Chemical Reaction Technique Research Articles

Optical, structural and photoluminescence properties of PbS nanoparticle synthesized by plasma-induced chemical reaction technique in aqueous solution

Optical, structural and photoluminescence properties of PbS nanoparticle synthesized by plasma-induced chemical reaction technique in aqueous solution

Chiral Herbicide 2,4-D Ethylhexyl Ester: Absolute Configuration, Stereoselective Herbicidal Activity, Crop Safety, and Metabolic Behavior on Maize and Flixweed.

This study represents the initial examination of the herbicidal efficacy, crop safety, and degradation patterns of 2,4-D ethylhexyl ester (2,4-D EHE) at the enantiomeric level. Baseline separation of 2,4-D EHE enantiomers was achieved using a superchiral R-AD column, with their absolute configurations determined through chemical reaction techniques. Evaluation of weed control efficacy against sensitive species such as sun spurge and flixweed demonstrated significantly higher inhibition rates for S-2,4-D EHE compared to R-2,4-D EHE. Conversely, no stereoselectivity was observed in the fresh-weight inhibition rates of both enantiomers on crops or nonsensitive weeds. A sensitive HPLC-MS/MS method was developed to simultaneously detect two enantiomers and the metabolite 2,4-D in plants. Investigation into degradation kinetics revealed no substantial difference in the half-lives of R- and S-2,4-D EHE in maize and flixweed. Notably, the metabolite 2,4-D exhibited prolonged persistence at elevated levels on flixweed, while it degraded rapidly on maize.

Substantial improvement of thermal conductivity and mechanical properties of polymer composites by incorporation of boron nitride nanosheets and modulation of thermal curing reaction

AbstractThermal conductive polymer‐based composites synchronously with stable dielectric and excellent mechanical properties are urgently needed for high‐temperature‐resistant electronic devices. Here, a significant improvement in the thermal conductivity (TC), thermal stability, dielectric, and mechanical performance was simultaneously achieved in the polyarylene ether nitrile (PEN)/divinyl siloxane‐bisbenzocyclobutene (BCB) matrix through the incorporation of boron nitride nanosheets (BNNS) combined together with the post‐solid phase chemical reaction technique. The significant increase in the effective filler‐filler and filler‐crystal contacts in the composites was the main reason for the improvement in TC and dielectric constant. Besides, glass transition temperature (Tg) and mechanicals were enhanced in the presence of cross‐linked networks. By synchronously adding 15 vol% BNNS, the TC of composites after treatment reached up to 5.582 W/m.K, enhanced by 4.4 times higher than untreated. The dielectric constant was down to 2.93 at 1 MHz and the loss remained at a relatively low level. Meanwhile, the composite showed significantly enhanced thermal stability, mechanicals, and hydrophobicity (Tg = 336°C, T5% = 529°C, tensile strength and modulus was 94.5 MPa and 5.3 GPa, respectively, the contact angle was 101.76°). Thus, it promotes an effective strategy for fabricating a high‐performance‐polymer composite, which has the potential used in electronic materials.Highlights Crystallization‐crosslinking strategy optimizes overall performance. Crystals fill gaps between BNNS layers and connect thermal conductive pathway. Crosslinked networks limit molecular chain motion to reduce phonon scattering. The highest TC of the PEN/BCB/BNNS composite is up to 7.451 W/m.K. Thermal property shows significant improvement after crosslinking especially Tg.

Nanoengineered design of inside-heating hot nanoreactor surrounded by coolenvironment for selective hydrogenations.

Catalysts with designable intelligent nanostructure may potentially drive the changes of chemical reaction techniques. Herein, we designed a multi-function integrating nanocatalyst, Pt-containing magnetic yolk-shell carbonaceous structure, having catalysis function, microenvironment heating, thermalinsulation and elevated pressure into a whole, which induces selective hydrogenation within heating-constrained nanoreactors surrounded by ambient environment.As a demonstration, carbonyl of α, β-unsaturated aldehydes/ketones are selectively hydrogenated to unsaturated alcohols with a >98% selectivity at a nearly complete conversion under mild conditions of 40°C and 3bar instead of harsh requirements of 120°C and 30bar. We creatively demonstrate that the locally increased temperature and endogenous pressure (estimated as ∼120°C, 9.7bar) in the nano-sized space greatly facilitates the reaction kinetics under an alternating magnetic field. The outward-diffused products to the "cool environment" retain thermodynamically stable, avoiding the over-hydrogenation often occurs under constantly heated conditions of 120°C. Regulation of the electronic state of Pt by sulfur doping of carbon allows selective chemical adsorption of the -C = O group and consequently leads to selective hydrogenation. It is expected that such a multi-function integrated catalyst provides an ideal platform for precisely operating a variety of organic liquid-phase transformations under mild reaction conditions. This article is protected by copyright. All rights reserved.

