bluuebunny/crossref_metadata_2025 huggingface dataset:
Developing High Cycling Stability Graphite/LiNi0.5Mn1.5O4 Li-Ion Cells
Authors: Gabrielli Giulio , Axmann Peter , Wohlfahrt-Mehrens Margret
Published: February 2020

Key issues for the next generation of Li-Ion batteries are increasing the specific energy and reducing the cell cost. It is possible to achieve both this targets by adopting innovative and cheap cathode materials presenting either higher capacity or higher operating potential than standard cathode materials. Among the high voltage materials, LiNi0.5Mn1.5O4 (LMNO) is one of the most promising candidates for Li-Ion cells application because of its operating potential of 4.7 V vs. Li/Li+, its good specific capacity (147 mAh g-1) and low cost. Graphite/LMNO cells guarantee considerable improvements in the specific energy of Li-Ion batteries by increasing the cell operating voltage to ca. 4.6 V. Unfortunately Graphite/LMNO systems undergo a strong aging process and a rapid capacity fade because of the electrolyte degradation reactions occurring at high potential. Thus, it is necessary to adopt different strategies such as the optimization of the active material, the adoption of coatings and the optimization of the electrolyte in order to stabilize the cathode/electrolyte interface. Adopting these strategies, it was possible to significantly increase the cycling life of Graphite/LMNO cells up to more than 700 cycles (Figure).

The development of stable Graphite/LMNO cells starts with the optimization of the cathode active material. Thus, we studied and tailored morphological properties of LMNO such as particle architecture, composition, crystallite size and particle size. This study aimed to realize an optimized LMNO, presenting features in line with commercial cathode materials and the best compromise between electrochemical performance and reduced electrolyte degradation. The optimized LMNO in full-cells vs. graphite anodes showed remarkable electrochemical performance and a stable reversible capacity for more than 300 cycles.

Additional strategies for improving the cycling life of Graphite/LMNO cells included a facile oxidic treatment of the LMNO particles surface. The aim of this treatment was to further stabilize the cathode/electrolyte interface without altering the electrochemical performance of the active material. Moreover, we pointed out the importance of using a suitable electrolyte composition, which guarantees high voltage stability without interfering with the performances of the full-cells. Electrochemical studies in full-cells showed a significant contribution of these improvements to the cycling stability of Graphite/LMNO cells and the validity of the adopted strategies.

Figure 1
Selenides Based Sodium Superionic Conductors
Authors: Bo Shou-Hang , Wang Yan Eric , Kim Jae Chul , Richards William Davidson , Ceder Gerbrand
Published: February 2020

All-solid-state Na-ion batteries that operate at or close to room temperature are a promising next-generation battery technology with enhanced safety and reduced manufacturing cost. An indispensable component of this technology is the solid state electrolyte that allows rapid shuttling of the mobile cation (i.e., Na+) between the cathode and anode. However, there are very few fast Na-ion conductors with ionic conductivity approaching that of the liquid counterparts (i.e., 1 mS cm-1).

Compared to oxides and sulfides, selenides form a huge unexplored chemical space for fast ionic conductor discovery. Based upon ionic size considerations, selenide-based compounds may provide a more suitable structural framework for the rapid diffusion of the much larger Na+ cations compared with Li+. This consideration led us to an extensive search of fast Na-ion conductors in the Se-based chemical space via high-throughput computational screening, and has identified cubic Na3PSe4 as one of the most promising candidates.

In this work, we present the synthesis and structural characterization of Na3PSxSe4-x (x = 0, 1, 2, 3, 4). The structures of these phases are determined from high-resolution synchrotron X-ray diffraction data, which allow us to unambiguously identify a tetragonal-to-cubic phase transition with increasing Se concentration in Na3PSxSe4-x. The Na-ion conductivity and activation energy for Na-ion diffusion were further characterized via variable temperature impedance spectroscopy, from which a negative correlation between the activation barrier and Se concentration can be established. Of particular note is that the x = 4 end member (i.e., cubic Na3PSe4) possesses a room-temperature ionic conductivity exceeding 0.1 mS cm-1, and does not require high temperature sintering to minimize grain boundary resistance, making it a promising solid-state electrolyte candidate for all-solid-state Na-ion battery applications. These experimental results were complemented by ab initio computation through which we demonstrate an intriguing interplay between the tetragonal-to-cubic phase transition, defect formation, and Na+ migration.

This work has two important implications for future studies in related fields: (1) selenide based compounds represent a promising platform for the discovery of new fast Na-ion conductors; and (2) the current study opens up new opportunities for the exploration of Se and/or S based battery chemistry, such as the construction of all-solid-state Na/Se battery.
Effects of Electrolyte Salt Concentration on Performance of Li-Oxygen Batteries
Authors: Mohazabrad Farhad , Wang Fangzhou , Li Xianglin
Published: February 2020

