Two-step Oxidation Method Research Articles

A Novel Aggregation-Induced Emission-Based Electrochemiluminescence Aptamer Sensor Utilizing Red-Emissive Sulfur Quantum Dots for Rapid and Sensitive Malathion Detection.

Rapid, effective, and cost-effective methods for large-scale screening of pesticide residues in the environment and agricultural products are important for assessing potential environmental risks and safeguarding human health. Here, we constructed a novel aggregation-induced emission (AIE) electrochemical aptamer (Apt) sensor based on red-emissive sulfur quantum dots (SQDs), which aimed at the rapid screening and quantitative detection of malathion. SQDs were prepared using a two-step oxidation method with good electrochemiluminescence (ECL) optical properties. These SQDs were modified onto the electrode surface to serve as ECL luminophores. Subsequently, Apt was introduced and modified to form a double-helix structure with the complementary chain (cDNA). The ECL signal was reduced because the biomolecules had poor electrical conductivity and inefficient electron transfer. When the target malathion was added, the double helix structure was unraveled, the malathion Apt fell off the electrode surface, and the ECL signal was restored. The linear range of detection was 1.0 × 10-13-1.0 × 10-8 mol·L-1, and the detection limit was 0.219 fM. The successful preparation of the sensor not only develops the ECL optical properties of SQDs but also expands the application of SQDs in ECL sensing.

Rational selection of the oxygen source for atomic layer deposition Al2O3 insulators

Insulating gate dielectric is an important component of thin film transistors (TFT) and non-volatile memories, whose properties directly affect the electrical performance of the devices. In this study, the Al2O3 insulators were prepared by atomic layer deposition (ALD) using different oxygen sources and their properties were systematically studied. Based on the two-step oxidation method (H2O + O3), the Al2O3 thin films exhibited a small gate leakage current and a big breakdown field of 9 MV/cm. However, the use of the O3 increased the C-related impurities causing a large sweep hysteresis voltage of the TFTs, i.e., 8.65 V and 4.66 V for that with Al2O3 (O3) and Al2O3 (H2O + O3), respectively. Attributed to a small amount of impurities in the Al2O3 (H2O) insulators as well as the appropriate amount of Al element diffusion at the Al2O3/ZnO interface, the TFTs using Al2O3 (H2O) as insulators presented a high mobility of 36.1 cm2V−2s−1, a subthreshold swing of 0.25 V/dec and a small sweep hysteresis voltage of 0.42 V. Therefore, the properties of the ALD-Al2O3 films can be easily controlled by changing the type of the oxidizer. The Al2O3 thin films with H2O as oxidant can be used as the insulators of the TFTs, while the Al2O3 thin films based on O3 have great potential as the charge trap layer of the memories.

Enhanced Negative Bias Illumination Stability of ZnO Thin Film Transistors by Using a Two-Step Oxidation Method

In this study, we illustrate a novel way to improve the stability under negative bias illumination stress (NBIS) of ZnO thin-film transistors (TFTs) by adding O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> treatment after each cycle of growth at 100°C by atomic layer deposition. Compared with the TFTs without O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> treatment, the shift of threshold voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta {V}_{th}$ </tex-math></inline-formula> ) is reduced from −4.39 to −0.98 V under NBIS, while the mobility decreased from 31.2 to 18.4 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> . (H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O and O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> as oxidants)/ZnO (H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O as oxidant) bilayer structure, a high filed-effectmobility of 32.1 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> and an excellent stability ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta V_{\mathrm {th}} = -2.34$ </tex-math></inline-formula> V) have been obtained simultaneously. These improved performance and stabilities are attributed to the bilayer channel structures and the reduction of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_o$ </tex-math></inline-formula> in the ZnO channel layer treated by O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> .

Characterization of an α 4/7-Conotoxin LvIF from Conus lividus That Selectively Blocks α3β2 Nicotinic Acetylcholine Receptor.

