We succeeded in the wide-range control of the period for the swelling-deswelling self-oscillation of a novel polymer gel by selection of the initial concentration of the Belouzov-Zhabotinsky (BZ) substrates and the temperature. The novel polymer gel was composed of a non-thermoresponsive and biocompatible poly(vinylpyrrolidone) (PVP) main chain covalently bonded to the ruthenium catalyst for the BZ reaction. In this study, we clarified the influence of the initial concentration of the BZ substrates and the temperature on the period and the self-oscillating behavior. By optimizing the initial concentration of the BZ substrates, we caused the swelling-deswelling self-oscillation in 0.5 Hz. The maximum frequency (0.5 Hz) of the novel gel was 20 times as large as that for the conventional-type self-oscillating gel. Moreover, we showed that the displacement of the self-oscillation for the gel has a tradeoff relationship against the period of the self-oscillation.

Electron transfer across proteins plays an important role in many biological processes, including those relevant for the conversion of solar photons to chemical energy. Previous studies demonstrated the generation of photocurrents upon light irradiation in a number of photoactive proteins, such as photosystem I or bacteriorhodopsin. Here, it is shown that Sn-cytochrome c layers act as reversible and efficient photoelectrochemical switches upon integration into large-area solid-state junctions. Photocurrents are observed both in the Soret band (λ = 405 nm) and in the Q band (λ = 535 nm), with current on/off ratios reaching values of up to 25. The underlying modulation in charge-transfer rate is attributed to a hole-transport channel created by the photoexcitation of the Sn-porphyrin.

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