High Temperature Refluxing Research Articles

A colorimetric/down-conversion fluorescence dual-readout probe for the recognition of Cu2+ and its application in environmental water by single PEI@NaYF4: Eu3+ nanoparticles

The pollution caused by heavy metals like Cu2+ remains a pressing issue, as the release of Cu2+-laden sewage can lead to detrimental effects on both soil ecosystems and human well-being. Herein, a novel colorimetric and down-conversion fluorescence probe, i.e. PEI@NaYF4: Eu3+ NPs, for selective and sensitive detection of Cu2+ with colorimetric and down-conversion fluorescence dual signal changes was reported. Such dual-signal detection mode offers enhanced sensitivity, accuracy, and cost-effectiveness in detecting Cu2+. The probe with spherical shape and excellent monodispersity was synthesized by a high temperature reflux method. The PEI moiety of the NPs is chosen due to the ability to chelate Cu2+ forming copper amine complexes. Such a unique feature is invoked to develop a versatile detection platform for the colorimetric detection of Cu2+ ions. In the presence of Cu2+, the visual color of probe in solution changes from colorless to blue with a low detection limit of 100 nM without any assistance of equipment. The probe emits down-conversion fluorescence with two main typical emission peaks centered at 592 and 614 nm under an excitation of 394 nm. The copper amine complexes formed by the combination of Cu2+ and the PEI moiety of the NPs quench down-conversion fluorescence by an internal filtration effect. Probe shows a specific on–off response to Cu2+ in aqueous solution with nanomolar LOD, fast response, and good selectivity, and without interference by a range of metal ions. A practical application shows that PEI@NaYF4: Eu3+ NPs have good recovery ranges of 96–105 % for Cu2+ detection in real environment water samples from different locations. This strategy proves that a colorimetric and down-conversion fluorescence probe is a potential tool for addressing heavy metal ions-induced water pollution.

Preparation of HfSiO4 via Non-Hydrolytic Sol-Gel method at low temperatures

Hafnon (HfSiO4) can be applied in electronics, dielectric films, refractory materials, and many other critical application areas. To explore an efficient preparation process of HfSiO4, a novel non-hydrolytic sol-gel (NHSG) method was used to synthesize high-purity HfSiO4 in this study. X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), energy-dispersive spectrometer (EDS), thermogravimetric differential scanning calorimetry (TG-DSC), Fourier transform infrared spectroscopy (FT-IR), and infrared thermal imaging (ITI) were used to investigate the synthesis temperature and mechanism of HfSiO4 and the effects of process parameters on its synthesis efficiency. The results show that the prepared sols undergo a highly reactive non-hydrolytic polycondensation reaction at room temperature. High temperature reflux or long time aging step is not necessary to form the strong Hf-O-Si bonds. Furthermore, with the introduction of the mineralizer agent LiF, the synthesis temperature of HfSiO4 can be drastically reduced, and the HfSiO4 with high purity can be synthesized at low temperatures. A moderate molar ratio of silicon to hafnium (Si:Hf) and molar concentration of the solution contribute to improve the synthesis efficiency of HfSiO4, and the purity of HfSiO4 products can reach up to 98.12 %.

Preparation of Sulfonated Polystyrene-Iron Composite Material and Study of Their Cationic and Anionic Dyes Adsorption Properties

A sulfonated polystyrene-iron composite magnetic material (PSSFe), which is nonpolluting, was synthesized using high-temperature reflux in a simple system. It was applied for the first time to the adsorption and removal of two dyes (methylene blue (MB) and congo red (CR)) from wastewater. The cost of synthesis is lower and simpler and then that of the large sites active in PSSFe, making it efficient cost effective for a large variety of dyes. Scanning electron microscopy (SEM), x-ray diffraction (XRD), thermogravimetric analysis (TGA-DTGA), infrared spectroscopy (FTIR), and the pH of the point of zero charge (pHPZC) were used to characterize the morphology and microstructure of the magnetic sample. The adsorption of methylene blue and congo red as a function of various factors, such as the effect of pH, time and temperature, was investigated. The results demonstrated that the Langmuir model well represented the isotherms, supporting monolayer and homogeneous adsorption, and the pseudo-second-order model could also capture the kinetic process of adsorption. The PSSFe exhibited adsorption capabilities (qe) of 99.7 and 76.9 (mg/g) for MB and CR, respectively. The adsorption of MB on PSSFe was endothermic, whereas the adsorption of CR on PSSFe was exothermic. During the first cycle, both MB and CR were successfully desorbed from PSSFe, with 99.7% and 92.5% removal percentages, respectively.

