bluuebunny/crossref_metadata_2025 huggingface dataset:
Room Temperature Atomic Layer Deposition of ZnO Observed By in Situ IR Absorption Spectroscopy
Authors: Yoshida Kazuki , Saito Kentaro , Miura Masanori , Kanomata Kensaku , Hirose Fumihiko
Published: February 2020

Zinc oxide (ZnO) is an attractive material for flexible electronics since it has various merits of nontoxicity, wide bandgap, low resistivity, and a high optical transmittance. The ZnO deposition has been intensively studied as transparent conductive films for the liquid crystal displays and thin film solar cells. Furthermore, ZnO has been used as buffer layers for gas barrier films on organic electronics devices. The ZnO deposition has been already reported by DC magnetron sputtering, chemical vapor deposition (CVD), and metal organic CVD (MOCVD). However, it was difficult to control the film thickness with a nanometer precision. In addition, these require high-temperature treatments exceeding 300 ºC, which might be problems for organic electronics and micromachines. To achieve the room temperature growth with a nanometer scale precision, we developed RT atomic layer deposition (ALD).

In this study, we report a new RT ALD with dimethyl zinc (DMZ) and an oxidation gas of plasma excited humidified Ar. We used an in-situ multiple-internal-reflection IR absorption spectroscopy (MIR-IRAS) equipped ALD system to investigate the saturation behavior in precursor adsorption and oxidization. We determined injection conditions of the precursor and oxidization gas for the RT ALD based on the IRAS experiment. The RT ALD of ZnO was performed to confirm the ZnO formation on a silicon substrate. In figure 1, we show ZnO thicknesses as a function of ALD cycle which were measured by spectroscopic ellipsometry. The growth per cycle was estimated as 0.046 nm/cycle. We evaluate its composition by using X-ray photoelectron spectroscopy and confirmed that it was fully oxidized. We assume that the deposited film was amorphous from the X-ray diffraction pattern. In addition, we discuss the reaction mechanism in this ALD with Langmuir equation fitting applied to the saturation curve plotted from the result of IR absorption spectroscopy. We depict the surface reaction scheme of the ZnO RT ALD in this paper.

Acknowledgment; This work was partly supported by JST-CREST Grant Number JPMJCR14F3, Japan. It was also partly supported by JSPS KAKENHI Grant Numbers 15H03536 and 16K17494.

Figure 1 Growth thicknesses of ZnO as a function of the ALD cycle number.

Figure 1
Analytical Modeling of Two-Phase Water Transport in a PEMFC
Authors: Rahman MD Azimur , Mojica Felipe , Chuang Po-Ya Abel
Published: February 2020

While significant progress has been achieved in PEMFC modeling, simulating liquid water formation and transportation in a PEMFC remains a challenge. Under wet operating conditions, liquid water may condense in the channel, gas diffusion layer, or electrode, which introduces significant complexities in simulating fuel cell performance. There have been several approaches to model two-phase water transport using both macroscopic and microscopic methods. Two-phase macroscopic models are mostly based on volumetric averaged method and solve the governing equation using CFD techniques, which require intensive computational resources. In recent years, microscopic approaches based on Lattice Boltzmann Method (LBM) and pore-network approach have been applied to detailed morphological geometric domain of gas diffusion layer. While microscopic approach provide useful information, they cannot be coupled with a full fuel cell model. Therefore, constructing an effective analytical two-phase model is crucial in developing materials and design to optimizing fuel cell performance. In this work, we present an empirical-based, steady-state, 1-D, non-isothermal, and two-phase PEMFC model that includes full cell geometry and water balance. Limiting current experiments based on Caulk and Baker [1] is employed to study both dry and wet oxygen transport phenomena with wet-proofed Toray-H-060 carbon fiber paper with microporous layer. Specifically, the ratio of tortuosity and porosity under wet and dry conditions are characterized by the limiting current method and incorporated into the model. The two-phase model uses tendril length to represent the liquid water saturation and penetration in the diffusion layer. Figure 1 shows that the newly constructed two-phase model can capture the total transport resistance as a function of limiting current density in the dry, transition, and wet regions well for operating conditions at 300 kPa, 70°C, 80% and 90% relative humidity. This two-phase model also includes a two-phase electrode model, which correlates electrode relative humidity to available ECSA for fuel cell performance simulation. The details of the model and prediction results will be presented at the conference.

Referece:

1. Caulk, D.A. and Baker, D.R., 2010. Heat and water transport in hydrophobic diffusion media of PEM fuel cells. Journal of The Electrochemical Society, 157(8), pp.B1237-B1244.

Figure 1
Electrodeposited Co-Mo-TiO2 Electrocatalysts for the Hydrogen Evolution Reaction (HER)
Authors: Wang Cheng , Podlaha Elizabeth J.
Published: February 2020

