bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrophilicity Control of Laser Induced Amorphous Carbon Capsuled Carbon Nano-Onions and Application for Proton Exchange Membrane Fuel Cells Under Low Humidity
Authors: Yeon Je Hyeon , Choi Jiwoo , Jang Segeun , Choi Mansoo
Published: May 2020

Proton exchange membrane fuel cells (PEMFC), which are promising eco-friendly energy sources, need to operate under low humidity conditions in order to be applied for small electrical devices. In such low relative humidity condition, hydration of membrane electrode assembly in the fuel cell system is an important key to prevent performance degradation due to decreased ion conductivity of the Nafion® membrane. Herein, amorphous carbon capsuled carbon nano-onions (AC-CNO) were prepared by irradiating a laser to gaseous hydrocarbons flame capable of mass continuous production. The particles have high-quality graphitic layers in the form of spherical multi-shelled fullerenes and the outermost layer is surrounded by oxygen functionalized amorphous carbon. The particles of various sizes with the same morphology can be produced, and the hydrophilicity of particles with different sizes varies due to the structural characteristics in the catalyst layer and the amount of -OH functional groups attached to the amorphous carbon. The Pt/AC-CNO-3 catalyst layer made of AC-CNO with an average size of ~170nm was deposited on the anode electrode and the membrane electrode assembly (MEA) shows the best performance under low humidity, compared to MEAs with commercial Pt/C deposition; the current density reached 1200mA/cm2 at 0.6V and maximum power density reached 1080mW/cm2 with operating at 50% RH, 80℃ cell temperature under 1.8bar back pressure, while 870mW/cm2 in case of commercial catalyst Pt/C.
(Invited) Surface Engineered Pure-Chirality Carbon Nanotubes with Carbohydrate Functionalities
Authors: Xhyliu Fjorela , Chan Ka Keung , Sun Xue-Long , Ao Geyou
Published: May 2020

Interest in the use of engineered nanomaterials for biological sensing and imaging applications continues to grow due to the vast potential of tuning the surface chemistry of nanomaterials using various biomolecules. Carbohydrate recognitions of specific proteins play a crucial role in many biological processes, including cellular adhesion, cell-cell communication, immune response, cancer development and metastasis. In addition, the highly predictable electronic structures and optical properties of chirality-defined SWCNTs offer many advantages for biochemical sensing and imaging advancement. This work explored the photochemistry of pure-chirality single-wall carbon nanotubes (SWCNTs) using galactose-containing glycopolymers to create engineered fluorescent probes with precise optical and carbohydrate functionalities. These SWCNT-based fluorescent probes can be potentially utilized for profiling targeted carbohydrate-protein interactions in complicated biological samples and in vivo analysis.
(Invited) Clearance of Single-Wall Carbon Nanotubes from the Mouse Lung: A Quantitative Evaluation
Authors: Zhang Minfang , Yang Mei , Yudasaka Masako , Okazaki Toshiya
Published: May 2020

The biodistribution of single-walled carbon nanotubes (CNTs) was quantified after intravenous administration to mice based on their absorption of near-infrared light. CNTs with two different diameters, 1–5 nm (Ld-CNT) or 0.7–0.9 nm (Sd-CNT), were compared. The accumulation of Ld-CNTs in the lung was less than that of Sd-CNTs, and both were cleared almost completely within 60 days. The rapid clearance of CNTs could be due to their degradation by macrophages and/or to their trafficking to other organs via the vasculature. In the liver and spleen, the accumulation of Ld-CNTs was greater than that of Sd-CNTs. The quantity of Ld- or Sd-CNTs in the liver decreased for about 10% of the dose in 60 days. These results were confirmed by histological analysis. Levels of the cytokines TGF-β1, IL-6, INF-γ, and TNF-α in the plasma and organs of mice injected with Ld- and Sd-CNTs were low, suggesting the low toxicity of Ld- and Sd-CNTs.
(Invited) Biomolecular Sensors Based on Nanocarbon Field-Effect Transistors: Advances in Design, Fabrication and Characterization
Authors: Bouilly Delphine
Published: May 2020

Nanoscale field-effect transistors (FETs) embedded in microfluidics form a promising technology as compact and portable lab-on-a-chip biosensors for applications in biology and medicine. Such sensors can be designed to monitor a variety of biochemical mechanisms, at the ensemble or single-molecule scale, through fluctuations in the electrical conductance of the circuit. In particular, nanocarbon materials, i.e. carbon nanotubes and graphene, are materials of choice for FET biosensors, due to their high electrical conductance, the sensitivity of their electronic properties to the surrounding environment, and the versatility of their carbon-based surface chemistry. In this presentation, I will report on recent developments and key considerations in the design, fabrication and characterization of such nanocarbon-based biomolecular FET sensors. In particular, I will discuss approaches for chemical functionalization and structural patterning of nanocarbon materials to optimize their coupling with molecules. I will also describe hardware and software developments for the analysis of single-molecule measurements in hybrid biomolecule-nanocarbon FET devices.
(Invited) Engineering Single Wall Carbon Nanotubes for Sub-Cellular Drug Delivery
Authors: Islam Mohammad F.
Published: May 2020

