bluuebunny/crossref_metadata_2025 huggingface dataset:
All‐Printed Wearable Triboelectric Nanogenerator with Ultra‐Charged Electron Accumulation Polymers Based on Mxene Nanoflakes
Authors: Kim Kyeong Nam
Published: December 2024

The multilayer triboelectric nanogenerators (TENGs) are widely developed to enhance the output performance of device. However, these TENGs consisting of electron transfer, transport, trap layers toward a large volumetric charge density should be wearable and mass-produced for commercialization. Thus, appropriate material selection in respective layers and fabrication method are crucial for the commercialization of multilayer TENG. This study presents all-printed, sustainable wearable TENGs based on electron accumulation polymers (EAPs) with superior charge retention capability. The EAPs consisting of polytetrafluoroethylene (PTFE), carboxyl functionalized single-walled carbon nanotubes (SWCNTs:COOH), and Ti3C2Tx (MXene) in a fluorinated polymer matrix, are used. Compared to the reference, the EAPs not only lead to approximately six times higher output performance (300 V and 40 µA) but also four times more sustainable charge retention capability (92%) for an hour. These are attributed to the three-step electron-trapping mechanism with electron transfer/transport from PTFE/SWCNT and electron trapping in MXene. In addition, TENGs with EAPs exhibit excellent mechanical stability and reliability with fascinating single-electrode demonstrations. Finally, the TENG with EAPs can efficiently operate various portable electronics and pH monitoring systems with a pH sensor and a seven-segment display in realistic scenarios.
Promoting Oxygen Evolution Reaction Induced By Synergetic Geometric and Electronic Eﬀects of Irco Thin-Film Electrocatalysts
Authors: Shin Haeyong , Kim Kyu-Su , Jung Sang-Mun , Kim Yong-Tae
Published: December 2024

The advancement of water electrolysis technology has seemingly plateaued. Further advances require new strategies to address the key limitations of the oxygen evolution reaction: high overpotential and low stability of electrode materials. Herein, we designed a nanoporous Ir3Co-core@IrO2-shell electrocatalyst with 5 and 3 times higher mass activity and 6 and 2 times higher activity–stability factors than conventional IrO2 nanoparticles and Ir nanoporous electrocatalysts, respectively. The origin of the performance enhancement in the Ir3Co-core@IrO2-shell electrocatalyst was revealed in computational density functional theory calculations. The residual Co after the dealloying process resulted in a down-shift of the d-band center position, thus weakening the −OH* adsorption energy. In addition, the electronic conductivity was enhanced by the three-dimensionally interconnected structure. Under high-current-density operating conditions, the Ohmic losses were reduced by the ultrafast charge transfer pathway provided by the metallic IrCo core.
P and Bi Doped Pt-Zn Alloy as an Effective Electrocatalyst for Hydrogen Evolution Reaction: A First-Principles Study
Authors: Park Yonghak , Han Byungchan
Published: December 2024

Platinum (Pt) is a highly effective catalyst for the hydrogen evolution reaction (HER), but its high cost and scarcity have spurred efforts to reduce Pt usage without compromising catalytic performance. Various strategies, such as alloying Pt with earth-abundant elements and doping with other elements to modify the electronic structure and improve activity, have been explored to achieve this objective.

In this study, we propose a phosphorus (P) and bismuth (Bi) doped Pt-Zn catalyst with a reduced platinum content and enhanced HER activity. Using First-Principles calculations, we identified the stable structure of the PtZn alloy and the optimal doping configurations of P and Bi. In addition, we calculated the adsorption energies of a key intermediate to construct the reaction free energy diagram, validating the enhanced catalytic activity of the P and Bi doped Pt-Zn catalyst. To gain atomistic-level insights, we performed detailed calculations to analyze the electronic structure of the doped configurations, revealing the role of these dopants in optimizing the electronic structure at the active sites. Our analysis demonstrates that the introduction of P and Bi not only stabilizes the catalyst structure but also effectively modifies the electronic properties to improve HER activity. This approach offers a promising pathway to develop cost-effective and high-performance Pt-based catalysts for electrochemical applications.
Tribute to Professor Baldassare Di Bartolo - Rino
Authors: Bettinelli Marco , Collins John , Mishra Kailash C , Zych Eugeniusz
Published: December 2024

In the realm of science, there are those whose brilliance illuminates not only the paths of discovery but also the hearts and minds of their colleagues and students. Professor Baldassare Di Bartolo stands as a beacon among such luminaries, a figure whose scientific achievements, contributions to the field, and service to society are nothing short of exemplary.

With a keen intellect and boundless passion, he has made indelible marks across multiple disciplines, leaving a legacy that enriches our understanding of the universe. Professor Di Bartolo's scientific achievements are monuments to his dedication and ingenuity. His groundbreaking research has expanded the boundaries of our comprehension, from the intricate workings of quantum mechanics to the mysteries of photonics and beyond. Through his pioneering work, he has unlocked new insights into the fundamental nature of light and matter, paving the way for transformative advancements.

Yet, Professor Di Bartolo's impact extends far beyond the confines of the laboratory. With a steadfast commitment to disseminating knowledge, he has served as a catalyst for intellectual exchange and collaboration. Through his tireless efforts in organizing conferences and seminars, he has fostered vibrant communities of scholars, fostering dialogue and cross-pollination of ideas that have propelled scientific inquiry forward.

However, perhaps the true measure of Professor Di Bartolo's greatness lies not merely in his scientific achievements but in the profound impact he has had on the lives of those around him. His wisdom, generosity, and unwavering support have shaped countless careers, nurturing the next wave of scientific pioneers who carry his legacy into the future.

