bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chemiresistive and Switching Characteristic with Reduced Graphene Oxide Biosensor Fabricated Using Antibody-Antigen Binding System
Authors: Kim Yo-Han , Jung Hunsang , Lee Hyun Ho 
Published: February 2020

Bistable resistive switching within graphene-oxide (GO)-based memory devices have been recently developed by many research groups. Its switching mechanism was frequently explained by the formation and rupture of conducting filaments induced by the diffusion of metal or oxygen ions.1 Meanwhile, significant applications in biosensors have been continuously reported with the graphene or GO devices. Very recently, a stress hormone, cortisol, is being increasingly focused on in psychobiological stress research. For this end, salivary cortisol is a major correlator of the neuroendocrine stress response and has been increasingly studied as a stress biomarker.
In this study, we demonstrated reduced graphene oxide (rGO) biosensor structure for cortisol sensing with chemiresistive and its switching system.2 The device structure was stepwise self-assembly monolayers (SAMs) stacked by reduced graphene oxide between indium tin oxide (ITO) two electrodes. The GO`s surface was anchored with cortisol monoclonal antibody (C-mab) as probe molecules.
For the cortisol detections, the device, the current versus voltage (I-V) curve was examined by chemiresistive current and switching characteristics, which demonstrated the possibility of sensing mechanism. For the cortisol detection purpose, a microfluidic system was constructed on the GO chemiresistive sensor. Therefore, this research establishes the feasibility of chemiresistive real-time detection device for biosensor applications.
References

S.K. Kim, J.Y. Kim, S.Y. Choi, J.Y. Lee and H. Y. Jeong, Advanced Functional Materials, 25, 6710-6715 (2015)

Yusuke Tahare, Zhe Huang, Tesuro Kritoshi, Takeshi Onodera and Kiyoshi Toko, Bioengineering and Biotechnology, 2, 15, 1-6 (2014)

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Expanded Scope of Methodology and Polymer Functionality for Photoredox-Mediated Ring-Opening Metathesis Polymerization
Authors: Pascual Laura M M , Goetz Adam E , Dunford Damian G , Ogawa Kelli A , Ashikari Yosuke , Boydston Andrew J 
Published: February 2020

Photoredox-mediated ring-opening metathesis polymerization (Photo-ROMP) is an emerging polymerization method. In contrast to traditional ROMP, which uses a well-defined metal initiator (typically Ru, W, or Mo) that covalently bonds in stoichiometric amounts with each polymer chain end, Photo-ROMP utilizes a photo-oxidant to oxidize an organic polymerization initiator. This obviates the need for purification processes to remove the metal initiator for use of the resulting polymer in biomedical, electronics, and optics applications. We have recently studied the efficacy of a variety of photo-oxidants and expanded the monomer scope to include polar functionality. In an evaluation of pyrylium and thiopyrylium photo-oxidants, more electron-rich photo-oxidants (weaker photo-oxidants) achieved higher conversion to polynorbornene. Additionally, thiopyrylium photo-oxidants displayed higher rates of conversion than similarly functionalized pyryliums. While our previous studies identified 2,4,6-tris(4-methoxyphenyl)pyrylium tetrafluoroborate as an effective photo-oxidant for Photo-ROMP, in our recent evaluation of additional pyryliums and thiopyryliums, the correspondingly functionalized thiopyrylium emerged as a successful alternative for achieving rapid polymerization. In addition to evaluating various pyrylium and thiopyrylium photo-oxidants, we recently identified a variety of monomers and co-monomers with polar functionality for Photo-ROMP. Our previous studies identified norbornene, dicyclopentadiene, and dihydrodicyclopentadiene as effective monomers for Photo-ROMP. Recently, we've identified several new monomers. Remarkably, a TBS-ether-funtioncalized norbornene was co-polymerized with norbornene and homopolymerized in good yields. The resulting polymer was successfully deprotected to give the corresponding alcohol-functionalized polynorbornene. Additionally, a Boc-functionalized copolymer with norbornene was successfully synthesized and the Boc groups subsequently thermally removed. Interestingly, while 2-chloro-2,3-dihydro-endo-dicylopentadiene was precluded from copolymerization with norbornene due to slow initiation kinetics, it did successfully homopolymerize via Photo-ROMP to give the resulting homopolymer in moderate yields. These functionalized monomers could facilitate post-polymerization modification. In addition to these recent developments in expanding the methods and scope of Photo-ROMP, ongoing work in evaluating alternative photo-oxidants and monomers will also be discussed in this presentation.
Cyclic Voltammetry Studies of a Redox-Responsive 4 H-Bond Ureidopyrimidinone Alkyl-Pyridinium Capable of Self-Dimerization
Authors: Darzi Ghazwan M , Smith Diane K. 
Published: February 2020