Nicotinic acetylcholine receptor (nAChR), a member of pentameric ligand-gated ion channel transmembrane protein composed of five subunits, is widely distributed in the central and peripheral nervous system. The nAChRs are associated with various neurological diseases, including schizophrenia, Alzheimer’s disease, Parkinson’s disease, epilepsy and neuralgia. Receptors containing the α3 subunit are associated with analgesia, generating our interest in their role in pharmacological studies. In this study, α-conotoxin (α-CTx) LvIF was identified as a 16 amino acid peptide using a genomic DNA clone of Conus lividus (C. lividus). The mature LvIF with natural structure was synthesized by a two-step oxidation method. The blocking potency of α-CTx lvIF on nAChR was detected by a two-electrode voltage clamp. Our results showed that α-CTx LvIF was highly potent against rα3β2 and rα6/α3β2β3 nAChR subtypes, The half-maximal inhibitory concentration (IC50) values of α-CTx LvIF against rα3β2 and rα6/α3β2β3 nAChRs expressed in Xenopus oocytes were 8.9 nM and 14.4 nM, respectively. Furthermore, α-CTx LvIF exhibited no obvious inhibition on other nAChR subtypes. Meanwhile, we also conducted a competitive binding experiment between α-CTxs MII and LvIF, which showed that α-CTxs LvIF and MII bind with rα3β2 nAChR at the partial overlapping domain. These results indicate that the α-CTx LvIF has high potential as a new candidate tool for the studying of rα3β2 nAChR related neurophysiology and pharmacology.

Fabrication of CoFe2O4 Nanowire Using a Double-Pass Porous Alumina Template with a Large Range of Pore Diameters

In this work, CoFe2O4 nanowire was fabricated by using a self-designed double-pass porous alumina template. The double-pass porous alumina template was prepared by a two-step oxidation method using a mixed acid (phosphoric acid and oxalic acid) electrolyte and polymethyl methacrylate (PMMA) filler. The combustion of aluminum foil at a high voltage has been effectively resolved by using this mixed acid electrolyte. Additionally, the range of pore diameters has been obviously increased to 230–400 nm by using PMMA as the filler, which can prevent contact between the pore and solution when removing the barrier layer. Subsequently, CoFe2O4 ferrite nanowire arrays were successfully fabricated into the double-pass porous alumina template by an electrochemical deposition method, and show an anisotropic feature of magnetic properties.

Understanding the effect of functional groups on carbon nanotube towards oxygen reduction reaction

Carbon-based catalyst towards oxygen reduction reaction (ORR) has been investigated for years, one facile and typical strategy reported by a lot of literature to improve the ORR activity was the high-temperature annealing. Our group has previously studied the annealing process and confirmed the removal of oxygen-containing functional groups (OFGs) would bring benefits to ORR activity. However, the removal of which kind(s) of functional group will influence the ORR activity most has not been verified. In this work, a two-step oxidation method was applied by a weak oxidation treatment using H2O2 firstly and selectively adjusting the ratio of phenol and carbonyl/quinone. Then the ORR activity of the sample was carefully investigated by gradually removing specific OFGs with a rapid annealing process. The results suggested that the topological defects from the removal of phenol, carbonyl/quinone is the key to enhance the ORR activity of MWCNTs.

Dihydroactinidiolide, a natural product against Aβ25-35 induced toxicity in Neuro2a cells: Synthesis, in silico and in vitro studies

Synthesis of natural products has speeded up drug discovery process by minimizing the time for their purification from natural source. Several diseases like Alzheimer's disease (AD) demand exploring multi targeted drug candidates, and for the first time we report the multi AD target inhibitory potential of synthesized dihydroactinidiolide (DA). Though the activity of DA in several solvent extracts have been proved to possess free radical scavenging, anti bacterial and anti cancer activities, its neuroprotective efficacy has not been evidenced yet. Hence DA was successfully synthesized from β-ionone using facile two-step oxidation method. It showed potent acetylcholinesterase (AChE) inhibition with half maximal inhibitory concentration (IC50) 34.03 nM, which was further supported by molecular docking results showing strong H bonding with some of the active site residues such as GLY117, GLY119 and SER200 of AChE. Further it displayed DPPH and (.NO) scavenging activity with IC50 value 50 nM and metal chelating activity with IC50 >270 nM. Besides, it significantly prevented amyloid β25-35 self-aggregation and promoted its disaggregation at 270 nM. It did not show cytotoxic effect towards Neuro2a (N2a) cells up to 24 h at 50 and 270 nM while it significantly increased viability of amyloid β25-35 treated N2a cells through ROS generation at both the concentrations. Cytotoxicity profile of DA against human PBMC was quite impressive. Hemolysis studies also revealed very low hemolysis i.e. minimum 2.35 to maximum 5.61%. It also had suitable ADME properties which proved its druglikeness. The current findings demand for further in vitro and in vivo studies to develop DA as a multi target lead against AD.

