bluuebunny/crossref_metadata_2025 huggingface dataset:
Wearable Mouthguard Biosensor Integrated with Wireless Electronics
Authors: Kim Jayoung , Wang Joseph
Published: February 2020

Saliva is a great diagnostic fluid providing an alternative to direct blood analysis via the permeation of blood constituents without any skin-piercing for blood sampling. And significant progress has been made recently in developing wearable electrochemical sensors that detect metabolites and electrolytes in sweat, saliva, and tears. Despite these recent advances, the realization of wearable biosensors for real-time monitoring of chemical markers is limited by the lack of integrated wireless data transmission in measurement platforms. Herein, we demonstrate a wearable mouthguard biosensor system integrated with wireless electronics for health-care application. The biosensor compartment has been fabricated with screen-printed electrode on a mouthguard platform along with anatomically-miniaturized instrumentation electronics featuring a potentiostat, microcontroller, and a Bluetooth Low Energy (BLE) transceiver. The integrated wireless electronics enable real-time wireless transmission of the sensed information to standard smartphones, laptops, and other consumer electronics for on-demand processing, diagnostics, or storage. The new wireless mouthguard biosensor system allows non-invasive monitoring of biomarkers in saliva in real-time and continuous fashion, offering high sensitivity, selectivity, and stability towards electrochemcial detection in saliva. The developed mouthguard biosensor can be readily expanded towards multiple analytes sensing to enable an attractive wearable monitoring system for diverse health and fitness applications.

Figure 1
Faster Diagnosis of Alpha-1-Antitrypsin Deficiency through Electrochemical and Quartz Crystal Microbalance Testing
Authors: Materi Bryan Evans , Adams Bobby Gene , Sanders Jonathan , Rice Jeffrey , Rice Cynthia A.
Published: February 2020

Alpha-1-Antitrypsin (A1AT) Deficiency (A1AD) is a potentially debilitating inherited condition that can lead to reduced levels of A1AT in the lungs and increased levels in the liver. In the lungs, the condition is routinely associated with an imbalance in levels of Human Neutrophil Elastase (HNE) and its native inhibitor A1AT (predisposing those affected to early-onset emphysema). In the liver, certain genetic mutations lead to an accumulation of A1AT. No cure exists, and current approaches for diagnosis are insufficient as illustrated by the fact that A1AD is underdiagnosed and diagnosis is often delayed.1New methods for diagnosis are needed, and one possible route is the use of electrochemical techniques combined with quartz crystal microbalance (QCM) approaches.

Often, QCM and electrochemistry are combined using a gold working electrode that has been functionalized with a particular molecule. In our case, Porcine Pancreatic elastase (PPE), a surrogate of HNE, has been used as an enzymatic marker. When a potentiostat was combined in parallel to the apparatus, measurements of both the frequency and the current responses were simultaneously performed. PPE was immobilized to the surface of the gold electrode through the use of a crosslinker. The immobilized PPE was then incubated with various concentrations of N-Succinyl-Ala-Ala-Ala-p-Nitroanalide (SApNA), a chromogenic substrate for elastase, allowed to react, and the absorbance measured to determine the activity of the enzyme. This same test was also completed with the A1AT inhibitor in the solution with the SApNA and the absorbance measured again. From these results, the frequency was measured and converted to mass to determine the extent of inhibition. This data was then examined via kinetics-based models to estimate the kinetic parameters of inhibition.

Electrochemical measurements have been performed concurrently with the frequency measurements. Using phosphate buffered saline (PBS) in the presence of ferrocyanide/ferricyanide as the redox species, cyclic voltammetry was performed to determine the extent that the electrode surface is covered. As the SApNA and A1AT was added to the solution, the change in the ferrocyanide/ferricyanide peaks were observed.

It is the ultimate goal of this work to develop a test that can be used to determine the inhibition kinetics of HNE via A1AT, and thus shed light on new approaches to diagnose A1AD. Such an approach could also serve as a platform that could be useful in the early detection and diagnosis of many different diseases that could allow for preemptive treatment and could potentially improve life expectancy outcomes for those afflicted.

American Thoracic Society/European Respiratory Society Statement: Standards for the Diagnosis and Management of Individuals with Alpha-1-Antitrypsin Deficiency. (2003). Am. J. Respir. Crit. Care Med. 168(7): 818-900.
Breast-Cancer-Stem-Cell Sensor Using Igzo Nomfet Implemented with Au Nano-Particles
Authors: Lee Jong-Sun , Song Seung-Hyun , Kim Chul Geun , Park Jea-Gun
Published: February 2020

