bluuebunny/crossref_metadata_2025 huggingface dataset:
Oxygen Reduction over Dealloyed Pt Layers on Glancing Angle Deposited Ni Nanostructures and Efficient Water Oxidation over Easily Prepared Ir-Ni Oxide Nanoparticles
Authors: Wang Chao , Moghaddam Reza B. , Sorge Jason B. , Xu Shuai , Brett Michael J. , Bergens Steven H.
Published: February 2020

A challenge in the commercialization of proton exchange membrane fuel cells (PEMFC) is the large overpotential for the oxygen reduction reaction (ORR) at the cathode. Platinum is the most active single-component catalyst, but it has the inherent drawbacks of high cost and scarcity. Combining Pt with non-noble metals (eg. Ni, Fe, Cu etc.) has proven to enhance the ORR activity and reduce the Pt mass (1). We describe the use of glancing angle deposition (GLAD, developed by Brett et al. (2), a physical vapor deposition technique) to deposit Ni with controlled nanostructures on glassy carbon supports (Ni GLAD/GC). A unique electrodeposition method was utilized to deposit a thin layer of Pt over the surface of the Ni GLAD structure in a controlled and conformal way. The Pt loading was varied by interrupting the deposition at various coverages, and a series of the Ni GLAD{Pt}/GC deposits was evaluated towards the ORR in acid (3). These Ni GLAD{Pt}/GC deposits are remarkably more active and durable than {Pt}/GC during ORR in acid and in base (4). In addition, dealloying (selective electrodissolution of Ni to make a more robust and active resulting catalytic material) in acid further enhanced the activity of Ni GLAD{Pt}/GC towards the ORR.

Water electrolyzers (WEs) are used to store/transform energy from renewable sources. The sluggish kinetics for the water oxidation reaction (WOR) severely lowers the efficiency of WEs (5). Iridium is an active and stable catalyst for WOR in acid. Due to its high cost, Ir based catalysts with better activity and decreased loading are required for the widespread adoption of WEs. In this talk, we will present a one-pot synthesis of novel highly active and durable Ir-Ni oxide nanoparticles under mild conditions. A mass activity > 140 A g-1
Ir at 0.25 V overpotential was obtained for IrNi0.125 atomic composition. Long term galvanostatic polarization and duty cycles showed that the catalysts prepared by this procedure are remarkably stable (6).

References

1.      I. Katsounaros, S. Cherevko, A. R. Zeradjanin and K. J. J. Mayrhofer, Angewandte Chemie International Edition, 53, 102 (2014).

2.      K. Robbie and M. J. Brett, Journal of Vacuum Science & Technology A, 15, 1460 (1997).

3.      C. Wang, R. B. Moghaddam, J. B. Sorge, S. Xu, M. J. Brett and S. H. Bergens, Electrochimica Acta, 176, 620 (2015).

4.      S. Xu, C. Wang, S. A. Francis, R. T. Tucker, J. B. Sorge, R. B. Moghaddam, M. J. Brett and S. H. Bergens, Electrochimica Acta, 151, 537 (2015).

5.      E. Fabbri, A. Habereder, K. Waltar, R. Kotz and T. J. Schmidt, Catalysis Science & Technology, 4, 3800 (2014).

6.      R. B. Moghaddam, C. Wang, J. B. Sorge, M. J. Brett and S. H. Bergens, Electrochemistry Communications, 60, 109 (2015).

Figure 1
(Invited) Structure Design and Controlled Synthesis of Metal Electrocatalysts of High Surface Energy and High Activity
Authors: Sun Shi-Gang
Published: February 2020

Metal nanoparticles play a key role as electrocatalysts in electrochemical energy conversion, electosynthesis and other important fields. The electrocatalytic nanoparticles depend strongly both on their bulk and surface structures. The bulk structure could be tuned by changing the chemical nature and composition, while tuning the surface structure is more difficult, especially the high activity corresponding to high surface energy that leads to disappear the nanoparticles during their growth. We have focused, in recent years, on the structure design and controlled synthesis of nanoparticle electrocatalysts of high surface energy, prepared platinum group metal-based electrocatalysts through the development of electrochemical methods, and investigated systematically their catalytic property towards fuel cell applications.

(1)   Tuning the surface atomic arrangement of well-defined metal nanocatalysts. Well-defined Pt, Pd and Rh nanocrystals enclosed by high-index facets have been successfully obtained by developing electrochemically shape-controlled synthesis, such as tetrahexahedral nanocrystals (THH NCs) enclosed with {hk0} high-index facets, trapezohedral nanocrystals (TPH NCs) with {hkk} high-index facets, triambic icosahedral nanocrystals (TIH NCs) with {hhl} high-index facets and hexoctahedral Pt NCs (HOH NCs) with {hkl} facets. As high-index facets containing a high density of active centers, these NCs exhibit high electrocatalytic activity for small organic fuel oxidation reactions as anodic reactions of direct Fuel Cells.

(2)   Tuning the electronic structure of Pt- and Pd-based nanocatalysts. The electronic structure of NCs catalysts has been turned either by surface decoration using foreign adatoms, or through alloying Pt and Pd with other metals. Different adatoms such as Bi, Ru and Au were used to decorate the THH Pt NCs, and both THH and TPH Pt-based alloy nanocatalysts were prepared by electrochemically shape-controlled synthesis. The THH and TPH alloy NCs preserve the high-index facets while hold a synergy of electronic effect that enhances further the electrocatalytic activity.

Acknowledgements. The studies were supported by NSFC (21361140374, 21229301, and 21321062)

 

References:

Tian Na et al., Science, 2007, 316: 732-735.

Tian Na et al., J. Am.
Chem. Soc., 2010, 132: 7580.

