bluuebunny/crossref_metadata_2025 huggingface dataset:
Electro-Chemical Stripping and Capacitive Sensing Enabled Selective and Sensitive Ammonia Water Sensors
Authors: Lalwani Anand Vikas , Mu Linchao , Woo Kelly , Holiday Maximillian A , Senesky Debbie G , Tarpeh William Abraham
Published: May 2020

Harmful algal blooms (HABs) and eutrophication cause billions of dollars in damages and irreversibly damage our aquatic ecosystem. According to Bernard et al. (2014), the costs of monitoring is on the order of 1 billion USD annually and Kim (2006) reported that due to HABs, Japan lost over 1 billion dollars in aquaculture.

To monitor and predict such blooms, we need to cost-effectively and remotely monitor pollutants in our water bodies. One prominent pollutant that is a factor in causing harmful algal bloom is dissolved ammonia from agriculture and sewage treatment plants. To that end, we propose a novel and cost-effective sensing solution that can detect ammonia in water. Using selective membrane separation and electrochemical stripping, we are able to selectively isolate ammonium ions from dissolved river water and wastewater in our small-scale 3-chamber system. Through capacitive sensing, we can then measure with high sensitivity (28-bit resolution) and precision the concentration of ammonium ions present in our final chamber.

Between the first and second chamber, there is a cation exchange membrane that allows only cations to pass through. Amongst the cations, only ammonium and hydrogen ions form gases and diffuse through the gas-permeable membrane between the second and third chamber. The ammonia gas is then dissolved into the sulfuric acid present in the third chamber. The dissolved ammonium ions change the permittivity of the overall solution and this change can be measured using highly sensitive capacitive-based sensors.

Presently, we have higher than 99% selectivity in isolating ammonium ions from wastewater and river water. Our capacitive sensor has a noise floor of 0.3 femtofarad. The combination of high selectivity and high sensitivity unlocks the ability to detect small traces of dissolved ammonia at low power draw, thus enabling the use of such methods for immersible ammonia sensors for environmental sensing applications.

References:

Bernard S, Kudela RM, Velo-Suárez L. Developing global capabilities for the observation and prediction of harmful algal blooms. In: Djavidnia S, Cheung V, Ott M, Seeyave S, editors. Oceans and society: blue planet. Cambridge Scholars Publishing; 2014. Chapter 6

Kim HG. Mitigation and controls of HABs. In: Granéli E, Turner JT, editors. Ecology of harmful algae. Ecological Studies. Vol. 189. Springer-Verlag; Berlin: 2006. pp. 327–338
Nano-Optomechanical Systems (NOMS) for Gas Chromatography Sensing
Authors: Hiebert Wayne K , Maksymowych Matthew P , Venkatasubramanian Anandram , Roy Swapan K , Elhamel Nadia , Westwood-Bachman Jocelyn N , Firdous Tayyaba
Published: May 2020

Nano-optomechanical systems (NOMS) achieve high-precision measurement of displacement which enables very high sensitivity through mechanical resonance-shift sensing. A recent breakthrough [1] has shown that NOMS devices can operate in high-damping environment without sacrificing their frequency stability and sensing resolution. This is because stability losses from lower quality factor (Q) are offset by stability gains from a larger intrinsic signal-to-noise ratio.

We take advantage of this excellent stability to do atmospheric pressure resonant mechanical gas sensing with high sensitivity using NOMS [2]. In particular, we have set up a traditional gas chromatograph to output to a NOMS detector and shown parts-per-billion level detection [2]. By modifying the NOMS devices to make the silicon cantilevers porous, we have improved sensitivity by a further factor of 10 [3].

The next challenge, and opportunity, in using NOMS for mass sensing, is to separate the gas loading signals that affect both the mechanical and optical resonances in high optomechanical-coupling devices [4]. This is because, at high coupling, changes in optical resonance produce changes in mechanical resonance and vice versa. This effect can be used to amplify the sensing signal obtained when measuring mechanical frequency changes. In fact, it scales particularly well with high-finesse optical cavities and could lead to a situation where evanescent field gas loading on the optical cavity is transduced as a mechanical frequency shift with orders of magnitude better mass sensitivity than could be realized from the NEMS alone or the optical cavity alone. As an example, our present mass loading sensitivity is around 50 kDa [5]; improving the cavity linewidth merely by a factor of 10 should shrink that mass sensitivity by a factor of 1000, bringing it down to 50 Da. This level of sensitivity would allow studying chemical adsorption and desorption of individual gas chromatography molecules on the sensor surface and could provide a simple path for obtaining orthogonal information in gas chromatography detectors.

[1] S. K. Roy, V. T. K. Sauer, J. N. Westwood-Bachman, A. Venkatasubramanian, and W. K. Hiebert, Improving mechanical sensor performance through larger damping. Science
360, eaar5220 (2018); doi: 10.1126/science.aar5220.

[2] A. Venkatasubramanian, et al., Nano-optomechanical systems for gas chromatography. Nano Lett.
16, 6975-6981 (2016); doi: 10.1021/acs.nanolett.6b03066.

[3] A. Venkatasubramanian, et al., Porous nanophotonic optomechanical beams for enhanced mass adsorption. ACS sensors
4, 1197-1202 (2018); doi: 10.1021/acssensors.8b01366.

