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The Belousov-Zhabotinsky (BZ) reaction is an oscillating reaction due to periodic oscillations that happen in the concentration of some intermediates. Such systems can be applied together with hydrophobic membranes to create an autonomous behavior in artificial systems. However, because of a complex set of reactions happening in such systems, the interferences caused by hydrophobic membranes are not easily understood. In this study, we tested lipid membranes composed of trimethylammonium-propane (TAP) and phosphate (PA) lipids in an attempt to break down how the polar region of phosphatidylcholine (PC) lipid membranes affect the BZ reaction. According to our findings, the trimethylammonium group and membrane fluidity are crucial to change the frequency of oscillations in the reaction. In addition, the results also indicate a possible complexation of cerium ions with membranes with a phosphate head group.

The chlorine dioxide–iodine–malonic acid oscillating reaction is simulated by dynamic analysis software. The oscillation is watched for the concentration changes of triiodide ion, iodide ion, chlorite ion, and hydrogen ion. The initial concentration of malonic acid, chlorine dioxide, iodine, and pH value has certain effects on the oscillation. The amplitude and the number of oscillations is related to the initial concentration. The mathematical equation of reaction rate of triiodide ion, iodide ion, chlorite ion, and hydrogen ion varying with reaction time and the initial concentrations was got. The bifurcation curved surface between oscillatory and non-oscillatory phenomenon varying with pH values was got. The oscillatory ingredients lie below the surface. The spatial zone to arise oscillation phenomenon is reducing with the increase of pH value. The limits of oscillation with the initial concentrations of chlorine dioxide, iodine, and malonic acid is well represented by an equation. In the three-variable of [MA]o, [I2]o, and [ClO2]o, there is no lower and higher limited value on [MA]o for oscillation phenomenon at various pH value. On the other hand, there is higher limited value on [I2]o and [ClO2]o for oscillation phenomenon at various pH value. The initial concentrations of ClO2 and I2 for oscillation are decreasing with the increase of pH value.

A generalized Lengyel–Epstein oscillating reaction model is proposed and analyzed. The existence of limit cycles is proved using Hopf and Bautin bifurcation theory. We analyze the dynamics of the well known chlorine dioxide–iodine–malonic acid reaction, using a differential equations system. The numerical results are shown and these agree with the experimental data reported in the literature. We found that the oscillatory behavior depends on the stoichiometric coefficients and the reactant concentrations. This work gives valuable information for applications like design, optimization, dynamics and control of the industrial chemical reactors.

The present work proposes the development of an analytical procedure for paracetamol determination in pharmaceutical formulations using a system of continuous flow analysis associated with potentiometric detection allowing the study of the Belousov–Zhabotinskii (BZ) oscillating reaction. This method is based on paracetamol determination using the disturbance in the oscillation pattern of the BZ reaction promoted by this substance. The analytical curve showed the detection and quantification limits of 4 × 10–6 and 1.2 × 10–5 M, respectively. The relative standard deviation (n = 6) of the standard solution with paracetamol concentration of 6 mM was 2.3%. The analysis of real samples by the proposed and official methods (spectrophotometry/UV) showed similar results.

Briggs-Rauscher oscillating reaction has been investigated in hydrochloric acid media and in the presence of added chloride ions in phosphoric acid media in a batch reactor using ethylacetoacetate as the organic substrate. The changes in key oscillation parameters, namely, induction period, oscillation period, amplitude, and so forth, have been explained in terms of the steps of the skeleton mechanism proposed by Furrow and Noyes and by de Kepper and Epstein. In spite of several shortcomings as outlined in section 2 in the text, the same mechanistic steps are good enough to explain qualitatively most of the changes in oscillation parameters under different stirring rates and temperatures in phosphoric acid and hydrochloric acid media, particularly stirring effects explained well by the theory of imperfect mixing. Potential data indicate that 0.018 M HCl medium has the ability to exhibit near-zero/zero amplitudes before cessation of oscillations. Inhibition reactions from a low Cl- concentration in the 0.018 M HCl media appear to be responsible for this interesting dynamical transformation, as toward the end of oscillations, the difference between [I-] and [I-]crit [see eq J in the text] becomes very small because of depleted component chemicals due to chemical reactions.

Self-regulation of the dynamic actuation of a chemical oscillating reaction-based gel was realized by altering the network structure of the gradient double network gel. We demonstrated that the propagation mode of the chemical wave was influenced by the network structure, and consequently determined the dynamic feature of the gel actuator.