Developing batteries with high specific capacity and power density is essential in many applications such as electric vehicles and portable electronic devices. The Li-oxygen battery has a very high theoretical energy density of 11 kWh kg-1 and is considered as a promising battery technology. The concentration of the lithium ion in battery electrolyte is typically 1 M in both Li-ion and Li-oxygen batteries. Considering the high cost of the lithium salt and low current rates of Li-oxygen battery, this study investigated effects of salt concentration (LiPF6 in Tetraethylene glycol dimethyl ether) on battery performance through experiments and model simulations. Results showed that when the salt concentration decreased from 1 M to 0.05 M, the specific discharge capacity decreased from 557.7 mAh/g to 390.9 mAh/g, and the specific charge capacity also decreased from 512.7 mAh/g to 339.5 mAh/g at the current rate of 0.1 mA/cm2. Both the discharge and charge capacity decreased significantly to less than 31.1 mAh/g when the lithium salt concentration was lower than 0.005M. The electrolyte conductivity that can affect the ion transport in the electrolyte was also measured in the experiment. The measured conductivity decreased from 3010.0 μS/cm to 16.6 μS/cm when the concentration of electrolyte decreased from 1 M to 0.005 M, while the molar conductivity was almost constant (3.518 +/- 0.048 S.cm2/mol) in this concentration range. A one-dimensional model was also developed to illustrate the importance of mass transfer in the electrode and simulate the electrochemical performance of Li-oxygen batteries.
X-Ray Nanotomography of Cu6Sn5 Anode Material for Li-Ion Batteries
Authors: Ausderau Logan , Buckley Joseph , De Andrade Vincent , Nelson George J.
Published: February 2020

In recent years, great attention has been paid to tin as an alternative to graphite as a negative electrode material in Li-ion batteries due to the high theoretical capacity of its fully lithiated phase, Li4.4Sn (994 mAh∙g-1). However, tin suffers from large volume expansion during lithiation and delithiation causing capacity to drop quickly as a function of cycle number. Significant volume expansion of the negative electrode has severe effects that reduce the cycle lifetime of the electrode such as material pulverization, separation from the current collector, and instability of the solid electrolyte interphase. One way to reduce this expansion is to create an inert matrix to help support the Sn during electrochemical cycling such as the use of copper in the form of the intermetallic alloy Cu6Sn5.

As the issues stemming from this severe volume expansion all occur on a microstructural level, x-ray nanotomography (XNT) is used to image the anode material at a resolution of 60 nm. XNT provides the opportunity to non-destructively obtain the 3D structure of heterogeneous materials and provide a series of high resolution digital images for microstructural analysis and computational modeling. In this current study, Cu6Sn5 was synthesized by sintering copper and tin in the stoichiometric proportion to form the alloy anode material. XNT measurements were taken of the resulting non-lithiated material at 8.8 KeV over a 180° range of rotation. Single component and mixed samples containing the bronze alloy, Cu, and Sn were imaged. Based on absorption contrast regions of Cu, Sn, and Cu6Sn5 were differentiated throughout multiple samples. The capability to distinguish the different materials within mixed samples suggests that microstructure and composition changes resulting from lithiation and delithiation in Cu6Sn5 can be observed and better understood with 3D x-ray imaging methods. These methods may also be applicable to other intermetallic alloy electrode systems.
(Invited) Synthesis of Nitrogen-Embedded Buckybowl and Its Strong Association Behavior with C60
Authors: Hiroto Satoru , Yokoi Hiroki , Sakamaki Daisuke , Seki Shu , Shinokubo Hiroshi
Published: February 2020

Curved π-conjugated molecules have attracted considerable interest because of their unique properties originating from their curved π surface.  Besides their figurative beauty, the curved psurface generates unique functions such as chiroptical properties, anisotropic electron transitions, and dynamic motion in solution and solid states. However, the synthesis of such distorted molecules requires harsh conditions, which hamper an easy access to heteroatom-containing curved π-systems.

 Buckybowls represent important curved π-conjugated molecules, which can be precursors for the bottom-up synthesis of fullerenes and nanotubes. The nitrogen-embedded bowl-shaped molecules have been sought as model compounds for azafullerenes and nitrogen-doped carbon nanotubes. However, the synthesis of buckybowls with internal nitrogen atoms has been still challenging.

 Here we report the synthesis of a π-extended azacorannulene with nitrogen in its center. The oxidation of 9-aminophenanthrene provides tetrabenzocarbazole, which is converted to the azabuckybowl through palladium-catalyzed intramolecular coupling reaction. The structure was unambiguously elucidated by X-ray diffraction analysis, showing its bowl-shaped conformation.  The electron-donating nature and curved π surface of the azabuckybowl enable its tight association with C60 in solution and solid states.  The titration experiments with C60 by electronic absorption and emission spectroscopic analysis indicate the presence of intermolecular charge-transfer interaction between them.  In addition, high charge carrier mobility was observed for the azabuckybowl/C60 assembly in solid state. This new compound would be a novel molecular entity in the field of curved π systems as fullerene hosts, anisotropic π donors, and precursors to nitrogen-containing nanocarbon materials.

Figure 1
(Invited) Synthesis of Fluorescent Graphene Quantum Dots
Authors: Haino Takeharu
Published: February 2020

A Graphene quantum dots have received great attention for a potential role in the development of unique optoelectronic materials. In the development of optoelectronic devices, the preparation of GQDs that are controlled with their size and dimensions and are un-oxidized at the sp2 surfaces is needed. We developed GQDs functionalized with bulky dendritic wedges at the GQD periphery. The single-layered and size-regulated structures of the dendronized GQDs were revealed by atomic force microscopy. The edge-functionalization of the GQDs gave rise to uncommon white light emission.