[4] M. P. Maksymowych, J. N. Westwood-Bachman, A. Venkatasubramanian, and W. K. Hiebert, Optomechanical spring enhanced mass sensing. Appl. Phys. Lett.
115, 101103 (2019); doi: 10.1063/1.5117159

[5] Da = Dalton = 1 amu = 1 atomic mass unit ~ 1.66 x 10-27 kg.
A 3D-Printed Microfluidic Device with Integrated Electrochemical Sensors for Autonomous Habitability Assessment and Life Detection.
Authors: Thomson Seamus D. , Ricco Antonio J. , Koehne Jessica E. , Quinn Richard C.
Published: May 2020

A 3D-printed microfluidic device coupled with a fluidic processing system was developed to enable autonomous end-to-end sample handling and electrochemical characterization of an ocean world analogue solution – synthetic seawater (SW). This dual-channel microfluidic cell was populated with 14 electrodes and performed electrochemical measurements similar to those used in the MECA Wet Chemistry Laboratory on board NASA’s Phoenix Lander that landed on Mars in 2008. Biological and metallic redox events were evaluated using cyclic voltammetry with Au, Pt, and glassy carbon electrodes, with the latter displaying superior sensitivity and selectivity. Conductivity and pH were measured using Pt and iridium oxide electrodes respectively, and SW anions such as chloride were quantified using chronopotentiometry with a Ag electrode. The fluidic handling system demonstrated sample transportation to the microfluidic device for electrochemical measurements, and could be readily adapted to accommodate different pre-processing steps. Overall, this study demonstrates the use of electrochemical sensors as part of an autonomous microfluidic handling system that would be functionally analogous to an electrochemical instrument designed for Ocean World exploration.
A Fluorescent "Turn-Off" Probe for the Determination of Curcumin Using Upconvert Luminescent Carbon Quantum Dots
Authors: Ding Yaping , Yu Chenhong , Zhuang Qi , Li Li , Lin Jiaxin , Duan Yingchun , Duan Dingding
Published: May 2020

Curcumin is used as a natural pigment and flavoring agent and food additive in food processing industries. Also, curcumin has a wide range of applications in the medical industry and clinical treatment because of its anti-cancer, anti-oxidation, anti-coagulant, anti-HIV choleretic and hypolipidemic effects. Therefore, it is crucial to properly control the concentration of curcumin in food and medicine. In our work, a new and simple method for quantitative detection of curcumin was established by developing a “turn-off” fluorescence probe based on upconvert luminescent carbon quantum dots (p-CDs). The carbon quantum dots were synthesized with p-aminobenzoic acid (PABA) and ethanol by solvothermal method and have specific up-conversion luminescence properties which could be applied in other sensing field. In this sensor, the sensing mechanism of this fluorescent probe was based on the internal filter effect (IFE) between curcumin and p-CDs, the increasing in the concentration of curcumin causes the selective fluorescence quenching of p-CDs. Under optimum conditions, the fluorescence quenching intensity of p-CDs has a good liner relationship with curcumin in the range of 0.4-45 μΜ and with a detection limit of 0.133 μM. What's more, the fluorescent “turn-off” probe constructed with p-CDs exhibited high accuracy and recovery in the analysis of actual sample curry powder, demonstrating the fluorescence “turn-off” probe has potential application for the detection of curcumin in the complex matrixes.
Synergy Effect between BSA and Co2+ to Boost Chemiluminescence
Authors: Li Jing , Xing Huanhuan , Wang Erkang
Published: May 2020

Boosting the chemiluminescence (CL) with functionalized materials holds great promise for the ultrasensitive bioassays. Herein, synergy effect between BSA and Co2+ to boost chemiluminescence was revealed. By introducing BSA and Co2+ in the luminol system, sea urchin-like composites with hierarchical architecture named [O]BSA-Co were formed in-situ, which can be not only acted as the microreactors to enrich the CL-related reagents, but also exhibited strong oxidase-like capability to induce the generation of reactive oxide species. Surprising, the unique structure combined the oxidase-like feature of [O]BSA-Co and the capping reagents endowed over 100-fold CL enhancement compared with the classic luminol-Co2+ or luminol-BSA system with O2 as coreactant. Moreover, the proposed catalytical amplification mechanism could be extended to the different proteins such as lysozyme, protamine, thrombin, papain. Based on the fabricated system, a sensitive sensing platform was constructed for the determination of ascorbic acid with satisfied results. The high-efficiency enhancement catalyzed by [O]BSA-Co provided a simple and eco-friendly route for the construction of the novel CL sensing platforms.
Graphene/Au/SiC Optical Waveguide-Based Surface Plasmon Resonance Sensor for Chemical and Biomedical Sensing in Aqueous Medium
Authors: Du Wei , Zhao Feng
Published: May 2020

In chemical and biomedical sensing, identification and quantification of analytes in aqueous medium such as water, blood or other carriers are very important. It requires the core sensors to have the properties of low cost, high sensitivity, on-chip integration capability, etc. Various sensing methods have been developed such as prism coupler and grating coupler, etc. and among them, waveguide-based surface plasmon resonance (SPR) sensors, with sensitivity of the optical waveguide significantly improved by SPR, have been identified as a powerful tool for detection and quantitative characterization of chemical and biological species or biomolecular reactions in aqueous medium. For sensing in aqueous medium, the optical waveguide sensors are desirable to operate in the visible light wavelength to overcome the large absorption coefficient of water in the near infrared range. This high absorption coefficient causes optical energy in the near infrared incident light be absorbed by water rather than by the sensing medium. Conventional silicon (Si) is not the choice of material for such sensors due to the strong absorption below the wavelength of 1.1 μm due to its narrow bandgap (Eg=1.12 eV, 1.1 µm wavelength).

