bluuebunny/crossref_metadata_2025 huggingface dataset:
Probing DNA Stability in High Electric Fields: Electrochemical Melting Analysis
Authors: West Ryan
Published: July 2021

Here we present our results on the electric field-induced melting of surface-bound DNA (i.e. electrochemical melting). In particular, we examine the effects of the DNA-binding compound cisplatin on the stability of DNA within high electric fields. Cisplatin is an anticancer drug that has been used to successfully treat testicular, ovarian, and bladder cancers, among others (1). It crosslinks DNA between the N7 atoms of purine bases, resulting in changes in structure and stability, ultimately interfering with vital cellular processes in vivo.

Self-assembled monolayers (SAMs) of thiol-modified oligonucleotides on gold electrodes provide selective and sensitive interfaces for the development of chemical and biological sensors (2). While many transduction mechanisms have been utilized (including electrochemical, optical, and gravimetric) and many analytes targeted (e.g. small DNA-binding molecules, heavy metals, and specific DNA sequences), the unique steric and electrostatic environment of the crowded DNA in the electrical double-layer complicates the behavior of these biosensors (3). Electrical potentials applied at the DNA-SAM have been shown to modulate the behavior of these monolayers (4). Here, we utilize the electric field-effect to induce melting of the bound doublestranded DNA, and we monitor the kinetics of the melting process using square wave voltammetry (5).

We find that the effect of cisplatin on the melting behavior depends on the method used to the prepare the monolayer, in particular the melting depends on surface-coverage and heterogeneity of the resulting layers. Under some conditions, cisplatin results in an apparent stabilization of the DNA-SAM, and a destabilization in others. Significant differences in the resulting melting curves suggest that the mode of cisplatin-DNA binding varies depending on the SAM preparation method. The methodology presented here has the potential of (1) providing an electrochemical approach for studying the interaction between DNA and small molecules, and (2) providing a method for indirectly assessing the heterogeneity of DNA-SAMs via electrochemical melting in the presence of cross-linking agents.

1. R. A. Alderden, M. D. Hall and T. W. Hambley, Journal of chemical education, 83, 728 (2006).

2. J. J. Gooding and N. Darwish, The Chemical Record, 12, 92 (2012).

3. P. Gong and R. Levicky, Proceedings of the National Academy of Sciences, 105, 5301 (2008).

4. U. Rant, K. Arinaga, S. Fujita, N. Yokoyama, G. Abstreiter and M. Tornow, Organic & biomolecular chemistry, 4, 3448 (2006).

5. D. Ho, W. Hetrick, N. Le, A. Chin and R. M. West, Journal of The Electrochemical Society, 166, B236 (2019).
Quick Portable Electrochemical Sensing Platform to Detect Al3+ Content in Our Dietary Fruit Juices
Authors: Poudyal Durgasha , Dhamu Vikram Narayanan , Paul Anirban , Muthukumar Sriram , Prasad Shalini
Published: July 2021

Aluminum is one of the most widely distributed elements (7.5%) of the earth crust. The current research interest in the aluminum content in our foods and diets are related to the concerns about the possible association of excessive intake and/or elevated tissue levels of this element and linked with various disorders viz. Alzheimer's, Dialysis encephalopathy/dementia, bone disorder. Aluminum (Al) is present in our daily food naturally, but mostly in elevated level through the various food additives, by the use Al cookware, storage canes and Al wrappings. The migration of Al is known to increase with the acidity (pH of the food), duration of storage, and presence of salts and organic acids. As it is found commonly in our daily food products and it may not be the reach of every common people to have sophisticated laboratory test to understand the Aluminum content in the daily food products. Herein, we have developed a quick portable electrochemical platform to measure the threshold Al content in the readily available food samples mostly canned foods (juices having the pH acidic (pH 3.5-5.5). For that, we used Pd/C (palladium black catalysts) modified Au screen- printed electrode. The activity of the catalyst influenced by the added Al3+ content was analyzed using Electrochemical impedance spectroscopy. The calibrated dose rate (CDR) is obtained as a function of the change in Z mod (Ω) value from the Bode plot vs the concentration of added Al3+ in buffer of different pH in the concentration ranging 0.5µg/mL to 1mg/mL. The sensors were tested for real canned juice samples. Such method can be an easy and quick qualitative testing procedure for Aluminum poisoning in our everyday food products

Figure 1
Detection of Bacteria Using Near Infrared Fluorescent Nanosensors
Authors: Nißler Robert , Bader Oliver , Dohmen Maira , Walter Sebastian , Noll Christine , Selvaggio Gabriele , Groß Uwe , Kruss Sebastian
Published: July 2021

Infectious diseases are worldwide a major cause of morbidity and mortality. Fast and specific detection of pathogens such as bacteria is needed to combat these diseases. Optimal methods would be non-invasive and without extensive sample-taking/processing. Here, we developed a set of near infrared (NIR) fluorescent nanosensors and used them for remote fingerprinting of clinically important bacteria. The nanosensors are based on single-walled carbon nanotubes (SWCNTs) that fluoresce in the NIR optical tissue transparency window, which offers ultra-low background and high tissue penetration. They are chemically tailored to detect released metabolites as well as specific virulence factors (lipopolysaccharides, siderophores, DNases, proteases) and integrated into functional hydrogel arrays with 9 different sensors. These hydrogels are exposed to clinical isolates of 6 important bacteria (Staphylococcus aureus, Escherichia coli, ...) and remote (≥25 cm) NIR imaging allows to identify and distinguish bacteria. Sensors are also spectrally encoded (900 nm, 1000 nm, 1250 nm) to differentiate the two major pathogens P. aeruginosa as well as S. aureus and penetrate tissue (>5 mm). This type of multiplexing with NIR fluorescent nanosensors enables remote detection and differentiation of important pathogens and the potential for smart surfaces.
(Invited) Barcode-Based Biorecognition for Electrochemical and Photoelectrochemical Biosensing
Authors: Soleymani Leyla , Pandey Richa , Traynor Sarah , Victorious Amanda , Saha Sudip
Published: July 2021