Ni–Au magnetoplasmonic nanoparticles with a unique intertwined crystal structure showing excellent reduction and tunability of the superparamagnetic blocking temperature

Magnetoplasmonic bimetallic nanoparticles (NPs) are inevitable components of several research domains that have widespread applications. However, bimetallic NPs that possess simultaneous magnetic and optical properties are often tremendously hard to synthesize. We report an extremely straight-forward, facile, quick, cost effective and easily scalable chemical method for the synthesis of magnetoplasmonic bimetallic nickel–gold (Ni–Au) NPs possessing a unique intertwined crystal structure, exhibiting excellent magnetic and plasmonic properties. The chemical method employs minimal number of precursors and eludes the necessity of inert gas atmospheres, high temperature refluxing procedures and templates. Through extensive crystal structure, compositional and surface characterizations by combining XRD, HR-TEM, EDX, SAED and XPS techniques, the bimetallic NPs were seen to possess an interesting structure where the atomic planes of Ni and Au were intertwined within the whole of each NP, unlike conventional core–shells or alloys. Specifically, an exhaustive HR-TEM analysis methodology applied to each visible Ni–Au NP proved vital in disclosing the intertwined nature of the Ni and Au atomic planes. The Ni–Au NPs exhibited magnetization properties that were drastically different from those of the pure metallic Ni NPs. While Ni NPs showed superparamagnetism (SPM) at temperatures much higher than room temperature, Ni–Au NPs showed an SPM blocking temperature, TB, as low as 47 K. SPM in the bimetallic system also exhibited appreciable tunability, that was demonstrated by further decreasing the TB value in the Ni–Au NPs that were synthesized using smaller sized Ni NP seeds. In addition to showing the much desired SPM behaviour at room temperature, the broad plasmonic resonance in the visible wavelength region due to the presence of Au makes the Ni–Au NPs multifunctional and thus promising for various applications. The developed synthesis method highlights the possibilities towards synthesizing magnetoplasmonic bimetallic systems with unique property-specific architectures through much less expensive, unconstrained chemical synthesis pathways.

Experimental and Numerical Simulation Research on Flow, Combustion and NO x Formation of a New Swirling Arch-Fired Boiler

ABSTRACT Taking a 300-MWe arch-fired boiler as the research object, compared with original Babcock & Wilcox (B&W) combustion technology, the flow, combustion and NO x emission characteristics are comprehensively revealed under the novel biased-swirl-secondary-air combustion (BSSAC) technology with the help of cold-modeling experiments and numerical simulations. The results show that, for BSSA combustion technology, the dimensionless downward depth of the air flow from furnace arches is increased by 0.13, and the air flow fullness of whole the lower furnace is improved under the effect of burner secondary air near the water-cooled wall, vent air and staged air being injected step by step. The high-temperature reflux zone and gas reflux velocity under the furnace arch increase significantly, the ignition of primary pulverized coal air flow is advanced, and the combustion path of pulverized coal particles increases. The combustible content of fly ash decreases by 32.4%. At the same time, the ignition process of pulverized coal air flow near the center of the furnace is in a strong reducing and low oxygen atmosphere, and the multi-stage effective air supply is obtained in the downward process of pulverized coal combustion. The NO x emission concentration at the furnace outlet is reduced from 824 to 694 mg/m3 (O2 = 6%).

