bluuebunny/crossref_metadata_2025 huggingface dataset:
Photo-Physical Properties of Simple and Double Strand Multi-Porphyrinic Polypeptides
Authors: Solladie Nathalie
Published: February 2020

One of our research field concerns porphyrin-functionalized a-polypeptides to control the spatial organization of the chromophores and enable exciton migration through the pool of porphyrins to mimic the light harvesting antennae of the photosynthetic system.1

In the photosynthetic system, the solar energy is collected by pigment molecules attached to the light harvesting complexes, in which the chlorophylls are held in a parallel orientation by fairly short a-helical polypeptides. When a photon hits one of the chlorophylls, the absorbed energy spreads extremely rapidly to the others until the reaction center is reached.1 Succeeding in organizing the porphyrins in a similar way as nature does should provide information about the relation existing between the orientation of the chlorophylls and the efficiency of nature in transferring an excited state over a very long distance and with minimal loss of energy.

The right-handed 310 helical conformation adopted by our poly-L-lysine functionalized with eight porphyrins induces an overlap of the chromophores, which thus present sufficient electronic coupling to promote a good exciton migration within the molecular wire. We thus synthesized a good model of the light harvesting antennas of the photosynthetic system (studies realized in collaboration with Prof. T. Keiderling, University of Chicago, US and Prof. T. Majima, SANKEN, Osaka, Japan).2

Our peptides with pendant porphyrins were studied extensively throughout the world in collaboration with foreign colleagues, and found applications as organic photovoltaic cells,3 or redox molecular switches4 (studies realized in collaboration with Prof. S. Fukuzumi, Univeristy of Osaka, Japan and Dr. P. Ceroni, University of Bologna, Italy).

These polypeptides with pendant porphyrins also found applications for the successful purification of Single-Walled Carbon Nanotubes (studies realized in collaboration with Prof. S. Fukuzumi, Univeristy of Osaka, Japan).5

Acknowledgements

This work was supported by the CNRS and the French Ministry of Research.

References

W. Kühlbrandt, Nature
1995, 374, 497-498.

M. Fujitsuka, D. W. Cho, N. Solladié, V. Troiani, H. Qiu, T. Majima, J. Photochem. Photobiol. A
2007, 188, 346-350.

T. Hasobe, K. Saito, P. V. Kamat, V. Troiani, H. Qiu, N. Solladié, K. S. Kim, J. K. Park, D. Kim, F. D'Souza, S. Fukuzumi, J. Mater.
Chem.
2007, 39, 4160-4170.

Paola Ceroni, Giacomo Bergamini, Nicolas Aubert, Vincent Troiani, Nathalie Solladié, Chem.
Phys. Chem.
2005, 6, 2120-2128.

Kenji Saito, Vincent Troiani, Hongjin Qiu, Nathalie Solladié, Takao Sakata, Hirotaro Mori, Mitsuo Ohama, Shunichi Fukuzumi, J. Phys.
Chem. C
2007, 111, 1194-1199.
Photophysics and Photochemistry of Trifluoromethylfullerene Fluorophores
Authors: Castro Karlee P , Jin Yuhuan , Rack Jeffrey J , Ferguson Andrew , Blackburn Jeffrey L. , Strauss Steven H. , Boltalina Olga V , Popov Alexey A.
Published: February 2020

Five fluorescent trifluoromethyl fullerenes have been studied using time-resolved and steady-state spectroscopy. Prior to this study Nakamura et al. reported the highest quantum yield for a fullerene derivative of 0.24 with the molecule C60Ph10(CH2Ph)3Me2H (1). Three of the trifluoromethyl fullerenes presented exceed this, and one isomer of C70(CF3)10 has a quantum yield of 0.68 (2). The fluorescence lifetimes of three C70(CF3)10 compounds has been measured using time-resolved fluorescence spectroscopy. The compound with the highest quantum yield also has the longest fluorescence lifetime 51 ns. The ability of these compounds to sensitize the production of singlet oxygen has also been investigated.

Between isomers of C70(CF3)8 and C70(CF3)10 only one CF3 group is in a different location. This change in position results in 200 and 14-fold increases in the quantum yield. These isomers have very similar size and location of the remaining pi system; the remaining pi system had previously been hypothesized to be the determining factor for fluorescence quantum yields of C60 derivatives (1,3). Instead we propose that fluorescence quantum yields are more related to the oscillator strength and ΔS1−T1 energy gaps. These values can be predicted using time-dependent density functional theory calculations, which provides a method to target the most fluorescent fullerene derivatives.

References

1. T. Fujita; Y. Matsuo; and E. Nakamura, Chem. Mater.,
24, 3972 (2012).

2. K. P. Castro; Y. Jin; J. J. Rack; S. H. Strauss; O. V. Boltalina; A. A. Popov, J. Phys. Chem. Lett., 4, 2500 (2013).

3. Y. Matsuo; Y. Sato; M. Hashiguchi; K. Matsuo; and E. Nakamura, Adv. Funct. Mater.,
19, 2224 (2009).
Invited Presentation: Synthesis and Characterization of Graphene Layers (*†)
Authors: Pinczuk Aron
Published: February 2020

A variety of methods are being employed in the fabrication of graphene layers. These fabricated layers need to be carefully evaluated and compared to a benchmark represented by the graphene layers that are obtained by mechanical exfoliation of graphite.

Two cases are considered here. One is that of graphene layers obtained by chemical vapor deposition (CVD) on Cu. The other case is that of graphene layers obtained by molecular beam (MB) growth, a form of van der Waals epitaxy. The MB epitaxy approach employs a solid carbon source, similar to that used in molecular beam epitaxy. The MB grown layers are fabricated directly on dielectric substrates. This is an achievement that could enable applications in electronics and optoelectronics.

