bluuebunny/crossref_metadata_2025 huggingface dataset:
(Digital Presentation) Electrochemical Measurements of Solvent Co-Intercalation Phenomenon Enabling Sodium-Ion Electrolyte Optimization for Graphite Anodes
Authors: Åvall Gustav , Son Youhyun , Alvarez Ferrero Guillermo , Janßen Knut , Adelhelm Philipp
Published: July 2022

Sodium-ion batteries (SIBs) is one of the more promising battery technologies that are starting to see commercialisation, were the low cost, abundance of necessary raw materials, higher safety and power and similar energy densities compared to lithium-ion batteries (LIBs) are often mentioned as their key advantages. SIBs, due to their great similarities with LIBs have seen a rapid development. One of the key differences, however, is the carbonaceous negative electrode, where SIBs, due to Na+ not forming stable intercalation compounds with graphite, the anode of choice for LIBs, are forces to use hard carbons. But, it was recently discovered by Jache et al.
1 that Na+ can form stable ternary graphite intercalation compounds through a solvent co-intercalation mechanism, thus enabling the use of graphite in SIBs. This sparked several follow-up studies exploring solvent co-intercalation as a way to use graphite in SIBs2, but the question of how many solvent molecules are intercalated along with the cation, and thus the stoichiometry of the redox reaction, was never settled. Here, we present a novel electrochemical method to directly measure the number of solvents that are brought along by the cation into the graphite host structure.

The SIBs using the co-intercalation mechanism to enable the use of graphite has so far shown great kinetics, power densities and extreme cyclability, with great capacity retention over thousands of cycles2. They are, however, plagued by a low specific capacity, a great volume expansion, and high average voltage in half-cells vs. Na+/Na, leading to poor energy density. But, the knowledge of how many glymes entering the graphite host gained from our measurements enabled us to rationally design new electrolytes, composed of low amounts of glymes mixed with another co-solvent, that both increases the energy density of the system, by lowering the average voltage while retaining the capacity, and reduces the volume expansion, while also reducing the cost of the electrolyte (Figure 1). The impact of the new electrolytes on the structure of graphite is studies using operando dilatometry and XRD, while the local structure in the electrolyte is investigated with ab initio methods – together giving a comprehensive view of the system.

Figure 1. Voltage profile of new electrolytes, showing a lowering of the average voltage a second plateau, and snap shot from ab initio molecular dynamics.

References:

B. Jache, P. Adelhelm, Angew. Chem. Int. Ed. 2014, 53, 10169-10173, DOI: 10.1002/anie.201403734

J. Park, Z-L. Xu, K. Kang, Front.
Chem., 2020, 8:432, DOI: 10.3389/fchem.2020.00432

Figure 1
Fast Interfacial Kinetics for Multivalent Metal Batteries Enabled By Solvation Sheath Reorganization
Authors: Hou Singyuk , Ji Xiao , Gaskell Karen , Wang Peng-fei , Wang Luning , Xu Jijian , Sun Ruimin , Borodin Oleg , Wang Chunsheng
Published: July 2022

Rechargeable magnesium (Mg) and calcium (Ca) metal batteries (RMBs and RCBs) are promising alternatives to lithium (Li)-ion batteries due to their significantly higher crustal abundance and energy density. However, RMBs and RCBs are still plagued by high overpotentials associated with parasitic reactions and sluggish kinetics resulting from strong electrostatic interaction with the solvation sheath and cathode hosts. Here we significantly reduce the overpotentials associated with the interfacial charge transfer through reorganization of the methoxyethyl amine-based chelants in the first solvation sheath of Mg2+, enabling stable and highly reversible cycling of Mg||Mg0.15MnO2 full cell with energy density of 412 Wh kg-1 and Ca||Mg0.15MnO2 full cell with energy density of 471 Wh kg-1. The barrier for solvation sheath reorganization can be tuned by molecular structure of the chelants and the design principle is generally applicable in a variety of ether solvents, thus providing a highly versatile electrolyte design strategy for divalent metal batteries.
Localized High-Concentration Electrolytes for Multivalent Anode Batteries
Authors: Helms Brett , Cho SungJu , Self Julian , Carino Emily , Han Kee Sung , Persson Kristin A.
Published: July 2022

Magnesium is attractive as an anode owing to its high capacity and abundance in the Earth's crust. It remains a challenge to realize efficient plating and stripping in electrochemical cells with a Mg anode, due to its reactivity with conventional liquid electrolytes comprising fluorinated salts. We hypothesized that the reactivity of species in the electrolyte may be controlled through solvation structure in concentrated electrolytes as well as those featuring a fluorinated diluent, which aids in reducing the viscosity and maintaining high ionic conductivity. Here, I will describe our efforts to understand solvation structure and reactivity at Mg–electrolyte interfaces. In turn, I will highlight how specific compositions are impactful in sustaining the electroreversibility of Mg anodes for hundreds of hours of continuous operation with low overpotential. I will tie this behavior to the structure of the interphase, whose composition is divergent from what is typically observed for dilute and concentrated electrolytes. There are emerging implications stemming from our work that motivates the future design of artificial interphases for Mg anodes obviating the use of chlorides, which would otherwise corrode other components of the cell.
Hybridisation – the Future of the Electrochemical Engine
Authors: Yang Jia Di , Millichamp Jason , Suter Theo , Neville Toby , Brett Dan
Published: July 2022

