bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrochemical Sensor for Choline Based on Iron (III) Oxide and Functionalized Multi-Walled Carbon Nanotube at the Glassy Carbon Electrode Surface
Authors: Uwaya Gloria Ebube , Fayemi Omolola Esther
Published: July 2021

Iron (III) oxide nanoparticle (Fe3O4NP) was synthesized via green route using Callistemon viminalis leaf extract. A composite of Fe3O4NP with functionalized multi-walled carbon nanotube (f-MWCNT) was then applied as glassy carbon electrode modifier to develop a choline sensor. Electrocatalytic oxidation of choline on nanocomposite modified electrode (GCE/f-MWCNT/Fe3O4NP) was studied by cyclic voltammetry while mechanism of electron transfer process during choline electrocatalytic oxidation was monitored by electrochemical impedance spectroscopy at fixed potential 0.5 V with frequencies between 100 kHz and 0.01 Hz. Active surface coverage area of choline, charge transfer coefficient and number of electron transferred were reported. Square wave voltammetry (SWV) was employed for the determination of choline over a linear concentration range of 24.3 - 215.6 μM. A sensitivity of 0.0244 μA/μM and 9.9 μM detection limit was found. The sensor was selective to choline (0.1 mM) in the presence of 100 mM and 0.1 mM ascorbic acid (AA) and dopamine (DA) respectively using SWV and chronoamperometry. The designed electrode was reproducible and stable. The sensor was successfully used for choline detection in choline dietary supplements with resultant good recoveries. The fabrication of the sensor was simple and cost-effective.

Figure 1
Surfactant-Mediated Morphological Alteration of WO3 Nanostructures for Efficient NO2 Sensing
Authors: Patel Chandrabhan , Mandal Biswajit , Dubey Mayank , Mukherjee Shaibal
Published: July 2021

The addition of surfactant during hydrothermal growth greatly affect the surface morphology of nanostructures [1]. Here, to see the impact of surfactant in the hydrothermal growth of WO3 nanostructures, we have used Cetyl trimethyl ammonium bromide (CTAB) and Sodium chloride (NaCl) as surfactants during WO3 nanostructure formation. Flower-like WO3 nanostructure were successfully grown by CTAB surfactant while nanorod-like structures were obtained in the presence of NaCl at an optimized pH level. Na2WO4·2H2O salt was used with CTAB and NaCl surfactant separately in acidic (HCl (3M)) medium for the hydrothermal growth. The shape of nanostructures plays a crucial role for gas sensing [2]. WO3 nanorods grown by NaCl surfactant exhibited excellent sensitivity for NO2 at ppm level as compared to WO3 nanoflowers grown CTAB surfactant. In addition to the surface area, current conduction also depends on the surface morphology which is helpful to improve the response-recovery characteristics of the sensing device. Interestingly, we observe that hydrothermally grown WO3 with NaCl surfactant is an ideal candidate for NO2 sensing.

Fig. 1 FESEM image of WO3 nanostructure with (a) CTAB surfactant, (b) NaCl surfactant and (c) exhibit the sensitivity of WO3 with NaCl and CTAB surfactant at 150 °C on 100 ppm NO2 .

Figure 1
Ultra-Low Detection Limit MEMS Hydrogen Sulfide Sensor Based on Tungsten Oxide Nanorods with Lots of Oxygen Vacancies
Authors: Yue Wu , Xu Jiaqiang , Hu Qingmin , Guo Mengmeng , Zhe Dong
Published: July 2021

In this paper, tungsten oxide nanorods were successfully synthesized by using ordered mesoporous silica of SBA-15 as a template and 12-phosphotungstic acid as a precursor of tungsten oxide under a hydrogen (H2) atmosphere. XRD and HRTEM characterization show that the composition of tungsten oxide synthesized is WO2.83. The gas sensing test results show that WO2.83 can detect 5 ppb H2S. Moreover, the response of the sensor fabricated with WO2.83 to 200 ppb H2S at the optimal operating temperature of 280 °C is as high as 1.8, which is increased by nearly 50% than that of the common WO3 without redundant oxygen vacancies. The improved gas sensing properties can be attributed to rich oxygen vacancies in the WO2.83. Our present results also demonstrate that WO2.83 with a lot of oxygen vacancies can significantly enhance the gas response to ultra-low concentration H2S, and this method of manufacturing defects has great potential in improving the gas-sensing performance of metal oxide semiconductor.

Figure 1
Development of a Selective Mixed-Potential Ammonia Sensor for Automotive Exhausts
Authors: Nematbakhsh Abkenar Gita , Viricelle Jean-Paul , Rieu Mathilde , Breuil Philippe
Published: July 2021

One of the most effective technologies in decreasing large-scale NOx emission produced by diesel engine vehicles is Urea-SCR (selective catalytic reduction) system. In order to prevent inducing excessive ammonia to the environment, an NH3 sensor is required at the exit of this system [1, 2]. In this study, highly selective ammonia sensors were developed to detect ammonia emissions from automotive exhaust.

The sensors were fabricated with 8-YSZ electrolyte, a platinum reference electrode and a working electrode of Au-V2O5 (mass ratio 85/15), screen-printed on an alumina substrate. A platinum resistor was printed at the backside of the support to control the sensor temperature. The measured sensor’ response (ΔV) is the potential difference between reference and working electrodes. Figure 1 shows the responses of two identical sensors to 100 ppm CO, NO2, NO and 20 ppm of NH3 at four different temperatures. It can be seen that the sensors respond to all gases at lower temperatures while by increasing temperature to 600°C, the selectivity to NH3 is greatly improved. The selectivity of sensors was also confirmed by testing other possible interfering gases: no responses were observed for 20ppm of hydrogen and 100ppm of a hydrocarbon mixture.

