bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Corona Phase Molecular Recognition (CoPhMoRe) to Enable New Nanosensor Interfaces
Authors: Strano Michael S
Published: February 2020

Our lab at MIT has been interested in how the 1D and 2D electronic structures of carbon nanotubes and graphene respectively can be utilized to advance new concepts in molecular detection.  We introduce CoPhMoRe or corona phase molecular recognition1 as a method of discovering synthetic antibodies, or nanotube-templated recognition sites from a heteropolymer library. We show that certain synthetic heteropolymers, once constrained onto a single-walled  carbon nanotube by chemical adsorption, also form a new corona phase that exhibits highly selective recognition for speciﬁc molecules. To prove the generality of this phenomenon, we report three examples of heteropolymers–nanotube recognition complexes for riboﬂavin, L-thyroxine  and estradiol.  The platform opens new opportunities to create synthetic recognition sites for molecular detection. We have also extended this molecular recognition technique to neurotransmitters, producing the first fluorescent sensor for dopamine.  Another area of advancement in biosensor development is the use of near infrared fluorescent carbon nanotube sensors for in-vivo detection2.  Here, we show that PEG-ligated d(AAAT)7 DNA wrapped SWNT are selective for nitric oxide, a vasodilator of blood vessels, and can be tail vein injected into mice and localized within the viable mouse liver.  We use an SJL mouse model to study liver inflammation in vivo using the spatially and spectrally resolved nIR signature of the localized SWNT sensors.

Zhang, JQ et. al. Molecular recognition using corona phase complexes made of synthetic polymers adsorbed on carbon nanotubes.  Nature Nanotechnology, 8, 12, 2013, 959-968

Iverson, NM, et. al. In vivo biosensing via tissue-localizable near-infrared-fluorescent single-walled carbon nanotubes.  Nature Nanotechnology, 8, 11, 2013, 873-880
Applications of Single Nanotube Imaging Spectroscopy in Live Cells
Authors: Jena Prakrit Vaibhav , Roxbury Daniel , Galassi Thomas Vito , Horoszko Christopher , Budhathoki-Uprety Januka , Heller Daniel
Published: February 2020

The intrinsic near-infrared photoluminescence from a single nanotube can be detected within a live cell via epifluorescence. As the emission spectrum of a nanotube is exquisitely modulated by the immediate microenvironment of the nanotube, information contained in the peak emission wavelength, intensity, and full width half maximum can reflect physicochemical properties of the microenvironment. We have developed methods for detecting metabolites by employing changes in carbon nanotube emission.  By spatially localizing a polymer-functionalized nanotube to a subcellular organelle, and by measuring the spectral response of the nanotube to its environment, we demonstrate the use of single nanotube spectroscopy to quantify specific metabolites in live cells.
Biomedical Applications of Diamond Nanoparticles
Authors: Mochalin Vadym N , Gogotsi Yury
Published: February 2020

Nanomaterials hold tremendous potential in addressing the two major issues faced by our society: providing energy and improving healthcare. Nanodiamond powder produced by detonation and readily available in commercial quantities for moderate price, is one of the most promising carbon nanomaterials for theranostics [1], [2]. Made of ~5 nm diamond particles with large accessible surface and tailorable surface chemistry, it has unique optical, mechanical and thermal properties, and is non-toxic. These properties have recently started to attract a lot of interest among researchers working on different biomedical applications [3]. For tissue engineering scaffolds, the non-toxic fluorescent nanodiamond introduced into biodegradable polymers provides increased strength, visual monitoring, and enhanced biomineralization [4]. In drug delivery, the rational surface modification of nanodiamond allows for enhanced adsorption and chemical binding of the drugs for sustained or triggered drug release. In the area of biomedical imaging and diagnostics, luminescent nanodiamond with NV centers, as well as chemically modified fluorescent nanodiamond, hold tremendous potential to replace toxic semiconductor quantum dots, thus bringing this exciting potential application one step closer to the clinics [5]. The purification, characterization and surface modification of nanodiamond for biomedical applications will be discussed in detail. Recent progress in development of nanodiamond-biodegradable polymer scaffolds for tissue engineering and bone surgery will be reviewed. Surface modifications of nanodiamond for drug delivery exploiting adsorption/desorption mechanisms will be discussed, with illustrations of the use of adsorption/desorption data for rational design of nanodiamond surface for optimal drug delivery platform. Finally, an overview of surface modification of nanodiamond for biomedical imaging will be presented.

[1]. V. N. Mochalin, O. Shenderova, D. Ho, Y. Gogotsi The Properties and Applications of Nanodiamonds (Review), Nature Nanotechnology, 7 (1), p.11-23 (2012)

[2]. V. N. Mochalin, A. Pentecost, X.-M. Li, I. Neitzel, M. Nelson, C. Wei, T. He, F. Guo, Y. Gogotsi Adsorption of Drugs on Nanodiamond: Toward Development of a Drug Delivery Platform, Molecular Pharmaceutics, 10 (10), p.3728-3735 (2013)

[3]. O. Shenderova, D. Gruen, ed. Detonation Nanodiamonds: Science and Applications (2nd Edition). CRC Press, 2014

[4]. Q. Zhang, V. N. Mochalin, I. Neitzel, K. Hazeli, J. Niu, A. Kontsos, J. G. Zhou, P. I. Lelkes, Y. Gogotsi Multifunctional Nanodiamond-PLLA Scaffolds for Bone Tissue Engineering: Enhanced Mechanical Strength and Biomineralization, Biomaterials, 33 (20), p.5067-5075 (2012)

