bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simple Electrochemical Method for the Quantification of Chlorite in Aqueous and Non-Aqueous Media
Authors: Rudolph Michael , Schneider Sebastian , Fischer Christian , Terfort Andreas 
Published: May 2020

Chlorine-based disinfection technologies are most widely used to limit waterborne diseases and pathogenic organisms. Such disinfectants either are strong oxidants or species that generate oxidants as by-products. Especially for the use of chlorine dioxide as disinfecting agent the quantification of formed chlorite, likewise crucial for the regulatory issues of bleaching products [1,2], is of importance for the analysis of drinking water and process wastewater streams [2,3].
A robust differential pulse voltammetry (DPV) method for the quantification of chlorite (ClO2
-) down to the sub-ppm range has been developed. By using an electrolyte based on an ionic liquid (IL), both, aqueous and non-aqueous samples, could be employed. It was demonstrated that neither the other chlorooxo anions (hypochlorite OCl-, chlorate ClO3
- , or perchlorate ClO4
-) nor chloride interfere with the method. Different working electrode materials and ionic liquids were evaluated, of which the combination of glassy carbon with N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)azanide – based on the work of Hossain et al [4] – turned out to be the most suitable one. To demonstrate the feasibility of the method, a broad range of samples were investigated on their chlorite content, such as commercial disinfectants, bleaches, chlorinating agents, organic acid chlorides, as well as products of the Pinnick reaction, for which chlorite is used as a reagent.
[1] J. K. Skelly, J. Soc. Dyers Colourists, 76 (1960), 469-479.
[2] N. Oke, S. Singh, A. Garg, Water Sci Technol., 76 (2017), 2367-2379.
[3] J. N. Myers, W. H. Steinecker, Z. D. Sandlin, James A. Cox, G. Gordon, G. E. Pacey, Talanta, 94 (2012), 227-231.
[4] M. M. Hossain, E. Hosseini Bab Anari, L. Aldous, Electrochem. Comm., 34 (2013), 331-334.

Figure 1
Sub-ppb Sensing Level Hydrogen Sulphide at Room Temperature Using Doped Indium Oxide Gas Sensors
Authors: Al Shboul Ahmad , Izquierdo Ricardo 
Published: May 2020

Hydrogen sulfide (H2S) is a highly corrosive, harmful, and toxic gas. Whereas 130 ppb is the threshold for maximum safety exposure level. Thus, it has become mandatory to develop highly sensitive sensors operating at room temperature to detect low levels of H2S. Sensors based on electrochemical measurement principles, semiconducting metal oxides or p–n heterojunctions have showed promising results to detect H2S gas. To date, drawbacks have boon reported due to their extended response times, high operating temperatures, limited selectivity to the gas and/or sensitivity to humidity changes. Efforts have been made to develop sensors based on metal oxides operable at room-temperature for H2S detection.
Here, we describe novel flexible H2S gas sensors based on optimized composite mixture of indium oxide (In2O3), copper acetate (CuAc), graphite (Gt) and polystyrene (PS). While we employed Gt in sensor’s structure to reduce sensor’s resistance to ~ 0.5 MΩ, we used PS and enhance sensor’s integrity as well as the adhesiveness of the sensing layer on the top of carbon electrodes. Whereas we applied In2O3 as the active material in sensors due to its promising performance to detect ~ 100 ppb gas concentration. We used CuAc as activator when it converts to the form of copper sulfide (CuS) due to its high conductivity (10 S/cm). Hypothetically, upon exposing sensors to the H2S gas, In2O3 converts spontaneously to the metallic form In2S3 (eq.1). Alternately, CuAc plays two critical roles in the sensor composition. First, CuS formation drops sensor’s resistance significantly due its high conductivity (eq.2). At this point, In2S3 and CuS can form a continues metallic layer, thus it increases sensor’s conductivity. Second, CuS may play a similar role as same as noble metals, which can cause the formation the structure of noble-doped metal oxide and ease oxygen molecules adsorption/ionization on sensor’s surface (eq.3,4). This may facilitate oxidizing and/or adsorption H2S on the sensor’s surface (eq.5,6), which consists of releasing electrons to sensors and reduce sensors resistance dramatically. The developed sensors have showed high selectivity toward H2S gas, high sensitivity to H2S concentration of less than 100 ppb, fast detection time less than 60 seconds, and high resistivity to humidity changes.