Co-Mo alloys are well known as excellent electrocatalysts for hydrogen generation.1-3 Presented here, Co-Mo-TiO2 composite thin films were electrodeposited onto copper rotating cylinder electrode substrates from citrate electrolytes, and deposited galvanostatically at room temperature. TiO2 micro-scale particles were suspended in the electrolyte mechanically and captured into the growing alloy thin films. The addition of TiO2 particles to the Co-Mo matrix did change the alloy composition at low applied current densities (e.g., 20 mA/cm2), but not at higher current densities (e.g., 100 mA/cm2). The composite composition was very uniform over a wide range of current densities, and the partial current densities that dictate the composition, were all higher when particles were present compared to the particle free alloy. The HER polarization and Tafel slopes were characterized in 1 M sodium hydroxide, and the surface area was examined in a ferricyanide electrolyte. The HER kinetics in sodium hydroxide were dependent on both the Mo and TiO2 composition. The exchange current density exhibited a volcano-type behavior with the Mo composition in the deposit. At the maximum value of the exchange current density, the addition of TiO2 further increased its value to nearly 1 mA/cm2, approximately 3 times higher than the Co-Mo alloys. The overpotential at -10 mA/cm2, ƞ10, decreased when particles were present in the deposit by 22-55 mV compared to their alloy counterparts. The Tafel slope of all deposits with TiO2 were similar in the range of 70-75 mV/dec. The Tafel slopes of the alloy without TiO2, changed with the applied electrodeposited current density, while the composition was also altered, unlike the composites. Interestingly, adding particles to the electrodeposition electrolyte increased the metal partial current densities, but not HER, and in contrast, with the particles embedded into the deposit the HER in an alkaline electrolyte was considerably enhanced.

References

C. C. McCrory, S. Jung, I. M. Ferrer, S. M. Chatman, J. C. Peters, T. F. Jaramillo, J. Amer. Chem. Soc. 137, 4347 (2015).

P. Żabiński, H. Nemoto, S. Meguro, K. Asami, K. Hashimoto, J. Electrochem. Soc.
150 C717 (2003).

Y. Zhang, Q. Shao, S. Long, X. Huang, Nano Energy
45, 448 (2018).
High Surface Area Reverse Electroactuation Energy Harvesting
Authors: Adhikari Pashupati R. , Reid Russell C.
Published: February 2020

Manipulating a liquid droplet with applied electrical fields has long been studied and is known as electrowetting on dielectric (EWOD). In recent years, a new approach of energy harvesting that is related to EWOD has been demonstrated and it is termed reverse electrowetting energy harvesting or simply reverse electroactuation. Reverse electroactuation is opposite to electrowetting in which energy is generated by converting mechanical energy of the liquid motion into electrical energy. The amount of energy generated using this technique mainly depends on the contact area of the electrode-electrolyte interface. The contact area can be varied by applying a bias voltage to decrease the surface tension of the electrolyte resulting into a surface area increase. As an alternative, the contact area can also be varied by applying pulsating external pressure. In this study, we plan to model and experimentally demonstrate an AC current generation by applying pulsating external pressure to move the electrolytic fluid in and out of porous materials with high surface to volume ratio. The model is based on a simple solution to the Washburn equation which establishes the pressure dependency of fluid height in the pores. Various porous materials with both uniform and non-uniform pores are used in the analysis.
Hydrogen Isotope Effects during Water Electrolysis Using Liquid and Polymer Membrane Electrolytes
Authors: Silva Liyanage Mayura Sankalpa
Published: February 2020

Hydrogen isotope separation is highly important and equally challenging. Annual production of heavy water (D2O) is over a thousand tons to supply nuclear reactors and for medical and research applications worldwide. Current D2O production methods are expensive due to the low natural abundance of deuterium and high complexity of separation techniques. Demand for low-cost production of heavy water is inevitable with increased usage of nuclear power. Therefore, it is important to develop novel and economically viable methods to concentrate deuterium in water to overcome these demands. The purpose of this project is to study hydrogen isotope effects during the electrolytic decomposition water. Water electrolysis occurs via an oxygen evolution reaction (OER) at the anode and a hydrogen evolution reaction (HER) at the cathode. We have located OER and HER as the two main reactions that can have an isotope effect. Custom-built electrolyzers are used for the water electrolysis experiments where IrO2 is used as the catalyst layer at the anode and Pt on Carbon is used as the catalyst layer at the cathode. Results from using sulfuric acid in H2O and deuterated sulfuric acid in D2O as the liquid electrolytes for water electrolysis in a three-electrode conventional cell will be presented and discussed in the context of hydrogen isotope effects on the OER and HER. A similar comparison is made to study isotope effects at OER and HER in a proton exchange membrane (PEM) cell using Nafion 212 as the solid polymer electrolyte in a custom electrolyzer. Monolayer graphene in its pristine form has been shown to act as a selective barrier allowing proton transmission at rates much higher than deuteron transmission. We have incorporated a graphene layer in between two Nafion membranes to study the effect of graphene on the ability to separate deuterium from a hydrogen/deuterium gas mixture and also from H2O vs D2O electrolysis. Monolayer graphene’s barrier character together with isotope effects of OER and HER of the membrane electrode assembly (MEA) could contribute to a potential low-cost method to separate deuterium from a H/D isotope mixture.
Photoelectrochemical Properties of (K, Na)NbO3 (KNN) Thin Film
Authors: Kurohagi Masayuki , Mukouyama Yoshiharu , Ishii Satoshi , Ohsaka Hiroki , Kanno Isaku
Published: February 2020

Photoelectrochemical (PEC) and photocatalytic (PC) processes driven by solar energy, e.g., PEC and PC water splitting, have been paid increasing attention because the processes are promising candidates to address environmental issues and energy shortages. For decades, considerable efforts have been made to find a suitable semiconductor material for the processes. Recently, sodium niobate (NaNbO3) and potassium niobate (KNbO3), which have typical ABO3 perovskite structures, attract much interst in the field of photocatalysis because NaNbO3 and KNbO3 show excellent PC activities for H2 generation (1-4). The band gap of KNbO3 is 3.1 eV, which is slightly narrower than that of NaNbO3 (3.4 eV), and thus KNbO3 shows a higher PC activity than NaNbO3 due to the narrower band gap and higher mobile charge carriers (3).

