Self-sustaining Reaction Research Articles

Optimization of Tokamak Blanket Design to Minimize Neutron Flux on Magnets

Fusion energy, a promising solution to global energy challenges, replicates the same processes that give our sun its energy, notably through deuterium-tritium (D-T) fusion reactions that produce significant energy. This study explores the mechanics and challenges of various fusion reactions, emphasizing the pivotal role of lithium breeder blankets in producing tritium, essential for sustaining D-T fusion in tokamak reactors. The helium-cooled lithium lead (LiPb) blanket design was simulated to optimize tritium breeding and neutron flux management. Results indicated a tritium breeding ratio (TBR) of 1.15, surpassing the self-sufficiency target of 1.1, with further improvements through increased lithium content and blanket thickness. Effective neutron shielding ensured safe operational limits for reactor components. These findings demonstrate the feasibility of achieving self-sustaining fusion reactions, essential for the viability of fusion power as a sustainable energy source. Future research will focus on advanced materials, refined simulations, and enhanced cooling technologies to further optimize fusion reactor designs.

Low Volume Gas-Flow Seeding For Highly Resolved Velocimetry Of The Boundary Layer

Ensuring fire safety in polymeric materials, which are inherently flammable but widely used in various industries, is of significant societal and economic importance. This study is part of a broader effort to understand polymer combustion and flame retardant effectiveness at a fundamental level. A major focus is the behavior of polymers burning along a vertical wall, a configuration chosen to study the release of flammable gases during pyrolysis, which contributes to the self-sustaining combustion reaction of a fire. This process occurs predominantly near the polymer surface within the boundary layer, requiring detailed analysis to evaluate flame retardant effectiveness. Our experimental setup replicates polymer pyrolysis using a flame-wall interaction burner with a vertical jet and a small inlet to mimic the release of flammable gases. The primary challenge in this setup is the introduction of seeding particles for Particle Image Velocimetry (PIV) measurements at low volume flow rates, which is complicated by reflections from the wall and the small flow scale relative to the main flow. To address this problem, we have developed a novel piezo-based ultrasonic seeder capable of controlled seeding at extremely low flow rates, thereby improving the accuracy of PIV measurements in non-reactive configurations. This seeder uses a piezo ring to excite a perforated metal membrane, forming uniform aerosol droplets. The design ensures a steady supply of particles, which is critical for evaluating boundary layer conditions. Our results demonstrate the seeder’s ability to maintain sufficient seeding density in the low volume flow region, facilitating detailed velocimetry analysis. The innovative seeder design proves effective in overcoming the limitations of conventional methods and provides new insights into polymer combustion processes and the role of flame retardants.

Field-theoretic approach to neutron noise in nuclear reactors.

An operating nuclear reactor is designed to maintain a sustained fission chain reaction in its core, which results from a delicate balance between neutron creations (i.e., fissions) and total absorptions. This balance is associated with random fluctuations that can have two, very different, origins. A distinction must thus be made between low-power noise, whose origin lies in the inherently stochastic nature of neutron interactions with matter, and high-power noise, whose origin lies in the particular thermomechanical constraints associated with the environment in which neutrons propagate. Modeling the behavior of this noisy neutron population with the help of stochastic differential equations, we first show how the Martin-Siggia-Rose-Janssen-De Dominicis (MSRJD) formalism, providing a field theoretical representation of the problem, reveals a convenient and adapted tool for the calculation of observable consequences of neutron noise. In particular, we show how the MSRJD approach is capable of encompassing both types of neutron noises in the same formalism. Emphasizing then on power noise, it is shown how the self-sustained chain reaction developing in a reactor core might be sensitive to noise-induced transitions. Establishing an unprecedented connection between the neutron population evolving in a reactor core and the celebrated Kardar-Parisi-Zhang (KPZ) equation, we indeed find evidence that a noisy reactor core power distribution might be subject to a process analogous to the roughening transition, well-known to occur in systems described by the KPZ equation.

