bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
Photo-Physical Properties of Simple and Double Strand Multi-Porphyrinic Polypeptides
Authors: Solladie Nathalie 
Published: February 2020

One of our research field concerns porphyrin-functionalized a-polypeptides to control the spatial organization of the chromophores and enable exciton migration through the pool of porphyrins to mimic the light harvesting antennae of the photosynthetic system.1

In the photosynthetic system, the solar energy is collected by pigment molecules attached to the light harvesting complexes, in which the chlorophylls are held in a parallel orientation by fairly short a-helical polypeptides. When a photon hits one of the chlorophylls, the absorbed energy spreads extremely rapidly to the others until the reaction center is reached.1 Succeeding in organizing the porphyrins in a similar way as nature does should provide information about the relation existing between the orientation of the chlorophylls and the efficiency of nature in transferring an excited state over a very long distance and with minimal loss of energy.
The right-handed 310 helical conformation adopted by our poly-L-lysine functionalized with eight porphyrins induces an overlap of the chromophores, which thus present sufficient electronic coupling to promote a good exciton migration within the molecular wire. We thus synthesized a good model of the light harvesting antennas of the photosynthetic system (studies realized in collaboration with Prof. T. Keiderling, University of Chicago, US and Prof. T. Majima, SANKEN, Osaka, Japan).2

Our peptides with pendant porphyrins were studied extensively throughout the world in collaboration with foreign colleagues, and found applications as organic photovoltaic cells,3 or redox molecular switches4 (studies realized in collaboration with Prof. S. Fukuzumi, Univeristy of Osaka, Japan and Dr. P. Ceroni, University of Bologna, Italy).
These polypeptides with pendant porphyrins also found applications for the successful purification of Single-Walled Carbon Nanotubes (studies realized in collaboration with Prof. S. Fukuzumi, Univeristy of Osaka, Japan).5

Acknowledgements

This work was supported by the CNRS and the French Ministry of Research.

References

W. Kühlbrandt, Nature
1995, 374, 497-498.

M. Fujitsuka, D. W. Cho, N. Solladié, V. Troiani, H. Qiu, T. Majima, J. Photochem. Photobiol. A
2007, 188, 346-350.

T. Hasobe, K. Saito, P. V. Kamat, V. Troiani, H. Qiu, N. Solladié, K. S. Kim, J. K. Park, D. Kim, F. D'Souza, S. Fukuzumi, J. Mater.
Chem.
2007, 39, 4160-4170.

Paola Ceroni, Giacomo Bergamini, Nicolas Aubert, Vincent Troiani, Nathalie Solladié, Chem.
Phys. Chem.
2005, 6, 2120-2128.

Kenji Saito, Vincent Troiani, Hongjin Qiu, Nathalie Solladié, Takao Sakata, Hirotaro Mori, Mitsuo Ohama, Shunichi Fukuzumi, J. Phys.
Chem. C
2007, 111, 1194-1199.
Photophysics and Photochemistry of Trifluoromethylfullerene Fluorophores
Authors: Castro Karlee P , Jin Yuhuan , Rack Jeffrey J , Ferguson Andrew , Blackburn Jeffrey L. , Strauss Steven H. , Boltalina Olga V , Popov Alexey A. 
Published: February 2020

Five fluorescent trifluoromethyl fullerenes have been studied using time-resolved and steady-state spectroscopy. Prior to this study Nakamura et al. reported the highest quantum yield for a fullerene derivative of 0.24 with the molecule C60Ph10(CH2Ph)3Me2H (1). Three of the trifluoromethyl fullerenes presented exceed this, and one isomer of C70(CF3)10 has a quantum yield of 0.68 (2). The fluorescence lifetimes of three C70(CF3)10 compounds has been measured using time-resolved fluorescence spectroscopy. The compound with the highest quantum yield also has the longest fluorescence lifetime 51 ns. The ability of these compounds to sensitize the production of singlet oxygen has also been investigated.
Between isomers of C70(CF3)8 and C70(CF3)10 only one CF3 group is in a different location. This change in position results in 200 and 14-fold increases in the quantum yield. These isomers have very similar size and location of the remaining pi system; the remaining pi system had previously been hypothesized to be the determining factor for fluorescence quantum yields of C60 derivatives (1,3). Instead we propose that fluorescence quantum yields are more related to the oscillator strength and ΔS1−T1 energy gaps. These values can be predicted using time-dependent density functional theory calculations, which provides a method to target the most fluorescent fullerene derivatives.
References
1. T. Fujita; Y. Matsuo; and E. Nakamura, Chem. Mater.,
24, 3972 (2012).
2. K. P. Castro; Y. Jin; J. J. Rack; S. H. Strauss; O. V. Boltalina; A. A. Popov, J. Phys. Chem. Lett., 4, 2500 (2013).
3. Y. Matsuo; Y. Sato; M. Hashiguchi; K. Matsuo; and E. Nakamura, Adv. Funct. Mater.,
19, 2224 (2009).
Invited Presentation: Synthesis and Characterization of Graphene Layers (*†)
Authors: Pinczuk Aron 
Published: February 2020