While Raman spectroscopy is a primary characterization tool, techniques such as scanning tunneling microscopy (STM) and X-ray probes are employed to provide key insights.

The CVD graphene layers are coupled to the Cu substrate by weak van der Waals forces. Surprisingly, our studies reveal that strains that result from coupling to the substrate have significant impact on the quality of the graphene layers.

The van der Waals MB growth of single-layer graphene was demonstrated on h-BN and sapphire substrates.

(*) In collaboration with: Sheng Wang, Rui He, Lara Fernandes dos Santos, Liuyan. Zhao, U. Wurstbauer, J. M. García, A. N. Pasupathy, P. Kim, J. Hone, Lei Wang, C. R. Dean, Kenji Watanabe, Takashi Taniguchi, L. N. Pfeiffer, and A. S. Plaut.

(†) Supported by ONR and NSF
Invited Presentation: Logic Devices with Graphene PN Junctions
Authors: Lee Ji Ung
Published: February 2020

Graphene p-n junctions (GPNJs) can be configured as logic devices that can meet the scaling challenges of CMOS devices. In the present context, GPNJs are not rectifying diodes since graphene is gapless. Instead, they exhibit unique angle dependent transport properties that allow the development of new type of electron-optics devices. This angle dependence has been used to predict novel devices, including the Veselago effect, steep subthreshold slope devices, and wave guiding structures.

Here, we describe the fabrication and characterization of GPNJs. We use buried gates to electrostatically dope the graphene to form the p- and n-doped regions. The buried gates are fabricated in CNSE’s advanced 300mm wafer line, which is used to obtain an atomically smooth dielectric surface above the gates to preserve the intrinsic electronic structure of graphene.

Using the split gates, we study different angled GPNJs and perform electrical measurements to extract the junction resistance. We observe a strong angle dependent junction resistance and confirm Klein tunneling, the normal tunneling component with unity transmission. By blocking the Klein tunneling component, we observe high on/off ratio devices.
Simple Patterning of Large-Area Graphene By Metal Mask and Sacrificial Polymer Layer
Authors: Kang Narae , Smith Christian W. , Ishigami Masa , Khondaker Saiful I.
Published: February 2020

Graphene has attracted a lot of attention due to its extraordinary properties such as low resistivity, high mechanical/chemical stability, and high mobility. One particular area that has aroused recent interest is its use as an electrode material for organic electronics such as organic field-effect transistors (OFETs), organic flexible solar cell, and organic light-emitting diode (OLED). This is because, graphene has a high work function which matches to the highest occupied molecular orbital (HOMO) level of organic semiconductor, and has a strong π-π interaction with organic semiconductors which can reduce the injection barrier at the graphene/organic interface for enhanced the charge injection efficiency. However, for practical applications in organic electronics, large-area graphene film needs to be produced either via chemical vapor deposition (CVD) technique or via thin film of reduced graphene oxide (RGO) sheets and they need to be patterned in a specific dimension. The commonly used patterning technique is selectively etching of unwanted regions of graphene using metal etch mask and then the removal of the metal via harmful acid treatment.

In this work, we report a new approach for a simple patterning of graphene film by metal mask using a sacrificial methyl methacrylate (PMMA) polymer layer. Our method includes both spin-coated polymer layer as sacrificial layer and metal deposition by shadow mask as etching mask. After the graphene is placed on Si substrate, PMMA layer is spin-coated on top of the graphene film, and then the metal is evaporated through shadow mask. After the samples are exposed under plasma etching, the patterned graphene is obtained. The metal is then easily removed along with the with the PMMA layer by a acetone lift off. The size and shape of patterned graphene is the exactly same as the metal mask. We show that this new method can apply to different types of graphene film such as chemical vapor deposition (CVD) graphene and reduced graphene oxide (RGO) demonstrating as a reliable processing technique. In contrast to conventional metal etch mask patterning, our method does not include any harmful acid treatment of removing metal mask, making it an environmental-friendly method. We also fabricated OFETs by thermally depositing pentacene using patterned graphene electrode. Our devices show excellent device performance with a maximum mobility of 0.33cm2/Vs and current on-off ratio of ~105. We believe that this approach can open the new pathway for manufacturing other carbon-based thin film devices.
Semiconductor Nanomaterials for Dye-Sensitized Solar Cells
Authors: Lin Zhiqun , Xin Xukai , Ye Meidan , Wang Mengye , Lin Changjian
Published: February 2020

In this presentation, I will discuss low-cost, high-efficiency dye-sensitized solar cells (DSSCs) through the use of nanoengineered TiO2 (e.g., nanotubes and nanoflowers) as photoanode, dyes as sensitizer, and earth abundant, environmentally friendly quaternary semiconductor copper zinc tin sulfide (CZTS) as counter electrode.
Ultrafast Spectroscopy and Numerical Analysis of Inhomogeneous Electron Injection in Dye-Sensitized Solar Cells: Effect of Electrolyte
Authors: Furube Akihiro , Sunahara Kenji , Mahanta Subrata , Matsuzaki Hiroyuki
Published: February 2020

Ultrafast electron injection from a photo-excited dye molecule to semiconductor electrode is one of the most important reactions in the dye-sensitized solar cell (DSSC). The reaction occurs in the wide time region from femtoseconds to nanoseconds with a inhomogeneous manner.[1,2] Since the origin of such inhomogeneity has not been understood well, there still is many problems to improve the photo conversion efficiency of DSSC.[2]Here, we propose a quantitative reaction model of the electron injection dynamics to discuss the origin of the inhomogeneity. Our experimental results of transient absorption spectroscopy (TAS) were successfully analyzed by the model.

