bluuebunny/crossref_metadata_2025 huggingface dataset:
Graded Density Ion Exchange Polymer Films on Electrodes: Impacts on Structure and Transport
Authors: Knoche Krysti L. , Leddy Johna
Published: February 2020

The full expression of Fick’s second law includes a distance dependent diffusion coefficient, D(x). In one dimension, for distance x and time t, the concentration is expressed as shown in Equation 1.

Eyring models for transport as a function density and viscosity are predicated on an activation energy for short distance hopping of the diffusing species from one low energy site to an adjacent site of similar low energy. This results in a correlation between density and viscosity.

In turn, the Stokes Einstein relationship (Equation 2) specifies diffusion coefficient and viscosity η are inversely related. Equation is for a spherical diffusion species of radius r, k is the Boltzmann constant, T is temperature. If viscosity varies in space as η(x), then D(x) varies in space proportional to 1/η.

Ficoll® (GE Life Sciences) is a highly branched, water soluble, hydrophilic copolymer of sucrose and epichlorohydrin that is used to establish density gradients. On application of Ficoll films to electrodes, the density gradient is preserved. Cyclic voltammetry of outer sphere redox probes such as tetramethylphenylenediamine yields near steady state responses as scan rate slows. Modeling of the voltammetric responses establishes that the density gradient establishes a steady state flux of materials to the electrodes. Images of Ficoll films immersed in solution confirm a density gradient.

Here, Ficoll is used as a template to form a graded film of the ion exchange polymer, Nafion® (DuPont). Films are formed on electrodes by cocasting Ficoll and Nafion. Alternatively, a cast film of Ficoll can serve as the template for the Nafion. Films are evaluated by imaging. When compared to a uniform Nafion film, cyclic voltammograms for outer sphere redox probes that pass through the ion exchange polymer are altered. Sigmoidal as well as Gaussian voltammograms are observed, dependent on conditions of film formation. The structural morphology changes imprinted on formation of Ficoll Nafion layers alters flux through the ion exchange polymer layer.

References and Acknowledgments: Support of the National Science Foundation and the University of Iowa is gratefully acknowledged. Thanks also to Dick Buck for his example as a thoughtful scientist and mentor.

[1] Krysti L. Knoche and Johna Leddy, manuscript in preparation.

[2] K. L. Knoche, P. D. Moberg, C. Hettige, and J. Leddy, "Simulation of Fick's Second Law for Spatially Variant Diffusion Coefficients," ECS Trans. (2013) 53 (15) 1-6.
Carbon-Electrode Dielectrophoresis for Bioparticle Manipulation
Authors: Martinez-Duarte Rodrigo
Published: February 2020

Here I present the recent advances on the use of 3D carbon-electrode Dielectrophoresis (carbonDEP) for bioparticle manipulation. The ultimate goal is to develop practical platforms for a variety of applications including diagnostics, cell sorting, and food safety. Therefore, the priority is on high throughput, high efficiency and user-friendliness. I’ve previously shown that 3D electrodes penetrating the bulk of the sample improve the throughput of DEP devices by minimizing the distance from a targeted particle to the closest electrode. Moreover, the use of 3D electrodes allows for the widening of the channel cross section, particularly its height, which inherently increases the processed sample volume per unit of time. This work details the low cost fabrication process of tall (>100 μm-high) carbon electrodes and their integration to robust microfluidics networks to obtain DEP chips; as well as two user-friendly portable platforms: one based on a syringe pump and another one based in centrifugal microfluidics. At last, results in bioparticle manipulation obtained in collaboration are presented and include a cell viability assay, cell selection and washing to improve sensitivity of PCR, enrichment of M. smegmatis towards better drugs to treat tuberculosis, DNA concentration and on-chip electrical lysis.
Suspended Carbon Nanowire-Based Structures for Sensor Platforms
Authors: Lim Yeongjin , Heo Jeong-Il , Shin Heungjoo
Published: February 2020

2D nanostructures including nanowires, nanotubes, and nanobelts have shown exceptional physiochemical properties suitable for highly sensitive sensors. Typically these nanomaterials are patterned in contact with the substrate and this limits the functionality of the nanostructures due to the effect of substrate. However, deficiency of nanofabrication technologies limited the fabrication of nanomaterials in a suspended form. In this research, suspended single carbon nanowires and carbon meshes composed of nanowires were simply fabricated using carbon-MEMS (microelectromechanical system) process including successive polymer patterning and pyrolysis. The nanowire diameter could be reduced down to ~190 nm using conventional UV-lithography because of a volume reduction accompanied in the pyrolysis process. Owing to the longitudinal tensile stress developed during pyrolysis, the nanowire can be less influenced by stiction so that the nanowire surface can be selectively functionalized with gas sensing materials such as palladium and metal oxide nanowires using lift-off process and hydrothermal process. Owing to the suspended geometry and high surface-to-volume ratio of the carbon nanowires, they showed good gas sensing capability. The suspended carbon mesh was applied for an electrochemical sensor by integrating a substrate-bound carbon electrode below the carbon mesh. This novel configuration enabled the current signal from ferro-/ferricyanide to be amplified up to 37 times using redox cycling.
Extraordinary Hydrogen Evolution and Oxidation Reaction Activity from Carbon Nanotubes
Authors: Das Rajib Kumar , Wang Yan , Vasilyeva Svetlana V. , Donoghue Evan P. , Kamenov George D. , Cheng Hai-Ping , Rinzler Andrew G.
Published: February 2020

