bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessing Spatial Resolution of Cathodo-Luminescence Imaging and Spectroscopy at the Nanoscale for Inorganic Phosphor Powders
Authors: Fern George Robert , Harris Paul Gregory , Ireland Terry , Silver Jack
Published: February 2020

It is now possible to easily collect CL images (using a photomultiplier tube using total or filtered light) and emission spectra from individual nanometer sized particles using the commercially available Gatan Vulcan attachment for a transmission electron microscope (TEM).  In our case, at Brunel University London, we have fitted this to a JEOL 2100F field emission TEM. This work demonstrates the spatial resolution that has been achieved when imaging various phosphor nano materials and discusses the limitations of the technique.  It also demonstrates the uniformity of excitation/emission from various phosphors, and hence the effectiveness of the synthetic method used to manufacture the phosphor can be seen.   Conventionally, photoluminescence (PL) and cathodoluminescence (CL) spectra are collected from bulk phosphor samples and are the average of all of the particles in the sample.  This is true of most samples made either in the laboratory for research or commercial materials prepared by industrial companies.  Cathodoluminescence spectra have been collected from nanometer-sized crystals of quantum dots (spherical and rods) and various oxide and oxysulfide phosphors.  The latter phosphors have been implemented into CL applications on a vast scale whereas the quantum dot materials are not designed for CL application and therefore great care is required when imaging these materials to minimize the effect of beam damage. 

When observing mixtures of phosphors (Gd2O2S:Tb3+ and Y2O3:Eu3+) it is apparent that when the electron beam is positioned onto one of these two materials and the spectrum observed, then the other phosphor emission spectrum can be observed if the particles are nearby.  However when observing quantum dot materials the spatial resolution is only limited by the particle size.  A tentative explanation for this effect is given.

In this work we compare the spectra of nanometer sized phosphor crystals/particles in order to understand any variation in the emission spectra between the phosphor grains and to understand the effect of temperature on their luminescent properties.

Our results will be presented that could only have been found by using CL spectra obtained directly from single nanoparticles.  In conclusion:

1)  The effect of different TEM machine parameters will be discussed

2)  The CL spatial resolution will be demonstrated

Figure 1. Left) HAADF STEM of nanometre-sized single crystals of Y2O3Eu3+ and Gd2O2S:Tb3+; The green line spectrum image shows where 10 emission spectra were recorded at equally spaced intervals.  Right) Extracted spectra taken from opposite ends on the line scan show the characteristic CL emission spectrum for both the Eu3+ and Tb3+ are observed in both spectra.

Figure 1
Thermal Degradation of Nitride Phosphors
Authors: Xie Rong-Jun , Wang Chunyun , Takeda Takashi , Cho Yujin , Suehiro Takayuki , Hirosaki Naoto
Published: February 2020

Thermal stability of phosphors for solid state lighting is usually investigated by in-situ measuring the thermal quenching behavior of the sample heated up to ~ 300oC and held at each temperature for a certain time. However, thermal quenching does not have the same meaning with thermal degradation, which thus cannot evaluate the stability of the phosphor against thermal attacks comprehensively. In this work, we attempted to study the thermal degradation of nitride phosphors (i.e., SrSi2O2N2:Eu and CaAlSiN3:Eu) by baking the powders in air or in pressued water steam at high temperatures. The degradation mechanism was discussed and clarified by carrying out the surface state analysis using various techniques.

   For SrSi2O2N2:Eu, the PL intensity decreased as the baking temperature rises, degrading by 10 and 30% when the samples baked at 500 and 600oC, respectively. In comparison with Ca-α-sialon:Eu2+ that retained its luminescence up to 800oC, SrSi2O2N2:Eu showed a very serious thermal degradation. By conducting the high-temperature in-situ XRD analysis and TEM observations, an impurity phase of SrSiO3 was identified additionally, as a result of the oxidation of the host SrSi2O2N2. In addition, the activator ions were also oxidized during baking in air, with divalent Eu2+ changed into trivalent Eu3. It indicates that both of the oxidation of host and activators leads to the thermal degradation of SrSi2O2N2:Eu that is an irreversible decrease of luminescence.

   For (Sr,Ca)AlSin3:Eu (SCASN), the moisture-induced degradation was comprehensively investigated by treating it under a severe condition of high-pressure water steam. The degradation initiated at 150oC, and the luminescence of SCASN was seen to be quenched quickly, with the powder sample being bleached after the treatment. Both of the microstructure and phase changed obviously with the oxidation, and the host turned finally into NH3, (Sr,Ca)Al2Si2O8 and Ca(OH)2. By using a variety of spectroscopic, surface and microstructure analytic techniques, the degradation mechanism was clarified and proposed to occur viathe oxidant-gas penetration mechanism through the moisture-enhanced oxidation of both the SCASN host and divalent europium.

