bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Tailoring 2D Material-Based Aerogels for Energy Storage and Sensing Applications
Authors: Worsley Marcus A. 
Published: February 2020

Aerogels are nanoporous solids used in electrochemical processes relevant to a number of applications including, catalysis, batteries, supercapacitors, and sensing due to their high internal surface, composition, and small pore/particle size. Two-dimensional (2D) nanomaterials, such as graphene, boron nitride, transition metal dichalcogenides, also exhibit a range of distinct electronic and chemical properties, but are typically limited to thin films and coatings. Assembling 2D nanomaterials into monolithic aerogels expands their application space to include technologies and manufacturing processes that require a macroscopic 3D form factor. Furthermore, realizing the unique inherent qualities of 2D materials in a low-density, high surface area architecture creates new materials with novel properties and features only displayed within an aerogel framework. Here, we demonstrate recent work on assembling and tailoring various properties of aerogels made from several different 2D materials, (e.g. boron nitride, graphene, dichalcogenides, etc.). In particular, methods of controlling the composition via doping or hybrid aerogels (e.g. combining two or more layered materials), crystallinity, and macroscale architecture will be presented. The impact of those changes on aerogel properties and performance in energy storage and sensing devices will be discussed.
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Graphene and Graphene Oxide in Low Temperature Fuel Cells for Enhanced Performance.
Authors: Holmes Stuart Martin , Balakrishnan Prabhuraj , Perez Page Maria , Ozdincer Baki , Al Batty Sirhan 
Published: February 2020

The barrier and electrical properties of graphene and graphene oxide have been well documented with significant discussion around their efficacy as additives in low temperature PEM fuel cells. Graphene oxide has been demonstrated to be an ionic conductor but impermeable to dry gases and electrons. Graphene is an excellent in-plane electronic conductor but impermeable to all species apart from protons through the plane.
Here we will describe the work carried out at Manchester University incorporating Graphene, Reduced Graphene Oxide (RGO) and Graphene Oxide into PEM fuel cell Membrane Electrode Assemblies (MEA’s).
Reduced Graphene Oxide and boron and nitrogen doped RGO has been added to/replaced the carbon in the microporous layer adjacent to the cathode catalyst and provides enhanced fuel cell performance (up to 84% improvement in power density) due to greater electrical conductivity.
Graphene Oxide (GO) has been added to the Nafion binding layer in a Direct Methanol Fuel Cell (DMFC) providing additional tortuosity and hence reduced methanol permeability, the optimisation of the GO loading has led to superior performance(up to 50% improvement in power density) when compared to a standard DMFC.
The addition of CVD graphene (above 50oC) and hBN (at all temperatures) into the MEA has demonstrated no change in proton conductivity but lower fuel permeability [1], supporting the hypothesis of CVD graphene as a proton conductor and again increasing the power density achievable (30% in the initial experiment) by a DMFC. Figure 1
1. Holmes, S., Balakrishnan, P., Kalangi, V. S., Zhang, X., Ajayan, P. M., Lozada Hidalgo, M., & Raveendran Nair, R. (2016). 2-D Crystals Significantly Enhance the Performance of a Working Fuel Cell. Advanced Energy Materials. .

Figure 1
Phonon and Defect Induced Transparencies in the Mid-Infrared Spectrum of Grafted Single Layer Graphene
Authors: Lapointe François , Rousseau Bruno , Nguyen Minh , Aymong Vincent , Biron Maxime , Gaufrès Étienne , Desjardins Patrick , Côté Michel , Martel Richard 
Published: February 2020

The Drude-like response of graphene in the terahertz and infrared region of the spectrum has made it attractive for optoelectronic applications in this range, because the response can be controlled by gating and doping. [1] Graphene infrared response can further be tailored for photonics and plasmonics, as the patterned material harbors low energy plasmon modes. [2] However, the infrared spectrum of pristine single layer graphene (SLG) is monotonous; in contrast to Raman, there are no infrared-active phonon modes, while bilayer graphene displays a Fano resonance in the infrared at ~1600 cm-1. [3]