Dye sensitized TiO2 films with Ru-complex (N719) were prepared. The fs-TAS and ns-TAS measurements were carried out for the films in acetonitrile-based electrolytes. The results were numerically analyzed as a sum of non-adiabatic electron transfer reactions, which supported our experimental finding that the inhomogeneous energy distribution of the energy gap between the donor and acceptor states (Δ) was present.[2]

Fig.1 shows the results of population time profile of injected electron in DSSC. The profiles are measured by fs-TAS at <1 ns and sub-nsTAS >1 ns. The simulation result based on our model showed a good agreement with the experimental result. Furthermore, the effects of electrolyte with different potential controlling ion (Li+) concentrations and the electron concentration in semiconductor electrode were investigated experimentally and the obtained electron injection kinetics were well explained by the numerical simulation, indicating that the model is reasonable.

In some cases, however, the model does not seem to be easily applicable. For example, when we measured electron injection kinetics from excited N719 to TiO2 in the presence of ionic liquid (IL) as surrounding solvent, less efficiency was observed for some ILs with higher viscosity (> 30 cP). This suggests that not only the driving force but also restriction of molecular reorientation of the sensitizer may affect the reaction.

Some other examples of electron injection dynamics relating to the effect of electrolytes and solvents will be shown and the mechanism will be discussed [3, 4].

Acknowledgement: A part of this work is supported by NEDO Japan.

Fig.1Population time profile of injected electron in DSSC. Solid line shows a simulation result.

References

[1] Y. Tachibana et al., J. Phys. Chem. B, 104, 1198 (2000)

[2] K. Sunahara, A. Furube et al., J. Phys. Chem. C, 115, 22084 (2011)

[3] A. Furube, Z. Wang, K. Sunahara, K. Hara, R. Katoh, and M. Tachiya, J. Am. Chem. Soc., 132, 6614-6615 (2010)

[4] S. Mahanta, A. Furube, H. Matsuzaki, T. N. Murakami, and H. Matsumoto, J. Phys. Chem. C, 116, 20213–20219 (2012)
Role of Hole Conductors in Quantum Dot and Organometal Perovskite Based Solid State Solar Cells
Authors: Kamat Prashant V , Christians Jeffrey A
Published: February 2020

Semiconductor quantum dots (QDs) have the potential to design high efficiency solid-state QDSCs and ETA (Extremely Thin Absorber) solar cells. Tunable band gap and band edge through size quantization, large intrinsic dipole moments, and high extinction coefficients make them suitable light absorbing materials. A number of semiconductors have been explored in the design of solid state solar cells. These include CdS, CdSe, In2S3, and Sb2S3. Of particular interest is Sb2S3 which has a band gap of 1.7 − 1.8 eVallowing for light absorption throughout the visible range. Organometal perovskites such as CH3NH3PbI3 are the new semiconducting materials that have led to advances in thin film solar cells. However, hole transport remains a limiting factor in maximizing power conversion efficiency.

Using Sb2S3 (absorber) and CuSCN (hole conductor), we have constructed ETA solar cells exhibiting a power conversion efficiency of 3.3%. We have employed transient absorption spectroscopy to probe the hole transfer between Sb2S3 and CuSCN. In the Sb2S3 absorber layer, photogenerated holes are rapidly localized on the sulfur atoms of the crystal lattice, forming a sulfide radical (S−•) species. This trapped hole is transferred from the Sb2S3 absorber to the CuSCN hole conductor with an exponential time constant of 1680 ps. Similarly the hole transport properties in (CH3NH3PbI3) and hole conductor copper iodide has been probed by impedence spectroscopy. Charge separation in Sb2S3 and (CH3NH3PbI3) based solar cells which provide new insight into the design of new architectures for higher efficiency devices will be discussed.

ACKNOWLEDGMENT. The research described herein was supported by the Division of Chemical Sciences, Geosciences and Biosciences, Basic Energy Sciences, Office of Science, United States Department of Energy through grant number DE-FC02-04ER15533.
Single Nanostructure Extinction Spectroscopy
Authors: Kuno Masaru
Published: February 2020

Molecules and nanoparticles exhibit unique properties such as emission intermittency (i.e. blinking) and spectral wandering which are only observable at the single molecule level. Until recently, single molecule detection has mainly been restricted to fluorescent entities. Now techniques such as photothermal imaging and spatial modulation microscopy allow single molecules and nanoparticles to be detected, regardless of their ability to emit light. This opens up the possibility of discovering new absorptive properties and even photophysics that have previously been masked within ensemble measurements. In this talk, I describe the use of these direct absorption techniques for two case studies. The first is on CdSe nanowires, a material that has potential uses in renewable energy applications. Through direct absorption measurements, we obtain the first absorption size series of any nanowire system and reveal the complex interplay between competing effects such as confinement and dielectric contrast, which determine the optical response of the wires. In a second case study, we focus on graphene oxide, an important precursor in the production of chemically-derived graphene, another important material for renewable energy applications. We show, for the first time, the direct observation of laser-induced, single layer GO reduction through correlated changes to its absorption and emission. Acquired absorption/emission movies illustrate the initial stages of single layer GO reduction, its transition to reduced-GO (rGO) as well as its subsequent decomposition upon prolonged laser illumination. These studies reveal GO’s photoreduction life cycle and through it native GO/rGO absorption coefficients as well as their intrasheet distributions and spatial heterogeneities. Beyond these two case studies, the demonstrated single nanostructure absorption technique offers exciting possibilities for directly interrogating other systems that are not necessarily fluorescent, revealing insights beyond simple ensemble averages.
Observation of Surface-Enhanced Raman Scattering from Strongly Coupled Molecules and Localized Surface Plasmons in Resonance
Authors: Murakoshi Kei , Nagasawa Fumika , Takase Mai
Published: February 2020

