Local Chemical Reaction Research Articles

Nanocatalytic Tumor Therapy by Single-Atom Catalysts.

Initiating localized catalytic chemical reactions in tumor microenvironment (TME) can achieve appealing tumor-therapeutic efficacy concurrently with high specificity and desirable biosafety, which is mainly dependent on the high performance of biomedical nanocatalysts. This report demonstrates that PEGylated single-atom Fe-containing nanocatalysts (PSAF NCs) could effectively trigger the in situ tumor-specific Fenton reaction to generate abundant toxic hydroxyl radicals (•OH) selectively under the acidic TME. Based on density functional theory, it has been theoretically uncovered that the nanocatalysts could specifically catalyze the heterogeneous Fenton reaction via a proton-mediated H2O2-homolytic pathway. These generated radicals could not only lead to the apoptotic cell death of malignant tumors, but also induce the accumulation of lipid peroxides, causing tumor cell ferroptosis, which synergistically lead to an impressive tumor suppression outcome. In the meantime, the favorable biodegradability and biocompatibility of PSAF NCs also guarantee their desirable biosafety both in vivo and in vitro.

Advanced Nanopatterning Using Scanning Probe Technology

Abstract This paper demonstrates two different lithographic techniques for micro/nanofabrication, viz. electrolithography technique driven by electromigration, and constructive lithography driven by anodic oxidation. The principle of electrolithography is based on electric field induced material transport which can be used for drawing patterns having dimensions from a few nanometres to a few hundred micrometres. Here, a thin Cr film is used as a masking layer and a polymer layer beneath it is used as a pattern transfer layer. A negatively biased scanning probe is used to perform electromigration on the metal film. The best resolution achieved with this technique is 9 nm. On the other hand, with the help of constructive lithography, micro/nano patterns are drawn on a highly ordered organosilane monolayer, self-assembled on silicon, using localized chemical reaction induced by an electrically biased tip or a focused e-beam.

Scanning probe microscopy for real-space observations of local chemical reactions induced by a localized surface plasmon.

Localised surface plasmon (LSP) resonance has attracted considerable attention in recent years as an efficient driving force for chemical reactions. The chemical reactions induced by LSP are classified into two types, namely, redox reactions based on plasmon-induced charge separation (PICS) and chemical reactions induced by the direct interaction between LSP and molecules (plasmon-induced chemical reactions). Although both types of reactions have been extensively studied, the mechanisms of PICS and plasmon-induced chemical reactions remain unexplained and controversial because conventional macroscopic methods can hardly grasp the local chemical reactions induced by LSP. In order to obtain mechanistic insights, nanoscale observations and investigations are necessary. Scanning probe microscopy (SPM) is a powerful experimental tool to investigate not only the surface morphology but also the physical and chemical properties of samples at a high spatial resolution. In this perspective review, we first explain SPM combined with optical excitation, and then, review the recent studies using SPM techniques for real-space observations of the chemical reactions induced by LSP.

Thermodynamic modelling of the lead sintering roasting process

This work proposes a simulation strategy of the lead sintering process assuming that it takes place in a horizontally moving packed bed with transverse air flow. Some local chemical reactions occur at rates that depend on the temperature, and chemical species formed in one volume stage will flow for further reaction in other stages. To simulate this process, the model reactor is divided into a number of sequential stages. Condensed species flow horizontally, and gaseous species leave each stage vertically. The compositions and temperatures of the species are calculated considering that the local thermodynamic equilibrium is reached in each stage without external heat transfer, apart from the gas flow, before moving on to the next stage. The model calculates the temperature profile along the sintering machine, the compositions of the sinter and the exhaust gas. The results of the proposed model were compared with sinter pot experimental trials and a reasonably good agreement was obtained. This model can be used to optimize the operating conditions of the lead sintering process.

Transient analysis of diffusion-induced stress: effect of solid reaction

The chemical reactions taking place in lithium-ion batteries can trap lithium and alter the distribution of lithium and the deformation of the electrode during electrochemical charging and discharging. In this work, we incorporate the strain generated by chemical reactions in the transient analysis of diffusion-induced stress and numerically solve the one-dimensional problem under galvanostatic and potentiostatic operations, respectively. The numerical results show that both the diffusion and local chemical reaction contribute to the expansion of the electrode. Under the potentiostatic operation, lithiation introduces a stress spike at the fixed end at the onset of the lithiation. The chemical reactions play a significant role in controlling the temporal evolution of lithium and the deformation of electrode, which needs to be taken into account in the analysis of structural durability of lithium-ion batteries.

