bluuebunny/crossref_metadata_2025 huggingface dataset:
Photoelectrosynthesis of 2,5-Furandicarboxylic Acid (FDCA) and Impact of Band-Gap on Conversion Yield
Authors: Hosseini Seyyedamirhossein , Peters Dennis G
Published: February 2020

Electrooxidation of water to oxygen is a kinetically slow reaction; hence, a large overpotential is required to drive this process at a desired rate and to generate adequate electrons for hydrogen reduction at a platinum cathode. A possible alternative is to replace water with another species whose oxidation needs lower overpotentials. In this regard, electrooxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) has shown fast kinetics at low overpotentials Figure 1).1 Furthermore, this reaction features great industrial significance; HMF is a byproduct of the food industry (estimated annual production of 50 million tons) and its conversion to FDCA is an important process in the field of degradable polymers.2,3 FDCA is a cheap and green alternative for polyethylene terephthalic acid (PET) that has been used for fabrication of plastics.4–6

In the present work, we studied the electro- and photoelectrooxidation of HMF to FDCA with application of an anode made of NixCu1-xWO4 (0 ≤ x ≤ 0.1). In experiment 1, electrooxidation of HMF was carried out in the absence of light. The conversion yield has been reported for this experiment by measurement of the amount of hydrogen gas evolved and FDCA formed at the end of the electrolysis. Finally, the yield of the reaction was correlated to the doping amount of copper incorporated within the host of nickel tungstate.

For photoelectrochemical conversion of HMF, a similar setup to experiment 1 has been utilized; however, electrolyses were carried out in the presence of light (experiment 2). Conversion yield and oxidation overpotential in both experiments have been compared to evaluate the effect of doping on the photoelectrochemical properties of modified nickel tungstate. Present data revealed that lower oxidation overpotential is needed in experiment 2 in comparison with experiment 1. Moreover, we observed that, by enhancement of the copper amount (experiment 2), conversion yield was improved significantly.

References

Kubota, S. R.; Choi, K.-S. ChemsusChem. 2018, 11, 2138.

Rosatella, A. A.; Simeonov, S. P.; Raquel, F. M.; Afonso, C. A. M. Green Chem. 2011, 13, 754.

Howard, J.; Rackemann, D. W.; Bartley, C.; Samori, C.; Doherty, W. O. S. ACS Sustainable Chem. Eng.
2018, 6, 4531.

Li, K.; Mengmeng, D.; Ji, P. ACS Sustainable Chem. Eng.
2018
, 6, 5636.

Xu, S.; Zhou, P.; Zhang, Z.; Yang, C.; Zhang, B.; Deng, K.; Bottle, S.; Zhu, H. ACS Sustainable Chem. Eng.
2017, 139, 14775.

Macedo, N. G.; Gouveia, A. F.; Roca, R. A.; Assis, M.; Garcia, L.; Andres, J.; Leite, E. R.; Longo, E. J.
Phys. Chem. C
2018, 122, 866.

Figure 1
Use of Imidoxyl Radical Mediators for Electrochemical Oxidation/Depolymerization of Lignin
Authors: Rafiee Mohammad , Stahl Shannon S.
Published: February 2020

Lignin is an abundantbiopolymer with aromatic subunits in itsbackbone, and depolymerizationof this polymer could provide a source of valuable aromatic chemicals. The beta-O-4 unit, which features secondary benzylic and primary aliphatic alcohols (Figure 1), is the most prevalent linkage in the structure of lignin, and its cleavage provides high yields of aromatic monomers. The hydroxyl functional groups within this linkage are susceptible to oxidation, and their controlled oxidationprovides the basis for lignin depolymerization.[i]We have shown previously that the benzylic alcohol in lignin undergoes selective oxidation with an aminoxyl/NOxcocatalyst system under aerobic conditions. Subsequent treatment of the oxidized lignin with formic acid affords high yields of aromatic monomers.[ii]This talk will describe a complementary electrochemical method for selective oxidation of the benzylic alcohols in lignin.

N-Hydroxyimide derivatives undergo facile proton coupled electron transfer at electrode surfaces to generate an imidoxyl radical that promotes efficient hydrogen atom transfer from the of benzylic hydroxyl groups.[iii]Our advances in the use of electrochemically generated imidoxyl radicals for chemoselective oxidation of hydroxyl groups in the structure of lignin will be presented. Benzylic alcohol oxidation proceeds efficiently to the corresponding ketones using imidoxyl radicals as electrocatalyst in water/acetone as solvent and with acetic acid/acetate as buffer and supporting electrolyte. Treatment of the oxidized lignin with formic acid affords more than 30 wt% of monomeric aromatic compounds.

[i]. Li,C.; Zhao,X.; Wang,A.; Huber, G.W.; Zhang T. Chem. Rev.
2015,115, 11559.

[ii]. Rahimi, A.; Ulbrich, A.; Coon, J. J.; Stahl S. S.Nature
2014, 515, 249.

[iii]. Nutting, J. E.; Rafiee, M. R.; Stahl, S. S. Chem. Rev.
2018, 118, 4834.

Figure 1. Imidoxyl catalyzed electrochemical oxidation of lignin followed by formic acid catalyzed depolymerization.

