Real-time resonance Raman spectroscopic monitoring of the Briggs-Rauscher reaction.

The Briggs-Rauscher reaction is a prototypical oscillating system and is based on chemical mixtures of iodate (IO3-), hydrogen peroxide, malonic acid and Mn2+ ions in an acidic solution. Although the Briggs-Rauscher oscillatory behaviour can be seen visibly, conventional analytical methods lack molecular detail of the exact chemical reactions within this highly dynamic system. Using real-time resonance Raman spectroscopy at 785 nm excitation, we track iodine speciation through distinct triiodide and pentaiodide signatures. Fourier-transform analysis of these time-series Raman data reveals that increasing temperature accelerates oscillation frequency while destabilising oscillatory regularity at elevated temperatures (43 °C); higher iodate concentrations promote regular oscillations at intermediate levels but suppress them through excessive oxidation at high concentrations; and starch actively modulates the reaction by stabilising polyiodide formation and doubling the oscillation period relative to starch-free conditions. This study demonstrates Raman spectroscopy as a precise physicochemical tool for analysing chemical oscillations.