bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Photoelectrochemical Fabrication of Chiral Plasmonic Nanostructures By Circularly Polarized Light
Authors: Tatsuma Tetsu , Ishida Takuya , Nishi Hiroyasu
Published: July 2022

Chiral plasmonic nanostructures attracts attention because they are potentially applicable to optical materials such as enantioselective sensors and metamaterials, as well as photoelectrochemical devices. Chiral nanostructures are often prepared by electron beam lithography or synthesis based on DNA templates. We have recently developed a photoelectrochemical method, in which handedness of the chiral nanostructure can be controlled by right- or left- circularly polarized light.

The photoelectrochemical method is based on plasmon-induced charge separation (PICS),1,2 in which electrons are injected from a plasmonic metal nanoparticle to a semiconductor such as titania in direct contact. In PICS, anodic reactions often occur at the resonance sites of the plasmonic nanoparticle, at which electron oscillation is localized.3,4 Energetic electron-hole pairs generate at the resonance site, and holes are used for the local anodic reaction, probably via trap sites. On the basis of the mechanisms, we have demonstrated site-selective etching of silver nanoparticles and site-selective deposition of lead oxide on gold nanoparticles.

Under right-circularly polarized light (CPL), distribution of the resonance sites could be the mirror image of that under left-CPL.5 Therefore, we performed site-selective deposition of lead oxide on gold nanocuboids on titania under right- or left-CPL.6 As a result, lead oxide was deposited on the gold nanocuboids in a chiral geometry. The nanostructures thus obtained exhibited circular dichroism (CD), and the CD spectrum obtained for the structure prepared under right-CPL was opposite to that obtained for the structure prepared under left-CPL. Reversible switching of the handedness of the chiral plasmonic nanostructures can also be possible.7 This method also allows us to fabricate spiral nanostructures. 1. Y. Tian and T. Tatsuma, J. Am. Chem. Soc., 127, 7632 (2005). 2. T. Tatsuma, H. Nishi, and T. Ishida, Chem. Sci., 8, 3325 (2017) [review]. 3. I. Tanabe and T. Tatsuma, Nano Lett., 12, 5418 (2012). 4. T. Tatsuma and H. Nishi, Nanoscale Horiz., 5, 597 (2020) [review]. 5. S. Hashiyada, T. Narushima, and H. Okamoto, J. Phys. Chem. C, 118, 22229 (2014). 6. K. Saito and T. Tatsuma, Nano Lett., 18, 3209 (2018). 7. K. Morisawa, T. Ishida, and T. Tatsuma, ACS Nano, 14, 3603 (2020).
Improved Interfacial Contact Using Surface Modified Lithium Metal Powder in All-Solid-State-Lithium-Sulfur-Batteries
Authors: Kim Jiwoong , Yoon Woo Young
Published: July 2022

All-Solid-State-Lithium-Sulfur-Batteries(ASSLSBs) are the most promising candidate for next generation secondary battery because of its high theoretical specific capacity of Lithium metal (3860 mAhg-1) and elemental sulphur (1672 mAhg-1). However, the shuttle effect of Li-S battery is the major obstacles of commercialization. And there are still remaining safety issues due to dendrite formation during lithium deposition. Adopting solid state electrolyte can be a solution to these issues. Recent studies of all-solid-state-batteries have achieved high capacity and good stability. But there are still hindrances of interface problems between solid electrolyte and active materials. The interfacial issues of solid electrolytes can be solved by applying lithium metal powder. In this study, we fabricate composite electrode which have large specific contact area as well as intimate contact of electrode component by using solid electrolyte and lithium metal powder. Surface of lithium metal powder is modified by an ion conductive polymer material to prevent side reaction of solid electrolyte and lithium metal powder. This study can provide a new way of producing the surface modified lithium powder as an anode material for All-Solid-State-Lithium-Sulfur-Batteries.
Lithiated-Polyamic Acid-Coated Glass Fiber As a Functional Separator for High-Performance Li-S Batteries
Authors: Tran Nhan , Fang Chen , Zhu Tianyu , Liu Gao
Published: July 2022

Lithium sulfur batteries (LSB) can offer great opportunities for the next-generation energy storage systems required for electrical vehicles and grid energy storage applications due to its very high theoretical specific energy (2500 Wh kg−1). For the practical applications, the sulfur loading in the cathode should not be lower than 70wt% in order to achieve a high energy density. However, the electrical and/or ionic conductivity of the cathode can be reduced with a high S loading, respectively, leading to reduced sulfur utilization and slurry reaction kinetic. In order to overcome this issue, sulfur active species were first dissolved together with Li2S in the electrolyte to form lithium polysulfide (LiPolS) (e.g., Li2S8 and Li2S6) solution or catholyte. During cycling, the active sulfur (Li2S8) is deposited from the electrolyte into the S-free cathode conductive matrix, which could be made from carbon nanotube and carbon nanofiber. It has been demonstrated that the specific/areal capacity of Li – lithium polysulfide (Li-LiPS) cells show high specific capacity, indicating high S utilization as well as high reaction kinetic. However, the problem is the penetration of dissolved LiPSs through the separator to react with the Li metal anode and reduce to form short-chain LiPSs, resulting to the passivation of the anode with irreversible deposits on its surface. In order to mitigate this problem, a lithiated-polyamic acid functionalized glass microfibers (GF@PALi) was utilized as a functional separator to selectively transfer Li+ ions. The GF@PALi was prepared by simply dipping of commercial GF into aqueous solution of 5 wt% lithiated-polyamic acid and dried overnight at 60 oC in vacuum oven. Combined with CNTs on Ni foam electrode, catholyte of 0.4 M LiTFSI + 2.0 M Li2S8 + 1.0 M LiNO3 in DME/DOL and lithium anode, the fabricated LSB cell exhibits a high specific and areal capacities of 803 mAh g-1 and 2.43 mAh cm-2 at C/2 rate, respectively. In addition, the LSB cell with the GF@PALi separator presents a remarkable cycling durability until 200 cycles with 76% capacity retention, which is much more stable than the LSB cell with commercial Celgard PP separator working until 86 cycles. Such high durability could be attributed to the retarding polysulfide migration of the as-prepared GF@PALi separator.

