Showing papers by "Yeong Don Park published in 2023"

Low-Regioregularity Polythiophene for a Highly Sensitive and Stretchable Gas Sensor.

Abstract: In this study, we examined how the regioregularity of poly(3-hexylthiophene) (P3HT) affects molecular packing, free volume, charge transport, and gas sensing properties. Our results showed that the presence of regular alkyl side chains on the polymer backbone promoted a high degree of structural order in regioregular P3HT molecules, leading to a compact packing density and reduced free volume. Consequently, it was more challenging for NO2 molecules to interact with the hole charge carriers in the conductive channel. On the other hand, the regiorandom P3HT films displayed a larger free volume, attributed to the irregular side chains, which facilitated the gas-analyte interaction while impeding efficient charge transport. Thus, these films exhibited greater sensitivity to analyte gas molecules. The molecular order, packing density, and hardness of P3HT films were confirmed through the use of multiple techniques, including UV-vis spectroscopy, atomic force microscopy, and grazing-incidence X-ray diffraction. Additionally, the regiorandom P3HT films showed enhanced mechanical flexibility compared to the regioregular films. In conclusion, our findings emphasize that the regularity of polymer molecules plays a significant role in determining the charge carrier transport and gas adsorption characteristics.

Highly Sensitive and Selective Organic Gas Sensors Based on Nitrided ZSM-5 Zeolite.

Abstract: For next-generation gas sensors, conductive polymers have strong potential for overcoming the existing deficiencies of conventional inorganic sensors based on metallic oxides. However, the signal of organic gas sensors is inferior to that of inorganic metal oxide gas sensors because of organic gas sensors' poor charge carrier transport. Herein, the combination of an organic transistor-type gas sensor and a zeolite with strong gas-adsorbing properties is proposed and experimentally demonstrated. Among the various investigated zeolites, ZSM-5 with ∼5.5 Å pore openings enhanced the adsorption for small gas molecules when combined with a polymer active layer, where it provided a pathway for gas molecules to penetrate the zeolite channels. Moreover, nitrided ZSM-5 (N-ZSM-5) enhanced the sensing performance of NO2 molecules selectively because N in the N-ZSM-5 framework strongly interacted with NO2 molecules. These results open the possibility for zeolite-modified organic gas sensors that selectively adsorb target gas molecules via heteroatoms substituted into the zeolite framework.