bluuebunny/crossref_metadata_2025 huggingface dataset:
Holey Graphene for Energy Storage
Authors: Kanungo Rohit , Radich James
Published: February 2020

Graphene, owing to its large specific surface area (SSA) and excellent electronic conductivity has been a focus of research as an electrode material in electrochemical capacitors (EC). However, van der Wall’s attraction between the individual graphene sheets results in stacking of sheets while fabricating electrodes. This phenomenon decreases the SSA and restricts electrolyte diffusion pathways thereby deteriorating the performance of EC. Another challenge is that bulk manufacturing of graphene with a low cost process does not exist. These challenges can be resolved by using reduced graphene oxide (RGO) which is structurally similar to graphene with few oxygen functional groups and defects. Solution based process to synthesize RGO are indeed facile. Furthermore, previous studies indicate that modified RGO morphologies can be used as potential electrode material for electrochemical capacitors (EC). By creating nanopores within the RGO sheets, the specific surface area of electrode and diffusion of electroactive species can be improved. Here, we present a simple solution based process to manufacture holey graphene from graphene oxide (GO) via microwave (MW) radiations. GO aqueous dispersion prepared by modified Hummer’s method can be converted to RGO via thermal, chemical or photochemical methods. Then, RGO in presence of hydrogen peroxide is irradiated with microwaves. The application of MW radiation generates OH free radicals, which etch the carbon atoms present at the active defective sites on RGO. This creates a carbon vacancy on RGO sheet, consequently extending to form the nanopores. This holey graphene is characterized using TEM, XPS, BET, Raman & FTIR. Next, holey graphene is utilized to build an electrochemical capacitor and tested to show improved diffusion of electrolyte and higher energy density. The fundamental knowledge gained from this study can also be applied in the fields of batteries, hydrogen storage and catalysis.
Two Different Carbon Nanotube-Based Non-Pt Fuel Cell Catalysts with High Performance and Durability
Authors: Yang Jun , Cheng Junfang , Nakashima Naotoshi
Published: February 2020

Development of non-Pt-based electrocatalyst for fuel cells and batteries with high performance, durablity, and scalability is a strong social demand for the next-generation eco-friendly energy society[1-3].

In this meeting, we summarize our recent studies on i) development of a carbon nanotube (CNT)-based two different non-Pt type fuel cell catalysts, i.e, one is pristine multi-walled carbon nanotube/iron phthalocyanine hybrids with a well-defined nanostructure that show excellent efficiency and durability for oxygen reduction reaction[2], and the other is a decorating unoxidized-carbon nanotubes with homogeneous Ni-Co spinel (and related) nanocrystals that show superior performance for oxygen evolution/reduction reactions[3].

References

[1] T. Fujigaya, N. Nakashima, Adv. Mater., 2013, 25, 1666-1681.

[2] J. Yang, F. Toshimitsu, T. Fujigaya, N. Nakashima, J. Mater. Chem. A, 2017, 5, 1184-1191

[3] J. Yang, T. Fujigaya, N. Nakashima, Sci. Rep., 2017, 7, art.no.45384.
(Invited) Individualized Low-Dimensional Carbon Allotropes: Enabling Ground State and Excited State Charge Transfer By NIR Absorbing Heptamethine Cyanine
Authors: Guldi Dirk M.
Published: February 2020

At the focal point of our studies are mutual interactions between an anionic heptamethine cyanine and individualized single walled carbon nanotubes (SWCNT) / exfoliated nanographene (NG). Unprecedented is the distinct NIR absorption of the heptamethine cyanine, which assists in visualizing the electronic interactions in the ground state with ease and precision. In statistical Raman assays, we conclude from downshifted 2D- and G-modes for SWCNTs, as well as, upshifted 2D- and downshifted G-modes for NG that these electronic interactions result in stable n-doping of SWCNTs / NG . Key to this shift of charge density is the electron donating character of the heptamethine cyanine. In the excited state, a complete, but metastable transfer of charges is accompanied by a several nanoseconds lived radical ion pair state. Note such a time domain has never been realized, for example, in NGs to this date.
Carbon Nanotubes for Flexible Perovskite Solar Cells
Authors: Maruyama Shigeo
Published: February 2020

Single-walled carbon nanotubes (SWNT), graphene, and fullerene (C60 and PCBM) would be very efficiently used in lead halide Perovskite solar cells. A film of SWNTs or graphene can be flexible and stretchable transparent-conductive layer. At the same time, this film can be carrier-selective layers, i.e., electron-blocking-layers or hole-blocking-layers. Based on our experiences of using nanotube films for CNT-Si solar cells and organic polymer solar cells [1,2], we have explored the application of SWNT films for organic-inorganic perovskite solar cells. We have demonstrated the replacement of ITO in inverted-type perovskite solar cells, SWNTs/PEDOT:PSS/CH3NH3PbI3/PCBM/Al [3]. The flexible application on polyethylene terephthalate (PET) is also demonstrated [3]. With the improved perovskite structure, a film of carbon nanotubes or graphene can be practical replacement of ITO for the flexible transparent electrode of inverted perovskite solar cells [4].

