A series of alkyl chain end-capped oligofluorene−thiophenes have been prepared with high yields using Suzuki or Stille coupling reactions. The electronic and optical properties of the thin films deposited at different substrate temperatures have been investigated. Morphological studies using transmission electron microscopy (TEM) revealed well-interconnected microcrystalline domains in these thin films. X-ray diffraction measurements of the vacuum-evaporated films showed enhanced crystalline order with increasing substrate deposition temperature. Thermal analysis as well as electrochemical measurements of the materials indicated that the new oligomers have high thermal and oxidative stability. Highly ordered polycrystalline vacuum-evaporated films with charge carrier mobility as high as 0.12 cm2 V-1 s-1 have been achieved with 5,5‘-bis(7-hexyl-9H-fluoren-2-yl)-2,2‘-bithiophene (DHFTTF). Thin film field-effect transistor (TFT) devices made from these materials showed remarkable stability even after UV (366 nm) irradiation for more than 48 h in air. The semiconductors exhibit high on/off ratios (up to 105) and no significant decrease in mobility and on/off ratio over several months in air with exposure to ambient light. Finally, bright emission colors from greenish yellow to orange-red were observed in this new series of oligomer solid films excited with UV light (366 nm). In addition, a comparative study of the newly synthesized oligomers with α,α‘-dihexylsexithiophene (DH6T), one of the most widely investigated oligothiophenes, is presented. The current approach to the molecular design can be applied toward the rational design of new TFT materials.

A series of thiophene-containing oligomers that are less electron rich than alpha-6T were synthesized, and the thin film morphologies and field-effect transistor characteristics of the oligomers were evaluated. Phenyl and thiazole rings were included in many of the oligomers, and a new synthesis of perfluoroalkylmethyl-terminated oligomers was developed. Desirably low off currents were associated with calculated highest occupied molecular orbital energies above ca. 5.0 eV relative to vacuum. Some of the oligomers displayed mobilities above 0.01 cm 2 (Vs) -1 , but there was no correlation of mobility with calculated orbital energies and some compounds with seemingly continuous morphologies had low mobilities nonetheless. One compound, 1,4-bis(5′-hexyl-2,2′-bithiophen-5-yl)benzene, showed promising behavior as a solution-deposited semiconductor, with mobility up to 0.02 cm 2 (Vs) -1 and an on/off ratio up to 20 000.

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Tumor relapse after radiotherapy is a significant challenge to oncologists, even after recent the advances in technologies. Here, we showed that cancer-associated fibroblasts (CAFs), a major component of cancer stromal cells, promoted irradiated cancer cell recovery and tumor relapse after radiotherapy. We provided evidence that CAFs-produced IGF1/2, CXCL12 and β-hydroxybutyrate were capable of inducing autophagy in cancer cells post-radiation and promoting cancer cell recovery from radiation-induced damage in vitro and in vivo in mice. These CAF-derived molecules increased the level of reactive oxygen species (ROS) post-radiation, which enhanced PP2A activity, repressing mTOR activation and increasing autophagy in cancer cells. Consistently, the IGF2 neutralizing antibody and the autophagy inhibitor 3-MA reduce the CAF-promoted tumor relapse in mice after radiotherapy. Taken together, our findings demonstrated that CAFs promoted irradiated cancer cell recovery and tumor regrowth post-radiation, suggesting that targeting the autophagy pathway in tumor cells may be a promising therapeutic strategy for radiotherapy sensitization.

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