bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photoredox Catalyst Based on an Arylimidazole Oxidative Electrochemical Mediator
Authors: Lam Chiu Marco , Little R. Daniel 
Published: February 2020

Photocatalysis [1] and electrosynthesis [2] have been recognized as environmentally friendly methodologies for redox reactions, as they obviate the need for toxic or dangerous reagents. These approaches also allow for unstable reagents to be produced in situ, thereby permitting mild conditions. The reactive intermediates can be generated by the photoexcitation [1], or ionization of a mediator [2] at an electrode. The reagent can then perform redox chemistry with the substrate, and return to its original form to complete the catalytic cycle.
A class of oxidative electrochemical mediators based on the triarylimidazole framework has recently been investigated by Little, Zeng and Francke [2-5]. These mediators undergo one electron oxidation at the anode to form a radical cation that serves as an oxidative catalyst.
Recently, we have explored the potential of imidazole and phenanthroimidazole mediators to serve as photocatalysts. With an amine playing the role of a sacrificial reductant, the excited state serves as a reducing agent suitable for dehalogenation of aromatics, 5- and 6-exo,trig cyclizations of allyloxy and homoallyloxy iodo aromatics, as well as the photoredox equivalent of electrohydrocyclization [6].
Reference
[1] Tucker, J. W.; Stephenson, R. J. J. Org. Chem., 2012, 77, 1617-1622.
[2] Francke, R.; Little, R. D. Chem. Soc. Rev., 2014, 43, 2492-2521.
[3] Francke, R.; Little, R. D. J. Am. Chem. Soc., 2014, 136, 427-435.
[4] Zhang, N.-T.; Zeng, C.-C.; Lam, C. M.; Gbur, R. K.; Little, R. D. J. Org. Chem.

2013, 78, 2104–2110.
[5] Zeng, C.-C.; Zhang, N.-T.; Lam, C. M.; Little, R. D. Org. Lett., 2012, 14, 1314-1317.
[6a] Miranda, J. A.; Wade, C. J.; Little, R. D. J. Org. Chem. 2005, 70, 8017-8026.
[6b] Moëns, L.; Baizer, M. M.; Little, R. D. J. Org. Chem. 1986, 51, 4497-4498.
Electrochemical Behavior of Toluene in Adiponitrile
Authors: Cheek Graham T. 
Published: February 2020

Introduction
Previous studies from this laboratory have involved the characterization of adiponitrile (NCCH2CH2CH2CH2CN) / tetraethylammonium tetrafluoroborate (TEABF4) as a versatile solvent system for organic electrochemistry (1,2). One very valuable feature of this system is the wide potential limit range, as noted by others (3). Considering that the positive potential limit is +5 V vs Ag/AgCl, the system is particularly attractive for the study of hydrocarbon oxidation. The present paper is a continuation of the study of various hydrocarbons in adiponitrile (4).
Experimental
Adiponitrile was obtained from Sigma-Aldrich Corporation, and tetraethylammonium tetrafluoroborate (TEA BF4) was purchased from Southwestern Analytical Chemicals. Cyclic voltammograms were obtained on a PAR 283 potentiostat using PowerSuite software. Potentials are referenced against a Ag/AgCl reference electrode (1). Platinum and glassy carbon electrodes (1 mm diameter each) were obtained from eDAQ.
Results and Discussion
Cyclic voltammograms of 6.8 mM toluene in adiponitrile / 0.2 M TEABF4 are shown in the attached figure. An initial positive scan at platinum from 0.00 V produced a multicomponent, irreversible oxidation process between +2V and +3V vs Ag/AgCl, with considerable current on the second sweep (not shown). Results at glassy carbon were somewhat similar; however, there is little evidence of multiple oxidation processes. In addition, the lack of oxidation current on the second sweep at glassy carbon indicates that considerable electrode filming at glassy carbon is involved. Reported peak potentials in acetonitrile / NaClO4 are similar to the values observed in the present study (5). This study shows that adiponitrile / 0.2 M TEA BF4 is a useful solvent system for the electrochemical study of toluene.
References

G.T. Cheek, ECS Trans., 58(46), 45-51 (2014).

G.T. Cheek, ECS Trans., 61(30), 19-24 (2104).

H. Duncan, N. Salem, and Y. Abu-Lebdeh, J. Electrochem. Soc., 160(6) A838-A848 (2013).

G.T. Cheek, ECS Trans., 72(26), 1-5 (2016).

W.C. Neikam and M.M. Desmond, J. Am. Chem. Soc., 86, 4811-4814 (1964).