The Nb-related perovskite oxides have other interesting properties in terms of ferroelectric, piezoelectric, dielectric, and optical properties. Moreover, they exhibit photovoltaic effects due to spontaneous electric polarisation (i.e., due to their ferroelectric property). In these regards, potassium sodium niobate, (K, Na)NbO3 (KNN), has also been studied extensively. However, nothing has been studied on its PEC and PC behaviour, probably because the bulk band gap of KNN is relatively wide (4.28 eV) (5). Thus, this work aims to demonstrate the PEC behaviour of KNN thin films.

Figure 1(a) shows cyclic voltammograms (CVs) for a KNN thin film in 0.1 M (= mol/L) NaOH solution measured with and without ultraviolet-visible light irradiation. The potential (E) was scanned between -0.86 and 0.64 V vs. SHE at a rate of 0.1 Vs-1. The film was deposited onto a Pt/Ti/SiO2/Si substrate by using a radio frequency magnetron sputtering method. The KNN film exhibited a characteristic of n-type semiconductors: the oxidative photocurrent, which is likely to be due to the oxygen evolution reaction (4OH－
→ O2 + 2H2O + 4e－), started to flow at -0.5 V and increased as E increased. Figure 1b shows photo images of the KNN film before and after cycling the potential 100 times under the light irradiation. The film was hardly affected by the potential cycles, i.e., it was stable during the PEC reaction. We can thus say that the KNN is an active material for the PEC water splitting, which will be discussed in the presentation.

FIGURE CAPTION

Figure 1. (a) Photoelectrochemical behavior of a KNN thin film (the surface area: 130 mm2) measured in a 0.1 M NaOH solution. A 100W mercury lamp was employed to irradiate the KNN film electrode. (b) Photo images of the KNN film taken (left) before and (right) after cycling the potential 100 times. The potential was scanned between -0.66 and 0.64 V.

Figure 1
Liquid-Phase Exfoliation of Transition Metal Dichalcogenide Nanosheets with Zwitterionic Detergents and Their Inkjet-Printed Photodetectors
Authors: Lee Hyeokjung , Eoh Hongkyu , Kim Kang Lib , Park Cheolmin
Published: February 2020

Liquid-phase exfoliation (LPE) of transition metal dichalcogenide (TMD) nanosheets is a facile, cost-effective approach to large-area photoelectric devices including photodetectors and non-volatile memories. Non-destructive exfoliation of nanosheets using macromolecular dispersing agents is advantageous in rendering the TMD nanocomposite films appropriate for mechanically flexible devices. Here, an efficient LPE of molybdenum diselenide (MoSe2) with zwitterionic detergents is demonstrated, the exfoliation of nanosheets was facilitated through electrostatic repulsion between detergent-coated TMD nanosheets. The results demonstrate that the exfoliation depends upon both the number of alkyl chains and the concentration of the zwitterionic detergents. Under optimized conditions of number of alkyl chains and its concentration, zwitterionic detergents gave rise to a highly concentrated MoSe2 nanosheet suspension that was stable for over 1 month. Exfoliation of several other TMDs was also achieved using the zwitterionic detergents, indicating the scope of applications. Moreover, a zwitterionic detergents/MoSe2 suspension could use a inkjet-prinitable ink, a flexible composite film of zwitterionic detergents and MoSe2 nanosheets was fabricated by inkjet-printing. It showed outstanding photoconductive performances including a high Ion/Ioff ratio of 104.
Elucidating the SEI Formation and Composition As a Function of Binder on Si Anodes Using in Situ Neutron Reflectometry
Authors: Browning Katie L , Doucet Mathieu , Browning James F , Sacci Robert L , Veith Gabriel M.
Published: February 2020

This talk will highlight the use of in situ neutron reflectometry (NR) to explore the effect polymeric binders used in composite slurries have on the composition and formation of the solid electrolyte interface (SEI) on amorphous silicon (aSi) anodes. Due to the high-volume expansion, upwards of 300%, a polymeric binder is needed for added mechanical strength; however, little is known about binder interactions with Si and its effect on SEI formation. Two different binder systems, polyacrylic acid (PAA), the most commonly used binder to date, and PEFM, an electronically conductive binder, were explored using NR at various potential steps. Thin film architectures were used to provide a model electrode surface to better probe interfacial reactions. In this case vapor deposited aSi films were spin coated with low weight percent polymer binder solution to create an aSi/binder interface. NR measurements indicate changes in both the polymer layer and resulting SEI as determined by a change in material scattering length density (SLD), a measure of the composition of a layer, during the initial lithiation stage. Ex situ techniques, in this case x-ray photoelectron spectroscopy, were used in conjunction with NR measurements to confirm models of the data. Preliminary results indicate the formation of a predominantly inorganic SEI layer.

Neutrons interact with the nucleus of an atom, unlike x-rays, and as such scattering cross-section is not dependent on Z number. This allows for probing of lighter elements, especially Li, inherent to batteries. Because of their wave-like nature, neutrons follow Snell’s Law in which the beam is reflected and refracted at interfaces separating layers with different indices of refraction providing information on the thickness, roughness, and/or diffuseness of a layer and most importantly the composition described by the SLD. NR is an ideal tool to study interfaces, including buried such as those found in materials for energy storage.