The photoexcitation characteristics of materials have been investigated using surface enhanced Raman scattering (SERS) [1]. Signal enhancement by< 104 times of magnitude is caused by resonances that are induced by optical absorption. Previously documented studies have found that the absorption spectra of chromophores that were adsorbed to Au or Ag plasmonic nanoparticles can be strongly perturbed. This perturbation of the electronic transition should affect the SERS profiles in ways that differ from those predicted based on simple enhancement of the local electromagnetic field. Previously documented studies discussed about the SERS effect as involving transition dipole coupling between the chromophore and the metal, and also theoretical simulation including resonance coupling between the molecular electronic transition and the optical transition of the nanoparticles. Despite these attempts to research the Raman characteristics when the system achieved hybridized states, the Raman features in the strong coupling regime when using LSPR have not been clarified yet.

In this study, polarized Raman scattering measurement was carried out using a hybridized system of Ag nano-dimer structures and organic dye molecules. Tuning of the localized surface plasmon resonance energy leads to modulation of the hybridized polariton energy. The anti-crossing behavior of the polariton energy implies a strong coupling regime with maximum Rabi splitting energy of 385 meV. The observation proves the effective Raman enhancement via the excitation of the upper and the lower blanches of the hybridized states at the gap of the metal dimer. Maximum Raman enhancement was obtained at an optimized resonant energy between the hybrid states and Raman excitation.

Reference

[1] M. Takase, F. Nagasawa, H. Nabika, K. Murakoshi, “Single Molecule Surface-Enhanced Raman Scattering as a Probe for Adsorption Dynamics on Metal Surfaces", in Frontiers of Surface-Enhanced Raman Scattering: Single-Nanoparticles and Single Cells, Y. Ozaki, K. Kneipp, and R. P. Aroca, John Wiley & Sons, New York, (2014).

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Design and synthesis of ternary Ferrite/Graphene/polyaniline hierarchical nanocomposites for high-performance supercapacitors
Authors: Xiong Pan , Fan Ye
Published: February 2020

As typical active electrode materials for pseudocapacitor, transition metal oxides, hydroxides, and conductive polymers possess multiple oxidation states/structures that enable rich redox reactions for pseudocapacitance generation. Spinel ferrite oxides (MFe2O4, M=Fe, Co, Ni, Cu, Mn) has been conceived as a promising cost-effective and scalable alternative for supercapacitor. It is expected that ferrite oxides (MFe2O4) may offer richer redox reactions, including contributions from both M and Fe ions, than those of the monometallic oxide. However, it is noted that the pure ferrite oxides cannot be conductive to satisfactory performance. A promising approach to enhance the performance is designing novel ferrite-based hybrids.

Conducting polymer, such as polyaniline (PANI) is usually used to hybrid with metal oxides to enhance the electronic conductivity and achieve higher capacitance, owing to its low cost, environmental compatibility, excellent electrical conductivity, large pseudo-capacitance, and fast doping/dedoping rate. However, the poor cycling stability is a noticeable shortcoming. Graphene is a rising star in supercapacitor owning to its extremely high specific surface area, superior mechanical properties, good electrochemical stability and high intrinsic electrical conductivity. Recently, a hierarchically ternary composites composed of carbon nanomaterials, conducting polymers and transition metal oxides have been explored. This novel ternary hybrids provide a new direction for the fabrication of the next generation high-performance electrochemical electrodes. Based on the above, it is of great interest to fabricate the ternary ferrite-based composites as an capacitor material. To the best of our knowledge, very few studies on the synthesis of ferrite-based hybrids have been reported so far, especially this intriguing ternary nanostructure.

Herein, we first reported ternary ferrite/graphene/PANI hybrid by a facile two-step method. This ternary nanostructures show enhanced electrochemical capacitance and improved cycling stability than those of the three separated components and their corresponding binary hybrids.
Supramolecular Porphyrin Chemistry on Flatlands
Authors: Bonifazi Davide
Published: February 2020

Organic multidimensional networks featuring porous structures are of great interest since their cavities can be used as receptors for the confinement of functional molecules or nanoreactors for chemical transformations. The investigation and exploitation of these structures in solution presents several limitations due to the fact that the molecular components cannot be directly and individually addressed at the nanoscale level. In this respect, the deposition and the organization organic molecules at interfaces is an obligatory passage towards the exploitation of these systems in real devices. Specifically, the engineering of such architectures on metal surfaces represents a promising first approach as the structure of the molecular-based assemblies can be studied by scanning probe microscopies, such as Scanning Tunneling Microscope (STM) techniques. Herein we report on the synthesis, photophysical properties and self-organisation of a series of porphyrin derivaitives that, under under UHV conditions, undergo bidimensional self-assembly on metal surfaces leading to marocyclic supramolecules through transition-metal and lanthanide coordinative interactions. The synthesis of several porphyrin modules has been carried out. The synthetic strategy mainly involved the C(Sp2)-C(Sp) bond formation, achieved by exploiting cross-coupling-type reactions. The characterization of these arrays on surfaces has been accomplished by STM measurements.
Diporphyrin and Dipyrene Nanocalipers for Discrimination of Diameter and Metallicity in Single-Walled Carbon Nanotubes
Authors: Komatsu Naoki , Liu Gang
Published: February 2020

We have been developing host-guest methodology for separation of single-walled carbon nanotubes (SWNTs) according to the handedness and diameter with gable-type chiral diporphyrins, designated as diporphyrin nanotweezers, consisting of two porphyrins and rigid spacer in between [1-4]. In this paper, we will talk about next generation of the host molecules focusing on larger diameter of SWNTs, named “nanocalipers” (Figure 1) [5,6].

