bluuebunny/crossref_metadata_2025 huggingface dataset:
Photoactive Zn-Air-Batteries Suing Cobalt Oxide As the Photocatalyst at the Cathode
Authors: Tomon Chanikarn , Kalasina Saran , Duangdangchote Salatan , Krittayavathananon Atiweena , Sawangphruk Montree
Published: February 2020

Herein, we introduce a new design for the photoactive Zn-air batteries (ZABs). Spinel-type cobalt oxide is synthesized, coated on a transparent conductive indium tin substrate (Co3O4/ITO), and used as a photoactive cathode. The optical absorption of the Co3O4/ITO electrode show direct and indirect optical bandgaps for which the direct and indirect band gap values are 2.20 eV and 1.35 eV, respectively. These values are in the visible light region (1.8-3.1 eV)1. Under the exposure of visible light, the Co3O4/ITO exhibits ca. 30% higher current density than that under dark condition and provides the lower overpotentials of oxygen evolution reaction (OER) and oxygen oxidation reaction (ORR) around 10% - 20% as compared to those under dark condition. By assembling the photoactive ZAB cell, the higher battery performance is clearly observed under the visible light illumination. This new idea can open up opportunities in many applications requiring the conversion and storage of energy within a single cell.

Reference

Walsh, A.; Ahn, K.-S.; Shet, S.; Huda, M. N.; Deutsch, T. G.; Wang, H.; Turner, J. A.; Wei, S.-H.; Yan, Y.; Al-Jassim, M. M., Ternary cobalt spinel oxides for solar driven hydrogen production: Theory and experiment. Energy & Environmental Science
2009,
2 (7), 774-782.

Figure 1
Layered Hybrid Catalyst Containing N-Doped Graphene Oxide and Transition Metal Doped MnO2 with Enhanced Bifunctional Activity for Zinc Air Battery Applications
Authors: Mathur Ankita , Halder Aditi
Published: February 2020

Due to high cost and stability issues involved with precious metals, there is a quest for their alternatives for kinetically driving sluggish oxygen reduction and oxygen evolution reaction for metal air batteries and fuel cells. Herein, we have prepared 2D nanoflakes of δ-MnO2 via hydrothermal route. It acts as a bifunctional catalyst for total oxygen electrochemistry (ORR and OER), but it lacks adequate electrical conductivity. In order to enhance its activity, doping of Fe, Ni and Co transition metal has been done. Further the composites of these transition metal-doped 2D-MnO2 was made with nitrogen doped 2-D graphene oxide. Improvement in ORR and OER activity is observed as is evident by onset potential, Tafel slope and current densities, which is comparable to state-of-the-art Pt/C and RuO2 catalyst for ORR and OER respectively. Doped MnO2/NGO composites were then used as cathode material for rechargeable Zinc air battery. The assembled bifunctional doped MnO2/NGO composites electrode material exhibit high power density, with superior discharge capacity and cyclic stability than bare MnO2 and Pt/C. Our work demonstrates a low cost and efficient bifunctional catalyst material for renewable energy applications.
(Invited) Multiscale Molecular Modeling for Polymer Electrolyte Membrane for Fuel Cell
Authors: Shinoda Wataru
Published: February 2020

Multi-scale “molecular” modeling approach has been developed and applied to polymer electrolyte membrane. The goal of this work is to investigate the possible morphology, structure, dynamics, and mechanical properties of perfluorosulfonic acid (PFSA) membrane with realistic polymer chain lengths (>100 monomer units) by molecular dynamics (MD) simulations. First, we have carried out a series of all-atom (AA) MD simulations of PFSA polymer with a short chain length (10 monomer units) to yield reference structural data for building a coarse-grained (CG) molecular model. Although many phenomenological modeling based on dissipative particle dynamics has been proposed previously, a chemically accurate CG model should be beneficial to investigate the morphology in realistic membranes and to provide a concrete molecular design. Thus, we attempted to construct a predictive CG model for the structure and morphology of PFSA membranes that is compatible with the SDK CG water model. [1] As a first trial, we extended the parameter set in the SDK CG force field to examine a hydrated PFSA membrane based on thermodynamic and structural data from experiments and AA-MD simulations. However, a noticeable degradation of the morphology was detected, which motivated us to improve the structural properties by a combination with the iterative Boltzmann inversion (IBI) approach. The hybrid SDK/IBI model was determined to reasonably reproduce both the thermodynamic and structural properties of the PFSA membrane for all examined water contents. [2] In addition, the obtained CG model demonstrated good transferability. Then, we used the CG-MD to simulate realistic long-chained (including more than 120 monomer units) PFSA membranes. We obtained successfully a well converged structure for this long-chained membrane system. We also developed a reverse-mapping method and successfully used it to produce a well-equilibrated structure at all-atom resolution. We further investigated the mechanical properties of this realistic PSFA membranes at AA resolution. The uniaxial tension tests were conducted to understand the mechanical behavior of hydrated PEM membranes, especially the failure mechanism of the membranes. It was observed that the results (Poisson's ratio, free volume) of the uniaxial deformation were sensitive to the hydration level. This computational methodology will provide more chemically realistic predictions of the PEM membrane properties and give an insight into how to develop the large-scale atomistic PEM model in a multi-scale framework. We will further discuss the effect of equivalent weight (EW) and side chain length on morphology and dynamics of PFSA membranes.[3,4]

[1] Shinoda et al., Mol. Simul.
33, 27 (2007).