Figure 1
Chiral Self-Recognition and Self-Discrimination Processes in Different Subphthalocyanine Aggregation Regimes
Authors: Gonzalez Rodriguez David , Aparicio Fatima , Mayoral Maria Jose , Torres Tomas
Published: July 2022

We have recently shown that, as a result of its rigid cone-shaped structure, racemic SubPcs trisubstituted with peripheral amides can self-assemble in two distinct regimes as a function of the solvent environment.1 In toluene, an apolar aromatic medium that can efficiently solvate p-surfaces, such compounds associate as tail-to-tail dimers (regime A). In methylcyclohexane (MCH), in contrast, they undergo a cooperative supramolecular polymerization process to yield non-centrosymmetric head-to-tail columnar stacks (regime B).2

SubPcs, being intrinsically chiral molecule, constitutes an ideal probe to study chiral self-sorting processes, which is the objective of this work. As depicted in the figure below, a racemic mixture of a trisubstituted SubPc can in principle self-assemble into different species. Homochiral dimers/polymers may form through a chiral self-recognition process: each enantiomer has a preference to aggregate with itself leading to helical supramolecular structures with a preferred handedness. At the other extreme, heterochiral dimers/polymers would be instead formed via a chiral self-discrimination process, where each enantiomer prefers to associate with the other, yielding purely racemic dimers/polymers displaying no predilection for a given helical sense. As an intermediate case, the enantiomers might show no strong self-sorting preference and yield statistical dimers/polymers.

[1] C. G. Claessens, D. González-Rodríguez, M. S. Rodríguez-Morgade, A. Medina, T. Torres, Chem. Rev.
2014, 114, 2192.

[2] (a) J. Calbo, J. Aragó, P. M. Viruela, E. Ortí, T. Torres, D. González-Rodríguez, Angew. Chem. Int. Ed.
2015, 54, 2543; (b) M. J. Mayoral, J. Guilleme, J. Calbo, J. Aragó, F. Aparicio, E. Ortí, T. Torres, D. González-Rodríguez, J. Am. Chem. Soc.
2020
, 142, 21017.

Figure 1
2D and 3D Tetrapyrrole-Based Functional Materials: Preparation and Applications
Authors: Jiang Jianzhuang
Published: July 2022

A series of 2D and 3D tetrapyrrole-based functional materials have been designed and synthesized, including porphyrin-based covalent organic frameworks, phthalocyanine-based covalent organic frameworks, phthalocyanine conjugated polymers, and mixed phthalocyanine-porphyrin-based conjugated microporous polymers. These tetrapyrrole-based materials exhibited excellent oxygen reduction reaction catalytic activity, photocatalytic CO2 Reduction activity, and sensing performance. In particular, the well-defined chemical composition and the unambiguously identified structure of the active sites for these tetrapyrrole-based materials enabled to gain an in-depth understanding of the structure-function relationship.
Progress on Boron Subnaphthalocyanines (BsubNcs) and Associated Hybrids Towards Organic Electronic Applications and Their Electrochemical Properties
Authors: Bender Timothy P , Holst Devon , Francesca Farac Nina , Hildebrand Mariana , Kronik Leeor
Published: July 2022

For some time, our group has been focused on the molecular design, synthesis and application of boron subphthalocyanines (BsubPcs) and subnaphthalocyanines (BsubNcs), which are macrocycles with a chelated central boron atom via nitrogen and a p-conjugated ligand. Our focal point balances between the basic and applied chemistry of the BsubPcs and BsubNcs, their physical properties (electrochemistry included) and their application as light emitting, light absorbing and electronic conducting materials for application in organic light emitting diodes (OLEDs) and organic photovoltaics (OPVs)/organic solar cells (OSCs), the basic electrochemical and photophysical properties being critical to these applications.

For this presentation, I will focus on our progress on the development of BsubNcs. In the past we have shown that BsubNcs end up being a mixed alloyed composition based on bay-position halogenation that was formed randomly during the reaction of BCl3 with 2,3-dicyanonaphthalene at temperature to form the BsubNcs. The random bay-position halogenation has been shown to be impactful in a positive way within OPV devices, negative within OLED devices and also has electrochemical variations. However given it is random halogenation, it is desirable to truly understand its impact systematically.

We have recently been able to develop a separation method and therefore separate the mixed alloyed BsubNc compositions and acquire data to show the impact of the percentage/number of bay-position halogens, chlorine and bromine included, on the electrochemical potentials and the photoluminescence. I will also present a new synthetic methodology to avoid the random bay-position halogenation of the associated BsubNcs.

We have also applied a computational model to look at the relative impact of the random bay-position halogenation on the electronics. We have found that the frequency of halogenation has a larger impact on the predicted HOMO/LUMO energy levels than does the random halogen positioning around the bay-positions of the BsubNcs. As this was in parallel with the separations method that was developed, this computational data is therefore comparable to the acquired electrochemical data.

