bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Carbon Nanomaterials for High-Resolution, Multimodal Neural Interfaces
Authors: Vitale Flavia
Published: February 2020

Unraveling and controlling neural processes underlying cognition, sensation, volitional movement and neurological disorders require implantable electrodes capable of decoding the activity of millions of neurons at millisecond resolution, over months to years and without inducing foreign-body reactions. Since Luigi Galvani discovery of bioelectricity, metals have been used as electrode materials. Metals, however, are dramatically inadequate to address the chemical, optical and mechanical properties of neural cells: they are stiff, unstable in physiological environment and can induce severe mechanical and neurotoxic damage to the soft tissues. Furthermore, recent advances in neuroscience methods for imaging, stimulating and inhibiting neural activity are emerging as powerful tools, but there is no available material that can simultaneously provide optical, electronic, magnetic and electrochemical properties to interface with neural microcircuits across multiple modalities. Carbon-based nanomaterials like carbon nanotubes (CNT) and graphene combine intrinsically high mass-specific surface area, electrical conductivity, mechanical strength, flexibility, low magnetic susceptibility mismatch with tissues and biological stability, which makes them uniquely suited for interfacing with neural circuits. We have engineered CNT fibers into cellular-scale size microelectrodes for chronic recording and stimulating neural activity. CNT fibers have superior electrochemical impedance and charge transfer properties compared to metal probes of the same size, which allows minimizing implant footprint without affecting the efficiency of transduction of biological ionic currents across the electrode/tissue interface. In vivo biocompatibility, effective deep-brain stimulation and stable chronic recording neural recordings demonstrate the feasibility of CNT fiber microelectrodes for high-fidelity, minimally invasive neural interfaces. To study the wiring diagrams of neural circuits and elucidate the fundamental mechanisms giving rise to behavior and disease at high spatial and temporal resolution, we have also developed transparent graphene-based optoelectronic neural interfaces for simultaneous electrophysiology and imaging. By leveraging the optical and electronic properties of graphene we have fabricated thin-film multichannel electrode arrays with >90% transparency from the UV to the near-infrared range, making them compatible with most of the conventional and fluorescence-based neuroimaging modalities. Example of applications of these optoelectronic graphene devices are chronic platforms for in vivo optical and electrical recordings of neural microcircuits involved in epilepsy generation.
Xeno Nucleic Acids for Enhancing the Optical Stability of Nanosensors
Authors: Gillen Alice Judith , Gigli Carlo , Boghossian Ardemis Anoush
Published: February 2020

The unique optoelectronic properties of single-walled carbon nanotubes (SWCNTs) motivate their use as next-generation optical sensors. The intrinsic SWCNT near-infrared fluorescence offers many advantages in terms of bio-transparency, sensitivity, and photo-stability. Characteristics required for in vivo continuous sensing, such as selectivity, biocompatibility, and solubility, can be tuned by suspending SWCNTs with biomolecules such as single-stranded DNA (ssDNA). Despite the ubiquitous use of DNA-wrapped SWCNTs for a variety of in vivo sensing applications, their behaviour in the presence of varying concentrations of the different ions present in biological media has yet to be studied.

In this work, we present a systematic exploration of the effects of various cations and anions on the fluorescence of ssDNA-wrapped SWCNTs. The presence of multivalent cations was found to induce fluorescence shifting of near-infrared fluorescence through the transient formation of a metastable state. The incorporation of artificial oligonucleotides, or xeno nucleic acids, was shown to mitigate the effects of ion-induced conformal drift through improved conformational resiliency. The synthetic biology approach presented herein offers a powerful demonstration for enhancing sensor selectivity and stability while enabling a previously unexplored space for engineering oligonucleotide-based SWCNT sensors.
Nanocarbon-Based Field-Effect Transistor Biosensors (bioFETs) for Real-Time Detection of DNA Sequences
Authors: Bazan Claudia Marcela , Sauvage Madline , Huliganga Elizabeth , Bencherif Amira , Borduas Godefroy , Bouilly Delphine
Published: February 2020

Field-effect transistor devices based on functionalized nanocarbon materials (2-D graphene thin layers and 1-D carbon nanotubes) are a promising technology for biomolecular sensing applications. In particular, this type of devices allows for label-free detection of DNA hybridization with the advantage of an easy and direct electrical readout in comparison with most routine techniques.

In this work, we report on the design and fabrication of nanocarbon-based bioFETs for DNA hybridization detection. Employing a combination of microfluidics and real-time electrical measurements, we investigated the response of bioFETs to single-stranded DNA (ssDNA) probe tethering and hybridization with complementary target ssDNA in saline buffer solution. The bioFETs were assembled from individual carbon nanotubes or graphene nanoribbons connected by pairs of metallic electrodes using photolithography techniques. Transfer curves of bioFETs in saline buffer were measured using an immersed pseudo-reference electrode. We obtained transfer curves showing current modulation with high OFF-current at the charge-neutrality point. Probe and target ssDNA were chosen as 22-nucleotide-long complementary sequences. Probe tethering on nanocarbon was obtained using diazonium chemistry followed by EDC/NHS coupling of an amine moiety placed at the extremity of the DNA probe [1]. Transfer characteristics were measured before/after probe and target injection. Moreover, to further characterize the bioFETs response, probe immobilization and probe-target hybridization were recorded in real-time using electrical readout. The development of highly selective and ultra-sensitive sensors for DNA will open novel technological avenues to improve the detection of genetic biomarkers for various diseases.