Numerical Simulation of Polyacrylamide Hydrogel Prepared via Thermally Initiated Frontal Polymerization.

Traditional polymer curing techniques present challenges such as a slow processing speed, high energy consumption, and considerable initial investment. Frontal polymerization (FP), a novel approach, transforms monomers into fully cured polymers through a self-sustaining exothermic reaction, which enhances speed, efficiency, and safety. This study focuses on acrylamide hydrogels, synthesized via FP, which hold significant potential for biomedical applications and 3D printing. Heat conduction is critical in FP, particularly due to its influence on the temperature distribution and reaction rate mechanisms, which affect the final properties of polymers. Therefore, a comprehensive analysis of heat conduction and chemical reactions during FP is presented through the establishment of mathematical models and numerical methods. Existing research on FP hydrogel synthesis primarily explores chemical modifications, with limited studies on numerical modeling. By utilizing Differential Scanning Calorimetry (DSC) data on the curing kinetics of polymerizable deep eutectic solvents (DES), this paper employs Malek's model selection method to establish an autocatalytic reaction model for FP synthesis. In addition, the finite element method is used to solve the reaction-diffusion model, examining the temperature evolution and curing degree during synthesis. The results affirm the nth-order autocatalytic model's accuracy in studying acrylamide monomer curing kinetics. Additionally, factors such as trigger temperature and solution initial temperature were found to influence the FP reaction's frontal propagation speed. The model's predictions on acrylamide hydrogel synthesis align with experimental data, filling the gap in numerical modeling for hydrogel FP synthesis and offering insights for future research on numerical models and temperature control in the FP synthesis of high-performance hydrogels.

Preparation of HNS-based sticks through 3D printing and its combustion performance

Microscale energetic materials have garnered considerable attention because they can be integrated in microelectromechanical systems for several potential applications. Hexanitrostilbene (HNS) has been widely utilized in ignition and initiation devices owing to its excellent thermal and shock stability and high sensitivity to short pulse shock waves. To meet the energy release requirements of micro-detonation devices, HNS sticks were prepared using direct ink writing and their reaction and flame propagation properties were studied. HNS particles sized 17.5 µm to 5 µm and ∼500 nm was prepared. Then, the viscosity of HNS-based inks prepared via acoustic resonance technology decreased when the particle size decreased or when the HNS content reduced from 97 wt.%, 95 wt.%, and 92 wt.%, to 90 wt.%. Additionally, the HNS-based inks with different binders exhibited different viscosity. The effect of the inner diameter of needle (0.4 mm, 0.6 mm, and 0.9 mm), printing rate (13 mm/s, 15 mm/s, 17 mm/s, 19 mm/s), and pressure (0.05 MPa, 0.1 MPa, 0.15 MPa, 0.2 MPa) on the width of HNS sticks was also elucidated. HNS-based sticks with a diameter of 0.9 mm underwent self-sustaining combustion reactions, and the burning rate increased from 5.1 mm/s to 6.8 mm/s as the particle size decreased from 17.5 µm to 500 nm. Overall, this work provides an effective approach to prepare microscale HNS for integration into micro-energetic devices.

SPH simulation of shock-induced chemical reactions in reactive powder mixtures

Reactive materials (RMs) are a mixture of two or more nonexplosive solid components in which, under extreme conditions, self-sustaining chemical reactions occur with the release of a high amount of energy. Knowing the kinetics of chemical reactions in RMs plays the key role in their efficient applications. In this work, we propose a macroscopic mathematical model of shock-induced chemical reactions based on smoothed particle hydrodynamics (SPH) for particle-scale simulation. The model includes the elastic-plastic deformation of materials, heating due to deformation and chemical reactions, diffusion of components, and heat transfer. The test calculations performed for the zero- and first-order reactions in the Al/S mixture showed a need for a more reliable determination of criteria and constants of chemical reactions. For this purpose, we propose a schematic experimental arrangement for the experimental and theoretical determination of the critical reaction pressure and the rate constant of the reaction. The type and corresponding constants of chemical reactions can be determined, for example, by the maximum likelihood method. We theoretically determined the zones of chemical reaction with different modes and found the influence of the projectile velocity and the intensity of shock waves on the development and completion of chemical reactions.

