bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of Light-Absorbing ZnSnP2 Semiconductor Nanowires
Authors: Lee Sudarat , Gu Junsi , Fahrenkrug Eli , Maldonado Stephen
Published: February 2020

The conjecture of ZnSnP2 semiconductor nanowires as promising inexpensive solar absorber and the nanowire preparation method was discussed in this presentation. Single-phase crystalline ZnSnP2 nanowires have been prepared via simple chemical-vapor-deposition (CVD) of Zn and SnP3 powder in a custom-built tube furnace reactor, allowing the vapors to react with thermally evaporated Sn islands on 40 mm2 Si(111) substrate. Powder X-ray diffraction data and Raman scattering of the nanowire films, along with single-nanowire analysis using high-resolution transmission electron microscope (HRTEM) indicate that the as-prepared ZnSnP2 nanowires possess single-crystalline sphalerite structure, as opposed to the antisite defect-free chalcopyrite structure. Nonetheless, the nanowires show homogenous elemental distribution of Zn, Sn, and P, with chemical composition close to the 1:1:2 stoichiometric ratio. Photoelectrochemical measurements in aqueous electrolyte show the as-prepared ZnSnP2 nanowires exhibit stable cathodic photoresponse under white light illumination. Tapered nanowires that lead to formation of Zn3P2 nanowires dominate at extended growth duration, implying the Sn islands serve both as the vapor-liquid-solid (VLS) growth seed and sole contributor of Sn. Approaches to minimize consumption of Sn will be presented to ensure production of long nanowire with consistent diameter. This study presents a benign and straightforward approach to prepare single-phase Zn-IV-P2 nanowires suitable for energy conversion applications.
Understanding Transport Phenomena in Perfluorosulfonic-Acid Membranes
Authors: Weber Adam Z , Gostick Jeff T. , Kusoglu Ahmet , Crothers Andrew
Published: February 2020

One of the keys to optimizing polymer-electrolyte-fuel-cell performance is understanding its transport phenomena. This is especially important for the proton-exchange membrane, which helps to control the water management within the cell, an integral aspect for optimal cell performance. Typical fuel-cell membranes are perfluorosulfonic-acid based and are essentially random copolymers that phase separate into hydrophilic domains for water and ion movement supported by a hydrophobic backbone phase.

We have previously shown that water transport and uptake at the nano- and macroscale is similar and relatively fast in membranes, especially at higher humidities.1,2 Once water crosses the membrane interface, time-resolved studies show that changes at the nano and macroscale scales occur almost simultaneously. Unlike water incorporation, proton conduction depends not just on the domains but also their interconnectivity. Time-resolved studies such as that in Figure 1, show that unlike the water incorporation, there is more of a time delay due to reorientation of the domains and the transport pathways. In this talk, such issues will be discussed.

In particular is the need to explore the structure-function relationships for the transport properties and the critical aspects that the membrane interface plays in controlling transport. In addition to experimental results, a model methodology will be presented to explore proton conductivity. In the model, we propose a macroscopic treatment that utilizes data on the nanoscale relating to membrane morphology and physically relevant phenomena,3 but in a framework that still allows for easy incorporation into cell-level fuel-cell models. Extensions of the analysis and phenomena to the thin-film regime, which is critical for fuel-cell catalyst layers, will also be presented. 

Acknowledgements

We thank Steve Hamrock, Mike Yandrasits, and Greg Haugen at 3M for providing membranes and discussion; This work made use of facilities at the Advanced Light Source (ALS), supported by the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy. This work was funded by the Assistant Secretary for Energy Efficiency and Renewable Energy, Fuel Cell Technologies Office, of the U. S. Department of Energy under contract number DE-AC02-05CH11231.

References

1       Gi Suk Hwang, Dilworth Y. Parkinson, Ahmet Kusoglu, Alastair A. MacDowell, and Adam Z. Weber, ACS Macro Letters, 2, 288-291 (2013).

2       Daniel S. Hussey, Dusan Spernjak, Adam Z. Weber, Rangachary Mukundan, Joseph Fairweather, Eric L. Brosha, John Davey, Jacob S. Spendelow, David L. Jacobson, and Rodney L. Borup, J. Appl. Phys., 112, 104906 (2012).

3       Ahmet Kusoglu, Suchol Savagatrup, Kyle T. Clark, and Adam Z. Weber, Macromolecules, 45 (18), 7467-7476 (2012).

Figure 1
Structure and Transport Properties of Ionomer Thin Films in Membrane-Electrode Assemblies
Authors: Elliott James A
Published: February 2020

Perfluorosulfonic acid (PFSA) electrolyte membranes, such as Nafion, are widely employed in fuel cells due to their high proton conductivity combined with excellent chemical and thermal stability. However, the structure and ion transport properties of such materials differs markedly from those of the bulk polymer when confined to thin films, as commonly found in the catalyst layers of membrane-electrode assemblies (MEAs). Furthermore, the chemical nature of adsorbing substrate, whether metal catalyst or carbon electrode, also has a large influence on the structure and properties.

In this presentation, I will present results from density functional theory (DFT) and dissipative particle dynamics (DPD) simulations of model MEA systems in which the distribution of water and ionic groups at the interface in nanoscopic channels are compared with those in bulk membrane [1]. The results show that the structure of thin (5-10 nm) layers of PFSA membranes is quite different to that in bulk, and may play a key role in controlling performance of MEAs. In particular, the surface coverage of sulfonic acid groups is examined as a function of substrate hydrophilicity, hydration level and equivalent weight of ionomer. The results demonstrate that the anomalously voltage losses that occur at low catalyst loadings may be due in part to reduced effectiveness of proton transport in the ionomer films.