A variety of methods are being employed in the fabrication of graphene layers. These fabricated layers need to be carefully evaluated and compared to a benchmark represented by the graphene layers that are obtained by mechanical exfoliation of graphite.
Two cases are considered here. One is that of graphene layers obtained by chemical vapor deposition (CVD) on Cu. The other case is that of graphene layers obtained by molecular beam (MB) growth, a form of van der Waals epitaxy. The MB epitaxy approach employs a solid carbon source, similar to that used in molecular beam epitaxy. The MB grown layers are fabricated directly on dielectric substrates. This is an achievement that could enable applications in electronics and optoelectronics.
While Raman spectroscopy is a primary characterization tool, techniques such as scanning tunneling microscopy (STM) and X-ray probes are employed to provide key insights.
The CVD graphene layers are coupled to the Cu substrate by weak van der Waals forces. Surprisingly, our studies reveal that strains that result from coupling to the substrate have significant impact on the quality of the graphene layers.
The van der Waals MB growth of single-layer graphene was demonstrated on h-BN and sapphire substrates.

(*) In collaboration with: Sheng Wang, Rui He, Lara Fernandes dos Santos, Liuyan. Zhao, U. Wurstbauer, J. M. García, A. N. Pasupathy, P. Kim, J. Hone, Lei Wang, C. R. Dean, Kenji Watanabe, Takashi Taniguchi, L. N. Pfeiffer, and A. S. Plaut.

(†) Supported by ONR and NSF
Invited Presentation: Logic Devices with Graphene PN Junctions
Authors: Lee Ji Ung 
Published: February 2020

Graphene p-n junctions (GPNJs) can be configured as logic devices that can meet the scaling challenges of CMOS devices. In the present context, GPNJs are not rectifying diodes since graphene is gapless. Instead, they exhibit unique angle dependent transport properties that allow the development of new type of electron-optics devices. This angle dependence has been used to predict novel devices, including the Veselago effect, steep subthreshold slope devices, and wave guiding structures.
Here, we describe the fabrication and characterization of GPNJs. We use buried gates to electrostatically dope the graphene to form the p- and n-doped regions. The buried gates are fabricated in CNSE’s advanced 300mm wafer line, which is used to obtain an atomically smooth dielectric surface above the gates to preserve the intrinsic electronic structure of graphene.
Using the split gates, we study different angled GPNJs and perform electrical measurements to extract the junction resistance. We observe a strong angle dependent junction resistance and confirm Klein tunneling, the normal tunneling component with unity transmission. By blocking the Klein tunneling component, we observe high on/off ratio devices.
Simple Patterning of Large-Area Graphene By Metal Mask and Sacrificial Polymer Layer
Authors: Kang Narae , Smith Christian W. , Ishigami Masa , Khondaker Saiful I. 
Published: February 2020

Graphene has attracted a lot of attention due to its extraordinary properties such as low resistivity, high mechanical/chemical stability, and high mobility. One particular area that has aroused recent interest is its use as an electrode material for organic electronics such as organic field-effect transistors (OFETs), organic flexible solar cell, and organic light-emitting diode (OLED). This is because, graphene has a high work function which matches to the highest occupied molecular orbital (HOMO) level of organic semiconductor, and has a strong π-π interaction with organic semiconductors which can reduce the injection barrier at the graphene/organic interface for enhanced the charge injection efficiency. However, for practical applications in organic electronics, large-area graphene film needs to be produced either via chemical vapor deposition (CVD) technique or via thin film of reduced graphene oxide (RGO) sheets and they need to be patterned in a specific dimension. The commonly used patterning technique is selectively etching of unwanted regions of graphene using metal etch mask and then the removal of the metal via harmful acid treatment.
In this work, we report a new approach for a simple patterning of graphene film by metal mask using a sacrificial methyl methacrylate (PMMA) polymer layer. Our method includes both spin-coated polymer layer as sacrificial layer and metal deposition by shadow mask as etching mask. After the graphene is placed on Si substrate, PMMA layer is spin-coated on top of the graphene film, and then the metal is evaporated through shadow mask. After the samples are exposed under plasma etching, the patterned graphene is obtained. The metal is then easily removed along with the with the PMMA layer by a acetone lift off. The size and shape of patterned graphene is the exactly same as the metal mask. We show that this new method can apply to different types of graphene film such as chemical vapor deposition (CVD) graphene and reduced graphene oxide (RGO) demonstrating as a reliable processing technique. In contrast to conventional metal etch mask patterning, our method does not include any harmful acid treatment of removing metal mask, making it an environmental-friendly method. We also fabricated OFETs by thermally depositing pentacene using patterned graphene electrode. Our devices show excellent device performance with a maximum mobility of 0.33cm2/Vs and current on-off ratio of ~105. We believe that this approach can open the new pathway for manufacturing other carbon-based thin film devices.
Ultrafast Spectroscopy and Numerical Analysis of Inhomogeneous Electron Injection in Dye-Sensitized Solar Cells: Effect of Electrolyte
Authors: Furube Akihiro , Sunahara Kenji , Mahanta Subrata , Matsuzaki Hiroyuki 
Published: February 2020

