bluuebunny/crossref_metadata_2025 huggingface dataset:
Modulation of Excited State Dynamics in Semiconductor Electrodes with Electrical Bias
Authors: Samu Gergely F. , Balog Ádám , Scheidt Rebecca A. , Kamat Prashant V. , Janáky Csaba
Published: February 2020

Semiconducting materials are essential building blocks of the majority of devices in the 21st century. The ability of semiconductors to generate charge carriers under band gap irradiation makes them suitable for a myriad of applications (e.g., solar cells, photocatalysts, photodetectors). In recent years the emergence of organic-inorganic lead halide perovskites revitalized these research fields. As a result, the efficiency of derived solar cells reached 22.3% in less than 10 years. To unravel the reasons behind their outstanding performance, it is vital to understand their optoelectronic properties. Spectroelectrochemical methods are suitable to determine fundamental optoelectronic properties (band edge and trap state energies) and electrochemical bias induced chemical changes in these materials. However, to probe charge carrier dynamics in these materials, it is essential to utilize ultrashort laser techniques, as these fast processes fall into the femto- or picosecond timescale.

In my presentation the effect of applied bias on the charge carrier dynamics of semiconductor electrodes will be discussed. Ultrafast spectroelectrochemical experiments were carried out on FTO/TiO2/CsPbBr3 and ITO/CuI systems by coupling ultrafast transient absorption spectroscopy with electrochemical techniques.1 These two systems have practical relevance in perovskite based solar cells, and their excited state behavior under operating conditions was scrutinized. It was found that the excitonic features of both CsPbBr3 and CuI are responsive to the applied external bias, within their electrochemical stability window. The accumulation of electrons on the TiO2/CsPbBr3 or ITO/CuI interface have a pronounced effect on charge carrier lifetimes in these studied materials. The change in charge carrier lifetimes in both CsPbBr3 and CuI was completely reversible showing the dependence of excited state dynamics on the externally controlled charge carrier density. This validates the in situ electrochemical transient absorption measurement as a useful tool to probe the charge carrier injection process in different semiconductor systems.

Scheidt, R. A., Samu, G. F., Janáky, C. & Kamat, P. V. Modulation of Charge Recombination in CsPbBr3 Perovskite Films with Electrochemical Bias. J. Am. Chem. Soc.
140, 86–89 (2018).
Enhancement of Photocatalytic Hydrogen Generation of Ni Doped CdS Enabled By Improved Ultrafast Charge Transfer
Authors: Isimjan Tayirjan Taylor , Idriss Hicham
Published: February 2020

Ultrafast carrier dynamics of Cd0.992Ni0.008S nanoparticles with and without Pt have been investigated using femtosecond transient absorption spectroscopy (fs-TA) with broadband capabilities. A strong ground state bleaching (GSB) feature around 480 nm and a broad photo-induced absorption (PIA) feature around 600 nm were assigned for electron and hole signatures in Cd0.992Ni0.008S, respectively. In order to validate the inferences made from fs-TA studies, we have examined the photo-catalytic performance of Cd0.992Ni0.008S and Pt/Cd0.992Ni0.008 in the presence of a complex medium composed of acetic acid and benzyl alcohol. The results show that the Ni doping in Pt/CdS not only enhances the photocatalytic performance of the Pt/CdS but also improves the photo-stability by removing the photo-generated hole efficiently.

Figure 1
(Invited) Understanding Heterogeneous Functional Materials Via Scale-Bridging between Nano and Micro Transmission x-Ray Microscopy and Absorption Near Edge Structure
Authors: Zenyuk Iryna V.
Published: February 2020

Heterogeneous functional materials for energy-conversion and –storage, such as fuel cells, electrolyzers and batteries are hierarchical, porous, electroactive materials that rely on multi-scale imaging techniques for accurate morphological characterization. These materials are building blocks for the catalyst layers, gas diffusion layers and electrodes in fuel cells, porous transport layers (PTLs) in electrolyzers and porous electrodes within batteries. Functional materials electrochemical functionality can be assessed with various in-situ and operando techniques that probe chemical state during operation, such as x-ray absorption near edge structure (XANES). Synchrotron bright x-ray sources allow for nano-scale imaging combined with XANES, which state-of-the-art lab-scale systems are still lacking. Furthermore, these bright sources allow ultra-fast imaging on sub-second and micro-second temporal resolution. Optimization of temporal, spatial and chemical dimensions is critical to answer the morphological and chemical questions of interest [1]. Transmission x-ray microscopy (TXM) and its three-dimensional analog x-ray computed tomography (CT) allows 30 nm resolution with nano-CT set-up and 1 um resolution with micro-CT beamlines. The nano-CT beamlines have precise energy resolution to enable a combination of 3D imaging and XANES. The generated imaging data sizes exceed terabytes of space and requires modeling frameworks to interpret the findings. We have developed a scale-bridging algorithm to incorporate nano-scale findings into micro-scale using direct numerical simulations and coupling algorithms via effective properties and boundary conditions.

In this work we will present several examples of operando data collected on fuel cells, electrolyzers and batteries using nano and micro x-ray CT and in some instances with XANES or with sub-second radiography. Full-field x-ray imaging beamline 18-ID at National Synchrotron Light Source II has achieved 3 minutes nano-CT scan, what enables full 3D XANES scan within reasonable time-frame. Some of the questions that we attempt to answer include activity and water management of NiCu/KB electrocatalyst used in alkaline fuel cells as anode; electrocatalyst activity and its interface with the PTL within operating electrolyzers, and Li metal dendrite growth in solid polymer electrolyte batteries during cycling. Scale-bridging framework is applied to fuel cell electrodes to understand oxygen transport and reaction-diffusion processes for these multi-scale catalyst layers.

