bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) High Optical Absorbance Multilayer Film of Au and TiO2: Charge Generation Dynamics Under Plasmon Excitation
Authors: Furube Akihiro , Takahata Toshihiko , Yanagiya Shinichiro 
Published: February 2020

Metal-insulator-metal (MIM) structure using gold nanoparticles, titanium dioxide (TiO2), and gold (Au) film was fabricated. The optical absorption nature of the films in visible and NIR region with different TiO2 thickness were studied by steady-state extinction spectra and femtosecond transient absorption data. The Au nanoparticles were deposited on silane-treated glass by wet process, which showed enhancement of optical absorption of visible light due to its surface plasmon resonance (SPR). On the AuNP self-assembly, the titanium dioxide was deposited by magnetron sputtering. The extinction spectra of multilayer film showed the absorbance of the wide range of visible light. Further coating by Au film resulted in very broad absorption covering whole visible and NIR region. Transient absorption study proved that the generation of the conductive electrons by plasmon induced electron transfer from Au to the conduction band. The electron lifetimes in picosecond timescale depended on the film thickness the of TiO2 layer, suggesting that thicker film is appropriate to obtain long-lived carriers.
Authors appreciate Prof. Retsuo Kawakami in Tokushima Univ. for kind help while preparing the TiO2 films.
(Invited) Electrochemical Oxygen Reduction Catalyzed at Pt–Ni Nanostructured Electrocatalysts Immobilized on Nitrogen-Doped Carbon Supports
Authors: Kato Masaru , Ogura Kazuya , Nakagawa Shogo , Li Tianchi , Nakahoshiba Ryota , Tokuda Shoichi , Yagi Ichizo 
Published: February 2020

Oxygen reduction reaction (ORR) is the key reaction in future energy generation devices such as polymer electrolyte fuel cells (PEFCs) and metal–air batteries. To drive the ORR in state-of-the-art PEFCs, carbon-supported Pt–M alloys (M = Ni and Co) are used. Since platinum is rare and expensive, there is a need to develop ORR electrocatalysts with not only high catalytic activity but also high durability. Under electrocatalytic conditions, catalyst degradation mechanisms are known to involve many processes including particle detachment, agglomeration and metal dissolution.[1] These phenomena can be suppressed by increase metal/support interactions. Carbon black is typically used as the catalyst support and can be chemically modified by heteroatom-doping. Heteroatom-doped carbon supports can show strong metal/support interactions with Pt nanoparticles.[2]

Herein, we report the enhancement of electrocatalytic ORR activity and durability of Pt–Ni alloy nanoframes by immobilization on nitrogen-doped carbon supports. Strong metal/support interactions between the nanoframe and the support caused the downshift of the d-band center position of the surface Pt, proved by X-ray photoelectron spectroscopy and surface-enhanced infrared absorption spectroscopy.[3] In situ X-ray absorption spectroscopy also revealed that the Pt surface oxide formation was suppressed by the immobilization on nitrogen-doped carbon supports. Our findings demonstrate that tuning the electronic structure of nanostructured Pt alloy electrocatalysts via strong metal/support interactions will allow the development of highly active and robust electrocatalysts for the ORR.
References
[1] N. Hodnik, G. Dehm, K.J.J. Mayrhofer, Acc. Chem. Res., 49, 2015–2022 (2016).
[2] Q. Wang, Y. Tian, G. Chen, J. Zhao, Appl. Surf. Sci. 397, 199–205 (2017).
[3] M. Kato, K. Ogura, S. Nakagawa, S. Tokuda, K. Takahashi, T. Nakamura, I. Yagi, ACS Omega, 3, 9052–9059 (2018).
Electrochemical and Chemical Reactivity of Octahalogenated Meso-Tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)Porphyrins
Authors: Cong Lei , Chahal Mandeep K , Osterloh Ryan , Sankar Muniappan , Kadish Karl M. 
Published: February 2020

Two highly non-planar octahalogenated nickel(II) porphyrins were characterized for the first time as to their electrochemical and spectroscopic properties as well as their chemical reactivity in nonaqueous media. The complexes have the structures shown in Chart 1.