Professor Baltassare Di Bartolo, Rino, we salute you not only for what you have accomplished but for the light you have kindled in the hearts of all who have had the privilege of knowing you.

Figure 1
(Invited) Photoluminescence and Scintillation Properties of Heavy Single Crystal Scintillators for X- and Gamma-Ray Detection
Authors: Yanagida Takayuki , Nakauchi Daisuke , Kato Takumi , Kawaguchi Noriaki
Published: December 2024

Scintillators are one of the luminescent materials, and have a function to convert a quantum of ionizing radiation to thousands of low energy photons immediately via interactions between the material and ionizing radiation [1,2]. Generally, scintillators are combined with photodetectors, and when the scintillation photons are emitted from the scintillator, photodetectors convert them to electrical signals. When the target ionizing radiation is high energy photons such as X- and gamma-rays, heavy materials are preferable for scintillators since the detection efficiency against high energy photons depends on density and effective atomic number. Up to now, many types of materials have been examined for scintillators, such as single crystals, glasses, and opaque and transparent ceramics [2]. Among them, bulk single crystalline scintillators have been applied for scintillation detectors owing to a superior optical quality including high transmittance and luminescence efficiency.

In the conference, some recent results of development of heavy scintillators mainly containing Lu, Hf, Ta and Tl are introduced. These materials were synthesized by some single crystal growth techniques such as the floating zone and bridgman method. After the synthesis, they were examined on optical (photoluminescence excitation and emission spectra and decay curve) and scintillation (scintillation emission spectrum, decay curve, afterglow and pulse height) properties. In Lu-based crystals, rare earth doped Lu2O3 crystals are introduced, and especially, Tb- and Eu-doped ones show a high scintillation light yield. In Hf-based ones, some results of rare earth doped AEHfO3 (AE = alkali earth) crystals are presented, and Ce-doped (Mg,Ca)HfO3 shows a high scintillation light yield [3]. Among Ta-based crystals, Mg4(Nb,Ta)2O9 crystals have a high light yield due to charge transfer luminescence of Ta/Nb and O [4]. In Tl-based crystalline compounds, TlMgCl3 shows a high light yield and energy resolution [5]. In the conference, these results will be introduced.

References

[1] T. Yanagida, Proc. Jpn. Acad., Ser. B, Phys. Biol. Sci., 94(2) 75 (2018).

[2] T. Yanagida, T. Kato, D. Nakauchi, N. Kawaguchi, Jpn. J. Appl. Phys., 62 010508 (2023).

[3] H. Fukushima, D. Nakauchi, T. Kato, N. Kawaguchi, T. Yanagida, Jpn. J. Appl. Phys., 62 010506 (2023).

[4] T. Hayashi , K. Ichiba, D. Nakauchi, K. Watanabe, T. Kato, N. Kawaguchi, T. Yanagida, J. Lumin., 255 119614 (2023).

[5] Y. Fujimoto, M. Koshimizu, T. Yanagida, G. Okada, K. Saeki, K. Asai, Jpn. J. Appl. Phys., 55 090301 (2016).
Synthesis of Blue-Light Emitting Ag-Ga-S Quantum Dots for LED Application
Authors: Tozawa Makoto , Ofuji Shuto , Akiyoshi Kazutaka , Kameyama Tatsuya , Motomura Genichi , Fujisaki Yoshihide , Uematsu Taro , Kuwabata Susumu , Torimoto Tsukasa
Published: December 2024

Quantum dots (QDs), semiconductor nanocrystals smaller than 10 nm, can have their energy gap (Eg) adjusted by size due to the quantum size effect. So far, binary chalcogenide QDs, such as CdSe and PbS, have been widely investigated for their applications to liquid crystal displays and light-emitting diodes (LEDs), because they exhibit sharp photoluminescence (PL) peak with high quantum yields (QYs) and the PL peak wavelength can be controllable with the QD size. However, the use of toxic heavy metals such as Cd and Pb in these QDs poses significant environmental and health risks. To address this, we have developed multinary QDs using less toxic materials, such as Ag-In-Ga-S (AIGS), which exhibit sharp band-edge emission tunable from 500 to 600 nm by adjusting the In/Ga ratio [1]. Surface coating with gallium sulfide (GaSx) shell enhanced the peak intensity of band-edge emission due to the removal of the surface defect sites. We also successfully prepared green-light-emitting QD-LEDs with the use of AIGS QDs [2]. In this study, we report the synthesis of blue-light emissive QDs with AgGaS2 semiconductor, the bulk Eg of which is 2.7 eV. The obtained QDs exhibited a band-edge PL peak with a narrow peak width. These AgGaS2 QDs have been successfully utilized in the fabrication of blue-light QD-LEDs.

AgGaS2 QDs were synthesized by heating corresponding metal precursors and sulfur compounds in a mixture of oleylamine and 1-dodecanethiol. The resulting QDs were surface-coated with GaSx shell. TEM analysis revealed that spherical or polygonal nanoparticles with an average size of ca. 5 nm were formed. It was found from XRD measurements that the AgGaS2 QDs had a tetragonal crystal structure. Absorption spectra of AgGaS2 QDs were blue-shifted from ca. 460 nm to 450 nm with a decrease in the Ag/Ga ratio in the precursors. The obtained QDs exhibited a sharp band-edge PL peak at ca. 450 nm as well as a broader defect-site emission peak at longer wavelengths. The surface coating with GaSx shell to form core-shell-structured AgGaS2@GaSx QDs enhanced the band-edge PL peak, the peak width of which was 22nm. This was probably because the deposition of the GaSx shell eliminated surface defect sites acting as a non-radiative recombination site on AgGaS2 cores. QD-LEDs were fabricated with thus-obtained blue-emitting QDs as an electroluminescence layer. The resulting QD-LEDs exhibited a sharp electroluminescence peak at ca. 450 nm with an external quantum efficiency of 0.66%, demonstrating their potential in blue-light QD-LED applications.