Single wall carbon nanotubes (SWCNTs) have been rigorously studied and engineered for a myriad of applications including drug delivery due to their unique, desirable properties. Since SWCNTs bundle in aqueous media and the bundling substantially diminishes their desirable properties along with inducing cytotoxicity, strategies to disperse individually SWCNTs with therapeutic molecules and biologic excipients have been heavily investigated. However, a handful of studies has been performed to understand the interactions between therapeutic molecules and excipients with SWCNT interface as well as the mechanism of intracellular release for therapeutic effects. Additionally, little attention has been paid to how cell type and cell metabolic activity level influence internalization of SWCNTs with different lengths. In this talk, I will discuss cell type, cell metabolic activity, and SWCNT length dependent cellular processing of SWCNTs dispersed with diverse biocompatible dispersing agents. Our results demonstrate that proper choice of dispersing agent can allow for interaction with F-actin, accumulation in the endoplasmic reticulum for eventual expulsion, or accumulation in cell nucleus. Further, macrophages with relatively high cell metabolic activity level compared to other cell types such as fibroblasts have shown to internalize significantly higher amount of SWCNTs per cell. The total mass of SWCNTs internalized per cell increases with a decrease in SWCNT length. Lastly, I will discuss our recent effort to create a ternary complex of SWCNTs, drug, and protein for intracellular delivery and release of model drugs. To overcome the limitation of the existing methods being only plausible for model drugs that are soluble in aqueous solutions, we developed a facile schema to assemble stepwise various combinations of therapeutic molecules and excipients on SWCNTs in different solvents using a preformed SWCNT network. These ternary complexes allow dialing in delivery of therapeutic molecules and excipients to achieve desired cell viability reduction. These findings allow for the development of new SWCNT-based biological applications as they establish important parameters of biomolecule adsorption on SWCNTs, SWCNT internalization and subcellular processing, which are crucial for applications ranging from drug delivery to cell type-specific modulation.
(Invited) Creating Optical Nano-Biosensors from Engineered Antibodies for Protein Detection
Authors: Corrie Simon , Islam Jiaul
Published: May 2020

Biosensors based on fluoro-labelled antibody fragments combine the recognition and transduction element into the same molecule leading to real-time result detection and reducing the need for laborious, multi-step assays. The key challenge is the efficient site-specific modification of antibodies with environmentally-sensitive fluorescent dyes, without affecting binding functionality. Fluorescence labelling via unnatural amino acids (UAAs) is a relatively new and highly efficient method for 100% efficient site-specific fluorescence labelling, and can be genetically incorporated into any permissible site during protein synthesis. Although over 100 UAAs have been incorporated into various proteins for diverse applications including antibody drug conjugates and bispecific antibody development using Fab, to date none of the UAAs has been incorporated into scFv for biosensing applications nor has this been used for detection of large biomolecules (e.g. protein).

We demonstrate that incorporation of environmentally sensitive fluorescent UAA (Anap) into a permissible site of antibody fragments (e.g. anti-EGFR scFv) can be used for detection of target binding by monitoring the wavelength and/or intensity changes in emission spectra. A mutation screen was initially performed in order to identify the Anap mutation site that yielded the largest spectral change. We found that, across two different protein/antibody case studies, that only relatively hydrophobic amino acids within the binding interface could be mutated to generate optically-reactive species, and that the affinity of the mutants was not significantly affected. When immobilising these antibody fragments onto various surfaces (e.g. silica, carbon nanotubes, polymeric nanoparticles) for solid-phase biosensor development, we also observed unique behaviour indicative of the local hydrophilicity of the surface environment, which may be advantageous in identifying optimal surfaces for high specificity and sensitivity in complex biological environments. Here we will present our latest results on generalising this approach for protein detection in complex biological environments, and also to outline the challenges and opportunities for future developments

Figure 1
Carbon Nanotube Sensor Passivation Mitigates Inflammatory Response in Microglia
Authors: Yang Darwin , Landry Markita P
Published: May 2020

Non-covalent functionalization of single-walled carbon nanotubes (SWCNTs) has enabled advances in biomolecule imaging. In particular, modification of SWCNTs with select sequences of single-stranded DNA (ssDNA) produces near infrared optically active sensors for neurotransmitters such as dopamine, enabling high spatiotemporally resolved optical recording of synaptic and extrasynaptic signaling. However, the carbon lattice surface of SWCNT induces activation of the innate immune system, leading to an inflammatory response. Activation of microglia, the brain’s resident immune cells, is of particular relevance to imaging neuromodulation. Here, we show that non-covalent ssDNA-SWCNT nanosensor passivation with a PEGylated phospholipid can mitigate microglial activation while maintaining the nanosensor’s response towards dopamine. To do so, we screen a candidate library of PEGylated biomolecules, nonionic surfactants, and block copolymers against their ability to mitigate the microglial immune response as measured by transcriptomic analysis. We find that PEGylated phospholipids are capable of adsorption to ssDNA-SWCNTs without significant ssDNA displacement, with moderate reduction in nonspecific protein adsorption. These trends are recapitulated by a reduction in inflammatory response of SIM-A9 microglial cells, marked by lowered expression of cytokines CXCL2 and IL-6, mitigated morphological change, and decreased cytotoxicity. Taken together, these results suggest noncovalent passivation improves biocompatibility of DNA-SWNCT nanosensors and provides the groundwork for implementing similar passivation methods for other optical probes of this class.
Graphene Quantum Dots As Intracellular Imaging-Based Temperature Sensors
Authors: McKinney Ryan Lee , Hasan Md Tanvir , Naumov Anton V
Published: May 2020