[1]   J.A. Elliott, D. Wu, S.J. Paddison and R.B. Moore, Soft Matter, 7, 6820-6827 (2011).
What Determines the Detection Limit during Impedance Biosensing?
Authors: Suni Ian Ivar
Published: February 2020

Impedance biosensors have been widely studied for applications to biomedicine, environmental monitoring, food, and agriculture.  The most common format for AC impedance biosensors involves surface immobilization of an antibody, receptor protein, DNA strand, or other species capable of bio-recognition, and AC impedance detection of the binding event. 

For an electrode coated with a polymer film, electron transfer to a redox probe such as Fe(CN)6
3-/4- is essentially an electron tunneling process, so one expects exponential decline in the rate of electron transfer (kET) with film thickness (x) according to the equation below, where α is a constant for a given redox couple and l is the Marcus reorganization energy.  This relationship has been quantified most accurately through studies of Au-thiol self-assembled monolayers (SAM) of variable chain length.  Therefore, fundamental electrochemistry predicts that the detection limit should decline with increasing analyte molecular weight.   However, this functional dependence is complicated, since it is related to the different between two terms that depend exponentially on film thickness. 

Literature reports of detection limits during impedance biosensing will be summarized and discussed. Our results for impedance biosensing as a function of analyte molecular weight will also be discussed for impedance biosensing of peanut protein Ara h 1, cortisol, and endocrine-disrupting chemicals such as norfluoxetine and BDE-47.  In addition, detection of BDE-47 using an alpaca single domain antibody results in a lower detection limit (0.79 ng/ml) than use of a rabbit polyclonal antibody (1.3 ng.ml).  Possible electrostatic effects on detection limit are discussed through the use of oppositely charged Fe(CN)6
3-/4- and Ru(NH3)6
3+/4+ redox probes. 

Figure 1
Pt-Decorated Fluorine-Doped Tin Oxide Nanowire Arrays As Highly Sensitive H2O2 sensor Electrodes
Authors: Lu Shih-Yuan , Lee Kuan-Ting , Lo Yu-Chun , Liang Yung-Yung , Matsushita Nobuhiro , Ikoma Toshiyuki
Published: February 2020

Fluorine-doped tin oxide (FTO) nanowre aways were grown on top of commercial FTO glass through a vapor-liquid-solid process, by using Au nanocrystals as the anisotropic growth catalyst, tin powders as the precursor, and NH4F as the fluorine source. This extended 3-D FTO nanostructure was then decorated with Pt nanocrystals, with a polyol method, to serve as a sensing electrode for H2O2. These FTO nanowires not only offer greatly enlarged sensing area and fast charge transport channels, but also significantly enhance the hydrophilicity of the electrode, all beneficial for electrochemical sensing of aqueous samples. A two-order of magnitude improvement in sensitivity toward H2O2 over the plain commercial FTO glass was achieved, reaching a high sensitivity value of 272 mA/M.
Development of Multi-Parametric/Multimodal Spectroscopy Apparatus for Characterization of Functional Interfaces
Authors: Zhou Lang , Arugula Mary , Simonian Aleksandr , Easley Christopher J , Shannon Curtis
Published: February 2020

With increasing interest in functional interfaces, it becomes increasingly important to characterize chemical structures and biomolecules on surfaces in a quantitative fashion, and to test their proper allocation orientation, conformation, activities, stability, etc. This research integrates several synergistic surface characterization spectroscopy methods such as surface plasmon, fluorescence, and electrochemical spectroscopies into one new surface analytics, to enhance the power and capabilities of interface characterization sensing techniques. Since currently there is no such instrument available, the main objective of this proposal is to develop a multi-parametric/multimodal spectroscopy system (MPMS) for simultaneous application of these surface-mediated optical techniques. Electrochemical Proximity Assay (ECPA) is taken as a research model, which is a flexible method with high potential for quantitation of a variety of proteins in clinical laboratory settings or at the point-of-care. With fluorescent labels (green circle in figure) and methylene blue (blue circle in figure) incorporated into the DNA strands, the process of ECPA can be real-time monitored by fluorescent, electrochemical and SPR signals simultaneously. Among the steps of ECPA, SPR should generate signal upon assembly of each step, surface fluorescence will only change upon assembly of the labeled piece, while electrochemical signal will only change upon addition of the methylene blue (MB) labeled DNA strand. In this way, the SPR signal will thus give a non-biased view of all steps of assembly, fluorescence will give us the power to label and monitor specific portions, and electrochemistry will allow high sensitivity and quantitative characterization of surface coverage. Therefore, the MPMS system will allow an unprecedented level of fundamental understanding of the dynamics of the ECPA process.

Figure 1
Surface Plasmon Resonance (SPR) of Reusable DNA LOOP Formation Dynamics
Authors: Yang Fuling , Arugula Mary , Somasundaram Subramaniam , Easley Christopher J , Shannon Curtis , Simonian Aleksandr
Published: February 2020

Thiol-terminated single-stranded DNA (SH ss-DNA) monolayer assembly on gold as a probe is a significant model for various biosensors. In electrochemical proximity assay (ECPA), SH ss-DNA with complementary DNA loop moves a methylene blue (MB)-conjugated oligonucleotide (MB ss-DNA) close to a gold surface, which forms a DNA loop like structure,  for transferring electron when target protein is present. After treatment of urea in DI water, the MB ss-DNA and DNA loop dissociate from the DNA loop like structure for reusability. Surface plasmon resonance (SPR) is a powerful optical technique for studying dynamic matrix of affinity biosensors.