Optimization of Assay Conditions for t-RNA by Experimental Design

A design of an experiment is generally to fictionalize an execution of an experimental process and the term of experimental design strategy usually refers to a two-stage modeling. The first of all named as working strategy is the determination of the experimental execution model and the last one is that a mathematical model for response surface function to define the relationship between the experimental factors. In this work, it was selected optimization of assay conditions for t-RNA using Central Composite Design, the influence of three factors, namely pH, enzyme concentration and amino acid concentration as an experimental design application, and improved an experiment strategy in order to optimize the effective operation factors on this chemical reaction and mathematical solution techniques of the response surface function. As examining of the coefficients of the response surface equation and its graphics, we can say that the most effective parameter on the esterification process is enzyme concentration alone and together with pH.

Construction of the novel polyimide/Bi2MoO6-OVs p-n type heterojunction aerogel photocatalysts to enhance the photodegradation on organic pollutants driven by the internal electric field

To photodegrade the organic pollution, the Polyimide/Bi 2 MoO 6 -OVs p-n type aerogel heterojunction photocatalysts with rich pore structure and large surface area were synthesized by chemical amide reaction and supercritical ethanol drying technique successfully. The introduction of oxygen vacancies can be beneficial to the activation of molecular oxygen, which can inhibit photo-generated charge recombination to improve photocatalytic efficiency. Furthermore, the formation of Mo-N chemical bond between the coordination of N atoms of heptazine units and Mo atoms of Bi 2 MoO 6 is confirmed by structure analysis. And the ability of the heterojunction photocatalyst to degrade RhB is improved significantly, which is due to photogenerated electron-hole pairs can be quickly separated under the internal electric field within the space charge region under visible light. Simultaneously, the SEM images show the flocculent PI polymer is coated on the surface of flower-like Bi 2 MoO 6 -OVs microsphere, which can expand the light absorption range and enlarge the surface area. This work provides an innovative perspective to construct polymer aerogel with inorganic materials heterojunction photocatalyst with superior photocatalytic activity. • The introduction of oxygen vacancies to Bi 2 MoO 6 is beneficial to the activation of molecular oxygen. • The flocculent PI polymer coated on the surface of flower-like Bi 2 MoO 6 -OVs microsphere is prepared. • The Mo-N chemical bond formation, rich pore structure and large surface area improve photodegradation efficiency.

Development of core-shell nanomaterials for energy storage devices using chemical solution method

Professor Tomoya Ohno and Associate Professor Shigeto Hirai, Kitami Institute of Technology, Kitami, Japan, are collaborating on research on the composition and coating of catalysts used in rechargeable metal-air batteries. Ohno specialises in surface coatings and powder technology and Hirai is an expert in electro- and solid-state chemistry and so these combined specialisms lend themselves well to the work. The researchers are developing long-life, high-performance bi-functional catalyst particles that can be mounted on rechargeable metal-air batteries, and are also proposing positive particles coated with a solid electrolyte for use in all-solid state lithium-ion batteries. Due to the high density associated with the design of the metal-air battery, it has the potential to store a lot more energy than conventional batteries. This means that metal-air batteries could prove transformative for industry, with the potential to be used in electric cars, national grid energy storage and other devices that require regular charging. However, the technology of the metal-air battery is still in progress and key concerns are the reliability of the cathode as well as the harsh effects of charging at high cathodic potentials. Ohno and Hirai are working to overcome these challenges by using chemical reaction and powder engineering techniques to add thin films of protective materials for the potential catalysts that could help stabilise the cathode. So far, the researchers have found that the protective layer on the bi-functional catalyst particles that were mounted on the metal-air secondary battery significantly improved the stability. They also found that the effect varies depending on the structure of the coating layer.

