bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Tailoring Graphene for Spintronics
Authors: Miranda Rodolfo
Published: February 2020

The development of graphene spintronic devices requires that, in addition to its capability to passively transmit spins over long distances, new magnetic functionalities are incorporated to graphene. By growing epitaxially graphene on single crystal metal surfaces under UHV conditions [1] and either adsorbing molecules on it or intercalating heavy atoms below it, long range magnetic order or giant spin-orbit coupling, respectively, can be added to graphene.

i) Achieving long range magnetic order by a monolayer of electron acceptor molecules adsorbed on graphene /Ru(0001).

Epitaxial graphene is spontaneously nanostructured forming an hexagonal array of 100 pm high nanodomes with a periodicity of 3 nm [2]. Cryogenic Scanning Tunnelling Microscopy (STM) and Spectroscopy and DFT simulations show that TCNQ molecules deposited on gr/Ru(0001) acquire charge from the (doped) substrate and develop a sizeable magnetic moment revealed by a prominent Kondo resonance. The molecular monolayer self-assembled on graphene develops spatially-extended spin-split electronic bands. The predicted spin alignment in the ground state is visualized by spin-polarized STM at 4.6 K [3]. The system shows promising perspectives to become an effective graphene-based spin filter device.

ii) Introducing a giant spin-orbit interaction on graphene/Ir(111) by intercalation of Pb. The intercalation of an ordered array of Pb atoms below graphene results in a series of sharp pseudo-Landau levels in the differential conductance revealed by STS at 4.6 K. The vicinity of Pb enhances by four orders of magnitude the, usually negligible, spin-orbit interaction of graphene. The spatial variation of the spin-orbit coupling creates a pseudo-magnetic field that originates the observed pseudo-Landau levels [4]. This may allow the processing and controlled manipulation of spins in graphene.

References

[1] A.L. Vázquez de Parga et al, Phys. Rev. Lett. 100, 056807 (2008) [2] B. Borca et al, Phys. Rev. Lett. 105, 036804 (2010) [3] M. Garnica et al, Nature Physics 9, 368 (2013) [4] F. Calleja et al, Nature Physics 11, 43 (2015)
Peculiar Magnetic Properties in Doped and Edge Functionalized Silicene Nanoribbons
Authors: Mehdi Aghaei Sadegh , Monshi Md Monirojjaman , Calizo Irene
Published: February 2020

Motivated by the exceptional properties of graphene, other two-dimensional (2D) nanomaterials beyond graphene such as silicene have emerged with growing interest. Silicene is attractive for its exceptional characteristics and compatibility with silicon based nanoelectronics.  It is believed that silicene may challenge graphene due to a longer spin-diffusion time, a longer spin coherence length, and a much larger spin-orbit coupling gap. Half-metallic materials and spin-gapless semiconductors (SGS) are highly desirable for spintronics because they provide 100% spin-polarized currents around their Fermi level. Spin filters and spin field effect transistors (FETs) are one of the potential applications of these types of materials. Silicene nanoribbon (SiNR) as an approach to opening a band gap in a silicene sheet is a promising material for spintronics due to its unique magnetic properties. In this study, a first-principle method based on density functional theory (DFT) is used to investigate the stability, electronic, and magnetic properties of edge hydrogenated and fluorinated SiNRs. Edge functionalization of all possible types of SiNRs such as armchair, zigzag, Klein, reconstructed Klein, pentagon-heptagon, and the combination of the edges are studied.  It is found that edge fluorinated structures are much more stable than that of edge hydrogenated. It is also discovered that tri-fluorinated Klein edge SiNR and di-hydrogenated armchair edge SiNR are the most stable structures when the edges are terminated with fluorine and hydrogen atoms, respectively. While, the symmetric edge functionalized zigzag SiNRs show antiferromagnetic semiconductor behaviour. Considering spin-polarization, the asymmetry in edge functionalization bring various and extraordinary magnetic states, such as SGS, ferromagnetic metals or semiconductors, and antiferromagnetic metals. In order to discover the effects of doping on the magnetic and electronic properties of edge functionalized SiNRs, N- or B-doped SiNRs are considered. It is revealed that the dopants energetically prefer to be substituted with Si atoms at the edge of SiNRs. Interestingly, the remarkable SGS and half-metal character, as well as ferromagnetic metallic behavior are observed in N- or B- doped armchair, zigzag, and Klein edge SiNRs which are highly advantageous for spintronics applications. These new findings encourage further experimental investigations in the development of SiNRs based nanoelectronics with spin tuning.
(Invited) Electrostatically Tunable Graphene Metasurfaces for Controlling Mid-IR Radiation
Authors: Brar Victor Watson
Published: February 2020

Metasurfaces composed of sub-wavelength fabricated structures have shown potential for exceptional control of light.  In this talk I will show that by incorporating graphene into the structure of a metasurface, devices can be fabricated that have electrostatically tunable emissivities and reflectivities.  It will be shown that the thermal emission from a metasurface can be widely varied in terms of spectral shape, polarization and intensity, and that thermally emitting devices with Mhz response times can be created in this way.  By carefully controlling the DC permittivity, index of refraction, and thickness of the supporting substrate, it will also be demonstrated that the efficiency and optical response of these devices can be dramatically altered.  Notably, the coupling of graphene plasmons with substrate phonons is found to play an important role in the spectral response of these metasurfaces, and the use of high-k dielectrics can increase maximum efficiency and range of control attainable in graphene metasurfaces.
Cytotoxicity of Graphene Derivatives and Exfoliated Transition-Metal Dichalcogenides (MoS2, WS2, and WSe2)
Authors: Teo Wei Zhe , Chng Elaine Lay Khim , Sofer Zdeněk , Pumera Martin
Published: February 2020