References

[1] T. Kameyama, et al., ACS Appl. Mater. Interfaces
2018, 10, 42844-42855.

[2] G. Motomura, et al., ACS Appl. Mater. Interfaces
2023, 15, 8336–8344.
(Invited) Synergistic Interactions of Co-Dopants for Phosphor Functionalization
Authors: Zych Eugeniusz , Kulesza Dagmara , Zeler Justyna , Bukowska Paulina , Łukaszczuk Pola K. , Sójka Małgorzata , Carlos Luis D. , Brites Carlos D.S.
Published: December 2024

The functionalization of phosphors through co-dopant interactions represents an effective and encouraging avenue for enhancing their luminescent characteristics. Co-doping introduces additional dopant species into the host lattice, leading to intricate interactions that influence the material's luminescence behavior. The synergistic effects arising from co-dopant interactions result in tailored luminescent characteristics, including emission wavelength tuning and improved performance in diverse applications such as lighting, displays, biomedical imaging, temperature measurement, and thermal imaging. By elucidating the intricacies of co-dopant interactions, this research contributes to the rational design and optimization of functionalized phosphors for advanced technological applications. By carefully selecting and controlling the dopants, researchers can tailor the luminescent characteristics of phosphors to meet specific requirements, thereby unlocking their full potential. This presentation focuses primarily on possible advantages of using this approach in luminescence thermometry and thermal imaging.

Co-activating phosphors facilitates the development of multifunctional materials with diverse, not only luminescent, properties. By carefully selecting dopant combinations, controlling their concentrations, and managing the technological parameters, precisely designed phosphors exhibiting multi-modal functionalities can be fabricated.

In the presentation, we will show examples of the effective use of co-doping phosphors with selected lanthanide ions or a lanthanide and a d-element. An exemplary case is presented in Figure 1, where temperature-dependent luminescence spectra of a triply-activated strontium aluminate phosphor are presented together with the relative thermal sensitivities derived from decay times of the different emissions.

The Polish National Science Centre (NCN) financed the research under OPUS grant #UMO2023/49/B/ST5/04265.

Figure 1
Temperature Dependence of Mn4+ Emission Intensity and Lifetime in TriGain® Phosphor (K2SiF6:Mn4+)
Authors: Cohen William Erwin , Du Fangming , Beers William Winder , Brik Mikhail G. , Srivastava Alok M.
Published: December 2024

The modern-day pc-LEDs for general illumination is based on a blue-emitting InGaN chip coated with a blend of two phosphors, a green-yellow Cerium-doped garnet phosphor and a red phosphor which is required to induce a “warm-white” color temperature (2700–3500 K). Currently, one of the phosphors that satisfies the key performance requirements of a red emitter for white light pc-LED is the K2SiF6:Mn4+ (PFS/KFS) phosphor [1-3]. The phosphor is manufactured by Current Chemicals and sold under the trade name, TriGain®.

In this talk the temperature dependence of the Mn4+ luminescence and lifetime in TriGain® is discussed (Figure 1). The results are discussed in terms of dynamically induced increase in emission intensity and decay rate coupled with an Arrhenius-type thermal quenching. The parameters of our fitting to physical models are compared with those reported on laboratory synthesized K2SiF6:Mn4+ phosphor. This comparative study sheds light on factors responsible for non-radiative relaxation processes, which is fundamental to the understanding of phosphor quantum efficiency and performance. Due to low thermal conductivity of K2SiF6, it was necessary to develop protocols to ensure that the surface temperature of the phosphor was close to that of the cold finger in the closed cycle He cryostat. These will be discussed.

References:

M.G. Brik and A.M. Srivastava, J. Lumin., 133, 69 (2013).

W.E. Cohen, F. Du, W. W. Beers and A. M. Srivastava, ECS J. Solid State Sci. Technol., 12, 076004 (2023)

W.W. Beers, W. E. Cohen, A. M. Srivastava, ECS J. Solid State Sci. Technol.,12 (2023) 116002.

Figure 1
(Invited) Applications of Mn4+ and Cr3+ Ions for Lighting and Optical Thermometry
Authors: Brik Mikhail G. , Dramicanin Miroslav , Srivastava Alok M. , Beers William Winder , Cohen William E. , Piasecki Michal , Ma Chong-Geng , Kurboniyon Mekhrdod , Yamamoto Tomoyuki
Published: December 2024

Transition metal ions with the 3d3 electron configuration (Cr3+ and Mn4+, in particular) are widely used for the lighting (red and deep red emission) and non-contact optical thermometry. This is due to their specific energy level scheme and favorable relative position of the spin-quartet state 4T2 and spin-doublet state 2E. Complicated interplay of electronic properties of impurity ions and host materials (covalent bonding between dopants and ligands) is the main reason for wide tunability of emission wavelength of such phosphors. The main goal of this presentation is to review the fundamental spectroscopic properties of Mn4+ and Cr3+ ions to illustrate the fundamental role of the “structure-optical property” relationships and to illustrate how such studies can have applied importance as useful guides facilitating search for new efficient phosphors [1-9].

References:

[1] M. G. Brik, A. M. Srivastava J. Lumin. 133 (2013) 69.

[2] M.G. Brik, S. J. Camardello, A. M. Srivastava, ECS J. Solid State Sc. and Technol. 41 (2015) R39.

