bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Graphene Oxide-Based Membranes: Viscoelastic Properties and Application to Broadband Microspeakers
Authors: Szkopek Thomas , Hu Kaiwen , Cardenas William , Huang Yi-Chi , Wei Huijing , Gaskell Robert-Eric , Martel Eli , Cerruti Marta 
Published: July 2022

Graphene and graphene derivatives have attracted attention as materials for acoustic transduction [1-3]. Graphene oxide (GO) membranes and borate cross-linked graphene oxide (X-GO) membranes combine high stiffness, low mass density, and high loss coefficient. We show [4] that these mechanical properties are ideal for efficient, broadband, electro-acoustic transduction, where the acoustic diaphragm should be light, stiff, and internally damped. We present a quantitative comparison of the figure of merit, (E/ρ
3)1/2, where E is Young's modulus and ρ is the mass density, and the material performance index, tan δ (E/ρ
3)1/2, where tan δ is the loss coefficient. GO and X-GO exhibit high figures of merit, comparable to that of wood and exceeding that of aluminum and thermoplastics. The material performance indices of GO and X-GO exceed that of wood, thermoplastics, and aluminum. The latter are common diaphragm materials in acoustic transducers.
For acoustic applications, it is important to understand the frequency dependent viscoelastic response. The complex modulus G = G' + iG'' of GO and X-GO membranes was measured by dynamic mechanical analysis and analyzed by the application of the time-temperature superposition (TTS) principle of polymer rheology. We find that X-GO shows a more than 30% increase in storage modulus G’ over the frequency range of 1 to 10 kHz, exceeding 55 GPa at 10 kHz. There is a reduction in loss coefficient tan δ = G''/G' for X-GO of ≈30% over the same frequency range, reaching tan δ = 0.04 at 10 kHz, which is approximately one order of magnitude larger than that of aluminum.
A quantitative comparison of microspeaker performance was conducted at a fixed diaphragm mass m = 15-20 g and 14 mm x 8 mm size, including GO, X-GO, oak wood, polyethylene terephthalate (PET), aluminum, and titanium. Scanning laser measurements confirm pistonic operation of X-GO membranes. Microspeaker sound pressure level response was measured in both time and frequency domains. X-GO diaphragms exhibit 45% higher damping than aluminum membranes in microspeaker assemblies. Consequently, X-GO membranes enable the upshift of loudspeaker breakup frequency by 1/6 to 1/2 octave above speakers assembled with oak wood, PET, aluminum and titanium membranes. GO based materials are thus found to be an exceptional material for electro-acoustic transduction.
References:
[1] Q. Zhou, A. Zettl, Appl. Phys. Lett. 102, 223109 (2013).
[2] A. U. Khan, G. Zeltzer, G. Speyer, Z. K. Croft, Y. Guo, H. Nagar, V. Artel, A. Levi, C. Stern, D. Naveh, G. Liu, Adv. Mat. 33, 2004053 (2021).
[3] H. Tian, T.-L. Ren, D. Xie, Y.-F. Wang, C.-J. Zhou, T.-T. Feng, D. Fu, Y. Yang, P.-G. Peng, L.-G. Wang, L.-T. Liu, ACS Nano 5, 4878 (2011).
[4] K. Hu, R.E.Gaskell, W. Cardenas, H. Wei, Y.-C. Huang, M. Cerruti, T. Szkopek, Adv. Func. Mat. 2107167 (2021).

Figure 1
(Invited, Digital Presentation) Cooperative Effects of Fe and Cu Sites in N-Doped Carbon Nanotubes on Oxygen Reduction Activity and Selectivity
Authors: Kato Masaru , Abe Daiki , Xie Siqi , Fujibayashi Natsuki , Yagi Ichizo 
Published: July 2022