A self-deformable gel system is constructed by coupling a gradient structured gel with a chemical oscillating reaction. The system exhibits periodic and asymmetric shape change. The asymmetric shape change of the gel is based on the gradient structure.

Most analytical methods are based on "analogue" inputs from sensors of light, electric potentials, or currents. The signals obtained by such sensors are processed using certain calibration functions to determine concentrations of the target analytes. The signal readouts are normally done after an optimised and fixed time period, during which an assay mixture is incubated. This minireview covers another-and somewhat unusual-analytical strategy, which relies on the measurement of time interval between the occurrences of two distinguishable states in the assay reaction. These states manifest themselves via abrupt changes in the properties of the assay mixture (e.g. change of colour, appearance or disappearance of luminescence, change in pH, variations in optical activity or mechanical properties). In some cases, a correlation between the time of appearance/disappearance of a given property and the analyte concentration can be also observed. An example of an assay based on time measurement is an oscillating reaction, in which the period of oscillations is linked to the concentration of the target analyte. A number of chemo-chronometric assays, relying on the existing (bio)transformations or artificially designed reactions, were disclosed in the past few years. They are very attractive from the fundamental point of view but-so far-only few of them have be validated and used to address real-world problems. Then, can chemo-chronometric assays become a practical tool for chemical analysis? Is there a need for further development of such assays? We are aiming to answer these questions.

The current approach elaborates an innovative methodology for distinguishing four halide ions (F−, Cl−, Br− and I−) on their perturbation effects upon novel Briggs-Rauscher Reaction (BR) catalyzed by tetraaza-macrocyclic-nickel-complex (NiL)(ClO4)2. The lingand “L” in the complex is 5,7,7,12,14,14-hexamethyl-1,4,8,11 -tetraazacyclotetradeca-4,11-diene). Different oscillating profiles were exposed while the equal addition of four halide ions separately into active BR over the concentration range of 5.0 × 10−5-2.375 × 10−4 mol/L. Fluoride (F−) ion does not affect BR. Chloride (Cl−) ion could quench the potential oscillation at high potential and regenerate oscillation after a short inhibition time (tin). Bromide (Br−) ion could merely diminish the oscillation amplitude (A) and oscillation period (T) with no inhibition time whereas the iodate (I−) ion can restrain the potential oscillation at low potential and regenerate oscillation after a short inhibition time (tin). These four halide ions could be distinguished within 7 min. Cyclic voltammetry (CV) confirmed the redox reaction of potassium iodate with analytes while the bromination or the iodination products were testified by using mass spectrometry (MS) analysis after the perturbation of Br− or I−. Finally, a reasonable explanation of the perturbation mechanism for the BR was proposed based on well-known NF and FCA models.

The influence of adrenaline on two iodate based oscillating chemical reactions, the Bray–Liebhafsky (BL) and Briggs–Rauscher (BR) reactions was investigated. It was observed that the addition of adrenaline has different effects on the examined systems. Its addition to the BR system significantly changes the dynamics, while in the BL system, the presence of adrenaline does not show any effect. In order to find out the cause of such a different response of two similar oscillators, UV/VIS spectroscopy was used. Results obtained from recorded UV/VIS spectra indicated that, from all investigated stable reaction species, adrenaline interacts only with potassium iodate and iodine, which are present in both oscillating reactions. Because of this, the different response of the oscillators cannot be ascribed to the reactions between adrenaline and common iodine (stable and unstable) components. As a result, the considerable response of the BR system to adrenaline may be related to the reactions between adrenaline (or its oxidation products) and non-common derivatives of malonic acid or manganese intermediate species.

The oscillatory behavior is not the only interesting nonlinear phenomena that appeared in the Briggs–Rauscher (BR) reaction. The BR reaction containing malonic acid may undergo a sudden transition from low (the state I) to high iodide and iodine (the state II) concentration states. This paper focuses on the mixture with an immutable [CH2(COOH)2]0/[IO3 −]0 = 1.5 value, where state I to state II transition occurs after a time delay and BR reaction ended with a solution abundant of solid iodine. The state I to the state II transition curves obtained at different temperatures were analyzed using the Kolmogorov–Johnson–Mehl–Avrami (KJMA) theory. The KJMA theory was applied for monitoring the crystallization process of isolated solid iodine product at various levels of operating temperatures. At T