Non-invasive temperature sensing is necessary for the analysis of biological processes occurring in the human body including cellular enzyme activity, protein expression, and ion regulation. Considering that a variety of such biological processes occur at the microscopic scale, a novel mechanism allowing for the detection of the temperature changes in microscopic environments is desired. One-dimensional graphene quantum dots can serve as agents for such detection: they are promising non-invasive probes that because of their 2-5 nm size and optical sensitivity to temperature change enable sub-cellular resolution imaging. Both biocompatible bottom-up synthesized nitrogen-doped graphene quantum dots and quantum dots produced from reduced graphene oxide via top-down approach exhibit temperature-induced fluorescence variations. This response observed for the first time is utilized for deterministic temperature sensing in bulk suspension as well as inside mammalian cells. Distinctive quenching of quantum dot fluorescence by up to 19.8% is observed, in a temperature range from 25℃ to 49℃, in aqueous solution, while the intensity is restored to the original values as the temperature decreases back to 25℃. A similar trend is observed in vitro in HeLa cells as the cellular temperature is increased from 25℃ to 41℃. Our findings suggest that the temperature-dependent fluorescence quenching of bottom-up and top-down-synthesized graphene quantum dots can serve as a non-invasive, reversible, and deterministic mechanism for temperature sensing in microscopic sub-cellular biological environments.
Optimisation of Dyes@SWCNT Raman Nanoprobes
Authors: David Carolane , Allard Charlotte , Mal Suraj , Tang Nathalie , Martel Richard
Published: May 2020

Single-Walled Carbon Nanotubes (SCWNTs) have attracted a lot of attention in biomedical fields. Their easily functionalised surface and ability to encapsulate different materials make them interesting not only for imaging, but also for other applications, such as drug delivery and cell targeting. This work concerns specifically the use of SWCNTs to fabricate Raman nanoprobes for bio-imaging. These nanoprobes are composed of dyes encapsulated inside the SWCNTs and the nanotubes are grafted with anti-bodies functionalized on the outer surface.

First, we aim to optimize the encapsulation process so that the dye/SWCNTs nanohybrid gives a strong, uniform and reproductible signal that is easily detectable by Raman imaging. This is done by varying the parameters of the liquid-phase encapsulation process and crosschecking the results by Raman imaging. We also work to optimize the stability of the nanohybrid in biological media. This parameter is important to determine the best conditions for antibody attachment and cell/tissue interactions. Using different biological buffers, we study the dispersion of the assemblies with Dynamic Light Scattering (DLS) and their stability with Electrophoretic Light Scattering (ELS). The results of the analysis on the nanohybrids show an average hydrodynamic radius of 160 nm and a Zeta potential at -45 mV in aqueous media, proving that the stability of the short nanohybrids in water is favourable to the development of nanoprobes.
Dyes Encapsulated By Single Walled Carbon Nanotubes: A Raman Nanoprobe of Cancer Detection
Authors: Mal Suraj , Tang Nathalie , David Carolane , Allard Charlotte , Duarte Layane , Gaboury Louis , Ouellette S. Blais , Martel Richard
Published: May 2020

Carbon nanotubes are among the most promising platforms for biological applications such as cancer targeting, medical imaging and drug delivery. Herein we present a novel approach to modify single-walled carbon nanotubes (SWCNTs) into Raman nanoprobes capable of targeting biomarkers on cancer cells. The process involves cleaning and shortening in acids followed by encapsulation of specific organic dyes. Subsequently the as-synthesized Raman nanoprobes are then covalently attached with modified NH2-PEG-COOH to make a generic nanoprobe that is bio-compatible and highly dispersed in aqueous or buffer media. When covalently linked to specific antibodies anti-E-cadherin (monoclonal mouse anti-human) and CK19 (cytokeratin), such nanoprobes can be used to detect there bio-markers in the membrane of breast cancer cell lines.

Here, we will first discuss a modified synthetic approach to densify the covalent pegylation used to link bio-molecules on the SWCNTs and show results with nanoprobes incubated with T47D antibody (ab) and MDA231 cell lines. The immunofluorescence and Raman imaging data shows that dyes@SWCNT/PEG/ab composites can specifically target cancer cells overexpressing high affinity receptors of the specific biomarkers linked to the probes. By densifying the covalently attached PEGs, the results show higher stability and improved selectivity of the Raman nanoprobes towards bio-molecules on cancer cells.
(Invited) Determining SWCNT Partition Conditions in Aqueous Two-Polymer Phase Extraction Via Near-Infrared Fluorescence Spectroscopy
Authors: Sims Christopher M , Fagan Jeffrey A.
Published: May 2020