Multistep Wavelength Switching of Near-Infrared Photoluminescence Driven by Chemical Reactions at Local Doped Sites of Single-Walled Carbon Nanotubes.

Local chemical functionalization is used for defect doping of single-walled carbon nanotubes (SWNTs), to develop near-infrared photoluminescence (NIR PL) properties. We report the multistep wavelength shifting of the NIR PL of SWNTs through chemical reactions at local doped sites tethered to an arylaldehyde group. The PL wavelength of the doped SWNTs is modulated based on imine chemistry. This involves the imine formation of aldehyde groups with added arylamines, imine dissociation reaction, exchange reaction of bound arylamines in the imine, and the Kabachnik-Fields reaction of imine groups using diisopropyl phosphite. Using doped sites as a localized chemical reaction platform can exploit the versatile molecularly driven functionality of carbon nanotubes and related nanomaterials.

Microstructural Modification and High-Temperature Grain Stability of Aluminum in an Aluminum-Titanium Friction Stir Weld with Zinc Interlayer

In dissimilar friction stir welding (FSW), the presence of a third interlayer material can have a positive influence on local ternary chemical reactions due to complex mechanical mixing in the weld nugget. This leads to a reduction and distribution of intermetallic compounds as fine particles in the weld nugget. These fine particles can provide high-temperature grain stability. In the present investigation, a zinc (Zn) interlayer was used during the FSW of aluminum (Al) with titanium (Ti). X-ray computed tomography results revealed the occurrence of mechanical mixing of Zn with both Al and Ti. To understand the nature of the weld nugget at high temperatures, heat treatment of the weld was carried out at 500°C for 60 min. The detailed mechanisms leading to the superior grain stability of Al in the weld nugget were investigated. The improvement in grain stability of Al may open up a new area of research and development to produce new materials with high-temperature grain stability.

A numerical method for finite-strain mechanochemistry with localised chemical reactions treated using a Nitsche approach

In this paper, a novel finite-element based method for finite-strain mechanochemistry with moving reaction fronts, which separate the chemically transformed and the untransformed phases, is proposed. The reaction front cuts through the finite elements and moves independently of the finite-element mesh, thereby removing the necessity for remeshing. The proposed method solves the coupled mechanics-diffusion–reaction problem. In the mechanical part of the problem, the force equilibrium and the displacement continuity conditions at the reaction front are enforced weakly using a Nitsche-like method. The formulation is applicable to the case of large deformations and arbitrary constitutive behaviour, and is also consistent with the minimisation of the total potential energy.

Material instability under localized severe plastic deformation during high speed turning of titanium alloy Ti-6.5AL-2Zr-1Mo-1V

High temperature, large strain and fast strain rate resulting from the severe plastic deformation will cause local material instability, then physical and chemical reactions such as phase transition, grain redistribution and fracture may occur during this process. This paper presents an in-depth investigation about the material instability and corresponding microstructures during the serrated chip formation of titanium alloy Ti-6.5AL-2Zr-1Mo-1 V by high speed turning. Firstly, intense deformation during high speed cutting was verified. Phase transition under different loading conditions including temperature, strain and strain rate were also explored, followed by the domination of equiaxed α-phase due to suitably localized severe plastic deformation and sufficient cooling. Secondly, criterion for initiation of fracture of material was introduced and applied to chip breaking. Finally, particle redistribution phenomenon was analyzed accordingly and the so-called severe plastic flow was further verified.

Numerical study of tip opening of hydrogen/air Bunsen flame

Abstract To understand tip opening of a hydrogen–air Bunsen flame, the detailed flow, temperature and concentration fields of the flame were studied based on numerical calculations that use the exact transport properties and the full chemical reaction mechanism. The study has revealed that the local chemical reactions along the flame cone portion do not remain uniform; the H2 consumption rate decreases in the downstream direction. The lowering H2 concentration of the mixture coming into the cone, caused by the radial outward diffusion of mobile H2 molecules, leads to the slowdown of the main H2-consuming reactions downstream and causes the breakdown of the reaction at the downstream end of the cone. This is the tip opening.