The oxygen reduction reaction (ORR) is a key reaction in polymer electrolyte fuel cells (PEFCs) and metal–air batteries. Although platinum group metal (PGM)-based ORR electrocatalysts have been widely used in state-of-the-art PEFCs, PGMs are rare and expensive. For future wide-spread applications of PEFCs, non-PGM electrocatalysts with high ORR activity and product selectivity to H2O must be developed. Natural catalysts of metalloenzymes including laccases and cytochrome c oxidases are known to catalyze the ORR and therefore encourage us to develop metalloenzyme-inspired electrocatalysts based on non-PGMs for the ORR because these metalloenzymes use iron and/or copper ions as active sites [1-3].
We develop non-PGM electrocatalysts of Cu- Fe- and N-doped carbon nanotubes, (Cu,Fe)-N-CNT, for the ORR, inspired by the heterometallic active site of cytochrome c oxidase [4]. The co-presence of Cu and Fe active sites increase the ORR activity and selectivity to H2O in acidic media, compared with monometallic Fe-N-CNT or Cu-N-CNT. Kinetic analysis revealed that the selective 4-electron reduction of O2 to H2O is dominant for (Cu,Fe)-N-CNT whereas the sequential (2+2)-electron reduction mainly proceeds for Fe-N-CNT or Cu-N-CNT, indicating that the ORR mechanism can be modulated by the co-presence of Cu and Fe active sites. We will discuss details on the ORR mechanistic insights based on spectroscopic data including in situ X-ray absorption spectroscopy and Mossbauer spectroscopy.
References
[1] M. Kato, I. Yagi, e-J. Surf. Sci. Nanotechnol., 18, 81 (2020).
[2] M. Kato, T. Murotani, I. Yagi, Chem. Lett., 45, 1213 (2016).
[3] M. Kato, M. Muto, N. Matsubara,Y. Uemura,Y. Wakisaka, T. Yoneuchi,D. Matsumura, T. Ishihara, T. Tokushima, S. Noro, S. Takakusagi, K. Asakura, I. Yagi, ACS Appl. Energy Mater., 1, 2358 (2018).
[4] M. Kato, N. Fujibayashi, D. Abe, N. Matsubara, S. Yasuda, I. Yagi, ACS Catal., 11, 2356 (2021).
Dynamic Excitons in Nitrile-Functionalized Ladder-Type Oligo(p-Phenylene)s By Pulse Radiolysis Coupled with Time-Resolved Infrared Spectroscopy
Authors: Yan Juchao , Grills David C. , Mani Tomoyasu 
Published: July 2022

Research and development efforts toward organic solar cells (OSCs) for large-scale power generation have continued unabated throughout the world. In recent years, OSCs based on π-conjugated polymers and small molecules have received increasing interest due to favorable electronic properties, component versatility, and low production and installation costs. Despite the progress, many improvements are still needed prior to widespread commercialization, involving device efficiency, lifetime, and cost. Of these, increasing device efficiency, particularly power conversion efficiency (PCE), is the most challenging task. The currently achievable PCE, for example, is only 17.3%.1 The key to achieving high PCE is the search for new organic conjugated molecules that are capable of harvesting light, and transferring and transporting charges promptly and efficiently. This requires a full understanding of how electrons and holes are localized and delocalized in organic conjugated molecules.
Using time-resolved infrared (TRIR) detection combined with pulse radiolysis, Mani and co-workers2 have measured experimentally the degree of localization of an excess electron in a series of nitrile-functionalized oligofluorenes by the spectral shifts of nitrile vibrations. The nitrile vibrational bands in anions respond sensitively to the degree of electron delocalization (IR shifts) and the structural changes (IR linewidth). The electron is found to move back and forth within the oligomers, likely controlled by the movement of dihedral angles between monomer units.
Unlike the non-coplanarity of the fluorenyl-fluorenyl backbone in oligofluorenes, the rigid and planar structure of ladder-type, oligo(p-phenylene)s (Scheme 1)3 would facilitate π-electron delocalization and thus improve the multiphoton absorption response. Such a structure would also increase photoluminescence efficiency with enhanced thermal and photochemical stability. To investigate the coupling between charge distribution and vibrational motion and vibronic coupling, we incorporate nitrile group in each compound as the infrared reporter group.
In this talk, we report our molecular syntheses and characterizations of two of the title compounds (L3PCN and L4PCN, both neutral compounds and their radical anions) by TRIR followed by pulse radiolysis. Having no flexible dihedral angles, L3PCN and L4PCN exhibit sharper IR bands of the nitrile vibration than the oligofluorenes with the same number of benzene rings and some dihedral angles. Our results further demonstrate that the linewidth of the nitrile vibration, together with the IR shifts and intensities, reports on structural and accompanying electronic fluctuations,2 that is, on the dynamic excitons.

References

(1) Meng, L. X.; et al. Science 2018, 361, 1094.
(2) Mani, T.; et al. Journal of the American Chemical Society 2015, 137, 10979.
(3) Scherf, U.; et al. Makromolekulare Chemie-Rapid Communications 1991, 12, 489.

