bluuebunny/crossref_metadata_2025 huggingface dataset:
Combined Covalent and Noncovalent Functionalization of Carbon Nanotubes for Sensitivity Improvement of Electrochemical Biosensors
Authors: Krishnan Sadagopan , Premaratne Gayan , Niroula Jinesh
Published: February 2020

An amperometric nano-bioelectrode was designed that uniquely combined 1-pyrenebutyric acid units pi-pi stacked with carboxylated multiwalled carbon nanotubes on the surface of gold screen printed electrodes for covalent attachment of anti-insulin antibody or NAD+ dependent formaldehyde dehydrogenase. The designed enzyme bioelectrodes provided clinically relevant picomolar serum insulin measurements and detection of 6 ppb formaldehyde in 10-times diluted urine with a wide dynamic range, respectively. Fourier transform infrared, Raman, and electrochemical impedance spectroscopic characterizations confirmed the successful design of the bioelectrodes. Flow injection analysis provided lower detection limit and greater affinity for formaldehyde (apparent KM 9.6 ppm) than stirred solution method (apparent KM 19.9 ppm) due to better mass transport of the substrate. Moreover, selectivity assays revealed that the bioelectrode was selective toward formaldehyde with a moderate cross-reactivity for acetaldehyde (~ 25%) and negligible cross-reactivity toward propanaldehyde, acetone, methanol, and ethanol. The presented pyenyl carbon nanostructures-based bioelectrode design represents novelty and simplicity for enzyme-selective electrochemical detection of insulin hormone in serum and the small 30 Da formaldehyde marker present in urine. Similar strategy is broadly applicable for sensitive and selective electrochemical measurements of any other bio and small molecule markers present at ultra-low levels in complex clinical and environmental matrices.
Thermodynamics of Polymer Electrolyte Membranes in Contact with Concentrated Electrolyte Solutions
Authors: Peng Jing , Goenaga Gabriel A. , Zawodzinski Thomas A.
Published: February 2020

In this study, we build off our recent development of a database of data describing the composition of polymer electrolytes in contact with various acids, bases and salts. This situation is common in practical electrochemical systems such as redox flow batteries and electrochemical reactors. For example, the vanadium redox flow battery (VRFB) electrolyte solutions consist of several molar solutions of aqueous sulfuric acid (with other acids used in certain cases) and up to 2M vanadium salts. As we have shown, these concentrations cause the general phenomenon of breakdown of the Donnan exclusion effect in a variety of polymer electrolyte membranes, both cation and anion exchanging membrane types.1,2,3 A description of these processes would be useful in helping to separate the effects of various modifications of the membrane composition and structure on its behavior.

We develop the groundwork for a thermodynamic description of uptake of ionizable species by polymer electrolyte membranes in contact with concentrated solution electrolyte solutions using the VRFB membrane-electrolyte combination as our test case.

We note that all such descriptions of the behavior of polymer systems entails the assumption of a ‘local’ equilibrium, relevant for short times. Here the adjective short refers to times long enough for uptake processes to occur but short enough that the polymer itself does not have time to change from its initial state, set by its thermal history. This allows us to assess membranes that might be thermally ‘re-arranged’ as separate entities, thus isolating any effects of the treatment.

We first develop a description of the local equilibrium of the acid solution with the membrane. As Tang et al showed,1 this has several interesting features that are generic to acid uptake into Nafion and related polymer electrolytes. A convenience of this approach is the broad availability of descriptions of the acid solution properties.

Once a description of the acid-membrane equilibrium is available, we proceed to consider the situation with added vanadium. For simplicity, we will begin by developing the case for VOSO4 solutions in acid. In this case, we need to reassess the solution thermodynamics, adding some measurements specific to a given ternary composition. We will describe these measurements in the oral presentation.

Acknowledgements

We gratefully acknowledge the support of this work by the U.S. Department of Energy, Office of Electricity Delivery and Energy Reliability (Dr. Imre Gyuk) and by the Office of Naval Research. We also thank 3M for providing membranes.
(Invited) T-Chip, a Biosensor Based on the Electron Tunneling: Theory and Experiment
Authors: Park Young June , Yun Jun Yeon , Lee Won Cheol , Lee Young Eun , Kim Kyoung Yeon
Published: February 2020

The presentation covers an electrical biosensor platform (T-chip) based on the electron tunneling phenomenon between the metal electrode and the methylene blue (MB) molecules. Firstly, the general idea of the T-chip is introduced. Secondly, the practical application of the T-chip for detecting biomarkers of the cancer is suggested. Finally, the numerical simulation of the T-chip considering the electron tunneling and the transport of ions in the electrolyte is introduced.

To detect the target biomarkers in aqueous solution, the T-chip is integrated with the peptide molecules as the probe molecule of which end terminal was functionalized with the redox sites providing the electron states for tunneling. An asymmetric gold electrode structure of the T-chip facilitates a simple 2-electrode structure and reliable electrical measurement without adopting a reference electrode used in the conventional electrochemical system.

As an example of the biosensor application, we selected the matrix metalloproteinase-9 (MMP-9) as the target biomarker which indicates metastasis of the cancer and tumor invasion. As the probe molecules, a peptide sequence conjugated with the MB was designed to be cleaved by the MMP-9. As an electrical indicator of the probe-target cleavage event, the MB was chosen. The cleavage event causes the reduction of the number of the MB sites (electron tunneling states) which leads a decrease in the electron tunneling current.