Development and performance analysis of novel in situ Cu–Ni/Al2O3 nanocomposites

Cu–Ni/Al2O3 nanocomposite powders were manufactured using an in situ chemical reaction technique. This technique provides improved wettability and adhesion between the matrix and reinforcement phases. Aluminum nitrate, copper nitrate and nickel nitrate were used as start materials for the production of the composites. The powders were sintered in a hydrogen environment at 900 °C for 2 h after being cold pressed at 700 MPa. To determine the effect of Al2O3 on electrical and thermal conductivities and thermal expansion behaviors, the Cu–Ni matrix was supplemented with 3, 5, and 8 wt% Al2O3. The findings revealed that Al2O3 nanoparticles (20 nm) were dispersed uniformly throughout the copper-nickel matrix. Microhardness was improved from 53.3 HV for Cu–Ni matrix to 92.7 HV for Cu–Ni/8%Al2O3 nanocomposites. The electrical and thermal conductivities and thermal expansion coefficient were reduced as the amount of Al2O3 in the Cu–Ni matrix increased. The electrical conductivity was reduced by 38.7% by addition 5% Al2O3 nanoparticles to Cu–Ni matrix. The high interfacial bonding between Cu–Ni and Al2O3 nanoparticles was the main reason of the hardness improvement and maintaining relatively good electrical and thermal properties.

Enhanced visible light-driven photocatalytic degradation supported by Au-TiO2 coral-needle nanoparticles

The unique of coral-needle nanoparticles (CNPs) were prepared via a liquid chemical reaction and mediation technique to develop the eco-synthesis of Au-TiO2. Based on this study, Au-TiO2 has a high-performance compared with TiO2 for the degradation of methyl orange (MO) organic compound under visible light irradiation which evidenced by the optical properties of each product. Au-TiO2 CNPs has high-response of absorption activity in the visible light area in a range of 555–600 nm, whereas the activity of TiO2 remains a low-level absorption. Also, the successful decoration of Au exhibits that the Au-TiO2 CNPs has gives the sparkling morphologically effect and dramatically for plasmonic photocatalytic with the CNPs structure. We also testing photocatalytic activity that the increase of repetition the Au coated onto TiO2 is rationalized for high-sensitivity degradation of MO organic compound under visible light irradiation with % degradation of ∼36 % for 120 min. This study can provide useful new information about the design for the Au-TiO2 plasmonic photocatalysts for solar-to-chemical transformations.

Magnetoelectric and tunable DC electrical properties of PbZr0.58Ti0.42O3 – Ni0.5Co0.5Fe2O4 multiferroic nanocomposites

The potential properties of the magnetoelectric materials; such as magneto-impedance, magneto-dielectric, irreversibility of current with voltage and magnetoelectric coefficient provide a large research interest in the last few years. We have fabricated PbZr0.58Ti0.42O3 – Ni0.5Co0.5Fe2O4 nanocomposite having a 1:1 wt ratio through the low temperature pyrophoric chemical reaction and solid state reaction techniques. Structural characterization has been carried out through X-ray diffraction technique. We have investigated the magnetically tunable memory effect. The irreversibility in electrical property may be due to the interfacial polarization of the sample. The magnetic field provides a scattering of charge carriers resulting increment of current at a constant applied electric field. Furthermore, a large interfacial polarization of the sample attributes the current in the short circuit condition. Moreover, a large value of magnetoresistance has been found for the nanocomposite and it is ∼54% at a magnetic field of 3 kOe at room temperature.

Influence of annealing temperature of α- Fe2O3 nanoparticles on Structure and Optical Properties.

Abstract This work has been focused on the synthesis of the raw materials iron oxide nanoparticles; hematite (α-Fe2O3) from Iron (II) chloride tetra hydrate (FeCl2-4H2O) and iron (III) chloride hexahydrate (FeCl3-6H2O) using Solid State Chemical Reaction technique. Nanostructure powders were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), and UV-visible spectroscopy. XRD confirmed the formation of crystalline α-Fe2O3 nanostructured and its average crystallite size increased from ~ 12 to 28 nm with increasing annealing temperature from 200˚C up to 800℃ while SEM confirmed the morphology and the purity of the sample was evaluated from the energy dispersive spectrum (EDS). Moreover, strain decreased with increasing annealing temperature. UV-visible characterization indicated the existence of both direct and indirect band gap in the samples. All the annealed samples showed the direct band gap at ~ 2.21 eV. However, the indirect band gap increased from 1.6 to 1.94 eV when the annealing temperature increased from 200 up to 700℃ and remained almost the same for sample annealed at 800℃. The observed values of optical band gaps were in close agreement with the reported values. Our results indicated that the annealing would give rise to a good crystalline α-Fe2O3 nanoparticles with reduced strain

Influence of annealing temperature of α- Fe2O3 nanoparticles on Structure and Optical Properties.