Many 2D nanomaterials have been demonstrated to possess amazing physiochemical properties and are likely to be incorporated in future consumer products. Therefore, there is a urgent need to ensure that these nanomaterials do not cause adverse health effects. In this study, the cytotoxicity of three common exfoliated TMDs (exTMDs), namely MoS2, WS2, and WSe2, were compared with that of graphene oxides and halogenated graphenes to determine which group of 2D nanomaterials would display better biocompatability. Cell viability assessments using methylthiazolyldiphenyl-tetrazolium bromide (MTT) and water-soluble tetrazolium salt (WST-8) assays on human lung carcinoma epithelial cells (A549) exposed to varying concentrations of these 2D nanomaterials revealed that MoS2 and WS2 nanosheets induced very low cytotoxicity to A549 cells, even at high concentrations. On the other hand, WSe2 was found to exhibit dose-dependent toxicological effects on A549 cells, reducing cell viability to 31.8 % at the maximum concentration of 400 μg mL−1. In comparison with graphene oxides and halogenated graphenes, MoS2 and WS2 were much less hazardous, whereas WSe2 showed similar degree of cytotoxicity, suggesting that MoS2 and WS2 might be suitable and safe materials for potential applications. However, future in-depth studies should be built upon this first work on the in vitro cytotoxicity of MoS2 and WS2 to ensure that they do not pose acute toxicity. Lastly, nanomaterial-induced interference control experiments indicated that MTT assay is not suitable for measuring the cytotoxicity of exTMDs as inflated absorbance values will be obtained due to undesired reaction between exTMDs and the MTT assay viability markers, giving false impressions that the materials are less toxic.
(Invited) Porphyrin-Capped Au Clusters As Building Blocks for Energy Conversion
Authors: Teranishi Toshiharu
Published: February 2020

The structure of nanomaterial determines their individual properties and suprastructures they can form [1-3]. Therefore, it is very important to create the size controlled nanostructures with anisotropic binding sites. However, precious control over size of metal clusters and conformation of protective ligands has been a challenging subject. In this study, we report the synthesis of the Au clusters (AuCs) capped by a certain number of porphyrins derivatives in a face coordination fashion [4-7]. The ground state interaction and excited state photochemical behavior of these porphyrirn face-coordinated AuCs will be also presented.

[1]    Kanehara, M.; Arakawa, H.; Honda, T.; Saruyama, M.; Teranishi, T. Chem. Eur. J.
2012, 18, 9230.

[2]    Eguchi, M.; Mitsui, D.; Wu, H.-L.; Sato, R.; Teranishi, T. Langmuir
2012, 28, 9021.

[3]    Chen, L.; Sakamoto, M.; Sato, R.; Teranishi, T. Faraday Discuss.
2015, 181, 355.

[4]    Kanehara, M.; Takahashi, H.; Teranishi, T. Angew. Chem. Int. Ed.
2008, 47, 307.

[5]    Sakamoto, M.; Tanaka, D.; Tsunoyama, H.; Tsukuda, T.; Minagawa, Y.; Majima, Y.; Teranishi, T. J. Am. Chem. Soc.
2012, 134, 816.

[6]    Tanaka, D.; Teranishi, T. et al. Chem. Sci.
2014,5, 2007.

[7]    Eguchi, D.; Sakamoto, M.; Teranishi, T., to be submitted.
(Invited) Growth of Ordered ZnO Nanorods Arrays Using Anodic Porous Alumina Templates
Authors: Masuda Hideki , Kondo Toshiaki , Nakazono Takashi , Yanagishita Takashi
Published: February 2020

The fabrication of ordered semiconductor nanostructures has attracted increasing interest due to its applicability to various functional devices.  Among them, the semiconductor nanorods array is one of typical nanostructures available for the functional optical devices including solar cells, and display devices due to its unique physical properties originated from the geometrical structures.  Although various fabrication processes for the nanorod arrays have been reported, the efficient fabrication process of the ordered semiconductor nanorods array has not been established so far [1].  In the present report, the formation of the highly ordered semiconductor (ZnO) nanorods array based on anodic porous alumina templates will be presented.  The anodic porous alumina, which is formed by anodization of Al in acidic electrolyte, is one of typical self-ordered material with highly ordered hole arrangement [2].  The advantage of this material is its high controllability of the geometrical structures based on the anodizing conditions.  Especially, under the appropriate low voltage anodization condition, the highly ordered hole array structures with small hole interval and hole size can be obtained [3].  The hole interval and hole size in this highly ordered porous alumina were typically 25 nm and 10 nm, respectively.  In the present work, ZnO nanorods arrays were fabricated through the hydrothermal reaction [4] using the anodic porous alumina as a template for the synthesis.  Based on the present process, the highly ordered arrays of ZnO nanorods could be fabricated on the substrates.  The geometrical structures of the ZnO nanorods arrays were controlled by changing the structures of the porous alumina templates.  The obtained nanostructures will be applied to the fabrication of various kinds of energy conversion devices, which require the highly ordered nanostructures of semiconductors.