[2] Kuo et al., J. Chem. Phys. 147, 094904 (2017).

[3] Kuo et al., J. Phys. Chem. C 120, 25832 (2016).

[4] Kuo et al., Polymer, 146, 53 (2018).
(Invited) Discovering Design Principles for Anion Exchange Membranes with High Hydroxide Conductivity: An Ab Initio Molecular Dynamics Study
Authors: Tuckerman Mark E. , Zelovich Tamar E. , Long Zhuoran E.
Published: February 2020

It is clear that in the identification and development of clean energy sources, a range of technologies will need to be leveraged. Electrochemical devices are an important part of this mix of technologies, and among these, fuel cells constitute some of the cleanest and most sustainable. However, several key hurdles to harnessing the potential of fuel cells (as well as various other electrochemical technologies) remain to be surmounted. We have mounted a Materials Genome Initiative inspired project that aims to address these challenges by designing, synthesizing, and testing new materials for use in alkaline fuel cells and to discover a set of rules for best practices in the development of future materials for fuel cell applications. In particular, the focus is on anion exchange membrane(AEM) fuel cells, which have advantages over other types of fuel cells in not requiring precious metals and being operable with a variety of fuels at low temperature. The overall strategy of the project employs density-functional theory based first-principles molecular dynamics calculations and dissipative-particle dynamics. In this talk, I will present results from first-principle molecular dynamics component of the proposal, which includes simulations of bulk solutions and idealized confined geometries, both containing cations of interest in the AEM design. Connections to the dissipative-particle dynamics will be made, and comparative results of water structure and distribution, solvation structures and their lifetimes, and hydroxide diffusion constants as functions of temperature, water content, cation spacing, and confinement parameters will be presented. Suggestions of design principles that lead to AEMs with high hydroxide conductivity will be made.

Figure 1
Formation of Small Polaron and Polaronic Charge Transfer within BiVO4 Photocatalyst
Authors: Sarker Hori Pada , Huda Mohammad Nurul
Published: February 2020

Harnessing the power of solar energy plays an essential role in developing renewable energy technologies to supplement or perhaps replace fossil fuel utilization. The green energy technology has the potential to address the challenges of growing energy demand and climate changes around the world. Production of H2 from water splitting via photo-electrochemical process is one of the potential green technologies. BiVO4 is one of the best photoanode material for water oxidation as well as photo-catalyst for H2 evolution via water splitting. Despite being an efficient photo absorber material, it has poor charge transport properties. It is anticipated that some of the conduction electrons get bind to specific lattice sites and form polarons, and hence, the charge transfer within this material happens via the polaron hopping from one lattice site to another. In this present study, we have studied the polaron formation at cationic lattice sites and calculated the site to site polaron hopping barrier along a specific hopping pathway in the framework of density functional theory (DFT) with the Hubbard parameter U for self-energy correction of localized d electrons. Finally, the polaron transfer rate, mobility, and diffusion coefficient will also be presented.

The work of MNH is supported by NSF grant #1609811. We also acknowledge the computational time from Texas Advanced Computing Center (TACC).
(Keynote) Electrocatalysis on Nanostructured Metal Oxides
Authors: Chung Dong Young , Lopes Pietro Papa , Strmcnik Dusan , Markovic Nenad M , Stamenkovic Vojislav
Published: February 2020

Understanding of processes that are behind the mechanism for electrochemical evolution of hydrogen and oxygen from water is considered critical in for further advancement of materials that could be implemented in electrolyzers. Atomic scale insight at well-defined interfaces provides invaluable guidance to overcome limitations in operating efficiency of these devices. All of that points towards the need for development of more active, durable and cost effective oxygen evolution and hydrogen evolution electrocatalysts. Metal oxides are emerging as promising group of materials that could deliver desirable performance. While majority of research is placed on the catalyst design and synthesis aiming to improve their efficiency, not too much was done to resolve and understand the role of liquid phase including trace level of impurities or dopants. Molecular species from the electrolyte and the nature of their interaction with the catalyst surface will also be thoroughly discussed. The knowledge acquired from two-dimensional surfaces has been used to create real-world catalysts with superior properties.
(Invited) Charge Carriers Behaviour in Solar Energy Harvesting & Converting Semiconducting Systems.
Authors: Bienkowski Krzysztof , Jadwiszczak Michal , Dubiel Adrian , Arasimowicz Monika , Solarska Renata
Published: February 2020

Solar energy conversion to different types of energy which might be subsequently released by divers’ ways remains an unsaturated need, since the global demand for energy is continuously growing and will continue to rise. However, currently the field of renewable energy suffers from lack of an ideal material able to drive conversion of the solar energy with high efficiency and being stable enough to provide a long-term productivity. Therefore, multi-directional efforts including development of new materials and catalysts, incorporation of plasmonic nanostructures or creation of low-level sub- stoichiometry through different approaches including combination of intrinsic and surface modifications are continuously undertaken and devoted to minimisation of the required bias voltage, improvement of light capture or charge transport properties. Our recent achievements regrading employment of different in structure polyoxometalates as catalysts, sub-stochiometric semiconducting oxides, newly designed and engineered crystal structures in solar driven arrangements as well as their performance for photo induced processes such as oxidation or reduction will be presented and discussed in detail. Besides the extensive characterization of the above-mentioned systems, the kinetic assessment of the transient absorption phenomena will be approached. Use of transient absorption spectroscopy to study charge carrier behaviour in semiconductors-based systems allows to relate a photoelectrode architecture to the charge carrier origin, separation, collection, trapping, lifetime and therefore final efficiency. Presentation and comparison of the charge carrier dynamics occurring in semiconducting systems: bare, modified as well as mixed oxides, are particularly useful in clarifying the observed differences in in their photoelectrochemical performance.
(Invited) Nitride Plasmonics for Enhanced Electrochemical Oxidation
Authors: Simpkins Blake , Purdy Andrew , Epshteyn Albert , Giles Spencer , Wynne James , Baturina Olga A
Published: February 2020