The design of stimuli-responsive systems in which supramolecular structure changes in response to external signals, such as the change in voltage of an electrode, is important for many applications, for example, self-healing polymers and gels, triggered release of entrapped molecules for drug delivery, and “smart” materials. In this study, a four H-bond ureidopyrimidinone (UPy) array with an alkyl-pyridinium, (RP), redox center has been synthesized, UPy(RP), shown below. This array prefers the tautomer that presents an ADAD H-bond motif in the starting oxidation state. Due to electrostatic repulsions and unfavorable secondary H-bond interactions, this motif would form a dimer with relatively weak H-bonding. Upon 2e- reduction, where 1e-is gained per R-pyridinium redox center, the H-bond strength should increase due to the loss of the repulsive charges, making the nitrogen a stronger hydrogen acceptor. Because the nitrogen is now a better hydrogen acceptor, there could be a possibility of an intermolecular proton transfer. This would encourage the tautomer to have an AADD motif that will make the H-bonding stronger by increasing the favorable secondary H-bond interactions.
UPy dimers can exist in two tautomeric forms called pyrimidinol and pyrimidinone. In order to more efficiently study the electrochemistry of the two forms, two compounds, 4-acetylpyridinium (AcP) and N-methyl-4,4’-bipyridinium (MeV+), were used as model compounds. AcP resembles the pyrimidinone tautomer and MeV+ resembles the pyrimidinol tautomer. The cyclic voltammetry (CV) scans for the two model compounds in CH2Cl2 and CH3CN show two widely spaced, reversible redox waves. UPy(RP) is insoluble in CH2Cl2, but soluble in CH3CN. The concentration dependent NMR spectra suggest that UPy(RP) is a monomer in acetonitrile. The CV’s of UPy(RP) in CH3CN show three reductions. The first occurs at a potential very similar to that seen with simple model compounds. The second is considerably positive of that observed for the model compounds and the third is very close to the second reduction peak of the model compounds. The first reduction is reversible if the scan direction is switched immediately after the peak, but irreversible if the scan direction is switched after the second reduction peak. As the scan rate increases, the second and the third reduction peaks disappear and a new peak emerges in between. Going through the second and third reductions also leads to the appearance of new oxidation waves at more positive potentials. DFT calculations suggest the preferred tautomer changes upon reduction, and this may explain the unexpected voltammetry observed in acetonitrile where the compound is not dimerized. Further studies to help elucidate what is actually happening in this system will include using a new counter anion in the electrolyte to help the solubility of the compound in CH2Cl2.

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Electrocatalytic Generation of Amidyl Radicals for N-Heterocyle Synthesis
Authors: Xu Hai-Chao 
Published: February 2020

Nitrogen-centered radicals are versatile intermediates for the construction of N-heterocycles. Unfortunately, their use in synthesis is limited due to the difficulty associated with their preparation. We have developed electrocatalytic methods for the generation of amidyl radicals from stable and easily available N-H amides1. Application of these reactive intermediates in synthesis leads to the efficient and chemoselective construction of several classes of N-heterocycles including cyclic carbamates and ureas, indoles, imidazopyridines, and benzothiazoles.
References:
1. Zhu, L.; Xiong, P.; Mao, Z. Y.; Wang, Y. H.; Yan, X.; Lu, X.; Xu, H.-C. Angew. Chem. Int. Ed. 2016, 55, 2226.

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New Family of High-Efficieincy Oxygen Evolution Electrocatalyst Based on Ni-Fe Mixed Chalcogenides
Authors: Swesi Abdurazag T , Masud Jahangir , Nath Manashi 
Published: February 2020