Methods for rapidly determining the aqueous surfactant concentration conditions that yield upper or lower phase extraction for specific (n,m) species of single-wall carbon nanotubes (SWCNTs) in aqueous two polymer phase extraction (ATPE) separations are a missing component limiting rapid development and optimization of the ATPE technique. In this talk I will describe the use of near-infrared fluorescence measurements on single-phase dispersions of SWCNT species mixtures to determine these partition coefficient conditions without performing the ATPE separation. This new methodology enables dramatically swifter determination of partitioning conditions for individual (n,m) species and their handed enantiomers, while using dramatically less material and without the ambiguity of mass transfer limitations or interfacial absorption present when conducting the ATPE separation itself. The ability to fully describe the partitioning conditions for each (n,m) and (m,n) is expected for multiple surfactant composition competitions and surfactant variants. Investigation of complicating factors such as temperature effects, polymer compositions, SWCNT properties, and the redox environment are also enabled and will be described.
(Invited) Low-Temperature Electroluminescence Excitation Mapping of Excitons and Trions in Short-Channel Monochiral Carbon Nanotube Devices
Authors: Gaulke Marco , Peyyety Naga Anirudh , Alamgir Imtiaz , Riaz Adnan , Dehm Simone , Li Han , Lemmer Ulrich , Flavel Benjamin S. , Kappes Manfred , Hennrich Frank , Wei Li , Chen Yuan , Pyatkov Felix , Krupke Ralph
Published: May 2020

Single-walled carbon nanotubes as emerging quantum-light sources may fill a technological gap in silicon photonics due to their potential use as near-infrared, electrically-driven, classical or non-classical emitters. Unlike in photoluminescence, where nanotubes are excited with light, electrical excitation of single-tubes is challenging and heavily influenced by device fabrication, architecture and biasing conditions. Here we present electroluminescence spectroscopy data of ultra-short channel devices made from (9,8) carbon nanotubes emitting in the telecom band. Emissions are stable under current biasing and no quenching is observed down to 10 nm gap size. Low-temperature electroluminescence spectroscopy data also reported exhibits cold emission and linewidths down to 2 meV at 4 K. Electroluminescence excitation maps give evidence that carrier recombination is the mechanism for light generation in short channels. Excitonic and trionic emissions can be switched on and off by gate voltage and corresponding emission efficiency maps were compiled. Insights are gained into the influence of acoustic phonons on the linewidth, absence of intensity saturation and exciton-exciton annihilation, environmental effects like dielectric screening and strain on the emission wavelength, and conditions to suppress hysteresis and establish optimum operation conditions.
Innovation in Textile Electrode of Electrochemical Devices: Water Transport and Thread-Based Temperature and Humidity Sensors
Authors: Hasanpour Sadegh , Djilali Ned , Akbari Mohsen
Published: May 2020

Wearable health monitoring utilizing advances in textile technologies has already been demonstrated for transport of biomarkers and physiological sensing. These advances can potentially be translated to textile electrodes of electrochemical devices to allow managing reactants and by-products transport and for monitoring environmental parameters. Herein, a wicking properties and flexibility of threads are used (1) to control transport of water (by-product) within a textile gas diffusion layer (GDL) of the electrode of polymer electrolyte membrane fuel cells (PEMFCs), and (2) to develop thread-based sensors for local temperature and humidity monitoring.

By means of ex-situ and in-situ characterizations, it was found that the threads can be introduced in the GDL structure to inscribe water highways within the GDL with minimal impact on GDL microstructure (i.e. porosity, porosity distributions) and transport properties (i.e. permeability, diffusivity and conductivity). Furthermore, a low-cost procedure was developed to transform a commodity thread into temperature and humidity sensors by dip-coating the thread with carbon nanotubes (CNTs) ink. The resistance of CNT coated threads is responsive to both parameters. In this work, the response to humidity was cancelled by coating fluorinated ethylene propylene (FEP) on top of the CNT coated thread to develop a temperature sensor independent of humidity. In addition, a second thread was coated with polydimethylsiloxane (PDMS) to monitor the relative humidity (RH).

Thread-based sensors were characterized in an environmental chamber simulating environmental conditions in an operating fuel cell. A linear change of resistance with increasing temperature (~-0.31 %/T) was achieved for the temperature sensor, and the resistance of the thread coated with PDMS showed more sensitivity in high humidity regions (RH > 60%) and followed a quadratic function of RH. The thread-based temperature sensor capability was assessed via ex-situ experiments, and showed rapid response to change of temperature, and also the ability to map temperature in non-uniform temperature distributions. The combinations of both threads can allow simultaneous monitoring of local temperature and RH in the textile GDL of PEMFCs. This work enables local sensing and monitoring within textile electrodes without compromising the performance of PEMFCs.
(Invited) Controlling Carbon Nanotubes By DNA: From Separation to Integration
Authors: Zheng Ming
Published: May 2020

A unique feature of single-wall carbon nanotube (SWCNT) material is its structure diversity: within the same rolled-up graphene sheet structure framework one finds SWCNTs of different electronic bandgaps: metals with zero bandgap, quasi-metals with meV bandgap and semiconductors with ~ 1 eV bandgap. However, making use of SWCNT structure diversity requires a method to obtain SWCNTs of defined structures. In this contribution, we present our current state of DNA-based sorting of SWCNTs. In particular, we show our ability to put any DNA sequence on any SWCNT species, enabling DNA-based assembly of high-density SWCNT devices. In the end, we discuss the design of a device we call Photon Perceptron Array (PPA). PPA is an array of micron-sized spectrometer units that can measure the spectrum of incoming photon in the wavelength range of 200 nm to 2000 nm (and possibly going all the way to THz), with a spatial resolution comparable to the size of a single spectrometer unit. Each spectrometer unit is composed of a set of distinct photodetectors made of SWCNTs of defined atomic structures, placed in parallel with tube-to-tube separations controlled at nanometer precision by DNA origami technology. A high-density array of identical spectrometers can be constructed by placing DNA origami/carbon nanotube complexes in photolithographically-defined locations. PPA may be used for spectral imaging in many fields of science and technology.
(Invited) Organic/Inorganic Hybrid Interfaces between Perovskite Semiconductors and Semiconducting Swcnts for Energy Harvesting and Conversion
Authors: Blackburn Jeffrey L. , Hao Ji , Kim Young-Hoon , Lu Haipeng , Habisreutinger Severin N. , Luther Joseph M.
Published: May 2020