Refractory nitride plasmonics offer the potential to realize enhanced light interactions for energy harvesting and photo-driven chemistry with materials systems that are thermally rugged, inexpensive, and potentially catalytic. Here, we have embedded commercial and in-house synthesized titanium nitride (TiN) nanoparticles into matrixes of titanium dioxide (TiO2) and compared their ability to enhance electrochemical oxidation reactions to that of conventional gold (Au) nanoparticles. Although the photon-to-carrier conversion efficiencies were low (~10-4 %), the reaction rates were enhanced by a factor of 4 in the visible and near-infrared for Au and TiN, respectively, compared to a pure TiO2 control. The spectral dependence of reaction rate enhancement followed the nanoparticle extinction spectra and a linear power-dependence identifies a photo-excited carrier mechanism (i.e., decaying plasmons excite carriers which participate in chemistry rather than heating of the system). Lastly, photo-induced transients of the electrochemical signal are found to be consistent with the band structures of these heterosystems. Specifically, the TiN/TiO2 system, which has little or no Schottky barrier, exhibits a bias-dependent photoelectrochemical response rate while the Au/TiO2 system, which naturally forms a Schottky barrier that immediately separates charged carriers, exhibits a near-instantaneous response.
Single Nanoparticle Electrochromism Reveals Heterogeneous Charge Storage Rates and Ion Trapping Sites in Pseudocapacitive Smart Windows
Authors: Sambur Justin , Evans Russel Colby
Published: February 2020

Developing large area electrochromic smart windows based on nanoscale materials demands that trillions of nanoparticles modulate between transparent and colored states at the same rate. However, it is unclear how nanoparticle heterogeneity contributes to variable coloration dynamics. Here we demonstrate a single nanoparticle electrochromism approach to study optical modulation rates upon lithiationof isolated, clustered, and thin film tungsten oxide nanorod electrodes. We observe a particle-dependent waiting time for coloration (from 100 ms to 10 s) due to Li-ion insertion at optically inactive surface sites. Longer nanorods achieve higher OD modulation than shorter nanorods because they develop a Li-ion gradient that increases from the nanorod ends to the middle. Interestingly, electrochromic irreversibility increases monotonically with the number of particle-particle interactions due to ion trapping at nanoparticle interfaces. These findings lead us to propose a nanostructured electrode architecture that optimizes coloration magnitude, rate, and reversibilityacross large area elecrochromic smart windows.

Figure 1
A Highly Sensitive and Stable Electrochemical Sensor for Simultaneous Detection of Dopamine and Uric Acid Based on the Phosphovanadotungstate and CNTs Decorated By Chitosan
Authors: Bai Zhenyuan , Wang Jun
Published: February 2020

In current work, a highly sensitive and stable electrochemical sensor for simultaneous detection of dopamine (DA) and uric acid (UA) is constructed based on the phosphovanadotungstate (P2W17V), and CNTs decorated by chitosan (CNTs-CS). The combination of two active components endows the electrode with large specific surface area, high electrical conductivity and excellent electrochemical activity. The proposed sensor displayed excellent electrocatalytic performance towards DA and UA by differential pulse voltammetry in 0.2 M phosphate buffer solution (pH = 7.0). For the mixture containing DA and UA, the two compounds can well separate from each other with a potential difference of 101 mV. The sensor exhibited a linear dependence on DA and UA concentration ranging from 2.25×10-6 to 2.81×10-4 M and 1.25×10-6 to 1.66×10-4 M with a detection limit of 0.35 and 0.65 μM (S/N = 3), respectively. The influence of several possible co-existing substances were investigated. The applicability of the method for real samples analysis was tested by determination of DA and UA in bovine serums. This new sensor holds great promise for sensitive determination of DA and UA in real application. (This paper is funded by the International Exchange Program of Harbin Engineering University for Innovation-oriented Talents Cultivation.)