References:

1. C.Y. Wang, R.-J. Xie, F.Z. Li, and X. Xu, J. Mater. Chem. C. 2, 2735 (2014).

2. J. Zhu, L. Wang, T. L. Zhou, Y.J. Cho, T. Suehiro, T. Takeda, M. Lu, T. Sekiguchi, N. Hirosakia, and R.-J. Xie, J. Mater. Chem. C. 3, 3181 (2015).
The Exploration of Rare Earths Based Luminescence for Detection and Sensing in Radiation Security and Enhanced Oil Recovery
Authors: Chen Wei , Ma Lun , Sahi Sunil
Published: February 2020

Dirty bomb or radiation attack is a big threat to the world and the developing of high sensitive technologies for radiation detection is an emerging need. Also, the development of high-performance scintillating materials is essential for precision calorimetry in high energy physics, medical imaging and industries. The most frequently considered characteristics of scintillators are efficiency of energy conversion, stopping power, luminescence decay time, spatial resolution, and physical and chemical stability. Currently applied inorganic crystalline scintillators are not only limited by their high cost and scalability issues, but also limited by other intrinsic drawbacks. For example, high purity germanium must be operated at liquid nitrogen temperature, while sodium iodide crystal is highly hygroscopic. On the other hand, plastic scintillators based on polymeric materials are cheap and easy to manufacture, but have low light yield and low density. In this talk, I will present the strategy for how to design luminescence nanomaterials based on energy transfer for radiation detection.

Oil exploration and production are always the hot area as natural oil is still the major energy for our society. Luminescence materials may play an important role in oil exploration and extraction either as water tracers or as new materials for wettability enhancement. In addition, food quality and safety are related to our daily life. In this talk, I also present some new ideas and methods for the potential applications of luminescence materials for oil recovery and food safety.
Amber Full Conversion Ceramics for LED Applications
Authors: Zheng Yi , Montaner Jason , Raukas Madis , Tarry Chris , Kechele Juliane , Tragl Sonja , Strube-Knyrim Johanna , Eisert Dominik , Ferstl Klemens , Goeoetz Britta
Published: February 2020

Monochromatic amber light-emitting diodes (LEDs) have been widely adopted in the industrial and automotive applications. Although relatively efficient in room temperature, efficacy of direct AlGaInP amber LEDs suffers at higher application temperatures. The phosphor-converted LEDs overcome this drawback by generating amber light from all-nitride ceramic phosphor excited by an efficient blue InGaN chip. At room temperature and 700 mA drive current, the LED using such technique achieves a typical brightness of 135 lm. At application temperatures of 85 °C (Tj in the chip), the LED still achieves the impressive figure of 123 lm. In this talk, the effects of composition, phases and microstructure of (Sr,Ba)2Si5N8:Eu full conversion ceramic phosphors on the color binning,  efficacy, thermal quenching and lifetime of phosphor-converted amber LEDs are discussed generally.
Square Wave Voltammetric Method for Simultaneous Determination of Bleaching Agents in Skin Cosmetics
Authors: Calaça Giselle Nathaly , Machado Silvane , Wohnrath Karen , Pessoa Christiana Andrade , Nagata Noemi
Published: February 2020

Skin pigmentation disorders due to melanin excess, could have different causes. Kojic acid (KA) and hydroquinone (HQ) are depigmenting agents widely associated in pharmaceutical formulations to treat skin pigmentation disorders. An electroanalytical method was developed for simultaneous determination of these bleaching agents in skin whitening cosmetics. Cyclic voltammetry (CV) and square wave voltammetry (SWV) experiments were performed using a potentiostat/galvanostat µAutolab (Type III, Metrohm-Eco Chemie). A conventional three-electrode cell containing a glassy carbon (GCE) as working electrode (A=7,07 mm2), Pt disc (A=12,57 mm2) as counter electrode and Ag/AgCl (saturated aqueous KCl) as reference electrode were employed. Before use and between potential scans, the GCE surface was polished. Kojic acid exhibits a well-defined irreversible oxidation peak at 0.72V and hydroquinone a quasi-reversible redox peaks at 0.08 V and -0.02 V, characterized by adsorptive and diffusional processes, respectively. The influence of the pH was examined over the pH range from 2 until 8 in 0.04 mol L-1 Britton-Robinson buffer solution, the KA and HQ peaks potential shifts negatively with the increase of the pH value, due to the participation of protons in the oxidations processes. Others buffer solutions were examined at pH 8 and Mcllvaine was chosen to subsequent analytical purposes. The square wave voltammetric parameters were optimized by 23 Full Factorial Design including a central point assayed in quintuplicate. The statistical treatment of the data showed that the main effects and interaction effect of amplitude vs. frequency were significant at 95% confidence level. The best response is obtained at a= 40 mV, f= 40 s-1 and ΔES
= 1mV. Under optimized conditions, the calibration curves were obtained in the concentration ranges of 3.5x10-5 to 2.5x10-4 mol L-1 (R= 0.9996) for kojic acid and 1.5x10-5 to 1.6x10-4 mol L-1 (R= 0.9994) for hydroquinone, with  detection limits of 7.84x10-6 mol L-1 and 3.71x10-6 mol L-1 for KA and HQ, respectively. The proposed method was validated under parameters: specificity, linearity, range, limit of detection, limit of quantification, precision (repeatability and intermediate precision) and accuracy considering Brazilian Health Surveillance Agency (ANVISA) and International Conference on Harmonisation (ICH) guidelines. The developed and validated method has been successfully applied to the direct simultaneous determination of these compounds in real samples (gel and cream).
Electrochemical Detection of Colloidal Semiconductor Nanoparticles: From Single Nanoparticles to Aggregates
Authors: Alpuche-Aviles Mario A , Chhetri Pushpa , Barakoti Krishna K. , Recinos Andrew
Published: February 2020