 1. W. I. Park, D. H. Kim, S.-W. Jung, G.-C. Yi, Appl. Phys. Lett., 80, 4232 (2002).

 2. H. Masuda and K. Fukuda, Science, 268, 1466 (1995).

 3. H. Masuda, K. Takenaka, T. Ishii, K. Nishio, Jpn. J. Appl. Phys., 45, L1165 (2006).

 4. T. Shinagawa, S. Watase, M. Izaki, Cryst. Growth Des., 11, 5533 (2011).
(Invited) Photoinduced Electron Transfer Processes of Trifluorinated Molecules Dispersed in Conjugated Polymer Films and at Interfaces with Swcnts
Authors: Rumbles Garry , Blackburn Jeffrey L. , Ihly Rachelle , Reid Obadiah , Park Jaehong , Strauss Steven H. , Boltalina Olga V. , Coffey David C
Published: February 2020

The use of a Marcus formulation to describe photo-induced electron transfer processes in the complex blends of conjugated polymers and fullerenes associated with organic photovoltaics is rare. The conventional approach considers the polymer and fullerene to form a type II band offset similar to a picture for two inorganic semiconductors. A motivation for this presentation is to ask whether this simple model is correct and only the energetics need be considered when examining the driving force for the photo-induced electron transfer process. Or whether a re-organization energy is also required to describe the effect and therefore an optimum driving force is required to realize high charge separation yields.

This presentation will describe two studies using a series of trifluoromethylfullerenes (TMFs) dispersed at low concentration in a conjugated polymer film or in a bilayer forming an interface with a layer of chiral-pure single-walled carbon nanotubes (SWCNTs). The fullerene series provides exquisite control over a wide range of reduction potentials of the fullerene, and can thus influence the driving force for photo-induced electron transfer studies. In both experiments, the use of the electrodeless technique of flash photolysis, time-resolved microwave conductivity (fp-TRMC) which provides a sensitive probe of the yield and kinetics of charges generated in both systems.
(Invited) Infra-Red Photoresponse of Mesoscopic NiO-Based Solar Cells Sensitized with PbS Quantum Dot
Authors: Odobel Fabrice , Raissi Mahfoudh , Pellegrin Yann , Boujtita Mohammed
Published: February 2020

Sensitization of mesoscopic NiO films with molecular dyes has attracted a growing scientific interest because these photocathodes represent the key component of tandem dye-sensitized solar cells and tandem dye-sensitized photoelectrosynthetic cells. In this area, quantum dots (QDs) were much less investigated than molecular sensitizers although they proved to be particularly promising light collectors in other photovoltaic technologies such as Schottky type solar cells and conventional TiO2 based n-QDSSCs. In this presentation, we demonstrate that PbS QDs are promising inorganic sensitizers for NiO based p-DSSCs. Photocurrent is produced until far in the IR (above 950 nm) with a cobalt complex as redox couple supportting thus the real potential of quantum dot sensitized NiO-based photocathodes to exploit the low energy part of the solar spectrum.
(Invited) Insight into D-a-Pi-a Featured Organic Sensitizers
Authors: Zhu Weihong
Published: February 2020

The practical application of DSSCs requires further improvements in the power conversion efficiency and long term stability. Recently, we have systematically studied a novel concept of D−A−π−A model for the molecular engineering of organic photosensitizers. We highlights recent advance in the D−A−π−A based photosensitizers, specifically focusing on the mechanism of efficiency and stability enhancements. Also we take insight into the additional acceptor as well as the trade-off of long wavelength response. The basic principles are involved in the molecular engineering of efficient D−A−π−A sensitizers, providing a clear road map how to rationally extend the response wavelength, enhance molecular extinction coefficients, and step by step optimize photovoltaic efficiency.

Reference
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(a) Y. Z. Wu, W. H. Zhu, Chem. Soc. Rev. 2013, 42, 2039–2058 (Review article); (b) Y. Z. Wu, W. H. Zhu, S. M. Zakeeruddin, M. Grätzel, ACS App
l.

Mat
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Interfaces
2015, 7, 9307−9318. (Spotlight on Applications).

(a) Y. S. Xie, Y. Y. Tang, W. J. Wu, Y. Q. Wang, J. C. Liu, X.Li, H. Tian, W. H. Zhu, J. Am. Chem. Soc.
2015, 137, 14055−14058; (b) Y. S. Xie, W. J. Wu, H. B. Zhu, J. C. Liu, W. W. Zhang, H. Tian, W. H. Zhu, Chem. Sci.
2015, DOI: 10.1039/C5SC02778K.

(a) W. H. Zhu, Y. Z. Wu, S. T. Wang, W. Q. Li, X. Li, J. Chen, Z.-S. Wang, H. Tian, Adv.
Funct. Mater.
2011, 21, 756–763; (b) Y. Z. Wu, X.Zhang, W. Q. Li, Z. S. Wang, H. Tian, W. H. Zhu, Adv. Energy Mater.
2012, 2, 149–156; (c) Y. Z. Wu, M. Marszalek, S. M. Zakeeruddin, Q. Zhang, H.Tian, M. Grätzel, W. H. Zhu, Energy Environ.
Sci.
2012, 5, 8261–8272; (d) W. Q. Li, Y. Z. Wu, X, Li, Y. S. Xie, W. H. Zhu, Energy Environ.
Sci.
2011, 4, 1830–1837.

(a) K. Pei, Y. Z. Wu, A. Islam, S. Q. Zhu, L. Y. Han, Z. Y. Geng, W. H. Zhu, J. Phys. Chem. C
2014, 118, 16552−16561; (b) H. B. Zhu, Y. Z. Wu, J. C. Liu, W. W. Zhang, W. J. Wu, W. H. Zhu, J. Mater. Chem. A, 2015,
3, 10603–10609; (c) Q. P. Chai, W. Q. Li, J. C. Liu, Z. Y. Geng, H. Tian, W. H. Zhu, Scientific Reports
2015, 5, 11330; (d) H. B. Zhu, B. Liu, J. C. Liu, W. W. Zhang, W. H. Zhu, J. Mater.
Chem. C
2015, 3, 6882−6890.