[1] Bouilly, D. et al. Nano Letters 16, 4679–4685 (2016)
(Invited) Systematic Aqueous Two-Phase Separations of Carbon Nanotubes to Investigate the Separation Mechanism
Authors: Defillet Joeri , Martinati Miles , Wenseleers Wim , Cambre Sofie
Published: February 2020

Aqueous two-phase (ATP) separation has been demonstrated as a fast, highly-scalable separation technique to sort single-wall carbon nanotubes (SWCNTs) by diameter, chirality, metallicity, etc.[1-2] In ATP, two water-soluble, yet immiscible polymers are mixed together at sufficiently high concentration after which they spontaneously form two phases with different hydrophilicity. In a typical separation protocol, SWCNTs are added to this two-polymer mixture with a combination of different surfactants, resulting in separation of different chiral species among both phases. While very promising separations have been achieved, the separation mechanism is not well understood

In this paper, we present a series of ATP separations, in which surfactant combinations and concentrations are systematically varied. Absorption spectroscopy, multi-wavelength resonant Raman scattering and wavelength-dependent photoluminescence-excitation spectroscopy, combined with detailed two-dimensional spectral analysis, is applied to characterize the full composition of the resulting separated fractions and as such study the underlying separation mechanism. These systematic studies reveal that chirality-dependent surfactant interactions determine the separation order.

[1]. C.Y. Khripin et al., J. Am.
Chem. Soc.
2013, 135, 6822

[2]. N.K. Subbaiyan et al., ACS Nano
2014, 8, 1619
(Keynote) Carbon Nanotubes: Discovery and Beyond
Authors: Iijima Sumio
Published: February 2020

First I would like to present how the carbon nanotube (CNT) was discovered after my long research carrier in 1991, emphasizing on a scientific and convincing presentation of the finding [1]. It might be interesting to talk about what I have been doing before the discovery, where I should introduce my ample experiences with high resolution electron microscopy (HRTEM) and its use in structure characterizations of various nano-structured materials in atomic detail [2]. Without this tool and technique there will be no chance for finding the carbon nanotube. The carbon nanotubes brought us dual excitements in both academia as condensed matter physics and industrial applications. Such a broad range of the attraction is reflected in an extremely high Google citation, its number becoming over 45,000 only for the first paper reporting CNT in 1991. The number is still increasing even after 27 years of the discovery.

CNT, chrysotile asbestos, imogolite [3], and many structures in biological systems are known to have tubular structures, resulting from anisotropic growth in one particular orientation. In the case of CNT, the presence of catalytic metal particles in the tubule formation appears to control a tubular morphology. In general, the formation of nanometer-scale tubular structures is caused mostly by molecular conformation of a building block unit or a total energy minimization of the tubular structure system.

We have recently examined aluminum oxy-hydroxide gamma-AlOOH, boehmite, which has been known to form into a variety of morphologies from a fibril, low-dimensional sheet, platelets, to bulk crystal, depending on a synthesis process. One of them is a quasi-one-dimensional fibril structure, which grows in an aqueous solution as a sol form. We have studied detailed morphology of this fibril boehmite and found that the fibril grows selectively parallel to the c-axis and does not form in a tubular structure but a nanometer-sized ribbon [4]. Electronic energy band gaps of such a ribbon have been studied and showed interesting size-dependent band gaps [5]. The growth was not promoted by a particular catalytic substance so that such an anisotropic growth should be originated from the boehmite structure itself and surroundings.

Iijima, Nature, 345, 56-58 (1991).

Iijima, J. Appl. Phys., 42, 5891-5893 (1971).

Wada et al., Amer. Mineral., 54, 50 (1969).

Iijima et al., PNAS, 113, 11759-11764 (2016).

M. Toyoda & S. Saito,private communication 2017.
(Invited) Structure Characterization of Intermetallic Compound Catalysts and Single-Walled Carbon Nanotubes
Authors: Li Yan , Yang Feng , Yang Juan
Published: February 2020

Single-walled carbon nanotubes (SWNTs) have shown great potentials in various fields attributing to their unique structure-dependent properties, therefore, the structure-controlled preparation of SWNTs is a crucial issue for their advanced applications (e.g. carbon-based nanoelectronics) and has been a great challenge for about two decades. We developed a strategy to produce SWNTs with specific chirality by using tungsten-based intermetallic compound nanocrystals as catalysts. The characterization of catalyst structure is very important to reveal the growth mechanism of SWNTs. We used transmission electron microscopy (TEM) including high-resolution TEM, scanning TEM, as well as image simulation to probe the W6Co7 catalyst structure before and after the SWNT growth. In-situ TEM performed at 1100 oC was used to prove that the W6Co7 catalysts are crystalized and keep stable structure. High-resolution TEM measurements assisted with DFT simulations on the interface of SWNT/catalyst show that the chirality-specific growth is due to a good structural match between the nanotube and the metal atom arrangement of planes in the catalyst. The chirality characterization is also very important. We found that the electronic Raman scattering (ERS) can offer an accurate chirality assignment for metallic tubes. We also developed a bilayer plot for determining the chiralities of SWNTs under complex environment.
(Invited) Light-Directed Creation of Quantum Defects
Authors: Wu Xiaojian , Kim Mijin , Powell Lyndsey Rae , Wang YuHuang
Published: February 2020