Low-dimensional semiconductors provide a rich tapestry of tunable optical and electrical properties for a wide variety of applications. Semiconducting single-walled carbon nanotubes (s-SWCNTs) have shown tremendous potential in applications ranging from digital logic, biological imaging, quantum information processing, photovoltaics, and thermoelectric energy harvesting. Energy harvesting applications rely critically upon the creation of tailored interfaces that enable the movement of energetic species (excitons, electrons, holes) in specified directions. While organic energy harvesting devices often employ interfaces between distinct organic species such as polymers, fullerenes, and carbon nanotubes, hybrid interfaces between organic and inorganic semiconductors have unique properties that are relatively unexplored.

In this talk, I will discuss our recent efforts at constructing novel hybrid interfaces between s-SWCNTs and low-dimensional perovskite-based semiconductors. I will highlight time-resolved spectroscopy results that illustrate long-lived photoinduced charge separation across such interfaces, demonstrating utility for photovoltaics and photodetectors. Interestingly, some systems demonstrate additional transient processes that are exceptionally slow and may indicate ion movement within the hybrid systems. Complementary device studies demonstrate exceptional efficiencies for conversion of photons into stable photocurrent, and I will highlight several novel applications in which these interfaces can be employed.
Novel Covalent Approaches to Control the Doping Level within Carbon Nanotubes
Authors: Setaro Antonio , Fiebor Alphonse , Adeli Mohsen , Reich Stephanie
Published: May 2020

Achieving precise and controlled charge management of carbon nanotubes is a key element towards their technological applications. Here we will discuss how the covalent method through a triazine-based cycloaddiction we recently developed is beneficial not only in preserving and regenerating the pi-conjugation of the tubes but also in allowing electronic communication between the functional groups and the nanotubes themselves. We will discuss different groups that up- or downshift the position of the Fermi level within the tubes and highlight the consequences onto the phenomenology of their optical response.
(Invited) Thermal and Electrical Conductivity of Carbon Nanotube Network Materials: Theoretical Analysis and Mesoscopic Simulations
Authors: Volkov Alexey N. , Zhigilei Leonid V.
Published: May 2020

A general framework for theoretical analysis and numerical calculations of the effective thermal and electrical conductivity of homogeneous and isotropic disordered materials composed of carbon nanotubes (CNTs) is developed. The model utilizes similarity in the mathematical description of thermal and electrical transport in nanotube materials. The analysis accounts for both the inter-tube contact conductance and intrinsic conductivity of CNTs, and is performed in a wide space of governing parameters that includes the fiber aspect ratio, Biot number calculated for a single contact between nanotubes, and density ranging from values corresponding to the percolation threshold up to those characteristic of dense fiber networks. For dense networks, exact theoretical equations for the effective conductivity of materials composed of nanotubes with arbitrary aspect ratio and Biot number are derived. The effect of the intrinsic conductivity of nanotubes on the thermal and electrical transport is found to depend on the density of inter-tube contacts and, thus, is usually significant in the dense materials. The theoretical finding are confirmed in large-scale simulations of quasi-two-dimensional CNT films and three-dimensional CNT aerogels, where nanotubes form continuous networks of intertwined bundles. The simulations are performed based on a mesoscopic model of CNT materials, where every nanotube is represented by a curved chain of stretchable cylindrical segments. The dependences of the conductivity on the CNT length, Biot number, and material density predicted in these simulations agree well with the scaling laws derived theoretically. The comprehensive theoretical description developed in this work can facilitate tailoring thermal and electrical conductivity of CNT materials to the needs of practical applications by varying the material density, CNT length, and aspect ratio. Financial support for this work is provided by the National Aeronautics and Space Administration (NASA) through an Early Stage Innovations grant from NASA's Space Technology Research Grants Program (grant NNX16AD99G). A.N.V. also acknowledges support from the National Science Foundation through the CAREER award CMMI-1554589.
Additive Manufacturing of Carbon Nanotube-Based Three-Dimensional Multi-Scale Architectures
Authors: Fu Kun
Published: May 2020

Carbon nanotubes (CNT) have exceptional properties, but there is no effect to assemble CNT into macro-scale structures with desired architecture. Three-dimensional CNT-based multiscale architecture featuring the characteristics of both the constituent CNT material, which brings the effects of its nanoscale resolution and properties, as well as the structures across multiscale lengths offer breakthrough advances in many applications including ultra-light structural materials, energy storage, and biomedical devices. In my talk, I will introduce our recent work on additive manufacturing of three-dimensional CNT-based multiscale architectures, and demonstrate its potential application in battery application, including Li anode protection and solid state composite electrolyte.
Quantification of the Number of Adsorbed DNA Molecules on Single-Walled Carbon Nanotubes
Authors: Nißler Robert , Mann Florian , Chaturvedi Parth , Horlebein Jan , Meyer Daniel , Vuković Lela , Kruss Sebastian
Published: May 2020