Biosensors are devices that combine biorecognition with signal transduction to analyze biologically-relevant targets. In order for these devices to be used in disease management, clinical decision making, and health monitoring, they must deliver sufficient sensitivity, specificity, and speed at the point-of-care and rely on minimal sample processing. This work is focused on developing integrated biorecognition and signal transduction strategies for enhancing the performance metrics of biosensors.

Barcode-based biorecognition systems translate analyte capture to the release of specific signal transducing barcodes. We have focused on developing barcode-based systems that are compatible with photoelectrochemical and electrochemical readout for targeting proteins and nucleic acids. These systems translate molecular recognition elements using functional nucleic acids and antibody-DNA complexes for releasing an electroactive or a photoelectrochemical DNA barcode. We have combined these barcode-based systems with nanostructured electrochemical transducers for increased signal-to-noise-ratio and sensitivity.

By combining barcode-based biorecognition with electrochemical readout, we have developed handheld biosensors for clinical analysis of urinary tract infections. We have also used these strategies for detecting prostate cancer biomarkers. Integration of barcode-based biorecognition with photoelectrochemical readout presents a new modality for biosensing and opens the route for ultrasensitive and programmable biosensing.
(Invited) Development of Electrochemical 6-Well Plate for Immunosensors
Authors: Cui Feiyun , Zhou Zhiru , Zhou Hong
Published: July 2021

While developing low-cost and multiplexing electrochemical (EC) devices for bioassay is very attractive, the miniaturization of reference electrodes (RE) is a critical issue for fabricating EC devices. Herein, a polymer-based EC device, named EC 6-well plate, is proposed and fabricated using a non-photolithography method. Polyethylene terephthalate glycol (PETG) is used as a substrate and laser-cut polyester (PET) film is used as a mask for patterning the electrodes. Acrylic mold with wells (60 μL) was bonded to the PETG substrate. Schematic diagrams (Figure 1) are used to illustrate the preparation of electrochemical 6-well plates. The diameter of the working electrode (WE) is 900 μm, and each WE-modifying step only requires 1 μL of reagent.

Both electrochemical (HCl method) and chemical methods (FeCl3 method) were proposed to prepare the solid-state Ag/AgCl RE. Precise time control is critical for the preparation procedure. It is hard to control the time in 1 s or under 1 s using the chemical method. Hence, the electrochemical method was selected for continued work since the reaction time can be precisely controlled. The stability of solid-state Ag/AgCl and drift of open circuit potential (OCP) can be affected by anions present in the background electrolyte. Herein, 0.1 M KCl, 1 M KCl, and 0.1 M KNO3 containing 5 mM K3[Fe(CN)6]/K4 [Fe(CN)6] were compared as the electrolytes. Considering that 0.01 M PBS is the most commonly used buffer solution for bioassay, 0.01 M PBS containing 5 mM K3[Fe(CN)6]/K4 [Fe(CN)6] was also included. OCP was recorded in these electrolytes for 1 hour. These results revealed that 0.1 M KCl is the best choice for the background electrolyte. The solid-state Ag/AgCl RE-based three-electrode system, the all Au three-electrode system (3E), and all Au two-electrode system (2E) were used to develop the immunosensor forClostridium difficile toxin B detection. Differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) were applied to test the stability of the EC immunosensor. The three Au electrodes system showed just a minor DPV peak position shift and the standard deviation (SD) of OCP is about 0.0026 mV. The two Au electrodes system showed no DPV peak position shift and the SD of OCP is 0.32 mV. The solid-state Ag/AgCl RE-based three-electrode system showed a relatively large DPV peak position shift and the SD of OCP is about 4.6 mV. It is demonstrated that the all Au three-electrode system is superior to the solid-state Ag/AgCl RE-based three-electrode system for developing an immunosensor.

Figure 1
Simultaneous Electrochemical Determination of L-Dopa and Melatonin Using RGO-Spinel Nanocomposite Decorated Pt Electrode
Authors: R Leena , Madhavan Arya Sethu , Kunjappan Lineesh M
Published: July 2021

Melatonin(N-acetyl-5-methoxy tryptamine) is a paracrine hormone secreted by pineal gland in the brain. This endogenous hormone has the ability to maintain the body circadian rhythm.1 3,4-dihydroxy-L-phenylalanine (L-Dopa) is the intermediate precursor of the Neurotransmitter dopamine. L-dopa, as one of catecholamines, is widely used as a source of dopamine in the treatment of Parkinson’s disease and epilepsy.2

Here, we report a sensor based on Platinum electrode modified with hydrothermally synthesized RGO and spinel nanoferrate for the simultaneous determination of L-Dopa and Melatonin.