Our group develops electrochemical methods to study semiconductors in colloidal suspension to study photocatalytic processes of colloidal semiconducting nanoparticles (NPs). We have demonstrated the detection of individual anatase NPs interacting with an electrode by photoelectrochemical currents. The NPs are suspended in methanol under constant illumation and we present this as a model system of photocatalysis. However, under different experimental conditions, the photocatalytic currents go from steps to spikes. We have assigned the spike currents to aggregates. As illumination time increases, the current spikes also increase in size, consistent with the growth of agglomerates that can store a larger number of electrons. We propose that these interactions carry information about the photochemical process at the single agglomerate, and in turn, from the NPs that construct the aggregate. This seminar will present our advances towards measuring the particle by particle charge storage and the ability to allow electrons to flow across the NPs. We will also discuss the rate of photooxidation in the context of the agglomeration in solution and its implication on the detection of single NPs.
Processing and Properties of Nanocomposite Thin Films for Micro-Solid Oxide Fuel Cell Applications
Authors: Rottmayer Michael , Singh Raj , Huang Hong
Published: February 2020

Microfabricated solid oxide fuel cells (micro-SOFCs) have recently gained attention as a promising technology, with the potential to offer a low temperature (as low as 300oC), reduced start-up time, and improved energy density for portable power applications.  As a means for achieving the substantially reduced operating temperatures, new electrode materials with increased catalytic activity are being explored.  At present, porous Pt is the most common cathode being investigated for micro-SOFCs. However, there are significant technical challenges for utilizing pure metallic electrodes at the operating temperatures of interest due to their tendency towards Ostwald ripening, as well as low bulk ionic conductivity. Nanocomposite materials (e.g. Pt/YSZ) are being studied as a promising alternative approach for providing both microstructural and electrochemical stability to the electrode layer.  The microstructure and composition of the nanocomposite cathode material has been systematically investigated via controlled vacuum deposition conditions and resultant electrochemical properties measured by electrochemical impedance spectroscopy (EIS). Transmission electron microscopy (TEM) of the nanocomposite films reveals a percolating network of Pt and YSZ, along with interconnected nano-sized pores.  An improvement in charge transfer kinetics associated with the oxygen reduction reaction has been demonstrated as compared to a pure porous Pt electrode, along with a significant improvement in microstructural stability during extended mSOFC operation.  These results will be presented in detail.
Photocatalytic Reduction of CO2 with H2O By Engineered TiO2 Nanocomposites
Authors: Li Ying , Liu Lianjun
Published: February 2020

Photocatalytic conversion of CO2 with H2O to solar fuels is a promising technology to recycle CO2, a major greenhouse gas. However, the CO2-to-fuel conversion efficiency is typically low, mainly due to the fast recombination of photo-excited electron-hole pairs and limited absorption of sunlight by wide band-gap photocatalysts like TiO2. In addition, some scientific challenges have been overlooked including the photocatalyst’s ability to adsorb CO2 and the adsorption/desorption kinetics on the catalyst surface. To promote charge transfer, visible light response, and CO2 adsorption and activation, we have engineered a series of TiO2 nanocomposites including Cu/TiO2, oxygen deficient TiO2, TiO2 nanocrystals with mixed exposed facets, porous microsphere MgO/TiO2, and nano-TiO2 dispersed on MgAl-layered oxide materials. Photocatalytic CO2 reduction experiments have been conducted under UV and visible light irradiation, respectively, with CO and CH4 being the major products. Furthermore, we have compared the CO2 adsorption and reduction intermediates and reaction kinetics at near room temperature and near flue gas temperature (~150 oC), using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The higher reaction temperature enhanced intermediate/product desorption, and the addition of basic materials (MgO and MgAl-LDO) improves CO2 adsorption particularly in the presence of water vapor, thus enhancing the catalytic activity and stability of the photocatalyst.
Graphene Oxides and Their Hybrids for CO2 Conversion and Solar Fuels
Authors: Chen Li-Chyong , Chen Kuei-Hsien
Published: February 2020

Finding effective ways for conversion of CO2 into hydrocarbons (as energy fuels or chemical feedstock) is highly desirable to achieve sustainable development. Photocatalytic conversion of CO2 to hydrocarbons such as methanol makes possible simultaneous solar energy harvesting and CO2 reduction, two birds with one stone for the energy and environmental issues. In this talk, I will present our progress in using graphene oxides (GOs), along with their hybrids, as promising photocatalysts for CO2 reduction.

Modified Hummer's method has been applied to synthesize the GOs with tunable band gap. Under visible light, the photocatalytic CO2 to methanol conversion rate on our modified GOs is 0.172 μmol g-cat−1 h−1, which is six-fold higher than the popularly studied TiO2 [Nanoscale
5 (2013) 262]. Meanwhile, a novel one-step and effective electrochemical (EC) method is developed to directly exfoliate graphite into thin reduced graphene oxide (RGO) nanosheets at room temperature. The oxidation degree of the RGOs, hence the C/O ratio, depends on the switching potentials of the EC synthesis. The ability to control the light-absorption of the RGOs by simply adjusting the switching potentials can be further achieved. This approach presents us a possibility for the environmentally friendly, ultrafast, low-cost, and large-scale production of RGOs and great potential in solar-fuel applications.