To describe the physical model and evaluate the electrical characteristics of the T-chip, a numerical simulator (3-dimension) has been developed. To estimate the electron tunneling rates between the electrodes and the MB states, we used the non-equilibrium Green’s function (NEGF) method. Additionally, the ion motions in electrolyte is calculated by using drift-diffusion as the continuity equation. Finally, the terminal current due to the electron tunneling and ion movement was extracted by using the extended Ramo-Shockley theorem.

Theory and experiment of the tunneling based biosensor will enhance the potential of success of the electrical biosensor through detailed understanding of the molecules and surface chemistry involved in the sensor system.
(Invited) Electrochemical Paper-Based Sensors for Clinical and Environmental Diagnostics
Authors: Henry Charles S
Published: February 2020

One major push in sensor development is production of very inexpensive, easy to use sensors that require minimal external equipment. Microfluidic Paper-based Analytical Devices (mPADs) have received significant attention because they meet these requirements and can carry out a wide range of chemical and biochemical assays. Detection with mPADs is normally done with colorimetric reactions but these reactions can be limited in sensitivity and selectivity. Improvements in colorimetric detection as well as adaption of more sensitive detection methods are needed to meet the growing demand for point-of-need diagnostic applications. This talk will focus on recent developments from the Henry laboratory using electrochemistry with mPADs with applications in point-of-need sensing. Incorporating electrodes into mPADs is a key element for achieving targeted selectivity and sensitivity. Examples of carbon and metallic electrodes will be discussed as well as an innovative dual electrode system that enables simultaneous electrochemistry at two different solution conditions. Example applications will be shown for both environmental and clinical sensing. For environmental sensing, stripping voltammetry has been adapted to mPADs to measure trace metals in aerosolized particulate matter. In this application, the benefits of low volume and ease of sample preparation have enabled screening of hundreds of samples from wearable aerosol samplers to be analyzed for exposure. For biological sensing, example applications for detection bacteria and viruses will be shown. Bacteria can be detected by measuring the activity of enzymes produced by the bacteria or through electrochemical immunoassays. Viruses can be detected using electrochemical immunosensors incorporated into mPADs. Recent results for both applications will be discussed.
Silicon Anisotropic Etching in Ternary Solution Composed of TΜΑΗ+Triton+NH2ΟΗ
Authors: Swarnalatha Veerla , Narasimha Rao Avvaru Venkata , Pal Prem
Published: February 2020

Wet chemical etching is extensively used in the fabrication of microelectromechanical systems (MEMS) owing to its several benefits such as low cost, easy handling, and bulk production [1, 2]. TMAH and KOH are most widely employed etchants for silicon anisotropic etching. In these two etchants, TMAH is preferred when complementary metal oxide semiconductor (CMOS) compatibility is a major concern and the oxide layer is used as mask material [2, 3]. Etching behavior of TMAH can be modified by the incorporation of different kinds of additives such surfactants, alcohol, etc. [2-4]. Significant amount of research has been done to modify the etching characteristics by adding some additives, however very less is reported on TMAH-based ternary solutions. Present research reports the anisotropic etching characteristics of silicon in various concentrations of TMAH (5 wt%, 15 wt%, and 25 wt%) solutions containing 10% NH2OH and Triton-X-100 ranging from ppb to ppm level. The etch rate, undercutting at convex corners, and etched surface morphology are investigated in different compositions of ternary solutions (TMAH+NH2OH+Triton). Optical microscope, scanning electron microscope (SEM), and three-dimensional (3D) measuring laser microscope are employed for the characterization of etched surface morphology and to measure the etch depth and undercutting at convex corners. Figure 1 presents the etch rate of Si{100} and the undercutting rate (U
<110> = l
<110>
/d, l
<110>: undercutting length along <110> direction, d: etch depth) at convex corners. High etch rate and undercutting are achieved in NH2OH-added 15 wt% TMAH, while significantly less undercutting with reasonably good etch rate of Si{100} (Er = 18 µm/hr) is obtained in 25 wt% TMAH+10%NH2OH+1ppm Triton. The high undercutting is desirable when freestanding structures are fabricated, while it is unwanted effect when microstructures with convex corners have to be fabricated such as mesa structure. The present research is very useful for engineering applications for the fabrication of microstructures using CMOS-compatible silicon bulk micromachining for MEMS-based devices.

References:

[1] I. Zubel, M. Kramkowska, J. Micromech. Microeng. 1
5 485 (2004).

[2] P. Pal, and K. Sato. J. Micromech.Microeng. 19 055003 (2009).

[3] A. Ashok and P. Pal, Microsy. Technol. 1-8 (2015).

[4] Y.W. Xu, A. Michael, C.Y. Kwok, Sens. Actuators A 166, 164-171 (2011).

Figure 1
(Invited) Suspended Polymer Nanobridge on a Quartz Resonator
Authors: Kim Wuseok , Hwang Seokyung , Yoon Heewon , Jeon Sangmin
Published: February 2020