In this presentation, I will describe the synthesis and characterization of newly developed graphene quantum dots, and the unique photochemical features.

1)    Sekiya, R.; Uemura, Y.; Murakami, H.; Haino, T. Angew. Chem. Int. Ed.
2014, 53, 5619-5623.

Figure 1
(Invited) Photoinduced Charge Transfer Reactions and Excited State Properties in Triphenylamine C60 Donor-Acceptor Conjugates
Authors: Solà Miquel , Martínez Juan Pablo , Osuna Sílvia , Voityuk Alexander
Published: February 2020

The molecular heterojunction triphenylamine/C60 is a potential material to construct high-efficient dye-sensitized solar cells. We have carried out a combined molecular dynamics and time-dependent density functional theory study to analyze charge separation and exciton delocalization in excited states of two constitutional isomers of this interface.[1] Our results reveal the presence of exciton states characterized by partial charge-transfer character (hybrid states); which are suggested to promote the direct charge separation process by excitation. These states may have a significant impact on the efficiency of the light-harvesting ensembles. That is to say, a greater amount of such hybrid states is found at short distances between the triphenylamine fragment and the C60 cage; as a result, charge transfer reactions can occur faster. This trend resembles the experimental evidence since rate constants for photoinduced charge transfer reactions kct
are bigger for the constitutional isomer with the shortest distance between the triphenylamine fragment and the C60 cage.[2] We have also evaluated the performance of U-CAM-B3LYP/6-31G* and TD-CAM-B3LYP/6-31G* level of theories to compute the different parameters affecting kct
; that is the reorganization energy λ, the electronic coupling Vij
, and free energies ΔG.[3] Our study is done under the theory of nonadiabatic electron transfer. By using the standard Marcus formulation, our results show that the outer-sphere contribution to λ and ΔG for the recombination reaction are the parameters that more uncertainty introduces to the estimation of kct
. We implemented a low-cost methodology based on U-DFT for the evaluation of the outer-sphere part of λ and ΔG; wherein Franck-Condon and relaxed charge-transfer states are conveniently modeled, including properly the solvent reorganization energy, by U-CAM-B3LYP/6-31G* coupled to continuum solvation models. Finally, it is worth to mention that the replacement of the C60 cage by Ih
-Sc3N@C80 generates longer-lived charge-transfer states; which is attributed to the lower ΔG of the charge recombination reaction.[2] Our group is currently analyzing this trend for the whole family of endohedral metallofullerenes; for which dynamics is expected to be in the normal region of the Marcus parabola.

[1]      J. P. Martínez, S. Osuna, M. Solà, A. Voityuk, Theor. Chem. Acc.
2015, 134, 12.

[2]      J. R. Pinzón, D. C. Gasca, S. G. Sankaranarayanan, G. Bottari, T. Torres, D. M. Guldi, L. Echegoyen, J. Am.
Chem. Soc.
2009, 131, 7727–7734.

[3]      J. P. Martínez, M. Solà, A. Voityuk, 2015, in preparation.

Figure 1
(Invited) Fullerene-Based Multichromophoric Antennas
Authors: Bonifazi Davide
Published: February 2020

Based on the unique electronic and structural properties, carbon nanostructures and are promising candidates for the constructions of advanced multidimensional organic architectures. Therefore a detailed understanding of the chemical and physical properties of these all-carbon structures is crucial for the further and targeted development of advanced materials. The main purpose of our work is to design and investigate new classes of carbon nanostructures with defined structural, physical, and chemical properties which are suitable as functional materials, e.g. in the field of organic conductors, photonic applications, and biological applications.

Herein we report the recent progresses achieved in our laboratory on the synthesis, characterization, and physical studies of new classes of [60]fullerene-based reaction centers equipped with new chromophoric antennas.
(Invited) Carbon Nanotubes-Fullerene Hybrids
Authors: Langa Fernando , Gomez-Escalonilla María J. , Barrejon Myriam
Published: February 2020

The combination of two carbon nanostructures in a single material, giving rise to new hybrids with improved mechanical, electrical, and thermal properties, has sparked a great interest in the last years.[1],[2],[3] Hybrids combining carbon nanotubes and fullerene derivatives have been described by endohedral,[4] supramolecular[5] and covalent[1] approaches, showing, in general, rather poor solubility in common solvents, which hampered the study of the resulting photophysical properties. In this regard, the synthesis of nanohybrids bearing long alkyl chains,[2]
,
[6]improve the dispersibility in organic solvents, rendering them excellent candidates for their application in the semiconducting materials field.

In this presentation, we will discuss our recent studies involving the synthesis of nanohybrids combining carbon nanotubes and C60, as well as the new photophysical properties arising from the combination of both carbon nanomaterials.

[1] J. L. Delgado, P. de la Cruz, A. Urbina, J. T. López Navarrete, J. Casado and F. Langa, Carbon, 2007, 45, 2250.

[2] M. Vizuete, M. J. Gómez-Escalonilla, J. L. G. Fierro, M. Yudasaka, S. Iijima, M. Vartanian, J. Iehl, J.-F. Nierengarten and F. Langa, Chem.
Commun., 2011, 47, 12771.

[3] M. Vizuete, M. Barrejón, M. J. Gómez-Escalonilla and F. Langa, Nanoscale, 2012, 4, 4370.