The hydrogen evolution reaction, 2H+ + 2e- -> H2, has utility in the electrochemical production of hydrogen from water and is perhaps the most studied reaction in all of electrochemistry. Its converse, the hydrogen oxidation reaction, H2 -> 2H+ + 2e-, is the half cell reaction occurring in hydrogen fuel cells, which, by direct conversion of chemical to electrical energy avoids the Carnot efficiency limits intrinsic to heat pumps. These reactions are central to any realization of a hydrogen economy. Various forms of carbon have been used for decades as the precious metal catalyst support in these reactions. Here we report the unexpected result that single wall carbon nanotubes (SWNTs), can be activated by a simple process to exhibit an activity for these reactions, in acidic and pH neutral electrolytes, that exceeds that of all known non-precious metal catalysts. We have labored to exclude conventional metals as the source of this activity and concluded that it is due to the SWNTs themselves.
CNT/PAMAM LbL Films for the Electrogeneration of PtCo Electrocatalysts
Authors: Gasparotto Luiz Henrique da Silva , Castelhano André L B , Silva Anielle C A , Dantas Noelio O , Oliveira Osvaldo Novais de , Siqueira José Roberto
Published: February 2020

Herein we demonstrate that LbL films comprising PAMAM dendrimers and single-walled carbon nanotubes (SWCNTs) are efficient for controlling the morphology of electrogenerated platinum-cobalt (PtCo) nanostructures. While Co grew to the micrometer scale and poorly covered the ITO substrate, with the LbL matrix it was kept in the nanoscale regime and provided full substrate coverage. Co-decorated Pt nanoparticles were then generated with a single potential pulse in a solution containing simultaneously Co and Pt ions. Segregation of Pt and Co deposits was observed with field emission gun (FEG) images, but PtCo alloy was probably formed to some extent according to X-ray diffraction. The PtCo-LbL hybrid exhibited superior catalytic activity toward H2O2 reduction than the Pt-modified LbL film, which opens new prospects for applications in biosensing and fuel cells. Furthermore, the method based on LbL films as matrix is entirely generic and may be extended to other materials.
Invited Presentation: 1PA- and 2PA-PDT Photo-Inactivation of Cancer Cells with Deca- or Icosacationic [70]Fullerenes with Light Absorbing e‒-Donor Antenna
Authors: Chiang Long , Hamblin Michael
Published: February 2020

We report the synthesis and anticancer photodynamic properties of two new decacationic fullerene (LC14) and red light-harvesting antenna-fullerene conjugated monoadduct (LC15) derivatives. The antenna of LC15 was attached covalently to C60> in a close distance to cage of only <3.0 Ǻ to facilitate ultrafast photoinduced intramolecular electron-transfer (for type-I photochemistry) and photon absorption at long wavelengths up to 600 nm. Because LC15 was more hydrophobic than LC14 we compared formulation in Cremophor EL micelles with direct dilution from dimethylacetamide (DMA). We excited the fullerenes either with UVA (340‒380 nm) or white (400‒700 nm) light and studied their ability to generate singlet oxygen (1O2) and hydroxyl radicals (HO·) using specific fluorescent probes. HeLa human cervical cancer cells were studied in vitro for loss of viability, apoptosis and location of subcellular damage. LC14 produced more 1O2 than LC15, while LC15 produced much more HO·
than LC14. When delivered by DMA, LC14 killed more HeLa cells than LC15 when excited by UVA light, while LC15 killed more cells than LC14 when excited by white light consistent with the antenna effect. However LC15 was more effective than LC14 when delivered by micelles regardless of the excitation light. Apoptosis was produced more rapidly after illumination by micellar fullerenes compared to DMA delivery. Intracellular damage was more pronounced after micellar delivery and affected the endoplasmic reticulum as well as lysosomes and mitochondria. These novel structures may be used as photostable photosensitizers for topical application to superficial cancer.
Coating Hydrophobic Biopolymers Around Single-Walled Carbon Nanotubes for Biomedical Application
Authors: Xu Jia , Ziegler Kirk J
Published: February 2020

Single-walled carbon nanotubes (SWCNTs) have excellent sensing capabilities that can detect the interaction between the nanotube and the surrounding molecules. Understanding and ultimately controlling these interfaces are crucial because of its influence on reactivity, adsorption of pollutants, and interaction with biological materials. Poly(Butyl Cyanoacrylate) (PBCA) is a hydrophobic, biodegradable polymer that has potential applications in drug delivery and biosensors. A novel method is provided to coat PBCA around individual nanotubes. In the micelle structure of the nanotube, the hydrophobic monomer butyl cyanoacrylate will attach to the SWCNT surface and then go through polymerization, forming the PBCA-SWCNT composite. Photoluminescence, Raman and FTIR are used to characterize the coating process and demonstrate that PBCA-SWCNT forms a thin sheath around individual nanotubes. The cytotoxicity of the composite is studied and we will show how these systems could provide new avenues for loading drugs within SWCNTs.
Mechanical Method of Lithium-Ion Soh and SOC Measurement
Authors: Cannarella John , Arnold Craig B.
Published: February 2020

Despite the fundamental importance of state of health and state of charge determination in battery management systems, measurement of SOH and SOC is difficult and remains an area of active research. In this presentation we propose a novel approach to lithium-ion battery cell management which makes use of observed relationships between cell expansion and SOH/SOC to determine the SOH and SOC of a cell during operation using simple stack stress measurements.

