Kinetics of Thermal Dissociation–Restoration Processes of J-Aggregate

概要

論文の詳細を見る
We investigated the kinetics of thermally induced dissociation–restoration processes of the J-band in merocyanine (MS)–Cd arachidate mixed Langmuir–Blodgett (LB) films. The UV–visible absorbance spectrum $A$ of the as-deposited film is associated with a prominent J-band (Band III) with its peak located at ${\sim}590$ nm besides Bands I and II centered at 500–515 and 545–555 nm, respectively. In the case of dry-heat treatments (DHTs), the Band III fraction decreases and the Band I fraction increases as the process proceeds, while the Band II fraction remains almost constant. The remaining fraction of Band III is found to obey an exponential decay law, $ f(t_{\text{H}},T_{\text{H}}) = \exp[- k(T_{\text{H}})t_{\text{H}}]$, governed by an activation-type rate, $k(T_{\text{H}}) = k(\infty)\exp[- E/(RT_{\text{H}})]$ with $k(\infty) = 4.50 \times 10^{8}$ s-1 and $E = 79.7$ kJ/mol, where $t_{\text{H}}$ and $T_{\text{H}}$ are the heating time and temperature, respectively. The above $E$ is 12–16 kJ/mol higher than that for the J-band dissociation process in the first stage of the hydrothermal treatment (HTT) under 100% humidity. This difference is explained as a barrier-lowering effect due to the water present in the HTT case. In the DHT-treated LB films, further application of HTT restores the J-band in a similar manner to that observed in the second stage of HTT when HTT is directly applied to the as-deposited films. The J-band restoration is described in both cases as a first-order process where [Band I] $\rightarrow$ [Band III] predominates over the reverse reaction. The $k(\infty)$ and $E$ for the forward reaction of $5.13 \times 10^{7}$ s-1 and 68.5 kJ/mol, respectively, for the DHT-subjected films, are comparable to those of $4.31 \times 10^{7}$ s-1 and 64.8 kJ/mol in the case of second-stage HTT reported previously.
2009-05-25

Kinetics of Thermal Dissociation–Restoration Processes of J-Aggregate

スポンサーリンク

概要

著者

関連論文

スポンサーリンク