Surfactant-assisted fabrication of graphene frameworks endowing epoxy composites with superior thermal conductivity

With the rapid growth in electronic device performance,there has been an increasing demand for thermally conductive polymer composites to handle the thermal management issue,thus contributing to the great importance to develop the graphene framework,which is evaluated as the most promising reinforcements for enhancing the thermal conductivity of polymer.Vacuum filtration is a common method to fabricate graphene framework,whereas,it is available to prepare a framework with centimeter-scale thickness by filtrating the graphene-water dispersion,due to the fact of sample cracking caused by the mismatch of surface tension between graphene and water.In this work,a surfactantassisted strategy was proposed by adjusting the surface tension of the water close to that of graphene first,then performing a conventional filtration process,to fabricate graphene framework.As a result,a thick graphene framework(thickness:3 cm)was successfully prepared,and after embedding into epoxy,the framework endows the composite(13.6 wt%)with a high in-plane thermal conductivities of12.4 W/mK,which is equivalent to≈64 times higher than that of neat epoxy.Our method is simple and compatible with the conventional filtration process,suggesting great potential for the mass-production of graphene framework to meet the practical application requirements.     

Evidence for the Prerequisite Formation of Phenoxyl Radicals in Radical-Mediated Peptide Tyrosine Nitration In Vacuo

The elementary mechanism of radical-mediated peptide tyrosine nitration, which is a hallmark of post-translational modification of proteins under nitrative stress in vivo, has been elucidated in detail by using an integrated approach that combines the gas-phase synthesis of prototypical molecular tyrosine-containing peptide radical cations, ion–molecule reactions, and isotopic labeling experiments with DFT calculations. This reaction first involves the radical recombination of ^.NO₂ towards the prerequisite phenoxyl radical tautomer of a tyrosine residue, followed by proton rearrangements, finally yielding the stable and regioselective 3-nitrotyrosyl residue product. In contrast, nitration with the π-phenolic radical cation tautomer is inefficient. This first direct experimental evidence for the elementary steps of the radical-mediated tyrosine nitration mechanism in the gas phase provides a fundamental insight into the regioselectivity of biological tyrosine ortho-nitration.     

Design and operation of magnetophoretic systems at microscale: Device and particle approaches

Combining both device and particle designs are the essential concepts to be considered in magnetophoretic system development. Researcher efforts are often dedicated to only one of these design aspects and neglecting the interplay between them. Herein, to bring out importance of the idea of integration between device and particle, we reviewed the working principle of magnetophoretic system (includes both device and particle design concepts). Since, the magnetophoretic force is influenced by both field gradient and magnetization volume, hence, accurate prediction of the magnetophoretic force is relying on the availability of information on both parameters. In device design, we focus on the different strategies used to create localized high-field gradient. For particle design, we emphasize on the scaling between hydrodynamic size and magnetization volume. Moreover, we also briefly discussed the importance of magnetoshape anisotropy related to particle design aspect of magnetophoretic systems. Next, we illustrated the need for integration between device and particle design using microscale applications of magnetophoretic systems, include magnetic tweezers and microfluidic systems, as our working example. On the basis of our discussion, we highlighted several promising examples of microscale magnetophoretic systems which greatly utilized the interplay between device and particle design. Further, we concluded the review with several factors that possibly resulted in the lack of research efforts related to device and particle design integration.     

Disorder Engineering in Monolayer Nanosheets Enabling Photothermic Catalysis for Full Solar Spectrum (250–2500 nm) Harvesting

A persistent challenge in classical photocatalyst systems with extended light absorption is the unavoidable trade‐off between maximizing light harvesting and sustaining high photoredox capability. Alternatively, cooperative energy conversion through photothermic activation and photocatalytic redox is a promising yet unmet scientific proposition that critically demands a spectrum‐tailored catalyst system. Here, we construct a solar thermal‐promoted photocatalyst, an ultrathin “biphasic” ordered–disordered D‐HNb₃O₈ junction, which performs two disparate spectral selective functions of photoexcitation by ordered structure and thermal activated conversion via disordered lattice for combinatorial photothermal mediated catalysis. This in situ synthetically immobilized lattice distortion, constrained to a single‐entity monolayer structure not only circumvents interfacial incompatibility but also triggers near‐field temperature rise at the catalyst–reactant complexes’ proximity to promote photoreaction. Ultimately, a generic full solar conversion improvement for H₂ fuel production, organic transformation and water purification is realized.     