(a) Q. P. Chai, W. Q. Li, Y. Z. Wu, K. Pei, J. C. Liu, Z. Y. Geng, H. Tian, W. H. Zhu, ACS Appl. Mater. Interfaces
2014, 6, 14621–14630; (b) K. Pei, Y. Z. Wu, A. Islam, Q. Zhang, L. Y. Han, H. Tian, W. H. Zhu, ACS Appl. Mater. Interfaces
2013, 5, 4986–4995; (c) W. Q. Li, Y. Z. Wu, Q. Zhang, H. Tian, W. H. Zhu, ACS Appl. Mater. Interfaces
2012, 4, 1822−1830.
(Invited) Synthesis and Properties of Antiaromatic Porphyrins
Authors: Shinokubo Hiroshi
Published: February 2020

Norcorrole is a ring-contracted porphyrin bearing 16π-electronic conjugation, of which synthesis has been quite challenging.  Recently, we have succeeded to synthesize norcorrole Ni(II) complex 1 in over 90% yield from a dibromodipyrrin precursor via metal-templated strategy.  We elucidated the planar structure and distinct antiaromatic nature of 1. Contrary to our expectation, meso-dimesitylnorcorrole Ni(II) 1 was quite stable under air at room temperature.  The reactivity of 1 was also investigated. Although stable at room temperature, 1 was oxidized to 18π-aromatic oxacorrole under oxygen at 100 °C.  In addition, the facile reduction and oxidation reaction of 1was applied to fabricate rechargeable batteries, which exhibited excellent charge/discharge capacity and durability.

We have also prepared N,N’-dihydrodiazaporphyrins 2 through chemo- and regioselective reduction of diazaporphyrins.  The structure and properties of this novel porphyrinoids have been investigated. N,N’-dihydrodiazaporphyrins 2 was found to be antiaromatic because of their 20π-conjugation including lone pairs on nitrogen atoms and their highly planar structures.

Figure 1
(Invited) Design of High NIR Emissive Lanthanide Porphyrinoids
Authors: Zhang Jun-Long , Hu Ji-Yun , Ning Ying-Ying
Published: February 2020

Lanthanide (Ln) complexes have been widely used in biological imaging and functional materials due to their attractive optoelectronic and magnetic properties. Strongly absorbing ligand scaffolds such as conjugated macrocycles are of great interest for Ln complex construction, for the maintaining solution stability, preventing coordination of quenching moieties and serving as antennas.1 Porpholactones, in which one porphyrin b,b′-double bond replaced by a lactone moiety, could be potent candidate to further increase NIR emission of lanthanides.2,3 In this talk, we will report the synthesis and characterization of a series of Ln porpholactones as well as their photophysical properties. The lactonization of beta-periphery of porphyrins renders the lower triplate excited states compared to those in porphyrins, which enhances the NIR emission of Ln ions.4 More importantly, through beta-fluorination of porphyrin periphery, the life time of NIR emission is significantly increased, which is considered to block the non-irradtive pathway. Taken together, the beta-modification of porphyrin represent an effective approach to enhance the NIR emission of Ln ions, which has the potential to further improve the practical application of Lanthanide chemistry.4 

References:

1. V. Bulach, F. Sguerra, M. W. Hosseini, Coord. Chem. Rev. 2012, 256, 1468–1478;

2. Xian-Sheng Ke, Hongmei Zhao, Xiaoran Zou, Yingying Ning, Xin Cheng, Hongmei Su*, and Jun-Long Zhang* ,J. Am. Chem. Soc., 2015, 137, 10745-10752

3. Xian-Sheng Ke, Yi Chang, Jia-Zhen Chen, Jiangwei Tian, John Mack, Xin Cheng, Zhen Shen* and Jun-Long Zhang*, J. Am. Chem. Soc., 2014, 136, 9598-9607;

4. Xian-Sheng Ke, Bo-Yan Yang, Xin Cheng, Sharon Lai-Fung Chan, and Jun-Long Zhang*, Chem. Eur. J., 2014, 20, 4324-4333;

5. Data unpublished.

Figure 1
(Invited) Porphyrins Based Gas Sensors and Their Applications
Authors: Di Natale Corrado , Paolesse Roberto
Published: February 2020

The role of porphyrins in life processes is well known. Iron complexes for instance are prostetic groups of important proteins such as hemoglobine and cytochromes. On the other hand, reduced porphyrins, as magnesium chlorin complexes, are fundamental in the photosynthetic processes. Such richness of properties is particularly attractive for chemical sensing. The molecular framework of porphyrins is a unique site for a wide range of interaction mechanisms useful for analyte binding. the interactions span from Van der Waals forces to hydrogen bond, to π interactions and to the coordination to the central metal ion.

The concurrence of all these mechanisms makes difficult the development of selective sensors, even if selectivity can in some cases found or improved by a suitable design of the sensor. On the other hand, the sensitivity of porphyrins can be oriented, through a proper molecular design, towards different classes of analytes. This control is of great value for the design of sensor arrays where several sensors non-selective but different among them are considered together.

We have been interested since about two decades to the use porphyrins to develop sensors for volatile compounds and gases. The physical properties of porphyrins restrict the transduction mechanisms that can be exploited to create an electric signal from the porphyrin-analyte interaction. It is important to recall that a chemical sensor actually measures a physical quantity of the sensing material that is affected by the interaction with the analyte.

We developed sensors measuring the mass, the optical absorbance, the surface potential and the charge transferred either to or from an inorganic semiconductor.