Replacement of electron-blocking-layer and metal electrode in normal-type perovskite solar cells is demonstrated as well. Those devices can have comparable PCE as the conventional design with organic electron-blocking layer and top metal electrode. The normal-type perovskite solar cell, composed of ITO/C60/CH3NH3PbI3/SWNTs, can achieve a PCE of 17 % with spiro-MeOTAD as dopant to SWNTs [5]. This structure with a perovskite layer sandwiched by C60 and SWNTs can lead to the solar cells without hysteresis and with much improved air-stability [5]. The effective passivation of the degradation of perovskite material by moisture can be achieved with C60 and SWNTs [5]. More recent configuration is using a film of SWNTs for both anode and cathode electrode [6]. The new physical understanding of band alignment must be discussed based on the demonstrations of efficient carrier selective layers with these dry-deposited SWNTs which are composed of metallic and semiconductor nanotubes.

Part of this work was supported by JSPS KAKENHI Grant Numbers JP25107002 and JP15H05760.

References:

[1] I. Jeon, K. Cui, T. Chiba, A. Anisimov, A. Nasibulin, E. Kauppinen, S. Maruyama, Y. Matsuo, J. Am. Chem. Soc., 137, 7982 (2015).

[2] I. Jeon, C. Delacou, A. Kaskela, E. I. Kauppinen, S. Maruyama, Y. Matsuo, Sci. Rep. 6, 31348 (2016).

[3] I. Jeon, T. Chiba, C. Delacou, Y. Guo, A. Kaskela, O. Reynaud, E. I. Kauppinen, S. Maruyama, Y. Matsuo, Nano Lett. 15, 6665 (2015).

[4] I. Jeon, J. Yoon, N. Ahn, M. Atwa, C. Delacou, A. Anisimov, E. Kauppinen, M. Choi, S. Maruyama, Y. Matsuo, J. Phys. Chem. Lett., 8 (2017), 5395.

[5] N. Ahn, I. Jeon, J. Yoon, E. I. Kauppinen, Y. Matsuo, S. Maruyama, M. Choi, submitted.

[6] I. Jeon, S. Seo, Y. Sato, C. Delacou, A. Anisimov, K. Suenaga, E. I. Kauppinen, S. Maruyama, Y. Matsuo, J. Phys. Chem. C, (2017), online [DOI: 10.1021/acs.jpcc.7b10334].
DI Water Dispersed Graphene Oxide and Supercapacitors with Photoreduced Graphene Oxide Films
Authors: Sul Ji-Hwan , Kim In Gyoo , Kang Seok Hun , You In-Kyu
Published: February 2020

In recent years, graphene oxide (GO) has attracted a lot of attention as materials of an electrode for rechargeable batteries and supercapacitors. During the processes of GO conversion from a graphite, various oxygen containing functional groups and impurities such as sulfuric acid are engaged into the GO structure and GO flake, respectively, and they deteriorate the electrical properties and dispersivity of GO. In this study, we carried out washing process of GO flake using a centrifuge. Through the washing process, the remaining acid and impurities almost disappeared and the dispersivity of GO in DI water increased greatly. By using this GO dispersion, freestanding GO films of about 15μm thickness were prepared. Since these GO films have poor electrical conductivity and small specific surface area, they should be reduced in order to recover graphene like properties before being used as an electrode. For the reduction process, we employed an intense pulsed light (IPL) of Xe flash lamp and introduced a shadow mask between IPL and GO film during irradiation and the obtained photoreduced GO film showed improved properties compared to the photoreduced one without shadow mask. The photoreduced GO films were analyzed by Raman and infrared spectroscopy, and the electrochemical properties of supercapacitors with the GO electrodes were evaluated by cyclic voltammetry and impedance spectroscopy. The specific capacitance over 170 F/g was achieved.
Improvement of ORR Catalyst Layer with Highly Graphitized CNF in PEMFC
Authors: Chung Sunki , Lee Jae Kwang , Lee Jaeyoung
Published: February 2020

Polymer electrolyte membrane fuel cell (PEMFC) is regarded as a promising power source with the advantages of high power density and low operating temperature. However, there still remains water management problem. Water flooding is a phenomenon that the pores of the catalyst on gas diffusion layer are filled up with the excessive water produced near cathode side. And the pathway of oxygen (or air) could be blocked leading to the acceleration of the mass transfer limitation and degradation of durability because of the carbon corrosion reaction between carbon and water at cathode. Therefore, it is important to remain the right amount of water in membrane electrode assembly to keep the reaction working smoothly. In recent investigations,1,2 various types of catalyst layer structure have been studied in order to keep a proper humidity level in membrane electrode assembly (MEA) and reduce the oxygen transport resistance.

In this study, we incorporate a highly graphitized carbon nanofiber (CNF) into cathode catalyst layer for improvement mass transfer in PEMFC, and found out that graphitic CNF might serve as a pathway of water drainage and also diminish the ohmic losses due to the improved electrical conductivity of the electrode.

References

J. Joo, M. Choun, K. Kim, S. Uhm, Y. D. Kim and J. Lee, Curr. Appl. Phys., 14, 1374 (2014).

M. Choun, D. Nauryzbayev, D. Shin and J. Lee, Catal. Today, 262, 155 (2016).
Photodynamics at the Heterojunction between Semiconducting Single-Walled Carbon Nanotubes and Perylene Diimide Electron Acceptors
Authors: Kang Hyun Suk , Sisto Thomas J , Peurifoy Samuel , Zhang Boyuan , Ferguson Andrew John , Nuckolls Colin , Blackburn Jeffrey L.
Published: February 2020

Semiconducting single-walled carbon nanotubes (s-SWCNTs) have been intensively studied in optoelectronic applications due to several advantages such as band gap tunability, high charge carrier mobility, and low internal reorganization energy. However, the fundamental aspects of exciton dissociation at heterojunctions between s-SWCNT and electron acceptors still remain elusive. Here, we investigate the detailed photodynamics at the heterojunction between (6,5) SWCNTs and perylene diimide (PDI) based electron acceptors. While a number of studies have demonstrated efficient charge transfer at interfaces between s-SWCNTs and fullerenes, as well as s-SWCNT-fullerene photovoltaic devices with high internal quantum efficiencies, studies paring s-SWCNTs with non-fullerene acceptors are rare. PDI-based electron acceptors have several potential advantages over fullerene acceptors such as broader absorption, cheaper cost, higher robustness, and greater spectral tunability.