[4] B. W. Smith, M. Monthioux and D. E. Luzzi, Nature,
1998
, 396, 323.

[5] D. M. Guldi, E. Menna, M. Maggini, M. Marcaccio, D. Paolucci, F. Paolucci, S. Campidelli, M. Prato, G. M. A. Rahman and S. Schergna, Chem. Eur. J.
2006, 12, 3975.

[6] N. Mackiewicz, T. Bark, B. Cao, J. A. Delaire, D. Riehl, W. L. Ling, S. Foillard and E. Doris, Carbon, 2011, 49, 3998.
(Invited) Synthesis and Growth of the Phosphorene Precursor Black Phosphorus
Authors: Nilges Tom , Köpf Marianne , Grotz Carolin , Pfister Daniela
Published: February 2020

Black phosphorus and the 2D monolayer material called phosphorene gained reasonable interest in the past two years. Due to the structural anisotropy and the non-vanishing band gap few layer phosphorene and monolayer phosphorene are potential candidate for semiconductor, sensor and optical applications. Herein we will present a brief overview on the synthesis and growth of black phosphorus, the precursor material for phosphorene. A short range vapor transport results in the effective synthesis of large, high quality black phosphorus crystals which can be easily delaminated afterwards. This principle is commonly used to produce this allotrope in industry and academia. In situ experiments using neutrons have been performed to follow the growth of black phosphorus. A growing principle has been derived from isothermal measurements and an upper and lower synthesis temperature has been determined. We will present some applications of phosphorene and doped phosphorene thin-layer materials prepared by the above mentioned approach. After a short and brief overview on theoretically predicted and realized aspects and applications of phosphorus and phosphorene chemistry, we will try to compare this outcome with other 2D materials in the field.
(Invited) New Photocurrent Generating Pathways in Twisted Bilayer Graphene and Stacked Transition Metal Dichalcogenide Materials
Authors: Graham Matt W
Published: February 2020

The high-conductivity, low cost and relative ease of fabrication have made graphene well-suited to transform nanoscale electronics.  Unfortunately, as a gapless semimetal, photo-excited electrons in graphene recombine far faster than electron-hole pairs can be extracted.[1]  To make carrier lifetimes in 2D materials more competitive with carrier separation, we demonstrate promising, new electron extraction pathways in graphene-like systems including twisted bilayer graphene (tBLG) and transition metal dichalcogenides (TMD).  In tBLG, we show the emergence of twist angle-tunable excitonic absorption peaks that result from the rehybridization of constrained interlayer 2p orbitals[2]. Specifically, we use one and two-photon transient absorption microscopy to directly image the predicted[3] bright and dark stable, strongly-bound excitons states. This observation of strongly bound excitons is a first for a 2D metallic system, and serves to substantially increase graphene’s carrier lifetime, suggesting new pathways for photocurrent collection.   Unlike graphene, semiconducting 2D TMDs like WSe2, have long carrier lifetimes, but challenging mobility and exciton dissociation bottlenecks that inhibit photocurrent generation. By combining femtosecond resolved photocurrent microscopy[1,4] with ultrafast transient absorption, we have selectively imaged the dominant kinetics bottlenecks that inhibit photocurrent production in devices made from WSe2TMD materials.  Using these ultrafast space-time maps of the electron-hole dissociation dynamics, we hope to better engineer 2D material heterostructures devices to avoid efficiency-destroying, carrier recombination bottlenecks and maximize photocurrent yield.

(1) M.W. Graham, S. Shi, D.C. Ralph, J. Park, P.L. McEuen (2013), Nature Physics, 9, 103

(2) H. Patel, R. Havener, L. Brown, Y. Liang, L. Yang, J. Park, M.W. Graham (2015),  Nano Letters, 15, 5932-7

(3) Y. Liang, R. Soklaski, S. Huang, M.W. Graham, R. Havener, J. Park, L. Yang (2014), Phys Rev B, 90, 115418

(4) M. Massicotte, P. Schmidt, F. Vialla, K. G. Schädler, A. Reserbat-Plantey, K. Watanabe, T. Taniguchi, K.-J. Tielrooij, and F. H. L. Koppens (2015), arXiv:1507.06251 [cond-mat]
(Invited) Mechanisms of Branching Reactions in Melanin Formation - Ab Initio Quantum Chemistry Approach
Authors: Kishida Ryo , Kasai Hideaki
Published: February 2020

Melanin, a pigment commonly found in animals, consists of two types of oligomeric unit: eumelanin (black to brown) and pheomelanin (yellow to reddish brown). The color of the skin, the hair, and the eyes is mainly determined by the ratio of eumelanin/pheomelanin production. The biosynthesis of melanin has been extensively investigated over the past 100 years. Among all reaction steps in the biosynthesis, reactions of dopachrome and dopaquinone, precursor molecules of melanin, directly affect the composition of melanin.

Dopachrome is spontaneously converted into the monomer of eumelanin via or not via desorption of carboxyl group (decarboxylation). The former (decarboxylative) path is usually preferred whereas the latter (non-decarboxylative) reaction is catalyzed by metal ions such as Cu(II). Depending on the kinetic preference of the two pathways, the carboxyl moiety of eumelanin diversely changes, affecting its properties and functions.

