluminescence of P3HT, which is indicative of charge transfer between P3HT and fullerene.</P> <P>Graphic Abstract</P><P>A new, well-defined diblock copolymer (P3HT-<I>b</I>-C<SUB>60</SUB>) based on regioregular P3HT and fullerene showed phase separation on a nanometer scale, which allows the excitons generated in the P3HT domain to reach the donor–acceptor interface more efficiently. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b813368a'> </P>

MicroRNA signatures associated with immortalization of EBV‐transformed lymphoblastoid cell lines and their clinical traits

Lee, J.‐,E.,Hong, E.‐,J.,Nam, H.‐,Y.,Kim, J.‐,W.,Han, B.‐,G.,Jeon, J.‐,P. Blackwell Publishing Ltd 2011 Cell proliferation Vol.44 No.1

<P><B>Abstract</B></P><P><B>Objective: </B> MicroRNAs (miRNAs) are negative regulators of gene expression that play important roles in cell processes such as proliferation, development and differentiation. Recently, it has been reported that miRNAs are related to development of carcinogenesis. The aim of this study was to identify miRNAs associated with terminal immortalization of Epstein–Barr virus (EBV)‐transformed lymphoblastoid cell line (LCL) and associated clinical traits.</P><P><B>Material and Methods: </B> Hence, we performed miRNA microarray approach with early‐ (p6) and late‐passage (p161) LCLs.</P><P><B>Results and Conclusion: </B> Microarray data showed that nine miRNAs (miR‐20b*, miR‐28‐5p, miR‐99a, miR‐125b, miR‐151‐3p, miR‐151:9.1, miR‐216a, miR‐223* and miR‐1296) were differentially expressed in most LCLs during long‐term culture. In particular, miR‐125b was up‐regulated in all the tested late‐passage LCLs. miR‐99a, miR‐125b, miR‐216a and miR‐1296 were putative negative regulators of <I>RASGRP3</I>, <I>GPR160</I>, <I>PRKCH</I> and <I>XAF1</I>, respectively, which were found to be differentially expressed in LCLs during long‐term culture in a previous study. Linear regression analysis showed that miR‐200a and miR‐296‐3p correlated with triglyceride and HbA1C levels, respectively, suggesting that miRNA signatures of LCLs could provide information on the donor’s health. In conclusion, our study suggests that expression changes of specific miRNAs may be required for terminal immortalization of LCLs. Thus, differentially expressed miRNAs would be a potential marker for completion of cell immortalization during EBV‐mediated tumorigenesis.</P>

Chemodosimeter functionalized diatomaceous earth particles for visual detection and removal of trace mercury ions from water

Patil, Pravin,Madhuprasad, Pravin,Bhat, Mahesh P.,Gatti, Manasa G.,Kabiri, Shervin,Altalhi, Tariq,Jung, Ho-Young,Losic, Dusan,Kurkuri, Mahaveer Elsevier 2017 Chemical engineering journal Vol.327 No.-

<P><B>Abstract</B></P> <P>The rhodamine based receptor, P2 has been developed for the detection of environmentally hazardous Hg<SUP>2+</SUP> ions with a limit of detection, 1.5×10<SUP>−6</SUP> M. The P2 showed a significant colour change from colourless to pink upon binding with Hg<SUP>2+</SUP> ions. As a result, a new peak at 533nm was observed in UV–vis spectroscopy which was attributed to spirolactum ring opening followed by through bond energy transfer (TBET). In addition, the presence of other competing cations did not interfere the detection of Hg<SUP>2+</SUP> ions. Further, P2 has been successfully immobilized onto the naturally available and highly porous diatomaceous earth particles (P2D) for removal of Hg<SUP>2+</SUP> ions from water. The covalently attached organic molecule in P2D forms complex with Hg<SUP>2+</SUP> ion present in the water and thus traps the Hg<SUP>2+</SUP> ions. Based on this, a proof-of-concept cartridge has been developed for water purification. The cartridge having 450mg of P2D was able to purify 30mL of water containing 1ppm Hg<SUP>2+</SUP> ions. The efficiency of cartridge could be visualized with a colour change from colourless to pink.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Detection and removal of Hg<SUP>2+</SUP> from water using chemodosimeter P2 were realized. </LI> <LI> P2 has been successfully immobilized onto naturally available diatoms (P2D). </LI> <LI> Organic receptor and hazardous Hg<SUP>2+</SUP> ions were physically contained in diatoms. </LI> <LI> Eco-friendly cartridge containing P2D was developed for the removal of Hg<SUP>2+</SUP> ions. </LI> <LI> Device efficiency (time to replace) could be realized through visual colour change. </LI> </UL> </P>