Figure 1. Cyclic voltammograms of 6.8 mM toluene in adiponitrile / 0.2 M TEA BF4 at 100 mV/s.
Black (solid) curve : Platinum ; Red (dotted) curve : Glassy carbon

Figure 1
Invited: Efficient Proton Transport in Rhodopsins Biohybrid Electrochemical Materials and Systems
Authors: Xiang Yan 
Published: February 2020

Efficient and directional proton transport is a very necessary energy conversion step whatever in biochemical process and artificial electrochemical energy systems. Microbial rhodopsins photosynthesis is an extremely simple but efficient natural light-driven proton pump energy conversion system. With advanced materials science and manufacturing engineering, the biohybrid nanosystems based on microbial rhodopsins and functional materials have been paid much attention.
In past five years, we devote ourselves on hybrid nanosystem through the integration of proton pump microbial rhodopsin, bacteriropoin(bR) and proteorhodopsin (pR), with functional materials for energy conversion, sensoring and artificial version studies. We focus on the artificial use of bR and pR photoelectric energy conversion through enhancing photocurrent density and enriching photocurrent waveform. Surface plasmonic effect of Au nanoparticles and proton conductor assisted 3D proton transfer have successfully improved bR and pR photocurrent, and greatly ameliorate the photoelectric performance [1, 2]. Inspired by the plasma membrane capacitor-like behavior, we developed a pR bio-capacitor system and regulated photocurrent duration time (PDT) through nanochannel resistance. Consequently, pR original transient photocurrent has been transformed into square-like waveform, which would be of broad use in further nanoenergy conversion [3, 4]. Taking advantage of pR pH-dependent photoelectric characteristics, a pR-hybrid pH sensor has achieved real-time pH detection with quick response and high sensitivity [5]. Recently, bR and pR frequency-responsive characterization was identified in the as prepared photoelectric system and further introduced to construct artificial vision [6]. Moreover, particular effort has been paid on the cooperation and adjustment between bio-components and functional materials. These original findings improve the perception on rhodopsin protein and provide mechanism insights from pure biophysical studies into the design and regulation of artificial biohybrid devices.
References:
1. Z. Guo, D. Liang, S. Rao and Y. Xiang, Nano Energy, 2015, 11, 654-661.
2. S. Rao, Z. Guo, D. Liang, D. Chen and Y. Xiang. Advanced Materials, 2015. 27(16): 2668
3. S. Rao, S. Lu, Z. Guo, Y. Li, D. Chen and Y. Xiang, Advanced Materials, 2014, 26, 5846-5850.
4. S. Rao, K. J. Si, L. W. Yap, Y. Xiang, and W. Cheng, ACS Nano, 2015, 9 (11), 11218– 11224
5. S. Rao, Z. Guo, D. Liang, D. Chen, Y. Wei and Y. Xiang, Physical Chemistry Chemical Physics, 2013, 15, 15821-15824.
6. S. Lu, Z. Guo, Y. Xiang, L. Jiang, Advanced Materials, DOI: 10.1002/adma.201603809
Real-Time Monitoring of NADPH Oxidase Inhibitory Effect of ROS Production from THP-1 Cells Using Iron-Porphyrin Modified Carbon Electrode
Authors: Kasai Shigenobu , Prasad A. , Matsuoka R. , Takahashi A. , Nakagawa Atsushi , Sugiura Yamato , Koriyama Hiroki , Aoyagi S. , Aikawa T. , Kondo T. , Yuasa M. 
Published: February 2020

Immune cells such as monocytes and neutrophils responds to external stimuli and during the invasion by foreign body undergoes phagocytosis during which reactive oxygen species (ROS) such as superoxide anion radical (O2
•−), hydrogen peroxide (H2O2) and hydroxyl radical (•OH) are produced. The iron-porphyrin modified carbon electrode is prepared by the electropolymerization of 1-methylimidazole-coordinated iron meso-tetra (3-thienyl) porphyrin ([Fe(im)2(ttp)]Br) [1].
The detection of O2
•− is based on amperometry comprising of counter electrode and working electrodes. The counter electrode is a platinum plate (2.5×2.5mm) while the working electrodes (φ1mm) is an iron-porphyrin modified carbon electrode. Ag/AgCl was used as a reference electrode. The iron-porphyrin modified carbon electrode acts as O2
•−detection sensor (Fig. 1).
The O2
•− generation was measured in THP-1 cells (cell lines of myeloid leukemia patients) under the effect of differentiation inducer phorbol 12-myristate 13-acetate (PMA) in the absence and presence of exogenous addition 0.1 wt% Triton X at 25°C at a cell density of 3.0 × 106 cells/well. Triton X is known to permeabilize the membranes of living cells. The results obtained showed no considerable changes in reduction currents for O2
•− under the effect of inducer (PMA). However, the addition of Triton-X showed a fast increase in oxidation current for O2
•− by about approximately 2 nA followed by a gradual drop which continued for a time span of more than 3 hours. We further investigated the effects of inhibitors for the activity of NADPH oxidase that catalytically produce ROS; apocynin were selected as inhibitors of NADPH oxidase [2].
The production of O2
•−of real-time monitoring of NADPH oxidase inhibitory effect of PMA induced THP-1 cells using iron-porphyrin modified carbon electrode were detected by amperometory. The results shown in Fig.2 suggests that amperometory is mainly derived from the O2
•−,whose expression is induced by NADPH oxidase.
[1] M. Yuasa et al. Polym. Adv. Technol. 16 (2005)287–292.
[2] S.Kasai et al. Analytica Chimica Acta 549 (2005)14-19.