Chart 1. Structures of investigated porphyrins.
The UV-vis spectra of NiPorCl8 and NiPorBr8 vary with solvent and degree of axial coordination and are substantially different than spectra of the unhalogenated NiPor parent porphyrin. The NiPorBr8 and NiPorCl8 spectra are stable with time and interpreted in terms of four or six-coordinated derivatives in 14 different nonaqueous solvents but this is not the case for NiPorCl8 in DMF or DMSO where a transient 6-coordinate solvated complex is initially formed upon dissolving the compound followed by formation of a porphodimethene in solution. The combination of eight β-halogens and four meso-t-butyl-hydroxyphenyl groups on the NiPorX8 complexes exerts a powerful influence on the electrochemistry which is characterized by up to five redox reactions, the first 2 or 3 of which are irreversible at room temperature and assigned as involving the easily reducible meso-hydroxyphenyl groups followed by reduction of the π-conjugated system at more negative potentials. A rapid homogeneous chemical reaction occurs after the first electron transfer giving as the final product a nickel(II) porphodimethane at the electrode surface. This was confirmed by comparisons between redox potentials and UV-visible spectra of the in situ generated electroreduction products with that of chemically synthesized porphodimethenes formed in a reaction between NiPorCl8 and the added anions F-, CN-, OAc- or H2PO4
-.
Pentacene Fused Porphyrin Dimer Exhibiting High Stability and Solubility
Authors: Hu Yi , Wang Hong 
Published: February 2020

Acenes have the potential to be used in the next gengeration of electronic devices due to their unique electronic properties. Pentacene is one of the most widely utilized organic compounds for organic-filed effect transistor (OFET) because of its high charge mobility. However, solubility and stability are two critical factors that limit their use in practical application. Ethynylation has shown to be one of the best strategies to stabilize pentacene. Our group is interested in linearly fusing another aromatic chromophore such as porphyrin with alkynyl-substituted pentacene to further increase its stability and solubility.
In this work, a new pentacene fused porphyrin dimer with high stability and solubility was prepared and characterized. The new pentacene fused porphyrin dimer exhibits a narrow energy gap up to 1.4 eV. Photodegradation studies using UV-Vis and 1H NMR reveal that the new pentacene derivative exhibits an increased solubility and stability up to 16 times compared to 6,13-bis(phenyethynyl)pentacene.

Figure 1
Site-Specific Coordination Chemistry and Beyond: Novel Properties in Low Dimensional Supramolecular Architectures of Porphins at Surfaces
Authors: Girovsky Jan , Baljozovic Milos , Nowakowska Sylwia , Nowakowski Jan , Wäckerlin Christian , Dreiser Jan , Lobo Checa Jorge , Gade Lutz , Decurtins Silvio , Liu Shi-Xia , Oppeneer Peter , Ballav Nirmalya , Jung Thomas A. 
Published: February 2020

In our work, we establish porphin based on-surface architectures which exhibit extraordinary properties e.g. electronic, magnetic and quantum properties originating from the reduced dimensionality of the self-assembled and atomically precise architectures. Unconventional H-bonding as well as the direct site-specific interaction of the porphin’s center metal with the substrate direct the 2D architectures. The coordination and magneto-chemistry of binary 2D assemblies can be investigated by combining scanning probe microscopy / spectroscopy, photoelectron and photoabsorption spectroscopy and density functional theory. Complex electronic [1] and magnetic [2] interactions arise from the 2D periodicity which are also dependent on the state of adsorbed to physisorption and chemical reactivity. Sub-lattices in 2D ‘checkerboard’ architectures of magnetic molecules on magnetic substrates can be selectively switched by chemical ligation [3]. Also we have observed the first example of 2D ferrimagnetic long-range order and remanence for such a 2D architecture on non-magnetic Au(110) [2]. Uniquely, self-assembled 2D architectures contribute to our understanding of fundamental interactions involved in host-guest systems and allow for the specific operation of quantum states with a partial delocalization across the supramolecular on-surface architecture [4]. Thereby we unravel more and more of the on-surface chemistry [5] required to engineer low dimensional materials with unprecedented properties by controlling their architecture. In particular this involves the on-surface supramolecular, the on-surface coordination and the on-surface magneto-chemistry.
[1] Lobo-Checa, J. et al., Science 325:300 (2009)
[2] Girovsky, J. et al., Nat. Commun., DOI: 10.1038/ncomms15388 (2017).
[3] C. Waeckerlin et al, 10.1002/adma.201204274
[4] Nowakowska, S. et al., 10.1021/acsnano.7b07989
[5] Ballav N., et al., JPCL 4:2303 (2013) [4]

Figure 1
Light Triggers Molecular Shuttling in Rotaxanes
Authors: Guldi Dirk M. 
Published: February 2020