 Dopaquinone can immediately undergo intramolecular cyclization, which is a reaction to form a cyclic structure, resulting in eumelanin synthesis. In a competitive manner, another reaction, thiol binding, which is a reaction to form a covalent bond with a sulfhydryl group, can prevail above a certain concentration of thiol compounds in the solution, resulting in pheomelanin synthesis. Thus, the fate of dopaquinone is directly related to the ratio of eumelanin/pheomelanin production.

 Mechanistic understanding of the above-mentioned reactions is a key to predict or design the properties and functions of melanin. Therefore, we make use a theoretical approach in which quantum mechanics is applied to molecular systems. Thus, we employ first principles calculation based on density functional theory. 

Our results show that the rate-limiting step of dopachrome conversion is deprotonation from β-carbon (β-deprotonation) at the first step. Furthermore, the subsequent steps were found to be regulated by the protonation state of the quinonoid oxygens, which are zwitterionic oxygens bound with benzene ring. Our calculations reveal that the quinonoid protonation facilitates decarboxylation. Cu(II) coordinated by quinonoid oxygens was found to protect the oxygens against protonation, leading to suppression of decarboxylation.

 For dopaquinone, we investigate the first step of the cyclization and the thiol binding. To evaluate the effects of substituent bound with the benzene ring, we calculate some dopaquinone-like systems. Our results show that quinones presenting their highest occupied molecular orbital (HOMO) localized at the substituent are reactive for cyclization, and that an anti-bonding shape of lowest unoccupied molecular orbital (LUMO) in the benzene-substituent region is a signature for low reactivity toward thiol compounds.

 This view obtained here is consistent with experiments and would provide a physico-chemical basis of melanin synthesis. Our results will be clues for designing new materials using melanin.
(Invited) Synthesis and Property of Carbazole-Based Porphyrins
Authors: Maeda Chihiro
Published: February 2020

As carbazole is benzene-fused pyrrole, incorporation of a carbazole unit into fused porphyrinoids represents interesting possibilities. We have developed carbazole-based porphyrins which exhibited distinct aromaticity and strong NIR absorption due to the quadruple benzo-fusion moieties. Following the successful synthesis, we have investigated the peripheral and core modifications and ring-expansion of the macrocycle as well as the applications to BODIPY derivatives. Here synthesis and property of these carbazole-based porphyrins are reported.

Figure 1
Towards Electron Transfer Compounds with Rigid Resistor Units
Authors: Locke Gemma M. , Senge Mathias O.
Published: February 2020

In nature, the antenna chlorophylls in photosynthetic bacteria are arranged as non-covalent macrorings in a spatially defined manner to absorb and transfer solar energy efficiently to the reaction centers. To mimic this, porphyrin assemblies with rigid, well defined geometries are of interest. In the field of biomimetic porphyrins, the strategy for synthetic chemists has become one of designing novel porphyrin scaffolds that exhibit similar arrangements as those found in nature, for use as model compounds in electron transfer studies. For photochemical systems such as these the correct geometry and spatial arrangement of the molecular building block is mandatory, yet this aspect is often neglected in modern tetrapyrrole chemistry. Here we report on the synthesis of tailored multiporphyrin arrays with defined structures and regiochemical arrangement for use in electron transfer studies. This requires the availability of appropriate scaffold molecules and linker units. While many of these are available, there is a notable absence of rigid, non-conjugating units with defined geometry and we have undertaken to develop synthetic chemistry for the use of cubane and triptycene units in this context.

The lack of research into aliphatically linked, multiporphyrin systems can be explained by the inherent flexibility of standard sp3 linker units. Cubane, with a virtually inflexible carbon skeleton, overcomes this problem, theoretically allowing it to be used as an isolator in bridged porphyrin systems for electron transfer studies. Furthermore, unlike most linker systems used in organic chemistry, cubane is a saturated hydrocarbon, and thus will also serve as an electronic isolator, preventing through bond communication between substituents, a key goal necessary for electron transfer studies to investigate through space versus through bond ET processes. In addition, the rigid three-dimensional framework of triptycene together with its symmetry, shape persistency and ability to project up to six functional groups in a spatially defined 120° orientation makes it an especially attractive scaffold in modern synthesis. The key goal here is the synthesis of a multichromophoric arrays based on the triptycene scaffold to serve as a key model compound both in light harvesting and energy transfer studies, as well as antenna cores for optical drug delivery systems.
(Invited) Photoactive Biodegradable Nanoparticles As Anti-Cancer Nanovectors
Authors: Cunin Frederique
Published: February 2020

In cancer treatment, minimally invasive therapy such as photodynamic therapy (PDT), currently being applied in clinics, allows highly localized treatment by the use of focalized light on the tumor area. Moreover PDT is indicated for small size solid tumors for which heavy surgery or chemotherapy is not justified. However, persistent limitation for PDT is the low specificity of the photosensitizing agent for the tumor, with poor delivery at inadequate concentrations to the treatment area causing irreversible side-effects. Porous silicon (pSi) nanoparticles are attractive materials for the design of applicable nanotherapeutics, as they are biodegradable in vivo. Made from semiconductor silicon, pSi also exhibits intrinsic photoluminescence when excited in the visible and near infrared, which is very amenable for in vivo imaging, under both one and two photon excitation. Here we will present the high potential of biodegradable pSi nanoparticles functionalized with photosensitizers and targeting agents for one and two photon photodynamic therapy.
(Invited) Construction of Hemoprotein Assembly Via Heme-Heme Pocket Interaction and Its Photochemical Property
Authors: Hayashi Takashi , Mashima Tsuyoshi , Hirayama Shota , Oohora Koji
Published: February 2020