Figure 1
Bioelectrochemistry of Human Liver Microsomes Attached to Magnetic Nanoparticles
Authors: Krishnan Sadagopan , Nerimetla Rajasekhara , Premaratne Gayan , Liu Hongyun
Published: February 2020

Human liver microsomes (HLM) containing major drug metabolizing cytochrome P450 (CYP) enzymes and its reductase was electrostatically immobilized onto positively charged amine-functionalized magnetic nanoparticles (MNPamine, 100 nm hydrodynamic diameter). The MNP-adsorbed HLM biomaterial (MNPamine/HLM) was then coated onto a solid graphite disk electrode via a polycation glue to accomplish electrocatalysis and prodrug biosensing. Amperometric biosensing of CYP-specific drug candidates and electrocatalyzing drug conversion into metabolites were accomplished. The MNPamine/HLM bioelectrodes exhibited a formal potential of -0.46 V vs Ag/AgCl that was in agreement with the FAD/FMN cofactor containing CYP-reductase as the electron receiver from the electrode. A heterogeneous electron transfer rate constant of 19±5 s-
1 was determined from the MNPamine/HLM film voltammetry. Amperometric i-t curves with diclofenac drug concentration yielded the apparent Michaelis-Menten affinity constant (KM
app
) of 302±33 µM for the MNPamine/HLM film, and the KM
app
was 365±36 µM in the case of only HLM film with no MNPamine. This is the first electrocatalytic study of bioelectrodes featuring HLM-bound MNPamine for applications in prodrug activity assays, enhanced metabolite production, and sensitive biosensing of CYP-specific prodrugs and harmful environmental pollutants.
(Invited) High-Precision Analyses of True Single-Molecule Chemistry using Nanopore Methods
Authors: Ren Hang , Cheyne Cameron G. , Fleming Aaron M. , Burrows Cynthia J. , Edwards Martin A. , White Henry S.
Published: February 2020

Measurement of single-molecule reactions can elucidate microscopic mechanisms that are often hidden from ensemble analysis. This presentation report the acid–base titration of a single DNA duplex confined within the wild-type α-hemolysin (α-HL) nanopore for up to 3 hours. Analysis of the pH-dependent kinetics of >100,000 base flipping events of a single GC base pair using a hidden Markov kinetic model demonstrates that protonation/deprotonation occurs while the base pair is in the intra-helical state. Our experiments correspond to the longest single-molecule chemical reaction kinetic measurements performed using a nanopore.
Versatility of Time-Resolved Raman Spectroelectrochemistry: From the Resolution of Mixture of Vitamins to the Detection Pesticides
Authors: Fanjul Pablo , Ibáñez David , Junquera-Pérez Alejandro , González-García María Begoña , Hernández-Santos David
Published: February 2020

Electrochemical Surface-enhanced Raman scattering (EC-SERS) is a powerful analytical tool for the sensitive and selective detection of different molecules adsorbed on a nanostructured metal. This methodology consists of the electrochemical generation of metal nanostructures with excellent SERS properties and the analytical detection of different molecules in a unique experiment.

Detection of pesticides in food is an essential step in regulating and monitoring the levels of pesticides. However, there is currently a clear demand in the development of new and easy methodologies that allow a quick detection. In order to demonstrate the utility of EC-SERS in this field, two pesticides have been selected. Imidacloprid and permethrin are widely used for controlling different insects in agricultura and their detection is completely required. EC-SERS allows the fast and simple detection of these pesticides, opening new gates for future application in this field.

However, the versaility of EC-SERS has been demonstrated in this work since this technique can be also used in a different, way, and for example is really useful in the resolution of mixtures. As proof of concept, mixtures of different vitamins (B1, B2, B3, B6 and B12) have been studied by time-resolved Raman spectroelectrochemistry. Raman spectra show the characteristic bands of each vitamin, allowing us to differeciate between them. However, apart from differenciate the vitamins present in the mixture, this methodology allows the calculation of the chemical composition of different samples.
Clear-to-Black Dynamic Windows with Minute-Long Switching Using Reversible Metal Electrodeposition
Authors: Islam Shakirul M. , Hernandez Tyler S. , McGehee Michael , Barile Christopher J.
Published: February 2020

Dynamic windows possess electronically tunable transparency, which allows them to transition from clear to dark on demand. By controlling the flow of light and heat into buildings, dynamic windows can substantially increase the energy efficiency of homes and offices. Installing these "smart" windows in automobiles could also extend the battery range of electric vehicles by attenuating energy-intensive air conditioning use. Smaller versions of these windows have applications in actively switchable sunglasses as opposed to current passive photochromic transition lenses.

We are developing next-generation dynamic windows based on the reversible electrodeposition of metals. In this approach, window tinting is controlled via the electrochemical movement of metal between a transparent conducting working electrode and a counter electrode metal frame. This strategy offers several advantages over current windows based on electrochromic materials including minute-long switching times, neutral color, and the potential to be manufactured at low cost. To enable uniform electrodeposition over a large working electrode area, transparent conducting oxides are modified with a self-assembled monolayer of Pt nanoparticles, which serves as an inert metal seed layer for metal nucleation and enhances electrodeposit morphology. An aqueous electrolyte separates the two electrodes and consists of Ag+, Cu2+, and/or Bi3+ ions. We interrogated several electrodeposition chemistries and derived relationships between electrolyte composition and device performance.