A quartz tuning fork (QTF) has a unique geometry comprising two vibrating prongs separated by a specific gap. The symmetry of the two prongs reduces the number of possible vibration modes, which endows the QTF with a good quality factor. The high stability and low power consumption of QTFs allow them to be used in a wide range of applications, including in precision watches and force sensors. In addition to these conventional applications, there have been attempts to use QTFs as versatile gas sensors because the resonance frequency of a QTF decreases with increasing mass loading. However, the poor mass sensitivity of a typical 32.768 kHz bare QTF (50 ng/Hz) limits its broader applicability in gas sensors. We addressed this problem by attaching a polymer wire or membrane to the two prongs of a QTF. In this configuration, the polymer wire/membrane is stretched and compressed by the two vibrating prongs; the change in the mechanical force of the polymer due to gas adsorption is easily measured from the change in the resonance frequency. We fabricated various polymer wires and membranes and examined the polymer-coated QTF as a gas sensor. Upon exposure to solvent vapor, the resonance frequency of the polymer-coated QTF decreased due to the decrease in the modulus of the polymer wire, which was induced by the adsorption of solvent. Various methods will be discussed in this presentation for the sensitivity enhancement of the polymer-coated QTF.
Real Time Quantification of Phenolic Compounds in Oil and Gas Wells Produced Wastewater Using a QCM Sensor
Authors: Barrera Magda Lorena Lorena , Pedraza Julio Andrés , Ríos Fabián Alirio
Published: February 2020

Phenols (phenol, m-cresol, o-cresol and p-cresol) are contaminant compounds and due to its toxicity and persistence in the environment are listed in the Environmental Protection Agency as dangerous substances [1]; its presence in the environment is widely associated with wastewater effluents as is the produced water generated by oil and gas production.

One of the systems that has been gaining importance to measure phenols in real time is the Quartz Crystal Microbalance (QCM). This technique comprises a thin quartz crystal sandwiched between two metal electrodes and senses the changes in frequency that suffers the quartz crystal when a certain amount of mass is deposited on its surface [3].

In order to improve the sensibility of compounds to measurement using a QCM have been used coatings on quartz crystal electrode surface, for example for phenols determination polymethylmethacrylate (PMMA) is used. The main objective of this research is to determine in real time and in continuous flow the concentration of phenolic compounds in produced water using the technique QCM with PMMA as coating on quartz crystal electrode surface.

This work is conducted in three stages mainly: 1. Determination of a suitable layer of PMMA to use as coating, 2. Evaluation of the effect of the concentration of phenols, pH and flow rate in the measurements by QCM, 3. Comparison of sensitivity and time response obtained in the technique QCM with standard method by colorimetry.

Results have shown that the PMMA films are more uniform when is used dichloroethane as solvent instead of chloroform and the stability and sensitivity in the measurements improve due to the vapor pressure of solvent that allows more dispersion of the polymer during spin coating, which is consistent with other authors [2]. Increase in the concentration of phenolic compounds, the flow rate and the pH increases the changes in frequency of the quartz crystal.

 

Keywords

: Quartz crystal microbalance, PMMA, phenols, produced water, real time.

 

Mirmosheni, A., Oladegaragoze, A. Application of the quartz crystal microbalance for determination of phenol in solution. 2003. Sensors and Actuators, B: Chemical, Vol.98 (1), p. 28-36.

Mohajerani, E. Morphological and thickness analysis for PMMA spin coated films. 2007. Journal of optoelectronics and advanced materials, Vol. 9 (12), p. 3901-3906.

Reddy, S. Detection of phenol in aqueous solution using an AT-cut quartz thickness shear mode sensor. 2000. Materials Science and Engineering C, Vol. 12 (1), p. 23-28.
Effect of Surfactant and Alcohol Additives on Etching Characteristics in Aqueous Potassium Hydroxide Solutions
Authors: Narasimha Rao Avvaru Venkata , Swarnalatha Veerla , Pal Prem
Published: February 2020

Anisotropic wet etching is a low cost technique for silicon bulk micromachining to fabricate MEMS components such as cantilevers, diaphragms, etc. It is inevitable for the fabrication of microstructures with slanted sidewalls and to remove underneath material for the realization of freestanding microstructures. Potassium hydroxide (KOH) is a popular etchant as it provides high anisotropy between {100}/{110} and {111} planes. In order to alter the etching characteristics, the effect of various kinds of additives such as isopropyl alcohol (IPA), surfactants (Triton X-100) in pure KOH is studied [1-3]. In this work, we studied the etching characteristics of ternary solutions composed of KOH + Triton X-100 + IPA. The concentration of KOH is varied from 5-40 wt% in step of 5 wt%, while the concentrations of Triton and IPA are kept fixed at 0.1 vol% and 15 vol%, respectively. In the different compositions of ternary solutions, the etch rate and etched surface morphologies of Si{100}, Si{110} and Si{111} are investigated. In addition to that the undercutting at convex corners, which is very important parameter for designing compensation structure to protect convex corner and to estimate etching to release the structure from the substrate, is measured. In order to explore the thermal oxide as mask and structural material, the etch rate of silicon dioxide is also measured. In the ternary solution comprising low concentration KOH, the etching characteristics are more significantly affected by Triton than IPA. However, in the case of ternary solution containing high concentration KOH, IPA influences etching characteristics more prominently than Triton. The systematic study of etch rate, etched surface roughness, and undercutting at convex corners in ternary solution presented in this work is very useful to select the composition of ternary solution for MEMS applications as per the requirement.

References:

[1] I. Zubel, M. Kramkowska, Sens. Actuators A 101 255-261 (2002).

[2] P. Pal, A. Ashok, S. Haldar, Y. Xing, K. Sato, Micro Nano Lett. 10 224-228 (2015).

