bluuebunny/crossref_metadata_2025 huggingface dataset:
A Flow-based Multi-agent Data Exfiltration Detection Architecture for Ultra-low Latency Networks
Authors: Marques Rafael Salema , Epiphaniou Gregory , Al-Khateeb Haider , Maple Carsten , Hammoudeh Mohammad , De Castro Paulo André Lima , Dehghantanha Ali , Choo Kim Kwang Raymond
Published: July 2021

Modern network infrastructures host converged applications that demand rapid elasticity of services, increased security, and ultra-fast reaction times. The Tactile Internet promises to facilitate the delivery of these services while enabling new economies of scale for high fidelity of machine-to-machine and human-to-machine interactions. Unavoidably, critical mission systems served by the Tactile Internet manifest high demands not only for high speed and reliable communications but equally, the ability to rapidly identify and mitigate threats and vulnerabilities. This article proposes a novel Multi-Agent Data Exfiltration Detector Architecture (MADEX), inspired by the mechanisms and features present in the human immune system. MADEX seeks to identify data exfiltration activities performed by evasive and stealthy malware that hides malicious traffic from an infected host in low-latency networks. Our approach uses cross-network traffic information collected by agents to effectively identify unknown illicit connections by an operating system subverted. MADEX does not require prior knowledge of the characteristics or behavior of the malicious code or a dedicated access to a knowledge repository. We tested the performance of MADEX in terms of its capacity to handle real-time data and the sensitivity of our algorithm’s classification when exposed to malicious traffic. Experimental evaluation results show that MADEX achieved 99.97% sensitivity, 98.78% accuracy, and an error rate of 1.21% when compared to its best rivals. We created a second version of MADEX, called MADEX level 2, that further improves its overall performance with a slight increase in computational complexity. We argue for the suitability of MADEX level 1 in non-critical environments, while MADEX level 2 can be used to avoid data exfiltration in critical mission systems. To the best of our knowledge, this is the first article in the literature that addresses the detection of rootkits real-time in an agnostic way using an artificial immune system approach while it satisfies strict latency requirements.
AI-enabled IoT-Edge Data Analytics for Connected Living
Authors: Lv Zhihan , Qiao Liang , Verma Sahil , Kavita
Published: July 2021

As deep learning, virtual reality, and other technologies become mature, real-time data processing applications running on intelligent terminals are emerging endlessly; meanwhile, edge computing has developed rapidly and has become a popular research direction in the field of distributed computing. Edge computing network is a network computing environment composed of multi-edge computing nodes and data centers. First, the edge computing framework and key technologies are analyzed to improve the performance of real-time data processing applications. In the system scenario where the collaborative deployment tasks of multi-edge nodes and data centers are considered, the stream processing task deployment process is formally described, and an efficient multi-edge node-computing center collaborative task deployment algorithm is proposed, which solves the problem of copy-free task deployment in the task deployment problem. Furthermore, a heterogeneous edge collaborative storage mechanism with tight coupling of computing and data is proposed, which solves the contradiction between the limited computing and storage capabilities of data and intelligent terminals, thereby improving the performance of data processing applications. Here, a Feasible Solution (FS) algorithm is designed to solve the problem of placing copy-free data processing tasks in the system. The FS algorithm has excellent results once considering the overall coordination. Under light load, the V value is reduced by 73% compared to the Only Data Center-available (ODC) algorithm and 41% compared to the Hash algorithm. Under heavy load, the V value is reduced by 66% compared to the ODC algorithm and 35% compared to the Hash algorithm. The algorithm has achieved good results after considering the overall coordination and cooperation and can more effectively use the bandwidth of edge nodes to transmit and process data stream, so that more tasks can be deployed in edge computing nodes, thereby saving time for data transmission to the data centers. The end-to-end collaborative real-time data processing task scheduling mechanism proposed here can effectively avoid the disadvantages of long waiting times and unable to obtain the required data, which significantly improves the success rate of the task and thus ensures the performance of real-time data processing.
RLC: A Reinforcement Learning-Based Charging Algorithm for Mobile Devices
Authors: Liu Tang , Wu Baijun , Xu Wenzheng , Cao Xianbo , Peng Jian , Wu Hongyi
Published: July 2021

Wireless charging has been demonstrated as a promising technology for prolonging device operational lifetimes in
Wireless Rechargeable Networks
(
WRNs
). To schedule a mobile charger to move along a predesigned trajectory to charge devices, most existing studies assume that the precise location information of devices is already known. Unfortunately, this assumption does not always hold in real mobile application, because the activities of the vast majority of mobile devices carried by mobile agents appear dynamic and random. To the best of our knowledge, this is the first work to study how to wirelessly charge mobile devices with non-deterministic mobility. We aim to provide effective charging service to them, subject to the energy capacity of the mobile charger. We formalize the effective charging problem as a
charging reward maximization problem
(
CRMP
), where the amount of reward obtained by charging a device is inversely proportional to the residual lifetime of the device. Then, we prove that CRMP is NP-hard. To derive an effective charging heuristic, an algorithm based on
Reinforcement Learning
(
RL
) is proposed. The evaluation results show that the RL-based charging algorithm achieves excellent charging effectiveness. We further interpret the learned heuristic to gain deep and valuable insights into the design options.
On β-Plurality Points in Spatial Voting Games
Authors: Aronov Boris , De Berg Mark , Gudmundsson Joachim , Horton Michael
Published: July 2021

Let
V
be a set of
n
points in mathcal R
d
, called
voters
. A point
p
∈ mathcal R
d
is a
plurality point
for
V
when the following holds: For every
q
∈ mathcal R
d
, the number of voters closer to
p
than to
q
is at least the number of voters closer to
q
than to
p
. Thus, in a vote where each 
v
∈
V
votes for the nearest proposal (and voters for which the proposals are at equal distance abstain), proposal 
p
will not lose against any alternative proposal 
q
. For most voter sets, a plurality point does not exist. We therefore introduce the concept of
β-plurality points
, which are defined similarly to regular plurality points, except that the distance of each voter to
p
(but not to 
q
) is scaled by a factor 
β
, for some constant 0< β ⩽ 1. We investigate the existence and computation of
β
-plurality points and obtain the following results.

