Microelectrochemical transistor based poly

In this article we report the synthesis and electrochemical properties of the polymer derived from oxidation of X, poly(I), and the characteristics of a microelectrochemical transistor based on the polymer. Poly(I), which is formed by electrochemical oxidation of X, Equation 1, consists of a conducting polymer backbone, polythiophene. 

The poly(I)-based transistor is the first illustration of a microelectrochemical transistor based on a combination of a conducting and a conventional redox polymer as the active material. The transistor "turns on" at VG corresponding to oxidation of the polythiophene backbone. The resistivity of poly(I) declines by a factor of 105 upon changing VG from 0.4 V to 0.8 V vs. Ag+/Ag. When Vg is moved close to the one-electron reduction potential of V2+/+, the conventional redox conductivity gives a small degree of "turn on". A sharp Iq-Vq characteristic results, with an Ip(peak) at Vq = E° (V2+/+). Though the microelectrochemical devices based on conventional redox conduction have both slow switching speed and a... 

Sulfur-ojqrgen interactions have been proposed as a possible cause for the considerable stability of polyalkojQfthiophenes, based on ex situ investigations of a large selection of substituted thiophenes and their polymers [843]. The amplification of chemical and electrical signals has been applied in a microelectrochemical transistor based on poly(3-methylthiophene) [844]. 

Recently, several molecule-based microelectrochemical devices have been developed by the Wrighton group.(14.15.21-22) A microelectrode array coated with poly(I) results in a microelectrochemical transistor with the unique characteristic that shows "turn on" in two gate potential, Vq, regimes, one associated with the polythiophene switching from an insulator to a conductor upon oxidation and one associated with the v2+ + conventional redox centers. 

Scheme IV, A poly(I)-based microelectrochemical transistor that turns on when VG is moved from VG (ie +0.4 V vs. Ag+/Ag) where polythiophene is reduced and insulating to Vq4 (ie +0.7 V vs. Ag+/Ag) where polythiophene is oxidized and conducting. This transistor also turns on to a smaller extent at E0/ (V2+/+), Vq1 = -0.63 V vs. Ag+/Ag. At VG significantly (>0.2 V) more negative (Vq2 < -0.8 V vs. Ag+/Ag) or positive (+0.4 V > Vq > -0.4 V vs. Ag+/Ag) of E° (V2+/+) only the reduced or oxidized form of viologen redox centers is present, respectively, and this device is...

Figure 11. Drain current, Id, vs. gate voltage, Vg, for various drain voltages, Vq (25, 50, 100 mV) for a poly(I)-based microelectrochemical transistor. The gate voltage, Vq was scanned at 1 mV/s.

The characteristics of the polymer-based microelectrochemical transistors are as follows. The current between source and drain. Ip, is a function of the potential between source and drain, Vp, at various fixed gate potentials, Vq. When the Vg using poly(3-methylthiophene) or PP is held at negative potentials where the polymer... 

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