bluuebunny/crossref_metadata_2025 huggingface dataset:
Sensitivity to Acetone By Epsilon-Phase Tungsten Trioxide Films Produced By Reactive Spray Deposition Technology
Authors: Ouimet Ryan J. , Ebaugh Thomas Allen , Bonville Leonard J. , Maric Radenka
Published: February 2020

Studies have shown that when an individual with diabetes has low insulin levels, the body is unable to burn glucose and converts those molecules into ketones, predominantly acetone. That acetone then transfers into the blood stream before being exhaled by an individual’s breath. Rather than using current methods to monitor diabetes, such as a blood test conducted by a finger prick, some researchers have suggested measuring the acetone in exhaled breath as a noninvasive method to monitor diabetes [1].

This noninvasive diabetes monitoring method is made possible by using resistive sensors that utilize a thin-film deposited on interdigitated electrodes. While healthy individuals will exhale 300-900ppb acetone, individuals suffering from diabetes may exhale up to 1800ppb acetone [2]. Recent studies have shown an ability of these sensors to reach the sensitivity required to sense acetone in these diabetic cases. When the sensor is heated, the conductivity of the film increases and allows for the flow of electrons between digits of the sensor. When acetone is present, the acetone adsorbs onto the acetone-sensitive material causing a noticeable change in resistance. As the concentration of acetone increases, the amount of acetone adsorbed on the film increases, causing a change in resistance which allows researchers to correlate acetone concentration with a sensor resistance.

One acetone-sensitive material that researchers are studying is epsilon-phase tungsten trioxide. While other forms of tungsten trioxide, such as the gamma-phase, can also sense acetone, the specific structure and surface dipole of the epsilon-phase allows for a particular sensitivity to high dipole moment compounds such as acetone [2]. Unfortunately, this material is prohibitive to use, as the epsilon-phase tungsten trioxide is not the thermodynamically preferred structure at the operating temperature [1]. Some researchers have used dopants, such as silicon or chromium to stabilize the epsilon-phase. However, past research has shown that by using Reactive Spray Deposition Technology (RSDT), it is possible to directly deposit tungsten trioxide onto sensors and anneal the material to achieve the epsilon-phase [3]. Using these undoped epsilon-phase tungsten trioxide sensors, as seen in the scanning electron micrograph in Figure 1, we are able to achieve a sensitive and durable film which can be used to detect the concentrations of interest for diabetes monitoring. This work will examine the acetone sensitivity of the undoped epsilon-phase tungsten trioxide films developed using RSDT and compare them to other research.

References:

[1] L. Wang, A. Teleki, S.E. Pratsinis, P.I. Gouma. Chem. Mater. 20 (2008) 4794-4796.

[2] M. Righettoni, A. Tricoli, S.E. Pratsinis. Chem. Mater. 22 (2010) 3152-3157.

[3] R. Jain, Y. Wang, R. Maric. J. Nanotech. Smart Mater. 1 (2014) 1-7.

Figure 1
Electric Field Induced Melting: Effect of Non-Specifically Absorbed DNA
Authors: West Ryan M , Hetrick Wesley
Published: February 2020

Electric-field induced melting of surface-bound DNA can be carried out using electrochemical detection without parallel spectroscopic monitoring. With proper selection of applied potentials, ionic strength, and DNA coverage, discrimination of single mismatches based on the kinetics of DNA melting can be carried out quickly and reproducibly. Electrodes are prepared by the sequential exposure to thiol-modified oligonucleotides, mercaptohexanol, and finally hybridization with complimentary target oligonucleotides. The target is subsequently melted off the electrode by applying a sufficiently negative potential. The mechanism of e-melting is up for debate but likely involves the electrostatic repulsion between DNA’s phosphate backbone and the electrode surface, destabilization of the base pair hydrogen bonding or pi stacking, or some combination of these effects and others.

The mercaptohexanol passivation layer plays an important role for electrochemical DNA sensing, particularly when the effects of electric field are crucial to the detection scheme as is the case in electrochemical melting. The mercaptohexanol layer, or some other alkyl thiol layer is almost universally used to remove non-specifically absorbed DNA from the surface and prevent further non-specific absorption. Physisorbed oligonucleotides that are not removed by the passivation layer are expected to have ill-defined interaction energies with the surface and will be expelled from the surface at potentials and rates different than the hybridized target oligonucleotides. Additionally, a uniform mercaptohexanol layer is necessary for a uniform electric field. In this work, we examine the extent to which non-specific absorption occurs even when the mercaptohexanol layer is present. We examine how non-specific absorption effects the melting behavior, including the melting potential, melting rate, and the reproducibility. Finally, we compare various methods for mitigating non-specific absorption. These methods include the use of surfactants during electrode modification, applications of potential pulse sequences to destabilize and remove physisorbed oligomers, and the use of elevated temperatures.
Easy Monitoring of L-Lactic Acid in Wine Samples Using Disposable Electrochemical Enzymatic Sensors
Authors: Fanjul Bolado Pablo , Pereira Silva Neves Marta Maria , González García María Begoña , Hernández Santos David
Published: February 2020

In wine industry, the malolactic fermentation, employed to lower the overall tartness of wine, is usually monitored by following the diminishing level of L-malic acid and the increasing level of L-lactic acid. Consequently, the monitoring of L-lactic acid levels in the course of the fermentation plays an important role in wine quality testing [1-2]. L-lactic acid is typically determined using chromatography based techniques. However, although these methods are precise, require bulky instrumentation, trained personnel and are costly. Therefore, electrochemical biosensors appear as promising alternative for the development of simple, fast, low-cost and portable platforms for in situ L-lactic acid analysis.