Quantum defects are an emerging class of synthetic quantum emitters that have recently captured significant interest because of their fascinating optical properties and synthetic flexibility. In this contribution, we will discuss a series of new experiments that aim at directing the synthesis of quantum defects with light. Implications of this type of precision control will also be discussed. Examples may include lithographically patterned quantum emitters for applications in near-infrared imaging, chemical sensing, and solid state quantum electronics.
(Invited) Interplay of Spectral Diffusion and Phonon Broadening in Carbon Nanotubes: Implications for Quantum Optics
Authors: Claude Théo , Jeantet Adrien , Lauret Jean-Sébastien , Chassagneux Yannick , Voisin Christophe
Published: February 2020

We performed a thorough and quantitative investigation of spectral diffusion at low temperature in carbon nanotubes wrapped in PFO and embedded in a polystyren matrix, a system of interest for applications for quantum light states generation. We show that an intrinsic line shape typical of exciton-acoustic phonon coupling can be traced back down to the µs time-scale, while spectral diffusion yields a feature-less spectral broadening of the zero-phonon line. By tuning physical parameters such as temperature and pump power we investigate the line-shape deformation at several integration time-scales. Finally, we discuss the implications of these optical properties as regards the efficiency of the static and dynamical coupling of carbon nanotube to optical micro-cavities for single photon generation.
Quantum Optical Studies on Sp3 Defects in Carbon Nanotubes
Authors: He Xiaowei , Htoon Han , Doorn Stephen K.
Published: February 2020

The intentional incorporation of impurities and defects can serve as a powerful tool for modification of the electronic and optical properties of host nanomaterials and enabling of new functionalities.1 Introduction of sp
3 defects by covalent functionalization to single-walled carbon nanotubes (SWCNTs) generates new emission states red-shifted from the optical bandgap (E11) of SWCNTs by 100 to 300 meV.2 With controllable emission wavelengths and high quantum yield, these defect states open up new opportunities for the applications of SWCNTs in photonics such as lasing, photon upconversion and single photon emission.3-4

Recently, it has been shown that such doping sites are capable of emitting single photons at room-T, with single photon purity as high as 99% and emit at wavelengths from 1.1 μm to 1.55 μm covering the telecom O- and C-bands4. While the high single photon purity is of great importance, another critical criterial for an ideal single photon generator is photon indistinguishability, which requires the emission linewidth to be narrowed down to the Fourier transform-limitation.5

In this work, we investigated the environmental influences on the linewidth of defect-state emission in SWCNTs at cryogenic temperature (4K). sp3
defects were generated on the surface of surfactant and poly[9,9-dioctylfluorenyl-2,7-diyl] (PFO) wrapped (6,5)SWCNTs by aryl diazonium functionalization. Photoluminescence (PL) spectra of defect states were investigated under different environmental conditions, including surfactant wrapping, surfactant-free, PFO-wrapping tubes on polymer substrates. The result showed that the linewidth of the PL peaks is in the order of a few hundred of micro-eV for surfactant-free and PFO wrapping tubes. Furthermore, dynamic measurements revealed that for clean tubes, the PL lifetimes (T1) are as high as a few nanoseconds, reaching to the radiative decay limitation. These results indicate that the observed linewidth is largely contributed by dephasing time (T2). Increasing T2 will be the critical issue for further narrowing the linewidth to the transform-limitation region.

[1] Piao, Yanmei. et al. Nature Chem. 2013, 5, 840.

[2] Hartmann, Nicolai F. et al. Nanoscale. 2015, 7,20521.

[3] Ma, Xuedan. et al. Nature Nanotech. 2015, 10, 671.

[4] Xiaowei He. et al. Nature Photonics. 2017, 11, 577.

[5] Yue Luo. et al. Nature communication. 2017, DOI: 10.1038/s41467-017-01777-w
(Invited) Aryl-Functionalized Single-Walled Carbon Nanotubes Embedded into Metallo-Dielectric Antennas
Authors: Shayan Kamran , He Xiaowei , Luo Yue , Li Xiangzhi , Blackburn Jeffrey L. , Doorn Stephen K. , Htoon Han , Strauf Stefan
Published: February 2020

Creating exciton localization via covalent sp3 functionalization of single-walled carbon nanotubes (SWCNTs) is a promising route to enhance the optical quantum yield and can furthermore lead to single-photon emission at room temperatures [1]. Of recent interest are aryl-functionalized SWCNTs that are protected by polyfluorene, for which we have recently shown that a variety of chemically and energetically distinct defect state exist that have their origin in topological variation in the chemical binding configuration of the monovalent aryl groups [2]. Here we extend our study by embedding aryl-functionalized SWCNTs into metallo-dielectric antennas that provide broadband coupling with near-unity light collection efficiencies by trapping air gaps on chip that form cavity modes. Scalable implementation is realized by employing polymer layer dry-transfer techniques that avoid solvent incompatibility issues, as well as a planar design that avoids solid-immersion lenses, resulting in a narrow output cone of ±15° that enables a priori fiber-to-chip butt coupling. In these devices the exciton emission from the aryl-functionalized sides (E11*) remains spectrally sharp with linewidth values near the resolution limit of about 35 meV. Interestingly, we find that the pump-induced dephasing for E11* exciton (0D exciton) is significantly reduced by more than 300% as compared to the E11 exciton (1D exciton), thereby preserving exciton coherence even into the high pump power regime, as needed for practical devices in quantum photonics. We will discuss how these findings provide a foundation to build unified descriptions on emergence of novel optical behavior from the interplay of covalent dopants, dispersants, and excitons in SWCNTs.