Acknowledgement: This research was supported by the Vehicle Technologies Office, Hybrid Electric Systems Program, David Howell (Manager), Battery R&D, Brian Cunningham and Peter Faguy (Technology Managers), at the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy. Neutron reflectometry measurements were carried out on the Liquids Reflectometer at the Spallation Neutron Source which is sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy.
Operando study of Chemical and Structural Evolutions of TiS2 in Li-Ion and Na-Ion Batteries
Authors: Lin Cheng-Hung , Sun Ke , Attenkofer Klaus , Topsakal Mehmet , Bai Jianming , Zhao Chonghang , Lu Deyu , Dooryhee Eric , Stavitski Eli , Northrup Paul , Gan Hong , Chen-Wiegart Yu-chen Karen
Published: February 2020

Since the first report of the inserting reaction of alkali metals in layered dichalcogenides in 1959, titanium disulfide (TiS2) has been widely studied as a model material of intercalation host compound in energy storage for Li-ion batteries. Due to its high electric conductivity, fast rate capability, good cycling performance and natural abundance, TiS2 electrode also became a promising candidate for the low-cost Na-ion battery system. However, the differences regarding the detailed chemical and structural evolutions and reaction mechanism of TiS2 in Li-ion and Na-ion batteries are not yet well understood. In this work, the chemical and structural evolutions of TiS2 in both Li-ion and Na-ion batteries are investigated via operando synchrotron absorption spectroscopy (XAS) at both the sulfur and titanium K-edges using complementary hard x-rays and tender x-rays at the National Synchrotron Light Source II. By combining X-ray diffraction and operando XAS with the Multivariate Curve Resolution - Alternating Least Squares (MCR-ALS) method, we reveal the chemical speciation during the electrochemical cycling. Our study also sheds light on the reaction mechanism of Na-TiS2, which is compared with that of the Li-TiS2 system.

ACKNOWLEDGMENT

We thank DOE Office of Energy Efficiency and Renewable Energy under the Advanced Battery Materials Research (BMR) program, Contract No. DE-SC0012704; we thank ISS, TES, and XPD beamlines of NSLS-II, supported by DOE Office of Science. This research used resources of the Center for Functional Nanomaterials, which is a U.S. DOE Office of Science Facility, at Brookhaven National Laboratory under Contract No. DE-SC0012704. Funding was supported by Stony Brook University and Brookhaven National Laboratory.

Figure: An illustration of the structural and chemical evolutions during sodiaiton observed by operando XAS and ex situ XPD approaches.

Figure 1
(Invited) Speciation and Electrochemical Properties of Magnesium-Ion Electrolytes
Authors: Merrill Laura C. , Park Bumjun , Schaefer Jennifer L.
Published: February 2020

Rechargeable batteries with magnesium metal anodes are of recent research interest due to their potential for high energy density and the widespread availability of magnesium. Magnesium electrolytes are complex due to the divalent nature of Mg2+ and hence the multitude of distinct ionic entities that may exist. Characterizing the ion states is crucial for interpreting the observed bulk properties of the electrolytes. In this presentation, characterization of liquid magnesium electrolytes based on ethers and/or sulfones with mixed salts as well as polymeric magnesium electrolytes will be discussed. Electrospray ionization mass spectrometry (ESI MS), nuclear magnetic resonance spectroscopy (NMR), and Raman spectroscopy are used to provide insight into ion complexation.
(Invited) Β-SnSb for Sodium Ion Battery Anodes: Phase Transformations Responsible for Enhanced Cycling Stability Revealed By in Situ TEM
Authors: Mitlin David
Published: February 2020

The alloy β-SnSb is known to be a highly stable anode for sodium ion batteries during cycling, but its sodiation−desodiation alloying reactions are poorly understood. Combining in situ TEM with electroanalytical methods, we demonstrate that β-SnSb forms Na3Sb and Na15Sn4 in sequence upon sodiation and re-forms as β- SnSb upon desodiation. The negative enthalpy of mixing for Sn and Sb is suﬃcient to cause sequentially deposited bilayers of Sn/Sb to transform into β-SnSb, resulting in comparable cycling stability. The good cycling stability of β-SnSb results from the complex two-phase amorphous−nanocrystalline microstructure in the partially charged− discharged states, as well as the intrinsic mechanical toughness of the β phase. Per the in situ TEM results, the sequential phase transformation shows minimal fracturing of the β-SnSb, indicating facile buﬀering of stresses. Extensively cycled specimens eventually show crystalline Sn phase segregation, which may be the source of the ultimate capacity fade in the alloy and bilayers.
Examination of High Porosity Activated Carbon Obtained from Dehydration of White Sugar (ASC) for Electrochemical Capacitor Applications
Authors: Oyedotun Kabir Oyeniran , Barzegar Farshad , Mirghni Abdulmajid , Khaleed Abubakar Abubakar , Masikhwa Tshifhiwa Moureen , Manyala Ncholu
Published: February 2020

In this research study, we have presented a simple two-step synthesis path to producing a cost-effective high porosity carbon material via acidic dehydration of white sugar. The electrochemical behaviour of the activated sugar-based carbon material (ASC), activated at 400°C (ASC 400) and adopted as a supercapacitor electrode in a symmetric device demonstrated a limit specific capacitance of 242.67 F g-1 at 1 A g-1. The device also demonstrated a good efficacy as an established material for supercapacitors suitable for high power applications with a satisfactory energy density of 19 Wh Kg-1 and power density, 750 W kg-1 at a gravimetric specific current of 1 A g-1. The results obtained provide a potential route to converting cheap refined biomass sources into highly porous nanostructured materials for energy storage device applications.