In this work, an enzymatic electrochemical sensor for the determination of L- lactic acid in wine samples has been developed. These single-use, small sized, sensors allowed the specific determination of L-lactic acid between 0.02 mM and 0.3 mM. Different wine samples were assayed with the proposed sensors and the obtained results indicate that the developed methodology has an accurate performance.

In summary, these enzymatic electrochemical sensors revealed to be robust, highly stable, user-friendly and time-saving, demonstrating the possibility of being used for the decentralized monitoring of L-Lactic acid in wine samples as an analytical trustful tool.

References

[1] Analytical and Bioanalytical Chemistry (2014) 406:123–137.

[2] Biochemistry and Biophysics Reports (2016) 5:35–54.
Characterization of Defect-Rich Poly-SnO2 Nanofiber Material for Electrical Transport Mechanism Application
Authors: Lai Chun-Yen , Huang Li-Wei , Lai Po-Hao , Wang Yong-Jia , Hong Zhong-Jie , Wu Wen-Wei , Yeh Ping-Hung
Published: February 2020

Over the past few decades of research on the nature inspired material has given us new opportunities and challenges. The focus of nature inspired material not only inspired people’s imagination and hope, but also combined many study filed like architectural design, engineering, material science and electronic engineering development. In this research work, we used electrospinning instrument to make a nature inspired defect-rich poly crystal SnO2 nanofibers (PC-SnO2 NFs) as a broadband light sensor (365, 465, 595, 730, 850, 940 nm) and toxic gas sensor. In order to describe the defect appear in the interface grain by grain, we used the STXM-XANES, EXAFS, XPS and Raman to analysis and shows a best result of defect intensity in the nanofibers which give a strong evidence for oxygen defect. The Oxygen surface defect rich structure can give our PC-SnO2 NFs more applications, such as distinguished photoelectric property, outstanding gas detection ability and attractive cell regeneration, etc. In this research, we will use the defect structure to make kind of device by one material.
Hybrid Flexible Plasmonic SERS Substrate with Improved Assemblage of Ag@SiO2 Nanocubes on a Miniaturized Paper Platform
Authors: Mekonnen Menbere Leul , Chen Ching-Hsiang Chen , Su Wei-Nien , Hwang Bing-Joe
Published: February 2020

Surface Enhanced Raman Scattering (SERS), benefitted by its fingerprinting ability of molecules can be a reliable option for trace chemical analysis. Since the sensitivity of a SERS, method is highly dependent on the degree, to which the Raman signature is enhanced, fabrication substrates that could adequately amplify the local field through excitation of localized surface plasmon resonances (LSPRs) is critical. Hence, control over the nanostructures morphology and improving their inter-particle distance is important for obtaining improved SERS activity. In addition, flexible platforms like paper offer the means for improving the nanostructures assemblage with ease of fabrication at low cost and improved sample collection efficiency.Here in, inexpensive, flexible paper-plasmonic hybrid SERS substrate is reported by loading Ag@SiO2 nanocubes on a miniaturized filter paper through vacuum filtration. The miniaturized sensing platform owes a reasonable distribution and inter-particle spacing of nanocubes. The fibrous structure of paper promotes the assemblage of sharp-edged nanostructures which significantly improve their distribution and SERS activity.The thin silica shell improved the stability and inter-particle spacing of silver nanocubes in the sensing platform, rendering enhanced SERS activity through plasmon-coupling effect as compared to a conventional rigid substrate. Assessment of analytical performances of the substrate for melamine quantification showed a good linearity (R2 = 0.9947) up to 1 mg/L with a limit of detection 0.06 mg/L. The detection limit in liquid milk was down to 0.17 mg/L, which is below the permissible residue limit signifying adequate sensitivity for real sample analysis with less sample treatment.
Increasing the Efficiency of Amino Acids Detection By Electrochemical Methods on Amorphous Carbon Nitride a-CNx Electrodes
Authors: Faure Mathilde , Billon Florence , Le Potier Isabelle , Haghiri-Gosnet Anne-Marie , Tribollet Bernard , Deslouis Claude , Pailleret Alain , Gamby Jean
Published: February 2020

The naphthalene-2,3-dicarboxyaldehyde (NDA) label is widely used for the derivatization of amino acids (AAs) to form N-2-substituted-1-cyanobenz-[f]-isoindole derivatives (CBI) which are both fluorescent and electroactive. [1],[2] Optimal conditions for labeling were previously obtained when [NDA]tot/[CN-] ratio =1 and [NDA]tot /[amino acid or peptide]=40 with a buffer pH of 10. [3],[4] The detection step was achieved by using a carbon reference material (glassy carbon electrode ) exhibiting an obvious oxidation peak for CBI-AA observed at 0.5V/SCE [1]. These experiments confirmed that NDA can by used as a derivative agent for non electroactive AA, allowing for simultaneous electrochemical and fluorescence detections. In this work, amorphous carbon nitride a-CN0.26 thin films were elaborated on transparent and conductive glass/indium-tin oxide (ITO) wafers to improve the electroanalytical detection of AAs. The results obtained on as-grown a-CN0.26 were compared to the glassy carbon (GC). It was shown that a soft anodic pre-treatment protocol on glass/ITO/a-CN0.26 electrode in KCl solution drastically improved the CBI-AA oxidation peak performances. The oxidation peak potential for all CBI derivatives varied in the same range that those on GC and pre-treated glass/ITO/a-CN0.26, while no discrimination could be obtained for as-grown glass/ITO/a-CN0.26. For almost all the tested CBI derivatives, the electrochemical properties determined by electrochemical impedance spectroscopy (R
ct, charge transfert resistance) and by differential pulse voltammetry (peak areas, full-widths at peak mid-height, peak current density and their SD values) were improved on pre-treated a-CN0.26 in comparison with GC.