[1] He, X. et al. Tunable room-temperature single-photon emission at telecom wavelengths from sp3 defects in carbon nanotubes. Nature Photonics
11, 577–582 (2017).

[2] He, X. et al. Low-Temperature Single Carbon Nanotube Spectroscopy of sp3 Quantum Defects, ACS Nano, Articles ASAP (2017); DOI:10.1021/acsnano.7b03022
Magneto-PL Spectroscopy in Aryl Functionalized CNTs
Authors: Kim Younghee , He Xiaowei , Doorn Stephen K. , Htoon Han
Published: February 2020

Recent developments in single wall carbon nanotube (SWCNT) functionalization chemistry introducing sp
3 defect sites via covalent attachment of chemical functional groups have made SWCNTs a promising material system for a variety of technologies. These defect states boost photoluminescence (PL) quantum yields and open new possibilities for SWCNTs as unique photon sources in emerging applications. In 2015, solitary oxygen defect states incorporated onto SWCNTs were shown to serve as room temperature (RT) single photon emitters at ~1300 nm [1]. More recently, this RT single photon emission (SPE) was further extended to cover 1550 nm telecommunication wavelength band via aryl sp
3 defect sites in SWCNTs of larger diameters [2]. The SPE of aryl sp
3 are also characterized with ultrahigh single-photon purity and enhanced emission stability approaching the shot-noise limit. While these properties make sp3
defects of SWCNTs very promising material of quantum information technology, establishing the functionalized SWCNTs as transformative materials for quantum technologies demands a detailed understanding and control of their fine electronic structure and quantum coherence properties. Aiming to meet this challenge here, we performed single defect magneto-PL optical spectroscopy on sp
3 defects of aryl functionalized SWCNT. Our work reveals indications that the defects possess complex excitonic fine structure that may open a route toward manipulating spin and/or angular momentum of the defect bound exciton for quantum information technology applications.

References

[1] X. Ma et al., Nat. Nanotech., 2015, 10, 671.

[2] X. He et al., Nat. Photon., 2017, 11, 577
(Invited) Single-Molecule Sensor Arrays with Carbon Nanotube Transistors
Authors: Collins Philip G.
Published: February 2020

Electronic conduction in one dimension is uniquely sensitive to single point perturbations. As quasi-one-dimensional conductors, single-walled carbon nanotubes are ideal examples of this sensitivity, and they can be exploited as single-molecule sensors in air, liquid, or vacuum. Even in complex physiological solutions, dynamic biochemical activity has been monitored with single-bond and microsecond resolution. However, past work along these lines was achieved on individual devices with low success rates of 10-20%. Here, we describe simultaneous progress on three fronts that has produced large-scale arrays of single-molecule devices. First, precise control of catalytic chemical vapor deposition has dramatically increased our yield of usable single-nanotube devices across 4” substrates. Second, contamination control methods have reduced charge-trap fluctuations that previously disqualified many transistors from single-molecule sensing experiments. Thirdly, new surface modification protocols have brought predictability and control to single-molecule biofunctionalization of the nanotube surfaces. When combined, these techniques scale up single-molecule dynamic sensing from single devices to large arrays. New research directions with these arrays include massively parallel sensing applications such as drug discovery and DNA sequencing.
(Invited) Dense Layers of (6,5) Nanotubes for Optical and Charge Transport Applications
Authors: Zaumseil Jana
Published: February 2020

Large volumes of highly purified dispersions of monochiral (6,5) single-walled carbon nanotubes are readily available through polymer-wrapping and shear-force mixing. They enable the deposition (e.g. by aerosol jet printing or filtration) of semiconducting layers of variable thickness from sparse networks to 300 nm thick films with large optical density. These layers can be applied in lateral and vertical field-effect transistors with excellent device performance but also as electrochromic notch filters or for organic light-emitting diodes in the near-infrared. Here, we present examples of such applications and investigate the impact of novel n-dopants on nanotube networks, temperature-dependent charge transport within monochiral and mixed layers and their optical properties at different charge carrier densities.
(Invited) Avalanche Photoemission in Suspended Carbon Nanotubes: Light without Heat
Authors: Cronin Stephen B. , Wang Bo
Published: February 2020

We report bright electroluminescence from suspended carbon nanotube (CNT) field effect transistors (FETs) under extremely low applied electrical powers (∼nW). Here, light emission occurs under positive applied gate voltages, with the FET in its “off” state. This enables us to apply high bias voltages (4 V) without heating the CNT. Under these

conditions, we observe light emission at currents as small as 1 nA and corresponding electrical powers of 4nW, which is 3 orders of magnitude lower than previous studies. Thermal emission is ruled out by monitoring the G band Raman frequency, which shows no evidence of heating under these small electrical currents. The mechanism of light emission is

understood on the basis of steep band bending that occurs in the conduction and valence band profiles at the contacts, which produces a peak electric field of 500 kV/cm, enabling the acceleration of carriers beyond the threshold of exciton emission. The exciton-generated electrons and holes are then accelerated in this field and emit excitons in an avalanche process. This is evidenced by an extremely sharp increase in the current with bias voltage (45 mV/dec). We also observe light emission at negative applied gate voltages when the FET is in its “on” state at comparable electrical powers to those reported previously (∼5 μW). However, substantial Joule heating (T > 1000 K) is also observed under these conditions, and it is difficult to separate the mechanisms of thermal emission from hot carrier photoemission in this regime.