• Define β
*
d
:= {β : any finite multiset
V
in mathcal R
d
admits a β-plurality point. We prove that β
*
d
= √3/2, and that 1/√
d
⩽ β
*
d
⩽ √ 3/2 for all
d
⩾ 3.

• Define β (
p, V
) := sup {β :
p
is a β -plurality point for
V
}. Given a voter set
V
in mathcal R
2
, we provide an algorithm that runs in
O
(
n
log
n
) time and computes a point
p
such that β (
p
,
V
) ⩾ β
*
b
. Moreover, for
d
⩾ 2, we can compute a point 
p
with β (
p
,
V
) ⩾ 1/√
d
in
O
(
n
) time.

• Define β (
V
) := sup { β :
V
admits a β -plurality point}. We present an algorithm that, given a voter set
V
in mathcal R
d
, computes an ((1-ɛ)ċ β (
V
))-plurality point in time
O
n
2
ɛ
3d-2
ċ log
n
ɛ
d-1
ċ log
2
1ɛ).
Say it well, say it often
Authors: Yaffe Philip
Published: July 2021

Each "Communication Corner" essay is self-contained; however, they build on each other. For best results, before reading this essay and doing the exercise, go to the first essay "How an Ugly Duckling Became a Swan," then read each succeeding essay.

Two people can give a speech on exactly the same subject, using almost exactly the same information, yet one speech will be a brilliant success and the other a dismal failure. How does this happen? Many factors contribute to success or failure, but only one factor virtually guarantees that your speech will stand out like a shining light or be clothed in darkness like a burned-out bulb.
Report on the 30th the web conference 2021 (TheWebConf2021)
Authors: Košmerlj Aljaž , Grobelnik Marko , Leskovec Jure
Published: July 2021

The Web Conference (TheWebConf2021) is the premier conputer science conference on the state of the Web and its related areas. It covers the Web from a wide spectrum of aspects, including technical areas of artificial intelligence, security, privacy, knowledge representation, mobile computing as well as social sciences, economics, policy, accessibility and others. The year 2021 marked the 30th edition that was organised in Ljubljana, Slovenia, but took place fully online due to the COVID-19 pandemic.
Effective and practical neural ranking
Authors: MacAvaney Sean
Published: July 2021

Supervised machine learning methods that use neural networks ("deep learning") have yielded substantial improvements to a multitude of Natural Language Processing (NLP) tasks in the past decade. Improvements to Information Retrieval (IR) tasks, such as ad-hoc search, lagged behind those in similar NLP tasks, despite considerable community efforts. Although there are several contributing factors, I argue in this dissertation that early attempts were not more successful because they did not properly consider the unique characteristics of IR tasks when designing and training ranking models. I first demonstrate this by showing how large-scale datasets containing weak relevance labels can successfully replace training on in-domain collections. This technique improves the variety of queries encountered when training and helps mitigate concerns of over-fitting particular test collections. I then show that dataset statistics available in specific IR tasks can be easily incorporated into neural ranking models alongside the textual features, resulting in more effective ranking models. I also demonstrate that contextualized representations, particularly those from transformer-based language models, considerably improve neural ad-hoc ranking performance. I find that this approach is neither limited to the task of ad-hoc ranking (as demonstrated by ranking clinical reports) nor English content (as shown by training effective cross-lingual neural rankers). These efforts demonstrate that neural approaches can be
effective
for ranking tasks. However, I observe that these techniques are impractical due to their high query-time computational costs. To overcome this, I study approaches for offloading computational cost to index-time, substantially reducing query-time latency. These techniques make neural methods
practical
for ranking tasks. Finally, I take a deep dive into better understanding the linguistic biases of the methods I propose compared to contemporary and traditional approaches. The findings from this analysis highlight potential pitfalls of recent methods and provide a way to measure progress in this area going forward.
Distortion in social choice problems
Authors: Anshelevich Elliot , Filos-Ratsikas Aris , Shah Nisarg , Voudouris Alexandros A.
Published: July 2021

The notion of
distortion
in social choice problems has been defined to measure the loss in efficiency---typically measured by the utilitarian social welfare, the sum of utilities of the participating agents---due to having access only to limited information about the preferences of the agents. Here, we provide a comprehensive reading list on the related literature.
Two-sided matching with diversity concerns
Authors: Aziz Haris
Published: July 2021

Diversity concerns come up in many important decision making settings including two-sided matching, in particular centralized student admission matching. We overview papers on the topic of two-sided matching with diversity concerns.
Transaction fee mechanism design
Authors: Roughgarden Tim
Published: July 2021