In a first time, we show experimentally that grafting SLG with halogenophenyl moieties induces optical transparencies at two specific energies: 1250 and 1600 cm-1 [4], in close similarity to the bands that can also be observed in carbon nanotubes as Fano resonances. [5] Unlike bands caused by the absorption of light by vibrational modes, these antiresonances show a decrease of the absorbance, an optical transparency effect. Moreover, we show that the amplitude of the transparencies can be modulated by changing the charge carrier density through doping, and by the defect density through controlled grafting.
In as second time, we will present a theory based on quantum mechanics to calculate the optical conductivity of grafted SLG. [4] The model puts into play phonon modes with momenta different from Γ that can be addressed through scattering on defects. Numerical simulations reproduce the experimental data with good agreement. The theory also captures the dependence of the signal on charge carrier density and defect density.
Our findings bring a new understanding for the physics behind the infrared activity of nanostructures, while opening new capabilities for tailoring the optical spectrum of nanomaterials.
References
[1] Horng et al. (2011) Phys Rev B 83:165113
[2] Low & Avouris (2014) ACS Nano 8:1086
[3] Kuzmenko et al. (2009) Phys Rev Lett 103:116804
[4] Rousseau et al. (2014) arXiv preprint arxiv:1407.8141
[5] Lapointe et al. (2012) Phys Rev Lett 109:097402
Doping of Graphene By Atomic Layer Deposition of Ruthenium
Authors: Kim Minsu , Kim Ki-Ju , Lee Seung-Joon , Kim Hyun-Mi , Cho Seong-Yong , Kim Min-Sik , Kim Soo-Hyun , Kim Ki-Bum 
Published: February 2020

Graphene has received enormous attention from both academia and industry owing to its excellent electrical, optical, chemical, and mechanical properties. A combination of properties makes graphene a strong candidate for the next generation of flexible and transparent conductive electrode (TCE) materials, but in practice the sheet resistance of a single, as-grown layer of graphene is still not sufficient for this purpose. One of the methods for creating highly conductive graphene films is to increase the charge carrier density through doping.
Here, we propose a novel method of graphene doping based on atomic layer deposition (ALD). Ideally, adsorption of precursor should be suppressed on clean surface of graphene since the surface is inert without dangling bonds and chemically active functional group. Defects (e.g., grain boundaries, wrinkles, cracks, holes and residual material) work as selective nucleation sites. Ru is selected due to it having a well-established precursor and recipe and the difference in work function between graphene and Ru can also allow for work function tuning and carrier generation.
The sheet resistance of graphene synthesized by chemical vapor deposition is found to be significantly reduced by the selective atomic layer deposition (ALD) of Ru onto defect sites such as wrinkles and grain boundaries. With 200 ALD cycles, the sheet resistance is reduced from ~500 Ω/sq to <50 Ω/sq and the p-type carrier density is drastically increased from 1013 cm-2 to 1015 cm-2. At the same time, the carrier mobility is reduced from ~670 cm2V-1s-1 to less than 100 cm2V-1s-1. This doping of graphene proved to be very stable, with the electrical properties remaining unchanged over 8 weeks of measurement. The selective deposition of Ru on defect sites also makes it possible to obtain a graphene film that is both highly transparent and electrically conductive (e.g., a sheet resistance of 125 Ω/sq with 92 % optical transmittance at 550 nm). The increase in the work function of graphene from 4.6 to 5.1 eV with Ru ALD provides clear evidence of hole carrier generation as a result of an electronic interaction between graphene and Ru. This demonstration of strong and stable doping of graphene with a high optical transmittance is therefore expected to contribute to the use of graphene as a TCE, and in other fields.
Figure 1. Ru ALD on graphene. (a) TEM images of graphene after 20 cycles of Ru ALD. (b) Sheet resistance of graphene as a function of the number of ALD cycles. Inset of (b) shows sheet resistance as a function of time.
Reference
Minsu Kim et al, ACS Appl. Mater. Interfaces, Article ASAP

