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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.

This work presents a new oscillating reaction based on chlorate and observed in a CSTR at room temperature. This can be the first member of a new family of oscillating reactions. In addition, it is also the first oscillating reaction to use nitrous acid as a reactant. Four different behaviors were observed: simple oscillations, mixed mode oscillations, bursts, and quasiperiodicity. The period of oscillations is very short, which is around 1 s. Together with the fact that it also shows fast bursts, it opens the possibility that it can be used to simulate fast biological events, like the neuron’s communications signals.

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.

The peroxidase-oxidase oscillating reaction was the first (bio)chemical reaction to show chaotic behaviour. The reaction is rich in bifurcation scenarios, from period-doubling to peak-adding mixed mode oscillations. Here, we study a state-of-the-art model of the peroxidase-oxidase reaction. Using the model, we report systematic numerical experiments exploring the impact of changing the enzyme concentration on the dynamics of the reaction. Specifically, we report high-resolution phase diagrams predicting and describing how the reaction unfolds over a quite extended range of enzyme concentrations. Surprisingly, such diagrams reveal that the enzyme concentration has a huge impact on the reaction evolution. The highly intricate dynamical behaviours predicted here are difficult to establish theoretically due to the total absence of an adequate framework to solve nonlinearly coupled differential equations. But such behaviours may be validated experimentally.

The calcium phosphate tungsten bronze (Ca-PWB) has been synthesized and characterized (TGA, DSC, XRPD, FTIR, SEM). The influence of solid insoluble materials Ca-PWB, as well as lithium doped (Li-PWB) and cation free phosphate tungsten (PWB) bronzes on the oscillatory Briggs-Rauscher (BR) reaction dynamics, is compared. The results show that doping with Li and Ca reduces sensitivity of the BR reaction towards bronzes addition. These findings suggest the usage of the BR reaction as an innovative method for testing of different properties of bronze material. The behavior of PWB in the BR reaction is significantly changed with divalent cation (Ca2+) doping. The reasons for the different bronzes behavior were found in their calculated unit cell volumes. Namely, the compressed Ca-PWB unit cell volume indicates the difficult availability of the active site for heterogeneous catalysis. Hence, the linear correlation (slope) of the BR oscillogram’s length (τosc) vs. mass of bronze in BR reaction might be considered as a new parameter for the evaluation of the bronzes catalytic activity. У овом раду синтетисана је и окарактерисана (TGA, DSC, XRPD, FTIR, SEM) нова калцијумом допирана фосфат волфрамова бронза (Ca-PWB). Испитан је и упоређен утицај фосфат волфрамове бронзе (PWB), литијумом допиране фосфат волфрамове бронзе (Li-PWB) и калцијумом допиране фосфат волфрамове бронзе (Ca-PWB) на осцилаторну динамику Briggs-Rauscher (БР) реакције. Резултати показују да допирање катјонима Li+ и Ca2+ смањује осетљивост БР реакције на додатак нерастворних бронзи, што се огледа у смањивању нагиба праве осцилаторног времена (τosc) БР реакције у функцији масе додате допиране бронзе. Добијени резултати сугеришу употребу БР реакције као иновативне методе за испитивање различитих својстава допираних и недопиране фосфат волфрамове бронзе. Разлози за различито понашање бронзи у осцилаторној реакцији пронађени су у различитим величинама јединичних ћелија PWB, Li-PWB и Ca-PWB. Наиме, најмања вредност, тј. сабијање јединичне ћелије допирањем калицијумом указује на тежу доступност активних места за хетерогену катализу. Каталитичка активност бронзи усмерена је ка реакцијама оксидације које укључују водоник-пероксид (један од реактаната БР реакције). Стога би се линеарна корелација (нагиб) τosc у функцији масе бронзе у БР реакцији могла сматрати новим параметром за процену каталитичке активности бронзе, али и других материјала.