Recently, many researchers have studied circulating-cancer-stem-cell (CCSC) to pre-recognize the presence of a cancer. Since, it has been that cancer cells include negative or positive charges, several electronic sensors have been attractively proposed. In our study, we designed an In-Ga-Zn-oxide (IGZO) based FET implemented with Au nano-particles on IGZO channel, as shown in Fig. 1(a). The average size and density of the Au nano-particles on the channel were 12.05 nm and 2.66×1011 cm-2, respectively. In particular, this FET has a unique time-dependent current characteristic such as depressing at a positive gate bias or facilitating at a negative bias, which determines whether or not the cancers present a fixed charge or mobile charges. In our experiment, breast-cancer-stem-cell (BCSC) connected with the cancer-anti-body (CD44) was dropped on the IGZO FET with Au nano-particles where a linker (8-Mercaptooctanoic acid) was attached on Au nano-particles, as shown in Fig. 1(b). The linkers were well uniformly absorbed and attached on Au nano-particles, confirmed by FT-IR, as shown in Fig. 2. First of all, we investigated the dependency of threshold voltage on the presence of Au nano-particles, linkers, and breast-cancer-stem-cells with anti-bodies shown in Fig.3. The threshold voltage of the IGZO FET without Au nano-particles was +2.4 V. The implementation of Au-nano-particles on the IGZO channel increased from +2.4 to +12.0 V because of the presence of positive fixed charges at the interface between the IGZO channel and Au nano-particles. The attachment of the linker on Au nano-particles decreased the threshold voltage from +12.0 V to +6.9 V since the functional group of the linker was carboxyl. Two kinds of breast-cancer-stem-cells were dropped on the linker connected with Au-nano-particles; i.e., the cells without or with anti-body. The cells without anti-body did not shift threshold while the cells with anti-body reduced -4.3 V where the concentration of BCSC was 8000ea/10ul. The threshold-voltage shift amount was well correlated with the concentration of BCSC, as shown in Fig. 4. The threshold-voltage shift amount increased linearly with the concentration of BCSC, having the slope of the threshold-voltage shift amount of 0.44V/(kea/ul). In addition, we confirmed that BCSC showed a negative fixed charge rather than mobile charge by testing time dependent drain-current characteristic. In our presentation, we will review the detailed mechanism by which BCSCs shift threshold voltage and show a negative fixed charge characteristic.

Reference

[1] F. Alibart et al. Adv. Funct. Mater. 20 330. (2010)

[2] K.-C. Kwon et al. Appl. Phys. Exp. 6, 067001 (2013).

[3] XiuHua Zhang
et al. Sensors, 3, 61-68 (2003)

Acknowledgment

This research was supported by the Converging Research Center Program funded by the Ministry of Science, ICT & Future Planning (Project No. 2015054348) and supported by Brain Korea 21 PLUS Program in 2014

Figure 1
Microwave Synthesized CdSe/ZnO Core-Shell Quantum Dots As a Biosensing Platform for Protein Detection
Authors: Jenrette Erin , Farrell Monique , Flowers Jasmin , Skuza Jonathan , Pradhan Aswini K
Published: February 2020

We demonstrate a highly sensitive, surface-plasmon-enhanced Raman spectroscopy (SERS) biosensing platform, composed of multilayer core-shell nanostructure of a CdSe core and surrounding ZnO monolayers for effective protein detection. This innovative technique uses a thermal decomposition method in the microwave to produce a rapid, less toxic, and a more convenient procedure of synthesizing nanometer thick metal oxide shells to form a core-shell structure. The benefit of using a metal oxide shell includes mitigating the toxicity of the core, increasing biocompatibility, and minimizing the photochemical and chemical corrosion of the semiconducting nanocrystals. In this study, we have presented a simple one-pot protocol for the formation of CdSe/ZnO core-shell quantum dots (QDs) in the microwave. Our study indicated the optimization of the recognition limit of bovine serum albumin (BSA) through a spectral signal at a considerably low concentration (2.5 µM). This nanoparticle core-shell system can be used for many thin film applications in the biomedical, alternative energy, and environmental fields.
Effects of Porous Structure for Gas Sensor on Sensitivity Using Tin Oxide with Low Density
Authors: Han Min-Ah , Jeong Ji Hea , Noh Hee Jun , Kim Hyun-Jong , Son Seong Ho , Park Jin-Seong , Lee Ho-Nyun
Published: February 2020

Recently, gas sensor has been studied because of increasing accidents caused by harmful and explosive gas, which is hard to detect olfactory system. Tin oxide is one of the most promising candidates for gas sensing materials owing to its many advantages, such as various gas detecting capability, good stability and high sensitivity.

In gas sensor, the kinds of sensing materials as well as detecting layer structures are important. The sensing materials with high surface areas show high sensing performance, so nanowire structure with mechanical contact between nanowires has been widely used. However, electric signal of nanowire along mechanical contacts is not stable and the external vibration and fast gas flow generates the inaccurate signal.

In this research, the low density tin oxide film with stable interconnection between nanoparticles was prepared using the physical vapor deposition by controlling the processing pressure, temperature and power. Macrostructure and interconnected structure between tin oxide nanoparticles were observed using scanning electron microscope (SEM) and transmission electron microscope (TEM) and crystal structure was analyzed by X-ray diffraction (XRD). Platinum and titanium electrodes were fabricated by lift-off process on the silicon substrate with the silicon nitride film of 300 nm, and then tin oxide with low density was deposited on it using shadow mask. The characteristics of the gas sensor were examined using carbon mono-oxide (CO) and ethanol (C2H5OH) changing concentration of gas, operating temperature and post heat-treatment temperature. In conclusion, porous nanostructure of tin oxide was composed of a lot of interconnected nanoparticles of about 10 nm and showed stable resistance in dry air. And post heat-treatment enhanced the stability in spite of inreasing the particle size. It could be suggested that the oxide films with lower density showed the superior sensitivity and the shorter response time than the oxide films with higher density.

Figure 1
Graphene Quantum Dots As Optical Sensor for Glucose Detection
Authors: Abdel-Fattah Tarek M , Ebrahim Shaker , Soliman Moataz , Shehab Mona
Published: February 2020

Graphene Quantum Dots (GQDs) show promise for many technological applications because GQDs have low toxicity and are chemically inert, biocompatible, and resistant to photobleaching [1].