The Dushman reaction (reduction of iodate by iodide) is a subsystem of the Briggs–Rausher oscillating reaction. We show that the previously observed effects of Ce(III) and Mn(II) on the kinetics of the Dushman reaction are mainly ionic strength effects. The observed decrease of the rate constant of the Dushman reaction when the ionic strength increases and the formation of the ion pairs MnSO4(aq) and CeSO4 + explain quantitatively our kinetic results. We also show why the original mechanism of the Briggs–Rausher reaction must be revised and propose a variant of the mechanism proposed in 2002 by Furrow, Cervellati and Amadori. This variant establishes a relationship with the reduction of iodate by high concentrations of hydrogen peroxide and the non-catalyzed BR reaction.

The simultaneous influence of temperature and flow rate (k0) in the oscillatory regime of the bromate-oxalic acid-acetone-Ce(III) oscillating reaction was investigated. The influence of temperature was evaluated in terms of the oscillatory activation energy (Eω), which was determined at different flow rates. Increasing k0, the oscillatory activation energy is decreased, tending to a limit value, Eω∞. The sensitivity of Eω with k0 is described by the parameter η = dEω/d(1/k0). Eω∞ and η are global properties of any particular oscillating reaction and describes a correlation between the dynamical behavior and temperature, and should be used when comparing different oscillating reactions.

The study involves the dynamic evolution of the Briggs–Rauscher (BR) reaction in the presence of various surfactants—SDS (sodium dodecyl sulphate) as anionic, CTAB (cetyl trimethylammonium bromide) as cationic and TritonX-100 [4-(1,1,3,3-(tetramethylbutyl) phenyl polyethylene glycol] as a neutral one in single as well as mixed mode conditions (SDS + TX-100 and CTAB + TX-100). The reaction has been monitored potentiometrically at 30 °C under CSTR conditions. These surfactants affect the reaction dynamics to an extent which depends on the nature and concentration of the surfactant and the formation of their self-assemblies. The experimental findings indicate that the oscillatory behavior of the BR reaction in the presence of surfactants is due to the efficacy of organized surfactant assemblies to selectively distribute the key species involved in the reaction, and their interaction with the counter ions in cases of ionic micelles. The study reveals that the evolution of oscillatory behavior is a characteristic feature of the surfactant.

An alternative approach for carbaryl determination based on the change in the oscillation period of the Belousov-Zhabotinsky (BZ) reaction under the addition of carbaryl is demonstrated. The oscillations were observed by spectrophotometric measurement at 320 nm, corresponding to the maximum absorption wavelength of cerium(IV) catalyst. The oscillation periods increase with the carbaryl concentrations, which can be discussed based on the Field-Körös-Noyes (FKN) mechanism. The increase of oscillation periods is proportional to the concentration of carbaryl in the range of 0.1-200 mg L-1 with the regression coefficient of 0.9938. The limits of detection and quantification were 0.044 and 0.147 mg L-1, respectively. The precisions in terms of intra-day and inter-day measurements were efficient with relative standard deviation (RSD) lower than 2.1%. Accuracy of carbaryl in different water samples was obtained with high recoveries in the range of 94-106% and also comparable to the results of high performance liquid chromatography (HPLC) analysis. The proposed method is precise, cost-effective and can be alternatively employed for the screening and determination of carbaryl residues in water samples.

Current efforts to design functional molecular systems have overlooked the importance of coupling out-of-equilibrium behaviour with changes in the environment. Here, the authors use an oscillating reaction network and demonstrate that the application of environmental forcing, in the form of periodic changes in temperature and in the inflow of the concentration of one of the network components, removes the dependency of the periodicity of this network on temperature or flow rates and enforces a stable periodicity across a wide range of conditions. Coupling a system to a dynamic environment can thus be used as a simple tool to regulate the output of a network. In addition, the authors show that coupling can also induce an increase in behavioural complexity to include quasi-periodic oscillations.