The sensing properties in all these devices can be related to the properties of the individual porphyrins, for instance the Hard and Soft Acids and Bases (HSAB) Pearson’s rule can be invoked to elucidate the sensitivity of porphyrins coated quartz microbalance sensors with regards to amines and alcohols.

In this paper, we will provide a rationale for the development of porphyrins based gas sensors discussing the pros and the cons of each transduction principle. A review of the applications will also be illustrated with a special emphasis on medical diagnosis through the analysis of volatile compounds.
(Invited) New Porphyrin-Based Probes for In Vivo Two-Photon Phosphorescence Lifetime Microscopy (2PLM) of Oxygen
Authors: Vinogradov Sergei , Esipova Tatiana
Published: February 2020

The ability to quantify oxygen in vivo in 3D with high spatial and temporal resolution is much needed in many areas of biological research. Our laboratory has been developing the phosphorescence quenching technique for biological oximetry - an optical method that possesses intrinsic microscopic capability. Recently we expanded our design on special two-photon enhanced phosphorescent probes. These molecules brought about first demonstrations of the two-photon phosphorescence lifetime microscopy (2PLM) of oxygen in vivo, providing new information for neouroscience and stem cell biology. However, current two-photon oxygen probes suffer from a number of limitations, such as sub-optimal brightness and high cost of synthesis, which dramatically reduce imaging performance and limit usability of the method. Here we present a new probe based on a porphyrin with internally enhanced two-photon absorption cross-section, therefore not requiring amplification by an external antenna. In this fully-symmetrical π-extended porphyrin strongly 2P active gerade-states are stabilized below the level of the B-state, ensuring excitation by ultrafast pulses without affecting direct S0-Tn transitions. The latter may possess non-negligible dipole strengths in phosphorescent metalloprhyrins due to strong spin-orbut coupling. The design of the porphyrin and of its surrounding environment to provide biocompatibility will be discussed. In addition to more than 50-fold increase in performance, the new probe can be synthesized by much more efficient methods, thereby greatly reducing its cost and making the method accessible to a broader range of researchers across different fields.
(Invited) Electrochemical Bistability of Porphyrin in Supramolecular Porphyrin/Phthalocyanine Assembly
Authors: Tanaka Kentaro , Yamada Yasuyuki
Published: February 2020

Recently, we have reported the formation of a porphyrin/phthalocyanine heterodimer in which cofacially stacked porphyrin and phthalocyanine are linked together by fourfold rotaxane (Figure 1). Mechanically interlocked supramoelcular linkages such as catenanes and rotaxanes are flexible enough to provide switching properties of the interactions among the components in the assemblies. We have reported supramolecular arrays of porphyrin and phthalocyanine and intramolecular electronic communication between the components. In this paper, we would like to reveal the electrochemical bistability of the porphyrin in the supramolecular assembly of a poprhyrin and a phthalocyanine connected by fourfold rotaxane linkage. Redox bistable systems are capable for taking two stable redox states separated by the energy barrier at the given electrochemical potential depending on the direction of the potential scan. During the negative scan on the cyclic voltammometry of 3, the porphyrin (Por) moiety was reduced into the anion radical (Por•–) at –1.72 V (vs. Fc/Fc+). Por•– generated was immediately protonated by intra- or inter-molecular proton transfer from the phosporamidate stopper of 3 to afford a neutral radical (PorH•). In the opposite (positive) scan, PorH• was not reoxidized into neutral Por until the potential reached at –0.94 V. Therefore, the two redox states, Por and PorH•, can exist stably at the same potential region depending on the direction of the potential scan.

Figure 1
Effect of Gases during Pyrolysis on Physical and Electrochemical Properties of SU-8 Photoresist Derived Carbon Film
Authors: Abd Hamid Sharifah Bee , Lee pui Kee , Ibrahim Fatimah , Madou Marc J
Published: February 2020

In this study, the effect of type of gases used in pyrolysis on the physical and electrochemical characteristic on SU-8 photoresist derived carbon film fabricated on silicon wafer was been investigated. Pyrolysis process was performed in the presence of nitrogen, argon and helium gas, repectively in temperature of 1100 °C in furnace. Thermogravimetric analysis, Raman spectroscopy, X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectroscopy techniques were used to charcterise the surface structure of fabricated carbon film. The electrochemical properties of the SU-8 fabricated thin film was analysed with cyclic voltammetry and electrochemical impedance spectroscopy. The results were then correlated with type of gases in pyrolysis process.

Acknowledgement

This research is supported by University Malaya Flagship Grant project FL001A-14AET, and Transdisciplinary Research Grant Scheme (TRGS TR002A-2014) from Malaysian Ministry of Higher Education, and MOSTI SF020-2014.
Fabrication of Biocompatible Hollow Microneedles Using the C-MEMS Process for Transdermal Drug Delivery
Authors: Pramanick Bidhan , Martinez-Chapa Sergio Omar , Madou Marc J
Published: February 2020

Microneedles are important component for the local delivery of drug with precise dose in controlled release to overcome the over dosage problem and decrease side-effects in drugs. These have been identified as a transformative technology for a painless, self-administered alternative to hypodermic injection and solid microneedles have been marketed for a many applications including scar treatment and improving skin permeability of topical drug formulations. Hollow microneedles have the potential to offer a large advantage in performance over these solid microneedle architectures. The architecture of hollow microneedle is more flexible and allows for delivery of larger drug molecules and volumes than other microneedle architectures. By integrating the hollow microneedles with micropumps, these can facilitate active control over the drug delivery profile to allow for continuous drug release for the applications such as insulin delivery. However the complications in the fabrication process are limiting towards future development of hollow microneedle platforms. A variety of microfabrication technologies have been developed for microneedles. The primary approaches for fabricating hollow microneedles have motivated on top-down approaches using the materials such as silicon, metal, or glass. However, the requirement to fabricate a hollow microneedle creates a substantial fabrication challenge for top-down approaches.