We report a simple route to prepare graphene quantum dots (GQDs) using glucose carbonization. GQDs functionalized with phenylboronic acid receptors were employed as a sensing material for a nonenzymatic glucose sensor. GQDs display high surface area and the carboxylic moieties at their edges provide them with water dispersibility and proper functional groups to be complexed with several compounds [2]. Therefore, GQDs considered as a good sensing probe. The prepared GQDs were characterized using different techniques such as UV-visible and photoluminance spectroscopies, X-ray diffraction, transmission electron microscopy (TEM) and Raman spectroscopy. TEM micrographs confirmed the preparation of 8-10 nm GQDs. The emission peak of the GQDs appears at 450 nm. The developed sensor has linear response to glucose over a concentration range of 5 -50 mM.

References:

1) Shen, J.; Zhu, Y.; Yang, X.; Li, C. Graphene Quantum Dots: Emergent Nanolights for Bioimaging, Sensors, Catalysis and Photovoltaic Devices. Chem. Commun. 2012, 48, 3686.

2) Liu, J.-J.; Zhang, X.-L.; Cong, Z.-X.; Chen, Z.-T.; Yang, H.-H.; Chen, G.-N. Glutathione Functionalized Graphene Quantum Dots as Selective Fluorescent Probes for Phosphate-Containing Metabolites. Nanoscale 2013, 5, 1810−1815
Incubation-Free Electrochemical Immunosensor Using a Gold-Nanocatalyst Label Mediating Outer-Sphere-Reaction-Philic and Inner-Sphere-Reaction-Philic Species
Authors: Fang Chiew San , Kang Cheolho , Yang Haesik
Published: February 2020

We reprots a new nanocatalytic scheme based on the facts that the redox reaction between a highly outer-sphere-reaction-philic (OSR-philic) species and a highly inner-sphere-reaction-philic (ISR-philic) species is slow that an OSR- and ISR- philic Au-nanocatalyst label can mediate the two different types of redox species. This scheme allows highly sensitive and incubation free detection of creatine kinase-MB (CK-MB). Outer-sphere to inner-sphere redox cycling occurs in the sequence of a highly OSR-philic ITO electrode, highly OSR-philic Os(bpy)2Cl2
+/Os(bpy)2Cl2, OSR- and ISR-philic AuNC, and highly ISR-philic hydrazine. Ultimately, using outer-sphere to inner-sphere electrochemical-nanocatalytic (ENc) redox cycling that allows high signal amplification. When the ENc redox cycling was applied to a sandwich-type immunosensor for the detection of CK-MB, the calculated detection limit was approximately 20 fg mL-1 for mouse IgG, reconfirming that the ENc redox cycling allowed ultrasensitive detection. In the case of another cardiac target (myoglobin), the chronocoulometric signal was similar to that of zero CK-MB, indicating that the immunosensor is selective. The results for clinical serum samples showed that the charge increased with increasing concentration of CK-MB with good reproducibility, indicating that the immunosensor is practically appealing.
(Invited) Electrochemical Biosensors for Food and Agricultural Applications
Authors: Ramasamy Ramaraja P.
Published: February 2020

Economic losses to agriculture due to pest and pathogen infections are estimated at $40 billion annually and the economic losses to the health care industry due to food borne illnesses are estimated at $15 billion in the U.S. alone. Early detection of pest or pathogen infection in agricultural crops and reliable detection of harmful pathogens in food are important to minimize agricultural productivity loss, ensure food safety, improve food quality and minimize food related public health issues. There is a pressing need to develop rapid, highly selective and sensitive detection technologies for early identification of plant and human pathogens. While a variety of molecular methods are currently being used for this purpose, an inexpensive, high selective, rapid method for the detection of pathogens is highly desired. Electrochemistry biosensors offer unique advantages to this application. Electrochemical sensors have been widely explored for medical and environmental sensing applications, but not as much for food and agricultural applications. An electrochemical biosensor uses a highly selective bio-recognition element such as enzymes, antibody, aptamer or virus and is capable of detecting biding events with ultra-low detection limits. This presentation will focus on some of the recent developments in our lab in the development of electrochemical biosensors for detection of crop diseases and food pathogens.
The Study of Self-Assembled Au Nanoparticles As an Efficient SERS Substrate for Environmental Sensing Applications
Authors: Flowers Jasmin , Rutherford Gugu , Jenrette Erin , Farrell Monique , Skuza Jonathan , Fletcher Sha'La , Carvajal Christian G , Pradhan Aswini K
Published: February 2020

The formation of self-assembled monolayers (SAM) of noble metals for optical sensing applications faces serious challenges when trying to achieve simplicity, cost efficacy, specificity, and versatility. Utilizing stable, SAM-forming alkanethiols, such as glutathione (GSH), enable for simple assembly and specific detection of proteins, trace metals, oxidants, etc., thus providing a sensing platform that not only can detect low levels of reactive oxygen species (ROS) for early determination of neurodegenerative diseases, but can also assess trace metals in freshwaters and marine waters, for example. Providing a universal device for detecting varieties of target materials would adapt, simplify, and reduce costs that come from current detection methods. Our research on improving these detection methods is demonstrated using the frequency-controlled self-assembly of a GSH-functionalized gold nanoparticle (Au NP) film as a platform for highly specific and sensitive sensing. We have previously demonstrated the use of an eco-friendly and highly sensitive surface enhanced Raman spectroscopy (SERS) substrate for biomedical diagnostic applications using an ultraviolet photochemical reaction of gold (III) chloride trihydrate (HAuCl4) to create a densely packed Au NP film that exhibits localized surface plasmon resonances [1]. By the firm anchoring of a thiol group to the Au NP surface, GSH assembles the Au NPs for SERS into a densely packed, dendritic structure. At a pH of ~1 in solution, GSH forms a y-shape [2], allowing its carboxyl and amino groups to create a hydrophilic interface and, therefore, be fully available for bonding to various functional molecules. Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), and ultraviolet-visible spectroscopy (UV-vis) were used to confirm the presence of GSH and enhancement capabilities of the SERS substrate. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) confirmed the Au NP film to be 90nm thick, with an average Au NP size of 125nm in diameter [1], and visually confirmed the dendritic assembly of the GSH-functionalized Au NPs. For application purposes, this study will evaluate the trace metal Pb2+ in water. The contamination of lead, and heavy metals in general, have a damaging impact on the health of both humans and our planet. The chelation of the GSH ligands with Pb2+ enables highly specific detection of Pb2+ in water. This method provides a simple, versatile SERS substrate with a dendritic assembly that creates intriguing optical properties and broadens the capability for potential applications.