Figure 1
Selective Nanomaterials for Glucose-to-Gluconate Oxidation in an Electrochemical Energy Converter: Cogenerating Organic Electrosynthesis
Authors: Holade Yaovi , Servat Karine , Napporn Teko W. , Kokoh Kouakou Boniface 
Published: February 2020

Glucose is an environmentally friendly and sustainable carbohydrate that is actually a cyclized aldehyde in aqueous solution i.e. a hemiacetal. Its selective oxidation by the anomeric carbon in C1-position without any function protection is of great interest for cogeneration because the electrochemical process enables converting this highly functionalized organic molecule into electricity, heat and added-value chemicals. For this objective, we decided to synthesize effective nanomaterials towards glucose conversion at the anode and the oxygen reduction reaction (ORR) in the cathodic side of a fuel cell. The physical characterizations of the prepared materials and their electrochemical analysis at each half-cell, permitted to optimize the activity of the electrodes according to their elemental composition and structure. Furthermore, a constructed direct glucose fuel cell (DGFC) delivered an open-circuit voltage of 1.1 V in 0.5 mol L‒1 NaOH and an outstanding output power of 2 mW cm‒2 in 0.5 M KOH (Figure 1a). Complementary analytical techniques were employed to quantify the reaction processes involved in each compartment, to determine the reaction products resulted from the glucose transformation and thereby, to understand reaction mechanisms of the glucose oxidation and the ORR over the synthesized electrode materials used in alkaline medium. As results, the identification of gluconate as the sole reaction product in the anodic side showed a selective 2-electron conversion of glucose (Figure 1b), while the ORR proceeded through a 4-electron pathway over the designed cathode catalyst (Figure 1c).

Figure 1: (a) Fuel cell polarization curves for different concentrations of glucose in a single fuel cell. Anode: 20 wt.% Au/C (0.18 mgAu cm‒2); cathode 20 wt.% Pt/C (0.17 mgPt cm‒2); Fumatech AEM. Anode: 0.5 mol L‒1 KOH + glucose (deoxygenated by N2); cathode: 0.5 mol L‒1 KOH + O2. (b) LC–MS negative ionization mass spectrum (M-1) of the product. (c) Electrochemical durability tests: Comparison of the ORR polarization curves (at 5 mV s−1) before (black) and after 1000 CVs (red); insets show the normalized specific electrochemical active surface area (SECSA) decay over the 1000 cycles from 0.05 to 1.1 V vs. RHE at 50 mV s−1.

Acknowledgments

The authors gratefully acknowledge financial support from the French National Research Agency ANR-ChemBio-Energy

References

1. Y. Holade et al., ChemSusChem, 9, 252 (2016).

Figure 1
Electrochemical Imaging of Copper Contamination on Self-Assembled Organic Monolayer Modified Silicon Surfaces Following a ‘Click’ Reaction with Light-Addressable Potentiometric Sensors and Scanning Photo-Induced Impedance Microscopy
Authors: Wu Fan , Watkinson Michael , Krause Steffi 
Published: February 2020