The stability of such sensors was studied at 550°C and 600°C. Since the sensors show no long-term stability at 600°C (electrode degradation), but remain stable at 550 °C, investigations were made to decrease the working temperature while maintaining selectivity. After testing different mass percentages of V2O5 in working electrode, we observed that by increasing this value to 50%, the working temperature of selective ammonia sensors could be decreased to 550°C with stable responses.

Further investigations will be performed in order to gain deeper insight in sensing mechanism of V2O5 based working electrodes, which governs the sensor’s performance.

References

[1] K. Shimizu, I. Chinzei, et al. "Doped-vanadium oxides as sensing materials for high temperature operative selective ammonia gas sensors," Sensors and Actuators B, 141, 2009, pp. 410-416.

[2] M. Van Nieuwstadt, I. Dpadhyay, et al. "Control of Urea SCR Systems for US Diesel Applications" in IFP Energies Nouvelles International Conference, Dearborn, USA, 2011, pp. 655-665.

Figure 1
(Invited) Epitaxial NiO-Graphene Gas Sensors
Authors: Schipani Federico
Published: July 2021

Integrated, highly sensitive and reversible sensor devices for toxic and hazardous gases in environmental pollution monitoring can be realized with graphene-based materials. Here we show that, single layer graphene grown on SiC can be utilized to implement sensor devices being extremely sensitive towards NO2 showing an n-type response. A second type of sensor with an added NiO layer on top of the single layer graphene changed its response to p-type but did not reduce its sensitivity. We show that the conduction switch from n-type to p-type was not a consequence of an alteration of the graphene layer but is found to be an effect of the NiO layer. We find that the NiO leads to lowering of the Fermi level to a point that a crossing of the Dirac Point in the graphene switched the conduction type. These sensors were tested in the 100 ppb NO2 regime, showing good response and a detection limit extrapolated to be below 1 ppb. This new NiO/graphene/SiC configuration can be an attractive p-type sub-ppb sensor platform for NO2 and related gases.
Excellent Toluene Sensing Properties Based on Monodispersed WO3 Nanoparticles
Authors: Wang Xi , Sun Yanfeng , Lu Geyu
Published: July 2021

The preparation of size-controlled materials has shown remarkable potential with regard to their reinforced sensing performance. Herein, we report a facile solvothermal synthesis of dispersed WO3 nanoparticles with porous nanostructure caused by particle assembly. Various characterizations of the as-obtained samples were analyzed. Furthermore, the gas sensing properties of WO3 samples on volatile organic compounds were investigated. The results reveal that the gas sensors based on synthesized WO3 samples with suitable hexamethylenetetramine (HMT) amount and sintering treatment exhibit the highest response (132.0) towards 100 ppm toluene at the optimal working temperature of 225°C with fast response/recovery time (2 s/6 s), which is attributed to the porous structure of the sensing film and the high resistance caused by well crystallization and grain boundary among the nanoparticles.
Graphene-Based Nanosensor Device for Rapid, Onsite Detection of E.coli in Water
Authors: Hossain Md Imran Imran , Hill James , Pu Haihui , Steeber Douglas , Chen Junhong
Published: July 2021

E. coli bacteria are widely accepted as the indicator bacteria to predict the presence of pathogens in water intended for human consumption. One of the strains of E. coli is the specific subspecies serotype E. coli O157:H7, which is the most prevalent bacterial contaminant and responsible for most E. coli outbreaks in the US. E. coli O157:H7 can cause bloody diarrhea, kidney failure and may even lead to death. E. coli infection in the U.S. afflicts ~70,000 people per year mostly from food, and ~ 15% of the cases are from tainted water according to the CDC. In May 2014, E. coli-contaminated water supply in Portland, OR, which covers several suburban cities, affected ~670,000 people. Several approaches have been developed to detect E. coli O157:H7, including the culture and colony counting method, polymerase chain reaction (PCR), and immunological methods; however, all these methods require long detection time and are unsuitable for in situ detection. We propose a novel method for real-time, in situ detection of E. coli in water by using a graphene-based sensor. Graphene has excellent electrical conductivity and is very sensitive to surface changes enabling it to detect E. coli bacteria down to a few colony forming units (cfu). The proposed sensor is based on a novel, micro-sized amperometric sensor that outperforms existing E. coli sensing methods and is simple to implement, eliminating many of the disadvantages associated with current practices. Additionally, we plan to integrate this sensor in a handheld electronic device with features such as high sensitivity and selectivity, rapid response, ease of use and affordability.
Nanomaterial-Based Electrochemical Sensors for Environmental and Biomedical Applications
Authors: Qian Lanting , Prins Scott , Chen Aicheng
Published: July 2021

The rapid growth of pharmaceutical industries has led to new biomedical and environmental concerns. There is an urgent need for sensitive, portable and cost-effective sensors for the detection of pharmaceuticals to either track patient overdosing or to monitor the pollutants in the environment. Nanomaterial-based electrochemical sensing technologies can readily tackle the aforementioned problems, which spurred significant research interests recently [1-3]. In this presentation, the synthesis of nanoporous gold and graphene oxide-based nanomaterials for the electrochemical sensing of acetaminophen, naproxen and isoniazid is discussed. The design rationale and the performance of the proposed electrochemical sensors are highlighted. Specifically, the hierarchical nanoporous gold exhibited high sensitivity of 58.16 µAµM−1cm−2 and a low detection limit of 1.01 nM. In addition, it was found that the oxygen content of the graphene-based nanomaterials played a critical role in both sensing of naproxen and isoniazid. The proposed electrochemical sensors were further tested using real samples, which showed their promising applicability in biomedical and environmental applications.