Demand for blockchains such as Bitcoin and Ethereum is far larger than supply, necessitating a mechanism that selects a subset of transactions to include "on-chain" from the pool of all pending transactions. EIP-1559 is a proposal to make several tightly coupled changes to the Ethereum blockchain's transaction fee mechanism, including the introduction of variable-size blocks and a burned base fee that rises and falls with demand. These changes are slated for deployment in Ethereum's "London fork," scheduled for late summer 2021, at which point it will be the biggest economic change made to a major blockchain to date. This short note provides an overview of recent work by the author that formally investigates and compares the incentive guarantees offered by Ethereum's current transaction fee mechanism and the new mechanism proposed in EIP-1559.
Reflections on Six Decades of Research
Authors: Elliott Delbert S.
Published: July 2021

A brief autobiographical history is presented covering my 57-year career as a criminologist. I begin with my early childhood experiences, growing up during World War II, my undergraduate and graduate school experiences, and my early career years at San Diego State University and the University of Colorado, Boulder. I then discuss two of the major themes in my research developed during these early career years: self-report measures of delinquent behavior and the Integrated Theory of delinquency. My later career years are described, and the third major theme of my work, the identification and promotion of effective delinquency prevention programs, is discussed.
Standardized Reference Diets for Zebrafish: Addressing Nutritional Control in Experimental Methodology
Authors: Watts Stephen A. , D'Abramo Louis R.
Published: July 2021

The ideal of experimental methodology in animal research is the reduction or elimination of environmental variables or consistency in their application. In lab animals, diet has been recognized as a very influential response variable. Reproducibility in research using rodents required the development of a unique diet of consistent ingredient and nutrient composition to allow for cross-comparisons of lab results, spatially and temporally. These diets are commonly referred to as standard reference diets (SRDs). The established validity of published nutritional requirements combined with the cooperation of commercial partners led to species-specific reference diets commonly used by the research community. During the last several decades, zebrafish ( Danio rerio) have become a widespread alternative animal model, but specific knowledge of their nutrition is lacking. We present a short-term approach for developing an SRD for zebrafish, similar to that eventually attained for rodents over decades. Imminent development of an open-formulation, commercially produced SRD for zebrafish will notably advance translational biomedical science.
Eyewitness Identification Is a Visual Search Task
Authors: Wixted John T. , Vul Edward , Mickes Laura , Wilson Brent M.
Published: July 2021

The simultaneous six-pack photo lineup is a standard eyewitness identification procedure, consisting of one police suspect plus five physically similar fillers. The photo lineup is either a target-present array (the suspect is guilty) or a target-absent array (the suspect is innocent). The eyewitness is asked to search the six photos in the array with respect to a target template stored in memory (namely, the memory of the perpetrator's face). If the witness determines that the perpetrator is in fact in the lineup (detection), then the next step is to specify the position of the perpetrator's face in the lineup (localization). The witness may also determine that the perpetrator is not present and reject the lineup. In other words, a police lineup is a detection-plus-localization visual search task. Signal detection concepts that have long guided thinking about visual search have recently had a significant impact on our understanding of police lineups.
Halide Ion Mobility of Mixed Halide Perovskites in Light and Dark
Authors: Kamat Prashant V
Published: July 2021

The intrinsic ionic defects, specifically halide ion vacancies, often dictate the mobility of halide species within the perovskite film during the operation of solar cells. Of particular interest is the halide ion mobility in metal halide perovskites, which plays an important role in determining the performance of perovskite solar cells. Photoinduced phase segregation seen in mixed halide perovskite films under steady state irradiation offers a convenient way to visualize halide ion segregation. Interestingly, upon storage in dark, the process is reversed and the original mixed halide composition gets restored. Whereas entropy of mixing explain the thermally activated mixing of halide ions to yield mixed halide perovskite, the opposite trend observed during photoirradiation remains an intriguing phenomenon. The threshold energy of incident light to observe halide segregation increases with increasing temperature. The diffusion of these halide species, which is tracked through changes in the absorption spectra at different temperatures, offers a direct measurement of thermally activated halide diffusion in perovskite films. The thermally activated halide exchange shows the challenges of stabilizing metal halide perovskites with varying bandgap in tandem solar cells.
(Invited) Rational Strategies for Efficient Perovskite Solar Cells
Authors: Zhang Meng , Lin Zhiqun
Published: July 2021

The past decade has witnessed tremendous advances in organometal halide perovskite solar cells (PSCs) due largely to the stellar set of optoelectronic properties of perovskites such as high absorption coefficient, long carrier diffusion length, and low electron–hole recombination rate constant. Notably, the organolead halide PSC has reached a certified champion power conversion efficiency (PCE) of 25.2%. Rapid progress in PCE has been realized by structure design, materials chemistry, process engineering, and device physics. In this talk, I will first introduce a meniscus-assisted solution printing method (MASP) towards large-grained perovskite films for morphology and crystallinity control. Intriguingly, the outward convective flow triggered by fast solvent evaporation at the edge of the meniscus ink imparted the diffusion of perovskite solutes, thus facilitating the growth of micrometer-scale perovskite grains, leading to perovskite film with good crystallization and preferred orientation. This robust MASP strategy may in principle be easily extended to craft other solution-printed perovskite-based optoelectronics. Secondly, I will demonstrate an interesting interface engineering approach with 2D ambipolar black phosphorene (BP) for high-efficiency and stable PSCs. BP carries a stellar set of physical properties such as conveniently tunable bandgap and extremely high ambipolar carrier mobility. Concurrently enhanced carrier extraction at both electron transport layer/perovskite and perovskite/hole transport layer interfaces was achieved through judicious design and position of BP with tailored thickness as dual-functional nanomaterials. Thirdly, a spatial poling approach will be introduced for perovskite recrystallization towards preferred orientation, crystallinity, and morphology. Finally, the challenges facing the future development and commercialization of PSCs will be summarized and provided.
(Invited) Surface Modification of Dye-Sensitized Hydrogen-Evolving Photocatalyst for Z-Scheme Solar Water Splitting
Authors: Kobayashi Atsushi , Yoshimura Nobutaka , Yoshida Masaki , Kato Masako
Published: July 2021

