bluuebunny/crossref_metadata_2025 huggingface dataset:
Epitaxially Grown PtxIr100-X Alloys with Enhanced Properties for Ammonia Electro-Oxidation
Authors: Sacré Nicolas , Galipaud Jules , Garbarino Sébastien , Roué Lionel , Guay Daniel
Published: February 2020

Ammonia is a highly toxic gas, a major environmental pollutant, and a potential fuel for fuel cells. Thus the electro-oxidation of NH3 has important applications in NH3 safety sensors, NH3 decontamination in wastewater, and power production. However, on most electrode surfaces, the electro-oxidation of NH3 is plagued with low surface reactivity and surface contamination by reaction intermediates.

The vast majority of studies on the NH3 oxidation reaction have been performed on Pt electrocatalysts, and Pt remains the electrocatalyst which shows the highest current density at the lowest overpotential for catalyzing the oxidation of NH3 to N2. On Pt, the oxidation of ammonia occurs predominantly on (100) terraces. However, to the best of our knowledge, the effect of strain in the outmost metal layers and hybridization of the Pt d-states with Ir atoms (ligand effect) on the electro-oxidation of NH3 have never been studied. Accordingly, we have investigated the epitaxial growth PtxIr100-x alloys model electrocatalysts that mimic single crystalline systems. This was achieved by deposition on MgO(100) via pulsed laser deposition.

It will be shown that Pt and Ir form a kinetically stable alloy and that the PtxIr100-x alloys grew with the desired PtIr(100)[010]//[010](100)MgO configuration over the whole composition range. Also, the XPS data show that a surface alloy is formed over the whole composition range.

Electrochemical measurements were performed in 0.5 M H2SO4 to highlight the preferential (100) surface orientation. Cyclic-voltametry and chrono-amperometry experiments in alkaline media were then carried out in presence of ammonia. They demonstrate the importance of the (100) surface structure for the electro-oxidation of ammonia compared to randomly oriented surface (polycrystalline sample). The presence of iridium decreases the surface poisoning at PtIr (100) alloys. Finally, it will be shown that surface poisoning can be further reduced using a simple cyclic-voltammetry procedure.
Screen-Printed Electrodes Modified with Multi-Walled Carbon Nanotubes for Cisplatin Detection
Authors: Materón Elsa María , Wong Ademar , Klein Stanlei Ivair , Sotomayor Maria del Pilar T
Published: February 2020

A screen-printed electrode modified with multi-walled carbon nanotubes functionalized with carboxyl groups (MWCNT-COOH/SPE) in a 0.1 mol L-1 NaCl solution (pH 7) containing 800 μmol L-1 of sodium dodecyl sulfate (SDS) was used in the selective quantification of the widely used antitumor drug, cisplatin (Fig. 1). The MWCNT-COOH/SDS/SPCE sensor was characterized by cyclic voltammetry, and the differential pulse voltammetry was used for the detection and quantification of analyte, or evaluated in presence of other antitumor drugs, like carboplatin, oxaliplatin, doxorubicin and gemcitabine. For solutions of cisplatin, the electrochemical analysis showed a linear correlation coefficient of 0.9974 to cisplatin at concentrations between 1.45 × 10-5 and 1.0 × 10-4 mol L-1, a sensitivity of 4.5 × 104 (±1.0×103) μA L mol-1, and detection and quantification limits of 4.6 × 10-6 and 1.4 × 10-5 mol L-1, respectively. The reproducibility of the sensor response evaluated by the analysis of three replicates, indicated a RSD of 3.91%.

The excellent response of the MWCNT-COOH/SDS/SPE cisplatin sensor allowed it to be test in samples of human blood serum whose levels of added cisplatin had been monitored by the HPLC. The average error % (sensor/HPLC) of 0.95 indicates that the combined methodology of MWCNT-COOH modified SPCE and the addition of a surfactant such as dodecyl sulfate is a convenient alternative for the use of HPLC for cisplatin quantitative determination in biological samples.

Figure 1
Tailoring Morphology of ZnO Nanostructures on Fabrics By Electrochemical Deposition for Gas Sensors
Authors: Lee Eunji , Park Hyejin , Chung Yoonsung , Lee Seokhee , Kim Dong-Joo
Published: February 2020

With significant advancements in field of nanotechnology, people are more interested in implementing the nanotechnology into practical and portable devices such as flexible and wearable devices. Research is actively focused on utilizing flexible substrates instead of solid and rigid substrates while sustaining excellent material properties to realize commercialization. For wearable devices, functional materials such as semiconductors need to be built on fabrics and/or fibers. Among various semiconducting materials, ZnO is an excellent candidate for many applications because of their facile fabrication of nanostructure and structure-driven electronic and optical properties.

There are many methods to fabricate ZnO nanostructures, but solution synthesis can be the most simple and effective way to construct ZnO on wearable substrates. Various parameters in solution process such as precursors, temperature, and pH have been investigated to change ZnO nanostructure and to understand the growth mechanisms. However, solution process with electrical bias on the morphological evolution has been rarely investigated. In addition, realization of ZnO nanostructures on various fabrics still remains as a key challenge for wearable electronics.

Therefore, we designed and investigated a simple solution method to control the morphology of ZnO nanostructures by applying external voltage on copper coated polyester taffeta fabrics. In addition, types of ZnO precursors in solution and types of fabrics were systematically investigated to determine the bias-driven morphology. The use of external voltage promotes nucleation of ZnO nanorods without ZnO seed layer. With the increase of external voltage, ZnO nanorods became agglomerate structures. The degree of agglomerates varies depending on the types of fabrics. Such comparative study in substrate effects provide insight on the growth mechanism in electrochemical deposition. Gas sensing properties of various ZnO nanostructures on fabrics are compared in detail.