X. Peng, N. Komatsu,* S. Bhattacharya, T. Shimawaki, S. Aonuma, T. Kimura, A. Osuka, "Optically Active Single-Walled Carbon Nanotubes", Nature Nanotechnology, 2 (6), 361-365 (2007)

G. Liu, F. Wang, X. Peng, A. F. M. M. Rahman, A. K. Bauri, and N. Komatsu, "Separation of Left- and Right-Handed Structures of Single-Walled Carbon Nanotubes through Molecular Recognition" Handbook of Biomedical Applications of Carbon Nanomaterials; K. M. Kadish and F. D'souza, Eds.; World Scientific: vol. 3, pp. 203-232 (2012).

A. F. M. M. Rahman, F. Wang, K. Matsuda, T. Kimura, and N. Komatsu,* "Diameter-based separation of single-walled carbon nanotubes through selective extraction with dipyrene nanotweezers" Chem. Sci., 2 (5), 862-867 (2011) [highlighted at the inside front cover].

F. Wang, K. Matsuda, A. F. M. M. Rahman, X. Peng, T. Kimura, and N. Komatsu,* "Simultaneous Discrimination of Handedness and Diameter of Single-Walled Carbon Nanotubes (SWNTs) with Chiral Diporphyrin Nanotweezers Leading to Enrichment of Single Enantiomer of (6,5)-SWNTs", J. Am. Chem. Soc., 132 (31), 10876-10881 (2010).

G. Liu, A. F. M. M. Rahman, S. Chaunchaiyakul, T. Kimura, Y. Kuwahara, N. Komatsu,* "Bis(tert-butylpyrene) Nanotweezers and Nanocalipers: Enhanced Extraction and Recognition Abilities for Single-Walled Carbon Nanotubes", Chem. Eur. J., published online (DOI: 10.1002/chem.201302799).

G. Liu, F. Wang, S. Chunchaiyakul, Y. Saito, A. K. Bauri, T. Kimura, Y. Kuwahara, N. Komatsu,* "Simultaneous Discrimination of Diameter, Handedness, and Metallicity of Single-Walled Carbon Nanotubes with Chiral Diporphyrin Nanocalipers", J. Am. Chem. Soc., 135 (12), 4805-4814 (2013) [highlighted in Chemical & Engineering News, 91 (12), p. 34, March 25, 2013].
Understanding Heme Enzyme Catalysis Starts with Their Active Site Coordination Structure: Identifying Heme Iron Axial Ligands Using Magnetic Circular Dichroism Spectroscopy
Authors: Dawson John H. , Sun Shengfeng , Bandara Indika , Sono Masanori
Published: February 2020

Magnetic circular dichroism (MCD) spectroscopy provides diagnostic spectral data sensitive to the identity of the axial ligands and to the spin and oxidation states of heme iron centers in proteins. In this effort, we have found the proximal ligand His93Gly myoglobin cavity mutant to be a remarkably versatile scaffold for preparation of model heme complexes of defined ligation. In particular, the difference in accessibility of the two sides of the heme iron center offers the advantage of forming ambient-temperature mixed-ligand heme model complexes, which are very difficult to prepare with model systems in organic solvents. Moreover, in the H93G Mb system, the protective environment provided by the protein allows for the formation of relatively stable oxyferrous and ferryl [Fe(IV)=O] complexes with variable ligands trans to the normally reactive dioxygen and oxo substituents. Ferrous, ferric and ferryl His93Gly Mb derivatives with various exogenous ligands have been prepared as models for native heme iron active sites ligated by proximal Lys (amines), Asp or Glu (carboxylates), Tyr (phenols), seleno-Cys (selenols), Cys (thiols) and Met (thioethers). Building upon this foundation, we have focused our attention on the use of the H93G Mb cavity mutant system to aid our investigation of the coordination structure of novel heme binding and transport proteins and heme-containing oxidative enzymes. (Funding NIH GM 26730)
Effects of Anions, Cations and Supporting Electrolyte on the Electrochemistry and Spectroelectrochemistry of Neutral, Protonated and Deprotonated Free-Base Porphyrins in Nonaqueous Media
Authors: Kadish Karl M. , Cui Yan , Zeng Lihan , Fang Yuanyuan
Published: February 2020

A series of free-base porphyrins were examined by electrochemistry and spectroelectrochemistry in nonaqueous media containing a variety of added anions or cations and different supporting electrolytes which were able to bind with the neutral and/or electrogenerated forms of the macrocycle. The investigated neutral porphyrins are represented as H2(P) while the protonated and deprotonated porphyrins are represented as [H4(P)]2+
, [H3(P)]+
, [
H(P)]-
and [(P)]2-
. The protonated porphyrins were generated by addition of an organic acid to solution, while the deprotonated porphyrins were formed by addition of base to give the compounds shown in Chart 1.

