bluuebunny/crossref_metadata_2025 huggingface dataset:
Novel Metal Oxide Electrode Materials for Vanadium Redox Flow Battery Application
Authors: Bayeh Anteneh Wodaje , Chang Yu-Chung , Liu Ting-Ruei , Chen Hsueh-Yu , Huang Hsin-Chih , Kabtamu Daniel Manaye , Wang Chen-Hao
Published: February 2020

Solar cell and wind power plant have been widely used in the earth as a renewable energy source. However, those alternative energy sources have one critical problem which is the energy output cannot provide stable electricity power for common use. Since these issues, scientists have developed energy storage technique in the past several decades, such as pumped hydropower, compressed air energy storage, lithium-ion batteries, and lead-acid batteries. Recently, vanadium redox flow battery (VRFBs) is the energy storage system which can provide larger energy capacity and longer lifetime. Basically, VRFBs system can be divided by three main parts which include an electrode, membrane, and electrolyte. Nowadays, the big challenge of the carbon-based electrode has lower energy conversion efficiency. Therefore, our studies are more focusing on the electrode material development. Carbon material modification by oxygen-containing functional group or metal oxide loading has been developed in the past years. Especially, tungsten oxide nanowire shows good energy efficiency 67.7 % in higher current density 160 mA cm-2 and still remain 79 % in the energy efficiency of 80 mA cm-2 after 50 cycles test.
Optimization of Energy Transfer during Active Balancing of Lithium-Ion Batteries
Authors: Moss Pedro L. , Rajagopalan Kannan Dhevathi Rajan , Sonavane Rohit , Weatherspoon Mark H
Published: February 2020

In the recent years, lithium-ion batteries are being used as an energy storage in electric vehicles (EV) and hybrid electric vehicles (HEV) to a greater extent. A battery management system consists of three important parts: balancing, management and protection. Balancing is one of the most important part concerning the battery life. Without the balancing system voltages of individual cell will drift over time.1 This will affect the capacity of the battery pack which will result in the battery system failure. Most applications require that cells be connected in series/parallel to meet the voltage requirements, however this can cause imbalance among the cells. Achieving higher charge efficiency by equalizing the unbalanced cells in the pack is the goal of active balancing systems. This project deals with the time optimization for energy transfer between series connected cells that uses an active balancing topology. There have not been many studies in the literature which deals with optimum switching time for energy transfer between the batteries during active balancing. The proposed charge equalization scheme is designed to reduce the time used to transfer energy from the highest charged cell in the stack to the weakest charged cell in the stack. The performance of the optimized energy transfer between high and weak cell using a dynamic duty cycle adaptation is demonstrated by simulation using MATLAB/Simulink.

Reference

J. Cao, N. Schofield, and A. Emadi, 3–8 (2008).
(Invited) Are There Still New Structural Elements in Fullerenes That Cause Violations of the IPR?
Authors: Balch Alan L. , Olmstead Marilyn M.
Published: February 2020

A number of structural elements can be identified in fullerene cages that cause violations of the isolated pentagon rule (IPR), which requires that each of the twelve pentagons in a fullerene are surrounded by five hexagons. Endohedral fullerenes need not obey this rule and several structural elements have been identified that cause violations of the IPR. For example, one isomer of Gd3N@C84 has a site in the cage fabric where two pentagons share a common edge. What other structural elements of this sort have been identified? We will consider these and speculate upon what new elements might be expected to occur.

Figure 1
Large-Scale Synthesis of MoS2 Monolayer Using Na-Containing Facilitators for Electromechanical Energy Harvesting
Authors: Jung Ye Seul , Choi Hong Je , Cho Yong Soo
Published: February 2020

The reliable synthesis method of large-area, continuous 2D MoS2 layer has been demanded for applications of next generation electronic and optoelectronic devices. Here, Na2S is introduced as a novel growth promoter to control over the grain size of full area coverage MoS2 monolayer. With Na2S solution-coated film, the nucleation density increases by the formation of reduced phase like NaMoO3-x. At the same time, additional sulfur from Na2S film affects the nucleation and growth mechanism resulting in changes of the domain geometry from triangular nanosheets to centimeter scale films. Moreover, by modulating the concentration of Na2S solution, the grain size of MoS2 monolayer has been changed. Thus, we propose a new approach of modulating nucleation density and grain morphology in polycrystalline full-coverage MoS2 films by using growth promoter, Na2S. The successful large-scale monolayer has been characterized for electromechanical energy conversion. As a result, a peak output of 253mV and 22nA was obtained when a strain of 0.26% was applied. Our results suggest the potential of large-scale 2D layer as an electromechanical energy converter.
Substitutional Nitrogen Defects Enhance Thermal Transport across Graphene Interfaces
Authors: Olson David , Zhu Haoyue , Granzier-Nakajima Tomotaroh , Terrones Maurcio , Hopkins Patrick E
Published: February 2020

We present on the thermal and electrical transport properties in nitrogen-doped single layer graphene. After synthesis via atmospheric pressure chemical vapor deposition under various parameter conditions, we characterize the degree to which nitrogen defects are present in these systems. Transmission electron microscopy exemplifies the fact that that the structural integrity and homogeneity of the doped graphene lattice is maintained. Using Raman spectroscopy, we find that the intensity of the D peak is directly correlated to the nitrogen substitutional concentration in these systems, consistent with other works in the literature. Further, using Raman spectroscopic mapping, we find that the doping effect is homogenous, important for microelectronic applications. Finally, we characterize the thermal and electrical transport properties in these systems using time-domain thermoreflectance and transfer line method, respectively. In all, the culmination of these characterization techniques provides a basis for nitrogen-doped graphene use in nanoelectronic applications contingent on optimizing boundary conductances from a thermal and electrical perspective.
Emergence of Broadband Plasmon Absorption in Gold nanoparticle-decorated Molybdenum Diselenide Nanosheets
Authors: Dunklin Jeremy R , Rose Aaron H , Zhang Hanyu , Liu Jun , van de Lagemaat Jao
Published: February 2020