Single-walled carbon nanotubes (SWCNTs) have unique photophysical properties and promise many novel applications. Noncovalent functionalization with single-stranded DNA (ssDNA) is one of the most used approaches and variation of ssDNA sequences lead to major advances in separation of SWCNT chiralities and SWCNT-based sensors. However, the exact number of adsorbed ssDNA molecules on ssDNA/SWCNT complexes vary in literature and are overall not precisely known. Here, we determine the number of adsorbed ssDNA molecules per SWCNT for different ssDNA sequences. For this purpose, we directly quantified free and adsorbed ssDNA and the concentration of SWCNTs using an approach based on filtration, absorption spectroscopy, and atomic force microscopy. The number of adsorbed ssDNA molecules on 600 nm long (6,5)-SWCNTs varied between ∼860 for (GT)5 and ∼130 for (A)30. The sequence (GT)15 occupied an average SWCNT segment of ∼2.3 nm, while the SWCNT segment length of (GT)x repeats increased linear with sequence length x. Molecular dynamics simulations with experimentally determined values as parameters showed that (GT)15 ssDNA stacked on top of each other on the SWCNTs in contrast to simulations with an excess SWCNT surface. By knowing the number of adsorbed ssDNA molecules per SWCNT it is further more possible to address ratio-specific DNA conjugation approaches. In summary, these results provide novel quantitative insights into the complex structure of DNA/SWCNT hybrids.
Fast Ion Diffusion in Carbon Nanotube Channels
Authors: Buchsbaum Steven F. , Jue Melinda L. , Chen Chiatai , Meshot Eric R. , Park Sei Jin , Sawvel April , Lau Edmond Y , Pham Tuan Anh , Wu Kuang Jen , Fornasiero Francesco
Published: May 2020

Many simulations and experiments have investigated pressure-driven fluid flow in carbon nanotubes (CNTs) and demonstrated enormous transport rates through these channels. Comparatively little attention has been given so far to concentration-driven transport1,2 in CNTs despite its importance in a large variety of fields. While several studies assumed bulk/hindered diffusion for small molecules through nm-wide CNTs, other simulations have predicted self-diffusion coefficients several times larger than in the bulk. These large uncertainties in the magnitude of the diffusion rates through CNTs have hampered their full exploitation in nanofluidic devices.3

To obtain a precise quantification of the diffusive flow in CNTs, we have fabricated membranes with a large but known number of single-walled carbon nanotubes (SWCNT) as fluid transport pathways. Contrary to previous membrane systems, this platform enables us to minimize uncertainties in the calculation of the per-pore flow rate. A series of stringent control experiments confirms that these membranes are defect free and that transport occurs only through SWCNTs. Once corrected for the boundary layer resistance at the membrane/fluid interface, our measurements reveal that the transport diffusivity of small ions in single-walled carbon nanotubes is one order of magnitude faster than in the bulk.4 The dependence of the flow enhancement on the ion chemico-physical properties is also discussed. Together with indicating that CNT membranes could enable dialysis processes with unprecedented efficiency, these results have important implications for a broad range of applications, such as energy storage/harvesting and chemical separation/detection, where ion permeation through nanoporous carbon materials is key.

References

1. Bui, E. R. Meshot, S. Kim, J. Peña, P. W. Gibson, K. J. Wu, F. Fornasiero, Adv. Mater., 28 (2016) 5871.

2. Li, C. Chen, E. R. Meshot, S. F. Buchsbaum, M. Herbert, R. Zhu, O. Kulikov, B McDonald, N. Bui, M. L. Jue, S. J. Park, C. Valdez, S. Hok, C. J. Doona, K. J. Wu, T. M. Swager, F. Fornasiero, submitted (2019)

3. S. Guo, E. R. Meshot, T. Kuykendall, S. Cabrini, F. Fornasiero, Adv. Mater. 28 (2015), 5871.

4. S. Buchsbaum, M. L. Jue, C. Chen,E. R. Meshot, S. J. Park, A. Sawvel, E. Lau, T. A. Pham, K. J. Wu, F. Fornasiero, in preparation (2019)

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
(Invited) Polymer-Wrapped and sp3-Functionalized (6,5) SWNTs for Charge Transport and Near-Infrared Emission
Authors: Zaumseil Jana
Published: May 2020

Polymer-sorted (6,5) single-walled carbon nanotubes are available in large amounts and can be used for a wide range of optoelectronic devices. Here, we report on the investigation of charge transport in dense semiconducting nanotube films in field-effect transistors using temperature and carrier density dependent mobility and Seebeck coefficient measurements. Furthermore, we show how both their emissive and charge transport properties can be tuned by adding light-switchable functional groups to the wrapping polymer and by selected sp3-defects created via diazonium chemistry or aryl halide chemistry in organic solvents.
Charge Modulation Spectroscopy of Pristine and sp3-Functionalized Single-Walled Carbon Nanotube Networks
Authors: Zorn Nicolas Frederic , Berger Felix Julian , Zaumseil Jana
Published: May 2020