We have also developed BsubNc + BsubPc hybrid materials. For the hybrids, there is a way to avoid bay-position halogenation and once this was avoided, we have the first example of electrochemical and photoluminescence data for the associated BsubNc + BsubPc hybrids. I will also outline our approach to accelerated development of BsubNcs, BsubPcs and the hybrids whereby their molecular design and synthesis was first been justified through a re-adopted computational model.

Figure 1
Phthalocyanines with Non-Traditional Early Transition-Metals
Authors: Leznoff Daniel
Published: July 2022

The synthesis, spectroscopic and redox properties of new metallophthalocyanines (PcM) are active areas of research. The rings of PcM complexes can be successively reduced using chemical, electrochemical, or photochemical methods to give rise to species containing ring-reduced Pc(3-), Pc(4-) or Pc(5-) ligands ; in the other direction, both ring-oxidized Pc(-1) and Pc(0)-containing systems can be accessed. These species are usually generated and characterized in situ and have only recently begun to be isolated and structurally characterized. In particular, there are few examples of phthalocyanines with early-transition and f-block metals - despite the rich organometallic-type reactivity of these metals - and thus we targeted new PcM complexes in this underdeveloped area of the periodic table. Given their larger ionic size, the unusual structural feature of the metal centre protruding far out of the Pc cavity is observed. Hence, the exposure of the coordination sphere of these Lewis-acidic (often d0) metals makes these PcM complexes attractive catalysts; this cis-oriented axial ligation also drastically improves the solubility, despite the Pc-ring remaining unsubstituted.

In this presentation the isolation and structural characterization of new PcM materials with M = scandium, zirconium, niobium and (time-permitting) molybdenum will be described, along with rare structurally characterized examples of their reduced Pc(4-) and Pc(3-)complexes. Their electronic structure and electrochemical behaviour will be discussed using a combination of spectroscopic and structural techniques. A series of moisture-sensitive, soluble PcZr(IV) and PcNb(V) alkoxides were prepared, characterized, and their catalytic activity towards the ring-opening polymerization of rac-lactide was studied and will be detailed. Reaction of PcScCl with LiO
i
Pr and NaO
t
Bu yielded two hydroxide complexes containing the PcScOH unit, obtained from the hydrolysis of the putative PcSc-alkoxide intermediate. The two structurally characterized systems have a tilted “butterfly” shape structure, reminiscent of bent metallocenes. The solubility of these early transition-metal based complexes present new opportunities for the advancement of this underdeveloped area of PcM chemistry. Time permitting, our related work on organometallic PcLnX complexes will also be described.

References

Zhou, D.B. Leznoff, Chem. Commun., 2018, 54, 1829-1832. W. Zhou, J.R. Thompson, C.C. Leznoff, D.B. Leznoff, Chem. Eur. J., 2017, 23, 2323-2331; R. Platel, W. Zhou, T.T. Tasso, T. Furuyama, N. Kobayashi, D.B. Leznoff, Chem. Commun.,
2015, 5986-89; D. McKearney, W. Zhou, V.E. Williams, D.B. Leznoff, Chem. Commun., 2019, 55, 6696-6699; Y. Ganga-Sah, E. Tajbakhsh, R.H. Platel, W. Zhou, D.B. Leznoff, J. Porph. Phthalocyanines, 2019, 23, 1592-1602; W. Zhou, D. McKearney, D.B. Leznoff, Chem. Eur. J., 2020, 26, 1027-31.
Radical Reactions Enabled By Porphyrinoids
Authors: Gryko Dorota
Published: July 2022

“
Look deep into
nature
, and then you will understand everything better.”

Albert Einstein

Porphyrinoids, also known as the pigments of life, are a class of naturally occurring organic dyes. They play key roles in crucial processes that support life - oxygen transport (hem), electron transport (cytochrome c), photosynthesis (chlorophyll a), and synthesis of DNA (vitamin B12). Vitamin B12 - a co-factor in many catalytic processes. Following nature, we have been exploiting the potential of this compound in catalysis.

Vitamin B12 - catalysis has been successfully translated into the laboratory and used in a small collection of reactions.[1-2] The advantage of using vitamin B12 as a catalyst lays in the complete stability of the central cobalt ion and by the definition it is nontoxic. It has also been well documented that the reaction mechanism usually follows a radical pathway, bringing a new dimension to this already interesting field.[2]

Along this line, we have developed new vitamin B12-catalyzed reactions involving reduction of Co(III) to Co(I) or Co(II) and subsequent reactions with electrophiles or radicals. Vitamin B12 derivative unusually catalyzes a new olefinic sp2 C-H alkylation reaction with diazo reagents as a carbene source,[3], acylation of activated olefins, alkylation of strained molecules.[4-6] These key findings emphasize the unique feature of vitamin B12 as a catalyst to achieve something unachievable with other methodologies or to find a greener approach.

References

[1] Banerjee, R. Chemistry and Biochemistry of B12, John Wiley & Sons, Inc, 1999

[2] Giedyk, M., Goliszewska, K., Gryko, D. Soc. Rev.
2015, 44, 3391-3404.

[3] Giedyk, M.; Fedosov, S.; Gryko, D. Commun.
2014, 50, 4674-4676.

[4] Ociepa, A. J. Wierzba, J. Turkowska, D. Gryko, J. Am. Chem. Soc.
2020, 142, 5355-5361.