Layered transition metal dichalcogenides (TMDs) represent a diverse, emerging source of two-dimensional (2D) nanostructures with intriguing optoelectronic and catalytic properties. Gold nanoparticles (AuNPs), supporting localized surface plasmon resonances, can complement TMDs, allowing their optoelectronic properties to be tuned for use in a broad range of applications. Plasmonic AuNPs offer an extraordinary ability to concentrate electromagnetic fields and confine light to sub-wavelength dimensions. While non-plasmonic enhancement of electrocatalytic HER performance in AuNP-decorated TMDs has been reported, light-induced plasmonic excitation and dissipation mechanisms and their effect on light absorption, charge transfer, and band structure in adjacent TMDs are of keen interest. Mechanisms of plasmon-active enhancement includes light scattering, local field confinement, resonant energy transfer, and interfacial charge transfer pathways. This work utilizes transient absorption spectroscopy, with pump tunability and broadband visible probing, to monitor the carrier excitation and dynamics in various AuNP-TMD heterostructures. In particular, a combination of both time-resolved and steady-state optical spectroscopies unveils the presence of a sub-gap absorption feature in AuNP-decorated molybdenum diselenide (MoSe2) nanosheets. Optical excitation of this low-energy feature generates long-lived, energetic carriers in MoSe2. This development could represent an important advance in the design and implementation of hybrid metal NP-TMD heterostructures for use in photoelectrochemistry.
(Invited) Light Scattering and Emission from Hetero-Structures
Authors: Ferrari Andrea C.
Published: February 2020

Heterostructures based on layers of atomic crystals have a number of properties often unique and very different from those of their individual constituents and of their three dimensional counterparts. The combinations of such crystals in stacks can be used to design the functionalities of such heterostructures. I will show how Raman spectroscopy can be used to fingerprint such heterosctructures, and how these can be exploited in novel light emitting devices, such as single photon emitters, and tuneable light emitting diodes.
(Invited) Plasmon−Plasmon Interactions and Radiative Damping of Plasmons in Graphene Nanoribbon Arrays
Authors: Perebeinos Vasili
Published: February 2020

While graphene absorbs only 2.3% in the mid infra red (IR) spectral region, graphene plasmons have much stronger absorption in the far IR. Plasmons tunability by the external electric fields and by the spatial confinment offer a promising platform for opto-electronic and sensor applications. In this work [1], we demonstrate both theoretically and experimentally that the plasmon−plasmon and plasmon−radiation interactions modify strongly the plasmon resonance energy, radiative damping, and oscillator strength in graphene nanoribbon arrays. Even for the moderate filling factors of about 50%, plasmon radiative lifetime reduces to a ps time scale from a convetional ns time scale in the isolated graphene nanoribbon. We find scaling of plasmons with respect to the graphene doping level and filling factor, which both modify the strength of the long-range Coulomb and plamson-radiative interactions. The surprisingly large plasmon energy shift and radiative damping significantly affect the graphene-based plasmonic device performance.

[1] Vyacheslav Semenenko, Simone Schuler, Alba Centeno, Amaia Zurutuza, Thomas Mueller, and Vasili Perebeinos, ACS Photonics 5, 3459–3465, 2018.
(Invited) From Field-Effect Transistors to Tunneling Devices and Resistive Random Access Memories in Two-Dimensional Van Der Waals Structures
Authors: Appenzeller Joerg
Published: February 2020

Devices from low-dimensional materials are fundamentally different from those in the conventional electronic world. The ultra-thin body of transition metal dichalcogenides (TMDs) and black phosphorus (BP) as examples of semiconducting layered structures enables electrostatics gate control that goes beyond what can be achieved by even the most aggressively scaled three-dimensional silicon FinFET technology. Moreover, the arrangement of bonds in a two-dimensional system defines a natural sub-nanometer channel thickness without loss of carrier mobility as would be typically observed when thinning down a three-dimensional semiconductor to similar dimensions. At the same time the anisotropic transport conditions in layered two-dimensional (2D) systems allow for novel device applications. In my talk, I will present three device implementations that take explicitly advantage of the unique properties of two-dimensional van der Walls (vdW) materials. First, I will discuss a multi-layer channel device from MoS2 that exploits the advantage of stacking 2D vdW materials in a three-dimensional (3D) integration approach. I will show how multi-channel TMD field-effect transistors (FETs) are fabricated, will discuss the associated challenges and finally present the experimental transport results. Next, tunneling field-effect transistors (TFETs) from black phosphorus (BP) will be presented that show record high tunneling current densities and good inverse subthreshold slopes in a reconfigurable device geometry. Last, I will present experimental and simulation results on the topic of resistive random access memories (RRAM) from multi-layer MoTe2 and Mo1-xWxTe2. Excellent switching characteristics of these novel types of two-terminal devices are presented in conjunction with a model to explain the observed switching behavior in terms of an electric field induced structural transition from a 2H semiconducting to a distorted transient structure (2Hd) and orthorhombic Td conducting phase.
(Invited) Covalent Functionalization of Graphene and MoS2: Chemical Versus Electrochemical Routes
Authors: Mali Kunal S. , De Feyter Steven
Published: February 2020

Atomically thin sheets of materials, the so-called two-dimensional (2D) materials arrived on the scene in early 2000s with the successful isolation of graphene as freestanding monolayer films. Graphene, a single atom thick sheet of sp2-hybridized carbon bonded in a honeycomb lattice, has exceptional electronic, optical, mechanical and thermal properties that outperform those of most of the existing materials. The research on graphene further fuelled emergence of related 2D materials such as black phosphorous, silicene, germanene and transition metal dichalcogenides (TMDs) such as MoS2. Due to their exotic properties, these materials offer virtually endless opportunities for fundamental research as well as cutting edge applications.