[3] K.P. Rola, I. Zubel, J. Microelectromech. Syst. 22 1373-1382 (2013).
A Novel Electrochemical Sensing Platform for the Simultaneous Trace Level Detection of Mercury, Cadmium and Copper
Authors: Shah Afzal , Iftikhar Faiza Jan
Published: February 2020

The present work is aimed at the development of highly sensitive electrochemical sensor based on immobilization of 1-phenyl-N-(pyridin-2-ylmethyl)ethanamine (PPE) on glassy carbon electrode (PPEGCE) for the simultaneous detection of toxic metal ions of mercury, cadmium and copper, employing electrochemical impedance spectroscopy differential pulse anodic stripping voltammetry and square wave anodic stripping voltammetry. We optimized several experimental parameters such as concentration of the modifier, pH, scan rate, number of cycles, accumulation time, deposition potential and supporting electrolytes for getting robust and intense signals of the analytes. The designed sensor showed nice voltammetric response in media of different pH, demonstrated good percentage recoveries and exhibited remarkable electrocatalytic activity. The results revealed the high sensitivity, stability and absolute discrimination ability of our designed sensor. A wide linear range with very low detection limits for the analytes as compared to reported methods revealed the applicability of our designed sensor as a preferred analytical tool. The limits of detection as low as 0.11, 0.18 and 0.13 nM were obtained for mercuric, cadmium and cupric ions using PPEGCE. These values are lower than the threshold concentration of our selected metal ions suggested toxic by World Health Organization (WHO) and Environmental Protection Agency (EPA). Thus, our results are expected to offer useful guidelines to the environmentalists and health stakeholders to apply measures for the protection of human and aquatic life from water toxins.
Our Surface Plasmon Coupled-ELISA with Enhanced Sensitivity Will Help Realize Point-of-Care Applications for Sustainable Future
Authors: Raghavendra Achyut J , Zhu Jingyi , Rao Apparao M. , Podila Ramakrishna
Published: February 2020

The sensitivity of enzyme-linked immunosorbent assays (ELISA) for biomarker detection can be significantly increased through the integration of fluorescence with plasmonics. In surface plasmon coupled ELISA (SP-ELISA), the fluorophore emission is generally enhanced through the so-called physical mechanism which entails an increase in the local electric field. Despite fairly high enhancement factors, translating SP-ELISA for point-of-care applications is still hampered due to the need for focusing optics and spectrometers. Here, we show that stacked Ag and C60 films promote molecular interactions between aromatic dyes and C60 to increase emission from Rhodamine B (RhB) labeled biomolecules by 20 folds without quenching its red color emission. This new chemiplasmonic-sensing paradigm is not only superior to the physical mechanism but essential for point-of-care applications. Lastly, we demonstrate a model 96-well plate SP-ELISA assay using Immunoglobulin G.
(Invited) Bottom-up Fabrication of Unique Nanostructured Biosensors and Bioanodes
Authors: Schmidtke David W
Published: February 2020

Layer-by-layer (LBL) self-assembly is one of the most popular methods for the preparation of multifunctional nanostructured thin films. This technique is primarily based on the sequential adsorption of oppositely charged compounds due to attractive electrostatic interactions, however other molecular interactions (i.e. hydrogen bonding, hydrophobic, or covalent bonding) can mediate the self-assembly process. Recently, our group has reported the successful synthesis of a series of novel redox polymers based on the attachment of ferrocene redox centers (Fc) to linear poly(ethylenimine) (LPEI) that are able to produce high current responses (> 1 mA/cm2) with a variety of enzymes (e.g. glucose oxidase, fructose dehydrogenase, laccase, and horserardish peroxidase). Based on their high current densities and the high density of amine groups they appear to be excellent candidates for LBL assembly. In this presentation we will describe the development, characterization and application of nanostructured films based on both electrostatic and covalent layer-by-layer assembly of redox polymers, biological molecules (e.g. enzymes, polysaccharides), and single-walled carbon nanotubes as a versatile means to produce functional coatings for biosensing and biofuel cell applications. When LBL assembly is employed to fabricate nanostructured composites of ferrocene redox polymers (Fc-LPEI) and glucose oxidase, current densities of 1.4 mA/cm2 are produced in response to glucose. Likewise these films can produce power densities of ~150 μW/cm2 when incorporated into biofuel cells as bioanodes. In this presentation we will also discuss the effects of redox polymer structure, LBL washing procedures, and solution pH during LBL assembly on the structure and performance of these films.
Fabrication of Three-Dimensional Woodpile Cerium Oxide Nanostructure Via Solution-Based Soft Nanoimprint Lithography for Enzymatic Glucose Sensor
Authors: Zhou Yiliang , Uzun Sema Demirci , Briseno Alejandro L. , Carter Kenneth R. , Watkins James J.
Published: February 2020

Fabrication of ultra-high surface area electrodes can improve sensitivity for analyte detection. Here we report a scalable method for producing three-dimensional, nanoscale woodpile structures of cerium oxide for use in glucose sensors. A CeO2 nanoparticle based ink was used to directly pattern 500 nm wide grid structures via a solution-based soft nanoimprint lithography technique. The residual layer of the imprinted pattern was minimized by optimization of CeO2 concentration, speed and time of spin coating. Multi-layered woodpile structures of CeO2 were then achieved by a layer-by-layer imprint strategy. To prevent defects at the intersection of the layers, titanium diisopropoxide bis(acetylacetonate) was added as a binder. SEM data revealed that three-dimensional woodpile cerium oxide structures were successfully fabricated over a large areas.