As a wide bandgap semiconductor, silicon carbide (SiC) is more desirable for such sensors with advantages of: (1) bandgap energy of 3.2 eV in 4H and 6H polytypes and 2.2 eV in 3C polytype with transparent wavelength in visible and near-infrared range, (2) excellent material properties especially the chemical inertness and biocompatibility, and (3) device fabrication compatibility with standard Si device fabrication for manufacturing and on-chip integration. Therefore, SiC is a desirable material candidate for SPR sensors for chemical and biomedical sensing in aqueous medium, and approaches to enhance its sensitivity have been explored. 2-D materials such as graphene, TMDCs (MoS2, WS2, MoSe2, WSe2), etc. and their applications in sensing technology has aroused wide attention because of their distinctive electrical and optical properties. SPR sensors with 2-D and Si to enhance the sensitivity have been studied by publications. In this paper, we investigated graphene/Au/SiC waveguide-based SPR sensors (Fig. 1) for aqueous medium sensing. The resonance frequency shift with different numbers of graphene layer were studied (Fig. 2). Comparison of resonance wavelength shift from conventional and proposed sensor were performed (Fig. 3). At the incident light of 633 nm, the confinement factor above 0.9 can be achieved at the refractive index of n=1.3~1.5. With the change of refractive index, the shift of resonant wavelength showed linear characteristics, and a sensitivity of 2580 nm/RIU (refractive index unit) was obtained in a refractive index range of n=1.34~1.36 (Fig. 4).

Figure 1
Development of Materials and Electrochemical Diagnostics for Fuel Cell-Based Ethanol Sensors
Authors: Easton E. Bradley
Published: May 2020

The most common application of electrochemical ethanol sensors is in breathalyzer devices, which are widely used by law enforcement officers for roadside screening to combat impaired driving. These state-of-the-art breath alcohol sensors (BrAS) employ an electrochemical sensor based upon fuel cell technology. At the heart of the sensor is a membrane-electrode assembly (MEA) that employs a porous polyvinyl chloride (PVC) membrane filled with H2SO4 (aq). Each electrode contains massive amounts of Pt black catalyst (~10 - 20 mg/cm2) and a Teflon binder. The market for these devices is growing rapidly in large part due to the adoption of alcohol ignition interlocks for offenders and new OEM automotive safety requirements in some countries. As such, substantial cost reduction is needed to improve economic viability and OEM cost targets.

Despite its commercial success over the last 4 decades, electrochemical BrAS have been sparsely studied in the academic literature. Very little is known about how electrode structure influences sensor performance. Furthermore, environmental conditions are known to influence sensitivity and operational lifetime, yet the mode of degradation is not well understood. Since these devices closely mimic fuel cell technology from three-decades ago, our approach to BrAS has been to adapt materials and methods initially developed for power generating fuel cells. We have developed new MEA compositions employ 97% less Pt but can still achieve sensitivity that is on-par with current BrAS commercial technology.

In this presentation, I will describe how chemical modification of the electrocatalyst materials can yield enhanced sensitivity and/or stability. In particular, BrAS fabricated from carbon supported Pt and Pt-alloy catalysts will be discussed. Likewise, I will describe how the use of in situ electrochemical diagnostic measurements in working breathalyzer cells can be used to gain insight into how sensitivity and durability are related to electrode composition and water retention properties of the MEA.

Figure 1
Effects of Graphene As Conductive Additive on the Energy Capacity of Supercapacitors
Authors: Hung Wu-Ching , Sun Pei-Kai , Wang Ming-Jia , Chang Chin-Lung , Wang Li-Chun
Published: May 2020

The brilliant electrical, thermal, and mechanical properties of graphene have drawn many attentions, and their possible applications on electronic devices, composite materials, gas sensors, and energy storage are intensively explored. Among many energy storage devices, supercapacitors have the advantages of providing higher power density, faster charge/discharge rates, longer cycle life, environment-friendly, and little maintenance. Supercapacitors have become indispensable in hybrid, renewable and high-pulse power systems, showing great market potentials from car, rail, electricity, communication to military industries. Present studies show that the mesoporous structures giving a high surface-to-volume ratio in graphene allow more extensive charge separation in the electrolytes of supercapacitors, endowing themselves significantly higher energy and power density.

The presently available supercapacitors in market mostly utilize activated carbon in their electrodes, while this material frequently shows low electrical conductivity, which greatly limits the energy capacity of the device. This study aims to investigate the effects of graphene, if taken as a conductive additive, on the performance of the supercapacitor. The graphene-based electrode was packaged as a cylinder cell with dimension of 40 x 138 mm. The supercapacitor utilizing 0.1 wt% graphene/5.9 wt% carbon black as the conductive additive of its electrodes showed higher capacitance (1728 F) than that with 6 wt% carbon black (1525 F) during the galvanostatic charge/discharge test at a current density of 44.5 A; the former further showed lower ESR(equivalent series resistance) (1.96 mΩ) while the later 2.86 mΩ. These results suggest that graphene as conductive additive in supercapacitors can effectively enhance the energy storage of the devices.
Aqueous All-Polyoxometalate Redox-Flow-Batteries
Authors: Pfanschilling Felix Leon , Cording Faye , Mitchinson Jack Oliver , Friedl Jochen , Holland-Cunz Matthäa Verena , Schricker Barbara , Fleck Robert , Wolfschmidt Holger , Stimming Ulrich
Published: May 2020

Lithium-Ion Batteries (LIBs) are widely discussed and investigated as versatile energy storage systems. However, LIBs may pose safety risks, such as flammability of the electrodes and the electrolytes, which is a problem that may be amplified when transitioning from small-scale to medium- or large-scale energy storage. Yet, large-scale low-cost energy storage is crucial for the transition from a fossil fuel-based energy economy to renewable energy sources and in order to utilise the already existing energy sources like wind and solar power more efficiently.