[1] M. Faure, S. Korchane, I. Le Potier, A. Pallandre, C. Deslouis, A.-M. Haghiri-Gosnet, J. Gamby, Investigating of labeling and detection of transthyretin synthetic peptide derivatized with naphthalene-2,3-dicarboxaldehyde, Talanta, 116 (2013) 8-13.

[2] M. Faure, A. Pallandre, S. Chebil, I. Le Potier, M. Taverna, B. Tribollet, C. Deslouis, A.-M. Haghiri-Gosnet, J. Gamby, Improved electrochemical detection of a transthyretin synthetic peptide in the nanomolar range with a two-electrode system integrated in a glass/PDMS microchip, Lab Chip, 14 (2014) 2800-2805.

[3] S. Korchane, A. Pallandre, C. Przybylski, C. Poas, F. Gonnet, M. Taverna, R. Daniel, I. Le Potier, Derivatization strategies for CE-LIF analysis of biomarkers: Toward a clinical diagnostic of familial transthyretin amyloidosis, Electrophoresis, 35 (2014) 1050-1059.

[4] M. Faure, I. Le Potier, A. Pallandre, S. Chebil, A.-M. Haghiri-Gosnet, C. Deslouis, E. Maisonhaute, J. Gamby, Determination of the isomeric forms proportion of fluorogenic naphthalene-2,3-dicarboxaldehyde in a binary mixture of water:methanol using electrochemical methods, Talanta, 148 (2016) 494-501.
(Invited) A Frequency Domain Optofluidics Dissolved Oxygen Sensor
Authors: Xiong Bo , Mahoney Eric , Lo Joe F. , Chau Colleen , Selvaganapathy Ravi , Fang Qiyin
Published: February 2020

Concentration of Dissolved oxygen (DO) is an important indicator of water quality. Fluorescence quenching is a commonly used optical method to measure DO. Steady-state fluorescence intensity measurements are easy to be influenced by acquisition artifacts, which makes determination of absolution DO values difficult. We developed a miniaturized, optofluidics frequency-domain DO sensor that measures fluorescence quenching using fluorescence lifetime changes of Ruthenium (Ru(dpp)3Cl2) rather than intensity. Dissolved oxygen is quantified by the phase shift between excitation modulation and emission modulation through process. Compact, low cost components such as diode lasers and photodiodes have been used for the potential of scalable distributed sensing applications. The sensor is evaluated using water samples with different oxygen concentrations. Experimental results show that the lifetime measured in frequency domain corresponds well to dissolved oxygen concentration. Long-term experimental demonstrates that the proposed sensor remains stable in the presence of photobleaching; since the measured phase shift is not affected by reduction of the fluorescence intensity. The sensitivity of the DO measurement is also enhanced through the total internal reflection design.
Simultaneous Electrochemical Determination of Purine and Pyrimidine Bases Using Cu Doped CeO2 Nanoparticles Modified Glassy Carbon Electrode
Authors: Lavanya Nehru , Sekar Chinnathambi , Neri Giovanni
Published: February 2020

Deoxyribonucleic acid (DNA) is an important hereditary substance in humans and in almost all other living organisms. It plays a vital role in the storage of genetic information and instructs the biological synthesis of proteins and enzymes through the process of replication and transcription of heritage information Thus, the identification and quantification of either individual and/or group of purine and pyrimidine bases are important for diagnosis of certain diseases and genetic disorders. Though there exits quite a few methods for such sensing, there is a great demand for a cheap, sensitive and interference free electrode for simultaneous determination of all the four neuclobases due to their important role in medical diagnosis, crime detection and biocomputing.

In the present work, an efficient electrochemical sensor has been fabricated for simultaneous determination of purine bases adenine (AD), guanine (GU) and pyrimidines bases thymine (TY), cytosine (CY) using Cu doped CeO2 nanoparticles modified glassy carbon electrode (Cu-CeO2/GCE). Direct electrocatalytic activities of DNA bases have been studied in phosphate buffer solution (PBS, pH 7.0) without any enzyme using voltammetric techniques. 3 wt% Cu doped CeO2 modified GCE showed two well defined anodic peaks each corresponding to the oxidation of purine (AD, GU) and pyrimidine (TY, CY) bases with significant peak to peak potential separation of 312 mV (AD-GU) and 200 mV (TY-CY) which were large enough for the selective and simultaneous determination of these bases in their mixture. Under optimum conditions, calibration plots for the simultaneous detection of the purine and pyrimidine bases were linear in the concentration range of 0.1– 500 μM for AD, 1–650 μM for GU, 1-300 μM for TY and 1-250 for CY with detection limit values of 0.021, 0.031, 0.024 and 0.038 μM respectively. Additionally the developed sensor exhibited good repeatability, reproducibility, sufficient stability and good anti-interference ability and was successfully applied for simultaneous detection of AD, GU, TY and CY in denatured DNA sample with satisfactory results.

