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Basant Elsebai, Mariana Emilia Ghica, Mohammed Nooredeen Abbas, Christopher M A Brett
A new amperometric hydrogen peroxide enzyme inhibition biosensor for the indirect determination of toxic mercury ions, Hg(2+), based on catalase immobilized on a glassy carbon electrode surface by cross-linking with glutaraldehyde and bovine serum albumin, is reported. The parameters influencing biosensor performance were optimized, including enzyme loading, the amount of hydrogen peroxide, the applied potential and electrolyte pH. It was shown that the inhibition of catalase by Hg(2+) species is irreversible, with a linear inhibition response between 5×10(-11) and 5×10(-10)M...
July 11, 2017: Journal of Hazardous Materials
Zedong Li, Fei Li, Yue Xing, Zhi Liu, Minli You, Yingchun Li, Ting Wen, Zhiguo Qu, Xiao Ling Li, Feng Xu
Paper-based microfluidic biosensors have recently attracted increasing attentions in point-of-care testing (POCT) territories benefiting from their affordable, accessible and eco-friendly features, where technologies for fabricating such biosensors are preferred to be equipment free, easy-to-operate and capable of rapid prototyping. In this work, we developed a pen-on-paper (PoP) strategy based on two custom-made pens, i.e., a wax pen and a conductive-ink pen, to fully write paper-based microfluidic biosensors through directly writing both microfluidic channels and electrodes...
July 1, 2017: Biosensors & Bioelectronics
Wei Cai, Shunbi Xie, Jin Zhang, Dianyong Tang, Ying Tang
In this work, an electrochemical impedance biosensor for high sensitive detection of Hg(2+) was presented by coupling with Hg(2+)-induced activation of Mg(2+)-specific DNAzyme (Mg(2+)-DNAzyme) for target cycling and hybridization chain reaction (HCR) assembled DNA hydrogel for signal amplification. Firstly, we synthesized two different copolymer chains P1 and P2 by modifying hairpin DNA H3 and H4 with acrylamide polymer, respectively. Subsequently, Hg(2+) was served as trigger to activate the Mg(2+)-DNAzyme for selectively cleavage ribonucleobase-modified substrate in the presence of Mg(2+)...
July 11, 2017: Biosensors & Bioelectronics
Alexander V Postnikov, Ilia V Uvarov, Mikhail V Lokhanin, Vitaly B Svetovoy
Using different experimental techniques we visualize a cloud of gas in water that is produced electrochemically by the alternating polarity process. Liquid enriched with gas does not contain bubbles strongly scattering visible light but its refractive index changes significantly near the electrodes. The change of the refractive index is a collective effect of bulk nanobubbles with a diameter smaller than 200 nm. Any alternative explanation fails to explain the magnitude of the effect. Spatial structure of the cloud is investigated with the optical lever method...
2017: PloS One
Yan Zhang, Jian Xiao, Qi-Ying Lv, Lu Wang, Xulin Dong, Muhammad Asif, Jinghua Ren, Wenshan He, Yimin Sun, Fei Xiao, Shuai Wang
In this work, we develop a new type of freestanding nanohybrid paper electrode assembled from 3D ionic liquid (IL) functionalized graphene framework (GF) decorated by gold nanoflowers (AuNFs), and explore its practical application in in-situ electrochemical sensing of live breast cell samples by real-time tracking biomarker H2O2 released from cells. The AuNFs modified IL functionalized GF (AuNFs/IL-GF) was synthesized via a facile and efficient dopamine assisted one-pot self-assembly strategy. The as-obtained nanohybrid assembly exhibits a typical 3D hierarchical porous structure, where the highly active electrocatalyst AuNFs are well dispersed on IL-GF scaffold...
July 20, 2017: ACS Applied Materials & Interfaces
Yuanyuan Chang, Ying Zhuo, Yaqin Chai, Ruo Yuan
In this work, an elegantly designed host-guest recognition-assisted electrochemical release was established and applied in a reusable electrochemical biosensor for the detection of microRNA-182-5p (miRNA-182-5p), a prostate cancer biomarker in prostate cancer, based on the DNA cross configuration-fueled target cycling and strand displacement reaction (SDR) amplification. With such design, the single target miRNA input could be converted to large numbers of single-stranded DNA (S1-Trp and S2-Trp) output which could be trapped by cucurbit[8]uril-methyl viologen (CB-8-MV2+) based on the host-guest recognition, significantly enhancing the sensitivity for miRNA detection...
July 20, 2017: Analytical Chemistry
Dana Schwarz, Yaroslav S Kochergin, Amitava Acharja, Arun Ichangi, Maksym V Opanasenko, Jiří Čejka, Uwe Lappan, Pal Arki, Junjie He, Johannes Schmidt, Petr Nachtigall, Arne Thomas, Michael Janus Bojdys
Donor-acceptor dyads hold the key to tuning of electrochemical properties and enhanced mobility of charge carriers, yet their incorporation into a heterogeneous polymer network proves difficulty due to the fundamentally different chemistry of the donor- and acceptor-subunits. We present a family of sulphur and nitrogen containing porous polymers (SNPs) that are obtained via Sonogashira-Hagihara cross-coupling and that combine electron-withdrawing triazine (C3N3) and electron donating, sulphur-containing linkers...
