bluuebunny/crossref_metadata_2025_split huggingface dataset:
Leveraging Nanoscale Phenomena in Electrochemically Dealloyed Nanoporous Gold for Gas Sensing
Authors: Wong Timothy , Newman Roger C. 
Published: February 2020

As the chemical environment grows more complex in research and industrial settings, there is an increasing demand for robust and flexible sensors for volatile chemicals. Nanomaterials are a promising new frontier of investigation to tackle these challenges. While the praise of nanosensors often focuses on their high surface area, the ability to exploit nanoscale phenomena for transduction opens up exciting possibilities. The drawback of many nanoscale sensing platforms is challenging fabrication. In this work, we utilize a simple but highly controllable electrochemical method to form nanoporous gold, as well as its Pt alloy derivatives with even finer pore sizes. Rather than applying nanoporous gold to a conventional aqueous electrochemical sensor, we leveraged unique nanoscale phenomena to apply nanoporous gold as the first reported multi-variate gas sensor.
Electronic conduction in nanoporous networks is fundamentally different from bulk metallic conduction. While conduction in bulk systems is limited by phonon scattering, electrons in nanoporous gold scatter off surfaces before they encounter a phonon. This behavior is strongly modulated by chemicals adsorbed to the surface. Since the quantity adsorbed on the surface depends on the equilibrium with the gas concentration, one can use changes in resistance to sense the gas concentration. We have demonstrated this detection principle for several model volatile chemicals (water, acetone, ethanol).
By monitoring both the in phase and out of phase electrical response, we also observed changes in the capacitive behavior. These capacitive changes were driven by pore filling. Condensed liquid within the pores allows for the formation of an electric double layer. This condensation occurs far below the typical saturation pressure due to the confined curvature of nanopores. By combining such data with changes in electrical resistance, we demonstrate robust and selective gas sensing.
In this work we demonstrate that a single multi-variate nanoporous gold gas sensor can detect multiple compounds (water, acetone, ethanol). We also measure sensor characteristics: sensitivity, delay, and hysteresis. These results show the potential for the application of nanoporous gold as a versatile and selective volatile chemical sensor.

Figure 1
Solid-Contact Ion-Selective Electrodes Comprising Hydrophobic Redox Buffers
Authors: Rousseau Celeste R , Buhlmann Philippe 
Published: February 2020

A calibration-free measurement with an ionophore-doped polymeric membrane ion-selective electrode requires that the phase boundary potential at the sample/sensing membrane interface is controlled by the activity of the target ion in the sample of interest, while all other phase boundary potentials in the electrochemical cell are constant and long term stable. Historically, the biggest difficulty lies in establishing a reproducible phase boundary potential at the interface of the sensing membrane and the underlying electron conductor. Efforts over several decades to use conducting polymers as an interlayer between the ion-selective membrane and an underlying electron conductor, such as a metal or carbon, have had limited success. While the performance of such devices has been much improved in terms of light sensitivity and hydrophobicity of the conducting polymer layer, devices that can be considered calibration-free are still elusive. To that end, hydrophobic redox buffers have been introduced as an alternative to conducting polymers. While hydrophilic redox buffers play central roles in all living organisms, control many geological and environmental processes, and are often utilized in the laboratory, buffering of redox potentials in hydrophobic media is a topic that has in the past been overlooked. This presentation will address principles for the use of hydrophobic redox buffers, and it will discuss recent examples of hydrophobic redox buffers suitable for the fabrication of ion-selective electrode membranes that are calibration-free.
(1) Redox Buffer Capacity of Ion-Selective Electrode Solid Contacts Doped with Organometallic Complexes, Zhen, X. V.; Rousseau, C. R.; Buhlmann, P. Anal. Chem.,
2018, 90, 11000-11007.
(2) Paper-Based All-Solid-State Ion-Sensing Platform with a Solid Contact Comprising Colloid-Imprinted Mesoporous Carbon and a Redox Buffer, Hu, J.; Zhao, W.; Bühlmann, P.; Stein, A., ACS Appl. Nano Mat.
2018, 1, 293–301.
Development of a 3D-Printed Force Sensor with Carbon Paste
Authors: Rubiano Alejandro , Shamkhalichenar Hamed , Choi Jin-Woo 
Published: February 2020