References:

V. Zenyuk, “Bridging X-ray computed tomography and computational modeling for electrochemical energy-conversion and –storage”, Current Opinion in Electrochemistry, Volume 13, 2019, Pages 78-85.
(Invited) Multi-Modal and Operando Synchrotron Investigation of Energy-Storage Materials
Authors: Chen-Wiegart Yu-chen Karen
Published: February 2020

Multi-modal and operando characterization at synchrotrons can provide unprecedented information for complex, heterogeneous materials system. A multi-modal approach combines multiple synchrotron techniques to gain complementary information. Novel coherent scattering techniques are now available to address dynamics on the order of sub-seconds and provide new possibilities in studying materials processing for energy storage materials. These capabilities are particularly powerful when used to study complex structures with morphological and chemical heterogeneity. This talk will address these applications in energy storage and conversion materials. It will discuss using a combination of X-ray diffraction, absorption spectroscopy and computational modeling to study the structural and chemical evolution of metal sulfide in Li-ion and Na-ion batteries. The development of novel time-resolved coherent scattering capabilities for operando studies of 3D printing processes of energy storage materials will also be discussed.
High-Performance Oxygen Electrodes for Low Temperature Solid Oxide Cells
Authors: Chart Yvonne Antonia , Lu Matthew Yunching , Barnett Scott A
Published: February 2020

Solid Oxide Cells (SOCs) present an efficient, environmentally friendly, and largely scalable method for converting fuel to electricity or generating fuels via electrolysis. It is generally believed that the commercial viability of SOCs can be improved by reducing the operating temperature, e.g., ≤ 650 °C. Since low temperature SOC performance is typically limited by the oxygen electrode, current research has focused on developing new oxygen electrode materials and architectures like Ba0.5Sr0.5Co0.8Fe0.2O3-δ, Sr0.5Sm0.5­CoO3-δ, and nanostructured electrodes with high surface areas in order to achieve low temperature performance. These materials, however, suffer from several degradation phenomena such as delamination, cation segregation, chemical reactivity, and coarsening. It was recently shown that PrOx infiltrated into a Gd-doped ceria scaffold provides very low polarization resistance values at low temperature.1 However, the long term stability is not known, nor is the mechanism for its good performance or its effect on other scaffold materials, either electronic conductors or mixed ionic and electronic conductors (MIECs).

Here we present results on PrOx infiltrated into Sr(Ti0.3Fe0.7-xCox)O3-δ (STFC) (0 < x < 0.15), STFC-GDC (Ce0.9Gd0.1O2-δ) composite, and La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) scaffolds. Figure 1 illustrates the performance enhancing effects of PrOx infiltrated into LSCF and STFC MIEC scaffolds at 550 °C. For example, it decreases the initial polarization resistance of STFC from 0.57 to 0.22 Ω·cm2. The initial resistance decrease for LSCF+PrOx was even greater, from 2.05 to 0.58 Ω·cm2. The performance improvement is seen in the low frequency response, which is attributed to the catalytic surface processes related the addition of PrOx. Similar performance improvements are seen at 650 °C. Furthermore, the resistance values of STFC+PrOx and LSCF+PrOx are reasonably stable over ~ 1000 h life tests at 550 °C. The LSCF+PrOx result is particularly interesting since the LSCF electrode degrades considerably. The composite STFC-GDC+PrOx electrodes generally provide reduced polarization resistance compared to STFC-PrOx.

References

Nicollet, C., Flura, A., Vibhu, V., Rougier, A., Bassat, J.-M. & Grenier, J.-C. An innovative efficient oxygen electrode for SOFC: Pr6O11 infiltrated into Gd-doped ceria backbone. Int. J. Hydrogen Energy 2–8 (2016). doi:10.1016/j.ijhydene.2016.04.024

Figure Caption

Figure 1 - Evolution of Nyquist and Bode plots during a life test at 550 °C for ~ 1000 hours of (a) La0.6Sr0.4Co0.2Fe0.8O3-δ with and without nano-infiltrated PrOx and (b) SrTi0.3Fe0.55Co0.15O3-δ with and without nano-infiltrated PrOx all supported on a Ce0.9Gd0.1O2-δ electrolyte.

Figure 1
(Invited) Recent Progress in PEFC Technology and Future Direction
Authors: Kamitaka Yuji , Shinohara Akihiro , Suzuki Takahisa , Yamada Haruhiko , Kodama Kensaku , Jinnouchi Ryosuke , Morimoto Yu
Published: February 2020

Since the inventions in 1980s of the basic structure, i.e. a layered structure of a perfluorosulfonic acid membrane and gas diffusion electrodes including Pt on carbon and an ionomer, significant advancement has been achieved and finally, commercial products are now in the market for automobile and stationary applications.

In this talk, key technologies established in this period were quickly reviewed and present status and issues were presented as well as on-going trends to address the issues.