Hemoproteins are metalloproteins which possess iron porphyrin as a prosthetic group (cofactor). These proteins have received much attention not only as biocatalysts but also as promising building blocks for development of new types of biomaterials. Particularly, the heme cofactor in several hemoproteins such as myoglobin, horseradish peroxidase, cytochrome P450, and cytochrome b
562 are replaceable with an artificial heme analog.  To functionalize the hemoproteins, our group has focused on the cofactor-substitution with several porphyrinoid metal complexes.1)  Furthermore, we have recently introduced a heme moiety onto the myoglobin surface via covalent linkage to obtain a supramolecular protein polymer via interprotein heme–heme pocket interaction.2)  In this presentation, we report the recent results of the hemoprotein assembly which is a model of a light-harvesting system.3)

     A hexameric tyrosine-coordinated heme protein (HTHP) containing photosensitizer molecules was prepared in an effort to construct a biomolecule with engineered photochemical properties.  Zn protoporphyrin IX (ZnPP) and Zn chlorin e6 (ZnCe6) are inserted into the apoprotein of HTHP to yield reconstituted proteins which maintain the original hexameric structure of HTHP.  Femtosecond transient absorption measurements indicate the occurrence of rapid singlet–singlet annihilation within a few picoseconds for each protein completely reconstituted with the six photosensitizer molecules.  This finding supports the fact that the photo-induced energy migration occurs whtin the protein with the zinc complex.  The fluorescence quenching efficiencies provided by methyl viologen as an electron acceptor for the completely reconstituted proteins with ZnPP and ZnCe6 are 2.3 and 2.6 fold-higher than that of the corresponding partially photosensitizer-inserted proteins, respectively.  This indicates that energy migration occurs among the photosensitizers bound within the protein matrices. These findings are expected to lead to development of new protein-based artificial light harvesting systems. 

1)  Hayashi, T. In Coordination Chemistry in Protein Cages; Ueno, T.; Watanabe, Y., Eds.; Wiley: Hoboken, US, 2013; Chapter 4, pp 87–110.

2)  Oohora, K.; Onoda, A.; Hayashi, T. Chem. Commun. 2012, 48, 11714–11726. 

3)  Oohora, K.; Mashima, T.; Ohkubo, K.; Fukuzumi, S.; Hayashi, T. Chem. Commun. 2015, 51, 11138–11140.
(Invited) Thermodynamics and Kinetics at the Solid-Solution Interface: Who Wins When?
Authors: Hipps K W , Mazur Ursula
Published: February 2020

The formation of self-assembled two dimensional structures at the solid-solution interface has long been treated as an equilibrium process.  In the case of porphyrin adsorption this is seldom true with kinetics often determining the structures observed at temperatures below about 50°C.  Using scanning tunneling microscopy (STM) we will demonstrate that molecular scale time evolution studies coupled with concentration variations are essential for determining the extent to which thermodynamics or kinetics control the observed surface structure.  Examples will be given of system in thermodynamic equilibrium and of those where kinetics is controlling.  We also will demonstrate how coadsorption of two species with very different desorption rates can produce new 2D structures.  An interesting example of cooperative adsorption will also be presented.
(Invited) Colour Bricks: Molecule-By-Molecule Supramolecular Arrays of Peryleneimides and Phthalocyanines on Solid Substrates
Authors: Efimov Alexander , Efimova Elena , Sariola-Leikas Essi , Hiltunen Arto , Hakola Hanna , Vivo Paola
Published: February 2020

Highly ordered thin molecular ﬁlms, from monolayer to multilayer assemblies, promise considerable development for micro- and nanotechnology. In particular, the application of supramolecular chemistry to the direct assembling of functional layers at surfaces added a new and highly diverse class of materials to modern material science. Multicomponent arrays are attractive materials for applications such as nonlinear optical materials, enzyme sensors, solar energy storage devices, and molecular rectiﬁers in several ﬁelds as optics, biotechnology, photo- and electrochemistry.

The talk will describe a recently developed set of perylene and phthalocyanine derivatives from which one can build highly organized multilayered structures on metal oxide surfaces. The essential finding is the use of terpyridyl-crowned perylenemonoimides monoanhydrides as the anchoring substances. Another key point is a proper choice of bis(terpyridyl)perylenediimide or terpyridyl-phthalocyanine linkers. Combination of these two factors allows to assemble highly colored and stable multilayered molecular films by a simple and reproducible procedure. As a proof of concept it has been demonstrated that molecular arrays can be successfully used in solid state DSSC even at ambient conditions.

One can expect many other potential uses of the proposed multilayers. The tpy-perylene spacers of a fixed length make possible a localization of specific ions or chromophores at a controlled depth inside the layer. This would allow to create a gradient of redox potentials across the film and to achieve, e.g. upon photoexcitation, a charge shift into a certain distance and direction. High absorbance of the multilayered films might eliminate the need of using porous structures, while the possibility to cover easily large surfaces is a great advantage in practical applications.