Most of these 2D materials however exist as single layers only when supported by another solid surface or when stabilized by physisorbed or chemisorbed organic molecules. Given their layered nature, most 2D materials are extremely difficult to disperse in typical solvents. Chemisorption of organic molecules onto their basal plane allows dispersion of these materials in (organic) solvents thereby improving their solution processability. Such dispersions can be used in composite materials and as functional inks. Moreover, covalent functionalization allows modification of the intrinsic electrical, electronic and optical properties of these 2D materials.

In this talk, I will discuss covalent modification graphene, graphite and MoS2 using diazonium chemistry. Two different routes for reductive decomposition of diazonium salts namely, chemical and electrochemical, will be discussed in detail. Special focus is on sub-nanometer characterization of modified materials using scanning tunneling and atomic force microscopy (STM and AFM). Initial results towards patterned covalent functionalization using physisorbed self-assembled templates will also be presented besides the discussion on the use of such surfaces as seed layers for atomic layer deposition (ALD).
Electronic Structure and Phase Stability of Ag and Sn Doped Cu2s: A DFT Study
Authors: Barman Sajib Kumar , Huda Mohammad Nurul
Published: February 2020

Cu2S is an important solar absorber material. Despite having excessive Cu vacancy formation tendency and being a degenerate semiconductor, it has gained wide attention due to its non-toxicity, earth abundance, suitable band gap and previously shown nearly 10% efficiency in thin film solar cells. A new theoretical phase of Cu2S, a DFT predicted acanthite like phase, has shown that Ag doping can help to reduce Cu vacancy formation tendency without altering its electronic structure much. Hence, doping Cu2S with suitable cations warrants more studies on its electronic structure and phase stabilities. Here, we are going to present a systematic DFT study for Ag and Sn doped Cu2S acanthite like and low chalcocite phases to explore the electronic structures, optical properties, Cu vacancy formation tendency, and crystal phase stabilities.
Fabrication of Efficient Perovskite Solar Cells in Ambient Air Using a Humidity-Insensitive Method
Authors: Wang Feng , Ye Zongbiao , Sarvari Hojjatollah , Park So Min , Abtahi Ashkan , Graham Kenneth , Zhao Yuetao , Chen Zhi , Li Shibin , Wang Yafei
Published: February 2020

Fabrication of perovskite solar cells (PSCs) in ambient air is of challenge due to its sensitivity to humidity. In this presentation, we report the fabrication of efficient CH3NH3PbI3 (MAPbI3) PSCs using an antisolvent method which yields decent device performance in a wide range of humidity levels (~ 0% RH, 20% RH, 40% RH, 50% RH and 60% RH). The MAPbI3 films obtained in those conditions are studied by characterizations including scanning electron microscope (SEM), X-ray diffraction (XRD), UV-vis absorption and steady-state photoluminescence (PL). Results exhibit that the quality of the MAPbI3 films shows no obvious difference as a whole. The greatly suppressed influence of humidity is ascribed to the rapid crystallization process due to the antisolvent method. The photovoltaic performances for the devices prepared at these relative humidity (RH) levels are found similar with average power conversion efficiencies (PCE) are around 15%. The storage stability is found similar as well. What’s more, the effect of water absorbed in the hydrophilic precursor to MAPbI3 films and associated solar cells is investigated and found ignorable. As a result, it is concluded that antisolvent method is an ideal humidity-insensitive route to fabricate efficient PSCs in ambient air and may pave the way for massive and low-cost manufacturing of solar panels.

Keywords: (perovskite solar cells, CH3NH3PbI3, anti-solvent method, crystallization process)
Thermodynamic Approach to Develop Lead-Free Halide Perovskites: Theoretical Study
Authors: Park Jong Goo , Chung Choong-Heui , Hong Ki-Ha
Published: February 2020

Metal halide perovskites (MHPs) are one of the promising candidates for next-generation photovoltaic materials. Since the Miyasa group first adopt methylammonium lead tri-iodides as a sensitizer of dye-sensitized solar cells, the efficiency of MHP solar cells has improved at an unprecedented speed. According to the recent report of national renewable energy laboratory, the certified power conversion efficiency (PCE) of MHP solar cells exceeded 23%. However, stability and toxicity are primary concerns for MHP solar cell commercialization. Among various efforts to develop Pb-free perovskite solar cells, Sn-based materials have shown the PCE. However, the stability of Sn-based perovskites is worse than Pb-based solar cells, and the multivalent features of Sn are considered to be the origin of the unstable performance.

Compositional engineering and additive control can be the effective ways to develop highly stable and efficient Pb-free perovskite solar cells. This study presents the effects of compositional engineering and various additives on the stabilization of Pb-free MHP materials via ab initio thermodynamics calculations. The concept of the ‘anti-stabilizer’ for the proper selection of the preferred phase is suggested by our previous report[1]. We present that the anti-stabilizing concept can be successfully applied to stabilize the proper band gap polymorph of black CsSnI3[2]and Bi-based layered perovskites. Additionally, the roles of additives including small alkali metal interstitials are discussed concerning thermodynamics.