Graphene oxide (GO)is a graphene derived material with oxygen containing functional groups. Graphene is a material with honey comb like structure of carbon atoms having sp2 bonding character. It exhibits high electrical conductivity, thermal conductivity and mechanical strength. GO containing functional groups like –OH, -COOH etc., acts as the site for the nucleation of metal oxide nanoparticles. It improves direct electron transfer between the electrode and the redox species by accelerating the electron transfer and enlarging the effective surface area.3 GO was synthesized by modified Hummers method. Chemically converted graphene RGO has been prepared by various reduction methods such as chemical, microwave, electrochemical, thermal, solvothermal/hydrothermal, by reducing its oxygen content.4 Green synthetic pathway of hydrothermal method was adopted for RGO synthesis to avoid hazardous chemical species and vigorous reaction conditions. Spinel ferrate like Copper Cobalt ferrate (CuCoFe2O4) was synthesized by sol-gel method and RGO/Spinel nanocomposite was prepared by physical mixing.5 The synthesized materials were characterized using various techniques like FTIR, XRD, FESEM etc. The electro catalytic activity of RGO/Spinel nanocomposite anchored platinum electrode for the simultaneous determination of melatonin and L-Dopa was studied using several voltammetric techniques. Bare platinum electrode was able to sense melatonin and L-Dopa both individually, but not simultaneously. Compared to RGO modified Platinum electrode, RGO-Spinel ferrate/Pt electrode exhibited good response in terms of lower potential of electrooxidation of L-Dopa and Melatonin with enhanced catalytic current with a peak separation of 0.48V. This enhancement in electrochemical performance is due to the increase in surface area as well as conductivity of the electrode upon modification with RGO-spinel nanocomposite which act as an excellent electrochemical oxidant for L-Dopa and melatonin.

References:

Levent, A.J. Diam. Relat. Mater.
2012, 21, 114-119

Yan, X.; Pan, D.; Wang, H.; Bo, X.; Guo, L.J. Electroanal. Chem.
2011, 663, 36-42

Pei, S.; Zhao, J.; Du, J.; Ren, W.; Cheng, H.J. Carbon.
2010, 48, 4466-4474

Luo, D.; Zhang, G.; Liu, J.; Sun, X.J. Phys. Chem. C.
2011, 115, 11327-11335

Elkholy, A. E.; Heakal, F. E.; Allam, K. A.J. RSC Adv.
2017, 7, 51888
(Invited) Electrochemical Detection of Gases in Ionic Liquids in Different Humidity Environments
Authors: Silvester Debbie S. , Doblinger Simon , Lee Junqiao
Published: July 2021

Amperometric gas sensors (AGSs) are widely used due to their many advantages, such as low-cost, portability, durability, wide linear range, high sensitivity and high selectivity [1]. They are available commercially from a number of companies [2], and can detect a range of redox-active gases. The sensor devices typically employ a water/sulfuric acid mixture as the electrolyte in contact with three electrodes, covered by a gas-permeable membrane. Room temperature ionic liquids (RTILs) have strong potential for use as alternative ‘designer solvents’ in membrane-free AGSs [3], which would solve the existing technological problems of commercial AGSs, including the slow diffusion through the membrane and solvent evaporation. Their non-volatility would enable the membrane to be dispensed with, and the entire sensor to be miniaturised to provide optimal functionality over a much wider range of ambient conditions and with a longer lifespan. This allows and encourages innovative designs, with the potential for gas sensors to move from single, finite devices to more sophisticated systems that exploit recent advances in portable electronics and computing.

In this talk, I will discuss some of the challenges facing ionic-liquid based sensors, such as solvent leakage, sensitivity to moisture and accumulation of electrogenerated products, and how we can innovatively design electrode materials and electrolytes to overcome these challenges. In particular, I will show that the choice of ionic liquid is crucial in high humidity gas environments, due to the structuring and layering of the ions in the electrical double layer [4]. Overall, it is clear that RTILs show tremendous promise as electrolytes in sensors, but more understanding of their long-term operation and utility in real environments is still needed.

References

[1] Stetter JR, Li J, Amperometric Gas Sensors – A Review Chem. Rev.
2008, 108, 352–366.

[2] Xiong L, Compton RG, Amperometric Gas detection: A Review Int. J. Electrochem. Sci., 2014, 9, 7152–7181

[3] Buzzeo MC, Hardacre C, Compton RG Anal. Chem. 2004, 76, 4583–4588.

[4] Doblinger S, Lee J, Silvester DS J. Phys. Chem. C
2019, 123, 10727−10737.

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Ultrasensitive Electrochemical Detection of per and Poly-Fluoroalkyl Species in Drinking Water
Authors: Khan Reem , Andreescu Daniel , Andreescu Emanuela
Published: July 2021

Per and poly-fluoroalkyl substances (PFAS) are persistent organic pollutants, adversely affecting the environment. The strong carbon-fluorine bonds of PFASs make them resistant to physical and metabolic degradation leading to bioaccumulation, which can have serious effects on human’s health, wildlife and ecosystem. The conventional analytical techniques for the quantitative determination of PFASs in environmental matrices are HPLC, GC-MS, etc. Despite their high reliability and accuracy, these laboratory-based techniques are expensive and can analyze only a limited number of samples, which impedes their broad applicability. To advance the analysis and fast screening of samples, there is a critical need to develop cost effective, sensitive, easy to handle and portable methods for field detection of PFASs. This presentation will describe rational design of an electrochemical approach to detect the PFAS below their maximum permissible limit in drinking water. The interaction of nanomaterials with selected PFAS species and their incorporation into an electrochemical sensing design will be discussed. The developed method has potential for the onsite, selective, and ultrasensitive detection of PFASs
Black Phosphorus-Titanium Dioxide Composites for Trace Nitrogen Dioxide Sensing at Room Temperature
Authors: Wang Yanjie , Zhou Yong , Wang Yuhang , Zhang Ruijie , Zang Zhigang
Published: July 2021