Two novel PDI-based electron acceptors were synthesized and coated on (6,5) SWCNT films to form donor-acceptor heterojunctions. The PDI-based electron acceptors are hPDI2-pyr-hPDI2, where pyrene (electron donor) is covalently connected to PDI oligomers (hPDI2), and Trip-hPDI2, where hPDI2 is connected to each side of triptycene. The steric hindrance from these acceptors prevents excessive aggregation, which has been a significant problem for PDI-based electron acceptors. Transient absorption studies reveal that the photoinduced electron/hole transfer at the (6,5)/PFO-bpy – PDI-based acceptor heterojunction occurs, and the separated charges live longer than 1.5 μs. For the photoinduced electron transfer from (6,5) SWCNTs to PDI-based acceptors, the electron transfer to hPDI2-pyr-hPDI2 occurs more efficiently than to Trip-hPDI2, and it is attributed to weaker electron transfer driving force for Trip-hPDI2 due to its higher LUMO level than that of hPDI2-pyr-hPDI2. Charge transfer across these s-SWCNT/PDI interfaces will be compared to the more commonly studied SWCNT/C60 interfaces.

These fundamental photophysical studies provide insight into how different electron acceptor materials can impact the s-SWCNT heterojunction energetics and how the energetics impacts the kinetics of exciton dissociation and charge recombination. The results help to inform design strategies for s-SWCNT-based solar photoconversion systems.
Tunable Surface Modification of Mesoporous Carbon Nanoparticles for Polysulfide Trapping in Lithium-Sulfur Batteries
Authors: Murphy Ian Alexander , Li Yun , Jang Sei-Hum , Yang Jihui , Jen Alex
Published: February 2020

Lithium-Sulfur (LiS) batteries are a front runner for next-generation secondary battery systems. This is partially due to the low cost, relative abundance, and environmentally benign nature of their active materials, but arguably most important is the order of magnitude increase in theoretical specific capacity of LiS cells compared to current state of the art lithium-metal oxide systems (~1,600 mAhg-1 vs ~160mAhg-1, respectively). Despite these inherent benefits, the commercialization of LiS systems has been impeded by a rapid loss of capacity upon repeated cycling due to the complexities of lithiation and delithiation at the carbon/sulfur composite cathode.

During discharge, elemental sulfur is sequentially reduced to lithium sulfide following the reaction S8 + 16Li+ + 16e-→ 8Li2S, where intermediates Li2S(8-2) are formed, their length depending on depth of discharge. Long-chain lithium polysulfides (LiPS), Li2S(8-4) are highly soluble in organic electrolytes and, once solvated, will migrate to the lithium metal anode. This leads to permanent capacity loss and internal shorting via lithium polysulfide redox shuttling. To combat this limitation, extensive efforts have been focused on trapping long-chain LiPS by both: 1. physically confining them in mesoporous carbons, and 2. chemically inducing electrostatic attractions with electron rich heteroatoms on the cathode.

In this work we not only aim to find synergy between these two approaches, but also investigate the potential for doubling the binding energy of electrostatic interactions by covalent tethering of long chain LiPS to the cathode surface via reversible di-sulfide bonding. Through a highly tunable one-step reaction, we functionalize mesoporous carbon surfaces with aromatic small molecules using in-situ generation of diazonium radicals. The flexibility of our approach allows for the introduction of a wide variety of surface functionality, and thus a platform to broaden our understanding of cathode/electrolyte interactions.

Our current progress focuses on the spectroscopic, physical, and electrochemical characterization of a thiophenol terminated carbon. Through this work we have demonstrated not only successful modification of carbon particles, but an ability to control the density of modifier groups on the surface. In conjunction with finding an optimal concentration of surface modifiers, we investigate the role of modifiers and carbon pore size in modulating the kinetics and capacity retention of LiS cells. By optimizing pore-size and modifier concentration, we have drastically increased the cycle life of our devices, which maintain >900 mAhg-1 over 150+ cycles at 0.1C. We hypothesize that the mechanism responsible for this improvement is a reversible covalent interaction based on electrochemical measurements, which indicate a concentration-dependent shift toward solid-phase reaction pathways.
(Invited) Non-Covalent Functionalization of Carbon Nanomaterials for Enzyme Electrochemistry
Authors: Ramasamy Ramaraja P.
Published: February 2020

