Synthesis and Properties of Bipolar Ladder-Like Polysiloxane with Carbazole and Triphenylphosphine Oxygen Groups.

In this study, a series of ladder-like polysiloxanes are synthesized by introducing double-chain Si-O-Si polymer as the backbone and the carbazole and triphenylphosphine oxide with high triplet energy as side groups. The ladder-like structures of polysiloxanes are achieved through a controlled polymerization method that involves the monomer self-assembly and subsequent surface-restricted solid-phase in situ condensation through freeze-drying. The introduction of siloxane improves thermal stability of the polymers and inhibits the conjugation of the polymers between the side groups, leading to an increase in the triplet energy level. Therefore, all these polymers perform higher triplet energy levels than phosphorescent emitter (FIrpic). The cyclic voltammetry measurements demonstrate that the bipolar polymer exhibits a high highest occupied molecular orbital (HOMO) value of -5.32 eV, which is consistent with the work function of ITO/PEDOT:PSS, consequently facilitating hole injection. Furthermore, the incorporation of triphenylphosphine oxide promotes electron injection. Molecular simulations reveal that the frontier orbital distributions of the bipolar polymer are located on the carbazole and triphenylphosphine groups, respectively, which facilitate the transport of electrons and holes.

Antibody array-based proteomic screening of novel biomarkers in malignant biliary stricture.

BACKGROUND: Distinguishing between benign and malignant bile duct strictures has long been a diagnostic challenge in clinical practice. OBJECTIVE: This study aimed to discover novel biomarkers in bile to improve the diagnostic accuracy of malignant biliary strictures. METHODS: Bile samples were collected from 6 patients with malignant or benign biliary stricture, respectively. Protein profiles of the bile were analyzed with a semi-quantitative human antibody array of 440 proteins. Then the differential expressed proteins were screened by Venn diagram analysis. Following this, the accuracy of these potential biomarkers for discriminating between malignant and non-malignant biliary strictures was validated in a larger (n= 40) group of patients using ROC analysis and the best biomarker combination was further selected by lasso analysis. RESULTS: Twenty proteins were found differentially expressed in malignant versus benign biliary strictures, 6 of which were identified by Venn diagram analysis to be up-regulated regardless of the location of biliary strictures. Among the 6 biomarkers, bile lipocalin-2, P-cadherin, and adipsin showed better diagnostic utility than that of bile CA19-9. Lasso analysis identified that lipocalin-2, P-cadherin and CA19-9 as a group of makers best distinguished malignant from benign strictures. CONCLUSIONS: Lipocalin-2 and P-cadherin measurements in bile could be clinically useful for the detection of malignant biliary strictures.

Photoluminescent Behaviors of Thermally Activated Delayed Fluorescence Polymeric Emitters in Nanofibers.

Anisotropic 1D nanostructures with high surface-area-to-volume ratio display the enhanced optoelectronic properties of light-emitting compounds compared to bulk or 2D systems. To study the effect of nanometer-constrained space on photoluminescent behavior of thermally activated delayed fluorescence (TADF) polymeric emitters, electrospinning technique is used to produce nanofibers of TADF emitters. Herein, two TADF polymer (P1 and P3) nanofibers with 90% polyacrylonitrile (PAN) are fabricated and their photophysical properties are studied and compared with their spin-coated film counterparts. The distinguishing polarized photoluminescencent properties of P1/PAN or P3/PAN electrospun nanofibers are obtained due to high orientation degree and superior molecular arrangement. Moreover, the better TADF properties in nanofibers can be observed comparing with their spin-coated films, including longer-lived excited states, higher photoluminescence quantum efficiency, lower internal conversion decay rate, and higher reverse intersystem crossing rate constant.

Synthesis and Charge-Transporting Properties of Dibenzothiphene Dioxide-Based Polysiloxanes.