Zhou Zhi-You et al., Angew.
Chem. Int. Ed., 2010, 49: 411.

Zhou Zhi-You et al., Chem. Soc.
Rev., 2011, 40: 4167.

Li Yan-Yan et al., Chem. Commun., 2012, 48: 9531.

Wei Lu et al., Chem. Commun., 2013, 49: 11152.

Tian Na et al. Faraday Discuss., 2013, 162 : 77.

Xiao Jing et al., J. Am.
Chem. Soc., 2013, 135: 18754.

Yu Neng-Fei et al. Angew. Chem. Int. Ed., 2014, 53: 5097.
Microbial Fuel Cell Prototyping for Pilot-Scale Applications
Authors: Jones Jason , Chen Shing , Phan Tony , Chan Shirley , Babanova Sofia , Phadke Sujal , Bretschger Orianna
Published: February 2020

Utilizing anode-respiring bacteria, microbial fuel cells (MFCs) are a technology that is able to remove organic materials from waste streams and generate electricity in the process.  MFCs have been considered as an alternative to conventional wastewater treatment using activated sludge, due to potentially lower cost of operation (no pumping of oxygen) and the ability to directly control the removal of organics.

Our study is focused on designing modular and scalable MFC reactors that can be utilized in pilot-scale installations.  We tested several operational parameters and two different anode electrode configurations to study the effect on current production and chemical oxygen demand (COD) removal.  The operational parameters included running the systems in MFC-mode with a constant resistance, alternating open circuit/closed circuit operation (open circuit for 30 minutes, once a day), and applying a set voltage to the circuit.  The different anode electrode configurations included graphite-coated stainless steel bolts or carbon fiber brushes.  All of the reactors utilized the same gas diffusion oxygen reducing cathode design.  Samples were taken daily to evaluate the COD removal rates, monitor/control pH, and determine the concentration of dissolved oxygen in the reactors.  Current production was monitored in real-time and polarization measurements were executed periodically for the electrodes to evaluate the activities of the associated microbial communities at the anodes, as well as the efficiency of cathode operation.

Reactors under alternating open circuit/closed circuit operation demonstrated improved performance longevity than those held under constant resistance (MFC-mode). This may be a result of decreased biofouling on the cathode per our previous work[1] or improving the charge storage capacity of the anode biofilms[2]. Our preliminary results showed that lowering the applied resistance to 22Ω yielded current production up to ~15 mA and COD removal rates of 55 mg/L/day, as compared to a resistance of 560Ω, which yielded ~1mA and 21 mg/L/day, respectively.  In regards to anode material performance, our studies showed that carbon fiber brushes allowed for COD removal rates over 10 times higher than the coated stainless steel bolts, and up to an additional ~8mA of current production. Future work will include an analysis of COD removal and current production normalized by electrode surface area and electrode-associated biomass to better compare results and elucidate the system parameters that are highly correlated to improved MFC performance.

Figure 1
Redox-Active Poly(ionic liquid)s As Active Materials in Energy Devices
Authors: Hernandez Guiomar , Isik Mehmet , Mecerreyes David
Published: February 2020

Poly(ionic liquid)s emerged from the incorporation of ionic liquids into polymers and have gained interest due to a wide range of applications in different technological fields such as polymer electrolytes for batteries and supercapacitors. Poly(ionic liquid)s provide enhanced mechanical stability, processability and spatial controllability over ionic liquids in electrolyte applications.

Incorporation of redox-active groups into poly(ionic liquid)s brings new possibilities to these materials in the energy field. Here we will present the combination of poly(diallyldimethylammonium) type poly(ionic liquid)s with redox-active counter-anions based on anthraquinone and nitroxide groups. First, we will present the electrochemical properties of the redox active poly(ionic liquid)s. Second, the potential use of these materials in different applications such as electrocatalysts for oxygen reduction reaction, cathodes in lithium batteries and redox flow batteries will be presented.
(Invited) Searching New Materials for Efficient Solar Driven Hydrogen Production
Authors: Yan Yanfa
Published: February 2020

Using sunlight and semiconductors to split water in a photoelectrochemical (PEC) process to generate hydrogen provides a viable way to produce renewable fuel. So far, the efficient PEC devices are exclusively based on epitaxial grown III-V semiconductors. However, these semiconductors are expensive to make, limiting their practical application for large scale PEC hydrogen production. PEC devices based on polycrystalline thin films can potentially lead to low-cost production of hydrogen by PEC. However, most PEC devices made of polycrystalline thin films have not achieved high efficiency yet. Searching for new semiconductors that can potentially lead to efficient PEC devices is still necessary.  In this talk, we will present general strategies for searching for such kind of semiconductors. We will show by density-functional theory that some new chalcogenides and oxides are promising candidates for efficient PEC applications. We will also present our latest results on experimental assessments on these new PEC materials.
(Invited) Multiple Roles of Gold Nanoparticles in Solar-Fuel Photocatalysts
Authors: Wu Nianqiang (Nick) , Cushing Scott Kevin , Li Jiangtian
Published: February 2020

This talk will discuss the multiple roles of gold nanoparticles in photocatalysts. First, the gold nanoparticle can serves as the plasmonic photosensitizers for enhancing the solar energy conversion. Second, the gold nanoparticles can act as the electron relays for facilitating the electron transfer between the quantum dots and semiconductors. Third, the gold nanoparticle can work as the electron sinks due to the Fermi equilibration effect. In addition, this presentation will discuss how to distinguish all the effects of gold nanoparticles in photocatalysis.
(Invited) Electrical Models for Fuel Cells
Authors: Fabregat-Santiago Francisco , Bertoluzzi Luca , Gimenez Sixto , Bisquert Juan
Published: February 2020