Figure 1
Halides Perovskite Piezoelectric Nanogenerators As Electroskin for Electromechanical Energy Harvesting and Physiological Monitoring
Authors: Kim Da Bin , Cho Yong Soo
Published: February 2020

There have been countless breakthroughs in the developments of flexible and wearable electronics in recent years, and the technology has imposed the challenge on corresponding power devices that they should possess commensurate flexibility and functionality. We report a flexible perovskite piezoelectric nanogenerator that enables both biomechanical energy harvesting and physiological monitoring based on inorganic piezoelectric perovskite nanocrystals (CsPbBr3). For the first time, flexibility and transparency are concurrently accomplished for an energy-harvesting device. It demonstrates a high piezoelectric charge coefficient (d33) of 17.2 pm V−1. The flexible device shows an energy conversion efficiency of 7.81%. A maximum recordable piezoelectric output voltage of 16.4 V and current density of 604 nA under periodically bending-release cycles and ultimately driving wearable electronics with energy converted from human motions, whereas the nanogenerator is strain-sensitive, enabling its application as artificial electronic skin for pressure recognition. Our work provides new insights for multifunctional power sources and potential avenues to overcome challenges associated with the next generation wearable technology.
Electrochemical Detection of Dissolved Hydrogen Sulfide By Platinum-Modified Multi-Walled Carbon Nanotubes Sensors
Authors: Mohajeri Soha , Dolati Abolghasem , Salmani Rezaie Salva
Published: February 2020

Multi-walled carbon nanotubes (MWCNTs) were synthesized by thermal chemical vapor deposition (CVD) technique on stainless steel substrates. To catalyze the growth of nanotubes, a thin layer of cobalt catalyst nanoparticles was electrodeposited on the substrates under the optimum deposition potential of −1.1 V vs. SCE, leading to the formation of bamboo-shaped MWCNTs. The structural and chemical characterization of carbon nanotubes by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) confirmed the growth of vertically aligned carbon nanotubes with close ends. The fabricated MWCNTs were subjected to a purification treatment by electrochemical oxidation in sulfuric acid solution. Fourier transform infrared (FTIR) spectroscopy verified the formation of oxygenated functional groups (primarily carbonyl and hydroxyl) at the nanotubes sidewalls after the treatment, and the morphological analyses demonstrated the opening of the nanotubes tips blocked by Co nanoparticles. To improve the catalytic activity of the functionalized MWCNT electrodes and boost their electrochemical performance as biosensors, surface modification of the nanotubes was carried out by the potentiostatic and pulse potential electrodeposition of platinum nanoparticles. The optimum operating parameters were determined as E = −0.6 V, t = 100 s and Eon = −0.6 V, Ton = 100 s, Eoff = −0.35 V, Toff = 10 s in the potentiostatic and pulse potential deposition techniques, respectively. The structural characterizations revealed that the Pt/MWCNT electrode prepared by pulse potential deposition possessed a highly uniform and compact structure of more refined Pt nanoparticles as compared to the Pt/MWCNT electrode modified by the potentiostatic electrodeposition technique. The methanol oxidation reaction (MOR) performance of the fabricated electrodes was investigated by the cyclic voltammetry (CV) tests in an electrolyte containing sulfuric acid and methanol, and the pulse-deposited Pt/MWCNT electrode exhibited superior electrocatalytic activity and anti-CO poisoning capability. The performance of the pulse-deposited Pt/MWCNT electrode as an electrochemical sensor for the detection of dissolved hydrogen sulfide was evaluated. The oxidation of sulfide anions on the designed sensor involved the formation of sulfate species, rather than elemental sulfur, through an irreversible diffusion-controlled process, with a sensitivity of 0.632 μA μM−1 cm−2 and a detection limit of 0.26 μM. These data indicate the remarkable capabilities of the fabricated sensor as a promising candidate for numerous applications in water and wastewater treatment technologies.
Optical Fiber-Based Corrosion Sensor with Fe/SiO2 Coating
Authors: Wright Ruishu Feng , Lu Ping , Ziomek-Moroz Margaret , Ohodnicki Paul R
Published: February 2020

Nondestructive online corrosion sensors serve as a powerful tool for structural health monitoring in oil and natural gas industry, energy infrastructure, buildings, and geotechnical structures to improve security, reliability, and sustainability. The ability to monitor corrosion online before the structural integrity is compromised can have a significant impact on preventing catastrophic events resulting from corrosion. Based on a concept of using corrosion proxy materials to probe corrosivity, we have demonstrated a distributed corrosion sensor using the Fe thin film coated optical fiber in previous studies. To improve the sensing capability, a Fe/SiO2 composite coating is integrated onto the optical fiber in the present work. The Fe/SiO2 layer is coated onto the optical fiber using sol-gel and electroless plating methods, and then the coating is characterized with SEM and XPS. The Fe/SiO2 coated optical fiber is tested in corrosive solutions at room temperature to measure the optical response as an indicator for corrosion. The light transmission increases as Fe dissolves away due to the decrease in light absorption. The Fe/SiO2 composite coating and the optical fiber configuration are optimized to improve the sensor quality.
High-Performance Ce0.9Sr0.1(Zr0.53Ti0.47)O4 Sensing Membrane Using a Sol-Gel Method for a Solid-State pH Sensor
Authors: Pan Tung Ming , Lou Bih Show , Chen Zong-Yi , Bag Sankar Prasad
Published: February 2020

In this paper, we developed a high-performance Ce0.9Sr0.1(Zr0.53Ti0.47)O4 (CSZT) sensing membrane by using a very simple sol-gel spin-coating process for a solid-state pH sensor. The structural properties of CSZT sensing membrane are correlated with its sensing characteristic. The CSZT EIS sensor exhibited a high pH sensitivity of 92.48 mV/pH, which is beyond the Nernst limit (59.4 mV/pH), and good reliability in terms of a low hysteresis voltage of 1 mV as well as a small drift rate of 0.15 mV/h. This result is attributed to the incorporation of Sr in the CSZT sensing membrane to enhance the change of Ce oxidation state from Ce4+ to Ce3+.