[5] Potrząsaj, A.; Musiejuk, M.; Chaładaj, W.; Giedyk, M; Gryko, D ChemRxiv, 2021, 143, 9368–9376. https://doi.org/10.26434/chemrxiv.13559852.v1

[6] Turkowska, J.; Durka, J.; Ociepa, M.; Gryko, D. Chem.
Commun., 2021, DOI https://doi.org/10.1039/D1CC05330B

Figure 1
Metallomacrocycle-Derived Atomically Dispersed Metal Electrocatalysts with Controlled Selectivity for Small Molecule Conversion Reactions
Authors: Joo Sang Hoon
Published: July 2022

Atomically dispersed metal catalysts or single-atom catalysts have recently emerged as a new frontier in the field of catalysis. They exhibit extreme atom efficiency and unusual catalytic activity and selectivity, which are hard to be attained with nanoparticle-based concentional catalysts. In this talk, we present metallomacrocyclic compound-driven syntheses of carbon supported atomically dispersed metal (M–N/C) catalysts toward selective small molecule conversion reactions, including oxygen reduction reaction reaction (ORR), CO2 reduction reaction (CO2RR), and chlorine evolution reaction (CER) [1-5]. The M–N/C catalysts provide unique catalytic selectivity in these reactions. For the ORR, tuning of metal type can direct the reaction pathway with Fe–N/C catalyzing the ORR via the four-electron (4e–) reduction to generate water (H2O) [1,2] whereas Co–N/C exhibiting preferred 2e– pathway to produce hydrogen peroxide (H2O2) [3,4]. In the CO2RR, Ni–N/C selectively reduces CO2 to CO while suppressing parasitic hydrogen evolution reaction [5]. For the CER, Pt–N/C catalyst is capable of catalyzing the CER with very high selectivity approaching 100% without competitive oxygen evolution reaction, even under low concentration of Cl– and neutral electrolyte, where OER is favored [6,7]. In contrast, traditional mixed metal oxide catalysts show substantially low CER selectivity. For the selective ORR and CER, in situ X-ray absorption spectroscopy combined with other spectroscopic techniques and density functional theory calculations have played a pivotal role in identifying the active sites and uncovering reaction kinetics and mechanisms.

References

J. Sa et al., J. Am. Chem. Soc. 138, 15046 (2016).

Woo et al., Chem. Mater. 30, 6684 (2018).

Ko et al., Nature Commun. 10, 5123 (2019).

Ko et al., Nature Catal. Accepted for Publication (2021).

J. Sa et al., ACS Catal. 10, 10920 (2020).

Lim et al., Nature Commun. 11, 412 (2020).

Lim et al., ACS Catal. 11, 12232 (2021).
(Digital Presentation) Chemically Modified Graphene for Real-World Applications: Graphene Oxide Liquid Crystal & Single Atom Catalysts
Authors: Kim Sang Ouk
Published: July 2022

Graphene Oxide Liquid Crystal (GOLC) is an emerging 2D carbon based soft material, which exhibits nematic type colloidal discotic liquid crystallinity with the orientational ordering of graphene oxide flakes in good solvents, including water. Since our first discovery of GOLC in aqueous dispersion at 2009, this interesting mesophase has been utilized over world-wide for many different application fields, such as liquid crystalline graphene fiber spinning, highly ordered graphene membrane/film production, prototype liquid crystal display and so on. Interestingly, GOLC also allow us a valuable opportunity for the highly ordered molecular scale assembly of functional nanoscale structures. This presentation will introduce our current status of GOLC research particularly focusing on the nanoscale assembly of functional nanostructures, including highly oriented 1D fibers, 2D films and 3D nanoporous structures. Besides, relevant research works associated to the nanoscale assembly and chemical modification of various low dimensional materials, including 1D carbon nanotubes, 2D TMDs and MXene, will be presented particularly aiming at energy and environmental applications. In the last part of presentation, our wold-first discovery of single atom catalyst will be introduced also, including other research efforts exploiting customized heteroelement doping of graphene based strucures.
(Digital Presentation) Peptide Targeting of Photosensitisers for Photodynamic Therapy and Drug Delivery Applications
Authors: Eggleston Ian M. , Yaghini Elnaz , Dondi Ruggero , Tewari Kunal M. , Edler Karen J. , Loizidou Marilena , MacRobert Alexander J.
Published: July 2022

The conjugation of photosensitisers to proteins or targeting peptides is a well-established approach for enhancing solubility and tissue selectivity for both photodynamic therapy (PDT) of cancer and light-activated drug delivery. A key innovation in the development of such targeted photosensitisers is the application of biorthogonal ligation techniques (e.g. azide-alkyne “click” chemistries) which allow the efficient attachment of various photosensitiser molecules to multifunctional peptides. Some of our work in this area will be described towards the generation of specific targeted conjugates between porphyrin and chlorin photosensitiser derivatives and tumour-homing or cell-penetrating peptide carriers [1, 2]. Conjugation of hydrophobic photosensitiser molecules to cationic cell-penetrating peptides (e.g. HIV Tat 48-57) can provide derivatives with improved water solubility, amphiphilicity, enhanced uptake and predictable sub-cellular localisation. This is very attractive for the light-triggered delivery of macromolecular therapeutics by photochemical internalisation (PCI), which will be illustrated in the application of these compounds for the delivery of the protein toxin, saporin [3].

Peptide targeting strategies are also of interest for PDT with 5-aminolevulinic acid (ALA) [4]. In ALA-PDT, administered ALA is converted within cells via the heme biosynthetic pathway to a classical photosensitiser- protoporphyrin IX. In this context, some recent chemical and biological data will be presented on the use of peptide targeting to enhance the delivery of multiple ALA units to a specific cell type [5].