To enhance carrier generation and separation, therefore the resultant photocatalysis reaction, Cu and MoS2 nanoparticles were further deposited on GOs as co-catalysts. Not only methanol, but also acetaldehyde was detected. Total solar to fuel yield of 6.8 μmole g-cat-1 h-1 has been achieved, which is 170 times enhancement relative to the commercial P-25 photocatalyst [Nano
Lett.
14 (2014) 6097]. In all the above-mentioned hybrids, the photo-catalytic performance is always superior to that of constituent component when used alone. Detailed preparation and characterization of the catalysts will be presented. The role and interplay of the constituent components will also be discussed.
Electrochemical Reactions at Ionic Liquid/Gold Interface Probed By Electrochemical Surface Plasmon Resonance
Authors: Nishi Naoya , Ikeda Yoichi , Amano Ken-ichi , Sakka Tetsuo
Published: February 2020

Ionic liquids (ILs) are promising materials for electrochemical devices.  To maximize the performance of such devices, studies on the interfacial structure, its dynamics, and the kinetics of electrochemical reactions at electrochemical IL interfaces are of crucial importance.  Previously we studied the dynamics of the structure at IL|Au interface by using electrochemical surface plasmon resonance (ESPR) [1].  The transient curves of the SPR angle, which reflects the change in the structure in the electrical double layer, showed extraordinarily slow relaxation on the order of minutes during multi-potential steps, and revealed asymmetry of the relaxation time to the potential step direction [1].  In the present study, electrochemical reactions at the IL|Au interface have been studied using ESPR. 

We have found that redox reactions at the IL|Au interface can also be sensitively probed using ESPR when we add redox species such as ferrocene and its derivatives in ILs.  Sigmoid curves of the SPR angle are observed during electrode potential scan.  We have analyzed the sigmoid curves by simultaneously using a theory and a digital simulation, and have revealed specific interaction between redox species and IL ions depending on their charges.

[1] N. Nishi, Y. Hirano, T. Motokawa, T. Kakiuchi, Phys. Chem. Chem. Phys. 15 (2013) 11615.
Digital Voltage-Current Time Differential Method for Operating Zirconia-Based NOx Gas Sensors
Authors: Woo Leta , Bell Frank , Boettcher Mike , Chee James , Fitzpatrick Joe , Henderson Brett , Sorensen Lee , Wang Victor , Novak Robert , Visser Jaco
Published: February 2020

Gas sensors are important for monitoring and controlling combustion technologies. In particular, NOx compounds (NO and NO2) that are present in diesel exhaust cause poor air quality and act as both pollutants and greenhouse gases. Commercially available NOx sensors for vehicle applications use high-temperature solid-state ceramic electrochemical technology similar to the ubiquitous automotive oxygen sensor; however, commercial NOx sensors are much more expensive than their oxygen sensor counterparts due to their complicated design with multiple cells (as opposed to the single-cell oxygen sensor) and their expensive electronics for measuring low-current signals (as opposed to the voltage signal from oxygen sensors). Therefore, a NOx sensor alternative that meets stringent operational requirements at a reduced cost is desired for automotive and other combustion applications.

Conventional solid-state electrochemical sensors operate with direct current (dc) methods that are either current-based/amperometric or voltage-based/potentiometric. In this work, we use alternating current (ac) impedance-based/impedancemetric operation of zirconia-electrolyte-based sensors for NOx detection. The solid-state electrochemical cells are comprised of two electrodes separated by the zirconia electrolyte, where both electrodes are exposed to the test gas. The impedance-based response of the simple single-cell sensor relies primarily on multiple concurrent non-equilibrium steady-state interfacial redox reactions. Impedance spectroscopy was used to investigate sensing mechanisms, and sensor operation was performed at pre-determined frequencies to demonstrate stable, reproducible sensor behavior.

Since laboratory impedance spectroscopy evaluation usually employs expensive analytical equipment, a novel, low-cost, portable signal processing method was developed using a digital voltage-current time differential method. The applied signal was an alternating current electrical waveform, and the response of the sensor was digitally measured directly in the time domain; laboratory impedance evaluation usually measures in the frequency domain. Results of the low-cost digital signal processing indicated the potential for increased NOx sensitivity and improved sensor performance compared to the much more expensive frequency-domain impedancemetric method.
Multiplexed DNA Biomarker Detection with Phase Change Nanoparticles
Authors: Su Ming
Published: February 2020

A number of microRNAs (miRNAs) are found in body fluids of patients. The challenge of using these biomarkers for early detection of diseases is that most of them have low concentrations, are not powerful enough when monitored singly, lacking sensitivity or specificity. Parallel to the efforts to find better biomarkers, one possible way is to detect more biomarkers and collectively analyze their profiles. 

This talk describes a multiplexed highly-sensitive technique to detect miRNA biomarkers using solid-to-liquid phase change nanoparticles. The nanoparticles of metals and eutectic alloys with sharp melting peaks will be modified with single strand DNAs (ssDNAs), which specifically bind to one end of miRNA biomarkers. A panel of nanoparticles with composition-dependent melting temperatures will be utilized to detect multiple biomarkers after establishing a one-to-one correspondence between one type of nanoparticle and one type of biomarker. An aluminum substrate with high thermal conductivity will be modified with a panel of ssDNAs that are complementary to the other ends of miRNA biomarkers. The detection scheme is that: (1) the receptor-modified nanoparticles will be incubated in a buffer containing biomarkers; (2) after centrifugation to remove unbound species in blood, biomarkers attached on nanoparticles will be re-suspended in another buffer; (3) the substrate will be immersed in the buffer to catch nanoparticles by forming DNA-RNA duplex; (4) the substrate will be washed to remove excess nanoparticles, and the attached nanoparticles will be readout with differential scanning calorimetry (DSC), where the temperature and area of melting peak reflect the presence and amount of biomarker.