Z-scheme water splitting system composed of water reduction and oxidation photocatalysts coupled with redox-reversible electron mediator has attracted considerable attention because of the promising activity for water splitting under visible light irradiation. To improve the activity of Z-scheme water-splitting photocatalyst, how to achieve the one-way electron transfer from O2 evolution photocatalyst to H2 evolution photocatalyst through electron mediator is crucial. Dye-sensitization is one of the promising approaches not only to enhance the light absorption ability but also to improve the charge separation efficiency at the dye-semiconductor interface. We recently found that the multilayering of Ru(II) dyes on the surface of water reduction catalyst Pt-TiO2 nanoparticle (nRu@Pt-TiO2, n = number of layers of Ru(II) dyes) significantly improved the photocatalytic H2 evolution activity.[1] In this work, to enhance the electron donation from iodide, we have synthesized two different 2Ru@Pt-TiO2 nanoparticles with different surface structures: P-2Ru@Pt-TiO2 having phosphate groups on the surface and ZrP-2
Ru@Pt-TiO2 with Zr4+-phosphate groups on the surface as well as our previously reported 2Ru@Pt-TiO2 without any surface phosphonates.[2]

Figure shows the results of photocatalytic H2 evolution reactions in 0.5 M aqueous KI solutions of three kinds of dye-double-layered nanoparticle photocatalysts with different surface structures. The amount of H2 produced after 6 h of light irradiation increased in the following order: 2Ru@Pt-TiO2 < P-2Ru@Pt-TiO2 < ZrP-2Ru@Pt-TiO2
. Notably, the AQY of ZrP-2Ru@Pt-TiO2 in the first hour of reaction was approximately 1%. The Ru(III)/Ru(II) redox potential of Ru(II)dye with phosphonic acid groups was reported to be shifted positively to less than 0.1 V by immobilization to the TiO2 surface or by coordination bond formation with Zr4+ cations[3], suggesting that the binding of Zr4+ to the phosphonic acid groups of Ru(II) dye has little effect on the driving force of the electron donation reaction from the iodide. The zeta potential of ZrP-2Ru@Pt-TiO2 was estimated to be +7 mV without KI, and it negatively shifted to −6 mV in the presence of 0.5 M KI. On the other hand, the shift of P-2Ru@Pt-TiO2 was estimated to be smaller (from −7 to −12 mV). The negative shifts in the 0.5 M KI aqueous solution could be ascribed to the attraction of iodide anions to the nanoparticle surface by electrostatic interactions with the surface Zr4+ cations in the case of ZrP-2Ru@Pt-TiO2, and by hydrogen-bonding interactions with the surface phosphonic acids for P-2Ru@Pt-TiO2. These results suggest that the surface structure of Ru(II) dye-sensitized Pt-TiO2 nanoparticle photocatalyst has a great influence on the reactivity with the redox mediator. Details will be discussed.

Figure 1
(Invited) Electrochromic Conjugated Polymers for Energy Saving Smart Windows with Integrative Functionalities
Authors: Kim Eunkyoung
Published: July 2021

Smart windows tend to integrate multiple functions with the purpose of controlling external or sunlight input, self‐power functionality, and display functionality. Among the several chromogenic mechanisms, electrochromic methods are fast and simple to control. Moreover, electrochemical principles for smart windows offer easier integration of functionalities due to the integrative principles in common working mechanisms for color, energy, and information carrier controls. Thus efforts toward the combination of functionalities have led to synergetic and technical breakthroughs over the years. Here, the recent electrochromic research on the integration of different functionalities will be presented along with the development of new electrochromic polymers and nanostructurization.
Electrochemical and Spectral Properties of Highly Distorted Rhenium Phthalocyanine Complexes
Authors: WANG Mengfei , Koike Yosuke , Murata Kei , Saito Daisuke , Kato Masako , Ishii Kazuyuki
Published: July 2021

Phthalocyanines exhibit distinct physicochemical properties by modifying the π-conjugated system which makes them as the suitable candidates for various applications. Recently, we synthesized and characterized rhenium phthalocyanine (Re1Pc, Re2Pc) and rhenium tetraazaporphyrin (Re1TAP, Re2TAP) complexes (Figure 1 (a)).1

In terms of electrochemical properties (Figure 1 (c)), compared to the corresponding Zn complexes (ZnPc, ZnTAP), both the first oxidation and the first reduction potentials of Re complexes (Re1Pc, Re2Pc, Re1TAP, Re2TAP) shift to the positive side owing to the introduction of electron-deficient [Re(CO)3]+ unit(s). On the other hand, by reducing the π-conjugated system from Pc to TAP, more positive oxidation potentials are observed in the ReTAP complexes. This trend is consistent with the changes in the calculated HOMO and LUMO energy levels (Figure 1 (b)). Notably, the positively shifted oxidation potentials of these complexes significantly improve the tolerance towards oxidation, which is essential for various applications.