[1] Dondi, R., Yaghini, E., Tewari, K. M., Wang, L., Giuntini, F., Loizidou, M., MacRobert, A. J. and Eggleston, I. M., Org. Biomol. Chem. 2016, 14, 11488-11501; [2] Yaghini, E., Dondi, R., Tewari, K. M., Loizidou, M., Eggleston, I. M. and MacRobert, A. J., Sci. Rep. 2017, 7, 6059; [3] Yaghini, E, Dondi, R., Edler, K. J., Loizidou, M., MacRobert, A. J. and Eggleston, I. M., Nanoscale 2018, 10, 20366-20376; [4] Tewari, K. M. and Eggleston, I. M., Photochem. Photobiol. Sci. 2018, 17, 1553-1572; [5] Tewari, K. M., Dondi, R., Yaghini, E., Pourzand, C., MacRobert, A. J. and Eggleston, I. M., Bioorg. Chem. 2021, 109, 104667.
Plasma-Assisted Fluorine Doping of Graphene Oxide for High Performance Supercapacitors
Authors: Moon Joonhee , Sim Yelyn , Surendran Subramani , Choi Hyeonuk , Jeon Cheolho , Choi Heechae , Sim Uk
Published: July 2022

Carbon-based materials are considered to be promising cadidates for energy storage systems because of their superior conductivity, low price, and high specific surface area. Moreover, heteroatom-doped graphene or graphitic carbons are prepared by various methods for modulating their physicochemical properties, improving their wettabililty, and achieving favorable pseudocapacity for use in electrochemical supercapacitors. Here we report a simple solvent-free scale-up technique to synthesis fluorine-doped graphene oxide (FGO) by direct plasma treatment of graphene oxide (GO) powder at ambient pressure. The FGO enabled fast electrochemical charge transfer and provided a large number of active sites for redox reactions during supercapacitor operation, and the mechanisms were thoroughly studied by various electrochemical analyses. As a result, fabricated symmetric supercapacitor using FGO electrodes exhibited a maximum power density (~3200 W/kg) and energy density (~25.87 Wh/kg) with superior cycle stability (20000 cycles) without capacitance loss. Furthermore, the computational calculation results clarified the roles of semi-ionic C–F bonding of FGO: huge charge accumulation on the electrodes and superior electrical conductivity. Thus, our study demonstrates a facile strategy to develop promising functionalized materials, which can enhance the viability of supercapacitor for the next generation of energy storage systems.
(Digital Presentation) Growth of Vdw Heterostructures with Tunable Moiré Patterns
Authors: Fortin-Deschenes Matthieu , Xia Fengnian
Published: July 2022

Overlaying two two-dimensional (2D) lattices with different periodicities or a relative twist angle gives rise to a larger (quasi-) periodic lattice called a moiré pattern. In van der Waals (vdW) heterostructures, the moiré pattern has recently been shown to display interesting novel physical phenomena. For instance, twisted bilayer graphene near the “magic angle” of 1.1° hosts flat electronic bands and strongly correlated states such as unconventional superconductivity [1, 2]. On the other hand, the moiré pattern has been found to both localize and tune interlayer excitons in transition metal dichalcogenides (TMDCs) heterostructures with small twist angle [3-5]. Such moiré heterostructures are generally produced by mechanical exfoliation and stacking to precisely control the twist angle and moiré periodicity. However, this laborious method leads to interfacial contamination and twist angle inhomogeneities and is inherently not scalable. In principle, direct growth of van der Waals heterostructures can overcome these limitations. However, due to energetic considerations, control over the twist angle, and therefore the moiré lattice, has not yet been achieved. Herein, using TMDCs as a model system, we demonstrate the scalable growth of moiré heterostructures with continuously tunable periodicity. By controlling the substitutional alloying of larger atoms within the same group of the periodic table (S, Se), we precisely engineer the lattice parameters of the 2D layers and the moiré period. The grown moiré heterostructures have lateral size up to 200 μm and are shown to host moiré excitons. These results lay the groundwork for the integration of moiré heterostructures in emerging quantum technologies.

[1] Cao, Y.; Fatemi, V.; Fang, S.; Watanabe, K.; Taniguchi, T.; Kaxiras, E.; Jarillo-Herrero, P. Nature 2018, 556 (7699), 43-50.

[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] Yu, H.; Liu, G.-B.; Tang, J.; Xu, X.; Yao, W. (2017). Science Advances 2017. 3 (11), e1701696.

[4] Seyler, K. L.; Rivera, P.; Yu, H.; Wilson, N. P.; Ray, E. L.; Mandrus, D. G.; Yan, J.; Yao, W.; Xu, X. Nature 2019, 567 (7746), 66.

[5] Jin, C.; Regan, E. C.; Yan, A.; Utama, M. I. B.; Wang, D.; Zhao, S.; Qin, Y.; Yang, S.; Zheng, Z.; Shi, S.; et al. Nature 2019, 567 (7746), 76.
(Digital Presentation) Carbon Quantum Dot Assisted Enhancement of S2 Fluorescence of Near-Infrared Dyes through Immobilization-Induced Emission Effect
Authors: Dimitriev Oleg , Piryatinski Yuri , Sharanov Illya , Slominskii Yuri
Published: July 2022

Aggregation-induced emission of organic dyes is a phenomenon in which organic luminophores show higher photoluminescence (PL) efficiency in the aggregated state than in a free molecule, due to the freezing rotational degrees of freedom of the luminophore which otherwise quench the PL emission. In many cases, however, coupling of molecules leads to quenching of their emission due to the concentration quenching or self-quenching (exciton-exciton annihilation) effect. Therefore, in order to realize an enhanced PL emission as a result of molecule-molecule interaction a fine balance should be achieved between freezing rotational degrees of freedom of the molecule and escaping self-quenching effect. This could be realized via immobilization of the luminophore onto the inert surface.