Periodical transformation of ferroin to ferriin is accompanied by changes in magnetic properties of liquids during Belousov&ndash, Zhabotinsky (BZ) reaction malonic acid, sodium bromide, sodium bromate, ferroin, and sulfuric acid. Instead of the earlier studied oscillation of microwave conductivity accompanying an oscillating reaction, we propose a flash technique to interrupt the BZ reaction by rapid freezing. Rapid cooling of a solution during chemical oscillations results in a frozen system with a fixed concentration of paramagnetic centers Fe3+. EPR spectrum recorded at different stages of the interrupted reaction corresponds to the exact concentration of the ferroin and ferriin components. Following unfreezing unblocks the BZ reaction, and oscillations are still observed. A simulated spectrum allows one to distinguish two groups of Fe3+ ions of different symmetries. The obtained results are important to explain the earlier observed effect of inhomogeneous magnetic field on BZ reaction front velocity.

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.

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...

Briggs-Rauscher (BR) oscillatory reaction is a chemical system very sensitive to different analyte addition. Changes in oscillatory dynamics, by analyte addition, could be successfully used for the determination of analyte concentration, as well as for its antioxidative/antiradical activity assessment. In this work, the BR reaction is used as a system detector for distinguishing solid unsolvable materials, such as phosphate tungsten bronze (PWB) and phosphate molybdenum bronze (PMoB), obtained by thermal treatment. The addition of different masses of PWB in BR reaction decreases its oscillation time, while the addition of different masses of PMoB had no effects on the BR oscillation time. Additionally, the BR oscillation time is the linear function of added PWB mass. The mechanism of bronzes action is investigated by using pH and electric conductivity measurements, as well as inductively coupled plasma and the cyclic voltammetry measurements, and it can be ascribed to PWB better catalytic activity then PMoB, under BR reaction condition. This work extends the practical aspect of the BR reaction for testing solid (insoluble) materials, and opening the possibility of using oscillatory reactions in material science and catalysis, in general.

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.

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.

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.

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.

This paper reports a new method for determination of VB6 (pyridoxine hydrochloride) by its perturbation effects on a novel Belousov-Zhabotinskii (BZ) oscillating system. This novel BZ system, in which malic acid serves as the substrate, contains an enzyme-like complex, macrocyclic complex {[CuL](ClO4)2}, as catalyst. The ligand L in the complex is 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene. Results show that the addition of pyridoxine hydrochloride can perturb the oscillation amplitude and period, and the change of the oscillation amplitude is linearly proportional to the concentration of pyridoxine hydrochloride in the range of 5×10−7−2.5×10−4 M. The obtained RSD with seven samples is 3.073%. An assay of pharmaceutical tablets of vitamin B6 was evaluated. Some foreign ions were studied with respect to their possible influence on the determination of pyridoxine hydrochloride. The factors which influence this reaction include the concentration of reactant, the temperature of the reaction, property of catalyst, etc. Furthermore, the possible reaction mechanism has been proposed using the Field-Körös-Noyes (FKN) model.

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.

The effect of electromagnetic radiation with a frequency close to the maximum of absorption of atmospheric oxygen on the Briggs-Rauscher self-oscillating reaction is described. It is shown that the radiation intensifies oxygen production and lengthens the duration of the self-oscillating regime by more than 20%.

When performing oscillating reactions, periodical changes in the concentrations of reactants, intermediaries, and products take place. Due to the mentioned periodical changes of the concentrations, the information about the diffusivity of the components included into oscillating reactions is very important for the control of the oscillating reactions. Non-linear dynamics makes oscillating reactions very interesting for analysis in different reactor systems. In this paper, the analysis of diffusivity of the oscillating reaction components was performed in a microreactor, with the aim of identifying the limiting component. The geometry of the microreactor microchannel and a well defined flow profile ensure optimal conditions for the diffusion phenomena analysis, because diffusion profiles in a microreactor depend only on the residence time. In this paper, the analysis of diffusivity of the oscillating reaction components was performed in a microreactor equipped with 2 Y-shape inlets and 2 Y-shape outlets, with active volume of V = 4 μL at different residence times.