[5]. G. Balasubramanian, A. Lazariev, S. R. Arumugam, et al. "Nitrogen-Vacancy color center in diamond-emerging nanoscale applications in bioimaging and biosensing." Current Opinion in Chemical Biology 20 (2014): 69-77
Thermodynamics of Quasi-Epitaxial Assembly of Fmn Around Various (n,m)-SWNTs
Authors: Papadimitrakopoulos Fotios , Sharifi Roholah , Samaraweera Milinda , Gascon Jose
Published: February 2020

The helical assembly of self-organized flavin mononucleotide (FMN) around single-walled carbon nanotubes (SWNTs) presents among the highest organization order in nanotube surfactants.  In this contribution, we quantitatively analyze and model for the first time the cooperative hydrogen bonding of adjacent flavin moieties as well as the concentric π–π interactions between the isoalloxazine moieties and the underlying graphene lattice as a function of (n,m)-SWNT chirality.  For this we use dissociation thermodynamics of FMN-wrapped (n,m)-SWNTs dispersed in both H2O and D2O as a function of FMN concentration.  The binding strength of these FMN assemblies has been assessed in terms of ΔH, ΔS and ΔG.  Atomistic molecular simulations were used to modeled these data and link their dependence in terms of nanotube diameter (dt
) the chiral angle (j).  The findings of this study provide the first quantitative proof of the quasi-epitaxial assembly of FMN around various (n,m)-SWNTs.[1]  This study demonstrates the architectural fidelity of FMN-wrapped SWNTs that closely emulates the dissociation mechanics of double-stranded DNA in its aqueous solutions.

[1] Sharifi, R.; Samaraweera, M.; Gascón, J. A.; Papadimitrakopoulos, F.; J. Am. Chem. Soc., 2014, 136(20), 7452–7463.
(Invited) Variance Spectroscopy: A New Bridge Between Ensemble and Single-Particle Studies
Authors: Streit Jason K. , Sanchez Stephen , Bachilo Sergei M. , Weisman R. Bruce
Published: February 2020

We have developed a new experimental technique that probes variations in the spectra from small regions of heterogeneous bulk samples resulting from statistical variations in composition. The method is demonstrated with suspensions of single-walled carbon nanotubes (SWCNTs) containing mixtures of distinct structural species. Using dilute SWCNT samples, focused excitation beams, multichannel detection, and quick data collection, we capture several thousand emission spectra sampling different spatial regions of the sample. The data are analyzed to find both the mean emission intensity and the variance of emission intensity as a function of wavelength. Those spectra are then combined to extract information that is not available from conventional experiments, including the abundances of different (n,m) species and their relative emission efficiencies. The variance data are further analyzed for correlations between intensity fluctuations at different wavelengths. This gives novel two-dimensional maps that reveal the spectra of homogeneous sub-populations within the heterogeneously broadened bulk spectra. The off-diagonal features in these maps show spatially correlated concentration variations for nanotubes of different types, which expose the earliest stages of SWCNT aggregation. Variance spectroscopy should prove a powerful new experimental tool that can extract sub-ensemble level detail from measurements on bulk nanoparticle samples.
(Invited) Photophysics of Localized Excitons in Carbon Nanotubes
Authors: Högele Alexander
Published: February 2020

Modification of carbon nanotube photophysical properties by charge-carrier doping, chemical side-wall functionalization or temperature-driven localization has emerged as an increasingly studied research topic over the past years. In this context, we will discuss signatures of cryogenic exciton localization in different carbon nanotube materials as well as experimental and theoretical aspects of Stark spectroscopy of individual carbon nanotubes in transverse electric field.
(Invited) Single-Walled Carbon Nanotube Spectroscopy in Complex Environments
Authors: Heller Daniel A
Published: February 2020

The real-time and spatially-resolved detection and identification of analytes present important goals for next-generation nanoscale sensors. Low-dimensional nanomaterials are improving the detection of molecular binding phenomena.  The resulting optical technologies may allow for the quantification of disease biomarkers and other bioanalytes.  The photoluminescence of single-walled carbon nanotubes may facilitate quantification of analytes within complex environments.   To build optical probes using these materials, we are developing new spectroscopic techniques to detect nanotube emission in biological samples and new polymers to control their optical properties.
(Invited) Inter-Nanotube Exciton Energy Transfer Modulation in Polymer-Encapsulated Single-Walled Carbon Nanotubes
Authors: Budhathoki-Uprety Januka , Jena Prakrit Vaibhav , Roxbury Daniel , Heller Daniel
Published: February 2020

The environmentally sensitive and intrinsically photostable near-infrared emission of single-walled carbon nanotubes (SWCNTs) shows promise for multiplexed, photostable, near-infrared (nIR) optical probes and molecular sensors. Use of nanotubes for such purposes requires the ability to simultaneously modulate nanotube fluorescence and functionally derivatize the nanotube surface via noncovalent encapsulation of the nanotubes. We report a systematic study on helical polymer cloaking of nanotubes and modulation of their optical properties. Individually-encapsulated nanotubes in these helical polymers, with specific functional pendant group substitutions, allowed the kinetic measurements of dynamic self-assembly and disassembly of nanotubes, and facilitated the first instance of inter-nanotube exciton energy transfer (INEET) in aqueous suspensions.
Synthesis and Characterization of Bis-Triruthenium Cluster Derivatives of an All Equatorial [60]Fullerene Tetramalonate
Authors: Chen Chia-Hsiang , Aghabali Amineh , Olmstead Marilyn M. , Balch Alan L. , Echegoyen Luis
Published: February 2020