[1] J. van der Zalm, S. Chen, W. Huang, and A, Chen, J.
Electrochem. Soc.,
167
,037532 (2020).

[2] L. Qian, S. Durairaj, S. Prins, and A. Chen, Biosens. Bioelectron., 112836 (2020).

[3] L. Qian, A.R. Thiruppathi, R. Elmahdy, J. van der Zalm, and A. Chen, Sensors.,
20,1252 (2020).
Monitoring of Technetium in Groundwater: Development of a Novel QCN Based Sensor
Authors: Papageorgiou Athanasios , Andrieux Fabrice
Published: July 2021

Technetium-99, a pure β-emitter with Emax =294 keV, is one of the most significant (t1/2 =2.1×105 y) nuclear waste isotopes, produced by the fission of U with a yield of 6%. Under normal environmental conditions, it is mostly encountered as the pertechnetate ion, TcO4
-, which is highly soluble and consequently mobile in water. For this reason, its monitoring into groundwater is a statutory requirement for every nuclear license site. Because of its relatively low concentration in environmental samples, current determination methods of 99Tc involve several steps, such as chemical separation from the matrix, purification and source preparation, prior to radiometric (e.g. liquid scintillation counting) or mass spectroscopic (e.g. inductively coupled plasma mass spectroscopy) determination. The detection of 99Tc may take up to several days, thus making these techniques inappropriate for an emergency situation. Hence, We report on the development of a sensor for the real time monitoring of 99Tc in groundwater based on the Quartz Crystal Nanobalance (QCN). The QCN is a piezoelectric resonator, which oscillates in a resonant frequency fs when an electric potential is applied across its body. It is capable of measuring very small changes in mass at its surface, through the change of the resonant frequency. We modify it to respond exclusively to the presence of TcO4
-, by application of a novel Ag-4,4bipyridine metal-organic framework thin film built layer-by-layer on a self-assembled monolayer of 4-mercaptopyridine on the gold surface. The film’s structure is characterised by several techniques such as XPS, AFM and XRD and we evaluate its response and selectivity by monitoring the changes in the resonant frequency as a function of the concentration of ReO4
-, which is a non-radioactive chemical surrogate for TcO4
-. Finally, we model the adsorption of ReO4
- and other interferences with adsorption isotherms such as Langmuir, Freundlich and Sips.
Chemosensor Based on Molecularly Imprinted Nanoparticles for Selective Determination of Glyphosate
Authors: Lach Patrycja , Cieplak Maciej , Garcia Cruz Alvaro Garcia , Canfarotta Francesco , Sharma Piyush Sindhu , Piletsky Sergey A. , Kutner Wlodzimierz
Published: July 2021

Glyphosate is a commonly used herbicide that can kill some weeds and grasses. Unfortunately, exposure to glyphosate is considered potentially harmful to humans. It may cause liver and kidney damage as well as can affect the endocrine system.1 Furthermore, the International Agency for Research on Cancer considers glyphosate as a probable carcinogen.2 Glyphosate determination often requires additional steps allowing quantification by commonly employed chromatographic techniques. Therefore, low-cost, rapid, and reliable ways to determine this pesticide are essential.

We devised and fabricated an electrochemical chemosensor for the selective determination of the target toxin, glyphosate. As a recognition unit in this sensor, electroactive molecularly imprinted nanoparticles (nanoMIPs) with an internal redox probe were used.3 The MIP nanoparticles were synthesized using a solid-phase synthesis protocol.4 The nanoMIPs were characterized by several methods, including dynamic light scattering (DLS), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The obtained nanoparticles were covalently immobilized on screen-printed platinum electrodes and successfully used for electrochemical determination of glyphosate in the absence of any external redox probe. Chemosensor fabricated that way demonstrated high sensitivity and selectivity with respect to structural analogs of glyphosate and other phosphate-containing analytes. The practical application of this self-reporting MIP-based chemosensor for detecting pesticide was further verified in river water samples with satisfying results. These results prove that our sensor's detectability is sufficient for the on-site detection of glyphosate pesticide.

References:

1 Myers, J. P., Antoniou, M. N., Blumberg, B. et al. Concerns over use of glyphosate-based herbicides and risks associated with exposures: a consensus statement. Environ Health. 15, 19 (2016)

2 Guyton, K. Z., Loomis, D., Grosse, Y. et al. International Agency for Research on Cancer Monograph Working Group ILF. Carcinogenicity oftetrachlorvinphos, parathion, malathion, diazinon, and glyphosate. Lancet Oncol. 16, 490-491 (2015)

3 Cruz, A. G., Haq, I., Cowen, T. et al. Design and fabrication of a smart sensor using in silico epitope mapping and electro-responsive imprinted polymer nanoparticles for determination of insulin levels in human plasma. Biosens. Bioelectron.
169, 112536 (2020)

4 Canfarotta, F., Poma, A., Guerreiro, A. et al. Solid-phase synthesis of molecularly imprinted nanoparticles. Nat Protoc
11, 443–455 (2016)
(Invited) Microfabricated Chemical Sensors for Industrial, Health and Environmental Monitoring
Authors: Maboudian Roya
Published: July 2021

