The richly functionalized basal plane bonded to polar organic moieties makes graphene oxide (GO) innately hydrophilic. Here, a methodology to synthesize fluorinated graphene oxide by oxidizing the basal plane of fluorinated graphite, allowing for tunable hydrophobicity of GO, is reported. Fluorine exists as tertiary alkyl fluorides covalently bonded to graphitic carbons, and using magic‐angle spinning (MAS) 13C NMR as a primary tool chemical structures for the two types of synthesized fluorinated graphene oxides (FGOs) with significantly different fluorine contents are proposed. The low surface energy of the C–F bond drastically affects GO's wetting behavior, leading to amphiphobicity in its highly fluorinated form. Ease of solution processing enables the fabrication of inks that are spray‐painted on various porous/non‐porous substrates. These coatings maintain amphiphobicity for solvents with surface tensions down to 59 dyn/cm, thus bypassing existing lithographic means to create similar surfaces. The approach towards fluorinating GO and fabricating graphene‐based surfaces with tunable wettability opens the path towards unique, accessible, carbon‐based amphiphobic coatings. 相似文献
The authors describe a voltammetric immunoassay for the carcinoembryonic antigen (CEA). It is based on the use of a self-assembled magnetic nanocomposite as multifunctional signal amplification platform. The core of the nanocomposite consists of Fe3O4 microspheres, and the shell of zirconium hexacyanoferrate loaded with gold nanoparticles (AuNPs@ZrHCF@Fe3O4). The material was synthesized by an electrostatic self-assembly process which is caused by the strong interaction between cyano groups and AuNPs. The surface of the Fe3O4 microspheres was functionalized with amino groups to facilitate the immobilization of ZrHCF which acts as an electron mediator. The nanocomposite was placed on a glassy carbon electrode which then displays noteworthy electrocatalytic activity toward the reduction of hydrogen peroxide (H2O2). The AuNPs serve as a support for the immobilization of antibodies by the interaction between AuNPs and amino groups on antibodies to construct a covalent Au-N bond. This facilitates electron transfer on the electrode surface using H2O2 as the electrochemical probe. Square wave voltammetry (measured typically at +0.2 V vs. SCE) was carried out to record the electrochemical behavior. Under the optimal conditions, a response is linear in the 0.5 pg·mL?1 to 50 ng·mL?1 CEA concentration range, and the detection limit is as low as 0.15 pg·mL?1 (S/N =?3). The method is selective, highly stable and acceptably reproducible.
To obtain high performance of nanocomposite films made of cellulose nanofibrils (CNFs) and montmorillonites (MMTs), highly ordered nanostructures and abundant interfacial interactions are of extreme importance, especially for CNF film with high MMT content. Here, we tend to unveil the influence of exfoliation degree of MMTs and their interfacial interactions with CNFs on the properties of ensuing nanocomposite films. Monolayer MMTs (ML-MMTs) prefer to form highly ordered nanostructure during water evaporation induced self-assembly. The obtained nanocomposite film with 30 wt% ML-MMTs exhibits a tensile strength of 132 MPa, a total light transmittance of 90.2% (550 nm), and water vapor transmission rate (WVTR) of 41.5 g mm/m2 day, better than the film made of original MMTs (O-MMTs) and CNFs (30 MPa strength, 60% transparency, and 78.7 g mm/m2 day WVTR). Moreover, the physical properties (153 MPa strength and 20.9 g mm/m2 day WVTR) of nanocomposite film can be further enhanced by constructing ionic interactions between the ML-MMT and CNF using 0.5 wt% cationic polyethylenimine (PEI). However, as the amount of PEI continues to increase, its performance will be deteriorated dramatically because of the disordered orientation of ML-MMTs. This work could provide an insight into the fabrication of high performance MMT/CNF nanocomposite film for advanced applications.
This paper discusses design and implementation of a millimeterwave monolithic integrated balanced mixer, the measured performance compared with the predicted one is also reported. By designing this MMIC mixer, various mathematical methods are used, in which the Method of Conversion Matrix has been extended by the author to meet the requirement of inter-modulation analysis. The mixer is realized in a 2×3mm2GaAs chip, working in Ka band with bandwidth of 5GHz with a noise figure less than 10 dB.相似文献
Human telomeres can form DNA G‐quadruplex (G4), an attractive target for anticancer drugs. Human telomeric G4s bear inherent structure polymorphism, challenging for understanding specific recognition by ligands or proteins. Protoberberines are medicinal natural‐products known to stabilize telomeric G4s and inhibit telomerase. Here we report epiberberine (EPI) specifically recognizes the hybrid‐2 telomeric G4 predominant in physiologically relevant K+ solution and converts other telomeric G4 forms to hybrid‐2, the first such example reported. Our NMR structure in K+ solution shows EPI binding induces extensive rearrangement of the previously disordered 5′‐flanking and loop segments to form an unprecedented four‐layer binding pocket specific to the hybrid‐2 telomeric G4; EPI recruits the (?1) adenine to form a “quasi‐triad” intercalated between the external tetrad and a T:T:A triad, capped by a T:T base pair. Our study provides structural basis for small‐molecule drug design targeting the human telomeric G4. 相似文献