We present here a novel method for fabricating hollow microneedles using Carbon-MEMS (C-MEMS) process. C-MEMS process is getting more attention since last 15 years for its low cost, reliability and simplicity in the process. The high aspect ratio carbon hollow microneedle structures are fabricated in two steps: fabrication of SU8 microneedles in one step photolithography and conversion of polymer structures to carbon in pyrolysis process. The ease of fabrication of high aspect ratio SU8 structure makes it a suitable candidate for microneedle application. We report here for the very first time the hollow microneedle with glassy-carbon nature which is biocompatible. The percentage of shrinkage of SU8 structures after pyrolysis is also reported in this work. The outer diameter shrinkage is around 42% for 200µm tall needle where the inner and outer diameter ratios are 1/5, 1/3, 1/2 and it is 34.92% for solid needle structure. The inner diameter is also shrunk for all the cases. However, the outer diameter is shrunk only around 15% when the ratio of inner and outer diameter is 2/3 and the inner diameter is expanded in this case. The integration of these needle structures with drug delivery system (micropump) is our ongoing work.

Figure 1
SU-8/MWCNT derived Electrospun Composite Carbon Nanofabric as a High Performance Anode Material for Lithium Ion Battery
Authors: Kakunuri Manohar , Kaushik Shubham , Saini Ayush , Sharma Chandra Shekhar
Published: February 2020

Introduction

Carbon nanofibers (CNFs) have drawn a great attention for being used as anode materials for lithium ion battery due to short lithium ion transport distances, high resilience to volume expansion during cycling even at high current densities and enhanced electronic conductivity (1). Electrospinning is a promising and scalable method for preparing continuous nanofibers. Among wide range of electrospun polymer fibbers high carbon yield polyacrylonitrile (PAN) derived carbon nanofibers were well studied for Li-ion battery application (2, 3).

In this work, we have synthesized SU-8/CNT composite carbon nanofibers web over stainless steel current collector. Thus prepared composite carbon nanofiber web was tested for lithium ion intercalation. Electrochemical performance of composite fibers was compared with SU-8 derived carbon fiber web and SU-8 derived carbon thin film (4).

Experimental

0.5% multi walled carbon nanotubes (MWCNTs) were dispersed into SU-8 (2015) photoresist solution using probe  sonication for 30 min. Electrospun composite nanofiber web was prepared by modified C-MEMS process to keep morphology intact during the baking and pyrolysis. Galvanostatic charge discharge experiments were performed at different C-rates using Li metal as reference electrode.

Results and discussions:

SU-8/CNT composite carbon nanofibers morphology was investigated by scanning electron microscopy. FESEM images of nanofibers before and after pyrolysis were shown in Fig. 1a and 1b. Electrochemical performance of these carbon fibers was studied at different current densities form 0.1 to 1 C as shown in Figure 1c. Initial reversible specific capacity found to be 1317 mAh/g for SU-8/CNT composite carbon fiber web at 0.1 C. This specific capacity value is far better than reversible capacity values of SU-8 derived carbon films (~385 mAh/g) and other electrospun carbon nanofibers. Furthermore these CNFs web shown very good cyclic performance at higher C-rates. Specific reversible capacity at 1C rate (372 mA/g) was found to be 516 mAh/g.  This performance can be ascribed to tolerance of expansion and shrinkage during lithium insertion and de-insertion and enhanced electronic conductivity due to CNTs presence during the pyrolysis. Detailed comparison of electrochemical performance of composite fibers with photoresist derived carbon thin films and other carbon nanofibers will be presented during the conference.

References:

S. L. Candelaria, Y. Shao, W. Zhou, X. Li, J. Xiao, J. G. Zhang, Y. Wang, J. Liu, J. Li, G. Cao, Nano Energy, 1, 195 (2012).

X. Mao, T. A. Hatton, G. C.  Rutledge, Curr. Org. Chem., 17, 1390 (2013).

J. K.  Lee, K. Wan, J. B. Ju, B. W. Cho, W. II. Cho, D. Park, K. S. Yun, Carbon, 39, 1299 (2001).

M. Kakunuri, C. S. Sharma, ECS Trans., 61, 37(2014).

Figure 1
Investigation on the Conversion Reaction Voltage and Reversibility of CuF2 Electrode in Li-Ion Battery
Authors: Seo Joon Kyo , Cho Hyung-Man , Sina Mahsa , Takahara Katsunori , Chapman Karena W , Borkiewicz Olaf J , Meng Ying Shirley
Published: February 2020

Li-ion conversion materials have a higher theoretical capacity than commercialized intercalation compounds.[1] During the conversion reaction, more than one electron are used per transition metal ion, which is promising energy storage compared to one-electron reaction of intercalation compounds. Among conversion materials, transition metal difluorides, MF2 (M=Fe, Ni and Cu), have a relatively higher theoretical reaction voltage (2.66, 2.96 and 3.55 V vs. Li/Li+).[2,3] The voltage discrepancy, however, is a well known issue on transition metal difluorides. The experimental voltage is lower than thermodynamically derived theoretical voltage.[4] In this study, we develop the formalism of conversion reaction voltage as a function of size of metal nanoparticle formed during the lithiation. Density functional theory (DFT) calculation shows that the conversion reaction voltage depends on the size of a metal nanoparticle generated. We take annual dark field-scanning transmission electron microscopy (ADF-STEM) on the lithiated CuF2 and NiF2 cell, which demonstrates the formation of Cu and Ni nanoparticles with average sizes of ~ 2.5 and 1.5 nm, respectively. Near-equilibrium potentiostatic intermittent titration technique (PITT) is conducted to display the lower voltage with respect to a thermodynamic voltage. We find that the surface energy of metal nanoparticles leads to lower voltage relative to the thermodynamic voltage.