Carbon nanostructures such as fullerenes, graphene and carbon nanotubes play an important role in biological electrochemistry as they serve as both immobilization supports for variety of biomolecules as well as act as nanostructured conductive carriers for transport of electrons to the active sites of the biomolecules. Accordingly, carbon nanostructures are used as conductive matrices in bioelectrochemical systems such as biosensors and biological fuel cells. Herein we report a specific type of biomolecule immobilization chemistry, which has had tremendous success towards the functionalization of carbon nanostructures with enzymes, antibodies, aptamers, cells, organelles and sub-organelles. The chemistry involves the use of a molecular cross-linker such as 1-pyrene butanoic acid-succinimidyl ester (PBSE), which contains an aromatic moiety and a covalent binding group on either sides of a long alkyl chain. The aromatic ring (pyrene or similar moiety) binds to the carbon nanotube or graphene non-covalently through the interaction of pi-pi bonds between the carbon nanostructure and the aromatic moiety. The interaction is strongly dependent on the material properties of the nanostructure such as chirality of nanotubes, curvature and electronic properties. The covalent binding group on the other end of molecular cross-linker is usually an amine-binding group such as succinimidyl ester. The interaction of the succinimidyl ester with the surface amines groups of enzymes, cell membranes and other biomolecules result in irreversible attachment of the cross-linker with the biomolecules resulting in a stable immobilization of biomolecules on carbon nanostructures. The presentation will discuss the strategies and methods to improve the stability of biomolecules on carbon nanostructures through this non-covalent functionalization.
Carbon Nanotube-Based Sensors for Early Cancer Detection
Authors: Heller Daniel A , Budhathoki-Uprety Januka , Galassi Thomas Vito , Frederiksen Rune , Harvey Jackson , Horoszko Christopher Peter , Jena Prakrit Vaibhav , Langenbacher Rachel E , Roxbury Daniel , Shah Janki , Williams Ryan M. , Baker Hanan
Published: February 2020

The early detection of cancer could lead to vastly improved patient outcomes. We aim to identify cancer biomarkers within the body at early disease stages, permitting detection before symptoms arise. We are developing implantable nanosensors, using the unique optical properties of carbon nanotubes, to facilitate non-invasive detection via optical detection through living tissues. The sensors could enable early detection of cancer in people at high risk for the disease, in successfully treated patients to monitor recurrence, or in patients who are undergoing treatment to inform clinical decisions.
(Invited) Near Infrared Chemical Imaging of Cellular Communication Using Carbon Nanotubes
Authors: Meyer Daniel , Mann Florian , Polo Elena , Hagemann Annika , Herrmann Niklas , Kruss Sebastian
Published: February 2020

Intercellular chemical communication proceeds with both spatial and temporal components. A very prominent example is neurotransmitter release from neurons. But so far there are no analytical tools available to detect release and propagation of signaling molecules on small length scales and fast time scales. We have developed fluorescent nanosensors to monitor interactions of cells with their environment e.g. for chemical imaging of small molecules released by cells.

For that purpose we used near infrared (nIR) fluorescent single-walled carbon nanotubes (SWCNTs) and chemically rendered them selective for small signaling molecules such as the neurotransmitter dopamine. When dopamine binds the quantum yield of the sensors increased by up to 400 % and we were able to report single dopamine binding events. Parallel imaging of many of those sensors provides a nIR image (900 nm -1300 nm) of the dopamine concentration around cells. Furthermore, we used a stochastic kinetic Monte-Carlo simulation to predict the collective image of many sensors and how on and off rate constants affect the spatial and temporal resolution of this approach. This technique was used to image hot spots and directionality of dopamine release from neurons and other cells. We observed localized, unlabeled release sites that correlate with membrane curvature and cell morphology.

We furthermore tailored SWCNTs to bind cell surface receptors such as integrins to monitor and investigate cell adhesion and migration on surfaces. These results illustrate how to use fluorescent nanosensors for quantitative chemical imaging of complex biological processes.
(Invited) Probing the Intracellular Fate of Carbon Nanotube-Based Near-Infrared Sensors
Authors: Safaee Mohammad , Gravely Mitch , Restrepo David , Roxbury Daniel
Published: February 2020

With the advent of nanotechnology in the diagnosis and treatment of cancer, many questions arise regarding whether novel nanomedicines, nanosensors, and nanoimaging agents are detrimental to living things. At a fundamental level, minute variations in size, shape, and charge can have overwhelming effects on the manner in which a live cell or animal will interact with a nanoparticle. A biomolecular corona, comprising proteins, carbohydrates, lipids, and small molecules, is known to form around nanoparticles and affects everything from the uptake of the nanoparticles into cells to the internal compartmentalization, processing, and eventual expulsion of the nanoparticles from the cells.

The intrinsic band-gap photoluminescence (fluorescence) of single-walled carbon nanotubes (SWCNTs) exhibits exceptional photostability, narrow bandwidth, near-infrared (NIR) tissue-penetrating emission, and microenvironmental sensitivity, enabling their usage in a variety of biomedical imaging and sensing applications. Of recent interest, a biocompatible formulation of carbon nanotubes has been used in the construction of a live-cell lipid accumulation sensor, a condition implicated in a variety of cancers. Additionally, fluorescent carbon nanotubes have been used to interrogate the permeability in multicellular tumor spheroid models. The biological identity of the nanotube sensor inside of the cell has not been thoroughly investigated. Here, by manipulating its composition, we examine the effects that the biomolecular corona has in determining the interactions between carbon nanotubes and live cells. In particular, we study the internalization, processing, toxicity, and long-term fate of the nanomaterial complexes in various types of mammalian cells. With a fundamental mechanistic understanding of the interactions between carbon nanotubes and live cells, we are able to engineer nanosensors with the most reduced toxicities, enhanced stabilities, and highest overall effectiveness.
(Invited) High Aspect Ratio Nanomaterials Enable Biomolecule Delivery and Transgene Expression or Silencing in Mature Plants
Authors: Demirer Gozde , Chang Roger , Zhang Huan , Chio Linda , Landry Markita P
Published: February 2020