We first present results from an aging study of constrained commercial lithium-ion pouch cells in which we observed an irreversible increase in stack stress during cycling [1]. The increase in stack stress is due to irreversible expansion of the solid battery electrodes against the rigid constraint of the cell housing. This increase in stack stress is not a result of gas evolution, as the same stress increase is observed in pouch cells with a slit cut in the pouch and cycled under argon atmosphere.

Plotting the stack stress against the SOH of the cell reveals a linear relationship between stack stress and SOH during cycling, as shown in Figure 2. This suggests a fundamental coupling between irreversible electrode expansion and capacity fade. By monitoring this irreversible expansion during cycling—either through stress or strain measurements of the pouch cell—we show that it is possible to determine the cell’s SOH from simple mechanical measurements. The simplicity of these measurements and their relationship to SOH offer many advantages to the current state of the art.

We also show that the same mechanical measurements can be used to determine the cell’s SOC by measuring reversible changes in the cell stress/thickness with cycling. The measured stress can be related to the SOC of the cell if the SOH is known. Stress measurements are advantageous to voltage measurements for determining SOC because voltage measurements are strongly affected by battery usage via overpotentials. This mechanical method of SOC determination is computationally simpler than Coulomb counting and is also able to account for discharge events such as internal short circuiting that Coulomb counting is unable to detect.

FIGURE CAPTIONS

Figure 1. Stress evolution of a constrained pouch cell during cycling showing an irreversible increase in stack stress.

Figure 2. Stack stress plotted against state of health shows a linear relationship between the two parameters.

Figure 3. Stack stress plotted against SOC at different states of health of the constrained pouch cell.

REFERENCES

[1]. J. Cannarella, C. B. Arnold, “Stress evolution and capacity fade in constrained lithium-ion pouch cells,” J. Power Sources
245(2014) 745-751.

ACKNOWLEDGEMENTS

Support was provided by the DoD through the NDSEG Program and by the Siebel Energy Challenge. J. C. also acknowledges the Rutgers-Princeton IGERT in Nanotechnology for Clean Energy.
From Ab-Initio Calculations to Multiscale Design of Si/C Core-Shell Particles for Li-Ion Anodes
Authors: Stournara Maria E. , Qi Yue , Shenoy Vivek B.
Published: February 2020

The design of novel Si-enhanced nanocomposite electrodes, that will successfully mitigate mechanical and chemical degradation, is becoming increasingly important for next generation Li-ion batteries. Recently, Si/C hollow core-shell nanoparticles were proposed as a promising anode architecture, which can successfully sustain thousands of cycles with high coulombic efficiency. As the structural integrity and functionality of these heterogeneous Si materials depend on the strength and fracture energy of the active materials, an in-depth understanding of their interface and intrinsic mechanical properties, such as fracture strength and debonding, is critical for the successful design of such composites. Here, we perform ab-initio simulations to calculate these properties for lithiated a-Si/ a-C interface structures, and we combine these results with linear elasticity expressions to model conditions that will avert fracture and debonding in these heterostructures. We calculate that the a-Si/a-C interface retains good adhesion, even at high stages of lithiation. For average lithiated structures, we predict that the strong Si-C bonding averts fracture at the interface; instead, the structure ruptures within lithiated a-Si. From the calculated values and linear elastic fracture mechanics, we construct a continuum level diagram, which outlines the safe regimes of operation in terms of the core and shell thickness and the state of charge. We believe that this multiscale approach can serve as a foundation for developing quantitative failure models, and for subsequent development of flaw-tolerant anode architectures.
Electrochemical Stress Measurements of Potential Induced Structural Changes in Sn Anodes for Li Ion Batteries
Authors: Tavassol Hadi , Gewirth Andrew
Published: February 2020

We report on electrochemical surface stress measurements of thin film Sn electrodes for Li-ion battery anodes at potentials <2.0 V vs. Li/Li+. In most anodes, mechanical changes are dominated and controlled by Li-host interactions. Graphite, Si, and a Au model system exhibit compressive stress resulting from Li insertion. Calculations support these experimental results. Anodes experience tensile stress resulting from Li removal. This tensile stress may create cracks, and cause capacity loss.

In contrast, Sn surfaces exhibit major compressive and tensile surface stress changes even before Li insertion. These features originate in conversion reactions between SnOx on the electrode surface and Li forming Sn and LiOx. During the cathodic scan, an intense compressive feature at ca. 0.7 V vs. Li/Li+ is observed. A major tensile release at ca. 0.6 V vs. Li/Li+ follows this compressive feature. Changes in the amount of oxygen in the surface film affect the electrochemical stress measurement dramatically, while having a more modest impact on the voltammetry. The SnOx/Li conversion reaction impacts the ability of Sn and its alloys to serve as an anode material for a Li ion battery.