Hybridisation of power sources can improve fuel economy, dynamics of operation, durability, safety, overall weight and cost of any given system. However, performed badly, it can have adverse effects. All-electric (electrochemical) hybrids represent the most elegant and synergistic form of hybridization, but the way in which they can and should be combined for any given application is not trivial and requires unique design in each case. A growing concern is that different electrochemical power sources are being compared in zero-sum terms with increasingly entrenched partisan arguments. In this project, we will argue that a hybridized approach will often be the best option if performed properly. The long term goal is to achieve a position where we no longer think of hybridization as a second-level design option, a compromise or a fix, but the natural way to design electrochemical power systems.
(Invited) N@C60 and N@C70 for Quantum Information Processing: Beyond Qubits
Authors: Porfyrakis Kyriakos
Published: July 2022

Endohedral fullerenes such as N@C60, where a single atomic nitrogen is trapped inside the fullerene cage, have been proposed as qubit architectures due to the remarkably long relaxation times of their p-electron spins (T1 = 0.375 ms, T2 = 0.25 ms). Molecular quantum computers are still at the fringes of the field as recent developments have focused on other implementations such as superconducting qubits. However, molecular approaches present some advantages such as the ability to use chemical functionalization for scaling up qubit architectures. This, combined with continuous progress on miniaturization of electrodes via e-beam lithography and other techniques, means that molecular approaches will continue to be of interest.

In this talk, I will review the field of fullerene-based quantum information processing. I will present progress on the synthesis, chemical functionalization and alignment of N@C60 and N@C70 in different matrices. Recently, we were able to align N@C60 and N@C70 derivatives in a liquid crystal matrix with ordering parameter Ozz
= 0.61. With the aligned samples, we were able to achieve addressability of the available 4-electron spin levels in endohedral nitrogen by coherent manipulations.

Furthermore, these functionalized molecules give rise to endohedral fullerene qudits: multi-level computational units alternative to the conventional 2-level qubits. Qudits offer a larger state space for encoding information and thus can offer enhancement of quantum algorithm efficiency. Indeed, we were able to demonstrate the first ever geometric phase using pulsed EPR; something that was first proposed over 30 years ago!
(Digital Presentation) 2D Silicon–Germanium-Layered Materials As Anodes for Li-Ion Batteries
Authors: Chen Xi , Loaiza Laura C. , Monconduit Laure , Seznec Vincent
Published: July 2022

To address the volume changes of Si-based and Ge-based anode materials during lithiation and delithiation, two-dimensional (2D) composites like siloxene and germanane have recently been developed. These 2D materials can insert alkali cations without an alloying reaction, thereby limiting the associated volume expansion. While Si has a high theoretical capacity and low cost, its electrical conductivity is low; on the other hand, Ge provides a higher electronic conductivity but at a higher cost. Therefore, we propose a series of 2D Si–Ge alloys, that is, Si1–x
Ge
x
with 0.1 < x < 0.9, referred to as siliganes, with reasonable cost and encouraging electrochemical performance. The layered siliganes were obtained by fully deintercalating Ca cations from the Ca(Si1–x
Ge
x
)2 parent phases and used as Li-ion battery (LIB) anodes. XRD, SEM, Raman spectroscopy, and infrared spectroscopy were used to characterize the materials and identify the mechanisms occurring during cycling in LIBs. Siligane_Si0.9Ge0.1 was identified as the best candidate; at a current density of 0.05 A g–1, after 10 cycles, it showed a reversible capacity of 1325 mA h g–1, with high capacity retention and coulombic efficiency.
Electrochemical Characterization and Application of Graphene Oxide Materials Obtained By Electrochemical Exfoliation of Graphite
Authors: LEI Yuting , Ossonon Benjamin , Perreault Jonathan , Tavares Ana
Published: July 2022

Graphene oxide (GO) materials possess oxygen functional groups located at the edges and at the surface of the graphitic layers, confering them dispersibility in water, biocompatibility, and high affinity for specific molecules. These properties are highly appealing for their use in electrochemical sensors. However, the density and type of functional groups and defects in these materials also influence the heterogeneous electron transfer rate of redox processes occurring at the GO-based electrodes 1,2. In this respect, it is necessary to investigate the physicochemical and electrochemical properties of GO materials to choose the most suitable one for a target application.

Here, we report a simple and facile platform for the electrochemical characterization of GO materials 3. The GO sheets are self-assembled on a glassy carbon electrode (GCE) through an aminophenyl-film linker (AP) through electrostatic interaction and pi-pi stacking, Figure 1a. Then, the modified electrodes are characterized by cyclic voltammetry with 1 mM [Fe(CN)6]3-/4- redox couple to determine the electrochemical surface area (ESA) through the Randles-Sevcik equation and to calculate the standard rate constant of electron transfer (k0) by the Nicolson method.

In this work, series of GO materials were obtained by electrochemical exfoliation of graphite in 0.1 M H2SO4. The electrochemical exfoliation of graphite in aqueous solution is an easy and “green” method that allows the synthesis of large amounts (in the order of grams) of materials (EGO: electrochemically exfoliated graphene oxide) with tunable composition in a short time (few hours). The applied voltage and the distance between the graphite and the counter electrodes were varied, Figure 1b, to obtain EGOs with different physicochemical properties such as the number of layers, structural defects, type and content of oxygenated groups. Transmission electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy analysis were used to investigate the physicochemical properties of the EGOs. As shown in Figure 1c, the measured ESA and k0 scale with each other and are sensitive to the physicochemical properties of EGOs. This confirms the suitability of the proposed platform to characterize the EGO materials 3.

Finally, selected EGO materials were used to fabricate electrochemical aptasensors for the detection of cocaine. The influence of the EGO physicochemical properties on the performance of the aptasensors will be presented and discussed.