Genetic engineering of plants is at the core of environmental sustainability efforts, natural product synthesis of pharmaceuticals, and agricultural crop engineering to meet the needs of a growing population changing global climate. The physical barrier presented by the cell wall has limited the ease and throughput with which exogenous biomolecules can be delivered to plants. Current techniques suffer from host range limitations, low transformation efficiencies, toxicity, and unavoidable DNA integration into the host genome. Herein, we demonstrate efficient diffusion-based plasmid DNA and small interfering RNA (siRNA) delivery into two species of mature plants with a suite of pristine and chemically-functionalized high aspect ratio carbon nanomaterials (Figure 1). Efficient DNA delivery and strong transient protein expression is accomplished in mature Eruca sativa (arugula) leaves with covalently-functionalized or pristine single-walled and multi-walled carbon nanotubes, with efficiencies comparable to agrobacterium based transfection. We also demonstrate nanotube-based transient protein expression in cell wall-free arugula protoplasts with 85% transformation efficiency. Lastly, we demonstrate a second nanoparticle-based strategy in which siRNA is delivered and activated in the Nicotiana benthamiana plant cell cytosol, effectively silencing a gene with 95% efficiency. Our work provides a promising tool for species-independent, targeted, and passive delivery of genetic material, without transgene integration, into plant cells for rapid and parallelizable testing of plant genotype-phenotype relationships.

Figure 1
(Invited) Nanoelectronic Lab-on-a-Chip DNA Sensors Based on Nanocarbon Materials
Authors: Bouilly Delphine
Published: February 2020

Nanoelectronic devices based on functionalized nanocarbon materials are emerging as a promising technology for lab-on-a-chip, molecular-scale biosensors. In this presentation, I will present the design and operation of such sensors to detect and monitor DNA sequences. Carbon nanotubes or graphene channels are immersed in microfluidics and functionalized with single-stranded DNA. Hybridization of complementary sequences with the tethered DNA induces a specific change in the electrical conductance of the devices. I will present recent experiments based on this design to detect specific DNA sequences and to monitor their dynamic interactions with single-molecule resolution.
Facial and Controllable Hydrothermal Synthesis of Manganese Doped Carbon Quantum Dots for Targeted Fluorescence and Biomedical Applications
Authors: Girma Wubshet Mekonnen , Lin Jin-Sheng , Chang Jia-Yaw
Published: February 2020

Herein, we developed facial greener approach for the synthesis of water-soluble heteroatom-doped Carbon quantum dots (CQDs). Doping heteroatom into CQDs, not only creates surface functional groups but also changes the electronic distribution. One-pot microwave-assisted synthesis was used for the synthesis of heteroatom-doped CQDs: prepared by doping the heteroatom into CQDs (Mn@CQDs). The higher quantum yields (QY) and optical properties of Mn@CQDs suggest that, a potential for the use fluorescent imaging agents. The blue emitting Mn@CQDs were conjugated with hyaluronic acid (HA) forming HA-Mn@CQDs, which enabled higher biocompatibility, less toxicity, and targeting capability. The targeting ability was confirmed towards CD44 overexpressed B16F1 cells and CD44 negative HeLa cells. Subsequently, our results showed that this synthesized multifunctional Mn@CQDs have excellent magnetic, fluorescent and structural properties enabled us to use for dual modal in vitro fluorescence and MR imaging. A chemotherapeutic application was done using doxorubicin (DOX) as a model drug for conjugation with HA-Mn@CQDs termed as HA-Mn@CQDs/DOX which enabled targeted drug delivery system. The as-prepared nanocomposite displayed apparent toxicity to B16F1 cells (CD44 positive). The in vitro and in vivo cytotoxicity results showed that heteroatom-doped carbon quantum potential uses for diagnostic and therapeutic applications.

KEYWORDS. Heteroatom-doped, hyaluronic acid, fluorescent imaging, MR imaging, targeted drug delivery
(Invited) Room-Temperature Single Photon Emission from Micrometer-Long Air-Suspended Carbon Nanotubes
Authors: Ishii Akihiro , Uda Takushi , Kato Yuichiro K.
Published: February 2020

Carbon nanotubes have a potential for becoming an ideal single-photon source as they have stable exciton states even at room temperature and their emission wavelengths cover the telecommunication bands. In recent years, single photon emission from carbon nanotubes has been achieved by creating localized states of excitons. In contrast to such an approach, here we utilize mobile excitons and show that single photons can be generated at room temperature in air-suspended carbon nanotubes with lengths of several microns [1]. We perform photoluminescence microscopy on as-grown air-suspended carbon nanotubes in order to determine their chirality and suspended length. Photon correlation measurements are performed on nanotube emission at room temperature using a Hanbury-Brown-Twiss setup with InGaAs single photon detectors. We observe antibunching with a clear excitation power dependence, where we obtain g
(2)(0) value less than 0.5 at low excitation powers, indicating single photon generation. We show such g
(2)(0) data for different chiralities and suspended lengths, and the effects of long exciton diffusion lengths and efficient exciton-exciton annihilation [2] on single photon generation processes are discussed.

Work supported by JSPS (KAKENHI JP16H05962) and MEXT (Photon Frontier Network Program, Nanotechnology Platform). T.U. is supported by ALPS and JSPS Research Fellowship.

[1] A. Ishii, T. Uda, Y. K. Kato, Phys. Rev. Applied, in press. Preprint available at arXiv:1707.05435 (2017).