The 25 cm2 or 100 cm2 device prototypes we developed display clear-to-black transitions with ~80% optical contrast in 1 minute and cycle thousands of times without significant deterioration. Future improvements in electrode and electrolyte design will increase the scalability and functionality of these devices.
Drop-on-Demand 3D Printed Lithium-Ion Batteries
Authors: Ben Barak Ido , Schneier Dan , Kamir Yosef , Goor Meital , Shekhtman Inna , Golodnitsky Diana , Peled Emanuel
Published: February 2020

The recent trend of accelerated miniaturization of electronic devices has increased the demand for microbatteries of different geometries and chemistries, with high customizability and low manufacturing cost. Devices for applications such as personal wearable electronics, medical implants and remote sensors require small-size, but high-energy-density batteries, often with extraordinary design restriction and highly specific requirements.

To facilitate the production of microbatteries of this type, we plan to use drop-on-demand dispensing, a highly robust printing method already used for various types of functional materials. This method, based on piezoelectrically actuated mechanical droplet formation, enables high accuracy and repeatability in the printing of active-material inks with different properties and rheology parameters.

We have used this method to print various types of active materials for lithium-ion batteries, including cathode (lithium iron phosphate, LFP) and anode (silicon-nickel-based nanoparticles). Both yielded repeatable printability at a resolution below 200µm, which allows customization of the printing to various geometries, including 3D construction of upright electrodes.

We found that the electrochemical performance of printed active materials is highly competitive with traditional manufacturing methods. Cathodes show very high specific capacity, up to 160mAh/g LFP, close to its theoretical capacity and good cyclability. Electrochemical impedance spectroscopy of cathodes shows that cathode chemistry and performance are unaffected by the printing process. Hence, direct implementation of well-established equivalent-circuit models is enabled for data analysis.

Anodes also show high capacity – up to 1200mAh/g anode – and electrochemical behavior consistent with that of anodes prepared by traditional methods. We studied the adhesion of printed anodes to several current collectors and present methods of improving it. The anodes with improved adhesion gave longer cycle life and better performance of microbatteries printed in nonconventional geometries.

Our results inspire further studies, development of manufacturing protocols, and designs for highly customizable batteries. Such development is of particular importance for small-scale and flexible production in many fields of applications, such as in-situ 3D printing of embedded batteries during the assembly process of electronic devices.
Nanomanufacturing Transition Metal Oxide Composite Electrode Architectures Via Electrodeposition
Authors: Spencer Michael , Yildiz Ozkan , Bradford Philip , Augustyn Veronica
Published: February 2020

Electrode architectures that combine a conductive carbon material and a high capacity active material have the potential to close the gap between batteries and capacitors. Going forward, more research efforts need to be focused on developing robust manufacturing and processing methods for hierarchical electrode architectures. In this work, we have used cyclic voltammetry to electrodeposit orthorhombic molybdenum trioxide (α-MoO3) onto a free-standing carbon nanotube foam (CNTF). The porous carbon mesostructure provides sufficient ion diffusion and electrical conduction throughout electrodes with high active material loading. Furthermore, α-MoO3 has a layered structure that is capable of intercalating up to 1.5 Li ions per mole of molybdenum (280 mAh/g), while having fast charge/discharge kinetics since the Li ions are intercalating into the interlayers instead of causing slow phase transformations in the active material. Electrodeposition of the α-MoO3 was carried out using an acidified disodium molybdate dihydrate aqueous precursor solution, in a process that only took ~3 to ~30 minutes depending on the user-defined parameters. This work investigated the effect of concentration and pH of the precursor and post-synthesis heat treatment on the morphology and electrochemical performance of the resulting electrodes. Scanning electron microscopy showed that the as deposited sample formed a smooth, conformal coating on the surface of the CNTs, while a faceted microstructure formed upon heat treatment. Raman spectroscopy confirmed that the as-deposited materials was an amorphous hydrated molybdate structure, in agreement with electrochemical results, while the heat treated material was α-MoO3. Electrochemical characterization was performed in a three-electrode configuration with a Li counter and reference electrode, α-MoO3/CNTF working electrode and a 1M LiClO4 in PC electrolyte. Cyclic voltammetry showed that electrodes with high active material loading (>4 mg cm-2) maintained similar rate capability to electrodes with low active material loading (~1 mg cm-2). Overall, this work has demonstrated that electrodeposition can be used as a robust synthesis technique for layered TMOs for high energy and high power density electrodes, and it revealed the effects of various synthesis parameters on the morphology and electrochemical performance of electrodeposited α-MoO3 on CNTFs.
Effect of Adscititious Water on the Mechanism of Mg2+ Intercalation in Tungsten Oxides from Non-Aqueous Electrolytes
Authors: Wang Ruocun , Kobayashi Takeshi , Zhang Yu , Bonnesen Peter V , Cummings Peter T , Pruski Marek , Augustyn Veronica
Published: February 2020