The controlled decoration of single-walled carbon nanotubes (SWCNTs) with luminescent sp3 defects has emerged as a powerful approach to enhance their usually low photoluminescence (PL) quantum yields and achieve tuneable emission across the near-infrared even for polymer-wrapped nanotubes [ACS Nano
2019, 13, 9259]. However, their application in optoelectronic devices requires a detailed understanding of the impact of sp3 functionalization on their electrical performance. While isolated sp3 defects on single SWCNTs increase the resistance by a few kΩ, the effect of functionalization on charge transport in networks of semiconducting SWCNTs remains unexplored. Charge modulation spectroscopy is ideally suited to probe the mobile charge carriers in SWCNT networks and has previously corroborated the notion that charge accumulation and transport in mixed SWCNT networks is highly chirality- and gate voltage-dependent. Here, we use charge-modulated PL (CMPL) spectroscopy to study the current pathways in field-effect transistors based on networks of pristine and functionalized (6,5) SWCNTs. We find that the defects are very efficiently sampled by mobile carriers and consequently, sp3-functionalized SWCNTs actively participate in the charge transport in these networks. In combination with voltage-dependent PL and electroluminescence measurements, our CMPL method provides fundamental insights into the interaction of charge carriers with sp3 defects in SWCNT thin film devices.

Fig. 1: Schematic of the charge modulation PL spectroscopy setup (left) and CMPL spectra of pristine and functionalized (6,5) SWCNT network field-effect transistors (right).

Figure 1
(Invited) Graphene Aerogels: From Self-Assembly to Applications
Authors: Cerruti Marta , Hu Kaiwen , Chen Yiwen , Szkopek Thomas
Published: May 2020

Graphene aerogels are highly porous and light structures that maintain most of the exceptional mechanical and electrical properties of graphene in a substrate that can be handled and used in practical applications. This is possible because the graphene flakes do not excessively restack during aerogel formation.

In this talk we will explore how we can direct the self-assembly of graphene oxide flakes to generate graphene aerogels with different structures and mechanical properties. We will at first show what happens during hydrothermal reduction of graphene oxide and describe the synthesis of reduced graphene oxide scaffolds with a highly reduced, compact shell and a less reduced porous core. We will then show how we can tune graphene oxide self-assembly during hydrothermal reduction by changing the amphiphilicity of the graphene oxide flaxes and generate elastic shell-less structures. We will show how composite structures can be made too, by maintaining the shell and using highly stable colloidal suspensions. Lastly, we will show that controlling amphiphilicity also allows generating scaffolds through high internal phase emulsions. We will briefly highlight applications for these structures in fields as varied as sensing, pollutant absorption, photocatalysis, and cell culture.
(Invited) Defect Engineering in Plasma-Treated Graphene Films
Authors: Stafford Luc , Vinchon P. , Bigras G. Robert , Glad X. , Martel Richard
Published: May 2020

Engineering of defects located in-grain or at grain boundary is central to the development of functional materials and nanomaterials. While there is a recent surge of interest in the formation, migration, and annihilation of defects during ion and plasma irradiation of bulk (3D) materials, the detailed behavior in low-dimensional materials remains most unexplored and especially difficult to assess experimentally. A new hyperspectral Raman imaging scheme providing high selectivity and diffraction-limited spatial resolution is here adapted to examine plasma-induced damage in a polycrystalline graphene film grown by chemical vapor deposition on copper substrates and then transferred on silicon substrates. For experiments realized in nominally pure argon plasmas at low pressure, spatially resolved Raman conducted before and after each plasma treatment shows that the defect generation in graphene films exposed to very low-energy (11 eV) ion bombardment follows a 0D defect curve, while the domain boundaries tend to develop as 1D defects. Surprisingly and contrary to common expectations of plasma-surface interactions, damage generation at grain boundaries is slower than within the grains. Inspired by recent modeling studies, this behavior can be ascribed to a lattice reconstruction mechanism occurring preferentially at domain boundaries and induced by preferential atom migration and adatom-vacancy recombination. Further studies were realized to compare the impact of different plasma environments promoting either positive argon ions, metastable argon species, or VUV-photons on the damage formation dynamics. While most of the defect formation is due to knock-on collisions by 11-eV argon ions, the combination with VUV-photon or metastable atom irradiation is found to have a very different impact. In the former, the photons are mainly thought to clean the films from PMMA residues due to graphene transfer from copper to silicon substrates. On the other hand, in conditions with both ion and metastable atom irradiation, the surface de-excitation of the latter seem to greatly enhance the self-healing of the grain boundaries due to an increase of the local energy deposition. Finally, these experiments were used as building blocks to examine the formation of chemically doped graphene film in such plasmas using argon mixed with either traces of N- or B-bearing gases.
(Invited) Hybrid Van Der Waals Heterostructures: From Fundamentals to Applications
Authors: Orgiu Emanuele
Published: May 2020

2D materials are held together by weak interplanar van der Waals (vdW) interactions. The incorporation of molecules in such materials holds an immense potential to understand and modify the fundamental physical properties of the pristine materials while creatin new artificial materials. Whilst nature offers a finite number of 2D materials, an almost unlimited variety of molecules can be designed and synthesized with predictable functionalities. The possibilities offered by systems in which continuous molecular layers are interfaced with inorganic 2D materials to form hybrid organic/inorganic van der Waals heterostructures (H-vdWH) are emphasized. Similar to their inorganic counterpart, the hybrid structures have been exploited to suggest novel device architectures. Moreover, specific molecular groups can be employed to modify intrinsic properties and confer new capabilities to 2D materials. In particular, I will highlight how molecular self-assembly at the surface of 2D materials can be mastered to achieve precise control over position and density of (molecular) functional groups, paving the way for a new class of hybrid functional materials.