References

Y. Deng, Y.L. Xia, C.H. Xiao, Biosens. Bioelectron. 31 (2012) 469–474.

N. Lavanya, C. Sekar, R. Murugan, G. Ravi, Mater. Sci. Engg. C 65 (2016) 278–286.
Electrodeposition of Both Carbon Nanotube and Glucose Oxidase on Pt Eectrode Using a Dispersed Electrolytic Solution
Authors: Yasuzawa Mikito , Uchimaru Masahiro , Jhong Huan-Ping , Kurashina Masashi , Wang Chen-Hao , Fuchiwaki Yusuke , Harada Toshihiko
Published: February 2020

Immobilization of the enzyme is one of the most critical processes for the fabrication of an enzyme sensor, since it will highly influence properties of the obtained sensor. Various procedure have been proposed for a the preparation of glucose sensor, such as covalent attachment, cross-linking, hydrogel entrapment, polymer film entrapment, and the combination of two or more methods. Among the various techniques, the electrodeposition method is interesting owing to its simple preparation, miniaturization, and precise localization of enzyme.

On the other hand, nanocarbons (NCs), such as carbon nanotubes (CNTs) and graphenes, are extremely attractive in biosensor application, since they can combine properties of the high surface area, high stability and good electrical conductivity. However, NCs is not soluble in aqueous solution, which is the least media to dissolve enzyme without reducing its activity. The use of surfactants is a candidate to preparer a disperse NCs in enzyme solution, while this may also reduce the enzyme activity. Therefore, processes of enzyme immobilization and NCs immobilization are commonly performed separately using different solutions.

In this study, stable dispersed solutions of glucose oxidase (GOx) and multi-walled CNT were developed using gellan gum, which is a polysaccharide manufactured by microbial fermentation used widely as a gelling agents. By using this CNT/GOx dispersed solution, both CNT and GOx were successfully immobilized on Pt-Ir electrode by a simple step of applying a constant potential of 1.3 V（vs. Ag/AgCl) to the electrode in this solution. The electropolymerization of o-phenylenediamine was followed in order to increase the stability of enzyme-immobilized electrode. The CNT/GOx immobilized electrode performed as a glucose sensor with a high sensor sensitivity. This indicate that the introduction of CNT in GOx-immobilized film increased the efficiency of electron transfer between the electrode and generated hydrogen peroxide. In addition, the reproducibility of electrode fabrication was satisfactorily improved by the use of gellan gum compared with that using Triton X-100 as a dispersing agent.
Suspended Graphene-Based Electrochemical Sensor for Ultra-Sensitive Detection of Electroactive Dopamine (neurotransmitter) Signals
Authors: Kumar Rakesh , Dang Caroline , Hadi Faisal , Dawood Omar , Sexton James , Missous Mohmad , Jackson Dean , Young R , Koehne Jessica E. , Boult Stephen , Dixon Neil , Migliorato Max
Published: February 2020

Graphene – a single atom thick 2D material, has demonstrated extraordinary potential as ultrasensitive and specific biological and chemical sensors1,2. This is because every carbon atom in suspended graphene is a surface atom which can be covalently/non-covalently interfaced with a wide range of chemical/biological species3 for detection at the single molecule level. Additionally, the charge transport through graphene can be modified via liquid gating, which forms a sensitive electrochemical method of detecting signals from charged species bonded to the graphene surface. Recently, graphene has demonstrated selective detection of electroactive signals from dopamine-a catecholamine neurotransmitters, which are found in the mammalian central nervous system4. Pristine graphene’s superior electronic and electrochemical properties can be exploited as analytical electrochemical sensors for measuring exocytosis during communication between cells under in vitro conditions, thereby monitoring cognitive and behavioural functions of living organisms

We have developed a 3 mm X 3 mm graphene chip with an array of two terminal devices, connected in parallel, in which each individual device consists of a monolayer graphene suspended over multiple cavities and clamped by two metal contacts. Suspended graphene, as opposed to substrate-based graphene, significantly reduces the surface charge hindrances and allows for ultrasensitive detection of electroactive signals. The fabricated graphene chip has been successfully tested as a VOC and electrochemical sensor. Currently, testing is underway to use the device as an electrochemical dopamine sensor. We intend to discuss initial electrochemical dopamine sensing results as well as to explore possible collaborations with research groups for testing the graphene chip as an in-vitro neurotransmitter sensor.

References:

1. Yuan, Wenjing, and Gaoquan Shi. "Graphene-based gas sensors." Journal of Materials Chemistry A 1.35 (2013): 10078-10091.

2. Kuila, Tapas, et al. "Recent advances in graphene-based biosensors." Biosensors and Bioelectronics 26.12 (2011): 4637-4648.

3. Shao, Yuyan, et al. "Graphene based electrochemical sensors and biosensors: a review." Electroanalysis 22.10 (2010): 1027-1036.

4. Jackowska, Krystyna, and Pawel Krysinski. "New trends in the electrochemical sensing of dopamine." Analytical and bioanalytical chemistry 405.11 (2013): 3753-3771.
High Throughput Droplet Microfluidic Platform for Single-Cell Lipid Analysis of Human Breast Cancer Cell Lines
Authors: Fernandez Renny Edwin , Monshi Md Monirojjaman , Bhushan Pulak , Bhansali Shekhar
Published: February 2020

Lipid metabolism has been viewed as an indicator of breast cancer. We report a single cell high throughput droplet microfluidic platform for lipid profiling of cells. Breast cancer cell lines (MCF7 and LLC1) are individually trapped in nanoliter droplets containing enzyme microbeads. Subsequently, the lipid contents of individual cells are hydrolyzed by the microbeads in the droplet followed by electrochemical detection using a microelectrode array. Our droplet-based microfluidic platform integrates cell lysis and localized hydrolysis within a micron sized aqueous drops (40 µm) in an inert carrier oil (Fig. 1). The quantity of the hydrolyzed products in each droplet correspond to the lipid profile of individual cells. The magnitude of electrochemical impedance variations are characterized and related to tumor progression. The cellular heterogeneity of an apparently homogenous cell population has been identified. The change in electrochemical signals is correlated to the amounts and types of lipids in breast cancer cell lines.