There is a high demand for low-cost energy storage devices with high energy density and excellent safety. Rechargeable magnesium batteries (RMBs) have the potential to achieve better performance than Li-ion batteries (LIBs) as they allow for the use of a dendrite-free Mg anode, which has about five times the volumetric capacity of the graphite anode in LIBs. One challenge for Mg-ion batteries is the improvement of intercalation kinetics in oxide-based cathode materials. The slow kinetics have been attributed to the higher cation charge/radius ratio of Mg2+­, which results in a high desolvation barrier at the electrode/electrolyte interface and introduces difficult redistribution of charges in the electrode and significant Coulombic interaction between the intercalating species and the host lattice. The addition of water in non-aqueous electrolytes has been shown to improve the kinetics of Mg2+ intercalation, but the mechanism and the effect of water concentration are still under debate. To shed light on these issues, this research focuses on a systematic addition of water into a 0.1 M Mg(ClO4)2 in acetonitrile electrolyte and its effect on Mg2+ intercalation in WO3 and WO3·H2O. Cyclic voltammetry (CV) was used to analyze the electrochemical performance. Solid-state 1H nuclear magnetic resonance spectroscopy (NMR), inductively coupled plasma – optical emission spectrometry (ICP-OES), and X-ray diffraction (XRD) were used to study the intercalation mechanisms in the cathodes. Solution 1H and 25Mg NMR and molecular dynamic (MD) simulation were used to study the electrolytes. An improved rate capability as a function of sweep rate and a decreased peak separation of the redox couples for both materials were found as more water was introduced to the electrolyte until the water concentration reached around 14,000 ppm. Based on these studies, we find that the most likely intercalation mechanism in these electrolytes is the co-intercalation of H+ and Mg2+. The findings elucidate how water improves the kinetic performance of Mg2+ intercalation in WO3 and WO3·H2O in non-aqueous electrolytes and is likely general to other oxides benefitting from the addition of water into non-aqueous multivalent electrolytes.
Evaluation of Changes in Bond Parameters in Sulfolane Under the Influence of Electron-Withdrawing Substituents
Authors: Yasko Andrey , Khamitov Edward , Kuzmina Elena , Kolosnitsyn Vladimir
Published: February 2020

The results of quantum-chemical calculations of the bond orders in the sulfolane molecule during the substitution of hydrogen atoms for fluorine atoms are presented. The change in the bond parameters were estimated.

Quantum chemical calculations were performed using the Gaussian09 software package. The optimization procedure and the calculation of the vibrational problem were performed using the TPSS/aug-cc-pVTZ method. Analysis of wave functions and calculation of bond orders by “fuzzy’ method were performed in MultiWFN software package.

The objects of study were sulfolane, monosubstituted and disubstituted fluorosulfolanes. A total of 15 structures. The nature of the change in bond orders shows the influence of the position of substituents on bond strength. It has been established that the substitution of hydrogen atoms for fluorine atoms has the greatest influence on the order of the C–S bond, reducing it, and the smallest on the S=O bond.

This work was performed as part of a Government Order to Ufa Institute of Chemistry of the Russian Academy of Sciences by the Ministry of Science and Higher Education of the Russian Federation (Theme No. AAAA-A17-117011910031-7).

Figure 1
Influences of Terminal Donor Unit in Dyes with D–D–π–a Architecture on the Regeneration Mechanism in DSSCs: A Computational Study
Authors: Hailu Yohannes Mulugeta , Jiang Jyh-Chiang
Published: February 2020

Dye-sensitized solar cells (DSSCs) have attracted much interest in converting sunlight into electrical energy.1-2 Nevertheless, the inherent dye/iodide interaction and their eventual reactions on the dye regeneration remains unclear. In the present study, we have designed a series of new organic sensitizers (Scheme 1) based on a D–D–π–A architecture to exhibit an easy electron transfer and to have remarkable light harvesting properties in the visible region by density functional theory (DFT) and time-dependent (TD)-DFT calculations. Further, the interaction of the organic sensitizers with the conventional redox electrolyte using triiodide/iodide couple (I–
3/I–) is investigated. Our calculations point out that incorporation of strong electron-donating groups remarkably improves the charge transfer characteristics, optoelectronic properties and rapid dye regeneration as compared to less electron donating substituents. On top, our study demonstrates the possibility of the second electron injection from the oxidized dye complex to the semiconductor surface, which further confirms our recently proposed dye regeneration mechanism.3-4

References:

Liang and J. Chen, Chem. Soc. Rev., 2013, 42, 3453-3488.

Ronca, M. Pastore, L. Belpassi, F. Tarantelli and F. De Angelis, Energy Environ. Sci., 2013, 6, 183-193.

M. Hailu, W.-R. Shie, S. Nachimuthu and J.-C. Jiang, ACS Sustain. Chem. Eng., 2017, 5, 8619-8629.

M. Hailu, M. T. Nguyen and J.-C. Jiang, Phys. Chem. Chem. Phys., 2018, 20, 23564-23577.

Figure 1
(Invited) Nanostructured-Metal-Oxide Functionalized-Supports for Noble Metal Catalytic Nanoparticles: Enhancement of Electrooxidation of Simple Organic Fuels
Authors: Rutkowska Iwona Agnieszka , Kulesza Pawel J.
Published: February 2020

There has been growing interest in utilizing small (simple) organic molecules, as alternative fuels to hydrogen, in electrochemical energy conversion systems. In addition to ethanol (biofuel), that can be ideally oxidized to carbon dioxide thus delivering twelve electrons, recent important systems include dimethyl ether as well. But realistically the respective reaction is rather slow at ambient conditions. Obviously, there is a need to develop novel electrocatalytic materials.

Platinum has been recognized as the most active catalytic metal towards oxidation of ethanol at low and moderate temperatures. But Pt anodes are readily poisoned by the strongly adsorbed intermediates, namely by CO-type species, requiring fairly high overpotentials for their removal. To enhance activity of Pt catalysts towards methanol and ethanol oxidation, additional metals including ruthenium, tin, molybdenum, tungsten or rhodium are usually introduced as the alloying component. More recently it has been demonstrated that catalytic activity of platinum-based nanoparticles towards electrooxidation of ethanol has been significantly enhanced through interfacial modification with ultra-thin monolayer-type films of metal oxo species of tungsten, titanium or zirconium.