Bo Wang, Fatemeh Rezaeifar, Jihan Chen, Sisi Yang, Rehan Kapadia and Stephen B. Cronin, ACS Photonics , DOI:10.1021/acsphotonics.7b00455 (2017)
(Invited) Diameter-Dependent Optical Absorption and Energy Transfer from Encapsulated Dye Molecules to Single Wall Carbon Nanotubes
Authors: Wenseleers Wim , Van Bezouw Stein , Campo Jochen , Cambré Sofie , Defillet Joeri , Arias Dylan , Ihly Rachelle , Ferguson Andrew John , Johnson Justin C. , Blackburn Jeffrey L.
Published: February 2020

The hollow core and well-defined diameters of single-walled carbon nanotubes (SWCNTs) allow for creation of unique one-dimensional hybrid structures by encapsulation of various molecules. For instance, we previously demonstrated that in this way dipolar dye molecules can be naturally aligned in an ideal head-to-tail arrangement to create assemblies with a giant total nonlinear optical response.[1] Here, we show that the optical properties of dye molecules encapsulated in SWCNTs can be strongly modulated by the SWCNT diameter, indicating very specific diameter-dependent stacking and interactions of the molecules. The filling is thoroughly characterized by optical absorption, resonant Raman, and two-dimensional infrared photoluminescence excitation (PLE) spectroscopy. Energy transfer probed by PLE spectroscopy shows the absorption spectrum of the dyes to be strongly diameter-dependent, and transient absorption spectroscopy, simultaneously probing the encapsulated dyes and the host SWCNTs, demonstrates sub-picosecond EET from encapsulated molecules to the host SWCNTs. The design of these functional hybrid systems, with tuneable dye absorption, EET depending on the SWCNT diameter and the ability to remove all metallic SWCNTs by subsequent separation, demonstrates potential for implementation in dedicated photo-conversion devices.

[1] S. Cambré, J. Campo et al., Nature Nanotechnol. 10, 248 (2015).
(Invited) How Can We Improve C2-Poducts Selectivity in the Electrochemical CO2 Reduction?
Authors: Lee Min Hyung
Published: February 2020

In recently, a lot of efforts have been devoted to developing electrocatalysts capable to convert CO2 into chemical fuels. Especially, CO2 conversion into multiple carbons (≥ C2) are desired due to higher volumetric energy density and lower volatility than C1 chemicals. Among transition metals, Cu is the only one that can produce C2 products; however, selectivity of the C2 chemical is very low. In this presentation, the selectivity control of C2 chemicals depending on morphology of Cu nanomeshes will be introduced. Faradaic efficiencies of 38 % and 46 % for ethylene and ethane, respectively, have been achieved thanks to local pH and flow field controls in small nanopores. Our approach provide a new strategy for systematic tunability of the product selectivity and reaction kinetics of CO2 reduction.

Figure 1
High-Performance Flexible Bio-Electronics for Electrophysiological Recordings
Authors: Jeon Jun-Young , Kang Byeong-Cheol , Ha Tae-Jun
Published: February 2020

Recently, bio-electronic devices which can in real-time collect electrophysiological signals such as electrocardiograms (ECGs), electromyograms (EMGs), and electroencephalograms (EEGs) have been actively investigated corresponding to the change in healthcare monitoring paradigm. Flexible bio-electronics which are attachable to the human skin can collect the important bio-signals regardless of spatial and temporal constraints differently with conventional rigid bio-electronics. However, most of studies on the fabrication of flexible bio-electronics require high-cost equipment and complicated process. In this presentation, we will demonstrate highly sensitive flexible bio-electrodes using biocompatible composite materials, which can detect electrophysiological signals (such as EMG, and ECG) more accurately without the negative aspects during the wearing. We will also discuss the practical approach for the flexible bio-electronics fabricated using solution-process at low-temperature in an ambient atmosphere. We believe that this work can contribute to realize wearable nanoelectronics embedded into the healthcare monitoring systems. This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (NRF-2017R1A2B2003808).
(Invited) First-Principles Investigation of Single Layer of Pt on Graphene
Authors: Choi Ji Il , Alamgir Faisal M , Jang Seung Soon
Published: February 2020

Platinum is a face centered cubic structured crystal that has been widely known as a superior catalyst for various chemical reactions, while low-dimensional structures, such as mono- or bi-layer platinum, have attracted less attention due to experimental difficulties in synthesizing such 2D structures. In this study, for the first time, we present a computational research on the unique architecture of epitaxial platinum (mono/multi) layers grown on graphene (Pt_ML/GR), in support of remarkable recent progress in the synthesis of these architectures in simple cubic-like (SC-L) and face-centered cubic-like (FCC-L) phases on the graphene. In these architectures, Pt exhibits registry with the C-C bridge sites along the armchair and zigzag directions. Here, the detailed band structure and the partial/total densities of state (DOS) of the Pt_ML/GR architectures, with Pt in an SC-L registry, is presented. Pt atoms on graphene prefer bonding with two carbons covalently, turning C-C sp2 bond to sp3 bond, while metallic bonding prevails on the Pt atoms. Investigation of the hybrid bonding configuration and electronic properties requires well-described ground-states of the metallic and covalent bonding configuration, simultaneously. Recently proposed strongly constrained and appropriately normed (SCAN) density function study (DFT) is employed to investigate the structural and electronic properties of the epitaxial SC-L Pt layered graphene. First, the epitaxial geometry of Pt layers as well as inter-layer distance between graphene and Pt layer are in good agreement with the experimental observations. Second, the covalent bond character is observed between Pt and C while Pt layer attains the metallic bond character. Furthermore, as an application for electrochemical system such as fuel cells, the efficacy and the stability of Pt ML/GR catalysts under the canonical oxygen reduction reaction are presented.
Covalently Fabricated Graphene Interface for Electrochemical Detection of Resorcinol an Endocrine Disruptor in Solubilized Ionic Liquid System
Authors: Rather Jahangir Ahmad , Alsubhi Zamzam , Khan Imran , Khudaish Emad , Kannan Palanisamy
Published: February 2020