A part of this study was financially supported by the New Energy and Industrial Technology Development Organization.
Semi-Automated Electrochemical Microfluidic Immunoarray for Cancer Diagnostics
Authors: DhanapalaMudiyanselage Lasangi , Jones Abby L , Rusling James F
Published: February 2020

Over-expression of Parathyroid hormone-related peptide (PTHrP) is recognized as the main causative agent of the paraneoplastic syndrome, humoral hypercalcemia of malignancy (HHM). PTHrP is known to be indicative of progression and metastasis of several human cancers. The established prognosis method of PTHrP, immunoradiometric assay (IRMA), is unable to determine the peptide levels prior to the advancement of hypercalcemia due to insufficient sensitivity. Prostate specific antigen (PSA) is a biomarker that has been extensively used as a diagnostic tool in prostate cancer. Unfortunately, PSA is limited in its’ inability to distinguish cancer from other prostate conditions such as Benign Prostatic Hyperplasia (BPH) or Prostatitis. These inaccuracies lead to unnecessary treatments including surgery on indolent cancer patients that adversely affect the patients’ quality of life. Therefore, there is strong appeal for the development of ultrasensitive, low cost multiplexed detection of appropriate biomarkers in clinically relevant ranges to assist the diagnosis and progression of cancers. Here we have employed a lab-developed microfluidic immunoarray for small samples, that features automation, miniaturisation, sensitivity adjustable to the sample characteristics, rapid analysis, and low reagent consumption for the detection of PTHrP and PSA in human cancer patient serum. The immunoarrays employ nanostructured sensors decorated with capture antibodies to perform a sandwich immunoassay using poly-horseradish peroxidase (poly-HRP) with about 80 HPRs per molecule that links to a secondary antibody bound to analytes on the sensor for high sensitivity detection. Incubation times were tailored to obtain limits of detection (LOD) in sub-fg mL-1 without a significant compromise in sensitivity leading to a simple, quick cancer diagnostics and personalized cancer therapy strategies. This may be able to transform the current methods of prostate cancer diagnosis. This system will be utilized to evaluate PTHrP peptides as aggressive prostate cancer biomarkers by analysis of human serum samples from patients.
Nonlinear Time Series Analysis of Nickel in Sulfuric Acid
Authors: Clark David Q. , Wipf David O
Published: February 2020

Nickel is one of the most important passive metals used in electrodeposition processes in the world. These processes alone consume several million metric tons of nickel yearly. Nickel is well known for its corrosion resistant properties. However, nickel does corrode in H2SO4 and can produce current or potential oscillations in potentiostatic or galvanostatic experiments.

Traditional electrochemical studies on Ni oscillating systems are performed by applying applied potential or current during the electrodissolution (corrosion) of single wire electrodes in highly concentrated solutions. External forcing, in which perturbations are applied to systems by an external source, have provided a better understanding of oscillating systems. However, little attention has been given to performing electrochemical studies on electrodeposited metals that produce oscillating systems in lower concentrations of acidic solutions (0.1 M – 1.0 M) and no attention has been given to the possibility for external forcing of these unique systems via concentration change and local heating at the electrode surface until now. The presented work examines the changes in frequency, magnitude, and shape of periodic oscillations and the change in kinetics from temperature changes due to electrical heating and external forcing by independently changing the proton concentration at a nickel electrode. This work improves the understanding of the relationship between periodic oscillation phenomena and the corrosion process of the nickel system in H2SO4.
Epitaxial Growth of Iron Tungstate Nanosheets on One-Dimensional Photoanodes for Efficient Solar Water Oxidation
Authors: Lin He , Yang Shihe
Published: February 2020

Type-II heterojunctions have been recognized as an effective structure to significantly improve the charge transport efficiency of photoelectrodes. Herein, a facile method was developed for in-situ epitaxial growth of Iron Tungstate (Fe2WO6) nanosheets on various one-dimensional nanowire arrays including Fe2O3 and WO3, generating the bespoke photoanodes. Photogenerated electron can be easily transported through the interface between Fe2WO6 and Fe2O3 (/WO3) because of lattice match and less Fermi-level pinning. The 2D Fe2WO6 nanosheets branching of 1D arrays in epitaxial fashion exhibited significantly enhanced solar water oxidation performance, which is clearly shown in improved light utilizations, enhanced charge separation, as well as decreased electrochemical impedance of the photoelectrode. This work advocates a new paradigm in interface design for optimizing the photoelectrochemical efficiency.
In-Situ Ultra-Low Frequency SERS Observation at Electrified Interfaces
Authors: Ikeda Katsuyoshi
Published: February 2020

Surface-selective spectroscopy is a powerful tool to study various interfacial phenomena such as electrochemical reactions at electrode/electrolyte interfaces. However, structural information on the solid and liquid phases next to the interface have been separately observed using different spectroscopic methods: e.g., X-ray spectroscopy for solid phases and vibrational spectroscopy for liquid phases. Recently, we have extended the detectable frequency range of surface enhanced Raman scattering (SERS) into the ultra-low frequency region down to 10 cm-1, which corresponds to THz region [1]. This enables us to observe not only molecular vibrations but also extramolecular vibrations and surface phonons of the metal lattice [2]. These information should provide deeper insight into catalytic and electrocatalytic reaction mechanisms. In this talk, we will demonstrate in-situ and simultaneous detection of vibrational information on both solid-electrode and liquid-electrolyte phases at the interface.

[1] M. Inagaki, K. Motobayashi, K. Ikeda, “Electrochemical THz-SERS Observation of Thiol Monolayers on Au(111) and (100) Using Nanoparticle-assisted Gap-Mode Plasmon Excitation” J. Phys. Chem. Lett., 8, 2017, pp. 4236-4240.

