bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Hot Electron Cooling in a Zener-Klein Graphene on BN Transistor: The Role of Hyperbolic Polaritons
Authors: Yang Wei , Baudin Emmanuel , Berthou Simon , Placais Bernard , Voisin Christophe
Published: February 2020

We investigate energy relaxation in a high-mobility graphene on BN transistors. Above a threshold bias voltage, the transistor is driven in a Zener-Klein tunnelling regime involving the creation of electron-hole pairs. Simultaneously, we record the electron gas temperature by means of high sensitivity GHz noise thermometry. We show that a new -extremely efficient- cooling mechanism sets in at the Zener-Klein bias threshold that we assign to the relaxation of electron-hole pairs to hyperbolic polariton modes sustained by the BN substrate. The most striking consequence is a reversal of the doping dependence of the electronic temperature due to the Pauli blocking of ZK-tunnelling at finite doping. HPP cooling is the most efficient mechanism in graphene and promotes graphene Zener-Klein transistors as a valuable route for RF power amplification.
Hybrid PN Diode and CMOS Inverters Composed of MoTe2 Nanosheet-Amorphous in-Ga-Zn-O Thin Film
Authors: Lee Han Sol , Kwon Hyeokjae , Im Seongil
Published: February 2020

We report a hybrid material system which couples a dry-transfer-processed p-type MoTe2 nanosheet and a conventional photolithography-patterned n-type amorphous InGaZnO (IGZO) thin-film. The PN junction diode shows a good ideality factor of 1.57 and a high ON/OFF rectification ratio of ∼3 × 104. Under illumination, our PN diode shows somewhat stable only responding to high-energy photons of blue and ultraviolet. Our CMOS inverter composed of p-MoTe2 bottom-gate field-effect transistor and n-IGZO top-gate field-effect transistors. Our 2D nanosheet – oxide thin film CMOS inverter shows high voltage gains as high as ~40 at 5 V, low power consumption less than ~ a few nW at 1 V, and ~200 μs switching speed.

Both hybrid PN junction diode and complementary (CMOS) inverters are realized by such novel hybrid material system that now opens any further possibilities toward practical applications of 2D nanosheets combined with existing technologies.

Figure 1
(Invited) 2D Diffusion Barriers for Ultra-Scaled Interconnect Technology
Authors: Lo Chun-Li , Zhang Shengjiao , Chen Zhihong
Published: February 2020

In this talk, I will show our characterization of graphene and other 2D materials as ultra-thin Cu diffusion barrier materials and back-end-of-line compatible 2D material synthesis will be presented as well.
(Invited) 2D Semiconductor Electronics: Advances, Challenges and Opportunities
Authors: Javey Ali
Published: February 2020

Two-dimensional (2-D) semiconductors exhibit excellent device characteristics, as well as novel optical, electrical, and optoelectronic characteristics. In this talk, I will present our recent advancements in defect passivation, contact engineering, surface charge transfer doping, and heterostructure devices of layered chalcogenides. We have developed a defect repair/passivation technique that allows for observation of near-unity quantum yield in monolayer MoS2. The work presents the first demonstration of an optoelectronically perfect monolayer. Forming Ohmic contacts for both electrons and holes is necessary in order to exploit the performance limits of enabled devices while shedding light on the intrinsic properties of a material system. In this regard, we have developed different strategies, including the use of surface charge transfer doping at the contacts to thin down the Schottky barriers, thereby, enabling efficient injection of electrons or holes. Additionally, I will discuss the use of layered chalcogenides for various heterostructure device applications, exploiting charge transfer at the van der Waals heterointerfaces.
Effect of Iodide Treatment on the Photovoltaic Performance of Mixed Halide Perovskite Solar Cells
Authors: Kamat Prashant V , Balakrishna Geetha , Kobosko Steven
Published: February 2020

Mixed halide lead perovskites offer a useful strategy for continuous tuning of the semiconductor bandgap. For example, by varying the halide composition of methylammonium lead iodide/bromide (CH3NH3PbBrxI3-x (x=0 to 3)) it is possible to tune the bandgap between 1.55 eV and 2.43 eV. The excited state characterization using emission and transient absorption spectroscopy has allowed us to probe the photoinduced processes. Of particular interest are mixed halide lead perovskites (e.g.,CH3NH3PbI3-xBrx) which undergo phase segregation to create Iodine-rich and Bromide- rich regions when subjected to visible irradiation. We have now investigated the effect of such phase segregation effect on the photovoltaic properties of mixed halide perovskites. The mixed halide solar cells upon exposure to white light exhibit a decrease in the photocurrent and photovoltage as the films undergo phase segregation. The iodide treatment helps to minimize these segregation effects and restore the photovoltage upon storing in the dark. The photovoltaic performance of perovskite solar cells with varying degree of halide treatment will be discussed.
High Photovoltage Sequential Series Multijunction Dye-Sensitized Solar Cells (SSM-DSCs)
Authors: Cheema Hammad , Delcamp Jared H.
Published: February 2020

Sequential series multijunction dye-sensitized solar cells (SSM-DSCs), which are mechanically stacked single illuminated area DSC devices wired in series, are reported to have the highest photovoltages obtained from a single illuminated area DSCs. The use of multiple photoactive films under one area within the SSM-DSC framework is made possible by fine tuning the thickness of TiO2 in each device and judicious dye selection to allow for excellent light distribution among the films, termed as “photon management”. Photovoltages (Voc
) ranging from 1.9-4.7 V are observed for SSM-DSCs fabricated from 2-5 stacked subcells constructed with metal-free organic dyes and cobalt redox shuttles. In SSM-DSCs photon management approach allows for incorporation of materials designed to use the maximal potential energy of photons in each region of the solar spectrum. Further optimizations through the inclusion of antireflection film and replacing organic dyes with efficient metal complex dyes, have achieved up to ~10% power conversion efficiency for three cell based SSM-DSC with photovoltage of 2.2 V for single illuminate area devices. As the results of these optimizations, SSM-DSCs were found have up to 6.5% solar to fuel (STF) efficiency for water splitting compared to 3% of STF previously reported. Studies are underway to characterize optimized SSM-DSCs for CO2 reduction, previously SSM-DSCs showed 2% STF efficiency (2.7% including H2 production) for the reduction of CO2 to CO with IrO2 and Au2O3 electrocatalysts without bias for the first time with DSCs.