In the electronic absorption spectra of these Re complexes, the unsymmetric coordination of the [Re(CO)3]+ unit(s) concomitantly produces a remarkable red shift of the Q band. Also, in ReTAP complexes, the broadening of the Q bands is uniquely observed.

DFT calculations indicate that the macrocycle skeletons in Pc and TAP are highly distorted, in contrast to the high stability towards oxidation. In the presentation, the distorted structures will be discussed in detail.

[1] K. Murata, Y. Koike, K. Ishii, Chem. Commun., 2020, 56, 13760-13763.

Figure 1. (a) Molecular structures of RePc and ReTAP complexes. (b) Energy plots of the molecular orbitals and (c) the electrochemical results of MPc and MTAP complexes.

Figure 1
(Invited) Helicate Europium Complexes for the Design of Efficient Luminescence and Electro-Luminescence Devices
Authors: Hasegawa Miki
Published: July 2021

Molecular structure in metal complexes enhances their electronic structure and physicochemical properties such as luminescence. It is well known that the number of coordination of a lanthanide ion is various from six to twelve. Here, we will introduce a series of helicate europium (Eu) complexes which having hexadentate ligand with chelate effect to keep the coordination of its aromatic ligand as photo-antenna to induce ff emissions of Eu.[1]

The Eu complex (EuL) has a neutral ligand consisted in two bipyridine moieties bridged by ethylenediamine and two nitrate ions, and takes a cationic complex. The molecular structure succeeded to form the efficient energy donor behavior from the measurement of electro-static potential by the synchrotron single crystal X-ray analysis (SPring-8, BL01B1), because the bipyridine moiety has kept the excited state like a terpyridine moiety. The luminescence band of Eu was observed at 616 nm with relatively high luminescent quantum yields (QY) by UV excitation.

The complex is also soluble in ionic liquids (IL) when the same counter anions were used in both the complex and IL such as PF6
-.[2] Luminescence and electronic absorption bands position of EuL in IL were same. Interestingly the QY of the complex drastically increased in IL because of the high viscosity.

IL was also useful for the application for electrochemistry as a medium. Actually, there are several papers of Eu complexes were reported to explain the possibility of luminescence color change by the redox reaction of Eu ion[3]. If Eu ion takes divalent state, the luminescence color will be shifted at blue, and can be switch the color between red and blue by electrochemistry.

In the case of EuL in IL, we adopted the solution to electronic cells and found the luminescence intensity changing at around +2.0 and -1.8 V [4]. It exhibites the reversibility with keeping the possible luminescence intensity. Thus, the stable halicate structure and cationic state of EuL act as a electrochemical active behavior in IL.

Author acknowledges Professor Y. Kim, Hokkaido University for the collaboration of electrochemistry in the ionic liquids.

[1] (a)M. Hasegawa, et al., New J. Chem., 2014, 38, 1225-1234; (b) M. Hasegawa, et al., ChemPlusChem, 2020, 85, 294-300; (c) M. Hasegawa, et al., Photochem. Photobiol. Sci., 2020, DOI: 10.1039/d0pp00069h, (d) M. Hasegawa & H. Ohmagari, Chem. Lett., 2020, 49, 845-854.

[2] Y. Hasegawa, M. Hasegawa, et al., Molecules, 2018, 23, 55.

[3] (a)K. Binnemans, Chem Rev, 2007, 107(6), 2592–2614; (b) M. Mukaigawa & H. Ohno, Solid State Ionics, 1998, 113-115, 439-442.

[4] Y. Kim & M. Hasegawa, et al., 2020, DOI:10.1021/acsami.0c13765.

Figure 1
(Invited) Beta, Beta-Functionalized Push-Pull Opp-Dibenzoporphyrins As Sensitizers for Dye-Sensitized Solar Cells: The Role of the Phenylethynyl Bridge and the Tertiary Amine Push Group
Authors: Wang Hong , Hu Yi , D'Souza Francis , Thomas Michael , Alsaleh Ajyal
Published: July 2021

Significant progress has been made on dye-sensitized solar cells sensitized by push-pull porphyrins in recent years.1-3 An effective way to significantly enhance power conversion efficiencies of porphyrin dyes is through installation of push (electron-donating) and pull (electron-withdrawing) groups at porphyrin meso-positions.4-6 In this presentation, we present a different strategy to install push and pull groups at porphyrin beta-positions. Three series of novel opp-dibenzoporphyrins were prepared using this strategy. Our studies show significant push-pull effects for these porphyrins.7 DFT calculations suggest that the inclusion of ethynylphenyl bridge between the donating group and porphyrin core significantly segregate the frontier orbitals, which is a much-favored feature for sensitizers in DSSC. The electronic and optical properties of these beta-extended porphyrins were measured using UV-Vis spectroscopy, life-time and steady state fluorescence spectroscopy, cyclic voltammetry and transient spectroscopy. Their photovoltaic performances were tested in dye-sensitized solar cells.

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M. Urbani, M. Gratzel, M. K. Nazeeruddin and T. Torres, Chem. Rev., 2014, 114, 12330-12396.

L. L. Li and E. W. Diau, Chem. Soc. Rev., 2013, 42, 291-304.

A. Yella, H.-W. Lee, H. N. Tsao, C. Yi, A. K. Chandiran, M. K. Nazeeruddin, E. W.-G. Diau, C.-Y. Yeh, S. M. Zakeeruddin and M. Grätzel, Science, 2011, 334, 629-634.