[2] M. Inagaki, K. Motobayashi, K. Ikeda, submitted.
Flexible Impedimetric Sensors for Detection of Pollutants
Authors: Stanciu Lia , Diaz Susana , Lin Li-Kai , Ulloa-Gomez Ana-Maria
Published: February 2020

A variety of sensors have been developed at the laboratory level within the past few decades. However, very few of these reached the market and are being used today.

We used roll-to-roll processing to develop field deployable flexible electrochemical sensors for the detection of environmental pollutants such as mercury and organophoshorous pesticides. The sensors are based on injket printed interdigitated gold electrodes, which were further functionalized for detection of organophosphorous pesticides and mercury, respectively. For the pesticide sensors, a mesh of zirconium oxide fibers was deposited via roll-to-roll on the electrodes, and the response to the target was quantified impedimetrically.

Mercury ions were detected upon the functionalization of the interdigitated electrodes with specific DNA aptamers, while the impedimetric transduction was maintained.

Sensors stability, selectivity and detection limits were measured for laboratory conditions and in real food and soil samples. The sensors show similar characteristics with the state of the art in the field, are field deployable and able to be manufactured in a consistent and repeatable fashion.
Effects of Porous Separators on Dendrite Growth in Lithium Batteries
Authors: Cannon Andrew , Ryan Emily
Published: February 2020

Dendrite growth on the surface of the anode in lithium batteries can diminish their energy storage capacity and increase safety concerns, i.e. risks of a short circuit. Dendrite growth consists of two stages, nucleation and growth. Favorable sites for the nucleation of dendrites are difficult to avoid and so suppressing dendrites after nucleation is a promising research direction. Previous work has suggested that the local mass transport in the electrolyte is closely related to the structure of dendrites. In this research, a mesoscale diffusion-reaction model is used to study the effects of various porous separator geometries and configurations on dendrite formation. The porous separators act to restrict the local mass transport near the anode surface, which effects dendrite structure and growth rates. The porous separator structures considered in this study highlight the importance of both porosity and tortuosity. These attributes are often simplified when reporting characteristics in experimental tests or ignored in other simulations. In this study, we directly observe the impact of separator characteristics on the local mass transport gradient through the separator and the subsequent dendrite growth. By taking into account the impact of both overall and local porosity and tortuosity on dendrite growth, battery design can be improved.
Role of Coprecipitation and Calcination of Precursors on Phase Homogeneity and Electrochemical Properties of Battery Active Materials
Authors: Dong Hongxu , Wang Anny , Koenig Gary
Published: February 2020

Coprecipitation is generally expected to produce particles with atomic level mixing between different cations, and thus has been extensively used to synthesize homogeneous and phase pure multi-component transition metal precursors that are converted to oxides for use as lithium-ion battery active materials. However, very few studies have attempted to quantitatively confirm the mixing level of ions by coprecipitation reactions, and neither have shown the superiority of local mixing for the homogeneity of final materials compared to alternative routes to producing battery active materials. In this talk, we will present experimental results from systematically comparing the phase purity and crystallinity of oxide powders that were either from a solution mixed multicomponent transition metal precursor via coprecipitation or from physically mixed single transition metal salts after calcination at the same conditions. A simple model was also applied to understand the diffusion limitations during the calcination process under various conditions. High voltage spinel LiMn1.5Ni0.5O4 was used as the target final oxide material composition and phase in this study, and electrochemical data will be provided to show the role that local mixing via coprecipitation plays in forming high crystallinity battery active materials with the desired phase.
Capacitive Deionization Systems for Water Desalination Applications: Role of the Electrosorption Resistance and Non-Electrostatic Binding in the Porous Electrodes
Authors: Salamat Yasamin , Hidrovo Carlos H.
Published: February 2020

The unprecedented global water scarcity and shortage of fresh water have drawn attention to an abundant yet overlooked water resource: Brackish ground water. Although the common desalination methods are energy intensive for low salinity water streams, Capacitive Deionization (CDI) offers a highly efficient and economical alternative for desalinating brackish water. In CDI, an electrically charged porous material is employed to remove ionic species from aqueous solutions. CDI includes different multi-scale transport phenomena and requires robust theories to accurately model its performance. In this work, we introduce a dynamic two-dimensional model which couples the diffusion and advection in the bulk solution with the diffusion and electrosorption in the porous material. The significance of this model lies in the incorporation of the transport theories with the adsorption/desorption resistances and non-constant chemical attraction forces in the micropores. A lab-scale CDI unit is employed to validate the proposed model at different transport time scales and electrochemical techniques are used to characterize these systems. Efficiency of the studied cases is also evaluated using the proposed inclusive figure-of-merits, where both numerical and experimental data present a trade-off between adsorption and energetic performance of the systems with low and high mass Péclet number. The results obtained here highlight the significant role of the rate limiting resistance for the ionic species transferring from macropores into the micropores in the porous electrode, especially at low initial concentrations.
On-Chip Optical Anodic Stripping Voltammetry with Closed-Cell Bipolar Electrode Arrays for Heavy Metals Detection in Water
Authors: Fahrenkrug Eli , Humphrey Nicholas , Miranda Jeronimo , Thomas Bradley
Published: February 2020