Fe/Au galvanic nanocells to generate self-sustained Fenton reactions without additives at neutral pH.

The generation of reactive oxygen species (ROS) via the Fenton reaction has received significant attention for widespread applications. This reaction can be triggered by zero-valent metal nanoparticles by converting externally added H2O2 into hydroxyl radicals (˙OH) in acidic media. To avoid the addition of external additives or energy supply, developing self-sustained catalytic systems enabling onsite production of H2O2 at a neutral pH is crucial. Here, we present novel galvanic nanocells (GNCs) based on metallic Fe/Au bilayers on arrays of nanoporous silica nanostructures for the generation of self-sustained Fenton reactions. These GNCs exploit the large electrochemical potential difference between the Fe and Au layers to enable direct H2O2 production and efficient release of Fe2+ in water at neutral pH, thereby triggering the Fenton reaction. Additionally, the GNCs promote Fe2+/Fe3+ circulation and minimize side reactions that passivate the iron surface to enhance their reactivity. The capability to directly trigger the Fenton reaction in water at pH 7 is demonstrated by the fast degradation and mineralization of organic pollutants, by using tiny amounts of catalyst. The self-generated H2O2 and its transformation into ˙OH in a neutral environment provide a promising route not only in environmental remediation but also to produce therapeutic ROS and address the limitations of Fenton catalytic nanostructures.

NUMERICAL SOLUTION OF COUPLED HEAT TRANSFER WITH PHASE CHANGE AND THERMITE REACTION

The thermite reaction is a self-sustained exothermic reaction commonly employed in welding processes of railway tracks, material synthesis, pyrotechnics, etc. More recently, this reaction has been assessed to plug depleted oil wells. The investigated geometry is modeled as a two-dimensional axisymmetric domain with a thermite mixture compressed between a polymethylmethacrylate (PMMA) lid and a stainless steel disk. First-order kinetic is assumed for the chemical kinetics model. The governing equations are discretized with the finite-volume approach. Experimental validation is performed by comparing numerical combustion velocities and peak temperatures with the experimental data in the literature. The results demonstrate a remarkable thermal gradient through the longitudinal direction, displaying higher thermal losses next to the thermite-steel interface. These heat losses also affect the melting of species, as a small portion of alumina remains entirely solid during the reaction.

Unearthing the Chicago Piles: A Monte Carlo perspective

The divergence of the Chicago Pile 1 (CP-1) on December 2nd, 1942, marks the birth of the nuclear age. Built under the West Stands of the Stagg Field in Chicago in slightly over two weeks, CP-1 was the first man-made nuclear reactor, conceived as a proof-of-principle physics experiment to demonstrate the feasibility of a self-sustained neutron chain reaction. The fuel consisted in a mixture of uranium oxide and metal uranium, with lumps of several sizes and shapes stacked within bricks of graphite used as moderator to form a cubic lattice. After only three months of operation, CP-1 was dismantled due to safety reasons and rebuilt at the Argonne Site in twenty-one days, under the name of Chicago Pile 2 (CP-2): the new pile had a longer life, contributing vastly to research on material science and nuclear reactor theory, and was finally decommissioned in 1954. Prompted by the eightieth anniversary of the Chicago Pile(s), in this talk we celebrate these astonishing scientific artifacts by building fully detailed three-dimensional digital twins of CP-1 and CP-2 using TRIPOLI-4®, the Monte Carlo code developed at CEA. Technological data for the models have been retrieved from published and unpublished documents of the Manhattan Project. We compare the simulation results to the available experimental measurements, encompassing the reactivity of the piles, the control rod worth, the kinetics parameters and several reactivity coefficients. For each, we examine the associated uncertainties due to missing or incomplete technological data as well as the bias due to nuclear data libraries.