Here, we demonstrate an enhancement of specific S2 emission of the near-infrared (NIR) dyes of tricarbocyanine family due to their immobilization on the surface of carbon nanoparticles that induce freezing a specific planar conformation of the molecule imposed by the carbon plane of the particle it interact with. Carbon quantum dots serve as inert particles that render an opposite influence on the S1 and S2 emission of the tricarbocyanine dyes. We demonstrate a dual emission of the NIR tricarbocyanine dyes with a bright green S2 fluorescence, which is relatively weak for the free dye molecule but whose quantum yield increases by 2-4 times, together with a strong enhancement of the spontaneous rate of S2 fluorescence, whereas the quantum yield of S1 emission in the NIR decreases by 2-7 times, respectively, as a result of immobilization of the dye molecule via the interaction with carbon quantum dots. The above changes are dependent on the terminal and meso-groups of the dye and the solvent used. The dye immobilization due to interaction with carbon quantum dots causes freezing rotational degrees of freedom of the molecule as indicated by suppression of the dye hot band absorption-assisted anti-Stokes S1 emission.

The observed “lighting up” of an anti-Kasha emission, i.e., the emission from Sn (n>1) excited levels, of the NIR chromophores which possess intensive S1 absorption and emission in the NIR region, but which are spectrally silent in the visible, can lead to their potential applications in the fields such as energy conversion, bio-imaging and bio-sensing, sensitization of solar cells, etc.
Ionic Liquid/Non-Ionic Surfactant Mixtures As Versatile, Non-Volatile Electrolytes: Double-Layer Capacitance and Conductivity
Authors: Lashkari Sima , Lashkari Sima A. , Pal Rajinder
Published: July 2022

Self-assembly of ionic liquids (ILs) on 2D materials such as graphene oxide and MXenes facilitated by non-ionic surfactants is a promising approach being increasingly used for the fabrication of high surface area electrodes resulting in high performance supercapacitors. However, the impact that non-ionic surfactants have on double-layer formation and ionic conductivity has yet to be explored. These surfactants are not ionically conductive, have low dielectric constants and high viscosity which are expected to impact the final performance of the electrode.

In this study we analyze the effect of adding two commonly used non-ionic surfactants, P123 and Triton X-100 (TX-100) to 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMImTFSI) on the double-layer capacitance formed at a glassy carbon electrode by means of electrochemical impedance spectroscopy. The results, surprisingly suggest an improvement of 75% and 116% in the double layer capacitance measured at the open circuit voltage for 40% of P123 and TX-100, respectively. We also interpret the changes in the DC potential dependence of the capacitance via the most up-to-date understanding of double-layer charging mechanisms with ionic liquids. Similar to previous literature on solvent-based diluents such as polycarbonate and acetonitrile, which cause a similar effect, the improved capacitance is attributed to the reduced Debye length resulting from an increased effective ionic charge accrued by the IL when surrounded by the low-dielectric constant surfactant.

Both electrolyte series show the same reduction in ionic conductivity (from 8.5 mS/cm to 1 mS/cm) with respect to concentration regardless of the higher viscosity measured for the P123 electrolyte series. Pulsed field gradient nuclear magnetic resonance, is used to determine the diffusion coefficient for the IL as a function of surfactant concentration and allow us to calculate the effective Stokes radius which is found to shrink significantly as a function of surfactant concentration. Similar to the improved capacitance, this is caused by a reduction in ion-ion interactions and an increase in the average effective charge on each ion. These effects make the electrolyte less sensitive than expected to the increased viscosity caused by addition of the more viscous surfactant phase.

The ability to improve the capacitance with non-volatile, low dielectric constant additives, without significantly sacrificing ionic conductivity, opens up an improved avenue for completely non-volatile, non-flammable electrolyte design.
(Digital Presentation) Investigation of Microgalvanic Corrosion in Magnesium Alloys Using Theoretical Analysis and Phase-Field Modeling
Authors: Goel Vishwas , Lyu Yanjun , Montiel David , Thornton Katsuyo
Published: July 2022

Magnesium and its alloys are the lightest structural metallic materials known, and therefore, hold vast potential for reducing the weight for various transportation modes such as airplanes, cars, buses, etc. Although the alloying of Mg with elements such as Al, Mn, and rare earth elements is known to improve the mechanical properties of Mg, the process is often detrimental to the corrosion performance of Mg. This increase in the corrosion rate occurs because of the microgalvanic couple that forms between the Mg-rich phase, which acts as an anode, and the alloying-element-rich phase, which acts as a cathode. Using both experiments and modeling, it has been reported that the rate of microgalvanic corrosion in the Mg alloys depends on the alloying element and microstructure. However, a deeper understanding is required for quantifying the effect of microstructure characteristics such as the fraction of the two phases, spacing between the two phases, the geometry of the two phases, etc., on the corrosion rate. This understanding is crucial for designing Mg alloys with optimal mechanical properties and high corrosion resistance. To bridge this gap in our understanding, we perform the continuum-scale phase-field modeling of different microstructures observed in Mg alloys. Furthermore, we complement the modeling work with theoretical analysis, where we develop analytical relations for studying the effect of various material and microstructural parameters on the characteristic corrosion length scale. The results from both these efforts will be summarized in our presentation.
(Digital Presentation) Offshore Gas Turbines
Authors: Abubakar Muhammad , Omavuezi Omefe , Sumner Joy
Published: July 2022

Offshore gas turbines are the main power drivers for offshore production facilities; they are used for gas lifting, pumping, power generation and compression due to their high power to weight ratio and size. It is therefore imperative to minimize their downtime to prevent production losses. The need to examine the how deposits formed on the blade surface limits the life and performance of the engine cannot be overemphasized.