Impedance spectroscopy is a widespread technique applied in the characterization of fuel cells. The use of appropriate electrical models allows accessing fundamental information of physic-chemical processes governing the response of these devices. In this work we will review the models applied in the analysis of a variety of photoelectrochemical and fuel cells and the interpretation the different resistances and capacitances typically employed in the equivalent circuits used to fit experimental impedance data. The relationship between current-voltage curves and impedance data will be also explained.
(Invited) Unassisted CO2 Photoconversion at Copper Oxide Electrodes
Authors: Nath Narayan Chandra Deb , Choi Seung Yo , Park Hyunwoong , Lee Jae Joon
Published: February 2020

Artificial photosynthesis of value-added chemicals from CO2 and water has received renewed attention and diverse technical solutions for high efficiency and durability systems have been explored. The photoelectrochemical (PEC) systems have been demonstrated to be technically viable with a number of semiconductor photoanodes (e.g., WO3, BiVO4, etc.) coupled to metal (Cu, Au, Ag, etc.) or metal oxide electrodes (CuO and Cu2O), as well as photocathodes (Si, Cu2O, CuO2, CuFeO2, etc.) coupled to metal/metal oxide anodes for CO2 photoconversion. A photoelectrochemical cell, composed of WO3/dye-sensitized solar cell and copper oxide wire arrays, is demonstrated as an unassisted, durable device for CO2 photoconversion. The high surface-to-volume copper oxide wire exhibits a promising electrocatalytic activity of CO2 reduction reaction at faradaic efficiencies of ~80% and ~60% at E = -0.2 and -0.4 V vs. RHE, respectively. The single-absorber cell of a WO3 photoanode and copper oxide wire cathode couple requires the minimum overpotential (h) of 0.7 V to drive CO2 conversion. In the unassisted cell, the long-wave band (l > ~450 nm) passes through the semi-transparent WO3 film is absorbed by dye. The unassisted cell shows a potential gain of ~0.7 V, successfully driving the CO2 conversion without any external power supply.
Convenient and Efficient Surface Reforming of LaTiO2 N Photocatalyst: Poly(4-styrenesulfonic acid) Treatment and Microwave Assisted CoO
x
Deposition
Authors: Akiyama Seiji , Yamada Taro , Domen Kazunari
Published: February 2020

The overall water splitting by solar-energy-driven photocatalysts is a crucial issue as a solution for today’s mass scale energy and environmental problems. The activity of those photocatalysts is to be improved by  their surfaces where the water splitting reactions take place. This time we report two useful tips to enhance the efficiency of LaTiO2N, an important candidate oxynitride for photocatalysis.  One is to clean off the debris and defects on the particle surface. Domen et al.1 reported a brief, effective aqua regia treatment was in removing surface defects of LaTiO2N. However, aqua regia accompanies drawbacks of its severe reactivity. We need quick, elaborate washing to stop etching of the oxynitride in a contolled manner, and we need to isolate the aqua regia’s corrosive fume from the environment. More convenient and effective altanative surface treatment reagents are wanted in this sense. Two is to modify the surface of LaTiO2N with CoO
x
nanoparticles as so-called co-catalysts.  The co-catalysts are supposed to assist the separation of photogenerated charges as well as promotion of surface reactions to evolve O2. CoO
x
nanoparticles, composed of earth abundant elements, are conventionally loaded by the liquid impregnation/calcination method.2  However the process of calcination on LaTiO2N brings about a complexity of heating in NH3 flow to avoid surface oxidation, simultaneously introducing chances of CoO
x
particle sintering and metallization. Our solutions for there problems are by rinsing in aqueous poly(4-styrenesulfonic acid) (PSS) solution followed by loading CoO
x
with a microwave assisted deposition. Static treatment of the LaTiO2N powder in PSS solution for 17 hours and microwave assisted one-pot loading of CoOx with Co(NH3)3Cl3 in Eyleneglycol solution, prior to fabrication into an electrode, increased the photoanodic current up to 8.9 mA cm-2 at 1.23 VRHE, which is 3 times larger than that without these reforming. We also confirmed that LaTiO2N was treated with PSS solution conveniently and care-freely in comparison with etching in aqua regia, and cocatalyst was coated throughout the surface of LaTiO2N particle by using microwave quick heating.

M. Matsukawa,  R. Ishikawa, T. Hisatomi, Y. Moriya, N. Shibata, J. Kubota, Y. Ikuhara and K. Domen, Nano Lett. 2014, 14, 1038−1041.

F. Zhang, A. Yamakata, K. Maeda, Y. Moriya, T. Takata, J. Kubota, K. Teshima,  S. Oishi and K. Domen, J. Am. Chem. Soc.,
2012, 134, 8348−8351.

Figure 1
Ultralow Power Gas Sensing for Societal Well-Being
Authors: Carter Michael T , Stetter Joseph R , Findlay Melvin W , Meulendyk Bennett J. , Peaslee David
Published: February 2020

Recent years have witnessed an explosion of chemical and physical sensing technologies driven by the Internet of Things (IoT), the advent of commercial wearable technologies and the rise of point of care diagnostics .  Business analysts expect  these trends to continue to grow substantially over the next decade.  This growth will provide ever increasing opportunities in sensor science and technology, particularly those aimed at wearables, as well as medical diagnostics and general health and wellness awareness in the home and environment. 