[1] G. Rutherford et al., ECS J. Solid State Sci. Tech. 4, S3071 (2015).

[2] M. Bieri and T. Burgi, Langmuir
2005, 21, 1354-1362.

Figure 1
Mobile Water Kit 2.0: A Field Deployable Solution for E. coli Detection in Potable Water
Authors: Gunda Naga Siva , Chavali Ravi , Mitra Sushanta
Published: February 2020

Escherichia coli (E.coli) is an indicator organism, the presence of which in potable water suggests that the water source has been compromised. Consumption of such water would cause huge health problem and even human mortality. However, one of the key challenges for water quality monitoring is to detect such indicator organism right at the source or at the point of consumption. Current technologies rely on collecting water samples and sending samples to microbiological laboratories, which through membrane filtration and plate count, provide conclusive results, typically within 24 – 48 hrs. Such lengthy wait period is very much precarious to the communities, particularly in rural Canada, counties in US, and limited resource regions of developing economies (i.e., India, China, Brazil), where even access to a reliable water quality monitoring laboratory is questionable.

In response to this global issue, we have developed a low-cost and extremely efficient test method known as the Mobile Water Kit (MWK) [Gunda et al., Analytical Methods, 6, (16), 6236-6246, 2014], which has greatly simplified the process of E.coli detection in the field, which wasn’t feasible until recently. The MWK can accurately detect extremely low concentrations of E.coli (2 CFU/100 mL) under an hour and is faster than the current conventional laboratory methods, which requires 24 to 48 hours to produce proper results. However, MWK may require a trained technician to perform the test as there are number of steps involved for water testing starting from collecting the water sample to broadcasting of test results. Moreover, MWK contains the chemical reagents in liquid form to be stored and handled in a careful and manageable way. In the present work, we resolved these two impediments by the following modifications to MWK: (a) reduced the number of steps required to perform water testing; (b) converted the liquid based system to a hydrogel impregnated chemical reagent based system (i.e., porous soft material) for ease of handling and deployment. This revised version of MWK (i.e., MWK 2.0) simplifies the testing method and make it amenable for regular field use without the help of a trained technician. In addition, the MWK 2.0 replaces syringes, filters, centrifuge tubes, pipette tips, etc., which were essential components for the original version of MWK. Moreover, MWK 2.0 allows sample concentration and detection in one single step. With MWK 2.0, we were able to detect E.coli concentrations of 4x106 CFU/mL to 4x105 CFU/mL within 5 min and 4x104 CFU/mL to 40 CFU/mL within 60 min.
Cd (II) Ion-Selective Electrode Based on 2 –Acetylthiophene Semicarbazone in Polymeric Membrane
Authors: Mohan Chandra , Sharma Kusum , Chandra Sulekh
Published: February 2020

A new polyvinylchloride membrane sensor for Cd+2 ions has been prepared using 2–acetylthiophene Semicarbazone ligand as an electroactive ionophore and dibutylphthalate (DBP) as a plasticizing agent. The best performance was recorded with a membrane composition of PVC: DBP: Ionophore: NaTPB as 31: 64: 3.2: 1.8 (w/w %).The sensor exhibits a Nernstian response for Cd+2 ions over a wide concentration range (1.0 ×10–5 to 1.0 ×10–1 M) with a slope of 29.4 ± 0.2 mV decade–1. It has a fast response time of ˂ 10 s and can be used for at least 5 weeks without any divergence in potential. The electrode can be used in the pH range from 3.4 to 7.6. The proposed sensorrevealed relatively good selectivity and high sensitivity for Cd+2 ions in presence of a number of mono, di andtrivalent interfering cations within the working range of the electrode. The electrode was successfully applied for the direct determination of Cd+2in solution and, as an indicator electrode, in potentiometric titration of cadmium ions using ethylenediamine tetraacetic acid (EDTA) as titrant.

Keywords: Ion Selective Electrodes, Cadmium, PVC membrane, semicarbazide
(Invited) Where Is Dielectrophoresis (DEP) Going?
Authors: Pethig Ronald
Published: February 2020

Fifty years have passed since the first demonstration that DEP can be applied to the biomedical sciences. Pohl and Hawk [1] gave the first report of a purely physical technique being used to simultaneously distinguish and separate live and dead yeast cells. Over the past 50 years the theoretical aspects of DEP have attained a high level of refinement, whilst applications that include the manipulation of DNA, proteins, viruses, bacteria, blood cells, cancer cells and stem cells have been demonstrated. Stainless steel electrodes [1] used to generate the required high field gradients have been replaced by devices taking advantage of microfabrication and microfluidics, ranging from: microelectrode arrays [2]; insulator-based DEP [3, 4]; streaming DEP [5]; liquid electrodes [6]; carbon electrodes [7].

The key advances and relative advantages or otherwise of these various DEP techniques will be reviewed, with the aim to identify niche biomedical applications.