Figure 1
Development of a Selective Mixed-Potential Ammonia Sensor for Automotive Exhausts
Authors: Nematbakhsh Abkenar Gita , Viricelle Jean-Paul , Rieu Mathilde , Breuil Philippe 
Published: May 2020

One of the most effective technologies in decreasing large-scale NOx emission produced by diesel engine vehicles is Urea-SCR (selective catalytic reduction) system. In order to prevent inducing excessive ammonia to the environment, an NH3 sensor is required at the exit of this system [1, 2]. In this study, highly selective ammonia sensors were developed to detect ammonia emissions from automotive exhaust.
The sensors were fabricated with 8-YSZ electrolyte, a platinum reference electrode and a working electrode of Au-V2O5 (mass ratio 85/15), screen-printed on an alumina substrate. A platinum resistor was printed at the backside of the support to control the sensor temperature. The measured sensor’ response (ΔV) is the potential difference between reference and working electrodes. Figure 1 shows the responses of two identical sensors to 100 ppm CO, NO2, NO and 20 ppm of NH3 at four different temperatures. It can be seen that the sensors respond to all gases at lower temperatures while by increasing temperature to 600°C, the selectivity to NH3 is greatly improved. The selectivity of sensors was also confirmed by testing other possible interfering gases: no responses were observed for 20ppm of hydrogen and 100ppm of a hydrocarbon mixture.
The stability of such sensors was studied at 550°C and 600°C. Since the sensors show no long-term stability at 600°C (electrode degradation), but remain stable at 550 °C, investigations were made to decrease the working temperature while maintaining selectivity. After testing different mass percentages of V2O5 in working electrode, we observed that by increasing this value to 50%, the working temperature of selective ammonia sensors could be decreased to 550°C with stable responses.
Further investigations will be performed in order to gain deeper insight in sensing mechanism of V2O5 based working electrodes, which governs the sensor’s performance.

References
[1] K. Shimizu, I. Chinzei, et al. "Doped-vanadium oxides as sensing materials for high temperature operative selective ammonia gas sensors," Sensors and Actuators B, 141, 2009, pp. 410-416.
[2] M. Van Nieuwstadt, I. Dpadhyay, et al. "Control of Urea SCR Systems for US Diesel Applications" in IFP Energies Nouvelles International Conference, Dearborn, USA, 2011, pp. 655-665.

Figure 1
Nanoporous-Based Sensors for Impedance Spectroscopy-Based Detection of Gaseous Pollutants
Authors: Schindelholz Mara , Small Leo J. , Henkelis Susan , Krumhansl James , Nenoff Tina M 
Published: May 2020

The advanced in situ detection of gaseous pollutants (e.g. NOx and SOx) is of great interest in many applications, such as the automotive and coal industries. Here, we leverage the previous successful development of impedance spectroscopy-based sensors for the detection of gaseous I2 to develop a novel sensor for the detection of these gaseous pollutants. During initial development of an I2 sensor, a metal-organic framework (MOF ZIF-8) material was utilized as an adsorbent layer deposited onto Pt interdigitated electrodes. The MOF was demonstrated to selectively adsorb I2, irreversibly, from a complex gas stream with a (>105x) change in measured impedance across the electrodes1. Further studies aimed at developing a robust sensor examined other materials, including zeolites2 and additional MOFs. It was demonstrated that utilizing MFM-300(X) (X= Al, Fe, In or Sc metal center) active materials enabled a reversible electrical response via gas adsorption/desorption3. The current work is focused on exploring these same nanoporous phases (MOFs, zeolites, etc.) for the real-time detection of NOx and SOx. The down-selection of candidate materials from bulk synthesis and gas selectivity testing will be discussed. Methods for deposition of these materials onto the Pt interdigitated electrodes and initial sensor performance during controlled gas exposures will be presented.

Acknowledgements

Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA0003525. This paper describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the U.S. Department of Energy or the United States Government.

References

1) Small, L.J and Nenoff, T.M., ACS Appl. Mater. Interfaces, 2017, 9 (51), 44649-44655.
2) Small, L.J.; Krumhansl, J.L.; Rademacher, D.X.; Nenoff, T.M. Micro. Meso. Mater., 2019, 280, 82-87.
3) Small, L.J.; Hill, R. C.; Krumhansl, J. L.; Schindelholz, M. E.; Chen, Z.; Chapman, K.W.; Zhang, X.; Yang, S.; Schroder, M.; Nenoff, T.M., ACS Applied Materials and Interfaces, 2019, 11(31), 27982-27988.
Optical Defects Engineering of Metal Oxide Nanosheets Toward Exceptional Chemiresistor
Authors: Kim Dong-Ha , Cha Jun-Hwe , Choi Sung-Yool , Kim Il-Doo 
Published: May 2020