A promising technology for this task are Redox-Flow-Batteries (RFBs). The RFB is the only type of battery where power output and energy capacity can be scaled independently, allowing it to be specifically tailored to a variety of applications. However, the most mature RFB so far, the All-Vanadium RFB, suffers from low energy density and low power density.

In order to overcome these challenges while maintaining the advantages of an aqueous RFB, like non-flammability and minimal self-discharge, we are investigating new redox chemistries. As redox systems, polyoxometalates (POMs) and specifically [SiW12O40]4- and [PV14O42]9- as nano-sized electron shuttles were investigated.1 These POMs exhibit fast redox kinetics (electron transfer constant k
0 ≈ 10-2 cm s-1 for [SiW12O40]4-) which together with their high solubility in water and multiple redox-centres per molecule provides the potential for for high power densities and high energy densities. The POMs that were used also exhibit high electrochemical and chemical stability, thus providing long cycle lifetimes. Other POMs were investigated as well.

The system was scaled up from a lab-sized cell of 25 cm2 membrane area to a cell of 1400 cm2 in order to assess the implications on efficiency and operational parameters.2 The cell was operated for 1400 cycles over a time of nearly three months, providing some very promising results; the Coulombic efficiency was nearly 100% with the energy efficiency dropping only from 86.1% to 85.1% during the whole period, indicating a highly stable system. The observed capacity loss of 0.011% per cycle could be attributed to ambient air leakage leading to oxidation of SiW12. Post-cycling analysis showed no sign of degradation of the electrolytes.

Acknowledgement

We acknowledge funding and the fruitful cooperation with SIEMENS AG. Also, funding from NECEM, the North East Centre for Energy Materials (EP/R021503/10) is thankfully acknowledged.
Sulfur Grafted Hollow Carbon Spheres for Potassium Ion Battery Anodes
Authors: Mitlin David
Published: May 2020

Sulfur-rich carbons are minimally explored for potassium ion batteries (KIBs). Here, we chemically incorporate a large amount of S (38 wt. %) into a carbon host, creating Sulfur-grafted Hollow Carbon Spheres (SHCS) for KIB anodes. The SHCS architecture provides a combination of nanoscale (ca. 40 nm) diffusion distances and C-S chemical bonding to minimize cycling capacity decay and Coulombic efficiency (CE) loss. SHCS exhibits a reversible capacity of 581 mAh g-1 (at 0.025 A g-1), which is the highest reversible capacity reported for any carbon-based KIB anode. Electrochemical analysis of S-free carbon spheres baseline demonstrates that both the carbon matrix and the sulfur species are highly electrochemically active. SHCS also shows excellent rate capability, achieving 202, 160 and 110 mAh g-1 at 1.5, 3 and 5 A g-1, respectively. The electrode maintained 93% of the capacity from the 5th to 1000th cycle at 3 A g-1, with steady-state CE being near 100%. Raman analysis indicates reversible breakage of C-S and S-S bonds upon potassiation to 0.01 V vs. K/K+. GITT analysis provides voltage - dependent K+ diffusion coefficients that range 10-10 to 10-12 cm2 s-1 upon potassiation and depotassiation, with approximately five times higher coefficient for the former.
The Effect of Organic Carbon Source on Performance of Liti(PO4)3/C Composite Electrodes in Aqueous Solutions
Authors: Wen Yuehua , Zhao Pengcheng
Published: May 2020

The spherical LiTi(PO4)3/C composites were prepared through spray drying method followed high-temperature calcination and used as anodes for aqueous lithium ion batteries. The effect of different organic carbon source based on different coating mechanisms and carbon content on the electrochemical properties of LiTi(PO4)3/C composite anodes were investigated. Results show that the amount of carbon coating is too low to prevent water from eroding. In contrast, if the amount of carbon coating is too high, the resistance of lithium ion diffusion will be high; the optimal carbon coating amount of LiTi2(PO4)3/C electrodes is 13%. The uniformity of carbon coating and the thickness of coating layer are the two main factors affecting the performance of coated electrodes. The coating mechanism has critical influence on the uniformity of carbon coating. The most uniform carbon coating was obtained by using polydopamine as the carbon source, followed by using the organic macromolecule, glucose as the carbon source. Polyacrylonitrile containing both carbon and nitrogen exhibits no special effect of nitrogen doping. (The two main factors affecting the performance of the carbon coated electrode are the uniformity and the thickness of the carbon layer.) The best performance is achieved by LiTi2(PO4)3/C anodes with the carbon amount of 13% prepared by using polydopamine as the carbon source. But, from a viewpoint of mass production and scale-up, it is more suitable to use low-cost and water-soluble glucose as carbon source.
PQQ-Glucose Dehydrogenase-Calmodulin Chimera Enzyme: Different Triggered Activation for Multipurpose Biosensors
Authors: Bollella Paolo , Melman Artem , Guo Zhong , Edwardraja Selvakumar , Johnson Wayne , Alexandrov Kirill A. , Katz Evgeny
Published: May 2020

In the last decade, the rise of synthetic biology has driven the efforts to construct artificial allosteric protein switches in order to detected and quantify natural and artificial chemistries in vitro and in vivo. Typically, this involves construction of chimeric enzymes via insertion of a regulatory receptor domain into the biocatalytic reporter domain. Construction of such chimeric enzymes utilizes the recombinant DNA technology that is a core technology of protein engineering [1].