 

1. Pohl, H. A., Hawk, I. (1966) Separation of living and dead cells by dielectrophoresis, Science 152, 647-649.

2. Price, J. A. R., Burt, J. P. H., Pethig, R. (1988) Applications of a new optical technique for measuring the dielectrophoretic behaviour of micro-organisms, Biochim. Biophys. Acta 964, 221-230.

3. Masuda, S., Washizu, M., Nanba, T. (1989) Novel method of cell-fusion in field constriction area in fluid integrated circuit, IEEE Trans. Ind. Appl., 25, 732-737.

4. Chou, C-F., Tegenfeldt, J. O., Bakajin, O., Chan, S. S., Cox, E. C., Darnton, N., Duke, T., Austin, R. H. (2002) Electrodeless dielectrophoresis of single- and double-stranded DNA, Biophys. J., 83, 2170-2179.  

5. Cummings, E. B., Singh, A. K. (2003) Dielectro-phoresis in microchips containing arrays of insulating posts: theoretical and experimental results, Anal. Chem., 75, 4724-4731.

6. Demierre, N., Braschler, T., Linderholm, P., Seger, U., van Lintel, H., Renaud, P. (2007) Characterization and optimization of liquid electrodes for lateral dielectro-phoresis, Lab Chip 7, 355-365.  

7. Martinez-Duarte, R., Camacho-Alanis, F., Renaud, P., Ros, A. (2013) Dielectrophoresis of lambda-DNA using 3D carbon electrodes, Electrophoresis 34, 1113-1122.
Process Integration of Electroformed MEMS Variable Capacitors for Magnetostriction Measurements
Authors: Finnegan Patrick Sean , Langlois Eric D , Arrington Christian L. , Hollowell Andrew E , Pillars Jamin Ryan , Monson Todd , St. John Christopher R.
Published: February 2020

Electrochemically deposited CoFe and CoFeB films are being studied for use as wireless remote sensors. Coded signals can be achieved through passive devices and interrogated to produce electronic signatures that are nearly impossible to replicate or counterfeit. A MEMS variable capacitor is being fabricated from a novel electroformed process with CoFe and CoFeB magnetostrictive films. This approach to MEMS fabrication is being used to incorporate electroplated ferric alloys into a variable capacitor, to study Joule magnetostriction. Such alloys are capable of a large change in material shape when subjected to a magnetic field. Integrating these films with a variable capacitor MEMS device allows for a unique approach to provide accurate microstrain measurements in low magnetic fields up to saturation, to provide feedback for the optimization without the use of expensive commercial setups. This process is unique to MEMS device fabrication and is differentiated by the use of a planar layered approach. Maintaining planarity by manipulating oxides to form electroplating molds, as well as provide a sacrificial material, results in an electrochemically deposited cantilever structure with an integrated magnetostrictive sensing element. This presentation will discuss the fabrication process of these devices.   Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000
Enhanced ZnO Nanorods Field Emitter with Adsorbed Silver Nanoparticles
Authors: Young Sheng-Joue
Published: February 2020

Zinc oxide is low-cost and practical Ⅱ-Ⅵ chemical materials, which utilized to absorb silver nanoparticle on zinc oxide. It can improve the electrical characteristics of the zinc oxide. In this study, ZnO nanorods were prepared via hydrothermal method and use silver nitrate solution to absorb silver nanoparticle on ZnO nanorods. Finally, surface morphology observation by SEM, crystal (XRD), optical properties (PL) , element content (EDS),(TEM) and measurement field emission were measured. The results indicate that ZnO nanorods which have an average diameter and maximum length of around 35nm~75nm and 2.14um, respectively. It was found that the silver nanoparticle on ZnO nanorods, and silver nanoparticle have an average diameter of around 18nm~95nm. The existence of Ag was examined by energy diffraction spectra (EDS). The structural characteristics of the ZnO were measured by X-ray diffraction (XRD). It was found that the peaks related to the wurtzite structure ZnO (002), (102), (103), and (112) diffraction peaks, the (002) peak indicates that the nanorods were preferentially oriented in the c-axis direction. The PL spectra of all the samples were shown in two emission bands, ultraviolet (UV) and visible (blue and green) bands, were observed in each spectrum. The UV emission is always ascribed to the band gap of ZnO, and the strong visible emission centered at around 500 nm is assigned to the defects (such as oxygen vacancies and interstitial zinc) in ZnO. It was also found that the turn-on electrical field reduced from 3.2 to 2.5 V/μm and the field enhancement factor enhanced from 748 to 2007.
Signal Switch and Signal Amplification for Electrochemical Biosensing
Authors: Ju Huangxian
Published: February 2020

Recently, the investigation on electrochemical biosensing has made great progress. The developed biosensors have extensively been used in different fields, particularly, the sensitive and accurate detection of DNA, protein and metal ions. The designs of specific signal switch and signal amplification strategies are becoming the main topic of electrochemical biosensing research. This presentation will introduce new signal switches and signal amplification strategies developed in last two years. For example, we prepared two electrochemical catalytic probes to design two molecular switches for electrochemical DNA sensing by coupling with porphyrin-encapsulated metal-organic frameworks. Several new signal amplification strategies based on nanotechnology and molecular biology have been presented for DNA detection and immunoassay. By the recognition of nucleic acids to metal ions, some signal switches and label-free methods have been developed for specific and sensitive detection of heavy metal ions. Some new electrochemiluminescent emitters have been synthesized and used for design of new ECL biosensing mechanisms. A wavelength-resolved ratiometric photoelectrochemical technique has also been developed for sensing applications. These works led to a series of amplified methods for sensitive detection of DNA, microRNA and protein.