Pnictogen-Functionalised C1 Ligands: MC-ARn (n=0, 1, 2, 3)

The chemistry of transition metal carbynes, L_nM≡CR, has historically been dominated by species bearing hydrocarbyl or amino ‘R’ substituents, with other elements appearing only sporadically. In recent years, carbynes and related ‘C₁’ species bearing other main-group substituents, particularly heavier elements of the p-block, have begun to emerge. This review details the chemistry of heavier pnictogen-functionalised C₁ ligands, MCAR_n (A=P, As, Sb, Bi; n=0–3), including their syntheses, properties and reactivities, and how these are distinguished from more traditional carbyne complexes. Recent developments in the closely related phospha-isonitrile L_nM(CPR), cya-phosphide and cya-arside ligands, L_nM(C≡A) (A=P, As), are also discussed.     

Electrochemically Induced Free‐Radical Polymerization for the Fabrication of Amperometric Glucose Biosensors

Electrochemically induced free radical polymerization was employed for the fabrication of amperometric glucose biosensors. Based on the electrochemical reduction of persulfate anion, an ultrathin poly(acrylic acid) (PAA) hydrogel coating was generated on both the bare and glucose oxidase (GOD) crosslinked platinum electrodes in a neutral phosphate buffer solution under a low ionic strength condition. This electrosynthetic approach offers a flexible and controllable way to prepare functional coatings for biosensors under a wide range of highly biocompatible conditions, significantly different from other electropolymerization technologies that usually cause the enzyme deactivation. Negatively charged PAA hydrogel coating not only results in a biosensor with good permselectivity and long‐term stability, but also remarkably enhances its sensitivity by improving the oxygen recycle supply and the enzyme activity. Combined with a simple drop‐evaporation procedure to control the GOD loading, the present method offers a versatile and biocompatible way for fabricating highly sensitive biosensor.     

Natural structural motifs that suppress peptide ion fragmentation after electron capture

Series of doubly and triply protonated diarginated peptide molecules with different number of glutamic acid (E) and asparagine (N) residues were analyzed under ECD conditions. ECD spectra of doubly-protonated peptides show a strong dependence on the number of E and N residues. Both the backbone cleavages and hydrogen radical (H^•) loss from the charge-reduced precursor ions ([M+2H]^+•) were suppressed as the number of E and N residues increases. A strong inhibition of the backbone cleavages and H^• loss from [M+2H]^+• was found for peptides with 6E residues (or 4E + 2N residues). The results obtained using these model peptides were re-confirmed by analyzing N-arginated Fibrinopeptide-B (i.e., REGVNDNEEGFFSAR). In contrast to the N-arginated peptide, ECD of the doubly-protonated Fibrinopeptide-B and its analogues show extensive backbone cleavages leading to series of c- and z-ions (∼80% sequence coverage). Based on these results, it is believed that peptide ions with all surplus protons sequestered in arginine-residues would show enhanced stability under ECD conditions as the number of acid-residue increases. The suppression of backbone cleavages and H^• loss from [M+2H]^+• are presumably attributed to the low reactivity of the charge-reduced precursor ions. One of the possible hypothesis is that diarginated E-rich peptides may contain hydrogen bonds between carbonyl oxygen of E side chains and backbone amide hydrogen. These hydrogen bonds would provide extra stabilization for [M+2H]^+•. This is the first demonstration of natural structural motifs in peptides that would inhibit the backbone fragmentation of the charge-reduced peptide ions under ECD conditions.