Preliminary studies reveal the potential of our droplet microfluidic platform in comparing the chemical composition between cell types and even between individual cells. Cell-to-cell variability, which is not reflected in the ensemble profiles, was preserved in the proposed method. The microfluidic platform is also being integrated with bioimpedance analysis for advanced bioimpedance profiling. We identified that this approach leads to (a) functional identification of lipid variation in cancer cell lines during various stages of growth, (b) Tumor progression related to lipogenesis and fatty acid synthesis. The platform is also being extended to pathogenesis and drug-discovery

Figure 1
3D Printing of Molds for Soft Lithography
Authors: Shah Shreyas , Shiblee MD Nahin Islam , Furukawa Hidemitsu , Kawakami Masaru , Nagahara Larry A , Thundat Thomas , Sekhar Praveen K. , Khosla Ajit
Published: February 2020

Microfabrication of PDMS based microfluidic devices involves fabrication of micromolds which need expensive infrastructure, such as clean room, photolithography equipment, photoresists, substrates, masks etc. In this paper, we present fabrication of micromolds using three dimension (3D) printing for soft lithography [1, 2]. By employing 3D printing technology overcomes the challenges posed by time consuming and difficult to manufacture, with state of the art 2-D MEMS fabrication technology [3]. Compared to the conventional method of microfabrication, 3D printed mold can be processed more rapidly, augment use of materials, intricate design which is challenging by photolithography [4,5]. Here, we designed and fabricated micro features using binder jetting printer (Objet30 Pro) and photopolymer jetting printer (Formlabs Form 2). Objet30 Pro uses the technique of depositing adhesive liquid onto the powder photopolymer on the build tray. Binding process between the powdered particles make a solid structure. During the printing of master no support structures where used. The master was also printed using the deposition of photopolymer using the Formlabs Form 2 printer. Concept behind the fabrication is curing the photopolymer by UV light which is deposited pointwise layer-by layer. Since, the fabrication of the master is done in slices the surface of the master was rutted which gave bumpy replication but, were able to print the feature (Round trench, Hexagonal trench) size of 200μm (Fig 1 and 2). Mold fabricated using the Objet30 pro printer gave fine structures with resolution of 300μm in depth and feature size of 500μm were printed flawless. This technique forms a 3D printed structure by holding the particles and does not require support structure.

References:

Khosla, Ajit, and Bonnie L. Gray. "(Invited) Micropatternable Multifunctional Nanocomposite Polymers for Flexible Soft NEMS and MEMS Applications." ECS Transactions 45.3 (2012): 477-494. doi: 10.1149/1.3700913

Khosla, A. (2011). Micropatternable multifunctional nanocomposite polymers for flexible soft MEMS applications (Doctoral dissertation, Applied Science: School of Engineering Science). http://summit.sfu.ca/item/12017

Khosla, Ajit. "Nanoparticle-doped electrically-conducting polymers for flexible nano-micro Systems." The Electrochemical Society Interface 21.3-4 (2012): 67-70.doi: 10.1149/2.F04123-4if

Takamatsu, K., Basher, S., He, S., Sato, K., Yoshida, K., Sakai, K., ... & Khosla, A. (2017, September). 3D Printing of Micromolds and Microfluidic Devices. In Meeting Abstracts(No. 49, pp. 2113-2113). The Electrochemical Society.

Takamatsu, K., Yamada, N., Wada, M., Ahmed, K., Kawakami, M., Kassegne, S., ... & Khosla, A. (2016, September). 3-D Printed Polymer MEMS. In Meeting Abstracts (No. 51, pp. 3861-3861). The Electrochemical Society.

Figure 1
(Invited) Fluorescence-Based Chemical Sensing and Imaging of Oxygen Concentrations for Microbial Processes in Microfluidic to Macroscale Habitats
Authors: Grate Jay W
Published: February 2020

As one of the most important electron acceptors in biology, oxygen is of particular interest as a factor in many microbial and biogeochemical processes. Gradients of molecular oxygen are of particular interest due to the fact that many important biological processes either occur at interfaces or are regulated by the flux of oxygen and other resources. The incorporation of chemical sensing within microfluidic structures, and the imaging of chemical concentrations therein, present particular challenges. Nevertheless, microfluidic structures offer unique opportunities to create microenvironments that set up gradients and environmental conditions that are relevant to biomedical or natural biogeochemical systems. In addition, chemical oxygen imaging creates the opportunity to identify hot spots or hot moments where biological activity is occurring. Here we describe primarily approaches to sense oxygen concentrations and gradients within microfluidic structures, using localized films of fluorescent oxygen sensing dyes. In addition, chemical imaging is described for macro-scale systems where chemical sampling timing and spatial location can be triggered by the observation of hot spots or hot moments. Diverse approaches will be contrasted for fabricating and imaging oxygen sensing devices and apparatus, including microfluidic pore network structures as models for natural systems at the pore scale.
Detection of Traumatic Brain Injury Biomarker with a Paper-Based Optofluidic Strip
Authors: Gao Xuefei , Wu Nianqiang
Published: February 2020