Black phosphorus (BP) as one novel two-dimensional material has exhibited a specific detection selectivity toward hazardous NO2 gas due to their strong adsorption energy and efficient electron transfer. However, the inherent shortcomings including sluggish response, reluctant recovery and fragile water-tolerance impede its further exploration. To overcome these obstacles, chemiresistive sensors featuring composites of BP nanosheets-porous titanium dioxide (TiO2) nanoparticles as the sensing layer were fabricated in this work. Compared with pure BP counterpart, BP-TiO2 sensor delivered favorable performance at room temperature (20 oC) in terms of boosted response (i.e., 66.6% vs. 40.3% toward 25 ppb NO2), more sufficient desorption, accelerated response/recovery speeds, and intensified humidity-resistant properties by occupying high-energy sorption sites when synthesizing the composites. Through subtly optimizing the mass fraction between BP and TiO2 components, the composite sensor with a mass fraction of 1:1 achieved the best sensing capability. Also, various characterization techniques including AFM, SEM, TEM, XRD, XPS and Raman spectrum were employed to interpret the outcomes. The proposed BP-TiO2 sensor afforded alternative strategies to impel further BP applications in the fields of exhaled breath monitoring and ultralow emission.

Figure 1
Ultrasensitive and Selective MEMS Xylene Gas Sensor Based on CuO/WO3 Hierarchical Structure
Authors: Guo Mengmeng , Xu Jiaqiang , Chen Yang
Published: July 2021

A p-n heterostructure has been proved as a good strategy to enhance the gas sensing performance of metal oxide semiconductor (MOS). Here, we reported a xylene gas sensor based on CuO/WO3 p-n hierarchical structure. CuO/WO3 were prepared by a two-step route. First, WO3 was synthesized by a reaction between CaWO4 and HNO3 under reaction condition was at 25˚C for 18 h, and then CuO/WO3 were prepared by immersion pyrolysis method. The prepared hierarchical CuO/WO3 hollow microspheres features an ordered assembly of two dimensional (2D) nanosheets with the thickness about 20 nm. Gas sensing tests displayed CuO/WO3 sensor had a good linearity property between the sensing responses and xylene concentrations range from 0.3 ppm to 50 ppm, and CuO/WO3 -3 (the mass ratio of CuO to WO3 is 3) sensor exhibited the highest response of 304.8 toward 20 ppm xylene gas at the optimal working temperature of 260˚C. Furthermore, it is obvious that CuO/WO3 -3 not only possessed superior response and recovery properties of 3 s and 6 s under 20 ppm xylene gas, respectively, but also showed outstanding selectivity and stability. The advantages of high sensitivity, simple manufacturing and outstanding selectivity indicate the promising application of CuO/WO3 xylene sensors in the field of air-quality and environmental monitoring, and p-n heterostructure can significantly enhance the gas-sensing performance of metal oxide semiconductor.

Figure 1
Highly Sensitive ZnO MEMS Sensor Fabrication with Atomic Layer Deposition Technique
Authors: Hu Qingmin , Xu Jiaqiang , Zhe Dong
Published: July 2021

To obtain integrated and miniaturized gas sensors with low cost and power consumption to meet the increasing request of the internet of things industry and other relative areas, this work presented an in-situ compatible manufacturing and high-throughout strategy to deposit gas sensing film on a 5-inch wafer integrated with more than 10,000 MEMS micro-hotplates (MHP). The-state-of-art atomic layer deposition (ALD) was employed to fabricate controllably the uniform ZnO thin film (20 nm) on Micro-Electro-Mechanical Systems (MEMS) chips for constructing gas sensors. The ALD ZnO based MEMS sensors display excellent sensing performance, including very high sensitivity and selectivity to H2S with a limit of detection (LOD) on ppb level, good stability and quick response and recover dynamics under 70 mW of power dissipation. The sensing film has higher to 1300 times in mechanical strength than the traditional film from drop-coating. Furthermore, The ALD technique offers a facile in-situ strategy and high-throughput fabrication of MEMS gas sensors.
New Materials for Extreme Environment Solid-State Electrochemical Sensors
Authors: Vaeth Alex , Akbar Sheikh , Lin Jay , Modroukas Dean , Peters Travis
Published: July 2021