Figure 1
Doping Poly(Acrylonitrile-co-Butadiene-co-Styrene) with Titanium Dioxide Nanoparticles to Create Novel Chemical Sensors
Authors: Skorski Matthew R , Fox Douglas M , Miller Abigail E
Published: February 2020

Introduction

The use of 3D-printing in the United States has skyrocketed in recent years. This has opened up the possibilities for cheap, reproducible, and modifiable chemical sensors that can be made in the lab. However, new polymers have to be developed that support these functions. To that end, this study will investigate the conductive properties of titanium dioxide (TiO2) nanoparticles suspended in Poly(Acrylonitrile-co-Butadiene-co-Styrene) (ABS). It is desired that the doped polymer be able to create 3D printed objects that can effectively conduct electricity. The applications for this technology would include 3D-printed chemical sensors, circuits, and other devices.

To study the mechanical strength and electrochemical effects of the TiO2, doped polymers are created for printing in 1,5, and 10 % by mass nanoparticle to ABS concentrations. The printed objects made from TiO2 doped ABS filaments will be compared to those objects made from store bought ABS filament.

Experimental

To create the doped polymer, ABS is mixed with the TiO2 nanoparticles in 10 mL of acetone per gram of doped polymer. After evaporation of the acetone the polymer is mixed in a DSM Xplore Micro 15cc Twin Screw Compounder before being molded into 3D printer filament with a Filabot Wee extruder. The 3D objects are printed with a FlashForge Creator. A MARK-10 advanced digital force gauge and an ESM301 motorized test stands are used to perform three point flexural tests and stress-strain tests. The electrochemical properties will be analyzed by using a Van der Pauw resistivity test.

Results and Discussion

Early work has shown that the ABS is able to suspend and disperse the TiO2 nanoparticles. While the Van der Pauw tests have not begun, preliminary mechanical testing has been completed. The mean and standard deviation for the stress and strain measurements of the 1% printed objects were 28.1 ± 9.5 MPa and 12.8 ± 4.4 %. The 5 % and 10 % graphs qualitatively showed similar large deviations for both values. The large standard deviation for both values is believed to be caused by the variation in the filament thickness. The filaments are expected to be 1.75 mm but were thinner along parts of the strand by up to 24%. When the tests were repeated with the filament diameters accounted for, the mean and standard deviation for the stress and strain measurements of the 1% printed objects were 39.4 ± 0.8 MPa and 8.93 ± 0.3 % (Figure 1). All future 3D prints will take the changing filament diameter into consideration.

Figure 1
The Relationship Between Carbon Nanotube Surface Status and Electrocatalytic Performance Toward Oxygen Reduction Reaction of Cobalt Phthalocyanine /Carbon Nanotube
Authors: Zhang Zhengping , Wang Feng , Ji Jing , Liu Jingjun , Li Zhilin
Published: February 2020

Recently, noble metals and their alloys nanoparticles supported on the carbon materials as carbon-based composite electrocatalysts are widely studied. However, on one hand, the high cost associated to these noble metals is still a drawback for full commercial application; on the other hand, their designing is limited by their characteristic. It is important to develop a new catalyst with low cost, high catalytic activity and wide designing for oxygen reduction reaction. Cobalt Phthalocyanine (CoPc) has high catalytic activity, and its special macrocyclic structure can perform well with the carbon materials toward Oxygen Reduction Reaction (ORR). Thus, the design of relationship between CoPc and its carbon-base is a necessary mission for this new catalyst for ORR.

 This abstract mainly focused on the different surface treatment of carbon nanotubes (CNTs) connect to CoPc and their electrocatalytic performance for the ORR process. Investigating raw CNTs, acidification CNTs (AF-CNTs) and activation CNTs gives us three different surface treatment CNTs coated by CoPc, which have higher electrocatalytic performance than CoPc itself. Here we find CoPc /AF-CNTs exhibit highest catalytic activity, and the Tafel Polarization curve test showed that CoPc/AF-MWCNTs perform the highest exchange current density (i0) in oxygen reduction reaction, and even its reaction rate is faster than commercial catalyst. The results indicated that the broken CNTs surface is beneficial for coating CoPc, as well as the charge transformation during the catalytic process. At the same time oxygen- containing groups on carbon-base can promote catalytic activity of CoPc for the ORR process.

Figure 1
Investigation of Lithium-Ion Diffusion and Irreversible Processes in Dual-Ion Cell
Authors: Balabajew Marco , Kranz Tobias , Roling Bernhard
Published: February 2020

In 2012 Placke et al. proposed so called „dual-ion cells“ as a new type of energy storage system. They reported an extraordinary cycling stability with a capacity retention of more than 99% after 500 cycles. Even though the achievable cell voltage in this kind of cells is about 4.6 V, the specific energy is still quite low compared to common lithium-ion batteries. The reason for this is a fundamental difference from conventional lithium-ion batteries, since not only the electrodes, but also the electrolyte acts as active material. During charging, lithium cations are reduced and deposited at a metallic lithium anode, while the anions are intercalated into graphite. During discharging, anions and cations are released back into the electrolyte (see figure 1).[1] Therefore the electrolyte acts as ion source, and the concentration hereby limits the energy density.

As the cell voltage of “dual-ion cells” is very high the electrolyte needs to have a wide electrochemical window. For this reason, typically ionic liquid based electrolytes are used for this application. However, the concentration of lithium salts in ionic liquids is strongly limited due to solubility, increasing viscosity and decreasing conductivity.[2] During cycling the concentration underlies changes due to the extraction of lithium salt. This fact gives the possibility to investigate fundamental processes during charging and discharging by measuring the electrolyte resistance. In this work we therefore use electrochemical impedance spectroscopy in 2- and 3-electrode setup to gather information about diffusion processes in the electrolyte and about the reversibility of the processes during charging and discharging.