Force sensors play an important role in the biomedical devices industry, especially in motion- and pressure-related devices. Such sensors are designed to collect force or pressure data by converting it into electrical signals. The data can then be sent to and analyzed by a local or cloud-based processing unit. It is vital that the sensors can be fabricated in a way that time efficiency, cost efficiency, and quality are all maximized. The advent of three-dimensional (3D) printing has greatly facilitated prototyping and customized manufacturing, as compared to older crafting methods (such as welding and woodworking), 3D printing requires less skill and involves less costly materials making it much more time- and cost-efficient. Technological advancements have also improved the quality of the actual sensing materials used in sensor-based devices, and notably, carbon-based materials have become increasingly favored for use as sensing elements. In the presented sensor, the modern sensor fabrication methods of 3D printing and using carbon materials as sensing elements are combined.
The sensor presented as a proof of the above concepts is a cantilever flex sensor. The sensor consists of a 30 mm-long cantilever extending from a 2.5 mm-thick wall, with a second wall of the same thickness parallel to the cantilever. After designing this structure and printing it using a 3D printer, the top surface of the cantilever was coated with a thin layer of conductive carbon paste and two copper wires were stripped and soldered to a pair of copper alligator clips, to be used for testing purposes. To test the sensor, the two copper wires were clipped onto the sensor (Figure 1A) and each wire was connected to a multimeter probe on the end opposite of the alligator clip. Then, using a set of four through holes in the parallel wall (along with a slotted rod), the tip of the cantilever was pressed down to an angle of 5, 10, 15, or 20 degrees (Figures 1B, 1C, 1D, and 1E, respectively) below the original plane of the cantilever and held there for 2 minutes. The resistance between the ends of the cantilever was measured throughout each trial by the multimeter, and the results (Figure 1F) for each angle were compiled and analyzed to determine the effect of each depression angle on impedance change, and thus, the overall effectiveness of the sensor. In the future, a notable improvement would be miniaturizing the sensor to facilitate in integration of the sensor in wearable and biomedical devices.

Figure 1
Peltier-Driven Temperature Control for Fluorescent Sensing Platform
Authors: Robertson Brianna , Shin Young-Ho , Choi Jin-Woo 
Published: February 2020

Fluorescence dyes are widely used in biomolecule detection/quantification, flow tracing reference for gases and liquids, pathogen detection, and other life science applications. However, fluorescence emission efficiency of the dyes is easily affected by several parameters, such as polarity, pH, and temperature. Therefore, it is essential to monitor and control these parameters for reliable and accurate measurements. We propose a 3D-printed copper cuvette holder (i.materialise, Belgium) joined with a Peltier-based temperature controller platform for stable reading of fluorescence emission from the dye. For demonstration of temperature effects on fluorescence efficiency, rhodamine B, which is one of the widely used fluorescence standards and probes in bioscience, was used.
For excitation, 530 nm wavelength lighting was utilized for stimulating the rhodamine B. A Peltier device was controlled with different levels of direct current (DC) to demonstrate the temperature controlling capability of the device and fluorescence efficiency of the rhodamine B was tested with a varying temperature level: 20 ºC to 80 ºC. For our device, the temperature will be monitored by temperature ICs that are attached at three different points of the copper body for uniform temperature heating of the solution in a cuvette. We have monitored the temperature distribution of the copper holder with an external temperature monitor, the DT304, and determined that the temperature is maintained to with a 5 ºC. We plan to monitor the solution temperature directly with the use of an infrared temperature sensor positioned down at the opening of the cuvette. The ambient temperature and the temperature of the opposite junction of the Peltier device will be monitored through the use of two thermocouples. An analysis of several different temperature components of the device allow for a better interpretation of what is happening in the system. Moreover, the implementation of a water-cooling apparatus will allow for a way to quickly decrease the temperature of the cuvette when desirable. These features allow for the sample to be monitored efficiently, allowing for proper stabilization techniques and the ability to fluctuate the temperature when required of an application.
In summary, we have developed an 3D-printed copper cuvette holder with a Peltier-based temperature controller platform for stable reading of fluorescence emission from the dye or fluorophore solution. Our compact temperature controller system provides viable option for any fluorometers to easily apply it for temperature stabilization during the fluorescence dye testing.