Figure 1
Study on Sulfonic Acid Functional Group Modified Imidazole Ionic Liquids for Oxygen Concentration Detection
Authors: Yin Wenyan , Zhang Milin
Published: February 2020

The ionic liquid is a kind of ionic salt capable of being liquid state at room temperature. As a new type of green organic solvent, ionic liquid has the advantages of good electrical conductivity, wide electrochemical window, very low vapor pressure, and is widely used in electrochemical, organic synthesis and other fields. The use of ionic liquids as electrolytes in electrochemical oxygen sensors can alter the shortcomings of the current sensor's inability to operate at high temperature and humidity conditions. Besides, ionic liquids with certain catalytic functional group could improve the response performance of sensing devices. Therefore, in this paper, ionic liquids based on imidazolium, 1-methyl-3-propanesulfonic acid imidazolium hydrogensulfate ([Psmim]HSO4) and 1-methyl-3-butpropanesulfonic acid imidazolium hydrogensulfate ([Bsmim]HSO4 )with sulfonic-acid catalytic functional group were studied. Both ionic liquids mentioned above were synthesized through a traditional two-step method. Electrochemical tests including linear scanning voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) of both ionic liquids were carried out with an electrochemical workstation to characterize the intrinsic electrochemical performance of both ionic liquids. On the other hand, cyclic voltammetry (CV) curves were tested, which shows a proportional linear relationship between oxygen reduction peak current and the oxygen concentrations from 0% to 100% O2 with the corresponding R2 (R2 >0.97), and chronoamperometric current tsests were also carried out to futher confirm the ionic liquids promising materials for oxygen sensing. (This paper is funded by the International Exchange Program of Harbin Engineering University for Innovation-oriented Talents Cultivation.)
The Effect of Size and Content of Cerium Oxide on the Efficiency of a Composite Sensor for Hydroxyl Radicals Detection
Authors: Duanghathaipornsuk Surachet , Alateeq Faisal , Alba-Rubio Ana C , Kim Dong Shik
Published: February 2020

Hydroxyl radicals (•OH) are one of the biomarkers that are recognized during an initial stage of severe disease development. High concentrations of •OH in a human body may cause cancer, Alzheimer’s disease or Parkinson’s disease. Thus, to diagnose the onset of those diseases, a very sensitive analytical device is needed for •OH detection at low concentrations. The combination of a recognition system with an electrochemical technique is regarded as a promising method for •OH detection due to the rapid and direct measurement without the pretreatment of samples. In the current experiment, a glassy carbon electrode was modified with a graphene oxide/cerium oxide (GO/CeO2) composite to be used as a sensing device for hydroxyl free radicals. The GO/CeO2 composite was synthesized through a low-temperature solution process. Transmission electron microscopy (TEM) was used to determine the average size of CeO2 nanoparticles in the composite. X-ray powder diffraction (XRD) helped to confirm the composition of the GO/CeO2 composite. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to characterize the interaction of the composite sensor with •OH in the Fenton reaction. The size and content of CeO2 nanoparticles in the composite were varied to study the effect of these two factors on the sensor performance. Regarding the effect of particle size on the sensor efficiency, 25 nm and 10 nm CeO2 nanoparticles were embedded in the composites separately. While the composite sensor with 25 nm CeO2 showed no oxidation current response with •OH, the composite with 10 nm CeO2 nanoparticles resulted in a significant increase in the oxidation current response. Different contents of CeO2 in the composite, 10, 25, 50, 75, and 90 % of CeO2 were also studied to determine the optimum ratio of CeO2 to GO. 75% of CeO2 in the composite showed the highest oxidation current response in •OH detection. Consequently, the composite sensor consisting of 25% GO and 75% of 10 nm CeO2 was found to be the most effective in the reaction with •OH. It is suggested that the size and content of CeO2 play an important role in the development of effective GO/CeO2 composite sensors for •OH detection.
Non-Enzymatic Electrochemical Detection of Mercury Ions on Graphene Quantum Dot-Based Electrodes
Authors: Fu Chun-Chien , Yang Jou-Wen , Hsieh Chien-TE , Juang Ruey-Shin
Published: February 2020

This study adopts an efficient method to electrochemically detect Hg2+ ions in aqueous solutions using graphene quantum dot (GQD) based electrodes. Previous studies reported that GQDs are capable of detecting metal ions (e.g., Hg2+ and Fe2+) at ultralow concentrations, showing an obvious fluorescence quenching in the presence of metal ions in aqueous solutions. However, there are few studies focusing on electrochemical detection of metal ions using GQD-based electrodes. The electrochemical detection technique is a convenient and simple method to accurately estimate real concentration of the contaminants based on the change of peak current density or ohmic resistance. In this study, GQDs were prepared by a hydrothermal technique using organic compound as precursor. The as-prepared GQDs with an average particle size of 5 nm were functionalized by surface oxygen groups, including carbonyl, carboxyl, and hydroxyl groups attached to basal planes and edges of sp
2-domain graphene. The non-enzymatic electrochemical detection of Hg2+ ions on GQD-based electrodes was carried out using cyclic voltammetry within a potential range between 0 and 1.7 V vs. Ag/AgCl. Experimental results showed that the reduction of peak current at 0.35 V is proportional to the concentration of Hg2+ ions. The detection limit of mercury ions by GQD-based electrode can reach as low as 0.1 mg/L. Accordingly, the unique design of GQD-based electrode displays the feasibility in application to electrochemical detection of environmentally pollution micro-inspection. Future work on how N-doping and dopant concentration on the sensitivity and selectivity of GQD-based electrodes is on-going.
(Invited) Progress in Photoelectrochemical Energy Conversion
Authors: Parkinson Bruce A
Published: February 2020