Figure 1
Synthesis of Rice Ball Shaped Rare Earth-Carbon Composite Electrode Material for Lithium-Ion Batteries
Authors: Lee Seunghyun , Park Chong-Yun , Son Yongkeun
Published: February 2020

The CeO2, known as one of the typical rare earth oxides, is seen to have considerable potential for being used as novel anode materials for secondary batteries because it shows excellent electrochemical redox properties. When it is considered as an anode material, the foremost advantages are that its volumetric and morphological changes are hardly observed, so it could provide good stability and longevity of secondary batteries. It is well explained by the fully reversible phase transformation between fluorite structured CeO2 and cubic structured Ce2O3 during the electrochemical reaction.

Nonetheless, it is essential to improve the conductivity problem of the CeO2 which has intrinsically low electron conductivity in order to apply it to secondary batteries. Meanwhile, there used to be a widely used method called carbon composite method to support nonconductive metal oxides.

In this study, we have synthesized the CeO2-Carbon composite sphere in the form of rice balls to improve the conductivity problems of the rare earth oxide during their electrochemical performance. A rice ball structure is expected to provide more advanced electronic conductive networks than a core shell structure does. Indeed, high stability was observed during the charging and discharging process of LIB due to the nanostructures in the form of rice balls.
(Invited) Controlling Energy Transport in Tailored Carbon Nanotubes Networks for Energy Harvesting Applications
Authors: Ferguson Andrew John , Blackburn Jeffrey L.
Published: February 2020

The ability to selectively extract semiconducting single-walled carbon nanotube (s-SWCNT) species from the raw material with high fidelity is leading to their incorporation as elements in a variety of optical and electronic applications. We have recently employed conjugated polymers based on the fluorene chemical moiety to produce tailored s-SWCNT samples that can be incorporated into photovoltaic, thermoelectric, and transistor architectures.

By controlling both the extent of carbon nanotube bundling and/or removing the insulating polymer that wraps the individual carbon nanotubes, we explore the complex effects of these morphological modifications on the transport of energy by excitonic species and charge carriers in enriched s-SWCNT networks. We show that removal of the insulating polymer, which is often strongly bound to the carbon nanotubes through van de Waals forces between the π-electron systems of the two components, results in a significant improvement in charge carrier transport. In contrast, exciton transport is subtly dependent on the specific nanotube-nanotube interactions in the network. For instance, exciton energy transfer to minority low-bandgap species within a bundle is extremely efficient, but this often traps the exciton in an individual bundle, thereby inhibiting long-range transport within the network.

As alluded to above, the performance of carbon nanotubes in these applications is sometimes strongly dependent on the interplay between the optical and electronic properties of the s-SWCNT networks, which can be controlled by tuning the charge carrier density. We have developed a number of processes that allow us to exert fine control over the charge carrier density injected by redox-active chemical dopants, including the ability to controllably dope the s-SWCNT network p-type and n-type. We will discuss how these strategies can be exploited to exert fine control over charge-carrier transport in the doped s-SWCNT networks, allowing us to target the optimum doping level for the desired application.

Finally, we will discuss the implications of our findings within the context of the incorporation of enriched s-SWCNT networks in energy harvesting applications.
Stable Lithium-Sulfur Full Cell Enabled By Dual Functional Interconnected Mesocarbon Array
Authors: Zhu Hongli
Published: February 2020

Lithium metal-sulfur (Li-S) batteries have gained wide attention due to extremely high energy density, but their application was hindered by the challenges in both Li anode and sulfur cathode. Herein, we designed a dual functional, highly ordered, and interconnected mesoporous carbon (MPC) to address the challenges in cathode and anode simultaneously. On the anode, a thin layer of MPC annealed at 500 ºC (MPC-500) was introduced to mechanically suppress Li dendrite, which provided interfacial protection on the Li metal and stabilized the Li plating/stripping. This novel anode showed excellent cycling stability with more than 300 hours at a high current density of 3 mA cm-2. On the cathode, MPC annealed at 1300 ºC (MPC-1300) was utilized to confine sulfur. The large surface area and nanopores significantly alleviated the shuttle effect, which contributes to the cycling stability of the Li-S battery. Meanwhile, the conductive carbon promote electron transfer. When a Li-S cell was assembled with MPC-500 and MPC-1300 as anode interface layer and cathode additive, respectively, an exceptional reversible capacity of 607 mA h g-1 was achieved at a current density of 1 C (=1675 mA g-1) and maintained at high capacity retention of 90% after 100 cycles.
Polyluminol Modified Carbon Nanotube Electrodes for Electrochemical Capacitors
Authors: N'Diaye Jeanne , Lian Keryn
Published: February 2020

Luminol exhibits electrochemical redox activity when electropolymerized on various substrates, and has been used for electrocatalysis and biosensors [1, 2]. This electrochemical behavior is due to the presence of different amine functional groups within the polymer structure. Recent studies have shown that introducing amine groups on a carbon surface improves the charge storage capacity and the conductivity of the obtained material [3]. Our work aims to leverage the electrochemical properties of polyluminol (Plum) for electrochemical capacitors (ECs). Firstly, the Plum was synthesized using a chemical approach and characterized using spectroscopic methods and electrochemical analyses. Secondly, the polymer was deposited on carbon nanotubes (CNT) to enhance the charge storage capacity for ECs.