Herein, we report on the bioelectrocatalytic properties of pyrroloquinoline quinone-dependent glucose dehydrogenase fusion with calmodulin (PQQ-GDH-CaM). This protein is catalytically inactive in its ground form but can be activated by the addition of calmodulin binding peptide that induces its conformational transition and activation. The PQQ-GDH-CaM was immobilized onto highly porous gold (hPG) produced electrochemically [2] by using a bifunctional linker, namely 4-mercaptobenzoic acid further activated through 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide (EDC/NHS) coupling to covalent bind the PQQ-GDH-CaM chimeric enzyme [3].

At first, we characterized the switchable features of PQQ-GDH-CaM by simply exposing it to the activating peptide. Subsequently we devised an approach to use proteolytic activation of a caged-peptide to generate activating peptide for PQQ-GDH-CaM. Furthermore, the system was utilized to study different pathways for PQQ-GDH-CaM triggered activation according to different logic gates in order to realize multipurpose biosensors (e.g., glucose detection, peptide detection etc.) [4].

References

Gamella, M., Guo, Z., Alexandrov, K., Katz, E. (2019). ChemElectroChem, 6(3), 638-645.

Bollella, P., Hibino, Y., Kano, K., Gorton, L., Antiochia, R. (2018). Analytical chemistry, 90(20), 12131-12136.

Koushanpour, A., Gamella, M., Guo, Z., Honarvarfard, E., Poghossian, A., Schöning, M. J., Alexandrov, K., Katz, E. (2017). The Journal of Physical Chemistry B, 121(51), 11465-11471.

Bollella, P., Katz, E. (2019). International Journal of Unconventional Computing, 14(3-4), 181-198.
Isoelectric Focusing in Liquid Plasticine for Protein Analysis
Authors: Niu Jicheng , Shi Haixiao , Xu Feng , Li Xiaoguang , Li Fei
Published: May 2020

Protein analysis has found widespread applications in biomedical fields (e.g., disease diagnosis and precision medicine), especially recently in point-of-care testing (POCT). Conventional protein analysis is large-equipment-dependent, which limits its applications in POCT. Herein, we proposed a strategy using a shaped liquid entity, termed liquid plasticine (LP), as a platform to perform isoelectric focusing (IEF)-based protein analysis. The LP-IEF system mainly consisted of a separation channel, a catholyte module and an anolyte module, which were all in the form of self-standing liquid micro-containers with specific shapes and connected together. The basic functions of the LP-IEF system were examined using three standard proteins, with the results showing a clear separation, 10-folds concentration, and a resolution of 0.03 pH, meaning that this system could serve for pretreatment and analysis of proteins from complex physiological samples. The developed LP-IEF system was further demonstrated as a colorimetric quantitative analytical platform of clinical microalbuminuria with a relative error of <9.4% compared to the results obtained by the traditional clinical detection methods. Moreover, the LP-IEF system was coupled to MALDI-TOF-MS and successfully used to identify a-1-microglobulin/bikunin precursor (AMBP) in clinical diabetic urines. The LP-IEF system proposed in this work opens a flexible, versatile, and low-cost way for POCT of proteins, which could inspire many practical applications in future.

References

[1] J. C. Niu, T. Zhou, L. L. Niu, Z. S. Xie, F. Fang, F. Q. Yang, Z. Y. Wu, Simultaneous Pre-concentration and Separation on Simple Paper-based Analytical Device for Protein Analysis, Analytical and bioanalytical chemistry 410.6 (2018): 1689-1695. Doi:10.1007/s00216-017-0809-5.

[2] X. G. Li, H. X. Shi, Y. Y. Hu, Rod-shaped Liquid Plasticine for Gas Diffusion Detection, Soft matter, 15(15), 3085-3088. Doi:10.1039/c9sm00362b.
Fluorescence Turn-on and Wavelength-Shift Dual Response for Methylamine Gas Sensing Using HPbBr3/PbBr2@SiO2 Nanospheres
Authors: Huang Yipeng , Chen Xi
Published: May 2020

The defect-tolerant nature of lead halide perovskites renders high PLQYs by simply confining them in nanopores. In view of this character, a fluorescence turn-on and wavelength-shift dual responsive methylamine (MA) gas sensor is achieved using HPbBr3/PbBr2@SiO2 nanospheres (NSs). In this composite, the hydrophobic silica shell not only provides mesopores for the penetration of MA gas, but enhances the moisture stability of the MAPbBr3 perovskite nanocrystals generated after reacted with MA gas, improving the sensing performance. When exposed to the MA gas, the fluorescence is rapidly turned on due to the formation of MAPbBr3 perovskite nanocrystals. The enhanced photoluminescence is linearly with the MA concentration in the range of 0.08 – 6.3 μM with a LOD of 3.1 nM (S/N = 3). In addition, the photoluminescence peak is consistently red-shift from 478.7 nm to 510.6 nm when the MA concentration is increased from 0.083 to 6.3 µM. Correspondingly, the emission color is changed from weak blue to cyan, and to bright green, which imparts the potential for colorimetric sensing. By combining the turn-on and wavelength-guide sensing modes, this MA sensor is more flexible and the result is more reliable.

