bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Effective Solution-Phase Dopant for Generating Thin Films of Single Walled Carbon Nanotubes with Varying P-Type Conductivity
Authors: Stanton Noah J. , Ihly Rachelle , Norton-Baker Brenna , Ferguson Andrew John , Blackburn Jeffrey L. 
Published: February 2020

Single-walled carbon nanotubes (SWCNTs) have the potential to revolutionize many areas of opto-electronics, particularly thin-film photovoltaics and thermoelectrics due to their high carrier mobility and low-dimensional structure. Much effort has been devoted to increasing the thermoelectric power factor of SWCNTs by controlling the doping levels and doping types for enhanced thermoelectric conversion. Controlling the Fermi energy level within these unique 1D structures is often afforded by charge transfer interactions between host species (SWCNT) and electron or hole accepting species (dopant). Recent advancement of polymer-wrapped SWCNTs allows for thin-films of SWCNTs to be to cast using solution-based processing techniques. Conventional methods to dope SWCNTs rely upon intercalation of dopant molecules within solid-state networks of SWCNTs in a thin film. Here, we discuss methods to dope polymer-wrapped SWCNTs directly in solution by adding a p-type charge transfer dopant, F4-TCNQ, to SWCNT dispersions prior to thin-film deposition. This approach provides more control and reproducibility of the doping level and allows for SWCNTs inks to directly create doped thin films without the need for post-deposition treatments.
Interestingly, we show that introduction of the dopant at varying stages of polymer wrapping process of SWCNT dispersion impacts the polymer selectivity for semiconducting vs. metallic SWCNTs. By controlling the dopant concentration in solution, we show that the degree of doping is retained upon thin film formation, enabling creation of SWCNT thin films with controllable carrier concentrations for opto-electronic applications. We characterize the thermoelectric properties of the solution-phase doped films, and demonstrate large, tunable power factors that correlate well with the degree of doping in both the solution- and solid-state. Additionally, I will briefly discuss the implications of these results on the chemical interaction of F4-TCNQ with SWCNTs of various band gaps. This work has implications in the improvement of SWCNT-based thermoelectric devices and capability to create doped SWCNT thin films directly from solution for use in other opto-electronic applications such as thin-film photovoltaics.
(Invited) Deep Tissue Fluorescence Imaging in the Second Near-Infrared Window (NIR-II Window) Using Carbon Nanotubes
Authors: Hong Guosong , Diao Shuo , Dai Hongjie 
Published: February 2020

In vivo fluorescence imaging in the visible and traditional near-infrared (NIR-I) windows with wavelengths of 400~900 nm has been limited with sub-optimal resolution at >500 µm depths, due to strong scattering and absorption of photons by the turbid biological tissue, as well as high autofluorescence interference from the tissue in these windows. By exploiting the unique second near-infrared (NIR-II, 1.0~1.7 µm) fluorescence of single-walled carbon nanotubes (SWNTs), in vivo fluorescence imaging can be significantly improved with crisper resolution at deeper tissue penetration. This talk will cover our recent research progress on NIR-II fluorescence imaging, from in vivo mouse hindlimb vascular imaging (Nature Medicine, 2012; Circ. Cardiovasc. Imag. 2014) to brain vascular imaging (Nature Photonics, 2014; Angew. Chem. 2015) using SWNTs as the NIR-II fluorophore. In the first work, we have demonstrated microvascular angiography with improved spatial resolution over X-ray based computed tomography (CT), and hemodynamic measurement with larger dynamic range than ultrasonography. Owing to the high resolution, deep tissue penetration and the ability to record fast dynamics, NIR-II fluorescence imaging has allowed us to detect ischemic blood hypoperfusion in an animal model of lower limb ischemia with high sensitivity. In the second work, we have achieved sub-10 µm resolution mouse cerebrovascular imaging at millimeter depth inside the mouse brain through intact scalp and skull, using chemically purified SWNTs with enriched fluorescence emission in two optimized NIR-II sub-regions, the NIR-IIa window (1.3~1.4 µm) and the NIR-IIb window (1.5~1.7 µm). The non-invasive NIR-II brain imaging has allowed us to visualize and quantify the severity of middle cerebral arterial occlusion in a mouse model of stroke. Finally I will discuss potential future directions of NIR-II fluorescence imaging, such as the development of novel NIR-II fluorophores with more favorable emission wavelength and higher quantum efficiency, and the use of NIR-II fluorescence imaging for understanding the brain functions with new technological advances of NIR-II imaging.