In addition, we develop a reversible CuF2 for the first time by coating NiO. Electron energy loss spectroscopy (EELS) elemental maps prove that the lithiation process mostly occurs in high NiO domain. We propose NiO as an artificial solid electrolyte interphase, which alleviates Cu dissolution during the conversion reaction.

Figure 1
A New and Facile Method to Improve the Electrochemical Performance of Si Anode: Ultrathin Polydopamine Coating upon Conductive Carbon Particles
Authors: Song Danoh , Jung Dae Soo , Choi Jaecheol , Kong Seokhyeon , Ryou Myung-Hyun , Lee Yong Min
Published: February 2020

Si-based active materials started to be used for small lithium-ion batteries (LIBs) such as 18650 cells with 3.5Ah (INR18650MJ1) in 2015 by LG Chem. However, its relative amount is known to be much smaller than graphitic materials due to the continuous pulverization caused by large volume change during cycling. The gas generation originated from electrolyte decomposition could lead to fast capacity decay of LIB cells. However, regardless of lots of trials such as how to construct nanostructured Si particles and design new adhesive binders, more efficient methods still have to be devised extensively. In this study, we are interested in modifying the surface property of conductive carbon materials, because they have relatively high volume ratio within the electrode and lots of contact points with Si particles. In addition, if there are some crosslinkable moieties upon the conductive carbons, all the Si particles will be well maintained electrochemically active within the electrode.

Based on these strategies, we tried to coat the polydopamine (PD) upon conductive carbons, Super-P, as thin as possible not to impede their electrical conduction. The prepared PD-coated Super-P (PD-SP) was well dispersed even within the aqueous medium. In particular, when polyacrylic acid (PAA) as a polymeric binder is introduced into aqueous anode slurry, the amine group in PD-SP and the hydroxyl group in PAA can react to form the crosslinking bonds. From the adhesion strength measurements by the surface and interfacial cutting analysis system (SAICAS) tool, we could find the increased adhesion properties. As a result, the cycle performance of Si anode was greatly improved to deliver about 1000 mAh/g after 1000 cycles even at 1.2 A/g.

Acknowledges

This work was supported by the Human Resource Training Program for Regional Innovation and Creativity through the Ministry of Education and National Research Foundation of Korea (NRF-2014H1C1A1066977) and the Energy Efficiency & Resources Core Technology Program of the Korea Institute of Energy Technology Evaluation and Planning(KETEP) granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea (No. 20142010102980).
Highly Porous Electrospun ZnCo2O4 Nanofibers for Lithium Ion Battery Electrodes
Authors: Kim Jae-Chan , Kim Da-Sol , Yeo In-Hyeong , Kim Dong-Wan
Published: February 2020

Lithium ion batteries have been widely used in a variety of fields such as electric vehicles, portable electronic devides, and large scale energy storage systems. In order to fullfill the stringent industrial requirements in these fields, novel electrode materials should be developed providing high electrochemical performances (high energy density and high power density). Transition metal oxides (TMO) are possible candidate materials to satisfy requirements of next generation anodes due to their high theoretical capacities. Among TMO materials, spinel Co3O4 which is a typical Li-conversion reaction material, represents the high specific capacity and reversibility. In addition, binary TMO such as NiCo2O4, CoMn2O4, MnCo2O4, and ZnCo2O4 have been suggested as novel high-capacity anode materials. Especially, ZnCo2O4 has the high theoretical capcity of 975 mAh/g based on both Li-alloying and –conversion reactions.

The nanostructuring of electrode materials is a key enabling factor to improve their electrochemical properties. An electrospinning process is the simple and versatile way to fabricate one dimensional fibrous nanostrcutured electrodes. In this study, we fabricated highly porous ZnCo2O4 nanofibers (P-ZnCo2O4 NFs) using simple electrospinning of ZnCo2O4/ZnO nanofibers by controlling the ratio of Zn to Co and selevtive etching of ZnO. Firstly, ZnCo2O4/ZnO nanofibers were fabricated by electrospinning and subsequent two-step heating processes. Zn and Co nitrate precursors with different Zn/Co ratios were completely dissolved in dimethyl formamide (DMF) containing Polyacrylronitrile. The mixed solution was loaded into a plastic syringe and metal-containing polymeric fibers were produced by appling a voltage of 15 kV to the nozzle. Then, the as-spun ZnCo2O4/ZnO nanofibers were stabilized in air to 280°C for 6 h and heated in Ar at 600°C for 2 h. For selective etching the excess ZnO, the ZnCo2O4/ZnO nanofibers were soaked in KOH solution. Finally, highly porous ZnCo2O4 nanofibers were obtained.

The fabricated P-ZnCo2O4 NFs with the diameter of ~120 nm provided large surface area and porosity by the selective etching of ZnO phase. Furthermore, P-ZnCo2O4 NFs exhibited enhanced electrochemical properties due to porous nature offering large contact area with electrolyte, efficient electron pathway, and short Li ion diffusion length.
High Performance Lithium Ion Batteries from Electrochemically Enhanced Conducting-Polymer/Inorganic Composites
Authors: Unur Ece
Published: February 2020

900 million vehicles meet the road almost every day around the world. 96% of these vehicles depend on combustion engines and thus fossil fuels for energy. Exhaustion of fossil fuels and emission of green house gases motivates the search for alternative energy sources. New environmental regulations enforces governments to support the use of electric vehicles in order to eliminate green house gas emissions and limit dependency on petroleum products. In order to persuade consumers to use electric vehicles some adjustments on the cost and safety must be done. Being the most expensive component of electric vehicles the main research must be focused on lithium ion batteries.  Since the research on lithium batteries started to hit the bottleneck, the focus must be shifted to novel, environmentally friendly and cheap materials.