Analysis of temperature field and noise characteristics of impinging jet of carrier-based aircraft engine

Objectives As the deflection angle has great influence on temperature and noise radiation near the deflector of the impinging jet of a carrier-based aircraft, determining an appropriate deflection angle can expand the safe area around the aircraft. Methods This paper analyzes the flow field, temperature field and sound field characteristics near the deflector of a certain type of engine tail nozzle in full afterburner conditions under different deflection angles (β=35°, 45°, 55°) and different monitoring distances (S=20D, 30D, 50D, 80D). Using large eddy simulation (LES) and acoustic analogy methods, a calculation model of a supersonic jet impinging on an inclined plate is established, and the correctness of the model verified by experimental data. Results The deflection angle changes the distribution of the temperature field. When β=45°, the deflector has a better effect, personnel and equipment behind the deflector can be protected most effectively, and the high-temperature reflux on the countercurrent side of the deflector will affect the carrier aircraft. The rear wheel basically has no effect. The deflection angle also has great influence on far-field radiated noise. When noise monitoring distance S=40D, the total sound pressure level increases with the increase of the deflection angle. When β=35°, the noise radiation range affecting the normal work of personnel is at its smallest. Conclusions In general, when β=45°, personnel and equipment near the deflector suffer the least high temperature and noise threat. Even so, in order to ensure that the ground crew can work normally at any angle, the tail nozzle should be kept above 80D.

High or low temperature extraction, which is more conducive to Triphala against chronic pharyngitis?

ObjectiveExplore the effects of high-temperature reflux extraction and low-temperature decompressing inner ebullition on Triphala's chemical composition and anti-chronic pharyngitis activity. MethodsThe network pharmacology was used to analyze the material basis, targets and pathways of Triphala for chronic pharyngitis. HPLC were used to compare the fingerprint profile and content of components between the two extracts. The antioxidant and anti-chronic pharyngitis activities of the two extracts were compared by DPPH assay and ammonia induced chronic pharyngitis model in rats. ResultsThe network pharmacology results showed that the active ingredients of Triphala for chronic pharyngitis are epigallocatechin-3-gallate, (+)-catechin, epicatechin, epicatechin gallate, (+)-gallocatechin, quercetin, luteolin, leucodelphinidin and other flavonoids; phenolic acids such as gallic acid and ellagic acid; alkaloids such as ellipticine, cheilanthifoline; hydrolyzed tannins such as corilagin and chebulic acid. The high-temperature reflux extract and the low-temperature decompressing inner ebullition extract have extremely significant differences in the fingerprint profile. Among them, the content of gallic acid, ellagic acid, chebulic acid, catechin, epicatechin, corilagin, quercetin, and epicatechin gallate in the reflux extract is 1.1–5.3 times as much as decompressing inner ebullition extract. The free radical scavenging ability of reflux extract is significantly stronger than that of decompression extract (p < 0.01), and it has a repairing effect on pharyngeal mucosal damage (reducing keratinization or hyperplasia of mucosal epithelium, reducing inflammatory cell infiltration and bleeding), and reducing IL-1β (P＜0.05), IL-6 (p＜0.05), TNF-α overexpression ability is stronger than the decompressing inner ebullition extract. Conclusionsgallic acid, ellagic acid, chebulic acid, catechin, epicatechin, corilagin and epicatechin gallate are the basic aglycones or oligomers of tannin. High temperature reflux extraction can significantly promote the occurrence of the hydrolysis of tannins and significantly increases the content of these components.Therefore, its anti-chronic pharyngitis activity is enhanced. It is suggested that high temperature reflux extraction should be used in the treatment of chronic pharyngitis.

Novel ZnO tetrapod-reduced graphene oxide nanocomposites for enhanced photocatalytic degradation of phenolic compounds and MB dye