Ten different metals that can form binary eutectic alloys among any two of them are identified. They can form 1,023 types of metallic and eutectic alloy nanoparticles. The compositions and melting temperatures of high order eutectic alloys are determined by calculation of phase diagram. Based on the eutectic compositions, nanoparticles are made by thermally decomposing organometallic precursors in a high boiling point solvent (ethylene glycol) using polyvinyl alcohol as surfactant. The nanoparticles and the aluminum substrate are modified with thiolated probe ssDNA and capture ssDNA, respectively. The lowest target concentration that can be detected is 80 pM. Further, the thermal ramp rates are remained constant to readout indium nanoparticles, but are changed from 1 to 10 °C/min to readout bismuth nanoparticles. The variable ramp rate in the same scan allows ten time adjustment of heat flux (sensitivity). Four different miRNAs are simultaneously detected with four types of nanoparticles, tin, tin-lead alloy, indium and bismuth.
Highly Selective Detection of Glucose, Cholesterol and Urea with Integrated ZnO Nanorods Field-Effect Transistors Array Biosensors
Authors: Ahmad Rafiq , Park Jin-Ho , Hahn Yoon-Bong
Published: February 2020

Nanotechnology revolution has led to the nanofabrication of sensor devices for rapid and specific identification of chemical/biological species. However, the development of multiplexed nanoscale biosensor for simultaneous detection of different analytes still remains a major challenge at the nanotechnology frontier. It is well recognized that diabetes mellitus is a metabolic disorder resulting in an abnormal blood glucose level and activation of several metabolic pathways related to inflammation and apoptosis events. We have developed ZnO nanorods (NRs) based, integrated field-effect transistors (i-FETs) array biosensor with simultaneously immobilizing GOx, ChOx and Ur enzymes on three different ZnO NRs arrays. In this lecture, we reoprt a novel straightforward approach for simultaneous and highly selective detection of multi-alanytes (i.e., glucose, cholesterol and urea) with the i-FETs array biosensor without interference in each sensor response. Compared to analytically measured data, performance of the i-FETs array biosensor is found to be highly reliable for rapid detection of multi-analytes in mice blood, serum and blood smaples of diabetic dogs. The development of an integrated, low-cost ZnO NRs i-FETs array biosensor will produce quick detection under critical patient conditions, early identification of disease/disorder, and also have an enormous impact on the future generations.
Detection of Salmonella
Enterica Typhimurium in Chicken Meat Using Phage Coated Magnetoelastic Sensors
Authors: Chen I-Hsuan , Horikawa Shin , Chin Bryan A. , Barbaree James M
Published: February 2020

According to the Centers for Disease Control and Prevention (CDC), from 2011-2014, there were at least several outbreaks in the U.S. due to Salmonella associated with chicken.  Our goal was to improve food safety in this area, and develop a real time detection system. We developed and demonstrated the use of our phage C4-22 immobilized onto a rapid magnetoelastic (ME) biosensor system for use as a front-line detection ligand to detect all Salmonella
enterica serotypes in TBS model.

Here, we confirm the phage peptide binding to Salmonella
typhimurium cells by fluorescent imaging (Fig. 1 and 2.) Figure 1 showed the Salmonella cells only without C4-22 phages with magnification of 100x. In figure 2, it is the binding of fluorescent labeled phages (1x1011 vir/ml) and Salmonella, viewing under fluorescent microscope with fluorescein isothiocyanate (FITC) filter and with magnification of 100x.

 Moreover, we show the construction of a chicken model to evaluate the detection of Salmonella on/in chicken meat using the phage coated sensor. In the surface detection system, S.  typhimurium solutions at four concentrations of 2.5x106, 5x106, 2.5x107, and 5x107 cfu/ml were inoculated on the surface of chicken breast. Three phage sensors as a test group were placed on the chicken surface for detection. Experiments were repeated twice. Phage sensors were prepared by coating the ME sensors with 1x1010 virons phage C4-22 in TBS. BSA (0.1%) was used as a blocking reagent on the sensor. Sensors coated with 0.1% BSA only served as controls. Cells of S. typhimurium detected on the sensor were eluted with 0.1M Glycine to break phage-Salmonella binding. The percent of Salmonella binding to the phage coated sensor was determined using a standard aerobic plate count method with TSA and BG plates. Phage C4-22 sensors demonstrated more than 12 times higher Salmonella binding capacity than the control sensors at the Salmonella loading concentration of 5x107cfu (Fig.2).

During the experiments, it was found that the spiked Salmonella solution was quickly absorbed by the chicken meat. In the second chicken model, phage sensors were placed at different depths (0.1cm; 0.5cm; 1.0cm below the surface; Fig. 3) inside the chicken after inoculation of Salmonella for 15min. Our data show more than 30% of the inoculated Salmonella cells absorbed inside the chicken meat below 0.1cm of the chicken surface. The percentage of the biosensor captured Salmonella decreased while the detection depth increased.

In summary, phage C4-22 ME biosensors detect well when there are high concentrations of Salmonella on the chicken surface. The inside meat detection allow us to effectively monitor Salmonella cells which were absorbed into the chicken and unable to detect by the biosensors while using a surface detection method.