[2] A. Ishii, M. Yoshida, Y. K. Kato, Phys. Rev. B 91, 125427 (2015).
(Invited) Nanoscale Imaging of Luminescent Excitons in sp3-Doped Ultra-Short Carbon Nanotubes
Authors: Danné Noémie , Kim Mijin , Godin Antoine G , Kwon Hyejin , Gao Zhenghong , Wu Xiaojian (James) , Hartmann Nicolai F. , Doorn Stephen K. , Lounis Brahim , Wang YuHuang , Cognet Laurent
Published: February 2020

Exciton localization in luminescing carbon nanotubes is subject of intense investigations due to its impact on nanotube emission properties. Using super-resolution microscopy based on single emitter localization, I will present our current efforts to study luminescent defect localization in ultra-short carbon nanotube having controlled chemical and morphological properties [1].

References

[1] Danné et al in preparation
(Invited) Cryogenic Spectroscopy of Chemistry-Modified Carbon Nanotubes
Authors: Högele Alexander
Published: February 2020

Covalent chemistry of semiconducting carbon nanotubes has emerged recently as a new tool to engineer and control photofunctional nanosystems down to the level of single molecular defects. Here, we report on our recent results obtained with photoluminescence and magnetoluminescence spectroscopy of individual defect-modified carbon nanotubes at cryogenic temperatures.
Aqueous Based Asymmetrical-Bipolar Electrochemical Capacitor with a 2.4 V Operating Voltage
Authors: Wu Haoran , Lian Keryn
Published: February 2020

A novel aqueous-based asymmetrical-bipolar electrochemical capacitor (EC) was developed. The EC device has leveraged the contributions from a Zn-CNT asymmetrical electrode and a KOH-H2SO4 dual-pH electrolyte. The positive and the negative electrodes operate in their respective electrolytes that have different pH values, leading to a cell voltage of 2.4 V. The potential tracking of both electrodes reveals that the Zn negative electrode maintains a potential of -1.2 V, while the CNT positive electrode is charged and discharged reversible up to +1.2 V. A bipolar ion exchange membrane effectively separates the acid and the alkaline from neutralizing. As a result, the aqueous-based asymmetrical-bipolar EC device has shown stable performance with a capacitance retention of 94 % and a coulombic efficiency of 99% over 10,000 cycles. The asymmetrical-bipolar design overcomes the thermodynamic limitation of water decomposition of the aqueous-based electrolyte, paving a new avenue towards aqueous-based ECs and energy storage systems with both high energy and power density.

Figure 1
(Invited) Photoluminescence from an Individual Double-Walled Carbon Nanotube
Authors: Michel Thierry , Levshov Dmitry , Paillet Matthieu , Arenal R. , Popov Valentin , Parret Romain , Nguyenvan Chuc , Rochal Sergei , Zahab Ahmed , Sauvajol Jean-Louis
Published: February 2020

In this communication, we report direct and unambiguous evidence of the existence of inner semiconducting tube photoluminescence (PL) from measurements performed on four individual freestanding index-identified double-walled carbon nanotubes (DWNTs). Based on thorough Rayleigh scattering, Raman scattering, and PL experiments, we are able to demonstrate that the inner semiconducting tube PL is observed with a quantum yield estimated to be a few 10-6 independent of the semiconducting or metallic nature of the outer tube. This result is mainly attributed to ultrafast exciton transfer from the inner to outer tube. Furthermore, by carrying out PL excitation experiments on the (14,1)@(15,12) DWNT, we show that the inner semiconducting tube PL can be detected through the optical excitation of the outer tube, indicating that the exciton transfer can also occur in the opposite way.
A New Method for Quantifying SWCNT Dispersion Quality from Absorption Spectra
Authors: Zheng Yu , Sanchez Stephen R. , Bachilo Sergei M. , Weisman R. Bruce
Published: February 2020

Individualization of single-walled carbon nanotubes (SWCNTs) in aqueous surfactant dispersions can vary greatly. We will present a new method for quantitatively assessing dispersion quality based on simple absorption spectra. In this method, the visible and short-wave infrared portions of a sample’s absorption spectrum are modeled as a superposition of two components. One component (labeled “S”) has sharp resonant features and is associated with the subpopulation of SWCNTs that are suspended as individuals or very small aggregates; the other (labeled “B”) has broad absorption features and is associated with stably dispersed materials such as carbonaceous impurities, imperfect nanotubes, and larger aggregates. Using absorption spectra from samples in various stages of purification by centrifugation or magnetic processing, we apply the method of multivariate curve resolution to extract the S and B component spectra and determine their relative contributions in samples of interest. The ratio of S to B content then provides a simple index of dispersion quality. We illustrate this new characterization method with measurements on both shear-dispersed and tip-sonicated SWCNT samples purified by three different processes: centrifugation, ultracentrifugation, and magnetic purification. We determine the dispersion efficiency of each sample preparation and find results that correlate well with those of established analytical techniques. In addition, we have further characterized the effects of these purification processes on the SWCNT length distribution (using the diffusion-based LAND method) and on SWCNT emissive properties (through variance spectroscopy). We believe that our new absorption-based method provides a practical tool for quickly assessing the dispersion quality of SWCNT samples.
Apply Intermittent Current Strategy to Discharge Li-O2 Batteries
Authors: Wang Fangzhou , Li Xianglin
Published: February 2020