Figure 1
Chemical Sensor Based on Molecularly Imprinted Organic-Organic Nanocomposite Film for the Analysis of Melamine in Infant Formula
Authors: Regasa Melkamu Biyana
Published: May 2020

Melamine (MA) is non-edible synthetic chemical intentionally added to foodstuffs such as milk and milk products including infant formula as the fake source of protein. Many evidences confirmed that this molecule is primarily responsible for kidney failure by forming kidney stones and then blocking the renal tubes. Therefore, a simple, sensitive and rapid method for online quantification of MA can avoid the consumption of milk products contaminated with MA and possible health risks resulted both socially and economically. The present work reports the development of a chemical sensor from aniline (ANI) and acrylic acid (AA) copolymer films by using concurrent electrochemical polymerization method using MA as a template. After optimization of important parameters and template removal, the performance of the film formed was studied by cyclic and differential pulse voltammetry. The proposed sensor showed a linear current response with various concentrations of MA. The linear range, limit of quantification and limit of detection were 0.1-200 x10-9 M, 5.73x10-11M, 1.72 x10-11M respectively. The sensitivity and selectivity of the sensor achieved may attribute to the synergistic effect of different functional units found on the polymer composite. These functional units competitively bind the template with non-covalent interactions. The sensor was also applied to analyze milk samples and obtained a recovery of 95.87-105.63% with RSD 1.11-2.23%. The good stability and reusability as well as strong affinity to the imprint molecule make the imprinted copolymers the promising functional materials for future sensor development.
Fabrication of Pd/ Ni Alloy Nanotubes Via Electrospinning for High Performance Hydrogen Detection
Authors: Song Lu , Bulemo Peresi Majura , Koo Won-Tae , Kim Il Doo
Published: May 2020

Hydrogen is one of the most important “next generation energy sources”, which is free for environment pollution, with water as the only emission. Due to the danger of hydrogen explosion when mixed with air, as well as the low specific heat capacity of hydrogen, the temperature required for combustion can be reached immediately even a little heat absorbed. Therefore, it’s necessary to search an effective way to monitor hydrogen leakage at room temperature.

In this study, the Pd based hydrogen sensor was investigated. During the transduction process, volumetric expansion occurred due to the hydrogen absorption at room temperature to achieve safe hydrogen detection. Previous research indicated that Pd/Ni alloy films/ nanofibers can achieve higher catalytic activity, stability and sensitivity than pure Pd films/nanofibers due to the synergistic effect between Pd and Ni
1

,2,3
. But both the films and nanofibers structures have limited specific surface area and therefore limited exposed hydrogen adsorption sites. To overcome these problems, we fabricated the porous Pd nanotubes alloyed with Ni by using Polyvinylpyrrolidone (PVP) and SiO2 templates electrospinning route, then the PVP and SiO2 templates were selectively removed by calcination and etching
4
, respectively. The sensing performance was measured by monitoring the resistance curves of sensing platform at various hydrogen concentrations. Compared to Pd/Ni nanofibers structures, tubular structures achieved lower LOD and higher sensitivity which are attributed to the high surface area and abundant hydrogen adsorption active sites. High performance Pd/Ni nanotubes can be successfully fabricated in an effective and facile approach for hydrogen detection at room temperature. At last, the effects of the concentration of Ni in Pd on the sensing performance was also investigated.

References

1. Guangyang Bao et al, “Synergistic effect of the Pd–Ni bimetal/carbon nanofiber composite catalyst in Suzuki coupling reaction.” Org. Chem. Front., 2019, 6,352.

2. Wang, Boyi et al. “Palladium Nanofiber Networks Hydrogen Sensor and Hydrogen-Actuated Switches: Proceedings of the 5th International Conference on Sustainable Design and Manufacturing (KES-SDM-18).” 10.1007/978-3-030-04290-5_12.

3. Feng, Li et al. “Pd–Ni Alloy Nanoparticles as Effective Catalysts for Miyaura–Heck Coupling Reactions.” The Journal of Physical Chemistry C 2015 119 (21), 11511-11515 DOI: 10.1021/jp510988m

4. Peresi Majura Bulemo et al, “Mesoporous SnO2 Nanotubes via Electrospinning−Etching Route:Highly Sensitive and Selective Detection of H2S Molecule.” October 17, 2019 at 10:40:01 (UTC).
Sensing Interfaces for Bioelectrocatalytic Stimulated Release
Authors: Masi Madeline , Bollella Paolo , Katz Evgeny
Published: May 2020

Signal-stimulated (bio)molecular release has been extensively studied and reported in numerous research papers, reviews and books,1 being motivated by various biomedical and biotechnological applications. Among many other molecular, biomolecular and nano-size species, DNA molecules have been studied for the signal-controlled release, being highly important for gene delivery therapy, biosensors, biochips, unconventional biocomputing, and for many other applications. Various signals triggering DNA release have been used including application of altering electromagnetic field, photochemical capture and release of DNA, thermally stimulated release of DNA, etc. Electrochemically triggered DNA release is particularly attractive due to its simple realization and versatility. Specifically, these developed systems are designed for different release processes triggered by various signals (electrical, biomolecular, illumination, etc.), thus representing a general interfacial platform for controlled release of different biomolecules and nano-size species.2

Herein, we report on the DNA releasing system controlled by local/interfacial pH changes triggered by a very small potential applied to reduce oxygen bioelectrocatalytically with the help of immobilized bilirubin oxidase (Box). Notably, the DNA release was only a convenient model, while the developed approach can be adapted to the electrically stimulated release of any negatively charged (bio)molecules or nano-species.3

1. Li, X.; Jasti, B. R. Design of Controlled Release Drug Delivery Systems, McGraw-Hill Education, New York, 2005.

2. Masi, M.; Bollella, P.; Katz, E. Electroanalysis
2019, 31, in press, published on-line (DOI: 10.1002/elan.201900377).

3. Masi, M.; Bollella, P.; Katz, E. ACS Applied Materials and Interfaces
2019, Submitted.
Lysozyme Aggregation Monitoring By Single-Particle Collision Electrochemistry
Authors: Kirk Kevin , Vasilescu Alina , Andreescu Daniel , Andreescu Silvana
Published: May 2020