We report synthesis, characterization and covalent fabrication of graphene nanosheets (GR) at gold (Au) electrode. The synthesized GR nanosheets were characterized by FTIR, UV-vis spectroscopy, XRD and FESEM techniques. The GR nanosheets were functionalized to produce GR–Ph–COOH. In another step, Au electrode was modified by cysteamine to form Au–S–CH2–CH2–NH2. The COOH groups of GR–Ph–COOH were covalently attached to amine groups of Au–S–CH2–CH2–NH2 through carbodiimide linkage using EDC and NHS as coupling agents. The GR–Cyst–Au interface was used for electrochemical determination of resorcinol (RS), an endocrine disruptor in solubilized ionic liquid (IL) ([C4mim][Cl]) system over a concentration range from 0.3 to 45.2 µM with a detection limit (LOD) of 0.02 µM. The faster electron transfer kinetics of RS in [C4mim][Cl] system were attributed to synergetic effects of large surface area, high conductivity, charge transporting abilities of GR and high intrinsic conductivity of [C4mim][Cl] system. The GR–Cyst–Au interface was applied for determination of RS in the Garnier hair color cream as a real sample. Computational quantum approach i.e. COSMO-RS model was used to study trend of interactions in ternary mixture of water, RS and solubilized system for proposed RS sensor.

Figure 1
(Invited) High Temperature Flexible Supercapacitors
Authors: Park Ho Seok , Rana Harpalsinh H.
Published: February 2020

With increasing demand for high performance energy storage systems, the feasibility of reliable and functional energy storage devices that well operates under extreme conditions is of prime importance for expanding applicative fields as well as for understanding materials’ intrinsic and extrinsic properties and device physics. Our group has been investigating ultracapacitive energy storage materials and devices operating under limited circumstances, where conditions are classified into thermodynamic (e.g. pressure, volume and temperature) and kinetic (e.g. high rate and frequency) variables. In this talk, I will introduce high temperature operating, flexible supercapacitors based on graphene electrodes and polymer or gel electrolytes that can efficiently deliver electrical energy under electrochemical, mechanical and thermal stresses.[1-4] In order to achieve high performance supercapacitor devices under thermal, mechanical and electrochemical stresses, the micro- and macroscopic structures and chemical compositions of graphenes are delicately controlled by chemical modification. For the case of electrolyte materials, both of electrochemical properties and mechanical integrity should be satisfied for high temperature device applications. A new generation of flexible supercapacitors, with the long-term durability and outstanding electrochemical properties, were realized, showing a high position of the Ragone plot, even under severe conditions.

References

[1] B. G. Choi, J. Hong, W. H. Hong, P. T. Hammond, ACS Nano, 5, 7205-7213 (2011).

[2] B. C. Kim, J. Y. Hong, G. G. Wallace, H. S. Park, Adv. Energy Mater, 5, 1500959 (2015).

[3] S. K. Kim, H. J. Kim, J. C. Lee, P. V. Braun, H. S. Park, ACS Nano, 9, 8569-8577 (2015).

[4] J. Y. Hong, B. M. Bak, J. J. Wie, J. Kong, H. S. Park, Adv. Funct. Mater., 25, 1053-1062 (2015).
Enhancement of PEC Water Splitting for Self-Carbon Doped TiO2 Nanorods / Au Nanoparticle / TiO2 Ternary Structure in All Solution Process
Authors: Hwang Jungyeon , Eom Kiryung , Han Hoseong , Seo Hyungtak
Published: February 2020

Titanium dioxide (TiO2) is an important metal-oxide semiconductor for photocatalytic applications due to its unique properties, such as photostability, low cost, abundance and nontoxicity. Despite of outstanding functionality, wide band gap of 3.2eV limits its application due to ultra-violet (UV) range absorption. In order to extend photo-excitation energy down to visible range, intensive efforts have made to manipulate bandgap of TiO2. In this study, we synthesized self-carbon doped TiO2 nanorods (C-TiO2 NRs) through hydrothermal synthesis to increase the absorption of visible light. Additionally, using the surface plasmonic resonance effect of gold nanoparticles, the photoelectrode was fabricated to increase the absorption of visible light. Then, TiO2 passivation layer deposited using the electro deposition to protect gold nanoparticle, which is typically vulnerable to photocorrosion. The synthesized C-TiO2 NRs/Au/TiO2 was characterized using X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). We confirmed that C-TiO2 NRs have rutile phase and the size of Au NPs is about ~10nm. UV-visible measurements confirmed the optical bandgap of the photoanode at the significantly lowered photon-energy. We carried out the X-ray photoelectron spectroscopy (XPS) to identify presence of carbon species and chemical oxidative states of C-TiO2 NRs. We investigated the PEC water splitting properties under 1sun illumination. We observed that C-TiO2 NRs/Au/TiO2 (1.6mA/cm2) show ~2 times higher current density than C-TiO2 NRs (0.75mA/cm2) and enhanced stability of photoelectrode.
The Frst Molecular Dumbbell Consisting of an Endohedral Sc3n@C80 and an Empty C60-Fullerene Building Block
Authors: Wei Tao , Hirsch Andreas
Published: February 2020