Fenton-like reaction triggered chemical redox-cycling signal amplification for ultrasensitive fluorometric detection of H2O2 and glucose.

An ultrasensitive fluorescent biosensor is reported for glucose detection based on a Fenton-like reaction triggered chemical redox-cycling signal amplification strategy. In this amplified strategy, Cu2+ oxidizes chemically o-phenylenediamine (OPD) to generate photosensitive 2,3-diaminophenazine (DAP) and Cu+/Cu0. On the one hand, the generated Cu0 catalyzes the oxidation of OPD. On the other hand, H2O2 reacts with Cu+ to produce hydroxyl radicals (˙OH) and Cu2+ through a Cu+-mediated Fenton-like reaction. The generated ˙OH and recycled Cu2+ ions take turns oxidizing OPD to produce more photoactive DAP, triggering a self-sustaining chemical redox-cycling reaction and a remarkable fluorescent enhancement. It is worth mentioning that the cascade reaction did not stop until OPD molecules were completely consumed. Benefiting from H2O2-triggered chemical redox-cycling signal amplification, the strategy was exploited for the development of an ultrasensitive fluorescent biosensor for glucose determination. Glucose content monitoring was realized with a linear range from 1 nM to 1 μM and a limit of detection of 0.3 nM. This study validates the practicability of the chemical redox-cycling signal amplification on the fluorescent bioanalysis of glucose in human serum samples. It is expected that the method offers new opportunities to develop ultrasensitive fluorescent analysis strategy.

Mechanistic insights into the adsorption and dissociation of nitrogen oxides on nickel phosphide (Ni2P) catalysts

The escalating concern regarding nitrogen oxides (NOx) emissions, linked to environmental challenges like smog, acid rain, ozone depletion, and global warming, necessitates effective strategies for their mitigation. DeNOx processes, including selective catalytic reduction (SCR), offer potential solutions, but costly precious metal catalysts hinder a widespread implementation. Alternatively, earth-abundant element compounds, particularly transition metal phosphides (TMPs), such as nickel phosphides (Ni2P), have garnered interest due to their promising catalytic performance. This study employed first-principles density functional theory (DFT) methods to investigate the catalytic properties of the (0001) Ni2P surface concerning NOx adsorption and dissociation. Both NO and NO2 are found to exhibit strong reactivity towards Ni2P-(0001)’s surface at the hollow triple-Ni sites, forming stable conjugated structures. Bader charge analysis indicates significant charge transfers during NOx adsorption from the interacting surface to the NOx, resulting in elongated N–O bond lengths, confirmed by vibrational frequency analyses. The dissociation process of NO2 was found to be both thermodynamically and kinetically favorable, with more heat being released than the subsequent NO dissociation’s activation barrier, resulting in a self-sustaining overall reaction. These insights provide valuable knowledge for designing efficient and sustainable Ni2P-based catalytic systems to address NOx emissions in environmental and industrial applications.

Combustion Synthesis of Materials for Application in Supercapacitors: A Review

A supercapacitor is an energy storage device that has the advantage of rapidly storing and releasing energy compared to traditional batteries. One powerful method for creating a wide range of materials is combustion synthesis, which relies on self-sustained chemical reactions. Specifically, solution combustion synthesis involves mixing reagents at the molecular level in an aqueous solution. This method allows for the fabrication of various nanostructured materials, such as binary and complex oxides, sulfides, and carbon-based nanocomposites, which are commonly used for creating electrodes in supercapacitors. The solution combustion synthesis offers flexibility in tuning the properties of the materials by adjusting the composition of the reactive solution, the type of fuel, and the combustion conditions. The process takes advantage of high temperatures, short processing times, and significant gas release to produce well crystalline nanostructured materials with a large specific surface area. This specific surface area is essential for enhancing the performance of electrodes in supercapacitors. Our review focuses on recent publications in this field, specifically examining the relationship between the microstructure of materials and their electrochemical properties. We discuss the findings and suggest potential improvements in the properties and stability of the fabricated composites based on the results.