There remains a strong need for miniaturized, low-power gas sensors that can be deployed in wireless applications for improved environmental protection, for public health, and for safe and efficient operation of many industrial processes. Leveraging the microfabrication technologies and utilizing innovations in high surface area nanomaterials are providing exciting opportunities towards low-power microchemical sensors. In this presentation, I will discuss one of the approaches we have been pursuing, which is based on a highly efficient microheater platform with fast response and recovery times. The design, fabrication and characteristics of this platform will be presented. I will also discuss the use of two-dimensional materials for gas sensing applications since they offer the highest possible surface area for gas interaction, leading to high sensitivity. Assembling these two-dimensional materials into three-dimensional assemblies, such as aerogels, provides a low-density material with large number of interconnected pores that increases the surface area available in a given footprint while maintaining the properties of the few-layer sheets. By integrating these nanomaterials with our microheater platform, we have achieved fast and sensitive detection of several health and environmental pollutants. The talk will end with current limitations and plans for future directions.
(Invited) Microfluidics Enabled Protein Fractionation and Soft Wearable Robots
Authors: Ren Carolyn
Published: July 2021

Microfluidics is a science that deals with small amounts of fluids at the microscale. The confinement brings in many advantages such as reduced reagent consumption, shortened analysis time, increased throughput and potential for portable systems. These advantages and others make microfluidic systems ideal enabling platform technologies that can be applied in a wide range of applications spanning from material synthesis, life science research, drug screening and environmental monitoring. This presentation summarizes Ren’s work on microfluidics that is dedicated to protein fractionation and soft wearable robots towards well-being. Protein fractionation techniques will include a suite of techniques such as isoelectric focusing, free flow focusing and pH elution. The soft wearable robots enabled by microfluidics will start with a brief introduction of soft robots and follow up with the unique angle that Ren’s team took for developing inexpensive, comfortable daily wearable assistive robots. Its demonstration and validation towards patients suffering from arthritis will be provided and discussed.
Leveraging Preconcentration and Partial Separations with Silicon Nanowire Arrays to Improve the Detection of Low Volatility Trace Explosive Vapors
Authors: Giordano Braden , Mullen Matthew , Johnson Kevin , Ratchford Daniel , Giles Spencer , Ryan Justin
Published: July 2021

Trace detection of explosive vapors in real world environments is hindered by strict sensitivity and selectivity requirements that need to be met in order for these techniques to be effective. The physical properties of most explosive molecules limit environmentally relevant vapor concentrations to the part per billion (ppbv) – part per trillion (pptv) range due to their saturated vapor pressures under real world conditions. Additionally, trace explosive vapor detectors must be able to discriminate against a number of potential chemical and biological interferents present in complex real world environments. In this work, we present silicon nanowire arrays (SiNW) as a novel tunable material aimed at providing trace explosive vapor detectors with the sensitivity and selectivity necessary for operational use.

Dense, highly ordered silicon nanowires are fabricated through a nanosphere lithography process and topped with a porous gold electrode resulting in a high surface area adsorptive substrate intrinsically capable of rapid, precise temperature control via Joule heating. Explosive vapors are selectively preconcentrated onto the SiNW array by exploiting their affinities for the surface (SiO2 or otherwise functionalized) of the nanowires. Chromatographic like partial separations of preconcentrated material on the array can be achieved through careful selection of desorption parameters. Using a multichannel detector, such as an IMS or MS, we demonstrate the preconcentration of a number of explosive vapors including 2,6-DNT, TNT, and RDX, while simultaneously exploring the effects of desorption flow rates and temperatures on the partial separation of 2,6-DNT, 2,4-DNT, TNT, and RDX vapors. In addition, we provide a strategy for chemometric deconvolution of array-based partial separations based upon evolving factor analysis and multivariate curve resolution by alternating least squares. This approach enabled qualitative and quantitative analysis of individual components without target analyte libraries or complete chromatographic separation.
(Invited) Discrimination and Selection of Target Cells from the Cell-Based Array Based on Dielectrophoresis
Authors: Yasukawa Tomoyuki , Hata Misaki , Suzuki Masato
Published: July 2021

Introduction: We have developed manipulation techniques to form cell-based arrays by positive dielectrophoresis (p-DEP) and to retrieve target cells from cell−based arrays selectively by negative dielectrophoresis (n-DEP). The novel devices with microwell arrays on microband electrodes were employed to manipulate cells. Hybridomas with the secretion ability of antibodies were trapped to form cell-based arrays. Then, the ability was discriminated by trapping the antibodies to the antigen immobilized on the bottom of wells. Finally, individual cells trapped in microwells were selectively retrieved by regulating the generation of electric fields in individual microwells. The development of series of these techniques could be useful to recover hybridomas producing antibodies with high affinity in large populations of cells without repeated steps of a culture and a limiting serial-dilution.

Experimental: The device comprises the upper substrate with indium-tin-oxide (ITO) microband electrodes and the lower substrate with microwell arrays on ITO microband electrodes. Hybridomas producing an anti-rabbit serum albumin (RSA) antibody suspended in the DEP medium were introduced in the channel. AC signal (3 MHz, 2 Vpp) was then applied to the upper and lower microband electrodes with opposite phase to form a cell-based array. Anti-RSA antibodies secreted from hybridomas trapped in the microwells were captured by RSA immobilized on the electrodes. Cell arrays were then treated with anti-mouse IgG antibody conjugated with Alexa 488 (a secondary antibody). Thereafter, a repulsive force of negative dielectrophoresis (n-DEP) was employed to retrieve the target hybridomas from the microwell array. To retrieve the target hybridoma, an AC signal in the n-DEP frequency region was applied to a pair of microband electrodes above and below the microwell with the target hybridoma.