[1] J. Jeon, T. Eom, E. Lee, S. Kim, S. Kim, K.-H. Hong, H. Kim, J. Phys. Chem. C 121 (2017) 9508–9515.

[2] J.H. Heo, J. Kim, H. Kim, S.H. Moon, S.H. Im, K.-H. Hong, J. Phys. Chem. Lett. 9 (2018) 6024–6031.
(Invited) Lead-Free Perovskite Solar Cells
Authors: Diau Eric Wei-Guang
Published: February 2020

Perovskite solar cells (PSC) have attracted much attention in recent years due to the rapid progress on the performance of PSC to attain PCE over 22 % within 5 years. However, conventional perovskite light absorbers contain the toxic lead element that should be replaced by other environmentally benign elements. Herein we report pure tin-based PSC based on various device configurations. To make a stable pure tin perovskite free of lead, we varied SnCl2/SnBr2 ratios to yield tin perovskites with three halides (I, Br and Cl) co-crystallized inside the tin-perovskite crystals (MASnIBr2-x
Cl
x
) according to the stoichiometric ratios of the precursors. When the SnCl2 proportion was equal to or greater than 50 % (x ³ 1), phase separation occurred to generate MASnI3-y
Br
y
and MASnCl3-z
Br
z
according to the stoichiometric proportions of their precursors, confirmed with the corresponding XRD analysis. A device with MASnIBr1.8Cl0.2 (SnCl2 = 10 %) showed the best photovoltaic performance: J
SC
= 14.0 mA cm-2, V
OC = 380 mV, FF = 0.573 and PCE = 3.1 %, with great reproducibility and long-term stability. For the inverted planar tin-based PSC, we investigated the doping effect of bulky organic cations with ethylenediammonium diiodide (EDAI2) and butylammonium iodide (BAI) as additives to enhance the performance and stability of the FASnI3 perovskite solar cells. The additive EDAI2 plays a key role to cause slow passivation of the surface and relaxation of crystal strain such that the device performance increases gradually with increasing duration of storage. In the presence of EDAI2 additive (1 %) the FASnI3 device attained the best initial efficiency 7.4 % and the device performance continuously increased as a function of duration of storage; the maximum PCE, 8.9 %, was obtained for a device stored in a glove box for over 1400 h with only slight degradation for storage beyond 2000 h. Moreover, hybrid cationic GA/FA tin-based PSC was optimized at precursor ratio GAI:FAI = 20:80 to attain PCE 8.5 % when prepared freshly; the efficiencies continuously increased to attain a record PCE 9.6 % after storage for 2000 h. The fresh device passed all strict verification steps and was certified to give the efficiency of power conversion 8.3 %. The great performance and stability of the device reported herein have attained a new milestone for lead-free perovskite solar cells on a path toward commercial development.
(Invited) Temperature-Dependent Photoluminescence and Stability of Methylammonium Lead Iodide (CH3NH3PbI3) and CsPbX3 (X=Cl, Br, I) Perovskite Nanocrystal Superlattices
Authors: Zhang Yangning , Thomas Cherrelle , Abney Michael , Korgel Brian A.
Published: February 2020

The temperature-dependent photoluminescence (PL) spectra and lifetimes, and thermal stability of ordered assemblies, of methylammonium lead iodide (CH3NH3PbI3, MAPI) and CsPbX3 (X=Cl, Br, I) nanocrystals were studied. These nanocrystals generally exhibit decreased PL lifetimes and decreased emission energy with lower temperature, unlike most semiconductors. Luminescent MAPI nanocrystals with cuboidal shape and tetragonal crystal structure are terminated by (110) and (002) facets based on grazing-incidence wide-angle scattering (GIWAXS) and high resolution transmission electron microscopy (TEM) and electron diffraction. In situ GIWAXS and GISAXS of the MAPI superlattices heated under nitrogen exhibit a phase transition from tetragonal-to-cubic structure at 60oC, similar to bulk MAPI. The MAPI nanocrystals start to decompose to PbI2 at about 90oC, which is 10oC lower reported for bulk MAPI thin films, and at slightly higher temperatures, the coexistence of hexagonal and rhombohedral PbI2 is observed. As PbI2 precipitates, there is simultaneously fusion of the MAPI nanocrystals in the superlattice. The thermal stability of superlattices of γ-orthorhombic CsPbI3 nanocrystals capped with either oleic acid (OA) or phosphinic acid (PA) were also studied. The capping ligands influences the orientation of the nanocrystals on the substrate, with OA and PA capping yielding nanocrystals oriented with (001)SL and (002)NC planes, or (110)NC and (002)NC planes, respectively, on the substrate. Heating the CsPbI3 nanocrystal assemblies to 300°C induced a transition from the γ-orthorhombic to the δ–orthorhombic (yellow phase) and the nanocrystals capped with PA were found to be more thermally stable than those capped with OA.
(Invited) Triplet Energy Transfer at Interfaces between Molecules and Perovskite or Metal Chalcogenide Nanostructures
Authors: Johnson Justin C. , Lu Haipeng , Sulas Dana , Anthony John , Miller Elisa M. , Beard Matthew C , Blackburn Jeffrey L.
Published: February 2020