We also report the results of matrix assisted laser desorption (MALDI) time of flight (TOF) mass spectrometry (MS) analysis of Sn electrodes. In a mixture of ethylene carbonate and dimethyl carbonate, long chain oligomers are observed following the first cycle. These oligomers are decomposed in the subsequent cycles showing that Sn surfaces form an unstable SEI. This decomposition results in oligomerized species, which are different from those formed at the end of the first cycle. We will discuss potential and solvent dependent oligomerization mechanisms and their effect on mechanical properties of Sn electrodes.
Prediction of Lithium Ion Cell Cycle Life By Coupled Chemical and Mechanical Degradation Modeling
Authors: Hasan Mohammed , Barai Pallab , Mukherjee Partha P.
Published: February 2020

Lithium-ion batteries (LIB), owing to their unique characteristics with high power and energy density, are broadly considered as a leading candidate for vehicle electrification. However, the limited cycle life, particularly during fast charging process, is a pivotal performance drawback of LIB. The irreversible formation of the Solid Electrolyte Inter-phase (SEI) at the anode particles surface is identified as a key aging mechanism for these batteries causing capacity loss and resistance rise [1]. Intercalation and deintercalation of Li ions inside the active particles generate significant amount of stress which leads to fracture. Formation of cracks creates new surface area during cycling. These fresh surfaces act as catalysis for SEI formation. At high charge or discharge rates, the diffusion induced fracture and crack propagation exacerbate that results in a higher side reactions rates [2]. Although the tremendous progress in using mathematical models in predicting the cycle life, limited studies have coupled the chemical and the mechanical aspects in cyclic life predictions. The significance of the coupling is manifested during high charge and discharge rates, that the intense intercalation poses high mechanical stresses to fracture the electrode.

In this study, we are investigating the influence of the coupled chemical and mechanical degradation mechanisms on the cycle life of LIB. The computational method comprises of; a first principle capacity fade model for chemical degradation predictions and a stochastic diffusion induced fracture for mechanical damage predictions incorporated in the single particle model [3, 4]. The coupled model is envisioned to present a fundamental elucidation of the high degradation and poor performance during fast charging and discharging rates.

V. Agubra, J. Fergus, Materials, 6 1310–1325 (2013).

J. Li, E. Murphy, J. Winnick, P.A. Kohl, J. Power Sources, 102, 160 (2001).

P. Barai and P. P. Mukherjee, J Electrochem Soc, 160 (6), A955 - A967 (2013).

R. Deshpande, M. Verbrugge, Y-T. Cheng, J. Wang, and P. Liu, J. Electrochem. Soc., 159 (10) A1730-A1738 (2012).

G. Ning, B. Haran, and B. N. Popov, J. Power Sources, 117, 160 (2003).
Deep TEM Study of Ageing Mechanisms of Li-Ion Batteries Associated with Renewable Energies
Authors: BEN Hassine Mohamed
Published: February 2020

The main objective of the ANR Vision project is to propose Li-ion batteries for energy storage application associated with renewable energy with a lifetime of 15-20 years. The scientific goal is to improve knowledge of long time aging mechanisms according to use conditions. This understanding would be helpful for improvement of prototypes that will be tested during the project. Batteries made of Li[Ni1-x-yMnxCoy]O2(NMC) and carbon a are investigated.

Electron microscopy techniques (Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), High Resolution-High Angle Annular Dark Field (HR-HAADF), Focused Ion Beam (FIB), Electron Dispersive Spectroscopy (EDS) and Electron Energy Loss Spectroscopy (EELS)), were deeply used to determine the degradation of the aged active materials: stress, strain, fracture, phase transformations, dissolution resulting from intense cycling.

By comparison of pristine and cycled materials, SEM investigation on FIB electrode slices revealed detachments and cracks inside and between active material and the binder (Figure 1) as well as preferential dissolution [1] of transition metal (EDS). SAED patterns show the creation of defects and highlight a transition phase from lamellar to spinel phase (Figure 2-A). In order to nicely visualized spinel domains [2, 3], images were recorded on a FEI Cs-corrected Titan Ultimate microscope fitted with HR-HAADF camera (Figure 2-B).

Afterwards, all these results, combined with information recorded by the other VISION partners, are used to make recommendations to create new generations of prototype cells.

[1] Nicholas P. W. Pieczonka et al., J. Phys. Chem. C 2013, 117, 15947−15957.

[2] A. Boulineau et al.,Chem. Mater. 2012, 24, 3558−3566.

[3] D. Mohanty et al., Journal of Power Sources 229 (2013) 239-248.

Acknowledgement: This work was funded by ANR (Agence Nationale de la Recherche) and is part of the VISION project.
Invited Presentation: Strong Nonlinear Photoluminescence Properties of Trions and Localized Excitons in Single-Walled Carbon Nanotubes
Authors: Matsuda Kazunari , Miyauchi Yuhei
Published: February 2020

Recently, the optical properties of carrier-doped single-walled carbon nanotubes (SWNTs) have been extensively studied [1-3]. We describe nonlinear photoluminescence (PL) properties of excitons and trions (charged excitons) in hole-doped SWNTs. We found that the PL intensity of the trions in hole-doped SWNTs exhibits a strong nonlinear saturation behavior as the excitation density increases, whereas that of the excitons shows a weak saturation behavior. The strong PL saturation of the trions is attributed to the state filling of trion states due to the limited number of doped holes. Moreover, the radiative lifetime of the trion was evaluated to be about 180 ns, which indicates that the experimentally observed PL from the trions originates from partially dipole-allowed transition in a SWNT. We will also discuss the nonlinear PL properties of localized excitons in oxygen-doped SWNTs [4,5].