Exohedral metal-C60 complexes exhibit unique physicochemical properties as a result of the metal cluster centers.1 This is important in the study of the reactivity and electrochemical properties of exohedral metal-C60 complexes, as it might result in the development of new nanomaterials.2

Kräutler et al. developed the orthogonal transposition method to synthesize C60 tetrakis-adducts with all addends located on the equatorial belt and the trans-1 positions available for further functionalizations.3 The presence of the tetrakis[di(ethoxycarbonyl)methano] groups should limit the number of possible bis-adduct regioisomers observed. We report that tetrakis[di(ethoxycarbonyl)-methano]-C60 reacts with triruthenium clusters to form the first anti-isomer C60-metal cluster complex : anti-[Ru3(CO)9]2{μ3-η2,η2,η2-C60[C(COOC2H5)2]4}. The two triruthenium groups are found in either an anti or a syn orientation, as determined by NMR. Only the anti form was characterized by X-ray crystallography, see structure below.

References

1. K. Lee, H. Song and J. T. Park, Acc. Chem. Res. 2003, 36, 78.

2.  Y.-J. Cho, T. K. Ahn, H. Song, K. S. Kim, C. Y. Lee, W. S. Seo, K. Lee,  S. K. Kim, D. Kim and J. T. Park, J. Am. Chem. Soc. 2005, 127, 2380.

3. R. Schwenninger, T. Müller and B. Kräutler, J. Am. Chem. Soc. 1997, 119, 9317.

Figure 1
(Invited) Graphene Plasmons: Properties and Applications
Authors: Avouris Phaedon
Published: February 2020

After a short introduction to the single particle excitations of graphene, I will focus on the collective excitations (plasmons) of this material [1,2]. The properties of graphene plasmons, will be compared with those of the surface plasmons of conventional metals concentrating mainly on localized plasmons in lithographically patterned nano- and micro-structures (quantum dots and ribbons) [2-7]. I will discuss their optical behavior in the infrared and THz regions of the spectrum, size effects, doping effects, effects of external magnetic fields, and the hybridization of the graphene plasmons with substrate and adsorbed overlayer optical phonons and the plasmon damping mechanisms [3,6,7,11]. 

Applications of graphene plasmons in passive THz optical elements, the enhancement of photocurrents in graphene infrared photodetectors [8-10], and the enhancement of infrared absorption spectra of molecules and deposited thin dielectric films [11-13] will be discussed.

[1] Grigorenko, A.N.; Polini, M; Novoselov, K.S., Nat. Photonics 6, 749 (2012).

[2] Low, T.; Avouris, Ph. ACS Nano 8, 1086 (2014).

[3] Yan, H.; et al. Nat. Nanotechnol. 7, 330 (2012).

[3] Yan, H.; et al. Nat. Photonics 7, 394 (2013).

[5] Freitag, M.; Low, T.; Xia, F.; Avouris, Ph. Nat. Photonics 7, 53 (2011).

[6] Yan, H. et al. Nano Lett. 14, 4581 (2014).

[7] Low, T. et al.; Phys. Rev. Lett. 112, 116801 (2014).

[8] Freitag, M; et al. ACS Nano (2014), DOI: 10.1021/nn502822z

[9] Freitag, M.; et al. Nat. Commun. 4, 1951 (2013).

[10] Avouris, Ph., Freitag, M., IEEE J. Topics in Quantum Electronics, 20, 6000112 (2014).

[11] Li, Y. et al.; Nano Lett. 14, 1573 (2014).

[12] Freitag, M; et al. ACS Nano 8, 8350 (2014).

[13] Wang, H.; et al. to be published.
(Invited) Spectroscopic Metrics for Determining Size and Thickness of Liquid Exfoliated Nanosheets in Dispersion
Authors: Backes Claudia , Coleman Jonathan
Published: February 2020

Over the last few years the study of 2-dimensional (2D) nanomaterials has become one of the most important areas of both materials science and nanotechnology. While this work originally focused on graphene, the palette of 2D materials currently under study includes transition metal dichalcogenides (TMDs) such as MoS2 and WSe2, layered transition metal oxides such as MoO3 and a host of other interesting structures such as GaS or phosphorene. Particularly useful is the diversity of 2D materials: depending on the combination of elements and their arrangement, they can be metals, semiconductors, insulators or superconductors.

Liquid-phase exfoliation has proven to be a powerful technique to obtain large quantities of exfoliated 2D materials in dispersion, ultimately making the materials processable. This method involves the sonication of layered crystals in certain solvents or solutions of surfactants or polymers. Even though being extremely versatile and useful, it has notable disadvantages such as the polydispersity of materials produced.

We have performed detailed spectroscopic and microscopic analysis on size-selected dispersions of exfoliated MoS2 nanosheets. This has led to the development of an in situ technique which allows nanosheet concentration, lateral size and thickness to be obtained simultaneously from an optical extinction/absorption spectrum. The combination of concentration-control, size-selection and measurement facilitates the preparation of dispersions with pre-determined properties. For example, monolayer-enriched dispersions can be produced, allowing the first measurement of direct-gap luminescence in liquid suspensions. In subsequent studies, we have developed similar metrics for other liquid-exfoliated nanosheets such as graphene, GaS and MoTe2. In the case of graphene, we propose simple metrics based on Raman spectra of size-selected graphene in restacked films to quantify size and thickness on the foundation of the G-band width or D/G ratio and changes in the 2D band shape.