Oscillating reactions are reactions in which it is possible to observe oscillations in the concentrations of some reaction intermediates. The reaction studied here is composed of acetone, sulfuric acid, bromate, oxalic acid, and Ce(IV). Chemical oscillators may have different behaviors in batch, for example, the presence of an induction period and change of oscillations' pattern. A much rarer event is the presence of a break, or pause, between two groups of oscillations, which is shown by this system. To better determine the conditions under which this behavior occurs, we built several phase diagrams for the initial concentrations of reactants. These phase diagrams show that there is a well-defined range of concentrations that produce a pause in the oscillations. The initial bromate concentration is special because increasing this concentration eliminates the pause in the oscillations, but a further increase can make a pause appear again. These results can be interpreted considering that the reaction mechanism is controlled by at least two intermediates. In addition, this work presents a representative set of data that must be acknowledged by any detailed proposal of mechanism for this oscillating reaction.

Localized oscillations can develop thanks to the interplay of reaction and diffusion processes when two reactants A and B of an oscillating reaction are placed in contact, meet by diffusion, and react. We study numerically the properties of such an A + B → oscillator configuration using the Brusselator model. The influence of a hydrodynamic viscous fingering instability on localized concentration oscillations is next analyzed when the oscillating chemical reaction changes the viscosity of the solutions involved. Nonlinear simulations of the related reaction-diffusion-convection equations with the fluid viscosity varying with the concentration of an intermediate oscillatory species show an active coupling between the oscillatory kinetics and the viscously driven instability. The periodic oscillations in the concentration of the intermediate species induce localized changes in the viscosity, which in turn can affect the fingering instability. We show that the oscillating kinetics can also trigger viscous fingering in an initially viscously stable displacement, while localized changes in the viscosity profile can induce oscillations in an initially nonoscillating reactive system., SCOPUS: ar.j, info:eu-repo/semantics/published

Belousov-Zhabotinsky chemical reactions and new variants were developed and studied at 277.5 K, 296.15 K, and 341.15 K using potassium bromate, sodium bromide, malonic acid, and ferroin as an indicator for the oscillating reaction. This reaction type is a minimal oscillator, which belongs to the fifth “uncatalyzed” family known as minimal bromate oscillators. A mathematical model is a proposal from the reaction mechanism of Zhabotinsky, the Oregonator model, and the modified Arrhenius equation. The control parameters of the mathematical model are the activation enthalpies of the oscillating reaction. Experimental and numerical results at 341.15 K show an increase in the amplitude and frequency of chemical oscillations and a decrease in the total oscillation time, while at 277.15 K the opposite mechanism happens.

The Briggs-Rauscher (BR) reaction is free radical based where the kinetics of formation of different iodide species leads to potentiometric and color oscillations. These oscillations were monitored in this study using a UV/Vis attenuated total reflection probe to develop an assay to measure the antioxidant content in complex matrices. The periodicity of the BR reaction was found to be very consistent (range 24–25 seconds, n = 16). Adding various amounts of ascorbic acid, a well-known antioxidant, led to an inhibition of the reaction with a linear calibration curve of antioxidant periodicity time (APT, r 2 > 0.99). The validity of this test in complex matrices was studied by determining the APT of nine fruits, and the resulting antioxidant capacity in ascorbic acid equivalency was calculated. The results generated by this assay were found be accurate through comparison with the well-established FRAP assay. These results show that visual or spectrometric monitoring of BR reaction can be used as a reliable, quick, and inexpensive alternative to more established assays with the added advantage that values generated from this assay is at pH 2 which is similar to that in the human stomach.

Pt is a common redox electrode used to follow oscillations qualitatively in the Briggs–Rauscher (BR) and the Bray–Liebhafsky (BL) reactions from the time of their discovery. Although the potential oscillations of the electrode reflect the temporal pattern of the reaction properly, there is no general agreement as to how that potential is determined by the components of the reaction mixture. In this article, first we investigate how iodine species in different oxidation states affect the potential of a Pt electrode. It was found that I(+3) and I(+5) species do not affect the potential; only I–, I2, and HOI may have an influence. Although the latter three species are always present simultaneously as participants of the rapid iodine hydrolysis equilibrium, it was found that below and above the so-called hydrolysis limit potential (HLP, where the iodide and HOI concentrations are equal) the actual potential determining redox couple is different. Below the HLP, it is the traditional I2/I– redox couple, but abo...