S. Mathew, A. Yella, P. Gao, R. Humphry-Baker, B. F. Curchod, N. Ashari-Astani, I. Tavernelli, U. Rothlisberger, M. K. Nazeeruddin and M. Gratzel, Nat. Chem., 2014, 6, 242-247.

G. Di Carlo, A. O. Biroli, F. Tessore, S. Caramori and M. Pizzotti, Coord. Chem. Rev., 2018, 358, 153-177.

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Rational Molecular Design of Nonfullerene Acceptors for Bulk Heterojunction Solar Cells
Authors: Imahori Hiroshi
Published: July 2021

Organic photovoltaics (OPVs) have received considerable attention as clean energy conversion devices because of their lightweightness, cost effectiveness, flexibility, and suitability for roll-to-roll printing. In the past few decades, the active layer of OPV devices has usually consisted of conjugated polymers as donors and fullerene derivatives as acceptors, which typically form a bulk heterojunction (BHJ) structure.1,2 The power conversion efficiency (PCE) of OPVs based on fullerene derivative acceptors has reached over 10%. However, it is difficult to further increase the PCE of fullerene-based OPVs due to their inherent limitations including arduous energy-level tunability and low absorption profile. To enhance the photovoltaic performance of OPVs, nonfullerene acceptors (NFAs) with aromatic fused-ring structures have been extensively developed in recent years to fabricate high-efficiency OPVs. Compared to traditional fullerene acceptors, NFAs possess several advantages, such as facile synthesis and high absorption profile. Most high-performance NFAs possess acceptor-donor-acceptor (A-D-A) type structures, in which fused multi-ring ladder structures are used as the D unit and 1,1-dicyanomethylene-3-indanone (IC) derivatives as the A unit.

In this talk I will give an overview of our recent studies on novel nonfullerene acceptors. In paticular, several nonfullerene acceptors possessing different D units have been designed and synthesized to address the relationship between the structure and the photophysical and photovoltaic properties of the A-D-A type nonfullerene acceptors.3,4

[1] T. Umeyama and H. Imahori, J. Mater. Chem. A (Feature Article), 2, 11545-11560 (2014).

[2] T. Umeyama and H. Imahori, Acc. Chem. Res.
52, 2046-2055 (2019).

[3] T. Umeyama, K. Igarashi, D. Sasada, Y. Tamai, K. Ishida, T. Koganezawa, S. Ohtani, K. Tanaka, H. Ohkita, and H. Imahori, Chem. Sci., 11, 3250-3257 (2020).

[4] T. Umeyama, K. Igarashi, D. Sasada, K. Ishida,T. Koganezawa, S. Ohtani, K. Tanaka, and H. Imahori, ACS Appl. Mater. Interfaces, 12, 39236-39244 (2020).
(Invited) Dipole Moment of Nonfullerene Acceptors: A Strategy for Green-Solvent Processed P3HT-Based Organic Solar Cells
Authors: Ie Yutaka
Published: July 2021

Organic solar cells (OSCs) based on poly(3-hexylthiophene) (P3HT) and nonfullerene acceptors have attracted steadily increasing attention due to their potential for large scale preparation at a low cost. However, irrespective of the demand for an environmentally sustainable non-halogenated process, P3HT/nonfullerene acceptors-based OSCs fabricated using a non-halogenated solvent are still limited due to the unclear strategies for controlling the properties of the blend-film. We developed new electron-accepting pi-conjugated compounds with low dipole moments for use in conjunction with nonpolar o-xylene as the green-solvent. In this presentation, the influence of acceptor structures on the green solvent process is discussed in detail.
Synthesis of Chiral Carbazole-Based Porphyrins and Bodipys
Authors: Maeda Chihiro
Published: July 2021

We have explored the synthesis and functionalization of carbazole-based porphyrins and BODIPYs showing NIR absorption and solid-state fluorescence. Here, we synthesized chiral carbazole-based porphyrins and BODIPYs. The former showed Cotton effect in the NIR region, while the latter showed CPL both in solution and in the solid state. In this presentation, chiroptical properties of this chiral dyes are reported.
Synthesis, Spectral and Electrochemical Studies of Phenothiazine Appended ‟Push-Pull” a3b Porphyrins and Their Utilization in Nonlinear Optics
Authors: Kumar Sandeep , Sankar Muniappan
Published: July 2021

Porphyrins are ubiquitous in nature [1] and playing a vital role in biological and material applications [2]. Particularly, ‘push-pull’ porphyrins are used in solar cells, nonlinear optics (NLO), toxic ion-sensing and catalysis [3]. Herein, we are reporting the facile synthesis of phenothiazine appended A3B porphyrins. The free base porphyrin, 5,10,15-tris(3-(N-ethylphenothiazinyl)-20-(4-nitrophenyl)porphyrin, H2A3B (1) and their metal Zn(II), Cu(II) and Ni(II) complexes were synthesized [4]. The phenothiazine appended A3B porphyrins exhibited red-shifted absorption and emission spectral features. We have also studied the electrochemical properties of all the synthesized porphyrins. ZnA3B (1a) porphyrin has shown cathodic shift for the first oxidation potential and marginal shift in reduction potential as compared to ZnTPP (Figure 1). The calculated ground state dipole moments of were in the range of 9.64-8.59D as compared to MTPPs (0.052-0.0013 D) and hence they are the potential candidates for NLO application. Ultrafast nonlinear optical (NLO) studies revealed strong two-photon absorption coefficients and cross-sections for these molecules. Further, femtosecond transient absorption studies demonstrated several ultrafast processes from various excited states in these push-pull porphyrin, useful for identifying the processes relevant for optical switching applications.

