Modulation of Turing Patterns in the CDIMA Reaction by Ultraviolet and Visible Light

Abstract

We have carried out the first systematic study of the effects of ultraviolet light, both alone and in combination with visible white light, on Turing patterns in the chlorine dioxide–iodine–malonic acid (CDIMA) reaction. The ultraviolet light used has a sharp peak at 368 nm and can perturb the system selectively. It primarily decomposes chlorine dioxide in a zeroth-order reaction, and when it is used to illuminate Turing patterns, shrunken spots are formed with an imperfect hexagonal arrangement. The ultraviolet light competes directly with the visible white light via the photoreaction with dissolved chlorine dioxide, which prevents the total suppression of patterns at intermediate intensities of white light. These results suggest that specific wavelengths of light in the ultraviolet spectrum selectively modify the chemistry behind the pattern formation and can be utilized to generate novel self-organized structures under forcing conditions. We propose a modified Lengyel–Epstein model to incorporate the effect of ultraviolet illumination and obtain good qualitative agreement between simulations and experiments. These results support the idea that chlorine dioxide photoreaction is a key step in modulating CDIMA patterns under ultraviolet illumination.

Insights from chemical systems into Turing-type morphogenesis

“…Many recent studies of chemical Turing patterns use the CDIMA reaction in a CFUR, where the patterns form in a quasi-two-dimensional gel with one-sided feeding [14,41,45,46]. A schematic for the experimental setup is shown in [14].…”

“…In general, the wavelength of Turing patterns generated by the CDIMA reaction varies inversely with the chlorine dioxide concentration [45,51] and is typically on the order of several hundred micrometres. Gaskins et al [41] showed that other chemical species added to the system can strongly influence the pattern wavelength.…”

“…Other wavelengths of light outside of the visible spectrum can lead to different patterning behaviour. A recent study by Nagao et al shows that ultraviolet (UV) light induces a side reaction with chlorine dioxide [45]. When both UV and full-spectrum visible light are used to illuminate the Turing patterns, the UV light reduces the impact of the white light, requiring a higher intensity of visible light to completely suppress the pattern [45].…”

Modulation of spatiotemporal dynamics in the bromate–sulfite–ferrocyanide reaction system by visible light

“…7,8 In addition, light as an external control parameter is particularly appealing in the study of nonlinear chemical reactions due to the easy tunability of intensity and spectral composition. [9][10][11] Many chemical oscillators are known to be sensitive to light irradiation, showing photoinduction and photoinhibition behavior in homogeneous and inhomogeneous systems. In the Ru(bpy) 3 2+ -catalyzed Belousov-Zhabotinsky (BZ) oscillator, the oscillatory frequency was inuenced by the illumination intensity, 12 while the rotating spiral waves transform to a labyrinthine standing-wave pattern by periodic light-perturbation.…”

“…13 By virtue of the process, photophobic and phototropic movements of a self-oscillating gel hosting the photosensitive BZ reaction were designed to approach its favorable environments spontaneously. 14,15 In another case, the photosensitive dissociation of molecular iodine was utilized in the chlorine dioxideiodine-malonic acid (CDIMA) reaction, Briggs-Rauscher reaction, and Bray-Liebhafsky reaction, leading to the cessation or promotion of oscillations, [16][17][18] and pattern structures modulation 11,19,20 under the forcing of light illumination.…”