References:

1. “Multifunctional in vivo vascular imaging using near-infrared II fluorescence” Nature Medicine 2012, 18, 1841-1846
2. “Near-infrared II fluorescence for imaging hindlimb vessel regeneration with dynamic tissue perfusion measurement” Circulation: Cardiovascular Imaging 2014, 7, 517-525
3. “Through Skull Fluorescence Imaging of the Brain in a New Near-Infrared Window” Nature Photonics, 2014, 8, 723-730
4. “Fluorescence Imaging In Vivo at Wavelengths beyond 1500 nm” Angew. Chem. Int. Ed. 2015, 127, 14971-14975
5. “Carbon Nanomaterials for Biological Imaging and Nanomedicinal Therapy” Chemical Reviews 2015, 115, 10816-10906
(Invited) Multiphoton Imaging of Carbon-Based Nanomaterials
Authors: Corr Stuart J. , Curley Steven A. , Wilson Lon J. 
Published: February 2020

Multiphoton Microscopy (MPM) has enabled an unprecedented level of dynamic exploration within living cells and organisms. The physical principle behind this imaging technique involves the use of near-infrared femtosecond lasers to excite optical processes in fluorescent molecules using two or more photons1. The use of long wavelengths (700 nm – 1000 nm) enables deep tissue penetration (up to 1000 μm) without inducing harmful biological effects. Previous studies include the examination of membrane potentials on the single-molecule scale2, the non-invasive observation of embryo development3, and the simultaneous multiplane imaging of calcium transportation in transgenic mice4. An excellent review of this field can be found in the literature5.
Herein we demonstrate a novel multiphoton-based technique for imaging non-fluorescent
carbon-based nanomaterials such as C60 fullerenes, single-walled carbon nanotubes, and graphene. More specifically, we demonstrate optical and photoluminescent activity in water-soluble C60-serinol, highly enriched (95 %) metallic and semiconducting single-walled carbon nanotubes, and functionalized graphene nanoribbons. This multiphoton imaging technique was also applied to in vitro and in vivo animal model studies. Various concentrations of the above mentioned nanomaterials were given to human pancreatic ductal adenocarcinoma (Panc-1) and hepatocellular carcinoma (Heb3B) cancer cell lines, as well as normal, healthy pancreatic ductal epithelial cells (HPDE). In all cases, imaging of these nanomaterials was possible using the MP imaging technique even though the nanomaterials exhibit no inherent fluorescent properties. We also examined the ability to image these nanomaterials, real-time, in vivo, using mice with orthotopic 4T1 breast tumors. Finally, we also include a range of spectroscopy data to examine the specific optical characteristics of the carbon nanomaterials.

References

1. Denk, W.; Strickler, J.; Webb, W. Science
1990, 248, (4951), 73-76.
2. Peleg, G.; Lewis, A.; Linial, M.; Loew, L. M. Proceedings of the National Academy of Sciences
1999, 96, (12), 6700-6704.
3. Chu, S.-W.; Chen, S.-Y.; Tsai, T.-H.; Liu, T.-M.; Lin, C.-Y.; Tsai, H.-J.; Sun, C.-K. Opt. Express
2003, 11, (23), 3093-3099.
4. Cheng, A.; Goncalves, J. T.; Golshani, P.; Arisaka, K.; Portera-Cailliau, C. Nat Meth
2011, 8, (2), 139-142.
5. Hoover, E. E.; Squier, J. A. Nat Photon
2013, 7, (2), 93-101.
Probing DNA Conformational Changes in Real Time Using Single-Molecule Electronic Sensors Based on Carbon Nanotube Field-Effect Transistors
Authors: Bouilly Delphine , Hon Jason , Daly Nathan S. , Trocchia Scott , Vernick Sefi , Warren Steven , Shepard Kenneth L. , Gonzalez Ruben L. , Nuckolls Colin 
Published: February 2020