Effect of light wavelengths on algal-bacterial symbiotic particles (ABSP): Nitrogen removal, physicochemical properties, community structure

The accumulation of nitrogenous waste, such as ammonia, and its biological nitrification products, namely nitrite and nitrate, poses one of the primary challenges in the water treatment process for Recirculating Aquaculture Systems (RAS). This study proposed the incorporation of light and algal-bacterial symbiotic particles (ABSP)into RAS as a viable solution to address these challenges. The findings indicated that ABSP achieved the RAS water quality standards (ammonia nitrogen <0.5 mg/L, nitrite nitrogen <0.1 mg/L) by the 14th day of operation, while red light achieved and maintained these standards from as early as the 9th day. Further analysis of chemical stoichiometry and functional genes revealed that microalgae (32.7%, 15.6%, 0%) and bacteria (47.7%, 55.8%, 48.4%) were responsible for the assimilation and removal of most organic and nutrient substances under red light, white light, and dark conditions, respectively. Additionally, it was observed that the presence of algae and bacteria in ABSP was significantly influenced by the wavelength of light. Under red light, an optimal distribution of functional species for both microalgae (Characium, Microcoleus, and Uronema) and bacteria (Nakamurella and Micropruina) was achieved, which is crucial for the self-sustaining synergistic reaction and stability of ABSP. This study may offer a promising engineering alternative with enormous potential to achieve energy-efficient and environmentally sustainable RAS water treatment.

A predictive theory on thermal runaway of ultrahigh capacity lithium-ion batteries

Ultrahigh capacity lithium-ion batteries (LIBs) with prudent safety measures are key to future transportation. The undesirable thermal events such as thermal runaway (TR) in LIBs can pose a direct risk to battery life and the consumers. In the present study, a set of new TR criteria are established by closely inspecting the relation between the rate of heat generation and dissipation to anticipate the TR at an early stage. From the proposed criteria, three alarming temperatures prior to TR are identified, such as the safe temperature limit TE (an intersection between heat generation curve and heat removal line), the maximum temperature limit TM (where second derivative of heat generation is zero), and the low temperature TC from the Semenov theory. For a safer battery operation, both the low and upper limit temperatures have to remain below the safety zone, i.e. TM < TE with TC < TE. The criteria are validated by implementing them on the ultrahigh capacity LIBs, which are subjected to the thermal abuse, wherein the rate of heat generation was determined from calorimetry. The state TM < TE indicates the first precursor to TR where a controlled measure can be taken to prevent the runaway. However, TE ≤ TM regarded as the critical state during which a self-sustaining reaction involving delithiated nickel-rich cathode, intercalated anode, and dissociated electrolyte progresses, resulting in an irreversible TR in the system. The validity of the proposed criteria is demonstrated, while additional work is considered in a broad class of batteries subjected to thermal abuse conditions for establishing a safety margin of operation.

Synthesis of nanoporous carbonaceous materials at lower temperatures.

Nanoporous carbonaceous materials are ideal ingredients in various industrial products due to their large specific surface area. They are typically prepared by post-synthesis activation and templating methods. Both methods require the input of large amounts of energy to sustain thermal treatment at high temperatures (typically >600°C), which is clearly in violation of the green-chemistry principles. To avoid this issue, other strategies have been developed for the synthesis of carbonaceous materials at lower temperatures (<600°C). This mini review is focused on three strategies suitable for processing carbons at lower temperatures, namely, hydrothermal carbonization, in situ hard templating method, and mechanically induced self-sustaining reaction. Typical procedures of these strategies are demonstrated by using recently reported examples. At the end, some problems associated with the strategies and potential solutions are discussed.