Figure 1
(Invited) Ionic Self-Assembly of Iron(III) Porphyrin into Nanoflowers As Highly Efficient Oxygen Reduction Reaction Electrocatalysts after Pyrolysis
Authors: Song Yujiang , Xie Yan
Published: February 2020

Non-noble metal electrocatalysts (NNMEs) with a high performance are urgently needed to rival Pt-based electrocatalysts for fuel cells and metal-air batteries. Exploration of unique synthetic approaches is the key to the creation of highly efficient NNMEs yet remains a challenge. Herein, we report an unprecedented synthetic route that combines ionic self-assembly (ISA) technology of iron (III) porphyrins (FePs) with traditional pyrolysis to prepare unique NNMEs with tunable structures. Remarkably, the original morphology of nanostructures of self-assembled FePs was nearly retained after carbonization, enabling highly desired manipulation over the size and shape closely related to the performance of NNMEs. Molecular Dynamics (MD) simulations turned out that pi-pi interaction of neighbouring FePs primarily contributes to the morphology maintenance after pyrolysis. The as-prepared NNMEs exhibited superb oxygen reduction reaction (ORR) activities, excellent durability and methanol tolerance in both alkaline and acidic solution. This approach opens up an innovative avenue to produce high performance NNMEs with controllable structural features that are difficult to be achieved prior to this study.
(Keynote) 2D+1D and 2D+0D Hybrid Nanostructures and Their Applications in Electrochemical Energy Storage
Authors: Zhao Mengqiang , Alhabeb Mohamed , Gogotsi Yury
Published: February 2020

Flexible and binder-free hybrid materials can be prepared by combining nanosheets of graphene, graphene oxide, MXenes (two-dimensional transition metal carbides) and other 2D materials with carbon onions, carbon black, porous carbide-derived carbon nanoparticles, and nanotubes. This helps to overcome the tendency of 2D sheets to restack, which minimizes their surface area accessible to the electrolyte and hinders their overall performance in electrochemical applications. Nanospacers such as carbon nanotubes (CNTs) are often introduced between reduced graphene oxide (rGO) sheets to enhance the electrolyte accessibility and electronic conductivity of the film. However, there are opportunities to use other 2D nanosheet-nanoparticle combinations that provide the desired set of properties due to synergistic effects of the nanoparticles. A brief overview of the carbon-carbon and carbon-carbide hybrids will be provided in this talk.

We have demonstrated fabrication of flexible, sandwich-like Ti3C2 MXene/CNT composite paper electrodes through alternating filtration of MXene and CNT dispersions. Spraying and other manufacturing methods can be used as well. Films containing onion- like carbon (OLC) and reduced graphene oxide (rGO) were also fabricated and compared with those with CNTs. The sandwich-like electrodes exhibited significantly improved electrochemical performance compared to those of pure MXene and randomly mixed MXene/CNT papers. Examples of Li-ion battery and electrochemical capacitor electrodes will be provided.

We also used highly porous carbide derived carbon (CDC) nanoparticles as spacers between graphene sheets and prepared rGO-CDC hybrid electrodes. The electrodes were made by thermal reduction of GO-CDC paper produced by vacuum-assisted filtration of aqueous solutions of GO-CDC composite containing 10-20 wt.% of CDC. Taking advantage of the high surface area and conductivity of rGO and the accessible pores of the CDC, the hybrid electrodes showed specific capacitances as high as 200-210 F/g at a scan rate of 100 mV/s. The addition of CDC between the rGO layers enhances the accessibility of electrodes to the electrolyte ions and good performance of the electrodes with the thickness to 40-50 μm was observed.
Fabrication, Characterization, Modification, and Application of Carbons Electrodes Derived from Paper
Authors: Garcia Carlos D , Benavidez Tomas E , Duran Gema , Rios Angel , Giuliani Jason , Comba Fausto , Evans Elizabeth
Published: February 2020

Since the first report in 1962, the field of biosensors has made astounding progress. Among those, electrochemical biosensors have now moved beyond the classic examples involving glucose oxidase and have been adapted to quantify a wide range of analytes, feature adequate sensitivity for clinical applications, offer independence from optical interferences, require minimal sample and power consumption, and are highly compatible with modern microfabrication techniques. While recent advances in nanotechnology have allowed the development of improved sensors based on modified metallic surfaces, the vast majority of the community has opted for carbon-based materials. These materials share a common structure composed of sp2-bonded atoms that supports electrical conductivity, the capacity to form charge-transfer complexes, unique optical properties, chemical reactivity, and the possibility to interact with a variety of biorecognition elements. While most of these materials have the potential to enable operational electrochemical sensors, most of them offer limited surface area and their application for the development of electrochemical biosensors is restricted by the resistivity of the material, which results in quasi-reversible or irreversible electrochemical behavior. Addressing these deficiencies, this presentation will describe the possibility of preparing electrodes by pyrolysis of paper. The resulting electrodes, which can be fabricated from a variety of substrates, feature low resistivity, large surface area, and uniform thickness. More importantly, the electrodes can be used for the development of biosensors by simply immersing them in a solution containing a selected enzyme. Herein we present results related to the selection of the substrate, the characterization performed (microscopy and electrochemical) as well as their potential for the development of an electrochemical biosensor. To increase the electrochemical activity of the sensors, the presentation will also discuss results related to a one-step method for the synthesis of paper-based carbon electrodes modified with CuNPs. The methodology is based on the pyrolysis (under reductive conditions) of paper strips pretreated with a CuSO4 solution. This process, one of the simplest reported to date, yields abundant CuNPs distributed on the surface of the carbonized cellulose fibers. The resulting electrodes were characterized by scanning electron microscopy, EDX, Raman spectroscopy, and electrical/electrochemical techniques. Their potential application as working electrodes for non-enzymatic determination of glucose in alkaline media was also demonstrated. Electrodes were also integrated to paper-based microfluidic devices and applied for the analysis of clinically-relevant analytes with limits of detection relevant to biomedical applications.