In humans and other vertebrates, the ends of chromosomes are protected by a buffer region of single-stranded DNA (ssDNA) called the telomere. Telomeric ssDNA is made of multiple repeats of the nucleotide sequence GGGTTA and can form three-dimensional folded structures called G-quadruplexes, which are stabilized by monovalent cations like K+ or Na+. The formation of G-quadruplexes has been shown to disrupt the activity of enzymes necessary for telomere maintenance, enzymes that are also upregulated in many types of cancer cells and play a significant role in regulating cellular senescence. As such, G-quadruplexes are considered a potential therapeutic target for inhibiting the proliferation of cancerous cells and for treating aging-associated diseases. In this work, we use single-molecule field-effect transistors (smFETs) made from carbon nanotube devices to characterize the folding and unfolding dynamics of short stretches of telomeric ssDNA, and investigate the stability of G-quadruplex structures. First, we demonstrate a method for reliably functionalizing a carbon nanotube device with an individual ssDNA, using a combination of nano-confined covalent chemistry and bioconjugation reactions. The resulting smFET devices are then used to detect changes in the conformation of the ssDNA, in real-time and over a broad range of time scales. In the presence of K+ or Na+, we observe quantized fluctuations between high and low states in the conductance, which we are able to assign to the unfolded and G-quadruplex conformations, respectively. We discuss the effect of the identity and concentration of these two cations on the folding dynamics of G-quadruplex-forming ssDNA. In particular, we find that the folded G-quadruplex structure is 10 times more stable in K+ than Na+. This approach paves the way for investigations of the folding dynamics of various biomolecules at the single-molecule scale.
(Invited) Chirality-Dependent Surfactant Interactions Unravelled By Systematic Ultracentrifugal and Aqueous Two-Phase Separations
Authors: Cambre Sofie , Defillet Joeri , Wenseleers Wim 
Published: February 2020

The discovery that natural bile salt surfactants are extraordinarily efficient at solubilizing individual, intact single-wall carbon nanotubes (SWCNTs) in water[1], soon enabled the separation of different SWCNT structures for the first time by density gradient ultracentrifugation (DGU),[2] and more recently also by aqueous two-phase extraction (ATP).[3,4] Despite very nice results for a limited number of small diameter SWCNT chiralities that have been isolated as individual species by DGU and ATP, the underlying mechanisms are not fully understood and the number of variables to be explored and optimized is enormous, preventing a systematic extension to other chiralities.
Based on the unique capabilities of optical spectroscopy for characterizing SWCNTs, we present a systematic study of the structure sorting of DGU and ATP. We combine a direct in situ optical characterization of the centrifuge tubes after DGU[5] with systematic concentration-dependent ATP separations for different (mixed) surfactants and as such obtain a more detailed understanding of and control over both separation mechanisms. These systematic studies reveal that chirality-dependent surfactant interactions determine the separation order.
[1] W. Wenseleers et al.,
Adv. Fucnt. Mater.
2004, 14, 1105
[2]. M.S. Arnold et al., Nature Nanotechnol. 2006, 1, 60
[3]. C.Y. Khripin et al., J. Am. Chem. Soc.
2013, 135, 6822
[4]. N.K. Subbaiyan et al., ACS Nano
2014, 8, 1619
[5]. S. Cambré et al., Nanoscale
2015
, 7, 20015
Fullerene-Assisted Quenching of Single-Walled Carbon Nanotubes Photoluminescence through a Flavin-Helix
Authors: Papadimitrakopoulos Fotios , Mollahoseini Mehdi , Karunaratne Erandika , Gascon Jose 
Published: February 2020

Maintaining single-walled carbon nanotubes in their pristine state (i.e. devoid of aggregation and inhomogeneous doping) within nanostructured photovoltaic devices is a major challenge. In this contribution, we report on the synthesis and self-assembly of a C60-functionalized flavin (FC60), composed of PCBM and isoalloxazine moieties attached on either ends of a linear aliphatic spacer. Small amounts of FC60 (up to 3 molar %) were shown to co-assembly with an organic soluble derivative of flavin (FC12) around SWNTs and impart effective dispersion and individualization. Steady state and transient absorption spectroscopy illustrate that 1% or higher incorporation of FC60 allows for an effective photo-induced charge transfer quenching of the encased SWNTs through the seamless helical encase. This is enabled via the direct π-π overlap between the graphene sidewalls, isoalloxazine helix and the C60 cage, that facilitates SWNT exciton dissociation and electron transfer to the PCBM moiety. Atomistic molecular simulations elucidate how the fullerene is brought in the vicinity of the isoalloxazine helix to quench the nanotube. The narrow ES
ii
linewidth for the resulting ground state complex indicates a new class of highly organized supramolecular nanotube architecture with profound importance for advanced nanostructured devices.
(Invited) Chiral, Semiconducting Polymer-Wrapped Single-Walled Carbon Nanotube Superstructures for Opto-Electronic Applications
Authors: Olivier Jean-Hubert , Park Jaehong , Deria Pravas , Glesner Mary , Bai Yusong , Bullad George , Therien Michael J. 
Published: February 2020