Results and discussion: Cell−based arrays were formed with the occupancy efficiency of over 90% in a few seconds by p-DEP. Antibodies secreted in microwell arrays were captured to discriminate target hybridomas in a few hours without repeated steps of a culture and a limiting serial-dilution. Furthermore, hybridomas trapped in microwells were retrieved from the cell−based array by applying an AC signal to band electrodes. The sequential system for forming cell−based arrays, discriminating hybridomas secreting specific antibodies, and retrieving target hybridomas was developed by using the novel microwell array device comprising 3-D microband array electrodes with an orthogonal arrangement.
Sensitive Electrochemical Detection of Nucleic Acids Following Electrokinetic Enrichment in a Bed of Bioconjugated Beads for Point-of-Care Testing
Authors: Anand Robbyn Kimberly , Berzina Beatrise , Peramune Umesha , Kim Sungu , Ganapathysubramanian Baskar
Published: July 2021

In this presentation, we demonstrate that ion concentration polarization (ICP) in the presence of fluid flow drives focusing and efficient capture of target nucleic acids within a bed of oligoprobe-conjugated beads. A key finding is that ion conduction along the surface of the bioconjugated beads is the dominant contributor to current to the electrode that drives ICP, under the condition of ICP-induced depletion of ions from the bulk solution. Therefore, hybridization of a target nucleic acid (a polyanion) to the bead surface leads to a shift in the slope of the current-voltage curve. This approach is versatile in that a target nucleic acid can be detected electrically, in the absence of a label, or electrochemically via a label that generates an electroactive product. The resulting approach allows for a plug-and-play nucleic acid sensor using off-the-shelf bioconjugated beads and simple electronics, making it advantageous for point-of-care testing.
(Invited) Why Do Dipole Effects on Charge Transfer Matter?
Authors: Vullev Valentine I.
Published: July 2021

Charge transfer (CT) and charge transport (CTr) are by far among the most important processes for sustaining life on Earth and for making our modern ways of living possible (Phys. Chem. Chem. Phys.
2020, 22, 21583-21629). In natural and manmade sensing systems, for example, well synchronized CT processes drive the conversion of mechanical, optical, chemical and thermal signals into electric outputs, which is essential for interfacing with processing modules. Concurrently, electric dipoles are everywhere and therefore, understanding how they affect CT and CTr is of principal importance for attaining and controlling the functionality of a wide range of materials and devices. Discussions of the idea about dipole effects on CT date back to the mid 20th century and reported experimental evidence from the 1990s and 2000s demonstrated their key importance. The dipole-generated localized electric fields induce Stark effects and modulate the electronic properties of the CT moieties in their vicinity. The notion for such effects focusses on dipole-induced changes in the reduction potentials of the donor and the acceptor, affecting the CT driving forces and thus, the Franck-Condon (FC) contributions to the CT kinetics. We recently demonstrated that to harness such effects, which are inherently enormous, (1) the dipoles should be placed as closed as possible to the electron donor and acceptor, and (2) the media polarity should be lowered (Angew. Chem.
2018, 57, 12365-12369). Polar media, indeed, stabilize charged states and in general enhances the rates of CT. Polar media, however, screen the field permeation and damps the dipole effect on the electron donor and acceptor. Using hydrocarbons as a medium, results in electron transfer rates along the dipole that are six times larger than the rates for the same system when in polar solvents, such as acetonitrile. The same localized field effects in non-polar medium completely shut down the electron transfer against the dipole. While in the vicinity of dipoles, the electric fields can reach GV/m, they fall of rapidly with distance. In our work, we incorporate the dipoles in the electron donors. This geometry provides the closest possible placement of the dipole to the CT moieties. Most importantly, it has also allowed us to discover for the first time dipole effects on donor-acceptor electronic coupling that dominate and oppose the established notion about effects on the FC contributions to the CT kinetics. These discoveries change the ways of thinking about dipole effects on CT and CTr, and set unprecedented paradigms for the development of electronic materials and devices.
Novel Mechanism Insight for Enhanced Electrochemiluminescence Signal
Authors: Valenti Giovanni , Zanut Alessandra , Fiorani Andrea , Marcaccio Massimo , Rapino Stefania , Paolucci Francesco
Published: July 2021

Electrochemiluminescence (ECL) is a leading technique in bioanalysis.[1] Since the excited species are produced with an electrochemical stimulus rather than with a light excitation source, ECL displays improved signal-to-noise ratio compared to photoluminescence, with minimized effects due to light scattering and luminescence background. The most challenging breakthrough in the development of analytical electrochemiluminescence (ECL) applications was reported from Bard and co workers that presented for the first time the generation of ECL with a coreactant.[1] This finding opened the application of ECL to large literature and transformed ECL from an academic curiosity to a real application and industrial success. In this context, the only real used materials for the ECL analytical and commercial application are tripropylamine (TPrA) as sacrificial ”oxidative-reductant” coreactant and Ruthenium(II)-tris(2,2’-bipyridine) ([Ru(bpy)3]2+) as emitting species. In this case the mechanism for the ECL generation was proposed by Bard and still nowadays the only one accepted.[2],[3]

Here we show an additional, and very efficient, mechanism pathway for the generation of ECL by using TPrA as coreactant. Thanks to the combination between ECL and microscopy we experimentally prove the alternative mechanism with the standard [Ru(bpy)3]2+/TPrA system.[3],[4] These mechanistic findings allow us to propose alternative amines as coreactant enhancing the ECL signal of more than one order of magnitude.