Xpeem Reveals the Local (electro-) Chemical Surface Reactions of the Ncm Cathode and Their Impact on the Lto Counter Anode

Understanding the electrode-electrolyte interface evolution during cycling as well as the surface structural change of the active materials is crucial to improve the safety and the life-cycle of Li-ion batteries. Despite the large effort directed at elucidating the nature and origin of the surface reactivity of the electrodes in liquid organic electrolytes, there is still no complete knowledge of the various mechanisms that take place at such interfaces. The lack of agreement in the reported findings is caused mainly by the surface complexity of the commercial electrodes (multiple particles, high roughness, and porosity) and by the intrinsic limitations of the commonly used surface characterization techniques (poor lateral resolution). Thus, in this contribution we use X-Ray Photoelectron Emission Spectroscopy (XPEEM) as a surface analytical technique capable of providing localized information on single particles of composite anode and cathode materials, while preserving their working environment (as in commercial-like electrodes). The unique combination of the nanoscale lateral resolution and the spectroscopic capability, confined to within the depth analysis range of 3-4 nm, enable us to finally provide the missing piece of the exact mechanism of the electrolyte-electrode interactions. The surfaces of two types of electrodes are investigated and will be presented, Li(Mn,Ni,Co)O2-Li2MnO3 (NCM) and Li4Ti5O12 (LTO), as promising industrially relevant positive and negative electrodes, respectively, for Li-ion batteries. A systematic study of the potential dependency of the surface evolution was performed during the early stage and after long cycling. The contrast images in Figure 1a,d attest the good spatial resolution of XPEEM and its capability to localize the different particles present on the surface. The local XAS spectra (Figure 1b) at the transition metals (TMs)-L edges acquired on NCM particles allow us to monitor its oxidation states and the surface structure modification. At the same time, the C-K edge provides direct information on the chemical changes and the electrolyte byproducts decomposition.[1] We find that, despite cycling the NCM to a highly oxidative potential of 5.1 V vs. Li+/Li, there is no formation of an oxidized electrolyte byproduct layer on the surface of the cathode particles (C K-edges Figure 1.b, c); instead, we show that a homogeneous organic-inorganic surface layer builds-up across the particles of the LTO counter anode (C K-edges, Figure 1.e f). In addition, we observe that such surface layer incorporates, already from the first charge, micrometer-sized agglomerates of TMs explained as due to the instability of a reduced layer of Mn, Co and Ni at the NMC-electrolyte interface that is mainly formed during the cathode delithiation (Mn L-edge, Figure 1.b). These results demonstrate that two simultaneous reactions take place at the NCM-electrolyte interface subject to a high working potential, namely, surface degradation of the NCM active materials and decomposition of the electrolyte which affect directly the anode surface and the overall cell performance through a cross-talk process. [1] D. Leanza, C.A.F. Vaz, I. Czekaj, P. Novák, M. El Kazzi, Journal of Materials Chemistry A 6 (8), 3534-3542 (2018) Figure 1

Primena hemijsko kinetičkih modela kod numeričke simulacije procesa nekatalitičke redukcije NOX-a amonijakom u produktima sagorevanja biomase

Research related to the development of secondary measures of denitrification of agrarian biomass combustion gases is becoming more and more actual due to the increasingly intensive application of this renewable fuel and the promotion of sustainable development, ie, the reduction of consumption of fossil fuels. Thereby, in spite of a number of advantages, agrarian biomass has an important disadvantage due to significant emissions of nitrogen oxides. The paper deals primarily with the chemical reactions of selective noncatalytic reduction of nitrogen monoxide using ammonia as a reagent. Two kinetic models, one rather simplistic, which takes into account only two net reactions and other, more complex with seven chemical reactions, are analyzed. The considered chemicalkinetic models are incorporated into a comprehensive CFD model of complex processes in an experimental denitrification chamber. The CFD model was included flow simulation, components mixing and monitoring of local chemical reactions. The results of presented numerical simulation were compared with literature experiments, as well as with the results of other authors' models. The same boundary conditions of the considered processes are provided, i.e. the input concentrations of the component are: 300 ppm NH3, 300 ppm NO, 4.0% O2, 4.5% H2O, and the residence time of the reactants in the chamber is 150 ms.

Impact sensitivity test of liquid energetic materials

This paper presents new experimental method for sensitivity evaluation at the impact. A large number of researches shown that the probability of explosion initiating of liquid explosives by impact depends on the chemical nature and the various external characteristics. But the sensitivity of liquid explosive in the presence of gas bubbles increases many times as compared with the liquid without gas bubbles. In this case local chemical reaction focus are formed as a result of compression and heating of the gas inside the bubbles. In the liquid as a result of convection, wave motion, shock, etc. gas bubbles are easily generated, it is necessary to develop methods for determining sensitivity of liquid explosives to impact and to research the explosives ignition with bubbles. For the experimental investigation, the well-known impact machine and the so-called appliance 1 were used. Instead of the metal cup in the standard method in this paper polyurethane foam cylindrical container with liquid explosive was used. Polyurethane foam cylindrical container is easily deforms by impact. A large number of tests with different liquid explosives were made. It was found that the test liquid explosive to impact in appliance 1 with polyurethane foam to a large extent reflect the real mechanical sensitivity due to the small loss of impact energy on the deformation of the metal cup, as well as the best differentiation liquid explosive sensitivity due to the higher resolution method.