In the present work, a bunch of ZnO tetrapod-reduced graphene oxide (ZTPG) nanocomposites (NCs) were synthesized via a simple and economical in-situ approach using high temperature refluxing method. The phase purity, morphology, optical and photocatalytic properties of NCs were studied comprehensively. Various weight percentage of rGO were proposed for efficient separation of electron hole pairs and improved photodegradation of phenolic compounds and methylene blue (MB) dye. The photocatalytic degradation of 4-chlorophenol (4-CP) and MB dye in aqueous system was performed for the assessment of photodegradation productivity of various ZTPG NCs with illumination of UV-light. The utmost mineralization after photodegradation attained about 94.8% for 4-CP over ZTPG-5 with UV-light exposure for 180 min. Similarly, the efficiency was also found 98.05% for MB dye photodegradation after 90 min UV-light introduction. The improved photocatalytic performance of ZTPG-5 NCs attributed to the enhanced adsorption capacity of 4-CP and MB dye over nanocomposite photocatalyst, effectual suppression of the recombination rate of electron hole pairs by synergistic influence among ZnO tetrapod and rGO sheet.

RGO-ZnO nanocomposites as efficient photocatalyst for degradation of 4-BP and DEP using high temperature refluxing method in in-situ condition

Persistent organic pollutants (mainly aromatic compounds) such as bromophenol and diethyl phthalate are dangerous and act as primary contaminants in aqueous system. In this study, efficient reduced graphene oxide zinc oxide (rGO-ZnO) nanocomposites were synthesized by using a simple and facile method for photocatalytic degradation of 4-Bromophenol (4-BP) and diethyl phthalate (DEP). The rGO-ZnO (rGZ) nanocomposites (NCs) with different weight ratio of rGO and ZnO (coded as rGZ-1, rGZ-2, rGZ-5 and rGZ-10) were synthesized via high temperature refluxing method. The crystalline structure and phase, surface morphological study, optical properties, crystal defects and existence of functional groups in rGZ NCs were studied by X-ray diffraction (XRD), field-emission-scanning electron microscope (FE-SEM), UV-Visible diffuse reflectance spectroscopy (DRS), Raman spectroscopy and FT-IR analysis, respectively. The elimination of 4-BP and DEP from water by UV-light exposure was considered to estimate the photocatalytic efficiency of prepared rGZ NCs. The maximum elimination of 4-BP and DEP via photodegradation (advanced oxidation process) was found about 99.04% and 98.63% over rGZ NCs after 180 min UV irradiation, respectively. The photodegradation study was examined by using high performance liquid chromatography (HPLC) technique. This study confirms the efficient photocatalytic activity of rGZ-5 towards degradation of 4-BP and DEP. Finally, degradation mechanism has been proposed for the degradation of 4-BP and DEP.

A Discrete Self-Assembled Pd12 Triangular Orthobicupola Cage and its Use for Intramolecular Cycloaddition.

Water-soluble Pd12 L6 coordination cage TC-1 was synthesized by coordination-driven self-assembly of symmetrical tetrapyridyl donor L with 90° ditopic acceptor cis-[Pd(NO3 )2 (tmeda)] [tmeda=N,N,N',N'-tetramethylethane-1,2-diamine]. The Pd12 L6 coordination assembly is an uncommon example of a coordination cage having triangular orthobicupola-like geometry. It was characterized by multinuclear NMR spectroscopy, ESI-MS, and single-crystal X-ray diffraction. Self-assembly of a tetratopic donor with a cis-blocked 90° ditopic acceptor generally yields tri-/tetra-/hexagonal barrels or closed cubic cages. However, in the present case the donor and acceptor are arranged in an unusual fashion to generate an orthobicupola geometry in which two triangular cupola share a common irregular hexagonal face. The cage was used to perform intramolecular cycloaddition reactions of O-propargylated benzylidinebarbituric acid derivatives in nitromethane. Several penta-/tetracyclouracil derivatives were synthesized through cage-catalyzed [4+2] cycloaddition reactions in a concerted manner with good to high conversion under mild reaction conditions, whereas in the absence of cage TC-1 similar reactions led to lower conversion to the cyclized products in organic solvent. This approach is of particular importance compared to the literature reports on the synthesis of similar compounds under high-temperature reflux conditions with high catalyst loading.

Catalytic Intramolecular Cycloaddition Reactions by Using a Discrete Molecular Architecture.

