Conventional Two-step Synthesis Research Articles

Engineering Stable and Affordable Meta-Aluminate Intercalated Mafic Hydrotalcite for Superior Bromate Remediation

In this study, one type of layered double hydroxide (LDH), the meta-aluminate intercalated mafic-modified hydrotalcite (LDH-2), was engineered through an unprecedentedly facile, affordable one-step procedure. In the interest of meticulous perception regarding our superior strategy, the conventional two-step synthesis method—the fabrication of optimal mafic-modified hydrotalcite through the coprecipitation and roasting process followed by a second aging step (LDH-1)—was also synthesized. After scrutinization of as-derived nanostructures, the adsorption capacity of both structures for bromate remediation was elaborated. When the effect of experimental variation was optimized and the impact of various ions was investigated, the more astounding performance of LDH-2 (0.97 mg/g) was detected when compared with conventional LDH-1 (0.90 mg/g). Therefore, the novel approach for the engineering of meta-aluminate intercalated mafic hydrotalcite not only introduces facile and practical procedures, but also furnishes a much more efficient adsorption system. In the matter of structure durability, the as-synthesized LDH-2 presented exceptional resistance, maintaining activity after five consecutive cycling runs. This investigation sheds light on the facile and affordable synthesis of the LDH construction.

A one-pot synthesis of high-density biofuels through bifunctional mesoporous zeolite-encapsulated Pd catalysts

Developing a powerful bifunctional catalyst for tandem reactions is essential to the future carbon neutrality by reducing the energy consumption in chemical industries. Herein, mesoporous zeolite-encapsulated palladium (Pd) nanoparticles (Pd@meso-ZSM-5) synthesized via emulsification-demulsification followed by a dry-gel transformation method were demonstrated to have a remarkable catalytic performance for a one-pot multiple tandem reaction of cyclic ketones (cyclopentanone, cyclohexanone) to bicyclic alkanes (bicyclopentane, bicyclohexane). Compared with supported catalysts (Pd/meso-ZSM-5) and microporous zeolite-encapsulated catalysts (Pd@ZSM-5) with a primary product of monocyclic alkane (cyclopentane, cyclohexane), Pd@meso-ZSM-5 shows much higher catalytic efficiency for the bicyclic alkanes synthesis, which was previously unattainable in the conventional two-step synthesis route. Controlled experiments and detailed characterizations show that mesoporosity provides sufficient space for the generation and diffusion of large molecular intermediates, and the intimate acid-Pd interface promotes the conversion of intermediates. This work proposes a design strategy for a mesoporous zeolite-encapsulated metal catalyst, which efficiently provides cooperative acid-hydrogenation catalysis.

Biomass-derived carbons physically activated in one or two steps for CH4/CO2 separation

The present study aims at evaluating the suitability of producing activated carbons (ACs) derived from wheat straw by a one-step synthesis approach, as an alternative to more conventional two steps production processes (i.e., pyrolysis and subsequent activation). The performance of the produced ACs, in one or two steps, as sustainable and selective CO2 adsorbents for CH4/CO2 separation is compared. In addition, the influence of pyrolysis conditions on the properties of the resulting two-step ACs is carefully analyzed. We show that the biochar-based precursors of ACs presenting the best textural properties were obtained under mild conditions of maximum temperature and absolute pressure during pyrolysis. The one-step ACs were fully comparable —in terms of textural properties as well as CO2 uptake and selectivity— to those produced by the more conventional two-step synthesis process. In addition, results obtained from breakthrough curve simulations highlight that the best AC in terms of CH4 recovery under dynamic conditions was produced by a one-step activation. Therefore, the one-step process appears to be as an attractive route for the production of engineered carbon materials, which can lead to significant cost savings in large-scale production systems.