Sensing technology for extreme temperatures and environmental conditions is becoming increasingly important for applications in space travel and hypersonic technology. Solid state electrochemical systems based on yttria-stabilized zirconia (YSZ), utilizing Pt or perovskite-oxide electrodes are candidates for ultra-harsh environment sensing. Little is known on the stability or sensitivity of these materials around their sintering temperatures (1200-1500°C). In this work, sensors consisting of 8 mol% YSZ with either sputtered or screen-printed platinum electrodes were characterized in-situ with electrochemical impedance spectroscopy over temperatures from 800-1400°C with oxygen concentrations ranging from 0.04 to 0.30 atm. Sensor degradation was present both during a single test and with subsequent testing. The source of the degradation can be found both in the electrolyte and the electrode. For the electrode, morphological, chemical, or diffusion-based reactions with the electrolyte could be the source. The degradation of the electrical conductivity of commonly used 8 mol% YSZ with time at temperatures above 1000°C is likely caused by nano-microstructural changes to the defect structure of the crystal. This leads to the need for new materials for high temperature sensors. These can be split into electrode materials and electrolyte materials. This work focuses on determining the high temperature stability of these new materials. For example, higher doping levels of YSZ have shown negligible conduction loss with time. Degradation testing has also revealed inconsistent electrical stability between single and poly crystalline YSZ electrolytes. Electrode materials will focus on oxide-perovskites like lanthanum-strontium-manganite and platinum alloys or composites aimed to prolong electrode stability/usefulness. Through this investigation, the chemical, thermal, and electrical stability of these materials alone and with respect to each other are explored using electrochemical impedance spectroscopy and electron microscopy. The work will guide future research in this topic with respect to material selection for extreme environment sensors.
H2S MEMS Gas Sensor Based on Ni Doped CeO2
Authors: Zhe Dong , Hu Qingmin , Xiaohong Wang , Xu Jiaqiang
Published: July 2021

Since the increasing concerns of the great harm to human and environment caused by H2S, to develop effective methods to detect this toxic and hazardous gas has become more and more important. The MEMS gas sensor is portable and gives a lower power waste than the general metal-oxide-semiconductor sensor. To fabricate this kind of instrument, the material with high gas sensitivity is needed. In this study, Ni doped CeO2 nanoparticles were prepared by using a simple hydrothermal reaction method andthe sensing mechanism of H2S on the surface of the material was studied by in situ IR. It proved that Ni doped CeO2 nanoparticles has a lower operating temperature than pure CeO2, and a certain amount of Ni doping in CeO2 has improved its gas sensitivity and selectivity a lot to H2S gas.The response of the MEMS gas sensor to 1 ppm H2S gas can reach to 1.47 at 200°C and it can even be used to detect 20 ppb H2S effectively.

Figure 1
On-Site Longitudinal Monitoring of Crop Health Using Vapor-Printed Polymer Tattoos
Authors: Andrew Trisha L. , Kim Jae Joon
Published: July 2021

Emergent wearable health-monitoring devices use a tissue-adhered electrode as their sensing element, which is typically created by applying a preformed polymer, nanoparticle/nanowire or carbon material film onto the outer surface of an organism. However, the surfaces of organisms display staggeringly diverse microscale features, and the complex biochemical, mechanical and transport phenomena that operate at the interface between such microstructured living tissue and a man-made device ultimately control the performance and longevity of tissue-adhered electrodes. Contemporary stick-and-play devices, such as smart patches and press-on buttons, are often susceptible to device delamination from the surface of living organisms and, often, perturb air/water/nutrient transport at the biointerface, reducing long-term viability. We demonstrate a new paradigm for vapor printing biocompatible polymer films directly onto a living organism, creating conformal and long-lasting electrodes that allow for long-term health monitoring using bioimpedance measurements. This approach enables on-site and longitudinal monitoring of otherwise hard to track abiotic stressors, such as ozone damage, even at low exposure levels. Oxidative damage produces a unique change in the high-frequency (>104 Hz) impedance and phase signals of leaves, which is not replicated by other abiotic stressors, such as drought. The polymer tattoos are resilient against ozone-induced chemical degradation and persist on the leaves of fruiting plants, thus allowing for frequent and long-term monitoring of cellular ozone damage in economically important crops, such as grapes and apples.
Fast Screening of Dithiocarbamate, Chloronicotinyl and Organophosphate Pesticides By Raman Spectroelectrochemistry Based on EC-SERS Effect
Authors: Weber Michael , Fanjul Pablo , Ibáñez David , González-García María Begoña , Hernández-Santos David
Published: July 2021

Electrochemical surface-enhanced Raman scattering (EC-SERS) effect is an outstanding procedure that ensures the enhancement of Raman signal by the electrochemical activation of the electrode surface. In that way, activation of metallic screen-printed electrodes (SPEs) by electrochemical routes leads to the generation of reproducible nanostructures with excellent SERS properties [1,2] and opens new gates for analytical applications.

In this work, detection of thiram, imidacloprid and chlorpyrifos pesticides is achieved by the development of a new procedure. This methodology offers a quick and easy protocol which consists of three steps: (1) preconcentration of the sample, (2) electrochemical activation of SPE and (3) Raman detection of pesticides (Figure 1).

Figure 1. Raman spectrum of thiram obtained following the proposed procedure.

Analysis of tap water samples provides suitable results that demonstrate the capabilities of the proposed method. In that way, Raman spectroelectrochemistry based on EC-SERS effect avoids the complicated instrumentation, tedious pretreatment protocols or time-consuming measurement procedures used in other methods, and offers an interesting alternative in fields as environmental and food safety.

References

[1] D. Martín-Yerga, A. Junquera-Pérez, M. B. González-García, J. V. Perales-Rondon, A. Heras, A. Colina, D. Hernández-Santos, P. Fanjul-Bolado, Electrochim. Acta 264 (2018) 183-190.

[2] D. Ibáñez, A. Junquera-Pérez, M. B. González-García, D. Hernández-Santos, P. Fanjul-Bolado, Talanta 206 (2020) 120190.

