bluuebunny/crossref_metadata_2025 huggingface dataset:
Amperometric Simultaneous Measurement of NO, CO and H2s during Induced Focal Seizures Using a Triple Microsensor
Authors: Seo Sunghwa , Lee Youngmi
Published: May 2020

In these days, nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H2S) are well known as endogenous neurotransmitters in mammalian cells and have been studied regarding their mechanisms playing the roles as neurotransmitters in vivo. However, the actual relations among these three gases in transmitting neuronal signals in brain are still controversial and therefore, direct real-time concurrent analysis of NO, CO and H2S is required to clarify their biological relations.

In current presentation, we demonstrate the fabrication of a NO/CO/H2S triple sensor and the simultaneous real-time measurements of these three gases at a rat brain surface under acute seizure using the sensor. This sensor consists of three platinum (Pt) disk working electrodes: 50, 76 and 50-μm diameter Pt microdisks (denoted as WE1, 2 and 3, respectively). The Pt disks of WE 2 and 3 are etched electrochemically and further electrodeposited with metal nanoparticles (Ru and Au, respectively). Then, the surface of each electrode is covered with a different intended target-selective membrane. These membranes are adapted for the selectivity to the gases excluding other biological interferences. Finally, these electrodes are applied with different optimized potentials, respectively to cause the oxidation of individual target gases and the oxidation currents are monitored. The developed NO/CO/H2S triple sensor is characterized in terms of its performances such as sensitivity, selectivity, etc. The sensors is utilized to monitor the concentration changes of NO, CO and H2S gases at a rat brain cortex under a seizure induced with administration of 4-acetamidophenol (AP). The actual patterns of the real-time concurrent changes of these gases were carefully investigated along with local field potential (LFP) signal changes. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT& Future Planning (NRF-2017R1A2A2A14001137).
The Gas Sensor Based on Novel Hierarchical Ni0.7Zn0.3o Hollow Porous Microspheres for VOCs Detection
Authors: Tian Kuan , Xing Lu , Li Zi-yuan
Published: May 2020

Bimetallic oxides have attracted substantial interest for gas sensing since their high compositional flexibility allows for tunable properties. In this work, we design and constructed a rocksalt solid solution Ni0.7Zn0.3O with hierarchical and hollow porous microspheres by deriving from bimetallic Zn/Ni-based metal-organic frameworks for the first time. This hollow spheres are constructed with a thin shell (100 nm) that assembled with smaller nanoparticles (15~30 nm). This unique morphology would provide a high special surface area that is very advantageous for gas sensing. The gas sensing performance of this rocksalt solid solution were investigated for the first time. The gas sensor based on these Ni0.7Zn0.3O microspheres exhibits a highly sensitivity toward to low concentration about 500 parts per billion (ppb) of acetone (S=1.21), aniline (S=1.44) and TEA (S=1.34) at 350 ℃, the response/recovery speed is extremely fast (less than 15 s) and selectivity is good (its responses to 5 ppm of other VOCs, such as ethanol, benzene, xylene, formaldehyde, ammonia, methylbenzene, formamide and ethanamide are less than 1.05). Even at low temperature (~200 ℃), the sensor still shows a good gas sensing performance. Moreover, a special response mode has been found in this work. This hierarchical nanostructured rocksalt Ni0.7Zn0.3O solid solution proposes a novel gas sensing material for achieving highly selective and sensitive gas sensing performance.

Figure 1
Membrane-Based Electrochemical Sensors for Detecting Internal Corrosion Risk of Natural Gas Pipelines
Authors: Ziomek-Moroz Margaret , Duffy Timothy , Hall Derek M. , Lvov Serguei N.
Published: May 2020

Internal corrosion monitoring programs are essential for the safe management of natural gas transmission pipelines. Electrochemical technologies can provide reliable, real-time monitoring of key risk factors, such as solution conductivity, corrosion rates, and localized corrosion risk. A novel, membrane-based sensor is being developed to perform electrochemical tests in both aqueous and gaseous environments, allowing for continuous operation and data collection within a pipeline environment. This sensor can be used to determine water content in the presence of a number of gases (CH4, H2S, CO2), to monitor the pipeline’s corrosion rate with and without a condensed phase, and to provide localized corrosion data in the presence of a pitting agent. Here, we explore the sensor’s design, validation through finite-element analysis, and performance data for general and localized forms of corrosion
Ultrahigh Sensitive NO2 Gas Sensor Based on WO3 Nanorods
Authors: Ren Xiaowei , Tang Zilong
Published: May 2020

Metallic semiconductor oxides are widely used to detect various toxic and harmful gases including nitrogen dioxide (NO2). In this work, tungsten oxide (WO3) nanowires were synthesized by a facile solvothermal methods, the surface morphology showed nanorods character with length ranging from 300-500 nm and had a diameter with 50 nm after calcined in 600 °C. Moreover, the WO3 nanorods exhibited a extremely high gas response of ~150 to 1 ppm NO2 at a relative low temperature (160 °C). The high specific surface area and rich oxygen vacancy may contribute to this high response. The sensor based on WO3 nanorods had a superior respond to very low concentration of NO2 revealed a promising candidate for the manufacture of cost effective gas sensors.
Mxene Nanosheets Preparation Sensitive Film for QCM Humidity Sensor
Authors: Xu Jiaqiang , Li Runlong
Published: May 2020