Then, an enzymatic glucose sensor was fabricated by printing such a CeO2 woodpile structure on a gold-coated substrate. Cyclic voltammetry and chronoamperometry were applied for detecting glucose in PBS buffer solution (50 mM, pH 7.0, 25 °C). Experimental data showed the sensitivity of glucose sensors can be improved by increasing the number of layers. The tetralayer CeO2 glucose sensors exhibited high sensitivity (8.2 µA mM-1 cm-2), short response time (1-2 s) and long linear range (0.02 mM-2.0 mM). These results indicated the three-dimensional woodpile structure of CeO2 is a promising material for high sensitivity biosensors.
Carbon Nanotube-Based Bioanalytical Sensors
Authors: Heller Daniel A , Jena Prakrit Vaibhav , Galassi Thomas Vito , Williams Ryan M. , Budhathoki-Uprety Januka , Langenbacher Rachel E , Roxbury Daniel , Shamay Yosef , Shah Janki , Frederiksen Rune , Horoszko Christopher Peter , Harvey Jackson Dean
Published: February 2020

The real-time and spatially-resolved detection and identification of analytes in biological media present important goals for next-generation nanoscale probes and sensors. To this end, we employ the intrinsic near-infrared fluorescence of single-walled carbon nanotubes which is photostable yet sensitive to the immediate environment. To build biomedical technologies that employ carbon nanotube photoluminescence, a better understanding of the optical response, as well as new methods to measure it in biological systems, are needed. We have developed new imaging platforms to quantify nanotube emission, including a method to conduct photoluminescence excitation/emission spectroscopy on living samples. We synthesized carbon nanotube-based photoluminescent sensors to interrogate analytes and processes in living specimens, including mammalian cells, 3D tumor spheroids, and whole organisms.
Development of an Electrochemical Impedimetric Biosensor for the Detection of Telomerase Activity in Cancer Cells
Authors: Cabrera Carlos R , Diaz-Cartagena Diana C , Hernandez Griselle , Cunci Perez Lisandro , Gonzalez Carlos I.
Published: February 2020

Developing novel strategies to effectively detect biomarkers is of utmost importance in the early detection of cancer cells to increase the chances of a successful therapy. The proposed biosensor microchips works by tethering a biomolecular probe on the interdigital gold electrode array surfaces. This biomolecule probe can be customized according to the target biomarker, in order to recognize the change of conformation or bond upon contact. Telomerase is an enzyme responsible for the elongation of the telomeres between each cell division, restoring their length and avoiding cell death. This enzyme is responsible for the immortalization of cancer cells and it consists of a reverse transcriptase bound to a single stranded RNA (ssRNA) that is used as a template for telomere lengthening. The innovative research proposed in this project takes advantage of the telomerase and its ssRNA template by tethering a telomere-like ssDNA biomolecule probe that consists of a spacer composed of ten thymine, and the repeating sequence present in the telomeres of eukaryotic cells, 5’-TTAGGG-3’. The telomerase binds and elongates the probe, blocking electronic and capacitive processes on the microelectrode array surfaces. This change is detected by measuring the impedance using electrochemical impedance spectroscopy, which is correlated to the activity of telomerase and the presence of cancer cells. Moreover, telomerase is currently the target of many pharmaceutical companies to block cancer cell proliferation due to its presence in ca. 85% of known cancer cells (e.g. prostate, breast, and colorectal cancers). This project provides a unique opportunity to study the surface chemistry, impedance sensing, detection limits, and robustness of this microchip technology for its possible use at the point-of-care. This is funded by NSF Grant titled "Label-Free Electrochemical Capacitance DNA Sensing with Passive Wireless Radio Frequency Identification Sensor Technology" CHE-1152940.
Non-Enzymatic Glutamate Sensor Based on Nickel Oxide Nanoparticle
Authors: Jamal Mamun , Chakrabarty Sumon , Shao Han , McNulty David , Yousuf Mohammad A. , Razeeb Kafil M.
Published: February 2020

L-glutamate is one of the 20 standard amino acids used by all organisms. It plays an important role in clinical applications and in food processing and well known as a flavor enhancer commonly found in various foods. The excessive intake of this flavor enhancer can cause toxic effect to the human health. Therefore, development of sensors or biosensors for the determination of glutamate has been of great interest over the past two decades owing to its importance in food and biomedical industries1-4.

In this work, a sensitive and enzymeless glutamate sensor has been constructed using highly dispersed NiO nanoparticle modified glassy carbon electrode (NiO/GCE). The NiO nanoparticle is synthesized using sol-gel method and has been characterized using scanning electron microscope (SEM), transmission electron microscope (TEM), Raman spectroscopy and X-ray diffraction (XRD). Electron microscopy analysis showed that the particles have an average diameter of 40 nm (Fig. 1(a-c)) and the selected area diffraction analysis confirmed the particles are polycrystalline (Fig. 1(d)). Cyclic voltammetry (CV) and amperometry were used to investigate the electrochemical behavior and catalytic properties of the assembled sensor for glutamate electro-oxidation in alkaline media. Nanoparticle modified electrode showed high electrocatalytic activity towards the oxidation of glutamate in 0.1 M NaOH solution. At an applied potential of +0.55 V, it gives a fast response time (<5 s) and a linear dependency (R = 0.997) for the glutamate concentration from 1.0 to 8.0 mM with a high sensitivity of 11 µA/mM/cm2 and a detection limit of 272 μM. Compared to glutamate, the interference study for the ascorbic acid, uric acid and glucose on the NiO/GCE yielded current response ranging from 6-13%. It allows a sensitive, simple and fast amperometric sensing of glutamate, which is promising for the development of a non-enzymatic glutamate sensor.

Acknowledgment

Authors acknowledge financial supports from the Ministry of Science & Technology, Bangladesh funded project “FACSens” under the special allocation to science & technology activity programme; and Science Foundation Ireland funded project “SweatSens” under the grant agreement No. 14/TIDA/2455.