In this study, we first confirmed DNA complementarities in flow mode with surface plasmon resonance detection. SPR results showed discriminative refractive angle change (DRA) in each DNA hybridization. However, the loss in DNA loop structure (SH-ssDNA or DNA loop) showed inconspicuous sensogram. Furthermore, we studied the effects of free thiols, which is a result of cleavage of disulfide precursors by reductant, in SH ss-DNA monolayer assembly on gold surface. Comparison of DRA in pure SH-ss DNA and non-purified SH-DNA in several concentrations showed free thiols can compete with SH-ss DNA on gold surface. DNA loop and MB ss-DNA added to two solutions is used for double confirmation of the recognition event. Mixture of different ratios of SH-ss DNA and free thiols were used to further study the competition between SH-ss DNA and free thiols. Moreover, we investigated reusable DNA Loop formation capable of several uses in simple matrix. Urea dissolved in DI water was utilized to dissociate DNA loop and MB ss-DNA from DNA loop-like structure. Optimization of concentration and pH of urea were performed. Study dynamics of this reusable DNA loop structure can improve sensitivity and feasibility of ECPA-based marker.
Development of Electrochemical Aptamer-Based Biosensors for the Detection of Hormonal Contaminants in Water
Authors: Contreras Jiménez Gaston , Eissa Shimaa , NG Andy , Zourob Mohammed , Siaj Mohamed
Published: February 2020

Endocrine disrupters (EDs) are compounds that specifically interfere with the normal functions of the body’s endocrine system (system of glands for hormonal secretion) by causing adverse effects in both human and wildlife. Therefore, routine, sensitive, reliable and cost effective detection methods for EDs are highly demanded. In this work we present the selection and characterization of ssDNA aptamers that exhibit high affinity, specificity and sensitivity to progesterone (P4), 17b-estradiol (E2) and, norethisterone (NET). The aptamer selection was conducted by in vitro selections by incubating a highly diverse ssDNA library of about  random 60mer sequences with the target analyte. After 15 cycles of selections, the enriched aptamers pool was cloned and sequenced. The dissociation constants (KD) of the selected aptamers determined by fluorometry and by electrochemical impedance spectroscopy (EIS) methods are in the subnanomolar order. Cross-reactivity tests for each aptamer demonstrated the high specificity to their target analyte. In addition, circular dichroism (CD) spectroscopy measurements of the selected aptamers for progesterone showed a marked conformational change upon binding the target analyte. This change in the conformation was exploited to design a biosensing platform to generate a measurable signal after binding the specific analyte by following the redox process of a couple composed for [Fe(CN)6]3-/4-. For first time, an impedimetric aptasensor for progesterone detection was developed with limit of detection of 0.90 ng/mL. We believe, based in our finding, that the continuous selection of high affinity aptamers for other EDs and their integration in a biosensing platform will facilitate the routine monitoring of EDs in environment as well as clinical and medical diagnosis purposes.

Figure 1
MWCNTS/Nickel Oxide Nanocomposite Supercapacitor Made from Two Electrode Coin Type Cells
Authors: Adekunle Abolanle Saheed , Mamba B. B. , Agboola B. O. , Oluwatobi O. S. , Ozoemena Kenneth I. , Ebenso Eno E
Published: February 2020

Studies have shown that carbon nanotubes-metal oxide (CNT/MO) nanocomposite modified electrodes exhibited huge capacitive current in some electrolytes [1-6]. Therefore, it becomes imperative to establish the charge storage properties of these materials as a potential source for energy generation in acidic and neutral medium since most reported work has been conducted in an alkaline environment. In this work, supercapacitive property of synthesised nickel oxides (NiO) nanoparticles integrated with multi-walled carbon nanotubes (MWCNT) in an acidic medium using a two-electrode coin cell type supercapacitor was investigated. Successful formation of the MWCNT-NiO nanocomposite was confirmed with techniques such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), electron dispersive X-ray spectroscopy (EDX) and X-ray diffraction spectroscopy (XRD). The supercapacitive behaviour of both the symmetry and the asymmetry MWCNT-NiO based supercapacitor in 1 M H2SO4 and 1 M Na2SO4 electrolytes was evaluated using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic constant current charge-discharge (CD) techniques. There was a good correlation between the CV and the CD specific capacitance (SC) values for the asymmetry supercapacitor. Asymmetry supercapacitor (MWCNT-NiO|H2SO4|MWCNT) gave the highest SC value of 925.9 mFcm-2 (53.9 F g-1) and energy deliverable efficiency of 101.0±8.1%. High SC values which are higher than most of those reported in literature were obtained. The electrodes demonstrated high stabilities with no significant changes in SC values over 1000 cycles.