Fast, sensitive and stable detection of humidity is essential. In this paper, a 2D ultra-thin nanosheet Mxene was used as the material to form a sensitive film to construct the quartz crystal microbalance (QCM) humidity sensor by drop coating method. The element A in the MAX phase was dislodged by a simple liquid phase etching method. The morphology and composition of Mxene were studied by means of a series characterization methods, it was found the sample take on a ultrathin grapheme-like nanosheet. The test results show that the humidity sensor has 12.8Hz/% RH sensitivity, 6s and 2s (@ 90%)response/recovery time, maximum humidity hysteresis of 1.16%RH, good stability and selectivity. Finally, the adsorption enthalpy of water molecules on the surface of Mxene was explored by DFT calculation. It was found that residual F- played an important role in humitity sensing

Introduction:

The new two-dimensional (2D) material Mxene has been widely used in energy storage , battery , catalysis , electromagnetic shielding and other directions since it was discovered by the research team of Professor Yury Gogotsi of Drexel University in 2011.Ti3C2Tx has good electronic conductivity and hydrophilicity, it is the most widely studied and mature of all Mxenes. This work combines Mxene-Ti3C2Tx with the QCM test platform to further enhance the application of Mxene materials on humidity sensors.

By optimizing the method in the previous literature, the Ti3AlC2 powder was etched in LiF / HCl solution to remove the Al element, some post-treatment such us ultrasonic was carry out to obtain a single-layer Ti3C2Tx solution that can be used to directly prepare the device. The obtained samples were characterized by XRD, SEM, TEM, EDS, XPS and BET, etc, it was found that Mxene with a large specific surface area has a good single-layer sheet structure, and the surface contains a large number of -OH, -O, -F functional groups. This single-layer sheet structure with large specific surface area and abundant active sites is more conducive to the adsorption of water molecules. By detecting the relative humidity of 11.3% - 97.3% shows that the sensor with the best performance has excellent sensitivity of 12.8Hz/% RH, 6s and 2s (@ 90%) rapid response/recovery time, maximum humidity hysteresis of 1.16%RH, good short-term repeatability, long-term stability, and excellent cross-sensitivity. Through characterization and simulation, it is found that -F functional group plays a certain role in the excellent humidity sensitivity. This not only provides a new possibility for the application of 2D materials in humidity sensor, but also widens the application of Mxene materials in sensor field.

Figure 1
Synthesis and Electrochemical Study of AgFeO2 Nanoparticles
Authors: Magdaluyo Eduardo , Veran Marvin
Published: May 2020

Delafossite silver ferrite nanoparticles have been widely studied due to their various applications as photocatalyst, bioactuators and biosensors. A simple coprecipitation method was used to prepare AgFeO2 delafossite, with varying soaking time during hydrothermal treatment. The different physicochemical characterizations of the obtained materials included x-ray diffraction, electron microscopy, dynamic light scattering technique, infrared and ultraviolet–visible spectroscopies and zeta-potential. The study revealed that the delafossite structure of AgFeO2 was enhanced with the increase of autoclaving time from zero up to twenty-four hours. The diffraction pattern showed peaks at 33.15°, 38.17°, 44.38°, 64.5°, and 77.42° which are characteristics of delafossite AgFeO2 with a mixture of hexagonal and rhombohedral structures. The results also showed dependence of the soaking time in the microstructure uniformity, absorption properties, particle size distribution and stability of the AgFeO2. Moreover, the electrochemical behavior of AgFeO2 delafossite was investigated in different electrolytic media. Voltammetric and amperometric studies were performed to identify the oxidation and reduction processes and the effect of Ag2+ and Fe2+ in the total reactivity of the delafossite material.
Host-Guest Complex for Heparin Binding and Sensing
Authors: Välimäki Salla , Beyeh Ngong Kodiah , Linko Veikko , Ras Robin , Kostiainen Mauri
Published: May 2020

Heparin is a naturally occurring highly charged polyanion and a well-known anticoagulant widely used in surgical practice.[1] More specifically, it is a negatively charged sulfated polysaccharide belonging to the group of glycosaminoglycans (Scheme 1). The anticoagulant effect of heparin is based on its ability to activate antithrombin-III, which, subsequently, inactivates vital coagulation cascade substance such as thrombin and factor Xa consequently preventing fibrin and clot formation.[2] To balance and neutralize heparin dosing, a heparin inhibitor is needed, and commonly, arginine-rich protein protamine sulfate (PS) is used for this purpose.[3] However, in recent years there has been an interest to investigate alternatives for protamine due to its adverse effects like hypotension and serious allergic reactions.[4]

In this study, a host-guest complex capable in selective heparin binding and sensing is presented.[5] Heparin binding affinity was studied in solution with a variety of polycationic macrocyclic hosts, a pillar[5]arene and multiple resorcin[4]arenes, by dynamic light scattering, dye displacement assay, isothermal titration calorimetry, and anti-Xa assay. The measurements reveal the significant importance of multivalency in the electrostatic host-heparin binding in competitive, application-relevant media. Additionally, to monitor heparin concentration, a host-guest indicator displacement assay was performed by following the free and bound state of methyl orange dye in UV-Vis spectroscopic experiments. Furthermore, this colorimetric sensing based on the tertiary host-guest-heparin supramolecular assembly was utilized in the construction of a calibration curve in a range of blood plasma concentrations.