Light-addressable potentiometric sensors (LAPS)1 and scanning photo-induced impedance microscopy (SPIM)2, both of which are based on photocurrent measurements at electrolyte /insulator /semiconductor (EIS) field-effect structures can be used to detect local surface electrical potentials and impedance, respectively. While LAPS measures local potential changes by recording the shift of the photocurrent-voltage (I-V) curve along the voltage axis, SPIM records changes in the maximum photocurrent while the EIS structure is biased towards inversion. Both techniques have been extensively applied for chemical ion sensing, biosensing, and the investigation of cell metabolism, extracellular potentials, cell surface charge and impedance. Importantly, they have been reported to be highly sensitive to the surface contamination on self-assembled organic monolayers3.
In this work, a copper (I) catalyzed azide alkyne cycloaddition (CuAAC) reaction, combined with microcontact printing was employed successfully to pattern alkyne-terminated self-assembled organic monolayer modified silicon surfaces (Figure 1a). Despite the absence of a copper peak in XPS spectra, copper contamination was found and visualized using LAPS and SPIM, after the ‘click’ modified silicon surfaces were rinsed with hydrochloric acid solution (Figure 1b), which has been frequently used to remove copper residues in the past. Different strategies for avoiding copper contamination, including the use of bulky chelators for the copper (I) catalyst and rinsing with different reagents, were tested. Only cleaning of the silicon surfaces with an ethylenediaminetetraacetic acid (EDTA) solution after the ‘click’ modification proved to be an effective method as confirmed by LAPS and SPIM results, which showed the desirable electrical properties (surface charge and impedance) of an organic monolayer (Figure 1c).
1. Hafeman, D. G.; Parce, J. W.; McConnell, H. M., LIGHT-ADDRESSABLE POTENTIOMETRIC SENSOR FOR BIOCHEMICAL SYSTEMS. Science
1988,240, (4856), 1182-1185.
2. Krause, S.; Talabani, H.; Xu, M.; Moritz, W.; Griffiths, J., Scanning photo-induced impedance microscopy - an impedance based imaging technique. Electrochim. Acta
2002,47, (13-14), 2143-2148.
3. Wang, J.; Wu, F.; Watkinson, M.; Zhu, J. Y.; Krause, S., "Click" Patterning of Self-Assembled Monolayers on Hydrogen-Terminated Silicon Surfaces and Their Characterization Using Light-Addressable Potentiometric Sensors. Langmuir
2015, 31, (35), 9646-9654.

Figure 1
Measurement of Thickness of High-Resistivity Substrate By Photoconduction Enhanced Capacitance Displacement Sensor
Authors: Lee T. -H. , Lin M. -C. 
Published: February 2020

Capacitive displacement sensors can offer non-contact, extreme resolution, and absolute accuracy thickness measurements. However, for general capacitive displacenent sensors, if the resistivity of a target substrate is within 105-107 ohm-cm, a measurement uncertainty will occur in the thickness measurement. The measnurement uncentration may be several microon meters. The common solution is to adjust the resistivity to be outside the range that causes the measurement uncertainty by implanting dopants and followed by an activation anneal, but this will unavoidably lead to changes in the material properties and morphology. Here, we exploit the photoconductive effect to generate sufficient high amount of electron-hole pairs, thereby temporarily decreasing the resistivity and thus enabling the capacitive displacement sensor to accurately measure the thickness at nanoscale resolution. After the measurement is complete, the resistivity of the substrate will return to its original status. The photoconductive effect can be simply induced via laser irradiation at the sensing point, which narrows or eliminates the gap in the measurement range of capacitive sensors to include high-resistivity substrates.
Electrooxidation of Hexacyanoferrate(II) Anions in the Microfabricated Electrochemical Sensor-Array System
Authors: Pitman Kätlin , Nerut Jaak , Lust Enn , Raud Merlin , Kikas Timo , Franssila Sami 
Published: February 2020

The field of application of micro-electrodes is very wide: from electroanalytical applications (detection of ultra-low quantities of analyte, biosensors, etc.), kinetic studies of very fast and complex reactions, to measurements in solutions of very low conductivity, etc.1-3 Often several micro-electrodes are combined into sensor-arrays for simultaneous analysis of various parameters.
In this work the microfabrication technique was used to prepare a six-channel sensor-array chip.4 The sensor-array has been fabricated of borosilicate wafer containing Pt electrodes and connection pads and the silicon wafer with through holes, which were bonded using adhesion bonding method with SU-8. Although the fabrication process of two wafers is simple, the extensively perforated silicon wafer is brittle and can break down during bonding step. However, with the customized bonding process, a good bonding was achieved and all the chips were applicable after dicing.
The cyclic voltammetry and electrochemical impedance experiments were carried out in a three-electrode electrochemical system to characterize the prepared sensor-array chips. Sputtered platinum was used for micro-electrodes, and Ag/AgCl/sat. KCl as a reference electrode. The high surface area Pt counter electrode has been used for studies.
It was shown that the measured current density depends on the electrode potential sweep rate, however both linear and radial diffusion mass transfer components are important at high electrode potential scanning rate. When using slow potential sweep rates (v = 0.005 V s‒1) the pseudo steady-state has been achieved and the electrodes behaved as the micro-electrodes. It was shown that the pseudo steady-state current density depends linearly on the concentration of potassium hexacyanoferrate(II) in the 1.0 M KCl aqueous solution.
Based on the electrochemical characterization data it can be concluded that the produced sensor array is suitable for future research including BOD biosensor-array construction. The sensor-array developed can be modified with microorganisms by immobilizing the bacteria into the cavities fabricated onto/into the chip.