This work has been focused on the synthesis of the raw materials iron oxide nanoparticles; hematite (α -Fe2O3) from Iron (II) chloride tetra hydrate (FeCl2-4H2O) and iron (III) chloride hexahydrate (FeCl3-6H2O) using Solid State Chemical Reaction technique. Nanostructure powders were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), and UV-visible spectroscopy. XRD confirmed the formation of crystalline α -Fe2O3 nanostructured andits average crystallite size increased from ~ 12 to 28 nm with increasing annealing temperature from 200 up to 80℃ while SEM confirmed the morphology and the purity of the sample was evaluated from the energy dispersive spectrum (EDS). Moreover, strain decreased with increasing annealing temperature. UV-visible characterization indicated the existence of both direct and indirect band gap in the samples. All The annealed samples showed the direct band gap at ~ 2.21 eV. However, the indirect band gap increased from 1.6 to 1.94 eV when the annealing temperature increased from 200 up to 700℃ and remained almost the same for sample annealed at 800℃. The observed values of optical band gaps were in close agreement with the reported values. Our results indicated that the annealing would give rise to a good crystalline α -Fe2O3 nanoparticles with reduced strain.

Synthesis of ultra-long aluminum nitride nanowires with excellent photoluminescent property by aluminum chloride assisted chemical vapor reaction technique

Abstract Aluminum nitride (AlN) nanowires were performed on iron substrate using aluminum powders as material precursor by anhydrous aluminum chloride (AlCl3) assisted chemical vapor reaction (CVR) method. Yield production of AlN nanowires was significantly enhanced with AlCl3 addition into Al powders due to generating of intermediate gaseous AlCl, which further reacted with N2 to form AlN nanowires. With AlCl3 addition, a thin Fe film on Fe substrate can be transformed into Fe nanoparticles, which served as a catalyst in promoting the formation of AlN nanowires. The length of single-crystalline AlN nanowires was up to hundreds of microns. The formation and growth of AlN nanowires were most likely controlled by vapor–liquid–solid growth mechanism and AlCl3 assisted chemical vapor transport mechanism. The luminescence bands in the range of violet-green luminescence suggest its promising application in light-emitting devices.

Structural, morphological, and Z-scan technique for a temperature-controllable chemical reaction synthesis of zinc sulfide nanoparticles

Zinc sulfide (ZnS) nanoparticles were fabricated using a new route chemical reaction technique. During growth, the temperature of the annealing was controlled between 200 °C and 500 °C. The structural, morphological and optical properties of as-synthesized nanoparticles were examined using scanning electron microscopy (SEM), X-ray diffraction and ultraviolet–visible (UV–Vis) absorption. The X-ray diffraction pattern exhibits a wurtzite crystal structure at room temperature. The thermal nonlinear refractive indexes of the ZnSNP films are calculated based on diffraction ring patterns and the Z-scan technique. The optical limiting properties were also studied. The efficiency of the optical limiting was found to depend on the temperature of the sample. The mechanism of optical limiting is found to be predominantly of a thermal origin. The evaluation of the figure of merit (W > 1) shows that the ZnSNP films are sufficient for application in all-optical switching technology. These results show that the ZnSNPs have potential application in nonlinear optics.

Effect of heat preservation time on the micro morphology and field emission properties of La-doped SiC nanowires

Lanthanum doped SiC nanowires (La-doped SiC NWs) were prepared using the chemical vapor reaction technique at different heat preservation times.

Synthesis and growth mechanism of aluminum nitride nanowires via a chloride-assisted chemical vapor reaction method

We report a large scaled fabrication of AlN nanowires via a chloride-assisted chemical vapor reaction technique at 1100 °C in flowing N2 atmosphere using aluminum powders as starting materials. The as-obtained hexagonal AlN nanowires had the length of hundreds of microns and diameter of 20–100 nm, and indicated a single crystalline characteristic. The yield production was significantly increased with ammonium chloride and aluminum chloride addition because of the formation of intermediate gaseous AlCl and HCl. The addition of ammonium chloride and aluminum chloride also promoted the formation of ferric chloride, which served as the catalyst and further facilitated the growth of AlN nanowires. The vapor–liquid–solid and vapor–solid growth mechanism are proposed and discussed in details.