References

[1] B. Casu, A. Naggi, G. Torri, Re-visiting the structure of heparin, Carbohydr. Res., 403 (2015), 60–68. https://doi.org/10.1016/j.carres.2014.06.023

[2] J. Hirsh, T.E. Warkentin, S.G. Shaughnessy, S.S. Anand, J.L. Halperin, R. Raschke, C. Granger, E.M. Ohman, J.E. Dalen, Heparin and Low-Molecular-Weight Heparin Mechanisms of Action, Pharmacokinetics, Dosing, Monitoring, Efficacy, and Safety, Chest, 119, (2001), 64S–94S. https://doi.org/10.1378/chest.119.1_suppl.64S.

[3] S.M. Bromfield, E. Wilde and D.K. Smith, Heparin sensing and binding – taking supramolecular chemistry towards clinical applications, Chem. Soc. Rev., 42, (2013), 9184–9195. DOI: 10.1039/C3CS60278H.

[4] M. Nybo and J.S. Madsen, Serious anaphylactic reactions due to protamine sulfate: a systematic literature review, Basic Clin. Pharmacol. Toxicol., 103, (2008), 192–196. https://doi.org/10.1111/j.1742-7843.2008.00274.x.

[5] S.Välimäki, N.K. Beyeh, V. Linko, R.H.A. Ras, M.A. Kostiainen, A supramolecular host–guest complex for heparin binding and sensing, Nanoscale, 10, (2018), 14022-14030. DOI: 10.1039/C8NR03132K
A Nanostructured Electrode for Photoelectrochemical Detection of Hydrogen Peroxide
Authors: del Real Mata Carolina , Siavash Moakhar Roozbeh , Mahshid Sara
Published: May 2020

Hydrogen peroxide (H2O2) acts as a critical second messenger in fundamental biological processes, which makes it a highly important target for direct detection in biological systems. Among various read-out techniques, photoelectrochemical (PEC) sensing offers a low limit of detection and high sensitivity. Here, a promising, non-enzymatic, sunlight-driven, simple photoelectrochemical (PEC) sensor for H2O2 detection is presented. The electrode is based on a Si wafer, a thick ZnO spacer, a thin Au layer and a graphene layer on top. The fabrication was done through conventional e-beam evaporation deposition technique for the spacer and metal film. An additional layer of graphene was drop-casted on top. The latter provides highly conductive scaffolds to ease electron transport and to increase the electrode sensitivity. The morphological characteristics and optical properties were investigated via FESEM and UV-Vis spectroscopy, respectively. Additionally, the electrochemical characterization was conducted using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry. Direct detection of H2O2 was studied via chronoamperometry method under simulated sunlight by using a three-electrode configuration in which stainless-steel served as both counter and reference electrodes and the fabricated electrode as the working electrode. The photo responses to gold and gold/graphene electrodes in a non-enzymatic and biocompatible PBS environment with a pH 7.2 were thoroughly investigated. The gold-graphene demonstrates boosted properties combining excellent photoelectroactivity and high sensitivity towards H2O2 with a superb limit of detection of 1pM in a linear range of 1pM-100mM.

Keywords: Hydrogen peroxide, gold, graphene, photoelectrochemical sensor
Superior Triethylamine Sensing Performance of Metal-Organic Frameworks-Derived In2O3 Nanostructured Materials
Authors: Xu Jiaqiang , Wang Xiaohong , Sun Yue
Published: May 2020

Volatile gas of triethylamine (TEA) may cause serious pollution to the environment and have a great impact on the respiratory system. Once inhaled into the lungs, it can cause pulmonary edema and even death. According to Occupational Safety and Health Administration (OSHA) regulation, the concentration of TEA allowed in air is limited to 10 ppm. Herein, we reported a TEA gas sensor, it can quantitatively detect on ppb level based on metal-organic frameworks-derived In2O3 hollow porous structure, which was successfully synthesized by calcinating the precursor In-MIL-68 at a suitable temperature 500˚C, and exhibited the highest response of 226 when exposed to 5 ppm TEA gas at the optimal working temperature 120˚C. Furthermore, In2O3-500 sensor not only possessed superior response and recovery properties of 9 s and 36 s under 5 ppm TEA gas, respectively, but also demonstrated outstanding selectivity, stability and moisture resistance. In addition, the In2O3-500 sensor exhibited the good response linearity within a wide TEA concentration range from 100 ppb to 5 ppm, and lower detection limit. Considering the superiority including facile fabrication, low cost and simple structure, In2O3-500 hollow porous structure is a promising candidate for high-performance TEA sensing applications.

key words: Gas sensor, Triethylamine , In2O3, Metal-organic frameworks

Figure 1
Highly Selective Ppb-Level NOx Sensing at Room Temperature By Tungsten Oxide-Based Nanocomposites
Authors: Wang Shih-Han , Yeh Kuei-Ling , Huang Shao-Ying , Chang Yi-Ju , Tsai Liren
Published: May 2020