Over the last several decades water oxidation has been investigated in pursuit of clean, sustainable and efficient energy conversion and a substitute for fossil fuels. During water oxidation, oxygen evolution reaction (OER) plays a critical role in the advancement of renewable energy technologies like metal-air batteries or solar-to-fuel energy production. However, OER involving a complex 4 electron process, has several steps that have large reaction barriers, which lead to large required overpotentials.1 Recently we have observed that the family of Ni-chalcogenides can function as more-efficient, stable, earth-abundant electrocatalysts for the OER reaction in alkaline medium with low overpotential thus enhancing the energy conversion efficiency.1 Interestingly, Ni is always found in combination with iron (Fe) on earth and Fe impurities in the nickel hydroxide (Ni(OH)2) electrodes can cause destructive effects on Ni-based alkaline batteries by greatly lowering the OER overpotential.3 This phenomenon inspired us to investigate the influence of Fe content and synthesizing a NiFe-composite compounds in order to obtain better OER electrocatalysts. Here we report, for the first time, a nickel−iron selenide (Ni1-xFexSey) thin film with high OER catalytic activity and stability.
The electrocatalysts NixFe1-xSey were grown by electrodeposition on conducting substrates and detailed electrochemical studies with stationary as well as rotating disc electrodes were performed to investigate the catalytic efficiencies. The deposition parameters including pH of the electrolytic bath, deposition potential were seen to have some influence on the catalytic activity. In some compositions these transition metal mixed chalcogenides even outperform the noble metal and oxide based catalysts like IrO2, RuOx and NiOx. Our studies indicate that the overpotential for producing 10 mA/cm2 current density under oxygen evolution conditions can be achieved to be as low as 210 mV by optimizing the ternary composition of the selenide films and tuning the structural details. In addition to low overpotentials, these NixFe1-xSey electrodeposited films were seen to be exceptionally stable under conditions of continuous O2 evolution for extended period (>24 h). We will present a systematic study of investigating the OER catalytic efficiencies of the ternary chalcogenides, Ni­1-xFexSey and their detailed characterization with powder X-ray diffraction, scanning and transmission electron microscopy, Raman, and X-ray photoelectron spectroscopy.
References:
1. E. Mirzakulova, R. Khatmullin, J. Walpita, T. Corrigan, N. M. Vargas-Barbosa, S. Vyas, S. Oottikkal, S. F. Manzer, C. M. Hadad, and K. D. Glusac, Nature Chem. 2012, 4, 794.
2 McCrory, C. C. L.; Jung, S. H.; Peters, J. C.; Jaramillo, T. F. J. Am. Chem. Soc. 2013, 135, 16977.
3. Munshi, M. Z. A.; Tseung, A. C. C.; Parker, J. J. Appl. Electrochem
. 1985, 15, 711.
Lipophilic Redox Buffers for Polymeric Solid-Contact Electrodes
Authors: Buhlmann Philippe , Zou Xu U. , Zhen Xue V , Hu Jinbo , Stein Andreas 
Published: February 2020

A calibration-free measurement with an ion-selective membrane requires that only the phase boundary potential at the sample/sensing membrane interface is variable, i.e., either dependent on the activity of the target ion in the sample, as in a potentiometric experiment, or determined by an applied potential, as in a voltammetric experiment. All the other phase boundary potentials in the electrochemical cell are constant. Unfortunately, one of the biggest challenges in the fabrication of devices comprising solid-contact membranes has been to establish a reproducible phase boundary potential at the interface of the hydrophobic ion-selective membrane and the underlying electron conductor. This talk will address our use of ion-selective membranes doped with lipophilic redox buffers, both in view of potentiometry and voltammetry.
Solid contact ion-selective electrodes (ISEs) typically have an intermediate layer between the ion-selective membrane and the underlying solid electron conductor that reduces the irreproducibility and instability of the measured electromotive force (emf). Nevertheless, the electrode-to-electrode reproducibility of the emf of current solid-contact electrodes in a zero-current measurement is widely considered to be unsatisfactory. To address this problem, we reported on lipophilic redox buffers consisting of the Co(III) and Co(II) complexes with hydrophobic ligands such as 1,10-phenanthroline (e.g., [Co(phen)3]3+/2+) paired with tetrakis(pentafluorophenyl)borate as counterion [1,2]. The resulting electrodes exhibit zero-current emf values with an electrode-to-electrode standard deviation as low as 1.7 mV after conditioning of freshly prepared electrodes for 1 h. While many prior examples of solid contact ISEs also used intermediate layers that contained redox-active species, the importance of selecting a balanced ratio of the reduced and oxidized species has typically been difficult and was often ignored, contributing to emf irreproducibility. The ease of the control of the [Co(phen)3]3+ / [Co(phen)3]2+ ratio explains the high emf reproducibility, as confirmed by the emf decrease of 58 mV per tenfold increase in the ratio of the reduced and oxidized redox buffer species. The result is an electrode-to-electrode standard deviation of Eº of 0.7 mV after 1 week of exposure to KCl solution. The use of this redox buffer in combination with colloid-imprinted mesoporous carbon [3,4] will also be discussed.
[1] Zou, X. U.; Cheong, J. H.; Taitt, B. J.; Bühlmann, P., Anal. Chem.
2013, 85, 9350–9355.
[2] Zou, X. U.; Zhen, X. V.; Cheong, J. H.; Bühlmann, P. Anal. Chem.,
2014, 86, 8687–8692.
[3] Hu, J.; Ho, K. T.; Zou, X. U.; Smyrl, W. H.; Stein, A.; Bühlmann, P. Anal. Chem.,
2015, 87, 2981–2987
[4] Hu, J.; Stein, A.; Bühlmann, P. Angew. Chem. Int. Ed., in press (DOI: 10.1002/anie.201603017).
Photoelectrochemical Evaluation of Single Nanoparticles
Authors: Tkacz Kevin , Sanborn Christopher D. , Ardo Shane 
Published: February 2020