Figure 1
(Invited) Efficient Dyes with Unexpected Colors for Dye-Sensitized Solar Cells
Authors: Lin Ching-Yao
Published: February 2020

We herein report three organic dyes with unusual colors for dye-sensitized solar cell (DSSC) indoor or outdoor applications.

The AN-11 dye is an anthracene-based dye. With a relatively simple chemical structure, AN-11 absorbs light at 528 nm and its solution appears red. Surprisingly, DSSCs sensitized with AN-11 show a very black color. We addressed this interesting phenomenon. For indoor applications, we examined a large module (active area = 26.8 cm2) sensitized with the AN-11 dye, along with the Z907 dye for comparison. Our study shows that overall efficiency (η) of the AN-11 module is superior to that of the Z907 counterpart, approaching 12% under 1000 Lux of T5 light.

The LS-01 and LS-11 dyes are air-stable bacteriochlorins with a push-pull chemical design. Photovoltaic measurements of our first generation bacteriochlorin dyes show that LS-01 (η = 4.67 %) and LS-11 (η = 5.36 %) significantly outperform the reference porphyrin dye, H2PE1, (η = 2.06 %) under one-sun irradiation. Intriguingly, the anodes sensitized with the LS-01 and LS-11 dyes give rise to pink and blue colors, respectively.

References:

S. Chakraborty, H.-C. You, C.-K. Huang, B.-Z. Lin, C.-L. Wang, M.-C. Tsai, C.-L. Liu, C.-Y. Lin* "meso-Diphenylbacteriochlorins: Macrocyclic Dyes with Rare Colors for Dye-Sensitized Solar Cells" J. Phys. Chem. C 2017, 121, 7081−7087.

C.-L. Wang, P.-T. Lin, Y.-F. Wang, C.-W. Chang, B.-Z. Lin, H.-H. Kuo, C.-W. Hsu, S.-H. Tu, C.-Y. Lin,* "Cost-effective Anthryl Dyes for Dye-sensitized Cells under One Sun and Dim Light " J. Phys. Chem. C 2015, 119, 24282−24289.

M.-C. Tsai, C.-L. Wang, C.-W. Chang, Y.-H. Hsiao, C.-L. Liu, Cheng Wei Hsu, C.-C. Wang, S.-Y. Lin, C.-Y. Lin* "A Large, Ultra Black, Efficient and Cost-effective Dye-sensitized Solar Module Approaching 12% Overall Efficiency under 1000 Lux Indoor Light", submitted.

Acknowledgments: This work was supported by the MOST, Taiwan, ROC.
Fullerene Derivatives As Electron Transporting Materials for Perovskite Solar Cells
Authors: Fernandez-Delgado Olivia , Castro Edison , Tian Chengbo , Ruiz Carolina , Echegoyen Luis
Published: February 2020

Perovskite Solar Cells (PSCs) have experienced an incredible rise in power conversion efficiencies (PCEs) starting from 3.8% in 2009 to 22.1% in 2016. Due to their electron transporting properties and low cost deposition techniques, fullerene derivatives are the most attractive semiconductors used as electron transporting materials (ETMs) in PSCs. The most widely used fullerene in inverted planar perovskite solar cells is [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM), which exhibits high performance. Devices based on that compound have achieved a maximum PCE of 20.15%, reduced hysteresis, and improved stability. In our laboratories, PC61BM like fullerene derivatives were synthesized via Bingel reaction at room temperature in high yields and incorporated into PSCs as ETMs. It was demonstrated that the branched alkyl chain of the fullerene derivative can highly influence the solubility, film morphology, passivation ability, ETL-perovskite contact, and electron extraction ability of the fullerene derivative. Overall device performance and stability were improved compared to those devices based on PC61BM.

Figure 1
Additives for TiO2 Modifications: A Case Study of Dye-Sensitized Solar Cells
Authors: Cheema Hammad
Published: February 2020

Historically, molecular additives aimed at modifying the properties of titanium dioxide (TiO2) have played a substantial role in the optimization of dye-sensitized solar cells (DSCs). Mesoporous TiO2 films based on different shapes (nano-particulate, spheres, hollow tubes) and sizes (18-30 nm or >100 nm) has been the preferred choice for DSCs since 1991, after the seminal report by O’ Regan and Grätzel. During the last two and half decades wealth of knowledge has been generated by researchers worldwide aiming at modifying mainly anatase TiO2 for band adjustment to facilitate electron injection from anchored dyes, and high electronic mobility for photo-generated electron collection in the domain of DSCs. In retrospection, there is a dire need to assimilate and summarize the findings of these valuable studies to further catalyze the research, better understanding and comparison of the structure-property relationship and efficiently integrate tailored properties in TiO2 for various photocatalytic, electrochemical and nanostructured applications. This poster will aim at categorizing the typical approaches used to modify TiO2 in the domain of DSCs such as through TiO2 paste additives, TiO2 doping, metal oxide layers, dye solution co-adsorbing additives, post staining surface treatment additives and electrolyte additives. A summary of the effect of these modifications on electron injection, charge extraction, electronic mobility, conduction band shift and surface states will be summarized, which is expected to hugely benefit the researchers employing TiO2 in energy, catalysis and battery applications.