C. Backes, ... J. N. Coleman, Using Edge and Confinement Effects for in situ Determination of Size and Thickness of Liquid-Exfoliated Nanosheets. Nat. Commun.
2014,
5, 4576.

Figure 1
Decorating of Graphene-Supported Palladium Nanoparticles with Nanostructured Tungsten Oxide Towards More Efficient Electrocatalytic Oxidation of Formic Acid
Authors: Ozimek Weronika , Rutkowska Iwona Agnieszka , Kulesza Pawel J
Published: February 2020

By depositing tungsten oxide nanostructures (nanorods) over palladium nanoparticles supported onto graphene nanosheets and dispersed onto glassy carbon substrate, enhancement of the overall electrocatalytic activity towards oxidation of formic acid in acid medium was observed. The effect was particularly evident from the increase of chronoamperometric currents at a fairly low potential of 0.04 V vs. RHE. It is reasonable to expect that introduction of graphene nanosheets to the system facilitates distribution of charge at the electrocatalytic interface.  Under such conditions, tungsten oxide nanorods seem to be partially and reversibly reduced not only to nonstoichiometric hydrogen tungsten(VI,V) oxide bronzes (HxWO3, 0<x<1) but also substoichiometric lower tungsten (VI,IV) oxides (WO3-y, 0<y<1). Mutual interactions between tungsten oxides or graphene and  Pd nanoparticles are likely to affect electrochemical characteristics of all components. The metal-oxide interactions, as well as high population of hydroxyl groups at the electrocatalytic interface (favoring oxidative removal of passivating CO adsorbates), are presumably responsible for the overall enhancement effect. In comparison to conventional electrodeposited microporous tungsten oxides, WO3 nanorods, despite their small dimensions, are more robust and less hydrated.  Electrochemical diagnostic experiments were supported with microscopic measurements aiming at monitoring morphology of catalytic surfaces with use of transmission (TEM) and scanning (SEM) electron microscopies. The palladium nanoparticles were of the sizes 10 to 20 nm, and the tungsten oxide nanorods had diameters of 50–70 nm while being approximately 5 μm long. Our ultimate goal is to minimize loading of noble metal nanoparticles while keeping the electrocatalytic activity at the high level.
A Novel Ambipolar Nonaqueous All-Organic Redox Flow Battery and Its State of Charge Detection By FTIR
Authors: Vemuri Rama Sesha , Hu Dehong , Duan Wentao , Wang Wei , Brushett Fikile R. , Wei Xiaoliang , Liu Jun
Published: February 2020

Nonaqueous redox flow batteries (NARFB) are considered as a promising next-generation grid scale energy storage solution because of their potential higher energy densities derived from the wide voltage window of nonaqueous electrolytes. Current research of NARFB is focused on redox materials development for various flow battery chemistries. Flow battery operation involves complexity associated with solvent-salt-redox species interactions, porous electrode, flow field, material crossover, etc., making it challenging to diagnose the real-time battery status. However, there is critical knowledge and technical gaps in this aspect. Especially, fast, robust and cost-effective diagnostic techniques are lacking to monitor state of charge (SOC) in a real-time manner to maintain safe and reliable long-term flow battery operations.

In this research, we report a novel all-organic redox flow battery based on an ambipolar redox material and demonstrate Fourier Transform infrared spectroscopy (FTIR) as an effective method of detecting the SOC of this flow battery.  The concentrations of the redox materials were derived from FTIR signal intensity by using the Beer-Lampert Law, which were used to calculate the SOC of the flow battery during the charge/discharge processes. The FTIR-based SOC determination agrees well with the electron spin resonance (ESR)-based measurements, demonstrating the feasibility of FTIR for online monitoring of the flow battery operation status. Also, the evolution of the FTIR spectra over repeated flow battery cycling offers a possible way to study the redox materials degradation and battery performance fading mechanism. This state of health (SOH) study can provide a direct prediction of cycle life of a NARFB.

Figure 1
Model-Based Investigation of Dual Energy Storage Selection for Advanced Start-Stop Vehicles
Authors: Zhang Zhenli , Jin Zhihong , Sisk Brian C
Published: February 2020

Dual energy storage solutions have seen significant interest as a means to combine high energy content and high power capability in a single energy storage architecture.  Such architectures, which can consist of batteries, capacitors, fuel cells, and other devices, have been used automotive and other applications, allowing the requirements of long-term energy support, high charging power, and high discharge power to be supplied by different devices.  Examples include 12V li-ion/lead-acid architectures for advanced start-stop, fuel-cell/li-ion high-voltage hybrids, Li-ion/capacitor combinations, and others.

A challenge in combining multiple energy storage devices is ensuring that they are matched in terms of operating characteristics, such as voltage, resistance, and other characteristics.  While power electronics (such as DC/DC convertors) are often used, another approach is to simply passively couple the devices.  Doing so requires that the energy and power of the devices should be compatible in terms of capacity, voltage and resistance to achieve the optimal system performance.  Typically, that means ensuring a high degree of voltage overlap between the two devices over their operational ranges, usually with a focus on open-circuit voltage. 