In living systems, there are many autonomous and oscillatory phenomena to sustain life such as heart beating. We developed “self-oscillating” polymer gels that undergo spontaneous cyclic swelling-deswelling changes without any on-off switching of external stimuli, as with heart muscle. The self-oscillating gels were designed by utilizing the Belousov-Zhabotinsky (BZ) reaction, an oscillating reaction, as a chemical model of the TCA cycle. We have systematically studied these self-oscillating polymer gels since they were first reported in 1996. Potential applications of the self-oscillating polymers and gels include several kinds of functional material systems such as biomimetic actuators, mass transport systems, and functional fluids. For example, it was demonstrated that an object was autonomously transported in the tubular self-oscillating gel by the peristaltic pumping motion similar to an intestine. Further, self-oscillating polymer brush surface like cilia, vesicles, or colloidosomes undergoing cell-like autonomous shape oscillations with buckling was prepared. Besides, autonomous sol-gel oscillation and amoeba-like motion were realized utilizing well-designed block copolymer solution. In this chapter, our recent progress on the self-oscillating polymer gels is summarized.

A simple chemo-chronometric method utilizing the Belousov-Zhabotinsky (BZ) oscillating reaction for the efficient detection of ethanol in alcoholic beverages has been developed. This visual detecting strategy only required a smartphone, without implemented instrumental detection systems, to video a unique colorimetric alternating (red-to-blue) feature of the BZ solution system containing 0.50 M bromate, 0.12 M malonic acid, 0.03 M bromide, 0.10 M sulfuric acid, and 0.2 mM ferroin under the perturbation of ethanol. The RGB intensity signals, termed the colorimetric oscillating signals (COS), could be drawn from recorded files through the image processing. We found from the COS characteristics that the oscillation period was inversely proportional to the ethanol levels as a consequence of its reaction with bromate in the studied system. Based on the established calibration, the ethanol content was effectively evaluated with good precision (

The Briggs-Rauscher (BR) oscillatory reaction is the oxidation of malonic acid in the presence of hydrogen peroxide and iodate in the acidic environment, which is catalyzed by ions of manganese. This reaction is very sensitive to the presence of additives. In this paper, the BR reaction has been used to investigate the phosphate tungsten bronze as well as calcium doped tungsten bronze, obtained by thermal treatment. The addition (0.01-0.08 g) of phosphate tungsten bronze and calcium doped phosphate tungsten bronze has a different effect on the dynamics of the Briggs-Rauscher reaction. In the case of the addition of phosphate tungsten bronze in the Briggs-Rauscher reaction, the linear dependence of the length of the oscillatory period on the mass of the added bronze was obtained, while in the case of addition of calcium doped phosphate tungsten bronze, the oscillatory period does not significantly change with an increase of added mass. The mechanism of calcium doped and undoped phosphate tungsten bronze action in BR reaction is probably adsorptive, and it will be the subject of future work. Keywords: oscillatory reactions, Briggs-Rauscher reaction, phosphate tungsten bronze, calcium doped phosphate tungsten bronze, thermal treatment.

Anisotropic chemical wave propagation of self-oscillating Belousov–Zhabotinsky (BZ) reaction was demonstrated in the poly(N-isopropylacrylamide) gel films embedded with macroscopically aligned liquid crystalline inorganic nanosheets. Although the average propagation rate of chemical wave v was 3.56 mm min–1 in the gels without nanosheets, the propagation was retarded in the gels with 1 wt % of nanosheets: v∥ = 1.89 mm min–1 and v⊥ = 1.33 mm min–1 along the direction parallel and perpendicular to the nanosheet planes, respectively. Thus, the wave propagation is anisotropic with the anisotropy ratio v∥/v⊥ = 1.42 in these gels and the periodic patterns formed by the BZ reaction were concentric ellipses, different from circles seen in isotropic gels. Furthermore, the propagation rate and degree of anisotropy were controllable by nanosheet concentration. These phenomena can be explained that the diffusion of molecules inside the gel is effectively hindered along the direction perpendicular to the nanosheet...

In order to propose mechanisms of complicated chemical systems, it is necessary to study simpler subsystems. The mechanism we have proposed for the Bray–Liebhafsky (BL) oscillating reaction is based on kinetic studies of several reactions of iodine compounds between them and with hydrogen peroxide. Because the reactants of the non-catalysed Briggs–Rauscher (BR) oscillating reaction are the same as those of the BL reaction plus malonic acid, we propose now to extend the mechanism of the BL reaction to the BR reaction. With this aim, we add radical reactions of iodine compounds and of malonic acid. The choice of these reactions is based on our recent study of the unusual kinetics of the iodate reduction by high concentrations of hydrogen peroxide.

By utilizing a chemical oscillating reaction as a periodical driving source, the fluorescence in a responsive polymer system is autonomously regulated based on the reversible formation of dynamic covalent bonds.