We demonstrate that highly charged, chiral anionic semiconducting polymers helically wrap single-walled carbon nanontubes (SWNTs) at periodic and constant morphology. These polymers can be used as tools to modulate SWNT electronic properties, provide expansive solubility, or engineer electron acceptor units (e.g., perylene diimide, PDI) at rigorously defined intervals along the nanotube backbone. Femtosecond pump-probe transient absorption spectroscopic experiments show that excitation into the SWNT E11 transition of a S-PBN(b)-Ph4PDI-[(6,5) SWNT] superstructure generates SWNT hole polaron [(6,5) SWNT(•+)n] and PDI radical anion (PDI−•) states. These studies demonstrate for the first time a photoinduced electron transfer process involving a SWNT and a semiconducting polymer in which: (i) the charge-separated products, and (ii) photoinduced charge separation and thermal charge recombination dynamics, are fully characterized. To fully exploit these and related polymer-SWNT hybrids in opto-electronic applications, we have developed solution-based processes to structure dense, highly aligned arrays of these nano-objects on solid substrates. Polyanionic semiconducting polymers designed to wrap SWNTs with a fixed helical screw axis, used in combination with ionic self assembly approaches, enable for the first time the production of functionalized SWNTs that are fully soluble in organic solvents and capable of assembly into complex hierarchical structures that feature aligned nanotubes at high areal density (2.5 x1010 SWNTs cm-2) that maintain the opto-electronic properties characteristic of individualized SWNTs. These porphyrin-polymer/SWNT superstructures can be engineered to undergo both photoinduced electron- and hole-transfer reactions, thereby defining unique energy conversion assemblies, compositions with which to interrogate mechanistic issues regarding photoinduced charge transfer reactions involving nanoscale objects, and utilized as building blocks for highly organized mesoscopic materials that make possible investigation of electron and hole polaron transport phenomena in the solid state, as well as new types of electro-optic materials.

Figure 1
Photoinduced Spontaneous Free-Carrier Generation of (7,5)-Chirality-Enriched Single-Walled Carbon Nanotubes in a Low Dielectric Solvent
Authors: Rumbles Garry , Park Jaehong , Reid Obadiah , Blackburn Jeffrey L. 
Published: February 2020

We demonstrate photoinduced spontaneous free-carrier generation in highly individualized (7,5)- chirality-enriched SWCNT samples ((7,5)-SWCNTs) suspended in a non-polar organic solvent. Frequency-resolved solution-phase flash photolysis time-resolved microwave conductivity (fp- TRMC), provides a contactless and quantitative measurement of the real and imaginary photoconductance of these individually suspended nanotubes. We use substantially lower excitation fluences than have been possible in previous studies, corresponding to absorbed photon densities of ~0.05 photons per micron length of (7,5)-SWCNTs, allowing us to avoid complications from dielectric screening by nearby excitons or exciton-exciton collisions. Even under these mild conditions, we unambiguously measure a photoconductance due to free carriers that are generated following excitation of both the first and second exciton transitions (S11 and S22, respectively). The low-fluence carrier generation quantum yield (Φ) with S22 excitation appears c.a. 2.4 times higher than that with S11 excitation, suggesting that the autoionization of S22 excitons clearly enhances the carrier generation efficiency. In contrast, the transient decay dynamics are independent of excitation wavelength, suggesting that the mobile carriers generated from either S11 or S22 excitation undergo identical decay pathways (i.e. trapping, recombination, etc.).
(Invited) Photoluminescence Relaxation Dynamics of Covalently Doped Carbon Nanotubes
Authors: Doorn Stephen K. , Hartmann Nicolai F. , Velizhanin Kirill , Ma Xuedan , Htoon Han , Olivier Jean-Hubert , Therien Michael J. , Kim Mijin , Wang YuHuang 
Published: February 2020