Figure 1
A Novel Catalyst for Electroreduction of CO2 to Ethanol
Authors: Fan Jiawei , Cai Li , Hao Qingli
Published: February 2020

Due to the large-scale consumption of fossil fuel, the increased CO2 concentration in the atmosphere are associated with greenhouse effect and climate change, which have gained increasing research attention [1,2]. Therefore, the possibly captured CO2 can be a potentially useful feedstock if it is converted into other hydrocarbon products. Electrochemical reduction is one of efficient methods for CO2 utilization and recycling, which may be carried out at moderate temperature and atmospheric pressure. It also shows relatively high product selectivity compared with other reduction methods, such as chemical and thermochemical methods. However, the high over-potential for the electroreduction of CO2 is the critical bottleneck. By now, various electrocatalysts have been shown to enable CO2 reduction at low overpotentials, which include metals, metal compounds, and other nanostructures, especially for copper based catalysts. The main conversion products are CO, CH4, HCOOH, and C1-related chemicals. The higher carbon-containing products have only been found in case of copper-related electrocatalysts used. Herein, we firstly reported a novel catalyst of cobalt/graphene nanocomposites for the electrochemical reduction of CO2 to ethanol with a high selectivity and a low overpotential. The XRD, TEM, XPS, Raman characterizations were used to confirm the chemical structure and morphology. The electrochemical performance of the cobalt/graphene catalyst was investigated systematically. A high efficiency towards CO2 electroreduction to ethanol has been found, which is attributed to the synergistic effect of two components. This work highlights the importance of combination of non-copper nanoparticles with carbon on its catalytic activities. It also provides a strategy to design efficient catalysts for CO2 electroreduction to higher carbon products in the future.
(Invited) Ag-Loaded Hydroxide-Modified Solid-State Photocatalysts for Photocatalytic Reduction of CO2 by H2o as an Electron Donor
Authors: Teramura Kentaro
Published: February 2020

The reduction in human-induced emissions of CO2 from automobiles, factories, power stations, etc., over the next 15 years is currently one of the most important issues facing the planet. We should therefore attempt to develop industrial processes using CO2 as a feedstock in order to build a sustainable society in the near future. Photocatlaytic conversion of CO2 has recently drawn increased attention due to allowing direct solar-to-chemical energy conversion. If H2O does function as the electron donor, then it is important to obtain a stoichiometric ratio between the amount of O2 evolved and the amount of CO2 reduced. Moreover, the reduction of H+, released from H2O molecules, usually competes with CO2 reduction when several heterogeneous materials are used as photocatalysts for the reduction of CO2 with H2O. Generally, the production of H2 via the reduction of H+ is the dominant pathway. Therefore, to achieve high selectivity in the photocatalytic conversion of CO2 with H2O, the electrons generated through the oxidation of H2O must be controlled to selectively. Moreover, we achieved highly selective photocatalytic reduction of CO2 by H2O by simultaneously using an inhibitor of H2 production and materials capable of CO2 capture and storage, e.g., Ag-modified ZnGa2O4/Ga2O3, La2Ti2O7, SrO/Ta2O5, ZnGa2O4, ZnTa2O6, Sr2KTa5O15, SrNb2O6, LDH/Ga2O3, and Pr2O3/Ga2O3.
(Invited) Nanostructured Conjugated Polymers As Promising Electrodes for Li-Ion Batteries
Authors: Zhang Qichun
Published: February 2020

Electrode materials play a critical role in approaching high energy density and long cycle life lithium-ion batteries (LIBs). The increasing concern about the traditional inorganic electrode materials on resources and environmental issues has strongly inspired scientists to switch on searching green energy electrodes. Organic compounds are potentially sustainable and renewable materials as many of them can be obtained from natural products and biomass. Additionally, the properties of organic compounds can be tuned through the modification of the structures as well as the introduction of functional groups. In this talk, I will present our recent progress on the preparation of novel conjugated polymers and their application in Li-ion batteries.

Key Words: Azaacene-based polymers, synthesis, Characterization, LIB application

[1] Z.-Q. Lin, J. Xie, B. Zhang, J. Li, J.-N. Weng, R.-B. Song, X. Huang, H. Zhang, H. Li, Y. Liu, Z. J. Xu, W. Huang,* Q. Zhang,* Nano Energy, 2017, 41C, 117-127

[2] J. Xie, P. Gu, Q. Zhang*, ACS Energy Letter, 2017, 2, 1985–1996.

[3] J. Xie, W. Chen, Z. Wang, K. C. W. Jie, M. Liu,* Q. Zhang*, Chem Asian J.
2017, 12, 868-876.

[2] J. Xie and Q. Zhang*, J. Mater. Chem. A.
2016, 4, 7091 – 7106.

[2] P.-Y. Gu, Y. Zhao, J. Xie, N. Binte Ali, L. Nie, Z. J. Xu,* Q. Zhang* ACS Appl. Mater. Interfaces, 2016, 8
,7464-7470.