[1] R. Matsunaga, K. Matsuda, and Y. Kanemitsu , Phys. Rev. Lett. 106, (2011) 037404. [2] J. S. Park, Y. Hirana, S. Mouri, Y. Miyauchi, N. Nakashima, and K. Matsuda, J. Am. Chem. Soc. 134, (2012) 14461.[3] S. Mouri, Y. Miyauchi, M. Iwamura, and K. Matsuda, Phys. Rev. B 87, (2013) 045408.[4] S. Ghosh, S. M. Bachilo, R. A. Simonette, K. M. Beckingham, and R. B. Weisman, Science, 330 (2010) 1656.[5] Y. Miyauchi, M. Iwamura, S. Mouri, T. Kawazoe, M. Ohtsu, and K. Matsuda, Nat. Photonics 6, (2013) 547.
Invited Presentation: Unifying the Low Temperature Luminescence Spectra of Carbon Nanotubes
Authors: Vialla Fabien , Chassagneux Yannick , Lauret Jean-Sébastien , Voisin Christophe
Published: February 2020

Photo-excited electron-hole pairs in carbon nanotubes form strongly bound and localized excitons that can recombine radiatively giving rise to near infrared luminescence signals. Due to the coupling to acoustic phonons, this PL line was predicted to be strongly broadened (even at low temperature), leading to asymmetrical meV-broad phonon sidebands. In addition, due to the peculiar one-dimensional geometry, the (possibly narrow) zero phonon line (ZPL) is completely merged into the phonon wings resulting in an overall broad and asymmetric PL line [1]. This picture was recently puzzled by the observation of ultra narrow PL lines in suspended nanotubes [2,3] raising questions about the electron-phonon coupling mechanisms. Here, we show that ultra narrow PL lines can also be observed for regular micelle wrapped nanotubes deposited on a substrate. However, a high resolution measurement allows to identify attenuated sidebands that are reminiscent of the one-dimensional electron-phonon coupling. This observation allows to interpret both the narrow and the broad lines in terms of modified electron-phonon coupling in a unified framework [4].

[1] Galland et al. PRL 101, 067402 (2008)

[2] Hofmann et al., Nature nano. 8, 502 (2013)

[3] Sarpkaya et al., Nature comm. 4, 2152 (2013)

[4] Vialla et al., submitted
Invited Presentation: Photoluminescence of Carbon Nanotubes at Room and Cryogenic Temperatures
Authors: Hofmann Matthias S. , Glückert Jan T. , Kneer Alexander , Noe Jonathan , Högele Alexander
Published: February 2020

Semiconducting carbon nanotubes exhibit excitonic transitions in the near-infrared. The past decades have established an extensive understanding of carbon nanotubes photophysics mainly based on room-temperature studies. More recently, cryogenic spectroscopy has identified non-classical emission from individual nanotubes which can be accompanied by spectrally narrow emission. We will present our latest results obtained with photoluminescence spectroscopy of single carbon nanotubes both at room and cryogenic temperatures and discuss the dependence of low-temperature spectra on transverse electric field.
Invited Presentation: Ensemble and Single Particle Spectroelectrochemistry of Semiconducting Single-Wall Carbon Nanotubes
Authors: Hertel Tobias , Hartleb Holger , Ruehl Nicolas
Published: February 2020

Spectroelectrochemical studies were used to investigate the photophysics of electrochemically doped (6,5) SWNTs. The optical properties of SWNT ensembles were here studied by quasi simultaneous absorption and photoluminescence spectroscopy over the NIR and VIS spectral ranges. This allowed correlating changes in the oscillator strength of first and second subband excitons with changes in the photoluminescence signals from the bright singlet exciton. The data thus provides a key link between photoluminescence quantum yields affecting PL measurements and the extent of SWNT p or n doping as evidenced by absorption spectra. The data also provides evidence for a shift of oscillator strength from exciton transitions to free carrier type transitions in higher lying subbands.
Invited Presentation: Understanding Energy Transfer Pathways in Semiconducting Carbon Nanotube Thin Films Using Two Dimensional White Light Spectroscopy
Authors: Arnold Michael S , Mehlenbacher Randy , McDonough Thomas , Wu Meng-Yin , Grechko Maksim , Ye Yumin , Zanni Martin
Published: February 2020

Carbon nanotubes are attractive materials for the light absorbing active layers of photovoltaic devices because of their tunable bandgaps, strong optical absorptivity, and ultrafast intra-tube charge and exciton transport. Also of critical importance in carbon nanotube devices are inter-tube charge and exciton transport processes. However, these are generally less well understood. We have developed two-dimensional white light spectroscopy (2D WL) as a novel probe of coupled thin films of semiconducting nanotubes and many other systems in the solar energy sciences. The advantage of exploiting 2D WL over typical 2D electronic spectroscopies is that the spectral bandwidth produced from supercontinuum generation is significantly broader than that accessible from an optical parametric amplifier. Thus, we are able to cover both S22 and S11 ranges with both pump and probe. By studying the evolution (as a function of waiting time) of crosspeaks between the Sii states for different bandgap nanotubes coupled together in thin film networks, we are able to map out Sii-Sjj inter-tube energy transfer pathways and rates and obtain maps of instantaneous photoexcitation distributions. Several surprising results will be reported.
Structure-Dependent Thermal Defunctionalization of Alkylated Single-Walled Carbon Nanotubes
Authors: Ghosh Saunab , Wei Fang , Fan Xiujun , Billups W. E. , Hauge Robert , Weisman R. Bruce
Published: February 2020