This study periodically rests Li-O2 batteries (for 5-10 min) between each discharge (for 2-10min) to improve the oxygen transfer within the porous electrode. Periodically resting the battery increases the specific discharge capacity by at least 50% at various current densities (0.1 - 1.5 mA/cm2). The performance improvement is mainly due to the enhanced O2 diffusion during rest between intermittent discharge. The customized electrode is fabricated by mixing acetylene black with polytetrafluoroethylene (PTFE) binder. The contact angle measurement shows that PTFE binder results in the lyophobicity of the electrode. The specific discharge capacity is 1629.5 ± 124.0 mAh/g at intermittent discharge current of 1.0 mA/cm2 while it is 1031.0 ± 22.8 mAh/g at continuous discharge current of 1.0 mA/cm2. Discharge plateaus are elongated and stabilized when the Li-O2 batteries are discharged intermittently. Multistep discharge at decreasing current rates (2.0, 1.5, and 1.0 mA/cm2) is also proposed to increase the overall discharge capacity with a given cutoff voltage. The specific discharge capacity can be increased from 423.4 ± 29.1 mAh/g to 855 ± 49.9 mAh/g when the multistep strategy is applied. This study emphasizes the importance of O2 diffusion and provides practical strategies to improve the deep discharge capacity of Li-O2 batteries, especially at high current rates (> 1.0 mA/cm2).
Gas Atmosphere Effects over the Anode Compartment of a Tubular Direct Carbon Fuel Cell Module
Authors: Glenn Michael , Mathan Bobby , Islam Monirul , Beyad Yaser , Allen Jessica A , Donne Scott W
Published: February 2020

The direct carbon fuel cell (DCFC) is an innovative low carbon technology option that has the potential to cause a paradigm shift in the way we generate electrical energy from coal resources. The technology is theoretically 100% efficient at extracting chemical energy of a carbon feedstock, with practically realizable cell efficiencies approaching 80% (cf. <40% in a state-of-the-art coal-fired power station). Since the reaction is the direct electrochemical generation of carbon dioxide, the flue gas has the potential to be pure, sequestration ready carbon dioxide with zero particulates with little to no flue gas treatment required.

This study examines the performance of a tubular 8 mol% yttria stabilised zirconia (YSZ) cell using a thermal coal char as the fuel, lanthanum strontium manganate (LSM) as the cathode material and a ternary alkali metal carbonate eutectic as the secondary electrolyte over the temperature range 700-900°C. The performance was compared when varying the gas atmosphere over the anode compartment between CO2 and N2 in separate experiments. It was found that the power density was two-fold as high under CO2 at 860°C. The reason for this is attributed to agitation provided to the fuel from reverse Bouduard gasification. This result implies that the anode performance is limited by mass transport of the carbon fuel to the silver current collector.
Fabrication and Characterization of Crystalline Thin Film MoS2 Prepared By RF Magnetron Sputtering
Authors: Gustavsen Kim R , Wang Kaiying
Published: February 2020

Thin film molybdenum disulfide (MoS2) exhibits unique physical and electrochemical properties. Most notably MoS2 has shown itself to be a viable candidate as an earth abundant catalyst for the hydrogen evolution reaction (HER) [1-3]. However, preparation of quality MoS2 thin films often involves complex synthesis techniques not capable of large-scale production. In this paper we present a study of thin film MoS2 prepared by radio frequency (RF) magnetron sputtering, which is an industrial large-scale thin film fabrication method. Substrate temperature during deposition and its effect on the morphology, electrical – and optical properties of the sputtered MoS2 thin films will be investigated.

The MoS2 thin films were deposited at room temperature (RT) and 400°C using an Argon atmosphere with a pressure of 5.9 mTorr, and RF power of 150W. Following deposition the samples were annealed at 550°C for three hours. A visual representation of the thin film MoS2 on quartz substrate after the annealing process is seen in Figure 1. Visually the MoS2 films have a gold brown color, where the sample deposited at room temperature is slightly darker. The absorbance spectra (250-850 nm) show that the film deposited at room temperature display no peaks associated with MoS2, while the thin film deposited at 400°C show a small 'C' transition peak at ~418 nm (Figure 2). Post annealing absorbance spectra of both films indicate the four transition peaks characteristic of MoS2. The 'A' and 'B' peaks are direct transitions related to the band-edge excitons, whereas the 'C' and 'D' absorbance peaks arise from van Hove singularities in the electronic density of states associated with layered MoS2 [4,5]. X-ray diffraction (XRD) was performed using a Si substrate and the existence of the (002) plane indicates that the thin films are crystalline (Figure 3).

In conclusion, we have determined the effect of substrate temperature during deposition and post annealing on the properties of the MoS2 thin films. Additionally, preparation of crystalline MoS2 has been demonstrated using a large-scale thin film production technique. The morphology, optical – and electrical properties have been studied on ITO glass and quartz substrates.

References

Wang, D.; Zhang, X.; Bao, S.; Zhang, Z.; Fei, H. & Wu, Z. J. Mater. Chem. A, The Royal Society of Chemistry, 2017, 5, 2681-2688

Hong Li, C. T., Ai Leen Koh, Lili Cai, Alex W. Contryman, Alex H. Fragapane, Jiheng Zhao, Hyun Soo Han, Hari C. Manoharan, Frank Abild-Pedersen, Jenk K. Nørskov, and Xiaolin Zheng (2016). Nature Materials 15

Haotian Wang, C. T., Desheng Kong, Karen Chan, Frank Nano Reasearch 8: 566-575.

Mak, C. Lee, J. Hone, J. Shan, and T. Heinz, Phys. Rev. Lett. 105, 136805 (2010).