[3] M. G. Brik, W. W Beers, W. Cohen, S. A. Payne, N. J. Cherepy, M. Piasecki, A. M. Srivastava, Opt. Mat. 91 (2019) 338.

[4] W. W Beers, D. J. Smith, W. E. Cohen, A. M. Srivastava, Opt. Mat. 84 (2018) 614.

[5] A. M. Srivastava, H. A. Comanzo, D. Smith, J. W. Choi, M. G. Brik, W. W. Beers, S. A. Payne, J. Lumin. 06 (2019) 398.

[6] M. Dramićanin, B. Milićević, V. Đorđević, Z. Ristić, J. Zhou, D. Milivojević, J. Papan, M. G. Brik, C-G Ma, A. M. Srivastava, ChemistrySelect. 4 (2019) 7067.

[7] J. Ueda, M. Back, M. G. Brik, Y. Zhuang, M. Grinberg, S. Tanabe, Opt. Mat., 85 (2018) 510.

[8] L. Marciniak, K. Kniec, K. Elżbieciak-Piecka, K. Trejgis, J. Stefanska, M. Dramićanin, Coord. Chem. Rev., 469 (2022) 214671.

[9] Y. Qin, F. Zhong, Y. Bian, S. Hariyani, Y. Cao, J. Brgoch, T. Seto, M. G. Brik, A. M. Srivastava, X. Wang, Y. Wang, Inorg. Chem., 61 (2022) 8126.
Optimizing Multifunctional Phosphors: Thermoluminescence and Luminescence Thermometry Processes
Authors: Zeler Justyna , Grzesiak Dominika , Małoń Aleksandra , Owczarek Aleksandra , Carlos Luis D. , Zych Eugeniusz
Published: December 2024

Multifunctional phosphors are extremely important in various applications, ranging from lighting to biomedical purposes. By employing thermoluminescence and luminescence thermometry-related techniques, the intricate processes governing the luminescent behavior of these phosphors can be better understood and controlled.

Our study focuses on investigating the thermometric and thermoluminescent properties of Cr3+-activated aluminate family materials, with a specific focus on the effects of co-doping with various lanthanide ions. Through systematic analysis, we aim to understand the influence of lanthanide co-doping on the temperature response and thermoluminescent properties of the phosphors, which can offer valuable insights into using these materials in biological applications.

The ultimate goal of our project is to incorporate these functionalized materials into cancer cells and understand their optical characteristics as theranostic materials, as shown in Figure 1. We will comprehensively examine physical processes related to thermo- and persistent luminescence and other thermally stimulated emissions in designed luminescent materials. Our goal is to gain valuable insights into optimizing their functionalities for future bio- and medical applications.

The research finances by the Polish National Science Centre under OPUS grant #UMO2023/49/B/ST5/04265.

Figure 1
Thermally Invariant, Highly Sensitive, Ratiometric Luminescent Manometry Based on Cr3+ Emission
Authors: Szymczak Maja , Runowski Marcin , Wozny Przemyslaw , Marciniak Lukasz
Published: December 2024

Pressure measurement leveraging the spectral response of a luminophore, known as luminescence manometry, presents numerous significant advantages over alternative detection methods, including rapid and dynamic response, electrical passivity, minimal invasiveness, and the capability for remote readings. Despite its recognition since the 1970s[1], the technique exhibits certain limitations. The current mainstream approach, employing a spectral shift of the 2E→4A2 band in Al2O3:Cr3+, offers high precision readouts but lacks sensitivity independence. Moreover, two-dimensional mapping of pressure variations using this methodology proves to be both time-consuming and economically burdensome.

To surmount these obstacles and facilitate thermally independent imaging of pressure changes, a novel technique is proposed that utilizes the ratio of emission intensities from the broad 4T2→4A2 band of Cr3+ ions, integrated across two distinct spectral regions[2-4]. The variation in crystal field strength impacting the Cr3+ ions, due to the compression of the material, prompts a shift in the spectral band, thereby altering the Luminescence Intensity Ratio (LIR) value. Conversely, temperature fluctuations have negligible (if any) impact on the spectral positioning of this band. Consequently, the application of this innovative method enables the realization of thermally independent imaging of pressure alterations. The practical viability of this strategy will be substantiated through various experimental demonstrations.

References

[1] R. A. Forman, G. J. Piermarini, J. Dean Barnett, S. Block, Science, 176, (1972) 284.

[2] M. Szymczak, P. Woźny, M. Runowski, M. Pieprz, V. Lavín, L. Marciniak, Chem Eng J, 453 (2022) 139632.

[3] M. Szymczak, M.Runowski, M.G. Brik, L. Marciniak, Chem Eng. J. 466 (2023) 143130.

[4] M. Szymczak, J. Jaskielewicz, M. Runowski, J. Xue, S, Mahlik, L. Marciniak, , Adv Funct Mater (2024) DOI: 10.1002/adfm.202314068.

Acknowledgements

This work was supported by the National Science Center (NCN) Poland under project no. DEC-UMO- 2020/37/B/ST5/00164.
Fabrication of (K,Rb)2CuCl3 and (K,Rb)2CuBr3 Single Crystal Scintillators with Efficient Luminescence
Authors: Yamabayashi Keishi , Okazaki Kai , Nakauchi Daisuke , Kawaguchi Noriaki , Kato Takumi , Yanagida Takayuki
Published: December 2024

Scintillators are phosphor materials that emit many low-energy photons upon exposure of high-energy ionizing radiation such as X- and γ-rays. They have been utilized in combination with photodetectors for radiation measurements, including medical imaging [1], underground resources exploration [2], luggage inspection [3], and structural analysis of materials [4]. The required characteristics of scintillators are different depending on the applications. For example, high light yield (LY) for high energy resolution and high signal-noise ratio, short decay time for high time resolution, large effective atomic number for high interaction probability with ionizing radiation, and low hygroscopicity for long-term usability are important. Halide crystals such as Tl-doped CsI and NaI have been utilized as practical scintillators because of their high LY owing to the medium bandgap energy (5.8–6.3 eV) [4, 5]. However, most halide crystals have issues related to chemical instability due to hygroscopicity. Thus, novel non-hygroscopic scintillators with high LY have been desired.