References

(1) Kampouris, D. K.; Banks, C. E. Chemical Communications
2010, 46, 8986-8988.

(2) Ambrosi, A.; Bonanni, A.; Sofer, Z.; Cross, J. S.; Pumera, M. Chemistry – A European Journal
2011, 17, 10763-10770.

(3) Lei, Y.; Ossonon, B. D.; Chen, J.; Perreault, J.; Tavares, A. C. Journal of Electroanalytical Chemistry
2021, 887, 115084.

Figure 1
Out-of-Plane Polarized Visible Luminescence and Electronic Resonance in Black Phosphorus
Authors: Schue Leonard , Goudreault Felix A. , Righi Ariete , Resende Geovani C. , Lefebvre Valerie , Godbout Emile , Pimenta Marcos A. , Cote Michel , Francoeur Sebastien , Martel Richard
Published: July 2022

After reports of high mobility and a tunable bandgap covering a wide spectral range from the visible to the mid-infrared region, layered black phosphorus (BP) has emerged as a promising 2D material for high performance electronic and optoelectronic devices. Owing to its orthorhombic crystallographic structure, black phosphorus expresses strong anisotropic properties. While recent investigations on few-layers crystals have extensively explored the in-plane anisotropy, much less attention has been given to the out-of-plane direction.

In this work, we use polarization-resolved photoluminescence (PL) and Raman spectroscopies to investigate the band structure anisotropy of bulk BP along the in-plane (zigzag, armchair) and out-of-plane directions. An unexpected room-temperature luminescence is detected in the visible, and strongly polarized in the out-of-plane direction. This emission, detected at 1.75 eV far above the band gap (0.3 eV), is surprising as it violates Kasha's rule which favors light emission from the lowest energy states. To elucidate its origin, we have systematically examined the characteristics of this luminescence as a function of polarization, temperature and excitation energy. These results reveal an unreported out-of-plane resonance at 2.3 eV in both the PL and Raman responses. Polarization selection rules and density functional theory (DFT) calculations of the complex dielectric permittivity are used to understand the origin of the strongly polarized optical response and demonstrate the remarkable extent to which the anisotropy influences the optical properties and carrier dynamics in black phosphorus.
(Invited) Van Der Waals Growth and in Situ Studies of Two-Dimensional Pnictogens
Authors: Moutanabbir Oussama , Fortin-Deschenes Matthieu
Published: July 2022

With their ns2 np3 electron configuration and sp3 hybridization, pnictogens (N, P, As, Sb, Bi) form a unique class of elemental van der Waals (vdW) and two-dimensional (2D) materials. The layered allotropes and the wide range of atomic masses span by pnictogens endows them with a broad spectrum of electronic, optical, and topological properties. For instance, few-layer black phosphorus and arsenic have thickness-dependent direct bands spanning the visible and near infrared, as well anisotropic transport properties. On the other hand, 2D-Sb and 2D-Bi are predicted to exhibit several topological phase transitions near atomic thicknesses, as well as a high-mobility single layer semiconducting phase. Despite the important technological potential of 2D pnictogens, stability and synthesis challenges impede their integration in emerging technologies. This talk presents theoretical and real-time electron microscopy studies of the vdW growth and stability of 2D pnictogens [1-6]. The insights obtained from these studies lay the groundwork for the integration of this new class of 2D materials in emerging electronic, optoelectronic, and quantum technologies.

References

Fortin-Deschênes, H. Zschiesche, T. O. Menteş, A. Locatelli, R. Jacobberger, F. Genuzio, M. J. Lagos, D. Biswas, C. Jozwiak, J. A. Miwa, S. Ulstrup, A. Bostwick, E. Rotenberg, M. S. Arnold, G. A. Botton, O. Moutanabbir. Pnictogens Allotropy and Phase Transformation during van der Waals Growth. Nano Letters. 2020; 20 (11), 8258-8266.

Fortin-Deschênes, O. Waller, Q. An, M. J. Lagos, G. Botton, H. Guo, O. Moutanabbir. 2D Antimony-Arsenic Alloys. Small. 2020; 16, 1906540.

Fortin-Deschênes, R. M. Jacobberger, C. A. Deslauriers, O. Waller, É. Bouthillier, M. S. Arnold, O. Moutanabbir. Dynamics of Antimonene–Graphene Van Der Waals Growth. Advanced Materials. 2019; 1900569.

Fortin-Deschênes, O. Moutanabbir. Recovering the Semiconductor Properties of the Epitaxial Group V 2D Materials Antimonene and Arsenene. The Journal of Physical Chemistry C. 2018; 122(16), 9162–9168.

Fortin-Deschênes, O. Waller, T. O. Mentes, A. Locatelli, S. Mukherjee, F. Genuzio, P. Levesque, A. Hebert, R. Martel, O. Moutanabbir. Synthesis of Antimonene on Germanium. Nano Letters. 2017; 17(8), 4970–4975.

Fortin-Deschênes, P. Levesque, R. Martel, O. Moutanabbir. Dynamics and mechanisms of exfoliated black phosphorus sublimation. The Journal of Physical Chemistry Letters. 2016; 7(9), 1667-1674.
(Invited, Digital Presentation) Molecular Self-assembly and Reactivity on 2D Layered Materials
Authors: De Feyter Steven
Published: July 2022

In the first part, we will focus on the principles of self-assembled molecular network formation at the liquid-solid interface on surfaces such as graphite, MoS2, and graphene. Then we will discuss how lateral confinement, induced by covalent functionalization of graphite and graphene, affects self-assembly. Several strategies will be demonstrated to realize two-dimensional lateral confinement, all based on the covalent modification of the surface, making use of bottom-up approaches or a combination of bottom-up and top-down approaches. The impact of these various types of confinement on the formation of self-assembled molecular networks will be discussed, including aspects such as nucleation and growth, directional self-assembly, on-surface chirality, polymorphism, and reactivity.