Nitric oxide (NO) and nitrogen dioxide (NO2) are major air pollutants produced by the combustion of fossil fuels and emission of exhaust from vehicle. NO2 sensing is one of the air quality index and NO is always co-exist with NO2, and they are the precursors of particular matters(PM). Besides, nitric oxide is also an important biomarker of respiratory diseases, and the degree of airway inflammation could be determined by exhaled NO concentration. For the outdoor air quality monitoring or biomedical applications, NO and NO2 concentrations are at ppb-level. Chemiresistive-based gas sensors have been extensively applied for NOx sensing. However, the application of resistive-based gas sensors is limited by their low selectivity and high operating temperature. In this study, a conducting polymer-tungsten oxide nanostructured p-n junction nanocomposites were used to enhance the sensitivity for NOx sensing at room temperature. Furthermore, the metallic electrocatalyst was incorporated to improve the selectivity. The sensors could detect the NO and NO2 concentration in the range from 0 to 500 ppb at room temperature, and the lower detection limits for NO and NO2 were 50 ppb and 15 ppb, respectively. The effect of potential interference gases, such as nitric oxide(NO), nitrogen dioxide (NO2), carbon monoxide (CO), sulfur dioxide (SO2) and ozone (O3) were evaluated. Both NO and NO2 sensors exhibited excellent selectivity. The sensing mechanism was investigated by in-situ FTIR. The results suggested that NO2 was reduced on the nanocomposite and NO was catalytically oxidized to NO2 by the nanocatalyst, which could eliminate the cross-talk of NO2 for NO sensor. In addition, the repeatability, stability, temperature effect, humidity effect were also studied. In summary, highly sensitive, selective and stable NO and NO2 sensors were successfully developed, and they were suitable for the purpose of air quality monitoring.
Hydrogen Efficient Sensor Based on Schottky Barrier Diode of the Point Contact between Pdxo Decorated TiO2 Nanotube Arrays
Authors: Ling Yunhan
Published: May 2020

To enhance the detection sensitivity towards hydrogen, a novel point contact TiO2 nanotube decorated with PdxO Schottky barrier diode (SBD) was proposed and investigated in this paper. TiO2 nanotube arrays were fabricated on Ti wires by electrochemical anodic oxidation, and Pd catalytic nanoparticles were modified by micro-emulsion electrochemical deposition. The surface morphology was characterized by field emission scanning electron microscopy (FESEM), and the hydrogen sensitivity of the point contact between TiO2 nanotubes was investigated. It exhibited high sensitivity under working temperature of 70oC, and the sensitivity of SBD to 2000ppm hydrogen was about 8500. Impedance spectroscopy, the current–voltage (I-V) characteristic measurement and infrared spectroscopy were also employed for further mechanism investigation. From the I-V curves, we found the Schottky barrier was formed on the contact and the barrier height decreased with increase of hydrogen. The sensing processes of the charge transfer were unveiled according to the different time constants and that mechanism was in reasonable support of IR surface analysis. This information may provide some insight on the understanding of the device physics of this new emerging nanotube array based SBD which will have broaden application in hydrogen energy and related security system.
A Cell-Based Electrochemical Biosensor to Detect Sub-Nanomolar Levels of Environmental Pollutants
Authors: Furst Ariel L
Published: May 2020

Endocrine disruptors, dangerous contaminants found in many household products as well as in the environment, have garnered increasing attention due to their pervasiveness. These compounds are found in many products we use daily, including medications, plastics, and pesticides and are implicated in many health problems, including cancer, infertility, and diabetes. These chemically dissimilar compounds all target a small number of hormone receptors in our bodies, and this dissimilarity makes detection of these compounds a challenge. We have developed a novel detection strategy for estrogenic compounds that is both rapid and portable. Our platform is based on E. coli engineered to surface express a native estrogen receptor construct, enabling recognition of many structurally dissimilar compounds. The large size of the cell affords inherent signal amplification from impedance measurements upon binding to a modified electrode. We have detected sub-ppb levels of the native hormone estradiol and ppm levels of the endocrine disruptor bisphenol A (BPA) in complex solutions. As our system reports the total estrogenic activity of a sample rather than the concentration of specific components, we can measure the activity of unknown compounds, including chemicals released from a BPA-free plastic baby bottle following microwave heating. Importantly, this approach is broadly applicable to the detection of chemically diverse compounds that bind to a single receptor.
Inkjet Printed Multi-Walled Carbon Nanotube Sensor for the Detection of Lead in Drinking Water
Authors: Rahm Connor E , Torres-Canas Fernando , Gupta Pankaj , Poulin Philippe , Alvarez Noe T.
Published: May 2020

The heavy metal lead has been a pollutant in our environment for many centuries and at low concentrations, lead can damage the human central nervous system, liver, kidney, and cardiovascular system and cause physiological and neurological problems in developing children who are most susceptible to lead poisoning. Lead in drinking water is currently regulated in the United States by the Environmental Protection Agency (EPA) with a maximum contamination level (MCL) of 15 ppb and the World Health Organization (WHO) has a MCL of 10 ppb of lead. Researches have identified high levels of lead in drinking water samples across the globe and the neurological development of young children is of great concern. A need for a rapid, sensitive, selective, reproducible, and affordable sensor for the trace detection of lead in true drinking water samples is needed. The detection of Pb2+ was performed using an inkjet printed multi-walled carbon nanotube (IJP-MW-CNT) electrode employing Osteryoung square wave stripping voltammetry (OSWV) as the detection method. The MW-CNT ink was prepared in water using bile salts (BS) as a surfactant, which were washed out extensively with DI water before using the printed MW-CNTs as electrodes. The IJP-MW-CNT electrode was used as the working electrode with a platinum wire and glass capillary Ag/AgCl as auxiliary and reference electrode, respectively. The electrodes performance was optimized in 0.1 M acetate buffer (pH = 4.3) and had a linear range of 5 – 50 ppb (R2 = 0.98235) a sensitivity of 20.15 nA/ppb and a limit of detection (LOD) of 1.632 ppb for Pb2+. The analytical applicability of electrode was tested in a real drinking water sample (i.e.) Cincinnati tap water with a linear range of 15 – 70 ppb (R2 = 0.98752) a sensitivity of 2.654 nA/ppb and a LOD of 1.269 ppb for Pb2+. The IJP-MW-CNT electrode’s results are comparable between different electrodes, and reproducible using the same electrode multiple times. The electrode can be easily and quickly be fabricated without modifications or in-situ additives needed, which makes up-scale production a feasible option. The sensor has been shown to perform well in an environmental sample (Cincinnati tap water) without any sample preparation or changes.The IJP-MW-CNT electrode can be implemented for the affordable and rapid detection of lead on-site in true water samples.
ZnO Nanorods Based Miniature Sensor Networks for Continuous Monitoring of Soil pH in Smart Agriculture
Authors: Akshaya Kumar A , Naveen Kumar S K , Bhansali Shekhar , Khosla Ajit
Published: May 2020

