bluuebunny/crossref_metadata_2025_split huggingface dataset:
GaN Based Carbon Dioxide Sensor
Authors: Jung Sunwoo , Baik Kwang Hyeon , Jang Soohwan 
Published: February 2020

It is necessary to detect promptly amounts of carbon dioxide for the safety of workplace and the health of workers because concentrations of 7 to 10% may cause an acute symptom such as unconsciousness even in the presence of high concentration of oxygen. It is colorless and odorless. Also, its density is higher than common air, so that it is easily accumulated on the ground in the enclosed construction. Carbon dioxide is used in chemical, biomedical, energy and food industries as a reactant, an intermediate, and a final product. Recently, there are growing market-driven demands for the carbon dioxide gas sensors to detect early risk of high concentration of carbon dioxide exposure and to monitor quality of air in daily lives. In this applications, low power consumption, compact size, as well as reliability and sensitivity of the sensor are required to be integrated with IoT (internet of things) devices. Semiconductor type gas sensors satisfy these requirements, and GaN based gas sensors shows many superior performances including reliability and sensitivity to other semiconductors.
ZnO is a direct bandgap II-V compound semiconducting material with wide bandgap energy of 3.37 eV and large exciton binding energy of 60 meV. One of the advantages of ZnO is facile nanorod growth via hydrothermal method, which is low cost, non-toxic, low temperature, and scalable process. In hydrothermal growth, growth rate of c-plane is faster than m-plane in wurtzite crystal structure due to the higher surface energy of c-plane, hence ZnO nanowires or or bundle of nanorods along c-axis are generally formed. These ZnO nanorods with high surface to volume ratio can be employed in the gas sensor device as a sensing material to obtain high sensitivity for target gas.
In this study, AlGaN/GaN HEMT (high electron mobility transistor) based carbon dioxide sensor using ZnO nanorods as sensing material was fabricated, and the response of the device to carbon dioxide gas was investigated. The device showed current increase in carbon dioxide ambient due to the increase enhanced channel conductivity from 150oC, and fast reliable repeatability to cyclic exposures of various concentrations of carbon dioxide gas. Also, effect of humidity on sensing behavior was discussed.
Photon Absorption Enhancement of TiO2 Nanotube Arrays Decorated with Aluminum Nanoparticles
Authors: Zhang Shuai , Du Kang , Liu Guohua , Yang Changping , Wang Kaiying 
Published: February 2020

Highly ordered TiO2 nanotube (NT) arrays fabricated by electrochemical anodization have shown promising potential for photocatalystic applications [1]. Loading metallic nanoparticles has been introduced to enhance photocatalytic activity of the TiO2 nanotubes. However, the applications are primarily focused on silver or gold due to their strong plasmonic behaviors at visible wavelength [2]. As a low cost alternative, nanoparticles Al exhibit strong plasmon resonances spanning much of visible region of the spectrum as well. In this paper, we fabricated nanoparticles Al on the wall of TiO2nanotube arrays by magnetron sputtering technique and investigated their optical characteristics.
A representative SEM (Scanning Electron Microscope) image of TiO2 nanotube structure is shown Fig.1. [3] The nanoparticles Al were deposited on TiO2 nanotubes by a radio frequency (RF) reactive magnetron sputtering system (Sputter AJA 4050). The deposition parameters were kept at pressure (4.2 mTorr), power (120 W), gas (10 sccm), stable deposition rate (0.4Å/S). The nanoparticle thin films Al have been calibrated on glass substrates and TiO2 with thickness from 0 to 20 nm, which can be well-controlled by the sputtering time, the photographs of various nanoparticles Al on glass (22 mm × 22 mm) and TiO2 (10 mm × 20 mm) are shown in the Fig. 2. Compared with pure TiO2 nanotubes, the absorbance spectra (400 - 850 nm) confirms that the absorption intensity of Al/TiO2 NTs increases with increasing the thickness of Al NPs. The 10 nm Al/TiO2 NTs sample exhibits a broad absorption peak centered close to 550 nm in the visible light region. The enhanced visible light absorption peak is ascribed to the enhancement of localized surface plasmon resonance of nanoparticle Al. These results indicate that the photo-response of TiO2 NTs could be easily extended to the visible-light region through the aid of nanoparticles Al (Fig. 3).
In summary, well-dispersed distribution of nanoparticles Al have been assembled on the TiO2 NTs by RF magnetron sputtering technique. The nanoparticles Al are readily controlled with thickness from 5 to 20 nm. The visible light absorption have been systematically studied. The optimized thickness is ~10 nm, which efficiently absorb light over a broad range of wavelength.