In a second part, we will focus on the formation of porous two-dimensional covalent organic frameworks at the liquid-solid interface, and reveal various interesting aspects at the molecular level such as nucleation and growth mechanisms, and the impact local electric fields may have on (de)polymerization processes.

The relevance and importance of scanning probe microscopes to investigate (and control) self-assembly and reactivity on surfaces will be illustrated.

C. Rodríguez González, A. Leonhardt, H. Stadler, S. Eyley, W. Thielemans, S. De Gendt, K. S. Mali, S. De Feyter, ACS Nano, 2021, 15, 10618–10627

Verstraete, S. De Feyter, Chem. Soc. Rev., Chemical Society Reviews, 2021, 50, 5884–5897

Bragança, A. Minoia, R. Steeno, J. Seibel, B. E. Hirsch, L. Verstraete, O. Ivasenko, K. Müllen, K. S. Mali, R. Lazzaroni, S. De Feyter, J. Am. Chem. Soc., 2021, 143, 11080–11087

Tahara, Y. Kubo, S. Hashimoto, T. Ishikawa, H. Kaneko, A. Brown, B. E. Hirsch, S. De Feyter, Y. Tobe, J. Am. Chem. Soc., 2020, 142, 7699–7708

Zhan, Z.-F. Cai, M. Martínez-Abadía, A. Mateo-Alonso, S. De Feyter, J. Am. Chem. Soc. 2020, 142, 5964–5968
Absorption and Emission of Chemically and Electrochemically Doped Graphene Nanoribbons
Authors: Lindenthal Sebastian , Zorn Nicolas Frederic , Settele Simon , Zaumseil Jana
Published: July 2022

Graphene nanoribbons (GNRs) are narrow stripes of graphene that exhibit unique optical and electronic properties depending on their width and edge type. Recent advances in the bottom-up synthesis of GNRs have enabled precise control over their structure and thus their bandgap. However, the systematic optical and electrical characterization of GNRs obtained from solution-mediated reactions has so far been prevented by the poor stability and processability of GNR dispersions. Here we employ liquid cascade centrifugation (LCC) to obtain size-selected and stable dispersions of bottom-up synthesized 9-aGNRs in toluene and tetrahydrofuran and investigate their intrinsic optical properties. Dispersions and films of these 9-aGNRs show well-defined absorption and photoluminescence bands between 800 and 1000 nm, with relative intensities depending on the LCC-fraction. The best GNR dispersions show photoluminescence quantum yields of up to 70 %. Trions are charged excitons with red-shifted emission that can be created in doped low-dimensional semiconductors, such as carbon nanotubes. Theoretical studies predict large trion binding energies (> 300 meV) in graphene nanoribbons (depending on their width). Hence their optical properties upon doping and possible new features are of interest. Chemical doping of our 9-aGNR dispersions with the strong molecular p-dopant F4-TCNQ and electrochemical doping of GNR thin films in ambipolar electrolyte-gated field-effect transistors results in the expected bleaching of the main absorption bands but also the emergence of new redshifted, charge-induced absorption peaks that may indicate the existence of trions in GNRs.
Unravelling the Topological Edge States of Twisted Bilayer Graphene
Authors: Fortin-Deschenes Matthieu , Pu Rui , Ma Chao , Zhou Yanfeng , Zhang Fan , Du Xu , Xia Fengnian
Published: July 2022

Stacking two slightly lattice-mismatched or relatively twisted two-dimensional (2D) materials gives rise to an unexpected richness of physical phenomena due to the emerging moiré pattern. In particular, twisted-bilayer graphene (t-BLG) has recently been shown to host strongly correlated phases as well as unconventional superconductivity [1, 2]. While recent studies have hinted at the non-trivial topology of the moiré bands [3, 4], direct experimental observations of the topological edge states are still conspicuously missing. Herein, using superconducting quantum interference, we reconstruct the real-space current distribution in t-BLG Josephson junctions (JJs) and reveal the presence of conductive edge states when the Fermi level is placed in the superlattice induced band gaps. These results suggest the non-trivial topology of t-BLG and lay the groundwork to understand and exploit the edge states in moiré materials.

[1] Cao, Y.; Fatemi, V.; Fang, S.; Watanabe, K.; Taniguchi, T.; Kaxiras, E.; Jarillo-Herrero, P. Nature 2018, 556, (7699), 43.

[2] Cao, Y., Fatemi, V., Demir, A., Fang, S., Tomarken, S. L., Luo, J. Y., ... & Jarillo-Herrero, P. (2018). Nature, 556(7699), 80-84.

[3] Park, M. J., Kim, Y., Cho, G. Y., & Lee, S. (2019). Physical review letters, 123(21), 216803.

