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
The oxidation of
polyÂ(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
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