Although, LiFePO4 has been the cathode material of choice (3.5 V vs Li/Li+), its conductivity must be enhanced. Another, material from phospho- olivine family, LiMnPO4,  has drawn attention with its high redox potential and thus energy density (~4.1 V vs. Li/Li+). But, it suffers from low conductivity. Silicon being one of the most abundant elements on earth crust and having unbeatable capacity is still the best choice for anode material for high performance lithium ion batteries (4200 mAhg-1). But, it suffers from mechanical degradation taking place due to volumetric changes arising from lithium alloying/dealloying process. Decreasing the particle size and carbon coating has been visited by many scientists to overcome issues of low mechanical stability and conductivity.

In this project; LiMn1-xFexPO4-LiFePO4
 cathode will be synthesized by coprecipitation of high potential LiMnPO4  and high performance LiFePO4. Partially lithiated Si will be used as an anode material. Synthesized materials will be coated by PEDOT:PSS to improve their electronic conductivities. Electronic conductivity and plasticity will be further improved by exposing the PEDOT:PSS to a plasticizing agent. Polypyrrole chains (PPy) will be electropolymerized onto PEDOT:PSS surface vertically to present pathways for easy diffusion of lithium ions. These conducting polymers will also aid in the overall capacity of the system.

Conducting polymer-inorganic composite cathode (Al-LiMn1-xFexPO4-LiFePO4-PEDOT:PSS-PPy) and anode(Cu-partially lithiated Si-PEDOT:PSS-PPy) will be combined to form a full lithium ion battery. The battery whose performance is enhanced by conducting polymers is expected to have an OCV of at least 3.5 V and a total energy density of 300 Wh kg-1 . The battery will make 1000 charge/discharge cycles at 1C rate by at least 50% capacity retention and 100 charge/discharge cycles at 10C rate by at least 75% capacity retention.
Effect of Densification Conditions on the Chemical, Electrochemical, and Mechanical Stability of 75Li2s - 25P2S5 (mol %) As a Potential Solid Electrolyte for Use in Electric Vehicles
Authors: Garcia-Mendez Regina , Mizuno Fuminori , Zhang Ruigang , Arthur Timothy S. , Sakamoto Jeff
Published: February 2020

Solid-state electrolytes have garnered significant attention for their potential to enable solid-state

batteries for electric vehicles with metallic Li as an anode. However, the stability between solid-state

electrolytes and metallic Li is not well understood. Lithium phosphorous sulfides are a promising class of

solid-electrolytes owing to their high ionic conductivity (10-4 – 10-3 S cm-1  at 25 °C), low interface

resistance against metallic lithium, and can be consolidated to > 90 % relative density at room

temperature1 . In this work, the chemical, electrochemical, and mechanical stability of hot-pressed 75Li2S-

25P2S5 (mol %), or LPS, between 200 and 550 °C was investigated. Hot pressing produced high relative

density and crystalline LPS pellets that were characterized using multiple electrochemical techniques. AC

impedance measurements were used to characterize the stability of the Li-LPS interface. The

electrochemical performance of LPS was analyzed as a function of current density between 0.01 and 1.0

mA cm-2  followed by cross-sectional microstructural analysis. It will be shown that: i) below or equal to

0.05mA cm-
2  ohmic behavior is observed, ii) at 0.1mA cm-
2  a transition behavior occurs identified by an

instability in polarization, and iii) above or equal to 0.5mA cm-2 , the potential decreases and is believed to

be related to the formation of an electronically conducting phase. Acoustic impulse excitation

measurements were used to determine changes in the elastic constants after DC cycling of Li-LPS.

Additionally, materials characterization such as Raman, XRD, and SEM will be presented to correlate the

densification conditions with DC cycling stability. We believe this is one of the first studies to

characterize the chemical, electrochemical, and mechanical stability of a Li-LPS interface. The

methodology established in this work could be applied to other solid-state electrolytes as well.

Reference

Sakuda, Atsushi, Akitoshi Hayashi, and Masahiro Tatsumisago. "Sulfide solid electrolyte with favorable mechanical property for all-solid-state lithium battery."Scientific reports 3 (2013)
(Invited) Reactions of Positive Active Materials of Lib
Authors: Ogumi Zempachi , Arai Hajime , Orikasa Yuki , Uchimoto Yoshiharu
Published: February 2020

Main issues for lithium ion batteries (LIBs) to grow in the application to advanced vehicles are durability, safety and cost. The durability is closely connected with safety, cost, energy density, etc.

LIBs are constructed by composite electrodes both of positive and negative electrodes, which are composed of pulverized active materials, conductive additives, and binders. The structure of LIBs is thus complicated and reaction distribution inside battery and composite electrodes often occurs. Uniform reactions distribution leads to the maximum performance of the battery. Many factors give major influences on the reaction distribution. Analytical methods to elucidate the reaction distribution were limited. In RISING project, different kinds of operando analytical technologies were developed. In the present work, some methods using SR X-ray devised in RISING are introduced and reaction distributions clarified by using this technology are explained mainly on positive electrode of layered and olivine type materials.

Acknowledgment

This work was supported by RISING of NEDO.