July 20, 2017: Chemistry: a European Journal
Li-Cheng Song, Xiao-Feng Han, Wei Chen, Jia-Peng Li, Xu-Yong Wang
A new series of the structural and functional models for the active site of [NiFe]-H2ases has been prepared by a simple and convenient synthetic route. Thus, treatment of diphosphines RN(PPh2)2 (1a, R = p-MeC6H4CH2; 1b, R = EtO2CCH2) with an equimolar NiCl2·6H2O, NiBr2·3H2O, and NiI2 in refluxing CH2Cl2/MeOH or EtOH gave the mononuclear Ni complexes RN(PPh2)2NiX2 (2a, R = p-MeC6H4CH2, X = Cl; 2b, R = EtO2CCH2, X = Cl; 3a, R = p-MeC6H4CH2, X = Br; 3b, R = EtO2CCH2, X = Br; 4a, R = p-MeC6H4CH2, X = I; 4b, R = EtO2CCH2, X = I) in 67-97% yields...
July 20, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Geordie Creste, Sihem Groni, Claire Fave, Mathieu Branca, Bernd Schöllhorn
Five N-phenylviologen (PV(2+)) derivatives have been synthesized and their electrochemical behavior in the presence of halide anions has been studied. Further investigations were carried out by (1)H and (19)F NMR spectroscopy at different chloride concentrations. This is the first time a systematic study combines cyclic voltammetry and NMR spectroscopy in order to analyse the contribution of halogen bonding among the various non-covalent interactions between iodinated N-phenylviologens. The results show strong evidence for a significant "halogen bonding effect" in the interaction between halides and the iodo-tetrafluoro-phenylviologen PV2+-C6F4I...
July 20, 2017: Faraday Discussions
Wolfgang Schmickler, Douglas Henderson
The storage of ions in narrow nanotubes is investigated by grand-canonical Monte Carlo simulations. The interaction between the ions is screened by the image charge on the wall of the tube, but at close distances it is still much larger than the thermal energy. Depending on the electrochemical potential imposed by the contact with an electrolyte solution, two different regimes can be distinguished at the potential of zero charge: for low values corresponding to an ionophobic pore the tube is almost empty; for high values - ionophilic pore - a one dimensional salt is formed...
July 20, 2017: Physical Chemistry Chemical Physics: PCCP
Zheng Zeng, Wendi Zhang, Durga M Arvapalli, Brian Bloom, Alex Sheardy, Taylor Mabe, Yiyang Liu, Zuowei Ji, Harish Chevva, David H Waldeck, Jianjun Wei
Carbon nanodots (CNDs) have attracted great attention due to their superior solubility, biocompatibility, tunable photoluminescence, and opto-electronic properties. This work describes a new fluorescence-based spectroelectrochemistry approach to simultaneously study the photoluminescence and wavelength dependent photocurrent of microwave synthesized CNDs. The fluorescence of CNDs shows selective quenching upon a reversible redox couple, ferricyanide/ferrocyanide, reaction during cyclic voltammetry. The CND modified gold slide electrode demonstrates wavelength dependent photocurrent generation during the fluorescence-electrochemical study, suggesting the potential application of CNDs in photoelectronics...
July 20, 2017: Physical Chemistry Chemical Physics: PCCP
Hyo Jin Jang, Samantha L Hopkins, Maxime A Siegler, Sylvestre Bonnet
The synthesis and characterization of [Ru(tpy)(R2bpy)(L)](X)n complexes (tpy = 2,2':6',2''-terpyridine, R2bpy = 4,4'-dimethyl-2,2'-bipyridine (dmbpy), or 4,4'-bis(trifluoromethyl)-2,2'-bipyridine (tfmbpy), X = Cl(-) or PF6(-), and n = 1 or 2) are described. The dmbpy and tfmbpy bidentate ligands allow for investigating the effects of electron-donating and electron-withdrawing ligands, respectively, on the frontier orbital energetics as well as the photoreactivity of these ruthenium polypyridyl complexes for five prototypical monodentate ligands L = Cl(-), H2O, CH3CN, 2-(methylthio)ethanol (Hmte), or pyridine...
July 20, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Inna L Soroka, Nadezda V Tarakina, Anton Hermansson, Lukas Bigum, Rickard Widerberg, Mikael S Andersson, Roland Mathieu, Alagar R Paulraj, Yohannes Kiros
A facile synthesis of 3d-metal based electro-catalysts directly incorporated into a carbon support was carried out by γ-radiation. Transition metals of period 4, i.e. Ni and Co, were precipitated and reduced from their respective salt solutions. The obtained materials were characterized by XRD, SEM, SQUID and the BET methods. Thereafter, the electrodes for fuel cells were fabricated out of synthesized material and their electrochemical performance for the oxygen reduction reaction in 6 M KOH was measured. Although the concentrations of Co and Ni in the electrode material were low (3...