[4] Ma, C.; Wang, Q.; Mills, S.; Chen, X.; Deng, B.; Yuan, S.; Li, C.; Watanabe, K.; Taniguchi, T.; Du, X.; Zhang, F.; Xia, F. Nano Letters 2020, 20, (8), 6076-6083.
(Invited, Digital Presentation) Synthesis and Atomic Scale Characterization of 2D Layered Heterostructures Atom by Atom: An Ultra-high Resolution Aberration-corrected Electron Microscopy Study
Authors: Alem Nasim
Published: July 2022

Defects can have a profound effect on the macroscale physical, chemical, and electronic properties of nanostructures. They can lead to structural distortions, introduce extra states in the band gap and give rise to excess potential locally at buried interfaces. While defects and interfaces have been a well-studied subject for decades, little is known about their local atomic and chemical structure, sub-Angstrom structural distortions within their vicinity.

Using ultra-high-resolution aberration-corrected S/TEM imaging and spectroscopy, this talk will discuss our recent efforts on the determination of the defect chemistry and sub-Angstrom relaxation effects in nanostructures around at the interfaces in the family of 2D crystal heterostructures. In the family of 2D crystal transition metal dichalcogenides (TMDs) alloys, we report how on anisotropy of the building blocks in the 2D heterostructure, such as ReS2/MoS2 and WS2/Graphene, and their epitaxy and strain at the interface can affect their nucleation and growth. This work will further uncover the structural distortions that occur in these heterostructure across various length scales and reveals the underlying physics of the formation of such heterostructures and their strain state resulting from CVD synthesis.
(Invited, Digital Presentation) Influence of Hemisphere-Shaped Nanodimples of Gold Electrode on Capacitance in Ionic Liquid
Authors: Imanishi Akihito
Published: July 2022

Ionic liquids (ILs) have attracted much attention as promising electrolytes for electrochemical devices due to their wide electrochemical window (stability) and negligible vaporization. For such applications, nanostructured electrodes have advantage on their large surface area leading to accumulation of large density energy at the interface. However, recent reports on IL/electrode interfaces revealed that quite unique structures can be formed, and it is not clear how the interface forms and how it changes by forming an electric double layer (EDL). In this study, we investigated the interfacial capacitance of nanostructured Au electrodes using electrochemical impedance spectroscopy (EIS) and IR measurements.

Polystyrene beads were self-assembled in a close packed form on a gold substrate by dipping in polystyrene beads solution and rapid drying. Au electrodeposition on thus prepared surface followed by removal of the beads resulted in the fabrication of a nanostructured Au electrode with periodic dimples. Electrochemical behavior of a ferrocene dissolved ionic liquid (1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl) amide (BMI-TFSA)) at the nanostructured and flat Au electrodes were investigated by EIS. We found that the capacitance of the nanostructured electrode was smaller than that of the flat electrode in the whole potential range. This result suggests that the thickness of the electric double layer formed in the nano-sized dimple is thicker than that formed on the flat surface. In the case of nanostructured Au electrode having 160 nm diameter dimples, the large capacitance was observed comparing with other electrodes having the dimples of different sizes. In addition, on the negative-going scan, the capacitance takes maximum at 0.1 V vs. Fc/Fc+, whereas no peak was found on the reverse positive-going scan. This result indicates that the exchange of cation/anion layers smoothly proceeded on the negative-going scan, whereas such a smooth exchange was prevented due to strongly surface-adsorbed BMIM+ on the positive-going scan. We also found that the hysteresis behavior was relatively suppressed in the case of the electrodes having 70 nm and 120 nm diameter dimples. We carried out the In-situ ATR-IR measurement to investigate the structure of ionic liquid molecules at the ionic liquid/electrode interface. The details of the relationships between the arrangement of ionic liquid at the interface and the capacitance of the electrode will be discussed.
(Invited) Synthesis and Photophysical Properties of Platinum(II) Complexes Having Electron Donor/Acceptor Moieties
Authors: Sakuda Eri
Published: July 2022

Boron containing π-electron chromophores represented by tri(9-anthryl)borane show quite unique spectroscopic and photophysical properties, owing to the presence of the vacant p-orbital on the boron atom. In practice, we demonstrated that the excited states of arylborane derivatives were characterized by charge transfer from the π-orbital of the aryl group to the vacant p-orbital on the boron atom: π(Ar) – p(B) CT. If such π(Ar) – p(B) CT interactions are introduced to the MLCT excited state of a transition metal complex, new and novel aspects into photophysics of the metal complexes could be demonstrated. We have previously reported our experiments on the platinum(II) complexes having arylborane-appended 2,2’:6’,2”-terpyridine (tpy) ligands to demonstrate synergetic metal(M) – ligand and π(Ar) – p(B) CT interactions.

In the present study, we focus on donor-acceptor interaction using an arylborane substituent and discussed about the charge separation on the spectroscopic and photophysical properties of their metal complexes. Then, we synthesized a novel cyclometalated-type platinum (II) complex using an NCN tridentate ligand with boron substituents, which is thought to cause intermolecular interactions, and investigated its spectroscopic properties.

Figure 1
(Invited) Photon Upconversion through Dynamic Exciton at Organic Semiconductor Interface
Authors: Izawa Seiichiro
Published: July 2022

Energy of photons, i.e. the wavelength of light, can be upgraded through interactions with materials—a process called photon upconversion (UC). Although UC in organic solids is important for various applications, such as in photovoltaics and bioimaging, conventional UC systems, based on intersystem crossing (ISC), suffer from low efficiency. Herein, we report a novel UC mechanism at heterojunctions of organic semiconductors in bilayer structures. The UC occurs by triplet formation during the charge separation and recombination through dynamic exciton: charge transfer (CT) state at the interface. This can efficiently convert the incident photons to triplets without relying on the ISC, whose rate is typically accelerated by the heavy-atom effect. As a result, a solid-state UC system is achieved with an external efficiency of two orders of magnitude higher than those of the conventional systems. Using this result, efficient UC, from near-infrared to visible light, cab be realized on flexible organic thin films under a weak light-emitting diode-induced excitation, observable by naked eyes.