Mechanisms of nanoparticle photocatalysis are not well understood. Like state-of-the-art photovoltaics, photocatalysis particles absorb light, separate charge, and generate photovoltages and photocurrents. However, unlike state-of-the-art photovoltaics, these photovoltaic parameters have never before been measured on single (to few) nanoparticles wetted by electrolyte. Prior work using scanning Kelvin probe force microscopy on dry mesoporous films has shown that photovoltages result from optical excitation but less is known about the behavior of particles wetted by liquid electrolyte on both sides.
Herein, using bipolar electrochemistry we report photovoltage responses from single (to few) photocatalyst nanoparticles jammed in a conical nanopore. The nanopore was etched in poly(ethylene terephthalate) or Kapton polyimide. Electrophoretic (or chemical) deposition jammed (or covalently linked) TiO2 nanoparticles into the nanopore therefore occluding ionic migration between the anolyte and catholyte. The circuit was completed when two redox reactions were driven on opposite poles of the nanoparticle to facilitate charge migration across the cell. Solar photocurrent was too small to be measured precisely using electrochemistry. However, motivated by work from the single molecule fluorescence community, single-particle open-circuit photovoltage measurements were taken every 200 ns. This timescale is important because it is on the order of the RC time constant to charge all interfaces yet slower than charge recombination.
Generally, less than 1 mV photovoltage responses were observed under illumination. This value was consistent with a hypothesis of double-layer charging or charging of a parallel plate capacitor with a TiO2 dielectric. The magnitude of this value also suggested that the full potential of the energized electron was not being sensed. We learned that using bipolar electrochemistry we cannot measure the majority of the photon energy transiently stored as the electron–hole pair. This is because the chemical potential change in electrons and holes is not sensed by the reference electrodes used in the studies.
Future efforts aimed at measuring the photoelectrochemical properties of single (to few) particles will be important. With this information, we hope to clarify the fundamental cause of photovoltaic action so that future nanoparticle materials properties can be rationally designed.
Profiling Carrier Generation in Semiconductor Microwire Arrays Via Photoelectrochemical Metal Deposition
Authors: Dasog Mita , Carim Azhar I , Yalamanchili Sisir , Atwater Harry A , Lewis Nathan S 
Published: February 2020

Semiconductor microwire arrays are promising next-generation solar absorption materials as their geometry enables decoupling of the direction of the light absorption and charge-carrier collection. The high aspect ratio of microwire arrays provides high surface area for catalyst placement to perform photo-electrochemical reactions. Since the light scattering and absorption dynamics of semiconductor microwire arrays are complex, it is important to place the catalyst in optimal place to enhance the device efficiency. Furthermore, precise catalyst placement allows for reduced wastage of the catalyst material. In order to understand the absorption of light in such semiconductor architectures, gold was photoelectrochemically deposited onto p-Si microwires on Si substrates to profile the photoinduced charge-carrier generation in individual wires in a photoactive semiconductor wire array. Along with the charge-carrier generation as a function of the incident light wavelength, influence of other factors such as microwire pitch, shape of the wires, and wire diameter was also investigated.
Study of the Ammonia Oxidation Mechanism By a Normal Pusle Voltammetry
Authors: Shirasaka Ryo , Shiroishi Hidenobu , Harada Yuya , Nishitani-Gamo Mikka , Nagai Keiji 
Published: February 2020