Visualizing ion transport mechanisms through oxide scales grown on mixed nickel- and cobalt-base model alloys at 900 °C using FIB-SIMS techniques

A set of five model superalloys with a γ′-precipitate strengthened structure and a nominal composition of Ni-xCo-9Al-8 W-8Cr were oxidized at 900 °C by the two-step oxidation method in normal oxygen and tracer oxygen-18 enriched gas atmospheres. Analysis at a nanoscale resolution by gallium focused ion beam sputtering and quadrupole-based secondary ion mass spectrometry of the surface oxide cross-sections provided evidence of both anion and cation motion during the second oxygen-18 oxidation where parabolic oxidation rate conditions can be assumed. These experiments provide new insights into the mass transport vectors for modeling the important oxidation mechanisms at extreme service conditions in mixed cobalt- and nickel-base alloys.

Effect of oxidation level on the inclusion capacity and solution stability of oxidized amylose in aqueous solution

The oxidized amyloses with high oxidation level and carboxyl content were successfully prepared through a two-step oxidation method using hydrogen peroxide as the oxidant and copper sulfate as the catalyst. The results showed that oxidation would prevent the oxidized product to crystallize and induce depolymerization of amylose molecules. Accordingly, the helices and inclusion capacity of oxidized amylose molecules were reduced. However, the solubility of oxidized amyloses in water was highly improved due to the introduced carboxyl groups. The solution stability of oxidized amylose-guest inclusion complexes in aqueous solution was efficiently improved to a large extent. The result suggested that the two-step oxidation method was an efficient way to highly broaden the applications of amylose-guest inclusion complexes in water environment.

Investigation of micro-arc oxidation coating growth patterns of aluminum alloy by two-step oxidation method

The micro-arc oxidation (MAO) process of 2A70 aluminum alloy in different electrolytes containing silicate or phosphate by two-step oxidation was investigated. The growth rate, surface roughness and element distributions of the micro-arc oxidation coatings were characterized. The results show that the coating growth patterns are different in Si and P electrolytes although they both grow inward. The discharge channels formed in Si-electrolyte and P-electrolyte are trumpet-shaped and dumbbell-shaped, respectively. The trumpet-shaped channel is conducive to gather heat and extend the reaction area inward, which leads to a layer growth pattern in P-electrolyte. The dumbbell-shaped channel limits the reactive area but introduces more electrolytes during the cooling process, which results in an island growth pattern in Si-electrolyte. Therefore, a newly formed P-rich layer can be observed between substrate and initially formed Si-rich layer after the second-step oxidation in P-electrolyte, but only localized Si-rich areas could be found when the second-step oxidation was performed in Si-electrolyte.

Preparation of Graphene Oxide Based on Expanded Graphite

Graphene oxide with high degree of oxidation and peelable has been prepared by two-step oxidation method used large flake graphite. The expanded graphite was prepared firstly and then prepared graphene oxide via further oxidation. The influence of oxidation time, oxidant dosage and high temperature reaction on the structure and degree of oxidation were studied. The morphology and structure of graphene oxide were characterized by X-ray diffraction, fourier transform infrared spectra, scanning electron microscope and transmission electron microscope. It was found that high degree of oxidation and large specific surface area graphene oxide was prepared at the ratio of sulfuric acid and expanded graphite was 75 mL : 1 g, the ratio of potassium permanganate and expanded graphite was 4 g : 1 g and the oxidation time at 35 °C was 24 h. This technology is simple without high-temperature reaction process, and solved the problem of low oxidation efficiency when used the large flake graphite as raw materials.