Reference: S. Izawa and M. Hiramoto, Nat. Photon., DOI: org/10.1038/s41566-021-00904-w.
(Invited) Titanium-Catalyzed Intermolecular Radical Addition to Ketones Via Sp
3 C-H Bond Activation
Authors: Mitsunuma Harunobu , Peng Xue , Hirao Yuki , Yabu Shunsuke , Sato Hirofumi , Higashi Masahiro , Kanai Motomu
Published: July 2022

Tertiary alcohols are widely present in natural products, pharmaceuticals, and agrochemicals. Radical addition reaction to ketones is a simple and waste-free synthetic method for preparation of tertiary alcohols with high functional group tolerance. Therefore, direct radical addition reactions to ketones can be applied to a wider range of substrates. However, radical addition to carbonyl groups is a thermodynamically unfavored process, especially in the case of intermolecular radical addition to ketones, where the resulting alkoxy radical can easily undergo β-fragmentation to yield the starting material. For successful radical addition, therefore, the alkoxy radical must be trapped by a proper trapping reagent. In this study, we have found that a ternary hybrid catalytic system consisting of acridinium photoredox catalyst, thiophosphoric imide (TPI) catalyst, and titanium complex catalyst can promote intermolecular addition reactions of various ketones with organic molecules by activation of sp3 C-H bonds. The thiyl radicals generated by the excited photoredox-catalyzed one-electron oxidation of TPI extracted hydrogen atoms from organic molecules such as toluene, benzyl alcohol, alkenes, aldehydes, and THF. The carbon-centered radical species thus generated are added to various ketones and aldehydes. This method can be applied to the first direct reaction to aliphatic ketones using a variety of hydrocarbon feedstocks. The unfavorable bond-forming step was facilitated by the simultaneous one-electron reduction of the intermediate alkoxy radical by catalytically generated titanium(III) species. This reaction provided an efficient and simple approach to tertiary alcohols and was successfully applied in the late-stage functionalization of drugs and their derivatives. The proposed mechanism was supported by both experimental and theoretical studies.

Figure 1
(Invited) Charge Carrier Recombination and Extraction Dynamics of the Perovskite Nanocrystals: Ultrafast Pump-Probe and Photoluminescence Blinking Studies
Authors: Samanta Anunay
Published: July 2022

The lead halide-based hybrid and all-inorganic perovskites are currently the focus of intense investigation because of their great potential in solar photovoltaic and light emitting applications.1 As utilization of full potential of these substances in different applications requires a thorough understanding of the pathways through which the photo-generated charge carriers relax and the rate of their relaxation and capture by other substances prior to recombination, we have been studying these substances for the last few years addressing a variety of issues including those mentioned above.2-9 This talk will focus on femtosecond pump-probe and single-particle photoluminescence studies that provide important information on the nature and energy states of the photo-generated species, pathways and dynamics of relaxation of the charge carriers, location and nature of the trap states and their role in fluctuation of the photoluminescence of different perovskite nanocrystals.

References

Dey, A. et. al. ACS Nano
2021, 15, 10775.

Mondal, N; De, A.; Das, S.; Paul, S.; Samanta, A. Nanoscale
2019, 4, 9796.

Mondal, N; De, A.; Samanta, A. ACS Energy Lett.
2019, 4, 32.

Seth, S.; Ahmed, T.; Samanta, A. J. Phys. Chem. Lett.
2018, 9, 7007.

Mondal, N; De, A.; Samanta, A. J. Phys. Chem. Lett.
2018, 9, 3673.

Ahmed, T; Seth. S.; Samanta, A. ACS Nano
2019, 13, 13537.

Paul, S.; Samanta, A. ACS Energy Lett.
2020, 5, 64.

Das, S.; De, A.; Samanta, A. J. Phys. Chem. Lett.
2020, 11, 1178.

Das, S.; Samanta, A. ACS Energy Lett.
2021, 6, 3780.
Arylphthalimidoporphyrins: New Approaches to Imaging pH and Temperature Simultaneously with Oxygen
Authors: Rao Allu Srinivasa , Troxler Thomas , Vinogradov Sergei
Published: July 2022

Tetraarylphalimidoporphyrins (TAPIP) and diarylphalimidoporphyrins (DAPIP) possess unique photophysical properties that enable new and superior approaches to optical biological sensing of pH and temperature in parallel with oxygen. The syntheses of TAPIP and DAPIP have been reported by our group recently. We also have reported the photophysical properties of free-base (H2), Zn(II), Pt(II) and Pd(II) DAPIP and TAPIP, including their non-linear spectroscopic properties, such as two- and three-photon absorption spectra. Using a combination of phosphorescent Pt complexes of TAPIP and DAPIP we are designing a phosphorescent sensor for pH and oxygen, termed pHOx, which operates by measuring ratios of phosphorescence lifetimes. Unlike all existing optical pH sensors, measurements by pHOx are not affected by optical heterogeneities of the medium and provide unbiased pH readings in vivo simultaneously with pO2. At the same time, Pd complexes of TAPIP have been shown to emit both phosphorescence and thermally activated E-type delayed fluorescence, providing a functional element for optical sensing of temperature. However, to make the temperature readings unobstructed by optical heterogeneities of biological tissue, a PdTAPIP-based probe is supplemented by another probe system, based on H2DAPIP, which emits prompt fluorescence at the same wavelengths and can serve as a correction standard for unbiased temperature measurements.
Catalytic and Photocatalytic Functionality of Diprotonated Porphyrins
Authors: Kojima Takahiko
Published: July 2022

Development of strategy in energy conversion and storage is indispensable for a sustainable society. So far, redox-active transition metal complexes have been used as efficient catalysts and photosensitizers in energy-converting reactions such as hydrogen evolution through thermal and photoinduced electron transfer (ET).