Energy, exergy and corrosion analysis of direct absorption solar collector employed with ultra-high stable carbon quantum dot nanofluid

Nanofluid offers remarkable thermal and optical properties favourable for direct solar absorption. The nanofluids prepared by the conventional two-step synthesis method have low colloidal stability, while that synthesized through the one-step method is costly. Hence the nanofluid synthesized using an economical one-step method has great significance. In the present study, a highly stable C-dot/water nanofluid was synthesized using an economical one-pot synthesis method. The optical characterisation, corrosion analysis and cost estimation of the nanofluid were conducted. The influence of C-dot/water nanofluid on the performance of direct absorption solar collector was analyzed. The direct absorption parabolic solar collector employed with C-dot/water nanofluid yielded a maximum thermal efficiency of 73.41% at Reynolds number of 2952, while that for water was 15.79%. Thermodynamic analysis of the system and cost estimation of the nanofluid was performed to establish its commercial suitability in various solar thermal devices. The maximum exergy destruction was found to be 924.3 W and was more or less constant at all flow rates. The main highlight of the new C-dot/water nanofluid is its significantly high colloidal stability and was found to be stable for more than six months. The corrosion rate of the new C-dot/water nanofluid was obtained as 0.094 mm/year, while that for the base fluid was 0.372 mm/year. With superior optical performance, corrosion resistance, and low production cost, the C-dot nanofluid has the potential to be a prospective working fluid in various direct absorption solar thermal systems.

Conventional synthesis of layer-like zeolites with faujasite (FAU) structure and their pathway of crystallization

Abstract The current know-how in the classical additive-free synthesis of layer-like faujasites is limited to a time for crystallization that is times longer than the few hours (5–8 h) necessary for the preparation of their octahedron-like counterparts. Furthermore, it is widely believed that the temperature for crystallization of layered-like assembles of FAU-type of zeolites should be lower (20–50%) than the one in conventional two-step synthesis of classical faujasites. In contrast, I present direct additive-free synthesis of nanolayer (0.15 ± 0.03 μm) intergrowths (1.3 ± 0.1 μm) of FAU-type of zeolites at the conventional 90 °C for the exceptionally short time of 4 h. Additionally, this work shows that in gel the layer-like structures are formed by oriented aggregation of nanoparticles that later crystallize to faujasite.

Template-free and fast one-step synthesis from enzymatic hydrolysis lignin to hierarchical porous carbon for CO2 capture

Abstract Conventional two-step synthesis (carbonization followed by activation) of porous carbon required long heating duration at high temperature, leading to high energy consumption. To obtain carbon with hierarchical porous structure, a templating method was typically used. In view of the above drawbacks, this study provided a template-free and fast one-step synthesis from enzymatic hydrolysis lignin to hierarchical porous carbon by microwave heating in humidified nitrogen. It was shown that moisture in humidified nitrogen acts as a physical activating agent combined with KOH to achieve a hierarchical porous structure consisting of abundant micropores and considerable meso-/macropores. The results show high dependency of porosity, amorphous structure, and surface chemical properties of porous carbon samples on microwave heating duration. In particular, a porous carbon with a prominent hierarchical pore structure (65.3% mesopores), high specific surface area (2870 m2/g) and total pore volume (2.02 cm3/g) was synthesized using a microwave heating duration of 30 min. Under this condition, a high content of O-C=O group (10.0%) was also achieved, implying the presence of a hydrophilic carbon surface. These properties of prepared porous carbon synergistically enhance its CO2 uptake (up to 1.31 mmol/g measured by thermogravimetric analyzer at 30 °C). This time-saving and energy efficient synthesis of hierarchical porous carbon could be an effective approach to utilize industrial lignin waste to reduce greenhouse gas emission.

Electrogenerated chemiluminescence from newly synthesized α-diimine-ligated heteroleptic iridium(III) complexes

A series of α-diimine ligands including alkyl-, bromo-, silyl- or silylethynyl-substituted 2,2′-bipyridines (bpy) for auxiliary neutral ligands on iridium(III) complexes were prepared. Using those ligands, α-diimine-ligated heteroleptic iridium(III) complexes with 2,4-difluorophenylpyridine as the primary cyclometalating ligand were synthesized by a conventional two-step synthesis followed by the anion exchange reaction using NH4PF6. The physical features such as spectroscopic, electrochemical and electrogenerated chemiluminescence (ECL) properties for the newly prepared complexes were characterized and compared to that of well-known tris(2,2′-bipyridine)rutheniun(II), [Ru(bpy)3](PF6)2, and previously reported (2,2′-bipyridine)bis[2-(2,4-difluorophenyl)pyridine]iridium(III), [Ir(dfppy)2(bpy)](PF6) (2), complex as the reference. All the iridium(III) complexes synthesized showed strong green emission and higher ECL intensities compared to the well-known Ru(bpy)32+. The iridium(III) complexes containing α-diimine ligands with electron donating dimethyl, trimethylsilyl, and triphenylsilyl groups on bpy showed the increased ECL intensities compared to that of the reference (2). Among those iridium(III) complexes, the complex ligated with 5-(trimethylsilyl)-2,2′-bipyridine and 2,4-difluorophenylpyridine showed the most intense ECL responses and exhibited ECL intensities as high as 7.6 times greater than that of the reference (2). However, the iridium(III) complexes containing α-diimine ligands containing more conjugated carbon-carbon triple bond showed the decreased ECL intensities compared to that of the complexes with no triple bond conjugation.