July 20, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Pinky Yadav, Muniappan Sankar, Xiangyi Ke, Lei Cong, Karl M Kadish
Di- and octa-phenylethynyl (PE) substituted π-extended copper corroles were synthesized and characterized as to their structural, electrochemical and spectroscopic properties. The addition of two or eight PE groups to the β-pyrrole positions of the corrole results in dramatic red shifts in the electronic absorption spectra and new reductions which are not seen for the parent compound lacking PE substituents. CuCor(PE)8 is reduced in four reversible one-electron transfer steps to give derivatives of [CuCor(PE)8](n-) where n = 1, 2, 3 or 4...
July 20, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Akitoshi Shiotari, Takahiro Nakae, Kota Iwata, Shigeki Mori, Tetsuo Okujima, Hidemitsu Uno, Hiroshi Sakaguchi, Yoshiaki Sugimoto
Controlling the structural deformation of organic molecules can drive unique reactions that cannot be induced only by thermal, optical or electrochemical procedures. However, in conventional organic synthesis, including mechanochemical procedures, it is difficult to control skeletal rearrangement in polycyclic aromatic hydrocarbons (PAHs). Here, we demonstrate a reaction scheme for the skeletal rearrangement of PAHs on a metal surface using high-resolution noncontact atomic force microscopy. By a combination of organic synthesis and on-surface cyclodehydrogenation, we produce a well-designed PAH-diazuleno[1,2,3-cd:1',2',3'-fg]pyrene-adsorbed flatly onto Cu(001), in which two azuleno moieties are highly strained by their mutual proximity...
July 20, 2017: Nature Communications
Yifan Dai, Alireza Molazemhosseini, Chung Chiun Liu
A simple in vitro biosensor for the detection of β-amyloid 42 in phosphate-buffered saline (PBS) and undiluted human serum was fabricated and tested based on our platform sensor technology. The bio-recognition mechanism of this biosensor was based on the effect of the interaction between antibody and antigen of β-amyloid 42 to the redox couple probe of K₄Fe(CN)₆ and K₃Fe(CN)₆. Differential pulse voltammetry (DPV) served as the transduction mechanism measuring the current output derived from the redox coupling reaction...
July 20, 2017: Biosensors
Shahnawaz Phulpoto, Jinhua Sun, Siqi Qi, Linhong Xiao, Shouke Yan, Jianxin Geng
The morphology of electrode materials plays an important role in determining the performance of lithium-ion batteries (LIBs). However, studies on determining the most favorable morphology for high-performance LIBs have rarely been reported. In this study, a series of F-doped SnO<sub>x</sub> (F-SnO<sub>2</sub> and F-SnO) materials with various morphologies was synthesized using ethylenediamine as a structure-directing agent in a facile hydrothermal process. During the hydrothermal process, the F-SnO<sub>x</sub> was embedded <i>in situ</i> into the three-dimensional (3D) architecture of reduced graphene oxide (RGO) to form F-SnO<sub>x</sub>@RGO composites...
July 20, 2017: Nanotechnology
Tobias Garling, Yujin Tong, Tamim Darwish, Martin Wolf, R Kramer Campen
Surfaces whose macroscopic properties can be switched by light are potentially useful in a wide variety of applications. One such promising application is electrochemical sensors that can be gated by optically switching the electrode <i>on</i> or <i>off</i>. One way to make such a switchable electrode is by depositing a self-assembled monolayer of bistable, optically switchable molecules onto an electrode surface. Quantitative application of any such sensor requires understanding how changes in interfacial field affect the composition of photostationary states, <i>i...
July 20, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Hyun S Ahn, Allen J Bard
Transition metal phosphides have been investigated heavily as hydrogen evolution reaction (HER) catalysts. One of the most active transition metal phosphides, CoP, has been tested for its stability and operability under mild conditions that it may be exposed to in its applications (photoelectrochemistry and artificial photosynthesis). Surface-interrogation scanning electrochemical microscopy (SI-SECM) revealed that CoP HER catalyst is vulnerable to oxidation (by oxygen and chemical oxidants). The degradation mechanism was shown to be surface oxidation by dioxygen, followed by acid etching of the oxidized layer...
July 20, 2017: Analytical Chemistry
Beibei Kou, Yaqin Chai, Yali Yuan, Ruo Yuan
The high catalytic efficiency of enzyme cascade reaction mainly depends on optimal interenzyme distance regulated by the special scaffolds. In this work, the rigid PtNPs with different sizes were employed as scaffolds to regulate interenzyme distance for efficient enzyme cascade amplification to construct electrochemical biosensor for sensitive detection of matrix metalloproteinases-2 (MMP-2), which overcame the drawbacks of instable construction and sophisticated preparation induced by conventional scaffolds such as metal-organic frameworks (MOFs), DNA nanostructures...
July 20, 2017: Analytical Chemistry
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