This presentation will review some of our recent work in the area of next-generation electrochemical gas sensors for environmental and health/safety applications.  Specifically, we will present on new hardware developed for wearable and other applications requiring ultralow power operation and its application to several areas including ozone monitoring for asthma sufferers, wearable environmental gas sensors and the detection and characterization of odors.
Paper-Based Test Strips for Detection of Nucleic Acids and Heavy Metals
Authors: Gao Xuefei , Wu Nianqiang (Nick)
Published: February 2020

Paper-based test strips are attracting immense attention because of their simplicity, low cost, portability and short test time. This talk will present our effort to develop the paper-based test strips for detection of nucleic acids and heavy metals. Nanomaterials are utilized to improve the sensitivity. The surface-enhanced Raman scattering and the colorimetric methods are employed for the signal transduction. The effects of the signal transduction method on the sensing performance are studied. The developed paper-based test strips have potential applications in point-of-care testing, especially in the resource-poor settings.
DNA Electrochemical Hybridization Detection in Droplets Using Gold Ultramicroelectrodes in a Two-Electrode Configuration
Authors: Horny Marie-Charlotte , Lazerges Mathieu , Siaugue Jean-Michel , Pallandre Antoine , Haghiri-Gosnet Anne-Marie , Gamby Jean
Published: February 2020

Biosensors are all about the limit of detection1 imposed by the molecular level changes in expression of biomolecules to hope to perform reliable diagnostics before symptoms of a disease appears. A special interest was driven to the DNA target, mimicking the liver-specific micro-Ribonucleic Acid 1222 (miRNA122). DNA hybridization is the most prized method compared to direct sequencing all the more now that long range electron transfer through the DNA duplex π-staking has been demonstrated3. The electronic coupling within its inner core of stacked array of heterocyclic aromatic base pairs is very sensitive to local disruptions such as mismatches making a DNA biosensor particularly sequence specific. In a DNA biosensor, the target sequence is recognized by a complementary DNA probe and hybridized. The basis pairing according to Watson and Crick’s rules4 is converted into an electrical signal. A 23-base DNA probe was self-assembled on the gold microelectrode via thiol adsorption. Long-range electron transfer was chosen for the monitoring of the hybridization step. Indeed, this direct transduction was significantly enhanced due to DNA-duplex π-stacking and the use of the redox methylene blue as DNA intercalator5. The electrochemical properties of the sensor were screened with the [Fe(III)(CN)6]3-/[Fe(II)(CN)6]4- redox couple in droplets by using cyclic voltammetry (CV) in a two-electrode configuration which is more adapted in the case of microliter biological samples. Voltammograms centered at potential zero are observed as expected for a working UME and a counter electrode made from the same metal and immersed in the same electrolyte. The 2 mm-gold counter electrode (very high area compared to the 25 μm gold working electrode) can be considered as a pseudo-reference electrode allowing a feeble potential drift during measurements. When working with thiolated SAM absorbed on gold substrates, the matter of desorption is not trivial all the more in chloride electrolytes. The reliability of 10-14 M limit of detection determined for DNA target quantification was deduced from differential current density measured compared with the blank measurements. The data analysis highlights the possible role of the desorption phenomenon of the thiolated DNA probes from the sensor surface that could explained the residual current densities measured for concentrations lower than 10-14M.

1           M. Lazerges and F. Bedioui, Anal. Bioanal. Chem., 2013, 405(11), 3705-3714.

2           J. a. Wilson and S. M. Sagan, Curr. Opin. Virol., 2014, 7, 11–18.

3           S. O. Kelley, E. M. Boon, J. K. Barton, N. M. Jackson and M. G. Hill, 1999, 27, 4830–4837.

4           J. D. Watson and F. H. C. Crick, Nature, 1953, 171, 737–738.

5           M. Lazerges, V. T. Tal, P. Bigey, D. Scherman and F. Bedioui, Sensors Actuators B Chem., 2013, 182, 510–513.

Figure 1
Detection of Volatile Plant Chemicals Using Novel Enzymatic Electrochemical Biosensor
Authors: Fang Yi , Ramasamy Ramaraja P.
Published: February 2020

Volatile organic compounds released by pathogen-infected and pest-infested plants can be used as fingerprints for plant disease and infestation detection via electronic nose technologies 1,2. p-ethylphenol (EP) and methyl salicylate (MeSA) were discovered as two most important volatile organic compounds. In this work, enzymatic based electrochemical biosensors were developed for the detection of EP and MeSA. For EP detection, a tyrosinase (TYR)-immobilized amperometric biosensor was developed. Cyclic voltammetry (CV) was used to study the electrochemical reaction. CV indicated that the sensitivity reached to 8.528 µA·cm-2·µM while limit of detection (LOD) reached to 0.210 µM. Steady state constant potential amperometry displayed lower sensitivity (4.052 µA·cm-2·µM), but better LOD (0.095 µM) than CV. For MeSA detection, alcohol oxidase and horseradish peroxidase were applied for detection of methanol that produced after hydrolysis of MeSA. CV and constant potential amperometry techniques were used to determine sensitivity of 0.112 and 0.283 µA·cm-2·µM, and LOD of 23 and 1 µM for the CV and DPV respectively. In order to obtain better sensitivity and higher specificity for MeSA detection, salicylate hydroxylase (SH) and TYR were immobilized on the multiwalled carbon nanotube modified glassy-carbon electrode. After hydrolysis of MeSA, salicylate reacts with SH and TYR to generate amperometric signal. The sensitivity and LOD generated from CV were reported to be 21.29 µA·cm-2·µM and 0.137 µM respectively. Constant potential amperometry was also applied for MeSA detection. The results display that sensitivity of 30.61 µA·cm-2·µM and LOD of 0.013 µM can be achieved. Interference and simulated analyte based studies indicate that the biosensor is suitable for application in agricultural sensing.