The real-time monitoring of soil pH would improve the management of the nutrients, leading to conservation of fertilizer as well as maintain the pH level in the agricultural field. This paper reports the interdigitated electrodes (IDEs) modified by ZnO nanorods (NRs) based miniature sensor networks for continuous monitoring of soil pH in smart agriculture. The pH sensor fabricated from a ZnO thin film layer followed by a hydrothermal growth lead to the uniform ZnO NRs patterns on the thermally evaporated IDEs. The soil pH sensor was analyzed and calibrated both standard and extracted soil samples in the range of pH 4 – 10. The sensor offers a sensitivity of 1.06 nF/pH in the range of pH 4 –10. The pH sensor is highly selective to hydrogen ions even when other ions are present at significant concentrations. The fabricated sensor networks were embedded by a central Atmega328 microcontroller for continuous data monitoring of soil pH in agriculture filed.

Figure 1
Assimilation of Interdigitated Electrodes (IDEs) with ZnO Nanorods (NRs) for Potassium Measurement Application
Authors: Naveen Kumar S K , Akshaya Kumar A , Bhansali Shekhar , Khosla Ajit
Published: May 2020

There is a significant interest to detect the level of nutrients concentrations available in the agriculture land. Among nutrients, the potassium ions play an imperative role in the plant growth and photosynthesis process. This paper presents the fabrication of IDEs based potassium sensors by using ZnO nanorods (NRs) active layers. The deposition of ZnO thin film layer followed by a hydrothermal treatment lead to the ZnO NRs on the thermally evaporated IDEs. The IDEs patterns with the dimension of 0.5 mm wide, 15 mm long and 0.5 mm distance between the adjacent fingers, designed and tested using AutoCAD software tool. The structural, compositional and electrical properties of the NRs were investigated and studied by using field emission scanning electron microscopy (FeSEM), atomic force microscopy (AFM), energy dispersive spectroscopy (EDS), X-ray diffractometer (XRD) and Keithley 4200 semiconductor characterization system respectively. The fabricated potassium sensor shows a noble current response with respect to the increasing potassium concentrations. The fabricated sensor detected potassium in the range of 5μM to 20μM potassium concentrations with a good correlation coefficient (R2) of 0.9389. The sensor displayed a sensitivity of 0.459 μA/μM in the range of 5μM to 20μΜ potassium concentrations
Highly Sensitive Dual-Signal Amplification Electrochemiluminescence Aptasensor Based on Platinum Electrode Modified with Multi-Walled Carbon Nanotubes-Titanium Dioxide and Thionine for Kanamycin Detection
Authors: Sun Xia , Cheng Shuting , Liu Junfeng , Guo Yemin
Published: May 2020

A dual-signal-amplified electrochemiluminescence (ECL) aptasensor based on multi-walled carbon nanotubes@titanium dioxide/thionine (MWCNTs@TiO2/Thi) was proposed to detect kanamycin (KAN) based on the chemiluminescence properties of luminol-hydrogen peroxide (H2O2) in alkaline solution. The MWCNTs@TiO2 with large specific surface area and advantageous biocompatibility could accelerate electron transfer and enable high loading of luminol to enhance ECL intensity. Thi, as a perfect electronic mediator, it can also accelerate electron conductivity to further enhance ECL intensity. With the high charge transfer property of MWCNTs@TiO2 and Thi, the ECL intensity of the aptasensor was obviously promoted. When the target KAN existed, ECL signal decreased significantly due to the specific interaction between KAN and the aptamer. Therefore, KAN concentration could be determined according to the intensity of ECL. Under the optimal conditions, the developed aptasensor showed a wide linear range from 1×10-3 to 1×105 ng mL-1 with a low detection limit of 0.073 ng mL-1 (S/N = 3). The aptasensor showed high specificity, good reproducibility and long-term stability. Simultaneously, the application of the proposed ECL aptasensor will open an efficient approach for highly sensitive detection of KAN in food safety.
Chemical Sensor for PFOA and PFOS Detection
Authors: Ryu Heejeong , Lei Yu
Published: May 2020

As emerging contaminants, per- and polyfluoroalkyl substances (PFASs) make up a large group of persistent anthropogenic chemicals that are persistent and not easily degradable in the environment. Recent studies in humans have shown that certain PFASs (e.g., perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS)) may negatively affect fetus development, child learning and behavior, adult fertility, hormonal balance, and liver function. Due to the long-term impact of these PFASs on human health, the lifetime exposure health advisory of PFOA and PFOS in drinking water recommended by the Environmental Protection Agency (EPA) is 70 parts per trillion (70 ng/mL or 70 ppt), which make their detection extremely challenge. In this study, we will develop a chemically functionalized surface or a sensing film, and then explore its applicability for PFOA or PFOS detection. The analytical characteristics such as the limit of detection, sensitivity and reproducibility will be systematically investigated.
Block-Copolymer Derived Nanoporous Thin Films for the Development of a L-BMAA Aptamer-Based Electrochemical Biosensor
Authors: Santiago Maldonado Xaimara , Nicolau Eduardo
Published: May 2020