We have been working on development of redox and photochemical functionality of diprotonated saddle-distorted porphyrins based on ET reactions. Herein we would like to highlight recent advance in our study of catalytic dioxygen reduction and hydrogen evolution using diprotonated forms of dodecaphenylporphyrin (H2DPP) derivatives as organocatalysts and photosensitizers.

A diprotonated form of a water-soluble H2DPP derivative can act as a photosensitizer (PS) in photocatalytic oxidation of organic substrates in water using Na2S2O8 as an oxidant under visible-light irradiation.1 On the contrary, diprotonated H2DPP has been used as a PS in photocatalytic H2 evolution using platinum nanoparticles as catalysts under near-infrared (710 nm) irradiation in the quantum yield of 17%.2

Diprotonated H2DPP (H4DPP2+) can serve as an organo-photocatalyst in highly selective and efficient O2 reduction to afford H2O2 under photoirradiation at 480 nm; the quantum yield of H2O2 generation was 12% and turnover frequency was 500 h–1.3

Interconversion of O2 and H2O2 has been achieved using an N21,N23-dimethylated H2DPP derivative.4 The porphyrin is reduced by H2O2 to form the corresponding isophlorin derivative as a two-electron-reduced product, which is in turn oxidized by O2 to afford the porphyrin and H2O2. We also developed efficient O2 reduction using N21,N22- and N21,N23-dimethylated H2DPP derivatives as catalysts; in the catalysis, catalytic mechanisms and performance depend on the structures of catalysts used in terms of interaction between O2 and the corresponding isophlorins.5

References

T. Ishizuka et al., Green Chem.
2018, 20, 1975.

H. Kotani et al., ACS Appl. Energy Mater.
2020, 3, 3193.

E. Aoki et al., Chem. Commun.
2019, 55, 4925.

W. Suzuki et al., J. Am. Chem. Soc.
2019, 141, 5987.

W. Suzuki et al., Chem. Eur. J.
2020, 26, 10480.
Integrating Subphthalocyanines and Porphyrazines into Singlet Fission
Authors: Guldi Dirk
Published: July 2022

The synergy of panchromatic absorption throughout most of the visible range of the solar spectrum and intramolecular singlet fission (i-SF) has been realized in a series of conjugates featuring different light harvesting subphthalocyanines (SubPc) / porphyrazines (Pz) and an energy accepting pentacene dimer (Pnc2). At the focal point was a modular approach, which was based on decorating the SubPc / Pz core with different peripheral substituents to tailor and fine-tune their optical properties. Transient absorption measurements assisted in corroborating that the SubPcs / Pzs act as energy-transfer antennas by means of unidirectional and quantitative intramolecular Förster resonance energy transfer (FRET) to the Pnc2, where an i-SF affords triplet quantum yields reaching unity.
Polypeptide Oligomers Comprised of Corroles – Hydrogen Bonding Provides “Short-Circuit” Coupling Pathways for Electron Transfer
Authors: Gryko Daniel T. , Orłowski Rafał , Clark John , Gray Harry B. , Vullev Valentine I. , Szumna Agnieszka
Published: July 2022

Electron flow through proteins is a crucial factor, which decides about their multiple functions in living organisms. Incorporating polypeptides as bridges in donor-bridge-acceptor (DBA) conjugates allows for examining how various structural features in proteins affect the kinetics of the CT processes they mediate. Based on the premise that hydrogen-bonds formation could serve to modify geometry and special orientation of donor and acceptor scaffolds in covalently linked bichromophoric system we designed and synthesized series of dyads comprised of perylene-bisimide and free-base corrole. Specifically, the object of the study was hydrogen-bonded discrete assemblies of corroles possessing core-NH as hydrogen bond donor and amide groups located at position meso-10 as hydrogen bond acceptor. The three dyads differ in type and number of bridging aminoacids’ moieties: L-alanine and L-phenylalanine and one or four respectively. These complex corroles were prepared via synthesis of perylenebisimide-amino acid conjugate possessing free NH2 group followed by amidation of COOH-corrole. Combined steady-state and time-resolved photophysical studies identified that electron-transfer occurs in all four bichromophoric systems. Our focus was on alanine tetramer that is long enough not to mediate too efficiently through-bond CT. A corrole moiety serves as an electron donor, and a perylenediimide as an acceptor. The picosecond rates of electron transfer suggests that the electronic-coupling pathways cannot be through-bond and most likely involve through-hydrogen bond interaction.

References

Orłowski, R.; Vakuliuk, O.; Gullo, M. P.; Danylyuk, O.; Ventura, B.; Koszarna, B.; Tarnowska, A.; Jaworska, N.; Barbieri, A.; Gryko, D. T. Commun.
2015, 51, 8284-8287.

Orłowski, R.; Cichowicz, G.; Staszewska-Krajewska, O.; Schilf, W.; Cyrański, M. K.; Gryko, D. T. Eur. J.
2019, 25, 9658-9664.