In particular, within such vdW heterostructures, currently assembled by mechanical superposition of different layers, periodic potentials naturally occur at the interface between the 2D materials. These potentials significantly modify the electronic structure of the individual 2D components within the stack and their alignment, thus offering the possibility to build up hybrid and novel materials with unique properties.

Also, I will show how the presence of ordered supramolecular assemblies bearing different functional groups can modify the pristine Shubnikov-De Haas oscillations occurring in graphene.

Finally, an example will be given of how a carefully designed H-vdWH could be used for sensing of different biomarkers.
Chemical Purification of Fullertubes and Isolation of C100-C200 Structures: Tubes or Balls?
Authors: Koenig Ryan M. , Seeler Tiffany L. , Tepper Katelyn R. , Franklin Hannah M. , Stevenson Steven
Published: May 2020

The goal of this research is to explore the world of larger size carbon cage clusters in the range of C100-C200. Despite the isolation of C60 nearly 30 years ago, many of these higher fullerenes remain a mystery. The paucity of scientific literature for these species is attributed to the following:

their low yield in typical soot extracts,

proliferation of structural isomers that create a separation nightmare,

HPLC co-elution of contaminant fullerene and metallofullerene species, and

lack of an efficient separation method.

In this presentation, we discuss our recent advances in separation science that allows us to now isolate an emerging number of carbon cages in the range of C100-C200. Whether these structures are tubular (FullerTubes) or spheroidal remains to be seen.
(Invited) Ab Initio Exciton and Phonon Dynamics in Transition Metal Dichalcogenides
Authors: Verstraete Matthieu J , Melo Pedro , Zanolli Zeila
Published: May 2020

Interest in the properties of transition metal dichalcogenides (TMDs) has increased due to the discovery of the coupling between spin and valley degrees of freedom, which can be seen experimentally using a circularly polarised laser. After excitation the newly formed carrier populations must move towards the other valley until balance is reached. However, this relaxation process is not entirely understood in the literature, where the relative importance of the electron-electron (e-e) or electron-phonon (e-p) interactions is still a subject of debate. Previous works on WSe2 [A. Molina- Sánchez, et al - Nano letters, 2017] have shown that the e-p interaction is a good candidate to describe the relaxation process. Using a fully ab-initio framework based on the Baym-Kadanoff equations [P. M. M. C. de Melo and A. Marini, Phys. Rev. B 93, 155102 (2016)] we study the influence of the e-p interaction on MoSe2 after its excitation by a laser field. We show how phonons allow carrier relaxation and how the Kerr signal and total magnetisation are affected at different temperatures, with the latter exhibiting a non-monotonic behaviour as the temperature increases.
(Invited) Electroluminescent Hyperbolic Cooling of Graphene Field Effect Transistors
Authors: Baudin Emmanuel , Voisin Christophe , Placais Bernard
Published: May 2020

Heat management is critical for the performance of most modern electronic devices. It was recently proposed that radiative heat transfer - which is usually negligible in the solid state - could be increased in hyperbolic metamaterials, i.e., materials having a hyperbolic electromagnetic dispersion relation. [1] However, artificial metamaterials can be difficult to fabricate and integrate.

Fortunately, most of Van der Waals materials are natural hyperbolic metamaterials. Indeed, due to their anisotropic layered structure, the in-plane and out-of-plane optical phonon energy splitting results in a hyperbolic dispersion of light in the Resstrahlen bands. As a consequence, in these materials, the strong light-matter coupling can give rise to a 102-105 increase in the e.m. local density of states, resulting in a dramatic enhancement of the radiative heat transfer. Moreover, the radiative character of heat exchange results in a propagative heat transport via hyperbolic phonon-polariton (HPhP) modes on micrometric scales.

We have studied heat transfer in graphene on hexagonal boron nitride: a natural 2D hyperbolic material. In our devices, graphene is used as a versatile heat source in the near field of a hyperbolic material, and as a sensitive noise thermometer. [2] Using mono-, bi- and trilayer graphene, we demonstrate a strong increase of the electron gas cooling resulting in a large temperature drop when the emission of HPhP sets in. This process shares many analogies with electroluminescence, except that it involves near-field modes. We experimentally evidence that the case of graphene is unique, with cooling powers reaching few milliwatts per micron square [3], i.e., nine orders of magnitude larger than previously reported in the literature.

Bibliography

[1] S. Biehs, et al "Hyperbolic metamaterials as an analog of a blackbody in the near field." Phys.
Rev. Lett.
109, 104301 (2012)

[2] W. Yang, et al "A Graphene Zener–Klein Transistor Cooled by a Hyperbolic Substrate." Nat. Nanotech.
13, 47 (2018)

[3] E. Baudin, et al "Hyperbolic Phonon Polariton Electroluminescence as an Electronic Cooling Pathway", Adv. Funct. Mat.1904783 (2019)

Figure 1