Quantum Dot−Block Copolymer Hybrids with Improved Properties and Their Application to Quantum Dot Light-Emitting Devices

Zorn, Matthias,Bae, Wan Ki,Kwak, Jeonghun,Lee, Hyemin,Lee, Changhee,Zentel, Rudolf,Char, Kookheon American Chemical Society 2009 ACS NANO Vol.3 No.5

<P>To combine the optical properties of CdSe@ZnS quantum dots (QDs) with the electrical properties of semiconducting polymers, we prepared QD/polymer hybrids by grafting a block copolymer (BCP) containing thiol-anchoring moieties (poly(para-methyl triphenylamine-b-cysteamine acrylamide)) onto the surfaces of QDs through the ligand exchange procedure. The prepared QD/polymer hybrids possess improved processability such as enhanced solubility in various organic solvents as well as the film formation properties along with the improved colloidal stability derived from the grafted polymer shells. We also demonstrated light-emitting diodes based on QD/polymer hybrids, exhibiting the improved device performance (i.e., 3-fold increase in the external quantum efficiency) compared with the devices prepared by pristine (unmodified) QDs.</P>

Liquid Crystalline Ordering and Charge Transport in Semiconducting Materials

Pisula, Wojciech,Zorn, Matthias,Chang, Ji Young,Mü,llen, Klaus,Zentel, Rudolf WILEY-VCH Verlag 2009 Macromolecular Rapid Communications Vol.30 No.14

<P>Organic semiconducting materials offer the advantage of solution processability into flexible films. In most cases, their drawback is based on their low charge carrier mobility, which is directly related to the packing of the molecules both on local (amorphous versus crystalline) and on macroscopic (grain boundaries) length scales. Liquid crystalline ordering offers the possibility of circumventing this problem. An advanced concept comprises: i) the application of materials with different liquid crystalline phases, ii) the orientation of a low viscosity high temperature phase, and, iii) the transfer of the macroscopic orientation during cooling to a highly ordered (at best, crystalline-like) phase at room temperature. At the same time, the desired orientation for the application (OLED or field-effect transistor) can be obtained. This review presents the use of molecules with discotic, calamitic and sanidic phases and discusses the sensitivity of the phases with regard to defects depending on the dimensionality of the ordered structure (columns: 1D, smectic layers and sanidic phases: 2D). It presents ways to systematically improve charge carrier mobility by proper variation of the electronic and steric (packing) structure of the constituting molecules and to reach charge carrier mobilities that are close to and comparable to amorphous silicon, with values of 0.1 to 0.7 cm<SUP>2</SUP> · V<SUP>−1</SUP> · s<SUP>−1</SUP>. In this context, the significance of cross-linking to stabilize the orientation and liquid crystalline behavior of inorganic/organic hybrids is also discussed.</P><P> <img src='wiley_img/10221336-2009-30-14-MARC200900251-gra001.gif' alt='wiley_img/10221336-2009-30-14-MARC200900251-gra001'> </P> <B>Graphic Abstract</B> <P>Liquid crystalline ordering offers the possibility of improving charge carrier mobility. This review discusses the potential of LC-mediated ordering of rod- and disc-like objects in pure organic and organic-inorganic hybrid structures. <img src='wiley_img/10221336-2009-30-14-MARC200900251-content.gif' alt='wiley_img/10221336-2009-30-14-MARC200900251-content'> </P>

Differentiating Congestive and Non-congestive Losses on TCP Endpoint

Nanjun Li,Werner Zorn 보안공학연구지원센터 2008 International Journal of Hybrid Information Techno Vol.1 No.2

Packet loss in IP networks can be congestive due to IP interrupt queue overflow on the nodes, and non-congestive due to hardware failure, signal-fading or obstacles. Recognition of two types of losses can largely help TCP endpoints in making right decisions. In this paper we apply the Visualized IP-based Network Simulator (VINS) to characterize the key differences between congestive packet losses and that of due to link disruption, which is noncongestive and commonly seen in wireless networks. Based on the analyses, suggested improvements for wireless TCP endpoints are proposed on both kernel and application levels in terms of avoiding useless keep-alive probing and congestion window tuning, but re-routing and re-establishing new connections.

Reduced efficiency roll-off in light-emitting diodes enabled by quantum dot-conducting polymer nanohybrids

Bae, W.,Lim, J.,Zorn, M.,Kwak, J.,Park, Y. S.,Lee, D.,Lee, S.,Char, K.,Zentel, R.,Lee, C. Royal Society of Chemistry 2014 Journal of Materials Chemistry C Vol.2 No.25

Characterization of Quantum Dot/Conducting Polymer Hybrid Films and Their Application to Light‐Emitting Diodes

Kwak, Jeonghun,Bae, Wan Ki,Zorn, Matthias,Woo, Heeje,Yoon, Hyunsik,Lim, Jaehoon,Kang, Sang Wook,Weber, Stefan,Butt, Hans‐,Jü,rgen,Zentel, Rudolf,Lee, Seonghoon,Char, Kookheon,Lee, Changhee WILEY‐VCH Verlag 2009 Advanced Materials Vol.21 No.48