We pursue a concept of utilization of mixed metal (e.g. zirconium/tungsten or titanium/tungsten) oxide matrices for supporting and activating noble metal nanoparticles (e.g. PtRu) during electrooxidation of methanol and ethanol. Among important issues is incorporation of Rh nanostructures capable of weakening, or even breaking, the C-C bond in the ethanol molecules. On the other hand, rhodium itself is not directly electrocatalytic toward oxidation of ethanol. The oxides and noble metal nanoparticles have been deposited in a controlled manner using the layer-by-layer method. Remarkable increases of electrocatalytic currents measured under voltammetric and chronoamperometric conditions have been observed. The most likely explanation takes into account possibility of specific interactions of noble metals with transition metal oxide species as well as existence of active hydroxyl groups in the vicinity of catalytic noble metal sites. In addition, formation of “nanoreactors” where ethanol is partitioned (at Rh) to methanolic residues further oxidized at PtRu cannot be excluded.
Purely Protonic Solar Cells Fabricated from Photoacid-Modified Ion-Exchange Membranes
Authors: Schulte Leanna , Ardo Shane
Published: February 2020

Analogies have been drawn between electronic semiconductors and water since 1956 when Fuller explained the similarity between silicon ionization, which generates an electron and a hole as mobile charge carriers, and water ionization, which yields a hydroxide and a proton as mobile charge carriers.1 Since then our group has taken steps to produce a water-based pn-junction solar cell that uses water as a protonic semiconductor. Toward this, we have demonstrated photovoltaic action using photoacid-modified Nafion membranes alone2 and when laminated to an anion-exchange membrane,3 yet each demonstration required the membrane to be wetted by an aqueous acid–base gradient.

In this report, a liquid-electrolyte-free photoacid-modified ion-exchange membrane–electrode–assembly (MEA) driving reversible H2 redox chemistry is described. The cell architecture consists of a three-layer membrane (cation-selective Nafion membrane, aminopyrene-functionalized polyphenylene oxide, anion-selective X37 membrane) that was characterized using direct membrane contacts consisting of platinized platinum mesh. The MEA achieved V
oc = 10 mV and J
sc = 7.5 μA/cm2 under low-intensity 405 nm illumination, resulting in an internal quantum efficiency of ~0.2%.

The reported composite MEA overcomes the problem of co-ion crossover by eliminating co-ions altogether while still exhibiting photovoltaic action due to the charge-separating potential across the membrane interfaces. Because photovoltaic performance persists in the absence of electrolyte gradients and because the potentiometric measurements conducted here are only sensitive to the electrochemical potential of protons, we can conclude that the light-induced voltage and current originate from protons and/or hydroxides, and no other ionic species. This MEA thus serves as a robust proof-of-concept of water’s role as a protonic semiconductor. It also offers a promising format for fundamental studies on the origin of photovoltaic action in photoacid–polymer-electrolyte membranes in the absence of the convoluting effects of liquid electrolyte.

Acknowledgments: This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Early Career Research Award under award number DE-SC0019162 from the Solar Photochemistry Program.

Fuller, C. S. Chem. Prog. 1956, 17, 75-93.

White, W.; Sanborn, C. D.; Reiter, R. S.; Fabian, D. M.; Ardo, S. J. Am. Chem. Soc.
2017, 139, 11726–11733.

White, W.; Sanborn, C. D.; Fabian, D. M.; Ardo, S. Joule
2018, 2, 94-109.
The Effect of Pore Structure on Coaxial Electrospun and Pyrolyzed Polyacrylonitrile Derivatives and Phosphotugnstic Acid for Hybrid Electrode Supercapacitors.
Authors: Garcia Juan Alexandro , Balkus Kenneth J. , Ferraris John P.
Published: February 2020

Global demand for alternative energy storage and improved energy infrastructure will require energy storage devices that can store large quantities of energy and deliver them quickly. These devices should do so for thousands upon thousands of cycles. Supercapacitor devices are an attractive method for future energy storage due to their highpower densities and cyclability compared to other battery devices. For supercapacitor devices to be a more viable choice energy density needs to be improved. One technique to do so is to create hybrid electrodes which combine the fast charging/discharging and cyclability of electrochemical double layer capacitor (EDLC) materials with high energy redox active metal oxides. A common technique is to decorate carbonaceous materials with nanostructured metal oxides (e.g., Ru, Mn, V, Mo, W), which can increase the energy but can limit accessibility to a high surface area conducting carbon. Several of these metal oxides have phases that will inhibit conductivity and limit the power of the device. Polyacrylonitrile derivatives and phase separated blends can be used to tailor a variety of pore sizes (micro & meso) to both increase energy and power of a device. The research to be presented uses coaxial electrospinning to form conductive porous carbon sheath with a multitude of pores calculated by QSDFT. This porous carbon encases a core of tungsten oxide derived from the heteropoly acid, phosphotungstic acid. The graded porous nature of the carbon sheath provides a high surface area EDLC material while simultaneously providing access of the electrolyte to the metal oxide.