Neutronic Chain Reactions for Polonium-210 Production

The production of the industrially significant radionuclide polonium-210 from the neutron irradiation of bismuth metal and the subsequent beta decay of bismuth-210 is highly inefficient due to the small neutron capture cross section of bismuth-209. In this paper, we report a previously undescribed self-sustaining nuclear chain reaction involving self-propagating neutron multiplication in bismuth salts that allow for rapid and cost-effective production of polonium-210. The reaction proceeds in a cycle of three alternating elementary steps – the capture of neutrons by bismuth-209 and the subsequent formation of polonium-210, the emission of high-energy alpha particles by polonium-210, and the production of more neutrons from (α, n) and (n,2n) reactions on light element and bismuth-209 nuclei respectively. Furthermore, the high hydrogen density of the compound also confers it intrinsic neutron moderation properties, increasing the neutron capture cross section of bismuth-209 at thermal neutron energies. The chain reaction was proven to have successfully occurred by irradiating a sample of the bismuth salt with a 80 μCi neutron source and monitoring the activity levels of the reaction. It was found that the activity of the reaction increased exponentially after an initial stable period following a derived formula for polonium production trends for the reaction, thus validating the occurrence of the reaction. Furthermore, alpha spectroscopy confirmed that polonium-210 had been produced by characterising the 5.30 MeV alpha emission peak of the reaction in addition to using beta spectroscopy to identify the parent nuclide bismuth-210, further proving that the reaction was successful. Hence, this paper reports the successful initiation and characterisation of a novel nuclear chain reaction, and its potential applications offered by a method of rapidly producing large quantities of polonium-210.

Alloying reaction mechanism of shocked Ni/Al nanolaminates regulated via atomic diffusion

The Ni/Al nanolaminates represent cutting-edge functional materials that exhibit alloying reactions and release substantial energy when subjected to shock loading. However, the extremely short timeframes of the shock loading and the induced reactions surpass the resolving capability of state-of-the-art monitoring techniques, rendering the alloying reaction mechanism of Ni/Al nanolaminates a challenging multi-physical problem. To address this issue, we conducted extensive molecular dynamics simulations on large-scale models of Ni/Al nanolaminates at varying shock velocities to investigate their in situ thermodynamics response and shock-induced kinetic evolution related to phase transitions and chemical reactions. Our simulations revealed that atomic diffusion plays a pivotal role in accelerating the activation and intensifying the alloying reaction. For a self-sustaining reaction to occur, the shock-induced pressure must surpass a threshold, triggering global atomic diffusion that overcomes lattice trapping barriers or fluid viscosity, facilitating the formation of a sufficient number of Ni–Al intermetallic bonds to store energy. Subsequently, interfacial and bulk atomic diffusion becomes unstoppable, leading to a uniform distribution of mixed atoms and a steady energy release accompanied by continuous temperature rise, thereby triggering self-sustaining alloying reactions akin to an avalanche. Our findings not only offer a valuable baseline for understanding reactions in real defective composites but also establish a lower bound on the required shock intensity for future experiments using new high-quality samples.

(Photoredox) Organocatalysis in the Emergence of Life: Discovery, Applications, and Molecular Evolution.

