Organic Field-Effect Transistors as Flexible, Tissue-Equivalent Radiation Dosimeters in Medical Applications.

Radiation therapy is one of the most prevalent procedures for cancer treatment, but the risks of malignancies induced by peripheral beam in healthy tissues surrounding the target is high. Therefore, being able to accurately measure the exposure dose is a critical aspect of patient care. Here a radiation detector based on an organic field-effect transistor (RAD-OFET) is introduced, an in vivo dosimeter that can be placed directly on a patient's skin to validate in real time the dose being delivered and ensure that for nearby regions an acceptable level of low dose is being received. This device reduces the errors faced by current technologies in approximating the dose profile in a patient's body, is sensitive for doses relevant to radiation treatment procedures, and robust when incorporated into conformal large-area electronics. A model is proposed to describe the operation of RAD-OFETs, based on the interplay between charge photogeneration and trapping.

Structural Diversity in 2,2'-[Naphthalene-1,8:4,5-bis(dicarboximide)-N,N'-diyl]-bis(ethylammonium) Iodoplumbates.

Crystallization from solutions containing 2,2'-[naphthalene-1,8:4,5-bis(dicarboximide)-N,N'-diyl]-bis(ethylammonium) diiodide ((NDIC2)I2) and PbI2 has been investigated. Eight different materials are obtained, either by variation of crystallization conditions or by subsequent thermal or solvent-induced transformations. Crystal structures have been determined for five materials. [(NDIC2)2Pb5I14(DMF)2]·4DMF (DMF = N,N-dimethylformamide) (1), [(NDIC2)Pb4I10]·4DMF (3), [(NDIC2)Pb2I6]·4NMP (NMP = N-methyl-2-pyrrolidone) (4), and [(NDIC2)Pb2I6]·2H2O (5) form 1-dimensional (1D) chains consisting of PbI6 (and, in the case of 1, PbI5(DMF)) octahedra, either solely face-sharing or a mixture of face-sharing and vertex-sharing. The structure of [(NDIC2)3Pb5I16]·6NMP (2) contains 0D clusters; these consist of three PbI6 octahedra and two unusually coordinated lead centers that exhibit three relatively short Pb-I bonds, two very long Pb-I contacts, and η2-coordination of an aromatic ring of NDIC2 to the lead. Close contacts between iodide ions and the imide rings of NDIC2 in four of the structures suggest that an iodide-to-NDIC2 charge-transfer interaction may be responsible for the observed red coloration of the materials. The optical and electrical properties of 1 have been studied; its onset of absorption is at 2.0 eV, and its conductivity was measured as 5.4 × 10-5 ± 1.1 × 10-5 S m-1.

Solution-Processed Organic and Halide Perovskite Transistors on Hydrophobic Surfaces.

Solution-processable electronic devices are highly desirable due to their low cost and compatibility with flexible substrates. However, they are often challenging to fabricate due to the hydrophobic nature of the surfaces of the constituent layers. Here, we use a protein solution to modify the surface properties and to improve the wettability of the fluoropolymer dielectric Cytop. The engineered hydrophilic surface is successfully incorporated in bottom-gate solution-deposited organic field-effect transistors (OFETs) and hybrid organic-inorganic trihalide perovskite field-effect transistors (HTP-FETs) fabricated on flexible substrates. Our analysis of the density of trapping states at the semiconductor-dielectric interface suggests that the increase in the trap density as a result of the chemical treatment is minimal. As a result, the devices exhibit good charge carrier mobilities, near-zero threshold voltages, and low electrical hysteresis.

Indacenodibenzothiophenes: synthesis, optoelectronic properties and materials applications of molecules with strong antiaromatic character.

Indeno[1,2-b]fluorenes (IFs), while containing 4n π-electrons, are best described as two aromatic benzene rings fused to a weakly paratropic s-indacene core. In this study, we find that replacement of the outer benzene rings of an IF with benzothiophenes allows the antiaromaticity of the central s-indacene to strongly reassert itself. Herein we report a combined synthetic, computational, structural, and materials study of anti- and syn-indacenodibenzothiophenes (IDBTs). We have developed an efficient and scalable synthesis for preparation of a series of aryl- and ethynyl-substituted IDBTs. NICS-XY scans and ACID calculations reveal an increasingly antiaromatic core from [1,2-b]IF to anti-IDBT, with syn-IDBT being nearly as antiaromatic as the parent s-indacene. As an initial evaluation, the intermolecular electronic couplings and electronic band structure of a diethynyl anti-IDBT derivative reveal the potential for hole and / or electron transport. OFETs constructed using this molecule show the highest hole mobilities yet achieved for a fully conjugated IF derivative.