Nowadays, Cu-based halide scintillators have received attention owing to good properties such as high photoluminescence quantum yield (PLQY), scintillation LY, and no hygroscopicity. We have focused on the alkali copper halide group such as A
2CuX
3 (A = K, Rb X = Cl, Br). They showed high PLQY (~100%) attributed to the recombination of self-trapped excitons under UV and X-ray irradiations [6, 7]. However, their scintillation LYs under γ-rays have not been clarified. According to Hume-Rothery rules [8], a continuous solid solution containing two or more components can be easily formed when two substances with similar ionic radius and crystal structure are partially mixed in the matrix. In continuous solid solutions, emission properties of phosphors were improved by optimizing energy levels in the bandgap and lattice defects involved in the luminescence [9]. On the basis of the rules, the continuous solid solutions of (K,Rb)2CuCl3 and (K,Rb)2CuBr3 can be grown. Thus, we fabricated (K,Rb)2CuCl3 and (K,Rb)2CuBr3 to enhance the scintillation properties. In this presentation, the scintillation properties such as the X-ray-induced scintillation spectra, the scintillation decay curves, afterglow curves, and pulse-height spectra of 1
37Cs γ-rays (662 keV) measurements will be presented.

[1] C.W. Eijk., Phys. Med. Biol., 47 (2002) R85. [2] A. Nikitin et.al., IEEE Nucl. Sci. Symp. Med. Imag. Conf. (2010) 1214. [3] V.D. Ryzhikov et.al., IEEE Symposium Conference Record Nuclear Science (2004) 4291. [4] V.V. Nagarkar et.al., IEEE Trans. Nucl. Sci.
45 (1998) 492. [5] M. Moszynski et.al., Nucl. Instrum. Methods Phys. Res. A (2004) 4291. [6] T.D Creason et.al., Chem. Mater.
32 (2020).
Electrocatalytic Hydrogenation of Pyridines in an Anion-Exchange Membrane (AEM) Reactor and Its Mechanistic Analysis by in Situ XAFS Measurement
Authors: Harada Juri , Shimizu Yugo , Yonezawa Akizumi , Kurihara Ryo , Iguchi Shoji , Kamiya Kazuhide , Shida Naoki , Atobe Mahito
Published: December 2024

Cyclic amines are useful compounds used as building blocks of pharmaceuticals. According to the US Food and Drug Administration (FDA), approximately 20 % of small molecular pharmaceuticals contain cyclic amines, which can be obtained by hydrogenation of nitrogen-containing aromatic compounds. Notably, piperidines are prominent among inhibitor, antihistamine, and anesthetic. [1]

A number of reactions using homogeneous [2] and heterogeneous [3] catalysts have been reported for the production of cyclic amines via hydrogenation of nitrogen-containing aromatic compounds. However, these require high temperature and high-pressure conditions and H2 gas as a reductant, leading to a large amount of energy consumption and CO2 emission. In addition, acid is also used in these hydrogenation reactions to activate the nitrogen-containing aromatic compounds in some cases. However, this procedure requires neutralization and purification processes in the reaction workup, and causes corrosion of the reactor. In contrast, electrochemical hydrogenation of nitrogen-containing aromatic compounds is a promising method because electrochemical reactions can be carried out under mild conditions. For example, the reduction of pyridine to piperidine requires six electrons and six protons. However, it is difficult to obtain the desired piperidine by direct electron transfer through conventional cathodic reduction because of the formation of radical anions, resulting in dimerization and partial hydrogenation reactions. [4]

In this work, we developed an electrocatalytic hydrogenation system using an anion exchange membrane (AEM) reactor. Using an AEM reactor equipped with carbon-supported Rh as the cathode catalyst, the hydrogenation of pyridine to piperidine was achieved at ambient temperature and pressure without any additives in the catholyte.

To gain insights into the reduction behavior of carbon-supported Rh during electrolysis, we also performed Rh K-edge in situ X-ray absorption fine structure (XAFS) measurements using a tailor-made AEM reactor equipped with polyimide windows for the X-rays. As a result, Rh (0) was found to be an active catalyst for the electrocatalytic hydrogenation of pyridine.

The authors gratefully acknowledged support by JST CREST Grant No. JP65R1204400, Japan.

[1] E. Vitaku, D. T. Smith, and J. T. Njardarson, J. Med. Chem.
2014, 57, 10257–10274.

[2] R. Adam, J. R. Cabrero-Antonino, A. Spannenberg, K. Junge, R. Jackstell, and M. Beller, Angew. Chem.
2017, 129, 3264–3268.

[3] K. Murugesan, V. G. Chandrashekhar, C. Kreyenschulte, M. Beller, R. V. Jagadeesh, Angew. Chem. Int. Ed.
2020
, 59, 17408–17412.

[4] J. G. Keay Comprehensive Organic Synthesis
1991, 8, 579-602.