Figure 1
(Invited) Ultrafast Solar Energy Conversion with Earth-Abundant Complexes
Authors: Chabera Pavel , Lindh Linnea , Rosemann Nils , Hai Yen Tran Hoang , Warnmark Kenneth , Yartsev Arkady , Sundstrom Villy , Persson Petter 
Published: July 2022

Transition-metal complexes are widely used as photosensitizers and photocatalysts, and in light-emitting devices.[1] We have studied ultrafast proceses in a variety of DSSC and photocatalytic aplications.[2,3] More recently we demonstrated the first iron complex [FeIII(btz)3]3+ exhibiting room temperature photoluminescence from a CT state and show that it has a 100 ps excited state CT lifetime which is unprecedented for any iron complex.[4] This was characterized as a rare low-spin FeIII
d5
complex with emission from a long-lived doublet ligand-to-metal charge transfer (2LMCT) state. Absence of intersystem crossing (ISC) in this complex avoids significant excited state energy losses as encountered in the prevailing class of d6
TM complexes of e.g. FeII and RuII. Furthermore, we have also shown [FeII(btz)3]2+ low-spin complex [5], a FeII analogue to [FeIII(btz)3]3+. It exhibits strong metal-to-ligand charge transfer (MLCT) absorption bands throughout the visible spectrum, and excitation of these bands gives rise to a 3MLCT state with a 528 ps excited state lifetime in CH3CN solution that is more than one order of magnitude longer compared to the MLCT lifetime of any previously reported FeII complex. Together, these results show that the FeII and FeIII oxidation states of the same Fe(btz)3 complex feature long lived MLCT and LMCT states, respectively. This demonstrates the versatility of iron N-heterocyclic carbene complexes as promising light-harvesters for a broad range of photophysical and photochemical applications, and on-going efforts for further improvements of the excited state dynamics of such systems will be outlined, including the very latest development of an iron compound [Fe(phtmeimb)2]+ with an excited state stable enough to emit light for 2 ns and able to engage in bimolecular electron transfer [6].
1 Ponseca, C. S., Jr.; Chabera, P.; Uhlig, J.; Persson, P.; Sundstrom, V. Ultrafast Electron Dynamics in Solar Energy Conversion.
Chem Rev
2017, 117 (16), 10940.
2 H. Imahori et al, Photoinduced Charge Carrier Dynamics of Zn−Porphyrin−TiO2 Electrodes: The Key Role of Charge Recombination for Solar Cell Performance,
J. Phys. Chem. A
2011, 115, 16, 3679-3690
3 M. Yamamoto et al, Visible light-driven water oxidation with a subporphyrin sensitizer and a water oxidation catalyst,
Chem. Commun.
2016,52, 13702-13705
4 Chabera, P. et al. A low-spin Fe(III) complex with 100-ps ligand-to-metal charge transfer photoluminescence. Nature 2017, 543 (7647), 695.
5 Chabera, P. et al. Fe(II) Hexa N-Heterocyclic Carbene Complex with a 528 ps Metal-to-Ligand Charge-Transfer Excited-State Lifetime, J Phys Chem Lett 2018, 9, 459−463.
6 Kjær, K. S. et al. Luminescence and reactivity of a charge-transfer excited iron complex with nanosecond lifetime. Science 2019, 363 (6424), 249-253.

Figure 1
(Invited) Kinetic Prediction of Reverse Intersystem Crossing in Thermally Activated Delayed Fluorescence Molecules
Authors: Aizawa Naoya 
Published: July 2022

Reverse intersystem crossing (RISC), the endothermic spin-flip process of producing an emissive singlet exciton from a non-emissive triplet exciton, is of increasing interest for applications in organic electroluminescent materials, photocatalysts, and biomedical probes. Theoretical prediction of the rate constant of RISC (k
RISC) may enable an efficient priori screening of new materials in chemical spaces; yet, the understanding of its kinetics in vastly different structures is challenging. Here, we demonstrate a theoretical expression that reproduces experimental k
RISC ranging over five orders of magnitude in twenty different molecules. We show that the spin flip occurs across the singlet–triplet crossing seam involving a higher-lying triplet excited state where the semi-classical Marcus parabola is no longer valid.1 The present model also leads to a newly designed TADF molecule with high k
RISC of 108 s–1.2

1. N. Aizawa, Y. Harabuchi, S. Maeda, Y.-J. Pu, Nat. Commun.
11, 3909 (2020).
2. N. Aizawa, A. Matsumoto, T. Yasuda, Sci. Adv.
7, 5769 (2021).

Figure 1
(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).
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
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.