Figure 1
(Invited) Colloidal Gold Nanoparticles Stabilized By Hydroxylated Fullerenes
Authors: Kokubo Ken , Sato Nozomi , Sakurai Hidehiro 
Published: February 2020

Since bare gold nanoparticles are unstable, they have to be stabilized by protecting with ligands, stabilizing with polymers or immobilizing on solids. Properties of gold nanoparticles depends on the design of their protecting ligands. Fullerene C60, a polyhedral carbon allotrope, possesses unique physical and chemical properties such as electron accepting character, high reactivity to radical species, low electrical conductivity, high thermal stability and so on, therefore utilization of fullerene derivatives to metal particles might be interesting, indeed, there are some reports on Au nanocomposites with C60. In order to prepare the colloidal dispersion of the Au and fullerene composites, soluble fullerene derivatives should be used. We have developed a series of polyhydroxylated fullerenes, C60(OH)n, and among them, C60(OH)36exhibits high water solubility up to 58.9 mg/mL and high dispersion on a molecular level.
Au:C60(OH)36 was synthesized by reduction with excess amount of NaBH4 from HAuCl4 aqueous solution in the presence of C60(OH)36. The colloidal particles are homogeneously dispersed in water and are stable for months. Its core size (measured by Transmission Electron Microscope) and colloid size (measured by Induced Grating Method) are 3.7 nm and 12.2 nm, respectively. X-rays photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) measurements revealed that the nanogold is negatively charged in total, but rather positively charged on the surface due to the interface interaction with C60(OH)36.
In this presentation, the catalytic activity of the thus-prepared gold nanoparticles will also be discussed.
(Invited) Thermoelectric Energy Conversion Optimized By Electrolyte Gating
Authors: Takenobu Taishi 
Published: February 2020

Thermoelectric energy conversion is one of the key technologies for energy harvesting devices to convert waste heat into electric power, and vice versa. In these devices, the Seebeck coefficient (= thermopower, S), which is the proportional constant to the voltage generation against an induced temperature gradient, is a significant factor in designing thermoelectric devices. Importantly, according to the Mott equation, Sis proportional to the energy derivative of the electronic density of states at around Fermi energy; therefore, it is critically important to control the energy band filling. Conventionally, the band filling is tuned by chemical doping and, in most materials, it is very difficult to establish precisely controllable doping methods.
Another important factor for thermoelectric energy conversion devices is the thermoelectric power factor S
2
·σ (σ
is conductivity). It should be strongly emphasized that the power factor has to be optimized to maximize the electric power output of thermoelectric devices. Consequently, this is a key parameter for applications. However, it is widely known that there is a trade-off between |S| and σ in terms of carrier density, n. Although σ is almost linearly proportional to n, |S| decreases with increasing n. Therefore, it is necessary to maximize S
2
·σ
by tuning n.
Here, we optimized thermoelectric energy conversion efficiency using the electrolyte gating technique. Importantly, owing to the high specific capacitance of electric double-layers (EDLs) (1−10 μF cm-2), we can continuously control the carrier density up to 1014 cm-2, which results in the tuning of the carrier polarity between p-type and n-type [1-6]. Based on this technique, we investigated the thermoelectric properties of transition metal dichalcogenide monolayers [7], single-walled carbon nanotubes [8,9], organic Mott insulators [10], organic molecules and organic polymers.
[1] J. Pu, L.-J. Li, T. Takenobu, et al., Nano Lett. 12, 4013 (2012).
[2] J.-K. Huang, T. Takenobu, L.-J. Li, et al., ACS Nano. 8, 923 (2014).
[3] J. Pu, L.-J. Li, T. Takenobu, et al., Adv. Mater. 12, 4013 (2016).
[4] H. Shimotani, T. Takenobu, et al., Adv. Funct. Mater. 24, 3305 (2014).
[5] Y. Kawasugi, T. Takenobu, et al., Nat. Commun. 7, 12356 (2016).
[6] Y. Yomogida, T. Takenobu, et al., Adv. Mater. 24, 4392 (2012).
[7] J. Pu, L.-J. Li, T. Takenobu, et al., Phys. Rev. B 94, 014312 (2016).
[8] K. Yanagi, T. Takenobu, et al., Nano Lett. 14, 6437-6442 (2014)
[9] S. Shimizu, T. Takenobu, et al., SMALL 12, 3388 (2016)
[10] Y. Kawasugi, T. Takenobu, et al., Appl. Phys. Lett. 109, 233301 (2016).
Impact of Carbon Addition on 1D Oxide – Chalcogenide Heterostructures
Authors: Subramanian Vaidyanathan 
Published: February 2020