Figure 1: Functionality of a dual-ion cell (derived from [1]).

[1] T. Placke, P. Bieker, S. F. Lux, O. Fromm, H.-W. Meyer, S. Passerini, M. Winter, Zeitschrift für Physikalische Chemie, 226, 391 (2012).

[2] T. Frömling, M. Kunze, M. Schönhoff, J. Sundermeyer, B. Roling, Journal of Physical Chemistry B, 112, 12985 (2008).

Figure 1
Device Simulation of Hydrogen-Terminated Diamond Mosfet and Extraction of Small-Signal Parameters
Authors: Zhou XI , Albin Sacharia
Published: February 2020

Diamond has exceptional properties suitable for electronic and photonic devices. In particular, hydrogen-terminated diamond (HTD) FET devices have been studied recently for potential radio-frequency (RF) applications by exploiting its high conductivity at diamond surface, high thermal conductivity and simple fabrication process [1-3]. However, the device simulation of such FET device is rarely reported because the surface conductive mechanism is not fully understood. 

In this work, a new device structure including a surface adsorbate layer (ADL) is presented and a possible explanation of the formation of surface conductive layer is provided. Based on our theory, the 2D device simulation is achieved using Sentaurus Technology Computer-Aided Design software; both the capacitance-voltage (C-V) and DC current-voltage (I-V) properties of the HTD MOSFET can be understood well. It is found that the current mainly flow at diamond surface when the drain-source voltage (VDS) is small but meander into the bulk when |VDS| becomes larger. The working mode of the device can change from enhancement to depletion as the gate length (Lg) shrinks, and the threshold voltage becomes very sensitive to Lg when Lg≤0.2μm. The off-state leakage current increases drastically when Lg is approaching 50nm, causing the on/off current ratio dropping from 106 to 103.

In addition, the radio-frequency (RF) small-signal equivalent circuit of the device is generated and the frequency responses of the circuit components are studied. For devices with small gate length (<0.2μm), the non-quasi-static (NQS) effect happens at the frequency over 10GHz, making the HTD device suitable for applications in microwave range. The simulated transition frequency fT is around 170GHz when Lg=50nm, but it is greatly affected by the source/drain series resistance. Finally, a strategy is presented to extract the values of circuit components from simulated two-port parameters, which works well up to 2GHz. 

[1] M. Schwitters, M. P. Dixon, A. Tajani, D. J. Twitchen, J. I. S. E. Coe, H. El-Haji et al., Diamond-MESFETs-synthesis and  integration, IEEE European Radar Conference, (2005) pp.1-4.

[2] M. Kasu, K. Ueda, H. Ye, Y. Yamauchi, S. Sasaki, T. Makimoto, High RF output power for H-terminated diamond FETs, Diamond and Related Materials, 15(2006) pp.783-786.

[3] J. L. Liu, C. M. Li, R. H. Zhu, J. C. Guo, L. X. Chen, J. J. Wei et al., RF characteristic of MESFET on H-terminated DC arc jet CVD diamond film, Applied Surface Science, 284 (2013) pp.798-803.
Room Temperature Processed Electrochromic Smart Windows with Flexible Film
Authors: Lee Sohee , Kim Haekyoung
Published: February 2020

Electrochromic (EC) devices, which dynamically change color under applied potential, are widely studied for use in energy-efficient smart windows. To improve the viability of smart windows, many researchers are utilizing nanomaterial, which can provide electrochromic devices with improved coloration efficiencies, faster switching times, longer cycle lives, and potentially reduced costs. We report the synthesis of nanomaterials for transparent conducting electrodes (TCE).  The smart window characteristics were measured and studied.

For fabrication of smart window, WO3 ink was spin-coated on ITO/glass and electrolyte of ethylene carbonate, dimethyl carbonate, and lithium perchlorate was used. The counter TCE was fabricated by bar coating method with silver nanowires (Ag NW) on PET film, which has 25 ohm/sq of sheet resistance and 90% of transmittance. EC device with Ag NW TCE was assembled and sealed with epoxy. The performances of smart window were characterized with the performance of Ag NW TCE. The potential range for coloring was 1.5 – 2.5 V and the transmittance was 87 %. The bleaching was observed at -2.5 V and the transmittance was below 40 %. The flexible TCE can be applied flexible and bendable smart window with low process cost.
Synthesis of Ruthenium Complexes for Semiconductor Device Using Atomic Layer Deposition
Authors: Jung Eun Ae , Han Jeong Hwan , Park Bo Keun , Kim Chang Gyoun , Son Seung Uk , Chung Taek-Mo
Published: February 2020

Ruthenium (Ru) has attractive material properties due to its promising characteristics such as a low resistivity (7.1 μΩ·cm in the bulk), a high work function (4.7 eV), and feasibility for the dry etch process. These properties make Ru films appropriate for various applications in the state-of-art semiconductor device technologies. Thus, it has been widely investigated as an electrode for capacitor in the dynamic random access memory (DRAM), a metal gate for metal-oxide semiconductor field effect transistor (MOSFET), and a seed layer for Cu metallization. Due to the continuous shrinkage of microelectronic devices, better deposition processes for Ru thin films are critically required with excellent step coverages in high aspect ratio (AR) structures. In these respects, atomic layer deposition (ALD) is a viable solution for preparing Ru thin films because it enables atomic-scale control of the film thickness with excellent conformality.