An unprecedented hybrid dumbbell consisting of a metallofullerene and an empty fullerene was afforded via simple click reaction of suitable precursor derivatives of Sc3N@C80 and a C60 hexakisadduct. The structure of synthetic endohedral clusterfullerene-based dumbbell was unambiguously characterized by MALDI-TOF mass spectrometry and 1H NMR spectroscopy. The electronic structure was carefully studied by UV-vis-NIR spectroscopy revealing its exceptional electronic behaviour compared to parental building blocks. In combine with the electronic property study of congener dimer on basis of solo C60, the peculiar electronic property of dumbbell is unveiled. Our success on the first construction of endohedral clusterfullerene dumbbell opens up a new perspective in fullerene chemistry.

Scheme 1: Schematic synthesis route of dumbbell

Figure 1
(Invited) Recent Developments Regarding Orientation Studies of Endohedral Nitrogen Fullerenes and Their Water-Solubilization
Authors: Porfyrakis Kyriakos
Published: February 2020

Paramagnetic endohedral fullerenes hold promise for a number of applications including quantum information processing and quantum sensing. In the case of endohedral nitrogen fullerenes such as N@C60 and N@C70, the nitrogen atom is almost completely isolated from the fullerene cage. This results in very long electron spin phase coherence times. The chemistry of endohedral nitrogen fullerenes has developed to a degree where it can be used to create functionalized systems with high aspect ratios that are prone to high alignment. In this talk, I will present our recent results for several N@C60 and N@C70 derivatives that we have aligned in liquid crystals. Within the liquid crystal matrix, we have achieved an order parameter factor Ozz
of 0.61. This is a significant improvement on the best result that has been previously reported for endohedral fullerene derivatives. More importantly, this allows us to manipulate the intrinsic zero-field splitting (ZFS) of the spin resonance signal. By in-situ rotating frozen endohedral fullerenes inside the magnetic field of the ESR spectrometer, we deliberately changed the orientation distribution of the molecules and tuned the splitting energy of ZFS. We achieved remarkable agreement between experimental values and simulation data. This work can be expanded to control of dipolar coupling for a two-qubit gate. Hence it is quite pertinent to research on potential applications of endohedral fullerenes. In my talk, I will also touch upon the water functionalization of N@C60. We have developed the first water-soluble derivative of N@C60 and we have shown that it has the potential to be used as a quantum sensor for other spin-active species.
(Invited) Synthesis of Graphene-C60 Hybrids
Authors: Langa Fernando
Published: February 2020

The combination of two carbon nanostructures in a single material, giving rise to new hybrids with improved mechanical, electrical, and thermal properties, has generated great interest in the last years. Although hybrids carbon nanotubes have been described, hybrids between graphene and fullerenes have received less attention.

In this talk, I´ll present our recent studies involving the synthesis of nanohybrids combining exfoliated Graphene and C60, as well as the new properties arising from the combination of both carbon nanomaterials.
(Invited) Purification and Frontier Orbital Characterisation of 19 Isomers of the OPV Acceptor Material Bis[60]PCBM
Authors: Dennis John , Shi Wenda , Hou Xueyan , Liu Tong
Published: February 2020

All 19 expected cyclopropa-fullerene isomers of the organic photovoltaic electron acceptor material bis-phenyl-C62-butyric acid methyl ester ("bisPCBM") have been isolated from the as-produced isomer mixture by peak-recycling high pressure liquid chromatography to a purity exceeding 99.5%, and their frontier orbitals characterised by UV-Vis absorption spectroscopy and cyclic voltammetry.

Using purified isomers in bisPCBM-based OPVs is expected to yield an increase in efficiency through the removal of energetic disorder and the removal of morphological disorder contributing to higher device currents; and through the using on isomers with higher LUMOs than the average for the isomer mixture contributing to an increase in device voltage. On the latter point above, an important factor in OPV efficiency is that the open-circuit voltage (“V
OC”) of OPVs scales linearly with the energy difference between the highest occupied molecular orbitals (“HOMOs”) of the donors and the lowest unoccupied molecular orbitals (“LUMOs”) of the acceptors. Hence, for a given donor, VOC is proportional to the LUMO level.

The LUMOs of the purified isomers were found to vary from -3.90 to -3.73 eV. As such, all isomers have LUMOs are above that of PCBM (-3.92 eV). Furthermore, the LUMOs of 13 of the 18 isomers are above that of the isomer mixture (-3.82 eV). OPV devices based on each of those 13 individual isomers will each have a higher V
OC than that of present devices based on the mixture. One isomer, with a LUMO ca. 100 meV above that of the mixture (and ca. 200 meV above that of PCBM), is particularly promising.