Fundamental knowledge about protein aggregation is critical for the understanding of many neurodegenerative diseases. Protein aggregation can be difficult to comprehensively study by traditional characterization techniques which may require sample pretreatment and alter the native state of the samples being studied. There is a great need for native state "in solution" measurements of protein monitoring in the biomedical field. We have utilized single-particle collision electrochemistry (SPCE) for the early tracking of lysozyme (Lyz) aggregation states by electrochemically analyzing lysozyme modified silver nanoparticle (Lyz-AgNPs) and their oxidation currents. When the modified nanoparticles collide with a microelectrode at a high enough potential, they can be oxidized at the surface of the electrode. Information can be extrapolated from the electrochemical data and help aid in the determination of particle stability and coverage. Our electrochemical determination method was compared to other measurements from UV-Vis spectroscopy, circular dichroism (CD) and atomic force microscopy (AFM) to validate our findings and determine the strutural changes of lysozyme protein on the surface of silver nanoparticles. This work demonstrates that this electrochemical technique could potentially be used to screen protein samples for formation of aggregates.
Near-Infrared Imaging of Serotonin Release from Cells with Fluorescent Nanosensors
Authors: Dinarvand Meshkat , Neubert Elsa , Meyer Daniel , Selvaggio Gabriele , Mann Florian , Erpenbeck Luise , Kruss Sebastian
Published: May 2020

Serotonin is an important neurotransmitter involved in various functions of the nervous, blood, and immune system. In general, detection of small biomolecules such as serotonin in real time with high spatial and temporal resolution remains challenging with conventional sensors and methods. In this work, we designed a near-infrared (nIR) fluorescent nanosensor (NIRSer) based on fluorescent single-walled carbon nanotubes (SWCNTs) to image the release of serotonin from human blood platelets in real time. The nanosensor consists of a nonbleaching SWCNT backbone, which is fluorescent in the beneficial nIR tissue transparency window (800–1700 nm) and a serotonin binding DNA aptamer. The fluorescence of the NIRSer sensor (995 nm emission wavelength for (6,5)-SWCNTs) increases in response to serotonin by a factor up to 1.8. It detects serotonin reversibly with a dissociation constant of 301 nM ± 138 nM and a dynamic linear range in the physiologically relevant region from 100 nM to 1 μM. As a proof of principle, we detected serotonin release patterns from activated platelets on the single-cell level. Imaging of the nanosensors around and under the platelets enabled us to locate hot spots of serotonin release and quantify the time delay (21–30 s) between stimulation and release in a population of platelets, highlighting the spatiotemporal resolution of this nanosensor approach. In summary, we report a nIR fluorescent nanosensor for the neurotransmitter serotonin and show its potential for imaging of chemical communication between cells.
(Invited) Switching on Elctrocatalytic Activity for Synthetic Fuel Production
Authors: Irvine John
Published: May 2020

The greatest challenge facing Solid oxide cells (SOC), in both fuel and electrolysis cell modes (i.e SOFCs and SOECs) is to deliver high, long-lasting electrocatalytic activity while ensuring cost and time-efficient electrode manufacture. Ultimately, this can best be achieved by growing appropriate nanoarchitectures under operationally relevant conditions, rather than through intricate ex situ procedures.

In our approach, metal particles are grown directly from the oxide support though in situ redox exsolution. We demonstrated that by understanding and manipulating the surface chemistry of an oxide support with adequately designed bulk (non)stoichiometry, one can control the size, distribution and surface coverage of produced particles. We also revealed that the emergent particles are generally epitaxially socketed in the parent perovskite which appears to be the underlying origin of their remarkable stability, including unique resistance of metal particles to agglomeration and to hydrocarbon coking, whilst retaining catalytic activit.

Operando redox treatments yield emergent nanomaterials at potentials in excess of 2V. Here we apply this technique to drive steam, CO2 and coelectrolysis processes at emergent metals and alloy particles.
High-Temperature Co-Electrolysis
Authors: de Haart L.G.J. , Dittrich L. , Jaekel E. E. , Nohl M. , Foit S. R. , Vinke I. C. , Eichel R.-a.
Published: May 2020

High-temperature Solid Oxide Electrolysis Cells (SOECs) possess the unique property to convert carbon dioxide and/or steam with a faradaic efficiency of 1 into carbon monoxide and/or hydrogen, respectively. High-temperature co-electrolysis of steam and carbon dioxide offers a suitable technology to provide 'white' syngas. Syngas, a mixture of hydrogen and carbon monoxide, as well as pure carbon monoxide are used in chemical industry for the synthesis of many basic chemicals as well as synfuels. Using renewable energy sources and the climate gas CO2 the high-temperature CO2 and co-electrolysis technology presents a sustainable alternative to conventional processes. The technology of co-electrolysis allows the adjustment of the H2 to CO ratio required for various down-stream catalytic processes in one step.

Investigations of the high-temperature electrolysis of steam or CO2 and the co-electrolysis of a mixture of both in the feed gas were performed on so-called fuel electrode supported cells consisting of a 8mol% yttria stabilized zirconia (8YSZ) electrolyte, a Ni/8YSZ support and fuel electrode and a (La,Sr)(Co,Fe)O3 air electrode. The experiments showed that the performance of the cell during CO2 electrolysis is lower than for steam and co-electrolysis, as is shown in the Figure. The performance can be characterized by the slope of the current-voltage curve, i.e. the area specific resistance (ASR). For the CO2 electrolysis the ASR at 900 °C and 1.5 A·cm-2 amounts to 410 mΩ·cm-2. For steam and co-electrolysis, the ASR values are nearly the same: 245 mΩ·cm-2. The lower performance for CO2 electrolysis is attributed to the slower kinetics of the CO2 reduction reaction compared to the H2O reduction reaction. Similar observations were made in fuel cell operation, in which the CO oxidation reaction is around a factor 5 slower than the H2 oxidation reaction. The similar ASR values for steam and co-electrolysis are attributed to the occurrence of the reverse water gas shift (RWGS) reaction, in which CO2 and H2 react to CO and H2O during co-electrolysis. The slower kinetics of the CO2 reduction reaction are by-passed in the RWGS reaction using the hydrogen generated through the steam reduction.