Figure 1
Electrochemical Quantification of Vanadium By Novel Electroanalytical Technique
Authors: Salazar-Gastelum Moises Israel , Botte Gerardine G
Published: February 2020

Background

The chemistry of vanadium is noticeable since four oxidation states are adjacent (+2, +3, +4, +5), moreover, vanadium can be founded in 65 different minerals and fossil fuel deposits such as petroleum, coals, lignite, oils, pet-coke and so on [1].

Due to the nature and complexity of vanadium samples, it is necessary to set up an analytical technique easy, fast and inexpensive. In this paper, the electrochemical measurement of multivalent cations concentration (EM2C2) technique is extended and demonstrated to determine the concentration of the redox pair V(IV)/V(V) in aqueous solutions simultaneously.

Methodology

The EM2C2 technique consists in the measurement of the limiting current under diffusion limitations using a rotating disk electrode [2]. Different parameters in the technique were investigated, such as scan rate potential, rotation rate of the electrode, and interferences in the measurements.

Results

Preliminary results show that V(IV) and V(V) could be determined measuring the upper and lower limiting current, respectively (Figure 1).

The upper liming current increases at higher concentrations of V(IV) and lower limiting current increases at higher concentration of V(V). Hence, the upper liming current is the analytical signal of V(IV) and lower limiting current is the analytical signal of V(V).

Preliminary results demonstrate that simultaneous quantification of V(IV) and V(V) could be achieved in 1 minute with a detection limit of 1.0 mM for both species.

However, due to the complexity of the samples, other factors may cause interferences in the measurements. Further results will be presented at the meeting including the effect of electrolyte, rotating speed and the presence of other ions in solution.

References

1. M. J. Ahmed, S. Banoo, “Spectrophotometric method for determination of vanadium and its application to industrial, environmental, biological and soil samples”, Talanta 48, (1999), 1085-1094

2. X. Jin and G.G. Botte, “Electrochemical technique to measure Fe(II) and Fe(III) concentrations simultaneously”, Journal of Applied Electrochemistry 39, (2009), 1709-1717.

Figure 1
Biomaterials Research Support at the National Science Foundation
Authors: Simonian Aleksandr
Published: February 2020

The NSF/DMR/BMAT perspective on biomaterials research and education will be presented, as well as a description of ongoing and forthcoming research funding opportunities. It will start by providing an overview of divisions and programs at the NSF where an applicant may consider submitting proposals for biomaterials related research. This presentation will be particularly useful to early career researchers in the field of biomaterials and biosensors.

The Biomaterials program supports fundamental materials researchrelated to (1) biological materials, (2) biomimetic, bioinspired, and bio-enabled materials, (3) synthetic materials intended for applications in contact with biological systems, and (4) the processes through which nature produces biological materials.  Projects are typically interdisciplinary and may encompass scales from the nanoscopic to the bulk.  They may involve characterization, design, preparation, and modification; studies of structure-property relationships and interfacial behavior; and combinations of experiment, theory, and/or simulation.  The emphasis is on novel materials design and development and discovery of new phenomena.

General information on all the programs in DMR can be found on the DMR Web page: http://www.nsf.gov/div/index.jsp?div=DMR. In addition, attendees will have the opportunity to interact “one on one" with NSF BMAT Program Director.
Pulse Excitation Method for Magnetoelastic Biosensors
Authors: Wikle Howard Clyde , Du Songtao , Horikawa Shin , Chin Bryan A
Published: February 2020

Magnetoelastic (ME) biosensors are being investigated to detect and monitor the presence of foodborne pathogens that may contaminate our foods between the farm and the table. ME biosensors are based upon free-standing, vibrating platforms that change their resonant frequency in response to the capture and accumulation of target pathogens upon the sensor surfaces. The sensor platform is caused to vibrate by an external magnetic excitation field. A common excitation method is to sweep the magnetic field across a range of frequencies that are expected to include the resonant frequency of the sensor. This requires that one know beforehand the resonant frequency and the anticipated frequency shift caused by the capture of the target species, or search for these during measurement. In this work, an alternative (pulse) excitation method has been investigated to measure the resonant frequency of ME biosensors. A pulsed magnetic field was used to excite ME sensors to vibrate with a damped oscillation that decays rapidly. The resonant frequency is determined from the sensor response to the pulse excitation. The performance of a system designed to excite and measure the resonant frequencies of ME biosensors is described and its performance characterized. The operation of the system is demonstrated through the detection of Salmonella on fresh produce.
Amperometric Detection of Plant Volatiles Using Metal Oxide Nanoparticles
Authors: Fang Yi , Ramasamy Ramaraja P.
Published: February 2020

Volatile organic compounds released by pathogen-infected plants can be used as fingerprints for plant disease detection via electronic nose technologies1,2. In this work, nanoparticles of TiO2 or SnO2 modified on screen-printed carbon (SP) electrodes have been developed for detection of fruit volatiles using amperometric techniques. p-ethylguaiacol, is a characteristic compound present in the volatile signature of  fruits infected with a pathogenic fungus called Phytophthora cactorum. The electroanalytical data obtained using cyclic voltammetry and differential pulse voltammetry showed that both SnO2 and TiO2 exhibited high sensitivity (174–188 mA cm-2 mM-1) and low detection limits (35–62 nM) for p-ethylguaiacol detection3. Both biosensors were evaluated for interference by adding common green leaf volatiles (cis-3-hexel-1-ol, hexyl acetate and cis-3-hexen-1-yl acetate). The results demonstrate that both metal oxides are a reasonable alternative to expensive electrode materials such as gold or platinum for amperometric sensor applications.