References

[1] Z. Endut, M. Hamdi, W.J. Basirun, Supercapacitance of bamboo-type anodic titania nanotube arrays, Surf. Coat. Tech. 215 (2013) 75–78.
[2] M.W. Knight, N.S. King, Lifei Liu, H.O Everitt, P. Nordlander and N.J. Halas, Aluminum for plasmonics. ACS Nano 8 (2013) 834-840.
[3] Kang Du, Guohua Liu, Xuyuan Chen, Kaiying Wang, PbS Quantum Dots Sensitized TiO2 Nanotubes for Photocurrent Enhancement, Journal of The Electrochemical Society,162(2015) E251-E257.

Figure 1
Aptamer Functionalized AlGaN/GaN HEMT Biosensor Array for Electrical Enumeration of Circulating Tumor Cells
Authors: Pulikkathodi Anil Kumar , Sarangadharan Indu , Chen Yi-Hong , Lee Gwo-Bin , Wang Yu-Lin 
Published: February 2020

This paper demonstrates a novel high sensitive FET biosensor array that can capture as well as count the number of captured Circulating Tumor Cells (CTCs) by the aptamer immobilized on the sensor. The FET used for this purpose is AlGaN/GaN HEMT (High Electron Mobility Transistor) because of its high sensitivity. Using a new and robust sensing technique the cell capture was able to be measured electrically and analyzed. The array enhances the capturing and detection capability of the sensors. The advantage of this sensor array is that the detection can be extended to any type of cells and cell lines to differentiate the normal and abnormal cells among them, and the behavior of cells can be studied in different kinds of mediums in which the cells are suspended.
Biosensors can be used as point of care testing devices. In order to do so, they must be compact, portable, highly sensitive and user friendly. Along with being highly sensitive, GaN HEMT also are biocompatible, high temperature tolerant, chemically resistive and have excellent electrical properties. These properties of HEMT makes it a candidate for rapid biosensing. CTC enumeration has been used as a prognostic marker for metastatic colorectal cancer (m-CRC). CTCs are migrating cells that are shed into the blood stream from primary and metastatic tumors. But cancer patients have only 1-10 CTCs per cc of blood which makes them hard to be detected among plethora of other blood cells. The HEMT biosensor array developed by our group overcomes this drawback by capturing CTCs and counting them electrically, with an accuracy of single cell binding.
The fabrication of AlGaN/GaN HEMT is done by forming mesa islands by ICP etching of epi-wafer which is followed by ohmic metal deposition, annealing and probing pad deposition. Finally individual chips of size 1mm X 1mm are embedded onto an epoxy substrate and interconnects are deposited making a planar sensing device. This fabricated chip is then passivated and only the gate electrode and channel regions are opened with an area of 10X60µm2 using photolithography.
Aptamer is immobilized on the gate electrode and CTCs are allowed to be captured for 5~10 minutes. The cells bound on the aptamer are observed and the capture can be confirmed electrically by measuring the change in current gain compared to the aptamer current level and the change in current gain of HEMT sensor corresponds to the number of CTCs captured by the aptamer. In this way, CTC enumeration can be carried out using electrical measurement. This sensing technique is highly sensitive and can provide up to single cell resolution. Apart from rare migrating cells, abnormal cells and other cell based disease biomarkers can be detected and enumerated using our GaN HEMT based biosensor array.