A dynamic understanding of metals in water requires an equally dynamic, sensitive, and ideally, deployable analytical process. Standard instrumental techniques are typically expensive, require technical expertise for operation, are time-consuming, and are inherently non-portable. While electrochemistry fits the bill for most criteria, it has long been limited by analysis speed and portability. We developed a new low-cost closed-cell bipolar electrochemical technique that couples conventional anodic stripping voltammetry with on-chip optical readout in an inherently parallelized fashion. This presentation will introduce our new sensing scheme which couples a new cathodic electrochemiluminescence (ECL) reaction at one pole of the bipolar electrode with an anodic stripping event of a heavy metal (i.e. Pb) at the opposite pole. When the chip is operated in a close-cell bipolar format, near 100% Faradaic efficiencies can be achieved. The influence of both the physical chip design as well as the electrolyte composition on the sensor functionality will be described. A rapid and economical fabrication protocol will be described which supplants typical cleanroom microfabrication tactics with simple programmable laser ablation on conductive glass substrates. Recent efforts towards replacing ECL readout with an all solid-state transduction mechanism will also be highlighted, with an emphasis on significantly increasing the analysis precision and chip reusability while achieving detection limits in the single part per billion range. Finally, sensor parallelizability will be discussed.
Planar and out of Plane Configuration Based Flexible Sensor of PVDF Polymer
Authors: Ganguly Ronit , Acharyya Amit , Ramadurai Ranjith
Published: February 2020

PVDF (Polyvinylidene fluoride) a piezo polymer has been a potential candidate for its functional properties and device applications like flexible sensors, energy harvesting and biomedical applications. [1] There are various methods to fabricate free standing PVDF thin films.[2] One of such is solution casting method. It is known from the literature that PVDF films synthesized from varying viscosities through solution casting method exhibits different behavioural pattern of ferroelectric polarization components.[3] The study indicated that films prepared from precursor viscosity of 2.9 Pa.s exhibits dominant out-of-Plane polarization whereas films prepared from precursor viscosity of 4.6 Pa.s exhibit dominant in-plane polarization

The orientation of these polarization components has an impact on the piezoelectric coefficient. [4] Piezoelectric coefficient is one of the important factor in deciding the efficiency and materials utilization in real time devices. The piezoelectric coefficient, d33 for the unpoled pure PVDF samples exhibiting dominant out-of-plane was found to be in the range of 0.4-4.24pm/v whereas the PFM scan shows the dominance of in-plane/planar domains indicates a significant value of d31.

In this work we have fabricated out-of-plane and planar electrode based sensors of PVDF and tested for vibration detection. Film for the planar sensor is fabricated from precursor viscosity of 4.6 Pa.s and out-of-plane sensor from precursor viscosity of 2.9 Pa.s. When the fabricated sensors were tested by finger taping, it is observed that planar configured sensor are more sensitive than out-of-plane sensor. In figure we could see the piezoresponse microscope images along with ferroelectric hysteresis loop which confirm the ferroelectric nature of PVDF films. Also response of the sensor for a given vibration caused due to finger tapping is shown from both the configuration.

REFERENCES

[1] A. Proto, B. Fida, I. Bernabucci, K. Vlach, V. Kasik, M. Penhaker, Wearable PVDF Transducer for Biomechanical Energy Harvesting and Gait Cycle Detection, IEEE EMBS Conference on Biomedical Engineering and Sciences (IECBES), Kuala Lumpur ,Malaysia, 2016, 62-66.

[2] P. Martins, A.C. Lopes, S. Lanceros-Mendez, Electroactive phases of poly(vinylidene fluoride):Determination, processing and applications, Prog. Polym. Sci. 39, (2014) 683 - 706.

[3] R. Ganguly, S. Bandyopadhyay, k. Mirilaya, V. Gunasekaran, S. Bhattacharya, A. Acharyya, R. Ramadurai, Tunable polarization components and electric field induced crystallization in polyvinylidenefluoride (PVDF); a piezopolymer, Polymer Crystallization ,(2018) . DOI:10.1002/pcr2.10027.

[4] S. K. Mahadeva, J. Berring, K. Walus, B. Stoeber, Effect of poling time and grid voltage on phase transition and piezoelectricity of poly(vinyledene ﬂuoride) thin ﬁlms using corona poling, J. Phys. D:Appl. Phys, 46, (2013) 285305

Figure 1
Ultra-Sensitive Electrochemical Determination of Rifampicin Using the TiO2nanoparticles Decorated Reduced Graphene Oxide Nanocomposite
Authors: Yenugu Veera Manohara Reddy , Švorc Ľubomír , Bathinapatla Sravani , Gajulapalle Madhavi
Published: February 2020

We report a facile one step hydrothermal method to synthesize TiO2 nanoparticles decorated by reduced graphene oxide (rGO) sheets. The morphology and chemical composition of the prepared TiO2/rGO nanocomposite were examined by using suitable characterization techniques. The TiO2/rGO nanocomposite was used to modify the glassy carbon electrode (GCE), which showed an effective electrochemical sensing platform for the detection of RIF, when compared to bare GCE. The differential pulse voltammetric studies, as prepared TiO2/rGO nanocomposite exhibited an extraordinary performance in quantifying the RIF. The fabricated sensor showed a low electrochemical detection limit of 0.03 µM over the linear dynamic range 0.01- 1 µM. The proposed electrochemical sensor was successfully employed for the determination of RIF in pharmaceuticals and biological fluids with good recoveries.
(Invited) Four Decades of Photoelectrochemistry and Semiconductor Electrochemistry: Some Reflections
Authors: Rajeshwar Krishnan
Published: February 2020

This retrospective talk will chart the progress made in the field of photoelectrochemistry and semiconductor electrochemistry and the challenges/opportunities that remain. The personalities that drove the field in the early years will be identified along with the key contributions they made to the field. The author’s own work will be placed in the context of these developments.
(Invited) Substrate-Directed Electrocrystallization As a Manufacturing Method for Nanowire Sensors
Authors: Mao Guangzhao , Kilani Mohamed , Yu Xuecheng
Published: February 2020