The interesting behavior of the Briggs–Raucher oscillating reaction does not stop with the end of oscillations. Depending on the initial concentrations, the classic mixture with malonic acid may undergo a sudden transition from a state with low [I2] and [I−], to a state with high [I2] and [I−]. A proposed mechanism involving radical attack on iodomalonic acid and diiodomalonic acid shows qualitative agreement with experiments.

It is shown that a solution featuring the Briggs–Rauscher (BR) oscillating chemical reaction can exhibit the properties of a photonic crystal with alternating bandgap width. Thicknesses and dielectric permittivities of structural elements in the BR reaction solution have been determined by measuring the reflection and transmission spectra of microwave radiation in the range of 5–8 GHz.

We consider the case of the Belousov–Zhabotinsky (BZ) oscillating reaction where the metal catalyst is confined in a discrete phase of cation-exchange resin particles. We show that modelling of the sudden transitions from the steady state to fully synchronized oscillations, which were previously described only in terms of quorum sensing, does not necessarily require fine-graining of the models into individual particles. As a minimal representation of the system, we propose a generalized version of the Oregonator with only one additional parameter φ that corresponds to the total volume fraction of the catalytic phase in the system. We show that the kinetic consequences of catalyst confinement can be interpreted through φ acting as the second variable stoichiometric factor in the Oregonator mechanism that decreases the order of autocatalysis and simultaneously weakens the negative feedback. Based on the proposed model, an analysis of the so-called quorum sensing is provided in terms of the standard concepts of Hopf bifurcation. The model reproduces correctly that (1) oscillations are only exhibited above a certain critical threshold of φ; (2) as φ decreases, so do the amplitudes of oscillations; whereas (3) the periods of oscillations are almost independent of φ. The model thus appears to be a reasonable minimal representation of uniform states in the BZ reaction with catalyst confinement, and therefore might be a convenient starting point for further refinements representing more complicated transitions in this system.

The Briggs-Rauscher reaction containing malonic acid may undergo a sudden transition from low (state I) to high iodide and iodine (state II) concentration states after a well-defined and strongly reproducible oscillatory period. This study clearly shows that even though the time-dependent behavior of the oscillatory state is reproducible, the time lag necessary for the appearance of the state I to state II transition after the system leaves the oscillatory state becomes irreproducible for an individual kinetic run. This crazy clock behavior of the state I to state II transition is identified by repeated experiments in which stirring rate is taken as a control parameter and all other parameters such as initial conditions, temperature, vessel surface, and the age of solution were kept constant. Surprisingly, a better stirring condition does not make the transition reproducible; it simply does not allow the transition to happen at all. The proposed mechanism, additional explanations, and proposals for this irreproducibility of state I to state II transition have been presented. Considering the fact that the number of crazy clock reactions is only a few, this study may contribute to a better understanding of fundaments of this phenomenon.

It is well documented that different surface structures of catalytically active metals may exhibit different catalytic properties. This is typically examined by comparing the catalytic activities and/or selectivities of various well-defined smooth and stepped/kinked single crystal surfaces. Here we report the direct observation of the heterogeneity of active polycrystalline surfaces under reaction conditions, which is manifested by multifrequential oscillations during hydrogen oxidation over rhodium, imaged in situ by photoemission electron microscopy. Each specific surface structure, i.e. the crystallographically different µm-sized domains of rhodium, exhibits an individual spiral pattern and oscillation frequency, despite the global diffusional coupling of the surface reaction. This reaction behavior is attributed to the ability of stepped surfaces of high-Miller-index domains to facilitate the formation of subsurface oxygen, serving as feedback mechanism of the observed oscillations. The current experimental findings, backed by microkinetic modeling, may open an alternative approach towards addressing the structure-sensitivity of heterogeneous surfaces., The structurally different domains of a polycrystalline material may exhibit differing catalytic properties. Here, the authors directly visualize this phenomenon by observing the catalytic hydrogen oxidation that oscillates, simultaneously exhibiting different frequencies for structurally different rhodium domains.