Mother Nature and our surroundings always inspire us with new Ideas to purse science. An outcome of one such motivation is the development of a family of 1D oxide chalcogenide composites with interesting architectures and their properties.
As a case study, I will present our recent contributions on the topic of titanium dioxide (TiO2) as a façade for the deposition of visible light agents for light absorbance and charge generation. We know that chalcogenides can aid in improving light harvesting properties of oxides. To this end, the synthesis of the 1D oxide followed by the deposition of a chalcogenide is presented. Of particular focus will be the role of carbon additives. The main insights presented in this talk is the method to integrate carbon, the type of carbon additives and their impact, and what are the possible benefits of the carbon presence in a oxide-chalcogenide system.
Visible Light-Driven Water Oxidation with Porphyrin Sensitizers and Water Oxidation Catalysts
Authors: Imahori Hiroshi 
Published: February 2020

Finding renewable energy sources is a crucial task in making our society sustainable. In this regard, exploitation of sunlight as an infinite energy source is attractive. Specifically realizing artificial photosynthesis, i.e., integration of light-harvesting, multi-step electron and proton transfer, and water oxidation for the efficient production of fuels, is a great challenge in chemistry. For the purpose, dye-sensitized photoelectrosynthesis cells (DSPSC) have been investigated, as the heterogeneous water splitting on inorganic semiconductor is promising for the upcoming large scale device operation. In DSPSC a molecular sensitizer adsorbed on a semiconducting electrode harvests visible light and injects an electron from the sensitizer excited-state (S*) to a conduction band (CB) of the electrode. Then, the sensitizer radical cation (S•
+) extracts an electron from a water oxidation catalyst (WOC) to regenerate the sensitizer and one-electron oxidized WOC. After repeating the cycle, high oxidation states of the WOC are generated, eventually transforming two water molecules into four protons and one oxygen molecule. As the sensitizer bis(2,2’-bipyridine)(4,4’-diphosphonato-2,2’-bipyridine)ruthenium(II) (RuP) has been frequently employed for the construction of molecular artificial photosynthetic systems, due to its sufficient first oxidation potential for water oxidation and a long lifetime of its excited state for electron injection. However, the light-harvesting ability of RuP is rather low in visible region beyond 500 nm. Given that yellow to red photons mainly shower down on the earth from sun, utilization of photons in visible region is important for efficient chemical conversion by sunlight. Along this line, porphyrins are promising as the sensitizer because of their excellent light-harvesting in visible region and facile tuning of their excited-states and redox properties by their peripheral functionalization. Nevertheless, molecular artificial photosynthetic systems with porphyrins as the sensitizer are so far limited owing to their low performance. One plausible reason is the occurrence of fast charge recombination (CR) between the electron injected into the CB of TiO2 (denoted as TiO2(e−)) and S•
+. CR from TiO2(e−) to the oxidized WOC is also reported to take place within a few microsecond. Undesirable CR from TiO2(e−) to water is also suggested. Therefore, to overcome the drawbacks, it is crucial to modulate the electron transfer (ET) properties at the interfaces. In this talk, I will give an overview of our recent initiatives on visible light-driven water oxidation with porphyrin sensitizers and water oxidation catalysts.
[1] M. Yamamoto, L. Wang, F. Li, T. Fukushima, K. Tanaka, L. Sun and H. Imahori, Chem. Sci., 7, 1430-1439 (2016).
[2] M. Yamamoto, Y. Nishizawa, P. Chábera, F. Li, T. Pascher, V. Sundström, L. Sun, and H. Imahori, Chem. Commun., 52, 13702-13705 (2016).
Bioinspired Vitamin B12 Catalysis
Authors: Gryko Dorota 
Published: February 2020