Currently traumatic brain injury (TBI) is diagnosed with Glasgow Coma Scale (GCS), computed tomography (CT) scans or magnetic resonance imaging (MRI). Herein a paper-based optofluidic test strip has been developed to detect the TBI protein biomarker, neuron-specific enolase (NSE). A Surface-enhanced Raman scattering (SERS) substrate has been incorporated into a paper-based lateral flow strip. This paper-based device has achieved high sensitivity and low limit of detection in the blood plasma samples taken from the clinical TBI patients.
Closed Bipolar Electrodes for Coupling Electroanalytical Events to Optical Readouts
Authors: Fu Kaiyu , Hu Jiayun , Lopez Arielle , Bohn Paul W.
Published: February 2020

Closed bipolar electrode (CBE) geometries can be used to couple analytically-directed redox processes occurring in one microfluidic cell - the analytical cell - to a variety of optical readouts (fluorescence, absorption, surface plasmon resonance shifts) occurring in a remote microfluidic cell – the reporter cell. In the fluorescence version, oxidation or reduction of reversible analytes in the analytical cell is accompanied by reduction or oxidation, respectively, on the proximal portion of a CBE and then monitored by the accompanying oxidation of dihydroresorufin or reduction of resorufin in the reporter cell. Changes in fluorescence intensity have been used to determine Ru(NH3)6
3+ at sub-nM concentrations, demonstrating high sensitivity fluorescence-mediated electrofluorigenic sensing. An electrochromic version of the strategy was developed using a methylviologen (MV) reporter system. CBE-enabled devices based on two thin-layer-cells of ITO and Pt were fabricated to couple an analytical reaction with a MV reporter reaction, producing a color change in the reporter cell, that was readout by a smartphone. Evolution of the device replaced the potentiostat with batteries to control potential, and augment the smartphone, thereby demonstrating the simplicity and portability of the device. This strategy was recently extended to non-electroactive analytes, by coupling enzyme-catalyzed oxidoreductases in the analytical cell to the same MV electrochromic reporter system, a construct which is being employed to develop a multiplex assay for sepsis biomarkers.
Sub-Nanomolar Detection of Limonin Using Cnps Integrated Silk Fibroin As Transducer on Organic Electrochemical Transistor
Authors: Saraf Nileshi , Barkam Swetha , Peppler Madison , Seal Sudipta , Metke Anna
Published: February 2020

Limonin is a biomolecule which is responsible for the bitter element in many citrus fruits and vegetables. It has proven to be antioxidants which are biologically active and exhibit anticarcinogenic activity. It is formed from a tasteless precursor called limonite β ring lactone, which is found in the juice sacs. During juice extraction from the fruit, the precursor encounters the acidic compound of the juice and is gradually lactonized to form bitter limonin. This bitterness is generally not desired, therefore quantification and detection of limonin is very crucial for improving fruit quality in the citrus industry. The current techniques available for detecting limonin in fruits are time consuming, expensive and not fit for active monitoring of limonin levels.

In this study, we have shown the applicability of ceria nanoparticles (CNPs) to be used as a transducer integrated in silk fibroins that is coupled with an organic electrochemical transistor to detect limonin. CNPs possess antioxidant properties which is attributed to the redox nature of dual oxidations states, Ce3+ and Ce4+, switching on the surface. This constant switching of oxidation states on the surface produce oxygen vacancies that act like hot spots for targeting electroactive entities like limonin. Therefore, in the present work, the electrochemical interaction between CNPs and limonin has been exploited to detect limonin using a transistor platform. Multiple characterization techniques were done to confirm the presence of CNPs in silk fibroins. The SOD and the catalase mimetic activity was assessed using SOD assay kit and Amplex red kit which showed the preservation of CNPs antioxidant properties in silk. Immobilizing and embedding CNPs in silk fibroins was studied to provide the most sensitive and efficient transducer for the OECT. In order to find the limit of detection of the OECT, limonin concentrations were varied and tested at different gate voltage (VG). The limonin OECT prepared in this study showed a detection limit of 10nM with a constant increase in the ID current with limonin concentration. A range of interfering species which are commonly available in citrus fruits, were also tested to investigate the selectivity of the sensor. It was observed that none of the analytes, other than the limonin, produced a noticeable change in current. Thus, the CNPs-OECT limonin sensor has potential applications in sensing limonin on field applications. Future field and research application of the CNPs-OECT sensor could include real time monitoring of the amount of limonin in fruit juices or to study and reduce the amount of limonin in citrus fruits and to quantify the dosage of limonin as a potential antioxidant material.
Fabrication of MEMS Electronics Devices Based on Fire-like ZnO Nanosheets By Low-Temperature Hydrothermal Synthesis Technology
Authors: Tsai You-Ting , Chang Shoou-Jinn , Hsiao Yu-Jen , Chu Yen-Lin , Tang I-Tseng , Ji Liang-Wen
Published: February 2020

The high-density novel morphology fire-like Zinc Oxide (ZnO) nanosheets grown on aluminum (Al) substrate. The fire-like ZnO nanosheets based MEMS technology gas sensors using zinc nitrate hexahydrate, and hexamethylenetetramine by using a low-temperature hydrothermal method. The structure and optical characteristics of fire-like ZnO nanosheets were measured by field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). The FE-SEM images show that the new morphology was fabricated and high of the ZnO nanosheets can be controlled by the different thickness of Al substrates, it was found that measured high of the ZnO nanosheets increased from 733.3 nm to 2000 nm and the response of ethanol was increased due to the high surface area nanosheets.