Figure 1
A New Approach for Selective Surface Functionalization of Carbon Electrodes in Biosensing by Plasma Direct-Writing
Authors: Thiha Aung , Ibrahim Fatimah , Abd Hamid Sharifah Bee , Madou Marc J
Published: February 2020

We have found that carbon electrodes fabricated by the C-MEMS process to be chemically very inert. Hence, surface modification is necessary for their use as biosensors and electrochemical electrodes. Functionalization of carbon electrodes in an oxygen plasma or by acid treatment has been reported previously. However, there is often a need for selective functionalization only at specific locations on the electrodes, so that they can function as sensor element and also retain pristine surface chemistry in other areas. In this paper, we introduce a novel plasma direct-writing technique for selective functionalization of carbon electrodes with carboxylic groups at room temperature and atmospheric pressure. We demonstrate the plasma direct-writing on two test platforms. On platform one, we draw patterns of carboxylic functional groups on flat glassy carbon electrodes derived from photolithographically patterned photoresist. The second platform is carbon hybrid structure composed of glassy carbon walls and graphitic carbon nanowires suspended in between them by electromechanical spinning. Functionalization was performed only on nanowires by plasma direct-writing technique. The resulting surface chemistry and wettability of the electrodes are investigated by means of water contact angle measurement, Fourier transform infrared spectroscopy and Raman spectroscopy. Carboxylic group functionalization is a first step towards immobilization of DNA or immunoglobulin for carbon based biosensors. Selective surface functionalization is important for better accuracy in biosensing by preventing unwanted immobilization and their interference. The plasma direct-writing technique not only enables controlled writing of functional groups but also enables control of the degree of functionalization in a simple one step procedure.

Acknowledgement

The authors would like to acknowledge Ministry of Science Technology and Innovation (MOSTI) Science Fund (SF-020-2014), Transdisciplinary Research Grant Scheme (TR002A-2014B), and University of Malaya Flagship Grant (FL001-14AET).
Development of Micro-Supercapacitor Electrodes Based on Hybrid Transition Metal Oxide, Carbonized Silicon Nanowire Array
Authors: Ortaboy Sinem , Alper John , Carraro Carlo , Maboudian Roya
Published: February 2020

Recently, silicon based supercapacitors have received considerable attention for application in mobile and remote sensing platforms due to their unique properties such as high surface area, low cost, long lifetimes, and excellent charge–discharge capability. These promising energy storage devices store more energy than conventional dielectric capacitors and deliver higher power with longer cycle life than available battery technologies. [1-4]. Recent studies in the field of supercapacitors have focused on the realization of hybrid materials to further improve the energy density of supercapacitors via the introduction of transition metal oxides and conductive polymers, which have pseudocapacitive properties.

Herein, we report the synthesis and the characterization of transition metal-oxide decorated carbonized silicon nanowires (TMO/C/PSiNWs) for high performance supercapacitor electrode materials. Porous silicon nanowires were synthesized using a metal assisted low-temperature wet etching procedure and encapsulated in an ultrathin graphitic carbon sheath by using chemical vapor deposition (CVD) technique. Growth of ultrathin TMO layer on C/SiNWs was carried out by a chemical bath deposition (CBD) method. Scanning electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy studies were performed to characterize of the hybrid electrodes. The energy and power density characteristics of the TMO/C/PSiNW electrodes were investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge/discharge techniques. All the electrochemical performances were characterized in an 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM-TFSI) ionic liquid electrolyte in a potential range of −0.4−1.6 V vs Ag. Electrochemical measurements revealed that TMO/C/PSiNW showed the significant improvements over the previously reported C/PSiNW in terms of energy density and cycling performance. The enhanced capacitance was attributed to the excellent pseudocapacitive behavior of the TMO..

References:

[1] J.P. Alper, M.S. Kim, M. Vincent, B. Hsia, V. Radmilovic, C. Carraro, R. Maboudian Journal of Power Sources 230 (2013) 298-302.

[2] M.R. Zamfir, H.T. Nguyen, E. Moyen, Y.H. Lee, D. Pribat, J. Mater. Chem. A 1 (2013) 9566–9586.

[3] J.P. Alper, S. Wang, F. Rossi, G. Salviati, N.Yiu, C. Carraro,R. Maboudian, Nano Lett. 2014, 14, 1843−1847.

[4] P. Huang, M. Heon, D. Pech, M. Brunet, P.L. Taberna, Y. Gogotsi, S. Lofland, J.D. Hettinger, P. Simon, Journal of Power Sources, 225 (2013) 240-244.

Acknowledgements

This study was supported by the Scientific and Technological Research Council of Turkey (TUBITAK) 2219- International Postdoctoral Research Fellowship Program (App. No:1059B191401401), and the National Science Foundation of the United States.