Vitamin B12 catalysis is inspired by the ultimate chemist Nature, as methylcobalamin and adenosylcobalamin are involved in numerous biocatalytic reactions including isomerization, methylation and dehalogenation.[1,2] This type of catalysis has been successfully translated into the laboratory and used in a small collection of reactions.[2, 3] The advantage of using vitamin B12 as a catalyst lays in the complete stability of the central cobalt ion, whereas most catalytic reactions require the addition of toxic metals plus complex ligands into a cocktail of reagents, vitamin B12in itself is a package deal. It has also been well documented that the reaction mechanism usually follows a radical pathway, bringing a new dimension to this already interesting field.
Along this line, we have proposed vitamin B12
photochemical activation in bond forming and cleavage reactions.[4] Our results show that TiO2 can be utilized in a catalytic system with vitamin B12, allowing for the efficient photocatalytic reduction of Co(III) to Co(I). Under light irradiation vitamin B12 derivative unusually catalyzes a new olefinic sp2 C-H alkylation reaction, with diazo reagents as a carbene source, instead of the expected cyclopropanation. Furthermore, we also use challenging acyl radicals in C-C bond forming reactions. Light-induced vitamin B12-catalyzed methods are also suitable for C-O bond cleavage. Our studies showed that reduced cyanocobalamin catalyzes C-O bond cleavage in allyloxyarenes.

These key findings emphasize the unique feature of vitamin B12as a catalyst to achieve something unachievable with other methodologies or to find a greener approach.

1. Banerjee, R. Chemistry and Biochemistry of B12, John Wiley & Sons, Inc, 1999
2. K. ó Proinsias, M. Giedyk, D. Gryko, Chem. Soc. Rev.
2013, 42, 6605-6619.
3. Giedyk, M.; Fedosov, S.; Gryko, D. Chem.
Commun.
2014, 50, 4674-4676.
4. a) Shimakoshi, H.; Nishi, M.; Tanaka, A.; Chikama, K.; Hiseada, Y. Chem. Commun. 2011, 47, 6548-6550. b) K. Tahara, Y. Hisaeda, Green Chem.
2011, 13, 558-561. H. Shimakoshi, L. Li, M. Nishi, Y. Hisaeda, Chem.
Commun.
2011, 47, 10921-10923.

Figure 1
Structural Characterization of Heme Uptake System in Corynebacteria
Authors: Aono Shigetoshi 
Published: February 2020