 

References:

1. L. Cui, J. Wu, H.X. Ju, Biosens. Bioelectron. 79, 861-865 (2016)

2. J. Zhu, X.H. Huo, X.Q. Liu, H.X. Ju,ACS Applied Mater. Interf. 8, 341-349 (2016)

3. P.H. Lin, J.P, Lei, L. Jia, H.X. Ju, Chem. Commun. 52, 1226-1229 (2016)

4. Y.Q. Feng, C.H. Dai, J.P. Lei, H.X. Ju, Y.X. Cheng, Anal. Chem. 88, 845-850 (2016)

5. Q. Hao, J.P. Lei, X.N. Shan, Y. Zang, Q.H. Yang, H.X. Ju, Chem. Sci. 7, 774-780 (2016)

6. Y. Huang, J.P. Lei, Y. Cheng, H.X. Ju, Biosens. Bioelectron. 77, 733-739 (2016)

7. Y. Zang, J.P. Lei, Q. Hao, H.X. Ju, Biosens. Bioelectron. 77, 557-564 (2016)

8. L. Cui, J. Wu, H.X. Ju, Anal. Chem. 87, 10635-10641 (2015)

9. L. Cui, J. Wu, M.Q. Li, H.X. Ju, Elctrochem. Commun. 59, 77-80 (2015)

10. L. Cui, J. Wu, H.X. Ju, Chem Eur. J. 21, 11525-11530 (2015)

11. Y.Q. Feng, Q.B. Wang, J.P. Lei, H.X. Ju, Biosens. Bioelectron. 73, 7-12 (2015)

12. P.H. Ling, J.P. Lei, H.X. Ju, Biosens. Bioelectron. 71, 373–379 (2015)

13. Y. Zang, J.P. Lei, P.H. Ling, H.X. Ju,Anal. Chem. 87, 5430–5436 (2015)

14. P.P. Ling, J.P. Lei, L. Zhang, H.X. Ju, Anal. Chem. 87, 3957–3963 (2015)

15. P.H. Ling, Q. Hao, J.P. Lei, H.X. Ju, J. Mater. Chem. B 3, 1335–1341 (2015)

16. K. Ren, J. Wu, F. Yan, Y. Zhang, H.X. Ju, Biosens. Bioelectron. 66, 345–349 (2015)

17. L. Cui, J. Wu, H.X. Ju, Biosens. Bioelectron. 63, 276-286 (2015)
Reduced Graphene Oxide Bridging Oriented Copper Nanowires for a Flexible, Annealing-Free and Air-Stable Electrode
Authors: Zhang Wang , Yin Zhenxing , Kim Youn Sang , Piao Yuanzhe
Published: February 2020

One-dimensional flexible conductive nanowires (NWs) are highly potential in the next-generation flexible devices. However, the unavoidable challenge is how to keep high conductivity, flexibility, and durability with economically feasible materials in a simple manufacturing process. Here, a straightforward solvothermal method is used to fabricate a flexible and conductive composite that contains reduced graphene oxide (RGO) nanosheets bridging oriented copper NWs. The GO-supporting way can successfully solve the problems listed above and help the composite films preserve good conductivity and durable flexibility without annealing or acid treatments. The Cu NW-RGO film under ambient conditions shows a high electrical property (0.808 Ω/sq) without any significant changes more than 30 days. Furthermore, it can be covered on polyester cloth as a lightweight flexible electrode with good durability and uncomplicated processability, which are highly promising in kinds of electronic devices
Real-Time Monitoring of DNA Amplification By Nanogap Ipedimetric Sensor
Authors: Lee Hyunjung , Keem Joo-Oak , Cho Hyunmin , Verma Neha , Lee Junghoon , Chung Bong Hyun
Published: February 2020

As our global society has been more complex and connected closely, infectious diseases could be easily and fast propagated to everywhere. And it makes early diagnostic detection be necessary with various ways based on optical, electrical and electrochemical methods. Real-time PCR (Polymerase Chain Reaction) has been powerful detection technology to recognize the amplified target DNA fragments that would be essential to diagnostic assays, but it needs optical labels and apparatus to detect the amplification of DNA. A variety of electric/electrochemical methods have been applied for label-free detection. Impedance assay is attractive tool for biomolecule real-time sensing, however, most of impedance studies are based on the immobilization of biomolecules on the electrode surface. That ascribes to additional steps and makes impossible to reuse electrode chip and biological samples. In this study, we aimed to develop the electrical impedance detection not optical method measuring the bulk impedance of PCR product solution by nanogap electrode. Electrical impedimetric nanogap devices could be very useful for detecting slight changes of amplifying DNA fragments in PCR cycling due to double layer capacitance and charge transfer resistance between two opposing nanogap electrodes. The electrode chip was fabricated using gold thin film by easy photolithography designed the nanogapped Si/SiO2 substrate by evaporation of oxide materials. Applying electric impedance measuring in nanogap chip avoiding the use of optical labels and immobilization on the electrode surface would be very impact detection system on DNA real-time screening.
Ionic Liquid Modified Carbon Paste Sensor Electrode for Determination of Antihypertensive Drug
Authors: BinSabt Mohammad , Atta Nada Farouk , Hassan Samar , Galal Ahmed
Published: February 2020