Figure 1
(Invited) Mesoscale Modeling Approaches for Hydrogen Generation and Storage
Authors: Heo Tae Wook , Ogitsu Tadashi , Wood Brandon C. 
Published: February 2020

Many of the biggest challenges in the hydrogen energy research are associated with the fact that the operating mechanisms often involve the complicated coupling of chemical/physical processes over vast ranges of multiple length and time scales. These kinetic phenomena tend to occur at or near several types of solid/solid, solid/liquid, and solid/gas interfaces, which in turn play key roles in determining the overall performance of hydrogen generation and storage processes. Examples include surface reactions with hydrogen gas or water; surface, bulk, and interface mass transport processes; structural modifications occurring under operation; and intermediate phase nucleation-and-growth processes associated with hydrogen incorporation or corrosion. Essentially, these are collective dynamic processes of atomic/molecular species that determine the thermodynamics and kinetics of nano- or micro-level characteristics. However, the lack of clear understanding of associated mechanisms and their impacts on hydrogen generation and solid-state storage reactions has hampered the acceleration of materials discovery and development. Therefore, it is obvious that several modeling approaches that cover different length and time scales ought to be properly integrated in order to comprehensively explore the underlying mesoscale science during the co-evolution of relevant processes. Mesoscale continuum modeling frameworks can provide a unified platform for integrating the necessary atomistic approaches, which typically provide higher accuracy for nanoscale chemical processes, and continuum approaches, which offer far greater flexibility and scalability and can describe materials at the microstructural level. In this talk, we present our integrated effort as part of the new DOE Advanced Water Splitting Materials consortium (HydroGEN) and Hydrogen Storage Materials—Advanced Research Consortium (HyMARC) under the Energy Materials Network (EMN) towards the multiscale modeling of solid-state hydrogen storage and hydrogen production via water splitting. In particular, we will discuss our recent efforts on the development of an integrated mesoscale modeling framework that can directly incorporate parameters derived from predictive atomistic modeling approaches such as ab initio calculations and molecular dynamics simulations. Several case studies will be presented, such as modeling phase transformations of complex metal hydrides during the (re/de)hydrogenation and modeling physical/chemical processes during the water splitting and corrosion.
*This work of was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
(Invited) Large Scale Many-Body Perturbation Theory Calculations: Methodological Developments, Data Collections, Validation and Applications
Authors: Govoni Marco , Galli Giulia 
Published: February 2020

One of the main tools used in first principle simulations of materials is Density Functional Theory; however, several of the approximate exchange and correlation functionals do not provide the level of accuracy required for predictive calculations of excited state properties. The application to large systems of more accurate post-DFT approaches such as Many-Body Perturbation Theory (MBPT) -- for example to heterogeneous systems, nanostructured, disordered, and defective materials -- has been hindered by high computational costs. In this talk recent methodological developments in MBPT calculations will be discussed, as implemented in the open source code WEST [1]. Results using a formulation that does not require the explicit calculation of virtual states will be presented for photoelectron spectra of aqueous solutions [2]. We will discuss online data collections which contain benchmarking results. Simplifications of MBPT calculations based on the use of static response properties, such as dielectric-dependent hybrid functionals [3], will also be presented. We will also briefly discuss the ongoing activities of the Midwest Integrated Center for Computational Materials (MICCoM) [4].
[1] www.west-code.org; M. Govoni et al., J. Chem. Theory Comput. 11, 2680 (2015).
[2] A. Gaiduk et al., J. Am. Chem. Soc. Commun. 138, 6912 (2016).
[3] J. Skone et al., Phys. Rev. B 89, 195112 (2014); J. Skone et al., Phys. Rev. B 93, 235106 (2016); N. Brawand et al., Phys. Rev. X 6, 041002 (2016).
[4] www.miccom-center.org.
In collaboration with: N. Brawand, A. Gaiduk, F. Gygi, I. Hamada, T.A. Pham, P. Scherpelz, H. Seo, J. Skone, M. Vörös.

Figure 1
Decomposition of Strong Carboxylic Acids Redox Catalyzed By Carboxylate Ions; Chemical Grafting of Carbon Surfaces
Authors: González Felipe J , Ramírez Vanessa , Mendez Alia 
Published: February 2020

In mixtures of trichloroacetate ion and trichloroacetic acid in acetonitrile, trichloromethyl radicals are produced as a result of the redox reaction between the acid and its conjugated base. The reaction follows a loop mechanism in which the trichloroacetic acid is slowly consumed by proton reduction while the trichloroacetate ion is oxidized like in an electrochemical Kolbe reaction [1]. The hydroquinone-trichloroacetate complex was a good sensor of this unexpected self-decarboxylation redox reaction [2]. According to the conceptual framework of this reaction, the acid-base mixture was also tested but using the compounds derived from 4-nitrophenylacetic acid. The reaction ocurrs also in this system, however, when a glassy carbon electrode was present in the reaction solution, the grafting of nitrobenzyl groups on the surface was detected, whereas 4-nitrotoluene was detected as the product of a paralel reaction in solution. Therefore, the reaction represent an alternative to the covalent modification of carbon substrates without electrochemical induction.
[1] Drochss P. Valencia, Pablo D. Astudillo, Annia Galano, Felipe J. González, Org. & Biomol. Chem., 2013, 11, 318-325
[2] Pablo D. Astudillo, Annia Galano, Jorge Tiburcio, Felipe J. González, J. Electroanal. Chem., 2007, 604, 57-64