Produced by diverse cyanobacteria, b-N-methylamino-l-alanine (L-BMAA) is a non-protein neurotoxic cyanotoxin that has been linked to an elevated incidence of neurodegenerative diseases such Parkinson’s and Alzheimer’s disease and Multiple Lateral Sclerosis. The continuing rising of water temperatures and eutrophication of the water bodies propitiate the increment and size of harmful algal blooms, subsequently increasing the production of L-BMAA and other cyanotoxins. This toxin is known to bioaccumulate in plants, animals and humans. Currently, the detection of L-BMAA in water is limited by its hydrophilicity, absence of ultraviolet and fluorescent properties, and the isomers that cause false positives. Given the threat that this cyanotoxin could represent to the long-term human health, it is imperative to develop new analytical techniques for its detection in water. Therefore, this project proposes the development of an impedimetric aptamer-based biosensor, using block-copolymer (BCP’s) derived nanoporous thin films as the electrode, for the detection of L-BMAA. Our hypothesis is that the development of such aptasensor will lead to the advancement of an innovative device for a sensitive, portable, economic and flexible way to achieve the detection of the cyanotoxin in water. To achieve this, we used BCP polystyrene-poly(methylmethacrylate) (PS-b-PMMA), known to form cylinder-like structures, to create recessed nanodisk-array electrodes (RNEs). These cylindrical nanostructures provide primary mass transport pathways for ionic and redox active species which changes upon analyte binding, making them ideal to use in biosensing applications. The nanoporous electrodes were prepared by spin-coating a PS-b-PMMA solution in toluene over gold-coated silicon wafers, followed by thermal annealing and UV etching. Different annealing times, temperatures and UV exposure has been used in order to produce the alignment of the cylindrical polymer microdomains in a vertical fashion over the surface of the electrode. The prepared films were characterized using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), to confirm the formation of RNE’s. Under specific sets of conditions, CV data shows sigmoidal curves at high scan rates characteristic of RNE’s, suggesting the formation of this type of nanopores with a sufficiently large distance among them to attain radial diffusion. Atomic force microscopy (AFM) images of the samples evidence the formation of vertical nanopores but mixed with horizontal alignments. Furthermore, grazing incident small angle x-ray scattering (GISAXS)11 suggests that the polymer was well-dispersed among the surface although the expected scattering profile for RNEs is missing. Future work includes the optimization of the electrode preparation methods and the selection of a L-BMAA specific aptamer through graphene oxide-assisted selection evolution of ligands by exponential enrichment (GO-SELEX).
Fabrication of Nanostructured Electrochemical Sensor Based on Gold Nanoparticles Thin Film Modified FTO Electrode for Detection of Arsenic in Aqueous Media
Authors: Huynh Le Thanh Nguyen , Le Viet Hai , Nguyen Hoang Thai
Published: May 2020

Although arsenic is naturally present in the environment, 99% of human exposure to arsenic is through ingestion. Throughout history, arsenic is known as “the king of poisons”; it is mutagenic, carcinogenic, and teratogenic. Even in smaller concentrations, it accumulates in the body and takes decades before any physical symptoms of arsenic poisoning show. According to the World Health Organization (WHO), the safe concentration of arsenic in drinking water is 10 µg/L. However, this limit is often ignored until it is decades too late, and people begin showing symptoms of having been poisoned. This is the current situation for Vietnam, whose legal arsenic concentration limit is 50 µg/L, five times higher than the WHO guidelines. Groundwater in Vietnam was already naturally high in arsenic due to arsenic‐rich soils releasing arsenic into groundwater. Then, in the past half-century, with the use of arsenic‐laden herbicides dispersed during Vietnam. This work aimed to fabricate a gold nanoparticles (AuNPs) electrochemical sensor on the surface of the conductive glass (FTO), which can detect the tiny concentration of arsenic. The AuNPs electrochemical sensors (Au thin films) are prepared on the surface of FTO following three methods: (i) electro-deposition, (ii) electrophoresis, and (iii) screen-printing. All methods allow the control of size and shape (nanorod, nano-star, branched-shape, quasi-spherical shape, spherical shape) of AuNPs that benefit the limit of detection (LOD).
Au Decorated WO3-X Nanoflake Arrays Used As Photoelectrochemical Detection and Surface Enhanced Raman Scattering
Authors: Luo Yan , Ling Yunhan , Gu Yanhong
Published: May 2020

The increasing of environment organic pollution in water body is calling for the development of high efficient sensors for fast and stable monitoring. Herein, a new Au decorated WO3-x nanoflake arrays sensor combined photoelectrochemical detection with surface enhanced Raman scattering (SERS) was proposed, in which self-doped tungsten trioxide (WO3-x) nanoflake arrays were synthesized by dealloying of Fe-W amorphous alloy and thermal treatment, following by surface decoration of sputtering Au nanoparticles. The effect of size and distribution of gold particles on the photocatalytic degradation of WO3-x was investigated. It was found that the annealing temperature plays an important role in the growth of gold particles, the optimal size is about 10nm (annealing temperature was 400 ℃); photoelectrochemical test revealed that the current density was positively correlated with the pollutant concentration with the detect limit of 10-9 mol/L; at the same time, these functional nanoflake arrays showed high sensitivity for R6G (10-8mol/L) in Raman spectrum detection. We believe that this technique will have a great prospect for qualitative and quantitative analysis of environmental pollutants.
Supercritical Fluids Synthesis of Catalyst Nanoparticles- Decorated Nanocarbon for Low Concentration Formaldehyde Sensing
Authors: Yang Cheng-Kang , Wang Shih-Han , Wen Meng-Jie , Liao Jin-Yi
Published: May 2020

