Recent Progress in Iron-Based Microwave Absorbing Composites: A Review and Prospective

With the rapid development of communication technology in civil and military fields, the problem of electromagnetic radiation pollution caused by the electromagnetic wave becomes particularly prominent and brings great harm. It is urgent to explore efficient electromagnetic wave absorption materials to solve the problem of electromagnetic radiation pollution. Therefore, various absorbing materials have developed rapidly. Among them, iron (Fe) magnetic absorbent particle material with superior magnetic properties, high Snoek’s cut-off frequency, saturation magnetization and Curie temperature, which shows excellent electromagnetic wave loss ability, are kinds of promising absorbing material. However, ferromagnetic particles have the disadvantages of poor impedance matching, easy oxidation, high density, and strong skin effect. In general, the two strategies of morphological structure design and multi-component material composite are utilized to improve the microwave absorption performance of Fe-based magnetic absorbent. Therefore, Fe-based microwave absorbing materials have been widely studied in microwave absorption. In this review, through the summary of the reports on Fe-based electromagnetic absorbing materials in recent years, the research progress of Fe-based absorbing materials is reviewed, and the preparation methods, absorbing properties and absorbing mechanisms of iron-based absorbing materials are discussed in detail from the aspects of different morphologies of Fe and Fe-based composite absorbers. Meanwhile, the future development direction of Fe-based absorbing materials is also prospected, providing a reference for the research and development of efficient electromagnetic wave absorbing materials with strong absorption performance, frequency bandwidth, light weight and thin thickness.     

Studies on Alternating Pulse Current-ChronopotentiometricStripping Analysis

BasedonthefirstideaspresentedbyBeck',anewmethodcalledalternatingpulsecurrent-chronopotentiometricstrippinganalysis(APC-CPSA)hasbeendeveloped.Inthistechnique,duringthestrippingstepthecurrentimposedontheelectrol,ysi$cellcomprisesofanalternatingpulsecurrent(APC)andtheinherentdirectcurrentofCPSA.TheAPCisoperatedwithahighfrequencyinasquarewavemode.isandiRisdefinedastheanodicandcathodicpulsecurrent,respectively,isandtRisthetimeforwhichthesecurrentsflow.So,whenisandiRalternates,partsofthestri…     

Solid-state electrochemiluminescence of a novel iridium(Ⅲ) complex

The sofid-state ECL behavior of a water-insoluble bis-cyclometalated (pq)2Ir(N-phMA) complex is presented, in which pq is a 2-phenylquinoline anion and N-phMA is N-phenyl methacrylamide, a monoanionic bidentate ligand. The MWNTs/(pq)2Ir(N-phMA) film, MWNTs/Ru(bpy)32+ film and (pq)2Ir(N-phMA) directly modified glassy carbon electrode were fabricated; only the MWNTs/(pq)2Ir(N-phMA) film can produce steady ECL in the presence of tri-n-propylamine as a coreactant.     

A Sensitive LC–ESI–MS–MS Method for the Determination of Huperzine A in Human Plasma: Method and Clinical Applications

A sensitive and specific liquid chromatography–electrospray ionization–tandem mass spectrometry method has been developed and validated for the quantification of huperzine A in human plasma. After the addition of trimetazidine, the internal standard (IS) and sodium hydroxide, plasma samples were extracted using 5 mL ethyl acetate. The compounds were separated on an Agilent Zorbax SB C₁₈ column (100 mm × 2.1 mm ID, dp 3.5 μm) using an elution system of 10 mM ammonium acetate solution–methanol–formic acid (18:82:0.1, v/v) as the mobile phase. The quantification of target compounds was obtained by using multiple reaction monitoring (MRM) transitions: m/z 243.1, 210.1 and 267.2, 166.0 were measured in positive mode for huperzine A and IS. Linearity was established for the range of concentrations 0.01–4.0 ng mL^?1 with a coefficient of correlation (r) of 0.9991. The lower limit of quantification (LLOQ) was identifiable and reproducible at 0.01 ng mL^?1. The method has been successfully applied to study the pharmacokinetics of huperzine A in healthy male Chinese volunteers.     

Development of core–shell structure Fe3O4@Ta2O5 microspheres for selective enrichment of phosphopeptides for mass spectrometry analysis

Protein phosphorylation is one of the most important post-translational modifications. Due to the dynamic nature and low stoichiometry of the protein phosphorylation, enrichment of phosphopeptides from proteolytic mixtures is often necessary prior to their characterization by mass spectrometry. Many metal oxides such as titanium dioxide and zirconium dioxide have been successfully applied to isolation and enrichment of phosphopeptides. Recently, niobium pentoxide was proved to have the ability for selective enrichment of phosphopeptides. Considering the proximity of tantalum to niobium, we supposed that Ta₂O₅ can be used as affinity probes for phosphopeptide enrichment. In the work, we synthesized Fe₃O₄@Ta₂O₅ magnetic microspheres with core–shell structure for selective enrichment of phosphopeptides. To demonstrate its ability for selective enrichment of phosphopeptides, we applied Fe₃O₄@Ta₂O₅ magnetic microspheres to isolation and enrichment of the phosphopeptides from tryptic digestion of standard proteins and real samples, and then the enriched peptides were analyzed by matrix-assisted laser desorption mass spectrometry analysis (MALDI-MS) or liquid chromatography coupled to electrospray ionization mass spectrometry (LC–ESI-MS). Experiment results demonstrate that Ta₂O₅ coated-magnetic microspheres show the excellent potential for selective enrichment of phosphopeptides.     