Fast and Green Synthesis of 3-Cyano-8-Methyl-2-Oxo-4-Substituted 1,2,5,6,7,8-Hexahydroquinolines

Ultrasound was used to synthesis 3-cyano-8-methyl-2-oxo-4-substituted 1,2,5,6,7,8-hexahydroquinolines in a one-pot multicomponent reaction of the corresponding aldehyde, 2-methylcyclohexanone, and excess ammonium acetate and ethyl cyanoacetate in boiling ethanol. The proposed method is uncomplicated, does not take much time, and provides higher product yield, in contrast to the conventional two-step synthesis involving formation of 2-arylidene-6-methylcyclohexanones via Claisen–Schmidt condensation followed by cyclocondensation with ethyl cyanoacetate and ammonium acetate. The structure of the synthesized compounds was confirmed by IR, 1H and 13C NMR spectroscopy and x-ray diffraction.

Doping effect of Y 3+ ions on the microstructural and electromagnetic properties of Mn–Zn ferrites

Mn–Zn ferrites doped with different contents of Y 3+ ions were prepared by conventional two-step synthesis method. The microstructure and electromagnetic properties of the as-prepared Mn–Zn ferrites were investigated. It was found that all the samples consisted of ferrite phases of typical spinel cubic structure, and when Y 3+ ion content was upto 1.5 mol%, yttriumirongarnet (Y 3Fe 5O 12) phase with garnet structure was detected. With increasing doping content of Y 3+ ions, the lattice constant and grain size increased, and after an increase to its maximum value, the sample apparent and relative densities dropped down. Through the analysis of magnetic properties, it was revealed that the saturation magnetization, and both the real and imaginary parts of permeability of the as-prepared samples raised with increasing doping content of Y 3+ ions but decreased with more Y 3+ ions, while their coercivity showed an opposite change trend; and the Curie temperature increased monotonously. The measurement of dielectric properties indicated that the dielectric constant of the doped Mn–Zn ferrites presented a rise with increasing Y 3+ ion content, and dropped down gradually when more Y 3+ ions were doped, while the dielectric loss tangent would decrease with Y 3+ content upto 1.5 mol%, but after that, it increased.

A new fluorescent sensor bearing three dansyl fluorophores for highly sensitive and selective detection of mercury(II) ions

A novel fluorometric sensor bearing three dansyl moieties based on tris[2-(2-aminoethylthio)ethyl]amine was prepared by a simple approach using a conventional two-step synthesis. The sensor exhibits highly Hg2+-selective ON–OFF fluorescence quenching behavior in aqueous acetonitrile solutions and is shown to discriminate various competing metal ions, particularly Cu2+, Ag+, and Pb2+ as well as Ca2+, Cd2+, Co2+, Fe3+, Mn2+, Na+, Ni2+, and Zn2+, with a detection limit of 1.15×10−7M or 23ppb.

Rhodamine B-based “turn-on” fluorescent and colorimetric chemosensors for highly sensitive and selective detection of mercury (II) ions

Two novel macromolecules based on 2-[3-(2-aminoethylsulfanyl)propylsulfanyl]ethanamine covalently bound to one and two units of rhodamine-B moieties, 1 and 2, were prepared and utilized as fluoroionophores and chromophores for the optical detection of Hg 2+ ions. The sensors were readily prepared by a conventional two-step synthesis. Especially, sensor 1 exhibits high sensitivity and selective OFF–ON fluorescence enhancement and chromogenic change upon binding to Hg 2+, which served as a “naked-eye” indicator by a noticeable color change of the solution (from colorless to pink–red color). 1 is shown to discriminate various competing metal ions, particularly Ag + and Cu 2+, as well as Cd 2+, Na +, Li +, K +, Ba 2+, Co 2+, Ni 2+, Mg 2+, Mn 2+ and Al 3+, with a detection limit of 10 ppb.