References:

1. A.S. Adekunle, K.I. Ozoemena, Electrochim. Acta 53 (2008) 5774.

2. A.S. Adekunle, K.I. Ozoemena, J. Solid State Electrochem. 12 (2008) 1325.

3. B.E. Conway, Electrochemical Super Capacitors, Kluwer Academic/Plenum Publishers, New York, 1999.

4. M. Winter, R.J. Brodd, Chem. Rev. 104 (2004) 4245.

5. Y.H. Lee, K.H. An, J.Y. Lee, S.C. Lim, Encycl. Nanosci. Nanotechnol. 1 (2004) 625.

6. E. Frackowiak, F. Beguin, Carbon 40 (2002) 1775.
Novel 3D Nanocarbon Electrodes for High-Rate Li-Ion Batteries
Authors: Wang Huan , Xie Jingyi , Follette Marissa , Amama Placidus B
Published: February 2020

Portable electronic devices are negatively impacted by power density limitations of current Li-ion batteries (LIBs). Architectures or materials for faster ion and electron transport are required. Graphene-based electrodes with a 3D hierarchical structure have shown promise in LIBs due to their short ion diffusion distance, excellent electrical conductivity and high surface area. However, techniques for fabricating such hierarchical nanostructures with textural properties that can be easily tailored are still complicated and not fully developed. In this work, a low cost, green, facile, controllable and scalable approach for the fabrication of 3D hierarchical graphene-based electrodes is proposed. The 3D hierarchical structures with adjustable pores and nanowrinkles are prepared from graphene oxide or chemically functionalized graphene sheets via a wet chemical method using polymeric micro-gels as the template.  The resulting 3D graphene electrodes have been used as a model 3D electrode system to establish correlations between the 3D properties (surface chemistry, defect density and textural properties) and the LIB performance (rate capability, energy capacity and durability).
Fabrication of Multiwalled Carbon Nanotube-Wrapped Ultrathin SnS2 Nanoplates and Their Superior Li-Ion Intercalation Performance
Authors: Guan Dongsheng
Published: February 2020

Two-dimensional ultrathin SnS2 nanoplates enwrapped into a multiwalled carbon nanotube (MWCNT) network are synthesized by a facile and one-step hydrothermal method with SnCl2∙H2O and thiourea as reactants and sodium dodecylbenzenesulfonate as surfactant. The highly dispersed carbon nanotubes in ethanol solution are found to reduce the thickness of SnS2 nanoplates during their growth and embed them into an interconnected network finally. In lithium-ion battery studies, the electrode fabricated from the SnS2 nanoplate/MWCNT hybrid material delivers excellent lithium-ion intercalation properties, with larger specific capacity, higher rate capability and better cycling stability than that of electrode made of bare SnS2 nanoplates. The improved electrochemical performance is ascribed to a fact that this porous, hybrid architecture effectively accommodates the volume change of SnS2 during charge–discharge to maintain structural stability, facilitates the easy access of electrolyte to the huge surface of nanoscale active materials, and also provides a continuous conductive network to significantly enhance the charge transfer kinetics at electrode.

Figure 1
Three-Dimensional Bi-Continuous Graphene Monolith from Hollow Ni Templates Via Polymer Templates
Authors: Zhu Yu
Published: February 2020

The stack of graphene sheets greatly reduces its exceptionally high specific surface area, which limits the potential utilization of graphene.  Here in this work, we report a method to fabricate three-dimensional, bi-continuous graphene monolith through a controllable hollow Ni templates derived from polymer blends. The poly(styrene)/poly (ethylene oxide) were used to fabricate a bi-continuous gyroid template with controllable phase separation. The nickel template was formed by electroless depositing metal on the polymer and the resulting hollow nickel structure exhibited very high porosity of 95.15%. Graphene was synthesized from this hollow nickel template by chemical vapor deposition and the free-standing bi-continuous graphene monolith was obtained in high throughput. The bi-continuous graphene monolith was used in the energy storage devices and exhibited promising results.

Figure 1
Highly Active Nitrogen-Doped Carbon Metal Oxide Hybrid Composites for Oxygen Reduction Reaction
Authors: Bayati Maryam , Scott Keith
Published: February 2020

Fuel Cells have been considered as clean and promising energy-converting devices due to their high efficiency and low/ zero emission. However, the cost and reliability are two challenges for their commercialization. The high cost of components, which is mainly due to the use of platinum-based catalysts for oxygen reduction reaction (ORR), is attracted extensive research works on finding alternatives synthesized from low-cost and more abundant compounds.

Recent studies on pyrolyzed metal inserted nitrogen doped carbon based catalysts for ORR show high performance, at level of platinum-based catalyst, and promising durability. Herein, we report synthesis, characterization and electrochemical analysis of hybrid composites consisting of N-doped (predominantly pyridinic N- and pyrrolic) carbons and transition metal (cobalt and iron) oxides for the ORR. XPS and XRD studies revealed the active nitrogen groups and crystallographic phases of nanoparticles. The composite catalysts were prepared via a solvothermal pyrolysis process. They exhibit high catalytic activity with the 4e or 2e reaction pathways and superior stability to Pt/C for ORR in alkaline media.

Figure 1. Cyclic voltammograms of hybrid composite of iron oxide inserted N-doped carbon nanomaterials in O2-saturated solution of 0.1 M NaOH at 20 ±2 °C under different rotation rates.( Sweep rate = 10 mVs-1)

Figure 1
Metal-Catalyst-Free Fuel Cells with Carbon As Catalysts
Authors: Li Wenzhen , Qi Ji , Benipal Neeva , Wang Hui , Chadderdon David J , Jiang Yibo , Wei Wei , Han Xiaotong , Qiu Yang , Hu Yun Hang
Published: February 2020