This talk will focus on substrate-mediated nucleation and crystal growth of organic charge-transfer salt crystals and its application towards scalable manufacturing of nanowire sensors. Nanowires are widely recognized as the next generation building block for ultrasensitive and ultrafast chemical detection. Despite the research progress very few nanowire sensors have reached the market due to their manufacturing complexity. We are exploring a simple, low-cost electrocrystallization method to deposit nanowires from a solution droplet at room temperature directly on electronic substrates. We observed a phenomenon of 1-D crystal growth on nucleation seeds of small sizes. While the 1-D nanostructures resemble those produced by vapor-liquid-solid (VLS) or solution-liquid-solid (SLS) methods, their growth mechanisms are completely different. In our case, the small nanoparticle seed size (or radius of curvature) is responsible for the small size and 1-D growth of the organic crystals. We now apply the seed-mediated mechanism for the electrocrystallization of charge-transfer salt nanowires as small as 7 nm in diameter. The organic-based charge-transfer salt crystals are an underutilized class of sensor materials compared to carbon nanotubes (CNTs), conducting polymers, and metal oxides. We are also prototyping a gas sensor for ammonia detection by nanowire electrocrystallization on electrode patterns. Our approach significantly deviates from the current competing technologies, which involve complex, multistep fabrication and surface modification procedures. We have made nanowire sensors using different charge-transfer materials including tetrathiafulvalene charge-transfer salts and tetracyanoplatinate salts. We improve control of the nanowire deposition by applied potential, reactant concentration, and surface pattern. These nanowire materials show partial selectivity towards ammonia, ethanol, and other volatile organic compounds. We show further improvement in selectivity by the construction of a sensor array and machine learning to extra sensor data from the impedance spectra of more than one type of sensors.
Electrochemical Sensors to Monitor Multi-Drug Resistant Organisms in the Gut Microbiome
Authors: Argun Avni , Rana Muhit , Weber Andrew , Manoukian Mourad , Koh Andrew , Toprak Erdal
Published: February 2020

Infections caused by multi-drug resistant organisms (MDROs) are responsible for over 2 million of hospitalization and 23,000 deaths annually in the United States, with direct financial impact of $20 billion a year. Microbiome dysbiosis (imbalance) is considered to be the main cause for MDRO colonization and the resulting infections. MDRO outbreaks need to be quickly detected and monitored for effective intervention to provide relief to the stressed patient community and healthcare facility. Unfortunately, current diagnostic methods for MDRO detection are slow and costly. Polymerase chain reaction (PCR) and enzyme immunoassay (EIA) techniques or the next generation sequencing (NGS) methods do not provide the low cost and rapid platform necessary for such MDRO pathology for a patient care facility. These methods often require several days to complete, use many reagents, and need skilled technicians in a resource intensive laboratory.

In this work, we report a rapid, accurate and cost-effective electrochemical sensor capable of MDRO detection down to 104 colony forming units (CFU)/g in mice and human stool samples. To achieve this, we utilize disposable screen printed electrodes (SPEs) modified with highly specific oligonucleotide probes capable of hybridizing (duplex formation) select target gene sequences associated with MDROs. In the presence of a redox mediator, the hybridized probe/target complex generates an electrochemical current signal that differs from a non-hybridized probe molecule. The signal is highly sensitive and selective of target gene sequences and can detect as little as 3.5 picomols of target DNA. Furthermore, the SPEs can be pre-functionalized, stored, and used when needed, reducing individual sample analysis time to less than an hour.

Several target sequences from two exemplary genes (AmpC and AcrB found in MDRO E. coli) have been identified and successfully detected in clinical stool samples with results comparable to the standard quantitative PCR method. Additional target genes associated with drug resistance (TEM-1, VanA, and SHV) have also been successfully detected in vitro and are ready to be tested in clinical samples. Our gut microbiome sensor is currently being developed for multiplexed operation to simultaneously detect up to eight MDROs genes, including the ones that are responsible for breaking down b-lactam containing antibiotics. This novel sensor platform will be an economical point-of-care device with little requirement of reagent handling or technical training.

Figure 1
(Invited) Electrochemical Preparation of Micro and Nano Structures and Systems in Silicon for (Bio)Sensing and Nano(Medicine) Applications
Authors: Barillaro Giuseppe
Published: February 2020

When dealing with biosensing and nanomedicine applications the length scale of targets may vary over more than 5 orders of magnitude moving from the molecular level (0.1-1 nm) up to the cell level (1-10 μm). A number of micro and nanostructuring technologies have been developed over the years to enable the preparation of both structures and systems with length scales suitable to match specific biological targets.

In this talk, electrochemical preparation of nano and micro structures and systems in silicon with length scales spanning over 5 order of magnitudes, able to target different applications both in (nano)medicine (e.g. sinusoid-like liver on a chip, nanopillars for cell transfection, 3D microincubators for tumor cell screening) and (bio)sensing (e.g. microneedles for transdermal biosensing, optical biosensors for point-of-care clinical diagnostics, chemitransitor sensors for environmental monitoring), is presented and discussed.