A recent investigation reported that the nucleation of ALD-Ru film was enhanced considerably by using a zero-valent metallorganic precursor, compared to the utilization of precursors with higher metal valences.

In this presentation study, we will display our research results on the synthesis and characterization of novel ruthenium complexes. The ruthenium compounds were easy synthesized by the reaction of ruthenium halide with appropriate organic ligands in protic solvent, and characterized by NMR, elemental analysis and thermogravimetric analysis.

ALD of Ru film was demonstrated using the new (zero-valent) Ru metallorganic precursor and O2 as the Ru source and reactant, respectively, at the deposition temperatures of 300-350oC. Self-limited reaction behavior was observed as increasing Ru precursor and O2 pulse time, suggesting that newly developed Ru precursor is applicable for ALD process. Detailed discussions on the chemical and structural properties of Ru thin films as well as its growth behavior using new Ru precursor will be also presented.
Cation Intercalation and High Volumetric Capacitance of Two-Dimensional Titanium Carbide
Authors: Lukatskaya Maria R. , Ghidiu Michael , Mashtalir Olha , Ren Chang E. , Zhao Meng-Qiang , Dall'Agnese Yohan , Barsoum Michel W. , Gogotsi Yury
Published: February 2020

We recently produced a new 2-D material, viz. Ti3C2, by selectively etching aluminium from a MAX phase Ti3AlC2 and labelled it MXene. MXenes represents a large family of transition metal carbides and carbonitrides, not just a single phase. MXenes allow a variety of chemical compositions and are establishing themselves as a new class of two-dimensional materials. MXenes possess good in-plane conductivity, which in combination with their rich surface chemistry makes them attractive for electrical energy storage applications. However their use in electrochemical capacitors was only recently demonstrated (Lukatskaya et.al, Science, 2013).

Here, we report on the intercalation of Li+, Na+, Mg2+, K+, NH4
+, and Al3+ ions between the 2D Ti3C2Tx layers. In most cases, the cations intercalated spontaneously. The intercalation of some ions, notably Al3+, can be promoted electrochemically. We also report on intercalation-induced high capacitance of >300 Farads per cubic centimeter (much higher than that of porous carbons) of flexible Ti3C2Tx paper electrodes in aqueous electrolytes. Material showed no degradation of the capacitive properties after more than 10,000 cycles. Several different electrochemical techniques were employed to understand the mechanism of charge storage, such as in-situ spectroscopy, X-ray diffraction and other techniques.
Cyclic Voltammetric Studies of Nitroimidazoles in Aqueous Solution with Additions of Cysteine
Authors: Darzi Ghazwan M , Smith Diane K.
Published: February 2020

Nitroimidazoles are antibiotics used to treat many infections by killing the bacteria that causes the infection. For example, metronidazole is a drug that belongs to the class of nitroimidazole antibiotics, and it is used to treat bacterial and protozoal infections. Nitroimidazoles need to be activated by a reduction reaction. Although it has been believed that the active form of this drug was the radical anion, there is increasing evidence which suggests that further reduced forms, such as the nitroso and hydroxylamine, are the active forms of this drug. Both species are known to react with cysteine and this may lead to cell death either by deactivation of key proteins or upsetting the redox balance in the cell.

Because of the high reactivity of the nitroso and hydroxylamine imidazoles, it is not generally possible to prepare and isolate them to study their reactivity directly. However they can be studied indirectly using cyclic voltammetry since upon reduction of the nitro group in aqueous solution new peaks due to the oxidation of the hydroxylamine and reduction of the nitroso can be seen.  By varying the scan rate, information on the stability of these species in aqueous solution can be obtained. Further information on the activity of the nitroso and hydroxylamine forms can be obtained by adding equivalents of cysteine to the cell in order to monitor the rate of reaction between cysteine and the nitroso and hydroxylamine forms of different imidazoles. 

This paper will describe the cyclic voltammetry of 1-methyl-5-nitroimidazole and 1-methyl-2-nitroimidazole in aqueous solution in greater detail. Rough estimates of the lifetimes of nitroso and hydroxylamine derivatives in water will be determined using the current vs. time data at different scan rates. If possible, better estimates of the lifetimes and the rates of reaction with cysteine will be obtained by simulation of the voltammograms.
Electrode for Voltammetric Evaluation of Insoluble Particles
Authors: Lovander Matthew Douglas , Gillan Edward , Leddy Johna
Published: February 2020

A working electrode was developed to test the electrochemical behavior of insoluble particles in aqueous acidic and basic electrolytes.  The hydrogen evolution reaction (HER), oxygen reduction reaction (OER), and pseudocapacitive behavior of nickel phosphide, nickel oxide, and cobalt oxide were evaluated.

The electrode consists of a coiled copper wire in a (55:45 wt. %) mixture of graphite and paraffin wax, housed in either glass or polyvinyl fluoroethylene (PTFE) tubing.  The malleability of the electrode surface allows for particles to be directly embedded into the surface without the use of binder materials such as Nafion or PTFE.  The electrochemical behavior of modified and unmodified electrodes of both the developed carbon-wax electrode and a commercially available glassy carbon electrode (GCE) is presented.  Cyclic voltammetry, linear sweep voltammetry, and chronopotentiometry were employed for electrochemical investigation into the hydrogen evolution reaction, oxygen evolution reaction, and pseudocapacitive behavior of nickel phosphide (NiP2), nickel oxide (NiO) and cobalt oxide (Co3O4) on both working electrode types.   The PTFE electrodes performed well in both acidic and basic media and their performance is comparable to the GCE.  The newly developed electrodes displayed reproducible electrochemical behavior and provide a method to evaluate insoluble particles voltammetrically.
The Effect of a Protective Overcoat on Mixed-Potential Sensor Response
Authors: Brown Shanice C. , Spernjak Dusan , Mukundan Rangachary , Reynolds Jonathan M. , Brosha Eric L. , Kreller Cortney R
Published: February 2020