Figure 1
Invited: Ammonia Generation at Algae Modified Electrodes: Some Mechanistic Considerations Drawn from Redox Potentials
Authors: Leddy Johna , Lyon Jacob , Paschkewitz Timothy 
Published: February 2020

Nature designs eloquent systems to effect electrochemical changes that pose daunting objectives for address by simple electrodes. In a sequence of electrochemical steps in a highly structured, bio-matrix, biological systems provide energy and kinetic control that yields important products from oxidized reactants. Examples are CO2 and water to form O2 and sugars and dinitrogen to form ammonia. By capturing these biological matrices on electrodes, the biomachines can generate products important in energy and materials.
Minteer and coworkers have demonstrated many systems of this type, including capture of the entire Krebs cycle on an electrode where the various components of the cycle are captured in a modified Nafion membrane. By analogy, we have captured algae on electrodes to generate ammonia. Cyanobacteria generates ammonia from dinitrogen with nitrogenase enzyme and from fixed nitrogen of nitrate and nitrite with nitrate and nitrite reductase.
Thermodynamically, the conversion of dinitrogen to ammonia is not energetically taxing, but the energetic cost to break the nitrogen nitrogen triple bond is high. In review of the kinetics for ammonia generation from N2, NO3
-, and NO2
- reactants, the thermodynamics were reviewed. From a potential axis and speciation diagram, some reactions are identified with sufficient energy to break the nitrogen triple bond. These reactions and other mechanistic steps in ammonia generation are presented and the role of local pH is considered. The protocol is anticipated applicable to identifying energy generating reactions important in other bioelectrochemical systems.
Real-Time Imaging of Oxygenic Photosynthesis in Spinach Using Bio-LSI
Authors: Kasai Shigenobu , Sugiura Yamato , Prasad A. , Sato Teruya , Inoue Kumi Y. , Ino Kosuke , Matsue Tomokazu 
Published: February 2020

In the present study, we used a large-scale integration (LSI)-based amperometric sensor array system, designated Bio-LSI, to image in-vivo light-induced oxygen release from Spinach Leaves. The Bio-LSI device consists of 400 sensor electrodes with a pitch of 250 μm for rapid electrochemical imaging of large areas. Fig.1 shows schematic diagram for detection of oxygen production from Spinach leaves during photosynthesis using Bio-LSI. The imaging of oxygen production from Spinach leaves using Bio-LSI was also measured at light intensities of 20 and 30 klx (Fig 2, A3; a and b) which was found to be considerably higher as compared to the dark control (Fig 2, A2). The real-time monitoring of oxygen reduction current in control and light illuminated samples has also been presented (Fig. 2B). The results shows almost no changes in oxygen reduction current in non-illuminated Spinach leaves while a considerable changes have been observed in leaves illuminated with intensities of either 20 klx and 30 klx which was found to drop immediately at the switching off of the light source.
Our results show that light induced oxygen release can be monitored using the device, suggesting that the Bio-LSI is a promising tool for real time imaging of oxygen release and the effects of stresses in whole Spinach leaf under in-vivo conditions. To the best of our knowledge, this report is the first to describe real time electrochemical imaging of light induced oxygen release in Spinach leaves using LSI-based amperometric sensors.

References

(1) T. Yasukawa, et al., Chem. Lett., 28,975-976, 1999.
(2) K.Y.Inoue, et al. Lab Chip. 5, 848-856, 2015.