Hydrogenation and hydrocarbonation and etching of single-walled carbon nanotubes

We present a systematic experimental investigation of the reactions between hydrogen plasma and single-walled carbon nanotubes (SWNTs) at various temperatures. Microscopy, infrared (IR) and Raman spectroscopy, and electrical transport measurements are carried out to investigate the properties of SWNTs after hydrogenation. Structural deformations, drastically reduced electrical conductance, and an increased semiconducting nature of SWNTs upon sidewall hydrogenation are observed. These changes are reversible upon thermal annealing at 500 degrees C via dehydrogenation. Harsh plasma or high temperature reactions lead to etching of nanotubes likely via hydrocarbonation. Smaller SWNTs are markedly less stable against hydrocarbonation than larger tubes. The results are fundamental and may have implications to basic and practical applications including hydrogen storage, sensing, band gap engineering for novel electronics, and new methods of manipulation, functionalization, and etching of nanotubes.     

Interface Engineering of a CoOx/Ta3N5 Photocatalyst for Unprecedented Water Oxidation Performance under Visible‐Light‐Irradiation

Cocatalysts have been extensively used to promote water oxidation efficiency in solar‐to‐chemical energy conversion, but the influence of interface compatibility between semiconductor and cocatalyst has been rarely addressed. Here we demonstrate a feasible strategy of interface wettability modification to enhance water oxidation efficiency of the state‐of‐the‐art CoO_x/Ta₃N₅ system. When the hydrophobic feature of a Ta₃N₅ semiconductor was modulated to a hydrophilic one by in situ or ex situ surface coating with a magnesia nanolayer (2–5 nm), the interfacial contact between the hydrophilic CoO_x cocatalyst and the modified hydrophilic Ta₃N₅ semiconductor was greatly improved. Consequently, the visible‐light‐driven photocatalytic oxygen evolution rate of the resulting CoO_x/MgO(in)–Ta₃N₅ photocatalyst is ca. 23 times that of the pristine Ta₃N₅ sample, with a new record (11.3 %) of apparent quantum efficiency (AQE) under 500–600 nm illumination.     

Efficient Two‐Photon Excited Amplified Spontaneous Emission from Organic Single Crystals

E, E‐1, 4‐bis[4′‐(N,N‐dibutylamino)styryl]‐2,5‐dimethoxy‐benzene (DBASDMB) organic crystals with high crystalline quality, large size and excellent optical properties are prepared. The linear and nonlinear properties in the crystal are comparatively studied. The relaxation dynamics pumped by two‐photon are very similar with that pumped by one‐photon. The crystal exhibits very strong two‐photon excited fluorescence and amplified spontaneous emission. Efficient two‐photon absorption, reasonably high fluorescent quantum efficiency, and high crystal quality together with stimulated emission make organic crystals ideal for the application in frequency upconversion and other optoelectronic fields.     

Preparation, evaluation and application of molecularly imprinted solid-phase microextraction monolith for selective extraction of pirimicarb in tomato and pear

A simple, rapid and sensitive method for the determination of pirimicarb in tomato and pear using polymer monolith microextraction (PMME) based on the molecularly imprinted polymer (MIP) monolith combined with high-performance liquid chromatography-photodiodes array detector (HPLC-PAD) was developed. By optimizing the polymerization conditions, such as the nature of porogenic solvent and functional monomer, the molar ratio of the monomer and cross-linker, an pirimicarb MIP monolith was synthesized in a micropipette tip using methacrylic acid (MAA) as the functional monomer, ethylene dimethacrylate (EGDMA) as the cross-linker and the mixture of toluene-dodecanol as the porogenic solvent. The MIP monolith showed highly specific recognition for the template pirimicarb. The monolith was applied for the selective extraction of pirimicarb in tomato and pear. Several parameters affecting MIP-PMME were investigated, including the nature and volume of extraction solvent, sample volume, flow rate and sample pH. Under the optimum PMME and HPLC conditions, the linear ranges were 2.0-1400 μg/kg for pirimicarb in tomato and pear with the correlation coefficient of above 0.999. The detection limits (s/n=3) were both 0.6 μg/kg. The proposed method was successfully applied for the selective extraction and determination of pirimicarb in tomato and pear.     

Surface transfer doping of semiconductors

Surface transfer doping relies on charge separation at interfaces, and represents a valuable tool for the controlled and nondestructive doping of nanostructured materials or organic semiconductors at the nanometer-scale. It cannot be easily achieved by the conventional implantation process with energetic ions. Surface transfer doping can effectively dope semiconductors and nanostructures at relatively low cost, thereby facilitating the development of organic and nanoelectronics. The aim of this review is to highlight recent advances of surface transfer doping of semiconductors. Special focus is given to the effective doping of diamond, epitaxial graphene thermally grown on SiC, and organic semiconductors. The doping mechanism of various semiconductors and their possible applications in nanoelectronic devices will be discussed, including the interfacial charge transfer and the energy level alignment mechanisms.