Reference:

T. Baldwin, A. Kessler and R. Halitschke, Curr. Opin. Plant Biol., 2002, 5, 351.

P. W. Par´e and J. H. Tumlinson, Plant Physiol., 1999, 121, 325.

Figure 1
The Investigation of Ti Doped Zinc Oxide Sensing Membrane in Bio-Sensor Applications
Authors: Su Yen Lin
Published: February 2020

In this study, we propose a highly sensitive electrolyte–insulator–semiconductor (EIS) pH sensor witha layer of novel metal-oxide. We compared the ZnO and Ti-doped ZnO sensing membrane applied in EIS structure and investigated the characteristics of Ti-doped ZnO sensing membrane. Furthermore, we studied the sensing performance of the ZnO and Ti-doped ZnO EIS structure in different (Na+, K+ , Urea, Glucose)solution.

     The EIS structures of a ZnO sensing membrane were fabricated on 4-in n-type (100) Si wafers. A 50 nm ZnO film was deposited on theSi substrate by radio frequency reactive sputtering from ZnO and Ti target in the ratio of Ar/O2 = 20/5. Subsequently, samples were annealed in O2ambient for 30 s by RTA at various temperatures from 600, 700, 800. After that, the back-side contact of the Si wafer was deposited by Al film with 300nm-thick. Then, the sensing area was defined by standard photo lithography process using a photo sensitive epoxy, SU8-2005. Finally, the samples were fabricated on the copper lines of PCB by silver gel. Epoxy package was used to separate the EIS structure.

Based on X-ray diffraction and atomic force microscopy data, it is found that Ti doped ZnO sensing membrane has higher surface roughness than the ZnO sensing film. High temperature annealing (700 ◦C) leads to the formation of crystalline oxide thin film with a rough surface. The pH sensing experiments of EIS with Ti doped ZnO membrane annealed at 700 ◦C shows that reference voltage is linearly dependent onsolution pH and an average sensitivity of 57.56 mV/pH. This outstanding pH sensitivity may be attributed to the high surface roughness of oxide membrane. Besides, Ti doped ZnO sensing film has lower drift rate (0.29mV/hr) and hysteresis voltage (2.79mV) than the ZnO sensing film.

     To study the urea and glucose sensing property of the ZnO and Ti-doped ZnO on EIS structure, we prepared the solutions of urea and glucose which concentration were controlled in a range from 1mM~32mM and 2mM~8mM. Then, we picked the conditions of ZnO sensing membrane for RTA temperature at 600oC in O2and Ti-doped ZnO sensing membrane for RTA temperature at 700oC. The sensitivity of Ti-doped ZnO in O2ambient has better quality than the ZnO, which sample in urea solution was 3.62mV/mM, the linearity was 87.36%. Besides, sample in glucose solution was 6.42mV/mM, and the linearity was 90.57%.

     Finally, we successfully demonstrate the use of Ti doped ZnO EIS structure with uricase-immobilized alginate film for the detection of uric acid in serum. The concentration of serum uric acid measured by EIS biosensor is comparable to that determined by commercial assay kit. This sensitive EIS based biosensorcan potentially be served as the diagnosis tool for general clinical examinations.
Voltammetric Reduction of Graphene Oxide and Spectroelectrochemical Characterization
Authors: Fanjul Bolado Pablo , Hernández Santos David , Navarro Hernandez Carla , González García Maria Begoña , Colina Alvaro , Heras Mª Aranzazu
Published: February 2020

Two graphene oxide (GO) materials with different layer size and proportion of functional groups in the basal planes (hydroxyl and epoxy) and in the edges (carbonyl and carboxyl) were used to modify the surface of commercially available screen printed electrodes. Cyclic voltammetry in 0.1 M KNO3 was evaluated as an easy to use electrochemical methodology to reduce GO attached to the surface of screen-printed electrodes (SPEs). A cathodic peak related to the reduction of GO was identified, and the peak potential was correlated to the difficulty to reduce GO to Electrochemically Reduced Graphene Oxide (ERGO) depending on the functional groups present in the basal plane and in the edges of the original GO monolayers. Time resolved UV-VIS spectroelectrochemistry is used for the very first time as an ‘in situ’ characterization technique for real time monitoring the electrochemical reduction of graphene oxide. Raman spectroelectrochemistry is used for the first time in combination with miniaturised screen printed electrodes as an ‘in situ’ characterization technique to follow the reduction too.
Energetically Stable LiMn2O4 Surface Structure and Its Equilibrium Shape
Authors: Kim Soo , Wolverton Chris
Published: February 2020

Here, we use the density functional theory (DFT) calculations to investigate the (001) and (111) surface structure of the LiMn2O4 (LMO) spinel cathode materials.1 We first test the effect of slab termination, relaxation, and reconstruction, as well as electronic and magnetic ordering for Mn to examine previous discrepancies on the calculated DFT surface energy for LMO in the literature. We reveal that the relative stability of (001) and (111) LMO surfaces significantly vary depending on the relaxation schemes and surface reconstruction. While our initial DFT calculations testing various numerical and physical factors represent a “closed” thermodynamic system at 0 K, in actuality, the system is open to exchange of materials to react with O2 molecule or Li+ ions. Therefore, we further investigate the surface stability of LMO as a function of the oxygen and lithium chemical potentials. Our calculations show that the (001) and (111) DFT surface energies are very close, suggesting the spectrum of cube-like to octahedron-like particles shapes can be observed under different experimental synthesis condition. We predict that higher temperature and high lithium chemical potentials should be avoided to mitigate the Mn dissolution in LMO, where the synthesized LMO particles are likely to contain more (001) surfaces that are more prone to Mn dissolution. In contrast, the (111) surfaces that are composed of Li-rich surface layers could be more resistant to the Mn dissolution.

Reference: [1] S. Kim, M. Aykol, and C. Wolverton, Phys. Rev. B, 2015, 92, 115411.