Nitrogen oxide (NOx) and ammonia (NH3) sensing technology is being developed for application in vehicle emissions monitoring of diesel and lean-burn gasoline engines.  In lean-burn engines, Selective Catalyst Reduction (SCR) utilizes NH3 to reduce NOx. The purpose of the NH3 sensor is to ensure that the NH3 is completely consumed in the NOx reduction reaction, and it is not emitted from the tailpipe. Both the NOx and NH3 sensors described herein are mixed-potential sensors that measure the non-nernstian potential created at an electrode/electrolyte interface exposed to a mixture of reducing/oxidizing gases. The NOx sensor is composed of La0.8Sr0.2CrO3 (lanthanum strontium chromite) and Pt electrodes with a YSZ electrolyte and a protective porous ceramic overcoat. The NH3 sensor is composed of Au/Pd and Pt electrodes with a YSZ electrolyte and protective overcoat. The purpose of the overcoat is to protect the electrodes from contaminants such as heavy metals and water present in harsh exhaust environments. We examine the effect of the protective overcoat on the sensor performance. Preliminary data on the NOx sensors indicates that the overcoat serves as a thermal blanket; decreasing the temperature difference observed between the heater and the sensing element in bare sensors. Sensing characteristics of response time, selectivity and sensitivity will be compared and discussed.
Effect of Contaminants on the Performance of a Proton Exchange Membrane Fuel Cell
Authors: Tavakoli Bahareh , Weidner John W.
Published: February 2020

The overall cost and performance of proton exchange membrane fuel cells (PEMFCs) are an issue of tradeoffs, and the optimal design depends on the application. For example, avoiding degradation via contamination by using expensive materials increases the initial cost to produce the system, but it can extend life and improve the overall performance. This may be desirable where reliability is paramount. In contrast, using less expensive materials reduces the initial cost, but at the expense of the life-time cost of the system and reduced performance.

During this study, a systematic and collaborative investigation was conducted to understand, characterize, and quantify the degradation mechanisms due to contaminants that arise from components that make up the fuel-cell system. Initially, the key contaminants that leach out of commercial assembly-aid materials were identified and screened for their detrimental effect on fuel-cell component performance (e.g. catalyst activity, membrane conductivity). Then, model compounds were selected and in-depth parametric studies were performed. In total, four model compounds in the assembly aid materials have been selected to study the degradation mechanisms, and the impact to PEMFC performance and durability of each compound was evaluated by in-situ infusion tests and in-situ membrane resistance tests. The results from these parametric studies were then used to develop mathematical models to quantify the performance loss and recovery of the fuel cell.
Effects of Preparation on the Silicon Nanowires Grown By Electroless Etching
Authors: Velez Victor H. , Mertens Robert George , Sundaram Kalpathy B
Published: February 2020

Highly oriented SiNWs arrays prepared by electroless etching method can significantly suppress light reflection across a broad spectrum [1]. The antireflective nature of Silicon nanowires (SiNW’s) revealed by their black color and dull appearances have drawn the attention of researchers [2]. Reflectivity studies on these show a significantly decrease in optical reflectivity down to 1.3% for 10 µm long SiNWs arrays [3]. Electroless etching is a top-down technique for growing SiNWs and does not need costly and expensive equipment to grow SiNWs as bottom-up methods usually do.

The electroless process begins with the cleaning of silicon substrates. They were cleaned in acetone, methanol and deionized water, then blow-dried with N2. They are dipped in hydrofluoric acid (HF) 49% solution for 1 min to remove any remaining oxide.

The silicon (Si) wafers are dipped for 15 minutes at room temperature in an electroless solution prepared in a petri dish containing silver nitrate (AgNO3) and hydrofluoric acid (HF) [4].

The substrates are dipped and galvanic reactions disperse silver ions on their surface, losing silicon as SiF6. As a consequence of this etching process, the removal of Si via Ag ions results in vertically aligned arrays of SiNWs covered with silver dendrites.

At the end of the etching process, the samples were dipped in two baths of deionized water and placed in diluted nitric acid (HNO3) 20% to remove the Ag dendrite layer formed on top of the SiNW arrays. Reflectance on different methods to remove the residual silver particles from SiNW’s when using an unstirred, stirred and sonicated diluted nitric acid (HNO3) 20% solution are presented Fig 1.

Figure 1
Electroforming Free Non-Volatile Resistive Memory Switching in Pulsed Laser Deposited Rare-Earth Oxides Thin Films
Authors: Sharma Yogesh , Pavunny Shojan P. , Katiyar Ram S.
Published: February 2020

In resistive random access memory (ReRAM) device, an electroforming process is necessary to activate the resistive memory cell and requires an extra high-voltage source in the memory circuit which leads to high power consumption and complex circuit design. Therefore, electroforming free reproducibleresistive switching(RS) phenomenon in ReRAM is required to reduce the power consumption, to simplify the circuit design and to have better uniformity in the device performance. Herein, we present the non-volatile RS behaviour of pulsed laser deposited polycrystalline thin films of rare-earth oxides. The electroforming free stable unipolar RS behaviour was observed in Pt/RE2O3/Pt memory cells (RE = Sm and Gd).The Pt/RE2O3/Pt cells showed a high-resistance ratio in the range of ∼105-106, a good data retention as long as 104 s measured at 100 °C, a reliable endurance for up to 100 cycles, and non-overlapping switching voltages (SET voltage VON ~2.7˗3.2 V and reset voltage VOFF ~ 0.6˗0.9 V). RS mechanism in Pt/RE2O3/Pt memory cells can be explained on the basis of oxygen vacancies assisted conductive nano-filamentary (thermo-chemical) model. The dominant charge transport mechanism in the oxide films was ascribed to space-charge-limited-current (SCLC) conduction.
Enhancing the Rate Capability of Hybrid Supercapacitors Based on Redox Active Electrolytes through High-Surface Area Reduced Graphene Oxide
Authors: Roldán Silvia , Bondarchuk Oleksandr , Carretero-González Javier , Rojo Teofilo , Mysyk Roman
Published: February 2020