A discrete tetragonal tube-shaped complex (MT-1) has been synthesised by coordination-driven self-assembly of a carbazole-based tetraimidazole donor L and a Pd(II) 90° acceptor, that is, [cis-(dppf)Pd(OTf)2 ] (dppf=diphenylphosphinoferrocene, OTf=CF3 SO3- ). Complex MT-1 was characterised by multinuclear NMR, ESI-MS and single-crystal X-ray diffraction analysis (SCXRD), which showed its symmetrical tetrafacial tube-shaped architecture possessing a large cavity described by four aromatic walls. This coordination cage was successfully utilised as a molecular vessel to perform intramolecular cycloaddition reactions of O-allylated benzylidinebarbituric acid derivatives inside its confined nanospace. The presence of a catalytic amount of MT-1 promoted [4+2] cycloaddition reactions in a regio- and stereoselective manner, yielding the corresponding penta/tetracyclouracil derivatives in good yields under mild reaction conditions. This protocol is interesting compared with the literature reports for the synthesis of similar chromenopyran pyrimidinedione derivatives under high-temperature reflux conditions or solid-state melt reactions (SSMRs).

Flower-like Fe2O3/polyaniline core/shell nanocomposite and its electroheological properties

Abstract： Flower-like Fe2O3/polyaniline core/shell nanocomposite was obtained via a two-steps method. Firstly, monodispersed flower-like iron oxide was synthesized by a high temperature refluxing method. Then flower-like Fe2O3/polyaniline core/shell nanocomposite was further obtained via the in-situ polymerization. Scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), SQUID MPMS, UV–vis and Haake rheometer were used to investigate its structure, morphology and properties. The obtained Fe2O3/polyaniline nanocomposite reveals an interesting morphological combination of hierarchical and core/shell structure. Its electrorheological (ER) behavior were investigated using a rotational rheometer under different applied electric field strengths when dispersed in silicone oil, which shown an obvious ER activity.

Flexible carbon nanotube/polypropylene composite plate decorated with poly(3,4-ethylenedioxythiophene) as efficient counter electrodes for dye-sensitized solar cells

In this study, we fabricate an efficient, flexible and low-cost counter electrode (CE) composed of a plasma-etched carbon nanotubes/polypropylene (designated as ECP) composite plate decorated with poly(3,4-ethylene dioxythiophene) (PEDOT) for dye-sensitized solar cells (DSCs). The PEDOT-decorated monolithic ECP CEs are fabricated via series of processes including high-temperature refluxing, thermal compression, oxygen plasma etching, and electropolymerization. The bottom ECP plate is used to replace conventional transparent conducting oxide (TCO) as a conductive substrate, and the top PEDOT layer is employed as catalyst for I3− reduction. According to the extensive electrochemical measurements, the as-fabricated flexible PEDOT coated ECP CE demonstrates a Pt-like electrocatalytic for I3− reduction. The DSC based on the flexible PEDOT-decorated ECP CE yields impressive energy conversion efficiency of 6.82% (or 6.77% even after the bending test), which is comparable to that of the DSC using the Pt CE (7.20%) under similar device architecture conditions. Therefore, the PEDOT-decorated ECP based CEs show the possibility of serving as low-cost and flexible CEs for efficient DSCs.

Characteristics and Preparation of multi-walled carbon nanotubes-polyvinyl alcohol nanocomposites via ionic mechanism

To improve compatibility of multi-walled carbon nanotubes (MWCNTs) with polymer matrix, chloride-functionals were applied to the MWCNTs by functionalization using HNO3/H2SO4 and thionyl chloride. The MWCNTs were conjunct by poly vinyl alcohol (PVA) surface via ionic mechanism using benzoyl peroxide (BPO) in water during a high temperature refluxing process. The results of Fourier transform spectrometer (FT-IR) and field emission scanning electron microscopy images (FE-SEM) confirmed the linkage of the MWCNTs to the PVA via a covalent bond and the attributes of MWCNTs-PVA nanocomposite were recognized by electrical conductivity (EC), disperse stability measurements and thermogravimetric analysis (TGA).

