2 research outputs found

    Unveiling the Complexity of the Degradation Mechanism of Semiconducting Organic Polymers: Visible-Light-Induced Oxidation of P3HT Films on ZnO/ITO under Atmospheric Conditions

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    The oxidation of poly­(3-hexylthiophene) (P3HT) films deposited on ZnO/indium tin oxide (ITO) under blue light irradiation in either dry or humid atmospheres was studied using X-ray photoelectron spectroscopy in combination with UV–vis absorption spectroscopy. From results up to 12 h of reaction, ring-opening was hardly found, and it is suggested that the water molecules chemisorbed competitively against O<sub>2</sub> (i.e., the major oxidizing agent), thereby decreasing the oxidation of P3HT. Beyond 12 h, thiophene ring-opening took place at the topmost surface layer of P3HT, and the humidity facilitated the ring-opening of P3HT. Regarding the oxidation of the entire P3HT thin film, the humidity did not have a large influence on the oxidation behavior of P3HT. Here, the degree of oxidation of P3HT abruptly increased when the reaction time exceeded 12 h. This suggests that the rate of oxidation of the entire P3HT film is determined by the slow diffusion of the activated oxygen species into the deeper layers of the P3HT films. We also demonstrate that the photoinduced degradation of P3HT can be retarded by turning off light between irradiation, which may be due to the reversible desorption of activated oxygen species under dark conditions

    Structural Effect of Thioureas on the Detection of Chemical Warfare Agent Simulants

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    The ability to rapidly detect, identify, and monitor chemical warfare agents (CWAs) is imperative for both military and civilian defense. Since most CWAs and their simulants have an organophosphonate group, which is a hydrogen (H)-bond acceptor, many H-bond donors have been developed to effectively bind to the organophosphonate group. Although thioureas have been actively studied as an organocatalyst, they are relatively less investigated in CWA detection. In addition, there is a lack of studies on the structure–property relationship for gas phase detection. In this study, we synthesized various thioureas of different chemical structures, and tested them for sensing dimethylmethylphosphonate (DMMP), a CWA simulant. Molecular interaction between DMMP and thiourea was measured by <sup>1</sup>H NMR titration and supported by density functional theory (DFT) calculations. Strong H-bond donor ability of thiourea may cause self-aggregation, and CH−π interaction can play an important role in the DMMP detection. Gas-phase adsorption of DMMP was also measured using a quartz crystal microbalance (QCM) and analyzed using the simple Langmuir isotherm, showing the importance of structure-induced morphology of thioureas on the surface
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