Covalent sidewall functionalization of SWCNTs with alkyl groups is an important process that allows nanotubes to be dissolved in organic solvents for further chemical processing, fundamental research studies, and applications development. Because of structure-dependent strain and reactivity, it is expected that the stability of functionalized SWCNTs may depend on nanotube diameter and roll-up angle. We report here a detailed study of variations in the rates of thermally induced defunctionalization for alkylated SWCNTs with a range of structures. Raw HiPco SWCNT samples were functionalized via reductive alkylation using lithium and alkyl halides in liquid ammonia. This gave high degrees of side-wall functionalization, as evidenced by the solubility and high Raman D to G peak ratios of the products. The alkylated samples were then heated for 30 min in an inert atmosphere at specific temperatures in the range of 100 to 500 °C and characterized by Raman, NIR fluorescence, and absorption spectroscopies, plus thermogravimetric analysis. It was found that the thermolysis treatment fully defunctionalized the nanotubes, but in a strongly structure dependent fashion, with larger diameter species becoming dealkylated at lower temperatures than smaller diameter species. This structure selectivity was especially evident from changes in the samples’ NIR fluorescence spectra. A quantitative interpretation of the results will be presented.
Invited Presentation: Ultimate Separation and Applications of Single-Wall Carbon Nanotubes
Authors: Kataura Hiromichi
Published: February 2020

Single-wall carbon nanotubes (SWCNTs) have attracted great attention for 20 years, because of their excellent physical properties. Especially, intrinsic high electron and hole mobilities are very attractive for the electronic device applications. However, mixed chirality production has been one of the most serious problems for both basic research and practical applications. To solve this problem, we have investigated separation methods of SWCNTs using gel column chromatography from 2008. Recently, we have clarified the separation mechanism of gel based separation methods, and realized high-purity and high-yield metal/semiconductor separation of SWCNTs as well as chirality separations. High quality sorted SWCNTs can be used for various applications such as thin film transistors and thermoelectric devices. We will show the latest results on the separation and the applications of SWCNTs.
Endohedral Fullerene Derivatives: Tether-Directed Functionalizations and Regioisomer Preferences
Authors: Echegoyen Luis , Izquierdo Marta , Ceron Maira
Published: February 2020

Addition reactions have been performed (carbene and addition-elimination, Bingel) on Sc3N@C2nto determine the preferred mono- as well as multiple addition positions both experimentally and via computations. It has been observed that carbene additions lead to many more isomers than the corresponding addition-elimination reactions of malonates (Bingel reaction), which lead to a rather small number of regioisomers. Theory predicts well the Bingel adducts that are observed experimentally and provides a kinetic rationale for the observations.

Tethered bis-additions have also been explored, especially on Lu3N@C80, and the results indicate very regioselective bis-additions, with only one bis-regioisomer observed in many cases for bis-carbene additions.

These and other results will be presented and discussed within the context of single and multiple functionalization of endohedral fullerene compounds and how the properties of the products can be controlled via functionalization.
Carbon Nanotube NIR Fluorescent Probes
Authors: Okazaki Toshiya
Published: February 2020

In clinical tests, detection of weak signals is especially important for detection of low concentration biomolecules. An enzyme-linked immunosorbent assay (ELISA) is often employed for antigen detection, where background fluorescence that is generated from the combination of autofluorescence from serum components and nonspecific binding serum proteins, limits detection sensitivity of an antigen by ELISA.

Near-infrared (NIR) fluorescence has attracted much more interests in diagnostic fields because of the lower background interference and the improved tissue penetration. Several NIR fluorescent molecules have been tried in enzymatic assays, DNA sequencing, capillary electrophoresis, immunoassay and so on. For example, by using NIR fluorescent nanoparticles, alpha fetoprotein was successfully detected even in whole-blood samples, which indicates a great advantage of NIR labels in clinical tests. Under these circumstances, novel NIR fluorescent molecules for biological label have so far been synthesized.

Single-walled carbon nanotubes (CNTs) have received much attention due to their superior mechanical, optical, thermal and electrical properties. In particular, CNTs have been considered as ideal labels for biological imaging in vitro and in vivo because CNTs show fluorescence in the wavelength region of 1000−1400 nm, so-called the second NIR window. In this wavelength region, indigenous tissue autofluorescence is much lower than that in the visible (400−750 nm) and shorter NIR (750−900 nm) regions, which enables clear vascular imaging with the CNT labels. This benefit is further enhanced by a large Stokes shift between emission and excitation resonances of CNTs, leading to further suppression of endogenous autofluorescence. Moreover, CNT photoluminescence does not show photobleach under prolonged duration of excitation as compared with NIR fluorescent dyes and quantum dots.

In the present work, to show the potential ability of the CNT labels in the immunological tests, we conjugated CNTs with immunoglobulin G (IgG) antibodies by using a linker molecule of phospholipid polyethylene glycol (PEG), and their immunoprecipitation using protein G magnetic beads was examined [1]. The combination of IgG and protein G was adopted because they specifically bind with each other. The present results, using CNTs as the NIR fluorescent labels for the immunoassay, will pave a new way for medical applications of CNTs.