In this work on rotaxanes comprising a strapped-porphyrin as a ring molecule and a dumbbell bearing one fullerene stopper, coordination forces are crucial for the excited state behavior. Distinct differences in the lifetime of the charge-separated state and the presence of more than a single lifetime were observed. Here, the coordinating properties and the polarity of the solvent have the strongest impact. For example, in apolar, non-coordinating toluene, a single lifetime was found for the charge-separated state, whereas in polar, coordinating PhCN, a short-lived and a long-lived charge-separated state evolved. In toluene and PhCl, these effects were also induced when a coordinating species, such as pyridine, was added.
Depending on the solvent polarity, the shuttling is either directional or random. In apolar toluene and in the presence of pyridine, Coulombic interactions in the ZnP•+-C60
•-radical ion pair dominate and, in turn, force a close proximity between the oxidized porphyrin and the reduced fullerene. This sets up the means for a directional molecular shuttling, which results in a drastically reduced lifetime of the charge-separated state. In highly polar benzonitrile, shuttling is random and allows the fullerene anion to move further away from the porphyrin cation. This enables the system to overcome the barrier of Coulombic attractions. As such, larger porphyrin-to-fullerene distances go hand-in-hand with a longer lifetime of the charge-separated state in a high-polarity coordinating solvent; longer relative to that in either non-coordinating solvents or low-polarity solvents. Independent confirmation for our hypothesis came from the absence of a longer and/or a shorter-lived charge-separated state in the presence of a coordinating solvent in analogous experiments with a system, which features a strapped free-base porphyrin rather than a zinc porphyrin.
Our results emphasize the importance of coordination interactions. To gain further insight, rotaxanes with longer, more rigid axles, which should enhance the effects on the distribution of lifetimes, are currently being designed and studied in our laboratories. Finally, a porphyrin with a metal center that binds pyridine more strongly than zinc, such as ruthenium, could exhibit interesting behavior.
Supramolecular Assemblies Recognized Gastric Cancer Biomarkers in Biological Fluids
Authors: Stefan-van Staden Raluca-Ioana 
Published: February 2020

Molecular recognition of gastric cancer biomarkers is essential for fast and early diagnosis of gastric cancer. To date, the standard methods are unable to detect most of these biomarkers in biological fluids.
Stochastic sensors represent a promising candidate for the molecular recognition of the biomarkers, because they can perform a qualitative analysis as well as a quantitative analysis of these biomarkers in biological fluids such as whole blood, saliva. Therefore, stochastic sensors based on supramolecular assemblies immobilized on carbon materials such as diamond, graphite, graphene were designed, characterized and validated for fast screening of biological fluids for early diagnosis of gastric cancer. The results obtained proved that they can be used for early diagnosis of gastric cancer.
(Invited) Nano-FTIR Correlation Nanoscopy for Organic and Inorganic Material Analysis
Authors: Mastel Stefan , Hartmann Nicolai F. , Gokus Tobias 
Published: February 2020

Scattering-type Scanning Near-field Optical Microscopy (s-SNOM) is a scanning probe approach to optical microscopy and spectroscopy, bypassing the ubiquitous diffraction limit of light to achieve a spatial resolution below 20 nanometers. s-SNOM employs the strong confinement of light at the apex of a sharp metallic atomic force microscopy (AFM) tip to create a nanoscale optical hot-spot. Analyzing the scattered light from the tip enables the extraction of the optical properties (dielectric function) of the sample directly below the tip and yields nanoscale resolved images simultaneous to topography [1]. In addition, the technology has been advanced to enable Fourier-Transform Infrared Spectroscopy on the nanoscale (nano-FTIR) [2] using broadband radiation from the visible spectral range to THz frequencies.
Recently, the combined analysis of complex nanoscale material systems by correlating near-field optical data with information obtained by other scanning probe microscopy (SPM)-based measurement methodologies has gained significant interest. For example, the material-characteristic nano-FTIR spectra of a phase-separated polystyrene/low-density polyethylene (PS/LDPE) polymer blend verifies sharp material interfaces by measuring a line profile across a ca. 1 µm sized LDPE island (Fig1). Near-field reflection/absorption imaging at 1500cm-1 of the ca. 50nm thin film allows to selectively highlight the distribution of PS in the blend and simultaneously map the mechanical properties like adhesion of the different materials [3,4].
Further, results will be presented that correlate the near-field optical response of semiconducting samples like graphene (2D) or functional SRAM devices (3D) in different frequency ranges (mid-IR & THz) to Kelvin Probe Force Microscopy (KPFM) measurements. Thus, s-SNOM systems represent an ideal platform to gain novel insights into complex material systems by different near-field and AFM-based method.
[1] F. Keilmann, R. Hillenbrand, Phil.
Trans. R. Soc. Lond. A
362, 787 (2004).
[2] F. Huth, et al., Nano Lett.
12, 3973 (2012).
[3] B. Pollard, et al., Beilstein J. of Nanotechn.
7, 605 (2016).
[4] I. Amenabar, et al., Nature Commun.
8, 14402 (2017).
Figure caption:

Fig 1.
Near-field correlation nanoscopy of a thin PS/LDPE polymer film, highlighting the phase separation of the materials by nano-FTIR measurements as well as the different mechanical properties of the polymers.