Figure 1
(Invited) Nano Composite Platforms: Synthesis and Biological Applications Including Cancer Diagnosis
Authors: Packirisamy M
Published: February 2020

Nanometal-polymer composite films are hybrid materials with inorganic nanoparticles immobilized and uniformly dispersed into a polymer matrix. Nanoparticles such as gold and silver, used to enhance the optical properties of the polymers, are called `optically effective additives` as they lead to new functionalities of the polymer based materials. Au (Ag)-polymer and copolymer composite films are suitable for applications such as waveguides, color filters, thermo-chromic materials etc. The strong plasmon band of Au and Ag nanoparticles (Localized Surface Plasmon Resonance) in the visible spectrum, that originates from the excitation of plasmons by the incident light, makes noble metal-polymer nanocomposites particularly adequate for sensing and biosensing applications. Furthermore, association of Au and Ag nanoparticles of various shapes with poly(dimethylsiloxane) (PDMS), allows the use of nanocomposite materials for microfluidic biosensing as well.

In this presentation, we will talk about the in-situ synthesis of Au-PDMS and Ag-PDMS nanocomposites both at the macroscale and inside the channel of a microfluidic chip. The in-situ synthesis of nanoparticles involves the reduction of gold ions in a gold precursor solution by the curing agent of the polymer. The kinetics of the reaction has been investigated and the effect of annealing temperature on the morphology of nanoparticles has been studied by using imaging and spectroscopic methods. The nanocomposite has been successfully used for sensing of antibody-antigen interactions, allowing the detection of various important proteins. Nanocomposies of metals integrated into other polymers such as PMMA, PVA, and PS have been synthesized as well by using UV, microwave and thermal reduction methods.

The effect of the particle`s shape on the properties of nanocomposites and their sensing abilities has also been studied by synthesizing nanostar particles and integrating them into microchannels.

Because of the biocompatibility and non-toxicity of gold and silver nanoparticles, their nanocomposites can be used for plasmonic detection of biological entities in cancer research.
(Invited) Diffusion Map Analysis of Physiological Signals
Authors: Nakamura Takashi , Hagan Scott
Published: February 2020

Physiological signals such as EEG and ECG can be mathematically modelled as dynamical systems expressed in terms of (almost always nonlinear) differential equations. The behaviour of a dynamical system may be visualised as a trajectory in phase space. For example, since the state of a weight suspended by a spring is fully described at any time by the weight’s position x and velocity v, its temporal behaviour creates a trajectory in phase space (x, v). It works similarly for physiological systems that produce time series data. From a single time series channel x(t) it is possible to approximately reconstruct the phase space trajectory using time-lagged variables x(t), x(t-1), x(t-2),…., x(t-n). In principle, the phase space trajectories can be used for anomaly detection, disease diagnostics, brain-computer interface, etc. It is, however, difficult to extract meaningful spatiotemporal patterns from noisy data because of the nonlinearity of the system and low signal-to-noise ratio. In this presentation, we will show that a method called diffusion mapping can extract the lower dimensional manifold in which the trajectory resides, and reveal the structure of the dynamics. It works even with strong nonlinearity or non-uniformly sampled data. We will demonstrate this technique using some toy models as well as real EEG signals.
(Invited) Inkjet Printing of Impedance Sensors for Living Tissues Monitoring
Authors: Bernasconi Roberto , Meroni Davide , Aliverti Andrea , Magagnin Luca
Published: February 2020

One of the most promising techniques recently applied to minimally invasive living tissues analysis is electrical impedance spectroscopy (EIS). This methodology is able to determine the state of the cells present in an organ by measuring variations in the impedance recorded between electrodes placed in contact with them [1]. The advantages of this approach with respect to invasive techniques like biopsy or others can be immediately individuated: no need to perform surgery on the patient, fast response, easiness and low cost. Moreover, by using EIS, different states (involving for example metabolic toxicity, perfusion loss or cancer development) can be reliably determined.

Typically, EIS is performed placing electrodes directly inside the tissue of interest. The most convenient way to do this is by inserting microneedles containing the electrodes through the skin and directly into the target organ. Moreover, microneedles can be used also to deliver drugs in case of need [2]. For this reason, current research is focusing deeply on the development of microneedles characterized by the highest possible biocompatibility and the lowest invasivity. Interesting examples of micromachined needles exist in literature [3], but they all make use of standard microfabrication techniques with limited flexibility and high cost during the fabrication process.

In the present paper, we discuss the production of EIS microneedles by inkjet printing coupled with electrodeposition. Both these techniques are more flexible than current state-of-the-art methodologies like lithography or sputtering. The shape of the devices is inspired to existing microneedle EIS sensors [3] and adapted to inkjet printing. To produce the sensors, SU-8 is printed to form a mask for the electrodes on a copper substrate. Pt is subsequently electrodeposited selectively inside the mask to form conductive tracks and planar electrodes for EIS. SU-8 is then inkjet printed on the electrodes to form the structural part of the sensor. Finally, the device is flipped and SU-8 is inkjet printed to form a mask on the surface of the sensor able to isolate the tracks from the sensing electrodes. At the end of the manufacturing process, sensors are characterized from the morphological and functional point of view.