Investigation of MAO coating growth mechanism on aluminum alloy by two-step oxidation method

A two-step oxidation method was explored to study the growth mechanism of micro-arc oxidation (MAO) coating. 2A70 aluminum alloy specimens were oxidized in silicious electrolyte in the first step; then the specimens with the as-oxidized MAO coating were transferred into the phosphatic electrolyte for further oxidation in the second step. Distributions of elements in MAO coatings were investigated by energy dispersion X-ray spectrometry (EDS). The results showed that P and Si were layered in the MAO coating. The newly formed coating, P-rich layer, formed in the second step was located under the layer formed in the first step, which increased the coating's thickness. Discharge channels can be found in MAO coating by the distribution of P, which connect substrate and the outside of coating. The inner newly formed P-rich layer increased its thickness as the oxidation time increased. These results give some direct experimental evidences for the inward growth mechanism of MAO coatings and indicate that discharge channels are the main ways to form the new coating which lead to the inward growth of MAO coating.

Study of Biosensors Based on Fe Nanowires

AbstractAnodic aluminum oxide (AAO) template was prepared by using anodizing voltage step-decreasing method after two-step oxide method. Based on AAO template, Fe nanowires arrays were electrochemically deposited. Fe nanowires were coated by chitosan. Fe nanowires/chitosan was synthesized by glutaraldehyde as cross-linking reagent. By crosslinking α-human chorionic gonadotropin (α-HCG), biological probes with Fe nanowires/chitosan/antibody were prepared. An easy operating, easy taking and rapid reacting magnetic detecting system was developed after optimizing the geometry parameters of detect coil. Different concentration samples with 1, 2 and 5 g(Fe)/L were detected. The results show that the sensitivity of system is 0.2 g(Fe)/L and can be improve better.

Effects of applied magnetic field on microstructure and magnetic properties of template-based Co nanowire arrays

Arrays of Co nanowires were fabricated by ac electrochemical deposition of metal into high order anodic alumina templates prepared through two-step oxidation method. The effects of applied magnetic field and the pH value of the electrolyte on growth of nanowires were investigated. Arrays of Co nanowires of hcp structure were deposited in the electrolyte whose pH values are 6.0 and 6.5 without magnetic field, then 0.3 T magnetic field was applied along the long axis of nanowires. The experimental results show that external magnetic field and adjustment of pH value of the electrolyte impel the easy magnetization axis of the hcp Co grain to grow along length direction of nanowires. The Co nanowire arrays show higher perpendicular anisotropy, larger coercivity and high M/Ms because the superposition of the crystal anisotropy of hcp Co grains and shape anisotropy of nanowire along length direction.

Performance of Co/Al2O3/NiFe magnetic tunnel junctions prepared by a two-step rf plasma oxidation method

A two-step rf plasma oxidation technique of an insulating layer has been performed to enhance electrical and structural properties of magnetic tunnel junction (MTJ) devices. Comparison was made by analyzing properties of the MTJ oxidized by conventional rf and two-step rf plasma oxidation methods. Experimentally observed results give improved surface imaging and sufficient oxygen contents of the insulating layer under the two-step oxidation method. In addition, electrical breakdown voltage and magnetoresistance of the MTJ were increased from 0.7 to 1.8 V and from 4.5% to 6.8%, respectively, correlated with improved structural information.

Influence of the metalloids on the properties of cast iron

A two-step oxidation method was explored to study the growth mechanism of micro-arc oxidation (MAO) coating. 2A70 aluminum alloy specimens were oxidized in silicious electrolyte in the first step; then the specimens with the as-oxidized MAO coating were transferred into the phosphatic electrolyte for further oxidation in the second step. Distributions of elements in MAO coatings were investigated by energy dispersion X-ray spectrometry (EDS). The results showed that P and Si were layered in the MAO coating. The newly formed coating, P-rich layer, formed in the second step was located under the layer formed in the first step, which increased the coating's thickness. Discharge channels can be found in MAO coating by the distribution of P, which connect substrate and the outside of coating. The inner newly formed P-rich layer increased its thickness as the oxidation time increased. These results give some direct experimental evidences for the inward growth mechanism of MAO coatings and indicate that discharge channels are the main ways to form the new coating which lead to the inward growth of MAO coating.