Balanced intake of protein and carbohydrate maximizes lifetime reproductive success in the mealworm beetle, Tenebrio molitor (Coleoptera: Tenebrionidae)

Rho, M.S.,Lee, K.P. Pergamon Press 2016 Journal of insect physiology Vol.91 No.-

<P>Recent developments in insect gerontological and nutritional research have suggested that the dietary protein:carbohydrate (P:C) balance is a critical determinant of lifespan and reproduction in many insects. However, most studies investigating this important role of dietary P:C balance have been conducted using dipteran and orthopteran species. In this study, we used the mealworm beetles, Tenebrio molitor L. (Coleoptera: Tenebrionidae), to test the effects of dietary P:C balance on lifespan and reproduction. Regardless of their reproductive status, both male and female beetles had the shortest lifespan at the protein-biased ratio of P:C 5:1. Mean lifespan was the longest at P:C 1:1 for males and at both P:C 1:1 and 1:5 for females. Mating significantly curtailed the lifespan of both males and females, indicating the survival cost of mating. Age-specific egg laying was significantly higher at P:C 1:1 than at the two imbalanced P:C ratios (1:5 or 5:1) at any given age throughout their lives, resulting in the highest lifetime reproductive success at P:C 1:1. When given a choice, beetles actively regulated their intake of protein and carbohydrate to a slightly carbohydrate-biased ratio (P:C 1:1.54-1:1.64 for males and P:C 1:1.31:1.36 for females). The self-selected P:C ratio was significantly higher for females than males, reflecting a higher protein requirement for egg production. Collectively, our results add to a growing body of evidence suggesting the key role played by dietary macronutrient balance in shaping lifespan and reproduction in insects. (C) 2016 Elsevier Ltd. All rights reserved.</P>

Controlling the interchain packing and photovoltaic properties via fluorine substitution in terpolymers based on benzo[1,2-c:4,5-c']dithiophene-4,8-dione and benzothiadiazole units

Kini, Gururaj P.,Choi, Jun Young,Jeon, Sung Jae,Suh, Il Soon,Moon, Doo Kyung Elsevier 2018 Polymer Vol.148 No.-

<P><B>Abstract</B></P> <P>We present a series of three terpolymers involving benzo [1,2-c:4,5-c']dithiophene-4,8-dione (BDD) and benzothiadiazole (BT) as acceptor units, and oligothiophene as the donor unit (PBDD-TnFBT terpolymers). We optimized the structures of these terpolymers by varying the number of fluorine (F) atoms on the BT unit and studied its effects on photovoltaic performance (<B>P1</B> (BT), <B>P2</B> (FBT), and <B>P3</B> (2FBT)). Density functional theory analysis, optical-electrochemical analysis, and X-ray diffraction study revealed that the fluorination of BT significantly decreased frontier energy levels, enhanced both intermolecular interactions and planarization of polymer backbone in the resulted polymers. As a result, <B>P3,</B> having two F substituents on BT, exhibited stronger intermolecular interactions, predominant face-on orientation with a shorter π-π stacking distance of 3.51 Å, high hole mobility, and optimal nanoscale morphology compared to single F substituent (<B>P2</B>) and zero F substituent (<B>P1</B>) counterparts. Consequently, polymer solar cells based on <B>P3</B> demonstrated higher power conversion efficiency (PCE) of 6.2% than those based on <B>P1</B> and <B>P2</B> (1.4 and 1.7% respectively). This study illustrates the interrelation between the degree of fluorination and photovoltaic performance and effectively contributes to the design of high-PCE polymer donors for photovoltaic application.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Three terpolymers involving BDD and BT with the different number of fluorine (F) atoms were introduced. </LI> <LI> The interrelation between the degree of fluorination with charge transport behavior and polymer performance in PSC were investigated. </LI> <LI> Fluorination of BT significantly decreased frontier energy levels and enhanced intermolecular interactions in polymers. </LI> <LI> The PCE of PSCs was greatly improved from P1 (BT) 1.4% to 6.2 % P3 (2FBT) by the addition of F-atoms. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Toward high efficiency organic photovoltaic devices with enhanced thermal stability utilizing P3HT-b-P3PHT block copolymer additives