Further experiments were conducted to investigate the role and importance of the RWGS reaction during co-electrolysis. At the boundary to pure CO2 electrolysis, the performance of feed gas mixtures with low steam contents were investigated. First results show a significant increase of the area specific resistance at a reduced (RWGS) equilibrium steam concentration of about 5 %. Above 15 % steam in the feed gas (in the RWGS equilibrium) the ASR is no longer influenced by the feed gas composition and similar to that of pure steam electrolysis. Experimental results are furthermore compared to theoretical calculations of syngas production on a thermodynamic and partially kinetic level.

Figure 1
Effect of Carbon Capture Endurance Conditions on Performance and Stability of Molten Carbonate Fuel Cell Cathode Electrode
Authors: Hilmi Abdelkader , Geary Timothy C , Franco Adam , Rosen Jonathan , Barckholtz Tim
Published: May 2020

Introduction

The molten carbonate fuel cell (MCFC) is one of the most advanced high-temperature and clean power generating devices. To date >8 billion kWh of electricity has been produced commercially using this new technology. The high operating temperature of MCFC (550-650 °C) dramatically improves the reaction kinetics and eliminates the need for a noble metal catalyst. The electrochemical reactions taking place during cell operation involve the CO2 transfer from cathode to anode in the form of carbonate ions (Figure 1). Therefore, MCFC stack technology can be used for power generation and simultaneously, as an effective CO2 separator. MCFC systems can be combined with conventional combustion-powered generators (coal and/or natural gas based power plants) to efficiently separate CO2 in the exhaust gas and produce additional electricity.

The state of the art MCFC cathode is porous lithiated nickel oxide. The cathode stability and performance are affected by several factors such as gas composition, temperature, electrode structure and electrolyte chemistry. To ensure long-term performance and material stability against NiO dissolution, polarization loss, and carbon capture efficiency, major considerations need to be taken into account in material selection, operating conditions, and electrode structure design.

FCE has tested many single cells (250 cm2) and technology stacks (30 kW) under carbon capture operating conditions (4-5% CO2 in the cathode inlet as opposed to >15% in baseline MCFC systems) to understand parameters affecting performance, life, and to investigate design solutions for further enhancement. Figure 2 highlights the effect of CO2 concentration on the cathode lithiation. These measurements were conducted using an out-of-cell test (OCT) where cathode samples were exposed to different oxidizing environments. It appears that lean-CO2 gas atmospheres (<5%CO2) lead to increased lithium content in the NiO cathode. This may impact the electrolyte distribution and the cathode microstructure. Therefore, the electrolyte inventory (fill level), the lithium content and the basicity need to be considered to achieving optimal operating conditions.

This paper will review the cathode material stability, microstructure, and durability under long-term carbon-capture operations. The effect of parameters such as electrolyte fill, gas composition, and electrolyte chemistry, as well as approaches to enhance the CO2 capture efficiency and life, will be discussed.

Figure 1
(Invited) Controlling the Size and Dispersion of Exsolved Catalyst Particles By Electrochemistry and By Strain
Authors: Yildiz Bilge , Dimitrakopoulos Georgios , Wang Jiayue , Fan Weiwei , Kyriakou Vasileios , Ghoniem Ahmed F. , Li Ju
Published: May 2020

Increasing the performance of Solid Oxide Electrolysis Cells (SOECs) for the production of hydrogen (H2) from water (H2O) splitting requires the use of cathodes with low polarization resistance. In-situ growth of metal catalysts from perovskite oxides (termed catalyst exsolution) has been proposed as a means to decorate the porous electrode with highly dispersed, nanometer-sized catalytic particles [1-3]. These particles are highly active towards reactions of interest and show increased resistance to agglomeration due to their socketed nature [4].

In this work, we investigate the in-situ, on demand exsolution of catalysts by using fuel and electrochemistry as a means to decrease the temperature and duration required to grow catalytic particles on the surface of electrodes. We study the performance, stability, particle morphology and distribution as a function of electrochemical polarization applied at the electrode. Substantial improvement of reaction kinetics is found, consistent with previous reports [5]. In addition, we probe the effect of electrochemical and temperature conditions on the particle size, shape and distribution. In addition, we propose tuning the reducibility of parent oxides to be a good strategy in controlling the size and dispersion of the exsolved particles, and demonstrate this approach on epitaxial perovskite thin films. Moreover, our observations suggest oxygen vacancies to be the potential nucleation sites of the exsolved particles.

The present study provides a new direction towards the generation of nanoparticle-size catalysts on the surface of perovskite oxides given the increasing demand for active and durable catalysts in the field of solid oxide cells and in other energy and fuels conversion processes.

References:

[1] G. Tsekouras et. al. Energy Environ. Sci., 2013, 6, 256–266

[2] Y. Sun et. al. J. Mater. Chem. A, 2015, 3, 11048–11056

[3] G. Dimitrakopoulos et. al. Sustainable Energy & Fuels 2019, 3, 2347-2355

[4] D. Neagu et. al. Nature Communications 8:1855 (2017)

[5] J. Myung et. al. Nature 537 (2016) 528-531