Figure 1
Phenol-Mediated Proton Shuttling Enables Electrochemical Hydrogenation of Phenol in Alkaline Electrolytes on Rhodium
Authors: Markunas Brianna , Snyder Joshua David
Published: December 2024

Thermal chemical hydrogenation (TCH) is a key reaction for upgrading petroleum and biomass feedstocks to value- added fuels and chemicals. TCH requires high operating temperatures and pressures which results in high energy consumption and CO2 emissions. Electrochemical hydrogenation (ECH) is a mild alternative where applied potential drives the hydrogenation of hydrocarbons with protons from the aqueous electrolyte near ambient conditions. Phenol is a simple representative compound for renewable lignocellulosic feedstocks that has been the focus of recent ECH studies. The added complexity from the electrolyte and applied potential in aqueous ECH systems requires a fundamental understanding of these reaction parameters on ECH activity in-order to overcome current limitations, including faradaic efficiency losses to the competitive hydrogen evolution reaction (HER). Furthermore, the wide range of reaction conditions employed in the phenol ECH literature makes comparison of the ECH performance difficult. Phenol ECH on PGMs is commonly performed in electrolytes in a pH range of 1-5, assuming that the ECH of phenol follows a Langmuir Hinshelwood (LH) mechanism [1, 2]. One study reported a 95% faradaic efficiency (FE) for phenol ECH on rhodium at pH 10 [3], but no further investigation into the source of this promising activity at alkaline pH has been conducted.

In this work we study the role of electrolyte pH on phenol ECH on platinum and rhodium. We show that there are differing pH trends for ECH activity between platinum and rhodium, with the highest ECH rates on platinum at pH 1 and the highest rates on rhodium at pH 9, near the pka of phenol. We show using cyclic voltammetry and in-situ electrochemical FTIR that this pH dependent behavior results from the interplay between hydrogen adsorption kinetics, differences in phenol/hydrogen coverage on each metal, and competition with HER. We show that the electrolyte pH dictates the balance between a hydrogen atom transfer (LH) mechanism and a phenol-mediated proton coupled electron transfer mechanism. With this insight, we show that the unique properties of rhodium and the acid-base chemistry of phenol and the electrolyte buffer can be leveraged for higher ECH rates and FE.

[1] Singh, N., et al., Aqueous Phase Catalytic and Electrocatalytic Hydrogenation of Phenol and Benzaldehyde over Platinum Group Metals. Journal of Catalysis 2020, 382, 372–384. https://doi.org/10.1016/j.jcat.2019.12.034.

[2] Song, Y., et al., Integrated Catalytic and Electrocatalytic Conversion of Substituted Phenols and Diaryl Ethers. Journal of Catalysis 2016, 344, 263–272. https://doi.org/10.1016/j.jcat.2016.09.030.

[3] Song, Y., et al., Aqueous Phase Electrocatalysis and Thermal Catalysis for the Hydrogenation of Phenol at Mild Conditions. Applied Catalysis B: Environmental 2016, 182, 236–246. https://doi.org/10.1016/j.apcatb.2015.09.027.
Paired Electrosynthetic Oxidations Using Multifunctional Ionic Liquids
Authors: Walsh Darren Anthony
Published: December 2024

The study of electrochemical oxidations has wide-ranging implications, from the development of new electrocatalysts for fuel cells for energy conversion, to the synthesis of fine chemicals. 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) has been used for decades as a sustainable, metal-free mediator for chemical and electrochemical oxidations. We describe here a novel approach to TEMPO-mediated electrooxidations, in which the chemical input and waste generated during electrooxidations of alcohols are minimized by using a paired flow electrosynthesis in a multi-functional solvent. Our three-pronged approach involves the following: (1) the use of a recyclable alkylimidazolium-based, room temperature ionic liquid (RTIL) to replace the electrolytes and volatile organic solvents typically used in TEMPO-mediated alcohol electrooxidations; (2) generation of required base at the counter electrode through reduction of the cationic component of the recyclable RTIL; (3) incorporation of the catalytic TEMPO moiety in our RTIL-based system. We demonstrate the possibilities offered by our strategy using a range of alcohol and allylic oxidations, illustrating the scope of reaction that can be driven using our strategy, and demonstrating the opportunities offered by RTILs to the development of task-specific, multi-functional electrolytes for electroorganic synthesis.
An Electrochemiluminescence Device Powered By Streaming Potential for the Detection of Amines
Authors: Inagi Shinsuke , Suzuki Rintaro , Iwai Suguru , Villani Elena , Sato Kosuke , Hasegawa George , Ishizuka Norio , Matsukawa Kimihiro
Published: December 2024

Herein, we report the design, development and optimization of an electrochemiluminescence (ECL) device powered by streaming potential for the detection of amines in flowing solution that can be activated without the need of an electric power supply (Figure 1). The device is based on the concept of streaming potential-driven bipolar electrochemistry [1,2], in which a flow of electrolytic solution passing through a microchannel with charged walls under a pressure gradient causes a streaming potential (E
str) as the driving force of bipolar electrodes (BPE).

In this study, we explored several experimental parameters to find the optimal operating conditions to drive the coreactant-type ECL reaction of a benzothiadiazole-triphenylamine (BTD-TPA) derivative in our streaming potential-driven device. The ECL emission was successfully detected by a photomultipulier tube (PMT), a digital camera and a spectrometer under the optimized electrolyte conditions including tripropylamine (TPrA) as a coreactant. Finally, we tested the ECL detection of several amines used as coreactants with the device.

References:

I. Dumitrescu, R. K. Anand, S. E. Fosdick, R. M. Crooks, J. Am. Chem. Soc., 2011, 133, 4687.

S. Iwai, T. Suzuki, H. Sakagami, K. Miyamoto, Z. Chen, M. Konishi, E. Villani, N. Shida, I. Tomita, S. Inagi, Commun. Chem., 2022, 5, 66.