In this work, we consider an alternate approach for highly-dynamic power profiles, such as those found in automotive hybrid or grid-based power regulation.  Here, we utilize mismatch between both the open-circuit voltages and resistances of the two devices to steer current into a higher-voltage, lower-resistance device during a high-current pulse, and then toward a low-voltage, high-energy device during periods of low current. We use electrochemical and equivalent-circuit models to study the current split, voltage, and SOC response during a variety of charge and discharge pulses and some designed driving profiles in order to understand the trade-offs between these different selections.
High-Performance Aqueous Redox Flow Battery Using Non-Toxic Organic-Inorganic Electrolyte
Authors: Lin Kaixiang , Chen Qing , Marshak Michael P. , Gerhardt Michael R. , Eisenach Louise , Gordon Roy G. , Aziz Michael J.
Published: February 2020

The use of quinone/hydroquinone couples in aqueous redox flow batteries  is a promising pathway toward cost-effective stationary electrical energy storage.[1]-[3] Remaining challenges, such as membrane crossover of undesired species, molecule stability, and cost of containment for toxic and corrosive electrolytes, are the subject of active research. Here we report a novel quinone-based aqueous redox flow battery employing inexpensive, stable and non-toxic electrolyte materials.  The open circuit voltage is over 1.2 V, the peak galvanic power density exceeds 0.35 W/cm2, the membrane crossover rate is orders of magnitude lower than with inorganic redox couples, and capacity fade is less than 0.1% per cycle.

[1] B. Huskinson, M.P. Marshak, C. Suh, S. Er, M.R. Gerhardt, C.J. Galvin, X. Chen, A. Aspuru-Guzik, R.G. Gordon and M.J. Aziz, “A metal-free organic-inorganic aqueous flow battery”, Nature
505, 195 (2014), http://dx.doi.org/10.1038/nature12909

[2] B. Huskinson, M.P. Marshak, M.R. Gerhardt and M.J. Aziz, “Cycling of a quinone-bromide flow battery for large-scale electrochemical energy storage”, ECS Trans.
61, 27 (2014)

[3]  B. Yang, L. Hoober-Burkhardt, F. Wang, G.K. Surya Prakash, and S.R. Narayanan, J. Electrochem. Soc.
161, A1371 (2014).
Neutron Radiography Applied to All-Vanadium Redox Flow Batteries for Side Reaction Detection
Authors: Clement Jason T. , Aaron Douglas , Hussey Daniel S , Jacobson David L , Mench Matthew M.
Published: February 2020

Redox flow batteries are a technology of interest due to their potential for large-scale energy storage [1]. Recent progress has led to improvements in materials, performance, and stability; however much improvement is still possible. In order to make further progress, these systems must be understood at a more fundamental level. In situ diagnostic techniques provide deeper insight into the underlying mechanisms governing their operation and limitations. Such tools have proven useful in enhancing understanding of other electrochemical cells. One diagnostic tool that has been implemented for fuel cells is neutron radiography [e.g. 2,3].

Neutron imaging of fuel cells involves the detection of liquid water in a gas-phase cell. Since the neutron attenuation coefficient of liquid is significantly larger than that of gas phase, the identification of liquid water droplets in a gas-phase cell is straightforward. When applied to a redox flow battery however, reactants are in liquid phase, so the implementation is the exact inverse: gas-phase products generated within the cell will be detected by greatly reduced neutron attenuation.

For an all vanadium redox flow battery, undesirable side reactions between the liquid electrolyte and porous carbon electrodes or flow field plates can cause gas evolution. Currently, no published studies have attempted to experimentally determine conditions under which these side reactions begin to generate gas within an operating cell. This work  address the implementation of neutron imaging as an in situ diagnostic technique to identify unfavorable operating conditions resulting in side reactions in vanadium redox flow battery systems. Figure 1 demonstrates the viability of this technique by illustrating that gas bubbles, identified by lighter colors, have been generated and detected within an all vanadium redox flow battery. Results from experiments at the National Institute of Standards and Technology Center for Neutron Research will be presented which show the bubble volume and onset of side reaction as a function of electrode materials and operating voltage.

1.  A. Z. Weber, M. M. Mench, J. P. Meyers, P. N. Ross, J. T. Gostick and Q. Liu, Journal of Applied Electrochemistry, 41, 1137 (2011).

2.  D. S. Hussey, D. L. Jacobson, M. Arif, K. J. Coakley, and D. F. Vecchia, Journal of Fuel Cell Science and Technology, 7, 021024 (2010).

3.  A. Turhan, K. Heller, J. S. Brenizer, and M. M. Mench, Journal of Power Sources, 160, 1195–1203 (2006).

Figure 1
Comprehensive Impedance Analysis of Carbon Electrode Materials in Vanadium Redox Flow Batteries
Authors: Pezeshki Alan , Aaron Douglas , Tang Zhijiang , Zawodzinski Thomas A. , Mench Matthew M.
Published: February 2020

Vanadium redox flow battery (VRFB) electrodes have been the subject of numerous studies, as they play a key role determining kinetic and mass transport losses within an operational battery1. Many studies have investigated modification of the electrodes through chemical and thermal treatments. These studies are typically confined to one type of electrode material. Enhanced performance is generally attributed to improved electrode kinetics or enhanced wettability.

Quantitative analysis of kinetic, ohmic, and mass transport losses is possible with electrochemical impedance spectroscopy (EIS), as Sun and coworkers have recently shown2. With this technique, the effects of electrode treatments on kinetics and mass transport can be resolved. In this work, a method by which to obtain noise-free low-frequency impedance data at flow rates much higher than the 1.5 mL min-1 by Sun and coworkers will be demonstrated. Fig. 1 shows the impedance-resolved losses of the negative electrode at a flow rate of 30 mL min-1.

The kinetics and mass transport overvoltages in carbon paper and carbon felt electrodes typically used in VRFBs will also be shown. Furthermore, the effects of chemical modification on both carbon paper and carbon felt will be shown; specifically resolving the effects of the treatments on both electrode kinetics and mass transport processes. A comparison of the ways in which specific treatments affect paper vs. felt will be discussed.