Figure 1: Molecular structures of synthesized porphyrins and their comparative UV-visible spectra in CH2Cl2 and Cyclic voltammograms in CH2Cl2 using TBAPF6 as supporting electrolyte at 298 K.

Reference

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2020, 49, 3198-3208.

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Figure 1
Synthesis, Photophysical and Electrochemical Studies of Β-Disubstituted Silver Corroles
Authors: Yadav Inderpal , Sankar Muniappan
Published: July 2021

β-Substituted corroles have been widely used in variety of applications and exhibit unique electronic and photophysical properties [1]. π-Extension at the β-position using functional groups such as phenylethynyl or pyrrolopyrazino induces intriguing stability and planarity of the macrocyclic core [2]. Keeping this in mind, a series of β-disubstituted silver tritolylcorroles (R2[TTC]Ag) have been synthesized via Pd-catalyzed reactions in good to excellent yields (Fig. 1a). Herein we are trying to investigate the effect of the various β-substituents such as methyl (Me), phenyl (Ph), methyl acrylate (MA) and phenylethynyl (PE) on photophysical and electrochemical properties. In cyclic voltammetric studies, the first oxidation potential of Me2[TTC]Ag 2 decreases (cathodic shift) by 70 mV compared to [TTC]Ag due the inductive effect of two methyl groups while in case of (MA)2[TTC]Ag 4, there is large anodic shift (170 mV) in the first oxidation potential probably due to strong electron withdrawing effect of two methyl acrylate group compared to 2 (Fig. 1b). Complex 4 depicted very high dipole moment (10.31 D), which could be utilized in NLO studies (Fig. 1c). We have investigated the effect of both electron-accepting and -donating substituents through single, double and triple bond on the macrocyclic ring using photophysical, theoretical and electrochemical studies. Complexes (2-5) exhibited remarkable broadening and increase in the intensity of red shifts of soret and Q bands of absorption spectra. Here, we have synthesized corroles with side extension of π-arm which helps in shifting of Q bands towards NIR region which could be helpful in PDT or optoelectronic applications.

Figure 1. (a) Molecular structures of R2[TTC]Ag; (b) Comparative Cyclic voltammograms (CVs) of [TPC]Ag, Me2[TTC]Ag and MA2[TTC]Ag complexes in CH2Cl2 at 298 K under argon atmosphere; (c) The directions of calculated dipole moment of MA2[TTC]Ag.

References

(a) R. Mishra, B. Basumatary, R. Singhal, G. D. Sharma and J. Sankar, ACS Appl. Mater. Interfaces
2018, 10, 31462–31471; (b) S. Gonglach, S. Paul, M. Haas, F. Pillwein, S. S. Sreejith, S. Barman, R. De, S. Müllegger, P. Gerschel, U. P. Apfel, H. Coskun, A. Aljabour, P. Stadler, W. Schöfberger and S. Roy, Commun.
2019, 10, 1–10; (c) W. Sinha, A. Mahammed, N. Fridman, Z. Gross, ACS Catal., 2020, 10, 3764–3772; (d) R. F. Einrem, A. B. Alemayehu, S. M. Borisov, A. Ghosh, O. A. Gederaas, ACS Omega
2020, 5, 10596–10601.

(a) P. Yadav, M. Sankar, X. Ke, L. Cong, K. M. Kadish, Dalton Trans.
2017, 46, 10014–10022; (b) M. Stefanelli, M. L. Naitana, M. Chiarini, S. Nardis, A. Ricci, F. R. Fronczek, C. Lo Sterzo, K. M. Smith, R. Paolesse, J. Org. Chem.
2015, 2015, 6811–6816; (c) B. Berionni Berna, S. Nardis, P. Galloni, A. Savoldelli, M. Stefanelli, F. R. Fronczek, K. M. Smith, R. Paolesse, Org. Lett.
2016, 18, 3318–3321.

Figure 1
Porphyrin Based Porous Materials for Catalytic Application
Authors: Lee Suk Joong
Published: July 2021

Porous materials (PMs) such as metal–organic frameworks (MOFs), porous coordination polymers (PCPs), porous organic polymers (POPs), and polymers with intrinsic microporosity (PIMs), have received much attention due to their wide range of applications including catalysis, separation, gas storage, drug delivery, biosensing, and imaging. Although they have been successfully obtained by various synthetic techniques, their preparations are still a major task because the translation of building blocks into well-defined structures is challenging. In this regard, metalloporphyrins would be good building blocks for the construction of such functional materials witnessed by a wide range of molecular architectures using porphyrin derivatives, such as molecular boxes, self-assembled arrays, CPs and MOFs with various applications. In addition, they are often used to fabricate various architectures and to mimic the extraordinary performances of enzymes. Particularly, the heterogenization of homogeneous catalysts, such as immobilization and/or site-isolation of homogeneous catalysts using supporters are widely used strategies. In this regard, I like to present the preparations and heterogeneous catalytic uses of metalloporphyrins in various porous materials.

References

D. Y. Shin, J. H. Yoon, S. H. Kim, H. Baik, S. J. Lee,* "Immobilization of Porphyrinic Mn(III) Catalyst on a New Class of Silica Support Comprising Three-Dimensionally Interconnected Network with Two Different Sizes of Pores",
Catal. Sci. Technol. 2018, 8, 6306-6310.