Ultrafast electron injection from a photo-excited dye molecule to semiconductor electrode is one of the most important reactions in the dye-sensitized solar cell (DSSC). The reaction occurs in the wide time region from femtoseconds to nanoseconds with a inhomogeneous manner.[1,2] Since the origin of such inhomogeneity has not been understood well, there still is many problems to improve the photo conversion efficiency of DSSC.[2]Here, we propose a quantitative reaction model of the electron injection dynamics to discuss the origin of the inhomogeneity. Our experimental results of transient absorption spectroscopy (TAS) were successfully analyzed by the model.
Dye sensitized TiO2 films with Ru-complex (N719) were prepared. The fs-TAS and ns-TAS measurements were carried out for the films in acetonitrile-based electrolytes. The results were numerically analyzed as a sum of non-adiabatic electron transfer reactions, which supported our experimental finding that the inhomogeneous energy distribution of the energy gap between the donor and acceptor states (Δ) was present.[2]

Fig.1 shows the results of population time profile of injected electron in DSSC. The profiles are measured by fs-TAS at <1 ns and sub-nsTAS >1 ns. The simulation result based on our model showed a good agreement with the experimental result. Furthermore, the effects of electrolyte with different potential controlling ion (Li+) concentrations and the electron concentration in semiconductor electrode were investigated experimentally and the obtained electron injection kinetics were well explained by the numerical simulation, indicating that the model is reasonable.
In some cases, however, the model does not seem to be easily applicable. For example, when we measured electron injection kinetics from excited N719 to TiO2 in the presence of ionic liquid (IL) as surrounding solvent, less efficiency was observed for some ILs with higher viscosity (> 30 cP). This suggests that not only the driving force but also restriction of molecular reorientation of the sensitizer may affect the reaction.
Some other examples of electron injection dynamics relating to the effect of electrolytes and solvents will be shown and the mechanism will be discussed [3, 4].

Acknowledgement: A part of this work is supported by NEDO Japan.

Fig.1Population time profile of injected electron in DSSC. Solid line shows a simulation result.

References

[1] Y. Tachibana et al., J. Phys. Chem. B, 104, 1198 (2000)
[2] K. Sunahara, A. Furube et al., J. Phys. Chem. C, 115, 22084 (2011)
[3] A. Furube, Z. Wang, K. Sunahara, K. Hara, R. Katoh, and M. Tachiya, J. Am. Chem. Soc., 132, 6614-6615 (2010)
[4] S. Mahanta, A. Furube, H. Matsuzaki, T. N. Murakami, and H. Matsumoto, J. Phys. Chem. C, 116, 20213–20219 (2012)
Role of Hole Conductors in Quantum Dot and Organometal Perovskite Based Solid State Solar Cells
Authors: Kamat Prashant V , Christians Jeffrey A 
Published: February 2020

Semiconductor quantum dots (QDs) have the potential to design high efficiency solid-state QDSCs and ETA (Extremely Thin Absorber) solar cells. Tunable band gap and band edge through size quantization, large intrinsic dipole moments, and high extinction coefficients make them suitable light absorbing materials. A number of semiconductors have been explored in the design of solid state solar cells. These include CdS, CdSe, In2S3, and Sb2S3. Of particular interest is Sb2S3 which has a band gap of 1.7 − 1.8 eVallowing for light absorption throughout the visible range. Organometal perovskites such as CH3NH3PbI3 are the new semiconducting materials that have led to advances in thin film solar cells. However, hole transport remains a limiting factor in maximizing power conversion efficiency.
Using Sb2S3 (absorber) and CuSCN (hole conductor), we have constructed ETA solar cells exhibiting a power conversion efficiency of 3.3%. We have employed transient absorption spectroscopy to probe the hole transfer between Sb2S3 and CuSCN. In the Sb2S3 absorber layer, photogenerated holes are rapidly localized on the sulfur atoms of the crystal lattice, forming a sulfide radical (S−•) species. This trapped hole is transferred from the Sb2S3 absorber to the CuSCN hole conductor with an exponential time constant of 1680 ps. Similarly the hole transport properties in (CH3NH3PbI3) and hole conductor copper iodide has been probed by impedence spectroscopy. Charge separation in Sb2S3 and (CH3NH3PbI3) based solar cells which provide new insight into the design of new architectures for higher efficiency devices will be discussed.

ACKNOWLEDGMENT. The research described herein was supported by the Division of Chemical Sciences, Geosciences and Biosciences, Basic Energy Sciences, Office of Science, United States Department of Energy through grant number DE-FC02-04ER15533.