[3] J. Wu, X. Rui, C. Wang, W.-B. Pei, R. Lau, Q. Yan*, Q. Zhang* Adv. Energy Mater., 2015,
5, 1402189

[4] J. Wu, X. Rui, G. Long, W. Chen, Q. Yan*, Q. Zhang*, Angew. Chem Int. Ed.
2015, 54, 7354-7358
(Invited) Reaction Site Analysis for Plasmon-Induced Charge Separation
Authors: Tatsuma Tetsu , Nishi Hiroyasu , Saito Koichiro , Ishida Takuya , Kao Kun-Che
Published: February 2020

Plasmon-induced charge separation (PICS)1-3 involves electron transfer from plasmonic nanoparticles of Au, Ag, or Cu to a semiconductor, typically TiO2.1-4 The electron transfer is caused by external photoelectric effects (including hot carrier injection) or interfacial electron transition.3 We have reported that oxidation of Ag to Ag+ occurs at the Ag nanoparticle surface in PICS of Ag-TiO2 systems,5 and this reaction occurs preferentially at the sites where optical near field is localized.6-8 This can be explained in terms of ejection of energetic holes from the nanoparticles as Ag+ ions.8,9 This possibility has been further investigated on the basis of other anodic reactions. For a system with isolated Au nanoparticles on TiO2, the interface mode may be more important than the full-surface mode. However, plasmon coupling between two nanoparticles, which enhances full-surface mode but not necessarily enhances the interface mode, increases the PICS efficiency. This could also indicate that not only injection of electrons from Au nanoparticles into TiO2 but also ejection of holes from Au nanoparticles play an important role in those PICS systems.

Y. Tian and T. Tatsuma, J. Am. Chem. Soc., 127, 7632 (2005).

Y. Tian and T. Tatsuma, Chem. Commun., 2004, 1810.

T. Tatsuma, H. Nishi, and T. Ishida, Chem. Sci., 8, 3325 (2017) [review].

E. Kazuma and T. Tatsuma, Adv. Mater. Interfaces, 1, 1400066 (2014).

Y. Ohko, T. Tatsuma, T. Fujii, K. Naoi, C. Niwa, Y. Kubota, and A. Fujishima, Nat. Mater.,
2, 29 (2003).

E. Kazuma, N. Sakai, and T. Tatsuma, Chem. Commun., 47, 5777 (2011).

I. Tanabe and T. Tatsuma, Nano Lett., 12, 5418 (2012).

K. Saito, I. Tanabe, and T. Tatsuma, J. Phys. Chem. Lett., 7, 4363 (2016).

Figure 1
Electrochemical Control of Plasmonic Metal Nanogap for Ultra-Small Light Confinement
Authors: Oikawa Shunpei , Minamimoto Hiro , Murakoshi Kei
Published: February 2020

Ultra-small nanogap of plasmonic metal dimer can confine light into molecular size. In this study, we have tried to establish the method for the control of the gap distance of Au nanodimer structures using electrochemical method. Au nanodimer structures were fabricated on a conductive glass substrate by the electron beam lithography method. Electrochemical dissolution of bridged Au nanodisk dimer was conducted under in-situ dark-field microscopy observation. The electrode potential was kept at the potential for Au dissolution. SEM images proved the formation of the gap between Au nanoparticles. From the time series scattering spectra of Au nanodimer, the drastic optical property changes has been observed at the gap formation. This optical property change can be assigned to the plamon mode change from the charge transfer mode to bonding dipolar mode due to the formation of the sub-nm gap at Au nanodimer. The present method is a useful tool for controlling the shape and the gap distance between Au nanoparticles in a single nanometer scale.
(Invited) Strongly Antiaromatic Porphyrins with Singlet Biradical Character
Authors: Shinokubo Hiroshi
Published: February 2020

Recently, antiaromatic compounds with 4n π-electrons have received much attention due to their intriguing properties, which are different from those of conventional aromatic compounds. They are expected to be applicable for ambipolar semiconductors and secondary batteries. Antiaromatic π-systems generally have a closed-shell configuration because of the lowering of the symmetry. Consequently, antiaromatic compounds generally show substantial bond-length alternation. It is quite challenging to investigate the properties of 4n π-conjugated systems upon enhancing their symmetry.

In this study, we have succeeded in preparing Ni(II) tetrabenzonorcorrole TBNc. Interestingly, the introduction of fused benzene rings resulted in bond-length equalization of the π-system of norcorrole NC. Moreover, we found that the enhancement of the symmetry of the norcorrole conjugation significantly decreases the HOMO–LUMO gap, which results in the emergence of a singlet diradical character and significant increase of the antiaromatic character.

Figure 1
(Invited) Structural and Photophysical Properties of Pentacene-Based Self-Assembled Monolayers on Gold Nanomaterials
Authors: Hasobe Taku , Sakai Hayato
Published: February 2020

Design and synthesis of organic-inorganic hybrid materials have attracted widespread interest in terms of fundamental and applied researches. Many different kinds of chromophores such as pyrene, porphyrin, phthalocyanine and fullerene have been used to assemble on the surface of gold nanoclusters by self-assembled monolayers (SAMs). In most cases, the excited states of chromophores are significantly quenched by surface-dipole energy transfer (SET) to the gold surface. Actually, the fluorescence emission decreases by more than 90% and generation of triplet states through intersystem crossing is basically negligible. The rate of SET is proportional to the inverse fourth power of the distance between the chromophore and gold surface in point-to-surface approximation. Accordingly, SET is highly related to Förster theory, where the rate constant of energy transfer is proportional to the spectral overlap between the donor (D) emission and acceptor (A) absorption and to the inverse sixth power of the distance between the D and A in point-to-point approximation. In contrast to the above-mentioned gold nanoclusters modified by chromophores, the number of reported examples on chromophore-modified gold nanorods is extremely limited. Little attention has been accordingly drawn toward the comparison of spectroscopic and photophysical properties of chromophore-modified gold nanomaterials with different sizes and shapes.

We have recently reported the synthesis and photophysical properties of 6,13-bis(triisopropylsilylethynyl) (TIPS)-pentacene-alkanethiolate MPCs [denoted as TP-Cn-X-MPC] with different chain lengths and particle sizes.[1] The occurrence of effcient singlet fission was successfully observed. However, supramolecular intercalation of TP-modified MPCs with guest molecules has yet to be examined. Based on the above points, our focus in this study is to newly synthesize TP-alkanethiolate monolayer-protected gold nanorods [denoted as TP-Cn-MPRs] and compare the spectroscopic and structural properties with the TP-Cn-MPCs. [2] The other point in this prsentation is control and switching of excited-state dynamics in self-assembled monolayes composed of plural chromophores on gold nanoclusters. The details on the structural and photophysical properties of these nanomaterials will be discussed here.