The chemical composition of the polymer was found to be a mixture of benzoid and quinoid segments, bonded via secondary (NH) or tertiary amine (=N-) groups, respectively. Such functionalities facilitated chemical, thermal, and electrochemical stability of the polymer. The composite electrode material was obtained by in-situ chemical polymerization of Plum on CNT. Morphological analyses of CNT confirmed the increase of the Plum thickness on CNT with polymerization time, reaching a saturation point of 6.5 nm. In addition, a 4x increase of charge storage capacity with good electrode stability was observed compared to bare CNT over a potential window of 1.2 V as seen in figure 1. Study of the redox reaction kinetics revealed a mostly capacitive contribution of the polymer on CNT. This work showed the successful surface modification and engineering of CNT using a simple and effective fabrication method, which is suitable for large-scale fabrication of composite electrode materials for ECs.

G.-F. Zhang and H.-Y. Chen, Analytica Chimica Acta, 419, 25 (2000).

A. Sassolas, L. J. Blum and B. D. Leca-Bouvier, Sensors and Actuators B: Chemical, 139, 214 (2009).

N. Phattharasupakun, J. Wutthiprom, P. Suktha, N. Ma and M. Sawangphruk, Journal of The Electrochemical Society, 165, A609 (2018).

Figure 1
(Invited) Fundamental Understanding of Faradaic and Non-Faradaic Processes in Carbon-Based Supercapacitors
Authors: Hwang Gyeong S
Published: February 2020

Nanostructured carbon materials, such as graphene and nanoporous carbon, have become increasingly prominent for use as electrodes in supercapacitors, owing to their high specific and volumetric surface area and good electrical conductivity. A conventional understanding of supercapacitors relates the high power to fast ion accumulation at the polarized electrode interface, forming the so-called electric double layer, and the low energy to limited electrode surface area (SA). As such, low-dimensional carbon nanostructures have been extensively explored. However, anomalous and nonlinear relationships between observed capacitances and SAs have prompted a need to revise our mechanistic understanding of charge storage. In this talk, we present our recent findings regarding charge storage mechanisms, along with possible faradaic reactions, in carbon-based supercapacitors from combined quantum mechanical and classical molecular dynamics simulations. Our first-principles studies suggest that the total interfacial capacitance (CT
) of graphene-based supercapacitors is determined from both electrode (CQ
) and electric double layer (CD
) capacitances which are in series. It has also been demonstrated that the CQ
, and thereby CT
, can be significantly enhanced as a result of changes to the electronic structure through chemical functionalization, doping, and/or structural deformation. Furthermore, our voltammetric molecular dynamics simulations have revealed the complex non-equilibrium processes associated with extreme confinement of ionic liquid electrolytes within subnanometer pores. Based on these results, we will also discuss a mechanistic perspective centered around ion reorganization kinetics, particularly the dependence of ion migration efficiency, and relatedly, the capacitance, on pore morphology. This talk will also briefly touch on possible faradaic reactions that may cause self-discharge.
Graphene Quantum Dots As Effective Formulations for Drug Delivery, Imaging, and Sensing
Authors: Campbell Elizabeth , Hasan Md Tanvir , Gonzalez-Rodriguez Roberto , Akkaraju Giridhar R. , Naumov Anton V
Published: February 2020

A field of molecular therapeutics has significantly advanced the treatment of many complex conditions, including cancer therapeutics. However many molecular formulations still lack the diagnostic power of tomography-guided approaches, and are restricted by dose-limiting toxicity. Multiple gene therapeutics, which have shown to be effective on a cellular level, require to be delivered in vivo to protect the payload from degradation in blood. This technical gap outlines a clear need for multifunctional delivery/imaging agents. Nanomaterials provide these capabilities, safely delivering therapeutics concomitantly imaging their delivery pathways. Recently graphene derivatives became a focus of intense scientific inquiry including their applications in the biomedical field. However, many issues arise with biocompatibility, degradability and imaging of these platforms. Graphene quantum dots (GQDs) produced via biocompatible bottom-up synthetic route in this work are attractive candidates for bioimaging due to their intrinsic fluorescence in the red/near-infrared spectral region, water solubility, pH mediated response to fluorescence emission, and smaller size for more efficient cellular internalization. We explore these properties to develop a family of graphene-based imaging/sensing/delivery platforms for molecular therapeutics. Our work utilizes three types of GQDs (boron-nitrogen doped, nitrogen doped, and sulfur doped GQDs), which show little to no cytotoxicity quantified via MTT assay up to the maximum imaging concentrations of 1 mg/mL. We use spectrally-resolved fluorescence imaging for in vitro detection in the spectral ranges specific to GQD emission. All GQD types exhibit efficient cellular internalization assessed via their emission within HeLa cells, suggesting a high potential for drug delivery applications and image-guided therapy. A pH dependent emission provides a ratiometric sensing mechanism for the acidic environments of cancer cells; as many cancer cell types excrete lactic acid, their environments are more acidic than those of healthy cells. The difference between fluorescence in healthy (HEK-293)/cancer (HeLa, MCF-7) cell environments is quantified for GQDs in this work via assessing the shifts in emission and/or variations in emission intensities at different wavelengths. As a result we propose GQDs as efficient multifunctional candidates for in vitro delivery of active agents, fluorescence imaging, and pH-sensing of cancerous environments.
(Invited) Aqueous Dispersion and Characterization of Carbon Nanotubes Functionalized By Biomimetic Glycopolymers
Authors: Cantwell Michael , Chan Ka Keung , Sun Xue-Long , Ao Geyou
Published: February 2020