Electrochemical sensor was fabricated based on carbon paste electrode modified with an ionic liquid crystal ILC (2-chloro-1,3-dimethyl –imidazolidinium hexafluoro phosphate) in presence of sodium dodecyl sulfate for the electrochemical determination of Terazosin (TR). The electrode performance was compared in presence of other ionic liquids ILs (1-Butyl-4-methyl pyridinium tetrafluoroborate) and (1-n-Hexyl-3-methyl imidazolium tetrafluoroborate). Ultrasensitive determination of Terazosin HCl at the ILC modified electrode in the linear dynamic ranges of 0.002 to 0.09 μmol L−1 and 0.1 to 30 μmol L−1 with correlation coefficients 0.996 and 0.995 and LODs 1.69 ´ 10-11 mol L-1 and 6.43 ´ 10-9 mol L−
1, respectively were achieved. Selective determination of TR in presence of uric acid and ascorbic acid and simultaneous sensing of binary mixtures of TR/dopamine, TR/paracetamol and TR/Morphine were also realized successfully using the modified sensor.
Monitoring Ammonium Ions in Oral Microbiome
Authors: Ummadi Jyothir Ganesh , Bahro Chris Bernhard , Koley Dipankar
Published: February 2020

Ion selective electrodes are used to measure real time ionic concentrations in biological systems including bacterial biofilms. The beneficial bacteria in the oral microbiome plays an important role by producing ammonium ions in the presence of L-arginine and urea. The production of ammonium ions creates an alkaline environment which neutralizes the acidity caused by the pathogenic bacteria. The neutralization of acidity is important to prevent dental caries. Measuring the ammonium ion concentration gives important details about the activity of the beneficial bacteria in different environments.

We developed a solid contact ammonium ion selective electrode to study the release of ammonium ions from the beneficial bacteria. The sensor had a nernstian response and a dynamic range of 10 µM to 100 µM and good selectivity against common interferants like Na+, K+, H+. The sensor was used to test the release of ammonium ions in the vicinity of pathological bacteria to study the neutralization of acidic environment. This study will help in determination of ammonium ion concentration required to maintain homeostasis in the oral microbiome. The characterization of ammonium ion sensor and the measurement of ammonium ions in the oral microbiome will be presented at the conference.

Figure 1
Ru-Core@Pt-Shell Nanosheet Anode Catalyst: High Activity and Durability for Hydrogen Oxidation Reaction in the Presence of CO
Authors: Takimoto Daisuke , Ohnishi Tomohiro , Nutariya Jeerapat , Shen Zhongrong , Ayato Yusuke , Mochizuki Dai , Demortiere Arnaud , Boulineau Adrien , Sugimoto Wataru
Published: February 2020

PtRu alloy nanoparticles are presently used as the anode catalyst for residential polymer electrolyte fuel cells due to its high carbon monoxide (CO) tolerance. Unfortunately, PtRu alloy is not as stable as pure Pt, and the gradual dissolution of Ru from the catalyst surface leads to catalyst degradation. In an earlier study, we have shown that the addition of metal or metal oxide nanosheets as co-catalysts to carbon supported PtRu/C catalysts can enhance the CO tolerance and durability 1,2. Here we describe the synthesis of Ru-core@Pt-shell nanosheets via surface limited redox replacement 3. The CO tolerance and durability of Ru-core@Pt-shell nanosheets towards the hydrogen oxidation reaction activity in the presence of CO is presented.

Metallic Ru nanosheets supported on carbon composite was prepared via thermal reduction 2. Pt shell was successively formed on metallic Ru nanosheets via galvanic displacement reaction between Cu and Pt2+ by repeating the displacement reaction twice. The electrochemically active PtRu surface area of Ru-core@Pt-shell nanosheets with 1.5 monolayer Pt-shell (Ru@Pt-1.5ML(ns)/C) was 95 m2 (g-PtRu)-1, and the hydrogen oxidation reaction activity in pure H2 of Ru@Pt-1.5ML(ns)/C was 2.4 times higher than benchmark commercial PtRu/C. The H2 oxidation activity in the presence of 300 ppm CO for core-shell nanosheets was 1.5 times higher than that of PtRu/C. In addition, the activity of Ru@Pt-1.5ML(ns)/C after durability test (0.05 (3sec)-0.40 V (3 sec) for 1000 cycles) was 2.0 and 2.3 times higher than that of PtRu/C and Pt/C, respectively. The high activity in pure H2 could be attributed to the large surface area of core-shell structure, and the enhanced CO tolerance could be attributed to the electronic effect from the Ru nanosheet core. Ru nanosheet core was completely covered with Pt-shell, thus, the degradation of activity due to dissolution of Ru was suppressed.

This research was supported in part by the “Polymer Electrolyte Fuel Cell Program” from the New Energy and Industrial Technology Development Organization (NEDO) of Japan.

1) D. Takimoto, T. Ohnishi, and W. Sugimoto, ECS Electrochem. Lett., 4, F35 (2015).

2) D. Takimoto, T. Ohnishi, Y. Ayato, D. Mochizuki, and W. Sugimoto, J. Electrochem. Soc., 163, F367 (2016).

3) J. Nutariya, M. Fayette, N. Dimitrov, and N. Vasiljevic, Electrochim. Acta, 112, 813 (2013).