In this study the Rolls Royce RB211, an aero derivative engine commonly used offshore was selected and its performance data obtained from PYTHIA engine simulation and diagnostic software. These values were used to calculate the rate of mass deposition of potassium sulphate (K2SO4), a potential corrosive salt.

In order to determine rate of mass deposition, contaminant levels for a clean gas and good filter were obtained from General Electric’s fuel specification while a higher contaminant level was assumed.

It was found that at high temperature corrosive salt tend to deposits on the blade surface when concentration of contaminants was calculated for both low and high impurity levels. It was also observed that the rate of mass deposition was high at the first stage of the turbine section where high gas temperature and pressure is usually experienced and drops as hot gas travel along the turbine and leaves as exhaust gas at very low temperature and pressure.

In order to minimize the risk of damage to turbine hot section components like nozzle guide vanes and blades, fuel purity specifications and an appropriate inlet air filtration system must be used. This keeps contaminants in the combusted gas below allowable contaminant levels as recommended by original equipment manufacturers.
Structure and Composition of the Passive Film Studied Using a Combination of X-Ray Photoelectron Spectroscopy, Secondary Ion Mass Spectrometry, and Scanning Transmission Electron Microscopy
Authors: Darwish Ahmed A , Christudasjustus Jijo , Witharamage Chathuranga S , Gupta Rajeev Kumar
Published: July 2022

Characteristics of the passive film and the ability of an alloy to repassivate in any event of passive film breakdown control the corrosion. Studying the passive film has been of great interest since late 1836 when first-time iron was called altered iron. Significant progress in understanding the passive film composition and factors causing breakdown, pit growth and repassivation has been made over the past several decades. However, the role of metallurgical parameters on the passive film structure, composition, crystallinity, chloride ion interaction needs further research attention. The composition and structure of the passive film in Al alloys and stainless steels have been studied using advanced analytical techniques with high depth and spatial resolution have been presented herein. We have used a combination of time of flight secondary ion mass spectrometry (ToF-SIMS), X-ray photoelectron microscopy (XPS), and scanning transmission electron microscopy to study the passive film and pits. The surface film was studied after potentiostatic polarization as well as immersion tests in NaCl solution with immersion time varying from 30 minutes to four weeks. The crystallinity of the passive film was dependent on the composition and microstructure of the alloy. The incorporation of chloride and its distribution in the passive film was dependent on the material and conditions used to produce the passive film. The thickness of the passive film was found to depend on the microstructure of the underlying substrate. The role of the microstructure on passive film structure, breakdown, and repassivation or pit growth will be discussed.
Corrosion Mechanisms in Additively Manufactured 316L Stainless Steels
Authors: Voisin Thomas , Zhang Yuliang , Sen-Britain Shohini , Qi Zhen , Kang Shinyoung , Keilbart Nathan Daniel , Cho Seongkoo , Zhu Yakun , Shi Rongpei , Matthews Manyalibo , Wang Y. Morris , Qiu Roger , Wood Brandon C.
Published: July 2022

Additively manufactured 316L stainless steels (316L SS) using laser powder bed fusion technique (L-PBF) exhibit an excellent combination of high strength and ductility compared to the conventional counterpart. The outstanding material mechanical properties originate from the sub-grain cellular structures developed during the rapid solidification inherent to L-PBF. These structures consist of elongated cells decorated by high density of dislocations, trapped solute, and fine precipitates at their boundaries. The impact of such cellular structures on corrosion resistances, however, remains incompletely understood. In addition, the L-PBF process leads to high surface roughness and usually around 0.1 to 0.5% of porosity. However, the pitting potential of the L-PBF 316L SS can be an order of magnitude higher than the conventional, well annealed counterpart.

In this talk, we will first present a detailed multi-scale characterization of the microstructural features unique to L-PBF 316L SS. In a second part, we will present our experimental-simulation integration approach where we combine surface chemistry mapping and electron and atomic force microscopy with multi-scale simulations to understand the effect of local microstructure variations on pitting and metal dissolution rates in NaCl and HCl environments.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Authors acknowledge the support of the Laboratory Directed Research and Development (LDRD) program (20-SI-004) at LLNL.
Highly Textured Zinc Thin Films through Novel Pulsed Electrodeposition Techniques and Their Applications
Authors: Martin Jason , Mack Ella , King Seth , Sen Sujat
Published: July 2022

The electrodeposition of zinc thin films has been widely investigated with extensive applications in corrosion, battery electrodes, photo- and electro-catalysis. Traditionally, the direct current (DC) method of electroplating has been explored in terms of varying current density to obtain changes in morphology, grain size, preferred crystalline orientation, which in turn have significant consequences for properties such as catalysis and corrosion resistance. We have recently demonstrated [1] a novel, additive-free pulsed plating method to control the specific crystalline growth orientations and average grain size of zinc electrodeposited on steel substrates.