Figure 1
Metallosupramolecular Assemblies of Phthalocyanines, Subphthalocyanines and Bodipys: Photosensitizers for Visible-Light Induced Processes
Authors: de la Torre Gema , Moreno Simoni Marta , Duran-Sampedro Gonzalo , Torres Tomas
Published: July 2022

Molecular self-assembly provides limitless possibilities to obtain stable and structurally well-defined supramolecules with different physicochemical properties than those of precursor building blocks. From all supramolecular interactions, strong and directional coordination-driven self-assembly allows a fine control over the rational design of two- and three-dimensional architectures with multiple potential applications. The preparation of cutting-edge metallo-supramolecular assemblies based on phthalocyanines, subphthalocyanines and BODIPYs is herein described. These ensembles have been applied for different purposes: i) as molecular receptors showing electronic interactions between the chromophore panels of the host and electroactive guests such as fullerenes and perylenediimides; ii) as hollow molecular containers able to influence a chemical reaction by providing an isolated cavity of particular size and shape, demonstrating, for example, the ability to induce unprecedented photoredox reaction with guest fullerenes, triggered by the porphyrinoid excited state; and iii) as metallosupramolecular amphiphilic systems, able to yield nanostructures via self-organization in aqueous media.

Figure 1
Atomic-Scale Oxide Growth and Dissolution Kinetics on Ni-Cr Alloys
Authors: Xiao Penghao , Orme Christine , Wood Brandon C.
Published: July 2022

Passivation oxide formation is the key for corrosion control of metal alloys. The kinetics of competing oxide formation and dissolution determines alloy corrosion behaviors in aqueous solution. Despite the important role of the multi-component oxide evolution, little has been known on the kinetics from the atomistic level. To this end, we have built a computational framework that enables simulations of competing kinetic processes in multi-component oxides from first principles. The effects of applied voltage, pH and temperature on oxide growth, dissolution and reprecipitation can all be captured in this model. Combining with our experimental measurements on alloy 22, we identified three voltage regimes with distinct oxide thicknesses and compositions. In the low voltage regime, oxide growth is the dominating process. The Cr/Ni ratio in the oxide is close to that in the alloy. In the medium voltage regime, Ni dissolves from the mixed oxide, NixCryO, and reprecipitates back as Ni oxide, NixO, to achieve phase separation. The resulted oxide film is significantly thickened with a duplex structure formed. In the high voltage regime, Ni dissolution dominates, and the Cr/Ni ratio increases. The temperature and pH dependencies have also been simulated. Higher temperature moves the dissolution-reprecipitation to the lower voltage; lower pH suppresses Ni reprecipitation and results in a thinner oxide film. These trends are also in agreement with the experiments.

The oxide energetics of various stoichiometries are calculated by the density functional theory (DFT). Then the obtained data are used to train a surrogate lattice Hamiltonian with the cluster expansion (CE) method. Finally, kinetic Monte Carlo (KMC) simulations are run with the cation hopping barriers calculated on-the-fly based on the local environments from the combination of the above Hamiltonian and the linear Brønsted−Evans−Polanyi (BEP) relation.
Electrochemical Surface Characterization of a Femtosecond Laser Treated and Anodized Ti and Ti6Al4V Alloy for Bone and Dental Implants
Authors: Knapic Dominik , Hassel Achim Walter
Published: July 2022

Pure Titanium (Titanium grade 2) and Ti6Al4V (Titanium grade 5) alloys are commonly used biocompatible materials for medical bone implants and dental protheses. As some implants have to be removed after a certain amount of time after the implantation, the osteo repellent surface is one of the most important property for the removable bone implants such as bone screws and plates. On contrary, for the dental protheses the property of the most importance is osseointegration. Femtosecond laser treatment causes ablation and produces LIPSS (“laser induced periodic surface structures”) which can consist of cones on macro scale and ripples on nano scale which showed structures and roughness similar to that of a bone. Therefore, surface modifications by electrochemical anodization and femtosecond laser could be seen as promising methods for improving both osteo-repellence and osteointegration properties of the bone implants and dental protheses. The aim of this work is electrochemical and surface characterization of the anodized Titanium and Ti6Al4V alloy treated by the femtosecond laser. Firstly, Titanium and Ti6Al4V samples were anodized potentiostaticaly up to 100V in 25% phosphoric acid solution for 120s. Following the potentiostatic anodization, samples were structured with femtosecond laser to produce micro cones and nano ripples on top of the cones. As a final step, laser treated spots were potentiodynamicaly anodized using a SDCM (Scanning Droplet Cell Microscopy) setup. Influence of different potentials, scan rates and electrolytes were studied and optimized, consequently. Morphology and topography were examined by the means of SEM (Scanning Electron Microscopy) and AFM (Atomic Force Microscopy), while crystallography was determined by the XRD (X-Ray Diffraction). Furthermore, the composition of the oxide layer was determined by the XPS (X-ray photoelectron spectroscopy). Oxide forming factor (kox), a relative permittivity εr, and ECSA (Electrochemical surface area) were obtained from the cyclic voltammograms (CV) and electrochemical impedance spectroscopy (EIS) experimental data. Electrochemical impedance spectroscopy data was modeled and compared between not preanodized, preanodized and anodized and not anodized after femtosecond laser structuring. Finally, bioassessment with osteoblast was done to examine the growth of the osteoblast cells on the modified surface structures. Value of the oxide forming factor (kox) for the pure Titanium and Titanium grade 5 were successfully calculated and compared with a Scanning Electron Microscopy. Calculated values of the relative permittivity εr are in agreement with the literature values. Finally, obtained results indicate that anodized and subsequently femtosecond laser treated samples could be used as medical bone and dental implants.