Comparative Study on Mn-Zn Ferrites by One-Step Synthesis and Conventional Two-Step Synthesis

Mn-Zn ferrites doped with Cr3+ were prepared by “one-step synthesis” and conventional two-step synthesis methods, respectively. Their phase compositions and microstructures were characterized by X-ray diffraction and scanning electron microscopy, respectively. And their magnetic magnetic performance, such as saturation magnetization (Ms), magnetic hysteresis, initial permeability μi and power loss were comparatively investigated by vibrating sample magnetometer. It was observed that the difference of magnetic performance of the samples prepared by both methods is little. The similar performance of both methods makes the “one-step synthesis” especially attractive for application when considering energy economization.

2-[3-(2-Aminoethylsulfanyl)propylsulfanyl]ethanamine Bearing Dansyl Subunits: An Efficient, Simple, and Rapid Fluorometric Sensor for the Detection of Mercury(II) Ions

Abstract A novel fluorometric sensor possessing two dansyl moieties based on 2-[3-(2-aminoethylsulfanyl)propylsulfanyl]ethanamine 1 was prepared by a ready synthetic approach using a conventional two-step synthesis. 1 exhibits highly sensitive and selective on–off Hg2+ fluorescence quenching behavior in aqueous acetonitrile solutions and is shown to discriminate various competing metal ions such as Cu2+, Ag+, Ca2+, Mn2+, Zn2+, Ba2+, Cd2+, Co2+, Na+, and K+ exhibiting a detection limit of 7 nM or 1.4 ppb with a working range of 1.8–15 ppb.

Comparative Study on Ni-Zn Ferrites by One-Step Synthesis and Conventional Two-Step Synthesis

The magnetic hysteresis parameters like coercivity (Hc) and saturation magnetization (Ms), and dielectric parameters like dielectric constant (ε΄) and dielectric loss (ε΄΄/ε΄) of Ni0.5Zn0.5Fe2O4 prepared by “one-step synthesis” and conventional two-step synthesis methods, respectively, were comparatively investigated. It was observed that the saturation magnetization, dielectric constant and dielectric loss for samples prepared by “one-step synthesis” method are lower than those of ferrite samples prepared by conventional synthesis method. However, the coercivity of the former is higher due to its smaller grain size. The low dielectric loss makes these samples especially attractive for use at high frequencies.

Synthesis and characterization of polyimides from bis(3-aminophenyl)-2,3,5,6-tetrafluoro-4-trifluoromethylphenyl phosphine oxide ( mDA7FPPO)

A novel diamine, bis(3-aminophenyl)-2,3,5,6-tetrafluoro-4-trifluoromethylphenyl phosphine oxide ( mDA7FPPO), was synthesized via Grignard reaction, followed by nitration and reduction. The monomer was characterized by FT-IR, NMR and melting point apparatus, and utilized to prepare polyimides with 6FDA, BTDA or ODPA via a conventional two-step synthesis; preparation of poly(amic acid), followed by solution imidization. The molecular weight of polyimides was controlled to 20,000 g/mol by off-stoichiometry and the polyimides were characterized by FT-IR, NMR, GPC, TGA and DSC. Solubility, intrinsic viscosity, dielectric constant and refractive index were also evaluated. The novel polyimides exhibited high T g (229–252 °C), excellent thermal stability (>500 °C), low dielectric constant (2.65–2.81) and low birefringence (0.0019–0.0049).

Partial Oxidation of Propane to Oxygenates in Dense CO2 Phase Using (VO)2P2O7 as Catalyst

The heterogeneously catalyzed, direct partial oxidation of propane to acrylic acid seems a promising alternative to the conventional two‐step synthesis using propene as starting material, yet until now, the industrial application of the direct oxidation of propane to its oxygenates has been limited by poor product yields. The objective of this work, therefore, was to investigate the application of (VO)2P2O7 catalysts for the oxidation of propane to acrylic acid in dense CO2 phase.