Specifically, we have observed a transition of the preferential (002) facets at low peak current density (or low duty cycle) to (101) preferring facets at higher peak current density (or high duty cycle) as determined by the analysis of texture coefficients. Further analysis using scanning electron microscopy reveals a transition from the conventional hexagonal-shaped particles of zinc to needle-shaped structures, accompanied by a change in average crystallite size from 33 to 19 nanometers, determined from X-ray diffraction studies. The variation in morphology is also correlated to crystallographic textures through the analysis of texture coefficients and an understanding of crystallization mechanisms occurring during deposition.

Herein, we report on an application of these highly textured zinc-coated steel substrates towards corrosion resistance, through accelerated electrochemical testing. Using industry-standard ASTM methods such as Linear Polarization Resistance (LPR), Linear sweep voltammetry (LSV) and electro-impedance spectroscopy (EIS) measurements, we report on preliminary findings of corrosion potential, current and corrosion rates expressed in mm per year as a function of crystalline texture of the zinc thin films.

References

[1] L. Fuller, J. Martin, S. King and S. Sen, “Control of Texture and Morphology of Zinc Films through Pulsed Methods from Additive-Free Electrolytes”, 6, 22, pp.5426 - 5434, ChemistrySelect, 2021
Effects of Interlayer Properties on Electrochemical Ion Intercalation and Electrosorption in Layered and 2D Electrode Materials
Authors: Fleischmann Simon
Published: July 2022

The kinetics of electrochemical intercalation and electrosorption processes are often limited by the solid-state diffusion of ions inside the lattice of the host material. While some of these limitations can be mitigated by nanostructuring of the electrode material, there is a large interest in the electrochemical energy storage community to find materials with structural motifs that allow for intrinsically fast ion diffusion, even in bulk-sized particles.

In this presentation, it will be highlighted how interlayer properties, such as interlayer distance and interlayer chemistry, affect electrochemical ion intercalation and electrosorption processes in layered host materials. Using the examples of hydrogen titanates1 and Ti3C2Tx MXenes2, it is demonstrated that the presence of structural interlayer atoms or molecules can increase the accessibility of ions to the interlayer space. In the model layered host material TiS2, it is shown that increased interlayer spacing and reduced deformation during ion intercalation can lead to a change from diffusion-limited to non-diffusion limited (or pseudocapacitive) charge storage behavior,3 providing some of the most compelling experimental evidence of the intimate relationship between deformation, interlayer distance, and intercalation kinetics in layered host materials.

This contribution will emphasize the importance of interlayer properties of layered and 2D materials for electrochemical ion intercalation and electrosorption processes and provide perspectives and design strategies for next generation ion insertion hosts with fast kinetics for high power energy storage.

Fleischmann, S. et al. Interlayer separation in hydrogen titanates enables electrochemical proton intercalation. J. Mater. Chem. A
8, 412–421 (2020).

Liang, K. et al. Engineering the Interlayer Spacing by Pre-Intercalation for High Performance Supercapacitor MXene Electrodes in Room Temperature Ionic Liquid. Adv. Funct. Mater.
31, 2104007 (2021).

Fleischmann, S., Shao, H., Taberna, P.-L., Rozier, P. & Simon, P. Electrochemically Induced Deformation Determines the Rate of Lithium Intercalation in Bulk TiS2. ACS Energy Lett.
6, 4173–4178 (2021).
Interface Engineering and Understanding for the Next-Generation Batteries
Authors: Zhao Yang
Published: July 2022

Lithium-ion batteries (LIBs) have become the most widely used energy storage systems for portable electronic devices and electric vehicles. With the increasing requirements of high energy density, next-generation batteries, including Li-metal batteries, Na-metal batteries and solid-state batteries, have received huge attention in recent years. For most batteries, the interfacial issues between the electrolyte (both liquid and solid) and electrodes are critical factors affecting the performance of the batteries. Atomic and molecular layer deposition (ALD and MLD) are considered as ideal strategies for overcoming the interfacial issues for the batteries.

In this talk, I will introduce our research about interface engineering and understanding for next-generation batteries. i) The interface is one of the key factors for the Li and Na deposition behaviors and battery performances. We developed ALD and MLD approaches to fabricate the artificial interface with significantly improved electrochemical performances and reduced dendrite formation for Li/Na metal anodes. ii) We further design different ALD/MLD thin films to stabilize the interfaces for solid-state Li batteries. iii) We have also developed ex-situ and in-situ synchrotron X-ray techniques for next-generation batteries.
Battery-like Supercapacitor of Graphene Supported 3D BiOBr Hierarchical Microspheres Electrode Prepared Using Solvothermal Method
Authors: Devarayapalli K.C. , Prabhakar Vattikuti Surya Veerendra , Shim Jaesool
Published: July 2022

Recent reports have proposed battery-like materials as the relevant bridal material between pseudocapacitors and battery materials. Such electrode materials have been widely used as electrodes in hybrid supercapacitors. From this perspective, graphene-supported 3D BiOBr hierarchical microspheres electrode materials were developed for hybrid supercapacitors in 6 M KOH electrolyte. The 2D/3D of graphene/BiOBr achieves the maximum specific capacity of 435.1 C/g at a current density of 0.5 A/g. It was found that the coulombic efficiency of the electrode was 98.6% after 1000 cycles. Using these electrodes, we have successfully fabricated an asymmetric supercapacitor device similar to a hybrid battery, which has a significant energy density of 32.5 Wh/kg at 8700 W/kg and 124.8 F/g at 0.5 A/g. Excellent capacitance, with remarkable cycle stability and a retention rate of 95.3% after 2000 cycles at 8 A/g. Due to the well-designed electrode materials, battery-like supercapacitors exhibit excellent electrochemical performance and are a source of inspiration for other energy storage devices.