Magnetically tunable alternating current electrical properties of (100-x)% La0.7Sr0.3MnO3 - x% paraffin wax(0.05[formula omitted]x[formula omitted]1.0) hybrid nanocomposites

We have investigated magnetically tunable AC electrical properties of (100-x)% La0.7Sr0.3MnO3 (LSMO) - x% Paraffin wax (weight%, x = 0.05, 0.1, 0.2 and 1.0) hybrid nanocomposites prepared through a chemical pyrophoric reaction technique at room temperature. The electric field applied across the composites is at perpendicular direction with applied magnetic field(H). The impedance(Z) of the samples is found to decrease with increase in H at low frequency regime indicating the presence of field dependent electrical relaxation process in the system. The decrement of Z with applied H is supposed to be due to gradual depinning of magnetic domain walls from the grain boundary pinning centres thereby enhancing the spin dependent transport in the composites. Nyquist plots have been fitted using parallel combinations of both grain and grain boundaries resistance and capacitance. The grain (grain boundary) resonance frequency fRG(fRGB) is observed to shift towards lower (higher) frequency region with H. This opposite variation of fRG and fRGB with H reveals evidence of two competing factors namely H induced enhancement of inductive part and H enhanced spin dependent transport causing fast relaxation processes in the system. Both fRG and fRGB are found to increase with Paraffin wax concentration upto 0.1% and 0.2% respectively. But both of them show a decreasing trend with further increase of Paraffin wax concentration to 1.0%. We have attributed this anomalous variation to multiple factors like increase in thickness of spin polarized Paraffin wax tunnel barrier with Paraffin wax and enhancement of Mn2O3 impurity phase in nanocomposites with 0.1% and 0.2% Paraffin wax concentration. Systematic decrease of RG observed with H is attributed to suppression of spin fluctuation by magnetic field within grains whereas observed increase in CG with H is expected due to some magnetocapacitive coupling in the grain of the samples. Systematic decrease of RGB observed with H is attributed to depinning of GB domain walls with H, from GB pinning wells whereas observed increase in CGB with H is expected due to presence of inhomogeneous Paraffin wax interface in the samples.

The effects of silica addition on the structural, electrical and mechanical characteristics of MgAl2O4 spinel ceramic phase

The ceramic compound Mg1-xSixAl2O4 (x= 0, 0.1, 0.2, 0.3, 0.4) was prepared from nano powder of Al2O3 and MgO doped with Nano powder of SiO2 at different molar ratios. The specimens were prepared by standard chemical solid reaction technique and sintered at 1450 oC. Structure of the specimens was analyzed by using X-ray diffraction (XRD). The X-ray patterns of the specimens showed the formation of pure simple cubic spinel structure MgAl2O4 phase with space group of ̅ . The average grain size and surface topology were studied by atomic force microscopy. The results showed that the average grain size was about 73-90 nm. The DC electrical properties of the specimen were measured. The apparent density was found to increase and the porosity and water absorption were found to decrease with increase of Si addition. Mechanical properties were characterized by Vicker’s micro hardness and Brazilian fracture test to measure the fracture toughness of the samples. The micro hardness decreased with Si addition increase. Fracture toughness increased with the increase in Si addition.

Evolução das propriedades efetivas do concreto sob ação da reação álcali-sílica

The present work develops a model of computer simulation of the actual properties of concrete under the action of alkali-silica reaction. Obtains a computational representation from the analysis of the chemical reaction and homogenenization techniques. Alkali-Silica reaction forms a gel that changes the effective properties of concrete and can lead to damage to structures, especially of hydroelectric dams. The model consists of three phases, generation of representative element of concrete, gel formation and dissemination by alkali-silica reaction and homogeneization of the final material. The first stage is the development of representative concrete element that is simulated from the granulometric curve and uses a computacional collision detection algorithm to ellipses. To model the behavior of chemical evolution, it uses a system based on equations of chemical kinetics, known as Guldberg - Waage Law and uses a gel diffusion model developed to mesh of representative element of concrete. To model the variation of the effective properties, it uses homogenization schemes (Reuss method, Voigt Method, Self-Consistent method and Mori-Tanaka method) to provide, thus, elasticity coefficientes of the composite material. The combination of the models allowed to predict the evolution and damage to the material over time and analyze the influence of the volume fraction of agregates in the lifetime of concrete.

Tunable Synthesis of SiC/SiO₂ Heterojunctions via Temperature Modulation.

A large-scale production of necklace-like SiC/SiO2 heterojunctions was obtained by a molten salt-mediated chemical vapor reaction technique without a metallic catalyst or flowing gas. The effect of the firing temperature on the evolution of the phase composition, microstructure, and morphology of the SiC/SiO2 heterojunctions was studied. The necklace-like SiC/SiO2 nanochains, several centimeters in length, were composed of SiC/SiO2 core-shell chains and amorphous SiO2 beans. The morphologies of the as-prepared products could be tuned by adjusting the firing temperature. In fact, the diameter of the SiO2 beans decreased, whereas the diameter of the SiC fibers and the thickness of the SiO2 shell increased as the temperature increased. The growth mechanism of the necklace-like structure was controlled by the vapor-solid growth procedure and the modulation procedure via a molten salt-mediated chemical vapor reaction process.