Figure 1
Magnetic Field Effect on Anodic Dissolution of Axle Steel in Bicarbonate Solution with Chlorides
Authors: Ning Fei , Zhang Kun , Cui Tongming , Ling Sichun , Ma Jiarong , Lu Zhanpeng , Yu Chengbing 
Published: February 2020

The vehicle axle in the railway locomotive is a very important component. Localized corrosion is a cause of its degradation. Localized corrosion is usually caused by corrosive environments especially in media containing chloride ions. Harmonic currents in the power supply loops (contact nets and guide rails) of the train during train travel can produce stray current that produces stray magnetic fields. Some studies have shown that magnetic fields can accelerate or inhibit localized corrosion of metals.
In this study, optical microscopy (OM) and electrochemical measurements were used to study the effects of magnetic field on the electrochemical behavior and corrosion morphology of axle steel in sodium bicarbonate solutions with and without chloride ions. Different scan rates were used in the measurements of anodic polarization curves. Potentiostatic polarization measurements were performed with applying or removing a 0.4 T magnetic field. The surface morphologies of the electrodes were observed after potentiostatic polarization.
Figure 1 show that, for axle steel in 0.05 mol/L NaHCO3 with or without 0.001 mol/L NaCl, the magnetic field increased the peak current, positively shifted the potential for the onset of passivation, and narrowed the passivation range. Chlorides increased the anodic current in the transpassivation region. The synergistic effect of magnetic field and chlorides on breakdown of passivation was more significant at high potential scan rate for the anodic polarization curve measurements. Obvious corrosion pits could be found after polarization, according to the morphology of the axle steel after polarization at a scan rate of 50 mV/min. It is found that the magnetic field significantly accelerated the corrosion. For axle steel in 0.05 mol/L NaHCO3 system, the potentiostatic polarization was carried out at -0.3 V(SCE). The current density decreased with increasing the polarization time. The current decreasing rate was mitigated by applying a 0.4T magnetic field, i.e., the anodic current density tended to be more stable under applied magnetic field, showing a significant magnetic field effect on anodic dissolution and pitting behavior of axle steel in this environments.

Figure 1
Electrochemical Noise Analysis of Aluminum Alloy 6061-T6 in Laminar Flow of Seawater
Authors: Veleva Lucien , Acosta Gloria 
Published: February 2020

Aluminum alloy 6061-T6 is widely used in many fields of engineering, especially in marine applications1. In the presence of chlorides localized corrosion occurs2. The goal of this study is characterize the alloy surface and its corrosion resistance in laminar flow conditions (0.1 ms-1), during the exposure in Caribbean seawater of Cozumel channel. As electrochemical techniques, open circuit potential (OCP) monitoring and electrochemical noise (EN) have been employed. OCP was correlated with changes on the alloy surface. The fluctuations of current, considered as EN3, were acquired up to 30 days and were transformed in the frequency domain. Their power spectral density (PSD) plots were obtained in order to gain information concerning dynamic of spontaneous release of energy. At the end of the experiment, the value of β exponent in PSD graph (Fig. 1a) suggests that AA6061-T6 corrosion process occurs as a persistent non-stationary process, which dynamics is controlled by fractional Brownian motion (fBm). The EN data provided the pitting index (PI = 0.95) and Rp value (1.44 kΩ cm2). The PI value indicates that Al6061-T6 presents pitting corrosion. Corrosion current (Icorr = 18.08 μA cm-2) was calculated based on Rp and Stern-Geary coefficient (B = 0.026 V) values.
Removing the corrosion products, SEM-EDX analysis showed undissolved intermetallic particles on the alloys surface, rich in Fe and in the presence of Si, as well as the presence of pit cavities (Fig. 1b).