Preliminary results on two unoptimized P3HT/BisPCBM OPV devices based on the most abundant isomer with (a) a below average LUMO, and (b) an above average LUMO, gave V
OCs of 0.77 V and 0.83 V, respectively; which compares favourably with V
OCs of 0.63 V and 0.73 V of fully optimized P3HT/PCBM and P3HT/bisPCBM devices, respectively.
Metal Oxides As Additives to Improve Anode Performance in Molten Carbonate Fuel Cells (MCFC)
Authors: Beyad Yaser , Islam Monirul , Glenn Michael , Mathan Bobby , Allen Jessica A , Donne Scott W
Published: February 2020

In molten carbonate fuel cells (MCFC), oxidation of solid carbon fuels takes place at extended three-phase boundary (TPB) as molten carbonate electrolyte enhances the reaction interface in the anode compartment of the cell and facilitates diffusion of reactants. It also acts as an electrochemical mediator in oxidising carbon or carbon monoxide to carbon dioxide. Several studies have already been conducted to improve electrolyte’s performance in anode by either changing its composition or adding additives, i.e. metal oxides. Electrolyte composition effect, in terms of using different metal carbonates and their quantity in the mixture, on the performance of MCFC has been extensively investigated in the literature. However, comparing different additives effect on the overall performance of a cell using available data in the literature is not viable. This is because of lack of consistency in previous studies’ experimental conditions and specifically in anode composition. Also, there is not an agreement on mechanism that metal oxides improve the performance of MCFCs.

In the current study, two different percentages (5 and 10 wt%) of SnO2, CeO2, Fe2O3, and Mn2O3 were used as additives to electrolyte and fuel mixture of the anode. Performances of the full cell with different additives were evaluated in the same conditions using polarisation (IV) and electrochemical impedance spectroscopy (EIS) tests. In addition, thermal gravimetric analysis (TGA) and differential thermal analysis (DTA) were performed on anode slurry samples to further investigate details of the interactions between the anode electrolyte components. Based on the results, we provide a clear comparison on the effectiveness of these metal oxides in improving the cell performance and also suggest a mechanism that metal oxides enhance performance of anode in molten carbonate fuel cells.
Molecular Design and Applications of Redox Active Molecules in Redox Flow Batteries for Grid Scale Energy Storage
Authors: Liu T. Leo , Hu Bo
Published: February 2020

Redox flow batteries (RFBs) are recognized as one of most promising battery technologies to integrate intermittent renewable energy sources (e.g., solar and wind). Particularly, organic redox flow batteries are highly attractive for sustainable and economical large-scale energy storage as redox active molecules are synthetically tunable, sustainable, and potentially inexpensive. Through rational molecular engineering, we have developed and applied redox active molecules including viologen, ferrocene, and TEMPO for both aqueous and non-aqueous organic redox flow batteries (AORFBs and NAORFBs). In this presentation, we will discuss electrochemical studies of methyl viologen/ferrocene RFBs in aqueous and non-aqueous supporting electrolytes. Through the case studies of methyl viologen/ferrocene RFBs, this presentation aims to provide a direct technological comparison of AORFBs and NAORFBs regarding solution chemistry, energy efficiency, current performance, and cycling stability.

References: (1) Hu, B.; Liu, T. L.*, J. Energy Chem. 2018, in press. (2) DeBruler C.; Hu, B.; Moss, J.; Luo, J.; Liu, T. L.*, ACS Energy Letters 2018, 3, 663-668. (3) Luo, J.; Hu, B.; DeBruler C.; Liu, T. L.*, Angew. Chem. Int. Ed. 2018, 57, 231-235. (4) DeBruler C.; Hu, B.; Moss, J.; Liu, X. Luo, J.; Sun, Y; Liu, T. L.*, Chem, 2017, 3, 1-18. (5) Luo, J.; Sam, A.; Hu, B.; DeBruler C. Liu, T. L.* Nano Enegry, 2017, 42, 215-221. (6) Hu, B.; Seefeldt, C., DeBruler C.; Liu, T. L.*, J. Mater. Chem. A 2017, 5, 22137-22145. (7) Hu, B.; DeBruler C., Rhodes, Z.; Liu, T. L.*, J. Amer. Chem. Soc., 2017. (8) Liu, T.;* Wei, X.; Nie, Z.; Vince, S.; Wang, W. Adv. Energy Mat. 2016, 6, 1501449. (9) Filed US Patents covering applications of water soluble viologen, ferrocene derivatives, and TEMPO for RFBs. (10) Group website: www.tianbiaoliu.org.
Hierarchically Structured Membranes for Flow Batteries
Authors: Liu Ping , Yue Xiujun
Published: February 2020

High conductivity and selectivity are required properties for membranes for flow batteries. Unfortunately, there is often a tradeoff between the two. We have developed a hierarchically structured cation exchange membrane by integrating a dense, crack-free tungsten oxide coating layer on Nafion. The Nafion layer is also infiltrated with tungsten oxide in its hydrophilic, ion cluster regions. The composite structure is essential to maintaining a stable interface between the oxide coating layer and Nafion. The formation of oxide inside the Nafion hydrophilic region reduces water uptake and swelling ratio. The dimensionally stable composite layer thus serves as a stable support for the dense oxide coating on top. Coated by a sol-gel method, the dense oxide layer selectively transports cations (proton and potassium). Combing these two components of the structure results in a hierarchical structure with mechanical stability, high conductivity, and excellent selectivity. The permeability for Fe(II) and Cr(III) ions through the membrane are 2.31×10-8 cm2s-1 and 8.34×10-9 cm2s-1 respectively, an order of magnitude lower than Nafion, while the conductivity is comparable. Furthermore, the top dense oxide layer is estimated to exhibit a permeability for multivalent cations of only less than 0.2% of Nafion. The hierarchical structure design is a promising candidate for flow battery membrane applications.