Heme uptake machinery of Corynebacteria including Corynebacteria glutamicum and Corynebacterium diphtheriae consists of heme binding proteins, HtaA and HtaB, and the ABC-type heme transporter HmuTUV. In this work, we have studied the structural and functional relationships of HtaA, HtaB and HmuT in Corynebacterium glutamicum.
Sequence analysis identified a conserved region (CR) of approximately 150 amino acids that is duplicated in HtaA and present in a single copy in HtaB [1]. HtaA consists of two homologous CRs in the N- and C-terminal regions. We have determined the crystal structures of the N-, and C-terminal CR of HtaA (HtaA-N and HtaA-C, respectively) and HtaB at the resolution of 2.0, 1.3, and 1.7 Å, respectively. HtaA-N consists of 11 β strands and two short α helices and accommodates one heme molecule with Tyr58 located in the first α helix as the heme axial ligand. Tyr58 forms a hydrogen bond with His111. A heme propionate forms hydrogen bonds with Ser54 and Tyr201. Heme is accommodated in an open pocket formed by hydrophobic amino acid residues.
HtaA-C and HtaB show similar global structures to HtaA-N. The key residues for heme-binding and recognition including the axial ligand of heme and residues involved in the hydrogen bonding interactions with heme are conserved among HtaA-N, HtaA-C, and HtaB.
We also determined the crystal structure of HmuT at the resolution of 1.4 Å [2]. HmuT consists of structurally similar two domains located in the N-terminal and C-terminal regions connected a long α helix. A single heme molecule is bound in the cleft between these domains. Heme iron is ligated by His141 and Tyr240, and Tyr240 forms a hydrogen bond with Arg242. Intriguingly, HmuT binds a heme with two different orientations.

References

[1] C. E. Allen, M. P. Schmitt. (2011) J. Bacteriol.
193, 5374-5385.
[2] N. Muraki, S. Aono. (2016) Chem. Lett. 45, 24-26.
Porphyrins As Photoredox Catalysts in Efficient C-C Bond Formation
Authors: Rybicka-Jasińska Katarzyna , Gryko Dorota 
Published: February 2020

Porphyrins are natural functional dyes which are utilized by Nature as prosthetic groups of various enzymes not per se because of their coordination characteristic, but due to the combination of other properties with absorption of light (which translates to color) being the most important.
Efficient C−C bond formation in a green, nontoxic, and inexpensive way has always been a challenge and development of light-induced methodologies is one of the means to achieve such a goal.1 Photoredox catalysis is based on a photoinduced electron transfer process (PET) between a substrate and a photoredox catalyst, commonly Ru- or Ir-complexes.2 Though organic dyes have been well-known for their ability to participate in photoinduced electron transfer processes, their use as catalysts in such reactions has been less explored as the replacement of Ir- and Ru-complexes with known organic dyes is not always possible.3 We wondered whether simple porphyrins could be used as photocatalysts.
Herein, we demonstrate a successful application of these compounds as efficient photoredox catalysts for C-C bond forming reactions involving the reductive or oxidative quenching. Employing dual catalytic system – photocatalysis merged with enamine-iminium catalysis alkylation of aldehydes at the a position was accomplished (Scheme 1a).4

We have also found that porphyrins with tuned physicochemical properties, via tailoring various substituents at the periphery of the macrocycle, are also effective in catalyzing light-induced direct arylation of heteroarenes and cumarins with diazonium salts (Scheme 1b).5 The reaction afforded arylated products in good yields and tolerates a wide range of functional groups.
Scheme 1. a) Alkylation of aldehydes at the a-position b) Arylation of heteroarenes
References:

a) M. Fintecave, Angew. Chem. Int. Ed. 2015, 54, 6946. b) Bucker, J. W.; Stephenson, C. R. J. J. Org. Chem. 2012, 77, 1617. C) Skubi, K. L.; Blum, T. R.; Yoon, T. P. Chem. Rev. 2016, 116,10035.

Prier, C. K.; Rankic, D. A.; MacMillan, D. W. C.Chem. Rev. 2013, 113, 5322.

Nicewicz, D. A.; Nguyen, T. M. ACS Catal. 2014, 4, 355.

K. Rybicka-Jasińska, W. Shan, K. Zawada, K. M. Kadish, D. Gryko J. Am. Chem. Soc. 2016, 138, 15451-15458.

K. Rybicka-Jasińska, B. Konig, D. Gryko, Eur. J. Org. Chem. - submitted

Figure 1