J. Yi, H. Y. Jeong, D. Y. Shin, C. Kim, S. J. Lee,* "Mn(III)-Porphyrin Containing Heterogeneous Catalyst based on Microporous Polymeric Constituents as a New Class of Catalyst Support",
ChemCatChem 2018, 10, 3974-3977.

J. Yi, H. M. Ahn, J. H. Yoon, C. Kim, S. J. Lee,* " Preparation of a bispyridine based porous organic polymers as a new platform for Cu(II) catalyst and its use in heterogeneous olefin epoxidation",
New J. Chem., 2018, 42, 14067-14070.
Multicomponent Layer-By-Layer Films of Chitosan/Phthalocyanine/AuNPs As Biosensing Platforms
Authors: Rodriguez-Mendez Maria Luz , Salvo-Comino Coral , Perez-Gonzalez Clara , Martin-Pedrosa Fernando , Garcia-Cabezon Cristina
Published: July 2021

The search of new biosensing platforms is crucial to improve the performance of electrochemical biosensors. In this work, Layer by Layer films containing combinations of materials with different functionalities were used to design electrochemical biosensor platforms for phenols detection [1-3]. Catechol and hydroquinone biosensors were obtained by depositing tyrosinase (Tyr) or laccase (Lac) on the surface of LbL films formed by alternating layers of chitosan (CHI), a cationic species which acted as enzyme linker, and layers of two anionic electrocatalytic materials (sulfonated copper phthalocyanine, CuPcS and citrate capped gold nanoparticles, AuNPs). Films with different sequences [(CHI)-(AuNPs)]2, [(CHI)-(CuPc)]2, [(CHI)-(CuPc)-(CHI)-(AuNPs)]2 [(CHI)-(AuNPs)-(CHI)-(CuPc)]2, and [(CHI)-(AuNPs/CuPc)]2 (with CuPcS and AuNP mixed in the same layer) were characterized by UV–visible, FTIR spectroscopy and AFM.

It was demonstrated that the resulting films provided an efficient immobilization surface for phenol oxidases. At the same time, the LbL platform improved the electron transfer between the enzymes and the electrode surface. Although all the biosensors obtained exhibited excellent performances, the sequence of the anionic and cationic layers strongly influenced the electron transfer process. The best results were obtained when CuPcS was present in the last layer which caused a 2-fold increase in the intensity over the response of the biosensor without the LbL platform. The [CHI-AuNP-CHI-CuPcS]2-Tyr bioelectrode showed an LOD of 8.7∙10-4 mM (S/N=3) for catechol and of 7.77∙10-4 mM (S/N=3) for hydroquinone. The LbL platform was not so efficient for laccase and the [CHI-AuNP-CHI-CuPcS]-Lac biosensor showed a LOD of 1.84∙10-2 mM (S/N=3) for catechol and of 1.27∙10-3 mM (S/N=3) for hydroquinone.

References

[1] C. Medina-Plaza, L.N. Furini, C.J.L. Constantino, J.A. De Saja, M.L. Rodriguez-Mendez, Synergistic electrocatalytic effect of nanostructured mixed films formed by functionalised gold nanoparticles and bisphthalocyanines, Anal. Chim. Acta. 851 (2014) 95–102. doi:10.1016/j.aca.2014.08.049.

[2] C. García-Hernández, C. García-Cabezón, F. Martín-Pedrosa, J. A. De Saja, and M. L. Rodríguez-Méndez, Layered composites of PEDOT:PSS/nanoparticles and PEDOT:PSS/phthalocyanines as electron mediators in sensors and biosensors, Belstein J. Nanotech. 7 (2016) 1948-1959

[3] E. G. R. Fernandes, L.C. Brazaca, M.L Rodríguez-Méndez, J.A. de Saja and V. Zucolotto, Immobilization of Lutetium Bisphthalocyanine in Nanostructured Biomimetic Sensors Using the LbL Technique for Phenol Detection, Biosens. Bioelectr. 26 (2011) 4715- 4719.

Acknowledgements

Financial support by MINECO-FEDER (RTI2018-097990-B-I00) and the Junta de Castilla y Leon FEDER (VA275P18) and AFM UVA01is gratefully acknowledged.
Photoelectrochemical Properties of Porphyrin-Functionalized Transition Metal Dichalcogenides
Authors: Ji Jaehoon , Zhang Hanyu , Choi Jong Hyun
Published: July 2021

Transition metal dichalcogenides (TMDCs) show promising electrochemical properties for the ultrathin and flexible light-harvesting devices due to their absorption in the visible range and high conversion efficiencies. In this work, we demonstrate a strong enhancement in photoelectrochemical conversion using porphyrin-functionalization on TMDCs and elucidate related light-harvesting mechanisms. We prepared large-area samples from Zn-centered protoporphyrins (ZnPPs) functionalized on films of liquid-exfoliated MoS2, WS2, MoSe2, and WSe2 flakes. WS2 and MoS2 demonstrate an order of magnitude greater anodic photocurrents with ZnPP functionalization, where ZnPP is working as photoactive layers. In contrast, MoSe2 and WSe2 serve as charge transfer media, demonstrating strong cathodic photocurrents with the porphyrins. Two distinct mechanisms were identified for observed photocurrent behaviors, which largely depend on the differences in the energy levels of TMDCs against the HOMO/LUMO of ZnPP. Our findings should be useful for designing high-performance TMDC-based photoelectrochemical devices.