In Situ Detection and Imaging of Telomerase Activity in Cancer Cell Lines via Disassembly of Plasmonic Core-Satellites Nanostructured Probe.

The label-free localized surface plasmon resonance (LSPR) detection technique has been identified as a powerful means for in situ investigation of biological processes and localized chemical reactions at single particle level with high spatial and temporal resolution. Herein, a core-satellites assembled nanostructure of Au50@Au13 was designed for in situ detection and intracellular imaging of telomerase activity by combining plasmonic resonance Rayleigh scattering spectroscopy with dark-field microscope (DFM). The Au50@Au13 was fabricated by using 50 nm gold nanoparticles (Au50) as core and 13 nm gold nanoparticles (Au13) as satellites, both of them were functionalized with single chain DNA and gathered proximity through the highly specific DNA hybridization with a nicked hairpin DNA (O1) containing a telomerase substrate (TS) primer as linker. In the presence of telomerase, the telomeric repeated sequence of (TTAGGG)n extended at the 3'-end of O1 would hybridized with its complementary sequences at 5'-ends. This led the telomerase extension product of O1 be folded to form a rigid hairpin structure. As a result, the Au50@Au13 was disassembled with the releasing of O1 and Au13-S from Au50-L, which dramatically decreased the plasmon coupling effect. The remarkable LSPR spectral shift was observed accompanied by a detectable color change from orange to green with the increase of telomerase activity at single particle level with a detection limit of 1.3 × 10-13 IU. The ability of Au50@Au13 for in situ imaging intracellular telomerase activity, distinguishing cancer cells from normal cells, in situ monitoring the variation of cellular telomerase activity after treated with drugs were also demonstrated.

Self‐limited crystallization‐mediated removal of hydroxyl in glass

AbstractThe effective removal of hydroxyl groups (OH) is receiving the attention of scientists interested in developing high‐performance photonic glass. Previous approaches rely on stringent control of the various drying techniques which meet with limited success in silicate glass obtained by the sol‐gel method. Here, we present a novel in situ strategy to remove structural OH groups, based on the self‐limited nanocrystallization‐triggered local chemical reaction between OH and F− in the glassy phase. The experimental data revealed that a more than 100‐fold increase in the emission intensity can be realized. Moreover, the mechanism was discussed and it can be attributed to the effective removal of structural OH with especially strong binding energy. The results suggest an innovative avenue for the development of photonic glasses with efficient luminescence, excellent optical transmission, and improved reliability.

An Open Pit Nanofluidic Tool: Localized Chemistry Assisted by Mesoporous Thin Film Infiltration.

Nanofluidics based on nanoscopic porous structures has emerged as the next evolutionary milestone in the construction of versatile nanodevices with unprecedented applications. However, the straightforward development of nanofluidically interconnected systems is crucial for the production of practical devices. Here, we demonstrate that spontaneous infiltration into supramolecularly templated mesoporous oxide films at the edge of a sessile drop in open air can be used to connect pairs of landmarks. The liquids from the drops can then join through the nanoporous network to guide a localized chemical reaction at the nanofluid-front interface. This method, here named "open-pit" nanofluidics, allows mixing reagents from nanofluidically connected droplet reservoirs that can be used as reactors to conduct reactions and precipitation processes. From the fundamental point of view, the work contributes to unveiling subtle phenomena during spontaneous infiltration of fluids in bodies with nanoscale dimensions such as the front broadening effect and the oscillatory behavior of the infiltration-evaporation front. The approach has distinctive advantages such as easy fabrication, low cost, and facility of scaling up for future development of ultrasensitive detection, controlled nanomaterial synthesis, and novel patterning methods.