Figure 1
Low Cost Wearable Multi-Gas Chemical Sensor Badges for First Responders
Authors: Jayaraman Ambalavanan , Haanstad Trevor , Haanstad Meredith , Dubovik Margarita , Chamot Matthew , Marotta Christopher
Published: July 2021

Introduction

Toxic Industrial Chemicals (TICs) are chemical substances which produce toxic effects if encountered in sufficient quantities and/or long durations. TICs are a great concern for the U.S. Department of Homeland Security (DHS) since they would be easier for terrorists to obtain and use than Chemical Warfare Agents (CWAs). Therefore, first responders need a small, rugged, wearable, monitor that alerts them when they are facing TICs, and if so, what is present and at what levels. While there are many commercially available handheld and personal gas monitors for TICs, most are bulky (more than 0.75” in thickness) and expensive ($500 or more). These monitors are primarily used in cities having a population of 100k or more. Hence, there is a need for a low cost (less than $100) wearable multi-gas sensor. Such wearable sensors will also find use in the much bigger application of industrial worker safety monitoring.

To address this need TDA Research (TDA) has developed a simple, low cost wearable smart chemical sensor badge that has high sensitivity and selectivity to multiple TICs at trace (low parts per million) concentrations and triggers distinct alarms at permissible exposure limit (PEL), and Immediately Dangerous to Life or Health (IDLH) concentrations. Our wearable smart sensor badge uses a Lab-on-a-chip, is smaller than 2” x 2” x 0.75”, and can detect multiple TICs ( 4 to 6) of interest, and has a low rate of false alarms so that easy and widespread deployment can be achieved.

TDA's sensor

We have demonstrated the operation of the sensor in a fully integrated prototype to detect four to six TICs among the H2S, NH3, PH3, HCN, Cl2, and NO2 at ppm levels and produce an electrical signal that can be used to identify and quantify them. We then obtained performance data that included results for these TICs both separately and together and in the presence of interferents, such as diesel and bleach. The sensor response was correlated and corrected based on ambient temperature, relative humidity levels and the air flow rate through the sensor. This low cost sensor is built using commercial-off-the-shelf (COTS) components along with TDA proprietary media and detection/quantification algorithms to detect and quantify TICs, eliminating false positives and false negatives. The sensors also have the ability to generate multiple alarms (audible, visual, and vibrate) at high (IDLH) and low (PEL) concentrations for four or more of the TICs in a small wearable form factor. TDA’s sensor has the unique ability to distinguish between different volatile organic compounds (VOCs) and oxidizes (Cl2, NO2 and even ozone). The attached figure is a photo of the TDA sensor. The results from the TDA sensor development and their performance under different threats at different humidity and temperature levels will be presented at the meeting.

Figure 1
A Portable Fluorometer with Multiple Excitation LEDs
Authors: SHIN Young HO , Gutierrez-Wing Maria Teresa , Choi Jin-Woo
Published: July 2021

Fluorescent probes are widely used in biological research due to their sensitivity, selectivity, and versatility [1, 2]. Many fluorescence probes, such as fluorophores, typically have a variety of absorption and emission peaks ranging from UV to near-infrared. Therefore, a wide range of excitation wavelengths is required to simultaneously detect multiple fluorescent target analytes. Here, we propose a portable fluorometer with 13 different excitation LEDs (280 – 730 nm) that can be a viable option for simultaneously detecting multiple fluorophores. For fluorescence detection, a monochromator module was implemented to separates the color components of fluorescent emission and sequentially scan a range of wavelength (400 nm – 780 nm) with 1 nm resolution. For demonstration, fluorescein was selected as target analyte for this study. Fluorescein is an organic compound dye that is commonly used in many bioscience applications.

For the excitation light source, different LEDs were used to offer a broad range of excitation wavelengths, ranging from 280 nm to 725 nm. Each LED was coupled with a color filter and a collimator lens to carry out a narrow excitation spectrum. LEDs were controlled by an LED driver IC and a microcontroller to provide a linear output current in the range of 0 to 300 mA. A multiplexer IC was implemented to sequentially turn on and off each excitation LED. The maximum absorbance and emission wavelength of fluorescein were 485 nm and 514 nm, respectively. For excitation, 434 nm LED was chosen instead of 470 nm to minimize spectral overlap between the excitation and emission spectra. The fluorescein was dissolved in methanol at a concentration of 220 mg/ml at room temperature (25 ºC). The figure shows the spectra of the excitation LED and fluorescein fluorescence measured with a developed portable fluorometer. The spectral profile of the excitation LED and the peak fluorescence of fluorescein was well-matched with previously measured value from the laboratory-based benchtop fluorometer (Fluorolog 3 FL3-22, Horiba, Japan).

In summary, we have developed a portable fluorometer multiple LEDs covering a broad range of excitation wavelengths to simultaneously detect multiple fluorescent targets. Our compact fluorometer provides a viable option for multi-analyte detection in a variety of remote sensing applications such as point-of-care or environmental monitoring.