<P><B>Quantum dot/conducting polymer hybrid films</B> are used to prepare light‐emitting diodes (LEDs). The hybrid films (CdSe@ZnS quantum dots excellently dispersed in a conducting polymer matrix, see figure) are readily prepared by various solution‐based processes and are also easily micropatterned. The LEDs exhibit a turn‐on voltage of 4 V, an external quantum efficiency greater than 1.5%, and almost pure‐green quantum‐dot electroluminescence. </P>

No short-term effects of calorie-controlled Mediterranean or fast food dietary interventions on established biomarkers of vascular or metabolic risk in healthy individuals

Marijo Parcina,Maik Brune,Vareska Kaese,Markus Zorn,Rainer Spiegel,Valerija Vojvoda,Thomas Fleming,Gottfried Rudofsky,Peter Paul Nawroth 한국영양학회 2015 Nutrition Research and Practice Vol.9 No.2

BACKGROUND/OBJECTIVES: This study addressed the question whether the composition of supposedly ‘healthy’ or ‘unhealthy’ dietary regimes has a calorie-independent short-term effect on biomarkers of metabolic stress and vascular risk in healthy individuals. SUBJECTS/METHODS: Healthy male volunteers (age 29.5 ± 5.9 years, n = 39) were given a standardized baseline diet for two weeks before randomization into three groups of different dietary regimes: fast food, Mediterranean and German cooking style. Importantly, the amount of calories consumed per day was identical in all three groups. Blood samples were analyzed for biomarkers of cardiovascular risk and metabolic stress after two weeks of the baseline diet and after two weeks of the assigned dietary regime. RESULTS: No dietary intervention affected the metabolic or cardiovascular risk profile when compared in-between groups or compared to baseline. Subjects applied to the Mediterranean diet showed a statistically significant increase of uric acid compared to baseline and compared to the German diet group. Plasma concentrations of urea were significantly higher in both the fast food group and the Mediterranean group, when compared to baseline and compared to the German diet group. No significant differences were detected for the levels of vitamins, trace elements or metabolic stress markers (8-hydroxy-2-deoxyguanosine, malondialdehyde and methylglyoxal, a potent glycating agent). Established parameters of vascular risk (e.g. LDL-cholesterol, lipoprotein(a), homocysteine) were not significantly changed in-between groups or compared to baseline during the intervention period. CONCLUSIONS: The calorie-controlled dietary intervention caused neither protective nor harmful short-term effects regarding established biomarkers of vascular or metabolic risk. When avoiding the noxious effects of overfeeding, healthy individuals can possess the metabolic capacity to compensate for a potentially disadvantageous composition of a certain diet.

Catalytic enhancement of platinum supported on zeolite beta for toluene hydrogenation by addition of palladium

Sirinuch Loiha,Karin Fottinger,Katrin Zorn,Wantana Klysubun,Gunter Rupprechter,Jatuporn Wittayakun 한국공업화학회 2009 Journal of Industrial and Engineering Chemistry Vol.15 No.6

This work focused on the preparation, characterization and catalytic performance of a bimetallic platinum–palladiumcatalyst for toluene hydrogenation. A catalyst with 3 wt% loading of each metal was prepared by co-impregnation on zeolite beta in proton form and denoted as 3Pt3Pd/HBEA. The structure of HBEA was retained after catalyst preparation and the metal occupied strong acidic sites of the zeolite. Compared to monometallic 3Pt/HBEA, the 3Pt3Pd/HBEA exhibited smaller Pt particle size due to better dispersion on the support. The catalytic performance of the bimetallic catalyst at various temperatures indicated that the presence of Pd enhanced toluene hydrogenation of Pt catalyst at high temperature. The most suitable temperature for toluene hydrogenation on 3Pt3Pd/HBEA was 150 8C for which a complete toluene conversion was obtained with methylcyclohexane as the only product.

Standardized 4-step technique of bladder neck dissection during robot-assisted radical prostatectomy

Mansour Alnazari,Marc Zanaty,Emad Rajih,Assaad El-Hakim,Kevin C. Zorn 대한비뇨의학회 2016 Investigative and Clinical Urology Vol.57 No.-

Bladder neck (BN) dissection is considered one of the most challenging steps during robot-assisted radical prostatectomy. Better understanding of the BN anatomy, coupled with a standardized approach may facilitate dissection while minimizing complications. We describe in this article the 4 anatomic spaces during standardized BN dissection, as well other technical maneuvers of managing difficult scenarios including treatment of a large median lobe or patients with previous transurethral resection of the prostate. The first step involves the proper identification of the BN followed by slow horizontal dissection of the first layer (the dorsal venous complex and perivesicle fat). The second step proceeds with reconfirming the location of the BN followed by midline dissection of the second anatomical layer (the anterior bladder muscle and mucosa) using the tip of the monopolar scissor until the catheter is identified. The deflated catheter is then grasped by the assistant to apply upward traction on the prostate from 2 directions along with downward traction on the posterior bladder wall by the tip of the suction instrument. This triangulation allows easier, and safer visual, layer by layer, dissection of the third BN layer (the posterior bladder mucosa and muscle wall). The forth step is next performed by blunt puncture of the fourth layer (the retrotrigonal fascia) aiming to enter into the previously dissected seminal vesical space. Finally, both vas deferens and seminal vesicles are pulled through the open BN and handed to the assistant for upper traction to initiate Denovillier's dissection and prostate pedicle/neurovascular bundle control.