Figure 1
In-Situ Synthesis of Tungsten Carbides Functional Support for PEMFC Catalyst
Authors: Oh JI-Won , Na Hyunwoong , Nahm Sahn , Choi Hanshin
Published: February 2020

Tungsten carbide nanoparticles supported by carbon black was designed in order to apply it for heterogeneous catalysts or functional support for precious metal catalysts. At the same time, the designed composite nanoparticle was synthesized to have uniform dispersion by a facile synthetic methodology, arc plasma deposition synthesis. During the process, vaporized tungsten gaseous species were directly deposited on mechanically agitating carbon black nanoparticles. Macroscopic homogeneity and particle properties were investigated with arc discharging numbers increasing. Particles followed island growth mode during heterogeneous condensation and two peculiar features are observed during the process. Firstly, tungsten carbides nanoparticles are developed by depositing tungsten ions on carbon black support in vacuum environment. W2C was stabilized from amorphous particle via intermediate pseudo-crystal state. Secondly, crystallinity of carbon black particle was prominently enhanced as tungsten carbides phase fraction increases. Both phenomena occurred in-situ and they were due to energetic deposition of W ions and interaction with carbon.
Synthetic Variations of Hollow Graphene Nanoshells for Li-Ion Battery Anode
Authors: McKenzie Kevin R. , Banek Nathan A , Hays Kevin Alan , Wagner Michael J
Published: February 2020

The pyrolysis of cellulose produces bio-fuels, a net carbon neutral energy source, and bio-char that can be used as a soil enhancer. The economic feasibility of the production of bio-fuel from fast growing plants that can grow rapidly on minimally viable land, such as switch grass, would be greatly enhanced by producing higher added value products from the bio-char. Pyrolyzing bio-char in the presence of metal halide catalysts with a CO2laser for a few seconds results in the production of hollow graphene nanoshells (HGNS), a carbon negative material, which can be used in place of graphite active materials in Li-ion battery anodes with remarkably higher charge rate capability and low temperature performance in relatively inexpensive electrolytes.

Graphite is the most widely used anode active material in commercial Li-ion batteries. With a standard reduction potential of -2.9 V vs SHE and theoretical gravimetric capacity of 372 mAh/g (at LiC6) it provides 2 to 3 times the energy density compared to aqueous battery chemistries. The challenge remains to charge graphite anodes at the very high rates required for applications such as electric vehicles while maintaining its capacity over thousands of cycles. Shortening the Li-ion diffusion distance in graphite crystallites allows one to increase the charging rate, however, small graphite particles have poor cycle life.

We utilize hollow graphene nanoshells that have orders of magnitude shorter diffusion distances than standard graphite as an anode active material. These HGNS are made up of concentric multilayer graphene shells ~50 nm in diameter that intercalate Li+ in manner analogous to graphite but with remarkably higher charge rate capability (up to 22% charge in 7.2 s) and low temperature performance in relatively inexpensive electrolytes such as PC. Unfortunately, the storage capacity for HGNS is lower than graphite (~220 mAh/g vs. ~330 mAh/g practical), which motivated us to investigate synthetic variation to improve HGNS. Here we will present the results of our studies, finding that simple, inexpensive modifications to the synthetic procedures can result in HGNS with 40% greater reversible capacity (320 mAh/g) with no capacity loss after 100 cycles and a Coulombic efficiency of 99.9%. This new form of carbon is a very promising anode active material that could enable Li-ion batteries with dramatically faster charging rates, longer cycle lives and much better low temperature performance than standard graphite anodes. Furthermore, adoption of this carbon negative material in place of synthetic graphite could have a significant impact on global climate change, both directly by CO2 sequestration and indirectly by improving the economic viability of bio-fuels.

Figure 1
Lithium - Redox Battery Using a Solvate Ionic Liquid
Authors: Sugiyama Masaru , Tachikawa Naoki , Yoshii Kazuki , Katayama Yasushi
Published: February 2020

Redox flow batteries have been expected as the large scale storage battery. Redox flow batteries utilize the oxidation and reduction of two soluble redox couples for charging and discharging without the solid phase reaction. Therefore, the cycle lives of the redox flow batteries are expected to be much longer than those of rechargeable lithium batteries using insertion-type active materials. Currently, vanadium redox flow batteries have been put into practical use to stabilize the supply of renewable energy. Vanadium redox flow batteries have low energy density compared to other batteries. Since aqueous solution is used for the electrolyte, the electrochemical window of the water limits the cell voltage. Although there has been various studies using an organic electrolyte in order to enlarge the cell voltage, the flammability and volatility of the organic solvents can be disadvantageous from the point of view of safety. 1)

 Recently, aprotic ionic liquids have attracted attention as nonaqueous electrolytes. Especially, aprotic ionic liquids containing bis(trifluoromethylsulfonyl)amide (TFSA-) have been studied extensively in the electrochemical field because they show favorable features such as incombustibility, involatility and wide electrochemical potential window. We have already reported the redox reactions of various metal complexes in the ionic liquids and their applicability to redox flow batteries. 2) However, there are a few reports regarding the redox battery using the ionic liquids probably due to lack of the suitable ion exchange membrane that can move the career ion in the ionic liquids.

 In the present study, a new redox battery, namely “lithium-redox battery”, was proposed using a redox reaction of an iron complex for a cathode reaction, dissolution and deposition of lithium for an anode reaction, and LiTFSA – tetraglyme (G4) solvate ionic liquid for an electrolyte. In addition, lithium ion conductive solid electrolyte (LICGCTM) was used as the diaphragm, which prevents penetration of the redox species and enables transfer of lithium ions. Tris(2,2'-bipyridine)iron(II) complex ([Fe(bpy)2]2+) was found to be soluble and stable in the solvate ionic liquid. The redox reaction between [Fe(bpy)3]2+ and [Fe(bpy)3]3+ was confirmed to be reversible by cyclic voltammetry. The formal potential of [Fe(bpy)3]3+/2+ was 4.1 V vs. Li|Li(I). Reversible charge-discharge cycling of the lithium redox battery having an average cell voltage of 3.9 V was possible for 30 cycles with a coulombic efficiency of more than 95%.

References

1) Y. Matsuda, K. Tanaka, M. Okada, Y. Takasu, and M. Morita, J. Appl. Electrochem., 18, 909 (1988).

2) Y. Katayama, M. Yoshihara, and T. Miura, J. Electrochem. Soc., 162, H501 (2015).