Figure 1
Printed-Circuit-Board (PCB) Based Multiplex Sensor for Ion Sensing
Authors: Zhang Zhehao , Papautsky Ian
Published: July 2021

Combining electrochemical sensing with microfluidic system presents an attractive approach for in vitro study of physiology and pathophysiology (e.g. organ-on-chip platform) [1] and for inline monitoring of environmental parameters (e.g. water quality) [2]. Ion-selective electrodes (ISE) are potentiometric sensors that measure activities of ions. They offer a simpler analytical method compare to voltammetric sensors or ISFETs. Solid-state ISEs differ from conventional ISEs in that the inner filling solution is replaced by a solid contact material. The removal of liquid compartment can make such sensor more durable and flexible, enabling it to be integrated with microfluidic device. In this work, we fabricated and evaluated a multiplex ion sensing platform by modifying the printed circuit board with solid-state ISEs. The choice of PCB platform allows straightforward multiplexing of electrodes and interfacing with downstream electronics by leveraging standardized PCB technology, which can also be cost effective in terms of fabrication. ISEs for potassium (K+) and nitrate (NO3-) approximately 1.5 mm in diameter were prepared by coating polymeric membrane and mesoporous carbon layers as the solid contact on a pre-patterned transfer tape. The electrode response was significantly stabilized by casting the membrane away from the underlying metal pads. The stabilizing effect was attributed to the increase of effective surface area of mesoporous carbon between membrane and conducting metal. The multiplex sensor was further integrated with a 3D printed microchamber for onchip analysis (Figure 1A). The K+ and NO3- electrodes displayed near-Nernstian slopes of 53 and -50 mV/dec (vs. Ag/AgCl/0.01 M Cl- reference) in KNO3 solutions, respectively. Despite some noise and baseline drift, both electrodes showed reasonable stability and reversibility upon switching solution (Figure 1B). The sensor can be stored dry between measurements. The slope of K+ electrode decayed over time, while NO3- electrode maintained sensitivity for at least one week. The slope decrease was likely due to the diffusion of ion-exchanger (tetraphenylborate) into the surrounding adhesive tape. During integration with the microchamber, the K+ electrode was also found subject to the bonding adhesive between the chamber and transfer tape, where possible reaction and/or degradation of the ion exchanger has caused complete loss of electrode response. Nevertheless, with further improvement, the PCB based multiplex ISEs provides a promising tool for ion sensing in many biomedical and environmental applications.

References:

[1] Sunghee Estelle Park, Andrei Georgescu, Dongeun Huh. Organoids-on-a-chip. Science, 2019, Vol. 364, Issue 6444, pp. 960-965, DOI: 10.1126/science.aaw7894

[2] Am Jang, Zhiwei Zou, Kang Kug Lee, Chong H Ahn and Paul L Bishop. State-of-the-art lab chip sensors for environmental water monitoring. Meas. Sci. Technol., 2011, Vol. 22, 032001, doi:10.1088/0957-

Figure 1
Utilizing Virtual Crowd for Global Software Development
Authors: Zhang Ying , Ali Farhad , Wang Kunhao , Nazir Shah , Leng Zeqi
Published: July 2021

Software firms are interested in outsourcing and developing of software globally to the virtual crowd for minimizing the product cost and for increasing the software quality. Developments in information technology (IT) have changed the organizational working environment from centralized to disperse development working practices. As a result, companies have recognized the value of virtual world networks that offer benefits such as efficient time management, lower cost of growth, reduced travel costs, and access to larger competent team members to select the right skilled individual. With the wide spread of Web 3.0 applications and improvements in cloud computation technologies, multinational, multiskilled, and diverse crowds carry out the software developmental process. The aim of this research is to select the effective virtual crowd for the development of quality software. The proposed “characteristic-based virtual crowd selection (CBVCS)” method will select the crowd according to their unique characteristics such as their skills, experiences, expertise, and knowledge.
Highly Expressed CYBRD1 Associated with Glioma Recurrence Regulates the Immune Response of Glioma Cells to Interferon
Authors: Qing Mingjie , Zhou Jiahao , Chen Weijian , Cheng Lijuan
Published: July 2021

Invasiveness, resistance to treatment, and recurrence of gliomas are significant hurdles to successful treatment regimens. Data sets from Gene Expression Omnibus (GEO), CGGA-RNAseq, and The Cancer Genome Atlas Glioblastoma Multiforme (TCGA-GBM) were analyzed, and an increased expression of Cytochrome B Reductase 1 (CYBRD1) was identified and could be associated with aggravated clinical outcomes. Gene ontology (GO) enrichment analysis indicated that CYBRD1 co-expressed genes are enriched during an immune response. CYBRD1 overexpression in glioma cell lines is enhanced, whereas CYBRD1 silencing attenuated the aggressiveness of glioma cells. In IFN-α-treated glioma cells, IFN-α suppressed the viability and migratory ability and invasive ability of glioma cells, whereas CYBRD1 overexpression attenuated the antitumor effects of IFN-α. CYBRD1 could potentially serve as a biomarker for glioma recurrence. CYBRD1 overexpression enhances glioma cell aggressiveness and attenuates glioma cell response to IFN-α.
A Survey on the AI and Spectrum Management for Cache‐Enabled Internet of Things in Smart Cities
Authors: Chen Liming , Kuang Xiaoyun , Zhu Fusheng , Lai Lijia , Fan David
Published: July 2021

In this paper, we provide a comprehensive survey for the artificial intelligence and spectrum management, which are used for cache‐enabled Internet of Things (IoT) in smart cities. In smart cities, there emerge a lot of new applications such as data collection and communication, environment monitoring, and real‐time processing, which cannot be supported by the conventional wireless transmission techniques. Hence, some new wireless transmission techniques should be developed to support the emerging applications in smart cities. In this survey, we focus on the artificial intelligence, spectrum management, and caching techniques, where the interference arises due to the limited spectrum resources. In particular, we first review the current research status of these new techniques and, then, give some challenges on the system design. We further provide several feasible solutions on these challenges, in order to implement the IoT networks in smart cities. Finally, we conclude the work in the part of conclusions and give some discussions on the future works.
Path Planning and Control of a Quadrotor UAV Based on an Improved APF Using Parallel Search
Authors: Huang Tianpeng , Huang Deqing , Qin Na , Li Yanan
Published: July 2021