Acknowledgements: This work was supported by Northwestern-Argonne Institute of Science and Engineering (NAISE).

Figure Caption: Different (001) to (111) surface energy ratio and the corresponding representative LMO particles shapes (as a function of lithium and oxygen chemical potential).

Figure 1
Doping Strategies to Enhance the Na+ Conductivity of the Cubic Na3PS4 Superionic Conductor
Authors: Zhu Zhuoying , Chu Iek-Heng , Deng Zhi , Ong Shyue Ping
Published: February 2020

Cubic Na3PS4 (c-Na3PS4) is a highly promising sodium superionic conductor solid electrolyte that can enable safer and more energy dense all-solid-state sodium batteries. First reported by Hayashi et al.,1 Na+ conductivities as high as 0.74 mS/cm have been achieved through improvements in synthesis and the addition of suitable dopants. In this work, we report a first-principles investigation of doping strategies to further enhance the Na+ conductivity of c-Na3PS4. We show that pristine c-Na3PS4 is an extremely poor Na ionic conductor, and the introduction of Na+ excess is the key to achieving reasonable Na+ conductivities observed in experiments. Using ab initio molecular dynamics simulations (AIMD), we predict that 6.25% Si-doped c-Na3PS4 has the Na+ conductivity of 1.66 mS/cm, in excellent agreement with previous experiment results (0.74 mS/cm). Remarkably, we find that Sn doping at the same concentration yields a much higher predicted Na+ conductivity of 10.7 mS/cm, though with a slightly higher dopant formation energy. We will also discuss the effect of other dopants and different doping concentrations on the Na+ conductivity. Finally, we will also discuss the role of topology and Na disorder in enabling fast ionic conduction in this material.

References:

[1] Hayashi, A.; Noi, K.; Sakuda, A.; Tatsumisago, M. Superionic Glass-Ceramic Elec- trolytes for Room-temperature Rechargeable Sodium Batteries. Nat. Commun. 2012, 3, 856.
Manganese Functionalized Graphene As a New Platform for Peroxynitrite Sensing
Authors: Kalil Haitham , Bayachou Mekki
Published: February 2020

Peroxynitrite (PON, ONOO−) is a powerful oxidizing agent generated in vivo by the diffusion-controlled reaction of nitric oxide (·NO) and superoxide (O2
·−) radicals. Peroxynitrite levels accumulate under oxidative stress. Elevated peroxynitrite levels are associated with chronic inflammatory disorders including neurological and vascular diseases, as well as a number of other pathophysiological conditions. The accurate detection of this analyte in biological systems is of paramount importance, not only to understand the genesis and causes of ailment at the tissue/cellular level, but also to suggest and design potential therapeutic routes.

In the past, we studied the sensitivity of carbon electrodes modified by polymerized hemin (iron protoporphyrin) as standalone and in combination with conductive polymer PEDOT (3,4-ethylendioxythiophene). These polymerized surfaces have been used as platforms for amperometric measurements of peroxynitrite both in still solutions and under flow conditions. More recently, we extended this line of research to the use of hemin functionalized graphene as a catalytic platform for PON oxidative detection.

In this work we explored and discussed the sensitivity of manganese-based interfaces for peroxynitrite amperometric determination. Surfaces of electrodeposited manganese (Mn), manganese-graphene, and manganese-decorated graphene/hemin-based nanostructures were formed on glassy carbon electrodes as well as on carbon fiber microelectrodes. The effect of graphene on the electrodeposition of Mn was investigated by cyclic voltammetry. We tested these interfaces for electro-catalytic sensing of peroxynitrite in solution using chronoamperometric technique. The morphology of the prepared manganese interfaces was characterized using scanning electron microscopy (SEM), Energy Dispersive X-ray Analysis (EDXA), Ultra-Violet/Visible (UV/Vis), X-ray Photoelectron Spectroscopy (XPS) and Raman spectroscopy. The results showed that manganese-functionalized hemin/graphene enhances peroxynitrite detection and quantification compared to hemin/graphene-only interfaces. We noticed that there is a synergistic effect of the presence of graphene with manganese nanoparticles in the prepared materials. We compared and contrasted on how graphene nano-sheets affect the electrochemical behavior of hemin-modified electrodes in the absence and presence of manganese nanoparticles. In conclusion, we found that the incorporation of manganese influences the sensitivity of PON-sensing hemin/graphene platforms.
Defect-Free Amorphous Indium Gallium Zinc Oxide Deposition Process By Magnetic Field Shielded Sputtering
Authors: Lee Dong Hyeok , Kim KyungDuck , Hong MunPyo
Published: February 2020

The amorphous InGaZnO (a-IGZO) is widely accepted as a promising channel material for thin-film transistor (TFT) applications owing to their outstanding electrical properties [1, 2]. However, a-IGZO TFTs have still suffer from their bias instability with illumination [1-4]. Up to now, many researchers have studied the sub-gap density of states (DOS) as the root cause of instability. It is well known that defect states can influence on the performances and stabilities of a-IGZO TFTs. The defects states should be closely related with the deposition condition, including sputtering power, and pressure. Nevertheless, it has not been reported how these defects are created during conventional RF magnetron sputtering. In general, during conventional RF magnetron sputtering process, negative oxygen ions (NOIs) can be generated by electron attachment in oxygen atom near target surface and then accelerated up to few hundreds eV by a self-bias; at this time, the high energy bombardment of NOIs induce defects in oxide thin films. Recently, we have reported that the properties of IGZO thin films are strongly related with effects of NOIs which are generated during the sputtering process [5]. From our previous results, the electrical characteristics and the chemical bonding states of a-IGZO thin films were depended with the bombardment energy of NOIs. And also, we suggest that the deep sub-gap states in a-IGZO as well as thin film properties would be influenced by the bombardment of high energetic NOIs during the sputtering process.