The formaldehyde (HCHO) is one of a major pollutants in indoor air and it is harmful to healthy even exposed in low concentration. It was regulated that the HCHO concentration should beyond 0.08 ppm[1]. The conventional methods to analyses formaldehyde are GC, HPLC and so on, but those methods are not user friendly. We aimed to develop an electrochemical formaldehyde sensor which is highly sensitive, quick response, cost effective and user friendly. In the previous study, platinum electrocatalyst has wildly applied for the catalytic oxidation of HCHO [2]. Furthermore, some other catalysts such as palladium and copper oxide were used as oxidation catalysts. In this study, the no surface tension property of supercritical fluids were exploited to decorate nanocatalyst onto nanocarbons uniformly. The surface morphology and chemical structure of the materials were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectrometer (FTIR), respectively. The bimetallic electrocatalyst decorated nanocarbon exhibited highly catalytic properties, and the oxidation potential could be less than 0.2 V vs. Ag/AgCl. The sensor showed a wide sensing range from 0-100 ppm and the lower detection limit was 1 ppb. All sensing properties of this HCHO sensor, including sensitivity, stability and repeatability were examined carefully. The selectivity to the potential interferences and the temperature effect were accessed. The experimental results demonstrate high feasibility of this nanocarbon-based HCHO sensor for the indoor air quality monitoring.

References

[1] Environmental Protection Administration Executive Yuan, ROC (2012)

[2] Nie, L., Yu, J., Jaroniec, M., & Tao, F. F. (2016). CATAL SCI TECHNOL, 6(11), 3649–3669. doi:10.1039/c6cy00062b
A Long-Range and Self-Powered Intelligent Food Monitoring System Based on Far-Field Energy Harvesting and Pressure Measurement
Authors: Do Huu-Dung , Chung Wan-Young
Published: May 2020

Introduction

Radiofrequency (RF) energy harvesting has recently become a promising solution to power wireless sensors networks. As this emerging technology allows low-power sensors and systems to be charged wirelessly, it is advantageous in various applications with low cost and fewer requirements for periodical maintenance [1]. On the other hand, food quality is one of the most concerned problems of our society, foodborne illnesses caused by eating spoilt food has been a serious threat to human health. Therefore, development of a low cost, rapid and sensitive monitoring system is essential to ensure food safety and security. However, conventional food monitoring methods, which are usually based on measuring gas concentration show some drawbacks in terms of power consumption, cost, and reliability [2].

In this study, we developed a high-efficient battery-less system that can be used for food monitoring based on the far-field RF energy harvesting technique.

Methods

Our proposed system consists of an RF energy harvester and a sensing circuit. The RF energy harvester can harvest energy from radio waves at an ultra-high frequency (UHF) of 915 MHz to supply the power for the operation of all tag components. To improve the received power and enhance the distance of power transfer, a Yagi type structure antenna with three elements (driver, director, and reflector) was implemented to achieve a high gain and fit into a compact footprint [3]. Besides, to overcome the disadvantages of conventional food monitoring methods, our study focuses on measuring the increase in air pressure inside the food package caused by gas emission during storage. To confirm the effectiveness of the proposed system, we performed experiments on different sorts of food such as chicken, pork and fish.

Results and Conclusions

As a result, the sensor module is designed using a high accuracy pressure sensor and other ultra-low-power components, allowed it to consume low average power of only 1mW. The designed Yagi antenna has a high gain of 5.23dBi in the direction of the maximum radiation and voltage standing wave ratio (VSWR) better than 1.3 in approximately 60Mhz band (890-950Mhz). Finally, the increase in air pressure during food spoilage was used to categorize food freshness, demonstrating the feasibility of our proposed system.

References

[1] T. Soyata, L. Copeland and W. Heinzelman, "RF Energy Harvesting for Embedded Systems: A Survey of Tradeoffs and Methodology," IEEE Circ. Syst. Mag., vol. 16, no. 1, pp. 22-57, Firstquarter 2016

[2] Chung, W. Y., Le, G. T., Tran, T. V., & Nguyen, N. H. (2017). Novel proximal fish freshness monitoring using batteryless smart sensor tag. Sensors and Actuators B: Chemical, 248, 910-916.

[3] S. Keyrouz, G. Perotto, H. J. Visser and A. G. Tijhuis, Novel broadband yagi-uda antenna for ambient energy harvesting, in IEEE 42nd European Microwave Conf. (EuMC), pp. 518-521, 2012
Biofilm Formation on Two Layer CVD Graphene and Its Change of Capacitance
Authors: Kanematsu Hideyuki , Nakagawa Ryoichi , Saito Kai , Miura Hidekazu , Ishihara Masatou , Ban Masato , Hirai Nobumitsu , Kogo Takeshi , Ogawa Akiko , Barry Dana M.
Published: May 2020

Biofilms formed on materials have brought about many industrial problems so far. Chronic diseases, the deterioration of hygiene conditions etc. could be mentioned for example. We have confirmed that graphene is easy to form biofilms on it in various ways. Therefore, we expect and predict it could be applied to a practical sensor for biofilm detections. In our precious studies, we produced mono layer graphene on glass specimens and confirmed that it was highly sensitive to biofilm formation in a flow type laboratory biofilm reactor. However, monolayer graphene is generally still lacking in uniformity and the non-coating area is often observed. Therefore, we investigated the sensitivity of two layer CVD graphene to biofilm formation and the possibility to biofilm sensor.