We designed and synthesized a dibenzothiphene dioxide-based homopolysiloxane, PDBTSi, and a carbazole-dibenzothiophene dioxide alternating copolysiloxane, PCzSi-alt-PDBTSi, respectively. Both PDBTSi and PCzSi-alt-PDBTSi possess an improved solubility, good film-forming ability and extremely high thermal stability due to introduction of polysiloxane main chains. Meanwhile, PDBTSi and PCzSi-alt-PDBTSi exhibit high triplet energy levels of 2.95 eV and 3.05 eV, respectively. Furthermore, PDBTSi possesses good electron-transporting property with an electron mobility of 1.02×10-4  cm2 V-1 s-1 and a relatively balanced hole mobility of 8.76×10-5  cm2 V-1 s-1 . In contrast, PCzSi-alt-PDBTSi exhibits an electron mobility of 4.65×10-5  cm2 V-1 s-1 and a hole mobility of 1.17×10-4  cm2 V-1 s-1 . Therefore, our results here provide a feasible strategy to obtain solution-processed polysiloxane materials with high and balanced electron- and hole-transporting properties.

Solution-Processed Blue/Deep Blue and White Phosphorescent Organic Light-Emitting Diodes (PhOLEDs) Hosted by a Polysiloxane Derivative with Pendant mCP (1,3-bis(9-carbazolyl)benzene).

The synthesis and characterization is reported of an efficient polysiloxane derivative containing the 1,3-bis(9-carbazolyl)benzene (mCP) moiety as a pendant unit on the polysiloxane backbone. In comparison with mCP, the mCP-polysiloxane hybrid (PmCPSi) has significantly improved thermal and morphological stabilities with a high decomposition temperature (Td = 523 °C) and glass transition temperature (Tg = 194 °C). The silicon-oxygen linkage of PmCPSi prevents intermolecular π-stacking and ensures a high triplet energy level (ET = 3.0 eV). Using PmCPSi as a host, blue phosphorescent organic light emitting devices (PhOLEDs) effectively confine triplet excitons, with efficient energy transfer to the guest emitter and a relatively low turn-on voltage of 5.8 V. A maximum external quantum efficiency of 9.24% and maximum current efficiency of 18.93 cd/A are obtained. These values are higher than for directly analogous poly(vinylcarbazole) (PVK) based devices (6.76%, 12.29 cd/A). Good color stability over a range of operating voltages is observed. A two-component "warm-white" device with a maximum current efficiency of 10.4 cd/A is obtained using a blend of blue and orange phosphorescent emitters as dopants in PmCPSi host. These results demonstrate that well-designed polysiloxane derivatives are highly efficient hosts suitable for low-cost solution-processed PhOLEDs.

Immobilization of lipase on porous monodisperse chitosan microspheres.

Porous monodisperse chitosan microspheres were synthesized for enzyme immobilization. The microspheres were prepared using microchannels and modified with glutaraldehyde. The microspheres had a mean diameter of 495 µm; the polydispersity indices were less than 0.08, and the specific surface area was between 121 and 173 m(2) /g. Candida sp. 1619 lipase was selected as a model lipase. Immobilization conditions such as enzyme loading, glutaraldehyde concentration, and immobilization time were optimized. The temperature, pH, and storage stability of the free and immobilized enzymes were also investigated. The immobilized enzyme had broad-ranging pH and temperature optima as compared with free enzyme. The storage stability of the immobilized enzyme was higher than that of the free enzyme.

Structure evolution of poly(3-hexylthiophene) on Si wafer and poly(vinylphenol) sublayer.

The structure evolution of P3HT thin films on Si wafer and PVPh covered Si wafer during heating, thermal annealing, and melt recrystallization processes has been studied in detail using X-ray analysis techniques. The effect of substrate on the crystallization behavior and interface structure of P3HT films was explored. For the P3HT films deposited on the Si substrate, it was found that the stability of P3HT crystals is orientation dependent. The crystals oriented with b-axis normal to the substrate, that is, a face-on molecular orientation, are less stable than those with the a-axis arranged normal to the substrate (side-on molecular orientation). Thermal annealing temperature plays an important role in the molecular structure of P3HT including crystal structure, film thickness, and surface roughness. After annealing at relatively high temperature, new crystals form during the cooling process accompanied by the shrinking of a-axis. Moreover, the melt recrystallization favors the formation of more stable P3HT crystals with side-on molecular orientation. The PVPh substrate does not affect the crystallization behavior of solution cast P3HT significantly but inhibits the formation of P3HT crystal with face-on molecular orientation. However, the interfacial morphology of P3HT and PVPh changes by annealing at elevated temperature. The P3HT/PVPh interface changes from a sharply defined one into a diffused one at around 160 °C. The PVPh sublayer inhibits the melt recrystallization of P3HT to some extent, leading to a slight expansion of the a-axis.