In this study, we have studied the gate bias instability and their density of states (DOSs) of a-IGZO TFTs as depending on the bombardment of NOIs during conventional magnetron sputtering. Finally, we will introduce our novel technology named as Magnetic Field Shielded Sputtering (MFSS) process to prevent the NOIs bombardment effects and present how much to be improved the instability of a-IGZO TFTs by this new deposition method.

1. M.G. Kim, M.G. Kanatzidis, A. Facchetti, and T.J. Marks, Nat. Mater. 10, 382 (2011).

2. K.K. Banger, Y. Yamashita, K. Mori, R.L. Peterson, T. Leedham, J. Rickard, and H. Sirringhaus, Nat. Mater. 10, 45 (2011).

3. M.D.H. Chowdhury, P. Migliorato, and J. Jang, Appl. Phys. Lett. 98, 153511 (2011).

4. X. Xiao, W. Deng, S. Chi, Y. Shao, X. He, L. Wang, and S. Zhang, IEEE Trans. Electron Devices 60, 4159 (2013).

5. D.H. Kim, J.N. Jang, S.B. Yoon, and MunPyo Hong, Appl. Phys. Express 7, 031401 (2014).
Nanoparticle-Polymer Surface Adsorption Relevant to CMP Applications
Authors: Wienck Richard A , Keleher Jason J
Published: February 2020

Chemical Mechanical Polishing (CMP) has emerged as a critical technology for the planarization of precision optical components, data storage media, and integrated circuit semiconductor devices. This process is a delicate balance between chemical surface modification and mechanical removal utilizing a nanoparticle dispersion (slurry) to remove defects/irregularities with the goal to attain angstrom level uniformity. As technology continues to advance, next generation nanoparticle dispersions and CMP slurries will increase in complexity to meet stringent performance demands, making it necessary to develop polymeric media that reduce overall surface defectivity and increase planarization efficiency. To uncover dynamics amongst the slurry additives, abrasives, polymeric interfaces, and the CMP substrate the molecular level interactions at the nanoparticle-polymer interface need to be explored. This work set out to explore these interaction mechanisms by using a modified electrochemical quartz crystal nanobalance (EQCN) technique. This modified technique utilizes thin film deposition to place a polymer on the electrode and then by applying the Sauerbrey equation it is possible to gain insight about the surface adsorption at the nanoparticle-polymer interface. The synergistic interaction of the slurry chemistry and the polymeric substrate is further explored to determine the role of surface reactions that alter the polymeric medium’s surface energy and subsequently alter the nanoparticle binding mechanisms.
Electrochemical Determination of Aluminium By Oxidation of Dopamine Using Platinum Nanoparticles on MWCNT As Sensor
Authors: Félix-Navarro Rosa María , García-Tapia Karelid , Reynoso-Soto Edgar Alonso , Silva-Carrillo Carolina , Lin-Ho Shui Wai , Paraguay-Delgado Francisco
Published: February 2020

Aluminum (Al) is the most abundant metallic element and constitutes about 8% of the earth's crust. The aluminium is related to different neurological disorders like Alzheimer's, bipolar, depression, etc. As well as anemia, also reduces the absorption of calcium causing pain, deformities and broken bones.1-2 The development of nanotechnology has led to a growing interest in the study and design of nanosensors, in order to improve selectivity, limit of detection, reproducibility and durability of the current sensors.4-5

In this paper is repoted the preparation of  hybrid material based on platinum nanoparticles (NP Pt) on  multiwall carbon nanotubes (MWCNT) prepared by inverse microemulsion method using sodium dodecyl sulfate (SDS) as surfactant in a mixture of hexane/isopropanol/water. The hybrid material was characterized by transmission electron microscopy (TEM). The hybrid material showed small spherical nanoparticles with average sizes of 2.15±0.54 nm, well as thermogravimetric analysis  a load of 20% platinum.

The NP Pt/MWCNT hybrid material use for determining Al+3 using dopamine as a chelating molecule for the indirect determination of the aluminum by differential pulse voltammetry in neutral medium. Under optimal experimental conditions it was determined the sensitivity of the NP Pt/ MWCNT sensor was 27.75 μA/ppb  Al+3 with a  linear response range from 0 up to 15 ppb Al3+.

References

1. C. Exley, Environ Sci: Process Impacts, 15, 1807, (2013).

2. WHO (World Health Organization), Safety  evaluation of certain food additives and contaminants, p.173, WHO, Geneva, 2007.

3. R. L. McCreery, , Chem. Rev. 108, 2646 (2008).

4. A. Hayat, G. Catanante, J. Louis Marty,  Sensors, 14, 23439 (2014).

Figure 1
The Analysis of Prussian Blue Bonding on the Electrochemically Functionalized Carbon Nanotubes
Authors: Je Lisa , Belli Stuart , O'Connor Thomas J.
Published: February 2020

We have explored the pseudocapacitance of Prussian blue (PB) modified carbon nanotube electrodes.The carbon nanotubes (CNT) are deposited by chemical vapor deposition (CVD) onto a nickel catalyst that had been electroplated onto a metal base electrode. The nanotubes were then characterized by Raman spectroscopy and cyclic voltammetry. Prussian blue was electrochemically deposited onto the CNT electrode from a solution of K3Fe(CN)6 by repeated cycling between -0.1 V and 1.0 V verses a Ag/AgCl reference electrode. The ferricyanide redox couple occurs at about 0.5 V while the deposition of PB was seen as a growing redox couple at about 1.0 V see Figure 1.