The movement of energy and charge at nanoscale interfaces between organics and inorganics could enable novel schemes for photoconversion. We have been exploring ligand exchange and functionalization for nanoscale semiconductors with tunable properties. Lead chalcogenide quantum dots (QDs) have near-infrared band gaps that are ideal for solar harvesting and can be tuned to resonance with molecular ligands that harbor triplet excitons. Photoexcitation of either ligand or QD sets in motion energy transfer processes that have kinetics defined by nanocrystal band gap, triplet energy, and the arrangement and distance of molecules on the QD surface. Energy or charge transfer on a ps timescale can inhibit production of triplets by singlet fission, but strategies for enhancing the singlet fission rate or isolating the molecules from direct contact with the QD surface are being studied to circumvent this problem. In CsPbBr3 nanocrystals, ligand exchange with pentacene derivatives produces complementary absorption spectra for organic and inorganic components. Excitation of the strongly absorbing nanocrystal leads to energy transfer to the pentacene singlet, which undergoes fast singlet fission. The yield of triplets compared to absorbed photons is greater 100%, and the triplet lifetime is into the microsecond time range. Further dependence on the preparation conditions of the system (e.g., solution vs. film) is being explored. Other investigations have involved incorporating specialized molecules for attachment to transition metal dichalcogenides (TMDCs). The focus is on producing a uniform layer of bound molecules on the planar surfaces and understanding the interplay between interfacial charge-transfer and other photophysical properties like singlet fission.
Electrochemical Investigation of Graphene Composited Plasmonic Photo Conversion Electrode
Authors: Suzuki Shinya , Yasuda Kensuke , Minamimoto Hiro , Murakoshi Kei
Published: February 2020

The light energy conversion using the wide-gap semiconductor, such as TiO2, has been recognized as the promising way for the realization of the sustainable society. Recently, the combination of the plasmon active metal nanostructures with the semiconductor electrode has been received much attention due to its wide range photo response ability. On the other hand, graphene is the one of the interesting two-dimensional material because of its physicochemical properties. In this study, we have fabricated the graphene composited plasmonic photo electric conversion electrodes as the new light energy conversion electrode. The system shows characteristic behavior at photo energy conversion due to modification of surface electronic structure at graphene/Au nanostructure inerfaces.
(Invited) Construction of Organic and Inorganic Hybrid Nanomaterials Utilizing Acene Derivatives for Efficient Singlet Fission
Authors: Hasobe Taku , Sakai Hayato
Published: February 2020

Singlet fission (SF) is highly expected to improve the solar energy conversion properties by generating two excitons from one photon absorption. Among various organic compounds, acene derivatives such as tetracene and pentacene are promising for occurrence of efficient SF. For example, pentacenes meet the energy-level matching condition between a singlet and two triplet states: [E(S1) ≥ 2E(T1)]. However, the molar absorption coefficients of pentacenes in the ca. 400–500 nm region are extremely limited, whereas quantum dots, such as CdSe/ZnS (QD), possess high fluorescence quantum yields and particle-size-dependent fluorescence wavelengths. Thus, a combination of QD (D) and pentacene (A) provides a system of both an enhanced light-harvesting efficiency throughout the solar spectrum and an efficient conversion of the harvested light into the triplet states by SF. Based on these points, m-phenylenebridged bis(triisopropylsilylethynyl) (TIPS)-pentacene dimer-functionalized QD was synthesized to examine the sequential photoinduced process from energy transfer to SF. In femtosecond transient absorption measurements, initial energy transfer from QD to pentacene (quantum yield: 87%) and subsequent SF were efficiently observed. The quantum yield of triplet states of pentacene units (Φ
T) based on the excitation of QD attained ~160%.[1] Additionally, the related molecular systems will be briefly discussed in this presentation.[2,3]

References

[1] Sakai, H.; Inaya, R.; Tkachenko, N. V.; Hasobe, T. Chem. Eur. J.
2018, 24, 17062-17071.

[2] Sakai, H.; Inaya, R.; Nagashima, H.; Nakamura, S.; Kobori, Y.; Tkachenko, N. V.; Hasobe, T. J. Phys. Chem. Lett.
2018, 9, 3354-3360.

[3] Nakamura, S.; Sakai, H.; Nagashima, H.; Kobori, Y.; Tkachenko, N. V.; Hasobe, T. ACS Energy Lett.
2019, 4, 26-31.
(Invited) Catalytic Reaction Networks Mimicking Photosynthetic Electron Transport Chain
Authors: Nakanishi Shuji
Published: February 2020

In natural photosynthesis, NADPH (reducing equivalent) and ATP (chemical energy) are produced during light conditions by photo-driven electron and proton transportation at thylakoid membranes. Then, during dark conditions, CO2 is fixed to organic compounds using the photo-generated NADPH and ATP via the Calvin cycle. Thus, various redox and acid/base reactions are wired in natural photosynthesis, enabling sophisticated photo/chemical energy conversions. Inspired by this strategy in natural photosynthesis, our research group is working on developing (photo-)functional materials carrying multiple catalysts on which reaction network is constructed. For example, we have shown that conductive carbon substrate carrying two different electrocatalysts (Cu- and Pt-modified covalent organic frameworks; COF) could catalyze selective nitrate reduction by H2 [Kamiya, et al., ACS cat. 2018]. Notably, the reaction selectivity can be controlled simply by changing the loading amount/ratio of Cu-COF and Pt-COF. Thus, the modification of the reaction network structures on the substrate can change the reaction selectivity. We have also successfully fabricated hollow TiO2 nano-spheres on which oxidation and reduction co-catalysts were loaded inside and outside of the sphere, respectively. Due to the spatially asymmetric loading of the different kind of catalysts on the hollow sphere, pH-gradient was generated at inside and outside the hollow spheres by light irradiation, just like that at the thylakoid membranes in chloroplasts.
(Invited) Ordered Nanoporous Semiconductors with Controlled Geometrical Structures By Anodization Processes
Authors: Yanagishita Takashi , Kondo Toshiaki , Masuda Hideki
Published: February 2020