In this study, we focused on the change of capacitance with biofilm formation on the graphene coating. The graphene coating specimens on copper and PET substrates were set to laboratory biofilm reactors and we formed biofilms on the specimens artificially. After the formation of biofilms, the specimens were checked by Raman spectroscopy and also observed by an optical microscopy. And the specimens' capacitances were measured, using a specially devised jig connecting to a LCR meter. The frequencies were changed from 700 to 2000Hz and the capacitances were measured.

As a result, biofilm formed specimens showed small peaks at some characteristics frequencies, while specimens without biofilms showed no peaks at all. Therefore, we presumed that dielectric polarization-relaxation and the loss would occur due to the existence of External Polymeric Substances (EPS) derived from biofilms. We discussed the application possibility of this phenomenon to biofilm sensing.
Monitoring of Technetium in Groundwater:Development of a Novel Qcn Based Sensor
Authors: Papageorgiou Athanasios , Andrieux Fabrice , Cooper Stuart
Published: May 2020

99Tc, a pure β-emitter with Emax =294 keV, is one of the most significant (t1/2 =2.1×105 y) nuclear waste isotopes, produced by the fission of U with a yield of 6%. Under normal environmental conditions, it is mostly encountered as the pertechnetate ion, TcO4
-, which is highly soluble and consequently mobile in water. For this reason, and because it often is the first contaminant to be present in detectable levels, its monitoring into groundwater is a statutory requirement for every nuclear license site. Because of its relatively low concentration in environmental samples, current determination methods of 99Tc involve several steps, such as chemical separation from the matrix, purification and source preparation, prior to radiometric (e.g. liquid scintillation counting) or mass spectroscopic (e.g. inductively coupled plasma mass spectroscopy) determination. The detection of 99Tc may take up to several days, thus making these techniques inappropriate for an emergency situation. Hence, We report on the development of a sensor for the real time monitoring of 99Tc in groundwater based on the Quartz Crystal Nanobalance (QCN). The QCN is a piezoelectric resonator, which oscillates at a resonant frequency fs when an electric potential is applied across its body. It is capable of measuring very small changes in mass at its surface, through the change of the resonant frequency. We modify it to respond exclusively to the presence of TcO4
-, by application of a novel Ag-4,4bipyridine metal-organic framework thin film built layer-by-layer on a self-assembled monolayer of 4-mercaptopyridine on the gold surface. The film’s structure is characterised by several techniques such as XPS, AFM and XRD and we evaluate its response and selectivity by monitoring the changes in the resonant frequency as a function of the concentration of ReO4
-, which is a non-radioactive chemical surrogate for TcO4
-.
Reagent-Free Detection of Lead Carbonate Using Stripping Voltammetry
Authors: Huseinov Artur , Alvarez Noe
Published: May 2020

Nowadays lead pipes are still present in many houses and could be a potential source of this metal in drinking water. Modern polyvinyl chloride pipes also contain compounds of lead, that can be leached from them, causing an increase of Pb concentration in drinking water. That is why regular and simple testing of tap water is necessary to avoid lead poisoning. Voltammetric sensors, due to their high sensitivity, simplicity and low cost, are very good for the detection of lead ions. In tap water, except of free ions, lead may present in various particulate forms (i.e. oxides, hydroxide, insoluble salts, etc.) that cannot be detected directly using electrochemical techniques.

A user-friendly sensor should exclude any sample preparation; however, this step is necessary to bring all the species to the ionic form. It has been reported the possibility of electrochemical pH reduction of water. Oxidation of water occurs easily on most inert electrodes (Pt, Au, etc.), producing hydrogen ions. Generated H+ can chemically interact with some lead species, revealing free lead ions.

The proposed method employs electrochemical generation of hydrogen ions, combined with stripping square wave voltammetry for quantification of lead species in particulate form, using lead carbonate as a model compound. The signal obtained using this method is linearly proportional to the amount of solid PbCO3 added to the solution in the range of 50-250 μg/l.
Controlled One-Step Manufacture of Charge Transfer Salt Nanowire Sensors for Gas Detection
Authors: Yu Xuecheng , Kilani Mohamed , Mao Guangzhao
Published: May 2020

Major barriers for commercializing nanowire sensors are complicated synthesis technique and lack of scalable device assembly methods. Charge transfer salts (CTS), like tetrathiafulvalene bromide (TTFBr), have been well known for unique electric and chemical property. This talk will bring a controlled one-step deposition method to fabricate CTS nanowire sensors. By applying certain potentials to designed substrates, TTFBr nanowires can be directly deposited onto the electrodes. Varying deposition conditions and design of substrates are able to control the geometry, density and composition of TTFBr nanowires. TTFBr nanowire sensor shows high sensitivity, selectivity, and fast response towards ammonia gas. The detection limit is less than 1ppm and the response time, at room temperature, is less than 1 minute. Other CTS, like Cu- tetracyanoquinodimethane, can also be fabricated into nanowire sensor using the same method. This research shows a promising scalable fabrication method for various nanowire sensors and is being commercialized.