Britnell et al., Science 340, 1311 (2013).

Figure 1
An Iodide-Based Complexing Agent for the Zinc-Iodide Flow Battery
Authors: Shakeri Hosseinabad Fatemeh , Yasri Nael , Roesler Roland , Maslovara Sladjana , Roberts Edward
Published: February 2020

The effect of iodide-based complexing agent on the electrochemical performance of zinc-iodide flow battery was investigated. The addition of a complexing agent that will stabilize triiodide during charging can reduce the self-discharge and increase the charge and voltaic efficiency. The hydrogen evolution and kinetics of the both electrode reactions in the presence of the complexing agent was assessed. Cyclic voltammetry and Tafel analysis were performed to evaluate the influence of complexing agent on zinc electrochemical kinetics. The results indicated that the complexing agent enhances the cell performance by increasing the kinetics, which will enable operation of the battery at increased current density, or increases in the charge-discharge efficiency. At the positive electrode a deposit was observed on the electrode surface. The deposit was characterized by SEM and EDS and the deposition process was found to change significantly in the presence of the complexing agent. The charge-discharge characteristics of the electrolyte system were investigated in an H-type glass cell, and polarization curves were obtained for the two half-cell reactions.
Macroporous Lithium Battery Cathodes Prepared By Aqueous Freeze Casting
Authors: Creager Stephen E , Azami-Ghadkolai Milad , Ventrapragada Lakshman K , Bordia Rajendra
Published: February 2020

Battery electrode microstructure strongly affects the mixed ionic / electronic conduction in electrodes that is necessary to achieve rapid charging / discharging, especially in very thick electrodes. Thick electrodes having low porosity will not provide access of the full electrode structure to electrolyte ions, which will limit the effective capacity at high rates. One strategy for combating this limitation is to incorporate macroscopic pores into the electrode. Electrolyte-filled macropores provide an electrolyte reservoir that can provide ions needed for rapid charging / discharging of a thick electrode, due to the shorter overall distance that ions have to travel during charge / discharge. This talk will present recent work on the use of freeze tape casting with water-based electrode slurries to create thick electrodes having large macroscopic through-pores that run perpendicular to the electrode plane. Electrodes having similar mass loading can be charged / discharged more rapidly when these macropores are present, compared with electrodes that do not have macropores. Implications of the work for fabrication of very thick electrodes capable of rapid charging / discharging will be discussed.

Figure 1
(Battery Division Research Award) Forming Interphases
Authors: Xu Kang
Published: February 2020

Solid electrolyte interphases (SEI) enable the battery chemistries to maximize energy density by operating beyond the thermodynamic stability limits of non-aqueous electrolytes 1
,2. The chemical building blocks of SEI come from the decomposition of either solvents or salt anion, depending on a host of interwoven parameters such as the HOMO/LUMO energy levels of these components (reduction/oxidation stability) as well as their interactions (solvation sheath structures). Designing electrolytes for new battery chemistries requires understanding of interphasial chemistries and the ability to manipulate them. This talk summarizes our efforts in interfacing various electrode chemistries to electrolytes of non-aqueous, aqueous and hybrid natures.

Reference
s
:

[1] K. Xu, Chem. Rev.,
2004, 104, 4303

[2] K. Xu, Chem. Rev.,
20
1
4, 1
1
4, 11503
(Battery Division Postdoctoral Associate Research Award Sponsored by MTI Corporation and the Jiang Family Foundation) Stable Li Metal Anode through Designed Solution Chemistry and Electrode Architecture
Authors: Liu Haodong , Liu Ping
Published: February 2020

Lithium metal is being extensively studied as an anode to replace graphite due to its high capacity and the lowest negative electrochemical potential. Current research focus is to mitigate lithium dendrite growth and to increase coulomb efficiency during electrochemical cycling by using various surface coatings, electrolyte additives. In addition, a 3D host can be beneficial due to the reduced volume change.

We have recently focused on designing interfacial chemistries that enable dendrite free cycling. In this regard, we report the synthesis of lithium methyl carbonate, a known compound in common anode SEI, via a simple one step reaction. This reaction is used to coat Li or Cu with a protection layer of pure LMC, which is supported by the cryo-TEM observations.1 This coating layer is shown to enable dendrite free Li cycling in a symmetric Li||Li cell even at a current density of 3 mA cm-2.2 Moreover, FIB-SEM shows this LMC coating layer loses thickness once it is transferred into EC/DMC, which reveals that it dynamically dissolves into the carbonate electrolyte. In order to enhance the sustainability of the LMC coating layer in commercial electrolytes, LMC powder is used to pre-saturate the organic electrolyte. As a consequence of the two strategies, the Li cycling CE in a commercial carbonate electrolyte is significantly improved from 90.5% to 96.1%. These findings provide new insights on designing effective protection layers and managing sustainable SEI formation for stable Li cycling. Recently, we have extended the one step reaction approach to the formation of a polymer gel electrolyte which enables the Li/Li cell cycled for 1000 hours without increase of resistance at a current density of 5 mA cm−2. Finally, we will discuss recent progress on a novel 3D electrode design that enables dendrite free and high coulombic efficiency of Li metal cycling in carbonate electrolytes.

Acknowledgements

This work was supported by the Office of Vehicle Technologies of the U.S. Department of Energy through the Advanced Battery Materials Research Program (Battery 500 Consortium) under Contract DE-EE0007764. Part of the work used the UCSD-MTI Battery Fabrication Facility and the UCSD-Arbin Battery Testing Facility.