References

[1] Hasobe, T. et al, Angew. Chem. Int. Ed.
2016, 55, 5230-5234.

[2] Hasobe, T. et al, J. Phys. Chem. C
2017, 121, 9043-9052.
(Invited) Understanding Product Selectivity in Electrochemical Conversion of CO2: A Combined in Situ Experimental and Theoretical Approach
Authors: Katayama Yu , Shao-Horn Yang
Published: February 2020

The electro-reduction of CO2 presents an attractive method for storing intermittent renewable electricity as energy dense fuels. Polycrystalline Cu surfaces are unique for catalyzing the conversion of CO2 to higher-order C1 and C2 fuels, including methane and ethylene, with moderate efficiencies. However, the long-lasting challenge has been attaining higher selectivity for desired products. The rational design of more selective and efficient catalysts requires mechanistic understanding of how Cu catalyzes the multi-proton and multi-electron conversion of CO2.

In this talk, the origin of the unique catalytic activity and selectivity of Cu on CO2 reduction reaction (CORR) is explored by tracking the surface intermediates using surface-enhanced FTIR (SEIRAS) and ambient-pressure XPS (APXPS), as well as density functional theory (DFT) calculations. Using this combined experimental and theoretical approach, we propose that not only M-C binding energy but also M-O binding energy plays a critical role in determining product selectivity for CORR. Key reaction intermediates on the surface as a function of potential have been identified and reaction mechanisms for the formation of experimentally detected reduced products have been proposed. Based on this new understanding, a strategy for rational electro-catalyst design for CORR that targets both activity and selectivity will be discussed. Perspectives for further optimization of the energetics of key reaction intermediates by tuning new knobs such as the interaction between intermediates and cations/anions in the electrolyte will also be considered.
Sensitization of p-Gap Photocathodes
Authors: Maldonado Stephen
Published: February 2020

This presentation describes efforts to construct sensitized p-type gallium phosphide (p-GaP) photocathodes capable of sustained operation in water. Specifically, data will be presented that shows the efficacy of planar and macroporous non-degenerately doped p-GaP photoelectrodes for supporting light stimulated hole transfer from an adsorbed dye or quantum dot. Spectroelectrochemical data, X-ray photoelectron spectra, and electron microscopy images are first presented that describe the loading and stability of various chromophores on p-GaP surfaces in the dark and under illumination. Some analysis from a finite-difference model will then be discussed that describes how these photoelectrodes should ideally operate. Finally, advances in methodologies to pin the chromophores persistently to the surface will be detailed.
Amphiphilic and Self-Organizing Tetraazaporphyrins By Molecular Design
Authors: Eichhorn S. Holger , Abdulhamied Elmahdy , DeWolf Christine , Ahmida Mohamed M , Kayal Himadri
Published: February 2020

In contrast to phthalocyanines, the self-organization and -assembly of tetraazaporphyrins (TAPs) is much better controlled by molecular design because their intermolecular interactions are less dominated by the cofacial interactions between TAP macrocycles. Presented here are different molecular designs for surface active amphiphilic TAPs and for self-organizing TAPs. The amphiphilicity and thin film structures of the former compounds were studied by the LB technique whereas the self-organization of the latter compounds was studied by optical microscopy, thermal analysis and X-ray diffraction. Also presented are self-organizing and amphiphilic TAPs that contain reactive groups for their cross-linking. Specifically, click chemistry based on azide and acetylene groups is shown to cross-link TAPs in LB-films and columnar mesophases and anisotropic polymeric materials containing TAPs were obtained by the polymerization of diacetylene groups.
Dynamic Molecular Invasion into Multiply Interlocked Catenane Composed of Porphyrin and Phthalocyanine
Authors: Tanaka Kentaro , Yamada Yasuyuki , Ito Ryohei , Ogino Sayaka , Kato Tatsuhisa
Published: February 2020

Commonly, in molecular inclusion phenomena or molecular recognition processes, flexibility on the molecular size or shape of a host molecule is incompatible with a high affinity of association and accuracy of selectivity. However, if the host has a narrow access for incorporating the guest, the transition process during the complexation requires a higher activation energy. A molecular elevator, which is a molecular machine composed of two planar molecular components joined with more than two interlock linkages, could solve the dilemma through dynamic molecular invasion of a guest molecule into the cage surrounded by the planar components. The movable component with macrocyclic rings fused with a planar core can migrate between two competitive recognition sites along the linear threads attached on the other planar component. However, although the macrocyclic rings are attracted to one of the recognition sites, the planar core with the rings still has the ability to move along the threads. This is because the affinity between the ring and recognition point does not help to anchor the ring at this position, but only increases the probability of the position. Therefore, this flexibility of the interlock linkage satisfies the requirement of the dynamic invasion of a guest molecule. The molecular system permits the invasion of a large guest molecule by expanding the access and stabilizing the host–guest interaction by induced fit based on the interactions between the ring and recognition point.

A multiply interlocked catenane with a novel molecular topology was synthesized; a phthalocyanine bearing four peripheral crown ethers was quadruply interlocked with a cofacial porphyrin dimer bridged with four alkylammonium chains (Figure). The supramolecular conjugate has two nanospaces surrounded by a porphyrin, a phthalocyanine, and four alkyl chains to accommodate guest molecules. Because the phthalocyanine is movable along the alkyl chains, it acts as an adjustable wall, permitting the invasion of large molecules to the nanospaces without spoiling the affinity of the association. The dynamic molecular invasion allowed the intercalation of dianionic porphyrins into both the nanospaces with a high affinity.