Figure 1
Electrodeposited Cadmium Oxide Semiconductor Electrodes for Protein Redox Characterization
Authors: Peters Dennis G , Gerroll Benjamin 
Published: February 2020

Semiconductor films have previously shown promise for the measurement of protein reduction potentials.1,2 An advantage gained with semiconductor working electrodes is the ability to take measurements while adsorption phenomena that occur at bare metal electrodes are avoided, which denature the protein and make sample recovery impossible. This denaturation may also affect the redox potentials.3 Thus, an ability to measure redox potentials accurately while maintaining protein integrity can find many applications in bioanalytical systems.
In this work we have synthesized and characterized cadmium oxide (CdO) working electrodes for electrochemical studies of native biomolecules in aqueous systems. Electrodeposited CdO films were generated through application of a constant current (4.5 mA/cm2) to an indium-doped tin oxide (ITO) working electrode immersed in a 0.1 M cadmium chloride (CdCl2) solution and subsequently annealed at 450 ˚C for 1.5 h. X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy methods were employed to characterize deposited material. As proof of concept, cyclic voltammetry of redox dyes with CdO working electrodes was performed to determine their redox potentials. Azurin, a copper blue protein from Pseudomonas aerunginosa,and cytochrome c, a small heme protein purified from bovine heart, were among the metalloproteins investigated. A novel small volume (50 and 750 µL) cyclic voltammetry cell was employed that facilitates sample recovery. Cyclic voltammograms were recorded at 10 mV/s for each sample with a CdO working electrode, a saturated Ag/AgCl reference electrode (–0.044 V vs. SCE), and a platinum counter electrode in aqueous solutions containing 100 mM Tris buffer and 200 mM KCl.

References

1. Valincius, G.; Reipa, V.; Mayhew, M. P.; Vilker, V. L. Electro. Chem. Comm.
2002,
4, 314-317.

2. Valincius, G.; Repia, V.; Vilker, V.; Woodward, J.; Vaudin, M. J. Electrochem. Soc.
2001, 148, E341-E347.
3. Hosseinzadeh, P.; Lu, Y. Biochimica et Biophysica Acta. 2015.
Figure 1. Small volume CV designed and used for metalloprotein analysis.

Figure 1
Extracellular Electron Transfer in Mixed Species Biofilms: The Role of Rikenella Microfusus
Authors: Grattieri Matteo , Abdellaoui Sofiene , Hasan Kamrul , Minteer Shelley D. 
Published: February 2020

The capability of microorganisms to transfer electrons to/from an electrode surface is critical for the development of bioelectrochemical systems. However, the extracellular electron transfer (EET) mechanisms have been elucidated only for few microorganisms, in particular Geobacter sulfurreducens (Sh.) and Shewanella oneidensis (G.S.) respectively. A Microbial fuel cell (MFC) is a bioelectrochemical system that couples the possibility to directly convert chemical energy from civil and industrial wastewater into electrical energy thank to the bioelectrocatalytic activity of bacteria colonizing the electrodes. For on-field application of the technology, a mixed bacterial community will be most likely obtained, since wastewater solutions and biomasses are commonly utilized as inoculum. The presence of mixed-species biofilm can also facilitate the oxidation of complex substrates, since many microorganisms capable of EET can only use low-molecular organic acids and alcohols provided by fermenting bacteria. Accordingly, it is important to understand how microorganisms rather than Sh. and G.S. can contribute to the EET process.
Different studies have reported a particularly high presence of Bacteroidetes in the microbial community at the anode and the cathode of MFCs. The biological characterizations have indicated an high percentages of Rikenella Microfusus (R.M.), which belong to the order of Bacteroidales, but only few information about its metabolism are available. R.M. was isolated by fecal materials, it is an obligated anaerobic, nonmotile and gram-negative bacterium, which is capable to oxidize a number of substrates as glucose, mannose, lactose producing acids.
Herein, a pure culture of R.M. (ATCC® 29728™) was anaerobically grown and the EET was investigated on carbon cloth electrodes (non-wet proofed, E-TEK) potentiostatically polarized at a positive potential (+0.2 V vs. Ag|AgCl Sat.) and maintained in anaerobic conditions by constant purging of nitrogen gas. For the study, glucose was used to provide the substrate for the bacterium. Electrochemical experimental evidences revealed that flavins might be involved in the EET, facilitating the communication of the bacterium with the electrode surface. Moreover, oxygen influence on the current response was detected, critically affecting the capability of the bacterium to perform EET. The impact of the new finding on future researches devoted to clarify the EET for real application of bioelectrochemical systems will be discussed.