Although ammonia is expected as the next generation of energy medium, even platinum, which is a relatively active ammonia oxidation (AO) catalyst, have an insufficient performance for direct ammonia fuel cells (DAmFCs) operating below 100°C. Highly active AO catalysts at low temperatures needs to be developed in order to use ammonia as a fuel for DAmFCs. AO mechanism on platinum is reported as follows: After NH3 is adsorbed on the platinum surface, the AO proceeds via two competitive paths. One is the formation of hydrazine analogues, followed by the oxidation of the analogues to release N2 molecules. The other is the oxidation of an ammonia molecule to form nitrogen atoms adsorbed onto the surface of platinum (Nads) known as poisoning species. However, after the surface of the platinum is covered with Nads, the elimination process of Nads is not known. In this study, the elimination process was studied by a normal pulse voltammetry.
33.6 wt% Pt/MWCNT (average particle size: 5.57 ± 0.11 nm) catalyst was synthesized by a microwave polyol method. A 2 mg of Pt/MWCNT was suspended in 1 mL of Pt/MWCNT-0.1 wt% Nafion-MeOH by ultrasonication for 10 min. 10 μL of the suspension was cast onto a glassy carbon (GC) disk electrode (6 mm φ), followed by drying for 1 h in air. Electrochemical measurements were performed with a conventional three electrode system equipped with the modified GC electrode, an Au wire counter electrode and a reversible hydrogen electrode (RHE) in 0.1 M KOH or 0.1 M NH3-0.1 M KOH. The normal pulse voltammetry was performed as follows: After the Nads was formed by applying 0.6 V for 180 s, E
recover (V) was applied for various times (1 s，5 s，10 s，20 s，60 s, and 180 s) to eliminate Nads. Then, the AO current at 0.6 V after 1 s was used as an indicator for the amount of Nads poisoning.
Fig. 1 shows the dependence of AO current at 0.6 V after 1 s on recovery potential. The AO current gradually recovered by maintaining the potential below 0.4 V vs. RHE, indicating that the adsorbed N atoms were eliminated from the catalyst surface. It took a few minutes to recover the AO current. In addition, the decrease in potential accelerated the recovery of the AO current, especially below 0.3 V vs. RHE. The final percentage of the recovery increased with a decrease in the potential. The recovery rates below 0.25 V called hydrogen adsorption/desorption region increased with decreasing potential, probably due to the reduction of Nads. The time dependence of the recovery rate was analyzed by the sum of two exponentials, suggesting that the fast and slow reactions exists in the recovery process.

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Mediated and Direct Electrocatalytic Oxidation of Glucose and Cellulose: Towards Glucose and Cellulosic Air Batteries
Authors: Aldous Leigh , Abdulkhaliq Habib 
Published: February 2020

The electrochemical oxidation of glucose has been widely explored, primarily for analytical purposes. The combustion of glucose is also well established to occur. By combining an electrocatalyst for glucose oxidation, as well as an oxygen reduction electrocatalyst, it is possible to assemble air-batteries or fuel cells that can (non-enzymatically) harvest useful electrical energy from glucose. Cellulose is the most abundant biopolymer in the world, is a non-food crop waste material, and is made up on glucose sub-units. By studying the electrocatalytic oxidation of glucose, it is possible to develop electrochemical devices that could use cellulose (and by extension, waste lignocellulosic biomass) as a fuel. All that is required is a suitable electrolyte that can dissolve cellulose (and lignocellulosic biomass). Ionic liquids and certain aqueous hydroxides fulfil these criteria.
We have been investigating the oxidation of glucose and cellulose, and developing genuine air-batteries that can exploit these materials. Focus has been upon (i) the electrolyte, which is critical in both solubilising the fuel, and in impacting electrocatalytic trends, (ii) dissolved molecules which can act as facile solution-phase electrocatalytic mediators for the oxidation processes, and (iii) nanostructured electrodes such as nanoporous gold, which can act as electrocatalytic electrodes for the direct oxidation of glucose and cellulose. In particular, it has been ensured that the electrolyte assists in the electrocatalytic processes and encourages depolymerisation of cellulose into glucose, ensuring high power electrochemical devices can be developed. Our progress in this area will be summarised.
(Invited) Quantifying the Impact of Ionic Liquid Cations on the Properties of Cellulose Nanocrystals
Authors: Gilman Jeffrey W. , Woodcock Jeremiah , Fox Douglas M 
Published: February 2020

Ionic liquids have you been used to modify the properties of many classes of materials. This includes their use as solvents and catalysts in simple chemical reactions. However, they have also been used to improve the synthesis and processing of materials as well. This presentation will review our efforts to utilize ionic liquids to enable the processing and enhance the properties of polymer composites. Specifically, we will cover composites based on multiwalled-carbon-nanotube (MWCNT), Montmorillonite (MMT) and cellulose nanocrystals (CNC). Novel measurement methods, used to characterize the impact of ionic liquids on the material properties of polymers, nanoparticles and polymer nanocomposites, such as fluorescence life-time imaging and inverse gas chromatography (iGC) will also be presented.

Figure 1