UV-vis spectra of the prophyrins were measured before, during and after the addition of different anions, cations and supporting electrolytes to solution. Cyclic voltammetry was used to measure the redox potentials for oxidation or reduction under the different solution conditions, while spectroelectrochemistry was used to monitor UV-vis spectra during each electron addition or electron abstraction. Formation constants for anion or cation binding were measured using both spectroscopic and electrochemical techniques. The measured shifts of absorption bands and shifts of reduction potentials were shown to vary with changes in the binding constants and this was markedly dependent upon both the nature of the porphyrin substituents and the porphyrin geometry, i.e., the planarity of the macrocycle. A proposed mechanism for anion and cation interaction with the free-base porphyrins will be presented.
Quinoline and Fluorene- Functionalized Porphyrins for Nanocrystalline Solar Cells
Authors: He Hongshan
Published: February 2020

Dye-sensitized solar cell (DSC) is an electrochemical device that has two electrodes with electrolyte between them. Recently the energy conversion efficiency of DSCs using a zinc porphyrin as a sensitizer has reached >12%. However, most porphyrin dyes exhibit narrow absorption in the visible region and relatively weak absorption in the red and near-infrared region; as a result, photons in these regions are not sufficiently converted to electrons, which has been a bottle-neck for high efficiency solar cells. Additionally, the widely used benzoic acid for attaching porphyrin dyes to titanium dioxide nanoparticles tends to dissociate into electrolyte, leading to poor long-term stability. In this presentation, synthesis, characterization, photophysical properties, electrochemical and photovoltaic properties of several novel porphyrin dyes with enhanced binding strength and broader light absorption capability will be discussed. We found that 8-hydroxylquinoline-functionalized porphyrin exhibited stronger binding capacity on the titanium dioxide nanoparticle surface, broader and stronger absorption in the red region compared to conventional benzoic acid-functionalized porphyrins. We will also discuss the porphyrins that are functionalized by alkyl fluorene groups. The results demonstrate the potential of these dyes for achieving high efficiency in DSCs.
Novel π-Conjugated Porphyrin Sensitizers for Dye-Sensitized Solar Cells
Authors: Diau Eric Wei-Guang
Published: February 2020

Inspired by the efficient energy transfer in naturally occurring photosynthetic reaction centers, numerous porphyrins have been designed and synthesized for dye-sensitized solar cell (DSSC) applications. The intrinsic advantages of porphyrin-based dyes are their rigid molecular structures with large absorption coefficients in the visible region and their many reaction sites, i.e., four meso and eight β positions, available for functionalization. However, porphyrins are known to suffer from dye aggregation due to their planar structural nature. In addition to the molecular design for potential porphyrin sensitizers, we have shown that co-sensitization of a zinc porphyrin with a well designed organic dye is a good strategy to change the aggregation morphology of the porphyrin adsorbed on TiO2 film to further improve its device performance. In this lecture, I will present our recent results based on a series of novel porphyrin sensitizers together with the approach of co-sensitization of porphyrins with organic dyes and/or porphyrin dimers. Extension of π-conjugation can be achieved by attaching various cyclic aromatic hydrocarbon substituents, such as anthracene, tetracene, pyrene, fluorene, and amino-substituted electron-donating groups opposite to the anchoring group of the target porphyrin. We will demonstrate that devices made of such porphyrins have reached the power conversion efficiency above 10 % using iodine-based electrolyte under one-sun irradiation. For the co-sensitization approach, combination of a porphyrin dye co-sensitized with an organic dye and a porphyrin dimer on a TiO2 film in a device according to a either a stepwise or a cocktail approach resulted in significant enhancement on both J
SC and V
OC relative to their individual single-dye sensitized devices. For characterizations, two different approaches based on time-resolved and frequency-domain techniques will be introduced. For the time-resolved approach, transient photocurrent and photovoltage decays were obtained based on several CW bias light irradiations of varied intensities at short-circuit and open-circuit conditions, respectively. A small-intensity LED pulse (~50 ms duration) at 630 nm was used as a perturbation probe to monitor the electron-transport kinetics at short-circuit condition or the charge-recombination kinetics at open-circuit condition. For the frequency-domain approach, electrochemical impedance spectroscopy (EIS), intensity-modulated photocurrent spectroscopy (IMPS) and intensity-modulated photovoltage spectroscopy (IMVS) measurements were also carried out. Both time-resolved and frequency-domain techniques were applied to various highly efficient DSSC systems based on porphyrin and porphyrin + organic dye systems to rationalize their photovoltaic performances.
Synthesis of Porphyrin Arrays and Investigation of Their Optical and Electrochemical Properties
Authors: Tamaki Takashi , Nosaka Takenori , Ogawa Takuji
Published: February 2020

Porphyrin arrays have attracted much attention in a wide range of scientific applications such as in artificial photosynthetic antenna1, electronic devices, and single-molecule devices2. Although various synthetic methods have been reported, they are applicable only to the homologous porphyrin arrays; in addition, it is difficult to synthesize the elaborate porphyrin arrays with programmable order of each unit. Thus, we synthesized porphyrin dimers and trimers that have varying sequences of the porphyrin units via the consecutive Suzuki coupling reactions using the same key porphyrin compound. The use of the consecutive Suzuki coupling reactions for the effective syntheses of elaborate oligoarenes by repetition of the same reaction at each elongation step3, has been reported. In this work, the consecutive Suzuki coupling was applied for the synthesis of porphyrin arrays of various orders.

We synthesized two porhpyrins as the starting monomers: porhyrin 2 bearing a triflate group, and the key porphyrin 3 bearing a boronic ester and a hydroxyl group. Porphyrins 2 and 3 were synthesized in three and four steps, respectively. The Suzuki coupling reaction between 2 and 3 in various combinations afforded four different dimers, as denoted by 4 in Scheme 1. After triflation of the hydroxyl group of 4, a further coupling of 4 with 3 afforded five different trimers, as denoted by 6 in Scheme 1. The porphyrin monomers were synthesized in gram scale in one batch, and the coupling reactions afforded moderate to good yields. The optical and electrochemical properties of these dimers and trimers were investigated.