References

1.   A.Z. Weber, M.M. Mench, J.P. Meyers, P.N. Ross, J.T. Gostick, Q. Liu, J. Appl. Electrochem., 41, 1137, (2011).

2.   C.-N. Sun, F.M. Delnick, D.S. Aaron, A.B. Papandrew, M.M. Mench, T.A. Zawodzinski, J. Electrochem. Soc., 161, A981, (2014).

Figure 1.Impedance resolved losses on negative electrode in VRFB.

Figure 1
Engineering Chemical Functionality in Graphene
Authors: Hernandez Sandra Catalina , Sheehan Paul , Tsoi Stanislav , Dev Pratibha , Robinson Jeremy , Junkermeier Chad , Whitener Keith , Lee Woo , Reinecke Thomas , Walton Scott
Published: February 2020

Graphene has attracted enormous attention due to its unique properties.  Equally important is the ability to further tailor these properties through modification of select attributes such as surface chemistry, number of layers, sheet width, and edge structures.  Manipulating the surface chemistry of graphene is important since the chemical composition strongly impacts the electronic properties as well as chemical reactivity both globally and locally. Precise control of the surface chemistry of graphene can also allow for subsequent surface procedures focused on band gap engineering, device fabrication and sensor applications. Given the strong impact of adsorbates, global chemical modification provides opportunities towards greater control over the properties of graphene films.  Control over the spatial distribution of these groups provides an even greater functionality in that the local graphene reactivity can be manipulated, opening up a wealth of opportunities in biosensing, plasmonics, catalysis, smart surfaces, and heterojunction devices. 

This work demonstrates the ability to manipulate the chemistry of graphene while regulating the spatial distribution of various functional groups on the surface. Spatial control over structural and chemical changes is characterized through micro (m-Raman and high-resolution x-ray photoelectron spectroscopy (XPS) mapping and electrical measurements are used to determine how local changes in chemistry influence the electronic properties.  Lastly, we show that the resulting chemical moieties can be used to manipulate the local surface reactivity of graphene, enabling programmable, site-specific electrochemical deposition. These findings demonstrate the ability to tailor the locality of the surface chemistry on graphene surfaces opening up a wide range of reactivity studies and synthesis capabilities, such as programmable material deposition.
Intelligent Self-Healing Coatings: Investigating the Role of Self-Healing Kinetics at the Delaminating Interface
Authors: Rohwerder Michael
Published: February 2020

The ultimate aim in the development of novel self-healing coating systems is to heal larger defects inflected into the coating reaching down to the metal, such as deep scratches. For this great amounts of self-healing agents have to be transported from the coating system to the defect site. This is a considerable challenge, especially since the self-healing agents to be stored in the coating system should safely stay inside it as long as they are not needed and they should still be available and active even after years of exposure. This requires reliable storage and very case-selective release mechanisms. At the same time, once the agents are released they should reach the defect site as fast as possible and in sufficient amounts. In many self-healing concepts found in the literature this is achieved by release through the coating surface. The transport to the defect site then occurs through the electrolyte. However, in most cases the self-healing coating will be covered by other coatings, such as e.g. for providing color or scratch resistance. Then the transport has to occur laterally. The best option for this is transport along the delaminating interface, as was recently shown for the release of inhibitors from conducting polymer based capsules incorporated in a PVB matrix [1, 2]. However, for really self-healing coating systems the transport of the active agents to the defect site will be impeded, if the delamination is stopped too early by a too fast self-healing at the interface before the defect site is healed [3]. First results of a more in-depth study of this problem will be shown. An important issue is to assess the degree of self-healing at the buried interface. For this a novel approach for studying the degree of interfacial degradation will be presented.

References

[1]A. Vimalanandan, L.P. Lv, T.H. Tran, K. Landfester, D. Crespy, M. Rohwerder

Redox-Responsive Self-Healing for Corrosion Protection

Advanced Materials 25(48)  (2013) 6980-6984

[2]L.P. Lv, Y. Zhao, N. Vilbrandt, M. Gallei, A. Vimalanandan, M. Rohwerder, K. Landfester, D. Crespy,

Redox Responsive Release of Hydrophobic Self-Healing Agents from Polyaniline Capsules

J. Am. Chem. Soc. 135 (2013) 14198-14205

[3]T.H. Tran, A. Vimalanandan, G.Genchev, J. Fickert, K. Landfester, D.Crespy, and M. Rohwerder Regenerative Nano-Hybrid Coating Tailored for Autonomous Corrosion Protection

Advanced Materials, accepted
High-Resolution Microscopy of Substrate/Coating Interfacial Regions of a Non-Chromate Organic Coating System on AA2024-T3 after Blister Formation
Authors: Holguin Kerrie , Scheltens Frank , Frankel Gerald
Published: February 2020

The corrosion of a coated metal system was investigated through the application of novel sample preparation and high-resolution microscopy techniques. An AA 2024-T3 substrate with a trivalent Cr process (TCP) conversion coating, a Pr-based primer, no topcoat and a machine-engraved scribe was tested. Preliminary electrochemical impedance spectroscopy experiments were completed to determine water uptake properties of the coating system. Samples were exposed in ASTM B117 neutral salt-spray until there was a visible blister under the coating, which took 13 days. Thin foil samples of the substrate/coating interface were prepared from exposed locations: (1) inside the scribe, (2) at the end of the blister, (3) near the end of the blister and (4) away from the blister. In addition, a thin foil sample was prepared from (5) an unexposed sample away from the scribe of the same sample type. High-resolution imaging and chemical analysis were performed on each thin foil, which seems to be the first time for such analysis under a coating. There were no detectable inhibitors (Pr or Cr) in the scribe. Mg was enriched on the substrate surface and in the TCP region of exposed and unexposed samples, likely an artifact of the coating preparation process. Additionally, chloride was found deeper in the primer and TCP regions at locations closer to the blister. Finally, there was no detectable corrosion under an intact coating after exposure. However, the caveat for all of this work is that each thin foil represented an extremely localized interfacial region.
Electrical Resistance-Emission Spectroscopy for Determining the Electrochemical Behavior of Anodized Aluminum in Aqueous Solutions
Authors: Habib Khaled
Published: February 2020