As a potential solution to sustainable energy concern, wide spread commercialization of fuel cell has long been hindered by limited reserve and relatively high cost of metal catalysts. Although there are achievements in terms of non-noble metal catalysts, it is still very challenging to replace metal catalysts at the anode side of low temperature fuel cells by non-metal catalysts, followed by achieving total removal of the metal catalysts from a fuel cell. As a carbon-only catalyst prepared by reduction of carbon monoxide with lithium oxide, 3D graphene is found to electrochemically catalyze carbohydrazide oxidation reaction efficiently. Similarly, CNT outperforms carbon black and 2D graphene in catalyzing carbohydrazide oxidation reaction. Prototypes of anode metal free and completely metal free anion exchange membrane fuel cell with 3D graphene anode catalyst generate peak power density of 75.1 mW cm-2 and 24.9 mW cm-2, respectively. In average, 4.9 electrons are electrochemically extracted from one carbohydrazide molecule, indicating the existence of C-N bond cleavage, which is a key factor contributing to high fuel utilization efficiency.
Electrically Conducting PDMS Nanocompsite Using in-Situ Reduction of Gold Nanostructures and Mechanical Stimulation of Carbon Nanotubes
Authors: Ozhikandathil Jayan , Khosla Ajit , Packirisamy Muthukumaran
Published: February 2020

Electrically conducting nanocomposite has numerous application potential in flexible MEMS and wearable electronics. Polydimethylsiloxane (PDMS) has been identified as an attractive candidate for the fabrication of Bio-MEMS devices due to its several benefits such as biocompatibility, good optical properties, easy and low-cost fabrication using soft-lithography, etc. In this work, an electrically conducting PDMS nanocomposite is synthesized using a novel combined process of in-situ reduction by curing agent of PDMS from aqueous gold chloride solution, and mechanical stimulation of multi-wall carbon nanotubes. The electrical and thermal properties of the nanocomposite is characterized for various concentration of gold chloride solution and conducting fillers in the PDMS matrix. Further, the nanocomposite is micropatterned to fabricate heating elements and electrical signal routing lines in flexible PDMS sheets.
(Plenary) Wearable Wireless Textile Based Nanosensor System for Early Detection of Concussion and Cardiac Arrest of Football Players
Authors: Varadan Vijay K
Published: February 2020

The prevalence of head injury and its subsequent effects among football players has been a persistent problem at all levels of the game. Research work over the past few decades has brought heightened awareness about the causes and long-term effects of severe or traumatic head injuries (TBI) and repeated concussions. The NFL and NCAA  have implemented policies for prevention and protocols for diagnosis and treatment. An injury surveillance system is in place, which comprises of injury spotting, sideline evaluation protocol and subsequent diagnostic using brain imaging. But mild and moderate head injuries can still occur and go undetected. The cumulative effect of these mild traumatic brain injuries can cause long-term residual brain dysfunctions. Often mild TBI are detected upon manifestation of these dysfunctions.

Improvement in impact detection and quantification, and injury diagnosis are required for timely medical intervention to prevent or minimize the damage due to head injury. In addition to that, a sensitive (neuro) feedback system is required for evaluation of therapeutics used for enabling players returning to play or cope with long term effects due to over-exposure to head injury. This requires a continuous unobtrusive monitoring of directional and rotational impact force, and monitoring of brain, cognitive and behavioral symptoms that is applicable to athletes of all ages.

The sudden death of an individual resulting from a sudden failure in heart function is referred to as Sudden Cardiac Death (SCD). Rigorous exercise increases the risk of SCDs in young athletes with underlying cardiovascular disorders (CVD). A recent study has shown that up to 82% of individuals who succumbed to SCD were engaged in strenuous exercise during or immediately before the incident. Nearly 58% of SCDs reported between 1980 and 2006 have been reported in basketball and football athletes.

In this talk, a wearable wireless textile based nanosensor system will be presented to monitor early warning symptoms of both concussion and cardiac arrest. Selected videos will be presented to show the efficacy of our nanosensor system network.
(Invited) Microneedle Array Features in Precise Moulding of Biocompatible Polymers
Authors: Ito Hiroshi , Taki Kentaro , Takayama Tetsuo , Uchiumi Kazuyasu , Yahagi Haruki
Published: February 2020

Microneedle array features were fabricated by micro-injection molding using biocompatible polymers such as polycarbonate (PC), polypropylene (PP) and polylacticacid (PLA). PC and PP based microneedle array features with high aspect ratio for needle height was fabricated by several injection molding techniques. Injection compression molding and injection molding with super critical carbon dioxide fluid with or without vacuum process inside the cavity of mold were performed. Effects of process parameters on processability and surface replication of the molded parts were evaluated. The height replication ratio for micro-needle was improved by using injection compression molding. Moreover, the effect of vacuum process inside cavity of mold under filling process was small. However the height replication ratio for micro-needle showed the highest values using the injection molding with super critical carbon dioxide fluid with vacuum inside the cavity of mold process.  In addition, hydroxyapatite (HAp) particle dispersed PLA composites based microneedle array features were also fabricated by twin screw extrusion and micro-injection molding. The viscosity of PLA was reduced by HAp dispersion because of acceleration of hydrolysis degradation during both processing. The micro-needle array of HAp/PLA composites for application to biomedical parts was obtained and the needle height was improved by the optimum composition of HAp to polymer.
Thiol-Sensitive Electrochemical Sensors for Advance Detection of Neurotoxins in Water and Biomass
Authors: Pilip Anna , Eremenko Arcadij , Kurochkin Ilijya , Russkikh Iana , Prokopkina Taisiya
Published: February 2020

A method for the analysis of thiocholine, as well as of butyrylcholinesterase (BChE) and its inhibitors using thiol-sensitive thick-film sensors has been proposed. Sensor sensitivity to thiocholine was achieved by mediator layer of manganese dioxide formed on the working carbon electrode. The detection limit for BChE and its inhibitor diazinon was 1·10-10 M and 1·10-9 M, respectively.