Reference

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

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

Y. Fang, Y. Umasankar and R. P. Ramasamy, Analyst., 2014, 139, 3804

Figure 1
Development of Simultaneous Measurement Method of Potentiodynamic Polarization Curve and Impedance Spectra Determined By Wavelet Transformation
Authors: Kato Seiya , Hoshi Yoshinao , Shitanda Isao , Itagaki Masayuki
Published: February 2020

Electrochemical impedance spectroscopy (EIS) is powerful method to analyze dissolution mechanisms of metals because time constants for elementary reaction steps and formation of reaction intermediate can be discriminated. Impedance spectrum is generally measured by using a frequency response analyzer (FRA) whose principle is on the basis of Fourier transformations of sinusoidal input and output signals. Ragoisha et al. (1) proposed a potentiodynamic electrochemical impedance spectroscopy (PDEIS), in which sinusoidal wavelet is superimposed on terrace of the each potential step during stepwise potential scan. Our group (2, 3) developed a simultaneous measurement method of a potential scanning impedance spectroscopy (PSIS) and impedance spectra determined by wavelet transformation (WT). In this method, it is possible to obtain the successive impedance spectra with measuring the potentiodynamic polarization curve of metal electrode simultaneously and to determine the instantaneous impedance. We used complex Morlet mother wavelet in order to obtain the complex number data in the frequency domain. This mother wavelet is obtained by combining the Gaussian function and sinusoidal term. The time-dependent impedance of the dissolving iron electrode can be determined by calculating cross spectra of the wavelet coefficients of current and potential signals. In the present paper, the potential step signal was used for the input signal. In the results, the impedance spectrum described the capacitive loop in the high frequency range and the inductive loop in the low frequency range, which was determined by WT. It was found that the impedance spectrum in the low frequency range determined by WT is related to the holding time of input potential signal. The inductive loop observed in the low frequency range and the holding time of input potential signal were discussed.

Reference:

1. G. A. Ragoisha and A. S. Bondarenko, Electrochimica Acta, 50, 1553 (2005).

2. M. Itagaki, K. Isobe, Y. Hoshi, I. Shitanda, 226th ECS meeting abstract, #753 (2014).

3. M. Itagaki, A. Taya, K. Watanabe, Electrochemistry,
70, 779 (2002).
Structure and Li+ Dynamics of the Single-Ion Conducting Polymer Electrolyte P(STFSI)-Ran-PEGMA
Authors: Schaefer Jennifer L , Orski Sara V. , Nieuwendaal Ryan C. , Oleshko Vladimir P. , Middleton L. Robert , Soles Christopher L.
Published: February 2020

Polymeric, solid-state, single-ion conducting electrolytes with high ionic conductivity are desired for application in high energy battery platforms.  Recently, PEO-based copolymers containing the lithiated STFSI monomer have been investigated for use as single-ion conducting electrolytes in lithium batteries.   These polymers exhibit wider electrochemical stability windows and sustain capacity of full cell battery cycling at higher discharge rates relative to traditional polymer electrolytes composed of PEO and a mobile, dopant salt. 

This presentation will report on the characterization of the morphology and dynamics of PSTFSI-ran-PEGMA copolymer electrolytes as a function of the monomer ratio (Li+ loading) and length of the polyethylene glycol comb.  Structure of the electrolytes is investigated by SAXS/WAXS, SANS, and TEM.  Lithium environment is examined using solid state MAS NMR spectroscopy, and ion dynamics are studied via PFG NMR spectroscopy and dielectric spectroscopy.  Polymer dynamics are investigated via QENS.  Together, this suite of characterization techniques reveals the structure and corresponding Li+ transport mechanisms in this family of high performing PEO-based single ion conductors.
Electrochemical Performance of Three Novel Bromine-Sequestering Agents for Zinc/Bromine Flow Battery Electrolytes
Authors: Rajarathnam Gobinath Pillai , Schneider Martin , Easton Max , Vassallo Anthony
Published: February 2020

Three different bromine-sequestering agents (BSAs) were proposed and assessed for their fitness-for-utilization in zinc–bromine redox flow batteries (Zn/Br RFBs). These BSAs included the bromide salts of the following cations: 1-ethyl-1-methyl-imidazolium ([C2MIm]+), 1-ethyl-1-hydroxymethyl-imidazolium ([C2OHMIm]+) and 1-ethyl-hydroxypiperidinium ([C2OHPy]+). Half-cell cyclic voltammetry and a.c. impedance spectroscopy as well as full-cell cyclic charge–discharge tests were performed to determine the influence of these agents on both on zinc- and bromine-side electrochemical performance. All three BSAs were found to increase peak currents in both zinc- and bromine-side half-cells. [C2MIm]+ and [C2OHPy]+ performed best for bromine- and zinc-sides, respectively, while [C2OHMIm]+ performed overall poorly compared to the other BSAs. Impedance spectra indicate bromine-side performance is strongly linked to Warburg diffusion limitations. On the other hand, voltammetry results indicate zinc-side half-cell performance improves with decreasing nucleation overpotentials during zinc electrodeposition. [C2MIm]+ gave the highest voltaic and coulombic efficiencies during full-cell cycling, while [C2OHMIm]+ again showed overall relatively poor performance. Scanning electron micrographs indicate a strong relationship between chemical structure of the BSA employed and the crystallinity of zinc electrodeposits. Both [C2MIm]+ and [C2OHMIm]+ were found to improve the quality of zinc plating, with the later producing nanocrystalline needle-like deposits. These findings warrant further investigation of BSAs made up of weakly-coordinating cations carrying diffuse positive charges. While these compounds have been proposed for application in Zn/Br systems, they are also potentially applicable to other types of RFBs which employ the Br2/Br– redox couple and require the use of electrolytes containing BSAs.
Fluoride-Doped Layered-Spinel Hybrid Lithium-Rich Cathode Material for Lithium Ion Battery
Authors: Yi-Chun Jin
Published: February 2020