The absorption and emission spectra of the dimers and trimers, possessing the same molecular formula, were different (Fig. 1) when the order of the units was different. The emission profiles of the arrays, 4-HZn and 6-HZnH, were attributed to that from the free-base porphyrin unit; however, the wavelengths and intensities of their emission were different. (Fig. 1.(b)). The differential pulse voltammograms of the monomers, 1-H and 1-Zn, and the dimer 4-HZn are demonstrated in Fig. 2. Certain redox peaks of the dimer 4-HZn were almost identical to those of the component monomers (1-H and 1-Zn); however, a few new redox peaks were observed, which indicated the emergence of new electronic states via interaction of each unit component.

(1) Nakamura, Y.; Aratani, N.; Osuka, A. Chem. Soc. Rev.
2007, 36, 831.

(2) Sedghi, G.; Garcia-Suarez, V. M.; Esdaile, L. J.; Anderson, H. L.; Lambert, C. J.; Martin, S.; Bethell, D.; Higgins, S. J.; Elliott, M.; Bennett, N.; Macdonald, J. E.; Nichols, R. J. Nat Nano
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(3) Noguchi, H.; Hojo, K.; Suginome, M. J. Am. Chem. Soc.
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Electrochemical Analysis of Phthalocyanine Grafted Polymer Nanofibers
Authors: Gokceoren Argun T , Kaplan Ekrem , Arsalanoglu Yasin
Published: February 2020

Nanofibers possess exclusive physical, chemical, and electronic properties. Although different methods are known [1-2], electrospinning has been used with an increasing impact because of the ease of proceeding and the use of a wide range of polymeric materials [3–4] in the production of nanofibers.

Metal free phthalocyanine grafted polypyrrole and cobalt metallated phthalocyanine grafted polypyrrole nanofibers were prepared by electrospinning method. The electrospun PPy and phthalocyanine grafted polypyrrole fibers were coated on indium tin oxide electrode surface for a proper investigation of the electrochemical activity of the fibers. Different methods were used to characterize the obtained fibers. Fourier-transform infrared spectroscopy, Scanning electron microscope and polarized optical microscope were used for their morphological characterization, while electrical behaviors of the nanofibers were characterized by direct current and electrochemical impedance spectroscopy measurements.

[1] Feng L, Li S, Li H, Zhai J, Song Y, Jiang L. Super-Hydrophobic Surface of Aligned Polyacrylonitrile Nanofibers. Angew Chem Int Ed 2002;41:1221–1223.

[2] Ma PX, Zhang R. Synthetic nano-scale fibrous extracellular matrix. J Biomed Mat Res 1999;46:60–72.

[3] Menon VP, Lei J, Martin CR. Membrane-Based Synthesis of Nanomaterials. Chem Mater 1996; 8: 2382-86.

[4] Joo J, Park KT, Kim BH, Kim MS, Lee SY, Jeong CK, Lee JK, Park DH, Yi WK, Lee SH, Ryu KS. Conducting Polymer Nanotube and Nanowire Synthesized by Using Nanoporous Template: Synthesis, Characteristics, and Applications. Synth Met 2003;135:7-13.
(Invited) Electrical Characterization of Defects in Al2O3
Authors: Schmid Alexander , Kersten Friederike , Rentrop Solveig , Abendroth Barbara , Meyer Dirk Carl , Heitmann Johannes
Published: February 2020

Nanocrystalline high-k dielectrics play a major role in semiconductor research and development. The semiconductor industry faces nanocrystalline dielectrics for MIM capacitors in DRAM devices [1] and rf applications, as well as for gate dielectrics in sub 45 nm devices.

However, the use of crystalline dielectrics lead to new effects like trapping, stress induced leakage currents [2, 3], change in the field extrapolation model of lifetime [4] and an increase of dielectric absorption effects [5]. Most of the described effects are connected to the formation of defect states within the bandgap of the dielectric material. We will review our work on electrical characterization of amorphous and crystalline dielectrics of materials like Al2O3, HfO2, ZrO2 and SrZrO. The time constants of the dielectric absorption of the dielectrics differ very strongly and mainly for the crystalline dielectrics they show strong load voltage dependence. This can be attributed to a very effective tunneling process into a defect band in the high-k-Material at voltages of 0.6-0.7 V. Additionally, optical stimulated leakage current measurements at 15 K will be shown. Here, defects states in the dielectric and at the interface dielectric-semiconductor can be optically stimulated with IR-light for different sub-band-gap energies.

By the different described methods a detailed characterization of the energy of the investigated bulk and interface traps of the high-K material in combination with Si and GaN substrates are carried out.

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Trans.
2,217 (2006).

[2] D. Zhou, U. Schroeder, J. Xu, J. Heitmann, G. Jegert, W. Weinreich, M. Kerber, S. Knebel, E. Erben, and T. Mikolajick, J. of Appl. Phys. 108 (2010) 124104.

[3] A. Paskaleva, M. Lemberger, A.J. Bauer, W. Weinreich, J. Heitmann, E. Erben, U. Schröder, and L. Oberbeck, J. Appl. Phys. 106 (2009) 054107.

[4] R. Agaiby, P. Hofmann, D. Zhou, M. Kerber, J. Heitmann, U. Schroeder, E. Erben, L. Oberbeck, IEEE Elect. Dev. Lett. 30 (4) (2009) 340-342.