Acknowledgements

This research was supported by the EU through the European Regional Development Fund (Centre of Excellence, 2014-2020.4.01.15-0011), Institutional Research Grant IUT20-13, and Estonian Science Foundation (Grant ETF 9136).

References

1. J. Heinze, Angew.
Chem. Int. Ed. Engl., 32, 1268 (1993).

2. A.M. Bond, Analyst, 119, 1R (1994).

3. A. J. Bard and L. R. Faulkner, Electrochemical methods: fundamentals and applications, John Wiley & Sons Inc., New York (1980).

4. K. Pitman, M. Raud, G. Scotti, V.P. Jokinen, S. Franssila, J. Nerut, E. Lust, and T. Kikas, Electroanalysis (2016). Published online (DOI: 10.1002/elan.201600559).
Autonomous Silicate Electrochemical Sensor in Seawater
Authors: Chen Legrand Dancheng , Barus Carole , Striebig Nicolas , Garcon Véronique 
Published: February 2020

Long term monitoring of dissolved inorganic nutrient concentrations such as silicate is the key to improve our understanding of biogeochemical cycles in the ocean. Electrochemical methods are proposed to measure in situ silicate concentration as they allow to develop miniaturized, reagentless sensor. We report here on the development and the optimization of the in situversion of our silicate sensor.
Silicate is a non-electroactive specie and its determination is performed by measuring its corresponding silicomolybdic complex formed in situ at acidic pH after the oxidation of a molybdenum electrode while the counter electrode is isolated behind a Nafion® membrane [1].
The mechanical design of the sensor has been adapted from the laboratory prototype containing two connected cells: one for the complexation and one for the detection on a gold electrode (Æ=2mm) by cyclic voltammetry. All the electrochemical and chemical parameters, such as the Mo oxidation, the complexation time, the silicomolybdic complex detection as well as the complex transfer from one cell to the other and the cleaning protocol have been optimized to detect the smallest silicate concentration possible with the shortest time. Reproducible calibrations performed with this sensor provided linear regressions between 2.5 µmol L-1 and 70 µmol L-1 and a limit of detection of 1 µmol L-1.
The 1st version of the sensor has been validated so far down to 50 meters using a pressure column and deployed in the Kiel fjord (Baltic Sea, Germany) down to 25 meters. The electronics (including datalogger) was also validated in situ as well as the solenoid pump placed into an equi-pressure compartment filled with dielectric oil. Some mechanical improvements have been done and the 2ndversion of the silicate sensor is currently in fabrication. This new version will be deployed off Chile (South of Coquimbo) in April 2017 and results obtained will be discussed.
[1] Lacombe et al., Talanta 77 (2008) 744-750.
Sensitive Double-Layer Coil Detector for the Detection of Salmonella Typhimurium Using Magnetoelastic Biosensors
Authors: Liu Yuzhe , Du Songtao , Horikawa Shin , Chai Yating , Wikle Howard Clyde , Suh Sang-Jin , Chin Bryan Allen 
Published: February 2020

The design, simulation, fabrication, and characterization of a highly sensitive double-layer coil detector, utilized with magnetoelastic (ME) biosensors to detect bacterial pathogens, is presented in this paper. The former coil detector was a single-layer coil employed to realize wireless Salmonella detection on various food surfaces, while the double-layer coil in this work has enhancement in sensor excitation and detection sensitivity. With the double-layer coil, not only the wireless detection distance can be further, but also a smaller ME biosensor can be used in the detection to provide higher mass sensitivity. Various coil design parameters, including the thickness of layers, width, height, and spacing of coil turns, were studied. Both theoretical calculations and experimental data showed that the above parameters have a significant impact on the signal amplitude and stand-off distance. Finally, with the newly fabricated double-layer coil detector, detection of Salmonella Typhimurium using multiple biosensors on a food grade Ultra-high-molecular-weight polyethylene (UHMW-PE) board surface was demonstrated. This double-layer coil detector, therefore, facilitates the detection of pathogens on food and food contact surfaces.