Keywords: Al thin films, hydrothermal, ZnO nanosheets

Figure 1
Limitations in Estimation of E1/2 from Cyclic Voltammetric Data
Authors: Parr Daniel , Leddy Johna
Published: February 2020

It is common practice to estimate the standard (E0) or formal (E0’) potential from cyclic voltammetric data. A frequent estimate of E0 or E0’ is taken from either the peak potential (Ep), the half wave potential (E1/2), or the average of the cathodic and anodic peak potentials (Epc+Epa)/2. Often, this suffices to identify the standard or formal potential within 100 mV, but confidence in such estimates is not always justified. Mechanisms that include both electron transfer (E) and chemical (C) steps can impact the quality of estimated standard and formal potentials. In some systems, limitations to the estimated standard and formal potentials depend on the rates of heterogeneous electron transfer and homogenous reactions.

Here, the quality of estimated standard and formal potentials based on peak potentials, half-wave potentials, and average potentials for the cathodic and anodic sweeps are described for various mechanisms. Cases where the standard and formal potentials are well estimated from measured cyclic voltammetric data are identified and the quality of the estimated standard and formal potentials are characterized. That is, specify whether the estimate is within 100 mV, 50 mV, or 10 mV for a given mechanism. Situations where the estimate fails are identified and alternative means to estimate the standard and formal potential are provided. Several reaction schemes that include EC, EE, CE, and the various ECE mechanisms are characterized.
Relationship between Hole Design on Anode Electrode, the Reaction Temperature and the Rate of Li+ Ion Pre-Doping Reaction to Porous Laminated Graphite Anodes
Authors: Tsuda Takashi , Ando Nobuo , Tanabe Toyokazu , Itagaki Kaoru , Soma Naohiko , Nakamura Susumu , Hayashi Narumi , Matsumoto Futoshi
Published: February 2020

In our previous paper (Electrochemistry
, 85(4) 186 (2017)), we have reported that the porous current collector could be produced with a pico-second pulse laser system and that graphite electrodes prepared with porous Cu current collectors improved the rate of Li+-pre-doping reaction in the laminated graphite electrodes. In this study, in order to speed up the rate of the pre-doping reaction more, the porous graphite electrodes were prepared by directly opening the holes on the surface of graphite electrodes with a pico-second laser. In the cell composed of laminated graphite electrodes and a lithium metal, the Li+-doping reaction proceeded much faster than in the cells of the graphite electrodes prepared with porous current collectors and a Li metal. In addition, the results of electrochemical impedance spectroscopy suggested that the transfer of Li+ ions though the holes on the graphite electrodes was a rate determining step of the doping reaction of Li+ to laminated graphite electrodes and that the decrease in the hole diameter at the constant of opening rate of holes on the graphite electrodes cased the reduction of resistance for Li+ ions, resulting in shortening the time for completing the doping reaction of Li+ ions.

Fig. 1 SEM images (1: low magnification, 2: high magnification) of prepared porous graphite electrodes in a view from the plane of the incident laser. The opening rate of hole on the electrode: 1%. The average hole sizes were (A) 50, (B) 20 and (C) 10 mm.

Figure 1
High-Voltage Aqueous Supercapacitors Based on Natfsi
Authors: Reber David , Kühnel Ruben-Simon , Battaglia Corsin
Published: February 2020

Replacing the acetonitrile-based electrolyte in state-of-the-art supercapacitors by an aqueous electrolyte could make these devices environmentally more benign, improve operational safety, and render supercapacitors potentially more cost efficient. The narrow electrochemical stability window of water (~1.23 V) is the main challenge in order to increase the energy density of water based devices. Recently it was reported that ultra-highly concentrated aqueous salt solutions can provide stability windows up to 3 V1. Salt concentrations higher than 21 mol kg-1 lead to increased kinetic stability, but result in reduced ionic conductivities of typically less than 10 mS cm-1. This renders such systems unsuitable for high power applications such as supercapacitors. In a recent study, we report beneficial effects in terms of electrochemical stability and conductivity for a moderately concentrated 8m NaTFSI aqueous solution2. Following a stringent test procedure, the stability window was determined to be 1.8 V and an ionic conductivity of 48 mS cm-1 was obtained, the latter being on par with modern organic electrolytes. A 1.8 V carbon/carbon supercapacitor displayed high maximum energy density of 14.4 Wh kg-1 on the activated carbon mass level and stable cycling over 100,000 cycles. Redox active potassium iodide was added to the system in order to boost its maximum specific energy to the very high value of 37.8 Wh kg-1, which is comparable to the performance of currently available commercial acetonitrile based supercapacitors.

Suo, L.; Borodin, O.; Gao, T.; Olguin, M.; Ho, J.; Fan, X.; Luo, C.; Wang, C.; Xu, K., "Water-in-salt" electrolyte enables high-voltage aqueous lithium-ion chemistries. Science
2015,
350, 938.