For the preparation of functional nanodevices for efficient energy conversion, the use of the naturally occurring self-ordered structures is considered an effective process due to its capability of formation of precisely controlled fine nanostructures. To optimize the performance of the obtained devices, fabrication of precisely controlled geometrical structures of metals and semiconductors is essential. For example, the fabrication of highly ordered structures of metal and semiconductors contributes to the efficient absorption of the incident light and also enhance the charge separation in the interfaces. The anodization processes of metals have been widely applied to the fabrication of nanostructures of metal oxides. One advantageous point of this process is controllability of the geometrical structures of the obtained porous structures based on the anodization conditions. In addition, the ordered nanoporous structures can be obtained under the appropriate anodization conditions. In the present report, recent results concerning the preparation of nanoporous semiconductors with controlled geometrical structures and its applications are described. As a typical example, naturally ordered processes1 or pretexturing process2were applied to the preparation of nanoporous TiO2 with controlled geometrical structures. In addition, a high through-put process for the preparation of the through-hole membrane of TiO2 was also described. This process is based on the two-layer anodization used for the preparation of porous alumina through hole membranes3. The tow-layer anodization, which generates TiO2 layers with different solubility, and subsequent selective dissolution generate the through hole membrane of TiO2
4. Repetition of the process allows the high-throughput preparation of the ordered TiO2 through hole membranes. In addition to the self-ordered TiO2, preparation of the ideally ordered TiO2 through hole membranes is demonstrated. The obtained TiO2 through-hole membranes with controlled geometrical structures will be applied to various types of energy conversion devices.

P. Roy, S. Berger, P. Schmuki, Angew. Chem. Int. Ed., 50, 2904 (2011).

T. Kondo, S. Nagao, T. Yanagishita, N. T. Nguyen, K. Lee, P. Schmuki, H. Masuda, Electrochem. Commun., 50, 73 (2014).

T. Yanagishita and H. Masuda, Electrochim. Acta, 184, 80 (2015).

T. Yanagishita, H. Inada, T. Kondo, N. T. Nguyen, P. Schmuki, and H. Masuda, J. Electrochem. Soc., 165, E763 (2018).
Synthesis, Photophysical and Electrochemical Redox Properties of Β-Octa and Hepta Substituted Chlorins and Porphyrins
Authors: Rohal Renu Kumari , Sankar Muniappan
Published: February 2020

Conformationally distorted tetrapyrroles can be used as appropriate biomimetic model compounds as they resemble naturally occurring pyrroles and also find applications in material chemistry [1]. Also, fused chlorins and porphyrins are having potential biological and material applications [2]. Nitroporphyrins are good precursors as they undergo nucleophilic substitution reaction with wide range of Michael donors [3]. Nucleophilic addition at the β-position results in the formation of porphyrins as well as chlorins based on the temperature and size of active methylene compound which can be further converted to mono- and di-fused porphyrins [4]. Herein, we report the facile syntheses, spectroscopic and redox properties of hepta- and octa-substituted porphyrins and their fused derivatives. CuDFP(MN)2Br6 and CuMFP(MN)Br6 exhibited anodic shift in redox potentials as compared to precursor porphyrins and hence lower HOMO-LUMO gap was observed. In this presentation, we will describe about the synthesis, structural, spectral and intriguing electrochemical redox properties of fused porphyrins and chlorins.

Fig. 1. Molecular Structure of β-monofused porphyrins and comparative CVs of CuTPP, CuMFPMNBr6 and CuDFP(MN)2Br6.

References:

1. (a) Senge, M. O.; Medforth, C. J.; Sparks, L. D.; Shelnutt, J. A.; Smith, K. M. Inorg. Chem. 1993, 32, 1716. (b) Chaudhri, N.; Cong, L.; Grover, N.; Shan, W.; Anshul, K.; Sankar, M.; Kadish, K. M. Inorg. Chem. 2018, 57, 13213. (c) Kumar. R.; Sankar, M. Inorg. Chem. 2014, 53, 12706.

2. (a) Bartoli, J. F.; Mansuy, O.; Le, B.-O.; Ozette, K. L. B.; Palacio, M.; Mansuy, D. J. Chem. Soc., Chem. Commun. 2000, 827. (b) Kozyrey, A. N,; Chen, Y,; Goshwami, L. N,; Tabaczvnski, W. A.; Pandey, R. K. J. Org Chem. 2006, 71, 1949.

3. (a) Serra, V. I. V.; Pires, S. M. G.; Alonso, C. M. A.; Neves, M. G. P. M. S.; Tome, A. C.; Cavaleiro J. A. S. Heterocycl. Chem.
2013, 33, 35. (b) Siri, O.; Jaquinod, L.; Smith, K.M. Tetrahedron Lett. 2000, 41, 3583. (c) Wickramasinghel, A.; Jaquinod, L.; Nurco, D. J.; Smith, K.M. Tetrahedron Lett. 2001, 57, 4261.

4. (a) Chaudhari, N.; Grover, N.; Sankar, M. Inorg. Chem.
2018, 57, 11349. (b) Kalsbeck, W. A.; Seth, J.; Bocian, D. F. Inorg. Chem.
1996, 35, 7935.