Metal oxide nanosheets (NSs) exhibit intriguing physicochemical properties such as high specific surface area, high fraction of reaction sites, thus leading to promising performance in various applications including energy storage, catalysis, and gas sensing. [1] Beyond the 2D metal oxide NSs, defect engineering and/or control of non-stoichiometry, that is, control of metal or oxygen vacancies, are a few of the powerful strategies to generate abundant active sites to enhance gas sensing performance. [2] Precise control of the heat treatment, ramping rate control or reducing heat treatment as examples, is an effective way to generate the oxygen vacancies, but is time-consuming which requires high thermal-budget. Building-up of hetero-junctions is another powerful method to boost up the sensing performance. [3] However, it has been a challenge to prepare thin-layered heterogeneous metal oxide NSs with abundant active defect sites.
An optical engineering to generate controllable oxygen vacancies and new crystal phases on various metal oxide nanosheets (NSs) is introduced via graphene oxide (GO) templating route followed by intense pulsed light (IPL) irradiation. Negatively charged GO flakes and metal ions readily self-assemble to form GO@M (where M = Sn2+, Co2+, Ti4+, and Zn2+) and polycrystalline metal oxide NSs, such as SnO2, Co3O4, TiO2, and ZnO, are successfully synthesized after calcination. Upon a few flashes of IPL irradiation (< 20 ms), a rapid increase in temperature (1200 °C) has induced evolution of defect sites and new crystal phases. As a representative, optically treated Pt-SnO2 NSs showed unparalleled formaldehyde (HCHO) response, excellent selectivity, low detection limit (100 ppb), and fast response speed (< 10 s) assisted by the synergistic effects of the Pt catalysts, numerous oxygen vacancies, and hetero-junctions formed by flash-induced partial reduction of n-type SnO2 to p-type SnO. This defects engineering method could greatly strengthen the design of various heterogeneous metal oxide NSs and their potential application toward various fields with the optimal customized physicochemical properties.

References

[1] Peng, L. et al. Holey two-dimensional transition metal oxide nanosheets for efficient energy storage. Nat. Comm.
8, 15139 (2017)
[2] Yuan, H. et al. ZnO nanosheets abundant in oxygen vacancies derived from metal-organic frameworks for ppb-level gas sensing. Adv. Mater.
31, 1807161 (2019)
[3] Miller, D. R. et al. Nanoscale metal oxide-based heterojunctions for gas sensing: a review. Sens. Actuators. B.
204, 250-272 (2014)
Flexible Ion-Selective Ca2+ and pH Microsensors to Study Biofilm/Biomaterials Interface in Real-Time
Authors: Koley Dipankar 
Published: May 2020

Solid-state potentiometric sensors have an inherent advantage of miniaturization. We developed a 125 µm diameter solid-state fast response ion-selective pH and Ca2+ wire-sensors. These flexible microsensors were applied to quantify the real-time change in pH and Ca2+ concentration at hard-to-reach biofilm-biomaterials interface while live biofilms were growing on the Ca2+ releasing smart biomaterials. These smart biomaterials or substrates used in these studies were bioactive glass (BAG) containing resin dental composites that are capable of releasing metal ions (Ca2+) at pH less than 5.5.
The newly developed solid-state pH microsensors showed a near-Nernstian response (50 mV/pH) with a fast response time of <500 ms. Similarly, the solid-state Ca2+ microsensors showed a near-Nernstian slope of 28 mV/log[Ca2+] with a linear range of 10 µM to 1 mM along-with response time of less than 0.5 s. Both the pH and Ca2+sensors were then used inside a micro incubator set-up to quantify the real-time pH change at the biofilm-biomaterials interface due to bacterial (S. mutans) metabolism and the corresponding Ca2+ release from the (BAG) containing resins. Our systematic study showed that the lactic acid produced by Streptococcus mutans (Sm) biofilm when exposed to 30 mM sucrose, in BHI/MOPS media at 37°C, caused a pH shift from 7.0 to 5.7 at the biofilm-biomaterial interface. Recent findings of the effect of Ca2+ ions on bacterial growth and metabolism on different compositions of BAG-resin composites will be presented in the conference.