Corresponding authors email addresses: mamun.jamal@chem.kuet.ac.bd and kafil.mahmood@tyndall.ie

Reference

M. Jamal, M. Hasan, A. Mathewson, and K. M. Razeeb, Biosens. and Bioelectron., 40, 213 (2013).

G. Hughes, R. M. Pemberton, P. R. Fielden, and J. P. Hart, Trends in Anal. Chem., 79, 106 (2016).

R. E. Özel, C. I, M. Ganesana, J. C. Leiter, S. Andreescu, Biosens. Bioelectron., 52, 397 (2014).

B. Batra, and C. S. Pundir, Biosens. Bioelectron., 47, 496 (2013).

Figure 1.(a, b) SEM images of NiO nanoparticles at different magnifications; (c) TEM images of NiO nanoparticles, (d) corresponding selected area electron diffraction (SAED) pattern.

Figure 1
CuO-MWCNTs for Enzyme-Less Electrochemical Detection of Glucose and Dopamine
Authors: Felix Sathiyanathan , Santhosh Chella , Nirmala Grace Andrews
Published: February 2020

Highly sensitive enzyme-less electrochemical glucose sensor based on copper oxide-multi-walled carbon nanotube (MWCNT) composite (CuO-MWCNT) modified glassy carbon electrode (GCE) was prepared by co-precipitation method. The as-prepared nanocomposites were characterized by field emission scanning electron microscope (FE-SEM), Raman spectroscopy, Fourier transform infrared spectroscopy and electrochemical analyses. The electrochemical results of cyclic voltammetry (CV) and chronoamperometry demonstrated that the CuO-MWCNT/Nf/GCE showed high electrocatalytic activity than the copper oxide nanoleaves (CuO-Nls) modified electrode toward glucose. The modified electrode showed enhanced electrocatalytic behaviour towards glucose in alkaline medium. The non-enzymatic glucose sensor based on CuO-MWCNT/Nf/GCE showed the highest sensitivity of 1038.6 µA mM−1cm−2 with the lowest detection limit of 0.1 µM (signal/noise ratio (S/N) = 3) under optimal experimental conditions. The fabricated sensor showed good accuracy, reproducibility and stability. The sensor was highly selective to detect the glucose in the presence of other common interfering species like ascorbic acid, uric acid and dopamine. Additionally, its application for detecting glucose concentration of human urine sample showed good agreement with the results obtained from automatic biochemical analyzer.

Keywords: CuO-MWCNT nanocomposites; electrocatalytic activity; cyclic voltammetry (CV); chronoamperometry; accuracy; reproducibility; stability

Figure 1
Automatically Turn-Off EOF Pump Based on Conical Nanopores with Lead Sensor
Authors: Xu Weihuang
Published: February 2020

Electroosmotic flow (EOF) is an electrokinetic phenomenon that occurs when an ionic current is passed through a channel or porous material that contains excess surface charge. We have found that net flow through a conical-pore membrane can be achieved by applying a symmetrical sinusoidal voltage waveform across the membrane. This is possible because the alternating current (AC) carried by ions through the nanopore is rectified. Here, the EOF pump based on polyethylene terephthalate (PET) membranes were modified with 18-crown-6 to selectively pump solution without lead ions. As more lead ions bound with 18-crown-6 on the surface, the surface charge was more neutral. Thus, the electroosmotic flow was less rectified. Finally, the net flow was zero meaning the pump was turned off if the lead concentration is high enough. The flow rate of EOF pump in a series of lead ions aqueous solution was investigated. We also reported the selectivity of this EOF pump in the aqueous solution with different metal ions.
Functionalized Deoxynucleotides and DNA Primers for Electrochemical Diagnostics of Disease Predispostions
Authors: Debela Ahmed Mehdi
Published: February 2020

Redox-labeled nucleotides are of increasing interest for next generation molecular tools and should meet requirements of being thermally stable, sensitive, and compatible with polymerase-mediated incorporation whilst also being electrochemically discriminable. We are reporting the labelling of deoxy and dideoxy nucleotides (dNTPs) and DNA primers for use in electrochemical array based primer extension for the detection of early dispositions for diseases. polyoxometalates (POMs), Organometalics, and organic molecules have been used to functionalize DNAs and investigate their potential use in diagnostics. POMs, which are inorganic metal oxido clusters, to DNA strands to obtain functional labeled DNA primers and their potential use in electrochemical detection have been investigated. Activated monooxoacylated polyoxotungstates [SiW11O39{Sn(CH2)2CO}]8− and [P2W17O61{Sn(CH2)2CO}]6− have been used to link to a 5′-NH2 terminated 21-mer DNA forward primer through amide coupling. The functionalized primer was characterized by using a battery of techniques, including electrophoresis, mass spectrometry, as well as IR and Raman spectroscopy. The functionality of the POM-labeled primers was demonstrated through hybridization with a surface-immobilized probe. The labeled primers were successfully used in the polymerase chain reaction (PCR) and the PCR products were characterized by using electrophoresis.Inaddtion to this POM-deoxynucleotide (POM-dNTP) bioconjugates linked through 7 deaza modified purines is also studied. The modified POM-dNTPs were used for polymerase based amplification of a DNA sequence specific for Yersinia Pestis and the amplified DNA detected via an electrochemical DNA sensor. This highlights the potential of polyoxometalates as thermally stable, sensitive and polymerase-compatible redox labels for exploitation in bioanalytical applications.
Impact of Different Graphite Anodes on the Performance of Lithium-Ion Cells with Ni-Rich NMC Cathodes
Authors: Mao Chengyu , Wood Marissa , Ruther Rose Emily , David Lamuel , Sheng Yangping , Wood David L
Published: February 2020