Figure 1
Adsorption and Desorption Rates for Pophyrins and Phthalocyanines on Gold from Solution.
Authors: Hipps K W , Mazur Ursula
Published: February 2020

In physisorption from the vapor phase, one generally finds that the activation energy is negligible. Further, because of their molecular mass and strong non-covalent interactions with conductors, the desorption energies into vacuum from a gold surface are very high, of the order of 3-4 eV. Thus, at room temperature the desorption rates of porphyrins and phthalocyanines from gold are essentially zero. Such is not the case for the solution-gold interface. In adsorption there are several possible processes that lead to a significant activation energy for adsorption. These include partial desolvation of the adsorbate and partial desolvation of the surface. In the case of adsorption, the adsorption energies measured in the vapor phase are significantly diminished by solvent-adsorbate and solvent-surface interactions. Thus, the desorption rates at the solid solution interface can be orders of magnitude larger than at the vapor-solid interface. Unfortunately, there is very little data on the adsorption and desorption rates of non-ionic porphyrins and phthalocyanines from solution onto gold. In this talk we will present new measurements covering several organic solvents and a selection of porphyrins and phthalocyanines. Preliminary models for understanding these rates will also be presented.
Helical Supramolecular Porphyrin Assemblies
Authors: Haino Takeharu
Published: February 2020

Supramolecular polymers are a class of molecular assemblies, which are held together by non-covalent interactions. Reversible nature of supramolecular polymers results in unique properties such as self-healing and stimuli-responsivity. Therefore, supramolecular polymers have attracted a great deal of interest in material science.

A bisporphyrin molecule, where two porphyrin rings are connected with a pyridyl linkage, demonstrates a unique head-to-head homodimeric associationthat is directed through a donor-acceptor interaction and a stacking interaction. A brand-new supramolecular polymer was fabricated by employing this unique supramolecular complex. The two bisporphyrin units needed to be connected with the butadiyne linkage to give rise to a homoditopic tetrakisporphyrin monomer 1. The formation of the self-complementary dimeric bisporphyrin at each end of 1 resulted in the supramolecular helical polymer. In this presentation, we will report the development of the chiral supramolecular polymer that is produced by cross-linking of the supramolecular helical polymer with a chiral bispyridine 2.

Figure 1
Photophysical and Electrochemical Studies of Β-Functionalized Arylaminoporphyrins
Authors: Prakash Kamal , Osterloh Ryan , Sankar Muniappan , Kadish Karl M.
Published: February 2020

β-functionalized porphyrins possess interesting photophysical, electrochemical and conformational properties that can be useful for applications in the area of non-linear optics, catalysis and anion sensing.1
β-nitration, β-formylation and β-halogenation of porphyrins have been utilized to prepare starting compounds which can be further converted into mixed β-substituted porphyrins.2 Only a few porphyrins having carbon-heteroatoms at their β-position are known and their electronic and redox properties have not been explored in great detail as compared to other β-functionalized porphyrins. The versatility of this synthetic approach to achieve new mixed β-functionalized porphyrins was previously demonstrated in the synthesis of medicinally related compounds as well as new types of ligands and DSSC materials.3 The substitution of an arylamino group onto a porphyrin through C-N bond formation provides a good porphyrin substrate which differs from previous systems in term of its chemical and photophysical properties.

In the present paper, we report the synthesis and electrochemical characterization of β-arylaminodibromoporphyrins shown in Chart 1. Five arylamino porphyrins, represented as (Br2NH(X)PorM), were fully characterized by UV-Vis, Fluorescence, 1H NMR spectroscopy and cyclic voltammetry techniques.

DFT studies indicate planar to moderate non-planar conformations of the porphyrins, revealing the effect of the different arylamines on the porphyrin core. Absorption spectra exhibited much broader and blue shifted Soret bands with fewer Q bands as compared to the precursor and other tri-subtituted porphyrins.2 Reduced emission spectra and lower lifetimes were also observed due to the presence of two bromo group.

Electrochemical studies were performed under different solution conditions and the data compared with that of other tri-substituted porphyrins. Changing the arylamino group from phenylamine to naphthylamine and then to 4-nitro/cyanophenylamine significantly altered the redox potentials of these porphyrins. In this presentation, we will discuss the structural, spectral and electrochemical properties of the newly synthesized β-arylamino functionalized porphyrins.

References:

(a) The Poprhyrin Handbook; Kadish K. M., Smith, K. M., Guilard, R., Eds.; Academic Press: San Diego, 2000-2003; Vol. 1-20. (b) Hiroto, S.; Miyake, Y.; Shinokubo, H. Chem. Rev.
2017, 117, 2910.

(a) Bhyrappa, P. Tetrahedron Lett.
2016, 57, 5150. (b) Kumar, R.; Sankar, M. Inorg. Chem.
2014, 53, 12706. (c) Prakash, K.; Kumar, R.; Sankar, M. RSC Adv.
2015, 5, 66824.

Higashino, T.; Imahori, H. Dalton Trans.
2015, 44, 448.

Figure 1
Morphology Controlled MnCo2O4.5 Induced By Graphene Quantum Dots and Their Application in Supercapacitors
Authors: Zhang Maiwen , Yu Aiping
Published: February 2020

Graphene quantum dots (GQDs) are an emerging type of zero-dimensional (0D) carbon nanomaterial, which have gained significant research attention due to the benefits it inherits from both graphene and quantum dots. Interestingly, GQDs for the first time are served as induce agent for the controllable growth of MnCo2O4.5 nanoarrays or nanoneedles on Ni foam via a simple hydrothermal method. Specifically, the resulting optimized MnCo2O4.5 with nanoneedle structure shows outstanding electrochemical performances including high specific capacitance of 1576 Fg-1 at the current density of 1 Ag-1 (about three times higher than that of MnCo2O4.5 prepared without GQDs), excellent rate capability, and long-term cycling stability. These results presented here demonstrate that GQDs can act as a induce agent during the material synthesis process to adjust the morphology and achieve interesting nanostructures, and improve their electrochemical properties for applications in supercapacitors and other energy storage devices.
Corrosion Behaviors of Ferritic and Martensitic Stainless Steels in H2o Containing CO2 and O2 at Elevated Pressures
Authors: Repukaiti Reyixiati , Teeter Lucas , Doğan Ömer N. , Ziomek-Moroz Margaret , Oleksak Richard P. , Thomas Randal B. , Huerta Nicolas , Baltrus John P , Tucker Julie
Published: February 2020