Figure 1
Biosensor for Detection of Methicillin-Resistant Staphylococcus Aureus
Authors: Patel Dhara , Zhou Yan , Ramasamy Ramaraja P. 
Published: February 2020

Bacterial pathogens are ubiquitous in nature and are important targets for detection in various applications. In the healthcare industry, Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterial pathogen that is resistant to many antibiotics. MRSA, if not treated promptly, can cause severe complications such as bloodstream infections, pneumonia, and surgical site infections leading to sepsis and eventual death [1]. Current conventional detection methods for pathogens usually take a few hours to days for identification and need skilled experts and tools such as cefoxitin disk screen tests, latex agglutination tests, and real-time PCR for analyses [2]. Biosensors, on the other hand, are simple, easy to use, and provide rapid results as well as aid in real-time monitoring. Specifically, electrochemical biosensors are advantageous over conventional methods with their ease of use, high specificity and sensitivity [3]. In the current work, a carbon nanotube-based impedimetric biosensor was developed for rapid and selective detection of live MRSA cells [4]. MRSA USA300 specific phage SATA-8505 was used as the recognition element for selective detection of its host bacteria cells. The detection mechanism uses an impedimetric measurement of the resistance changes on an electrode, where bacteriophages were immobilized onto functionalized carbon nanotube using an electric field-induced, charge-directed orientation strategy. Infectivity study using disk diffusion methods showed activity retention of immobilized bacteriophages on the electrodes. The established biosensor showed high selectivity toward MRSA USA300. The biosensor could potentially be integrated into lab-on-a-chip platforms for point of care use and for other health-care associated pathogens, such as Pseudomonas aeruginosa and Klebsiella pneumoniae.

References
1. Klevens, R.M.; Morrison, M.A.; Nadle, J.; Petit, S.; Gershman, K.; Ray, S.; Harrison, L.H.; Lynfield, R.; Dumyati, G.; Townes, J.M.; et al. Invasive Methicillin-resistant Staphylococcus aureus Infections in the United States. J. Am. Med. Assoc. 2007, 298, 1763–1771.
2. Datta, P.; Gulati, N.; Singla, N.; Vasdeva, H. R.; Bala, K.; Chander, J.; Gupta, V. Evaluation of Various Methods for the Detection of Methicillin-resistant Staphylococcus aureus Strains and Susceptibility Patterns J. Med. Microbiology. 2011, 60, 1613-1616.
3. Maalouf, R.; Fournier-Wirth, C.; Coste, J.; Chebib, H.; Saikali, Y.; Vittori, O.; Errachid, A.; Cloarec, J.-P.; Martelet, C.; Jaffrezic-Renault, N. Label-Free Detection of Bacteria by Electrochemical Impedance Spectroscopy: Comparison to Surface Plasmon Resonance Anal. Chem. (Washington, DC, U. S.) 2007, 79, 4879−4886.
4. Zhou, Y.; Marar, A.; Kner, P.; Ramasamy, R.; Charge-Directed Immobilization of Bacteriophage on Nanostructured Electrode for Whole-Cell Electrochemical Biosensors Anal. Chem. 2017, 89, 11, 5734-5741.
Multiscale Roughness Characterization of Electropolished 316L ALM Steel By Power Spectral Density Post-Treatment
Authors: Drynski Estelle , Doche Marie-Laure , Hihn Jean-Yves , Tardelli Joffrey 
Published: February 2020