The developed method of analysis using a thiol-sensitive sensor chip was applied for rapid determination of anticholinesterase substances in natural waters and to control the incoming water mass at water intakes. In this case, the analysis was carried out on a "common" neurotoxicity, which may be the cause of unauthorized releases of relevant toxins or harmful blue-green algae. Studies of natural reservoirs show seasonal changes "common" neurotoxicity, which generally confirmed by biological observations.

As a verification method for the analysis of natural water samples contained cyanotoxins and showed the presence of a "common neurotoxicity" the absence of phosphorus-organic and carbamate compounds of anthropogenic origin (pesticides, for example) also confirmed using high - performance liquid – chromatography – high-resolution -mass - spectrometry (HPLC-HRMS) (LTQ Orbitrap, Thermo Finnigan).
Combinatorial Structures of Graphene Oxide and SnO2 for Sensing various VOCs
Authors: Park Hyejin , Chung Yoonsung , Lee Eunji , Ahn Soohyun , Lee Seokhee , Ahn Hosang , KIM Dong-Joo
Published: February 2020

Graphene (GR) and reduced graphene oxide (r-GO) are outstanding candidates for gas-sensing elements due to extremely high surface-to-volume ratio and excellent electrical properties [1]. Their unique and attractive properties can lead to novel sensors with minimum power consumption, room temperature sensing, and sensitivity. But limitations of slow reaction speed and recovery rate of the GR based sensors were observed [2]. The addition of metal oxide to make combinatorial structures with GR is being exploited as a potential way to overcome such limits

The nanostructured metal oxides such as zinc oxide (ZnO) and tin oxide (SnO2) have been demonstrated as gas sensing materials with excellent semiconducting properties [3]. However, gas sensing of the metal oxide typically requires elevated temperatures, which causes energy consumption, and limits wide range of applications. Combination of GR/r-GO and metal oxide, especially SnO2, may present potential benefits by reducing energy consumption and enhancing response rate. Several approaches were attempted to make this combinatorial structure for gas sensing, but the approaches were mostly to utilize good electrical properties of r-GO. Few studies were conducted in applying non-treated graphene oxide (GO) for gas sensing. Since multilayer of GO has been demonstrated as good semiconducting materials [4], systematic approach to combine non-treated GO and metal oxide with changing the ratio as well as their combinatorial structures on gas sensing behaviors are investigated in this study.

Combinatorial structures of GO and SnO2 were fabricated via electrophoretic deposition (EPD). The hierarchical oxide nanostructure of GO and SnO2 was analyzed by SEM and XRD as shown in Fig. 1. Mixture ratio was adjusted by adding different amount of SnO2 nanoparticles, and its effect on gas sensing behaviors was investigated. Fig. 2 shows the gas sensing behaviors of the GO/SnO2 composite films with 100 ppm of formaldehyde gas (HCHO). Gas sensing performance with non-treated GO and GO/SnO2mixture were demonstrated at room temperature. The strategies to construct combinatorial structure and their sensing behaviors in conjunction with sensing mechanisms are discussed in detail.

This research was partially supported by a grant from a Strategic Research Project (2013-0132) funded by the Korea Institute of Construction Technology, and Auburn University IGP.

[1] Lu, G., Ocola, L. E., & Chen, J. Applied Physics Letters, 94(8), 083111. (2009).

[2] Dreyer, D. R., Park, S., Bielawski, C. W., & Ruoff, R. S. Chemical Society Reviews, 39(1), 228-240. (2010).

[3] Park, H., Ahn, H., Chung, Y., Cho, S. B., Yoon, Y. S., & Kim, D. J. Materials Letters, 136, 164-167. (2014).

[4] Wang, C., Yin, L., Zhang, L., Xiang, D., & Gao, R. 10(3), 2088-2106. (2010).

Figure 1
Photochemical Decoration of Metal/Metal-Oxide Nanoparticles on SnO2 Nanorods for Improved Hybrid Gas Sensors and Photodetectors for Environmental Applications
Authors: Carvajal Christian G , Kadri Killani , Rutherford Gugu , Pradhan Aswini K
Published: February 2020

Highly oriented SnO2 nanorods were grown on different substrates by using the Vapor-Liquid-Solid (VLS) technique. The nanorods films were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDX). Photochemical nanoparticle decoration using a UV radiation source of 254nm wavelength was carried out to generate dispersed metallic (Au & Ag) and metal-oxide (CuO & NiO) nanoparticles attached on separated samples. The pre-decoration precursor solutions were prepared at same morality ratio and were used for chemical bath decoration at same irradiation time. The resulting hybrid transducer properties will be extensively discussed.

Chemical sensing properties of the as-prepared hybrid films demonstrated high selectivity gas detection response to CO, H2S, C2H6O and C3H6O. Light sensitivity properties have been characterized as well; a significant increased photocurrent in response to UV radiation was observed. The devise processing and experimental measurement parameters will be described and preliminary results will be presented.