Electrochemical double layer capacitors, which are the most widespread type of supercapacitors, have inherent energy limitations due to the low energetic of electrostatic charge storage. Increasing the energy density of supercapacitors is therefore a major challenge to open up wider application market, with targeted energy values set nowadays at 20-30 Wh/kg. Ongoing energy improvement efforts focus on the following routes: i) materials and composites overcoming capacitance values of traditional nanoporous carbons; ii) innovative electrolytes; iii) hybrid supercapacitor configurations. A particular example of such work is the combination of redox active electrolytes and carbon materials in a hybrid configuration, which provides affordable aqueous-based systems allowing for more than doubling the maximum energy output. However, energy gains come at the expense of worsening power capability and cycle life, which are the main advantages of supercapacitors over batteries.

To alleviate the drawbacks of hybrid supercapacitors based on redox active electrolytes, we have developed an asymmetric system, in which a nanoporous activated carbon electrode is substituted by high-surface-area reduced graphene oxide (rGO). Importantly, rGO with surface area about 1000 m2 g-1 is made by a simple process route not involving any activation step.

Using high-surface-area rGO has led to a dramatic improvement in the rate capability of hybrid devices whereas the high surface area of rGO provided for effective charge balance. The high conductivity of rGO has allowed cycling hybrid cells up to a high current density of 6.5 A/g (considering the total active mass of both electrodes) without any significant capacitance fading. Significant energy improvements can further be expected by exploring different redox active electrolytes and graphene materials with even higher specific surface area.
In-Situ TEM Observation of ZnO Nanostructure Growth in Liquid
Authors: Hsieh Ting-Huan , Chan Jui-Yuan , Huang Chun-Wei , Li Wei-Che , Chang Chia-Fu , Wu Wen-Wei
Published: February 2020

Zinc oxide nanowires have attracted much attention due to the potential applications for optoelectronic, piezoelectric and biocompatible properties. Among the various of synthesis methods, hydrothermal method has advantages such as low cost, simple process and high yield. However, the lack information that how dose nanowire architectures grow from solvent by hydrothermal method remain unresolved.In this study, the liquid cells has been designed, which can sealed the solution and be able to observe in in-situ transmission electron microscopy (in-situ TEM). We used zinc acetate and HMTA as the precursor to synthesize the ZnO nanowires at 80°C by hydrothermal method. The nucleation and growth process of ZnO nanowires was successfully observed; besides, the thermodynamics and kinetic of the reaction was systematically studied. The understanding of these synthesis processes provide significant information for the design and synthesis of functional nanomaterials in solutions.
The Catalytic Activity of Pd Supported on TiO2 Nanotubes on the Formic Acid Oxydation in Alkaline Media
Authors: Aldana-González Jorge , Montes de Oca-Yemha Maria Guadalupe , Olvera Juan Carlos , Romero-Romo Mario Alberto , Uruchurtu Jorge , Palomar-Pardavé Manuel
Published: February 2020

Formic acid electrochemical oxidation was studied using an electrode formed by Pd electrodeposited on third generation TiO2 nanotubes (TiO2NTBs-Pd), see inset in Figure 1A, in an alkaline medium. The electrochemical response of TiO2NTBs-Pd electrode towards formic acid oxidation was better than those corresponding to Ti or TiO2 nanotubes, see Figure 1A. Figure 1 (B) shows the typical Pd voltammetric regarding both Pd oxide formation and its reduction. From CO adsorption, see Figure1B, the real area of Pd electrodeposited was measured.  The formic acid oxidation on the TiO2NTBs-Pd electrode is shown in 1D.

Figure 1
Plastic and Flexible Micro-Electrochemical Supercapacitor Based on Cluster-Assembled Carbon
Authors: Soavi Francesca , Arbizzani Catia , Bettini Luca Giacomo , Milani Paolo , Piseri Paolo
Published: February 2020

Flexible, thin micro-electrochemical supercapacitors (MES) are attracting much attention in electronics for their capability of delivering short power pulses with high stability over repeated charge/discharge cycling. Supersonic Cluster Beam Deposition (SCBD) is an effective strategy for the development of nanostructured, binder-free porous carbon electrodes. It consists in the deposition of low kinetic energy clusters producing films with very low-density and high porosity. The use of SCBD for carbon cluster deposition allows to obtain very high deposition rates and highly collimated beam (divergence <20 mrad) which are suitable for the room temperature deposition of patterned nanostructured films by using stencil masks  on a wide variety of substrates including polymers. We exploited SCBD, for the development of a planar, high voltage MES featuring nanostructured carbon electrodes deposited on a flexible plastic Mylar substrate and ionic liquid-based electrolyte. Here, the electrochemical performance at different temperatures of the MES which operate above 2.5  V with a capacitance density approaching approaching 10 F cm-3,and delivering 9 mWh cm-3 and 2.5 W cm-3 above room temperature  is reported.