This work is supported by the National Institute of Dental and Craniofacial Research (NIDCR) (Grant # R01DE027999).
Hydrogen Sulfide Detection for Medical Breath Analysis with Surface Functionalized ZnO Nanowires
Authors: Kaiser Angelika , Torres Erick , Mauritz Tanja , Liu Yujia , Huber Florian , Herr Ulrich , Thonke Klaus 
Published: May 2020

Over the past decade, the medical role of hydrogen sulfide (H2S) for therapeutic applications and diagnostics was extensively investigated and revealed the importance of H2S for medical breath analysis.
It was suggested that decreased production of the endogenous gaseous mediator H2S in tissues of the human respiratory system can be interpreted as an early detection biomarker for inflammatory diseases like asthma etc. In order to detect the H2S concentration levels of interest, a reliable selective device sensitive to H2S in the very low parts per billion (ppb) range is needed.
The main goal of our project is the development of such a highly sensitive, reproducible and reliable H2S gas sensor, acting as a future integrated component of a multiple-sensor array in an “electronic nose” type device for medical applications or for detecting trace concentrations in chemical industry.
We present here a planar resistive gas sensor design based on the gas sensing mechanism of a chemical field effect transistor (ChemFET) made from very high quality zinc oxide (ZnO) nanowires (NW) with gas sensitive open gate. The open gate operates as a transducer between adsorption/desorption of the ambient target gas and a measurable resistivity change in the NWs. This resistivity change results from the band bending effect of metal oxide surface exposed to different gas atmospheres and is analyzed by current-time (I-t) measurements.
To improve the selectivity of our ZnO NW sensor towards a certain target gas, we investigated the impact of surface modification by addition of catalytic metal layers on the detection limit of our ZnO NWs towards H2S. In particular, we studied the chemical affinity between gold (Au) and sulfur (S) which leads to catalytic effects between the sputtered gold nanoparticle layer and the target gas H2S. Accordingly, H2S molecules are expected to adsorb more efficiently on Au modified ZnO NWs and drastically improve the overall sensor performance towards H2S. Our modified ChemFETs showed higher signal-to-noise ratio (SNR), improved sensitivity, faster response time, and an exceptionally low detection limit of less than 10 ppb for H2S diluted in synthetic air at room temperature.
Ultra-High-Sensitive Detection Using Pulse-Heating of MEMS-Type Oxide Semiconductor Gas Sensor: (2) Detection of Ethanol in Ppb Level By Introducing Oxygen Supplier
Authors: Shimanoe Kengo , Hiroyama Yuki , Suematsu Koichi , Watanabe Ken 
Published: May 2020

As mentioned in previous presentation, gas sensor using pulse-heating of MEMS-type Pd-SnO2 could show ultra-high-sensitive (UHS) detection in ppt level to toluene. However, toluene is easy to oxidize on Pd-SnO2 because of aromatic compound. In order to apply the UHS sensor using MEMS-type for aliphatic compounds such as alcohol, the sensing layer needs some modifications because of improvement of oxidation. So we have investigated for UHS sensing to ethanol by using a composite material that consists of the perovskite-type oxide (Ba0.9La0.1FeO3-σ) and SnO2 nanoparticles. SnO2 powder was prepared through a hydrothermal treatment (1) and perovskite type oxide powder was prepared though an amorphous malic acid complex method. The powder mixed perovskite oxide and SnO2 particles was evaluated for the gas sensing properties in ethanol gas by using same apparatus as toluene detection. The obtained results indicated that perovskite type oxide added SnO2 nanoparticles exhibits higher sensor response to C2H5OH than that of pure SnO2, as shown in Fig. 1. In addition, the introducing of the pre-heating before measurement was effective for the sensor response as same as the case of toluene detection. It seems that the perovskite-type oxide plays a role of oxygen supplier to avoid the situation of oxygen absent or that the perovskite-type oxide works as a partial oxidation catalyst.
References
(1) K. Suematsu, Y. Shin, Z. Hua, K. Yoshida, M. Yuasa, T. Kida, K. Shimanoe, ACS Appl. Mater., 6, 5319−5326 (2014).
(2) K. Suematsu, W. Harano, T. Oyama, Y. Shin, K. Watanabe, K. Shimanoe, Anal. Chem., 90(19), 11219-11223 (2018).