Figure 1. AA6061-T6 after 30 days of exposure in Caribbean seawater of Cozumel channel with a laminar flow (0.1 ms-1): a) PSD plot of current noise signal and β exponent value and b) SEM-EDS of the surface after remove of the corrosion layer.
References:
1. Davis, J. R., Aluminum and aluminum alloys, alloying: understanding the basics,
ASM International, Materials Park, Ohio, (2001).
2. Szklarska-Smialowska Z., “Pitting Corrosion of Aluminum”, Sci., 41, 1743 (1999).
3. Dawson, J., “Electrochemical noise measurement: the definitive in-situ technique for corrosion applications” in Kearns J., Scully J., Roberge P., Reichert D., Dawson J., E
lectrochemical noise measurement for corrosion applications. West Conshohocken, PA: ASTM STP 1277, (1996).

Figure 1
Electrode Scratching Technique As a Robust Way to Decouple Erosion-Corrosion Components
Authors: Omirkhan Aigerim , Bos Tom , Yang Guoqiang , Stitt Camilla , Riley D. Jason , Ryan Mary P. 
Published: February 2020

The substantial number of parameters and their interdependence makes the modelling and prediction of erosion-corrosion rates a rather challenging task, yet owing to increasing computational capacity one that is potentially solvable. To accurately estimate the rate of material loss, universally accepted explanations of the mechanisms of combined erosion and corrosion must be developed. The absence of reliable data can undermine safety and predictability of industrial processes, such as oil and gas transportation. The aim of this work is to demonstrate the application of an electrode scratching technique coupled with microstructural characterisation for improved understanding of synergy in erosion-corrosion.
In this work, a rotating disc electrode scratching setup, with well-defined and controlled flow conditions, was developed to study individual contributions to erosion-corrosion. Linear potentiodynamic and potentiostatic polarization techniques were used to reproducibly monitor the kinetics of dissolution and repassivation of API X65 steel electrodes upon scratching. Samples characterized using high-resolution scanning electron microscopy (SEM) and white-light interferometry (WLI), confirm the synergy; the losses due to erosion-corrosion are larger than that of the summation of the separate contributions of erosion and corrosion. Focused Ion Beam (FIB) milling was implemented for in-situ lift-out of lamellae from scratched samples for Transmission Electron Microscopy (TEM) characterisation. We confirm distinct microstructural changes take place in the vicinity of scratches: with nanoscale grain refinement and orientation changes observed (See Figure 1). These results, coupled with electrochemical data and micro-hardness measurements, suggest time-dependent surface-hardening processes affect material loss rates during mechanical-electrochemical coupled corrosion.

Figure 1
Passivation Layer Tailoring Using Laser Powder-Bed Fusion Additive Manufacturing: A Tribocorrosion Study
Authors: Chiu Tse-Ming , Castaneda Homero 
Published: February 2020

Laser powder-bed fusion is an additive manufacturing high-energy laser beam creating near-end shape parts directly from a digital computer model. This technique has revealed new trends in manufacturing industry by producing parts with complex geometry and with topology optimizing the weight to strength ratio of structures. In this research, we characterize the corrosion behavior of a Ti6Al4V and AlSi12 alloy fabricated by using laser powder-bed fusion (L-PBF) when they were exposed to corrosive and tribocorrosion conditions. Two synthesis pathways (vertical and horizontal) were employed to produce alloy disks by using high and low laser power resulting in four different thermo-history profiles. The superfine microstructure of L-PBFed Ti6Al4V was revealed using EBSD and XRD, identified as α’ structure (an oversaturated HCP phase) with an n-type titanium oxide passive layer. The surface property was tailored by different 3D printing parameter resulting in a 30% increase in hardness 60% in wear loss and 28% decrease in the oxygen vacancies. The difference in oxygen vacancies tuned the corrosion to wear ratio from 25% to 15% at 2N normal load in simulated body fluid. The corrosion behavior of L-PBFed AlSi12 was tested in simulated acid water. The two different melt pool microstructure (shown in Fig1 (a) and (b)) engineered by the L-PBF building direction results in a difference in the suspiciously of pitting corrosion. The horizontal built specimens show better in pitting resistance, but with a broader probability distribution, which increases the uncertainty in engineering structurer design. The coarse grain silicon precipitation at melt pool boundary result in localized cathode barrier that deflects the pit propagation resulting in shallow pits. However, the heterogeneity of grain boundaries leads to the weakness in forming a protective surface layer under Cl- attack.
Figure 1 (a) Pit morphology and (b) melt pool structure and (c) accumulated pitting probability of AM-AlSi12 in dilute Harrison’s solution

Figure 1