New red-shifted emitting states in carbon nanotubes, introduced by stable covalently-bound dopants,1,2 are gaining attention for their potential to boost photoluminescence quantum yields,1,2 add new functionality,3 and serve as single photon emitters.4 Critical to these possibilities is the demonstration of exciton localization or trapping at individual dopant sites.5 As a consequence of trapping, exciton dynamics are significantly altered, with photoluminescence (PL) lifetimes being extended significantly.4 We will present a detailed study of the emission dynamics associated with dopant states introduced by aryl diazonium functionalization of semiconducting carbon nanotubes. Dopant-state PL lifetimes are found to increase by around a factor of 10 in comparison to E11 exciton lifetimes. Dependence of lifetimes on nanotube chirality, specific dopant, and dielectric environment will be presented and shown to exhibit a strong dependence on emission energy. Evidence for existence of an associated dark trap state will also be given. The results indicate multiple mechanisms for radiative and nonradiative decay. Of particular interest relevant to PL stability is the relation of PL decay to potential exciton detrapping. Possible contributing factors to detrapping, including detrapping energy, will be discussed.

References

1. Ghosh, S. et al., Science, 330, 1656 (2010).
2. Piao, Y. et al., Nature Chem., 5, 840 (2013).
3. Kwon, H. et al., J. Phys. Chem. C, 119, 3733.
4. Ma, X. et al., Nature Nanotech., 10, 671 (2015).
5. Hartmann, N.F. et al., Nanoscale, 7, 20521 (2015).
Functionalised Carbon Nanotubes As Components in Solid Acid Fuel Cell Electrodes
Authors: Naumov Olga , Lohmann Felix , Abel Bernd , Varga Aron 
Published: February 2020

We report on the role of as-grown and plasma treated multi-walled carbon nanotubes (MWCNTs) as cathode components in solid acid fuel cells (SAFCs). SAFCs combine a true solid state, proton conducting electrolyte, CsH2PO4 with good conductivity at mild temperatures slightly above 228 °C, with fuel flexibility and a high resistance to catalyst poisoning.1,2 The widespread application of solid acid fuel cells has been partly hindered by the necessity of the precious metal catalyst platinum in the electrodes.3,4

A general new approach in electrode catalysis bearing immense potential for electrochemical technologies is the prospect of precious metal free electrodes based on carbon nanomaterials.5,6

MWCNTs were synthesised by chemical vapour deposition using Ni nanoparticles as the growth catalyst on carbon paper current collectors. Oxygen plasma treatment was applied on selected samples with the dual effect of removing remaining amorphous carbon and increasing the concentration of oxygen functional groups on the surface. Symmetric electrochemical cells (MWCNTs|CsH2PO4|MWCNTs) were fabricated by uniaxial cold-pressing for impedance spectroscopy in a humidified oxygen environment at 240 °C. A good long term stability over a 19 day period and electrode impedances as low as 22 Ω cm2were measured, Figure 1. The oxygen plasma treated samples showed significantly lower impedances compared to as-synthesized. However, the application of a 500 mV DC bias voltage caused a dramatic drop in the electrode impedance when using as-synthesised MWCNTs. The impedance data suggests the electrochemical activity towards oxygen reduction and water splitting reaction after an initial reversible activation step. However, carbon corrosion is shown to have a non-negligible but small contribution to the measured currents. Scanning electron microscopy, Raman and XPS spectroscopy before and after the electrochemical measurements show increased oxygen concentration, increased graphitisation and slight morphological changes in all electrodes.
Caption Figure 1: (a) Scanning electron micrograph of representative MWCNTs on carbon paper fiber. (b) Electrode impedance of symmetric electrochemical cells (MWCNTs|CsH2PO4|MWCNTs) measured in humidied oxygen at 240 °C as a function of oxygen concentration of MWCNTs.
References
[1] S. M. Haile, D. A. Boysen, C. R. I. Chisholm and R. B. Merle, Nature, 2001, 410, 910-913.
[2] D. A. Boysen, T. Uda, C. R. I. Chisholm and S. M. Haile, Science, 2004, 303, 68-70.
[3] A. B. Papandrew, C. R. I. Chisholm, R. A. Elgammal, M. M. Ozer and S. K. Zecevic, Chemistry of
Materials, 2011, 23, 1659-1667.
[4] M. W. Louie, A. Hightower and S. M. Haile, ACS Nano, 2010, 4, 2811-2821.
[5] S. Zhang, Y. Y. Shao, G. P. Yin and Y. H. Lin, Journal of Materials Chemistry A, 2013, 1, 4631-4641.
[6] K. N. Wood, R. O'Hayre and S. Pylypenko, Energy & Environmental Science, 2014, 7, 1212-1249

Figure 1