Microstructure and phase composition of the solid corrosion products formed on commercial ferritic and martensitic steels with various chromium compositions were studied at conditions designed to simulate the working environment of low temperature components in direct supercritical CO₂ power cycles. All alloys were characterized prior to the corrosion experiments using wavelength dispersive X-ray fluorescence for determining elemental compositions, and microscopic evaluation for determining grain structures. Immersion experiments were carried out in a CO₂-saturated H₂O environment with dissolved O₂ at 50°C for 96 hours, at 0.1 MPa and 8 MPa. The corrosion products were characterized using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. Alloy corrosion rates were calculated from mass difference following removal of corrosion products. Complimentary electrochemical experiments were also conducted in the same environment at 0.1 MPa. Linear polarization resistance, cyclic polarization, and electrochemical impedance spectroscopy were used to further evaluate alloy corrosion resistance.
Electrochemical, Surface Morphology and Computational Studies on Some Quinoxalin-6-Yl-4,5-Dihydropyrazolylpropanones As Inhibitors of Mild Steel Corrosion in 1 M HCl Solution
Authors: Olasunkanmi Lukman Olawale , Ebenso Eno E
Published: February 2020

Corrosion of mild steel in 1 M HCl in the presence of 1-[3-(3-methoxyphenyl)-5-(quinoxalin-6-yl)-4,5-dihydropyrazol-1-yl]propan-1-one (Mt-3-PQPP) and 1-(3-(4-chlorophenyl)-5-(quinoxalin-6-yl)-4,5-dihydro-1H-pyrazol-1-yl)propan-1-one (Cl-4-PQPP) was investigated electrochemically using Tafel polarization and AC impedance techniques. Mild steel corrosion was observed to be retarded by the studied compounds such that an inhibition efficiency of up to 80% was achieved even at very low concentration (< 30 µM), especially with Mt-3-PQPP. Both compounds inhibit mild steel corrosion in 1 M HCl and the inhibition efficiency increases with increase in concentration. The Tafel curve for steel corrosion suggested that the studied compounds are mixed-type corrosion inhibitors. The protective adsorbed film of the inhibitors is pseudo-capacitive as revealed by the electrochemical impedance spectroscopy (EIS) analysis. Mt-3-PQPP molecules appeared to chemisorb onto the steel surface, while the adsorption of Cl-4-PQPP molecules involved both physisorption and chemisorption mechanisms. Comparison of mild steel surface immersed in 1 M HCl in the absence and presence of Mt-3-PQPP and Cl-4-PQPP revealed that the inhibitor-free acid solution damaged the steel surface more badly than the inhibitor-containing solutions. This further suggests that the inhibitor molecules protected the steel surface from unhindered attack by the corrosion acid ions. Quantum chemical calculations were carried out on the studied molecules and relevant reactivity parameters were used to provide molecular based explanations on the inhibitive behaviour of the Mt-3-PQPP and Cl-4-PQPP. Adsorption of inhibitor molecules on mild steel surface was simulated using the molecular dynamics method while the metal substrate was represented by Fe(110) cleaved surface. Theoretical quantum chemical calculations and molecular dynamics simulation results corroborate experimental electrochemical studies.
Prospects and Challenges of Supramolecular Approaches in Corrosion Prevention Strategies
Authors: Saji Viswanathan S.
Published: February 2020

Supramolecular chemistry, the ‘chemistry of molecular assemblies’ is a fascinating realm of modern science where researchers are constantly investigating the possibilities of the design of novel supramolecular structures, surfaces and techniques in different application areas including corrosion prevention. Supramolecular species are branded by the three-dimensional arrangement of their constituents and by the nature of the intermolecular interactions [1, 2]. They can be conveniently classified into (i) molecular self-assemblies, (ii) host-guest complexes, and (iii) molecules built to specific shapes (rotaxanes, dendrimers etc.). A supramolecular self-assembly can be defined as the spontaneous organization of a few or many components forming structurally well-defined supramolecules through non-covalent interactions in a given set of conditions. In the host-guest chemistry, a host (a large molecule, aggregate or a cyclic compound possessing cavity) binds a guest (another molecule) yielding a host-guest complex (supramolecule).

Corrosion is inevitable and causes material destruction and component failures [3, 4]. Recently, supramolecular concepts have found extensive interest in Corrosion Science and Technology where areas like smart coatings have been widely studied. The presentation aims to provide a comprehensive outlook on applications and potentials of supramolecular chemistry in corrosion prevention. The research advancements in this area will be presented under two subheads: surface coatings and corrosion inhibitors (Figure 1). In each section, advancements in polymeric, host-guest based systems, organic-inorganic hybrid systems, and other supramolecular structures and techniques will be discussed [5]. Recent updates in this area will be presented along with a few of our ongoing research efforts on mesoporous silica-based host-guest systems. Existing challenges to practical applications will be debated.

References

J.M. Lehn, Proc. Natl. Acad. Sci. USA, 2002, 99, 4763-4768.

J.W. Steed, J.L. Atwood, Supramolecular chemistry, Wiley, 2000, ISBN 978-0-470-51234-0.

V.S. Saji, J. Thomas, Current Science, 2007, 92, 51-55.

V.S. Saji, R. Cook, Corrosion control and prevention using nanomaterials, 2012, Elsevier Science, ISBN: 978-1-84569-949-9.

V.S. Saji, Corrosion Reviews,
2019, Submitted.

Figure 1