This work is supported by NSF-CREST organization.
Non-Invasive Biosensor for Measurement of Blood Urea Level in Human Subjects Using Reverse Iontophoresis
Authors: K Varadharaj Eswaramoorthy , Jampana Nagaraju
Published: February 2020

A screen printed potentiometric urea biosensor is developed to monitor blood urea level non-invasively using reverse iontophoresis. The extraction and sensing system consists of a reverse iontophoresis electrode, a working electrode and a reference electrode. The working electrode is screen printed using graphitic carbon paste, reference and reverse iontophoresis electrodes are screen printed using silver/silver chloride (Ag/AgCl) paste. Urease enzyme is immobilized in the polypyrrole matrix on the working electrode using cyclic voltammetry, having potential window of -0.1 v to 0.8 v and scan rate of 50 mV/s for 5 deposition cycles. Scan rate and deposition cycles are optimized for cyclic voltammetry to immobilize the urease enzyme in polypyrrole matrix to obtain maximum sensor performance. The stability of screen printed reference electrode (SPRE) is probed with standard calomel electrode and found to be stable for more than 60 minutes. The enzyme leaching test on working electrode is conducted using indophenol method and confirms that there is no leaching of enzyme from the electrodes. Scanning Electron Micrograph (SEM) of deposited polyrrole shows that microstructured film is deposited on the working electrode. X-ray diffraction (XRD) and Raman spectroscopy are performed to analyze composition of deposited film and they confirm the presence of all mandatory functional groups of polypyrrole in the deposited film. Electrochemical active area is calculated through cyclic voltammetry and there is 55- 60% increase in electrochemical active area compared to bare graphitic carbon electrode due to the formation of polypyrrole microstructure on the working electrode. The developed screen printed sensors exhibited sensitivity of 35.07 mv/decade and showed liner response for the range, 10 μM to 5 mM with correlation co-efficient of 0.995. Interference studies with KCl, NaCl and MgCl solutions are performed and found that there are no significant changes in the sensor performance. These tests affirmed that the developed sensors are useful for conducting in-vivo studies to measure blood urea level non-invasively through reverse iontophoresis. Developed urea sensor is validated by conducting clinical investigations on 10 human subjects. The correlation co-efficient is arrived between blood urea level and transdermal extracted urea level and it is found to be 0.391.

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Studies on Carbon Mediated Paste Screen Printed Sensors for Blood Glucose Sensing Application
Authors: K Varadharaj Eswaramoorthy , Jampana Nagaraju
Published: February 2020

Ready to use screen printed glucose sensors are fabricated using Prussian Blue (PB) and Cobalt PhthaloCyanine (CoPC) mediated carbon paste as working electrodes. The reference and counter electrodes are screen printed using silver/silver chloride and graphitic carbon paste respectively. The stability of screen printed reference electrode (SPRE) is examined with standard calomel electrode and found to be stable for more than 60 minutes. Optimal operating voltage for PB and CoPC screen printed sensors as determined by hydrodynamic voltammetric technique are 0.3 V and -0.1 V respectively. The sensing response of fabricated sensors towards H2O2 is conducted. Amperometric sensing response of PB screen printed sensor to H2O2 has limit of detection (LOD) of 0.5 μM with sensitivity of 63.690 mAcm-2/mM. Sensing response is found to be linear for the range, 1 to 4500 μM. While the CoPC screen printed sensor has LOD 0.05 μM with sensitivity of 56.66 mA cm-2/mM to H2O2. The response is linear for the range, 0.1 to 7500 μM. Glucose oxidase is immobilized on the working electrodes by cross-linking method using Glutaraldehyde and Nafion. Electrochemical sensing responses of the fabricated sensors for glucose are studied. PB mediated glucose sensor exhibits a sensitivity of 5.60 mA cm-2/mM with LOD of 7 μM. The response is observed to be linear for the range, 10 to1000 μM with linearity co-efficient of 0.9990. Sensitivity and LOD of CoPC mediated glucose sensor are found to be 5.224 mA cm-2/mM and 70 μM respectively. The amperometeric response is linear for the range, 100 to 1500 μM with linearity co-efficient of 0.9973. Inference studies on the fabricated glucose sensors are conducted with species like uric acid and ascorbic acid. PB mediated sensors showed a completely interference-free behavior, while CoPC mediated sensors are influenced by uric acid and ascorbic acid due to higher operating voltage.  The sensing response of PB mediated glucose sensors is also studied in diluted human serum samples and the results are compared with values obtained by standard spectrometric method.  The correlation co-efficient is found to be 0.935 and hence the sensor has potential application in clinical diagnostics.

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(Invited) Ionic Fluids Containing Both Strongly and Weakly Interacting Ions of the Same Charge Have Unique Ionic and Thus Chemical Environments As a Function of Ion Concentration
Authors: Rogers Robin Don , Wang Hui
Published: February 2020

Liquid multi-ion systems or Double Salt Ionic Liquids (DSILs; salts composed of more than two types of ions, liquid at low temperature (below 100 °C),[1]) made by combining two or more salts can exhibit charge ordering and interactions not found in the parent salts, leading to new sets of properties. This effect is investigated here by examining liquid systems made by mixing two miscible ionic liquids comprised of a single cation, 1-ethyl-3-methylimidazolium ([C2mim]+), and two anions with very different properties, acetate ([OAc]-) and bis(trifluoromethylsulfonyl)imide ([NTf2]-), namely [C2mim][OAc]x[NTf2](1-x), and made by dissolving a crystalline salt, ammonium acetate ([NH4][OAc]), in the ionic liquid [C2mim][OAc] in their miscible range, namely [NH4]x[C2mim](1-x)[OAc] (0 ≤ x ≤ 0.58). Through NMR and FT-IR spectroscopic analysis, we have shown that the electrostatic interactions present are quite different from those in the parent salts. We attribute this to the unique charge ordering arising from the ability of [OAc]- to form complexes with [C2mim]+ ions by drawing [C2mim]+ ions away from the less basic [NTf2]- ions or the ability of [NH4]+ cation to form complexes with [OAc]- ions by “stealing” [OAc]- from the less acidic [C2mim]+ ions. Solubility studies with various kinds of organic solutes (e.g., EtOAc, H2O, chloroform, benzene, tetrahydrofuran) and active pharmaceutical ingredients (ibuprofen and diphenhydramine) indicate that the solubilities of these solutes in the DSILs show dramatic, non-linear trends as a function of ion concentration, demonstrating that solubility of selected solutes can be finely tuned via changes in the ionic compositions. These kinds of DSILs provide potential solvent systems with unique and tunable properties to be used in the electrochemical and separation fields.