Modeliranje procesa u eksperimentalnoj komori za denitrifikaciju produkata sagorevanja biomase

In spite of the many advantages that promote biomass as a renewable energy source, its combustion emits certain pollutants, as any other fuel. Although these negative effects are less pronounced compared to the combustion of fossil fuels, they need to be identified and controlled. The nitrogen oxides (NOx) emission generated from the biomass combustion is one of the key challenges, and their controlling is necessary in order to meet the legal emission limit and to develop high-quality biomass combustion technologies. For a better understanding of the process of NOx reduction, the experimental apparatus was designed for testing of the secondary denitrification techniques at the biomass combustion. This paper provides a description of the experimental installation. Before accessing extensive experiments, it is very useful and important to carry out calculations and initial numerical simulations of processes that need to be in detail experimentally examined. The reactions of selective non-catalytic reduction of nitrogen-monoxide (NO) using ammonia (NH3) as a reagent are analyzed here first. The paper presents the dependence of the reaction rates of reduction and oxidation on the relation between NO and oxygen concentrations in the NH3-SNCR process under conditions of biomass combustion products. In the framework of the preparation of detailed experiments, a comprehensive CFD modeling of complex industrial denitrification processes has been applied, with a comprehensive process analysis including simulation of flow, mixing of components and monitoring of local chemical reactions, taking into account the effects of turbulence on global chemical kinetics.

Сканирующая зондовая микроскопия локальных химических реакций в осажденных тонких пленках

Сканирующая зондовая микроскопия локальных химических реакций в осажденных тонких пленках

Thermal auto-ignition in high-speed droplet-laden mixing layers

Numerical simulation is applied to perform fundamental studies of thermal auto-ignition in high-speed droplet-laden reacting mixing layers by means of the hybrid Eulerian-Lagrangian approach. The convective flux terms of the conservative equations of the gas-phase are discretized by an adaptive central-upwind WENO scheme and a sixth-order compact scheme is used for the viscous terms. Effects of initial droplet diameters and spray equivalence ratios are considered. The droplet dispersion associated with the entrainment of large eddies plays an important role in the thermal auto-ignition of fuel sprays. Ignition occurs at the hot boundary of the mixing layers, which is where preferential segregating droplets are evaporated to form fuel vapors for local chemical reactions. Droplets with a medium initial size discussed in this study have the shortest ignition delay time due to the combined effects of droplet dispersion and vaporization, while small droplets closely follow the rotation of the large eddy and cannot traverse into the hot boundary for evaporation to form reactive mixtures. The flame structure, which develops from the ignition kernel, is found to depend on the droplet size; large-sized droplets display a non-premixed flame, and small-sized droplets display a premixed flame. The droplet size also influences the values of the most reactive mixture fraction. A high spray equivalence ratio enhances scalar dissipation and evaporative cooling.

Designing Micro- and Nanoswimmers for Specific Applications

ConspectusSelf-propelled colloids have emerged as a new class of active matter over the past decade. These are micrometer sized colloidal objects that transduce free energy from their surroundings and convert it to directed motion. The self-propelled colloids are in many ways, the synthetic analogues of biological self-propelled units such as algae or bacteria. Although they are propelled by very different mechanisms, biological swimmers are typically powered by flagellar motion and synthetic swimmers are driven by local chemical reactions, they share a number of common features with respect to swimming behavior. They exhibit run-and-tumble like behavior, are responsive to environmental stimuli, and can even chemically interact with nearby swimmers. An understanding of self-propelled colloids could help us in understanding the complex behaviors that emerge in populations of natural microswimmers. Self-propelled colloids also offer some advantages over natural microswimmers, since the surface properties, propulsion mechanisms, and particle geometry can all be easily modified to meet specific needs.From a more practical perspective, a number of applications, ranging from environmental remediation to targeted drug delivery, have been envisioned for these systems. These applications rely on the basic functionalities of self-propelled colloids: directional motion, sensing of the local environment, and the ability to respond to external signals. Owing to the vastly different nature of each of these applications, it becomes necessary to optimize the design choices in these colloids. There has been a significant effort to develop a range of synthetic self-propelled colloids to meet the specific conditions required for different processes. Tubular self-propelled colloids, for example, are ideal for decontamination processes, owing to their bubble propulsion mechanism, which enhances mixing in systems, but are incompatible with biological systems due to the toxic propulsion fuel and the generation of oxygen bubbles. Spherical swimmers serve as model systems to understand the fundamental aspects of the propulsion mechanism, collective behavior, response to external stimuli, etc. They are also typically the choice of shape at the nanoscale due to their ease of fabrication. More recently biohybrid swimmers have also been developed which attempt to retain the advantages of synthetic colloids while deriving their propulsion from biological swimmers such as sperm and bacteria, offering the means for biocompatible swimming. In this Account, we will summarize our effort and those of other groups, in the design and development of self-propelled colloids of different structural properties and powered by different propulsion mechanisms. We will also briefly address the applications that have been proposed and, to some extent, demonstrated for these swimmer designs.