Holographic interferometry was utilized for the first time to determine the rate change of the electrical resistance of aluminum samples during the initial processes of anodization of the samples in aqueous solution without any physical contact. In fact, because the electrical resistance values in this investigation were obtained by holographic interferometry, electromagnetic method rather than electronic method, the abrupt rate change of the electrical resistance was called the electrical resistance –emission spectroscopy. The anodization process of the aluminum samples was carried out by the electrochemical impedance spectroscopy (EIS) test in different sulfuric acid concentrations (1.0–2.5% H2SO4) at room temperature. In the meantime, the real time holographic interferometry was used to determine the difference in the electrical resistance of two subsequent values, dR, as a function of the elapsed time of the EIS test for the aluminum samples in 1. 0, 1.5, 2.0 and 2.5% H2SO4 solutions. The electrical resistance–emission spectra of the present investigation represent a detailed picture of not only the rate change of the electrical resistance throughout the anodization processes but also the spectra represent the rate change of the growth of the oxide films on the aluminum samples in different solutions. Consequently, holographic interferometry is found to be very useful for surface finish industries, especially for monitoring the early stage of anodization processes of metals, in which the rate change of electrical resistance of the aluminum samples can be determined in situ.

Keywords: holographic interferometry; electrochemical impedance spectroscopy (EIS); anodization process; oxide film thickness; sulfuric acid; aluminum.
The Effects of Hydrophobic Coatings on an Insulative Skirt Layer to Decouple Galvanic Corrosion Between Mechanically-Coupled Aluminum Alloy and Carbon-Fiber Reinforced Polymer-Matrix Composites
Authors: Srinivasan Raghu , Hihara Lloyd H. , Nelson Jeffrey
Published: February 2020

Lightweight metals such as aluminum (Al) are being frequently coupled to polymer-matrix composites (PMCs) to reduce weight and improve performance in a multitude of applications in the defense, aerospace, automotive and civil-infrastructure industries. The intimate contact of carbon-fiber reinforced (CFR) PMCs with Al alloys can result in galvanic corrosion of the Al alloys. The electrically conductive carbon fibers in the CFR PMCs serve as cathodes and induce galvanic corrosion of the Al.

The galvanic corrosion between 6061-T6 Al and CFR PMC can be effectively attenuated by decoupling Al from CFR PMC using an insulating skirt layer. The deposition of salts on the insulative skirt, however, can create a continuous ionically-conductive electrolyte film that can bridge the CFR PMC and Al, thus reducing the effectiveness of the skirt.  The utilization of hydrophobic coatings on the skirt can help to attenuate galvanic corrosion by breaking up the continuous electrolyte film.

In this study, the effect of hydrophobic coatings on insulative skirt materials was investigated to attenuate galvanic corrosion between mechanically coupled 6061-T6 Al and CFR PMC.  Experiments were conducted in accelerated laboratory and outdoor conditions. The galvanic corrosion rates were monitored for coatings of different degrees of hydrophobicity, various skirt lengths, and exposure conditions and.

Initially, the galvanic corrosion rates for couples with different insulating-skirt lengths coated with a silane-based ceramer (i.e., Siloxel) were monitored in a humidity chamber at 30o C and 90% RH over a period of up to 3 days using the zero resistance ammeter (ZRA) technique. The couples were sprayed with salt solutions of different concentrations.  Results from this accelerated humidity ZRA experiment showed that a skirt length of only 0.5 inch was very effective in attenuating galvanic corrosion.  To study the effectiveness of different coatings, specimens were fabricated with a 0.5-inch long skirt and coated with either Siloxel, epoxy, polyurethane or latex. The resulting galvanic corrosion rates were then compared.

The two best coatings in attenuating galvanic corrosion (i.e., Siloxel and polyurethane) were selected for outdoor exposure. CFR PMC/Al galvanic couples with 0.5 inch insulating skirts (with either the Siloxel or polyurethane coatings, or no coatings) were exposed at rain forest (Manoa) and severe marine (MCBH) environments for 2 months. The CFR PMC/Al galvanic specimens at the severe marine site were exposed in two conditions: sheltered and unsheltered. The sheltered specimens were subjected to significant salt build up; whereas, the unsheltered specimens were subjected to cleansing effects of rain. The effect the salt deposition characteristics on galvanic corrosion between the sheltered and the unsheltered conditions was studied.
RF Sputtering Thermal Barrier Coating for Enhance Corrosion Efficiency of Aero-Engines Components
Authors: Achem Calahorra Jamnie Yazmin , Esparza Ponce Hilda Esperanza , Miramontes Jose Angel Cabral , Calderón Facundo Almeraya , Tiburcio Citlalli Gaona
Published: February 2020