In this paper we show that the active interplay of nonlinear kinetics and transport phenomena in a chemical oscillator can be exploited to induce and control chaos. To this aim we use as a model system the ferroin-catalysed Belousov-Zhabotinsky (BZ) oscillating reaction, which is known to evolve to characteristic chaotic transient dynamics when carried out under batch and unstirred conditions. In particular, chemical chaos was found to appear and disappear by following a Ruelle-Takens-Newhouse (RTN) scenario. Here we use medium viscosity as a bifurcation parameter to tune the reaction-diffusion-convection (RDC) interplay and force the reaction in a specific sequence of dynamical regimes: either (i) periodic → quasi-periodic → chaotic or (ii) periodic → quasi-periodic or (iii) only periodic. The medium viscosity can be set by adding different amounts of surfactant (sodium dodecyl sulphate), known to have a little impact on the reaction mechanism, above its critical micelle concentration. Experimental results are supported by means of numerical simulations of a RDC model, which combines self-sustained oscillations to the related chemically-induced buoyancy convection.

In this study, The volume oscillation of the microphase-separated, self-oscillating gel above the volume phase transition temperature is discussed. The self-oscillating gel is composed of N-isopropylacrylamide (NIPAAm) with a metal catalyst for the Belousov–Zhabotinsky (BZ) reaction, which is known as the oscillating reaction. The influence of temperature on the period and the self-oscillating behavior is clarified. The volume change of the gel is explained by a change of the Flory–Huggins interaction parameter, χ, which is induced by the hydration and dehydration of the polymer chain due to a valance change of the metal catalyst (Ru(bpy)32+ Ru(bpy)33+) below the volume phase-transition temperature. In contrast, the volume change of the gel is explained by a change of the Donnan osmotic pressure.

Hydroxyapatite-based materials are known to have several applications, most widely are used as implant coatings, but also as support in drug delivery. The impregnation of apatite with antioxidant substances could have a positive effect in both application areas, due to antioxidant-free radical scavenging properties, antimicrobial and antiviral effect, as in the case of red beetroot extract. By the variation of preparation parameters it is possible to control the properties of synthesized materials in function of the application field. In order to obtain hydroxyapatite-based materials with increased adsorption capacity different amounts of silica and copper ions were incorporated in the materials structure. These materials were analyzed by IR spectroscopy and TEM; particle size variation during synthesis was also monitored. Red beetroot is ranked among the ten most potent antioxidant vegetables, and their extract exhibits high antioxidant properties. The extract was examined by UV–Vis spectroscopy, and their degradation in time was monitored. The antioxidant capacity was determined by means of the Briggs–Rauscher oscillating reaction. The antioxidant activity was measured and expressed in Trolox units. The amount of adsorbed substance and adsorption efficiency was determined for the substituted materials. The adsorption mechanism was elucidated by kinetic studies involving different kinetic model evaluation. The kinetic data correlate best with the pseudo-second-order model, and the principal mechanism is the formation of chemical bonds between the active centers on the material surface and the antioxidant molecules.

As a novel biomimetic gels deffering from conventonal stimuli-responsive polymer gels, we have developed a “self-oscillating” gel that swells and deswells periodically under constant condition without on–off switching of external stimuli. The gel is composed of poly(N-isopropylacrylamide) to which the catalyst of the oscillating chemical reaction, called Belousov–Zhabotinsky reaction, is covalently immobilized. The chemical oscillation is converted to the mechanical oscillation of the gel through the change in hydrophilicity of polymer chains with the redox changes of the immobilized catalyst. By utilizing the self-oscillating gel, several kinds of functional material systems such as biomimetic actuators, etc. are expected. Here we review a potential application to functional surface to realize autonomous mass-transport by utilizing the peristaltic motion of the gel. With the propagation of the chemical wave, the loaded cargo is autonomously transported on the surface. In order to fabricate the self-driven gel conveyer for a wider use including biomedical applications, the interactions between the self-oscillating gel and the loaded gel cargo were investigated and their influence on the transport phenomena were evaluated.

A modified recipe for the Briggs–Rauscher oscillating reaction is suggested. The modified recipe, [H2SO4] = 0.10 M, [KIO3] = 0.020 M, [NaIO4] = 0.00062 M, [malonic acid] = 0.050 M, [MnSO4] = 0.0067 M, [H2O2] = 1.0 M with 0.01% starch, turns blue almost immediately, then oscillations start with two “slow” (∼25 s) cycles, then settle into regular approximately 12–15 s cycles. Oscillations end with a clear solution, avoiding cleanup of solid iodine resulting from the “standard” recipe, so that only neutralization of excess acid is needed before disposal. Effects of concentration variations are presented.