The interest in the direct storage of solar energy as a chemical fuel in a semiconductor based photoelectrochemical system started with the demonstration of solar photoelectrolysis of water with large band gap oxide semiconductor electrodes in the late 1970s. In the last decade or so there has been both and increased interest and increased funding towards achieving a goal of efficiently producing cost effective fuels from solar energy with either water or carbon dioxide as a feedstock. This talk will review the progress towards this goal considering recent developments. One of these developments is that the cost of photovoltaic systems has been decreasing rapidly to where currently the cost of the solar panels is now exceeded by balance of systems cost. The cost of electrolyzers will be also decrease as they are improved and scaled. Connecting these two existing technologies has the advantage of producing hydrogen where and when it is needed and at pressure. These facts mean that the window for direct solar photoelectrolysis is rapidly closing. One possible breakthrough is that a new stable, efficient, inexpensive, defect-tolerant and scalable new materials are identified that can quickly improve the efficiency of photoelectrolysis much like the hybrid perovskites are have done for photovoltaic devices. This talk will review the progress in combinatorial approaches to discover new materials for photoelectrolysis with some examples including one from the Solar Hydrogen activity Research Kit (SHArK) Project, a distributed science project that provides undergraduates and high school students with the resources to produce and screen metal oxide semiconductors for photoelectrolysis activity. In addition the reasons for producing hydrogen from water rather than direct carbon dioxide reduction to produce fuels will be reviewed. A new system for storing solar energy directly as redox equivalents, a solar chargeable redox flow battery, will also be introduced and its advantages and disadvantages compared to solar hydrogen generation will be discussed.
(Invited) Towards New Near-Infrared Triggered Theranostic Nanoplatforms
Authors: Vetrone Fiorenzo
Published: February 2020

Light triggered theranostic (therapy and diagnostic) platforms have gained a considerable attention in recent years. In theranostics, light as an external trigger stands out due to its non-invasiveness, high local precision and temporal resolution. Many such theranostic nanoplatforms employ high-energy (visible or UV) light to initiate the individual therapeutic and diagnostic modalities. However, light at these wavelengths suffers from inherent drawbacks such as having little to no penetration in living tissue, induces autofluorescence from inherent fluorophores or chromophores in tissues and can cause photodamage. The use of NIR light for excitation mitigates such drawbacks associated with high-energy excitation, for example, little to no background autofluorescence from the specimen under investigation as well as no incurred photodamage. Moreover, one of the biggest limitations is of course, that of penetration. As such, NIR light can penetrate tissues much better than high-energy light especially when these wavelengths lie within the three biological windows (BW-I: 700-950, BW-II: 1000-1350, BW-III: 1550-1870 nm) where tissues are optically transparent. At the forefront of NIR excited nanomaterials are rare earth doped nanoparticles, which due to their 4f electronic energy states can undergo conventional (Stokes) luminescence and emit in the three NIR biological windows. However, unlike other classes of nanoparticles, they can also undergo a multiphoton excitation process where the NIR excitation light is converted to higher energies resulting in anti-Stokes luminescence spanning the UV-visible-NIR regions (commonly known as upconversion). Due to the versatility of their optical properties, it now becomes possible to generate upconverted high-energy light (UV or blue) in situ to trigger other light activated therapeutic modalities (i.e. drug release) while using the NIR emission for diagnostics (i.e. bioimaging, nanothermometry). Here, we present the synthesis of various NIR excited (and emitting) rare earth doped core/shell (and multishell) nanoparticles and demonstrate how their luminescence properties can be exploited for potential use in theranostics.
Creating Clinically-Relevant Biosensors-Integrating Hierarchically Structured Transducers with Dynamic Signal Recognition Elements
Authors: Soleymani Leyla , Chan Yuting , Hosseini Amin
Published: February 2020

Biosensors combine biorecognition and signal transduction to analyze biologically-relevant species that are markers of disease or indicators of health. The performance metrics of biosensors, such as limit-of-detection and speed, are strongly influenced by the structure of the transducer. Designing material architectures that increase the sensor sensitivity, decrease background signals, and reduce analysis time is critical for entering biosensors into clinical decision making and health monitoring. Additionally, the specificity of biosensors are controlled by introducing biorecognition elements into the biosensing system. Developing biorecognition elements that specifically capture analytes of interest and effectively translate this capture to a detectible signal is the other critical piece of biosensor development. We have developed strategies for creating three-dimensional transducer architectures, combining them with dynamic biorecognition elements, and translating biorecognition into electrochemical signals.

All-solution-processing is used to create three-dimensional biosensing electrodes. This method combines self-assembly, electroless deposition, electrodeposition, and shape memory polymer substrates to create porous and wrinkled hierarchical electrodes. Biorecognition is achieved using molecular machines that release an electroactive DNA barcode in response to a target analyte, which is analyzed at the electrode surface using electrochemical readout.