Reber, D.; Kühnel, R.-S.; Battaglia, C., High-voltage aqueous supercapacitors based on NaTFSI. Sustainable Energy Fuels
2017, doi: 10.1039/C7SE00423K
An Intermediate Temperature Molten Li-Air Battery with Improved Performance
Authors: K Guruprakash , Prakash A.S.
Published: February 2020

Li-air batteries gained enormous interest in last few years for their attractive theoretical energy density compared to state-of-the-art Li-ion batteries. However, low rate performance, deteriorated cycle life and energy inefficiencies hinder the progress and adoptability. Performance of non-aqueous Li-air batteries are retarded due to adverse reactions associated with non-aqueous electrolyte. As an alternative to unstable non-aqueous electrolytes generally used in Li-air batteries, inorganic metal salts are investigated as molten electrolytes at intermediate temperature. Present study investigates the use of LiNO3-KNO2-CsNO3 (37-39-24) eutectic salt mixtures at 140 °C as electrolyte, lithium as anode and vulcan carbon as cathode to demonstrate improved cycle life and energy efficient molten Li-air battery. X-ray diffraction and FESEM are used to show that Li2Ox is reversibly formed during cycling with a charge-discharge overpotential of 0.3 V after 100 cycles (limited capacity of 500 mAhgcarbon
-1). Improved cyclability is attributed to better solubility of discharge product at preeminent temperature and the reduced cell resistance due to high ionic conductivity of molten electrolyte. Operating the Li-air battery in molten electrolytes at elevated temperature could open a new window for solving adverse problems associated with electrolytes.
Electrical and Structural Properties of ZrO2/Y2O3/ZrO2 Dielectric Film for DRAM Capacitor
Authors: Cho Seong Tak , An Cheol Hyun , Kim Sang Hyeon , Kim Dong Gun , Kwon Dae Seon , Cha Soon Hyung , Hwang C. S.
Published: February 2020

ZrO2/Al2O3/ZrO2 (ZAZ) structure is widely used as a capacitor dielectric film of Dynamic Random Access Memory (DRAM). This is a structure in which Al2O3 film is added as an interlayer to improve the leakage current in the ZrO2 material which can meet the dielectric constant and leakage characteristics required by the device. Nonetheless, the added Al2O3 film decreases capacitance density compared with a capacitor composed of the single ZrO2 layer, because the Al2O3 film itself has a low dielectric constant and the upper ZrO2 film is not crystallized properly. Although this ZAZ structure has been extensively used to meet the device requirements of DRAMs down to the design rule of ~20nm, it is difficult to further use it for the DRAM with design rule lower than 20nm. Accordingly, there are active research and studies in progress to discover a new dielectric material to replace the ZAZ structure.

In this study, Y2O3 was used to replace Al2O3 to suggest a strategy to increase the total dielectric constant while maintaining the role of improving the leakage characteristics performed by the Al2O3 film. The dielectric constant and bandgap of Y2O3 are higher than that of Al2O3 and that of ZrO2, respectively, and it is also known as a material stabilizing the phase of ZrO2 into high-k phase.[1] Therefore, Y2O3 is considered a promising candidate to replace Al2O3.

The evaluation was carried out using Y(iPrCp)2(iPr-amd) precursor, synthesized by Air Liquide Co., which is liquid at room temperature, and O3 as the oxygen source. The saturated deposition rate of the Y2O3 thin film was ~0.14nm/cycle when it was grown by an atomic layer deposition (ALD) method. Cubic phase Y2O3 film was observed by X-ray diffraction.

For comparison, ZAZ and ZrO2/Y2O3/ZrO2(ZYZ) were deposited on TiN substrate by ALD method, and their electrical and physical properties were evaluated. As expected, the equivalent oxide thickness could be decreased by ~0.2nm at a physical thickness of ~10nm, while the leakage current level remained almost invariant (~9 X 10-
10A/cm2 to ~4 X 10-
9A/cm2 at 0.8V) when the Al2O3 was replaced with the Y2O3 layer. The effect of heat treatment on the crystal structure of ZrO2 in ZAZ and ZYZ dielectric films and the electrical properties according to variations in their thickness were also studied. These results are promising as the newly suggested ZYZ structure may replace the present ZAZ without any major changes in electrode and integration strategy.

References [1] Bo-Eun Park et al., Journal of Alloys and Compounds 722 (2017)

Figure 1
A Paper-Based Spectroelectrochemical Platform Integrated with Electrodes and Surface Enhanced Raman Scattering Zones
Authors: Andersen Nalin I , Artyushkova Kateryna , Gonzales Ivana , Atanassov Plamen
Published: February 2020

We report the fabrication and use of a paper-based analytical system to study multiple modalities of catalysts utilized for the same global reaction. Presented here is a porous media device that couples quasi-stationary flow, stencil-printed electrodes, and surface enhanced Raman spectroscopy zones for rapid determination of catalytic transformations. The methodology of a paper-based platform is extended to demonstrate how multiple chemical reactions can be performed in sequence by use of both enzymes and electrocatalysts. Enzymes play a contributing role in the electrocatalytic conversion of glycerol to carbon dioxide, which is a complex cascade system 1,2. Specifically, the use of oxalate decarboxylase has been shown to catalyze the conversion of mesoxalic acid (6) to glyoxylic acid (7) and oxalic acid (8) to formic acid (9) as shown in Figure 1. The platform allows rapid determination of catalytically transformed analytes. It also serves as a method for understanding the optimum reaction conditions necessary for using different modalities of catalysts together.

References:

Hickey, D. P., McCammant, M. S., Giroud, F., Sigman, M. S. & Minteer, S. D. Hybrid enzymatic and organic electrocatalytic cascade for the complete oxidation of glycerol. J. Am. Chem. Soc.
136, 15917–15920 (2014).

Abdellaoui, S., Hickey, D. P., Stephens, A. R. & Minteer, S. D. Recombinant oxalate decarboxylase: enhancement of a hybrid catalytic cascade for the complete electro-oxidation of glycerol. Chem. Commun.
51, 14330–14333 (2015).

Figure 1