The interplay of reaction and diffusion processes can trigger localized spatiotemporal patterns when two solutions containing separate reactants A and B of an oscillating reaction are put in contact. Using the Brusselator, a classical model for chemical oscillations, we show numerically that localized waves and Turing patterns as well as reaction-diffusion (RD) patterns due to an interaction between these two kinds of modes can develop in time around the reactive contact zone depending on the initial concentration of reactants and diffusion coefficients of the intermediate species locally produced. We further explore the possible hydrodynamic destabilization of an initially buoyantly stable stratification of such an A + B → oscillator system, when the chemical reaction provides a buoyant periodic forcing via localized density changes. Guided by the properties of the underlying RD dynamics, we predict new chemo-hydrodynamic instabilities on the basis of the dynamic density profiles which are here varying with the concentration of one of the intermediate species of the oscillator. Nonlinear simulations of the related reaction-diffusion-convection equations show how the active coupling between the localized oscillatory kinetics and buoyancy-driven convection can induce pulsatile convective fingering and pulsatile plumes as well as rising or sinking Turing spots, depending on the initial concentration of the reactants and their contribution to the density.

Based on a ten-step chemical model involving the concentrations of I2(aq), O2(aq), and the intermediates of I- and HIO2, four independent variables and seven irreversible steps, the nonlinear behavior of Bray-Liebhafsky (BL) oscillating reaction was investigated. The results showed that with different values of initial concentrations of reactants in the process of simulation, both periodic oscillation and chaotic behavior could be observed. In addition, at the same initial concentrations and rate constants, the system becomes more and more regular after being chaos. That is to say, the translation from chaos to periodic oscillation at the same initial conditions appeared in the BL system. The nonlinear behavior of system was also investigated briefly

The KSCN-H2O2-NaOH-Cu(II)-catalyzed system is one of the few reactions in which chemical oscillations can be observed in batch conditions. In the present paper, this oscillating reaction was revisited in a wide range of initial concentrations of all components in batch. A mixture with a long lasting oscillation time (1 h 34 min) and a great number of oscillations (24) was found and used to investigate the effect of temperature. An Arrhenius-type temperature dependence was observed from which an apparent “average activation energy” Eav = 76 ± 5 kJ for the overall oscillatory reaction was observed. A mechanistic study based on a modified model analyzed by the stoichiometric network analysis approach gave a satisfactory agreement between calculated and experimental oscillating behaviors and temperature dependence. The addition of the three diphenols (catechol, resorcinol, and hydroquinone) causes perturbations similar to those observed in the Briggs-Rauscher oscillating system, i.e., an inhibition of the oscillatory regime. These inhibitory effects were described in detail, and a reasonable qualitative interpretation is given.

Catalytic micro- and nanoparticles are widely employed to study the global behavior of large networks of coupled chemical oscillators. In this paper, we present a new class of catalysts for the BZ oscillating reaction, based on the functionalization of natural inorganic materials (1:1 and 2:1 clays) through the sorption of the iron-complex ferroin on their surface. The small size of the clay basic units (diameter < 2 μm) and their colloidal nature make these particles interesting for studying systems having dimensions at the border between the nano- and the mesoscale. In the first part of this paper, we present the synthesis and the characterization of the ferroin-functionalized clay. We then show an extensive study on the oscillatory dynamics of the BZ reaction catalyzed by the clay. Through a direct comparison with a classical ferroin-catalyzed BZ system, we describe the modifications of the oscillation mechanisms induced by the new catalyst. Finally, we illustrate an application of the microparticles a...

The hydrogenase-catalyzed oxidation of H 2 includes an autocatalytic step in the reaction cycle. The reaction also exhibits different pH dependence in the H 2 oxidation and in the proton reduction directions. This is not only due to the pH titration of the amino acid side chains as protons are also either the substrates or the products of the reaction. Utilizing the autocatalytic nature of the hydrogenase reaction and the multiple roles of protons therein, together with appropriate limitation of the substrate (gaseous H 2 ) supply, oscillations can be induced in the system. The reaction oscillates both in space and in time, and can last for days with decreasing frequency until reaching chemical equilibrium. Of all biological oscillating systems described so far, this one is the simplest in that it has the fewest biological components.

The classical Oregonator model of the Belousov–Zhabotinsky reaction is used to examine the response of an oscillating reaction to a chemical perturbation in a batch calorimeter. To do this, a reaction step for the perturbing chemical substance and the energy balance equation are added to the model. Changes in the frequency and amplitude of the oscillations occur as a function of the concentration of the perturbing substance, and these changes are quantified by applying the thermodynamics of irreversible processes in order to determine the rate of entropy production. Various criteria are proposed to evaluate the time series and measurable quantities with linear correlations between the entropy production due to transfer and the concentration of the chemical perturbation are obtained, showing that it is possible to implement experimental protocols in the proposed methodology.