Figure 1
Ppb-Level of Ammonia Sensor on Reduced-Graphene Oxide Nanocomposite By the Supercritical Fluid Technique
Authors: Syu Wei-Jie , Wang Shih-Han , Chen Bo-Rong 
Published: May 2020

Ammonia is an important indicator for the environment quality and agriculture safety applications. Besides, various medical reports have indicated that exhaled ammonia gas is considered to be a non-invasive biomarker of liver and kidney diseases. The exhaled ammonia gas concentration for healthy human is in the range of 200-2000 ppb [1], and for the environmental quality evaluation it should be lower than 50 ppb [2]. Due to the low concentration and the complicate sample gases, it is important to develop a highly sensitive and selective ammonia sensor. Several materials such as metal oxide, conducting polymer and carbon nanomaterials have been extensively examined for ammonia gas sensing. In this study, tungsten oxide and polyaniline was incorporated into easily functionalized reduced graphene in supercritical fluid to form a p-type nanocomposite. Metallic nanocatalyst was doped to enhance the sensitivity and selectivity. Ammonia was adsorbed onto the sensing membrane and then oxidized at room-temperature. Therefore, the resistance of sensing membrane increased with ammonia concentration. The sensor could detect the ammonia concentration in the range from 0 to 100 ppm at room temperature. The sensitivity was enhanced 4 times by the nanocatalyst, and the lower detection limit was 50 ppb. The effect of interference gases, including nitric oxide (NO), carbon monoxide (CO), carbon dioxide (CO2), sulfur dioxide (SO2) has been evaluated as well, and all the cross-talk was less than 10%. Furthermore, ammonia gas is highly water soluble, the sensing resistance could shift significantly with humidity, especially in higher humid atmosphere. In order to solve the problem, the electrode surface was designed to be more hydrophobic. After surface modification, the humidity effect decreased. The sensing mechanism of electrode and effect of humidity was also investigated. The experimental result suggested that the catalyst doped nanocomposite had high sensitivity, stability and selectivity for low concentration ammonia sensing at room temperature. A room temperature operated ppb-level ammonia sensor could be valuable solution for exhaled gas or environmental quality monitoring.
[1] S. Abdulla, J. Dhakshinamoorthy, V. Mohan, D. V. Ponnuvelu, V. K. Kallidaikuruchi, L. M. Thalakkotil, B. Pullithadathil. J. Breath Res. 13 (2019) 046005; doi: https://doi.org/10.1088/1752-7163/ab278b
[2] M. Insaustia, R. Timmis, R. Kinnersley , M. C. Rufino. Sci. Total Environ. (2019) 135124； doi: https://doi.org/10.1016/j.scitotenv.2019.135124.
Electrochemical Detection Using Nanoporous Structures
Authors: Jiang Junhua , Wang Congjian 
Published: May 2020

Nanoporous electrodes are a unique class of nanostructured electrodes for promising electrochemical sensor applications because of a range of important attributes which include but are not limited to: high surface area, interesting catalytic properties, fast mass transport and low Ohmic resistance drops, potentially low cost and good fouling tolerance [1, 2]. In addition to the conventional concept of enlarged surface area, nanoporous structures provide a unique environment for reactive molecules. Once a reactant molecule enters a nanopore, the probability of interaction between the nanoporous electrode surface and the molecule is increased compared with that on a flat electrode. The molecule involved in a sluggish electrochemical reaction can enter deep into the nanopore, leading to longer penetration depth. Consequently, the heterogeneous charge transfer gets facilitated and the amperometric response of sluggish faradaic reactions can be selectively enhanced. This will selective amperometric detection, in which the selectivity and sensitivity could be tuned by the depth, shape, and interconnectivity of the nanopores. In addition, the nanoporous structures resulted nano-confinement effects can prevent reactive intermediates from escaping back to the bulk solution. Expedited by the rapid advance of nanomaterial engineering and manipulating technology, nanoporous electrodes will be a strong impetus to a wide range of emerging areas such as in-situ and remote monitoring and controls [3, 4].
In this presentation, we will introduce the structural effects of nanoporous materials including discriminative electrokinetics, the nano-confinement effect and electrical double layer overlapping, the fabrication nanoporous microelectrodes, the characterization of their porous structures, and their nanopore-induced enhanced electrochemical responses to several interesting molecules such as nitrate, nitrite, and chlorides.

References

[1] F. Nicholas and C. Knospe, Fabrication and characterization of nanoporous gold electrodes for sensor applications, Adv. Eng. Mater., 21, 1800857 (2019).
[2] Z. Li, et al., Confinement effects on an electron transfer reaction in nanoporous carbon electrodes, J. Phys. Chem. Lett.,
8, 1925 (2017).
[3] K. Fu and P. Bohn, Nanopore electrochemistry: a Nexus for molecular control of electron transfer reactions, ACS Cent. Sci.,
4, 20 (2018).
[4] H. Qiu, X. Li, H. Xu, H. Zhang, Y. Wang, Nanoporous metal as a platform for electrochemical and optical sensing, J. Mater. Chem. C, 2014, 2, 9788 (2014).