Facile and green method for polystyrene grafted multi-walled carbon nanotubes and their electroresponse

Polystyrene (PS) microspheres with a mean diameter of 69nm were prepared by emulsion polymerization. The PS microspheres were successfully decorated to multi-walled carbon nanotubes (MWNTs) induced by benzoyl peroxide in water during a high temperature refluxing process under nitrogen atmosphere. The as-prepared multi-walled carbon nanotube/polystyrene (MWNT/PS) nanocomposites were characterized by FTIR spectroscopy, Raman spectroscopy, SEM, TEM, differential scanning calorimetry (DSC), and electrical resistance measurements. The results reveal that PS microspheres are mainly covalently grafted onto the walls of MWNTs. The PS-decorated MWNTs show high solubility in toluene and xylene without sedimentation after 24h. With MWNTs in the hybrids, PS achieved a considerable increase in electrical conductivity and glass-transition temperature (Tg). In particular, the obtained MWNT/PS composites were examined for electrorheological (ER) fluids, which showed thin and dense chains of particles after the application of an electric field. The facile and environmentally friendly technique presented in the present study could be an effective and promising method for the functionalization of MWNTs by other polymers.

Strong green emission from ZnSe–Ag2Se nanocomposites

Nanocomposite materials usually exhibit unique properties compared to their single phase counterparts. In this work, ZnSe–Ag2Se nanocomposites were prepared via a high-temperature reflux route. The nanocomposites demonstrated strong green light emission, which was a significant red shift compared to that of ZnSe nanoparticles. The red-shifted photoluminescence (PL) was attributed to the defects arising from Ag doping in the domain of ZnSe nanocrystals of the nanocomposites, based on the results of PL and PL excitation measurements.

ZnO–Au hybrid nanocrystals via a high temperature reflux route

ZnO–Au hybrid nanocrystals with good dispersibility and uniform size are prepared via a high temperature reflux route. The structure, morphology, interface structure and optical properties were characterized by X-ray diffraction high resolution transmission electron microscope and UV–vis absorption spectrophotometer. The formation of hybrid nanocrystals was believed to arise from the heterogeneous nucleation and epitaxial growth, high temperature and surfactant are proposed as the key factors for producing fine and uniform hybrid nanocrystals.

Preparation, solubility, and electrorheological properties of carbon nanotubes/poly(methyl methacrylate) nanocomposites by in situ functionalization

Poly(methyl methacrylate) (PMMA) nanobeads-decorated multi-walled carbon nanotubes (MWNTs) and single-walled carbon nanotubes (SWNTs) nanocomposites were prepared using two processing steps. Initially, spherical PMMA nanoparticles were synthesized using an emulsion polymerization method. Afterward, the PMMA nanobeads were decorated to MWNTs and SWNTs using benzoyl peroxide as an initiator in water during a high temperature refluxing process. The results confirmed the linkage of the nanotubes to the surrounding PMMA nanobeads via a covalent bond. The resultant nanocomposites showed high solubility in chloroform without flocculation after 24 h. In addition, the nanotubes/PMMA nanocomposites were characterized by electrical resistance measurements to analyze their electrical conductivity and examined as electrorheological (ER) materials when dispersed in silicone oil.

A One-Pot Method to Prepare Gold Nanoparticle Chains with Chitosan

A biocompatible, water-soluble, lower molecular weight chitosan has been used for, via a one-pot high-temperature refluxing strategy, the simultaneous synthesis and assembly of gold nanoparticles. Transmission electron microscopy (TEM) and ultraviolet−visible−near-infrared (UV−vis−NIR) extinction spectra allowed us to identify the existence of nanoparticle linear aggregates. Importantly, through such a preparation procedure, the chain length of the nanoparticle aggregates could be tuned by facile adjustment of the reaction reagent ratio. Further, the growth and assembly processes of gold nanoparticles were studied by quenching the intermediate reaction solutions with an ice−water bath. The structure evolution proceeded through a two-stage process: initial generation of isolated nanoparticles, followed by the interconnection of nanoparticles into an aggregated morphology. A mechanism based on the nonuniform distribution of capping ligands is proposed to account for the one-dimensional chain structure form...