Three-dimensional electrodes, biorecognition elements, and signal transduction components are integrated into microfluidic networks for sensing small molecules, nucleic acids, and proteins. This integrated biosensing platform is used for analyzing clinical samples, and a test with a clinically-relevant limit-of-detection is achieved.
(Invited) Toward Self-Powered and Skin-Conformal Sensor Devices - Integration of Ultra-Thin Sensors with Organic Solar Cells
Authors: Fukuda Kenjiro , Someya Takao , Park Sungjun
Published: February 2020

Self-powered system and conformability are important keywords for next biomedical devices. Using organic semiconducting materials can open new avenue towards such self-powered sensor system. Especially, conformal solar cells play important role in the development of compact, portable, and sustainable power source for on-skin electronics. Their direct integration with functional electronic devices opens unprecedented possibilities for a variety of microelectronics to be operated without demand of external bulky and rigid power supplies. Here, we report integrated self-powered ultra-flexible electronic devices that can measure biometric signals with very high signal-to-noise ratios when applied to skin or other tissue. Such devices has been achieved by integration of highly efficient and stable organic solar cells with organic chemical transistors as sensor devices.
A Real-Time Wearable Sensor to Monitor Alcohol Consumption through Ethyl Glucuronide Detection
Authors: Lin Kai-Chun , Sankhala Devangsingh , Muthukumar Sriram , Prasad Shalini
Published: February 2020

Here we demonstrate for the first time a wearable sensor that can differentiate Ethyl Glucuronide (EtG) concentrations in synthetic human sweat correlating to the predicted alcohol consumption profiles of moderate drinkers. Alcohol consumption monitoring devices typically report blood alcohol content (BAC) through correlation with breath alcohol content (BrAC). However, the rapid decay of expressed ethanol can limit the application space of these devices. Alcohol is metabolized and excreted from the body by different processes or pathways, ethyl Glucuronide (EtG) is one of them and is produced in the liver. EtG is readily expressed and detectable in transdermal human sweat making it a promising candidate for wearable alcohol consumption monitoring.

A wearable biosensor device capable of reporting EtG levels in sweat both continuously via low power impedance spectroscopy is reported. The device was not only able to detect and respond to EtG present in the samples, but also able to differentiate each test scenario from one another. The three distinct EtG concentrations was designed as simulated drinking scenarios estimated to be 1, 2, and 3 standard U.S. drinks consumed over a duration of 60 minutes. It shows the ability for this device to act as an accurate reporter of EtG levels in low volume sweat (less than 5 microliter). The device will serve as a candidate tool for researchers to better understand and characterize the relationship between sweat EtG and consumed alcohol in real-time.
Facile Mn Surface Doping of Ni-Rich Layered Cathode Materials for Lithium Ion Batteries
Authors: Kim Jong Hwa , Cho Woosuk , Park Min-Sik
Published: February 2020

As the electric vehicles (EVs) market is growing rapidly, lithium ion batteries (LIBs) have received great attention as a suitable power source owing to its high-energy density and excellent power characteristic. To extend a driving mileage of the EVs, it is crucial to further improve the energy density of LIBs. Since the specific capacity and operating voltage of cathode materials are important factors for determining the energy density of LIBs, many researches focus on the development of advanced cathode materials with high specific capacity and high operating voltage. Among various cathode materials, layered cathode materials (e.g., LiMO2, M = transition metal) have been one of the most popular cathode materials in LIBs. The electrochemical properties of these cathode materials are tunable by the choice of transition metals in the host structure; i) Mn secures structural stability, ii) Co increases power characteristic, and iii) Ni contributes to a specific capacity of the materials. In order to increase the achievable specific capacity, researchers have designed the layered cathode materials with a high Ni content (>80%) and they offer a high reversible capacity more than 190 mA h g-1. Unfortunately, Ni-rich layered cathode materials suffer from poor thermal and structural stabilities arising from the high Ni content in the structure. To overcome these limitations, therefore, structural modifications on the Ni-rich cathode materials is highly required to suppress undesirable side reactions and formations of impurities (e.g., NiO).

Herein, we prepare Mn surface-doped NCM811 (Mn-NCM811) with a core-shell structure via a simple wet-coating process using lithium ethoxide and Mn acetate precursors. Various structural and electrochemical investigations support that Mn-rich shell can effectively improve the structural and thermal stabilities of Ni-rich core, leading to the significant improvement in electrochemical performance of Ni-rich layered cathode materials even at a high operating temperature of 60 °C. From the results, we emphasize the importance of material design and this study will provide practical guidelines for development of Ni-rich layered cathode materials for LIBs.

References

[1] Y. –K. Sun, S. –T. Myung, B. –C. Park, J. Prakash, I. Belharouak, K. Amine, Nat. Mater.
8, 320-324 (2009).

[2] J. Lu, C. Zhan, T. Wu, J. Wen, Y. Lei, A. J. Kropf, H. Wu, D. J. Miller, J. W. Elam, Y. –K. Sun, X. Qiu, K. Amine, Nat. Commun.
5, 5693 (2014).