1. S.Mariani, V. Robbiano, L. M. Strambini, A. Debrassi, G. Egri, L. Dähne, G. Barillaro, Layer-by-layer biofunctionalization of nanostructured porous silicon for high-sensitivity and high-selectivity label-free affinity biosensing, Nature Communications, 9, 5256, 1-13 (2018)

2. B. Delalat, C. Cozzi, S. R. Ghaemi, G. Polito, F. E. Kriel, T. D. Michl, F. J. Harding, C. Priest, G. Barillaro, N. H. Voelcker, Microengineered Bioartificial Liver Chip for Drug Toxicity Screening, Advanced Functional Materials 1801825 (2018).

3. Robbiano, G. M. Paterno, A. A. La Mattina, S. G. Motti, G. Lanzani, F. Scotognella, G. Barillaro, Room-Temperature Low-Threshold Lasing From Monolithically Integrated Nanostructured Porous Silicon Hybrid Microcavities, ACS Nano12, 4536−4544 (2018).

4. J. Harding, S. Surdo, B. Delalat, C. Cozzi, R. Elnathan, S. Gronthos, N. H. Voelcker, G. Barillaro, Ordered Silicon Pillar Arrays Prepared by Electrochemical Micromachining: Substrates for High-Efficiency Cell Transfection, ACS Applied Materials and Interfaces, 8 (43), 29197-29202 (2016).

5. Mariani, L. M. Strambini, G. Barillaro, Femtomole Detection Of Proteins Using A Label-Free Nanostructured Porous Silicon Interferometer For Perspective Ultra-Sensitive Biosensing, ACS Analytical Chemistry, 88 (17), 8502-8509 (2016).

6. Mariani, L. Pino, L. M. Strambini, L. Tedeschi, G. Barillaro, 10000-Fold Improvement in Protein Detection Using Nanostructured Porous Silicon Interferometric Aptasensors, ACS Sensors, 1, 1471-1479(2016).

7. M. Sainato, L.M. Strambini, S. Rella, E. Mazzotta, G. Barillaro, Sub-Parts Per Million NO2 Chemi-Transistor Sensors Based on Composite Porous Silicon/Gold Nanostructures Prepared by Metal-Assisted Etching, ACS Applied Materials and Interfaces 7, 7136 (2015).

8. M. Strambini, A. Longo, S. Scarano, T. Prescimone, I. Palchetti, M. Minunni, D. Giannessi, G. Barillaro, Self-Powered Microneedle-Based Biosensors for Pain-Free High-Accuracy Measurement of Glycaemia in Interstitial Fluid, Biosensors and Bioelectronics,66, 162 (2015).
PDMS/Uhmwpe Dura Mater Substitute Laminated with Conductive Graphene for Intracranial Pressure Sensing
Authors: Zhang Qinghua , Li Runlai , Li Jin , Gao Ping
Published: February 2020

Dura mater, which is the outermost meninges under the skull, functions to protect the central nervous system. Brain tumor, subdural haematoma, trauma brain injuries and improper mending of dura mater may cause encephalocele, epilepsy, hydrocephalus (leakage of cerebrospinal fluid (CSF)) and infections. Consequently, these defects should be mended using dura replacements timely. Bio‐electronic grafts with high sensitivity, stretchability, multidirections and multifunctions are desired to address the issues in medicine. Here, we developed and fabricated soft, compliant, transparent and biocompatible electronic dura mater (e-dura) which matches the mechanical property and mimics the structure of natural dura mater, and can simultaneously act to monitor intracranial pressure change via piezo-resistivity sensing. The e-dura is a hierarchical structure consisting of hybridization of polydimethylsiloxane (PDMS) with biaxially stretched nanoporous ultrahigh molecular weight polyethylene (UHMWPE) membrane laminated with an electronically conductive chemical vapor grown mono layer graphene. It is fabricated by firstly laminating the UHMWPE membrane with a monolayer graphene followed by hybridization with the PDMS elastomer. Before hybridization with graphene covered UHMWPE membrane, the PDMS monomer and crosslinker were diluted inside hexane solvent to form a dilute solution mixture. The dilute solution mixture was then introduced onto the UHMWPE nanoporous membrane via spin coating. Strong interfacial bonding between PDMS and UHMWPE was achieved via the infiltration of dilute PDMS monomer solutions into the nanopores of UHMWPE membrane and subsequent nanoconfinement of PDMS polymer upon temperature induced crosslinking. The resulting e-dura exhibits high optical transparency, low friction coefficient, high piezoresistive gauge factor in excess of 1300 and tensile modulus and ductility mimicking human dura. Thus the new e-dura developed in this study shows strong potential in the application as e-dura for next-generation intracranial pressure sensing.
Layer-By-Layer Biofunctionalization As a Novel Route for High-Sensitivity and High-Specificity Label-Free Affinity Biosensing with Nanostructured Materials
Authors: Mariani Stefano , Robbiano Valentina , Strambini Lucanos , Debrassi Aline , Egri Gabriela , Daehne Lars , Barillaro Giuseppe
Published: February 2020

Nanostructured materials hold the promise to revolutionize the label-free biosensing of analytes at concentrations down to those required for clinical applications, beyond what microstructured materials did so far, by leveraging the deeper interaction between materials and analytes with comparable size. On the other hand, when the characteristic dimension of the materials gets down to the nanoscale, the biofunctionalization chemistry commonly used to promote the binding of bioreceptors and enable, in turn, the specific detection of target analytes becomes less effective.