Figure 1
Programmed Self-Assembly of Highly Fluorescent Nanostructures Formed By Host-Included Porphyrins
Authors: Jayawickramarajah Janarthanan , Pathak Pravin , Vik Ryan S
Published: February 2020

The propensity for pi-rich aromatic chromophores such as porphyrins and phthalocyanines to aggregate in water is a critical issue that limits the full application of these photoactive molecules. In this talk, we will illustrate how defined self-assemblies and nanoarchitectures containing well-placed porphyrin moieties can be achieved in water using hierarchical self-assembly that focuses on inter- and intra-molecular host-guest chemistry and other assembly modalities such as programmable DNA self-assembly. Importantly, the individual porphyrin units in these architectures are precluded from detrimental aromatic stacking interactions (via host-guest assembly) and thus exhibit enhanced photophysical properties. We will commence by discussing the generation of multi-porphyrin containing wires, spheres, and thin films. We will then detail our recent work on photonic nanocylinders composed of porphyrins and other complementary chromophores via DNA quadruplex assembly.
Mitochondrial Reactive Oxygen Species Accelerated Cancer Specific Porphyrin Accumulation to Enhance Photodynamic Therapeutic Effect in Gastric Epithelial Cells
Authors: Matsui Hirofumi , Kurokawa Hiromi
Published: February 2020

Photodynamic therapy is useful for the treatment of cancer because it is minimally invasive for patients. Certain porphyrin compounds and their derivatives have been used as the photosensitizer because they accumulate specifically in cancerous tissues. However, the detailed mechanism of this phenomenon has not been clarified. We previously reported that a proton-coupled folate transporter, HCP1, transported porphyrins and that regulation of the protein was associated with cancer-specific reactive oxygen species from mitochondria (mitROS) (Hiyama K et al. J PorphPhtal. 2013; 17: 36–43). Therefore, over-generation of mitROS could increase HCP1 expression and the effect of photodynamic therapy. We investigated whether pretreatment with indomethacin influenced photodynamic therapy by using a rat normal gastric mucosal cell line, RGM1, its cancer-like mutated cell line, RGK1, and a manganese superoxide dismutase (MnSOD)-overexpressed RGK cell line, RGK-MnSOD. Indomethacin promotes the generation of cellular mitROS by inhibiting the electron transport chain, and MnSOD scavenges the mitROS. We elucidated that hyperthemia enhanced cancer-specific mitROS generation and increased HCP1 expression. Furthermore, RGK1 cells showed higher cellular incorporation of hemato-porphyrin and better therapeutic effect with indomethacin treatment whereas RGK-MnSOD cells did not show a difference. Thus, we concluded that hyperthermia improved the effect of photodynamic therapy by inducing increased mitROS generation in cancer cells.

References

1. Ito, H., H. Matsui, A. Hirayama, H. P. Indo, H. J. Majima and I. Hyodo (2016) Reactive oxygen species induced by non-steroidal anti-inflammatory drugs enhance the effects of photodynamic therapy in gastric cancer cells. Journal of clinical biochemistry and nutrition 58, 180-185.

2. Ito, H., M. Tamura, H. Matsui, H. J. Majima, H. P. Indo and I. Hyodo (2014) Reactive oxygen species involved cancer cellular specific 5-aminolevulinic acid uptake in gastric epithelial cells. Journal of clinical biochemistry and nutrition 54, 81-85.

3. Ito, H., H. Matsui, M. Tamura, H. J. Majima, H. P. Indo and I. Hyodo (2014) Mitochondrial reactive oxygen species accelerate the expression of heme carrier protein 1 and enhance photodynamic cancer therapy effect. Journal of clinical biochemistry and nutrition 55, 67-71.
Electrocatalytic Behaviour of Surface Confined Pentanethio Cobalt (II)Binuclear Phthalocyanines Towards the Oxidation of 4-Chlorophenol
Authors: Khene Samson , Makinde Zainab , Mashazi Philani , Nyokong Tebello
Published: February 2020

Cobalt binuclear phthalocyanine (CoBiPc) bearing pentanethio substituents at the peripheral positions were synthesized. The immobilization of the synthesized cobalt phthalocyanines on gold electrode was achieved using self-assembled monolayer method (SAM). X-ray photoelectron spectroscopy (XPS) and Kelvin Probe (KP) techniques were used to characterise the formation of monomeric and binuclear phthalocyanine SAMs on the gold surface. The phthalocyanine SAMs on gold electrodes were investigated for electrocatalytic oxidation of 4-chlorophenol. The electrocatalytic properties of tetra- and octa- pentanethio substituted cobalt binuclear phthalocyanine (CoBiPc) are compared with their tetra- and octa-pentanethio substituted phthalocyanine (CoPc). The SAMs modified gold electrode surfaces showed a peak current enhancement and stability and reduction in electrocatalytic potentials compared to the bare or unmodified electrodes towards the detection of the 4-chlorophenol. The SAMs of cobalt binuclear phthalocyanines exhibited more enhanced electrocatalytic properties in terms of stability, detection peak current and reduction of the electrocatalytic over potential reduction.
Development of New CO2 Reduction Catalysts and Construction of Efficient Electro-Reduction Systems
Authors: Naruta Yoshinori
Published: February 2020