[1] P. Heroux, M. Bourdages, Ann. Biomed. Eng. 22(3), 328-337 (1994)

[2] Y.C. Kim, J.H. Park, M.R. Prausnitz, Adv. Drug Deliv. Rev. 64(14), 1547-1568 (2012)

[3] M. Tijero et al., Biosens. Bioelectron. 24, 2410-2416 (2009)
Microfabrication and Characterization of Gold Nanoring Electrodes on Silicon Micro Pillar for Neurochemical Sensing
Authors: Yin Haocheng , Tan Chao , Siddiqui Shabnam , Arumugam Prabhu U
Published: February 2020

Nanoelectrodes provide unique size-dependent properties such as enhanced analyte transport, low charging currents and high signal-to-noise ratio (SNR), which allow them to be utilized as a sensitive detector in several areas of electrochemistry. In recent times, there is a tremendous interest in the use of nanoscale band, disk and hemispherical electrodes for novel electroanalytical applications. One major drawback is that they do not provide a 3D geometry that are more suitable for interrogating cells and tissues because of the difficulty in fabricating such nanoelectrodes onto to a 3D platform. Besides, they are bulky and lack multiplexing and multimodal capability. In this work, we report the fabrication and characterization of a gold nanoring nanoelectrode (Au NRE) that is 165±10 nm wide and micropatterned onto a 4.6±1 µm diameter 17.5±2.5 µm long silicon (Si) micropillar with an intervening 50 nm thick hafnium oxide insulating layer. The electrochemical behavior of the Au NRE was characterized by a steady-state cyclic voltammogram with extremely high SNR of 2500 and charging currents as small as 1.5±0.3 pA. A kinetically controlled voltammetric current response, which is unique to nanoscale electrodes, is indicated by a “semicircle spectrum” from the Nyquist plot. Suggested by circuit fitting of the electrochemical impedance spectra, the NRE geometry can be varied from inlaid to nanotrench with depths controllable by the etching process, which results in differing stead-state voltammetric current and interfacial properties in terms of charge transfer resistance, constant phase element and trench resistance values. The applicability of Au NREs to electrochemical sensing is demonstrated by detecting lead, a neurotoxin at 100 ppb levels. Also, by surface-modification with multi-walled carbon nanotubes, dopamine, a neurochemical implicated in various brain disorders, is detected at a sensitivity as low as 100 nM with 1000-fold selectivity versus common interferences.
An Improved Amperometric Microsensor Microarrays with High Sensitivity and High Selectivity for Ex-Vivo Glutamate Detection
Authors: Tan Chao , Doughty Phillip , Magee Katherine , Murray Teresa , Siddiqui Shabnam , Arumugam Prabhu U
Published: February 2020

Direct real-time detection of neurochemicals is crucial for a better understanding of their roles in various signaling mechanisms and implications in brain disorders. In this work, a platinum (Pt) microelectrode array (MEA) was modified with glutamate oxidase enzyme and polymer layers to detect glutamate (Glu), a major excitatory neurochemical, with high sensitivity and high selectivity in a complex brain tissue environment. We have developed a comprehensive understanding of key process parameters involved in determining the performance of the enzyme-based glutamate microbiosensor. For e.g. the effect of Pt microelectrode surface cleaning methods, enzyme concentration and loading, meta-polyphenylene diamine (mPD) interferent layer, storage methods and self-referencing techniques were investigated. We report a Glu microbiosensor with high sensitivity (212±4 to 530±34 nA/cm2µM, mean ± SEM), high selectivity towards ascorbic acid, a major interferent (244±5 to 841±54, mean ± SEM) and excellent long-term stability in vitro. The microbiosensor was validated in rat brain slice model in response to an electrical stimulation with varying pulse parameters and detecting Glu in real-time with fast response time (<8 s).
(Invited) Stationary Phase Coatings for a Microfabricated GC Column Integrated with Low Power Ion Trap Mass Spectrometer for Analysis of Volatile Organic Compounds
Authors: Chang Tzu-Hsuan , Struk Daniel , Navaei Milad , Doroshenko Vladimir M. , Laiko Victor , Moskovets Eugene , Novoselov Konstantin , Dimandja Jean-Marie D. , Hesketh Peter J
Published: February 2020

Miniature gas chromatography (GC) columns of length 6m were fabricated in silicon using eutectic bonding to achieve a column with improved temperature control. The micro GC column includes an integrated platinum thin film heater and temperature sensors for closed loop temperature programing. In order to achieve low power operation the GC column was mounted inside the vacuum chamber of an ion-trap mass spectrometer. This approach provides much lower power consumption than a laboratory instrument. The ion trap electronics were miniaturized and operate at lower power, to demonstrate a portable instrument able to operate at with less than 25W, including vacuum pumps. This instrument will have a range of applications from environmental monitoring, to food safety and medical diagnostics, including breath analysis.

Static coating of the stationary phase in the microfabricated column was carried out by injection using a solvent and extraction at reduced pressure to improve resolution. This paper reports the results of different stationary phases investigated to separate mixtures of volatile organic compounds, specifically OV-1 and OV-215. The properties of the stationary phases where characterized using a novel probe mixture for microcolumn evaluation and six McReynolds probes to identify the Kovats indices and the polarity of the column. The dependence of polarity on the coating technique and temperature of the column during analysis was also investigated. Results are presented with both an FID and ion-trap mass spectrometer to achieve rapid temperature programmed analysis of mixtures of up to 18 organic compounds.
Vertically Aligned Laminate Porous Electrode: Amaze the Performance with a Maze Structure
Authors: Li Xianfeng , Zhang Hongzhang , Yu Ying
Published: February 2020

The innovation of electrode structures has been lagging far behind that of materials, hampering the industrialization process of high performance batteries. Especially for thick electrodes with high active materials loadings, it’s inadequate to achieve satisfactory performance, especially working at higher current densities, due to the restricted ion transport rate across the electrodes with traditional densely packed structure [1]. To solve the above issue, a vertically aligned laminate porous structure is designed and fabricated for the first time [2]. It seems to cut the thick electrode into thousands of slices vertically arranging like a maze in the X-Y plane, leaving thousands of straight slits (working as ions transport channels) in the Z axis direction. As a result, the electrolyte composition in the slits keeps similar to that on the surface of the electrodes, ascribe to the really large mass effective diffusivity in these slits with lowest tortuosity. Then the real ions transport resistance only exists in the slices, which is much smaller than traditional thick electrodes.