ConspectusLife as we know it is built on complex and perfectly interlocking processes that have evolved over millions of years through evolutionary optimization processes. The emergence of life from nonliving matter and the evolution of such highly efficient systems therefore constitute an enormous synthetic and systems chemistry challenge. Advances in supramolecular and systems chemistry are opening new perspectives that provide insights into living and self-sustaining reaction networks as precursors for life. However, the ab initio synthesis of such a system requires the possibility of autonomous optimization of catalytic properties and, consequently, of an evolutionary system at the molecular level. In this Account, we present our discovery of the formation of substituted imidazolidine-4-thiones (photoredox) organocatalysts from simple prebiotic building blocks such as aldehydes and ketones under Strecker reaction conditions with ammonia and cyanides in the presence of hydrogen sulfide. The necessary aldehydes are formed from CO2 and hydrogen under prebiotically plausible meteoritic or volcanic iron-particle catalysis in the atmosphere of the early Earth. Remarkably, the investigated imidazolidine-4-thiones undergo spontaneous resolution by conglomerate crystallization, opening a pathway for symmetry breaking, chiral amplification, and enantioselective organocatalysis. These imidazolidine-4-thiones enable α-alkylations of aldehydes and ketones by photoredox organocatalysis. Therefore, these photoredox organocatalysts are able to modify their aldehyde building blocks, which leads in an evolutionary process to mutated second-generation and third-generation catalysts. In our experimental studies, we found that this mutation can occur not only by new formation of the imidazolidine core structure of the catalyst from modified aldehyde building blocks or by continuous supply from a pool of available building blocks but also by a dynamic exchange of the carbonyl moiety in ring position 2 of the imidazolidine moiety. Remarkably, it can be shown that by incorporating aldehyde building blocks from their environment, the imidazolidine-4-thiones are able to change and adapt to altering environmental conditions without undergoing the entire formation process. The selection of the mutated catalysts is then based on the different catalytic activities in the modification of the aldehyde building blocks and on the catalysis of subsequent processes that can lead to the formation of molecular reaction networks as progenitors for cellular processes. We were able to show that these imidazolidine-4-thiones not only enable α-alkylations but also facilitate other important transformations, such as the selective phosphorylation of nucleosides to nucleotides as a key step leading to the oligomerization to RNA and DNA. It can therefore be expected that evolutionary processes have already taken place on a small molecular level and have thus developed chemical tools that change over time, representing a hidden layer on the path to enzymatically catalyzed biochemical processes.

Cascade signal amplification strategy by coupling chemical redox-cycling and Fenton-like reaction: Toward an ultrasensitive split-type fluorescent immunoassay

An ultrasensitive split-type fluorescent immunobiosensor has been reported based on a cascade signal amplification strategy by coupling chemical redox-cycling and Fenton-like reaction. In this strategy, Cu2+ could oxidize chemically o-phenylenediamine (OPD) to generate photosensitive 2, 3-diaminophenazine (DAP) and Cu+/Cu0. On one hand, the generated Cu0 in turn catalyzed the oxidation of OPD. On the other hand, the introduced H2O2 reacted with Cu + ion to produce hydroxyl radicals (·OH) and Cu2+ ion through a Cu + -mediated Fenton-like reaction. The produced ·OH and recycled Cu2+ ion could take turns oxidizing OPD to generate more photoactive DAP, which triggering a self-sustaining chemical redox-cycling reaction and leading to a remarkable fluorescent improvement. It was worth mentioning that the cascade reaction did not stop until OPD molecules were completely consumed. Based on the H2O2-triggered cascade signal amplification, the strategy was exploited for the construction of split-type fluorescent immunoassay by taking interleukin-6 (IL-6) as the model target. It was realized for the ultrasensitive determination of IL-6 in a linear ranging from 20 fg/mL to 10 pg/mL with a limit of detection of 5 fg/mL. The study validated the practicability of the cascade signal amplification on the fluorescent bioanalysis and the superior performance in fluorescent immunoassay. It is expected that the strategy would offer new opportunities to develop ultrasensitive fluorescent methods for biosensor and bioanalysis.

Про можливість самопідтримної ланцюгової реакції поділу в об’єкті "Укриття" на теперішній час

Based on new modern data regarding the state of the fuel-containing masses (FCM) of the "Shelter", as well as taking into account the neutron incident of 1990 and the physical properties of the FCM of the "Shelter", the possibility of the occurrence and development of a self-sustaining chain nuclear fission reaction was considered in the FCM. It is shown that the drying of the FCM can lead to the occurrence of a single neutron burst with an amplitude comparable to the amplitude of neutron oscillations in 1990. It is also shown that the amplitude of the burst can be reduced if the rate of drying of the FCM is increased. The evaluations show that such a burst would have no impact on the environment.