The development of nickel-rich NMC cathodes (LiNixMnyCo1-x-yO2 with x > 0.5) is among the most promising routes to deliver lithium-ion cells with energy densities exceeding 250 Wh/kg. Achieving this ambitious target will require cycling cells to higher voltage (>4.35 V) and developing new strategies to mitigate undesirable side-reactions like electrolyte oxidation and cathode surface reconstruction. Since the cathode has long been considered the limiting factor in developing high-energy, high-voltage cells, the impact of the graphite anode has been largely ignored. In this contribution, we show that the choice of graphite significantly impacts both the rate capability and long-term cycling stability of cells with Ni-rich NMC cathodes. Six commercially-available natural and synthetic graphites were tested in full cells with NMC 811 cathodes (LiNi0.8Mn0.1Co0.1O2). The variations in cell performance were correlated with the chemical, morphological, and mechanical properties of the different graphite anodes. Surface chemistry was systematically investigated using X-ray photoelectron spectroscopy (XPS), while electron microscopy and mercury porosimetry were used to understand how electrode structure impacts the electrochemical performance. Peel tests were used to identify the importance of mechanical adhesion of different graphites to the current collector. In-depth electrochemical studies including impedance spectroscopy further shed light on the nature of capacity fading. Our study illustrates the important role of the graphite anode in developing high-energy, high-voltage Li-ion batteries. This work serves as a guide to select the appropriate graphite to optimize performance of Ni-rich NMC cells.

Acknowledgement: This research at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) under contract DE-AC05-00OR22725, was sponsored by the Office of Energy Efficiency and Renewable Energy (EERE) Vehicle Technologies Office (VTO) (Deputy Director: David Howell) Applied Battery Research subprogram (Program Manager: Peter Faguy).
Porous Silicon and Conductive Polymer Binder Composite Electrode for Lithium Ion Batteries with Stable Cycling
Authors: Zheng Tianyue , Yuan Wen , Langer Thorsten , Lund Isaac , Lux Simon , Gentschev Ann-Christin , Liu Gao
Published: February 2020

Silicon (Si) with porous structure could possibly accommodate the large volume expansion of Si in lithium ion batteries, avoiding fast capacity fading during charge/discharge. Herein, we report a composite electrode made from porous Si with only 5 wt% conductive polymer binder. By limiting the lithiation level, we demonstrate a stable cycled cell with a greatly extended cycle life and high coulombic efficiency beyond 99.5%. Both the morphology study and electrochemical characterization suggest that electrodes are able to accommodate over 50% volume change without any capacity fading during cell operation.
The Effect of the Transition Metal Dichalcogenide Additives in Carbon Electrode for Lithium-Air Battery
Authors: Jang Yoonhee , Choi Yusong , Kim Jiyeon , Cho Janghyeon , Seo Ilsung
Published: February 2020

Lithium-air batteries(LAB) utilize oxygen from the air as a cathode active material and pure metal lithium as an anode. Recently, LAB have attracted much interest due to their high theoretical energy density over lithium-ion batteries. However, most of the R&Ds are in their early stages. The main obstacle of LAB for real-life application is cathode, which commonly use carbon materials such as super-P, carbon black. Super-P, among the carbonaceous cathode materials for LAB, reported good performances in specific energy density because of its unique meso porous structure.

 In this study, the effect of the transition metal dichalcogenide(TMDC) additives in carbon electrode on th electrochemical performances of LAB is evaluated. On a LAB during discharge, the lithium in the anode is oxidized to lithium ions(Li+). Li+ are transported through the electrolyte to catode and react with oxygen. The oxygen combines with metal ions from TMDC, that prevent generating of lithium Oxide(Li2O) and lithium peroxide(Li2O2) in the cathode.

 In this research, TMDC additives(e.g. MoS2, WS2) in carbon black cathode were prepared and then assembled into coin cell(CR2032). The discharge performances according to the weight percentage of TMDC in carbon black were investigated. Microstucture and electrochemical characteristics of the discharged cathode and pristine cathode were analyzed by XRD,SEM and EDS.
Precursor Chemistry of Lithium Phosphorus Oxynitride Film for Metalorganic Chemical Vapor Deposition
Authors: Yoshii Naoki , Fujibayashi Takashi
Published: February 2020

In this study, precursor chemistry of lithium phosphorus oxynitride (LiPON) film is investigated for metalorganic chemical vapor deposition (MOCVD). As a solid-electrolyte, LiPON film is widely used for all solid state thin film batteries. All solid state thin film batteries can provide as much power as conventional coin batteries, but is small enough to be used to provide power to semiconductor-related chips. The battery is safer, thinner and has faster charge and discharge current rate than conventional liquid batteries. It offers the prospect of supplying micro systems with long lasting, environmentally friendly and sustainable electrical power.

In general, a sputtering method is applied to deposit LiPON film. LiPON film deposited by sputtering methods has some problems such as the generation of pin-holes, poor coverage and low deposition rates. These problems lead to higher cost and inferior properties of all solid state thin film batteries. In order to overcome these problems, we investigated the possibility of LiPON film deposited by MOCVD. A variety of Li precursors such as lithium tert-butoxide (LiOtBu), lithium hexamethyldisilazide (LiHMDS) and 2,2,6,6-tetramethyl-3,5-heptanedionato lithium (LiTMHD) shown in the table on the left below, were used in our experiments. Regarding P precursor, tris(dimethylamino)phosphine (TDMAP) was used in our experiments. We found the appropriate Li and P precursor chemistry for depositing LiPON films. In addition, as shown in the figure on the right below, it was confirmed that N atom concentration in all LiPON films is precisely controlled due to NH3 and O2 gas chemistry.