The as proposed maze-like electrode structure (MLPE) is realized by a scalable freeze casting process. Electrodes with such novel structure have shortened ion diffusion channels to rapidly supply electrolyte for reaction and significantly increase active materials loading. The capacity at 2C of Li-S is increased by 50% compared to electrodes directly drying (447mAh g-1). In addition, electrodes with 8 mg cm−2 sulfur can also be easily prepared and show excellent cycling stable at 0.1C (initial discharge capacity: 949 mAh g-1, capacity retention: 98.2%). What’s more, capacities of 89 and 115 mAh g-1 at 10C have achieved for LiFePO4 (LFP) and NaTi2(PO4)3 (NTP) electrodes, respectively, which is over 70% and 130% compared to their contrast with active substances loading of 8.8 and 5.5 mg cm−2.

Fig. a) Schematic illustration of MLPE. b) Schematic illustration of ion transport in the MLPE. c) Rate performance of MLPE-S. d) Cycle performance of MLPE-S. e) Rate performance of MLPE-LFP. f) Rate performance of MLPE-NTP.

References

[1] Y. Yu, H. Zhang, X. Yang, Y. Chen, Z. Jia, J. Yan, H. Zhang, X. Li, J. Mater. Chem. A, 2018, 6, 24066

[2] Y. Yu, H. Zhang, X. Yang, J. Gou, X. Tong, X. Li, H. Zhang, Energy Storage Materials, doi.org/10.1016/j.ensm.2018.09.016

Figure 1
Electrical Characterizations of Amorphous Silicon Carbide
Authors: Geramifard Negar , Joshi-Imre Alexandra , Cogan Stuart F.
Published: February 2020

Introduction: Emerging applications involving electrical stimulation and recording of nerve employ highly dense thin-film multielectrode arrays fabricated on flexible polymer substrates. Several failure mechanisms including the degradation of encapsulation and interlayer delamination have been identified in multilayer thin-film neural devices. A number of materials such as silicon oxide and silicon nitride have been used enhance the insulation hence increasing the density of the circuits; however, the incompatibility to biological environment, low breaking down field strength and frequency dependence behavior impede the use of these materials for bio applications. In this research, we report on the use of amorphous silicon carbide (a-SiC) which is a biocompatible insulator for electrical components and its electrical characterization in the metal insulator metal(MIM) capacitors.

Materials and Methods: Different thicknesses of amorphous SiC (100-500 nm) deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) was sandwiched between two metal layers (TiAuTi 40,300,40nm thick) to create MIM capacitors. Metal layers were deposited by e-beam evaporation and patterned using thin film photolithography techniques. Studies involved current leakage measurement of insulator between two metal electrodes, current-voltage measurement and dielectric constant measurement using parametric test systems.

Tests and Results: In Current-Voltage (I-V) measurement method, voltage was swept from 0-40V with a rate of 50mV/s and current response was accordingly recorded to find the breaking down field potential. Resistivity of material for different thicknesses have been calculated to be around 5e12 ohm.cm ([Fig. A] comparable to silicon nitride), in addition, a low leakage current in the order of picoamp in electric potential of 0.125MV/cm was measured indicating reliability of a-SiC insulation property. Furthermore, dielectric constant of a-SiC was calculated from the capacitance-voltage and capacitance-frequency measurements [Fig. B] showing a linear behavior over the frequency of 0.1 MHz to 10 MHZ which is an indicator of great insulation within biological recording-stimulation frequency range.

Conclusion: We have fabricated a-SiC based MIM capacitor and studied its electrical properties and achieved a comparable dielectric constant with a high resistivity to commonly used materials. The data suggests that a-SiC is a promising candidate for encapsulating highly dense electrical circuits for bioapplication and compatible to thin film microfabrication. Future work will include additional chemical characterization of a-SiC using FTIR to assess the long term chemical stability of this insulator.

Figure 1
Characteristics of AlxGa1-Xn/GaN Grown on Sapphire Substrates with Different AlN Layers Inserted
Authors: Bun Kheam
Published: February 2020

The effect of a thin AlN layer inserted between AlxGa1-xN/GaN heterostructures grown on sapphire substrates was investigated for possible application in optoelectronic and power electronic devices. The heterostructures with two different Al compositions (0.35 and 0.49) were applied to study. After growing a thin AlN (~21nm) on the buffer GaN/sapphire substrate, then a thick AlxGa1-xN/GaN heterostructure were grown and investigated the Al mole fractions. Low rocking curves were also achieved with 0.35 and 0.48 for the 0.3 and 0.49 Al compositions, respectively. The experimental results show that with an increasing of Al composition, the crystallinity is also improved with lower surface roughness. The AlxGa1-xN/GaN heterostructures with 0.35 and 0.49 Al compositions were also investigated the electrical characteristics to confirm that they are suitable for development in optoelectronic and power electronic devices such as HEMTs, LED, etc.