Detecting Cis-Trans Isomerization of Para Methyl Red by using Silicon Field-Effect-Transistors

• Main Authors: XinKui Huang, 黃信魁
• Other Authors: 蔡麗珠
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/662zbn

碩士 === 國立臺北科技大學 === 有機高分子研究所 === 105 === We showed detection of the transition between cis and trans states of a para-methyl red using silicon field-effect-transistors. Para-methyl red is a photoisomerizable molecule: the transition from low-energy trans to high-energy cis states can be stimulated by irradiation of 365 nm UV light, and the reversed process can be accelerated by irradiation of 450 nm visible light. The structural change can produce a change in the electron cloud distribution, and hence a change in the molecular dipole moment, which can be detected by the field-effect-transistors. In this study, the photon-trigged structural transitions were conducted in vacuum, in the air and in various liquid conditions. It was found that in pure water the photon trigged molecule structural changes were most prominent and reproducible. It took about 3 minutes of UV irradiation to excite the molecules to the cis equilibrium state, and the spontaneous relaxation time from the cis equilibrium state to trans equilibrium state was found to be about 112 sec. It was also found that by irradiation of visible light for 60 sec, this relaxation process could be accelerated and shortened to 3 sec. Since field-effect-transistors detect the molecular dipoles, and thus would not apply force of any kinds to the molecules under study. This is in contrast to the popularly used optical detection technologies in which the probe light may, to a certain extent, disturb the molecule structure. In view of that, our field-effect-transistor based detection method provides a unique approach to reveal the nature of the structural state transitions.