Optical imaging of the CNT electrode showed a distinct blue-green tint that together with the cyanide stretch in the Raman spectrum gave evidence that PB had been deposited, see Figure 2. This suggests that this electrochemical technique utilizing CV is a viable method to functionalize CNT electrodes. Electrodes thus modified show increased pseudocapacitance compared to the unmodified CNT electrodes. The exact structure and location of the PB bonding is unknown and was the focus of this study. Scanning electron microscopy was utilized to image the electrode surface after each step of the process in order tostudy PB bonding onto the CNT electrode.

Figure 1: A CNT electrode undergoing functionalization in ferricyanide solution. The peaks growing in are thought to be Prussian blue being deposited onto the carbon nanotubes.

Figure 2: Raman spectra of functionalized and unfunctionalized carbon nanotube electrodes.  The G and D bands due to the nanotubes are seen in both spectra at the expected 1587 and 1340 cm-1, respectively.  For the functionalized electrode, additional peaks in the 2100 cm-1 range due to cyanide stretching are observed.

Figure 1
(Invited) GaAs Quantum Dots in Gap Nanowires: Growth and Luminescence
Authors: LaPierre Ray R , Kuyanov Paul , Boulanger Jonathan
Published: February 2020

Nanowires are rod or whisker-like structures with length on the order of microns and diameter from tens to hundreds of nanometers.  They represent a new class of three-dimensional materials, and the next step in the evolution of conventional two-dimensional thin films, quantum wells, or heterostructures. Nanowires are typically fabricated by the assistance of foreign metal catalysts, such as Au, that collect deposited material, resulting in localized growth of nanowires. However, the use of foreign metal particles can result in contamination of the nanowires and reduction in the carrier lifetime, which degrades device performance. In the present work, we present the self-assisted growth of GaP nanowires by molecular beam epitaxy, using Ga droplets as a seed particle without the use of any foreign metal catalysts.  Growth of the nanowire occurs by selective-area epitaxy using a patterned array of holes in an SiOx mask. The holes collect Ga adatoms forming a Ga droplet that seeds the nanowire growth. The size of the Ga droplet can be controlled by a novel evaporation process, resulting in ultra-thin nanowire structures.  GaAs heterostructures were introduced into the GaP nanowires during growth resulting in quantum dots.  The quantum dots are encapsulated in GaP, resulting in passivation of the QD surfaces.  Photoluminescence emission was observed from the QDs in the visible range.  The emission wavelength is tunable by the size or composition of the QDs.  This process results in controlled luminescence emission with application in single photon sources, light emitting diodes, or laser diodes.
Material Conversion of GaAs Nanowires
Authors: Nishioka Kohei , Ishikawa Fumitaro
Published: February 2020

We propose material conversion of compound semiconductor GaAs nanowires for its extension of their functions and structures. As utilized for the oxidation technique of AlGaAs within GaAs-based vertical cavity surface emitting lasers for the electrical and optical confinement, such kind of material conversion enables functions which cannot be utilized without the introduction of contrastive materials. If we can convert nanoscale materials with keeping its structure, which can widely extend the tunability of wide range of materials properties such as electric, dielectric, as well as mechanical properties. Recently, we proposed precise selective oxidations to GaAs/AlGaAs heterostructure, enabling the synthesis of semiconductor/oxide composite GaAs/AlGaOx and full-oxide and finely structurally controlled GaO/AlGaOx nanowires. Characteristically, the composite nanowire provide specific white luminescence, which cannot be achievable for conventional compound semiconductors without the material conversion for nanoscale oxides[1,2] To further develop the material conversion technique for GaAs nanowires, we investigate two-step materials conversion consisting of the thermal treatment within liquid In, and nitrogen gas flow under atmospheric pressure. By the technique, we show the conversion of GaAs nanowire constituents to In, oxygen, as well as silicon from the substrate, eventually forming Ga(In)As and In(Si)O nanowires.

We used GaAs nanowires having about 100 nm diameter with 5mm length on Si substrate, synthesized by molecular beam epitaxy. The conversion was carried out in a furnace introducing nitrogen gas under atmospheric pressure. During the conversion, the nanowires were dipped into a custom-made qualz pod with In melt, which was weighted down with qualz cap. By heating the sample up to 600oC for an hour, we observe the introduction of In into the GaAs nanowire. We then carry out the heating without using the pod but just pasting the In onto the substrate surface having GaAs nanowires. As a result, the wire was converted from GaAs nanowire to InO with the constituent of substrate Si. These results suggest a possible technique realizing the introduction of wide range functionalities into the optically active and electrically high-speed compound semiconductor GaAs nanowires.

[1] H. Hibi, M. Yamaguchi, N. Yamamoto, and F. lshikawa, Nano Lett. 14, 7024, 2014.

[2] F. Ishikawa and N. Yamamoto, ECS transactions, 69, (In press), 2015.
Modulation of Fluorescence Biomolecule Signals By Semiconducting Nanowire Antanna Effects
Authors: Frederiksen Rune
Published: February 2020

High aspect ratio semiconducting nanostructures have gained increasing interest as platforms for fluorescence based biosensing. Here, well-defined biofunctionalized vertical semiconducting nanowires are used to map the interaction of light with nanowires. We identified how nano-optical effects modify biosensing fluorescence detection at the nanowire interface - as it modulates the photon flux in their surroundings through interactions with the electromagnetic field of the light. We presented a novel approach to understanding the complex effects at the nanostructure-biomolecule-light interface, both experimentally and theoretically. We show how nanowires act as antennas modifying the light distribution and the emitted fluorescence This work highlights the important of nano-optical phenomenon at nanostructures to obtain highly sensitive fluorescence based biosensing platforms.