Figure 1
Rational Design of a Dual-Function Hybrid Cathode Substrate for Lithium-Sulfur Batteries
Authors: Luo Liu , Manthiram Arumugam
Published: February 2020

Reliable sulfur cathodes hold the key to realize high-performance lithium-sulfur (Li-S) batteries, yet the electrochemical inefficiency and instability arising from the poor conductivity of sulfur and lithium sulfide together with polysulfide shuttle remain challenging. Here, a unique three-dimensional (3D) hybrid sponge with chemically coupled nickel disulfide-reduced graphene oxide (NiS2-RGO) framework is rationally developed as an effective polysulfide reservoir through a biomolecule-assisted self-assembly synthesis. An optimized amount of NiS2 (~ 18 wt.%) with porous nanoflower-like morphology is uniformly in-situ grown on the RGO substrate, providing abundant active sites to adsorb and localize polysulfides. The improved polysulfide adsorptivity from sulfiphilic NiS2 is confirmed by experimental data and first-principle theoretical calculations. Moreover, due to the chemical coupling between NiS2 and RGO formed during the in-situ synthesis, the conductive RGO substrate offers a 3D electron pathway to facilitate charge transfer towards the NiS2-polysulfide adsorption interface, triggering a fast redox kinetics of polysulfide conversion and excellent rate performance (C/20 – 4C). Therefore, the self-assembled hybrid structure simultaneously promotes static polysulfide-trapping capability and dynamic polysulfide-conversion reversibility. As a result, the 3D porous sponge enables a high sulfur content (75 wt.%) and a remarkably high sulfur loading (up to 21 mg cm-2) and areal capacity (up to 16 mA h cm-2), exceeding most of the reported values in the literature involving either RGO or metal sulfides/other metal compounds (sulfur content of < 60 wt.% and sulfur loading of < 3 mg cm-2). This integrated hybrid system could be extended to other metal-sulfides and it provides a new possibility to engineer advanced sulfur cathodes for high-performance Li-S technology with a necessary high sulfur loading.

Figure 1
Improvement of High-Rate Discharging Performance of LiFePO4 Cathodes By Forming Micrometer-Sized through-Holed Electrode Structures with a Pico-Second Pulsed Laser
Authors: Tsuda Takashi , Gunji Takao , Ando Nobuo , Tanabe Toyokazu , Nakamura Susumu , Soma Naohiko , Hayashi Narumi , Ohsaka Takeo , Matsumoto Futoshi
Published: February 2020

Holing of lithium iron phosphate (LiFePO4, LFP) cathodes with a pico-second pulsed laser, whose the average diameter and opening rate were 20-30 mm and 1-2%, respectively, could retain the high-rate discharge performance even in the LFP cathodes having the thickness of LFP layer over 40 mm on an aluminum current collector. The conventional thick and flat LFP cathode electrodes exhibited the degradation of discharge retention at the high-rate discharge because of the low utilization of LFP materials in the case of the thick cathode layer. On the other hand, in through-holed and non-through-holed LFP cathodes, Li+ ions can do more efficient insertion/deinsertion to/from the LFP materials through the holes formed in the LFP layer, resulting in retaining the high-rate charge-discharge performance even in thick LFP cathodes. The electrochemical impedance spectroscopy analysis confirmed that the formation of through-holes in the thick LFP layer is significantly effective to improve the high-rate discharging performance as a result of the decreased charge-transfer resistance of the LFP discharge process. The decrease in the charge-transfer resistance was brought from the increase in the area for the LFP discharge process based on the fact that the sidewalls of the holes are also available for the process.

Fig. １ Schematic description of the cell arrangement of the cells used. (A) Non-holed, (B) through-holed and (C) non-through-holed LFP/LFP cathodes.Two Li metal were used as anodes.

Figure 1
Spectroscopic Investigation of Complex Redox Equilibria in Cupric Chloride Subtractive Etching for Cu High Density Interconnects
Authors: Issac Goutham , Lambert Alexander , Caperton Joshua , Salunke Ashish , Lu Luwen , Chyan Oliver
Published: February 2020

The continuously increasing demand for innovation in the miniaturization of microelectronics has driven the need for ever more precise fabrication strategies for device packaging, especially for printed circuit boards (PCBs). Subtractive copper etching is a fundamental step in this processes, requiring very precise control of etch rate and etch profile. Cu etching baths are typically monitored with several parameters including oxidation-reduction potential, conductivity, and specific gravity. However, the etch rate and etch profile can be difficult to control even under strict engineering controls of those monitoring parameters. The basic understanding of the Cu etching is shown in the figure below [Fig 1], whereas the reality is that the mechanism of acidic cupric chloride etching, regeneration and recovery is complex [Fig 1], and the current monitoring strategies can have difficulty controlling the complex interlocking chemical equilibria. We report that thin-film UV-Vis spectroscopy has the capability to effectively monitor the electrochemical processes and its complex redox changes to the etch bath from beginning to end. We report that the complex equilibria has direct control on the etch rate and its regeneration process. UV-Vis spectroscopy also reveals various underlying mechanism reasons for etch bath behavior and illuminates the roles of H+ and Cl- to the etch bath while also providing a means to monitor the Cl-. By implementing thin film UV-Vis, we are able to probe and monitor the equilibria in real time to maintain a consistent etch rate throughout while also achieving proper regeneration and recovery for repeated use. Additionally, we’ve shown that this technique is sufficient in supplementing oxidation-reduction potential, conductivity, and specific gravity methods. This addition be can utilized to improve current monitoring strategies as it can identify and predict etching behavior that the current standard methodologies may have difficulty predicting.

Figure 1