Reduction of CO2 in exhaust gases and its conversion to useful carbon resources are an urgent and important issue to prevent . Carbon positive processes, which consume CO2, are the more effective way to reduce CO2 and to be able to recycle it. We have found that the porphyrin dimers bearing two iron metal centers separated by an appropriate separation as homogeneous catalysts realize CO2 reduction at remarkable high catalytic turnover frequencies (log TOFmax = 5.8), low overpotentials (η > 0.4 V), and high CO selectivity under neutral wet conditions, i.e. without any addition of acidic reagents.[1, 2] According to this highly efficient CO2 reduction, the performance of these dinuclear iron catalysts becomes a bench mark of CO2 reduction catalysts. Such high catalytic activity comes from the CO2 binding to the Fe(II) dimer, though an Fe(II) porphyrin monomer is intact in CO2 atmosphere. The formation of these pre-associated complexes could efficiently promote the succeeding reduction of the bound CO2-to-CO. In order to apply this kind of catalysts to aqueous heterogeneous electro-reduction system, a FTO electrode is modified with Fe porphyrin dimers bearing a phosphonic acid anchor group (Fe2DPPO3H2
) on its surface.[3] Electrochemical CO2 reduction with the resultant catalyst-modified electrode in a neutral aqueous solution shows CO and H2 formation without any selectivity. Proton reduction could occur on the bare SnO2 surface. The SAM modification of the unmodified FTO surface can successfully block H2 formation by the prevention of the contact of the electrode surface from the solution. However, the low amount of the surface modified catalyst (Γ ≈ 5 x 10-12 mol/cm2) only gave 30-40 μA/cm2 in the electrolysis at -0.95 V vs. NHE (η = 0.42 V) in CO2-saturated 0.1 M KPi solution (pH = 7). In order to increase the surface area of the electrode, meso porous SnO2 layer modification with nano SnO2 particles was applied to a FTO. The resultant 2-μm SnO2 layered electrode co-modified with Fe2DPPO3H2
and SAM was applied to CO2 reduction in 0.1 M KPi and gave 10 times higher current density (i = 1.5 mA/cm2) than that of an ordinary catalyst-modified FTO. The continuous electrolysis for 6 h showed stable current and this proved the electrode is sufficiently stable under these conditions. Since the thickness of the meso porous SnO2 layer on a FTO can be increased up to ≈10 μm, further increase of the current density is possible. In this talk, the latest results of the cell-electrode system involving a non-precious metal anode will be discussed.

References

[1] E. A. Mohamed, Z. N. Zahran, Y. Naruta, Chem. Commun., 2015, 51
, 16900-16903.

[2] Z. N. Zahran, E. A. Mohamed, Y. Naruta Sci. Rep., 2016, 6, 24533.

[3] E. A. Mohamed, Z. N. Zahran, Y. Naruta, Chem. Mater.
2017, 29, 7140–7150.
Porphyrinic Metal-Organic Frameworks for CO2 Capture and Conversion
Authors: Zhang Li , Su Cheng-Yong
Published: February 2020

As an effective strategy to establish a sustainable society, reliable materials and technologies for CO2 capture and conversion are highly required. Due to large surface area, high porosity and tunability, metal-organic frameworks (MOFs) are promising candidates for CO2 capture and conversion. On one hand, MOFs have been widely used for CO2 adsorption and separation owing to their cavities. On the other hand, the structures and functionality of MOFs are easily tuned, and then the catalytically active centers for CO2 conversion can be incorporated into the framework. Our work herein is concentrated on the synthesis and application of porphyrinic metal-organic frameworks (PMOFs) in CO2 capture and conversion. Catalytic results show that under the visible light (> 400 nm) irradiation without any additional photosensitizer, our PMOFs are powerful to catalyze CO2 reduction to the formate ion with up to 99% selectivity and can be recycled and reused for 3 runs without significant loss of the activity. Furthermore, our PMOFs can promote the cycloaddition of CO2 and epoxides under low CO2 concentrations (e.g. 50%, 30%, 15% and 5%) due to the CO2 concentrating effect from the pore spaces.

Figure 1
Properties and Chemistry of Planar, Anti-Aromatic, Hexapyrrolic Porphyrinoids
Authors: Firmansyah Dikhi , Lee Chang-Hee
Published: February 2020

Annulated, hexapyrrolic anti-aromatic rosarin, a β,β′-two-carbon bridged-(1.0.1.0.1.0)hexaphyrin derivatives are Huckel’s 24π antiaromatic system. These are also known to form stable one-electron reduced species 25π species upon exposure to the multiple protons. However, the general synthesis of peripherally substituted analogues were hurdled due to the difficulties of the accessibility of the key building blocks. With this presentation, we report the synthesis of new building blocks that can lead to the peripherally substituted hexapyrrolic rosarins. The properties of the corresponding new rosarians including redox properties, spectroscopic properties and protonation behavior will be presented. The redox chemistry and protonation behavior of the unsubstituted rosarian and peripherally substituted analogues will be systematically compared. The time-dependent spectral changes after addition of excess acids indicates that the single electron reduction is faster in hexa-fluoro substituted one compared with the unsubstituted one. Slightly increased reduction potential of substituted rosarian and the electron withdrawing nature of fluoride exhibited dramatically different properties. Detailed studies will be presented.
Porphyrin Sensitizers Sensitizers Exceeding a World Champion Porphyrin Dye for Dye-Sensitized Solar Cells and Their Tandem Solar Cells
Authors: Kim Hwan Kyu , Kang Sung Ho
Published: February 2020