Y. Iizumi, T. Okazaki, Y. Ikehara, M. Ogura, S. Fukata and M. Yudasaka, ACS Appl. Mater. Interfaces, 5, 7665−7670 (2013).
Manipulating Reactivity Differences for Isolating New Endohedral Metallofullerenes
Authors: Stevenson Steven
Published: February 2020

Much excitement is due to the production of new types of endohedral clusters inside fullerene cages. Scientists are also investigating the effect of increasing cage size versus the type and geometry of the entrapped cluster. Along with the enthusiasm of synthesizing diverse families of metallofullerenes comes the technical hurdle of isolating purified compounds from increasingly complex mixtures in raw soot extract. Based on reactivity differences between empty-cage fullerenes and endohedrals, one can fractionate and obtain separate samples of fullerenes and endohedrals. Our newest results show even further selectivity such that we can now achieve a separation of endohedrals from other endohedrals. An advantage of our new separation science is the non-HPLC approach. I will discuss the complexation/decomplexation approach with Lewis acids to distinguish between different classes of endohedrals. Further selectivity can be achieved by manipulating a binding step to amines, followed by kinetic differences during their release.
A Complete Guide on the Influence of Metal Clusters in the Diels-Alder Regioselectivity of Ih
-C80 Endohedral Metallofullerenes
Authors: Garcia-Borràs Marc , Osuna Sílvia , Luis Josep Maria , Swart Marcel , Solà Miquel
Published: February 2020

The chemical functionalization of endohedral metallofullerenes (EMFs) arouses considerable interest for the possibility to synthesize new species with potential applications in materials science and medicine. Experimental and theoretical studies on the reactivity of endohedral metallofullerenes are scarce. To improve our understanding of the endohedral metallofullerene reactivity, we have systematically studied with density functional methods the Diels-Alder cycloaddition between s-cis-1,3-butadiene and practically all X@Ih
-C80 EMFs synthesized up to date: X = Sc3N, Lu3N, Y3N, La2, Y3, Sc3C2, Sc4C2, Sc3CH, Sc3NC, Sc4O2, and Sc4O3.1,2 We have studied both the thermodynamic and the kinetic regioselectivity, taking into account the free rotation of the metallic cluster inside the fullerene. This systematic study has been made possible through the use of the Frozen Cage Model, a computationally cheap approach to accurately predict the exohedral regioselectivity of cycloaddition reactions in EMFs. Our results show that the reactivity of all metal clusters studied is lower than that of the hollow Ih
-C80 cage. Except for the Y3 cluster, the addition takes place predominantly over the [5,6] bond. In many cases, however, a mixture of the two possible regioisomers is predicted. In general, the [6,6] addition is favored in EMFs that have a larger charge transfer from the metal cluster to the cage or have a voluminous metal cluster inside. The present investigation represents the first complete and exhaustive guide on the reactivity of Ih
-C80 based EMFs.

[Figure 1 here]

1. M. Garcia-Borràs, S. Osuna, J.M. Luis, M. Swart, and M. Solà, Chem. Eur. J. 2013, DOI: 10.1002/chem.201302202.

2. S. Osuna, R. Valencia, A. Rodríguez-Fortea, M. Swart, M. Solà, J.M. Poblet, Chem. Eur. J. 2012, 18, 8944.
Cyanation of Fullerene(CF3)
n
Does Not Always Increase Electron Affinity: Experimental and Theoretical Study
Authors: Clikeman Tyler Tranel , Deng S. H. M. , Avdoshenko Stanislav , Wang Xue-Bin , Popov Alexey A. , Strauss Steven H. , Boltalina Olga V.
Published: February 2020

Trifluoromethylfullerenes have highly tunable electronic properties and can be used as adaptable building blocks for advanced organic electronics. Previously, our group has shown that the frontier orbitals of a series of C60(CF3)
n
are greatly influenced by the addition pattern of CF3 groups, which in turn, has a profound influence on electron affinities.1 Judicious additions of strong electron-withdrawing groups, such as CN or CF3, to fullerene cages are typically expected (and theoretically predicted) to increase electron affinity.

Indeed, regioselective synthesis of a new SPP derivative with three unique addends, C60(CF3)4(CN)H, made possible due to the use of a new isomer of C60(CF3)4 as a substrate, resulted in the experimental and theoretical identification of a family of superhalogen fullerene radicals, species with the gas-phase electron affinity higher than that of the most electronegative halogens, F and Cl.2 The addition of one CN group to C60(CF3)4 increases the measured gas-phase electron affinity by more than 1 eV to 4.28(1) eV; such a large increase is likely due to a significant stabilization of the skew pentagonal pyramid pattern (SPP), and electron-withdrawing effect of CN group. In contrast, the measured electron affinity of another SPP open shell molecular species, C60(CF3)4H, is considerably lower, 3.96(1) eV.

Regioselective cyanation of several C70(CF3)
n

compounds has also been carried out using recently described technique.3 In the case of C
1-C70(CF3)10, the addition of two CN groups results in an expected increase in the measured gas-phase electron affinity by 0.22 eV. Surprisingly, the addition of two electron-withdrawing CN groups to Cs
-C70(CF3)8 results in a decrease in the measured gas-phase electron affinity! This decrease is observed for two different CN addition patterns. The underlying reasons and implications for the design of electrophilic fullerene derivatives are rationalized using DFT calculations.

References

1 Popov, A. A.; Kareev, I. E.; Shustova, N. B.; Stukalin, E. B.; Lebedkin, S. F.; Seppelt, K.; Strauss, S. H.; Boltalina, O. V.; Dunsch, L. J. Am. Chem. Soc.
2007, 129, 11551.