The limitation of theoretical capacity in cathode material is a technological bottleneck for developing next generation lithium ion battery. For this regard, researchers recently focus on lithium-rich composite cathode (1-yLiMn2O3-yLiNixMn1-xO2) due to its high versatility of capacity output ranged from 280 to 320 mAhg-1(usually charge/discharge in 0.1C). In this study, we have proposed a novel design and feasible synthesis of layered-spinel hybrid lithium-rich cathode, modiﬁcation by appreciable fluoride doping. This is the first use of polymeric fluoride as a dopant source in non-aqueous co-precipitation batch. In a detailed structural analysis, spinel phases are spontaneous formed and encapsulated onto the layer matrix after fluoride doping. The electrochemical result shows an extra high voltage charge-discharge character around 4.8V, speculated as LiNi0.5Mn1.5O4 intercalation process. It delivered stable cycleability and improved C-rate performances as compared with the traditional layered cathode. A fast lithiated /delithiated process is attributed to well-distributed 3D diffusivity tunnel in the spinel-embedded Li-rich layer material.

Figure 1
Structural Ambiguity in Li- and Mn-Rich Transition Metal Oxides: Trigonal, Monoclinic, or Both?
Authors: Shukla Alpesh Khushalchand , Ramasse Quentin , Ophus Colin , Duncan Hugues , Chen Guoying , Dahmen Ulrich
Published: February 2020

Li- and Mn-rich transition metal oxides have been extensively studied recently for their potential application in Li-ion batteries. These materials have attracted a lot of interest due to the high capacity offered by them. However, the structure of these materials in their pristine state is not clearly understood. Several reports have assigned their structure to be trigonal (R-3m), monoclinic (c2/m), or a combination of both (composite). The present study discusses the structure of Li1.2(Ni0.13Mn0.54Co0.13) O2 prepared with two different morphologies: plates and needles, using the results obtained from aberration corrected scanning transmission electron microscopy (STEM) imaging, electron energy loss spectroscopy (EELS) and X-ray energy dispersive spectroscopy (XEDS). 3-dimensional information was obtained by imaging the material at different zone axes and it was found that the primary particles are made up of a single phase, consisting of domains that correspond to variants of monoclinic structure, save for rare localized defects and a thin surface layer on certain crystallographic facets. These findings were further confirmed on two commercially available Li-and Mn-rich transition metal oxides, namely TODA HE5050 and Envia HCMR XLE2 . It will be shown how diffraction-based techniques can lead to ambiguous interpretation of structure in this class of materials. The study not only solves the ambiguity in the structure determination of this class of complex oxides but also highlights the importance of atomic resolution imaging performed on multiple zone axes when it is used for similar investigations.

Figure 1
(Invited) Surface Modification Effect on the First Charging Process over 4.5 V and the Enhancement of Energy of LiNi1/3Co1/3Mn1/3O2
Authors: Sakaebe Hikari , Yano Akira , Shikano Masahiro , Ogumi Zempachi
Published: February 2020

Surface modification of the positive electrode materials by coating technique with metal oxides, phosphate, and so on is commonly used in these days for stabilizing the electrolyte/positive electrode material interface [1-3]. We can not only extend the battery life, but also have a chance to increase the battery energy by charging to higher voltage by the stabilization.

Authors have developed the sol-gel based coating procedure to make the thin and uniform layer of Al oxide on the commercially available LiNi1/3Co1/3Mn1/3O2 (NCM), by which the decrease of the initial capacity was suppressed [4]. Using this modified NCM, first charging process was precisely investigated electrochemically varying the charge cut-off voltage up to 4.8 V. Below 4.7 V, discharge capacity increased as the charge cut-off voltage was elevated with/without modification. Coulombic efficiency, average voltage, cycling properties were improved by surface modification.

Comparison of AC impedance spectra and dQ/dVof the galvanostatic charge-discharge curves, with the aid of TEM results of the surface region, for modified/bare NCM revealed that the surface of the bare NCM was damaged to be high-resistant in very early stage of first charge, as was observed by surface analysis using synchrotron facilities [5]. Al-oxide modification suppressed the increasing rate of interfacial resistance of Li+ intercalation/deinercalation at the surface.

References

[1] Z. H. Chen, et al., Electrochimica Acta, 49(7), 1079 (2004).

[2] B. C. Park, et. al., Journal of Power Sources, 178(2), 826 (2008).

[3] .A. T. Appapillai, et.al., Chemistry of Materials, 19(23),5748 (2007).

[4] A. Yano, H. Sakaebe, et. al., J. Electrochem. Soc., 162(2), A3137-A3144 (2015).

[5] D. Takamastu, et. al., Angewandte Chemie,
124(46), 11765–11769 (2012).