This paper reports a new method for determination of tracing amounts of eugenol (EUG) by its perturbation effects on a novel Briggs–Rauscher (BR) oscillating system catalyzed by a macrocyclic complex [NiL](ClO4)2. The ligand L in the complex is 5, 7, 7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene. In this novel BR oscillator, not only a macrocyclic complex was used as a catalyst to replace Mn2+, but the value of pH in the system was kept at pH of stomach fluids (pH ≈2.0) as well. Experimental results have shown that addition of EUG into the BR system could quench and then successively regenerate the oscillations, accompanying by an inhibitory time that relies on the concentration of the EUG added. An assay was thus established by employing such a BR system for determining EUG. The relationship between inhibition time and EUG concentrations is obtained over the range between 5.00 × 10−7–2.50 × 10−5 M. Two calibration curves are thus achieved: linear regression over the range 5.00 × 10−7 to 1.25 × 10−5 M of EUG, and polynomial regression over the range 1.25 × 10−5 ∼ 2.50 × 10−5 M of EUG. The obtained RSD from seven measurements of 1.00 × 10−5 M of EUG is 3.75%, and from 1.50 × 10− 5 M of EUG is 2.05%. Some factors influencing the determination were also examined. Not only has the method been successfully applied to determine EUG but it could be extended to determine other lipophilic antioxidants as well. Furthermore, the possible reaction mechanism using the FCA model has been proposed.

In this paper, the fuel-air dispersion and explosion experimental system was designed and experimental simulation on fuel-air mixture spreading and exploding in long-narrow underground fuel depot was carried out. The special phenomena of fuel-air mixture dispersion and explosion process, the characteristic feature of the pressure curve and mechanism were analyzed. The explosion process can be divided into three stages: flame accelerating section, oscillating reaction section and wave dissipating section. And under the same initial conditions, if the ignition time advanced, there is a significant intermittent and large fluctuations phenomenon.

This article deals with the influence of micelles of the anionic surfactant sodium dodecyl benzene sulfonate (SDBS) on the BelousovZhabotinsky (BZ) oscillating reaction catalyzed by a tetraazamacrocyclic copper(II) complex [CuL](ClO4)2, an enzyme-like catalyst (L=5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene). Unlike the classical BZ oscillator in which malonic acid is usually used as a substrate, malic acid (an intermediate in the Krebs cycle) is involved in this oscillating system. Experiments reveal that formation of the SDBS micelles markedly affects the behavior of the oscillating reaction. It is found that there is a linear relationship between the change in the oscillation amplitude (ΔA) and the concentration of SDBS, whereas the change in the oscillation period (ΔT) is linearly proportional to the SDBS concentration. The most likely mechanism that involves the formation of the SDBS micelles and the effects of the micelles on the oscillating chemical system can be rationalized by assuming that the SDBS micelles are so negatively charged that they attract more [CuL]3+ than [CuL]2+. This hypothesis was confirmed by UV/VIS spectrophotometric measurements of a constant concentration of [CuL](ClO4)2 in different concentrations of SDBS; as the SDBS concentration increased, the absorbance of [CuL](ClO4)2 increased, while the maximum absorption wavelength for [CuL](ClO4)2 remained at 502 nm.

Perturbations with chemical species that have dissimilar physico-chemical properties, such as bromide ions, polyphenols or iron complexes, are often used to investigate the detailed molecular mechanism of the Briggs-Rauscher (BR) oscillating reaction. We describe in this review the effects caused by some of these species and present their mechanistic interpretations. Some new original results are also reported.

A new chlorine dioxide–iodine–sodium thiosulfate chemical oscillatory reaction was studied by the UV–Vis spectrophotometric method. The initial concentrations of sodium thiosulfate, chlorine dioxide, iodine, sulfuric acid, and pH have great influences on the oscillations observed at wavelength 238 nm. The oscillations occur as long as the reactants are mixed. The amplitude and the number of oscillations are associated with the initial concentrations of reactants. The equations for the triiodide ion reaction rate changes with reaction time and the initial concentrations in the oscillation stage are an attenuation sine function. Based upon the experimental data in this work and in the literature, a plausible reaction mechanism was proposed for the oscillation reaction.