 ACKNOWLEDGMENTS

RFO, Ricerca Fondamentale Orientata, is acknowledged for financial support.
Understanding Field-Dependent Leakage Current Mechanisms in Amorphous Hydrogenated Boron Carbide As a Function of Electronic, Dielectric, and Disorder Parameters
Authors: Paquette Michelle M. , Nordell Bradley J. , Keck Christopher L. , Bhattarai Gyanendra , Nguyen Thuong D. , Purohit Sudhaunshu , Caruso A. N. , Lanford William A. , King Sean W.
Published: February 2020

Thin-film carborane-based amorphous hydrogenated boron carbide (a-B
x
C:H
y
), grown by plasma-enhanced chemical vapor deposition (PECVD), has emerged as a promising semi-insulating, low-dielectric-constant (low-κ) (κ < 3.5) material for intra/interlayer dielectric (ILD) and/or copper diffusion barrier/etch stop applications. Of the many integration challenges faced by candidate materials for low-κ ILDs or more specialized layers, one of the most important is the need for extremely low leakage currents up to high electric fields. In the case of a-B
x
C:H
y
, the leakage current at a given field can span nearly ten orders of magnitude, depending on the fabrication conditions and resulting physical properties of a given film. In order to go beyond a brute force process–property approach toward optimizing the electrical properties in thin-film a-B
x
C:H
y
, we explore their origin and relationship to electronic, dielectric, and disorder properties.

This contribution will describe the charge transport mechanisms in a-B
x
C:H
y
films in different electric field regimes, which include Ohmic, space-charge-limited-current, and Poole–Frenkel behavior. These mechanisms, and the underlying electrical properties that define these mechanisms (e.g., resistivity, mobility, trapping), are related to individual and combined electronic (band gap), dielectric (electronic and atomic/distortion polarization), and disorder (Urbach energy, Tauc parameter, dispersion energy) parameters. We further discuss how balancing the contributions of these different parameters via hydrogen and carbon content, through varying growth parameters, allows us to control the underlying charge transport mechanisms at both low and high fields, to ultimately obtain leakage currents on the order of 10–8 A/cm2or lower at 2 MV/cm.

Figure 1. (a) Leakage current density (J) as a function of electric field (E) for a selection of a-B
x
C:H
y
films. (b) and (c) Correlations between charge transport and disorder parameters: zero-field mobility extracted from steady-state space-charge-limited current measurements (μ
0(SS-SCLC)) as a function of E
g
E
u
B
–1/2 disorder parameter, and resistivity (ρ) extracted in Ohmic regime as a function of dispersion energy (E
d).

Figure 1
Understanding the Effect of MgO Interfacial Layer on ZnO/High-K/Fto Transparent Thin Film Transistor for Large-Area Transparent Electronics Applications
Authors: Jha Rashmi , Thapaliya Prem
Published: February 2020

ZnO and doped-ZnO based thin film transistors (TFT) have been widely studied for transparent electronics applications [1-2]. However, majority of the previous work have evaluated the performance of TFT using Indium Tin Oxide (ITO) as transparent gate electrodes which is expensive and may not be sustainable for large-area transparent electronics applications, such as transparent electronics integrated glass windows and glass walls in buildings [3-4]. In addition, replacing ITO with low-cost and scalable material such as Fluorine-Doped Tin Oxide (FTO) coated glass substrates also has potential to reduce the cost of displays in consumer electronic devices. Towards addressing this issue and extending the application of ZnO-TFT in large-area transparent electronics that is cost-effective and sustainable, we have evaluated the performance of ZnO TFT with commercially available FTO as gate electrodes. ZnO was deposited at room temperature using RF magnetron sputtering while reactively sputtered HfO2, deposited at 300◦C, was used as high-k gate dielectric.  The devices indicated well-behaved transistor characteristics with field effect mobility of 0.84 cm2V-1s-1, the ON/OFF current ratio of 2.5×103 and sub-threshold swing 140 mV/decade. To understand the cause of low field effect mobility and large sub-threshold slope, the defect characteristics at ZnO/HfO2 interface was studied using admittance spectroscopy (Gp/ω vs. ω) measurements. The interface state density was found to be on the order of 1013 eV-1 cm-2 which is 1-2 orders of magnitude higher than typically reported for ZnO-TFT [5-6]. This work will present our systematic understanding on the role played by FTO electrode in governing the FTO/HfO2 and HfO2/ZnO interface characteristics which finally plays an important role in governing the performance of the transistor. In particular, the role of fluorine diffusion in the stack and possibility of engineering the FTO/HfO2 and HfO2/ZnO interfaces via the insertion of interfacial layers such as MgO will be presented and supported with experimental results.

[1] R. L. Hoffman, B. J. Norris, and J. F. Wager, Appl. Phys. Lett. 82, 475 (2003)

[2] J. S. Seo, J. H. Jeon, Y. H. Hwang, H. Park, M. Ryu, S. H. Park and B.S. Bae,  Nat. Sci. Rep, 3, 2085 (2013)

[3] L. Zhang, J. Li, X. W. Zhang, X. Y. Jiang, and Z. L. Zhang, Appl. Phys. Lett. 95, 072112 (2003)

[4] J. Zhang, Z. Li, L. Shen, C. Ye, B. Wang, and H. Wang, Thin Solid Films 544, 281 (2013)

[5] P. F. Carcia, R. S. McLean, and M. H. Reilly, Appl. Phys. Lett, 88, 123509 (2006)

[6] J. J. Siddiqui, J. D. Phillips, K. Leedy, and B. Bayraktaroglu, IEEE  Electron Devices Lett.32, 1713 (2011)
Growth of Nickel Silicide/Platinum Silicide Axial Nanowire Heterostructure through Solid-State Reaction
Authors: Wu Yen-Ting , Huang Chun-Wei , Chan Jui-Yuan , Huang Yu-Ting , Chiu Chung-Hua , Hsieh Yu-Shun , Chang Chia-Fu , Wu Wen-Wei
Published: February 2020

Nickel monosilicide (NiSi) with the addition of platinum has been highly regarded as paramount candidate for excellent contact in semiconductor industry for its low electrical resistance and high thermal stability. With the transition of device dimension to nanoscale, 1-D NiSi nanostructures with excellent metallic contact to Si nanostructures have attracted much interests in the field of nanoelectronics. Therefore it is important to investigate the nickel silicide formation and transformation mechanism in 1-D system to gain the control of specific nanostructure since it different from bulk system.