Control and path planning are two essential and challenging issues in quadrotor unmanned aerial vehicle (UAV). In this paper, an approach for moving around the nearest obstacle is integrated into an artificial potential field (APF) to avoid the trap of local minimum of APF. The advantage of this approach is that it can help the UAV successfully escape from the local minimum without collision with any obstacles. Moreover, the UAV may encounter the problem of unreachable target when there are too many obstacles near its target. To address the problem, a parallel search algorithm is proposed, which requires UAV to simultaneously detect obstacles between current point and target point when it moves around the nearest obstacle to approach the target. Then, to achieve tracking of the planned path, the desired attitude states are calculated. Considering the external disturbance acting on the quadrotor, a nonlinear disturbance observer (NDO) is developed to guarantee observation error to exponentially converge to zero. Furthermore, a backstepping controller synthesized with the NDO is designed to eliminate tracking errors of attitude. Finally, comparative simulations are carried out to illustrate the effectiveness of the proposed path planning algorithm and controller.
Mechanical and Thermal Properties of RCB Masonry Containing Three Rows of Holes
Authors: Yuan Hanquan , Zhu Lihua , Wang Yixuan , Zhang Fengjian
Published: July 2021

In order to promote and apply the structures of the recycled concrete block (RCB) masonry, the thermal and mechanical properties of the recycled concrete specimens were tested in this study. The RCB can meet load‐bearing and seismic requirements and was prepared through experiments. Concurrently, the mechanical property experiment was conducted on the RCB masonry, and then its failure process and mode were discussed. In addition, a thermal property test was completed on the RCB wall, and the difference in the thermal properties of single‐row hole, three‐row hole, and solid blocks was analyzed by theoretical calculations. The results indicated that the mechanical properties of the RCB masonry were basically the same as those of the natural concrete block masonry, and they have good compressive stability. The calculation formulas of the compressive and shear strengths of the natural concrete block masonry are applicable to the RCB masonry. The RCB masonry containing three rows of holes owns more outstanding thermal property than natural concrete block masonry and satisfies the requirements for related codes.
The Product-Type Operators from Hardy Spaces into
n
th Weighted-Type Spaces
Authors: Abbasi Ebrahim
Published: July 2021

The main goal of this paper is to investigate the boundedness and essential norm of a class of product-type operators

T

u
,
v
,
φ

m

,
m
∈
ℕ

from Hardy spaces into

n

th weighted-type spaces. As a corollary, we obtain some equivalent conditions for compactness of such operators.
Overexpression of TOLLIP Protects against Acute Kidney Injury after Paraquat Intoxication through Inhibiting NLRP3 Inflammasome Activation Modulated by Toll-Like Receptor 2/4 Signaling
Authors: Zheng Qiang , Zhao Hang , Jia Dong , Han Xu , Liu Zhenning , Zhao Min
Published: July 2021

Paraquat (PQ) can cause multiorgan failure including acute kidney injury (AKI). Our prior study showed that Toll-interacting protein (TOLLIP) protected against PQ-induced acute lung injury. However, the role of TOLLIP in PQ-induced AKI remains undefined. This study was aimed at understanding the role and mechanism of TOLLIP in AKI. Six-eight-week-old male Wistar rats were intraperitoneally injected with 25 mg/kg PQ to induce AKI for 24 h in vivo. HK-2 cells were treated with 300 μM PQ for 24 h to induce cellular injury in vitro or 300 μM PQ and 5 μM nuclear factor-κB (NF-κB) inhibitor BAY11-7082 for 24 h. Rats were infected with adenovirus carrying TOLLIP shRNA via tail vein injection and HK-2 cells with adenovirus carrying TOLLIP shRNA or TOLLIP 48 h before PQ exposure. Results showed that TOLLIP and Toll-like receptor 2/4 (TLR2/4) expressions were boosted in the kidney after PQ intoxication. The toxic effect of PQ on the kidney and HK-2 cells was exacerbated by TOLLIP knockdown, as evidenced by aggravated glomerulus and tubule injury, inflammatory infiltration, and cell apoptosis in the kidney and increased loss of cell viability and apoptotic cells in HK-2 cells. TOLLIP knockdown also enhanced PQ-induced NLR family pyrin domain-containing 3 (NLRP3) inflammasome activation in vivo and in vitro and TLR2/4-NF-κB signaling in vitro, reflected by increased contents of proinflammatory cytokines and expressions of NLRP3 inflammasome-related proteins in the kidney and HK-2 cells and expressions of TLR2, TLR4, and nuclear NF-κB p65 in HK-2 cells. However, TOLLIP overexpression inhibited PQ-induced loss of cell viability, cell apoptosis, NLRP3 inflammasome activation, and TLR2/4-NF-κB signaling in vitro. Additionally, BAY11-7082 abolished TOLLIP knockdown-induced NLRP3 inflammasome activation in vitro, indicating that TOLLIP protected against NLRP3 inflammasome activation in PQ-induced AKI through inhibiting TLR2/4-NF-κB signaling. This study highlights the importance of TOLLIP in AKI after PQ intoxication.