2 Clikeman, T. T.; Deng, S. H. M.; Avdoshenko, S.; Wang, X.-B.; Popov , A. A.; Strauss, S. H.; Boltalina, O. V. Chem. Eur. J.
2013, 19, 15404.

3 Clikeman, T. T.; Kuvychko, I. V.; Shustova, N. B.; Chen, Y.-S.; Popov, A. A.; Boltalina, O. V.; Strauss, S. H. Chem. Eur. J.
2013, 19, 5070.
Synthesis, Structure, and Properties of C60-Pd Spherical Nanoparticles
Authors: Winkler Krzysztof , Brancewicz Ewa , Gradzka Emilia
Published: February 2020

Synthesis, structure, and properties of C60-Pd spherical nanoparticles

Krzysztof Winkler, Emilia Gradzka, Ewa Brancewicz

Institute
of Chemistry, University of Bialystok, Hurtowa 1, 15-399 Bialystok, Poland

The C60-Pd polymer can be synthesized electrochemically1 or chemically.2 The electrochemical synthesis results in the formation of thin and uniform film on the electrode surface. The film is electrochemically active at negative potentials due to the fullerene cages reduction.1

The chemical synthesis of C60-Pd polymer, carried out in benzene solution containing Pd2(dba)3·CHCl3 and fullerene C60, results in formation of large crystalline superficial structures which are composed of a small spherical particles 20-200 nm in diameter (Fig. 1). These cubic semi-crystals can be disintegrated to spherical nanoparticles with the high energy ultrasound. The size of synthesized C60-Pd nanoparticles can be controlled by composition of grown solution, time of polymerization, temperature of synthesis, and stirring conditions. The most uniform in size particles were synthesized in solution containing 3:1 ratio of [Pd] to [C60] concentration. Dispersed C60-Pd nanoparticles are stable in many organic protic and aprotic solvents. The electrochemical properties of films formed from chemically synthesized nanoparticles were investigated. Special attention was paid to capacitance properties. The electrochemical behavior of these films resembles the one observed for electrochemically synthesized polymers. Capacitance properties of films formed from C60-Pd nanoparticles depend on the size of polymeric nanoparticles. The specific capacitance of polymer formed in solution containing 1:1 ratio of [Pd] to [C60] reaches the value obtained earlier for electrochemically synthesized material.

The electrochemical properties of colloidal solutions of C60-Pd nanoparticles were also studied using ultramicroelectrodes. Diffusion controlled voltammograms are recorded for these systems.

Two component nanoparticlec composed of C60-Pd core and polypyrrole shell were synthesized. The electrochemical properties of such p-nspherical nanojunction were studied both in solid phase and in the solution.

Fig. 1. SEM (left panels) and TEM (right panels) images of chemically synthesized C60-Pd in benzene solution containing 0.48 mM C60 and 0.73 mM Pd2(dba)3·CHCl3

1. A.L. Balch, D.A.Costa, K. Winkler, J. Am.
Chem. Soc.,
120, 9614 (1998).

2. H. Nagashima, A. Nakaoka, Y. Saito, M. Kato, T. Kawanishi, K. Lotha, J. Chem. Soc.
Chem.

Commun., 377-379 (1992).
Solution-Processed Organic Photovoltaic Cells Fabricated Via the Precursor Approach Using α-Diketone Derivatives of Acenes
Authors: Suzuki Mitsuharu , Yamaguchi Yuji , Uchinaga Kensuke , Yamamoto Shinpei , Nakayama Ken-ichi , Yamada Hiroko
Published: February 2020

Acenes and their derivatives are commonly employed in organic electronics studies. However, they often lack the required solubility for solution deposition, which considerably limits their applicability to cost-effective devices. One of the proposed methodologies to evade this obstacle is the precursor approach, in which a soluble precursor is first deposited by a solution process then converted to a target acene compound within resulting thin films.

The focus of this study is to develop solution-processed thin-film organic photovoltaic (OPV) cells by employing α-diketone derivatives of acenes in active-layer deposition by the precursor approach.1 α-Diketone-type precursors are characterized by clean, quantitative conversion to corresponding acene compounds by visible-light irradiation even in the solid state. For example, anthradithiophene (ADT) can be obtained from its α-diketone-type precursor (ADTDK) in thin films, allowing solution-process fabrication of planar-junction OPV cells based on ADT as a p-type semiconductor. The maximum photo-conversion efficiency (PCE) of 1.54% was obtained when PC71BM was used as an n-type semiconductor.2 In another case, dithienylanthracene (DTAnt) was generated in thin films from its precursor DTAntDK, and the combination with PC71BM led to 1.66% PCE in a p–i–n type OPV cell. Results with more p-extended systems will also be presented.

Suzuki, M.; Aotake, T; Yamaguchi Y.; Noguchi, N.; Nakano, H.; Nakayama, K.; Yamada, H. J. Photochem. Photobiol. C.
2014, 18, 50–70.

Yamada, H.; Yamaguchi, Y.; Katoh, R.; Motoyama, Y.; Aotake, T.; Kuzuhara, D.; Suzuki, M.; Okujima, T.; Uno, H.; Aratani, N.; Nakayama, K. Chem. Commun.
2013, DOI: 10.1039/C3CC46178E.