In summary, we concluded that NH3 and O2 gas chemistry, and the combination of LiOtBu as Li precursor and TDMAP as P precursor, are critical factors for depositing LiPON film using MOCVD.

Figure 1
Tuning the Mn Deposition on the Anode to Improve the Cycle Performance of the Mn-Based Lithium Ion Battery
Authors: Zhan Chun , Qiu Xinping , Lu Jun , Amine Khalil
Published: February 2020

Capacity fading of lithium-ion batteries with Mn-containing cathodes is closely related to Mn dissolution from the cathode and, more importantly, the subsequent Mn deposition on the anode. In this work, we propose a new method for solving the Mn deposition issue: tuning the Mn deposition instead of simply decreasing the concentration of Mn deposited on the anode. Two commonly used electrolyte additives, fluorinated ethylene carbonate and vinylene carbonate, are found to improve the cycle performance of the battery but, surprisingly, to enhance the Mn deposited on the anode at the same time. According to the ion-exchange model in our previous work, this increased Mn2+ deposition can be attributed to the increased amount of the Li+ ions in the additive-modified solid-electrolyte interface (SEI), as the Mn deposition can occur via an ion-exchange reaction between the Li+ in the SEI and the Mn2+ in the electrolyte. The improved capacity retention can be attributed to the enhanced robustness of the SEI layers against the attack of Mn2+ ion because of the sufficient amount of mobile Li+ in the SEI layer for ion transport. This work sheds new light on solving the capacity fade issue of Mn-based Li-ion batteries by manipulating the Mn-Li ion-exchange process.
Thermal Behavior and Heat Generation Modeling of Lithium-Sulfur Batteries
Authors: Stroe Daniel Ioan , Knap Vaclav , Swierczynski Maciej , Schaltz Erik
Published: February 2020

In the past years a lot of research has been carried out in order to develop batteries with very high energy density levels and improved safety, which could fulfill the requirements of next generation electrical vehicle and military applications. This is the case of Lithium-Sulfur (LiS) batteries, which are characterized at present by very high theoretical specific capacity (i.e., 1675 mAh/g) and energy density (2600 Wh/kg) as well as improved safety levels (1). However, their market penetration at a large scale is prevented by their inherent polysulfide shuttle mechanism, which causes fast capacity fade and poor coulombic efficiency (2).

Several aspects regarding the behavior of LiS batteries have been studied and are presented in literature. For example, in (3), the authors have analyzed the self-discharge behavior of the Li-S batteries, while in (4), Stroe et al, have performed an in-depth electrochemical impedance spectroscopy characterization of a LiS pouch battery cell. In this work, we fully characterize the thermal behavior of a pre-commercial 3.4 Ah LiS battery cell by performing extended capacity (Figure 1), internal resistance (Figure 2), entropic heat coefficient, heat capacity and emissivity measurements. Based on the obtained results, a model which is able to accurately estimate the reversible and irreversible heat generation is proposed.

P. G. Bruce, L. J. Hardwick, and K. M. Abraham, MRS Bulletin, 36(7), 506-512 (2011).

Z. Deng et al., J. Electrochem.
Soc., 160(4), A553 (2013).

V. Knap et al., J. Electrochem.
Soc., 163(6), A911 (2016).

D.-I. Stroe et al., ECS Trans.,
72(12), 13-22 (2013)

Figure 1
Novel Approach for the Determination of Active Lithium Loss in Lithium Ion Batteries
Authors: Holtstiege Florian , Wilken Andrea , Winter Martin , Placke Tobias
Published: February 2020

Lithium consuming parasitic reactions which induce active lithium loss (ALL) are a major reason for capacity fading in lithium ion batteries (LIBs).[1, 2] As a consequence of capacity fading, the usable energy density is reduced. Typically, the ALL is set equal to the accumulated irreversible capacity (sum of the differences between charge and discharge capacity in each cycle, AIC). However, regarding the AIC it is known that it includes all parasitic reactions which generate a parasitic current. Hence, the AIC cannot be directly equated with ALL. Due to this, we proposed a novel approach in the following named as IRLC method, which is based on the remaining active lithium content of the cell, in order to determine the ALL with a higher accuracy. Therefore, a cell with a three electrode set-up is cycled and afterwards the positive electrode is de-lithiated with help of the former reference electrode in order to obtain the remaining active lithium content. Finally, the ALL can be calculated by using the remaining and the initial active lithium content. In order to evaluate the IRLC method we investigated different anode materials. It can be shown that within the first cycles the ALL can be described moderately well with help of AIC. However, with increasing cycle number the difference between ALL and AIC increases, most likely attributed to the fact that the impact of SEI formation and repair becomes smaller in comparison to other parasitic reactions which do not consume lithium. Furthermore, one additional advantage of the IRLC method is that it allows a statement whether the reduction of lithium content is crucial for capacity fading or whether the fading is related to host material losses or other degradation mechanisms e.g. a higher charge transfer resistances due to a growing SEI film.

1. Krueger, S., et al., How Do Reactions at the Anode/Electrolyte Interface Determine the Cathode Performance in Lithium-Ion Batteries? Journal of the Electrochemical Society, 2013. 160(4): p. A542-A548.

2. Vetter, J., et al., Ageing mechanisms in lithium-ion batteries. Journal of Power Sources, 2005. 147(1-2): p. 269-281.