The reported results, besides contributing to a better understanding of the mechanisms operating in the chemiluminescence generation, also pave the way for the development of very highly efficient ECL coreactants for ultrasensitive bioanalysis.[5]

[1] Miao W.; Choi J. P.; Bard A. J., J. Am. Chem. Soc.
2002, 124, 14478-14485

[2] Sentic M.; Milutinovic M.; Kanoufi F.; Manojlovic D.; Arbault S.; Sojic N., Chem. Sci.
2014, 5, 2568-2572

[3] Valenti G.; Scarabino S.; Goudeau B.; Lesch A.; Jović M.; Villani E.; Sentic M.; Rapino S.; Arbault S.; Paolucci F.; Sojic N., J. Am. Chem. Soc.
2017, 139, 16830-16837.

[4] a) Valenti G.; Zangheri M.; Sansaloni S. E.; Mirasoli M.; Penicaud A.; Roda A.; Paolucci F., Chem. Eur. J., 2015, 21, 12640–12645; b) Zanut A.; Fiorani A.; Rebeccani S.; Kesarkar S.; Valenti G., Anal. Bioanal. Chem., 2019, 411(19), 4375-4382.

[5] Zanut A. at al Nature Commun. 2020, 11, 2668

Figure 1
Amplification-Free Electrochemiluminescence Molecular Beacon-Based microRNA Sensing Using a Mobile Phone for Detection
Authors: Kerr Emily , Henderson Luke , Hayne David J , Farr Ryan , Dearnley Megan , Doeven Egan H , Alexander Richard , Guijt Rosanne M , Nai Yi Heng , Prieto-Simon Beatriz , Francis Paul S , Voelcker Nicolas
Published: July 2021

The burgeoning field of miRNA detection using electrochemiluminescence (ECL) has garnered a great deal of attention in recent times.1 ECL presents many advantages over alternative detection strategies as ECL analyses generally exhibit low-background signals, high sensitivity, are reproducible and scale-able.2 When combined with magnetic-beads for the immobilisation of biological recognition elements, ECL biosensors offer exceptional sensitivity owing to the ability to disperse the beads in large sample volumes to capture the biological target of interest via mixing then concentrate prior to analysis via magnetic extraction.3, 4

Herein, we present a novel biosensor for the sensitive detection of miRNA-21 comprising a molecular beacon ECL probe immobilised on magnetic beads. We obtained a limit of detection of 500 attomoles for miRNA-21 without enzymatic amplification or the addition of detection probes or intercalating labels, negating the need for lengthy and stringent washing procedures to reduce the background signal. Furthermore, we demonstrate the immense potential for point-of-care applications by developing a fully integrated miRNA detection platform. The platform comprises a portable potentiostat for ECL generation, mobile phone for ECL detection and a custom 3D-printed cell holder to readily interface a disposable screen-printed electrode with the potentiostat and mobile phone.

We applied our magnetic miRNA extraction technology to the detection of miRNA-21, a promising biomarker for the early diagnosis of chronic kidney disease, in human urine RNA extracts.5 Urine is an ideal sample matrix as it is non-invasive to obtain in large volumes, does not require a phlebotomist to acquire and miRNAs in urine are stable in exosomes. When combined with point-of-care miRNA extraction methods, the molecular beacon based ECL system we have developed presents a promising tool for point-of-care diagnosis and management of numerous diseases.

References

P. K. Kalambate, N. S. Gadhari, X. Li, Z. Rao, S. T. Navale, Y. Shen, V. R. Patil and Y. Huang, TrAC, Trends Anal. Chem., 2019, 115643.

Y. Cheng, L. Dong, J. Zhang, Y. Zhao and Z. Li, Analyst, 2018, 143, 1758-1774.

M. H. Shamsi, K. Choi, A. H. Ng, M. D. Chamberlain and A. R. Wheeler, Biosens. Bioelectron., 2016, 77, 845-852.

W. Liu, X. Zhou and D. Xing, Biosens. Bioelectron., 2014, 58, 388-394.

M. L. Alvarez, M. Khosroheidari, R. Kanchi Ravi and J. K. DiStefano, Kidney Int., 2012, 82, 1024-1032.
Effect of Nobel Metal Ions on the Synthesis of Metal Nanoclusters for Selective Detection of Various Heavy Metals
Authors: Nain Amit , Tseng Fan-Gang , Chang Huan Tsung
Published: July 2021

In this study, effect of noble metal ion (Au, Ag and Cu) on the synthesis of metal nanoclusters (MNCs) has been investigated. Through heating at 70ºC, TSA/BSA-Au, -Ag and -Cu NCs were separately prepared from Au3+, Ag+, and Cu2+in the presence of bovine serum albumin (BSA) and thiosalicylic acid (TSA). They exhibit photoluminescence (PL) at 700, 624 and 430 nm, with average life times of 1500, 100 and 11.71 ns, respectively, when excited at 350 nm. X–ray photoelectron spectroscopy (XPS) data support the presence of metal core (M0) and metal–thiolate shell (Mn–SRm), each in the TSA/BSA-MNCs. Spectroscopic measurements reveal the formation of Au32–SR, Ag9–SR and (Cu4–Cu13)–SR species separately in the TSA/BSA-Au, -Ag and -Cu NCs. Through PL quenching of the TSA/BSA-Au, -Ag and -Cu NCs, they have been used separately for quantitation of Hg2+, As3+and Cr6+ , with linear ranges of 10-400, 4-18, and 40-400 nM and limits of detection (LODs) of 0.25, 2.34 and 3.54 nM, respectively. The PL quenching is mainly due to aggregation of the MNCs through metallophilic or metal–thiol complexation. The stable TSA/BSA–Au, -Ag and -Cu NCs have been employed separately for the determination of the concentrations of Hg2+, As3+and Cr6+ions in the spiked sea water samples, showing advantages of simplicity, rapidity, high selectivity, and sensitivity.
Light-Addressable Potentiometric Aptasensor for Label-Free Detection of Marine Toxin
Authors: Tian Yu-lan , Zhu Ping , Chen Ya-ting , Du Li-ping , Chen Wei , Wu Chunsheng , Wang Ping
Published: July 2021