Electrolytic polishing (EP) is a well-known technology which may replace mechanical polishing in finishing treatment of complex geometry substrates produced by additive manufacturing (AM). This consists in an anodic dissolution process, allowing a mirror finish to be obtained by uniform roughness reduction on metallic parts immediately after the machining step. This is achieved by controlling electrolyte nature and operating parameters such as dissolution potentials, process duration and temperature [1]. Nevertheless, in the specific case of additive manufacturing, where high level of roughness can be observed, it is important to discriminate the microscopic and macroscopic scales of etching. The roughness value can be measured at different scales by several technics (mechanical sensor, optical profiler, AFM…), but the results (Ra, Sa…) are dependent on the spatial resolution of the device and on the measurement procedure like cut-off application. A way to overcome this problem consists in making these parameters independent of the roughness scale by integrating the fractal dimension of topographic records [2].
In this study, 316L stainless steel samples obtained by additive manufacturing were electropolished and compared to raw and mechanically polished samples. The characterization of the surface roughness was carried out by optical profilometry, and the 2-D data were analyzed to plot Power Spectral Density as a function of spatial frequency (PSD) [3]. Then, the curves obtained are fitted by the Weierstrass-Mandelbrot function to determinate the fractal dimension, which allows quantification of the surface irregularity level [4].
Acknowledgments : the authors would like to thank the IRT-M2P program AFTER ALM for its financial support.
[1] C. Rotty, A. Mandroyan, M.-L. Doche, and J. Y. Hihn, Surf. Coat. Technol., 307 Part A, 125–135 (2016)
[2] Majumdar, A., Tien, C.L.: Fractal characterization and simulation of rough surfaces. Wear 136(2), 313–327 (1990)
[3] Prashant Pendyala, M. S. Bobji, Giridhar Madras. Evolution of Surface Roughness During Electropolishing, (2014). Springer Science Editions
[4] S. Panda, A. Panzade, M. Sarangi, S.K.R. Chowdhury, Journal of Tribology, 139 031402-1/9 (2017)

Figure 1
Electrochemical Polarization Behavior of 304L Stainless Steel in a Thin Layer of Chloride Solution
Authors: Korjenic Alen , Kundu Arnab , Charit Indrajit , Raja Krishnan S. 
Published: February 2020

Spent nuclear fuels are stored in stainless steel canisters. The containers are cooled naturally by a convective airflow through the annulus between the overpack and the canister. This air flow draws dust into the overpacks, and the surfaces of containers are covered with dust. Salts carried by the dust will deliquesce as heat generated by radioactive decay declines over time. The deliquescence of salt deposit could induce various forms of corrosion attack such as pitting and chloride-induced stress corrosion cracking (SCC). In this study, the corrosion behavior of 304L SS - a typical dry storage container material, is evaluated by simulating the deliquescence of salt deposit using a thin electrolyte test condition.
Electrochemical corrosion test was performed on 304L Stainless Steel in 3.5 wt% NaCl solution at 20 OC. The tests were carried out in a newly fabricated electrochemical cell with exposed surface area of test specimen being 1 cm2. The cell has a movable PTFE wall which houses a Pt foil as a counter electrode. The adjustable wall enables the thickness of electrolyte to be varied between the SS specimen and the counter electrode. The thickness of the electrolyte was maintained at 1 mm in all the tests. This resulted in the volume of the electrolyte to be 10 ml. Open circuit potential, cyclic polarization and potentiostatic tests at different passivation potential were carried out. The potentiostatic passivation tests were followed by electrochemical impedance spectroscopy and Mott-Schotky analysis in order to understand the initiation of localized corrosion. For comparison, the electrochemical tests are being performed by using bulk electrolytes. The electrochemical polarization behavior in the thin film electrolyte was more or less similar to that in the bulk electrolyte. However, the pitting protection was shifted in the negative direction by about 80 mV in the thin electrolyte as compared to that of bulk electrolyte. Potentiostatic tests conducted at potentials below the pitting protection potential did not show pit initiation. Relatively a quick pit initiation event was observed when the applied potential was 60 mV anodic to the pitting protection potential. Bulk electrolytes showed no passivity breakdown at this potential. The results will be analyzed based on the EIS data, semiconducting properties of the passive film, and UV-Vis absorption of the test electrolytes.
Galvanic Corrosion Processes of Aluminum Coupled to Iron in Chloride Solutions at Near-Neutral pH
Authors: Kosaba Takumi , Muto Izumi , Sugawara Yu 
Published: February 2020

