Design of non-autonomous pH oscillators and the existence of chemical beat phenomenon in a neutralization reaction

Shearer, Lawson Hugh and Holló, Gábor and Német, Norbert and Teraji, Satoshi and Nakanishi, Hideyuki and Horváth, Róbert and Lagzi, István László (2021) Design of non-autonomous pH oscillators and the existence of chemical beat phenomenon in a neutralization reaction. SCIENTIFIC REPORTS, 11 (1). No.-11011. ISSN 2045-2322

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Abstract

The beat in physical systems is a transparent and well-understood phenomenon. It may occur in forced oscillatory systems and as a result of the interference of two waves of slightly diferent frequencies. However, in chemical systems, the realization of the latter type of the beat phenomenon has been lacking. Here we show that a periodic titration of acid and alkaline solutions with each other using programmable syringe pumps in a continuous stirred-tank reactor exhibits the beat phenomenon in the temporal pH oscillation pattern if the time periods of sinusoidal infow rates of the reagents are slightly diferent. Interestingly, the frequency of the chemical beat pattern follows the wellknown relationship from physics, namely the frequency of the beat is equal to the absolute value of the diference of the two wave frequencies. Based on our strategy, we can design and engineer non-autonomous pH oscillatory systems, in which the characteristics of the temporal oscillations (amplitude, time period) can easily and precisely be controlled by the experimental conditions such as the infow rates and feed concentrations. The demonstrated phenomena can be exploited in practical applications, we use the non-autonomous pH oscillators to drive the reversible assembly and disassembly of pH-sensitive building blocks (oleic acid and gold nanoparticles), both highly relevant in nanotechnology and biomedical applications.

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