Okadaic acid (OA) is one of the most common marine toxins, which can cause human poisoning or even death. It is desirable and essential to develop novel approaches for OA detection in a convenient, practical and low-cost manner. In this study, a novel light-addressable potentiometric aptasensor was designed for label-free detection of OA. The aptamers specifically binding with OA were used as the sensing elements, light-addressable potentiometric sensor (LAPS) chip was used as the transducer, LAPS detection and imaging system was constructed for signal detection. The results showed that this biosensor had high sensitivity and specificity for the detection of OA. The research on this biosensor provides a novel approach for inexpensive, rapid, ultrasensitive, highly specific and label-free detection of OA as well as other marine biological toxins.

keywords: Biosensor; LAPS; Aptamer; OA
Fabrication of Plasmonic Nano-Aperture Platform for Singe-Molecule Detection and Self-Cooling Thermal Emission
Authors: Choi Seong Soo , Bae Byung Seong , Lee Yong MIn , Kim Hyun Tae , Choi Soo Bong
Published: July 2021

In this report, the optical emission characteristics from the nano-apertures on the Au nano-plasmonic platform will be reported. Regardless of the nano-aperture type of either circular type or nanoslit type, the spp-mediated optical emission characteristics dependent upon the sample thickness and aperture size are observed. However, the spp mediated optical characteristics are found to be increasing with decreasing the aperture size, and to be independent of the nano-aperture shape, which observation fits to Lord Raleigh’s diffraction theory of small particle with its size much smaller than the wavelength and Babinet principle. The fabricated nanometer slit arrays with its size of (~10 nm width and ~ 300 nm length) with its optical characterization are provided in Figure 1. The fabricated platform device can be utilized as various applications such as plasmonic single molecule sensors and plasmomic self- cooling device from its broad emission spectra from visible to infrared regime.

Figure 1
Fabricating SERS-Active Nanofibers Covered with Au Nanoparticles for SERS Optophysiology
Authors: Zhao Xingjuan , Wallace Gregory Q , Bazuin C. Geraldine , Masson Jean-Francois
Published: July 2021

Nanofibers as biosensors have attracted great attention due to its facile removal from the biosystem after a period of intra- or extracellular measurements and site-specific measurement among others. The application of nanofibers covered with Au nanoparticles as SERS sensor circumvents the aggregation and accumulation of Au nanoparticles in vitro or in vivo, in addition to the greater Raman enhancement of signal than on planar surface. We report here on a strategy using block copolymer brush-layer templating and ligand exchange for fabricating highly reproducible and stable SERS-active nanofibers with tip diameters down to 60 nm and covered with well-dispersed and uniformly distributed branched AuNPs, which have intrinsic hotspots favoring inherently high plasmonic sensitivity. In addition, AuNPs with tunable morphology and adjacent spacing on the nanofibers can be adjusted using an in situ growth technique, thereby enhanced SERS sensitivity was obtained due to the asymmetric structure and coupling between the adjacent AuNPs. Tunable AuNP morphologies and hence the optical characteristics of the AuNPs on the nanofibers can be easily controlled by choice of experimental parameters, particularly the growth time. Besides, finite difference time domain (FDTD) simulations were performed to gain more insight into the electric-field enhancement of AuNPs on the high-curvature substrates. Furthermore, SERS application of these nanosensors in pH sensing and Hg2+ detection is demonstrated here, offering appealing and promising candidates for real time monitoring of extra/intra-cellular species in vitro or in vivo. In addition to SERS sensing, these highly uniform nanosensors have other far-reaching implications, including medical diagnostics, therapeutics and so on.

Figure 1
Fabrication of Plasmonic Nano-Slit Pore Double Layer for Single Molecule Detection
Authors: Choi Seong Soo , Lee Yong MIn , Bae Byung Seong , Park Myoung Jin , Kim Kyoung Jin , Kim Hyun Tae , Choi Soo Bong
Published: July 2021

We fabricated the plasmonic nano-slit pore platforms for single molecule detection and other various applications. The nano-apertures on the Au/insulator/Au/SiN flat membrane, in addition to the 200 nm thick Au film on ~ 20 nm thick SiN membrane were fabricated using a focused ion beam drilling technique. The insulating materials of SiO2 or Al2O3 were deposited using an atomic layer epitaxy technique. The nanopores with a few nanometer size were fabricated under the proper control of drilling depth and pore opening. Optical characteristics were carried out dependent upon the pore opening width and sample thickness. The broad emission spectra from the (7x 7) slit pore array are obtained via spp-mediated emission on the ~200 nm thick Au/~ 20 nm thick SiN flat samples. A sharp strong infrared emission peak is also obtained due to Au nanoparticle. The fabricated Au double layer platform will be investigated for a single molecule sensor device and a possible radiative thermal energy transfer device.
Terahertz Chemical Microscope Imaging System for 2, 4, 6-Trinitrotoluene Detection
Authors: WANG Jin , Nagata Hiroki , Sakai Kenji , Tsukada Keiji , Kiwa Toshihiko
Published: July 2021

In this study, a terahertz chemical microscope (TCM) imaging system was developed for visualization and detection of 2, 4, 6-trinitrotoluene (TNT) explosive. The organic ligand 3-aminopropyltriethoxysilane (APTES) was one-step immobilized on the silicon dioxide (SiO2) film coated TCM sensing plate to interact with TNT molecule. The APTES modified surface was optimized and confirmed by using atomic force microscope. Electrical potential shift was occurred due to the formation of a charge-transfer complex (Meisenheimer complex) between electron-rich amino-silane APTES and electron-deficient TNT molecule on the sensing plate surface. By measuring the terahertz pulse’s amplitude caused by this electrical potential shift using the TCM imaging system, the chemical imaging and detection of TNT explosive were demonstrated.