Multimaterial structures are effective for weight reduction of automobiles, which contributes to the prevention of global warming and the decrease in CO2 emission. Steel-aluminum joints have many advantages such as low cost, high strength, and high corrosion resistance. However, galvanic corrosion was expected to occur because the corrosion potential of aluminum alloys is usually different from those of iron and steels. Considering the galvanic corrosion processes in chloride-containing near-neutral pH solutions, the existence of surface oxides is an important factor affecting the initiation of corrosion. In this research, the galvanic corrosion behavior of aluminum alloy coupled to iron and the steel in near-neutral pH solutions was investigated.
Pure iron, AISI 1045 carbon steel, pure aluminum, and A5083-O(Al-Mg alloy) were used as the specimens in this research. The surfaces of pure iron and AISI 1045 were polished down to 1 µm. Pure aluminum and A5083-O were polished down to 0.25 µm with a diamond paste and cleaned ultrasonically in ethanol before electrochemical measurements. The electrode area was ca. 1 cm2. Ag/AgCl (3.33 M KCl) was used as the reference electrode.
In diluted synthetic seawater (200mg/L [Cl-], pH 8.2, naturally aerated, galvanic current was measured for 20 h using zero resistance ammeter technique. The distance between two electrodes was 1 cm. Fig. 1(a) shows the time variation of the galvanic current and electrode potential of pure aluminum coupled to pure iron. From the beginning of the immersion to 30 ks, many current transients were generated. However, after 30 ks, the galvanic current became a constant value of approximately 0.15 µA cm-2. The potential gradually decreased with time. The pH of the electrolyte decreased from 8.2 to 6.7 by galvanic corrosion. Fig. 1(b) and 1(c) shows the electrode surfaces of pure iron and pure aluminum after galvanic current measurements. Rust was observed on pure iron, and filiform corrosion was generated on pure aluminum.
Anodic polarization curves were measured in diluted synthetic seawater (200mg/L [Cl-], deaerated), and the pH was adjusted to 8.2, 6.7, 5.2, 3.7, and 2.2 with NaOH or H2SO4. Potentiodynamic polarization was started from corrosion potential, and the scanning rate was 23 mV min-1. The electrode potential of pure aluminum under galvanic coupling conditions was found to be lower than the pitting potentials of pure aluminum. But, corrosion was initiated on the aluminum surface (see Fig. 1(b, c)). The galvanic corrosion behavior of pure aluminum and aluminum alloy AA5083 were discussed in terms of the surface properties of the specimens and solution chemistry.

Figure 1
Assembly of SnO2-ZnO Composite Hollow Nanofibers for CO2 reduction Reaction to Formate
Authors: Tan Daniel , Kim Young-Eun , Lee Wonhee , Park Ki Tae , Jeong Soon Kwan 
Published: February 2020

Tin oxide (SnO2) is a well-known material that has been applied widely in various fields, such as catalyst, solar cell and gas sensor. As electrode material, its high selectivity through formate during carbon dioxide reduction reaction (CO2RR) make it attractive to be explored further. In addition, it is found that compare to a pure substance, composite material exhibits better performance due to the enhanced inner electric field at the particle interface. Zinc oxide (ZnO) becomes one of the promising candidates as a composite material with tin oxide due to low cost, suitability, good chemical stability, and electrochemical properties as well as its selectivity to formate. A wide range of metal oxide have been synthesized by various physical and chemical techniques. Among the techniques, electrospinning is one of the promising and versatile method to create one-dimensional nanostructures such as nanofiber, nanotubes, and nanowires with tunable diameters size and morphology. The high surface to volume ratio can provide large surface areas and also able to reduce mechanical strains within particle thus can increase the performance.
SnO2-ZnO composite hollow nanofibers were synthesized by electrospinning followed by annealing using SnCl2.2H2O and Zn(NO3)2.6H2O as main precursors. The physical characterization were investigated by field emission scanning electron microscopy (FESEM) and x-ray diffraction (XRD). As a comparison, pure SnO2 nanofibers were also prepared. It shows that the crystals phase intensity is proportional to the annealing temperature. While the diameter size of the fibers strongly depends on ZnO contents associated with the Kirkendall effect which describes diffusional mobility along radial direction during annealing. The electrochemical performances were investigated in a H-type cell with 1cm2 catalyst-coated carbon fiber paper as a working electrode. While an Ag/AgCl electrode was used as a reference electrode along with a Pt coil as a counter electrode. The aqueous solution of KHCO3 and KOH were used as catholyte and anolyte respectively, with Nafion 115 as the separator. The quantitative analysis were caried out by gas chromatography (GC) and high-performance liquid chromatography (HPLC) to investigate the FE, PCD, and concentration of formate.