Nickel base superalloys have been widely used for manufacturing key structural materials for aircraft engine blades. These alloys are developed to withstand the most deleterious degradation mechanisms as creep damage, fatigue, loss of thermal stability and environmental attacks as oxidation and hot corrosion during service. The damages can compromise the structural integrity of the aircraft and in the next generation of advanced engines they will require even higher gas temperature. Consequently, much work has been done in order to develop protective approaches that will increase component lifetimes and meet the development of advanced gas turbine engines. One of such is the used of thermal barrier coatings (TBCs). Thus the aim of the present investigation is to study the electrochemical behavior of YSZ coatings deposited by physical vapor deposition (PVD) on an aeronautical nickel based superalloy to improve the oxidation resistance. The electrochemical techniques conducted on Incoloy 800HT substrates, show that the corrosion velocity decreased with the YSZ coating system.
(Invited) Inhomogeneity of Barrier Layer Inducing Irregularity of Porous Anodic Oxide Film on Aluminum
Authors: Ono Sachiko , Asoh Hidetaka
Published: February 2020

Porous anodic oxide films formed on various metals, especially anodic alumina, have attracted huge attention as a starting material in the fabrication of nano-devices because of the high controllability of porous structures in nanometer scale such as pore size, pore interval, as well as pore depth by changing electrolysis condition in addition to their high regularity of pore arrangement. In recent years, mechanism of self-ordering of anodic alumina films has been intensely studied. We proposed anodizing under high electric field strength as a key factor for self-ordering of pore arrangement (1). However, only a few reports are found on the mechanism of irregularity or defects formation of porous anodic oxide films. For example, an regular deposition of metals into all anodic pores are often difficult because of irregularity of the barrier layer. In the case of anodic films formed on aluminum in chromic acid solution, for example, sever pore blanching appears especially at the higher voltage. Anodic alumina films formed in phosphoric acid and Ematal bath also indicates numerous pore branching and caved pores in the cell wall (2, 3) where anodizing conditions such as high formation voltage and relatively low dissolution ability of electrolytes to anodic oxides are used. These irregularities were caused by defects/holes induced by electric breakdown between pore bottom and protrusion at triple points of cell boundary. Impurity elements in metals and alloys also bring defects and irregularity into porous structures. Furthermore, anodic films formed at some specific condition, especially on titanium, yielded tubular structure having interspaces at cell boundaries. All of these irregularities should be created only at the barrier layer grown under the anodic field by specific reactions other than stable anodic oxide growth. This inhomogeneity of barrier layer such as unevenness of the thickness and voids that induce irregularity in porous oxide seems to be playing an important role at an application for industry both in a positive and negative way. In this paper, we report the specific futures of irregularity appeared in porous anodic oxides films formed on aluminum and evaluated to get unified formation mechanism of such imperfections to be induced in the oxides grown on various substrates.

 [1] S. Ono, M. Saito, M. Ishiguro and H. Asoh, J.Electrochem. Soc., 151, B473 (2004).

[2] S. Ono, H.Ichinose and N. Masuko, J.Electrochem.Soc.,
138, 3705 (1991)

[3] S. Ono and N. Masuko, J. Jpn Inst. Light Metal,
43, 453 (1993).
Electrochemical and Thermal Contributions to Ultra-Deep AAO Growth: Aspect Ratio >104
Authors: Solomon Mitchell L , Schwartz Nicholas R , Cox Philip , Hill Justin J
Published: February 2020

Self-ordered anodic aluminum oxide (AAO) nanopores is the focus of intense research for many diverse fields including photocatalysts, electrochemical energy storage, thermoelectrics, and optics.  Furthermore, the self-ordering of densely packed pores serves as an ideal template for 1-D nanostructure fabrication. Currently, hard anodization has achieved the highest growth rates (50 – 100 μm h-1) to >1000 aspect ratio1, but no further research has been presented on extended depth regimes. Technical and economic success of many of these technologies, is dependent on fast fabrication of ultra-high aspect ratio (>104) AAO arrays. We present here the high-speed growth of AAO pores with ultra-high aspect ratios achieved by balancing the thermal and electrochemical physics of pore ordering during initiation and extended steady-state growth rate.

Effective management of reaction and joule heating is paramount to achieving self-ordering and preventing thermal failure of AAO during pore initiation. Traditionally, slow ramp rate (1 v/s), low concentration (~0.05M), and low electrolyte temperature (~0°C) conditions have been used to prevent initial thermal failure of potentiostatic anodizations at the cost of well-defined pore ordering. However, recent studies have shown that thermal control of the working electrode is much more effective than chilling the electrolyte2. The effect of direct potential application with sufficient heat removal by electrode cooling is discussed.

Furthermore the effect of temperature was studied to optimize the rate of hard anodization at steady-state. During steady-state, isothermal anodization rate decays exponentially as a function of time making the rate infeasible to economical production of deep arrays. Electrode temperature step experiments were conducted and its effect on steady-state anodization rate is discussed.

Long-term, isothermal anodizations exhibit a radial distribution of pore lengths with pore lengths decreasing with increasing radial dimension, resembling a cone structure. This effect is unfavorable as it suggests a non-ideal distribution of current thus complicating the geometry of the array. Forced ideal current distribution and its effect on extended depth anodizations is discussed. Additional technical hurdles and the results of these tests will be presented.

1.             Lee, W., et al., Fast Fabrication of Long-Range Ordered Porous Alumina Membranes by Hard Anodization. Nature Materials
2006,
5 (9), 741.

2.             Aerts, T., et al., Control of the Electrode Temperature for Electrochemical Studies: A New Approach Illustrated on Porous Anodizing of Aluminium. Electrochemistry Communications
2009,
11 (12), 2292.