Carbohydrate recognitions are crucial events in many biological processes including cellular adhesion, cell signaling, cell-cell communication, immune response, cancer development and metastasis. Understanding the specific interaction between carbohydrates and carbohydrate-binding proteins (CBPs) could lead to clarifying the functions of both molecules and their underlying molecular mechanism and discovering therapeutic and diagnostic mechanism as well, but it is a challenging task. This work demonstrates aqueous dispersions of single-wall carbon nanotubes (SWCNTs) stabilized by multivalent, galactose-containing glycopolymers that closely mimic the natural glycan structures and functions. In addition, the specific binding behavior of glycopolymer-functionalized SWCNTs with CBPs and its role as an effective measurement tool for profiling carbohydrate-protein recognitions will be discussed.
A Nanobioengineering Frontier for Next-Generation Optical Devices
Authors: Boghossian Ardemis Anoush
Published: February 2020

The vast expansion of available synthetic biology tools has led to explosive developments in the field of materials science. No longer confined to engineering just synthetic materials, the increased accessibility of these tools has pushed the frontier of materials science into the field of engineering biological and even living materials. By coupling the tunability of nanomaterials with the prospect of re-programming living devices, one can re-purpose biology to fulfill needs that are otherwise intractable using traditional engineering approaches.

Optical technologies in particular could benefit from capitalizing on untapped potential in coupling the optical properties of nanomaterials with the specificity and scalability of biological materials. This presentation highlights specific applications in optical sensing and light-harvesting energy technologies that exploit the synergistic coupling of nanobio-hybrid materials. We discuss the development of bio-conjugated single-walled carbon nanotubes (SWCNTs) for near-infrared fluorescence sensing and the application of these nanobioptic sensors for continuous measurements in living cells and organisms. We further explore the development living photovoltaics based on bioengineered, photosynthetic organisms with augmented capabilities.
Protein Biomarker Detection with Carbon Nanotube-Based Sensors
Authors: Budhathoki-Uprety Januka , Heller Daniel A.
Published: February 2020

Proteins are widely used biomarkers in disease diagnosis. A vast majority of clinical methods for the detection of the marker proteins use antibodies. Such methods are sub-optimal to function in global health applications and point-of-care assays. We are developing single-walled carbon nanotube-based optical sensors for straight-forward, rapid and sensitive measurement of proteins for accurate disease diagnosis. Single-walled carbon nanotubes, with intrinsic photoluminescence and high optical sensitivity towards molecular interactions, upon the surface modification with polymeric materials provide unmatched basis for the development of optical sensors.
Effect of DNA on Fundamental Characteristics of Single-Walled Carbon Nanotubes; Length Distribution and Thermal Stability
Authors: Safaee Mohammad Moein , Gravely Mitchell , Roxbury Daniel
Published: February 2020

Single-stranded DNA has been demonstrated to enable single-particle exfoliation of single-walled carbon nanotubes (SWCNTs) in aqueous environments as well as suppress their known toxicological effects. The resultant fundamental properties of DNA-SWCNT hybrids are significant when these nanomaterials are applied to mechanical and biological systems. Accurate characterization of their length distributions is of great importance regarding their application as a clinical diagnostic agent. Here, we show that DNA-SWCNT hybrids differentially bind to freshly-cleaved mica in a manner that significantly depends upon the sequence of DNA. By displacing the DNA from the SWCNTs, we show that the length distributions of the resulting surfactant-coated SWCNTs are statistically identical and suggest that a DNA-wrapping can give inaccurate length distributions in image-derived approaches. Secondly, enhancing the thermal stability of SWCNTs is crucial when these materials are applied to high temperature applications. We examined the thermal decomposition temperature and rate of DNA functionalized carbon nanomaterials using thermogravimetric analysis and found that functionalization with DNA significantly increases the thermal decomposition temperature of all examined carbon nanomaterials in the order SWCNTs > C60 > RGO > MWCNTs. We attribute these increases in decomposition temperature to the fact that DNA, an intumescent molecular entity that increases in volume upon heating, shields the hybridized carbon nanomaterials from flame and elevated temperatures. Enhancing the thermal decomposition properties of carbon nanomaterials with non-toxic flame retardants enables the realization of environmentally friendly high temperature sensing and electronics applications.
(Invited) Strategies for Alignment and Spatial Localization of Semiconducting Single-Walled Carbon Nanotubes
Authors: Gopalan Padma , Dwyer Jonathan , Jinkins Katherine R , Arnold Michael S.
Published: February 2020