In this work, we fabricated two different metal pads (nickel/platinum), served as contact with silicon nanowires (NWs) to study nickel silicide/platinum silicide axial heterostructure through solid-state reaction. The as-fabricated Si NWs with two contact electrodes were annealed in ultrahigh vacuum in-situ transmission electron microscopy (UHV in-situ TEM) at 550℃ for observation of the reaction process. The structural information of dual silicide nanostructure was analyzed by spherical aberration corrected scanning transmission electron microscopy (Cs-corrected STEM) and we successfully got nickel silicide/platinum silicide axial heterostructure.

With the understanding of the nickel silicide transformation mechanism in 1-D system, reliable 1-D NiSi nanostructures would be generally applicable to semiconductor industry.
The Complete Oxidation of Glycerol to CO2: A Hybrid Enzymatic and Organic Electrocatalytic Cascade
Authors: Minteer Shelley D. , Hickey David P , McCammant Matthew , Giroud Fabien , Sigman Matthew S
Published: February 2020

There has been a significant interest lately in the complete oxidation of biofuels to CO2. The use of multiple biocatalysts allows for deeper biofuel oxidation and thus maximizes the energy density that can be extracted per molecule of biofuel. However, there are still many biofuels for which a suitable biocatalyst is not known. We have recently taken an alternative approach to combine the high catalytic activity of enzymatic biocatalysts with the promiscuous nature of small molecule organic catalysts. We demonstrate the complete electrochemical oxidation of the biofuel glycerol to CO2 using a hybrid enzymatic and small-molecule catalytic system. Combining an enzyme, oxalate oxidase, and an organic oxidation catalyst, 4-amino-TEMPO, we are able to electrochemically oxidize glycerol at a carbon electrode, while collecting as many as 16 e-s per molecule of fuel. Additionally, we investigate the anomalous electrocatalytic properties that allow 4-amino-TEMPO to be active under the acidic conditions required for oxalate oxidase to function.
Metabolic Engineering to Create New Class of Nature-Inspired Corrosion Inhibitors
Authors: Kamal Ahmadi Mahmoud , Pfeifer Blaine
Published: February 2020

For decades, natural products have indispensable role on drug discovery. But, if natural products applications are limited to therapeutic uses? To explore new horizons, we have applied our expertise on metabolic engineering to heterologously overproduce a siderophore titled Yersiniabactin (Ybt) in E.coli . E
.
coli host offers advantages of rapid growth rate, easy and cheap large-scale cultivation and well developed genetic manipulation and characterization techniques. Siderophores naturally show great affinity toward metal ions and surfaces. We have tested directing this innate ability toward corrosion inhibition. Preliminary data demonstrates adding reduced quantity of Ybt leads to 50% decrease in corrosion rate of stainless steel in acidic solution, mainly due to preventive layer formation. Moreover, precursor-directed biosynthesis has been applied to generate new Ybt analogues with the potential for improved or altered metal surface binding capabilities. Novel analogues with higher binding constant and those with higher spatial surface area may enhanced corrosion inhibitory. Small molecules were characterized using HPLC and LC/MS. Corrosion study was performed using weight loss experiment and direct measurement by potentiostat . Our findings confirms nature can be a sustainable source for discovering new anti-corrosion small molecules which in contrast to common corrosion inhibitors are not environmental hazardous or human health risks.

Figure 1
(Invited) Developing Short-Wave Infrared Fluorescent Immunoprobes Based on Single-Walled Carbon Nanotubes
Authors: Beckingham Kathleen M. , Vu Michael , Lin Ching-Wei , Bast Robert C. , Weisman R. Bruce
Published: February 2020

Progress will be reported on a project to develop a new type of fluorescent immunoprobe containing antibodies conjugated to structurally sorted single-walled carbon nanotubes (SWCNTs). The (n,m)-sorted SWCNTs display sharp and distinct fluorescence at wavelengths in the short-wave infrared (SWIR) region, allowing effective spectral multiplexing and minimal interference from autofluorescence backgrounds. To avoid fluorescence quenching from covalent functionalization of nanotube sidewalls, the antibodies are linked to PEG side chains of a phospholipid surfactant that noncovalently coats individualized SWCNTs. We are preparing SWCNT-based immunoprobes containing the OC125 antibody, which binds specifically to the CA125 ovarian cancer biomarker. SWIR fluorescence microscopy is being used to assess specificity of binding to cultured ovarian cancer cells. We will also describe new developments that aid in the testing of SWCNT-based probes. One is a custom optical apparatus that scans specimens in two dimensions to sensitively measure SWIR fluorescence spectra as a function of position. The device is used to read dot blots of selected antigens spotted onto a cellulose membrane and probed by SWCNT-conjugated antibodies. Using this approach, one can quickly and quantitatively assess efficiencies of SWCNT conjugation and antigen binding.