Zhu, M.,Kim, H.,Jang, Y.,Park, S.,Ryu, D.,Kim, K.,Tang, P.,Qiu, F.,Kim, D.,Peng, J. Royal Society of Chemistry 2016 Journal of Materials Chemistry A Vol.4 No.47

<P>Organic photovoltaics (OPVs) have drawn an extensive amount of attention due to their low cost, processibility and flexibility. However, a cell based on a blend of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C-61-butyric acid methyl ester (PC61BM) has a limited power conversion efficiency (PCE) due to the short exciton diffusion length of similar to 10 nm. We address this issue by designing a series of all-conjugated diblock copolymers, poly(3-hexylthiophene)-b-poly(3-(6-diethylphosphonatohexyl) thiophene) (P3HT-b-P3PHT), intended for use as additives to improve the performance of P3HT:PC61BM-based photovoltaic devices. The PCE of the devices improved from 3.30% to 4.03% with the addition of P3HT-b-P3PHT (3 : 1). The thermal stability of devices with P3HT-b-P3PHT additives improved significantly relative to that of the P3HT:PC61BM reference device, where the devices including a copolymer with a higher P3PHT content exhibited a better thermal stability. It was found that the fill factor (FF) could be regulated by simply varying the block ratio of P3HT-b-P3PHT and played a crucial role in improving both the PCE and the thermal stability. The P3HT-b-P3PHT diffused at the P3HT:PC61BM interface, improved the miscibility between P3HT and PC61BM, optimized the nanoscale morphology of the photoactive layer, and reduced the active layer roughness, all of which improved the FF and thus contributed to an improvement in device performance.</P>

Growth Mechanism and Electronic Structure of Zn₃P₂ on the Ga-Rich GaAs(001) Surface

Jeon, Seokmin,Bosco, Jeffrey P.,Wilson, Samantha S.,Rozeveld, Steve J.,Kim, Hyungjun,Atwater, Harry A. American Chemical Society 2014 The Journal of Physical Chemistry Part C Vol.118 No.24

<P>The growth of epitaxial Zn<SUB>3</SUB>P<SUB>2</SUB> films on III–V substrates unlocks a promising pathway toward high-efficiency, earth-abundant photovoltaic devices fabricated on reusable, single-crystal templates. The detailed chemical, structural, and electronic properties of the surface and interface of pseudomorphic Zn<SUB>3</SUB>P<SUB>2</SUB> epilayers grown on GaAs(001) were investigated using scanning tunneling microscopy/spectroscopy and high-resolution X-ray photoelectron spectroscopy. Two interesting features of the growth process were observed: (1) vapor-phase P<SUB>4</SUB> first reacts with the Ga-rich GaAs surface to form an interfacial GaP layer with a thickness of several monolayers, and (2) a P-rich amorphous overlayer is present during the entire film growth process, beneath which a highly ordered Zn<SUB>3</SUB>P<SUB>2</SUB> crystalline phase is precipitated. These features were corroborated by transmission electron micrographs of the Zn<SUB>3</SUB>P<SUB>2</SUB>/GaAs interface as well as density functional theory calculations of P reactions with the GaAs surface. Finally, the valence-band offset between the crystalline Zn<SUB>3</SUB>P<SUB>2</SUB> epilayer and the GaAs substrate was determined to be Δ<I>E</I><SUB>V</SUB> = 1.0 ± 0.1 eV, indicating the formation of a hole-depletion layer at the substrate surface which may inhibit formation of an ohmic contact.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2014/jpccck.2014.118.issue-24/jp4127804/production/images/medium/jp-2013-127804_0010.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp4127804'>ACS Electronic Supporting Info</A></P>