Figure 1
Synthesis of Tetrabutylammonium Tri(1,1,1,3,3,3-hexafluoro-2-propanol)-Coordinated Fluoride and Its Application to Anodic Fluorination
Authors: Mochizuki Aika , Homma Haruka , Kitajima Nobutaka , Tajima Toshiki
Published: December 2024

Organofluorine compounds are widely used in pharmaceuticals, agrochemicals, and functional materials due to their specific properties. However, organofluorine compounds are rarely found in nature. Therefore, organofluorine compounds must be synthesized using fluorinating agents. While Hydrogen fluoride (HF) is the most typical nucleophilic fluorinating agent, it is toxic and corrosive. Furthermore, HF is a gas at room temperature, making it difficult to handle in the ordinary laboratory. On the other hand, potassium fluoride (KF) is one of the safest and cheapest fluorinating agents, but KF is insoluble in most organic solvents. In contrast, 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) dissolves KF at high concentrations.

Tetrabutylammonium fluoride (TBAF) is a highly reactive fluorinating agent that is soluble in organic solvents. However, preparation of anhydrous TBAF is difficult, because TBAF readily forms hydrates due to its high hygroscopicity. The reaction of tetrabutylammonium cyanide with hexafluorobenzene is one of the most promising methods for the synthesis of TBAF. On the other hand, TBAF-alcohol complexes such as TBAF(t-BuOH)4 have been reported as fluorinating agents with low hygroscopicity. With these facts in mind, we investigated the synthesis of TBAF from KF based on the ion exchange reaction between KF and tetrabutylammonium bromide (TBABr) in HFIP in this work.

First, TBAF was synthesized by the ion exchange reaction between KF and TBABr in HFIP. 1H and 19F NMR measurements of the obtained product revealed that it is not TBAF but TBAF(HFIP)3 with three molecules of HFIP coordinated to TBAF. The TBAF(HFIP)3 was obtained in excellent yield without complicated operations. Next, anodic fluorination of a sulfide was investigated using TBAF hydrate or TBAF-alcohol complexes. As results, the corresponding fluorinated product was obtained in good yield only when TBAF(HFIP)3 was used. These results may be due to the low nucleophilicity and oxidation resistance of HFIP. From these results, TBAF(HFIP)3 would be a promising new supporting electrolyte and fluorinating agent.

Figure 1
Transition-Metal-Catalyst-Free Electroreductive Hydroarylation of Alkenes with Aryl Halides
Authors: Yamamoto Kosuke , Arita Kazuhisa , Shiota Masashi , Kuriyama Masami , Onomura Osamu
Published: December 2024

The radical hydroarylation of alkenes provides synthetically valuable linear alkylarenes with high anti-Markovnikov selectivity. Aryl halides are ideal radical precursors owing to their chemical stability and wide commercial availability. Over the past few decades, electrochemistry has proven to be an convenient approach for accessing open-shell intermediates through a single-electron transfer process, and the electroreduction of aryl halides has been demonstrated as a powerful method to generate aryl radical species.1 Despite recent progress in the development of aryl radical-involved electroreductive coupling reactions, the reported intermolecular radical hydroarylation of alkenes without transition-metal catalysts still has some drawbacks, such as the use of a Hg pool cathode and liquid NH3 solvent.2

Hearin, we report a transition-metal-catalyst-free elctroreductive hydroarylation of alkenes using aryl halides as radical precursors. The hydroarylation was performed in acetonitrile using an undivided cell equipped with an Al anode and a Pt cathode, and the use of 1,3-dicyanobenzene as a redox mediator under visible-light irradiation enabled the desired transformation to proceed with high efficiency. Electron-deficient (hetero)aryl chlorides and electron-rich aryl iodides successfully reacted with various Michael acceptors and styrene derivatives, providing a variety of linear alkylarenes in good to high yields. Mechanistic investigations indicated that this transformation would proceed through a reductive radical-polar crossover pathway.

(1) Xiang, H.; He, J.; Qian, W.; Qiu, M.; Xu, H.; Duan, W.; Ouyang, Y.; Wang, Y.; Zhu, C. Molecules
2023, 28, 857.

(2) Chami, Z.; Gareil, M.; Pinson, J.; Savéant, J.-M.; Thiébault, A. J. Org. Chem. 1991, 56, 586–595.

Figure 1
Synthesis of Thienoacenes By Electrochemical Double C–S Cyclization Promoted By a Halogen Mediator
Authors: Mitsudo Koichi , Nagahara Takuya , Suga Seiji
Published: December 2024

Thienoacenes, sulfur-containing π-conjugated molecules, have been widely used as active compounds for organic materials such as organic field-effect transistors (OFETs) and organic photovoltaics (OPVs). In particular, thienoacenes bearing thieno[3,2-b]thiophene (TT) moieties, such as [1]benzothieno[3,2-b][1]benzothiophene (BTBT), dinaphtho[2,3-b:2’,3’-f]thieno[3,2-b]thiophene (DNTT), and dibenzo[d,d’]thieno[3,2-b;4,5-b’]dithiophene (DBTDT), exhibited excellent OFET properties. While there have been many reports on the synthesis of thienoacenes, one of the most efficient ways to synthesize such thienoacenes is multiple C–S bond formation in one step. Because unprotected S–H bonds are easily oxidized to S–S bonds, protection of the S atom is often required and methyl protection has been used widely. For instance, Takimiya and co-workers reported the reaction of bis(naphthalenyl)ethene bearing two methylsulfanyl groups with an excess amount of iodine to afford a highly π-expanded thienoacene such as DNTT.1 While this strategy is efficient for constructing a BTBT skeleton, an excess amount of iodine was required, and highly π-extended substrates could only be applicable. Therefore, developing an efficient method for the one-step construction of multiple C–S bonds is still challenging, and it should be a powerful tool to construct thienoacenes efficiently.