[5] M. Kerber, C. Fachmann, J. Heitmann, S. Kudelka, U. Schröder, H. Reisinger, J. Vac. Sci. Technol. B 27(1) (2009) 321-324.
(Invited) Temperature Impact on Reliablity and Manufacturing of Embedded HfOx-Based RRAM: a Novel Pre-coding Method for Bypassing Soldering Reflow
Authors: Tirano Sauveur , Perniola Luca , Cagli Carlo , Jalaguier Eric , Jousseaume Vincent , Deleruyelle Damien , Muller Christophe , de Salvo Barbara , Reimbold Gilles
Published: February 2020

This paper provides an overview of the temperature impact on the electrical behavior of oxide-based RRAM, during forming, low-field resistance reading, SET/RESET, disturb, data retention and endurance. HfO2-RRAM devices (in a 1T1R configuration) integrated in an advanced 65 nm technology are studied for this aim. We show that forming operation is strongly activated in temperature (i.e. -0.5 V per hundred Celsius degree), being much less for SET and RESET voltages (i.e. < -0.05 V per hundred Celsius degree); disturb of HRS at fixed voltage showed to be independent of temperature; endurance up to 3.106 cycles, with optimized set of stress parameters showed no significant variation; data retention at 150 °C up to 68 days showed stable programming window, after different initial programming algorithms. After having overviewed the basic cell performances working under variable temperature, the issue of packaging thermal stress on HfOx-based RRAM cells will be analyzed in detail. Certain applications (for instance secure smartcards) require writing the content of information in memories before packaging. The thermal stress during this step poses serious troubles to the stability of the information in RRAM. The presentation will overview the different efforts that are spent on this topic, providing, for the first time in the literature, the results of data retention under 260°C up to 375°C (general temperature range experienced during packaging thermal stress) and innovative precoding methods to bypass the thermal issue associated to packaging.
Characterization of a Novel Radical Nitrogen Plasma Source for Semiconductor Nitridation
Authors: Lucero Antonio Tomas , Cho Taiheui , Kim Jiyoung
Published: February 2020

Surface nitridation has long been desirable for surface and interface passivation to realize ultra-low equivalent oxide thickness (EOT) dielectric layers on Si and III-V materials. Various nitridation techniques exist, including thermal and plasma nitridation. Thermal processes rely on high temperatures which are difficult to control for very shallow nitridation without any significant diffusion. Thermal budgets become stricter when moving to III-Vs, unless special steps are taken to reduce or eliminate loss of low vapor pressure materials (ie. As, In). Conventional plasma processes allow lower temperatures but can expose the substrate to damaging, high energy ions. Shallow channel devices are particularly vulnerable to substrate damage, degrading mobility.

We will report nitridation of Si and GaAs using a novel, remote nitrogen radical generator system. The generator is a custom, atmospheric plasma source capable of generating a large concentration of N radicals without exposing the substrate to plasma. Processes are carried out at low pressures, 1-10 Torr, and the generator is connected to the process chamber by an orifice, precluding direct line of site to the plasma. The system is integrated with an atomic layer deposition (ALD) chamber for both radical enhanced and thermal ALD, allowing in-situdeposition of dielectrics.

Growth temperatures range from room temperature to 400 °C. Aluminum oxide, aluminum nitride and zirconium oxide ALD dielectric stacks will be analyzed using ex-situ x-ray photoelectron spectroscopy (XPS) to gauge the surface chemistry and nitridation stability. Metal-oxide-semiconductor capacitors will be measured using capacitance-voltage (C-V) measurements to look at the nitridation contribution to electrical properties. Emphasis will be places on zirconia-alumina-zirconia (ZAZ) stacks, with nitridation at the interface and the dielectric bulk.

We would like to thank Samsung Electronics for their financial support and Toshiba Mitsubishi-Electric Industrial Systems Corporation (TMEIC) for providing the nitridation system.
Heterogeneous Integration of Plasmonics with Si-Photonics & Microelectronics for High-Performance Optical Routing
Authors: Tekin Tolga , Pleros Nikos , Bozhevolnyi Sergey I. , Dereux Alain , Avramopoulos Hercules , Waldow Michael
Published: February 2020

Advanced packaging technologies impact future systems, since packaging determines functionality, cost and reliability of future systems. The future systems are very high complex systems and contain different physical functions. Therefore modularity in heterogeneous integration is required. Future systems combine optical and ultra high frequency functions. With this a large variety of materials will be applied. For all these components a common smart support substrate such as ‘Silicon’ will be of importance for future systems. Furthermore, System-in-Package is must for future subsystems in order to overcome the challenges.

In tems of of today’s Peta-flop High-Performance Computing (HPC) applications the size and power consumption appear to be critical issues, signifying that new technological and architectural considerations are required in order to be able to move towards Exascale-computing powers. Whereas silicon photonics emerges as a powerful technology for low-loss and high bandwidth optical connectivity in integrated circuit environments, servers and network switches are already consolidating into high-density blade enclosures in order to reduce space and cooling requirements. These considerations determine additional tasks for switching infrastructures of miniature data networks: the next generation of routing circuitry has to provide high throughput capabilities while keeping in line with the requirements of small foot-print, low power consumption and low latency. Here, next generation computing architectures are needed with ultra low power consumption; ultra high performance with novel photonic interconnection technologies. The objective of the recently proposed high bandwidth photonics interconnection layer for converged microsystems using System-in-Package Technology, is to develop a CMOS compatible underlying technology to enable next generation optical computing architectures.

We present within the framework of EU-PLATON project a photonic integrated system-in-package platform for Tb/s optical routing, where three different technologies, silicon photonics, plasmonics and electronics are merged. Compatibility between various components has to be ensured to allow for their seamless interfacing and interoperability. The 4x4 router architecture exploits a SOI platform employing 340x400nm2 waveguide structures and hosting four 7:1 SOI multiplexing circuits, four photodiodes, an electronic IC control circuit and the 4x4 dielectric-loaded surface plasmon-polariton (DLSPP)-based switching matrix.

This work has been partly supported by the European FP7 research program PLATON, Contract Number 249135. www.ict-platon.eu