The wide scale utility of semiconducting carbon nanotubes (CNTs) depends on its electronic purity as well as development of methods to process them on the wafer-scale into the ideally organized and aligned arrays for integrated device structures. Now we can routinely achieve > 99.99% semiconducting CNTs with a suitable diameter distribution using conjugating polymers as sorting agents in organic solvents. However, the spatial localization using a scalable method still remains a challenge. This is important as now there are many methods available to get aligned CNTs, however an ideal array with the optimal spacing between the tubes remains elusive. An ideal CNT array microstructure for high-performance FET channels is predicted to consist of a sub-monolayer of electronic-type controlled semiconducting CNTs that are laterally aligned and evenly spaced with a packing density of 100-200 CNTs µm-1. In order to achieve this goal, we present our studies on understanding the multitude of factors from surface energy of the wafer, role of the polymer wrapper on the CNT, chemistry of the substrate, surface topography, chemical pattern, and the type of solvent used on the adsorption or desorption of the CNTs on substrates. These studies so far show that the static water contact angle of the substrate alone cannot fully explain the adhesion of CNTs to certain substrates. The surface roughness also plays a critical role. Through these studies we hope to lay down a rational basis for designing chemical patterns that can control the spatial localization of CNTs.
One Dimensional Van Der Waals Heterostructures Wrapped Around Single-Walled Carbon Nanotubes
Authors: Xiang Rong , Inoue Taiki , Maruyama Shigeo
Published: February 2020

We have synthesized a new coaxial nanotube structure, in which mono- or few-layer hexagonal boron nitride nanotube (BNNT) seamlessly wrap around a single-walled carbon nanotube (SWCNT), and result in an atomically smooth coaxial tube consisting two different materials, as shown in Fig. 1(a). TEM-EELS clearly demonstrated the BNNT-SWCNT coaxial structure. We have tried various morphologies of SWCNTs as starting material, e.g. vertically aligned array, horizontally aligned array, suspended SWCNTs, and dry-deposited random network films. We can clearly observe the coaxial structure from originally isolated SWCNTs. We found no correlation between chiral angle of inner SWCNT and outer BNNT for ‘double-walled’ SWCNT-BNNT shown in Fig. 1(b). We concluded that these are one-dimensional van der Waals heterostructure. We have further developed the 1D coating CVD for transition metal dichalcogenide nanotubes, such as MoS2 nanotube as shown in Fig. 1 (c). We can grow MoS2 nanotubes around relatively large diameter SWCNT or SWCNT@BNNT [1]. We will discuss properties of the 1D heterostructures though optical absorption, Raman scattering, photoluminescence, FT-IR, and cathode luminance.

Reference:

[1] Rong Xiang et al., arXiv:1807.06154 (2018).

Figure 1
Controlled Growth of Metal Nanoparticles on Multi-Walled Carbon Nanotubes for Chemical Sensing Applications
Authors: Smart Christopher J. , Belli Stuart , Afreen Samira , Muresan Rebeca , Waltz-Chesnaye Charles
Published: February 2020

We have grown nanoparticles of gold, silver, copper, cobalt and nickel on the surface of carbon nanotubes which are deposited by CVD on gold wires bearing a nickel catalyst layer. A study of the CVD reaction as a function of time revealed that one-minute and ten-minute deposition times yielded qualitatively similar coatings. Metal nanoparticles were grown from electroplating solutions by using the nanotube-coated wire as the working electrode and running a galvanostatic, electrochemical deposition. For gold depositions, we were able to show that varying the conditions of current, plating bath concentration and deposition time allowed control of the size of the deposited nanoparticles within the range of 10 – 150 nm. The morphology of the gold nanoparticles was approximately spherical, except under unique conditions where spiked spheroids, also known as nano-urchins, were observed. By using the gold nanoparticle-decorated CNT electrode as one plate in a parallel-plate capacitor, we were able to show a change in electrical properties, such as capacitance, by comparing voltammograms before and after exposure of the electrode to a dilute solution of organic thiols. This demonstrates the potential utility of the electrode structure as a chemical detector. The two SEM images below show typical results. On the left, CVD carbon nanotube growth prior to electrodeposition of metal nanoparticles; note the presence of nickel catalyst particles at nanotube tips. On the right, carbon nanotube sample after electrodeposition of gold nanoparticles.

Figure 1
Multifunctional NIR-Fluorescent Carbon Nanotubes for Imaging and Sensing By Using Defect Chemistry
Authors: Herrmann Niklas , Mann Florian , Kruss Sebastian
Published: February 2020

Single-walled carbon nanotubes (SWCNT) are versatile materials for imaging and sensing in the near infrared (nIR) range. Non-covalent adsorption with (bio)polymers such as ssDNA is a powerful approach to functionalize SWCNTs. This approach lead to sensors that detect the release of biomolecules such as neurotransmitters from cells with high spatiotemporal resolution. However, covalent approaches would be beneficial for many applications because of higher stability and photophysical signal transduction. It has been reported that reactions with diazonium salts create covalent defects and a red-shifted peak in the nIR fluorescence spectrum attributed to a formerly dark exciton.

Here, we use defect chemistry to covalently modify SWCNTs and at the same time change their fluorescence spectrum in a well-defined way. For that purpose, we synthesized a maleimide-carrying diazonium salt and used a light-catalyzed reaction to introduce defects. The maleimide group can be further functionalized using thiols in a thiol-en click reaction. The modified SWCNTs were additionally wrapped in DNA for solubilization and characterized via nIR spectroscopy and atomic force microscopy (AFM). Our results show that depending on the attached thiol compound these SWCNTs respond differently to small molecules such as the neurotransmitter dopamine. This approach was then used to optimise the selectivity profile and sensitivity for fluorescent sensing applications. Furthermore, we covalently conjugated antibodies to the SWCNTs and used them for nIR labeling in cells.

In summary, we present a new approach to covalently functionalize SWCNTs using defect chemistry and demonstrate applications in nIR imaging and sensing.