We recently reported an electrochemical dehydrogenative C-S bond formation to synthesize thienoacenes.2 This time, we developed a more straightforward method to construct thienoacenes: an electrochemical approach for synthesizing BTBT derivatives from S-protected bis(o-sulfanylphenyl)acetylene derivatives. In the presence of Bu4NBr as a halogen mediator, electrochemical double C–S cyclization proceeded smoothly. Using the Bu4NBr as a mediator is important, and only a trace amount of the desired product was obtained without Bu4NBr. Appropriate protection was also essential for the reaction. While S-Me or S-p-methoxybenzyl (PMB) protected bis(o-sulfanylphenyl)acetylenes did not afford BTBT and bromocyclized products were obtained, the electrochemical reaction of S-MOM protected bis(o-sulfanylphenyl)acetylenes afforded BTBT derivatives selectively. Adding H2O was required for efficient reaction progression, which works as a sacrificial agent and a trapping agent for the eliminated MOM group. Various symmetrical and asymmetrical BTBT derivatives were obtained under the optimal conditions. The S-MOM protection strategy is also effective for the electrochemical synthesis of a more π-expanded thienoacene, such as DBTDT.

(1) Yamamoto, T.; Takimiya, K. J. Am. Chem. Soc.
2007, 129, 2224–2225.

(2) Mitsudo, K.; Matsuo, R.; Yonezawa, T.; Inoue, H.; Mandai, H.; Suga, S. Angew. Chem., Int. Ed.
2020, 59, 7803–7807.

Figure 1
Autonomous and Closed-Loop Exploration and Optimization of Bioelectrocatalytic Systems
Authors: Pence Michael A. , Boucher Dylan G. , Nguyen Zachary A , Rodriguez Lopez Joaquin , Minteer Shelley D.
Published: December 2024

Automated electrochemistry platforms provide a pathway for speeding up the discovery and optimization of electrochemical systems, especially when a broad range of molecules and reaction conditions must be explored.1-3 Additionally, incorporation of machine learning enables closed-loop optimization campaigns, where the obtained experimental data guides the selection of the next set of experimental parameters to test. This type of autonomous exploration is ideally suited for the study of enzyme electrocatalysis, as the combinatorics of different enzymes, substrates, and redox mediators creates a prohibitively large parameter space. Even within a single enzyme class, mutations to the amino acid sequence can significantly impact rate, function, and selectivity of the catalyzed reaction. Thus, an automated electrochemical platform that enables rapid sampling both reaction parameters and amino acid sequence space would enable discovery of new, non-native enzymatic reactions.

In this work we use an open source and modular automated electrochemistry platform to study enzyme electrocatalysis in several common bioelectrocatalytic systems, such as glucose oxidase, glucose dehydrogenase, and aldehyde dehydrogenase. We use automated cyclic voltammetric substrate titration experiments (Figure 1) to gain insight into the kinetics of the redox-mediated enzymatic catalysis and demonstrate the reaction conditions in which traditional mechanistic simplifications, like Michaelis-Menten, break down. Additionally, the automated electrochemistry platform allows for the rapid screening of different substrate molecules, enabling the quantification of substrate promiscuity in these enzymatic catalysts. We show how Bayesian Optimization can be incorporated into our workflow to autonomously tune solution parameters to promote increased reaction rates. These studies demonstrate the power of autonomous electrochemistry for understanding and screening biocatalytic systems and represent a significant step towards totally machine-guided biocatalyst evolution.

[1] Oh, I. ; Pence, M. A.; Lukhanin, N.; Rodriguez, O.; Schroeder, C. M.*; Rodriguez-Lopez, J.*, “The Electrolab: An open-source, modular platform for automated characterization of redox-active electrolytes” Device,
2023,
1, 5, 100103

[2] Rodriguez, O.; Pence, M. A.; Rodriguez-Lopez, J.*, “Hard Potato: An Open Source Python Library to Control Commercially Available Potentiostats and Automate Electrochemical Experiments” Anal. Chem.,
2023,
95, 4840–4845

[3]Pence, M. A.; Rodriguez, O.; Lukhanin, N.; Schroeder, C. M.*; Rodriguez-Lopez, J.*, “Automated Measurement of Electrogenerated Redox Species Degradation Using Multiplexed Interdigitated Electrode Arrays”, ACS Meas. Sci. Au,
2023,
3, 62–72

Figure 1
Photobioelectrodes through Photopolymerization of Pyrrole by Photosystem I
Authors: Lowery William , Jennings Kane , Cliffel David E.
Published: December 2024

Conductive polymers can be used to wire biomolecules with man-made materials to create hybrid composites that exhibit synergistic properties, particularly in regard to photoactivity. Photosystem I (PSI), a protein isolated from the photosynthetic chain in green plants, can be interfaced with such polymer networks to utilize the photoactivity of PSI to power light-driven reactions. The conductive polymers aid the protein’s performance by providing pathways for the electrons to be shuttled to and from the active sites. One of the primary challenges in wiring PSI to conductive polymers lies in properly aligning the active sites with the conductive material. A variety of approaches have been used to solve this problem, such as vapor deposition and electropolymerization. Recently, we showed how PSI could be utilized to photopolymerize conductive polymers in direct contact with one of the active sites. Building upon this previous work, we show how a composite film can also be obtained through a similar photopolymerization process, while yielding a product much closer to the electropolymerization entrapment scheme where proteins are entrapped within the polymer network. These composite films demonstrate how the system’s photoactivity can be greatly improved through the direct photopolymerization connections, bringing the field even closer to more practical and efficient PSI applications.