Push–pull structured (D–π–A) Zn(II)–porphyrin sensitizers, containing various electron donor groups for the enhancement of the light-harvesting ability within the expanded absorption region and efficient prevention of undesirable charge recombination of the sensitising dyes in dye-sensitized solar cells (DSSCs) were newly designed and synthesised through molecular engineering.1 We investigated the effect of bulky donor groups in the D-p-A structured porphyrins on retarded charge recombination between the electrolytes and TiO2 surface and enhanced power-conversion efficiency (PCE). The photovoltaic (PV) performance of the SGT sensitizer-based DSSCs, employing cobalt redox couples, were systematically evaluated in a thorough comparison with SM315 as a reference sensitizer. By introducing a more bulky fluorene unit containing alkoxyphenyl unit to the amine donor group in the world champion SM315 porphyrin dye, for efficient prevention of undesirable charge recombination, the PCE was enhanced. As a consequence, we observed a maximum 12.05% PCE for SGT-021 under simulated one-sun illumination (AM1.5G, 100 mWcm-2), whose PCE was much higher than the 11.67% PCE of SM315, which was known as the world champion dye with a world record PCE of 13%. To further improve the maximum efficiency of the DSSCs, the first parallel-connected (PC) tandem DSSCs employing cobalt electrolyte in the bottom cell with SGT-021 and the top cell with SGT-137
2 were demonstrated and an extremely high efficiency of 14.64% was found, which is currently the highest reported value for dye-sensitised tandem solar cells. In this presentation, Zn-Porphyrin sensitizers for superior performance dye-sensitized solar cells and their tandem solar cells will be described.

References

S. H. Kang and H. K. Kim, et.al., Adv. Energy Mater. 7(2017) 1602117.

Y. K. Eom and H. K. Kim, et.al., J. Mater. Chem. A, 5(2017) 2297.
Substituents Effect in Magnesium Tetraethynylporphyrin for Bulk Heterojunction Organic Solar Cells
Authors: Matsuo Yutaka
Published: February 2020

Porphyrin-based small-molecule electron donors have recently emerged as a new option for use in bulk heterojunction organic solar cells (OSCs) and dye-sensitized solar cells. High power conversion efficiencies (PCEs) in OSCs have been realized with these electron-donating materials by using high light absorption efficiency of porphyrins and their wide absorption range that extends to the near-IR region when the porphyrin units are conjugated with electron-deficient units such as diketopyrrolopyrrole (DPP).

Magnesium tetraethynylporphyrin complexes with two aryl groups (Ar = Ph, C6H4-n-hexyl-4, C6H4-CF3-4, and C6H4-NMe2-4) and two thienyl-substituted diketopyrrolopyrrole units were synthesized by Sonogashira coupling reactions. Electrochemical measurements and photoelectron yield spectroscopy showed that the energy levels of the compounds could be effectively tuned by electron-withdrawing and -donating substituents on the aryl groups. Theoretical calculation revealed that the electronic effects of the Ar group substituents strongly affected the energy level of highest occupied molecular orbital (HOMO) because the localized HOMO on the porphyrin core was conjugated with the Ar groups through the ethynyl linkers. Bulk heterojunction small-molecule organic solar cells with these magnesium porphyrin electron donors were fabricated to evaluate the morphological and electronic effects of the Ar group substituents. The n-hexyl groups promoted formation of phase-separated structures with a high fill factor, yielding a respectable power conversion efficiency of 5.73%. Use of the electron-withdrawing CF3 group gave a high open-circuit voltage of 0.79 V because of the lowered HOMO level, while use of the electron-donating NMe2 group produced a low band gap that extended the incident photon-to-current conversion efficiency spectrum to 1100 nm.

Figure 1
Estructural Design of Funcionalized Porphyrins for Very Efficient (> 9%) BHJ Solar Cells
Authors: Langa Fernando
Published: February 2020

Natural photosynthetic structures utilize chlorophylls to absorb light and carry out photochemical charge separation to store light energy. Porphyrins and related derivatives, as analogues of chlorophylls, have been investigated as active materials for dye-sensitized solar cells and a record PCE of 13% has been achieved. Although porphyrins have been less studied for solution-processed BHJ OSC, impressive progress has been made in this field along the last years achieving remarkable efficiencies as high as 9.06% [1].

In this presentation, I will present our recent work tailoring porphyrin-based A-D-A [2][3] and D-A-D [4] small molecules used as donor materials in BHJ solar cells, reaching excellent efficiencies, higher than 9% with energy loss lower than 0.6 eV [5]. The influence of modification of the substitution in meso positions, role of the conjugated bridge and nature of the acceptor groups on the frontier orbital levels and band-gap as well as the photophysical and electrochemical properties will be discussed.

Gao, J. Miao, L. Xiao, W. Deng, Y. Kan, T. Liang, C. Wang, F. Huang, J. Peng, Y. Cao, F. Liu, T. P. Russell, H. Wu, X. Peng. Adv. Mater.
28, 4727 (2016).

Morán, S. Arrechea, P. de la Cruz, V. Cuesta, S. Biswas, E. Palomares, G.D. Sharma, F. Langa. J. Mater. Chem. A,
4, 11009 (2016).

Arrechea, A. Aljarilla, P. de la Cruz, E. Palomares, G. D. Sharma, F. Langa. Nanoscale
8, 17953 (2016).

Arrechea, A. Aljarilla, P.de la Cruz, M. K. Singh, G. D. Sharma, F. Langa. J. Mater. Chem. C. 5, 14259 (2017).

Vartanian, S. Arrechea, R. Singhal, P. de la Cruz, F. Langa, G. D. Sharma. Submitted.
Surface Chemistry of Porphyrins
Authors: Lytken Ole
Published: February 2020

Porphyrins adsorbed on surfaces may undergo several reactions with the surface, including metalation, where a metal atom from the surface is inserted into the porphyrins molecule, and dehydrogenation, fusing adjacent molecules or pyrrole and phenyl rings within one molecule. Using synchrotron- and laboratory-based XPS, NEXAFS and TPD measurements, examples will be given of reactions of tetraphenylporphyrin molecules with oxide and metal surfaces, both in ultrahigh vacuum and in aqueous solution.