Here, we propose an effective and robust route for the surface biofunctionalization of nanostructured materials based on the layer-by-layer electrostatic nano-assembling of oppositely-charged polyelectrolytes, which were engineered with bioreceptors covalently linked to the polymer chain. LbL biofunctionalization allows stability, density, and distribution of bioreceptors available on the transducer surface to be carefully controlled, thus solving most of the drawbacks of the common biofunctionalization chemistry on nanostructured materials.

The proof-of-concept demonstration of advantages of LbL biofunctionalization is given on nanostuctured porous silicon (PSi) interferometers, which are biofunctionalized for the affinity detection of streptavidin in raw saliva via LbL nano-assembling of a positively-charged poly(allylamine hydrochloride) (PAH) with a negatively-charged biotinylated poly(methacrylic acid) (b-PMAA). LbL-biofunctionalizion of PSi interferometers results to be very effective and highly robust, enabling high-sensitivity and high-specificity detection of streptavidin with a detection limit of 600 fM. This represents a 100000-fold improvement with respect to control PSi interferometers biofunctionalized using common silane-based chemistry and a 300-fold improvement with respect to best PSi label-free biosensors reported in the current literature, pushing PSi optical biosensors to performance comparable to those of best label-free plasmonic and photonic platforms.

[1] Layer-by-layer biofunctionalization of nanostructured porous silicon for high-sensitivity and high-selectivity label-free affinity biosensing, S Mariani, V Robbiano, LM Strambini, A Debrassi, G Egri, L Dähne, G. Barillaro, Nature Communications 9 (1), 5256 (2018)
Understanding How Structure Influences Electrochemical Behavior When ZnO Is Used to Suppress Aluminum Corrosion in Alkaline Electrolytes
Authors: Faegh Ehsan , Shrestha Sujan , Zhao Xinyi , Mustain William E.
Published: February 2020

The severe corrosion rate of aluminum (Al), coupled with hydrogen evolution (H2 gassing), is the major roadblock preventing the widespread deployment of Al as the anode material in primary and secondary alkaline batteries. One of the most successful approaches to reduce this corrosion has been the addition of ZnO to the alkaline KOH electrolyte, which results in the spontaneous electroless deposition of a protective metallic Zn film on the Al surface. However, the fundamental structural and electrochemical characterization of Zn on Al as well as the influence of ZnO/KOH composition need to be investigated.

This study aims to develop a novel fundamental understanding of the protection mechanism against Al corrosion when zincate (from dissolved ZnO) is added to KOH electrolytes. The effects of both ZnO concentration and KOH concentration are probed. Morphological studies of the spontaneous Zn film were realized using SEM, XRD, N2 adsorption and measurements of real time H2 gas evolution. These were coupled with discharge experiments to create a new structure-function understanding for ZnO protection of Al. It should be noted that electrolytes enabling protective Zn films with good adherence and density were found, and capacities near the Al theoretical capacity were achieved.
Ultrasmall NiMoO4 Nanoparticle Embedded on Carbon Matrix for High Performance Asymmetric Supercapacitors
Authors: Sharma Gyan Prakash , Pala Raj Ganesh , Sivakumar Sri
Published: February 2020

Psuedocapacitive materials are popular choice nowadays for electrochemical supercapacitor application due to their high capacity and energy density. However, the performance of psuedocapacitor is limited mainly due to 1) reduced surface area, 2) poor recyclability, and 3) low mass loading of active material. To overcome these challenges, we report a facile synthesis of ultrasmall NiMoO4 nanoparticle on active carbon with high specific capacity and long-term cycle stability. The ultrasmall NiMoO4-active carbon composite (NiMo@AC) sample displayed an excellent specific capacity of 665 C/g (1662.5 F/g or 184.7 mAh/g) at current density of 1 A/g. An asymmetric supercapacitor fabricated from NiMoO4@AC nanocomposite displayed a high specific capacity of 131.5 C/g (87.7 F/g or 36.5 mAh/g), energy density of 27.4 Wh/Kg and a power density of 184W/Kg at a current density of 1 A/g. This high capacity can be attributed to the maximized specific area of electroactive material. The fabricated supercapacitor retains ~92% of initial capacity after 4000 cycles. Active carbon not only provide better dispersion to nanoparticle, but also contribute towards the structural stability due to embedment of the particles into the carbon matrix. The results indicate that NiMo@AC nanocomposite is a potential candidate for electrochemical energy storage.

Figure 1
Corrosion Behaviour of Fecral Alloy for Anode Current Collector in Hot Liquid Silver
Authors: Lim Gyu-Seok , Cho Soo-Haeng , Kwon Suk-Cheol , Lee Jong-Hyeon
Published: February 2020

Soild Oxide Membranes (SOMs) process have been applied to metal production through metal oxide by direct electroreduction. In particular, the SOM process has advantages in overcoming the challenges of the low current efficiency and environmental pollution, which are the key obstacles to the electrochemical extractive metallurgy. The SOM anode used in the direct electroreduction was composed of the solid-oxide oxygen-ion-conducting membrane tube filled with the liquid medium for transporting oxygen ions generated from the electrochemical reduction reactions and the metal rod and/or wire used to conduct electric current. The transported oxygen ions from the cathode during the direct electroreduction reactions may create a chemically aggressive environment that can be corrosive for the metal. Therefore, there is a need to understand the hot corrosion behavior of FeCrAl alloy in hot liquid medium under a dissolved oxygen atmosphere. In this study, the hot corrosion behavior of FeCrAl alloy was investigated at 1150 °C in liquid silver as a liquid medium under an oxidizing atmosphere. The surface and cross-sectional morphologies and the characteristics and elemental distribution of the corroded layers were discussed.