Figure 1
Low-Frequency and High-Frequency Modulation of the Local Field Potential Spectrum of Genetically Engineered Rats Induced By Odor Stimuli
Authors: Zhu Ping , Tian Yu-lan , Liu Shu-ge , Chen Ya-ting , Chen Wei , Du Li-ping , Wu Chunsheng
Published: July 2021

The local field potential (LFP) oscillations of the olfactory bulb are regulated by odor stimulation, and the mechanism of this regulation supports the causal relationship between LFP oscillations and odor recognition. We tested the neuronal activity and LFP oscillation of the mitral/tufted cells in olfactory bulb of rats overexpressing the olfactory receptor OR3 under the stimulation of ligand odor. We found that compared with non-ligand odor, OR3 ligand odor stimulus changed the oscillating power of beta band and gamma band in a part of M/T cells, and affected the phase synchronization of spikes activity and LFP of M/T cells. These results indicate that the genetically engineered rats are more sensitive to odors, and the synchronization of spike activity and LFP oscillations may affect neural coding.

Key words: olfactory system; odor detection; genetic engineering; local field potential; neural oscillation
Aluminum-Ion Electrolytes with Weakly Coordinating Anions
Authors: Wen Xiaoyu , Guo Juchen
Published: July 2021

The conventional chloroaluminate ionic liquid electrolytes for rechargeable aluminum (Al) batteries are challenged by intrinsic limitations including corrosivity and poor chemical stability due to the active chloride content. Here, we report the first synthesis and characterizations of an Al “simple salt” electrolyte composed of aluminum hexafluorophosphate (Al(PF6)3) in dimethyl sulfoxide (DMSO). Al(PF6)3 salt was synthesized via the reaction between triethylaluminium (Et3Al) and ammonium hexafluorophosphate, and purified via recrystallization. The single crystal X-ray diffraction reveals that the Al3+ cation is solvated with six DMSO molecules (Al(DMSO)6(PF6)3) in the salt crystal structure. The 0.25 M Al(PF6)3 solution in DMSO demonstrates high ionic conductivity at approximately 1.3×10-2 S cm-1. With characterizations including nuclear magnetic resonance spectroscopy, scanning electron microscopy and X-ray photoelectron spectroscopy (XPS), we demonstrate the reversibility of Al deposition-stripping in the electrolyte, which can be improved by the addition of trace amount of Et3Al as the electrolyte additive. The side reaction involving the reductive decomposition of DMSO to form aluminum oxide during Al deposition is identified by a combination of XPS and gas chromatography/electron ionization-mass spectrometry. Another Al-ion electrolyte with weakly coordinating tetrakis(hexafluoroisopropyloxy) borate ((B[hfip]4)-) anion in DME was also synthesized and characterized. These Al-ion electrolytes with weakly coordinating anions exhibit distinct chemical and electrochemical properties comparing with chloroaluminate ionic liquid electrolytes. They create an opportunity to develop new Al electrolyte system.
Electrochemical Competitive Magneto-Immunoassay for Determination of Neurotoxin Domoic Acid
Authors: Weber Michael , Fanjul Pablo , Izquierdo-Bote Daniel , González-García María Begoña , Hernández-Santos David
Published: July 2021

Domoic acid is heterocyclic amino acid neurotoxin and the principal toxin associated with amnesic shellfish poisoning (ASP) produced by certain species of marine diatom. It can bio accumulated at high concentrations in the shellfish tissues when the toxic phytoplankton is high in concentration in the surrounding waters. Ingestion of domoic acid contaminated shellfish leads to ASP, which is characterized by both gastrointestinal and neurological symptoms, including severe headache, seizures, tremors, and either temporary or permanent memory loss.

Herein, the detection of domoic acid is carried out through an enzymatic immunoassay that uses magnetic beads as support of the immunoreaction and screen-printed electrodes as suitable detector of the enzymatic product. Thereby, the immunological reaction is performed in solution, where the domoic acid, antigen, domoic acid labeled with horseradish peroxidase are incubated with the rabbit IgG antibody against domoic acid. Subsequently, the antibody-antigen complex is captured by the anti-rabbit IgG modified magnetic beads. Then, the magnetic beads are deposited onto the electrode surface with the help of the magnet placed under the screen printed electrode. Finally, the analytical signal is obtained by amperometric detection of the product enzymatically generated from the mixture of H2O2and 3,3,5,5-tetramethylbenzidine (TMB).

The use of magnetic beads provides the capability to preconcentrate the sample and avoid the poisoning of the electrode surface through non specific absorptions.

The experimental conditions of the magneto-immunological assay has been optimized and a calibration curve has been obtained between 0-2 ng/mL domoic acid, being able to detect down to 100 pg/mL domoic acid.

Acknowledgements

This work has been carried out in the framework of FLAshMoB project. This project is funded by the MarTERA partners; Italian Ministry of Education, Universities and Research (MIUR), French National Research Agency (ANR) and Spanish Centre for the Development of Industrial Technology (CDTI) and co-funded by the European Union.