References

[1].   G. Chatel, J. F. B. Pereira, V. Debbeti, H. Wang and R. D. Rogers, Green Chem., 16, 2051 (2014).
(Invited) Ionic Liquids in Gas Sensors: Recent Progress and Future Prospects
Authors: Carter Michael T , Stetter Joseph R , Findlay Melvin W , Patel Vinay
Published: February 2020

Since the initial report of Hurley and Weir in 1951 [1] room temperature ionic liquids (RTILs) have been researched extensively for over five decades, starting with the binary eutectic mixtures based on haloaluminates [2,3] and proceeding through a wide array of single component salts containing many different organic cations and organic or inorganic anions [4-6].  The driving force behind research into these media was not only the sheer novelty of them as opposed to molecular liquids, but also the promise of new properties and capabilities, for example, in enabling improved separations, more efficient chemical syntheses and higher performance sensors and analytical methods.  These possibilities are all the more interesting because the single component salts are typically air and moisture stable and therefore much easier to work with under practical conditions than the reactive haloaluminates, which need to be kept under dry, inert atmosphere. 

Our particular interest as a commercial gas sensor developer and manufacturer is whether and how RTILs could be leveraged to improve amperometric gas sensor performance, most importantly in ways that add value to the sensor product from the customer’s point of view.  We are using a new, next generation amperometric gas sensing technology for a variety of toxic gases and gases of environmental interest including CO, H2S, NO2, SO2, O3, NH3 and others.  This approach adapts the conventional ideas of amperometric gas sensing into a printed package that is very small and ultralow power for modern applications (Figure 1).  Can RTILs be used effectively as electrolytes in amperometric gas sensors?  How do RTILs compare to conventional aqueous acid electrolytes? Can RTILs impart new capabilities and performance improvements (sensitivity, response time, stability, operational life, tolerance of extreme environmental conditions) to amperometric sensors?  How does one go about selecting the right RTIL from the vast array of possibilities?  What are the materials compatibility issues? What about cost?

This presentation will address these issues from the perspective of several programs on gas sensor development for toxic and environmental gases at KWJ Engineering.

References

[1] F. H. Hurley and T. P. Weir, J. Electrochem. Soc., 98, 203 (1951).

[2] H. L. Chum, V. R. Koch, L. L. Miller and R. A. Osteryoung, J. Am. Chem. Soc., 97, 3264 (1975).

[3] J. S Wilkes, J. A. Levisky, R. A. Wilson and C. L. Hussey, Inorg. Chem., 21, 1263 (1982).

[4] J. S. Wilkes and M. J. Zaworotko, Chem. Commun., 965 (1992).

[5] J. G. Huddleston, A. E. Visser, W. M. Reichert, H. D. Willauer, G. A Broker and R. D. Rogers, Green Chemistry, 3, 256 (2001).

[6] P. Wasserscheid and T. Welton (Eds.), “Ionic Liquids in Synthesis,” Wiley-VCH, Weinheim (2003).

Figure 1.  Printed amperometric gas sensor (15 x 15 x 1 mm).

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Transparent Nanowire Electrodes As a Tool for Electrochemical Detection
Authors: Lefèvre Florent , Poorahong Sujittra , Perron Marie-Claude , Juneau Philippe , Izquierdo Ricardo
Published: February 2020

The development of new nanomaterial like carbon nanotubes, graphene and nanowires brings new possibilities to existing technologies. With the emergence of transparent electrode based on these materials, we could imagine new type of sensors, which combines transparency and flexibility. Silver nanowire transparent electrodes are currently transforming this industry. Touch screen sensors, OLED and solar panel can now be fabricated on flexible plastic sheets with low cost printing techniques. In the same way, this new type of electrode could bring electrochemical sensor toward new transparent and flexible sensing application for life science.

In our study, we fabricate and characterize transparent electrode based in metal nanowires for electrochemical detection. By changing the length, diameter and amount of deposited nanowires, we can vary their transparency (up to 90% transparent), sheet resistance (up to 0.1 ohm/square) and effective surface area. Compared to conventional evaporated plain electrodes, printed nanowire electrodes can achieve more than 80% transparency (in visible range) with the same electrochemical effective surface area. Using these electrodes, we can fabricate new sensors with high transparency (> 90%), flexibility and high sensitivity to oxygen and hydrogen peroxide. The detection of these two components is predominant in healthcare and environmental monitoring.

The combination of those properties could allow us to use this type of sensors as opto-electrochemical sensors for monitoring living cells and also for glucose detection on humans. Transparent nanowire electrodes can also be a real alternative to existing indium tin oxide (ITO) transparent electrodes for other applications.

Figure 1.Pictures of electrochemical sensors based on metal nanowires on PET transparent substrate. WE and REF electrodes are made from metal nanowire have 80% transparency, CE electrode are made from gold.

Figure 2. SEM image of silver nanowire electrode and the size distribution of nanowires. 

Figure 3.  Voltammetry response of the nanowire based electrochemical sensor to hydrogen peroxide in phosphate buffer (pH=7)

Figure 4. Dose-response curve to hydrogen peroxide using the nanowire-based sensor in phosphate buffer (pH=7)

Figure 1